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A Q-switched mode-locked (QML) thulium-doped fiber laser based on nonlinear polarization rotation (NPR) and negative group velocity dispersion (GVD) is demonstrated. This regime consists in the generation of a mode-locked (ML) pulse train under a Q-switched (QS) envelope. In this regard, by properly adjusting the polarization controllers and increasing the pump power in a range from 1 to 3 W, QML regime is obtained. With a maximum pump power of 3 W, a QS pulse duration of 1.46 μs and a pulse energy of 5.96 μJ are obtained. The maximum frequencies reached are 26 kHz and 2.63 MHz, corresponding to the Q-switched and mode-locked pulses, respectively. This method for generating a QML at 2 μm has the advantages of being eye-safe and robust, providing an ideal dual-frequency comb (DFC) generation method with high potential for various applications. [ABSTRACT FROM AUTHOR]

An online torque sharing function (TSF) with instantaneous torque error compensation method for switched reluctance machines is proposed to maintain a minimized ripple operation. The proposed method adjusts the shared torque between the phases based on instantaneous torque error different than the existing TSF methods formulated with a mathematical expression. The objective of this approach is to benefit from the outgoing phase torque as it has slow current dynamics due to the high inductance. Also, the incoming phase is turned on as soon as it can generate positive torque. During this process, the total torque is estimated instantaneously using lookup tables, and a correction current is calculated and injected into the incoming phase reference current as the inductance is low and current dynamics are fast. This way, the torque ripple is reduced for a wide speed range. Compared to the conventional linear, sinusoidal, exponential, and cubic TSFs, better torque ripple performance is obtained. [ABSTRACT FROM AUTHOR]

In this study, effects of hydrogen addition on combustion and flame propagation characteristics of methane/air mixtures were investigated in a constant volume combustion chamber. Tested gas mixtures are 100% CH 4 , 05% H 2 – 95% CH 4 , 10% H 2 – 90% CH 4 and 15% H 2 – 85% CH 4 , and such mixtures were ignited using a passively Q-switched Nd:YAG laser ignitor which has a pulse energy of 12.3 mJ, pulse duration of 2.4 ns and wave length of 1064 nm. A Schlieren setup coupled with a high-speed camera enabled evaluating flame propagation behavior, while pressure curve analysis provided necessary data for characterization of combustion properties. Additionally, lean flammability limits of gas mixtures were also determined at the test conditions. The unique properties of hydrogen (such as low density, high reactivity, high diffusivity etc) widened lean flammability limit. Rate of pressure rise and measured pressure values increased with hydrogen addition, regardless of the air-fuel equivalence ratio (λ). Lastly, hydrogen addition uniformly affected flame propagation characteristics and flame luminosity. Combustion process became more stable with hydrogen addition. • 5%, 10% and 15% hydrogen (by volume) were added to methane. • H2/CH4 mixtures were ignited by a laser ignitor. • Hydrogen content and equivalence ratio (λ) effects were investigated. • Maximum heat release rate, ignition delay time and combustion duration were calculated. • Hydrogen addition improved all combustion performance metrics, irrespective of the λ. [ABSTRACT FROM AUTHOR]

Here we demonstrate the effect of dielectric and plasmonic nanoparticles on the random lasing behaviour of a polymer optical fibre coated with an organic dye, Rh-640- perchlorate. Coherent random lasing was observed both in the presence of ZnO nanorods and Au nanourchins upon transverse optical pumping using a Q-switched Nd: YAG laser. With the same particle density, a significant reduction in the lasing threshold was observed in the case of the plasmonic random laser. The polymer optical fibre was fabricated using a custom-made fibre drawing tower, and the random lasing media was coated on its surface by the dip-coating method. The present analysis demonstrates that the combined effect of scattering by the nanoparticles and the cylindrical fibre geometry is responsible for the low threshold coherent random laser. [ABSTRACT FROM AUTHOR]

This work investigates the feasibility of laser engraving of silicon carbide by adopting a Q-Switched fiber laser. To study the effect of the laser parameters on the laser-material interaction, a 33 full factorial plan was developed and tested. During the tests, the following laser parameters were varied: scanning speed, pulse frequency, which affects the pulse power, and the number of repetitions, i.e., the number of times the laser beam passes on the same line. After the tests, digital microscopy was used to measure the depth of the engraved pocket, and a 3D laser profilometer was used to acquire the pocket surface and morphology and to calculate the main roughness parameters. The analysis of variance (ANOVA) was carried out in order to detect how the process parameters affect laser machining. The Response Surface Methodology (RSM) was additionally performed to obtain the regression model and finally, the Multi-Response Optimization (MRO) was implemented to identify the optimal process conditions. The results show that it is possible to machine pockets with low roughness (Ra <1 μm) at high material removal rates (MRR> 0.1 mg/s). [Display omitted] [ABSTRACT FROM AUTHOR]

Key challenges in the management of pigmentary disorders such as melasma and postinflammatory hyperpigmentation are their resistance to treatment, tendency to recur after treatment, and the risk of exacerbating hyperpigmentation with many treatment modalities. The second article in this 2-part continuing medical education series on pigmentary disorders focuses on the evidence behind medical and procedural treatments of dyschromias, including photoprotection, topical lightening agents, oral agents, chemical peels, and laser therapy. [ABSTRACT FROM AUTHOR]

In this paper we analyze the possibilities of using machine learning algorithms for analysis of optical spectra of electric discharge spark in atmosphere. Breakdown in air can be initiated by intense laser pulse, making plasma which has a significant electrical conductivity. The formed plasma can be further maintained by electric current obtained from capacitor discharge. In such a case the capacitor voltage can be much lower than the striking voltage (the voltage needed to initiate the electric breakdown in air). Present setup has timing precision and low jitter of fast laser and arbitrary high energies corresponding to capacitance and voltage to which the capacitor is charged. We have used a streak camera equipped with a spectrograph to analyze optical emission of plasma obtained in this way. Q-switched Nd:Yag laser was used to achieve the initial breakdown in air. Machine learning methods were used in order to classify optical spectra of plasmas with different electron temperatures obtained with different excitation energies. We have shown that, instead of using the usual way of identifying the spectral peaks and calculating their intensity ratio, it is possible to train the computer software to recognize the spectra corresponding to different electron temperatures. Principal component analysis was used to reduce the dimensionality of problem. We present possibilities of plasma electron temperature estimation based on several clustering algorithms. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new and efficient ferroelectric nanostructure metal oxide lithium niobate [(Li 1.075 Nb 0.625 Ti 0.45 O 3), (LNTO)] solid film as a saturable absorber (SA) for modulating passive Q-switched erbium-doped fiber laser (EDFL). The SA is fabricated as a nanocomposite solid film by the drop-casting process in which the LNTO is planted within polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE)] as host copolymer. The optical and physical characteristics of the solid film are experimentally established. The SA is incorporated within the cavity of EDFL to examine its capability for producing multi-wavelength laser. The experimental results proved that a multi-wavelength laser is produced, where stable four lines with central wavelengths at 1529.5, 1530.5, 1531.5, and 1532 nm are observed on the laser spectrum at 157 mW pumped power. Furthermore, at maximum available pumped power (157 mW), laser pulses are running with a rate of 178 kHz and pulse width of 2.64 μs. The output power of 3.7 mW is attained at pumped power of 157 mW. The result proved that the LNTO-SA could be a potential candidate for generating multi-wavelength passive Q-switched fiber laser pulses. • Nanostructure metal oxide lithium niobate (LNTO) is utilized to form saturable absorber (SA). • A new and efficient SA based LNTO is proposed. • LNTO film is one of an excellent promising material for a various photonic applications. • The proposed Q-switched EDFL can generate multi-wavelength laser pulses. [ABSTRACT FROM AUTHOR]

Interlayer engineering offers a promising approach to modifying the structure of layered vanadium-based oxides, enhancing their saturable absorption effect and making them a desirable choice for developing infrared wavelength-range photonics devices. This experimental work synthesizes interlayer vanadium pentoxide (V 2 O 5) using hydrothermal techniques to produce an excellent saturable absorber (SA). The interlayer engineering strategy enhances strong saturable absorption and self-defocusing effects in V 2 O 5 -based SA, enabling the generation of ultrashort pulses in the infrared region. Their superior nonlinear optical characteristics are demonstrated by a modulation depth of 13.9 % and saturation intensity of 0.42 GW cm−1, respectively. By utilizing a transmission coupling fiber-based V 2 O 5 -SA inside an Er-doped fiber laser cavity, a passively Q-switched (PQS) laser with a narrow pulse width of 2.78 μs and signal-to-noise ratio (SNR) ∼50 dB is realized for the first time. Furthermore, we explore a V 2 O 5 NPs-SA long-term stability and high damage threshold. The results not only offer additional proof of the capable potential of interlayer V 2 O 5 as a photo-bleaching absorber for realizing pulsed lasers in the NIR band but also cover the method for advancing their probable applications in optoelectronic devices. • In this work, interlayer vanadium pentoxide (V 2 O 5) is synthesized using hydrothermal techniques to produce a high-quality photo-bleaching device (SA). • The saturable absorption property of V 2 O 5 NPs-SA was measured by a balanced twin-detector system with a modulation depth of 13.9 % and a saturation optical intensity of 0.42 GW/cm2. • Furthermore, by inserting the V 2 O 5 NPs-based saturable absorber, a passively Q-switched (PQS) laser operating at 1562.0 nm was obtained with a short pulse duration of 2.78 μs and maximum average output power of 5.6 mW. • TMO V 2 O 5 NPs-SA provides better long-term stability with a high damage threshold and a better tolerance were examined. [ABSTRACT FROM AUTHOR]

• A high power, multi-regime Tm,Ho:YAG laser oscillator operating at room-temperature was demonstrated. • In CW regime, maximum output power of 44.68 W was obtained with a brightness of 87.57 MW/cm2·sr. • In Q-switched regime, maximum pulse energy of 22.85 mJ was obtained at 1 kHz with a pulse width of 443.3 ns. • In QCW regime, maximum pulse energy of 31.85 mJ was obtained at 200 Hz with a pulse width of 370 μs. A high-power diode-pumped 2.09 μm Tm,Ho:YAG laser oscillator with multi-regime operation is demonstrated. In the continuous-wave (CW) regime, it delivers 44.68 W output power with M2 = 3.47, yielding a record-high brightness of 87.57 MW/cm2·sr. In the Q-switched mode, stable laser performance across pulse repetition frequencies (PRFs) from 1 kHz to 4 kHz is achieved. At a PRF of 1 kHz, single pulse energy reaches 22.85 mJ with a pulse width of 443.4 ns and M2 = 3.50. In the quasi-continuous-wave (QCW) operation, a pulse energy of 31.85 mJ is obtained at 200 Hz with a 370 μs pulse width and M2 = 4.49. These pulse energies are the highest reported to date for Tm-Ho co-doped laser oscillators at high PRF. This also marks the first demonstration of a versatile 2 μm laser that can operate at room temperature while delivering high-energy, high-repetition-rate pulses in both nanosecond and microsecond durations within a single device, making it highly appealing for scientific and industrial applications. [ABSTRACT FROM AUTHOR]

• For the first time, a high pulse repetition frequency has been achieved in a bulk LiNbO 3 acousto-optic Q-switched Er:YAP laser. Stable pulse trains were obtained at a pulse repetition frequency of 1 kHz. • A maximum output energy of 0.34 mJ was attained, with a corresponding pulse width of 64.5 ns, peak power of 5.3 kW, and a central wavelength of 2730.7 nm. • This work paves the ways for using Er:YAP lasers as efficient pump sources for 3–5 μm and 8–12 μm optical parametric oscillator applications. In this paper, we present, for the first time, a bulk LiNbO 3 (LN) acousto-optic (AO) Q-switched Er:YAP laser operating at a pulse repetition frequency (PRF) of 1 kHz. At this frequency, the laser achieves a maximum single pulse energy of 0.34 mJ, with a corresponding pulse duration of 64.5 ns and a peak power of 5.3 kW. Additionally, we characterize the laser beam quality factors, M x 2 = 2.7 and M y 2 = 2.5, and its central wavelength at 2730.7 nm, all at 1 kHz. These results highlight the significant potential of LN AO Q-switched Er:YAP lasers for enhancing mid-infrared laser applications. [ABSTRACT FROM AUTHOR]

• Diode pumped Nd: KNaY (WO 4) 2 crystal has been used for the first time to obtain laser output operating at 1.07 µm. • A stable passively Q-switched Nd: KNaY (WO 4) 2 laser with pulse width of 6 ns had been successfully achieved. • The effect of Cr4+: YAG initial transmission on the output pulse of passively Q-switched was studied by simulation. To our knowledge, a compact diode-pumped Nd: KNaY (WO 4) 2 laser operating at 1.07 µm has been successfully achieved for the first time. The passively Q-switched Nd: KNaY (WO 4) 2 pulse laser with the narrowest pulse width of 6.23 ns and peak power of 1.34 kW was obtained by experiment, and its laser characteristics were studied in detail. The effect of Cr4+: YAG initial transmission for pulse width of Nd: KNaY (WO 4) 2 output laser was investigated by theoretical analysis and numerical simulation. Finally, it was found that the theoretical and experimental results are basically in agreement. [ABSTRACT FROM AUTHOR]

• Efficient and user-friendly thermal simulation instructions for side-pumped lasers. • Reliable laser mode matching in the resonant was computed and designed. • Pulses lasers with high repetition- rates and excellent stability were obtained. • Potentially beneficial applications like PLIF and laser remote sensing. A theoretical and experimental investigation is conducted on a high repetition-rate side-pumped burst-mode Nd:YAG laser. The absorbed pumping power distribution and laser resonator are meticulously optimized to enlarge the area of the fundamental mode and improve thermal stability. With the 1 ms pumping duration and a pumping frequency of 10 Hz, the pulsed laser's burst energy, peak power, and pulse width achieve 0.29 J, 347 kW, and 16 ns, respectively, with the Q-switched repetition rate of 50 kHz. The minimum coefficient of variation for the laser pulse train remains below 5 %. This study represents the first demonstration of a long-term reliable output from a high-energy, nanosecond-pulsed, side-pumped Nd:YAG burst laser operating at 50 kHz. [ABSTRACT FROM AUTHOR]

• A tri-corner cube Q-switched Ho:YAG spatial ring cavity laser has been firstly developed. • The maximum output energy of 9.86mJ with a pulse width of 178.8 ns was achieved at a repetition rate of 100 Hz. • Tri-corner cube Ho:YAG lasers in this paper demonstrate good anti-misalignment capabilities. We demonstrate a tri-corner cube Q-switched Ho:YAG spatial ring cavity laser, which was resonantly pumped by a 1908 nm fiber laser. The polarization state of the intracavity oscillating laser was adjusted by a half-wave plate, and a continuous s -polarized laser of 2.57 W at 2090.9 nm was obtained at a pump power of 18.5 W, corresponding to an optical-to-optical conversion efficiency of 13.9 % and a slope efficiency of 33.3 %. When the corner cube prism, which has the weakest anti-misalignment capability, was tilted vertically by 1° or horizontally by 0.92°, the laser could still output the laser. For Q-switched operation, the tri-corner cube Ho:YAG laser has a pulse energy of 9.86mJ and a pulse width of 178.8 ns at a repetition rate of 100 Hz. At the maximum output energy, the beam quality was M x 2 = 1.3, M y 2 = 1.2. [ABSTRACT FROM AUTHOR]

• Designed and assembled a high-quality, fully solid-state 1064 nm laser using a passive Q-switching crystal. • Theoretically analyzed the impact of various factors on efficiency improvement during the optical parametric oscillation process. • In the design for compact devices, we effectively balanced the OPO oscillation threshold and walk-off effects by optimally selecting the crystal length. A 100 Hz compact 2 μm optical parametric oscillator (OPO) based on a type II non-critically phase-matched KTiOPO4 crystal (KTP) was reported. The monolithic KTP crystal was pumped with a passively Q-switched 1064 nm Nd:YAG laser. At a repetition rate of 100 Hz and a single pulse energy of 5.8 mJ of pump light, a 2128-nm laser output was achieved with a maximum of 1.17 mJ of parametric light at the degenerate point, with a parametric light pulse width of approximately 10.5 ns, corresponding to a pump to parametric light conversion efficiency of 20.1 %. [ABSTRACT FROM AUTHOR]

We report an electro-optic Q-switched Yb:YAG thin disk laser with widely continuously tunable pulse width ranging from 16.4 to 432.2 ns. The tunability was achieved through a simple and convenient method by rotating both the Pockels cell and the quarter-wave plate at either identical or slightly different angles. Based on the 72-pass pump module and 224.4 W laser diode pumping source, a pulsed output of over 80 W was attained at a repetition rate of 100 kHz. The output power and output pulse train remained stable in the whole tuning range. The corresponding output power was 82.7 W and 84.4 W for the minimum and maximum pulse width, respectively. A model which was exceedingly more accurate than previous models describing the tunability of the pulse width were proposed and the simulation results of this model exhibited strong agreement with the experimental measurements. • Utilizing the high threshold feature of thin disk laser to achieve widely tunable Q-switched output pulse width from 16 to 432 ns. • Convenient tuning method by rotating the Pockels cell and wave plate at identical or slightly different angles. • Stable over-80-W output power in the whole tuning range. • Proposing a accurate model to explain the wide tunability. [ABSTRACT FROM AUTHOR]

Nb 2 SiTe 4 is a novel narrow-bandgap (∼0.39 eV) two-dimensional material with a high optical absorption coefficient, high carrier mobility, and outstanding air stability, which shows great application potential in broadband optical switches. In this study, high-quality layered Nb 2 SiTe 4 nanosheets were efficiently fabricated by the mechanical exfoliation method, and the basic characterizations were carried out comprehensively. Nondegenerate pump-probe technology was implemented to systematically explore the photocarrier dynamics in the Nb 2 SiTe 4 nanosheets, which exhibit the ultrafast recovery time of Nb 2 SiTe 4 (∼0.3 ps). Furthermore, broadband passively Q-switched lasers operating at 1.0, 2.0, and 2.8 μm with the shortest pulse width of 380, 549, and 218 ns were achieved based on Nb 2 SiTe 4 saturable absorber. This work demonstrates the significant advantages of an optical switch based on Nb 2 SiTe 4 saturable absorber, including a narrow output pulse width, wide working bandwidth, high damage threshold, excellent oxidation resistance, and a straightforward synthesis method, which underscore the immense potential of Nb 2 SiTe 4 broadband optical switches in applications involving mid-infrared lasers. • Nb 2 SiTe 4 was used for the first time as a broadband saturable absorber (SA) in 1.0, 2.0, and 2.8 μm solid-state lasers. • Nondegenerate pump-probe technology was implemented to explore the photocarrier dynamics in the Nb 2 SiTe 4 nanosheets. • Compared to other SAs, the output powers and pulse widths obtained by using Nb 2 SiTe 4 as SA are more competitive. [ABSTRACT FROM AUTHOR]

A diode-end-pumped self-Q-switched Tm:YAlO 3 laser at 2362 nm based on 3H 4 →3H 5 transition is proposed for the first time according to the references. The max mean output power of 0.41 W with a slope efficiency of 14.1% was obtained under the absorbed pump power of 6.7 W, corresponding pulse width and pulse repetition frequency were 7.82 μs and 45.09 kHz respectively. By analyzing the laser beam spatial distribution, the self-Q-switched Tm:YAlO 3 laser at 2362 nm was originated from the time-dependent lens mechanism. The present research provides an approach for generating Q-switched lasers in the 2.3 μm spectral region. • The self-Q-switched Tm:YAlO 3 laser at 2362 nm based on the 3H 4 →3H 5 transition is firstly reported. • The maximum average output power of 0.41 W with pulse width of 7.82 μs is obtained. • The generation mechanism of self-Q-switched pulse is clarified. [ABSTRACT FROM AUTHOR]

• First demonstration of Q-switched NLP operation in the Yb-doped fiber laser. • First observation of optical rogue wave among Q-switched NLP regime. • Multi-wavelength structure is measured by dispersive Fourier transformation. • Emergence of rogue wave is directly influenced by the sinusoidal filter. Q-switched noise-like pulses (NLPs) with rogue waves in a Yb-doped fiber laser is reported. It is demonstrated that the fiber laser can operate in the mode-locked NLP state or Q-switched NLP state via adjustments to the spectral filter and pump power. To the best of our knowledge, this is the first demonstration of Q-switched NLP operation in the Yb-doped fiber laser. By increasing the period of the spectral filter, the high-energy events are observed among the Q-switched NLPs. Statistical analysis confirms the occurrence of rogue waves. The energy of a single-shot giant pulse is measured ∼ 15.1 times that of the mode-locked NLP. The single-shot spectra measured by the dispersive Fourier transformation (DFT) system reveal a new type of rogue wave phenomenon. The rogue wave manifests as bound complexes consisting of an NLP and its amplified spontaneous Raman radiation, and 85 % of the pulse energy is contributed by the Raman component. We believe that the occurrence of the rogue wave is induced by sporadic Raman noise in the NLP, which is wavelength-selected by periodic transmittance of a Lyot-filter, and is rapidly amplified by Yb-doped fiber as well as the Raman effect in a few roundtrips. [ABSTRACT FROM AUTHOR]

• In this study, we first report the Q-switched temperature fiber laser sensing device. The large core multimode fiber - graded index multimode fiber is used as the saturable absorber to generate pulsed laser, and the D-shaped multimode fiber is used as the sensing unit for temperature detection. For your reference, a brief summary of the novelty of our work is provided below. • Strong Nonlinear Optical Response. The prepared saturable absorber had excellent linear and nonlinear capability at 1560nm. • Excellent nonlinear optical properties. The Q-switched laser with a central wavelength of 1561nm was realized. • A high-performance Q-switched temperature sensing device. Temperature Q-switched sensing can be achieved. In the paper, a Q-switched temperature sensing device is proposed and verified, which consists of a modulator based on a large core multimode fiber and a graded index multimode optical fiber (LMF-GIMF), and a sensing unit formed by sandwiching a D-shaped multimode fiber (MMF) between two single mode fibers (SMF). Utilizing the modulator to transform continuous light into pulsed laser, a stable Er3+-doped Q-switched laser with a repetition frequency of 23.04 kHz and a modulation depth of 7.47 % has been achieved. Under its pumping, the SMF-MMF-SMF sensing structure performed thermal detection with a sensitivity of −81.5 pm/℃ as temperature varies in the range of 25 °C to 65 °C. The temperature sensing device based on Q-switching can be used as an independent pulse laser to realize the switch between the light source and the sensing device. At the same time, the sensing device can provide real-time feedback according to the change of the central wavelength, which allows for immediate adjustments in the operational state, enhancing the flexibility and responsiveness. In addition, the characteristics of the sensor based on Q-switched laser can reduce thermal damage and extends the service life of the sensor. As far as we know, this is the first report on Q-switched temperature sensing based on the LMF-GIMF modulator. The proposed sensing device has the advantages of high signal-to-noise ratio, low operating threshold, minimal thermal damage, and serves as an independent Q-switched laser source, which can be applied to pulse laser measurement with high precision and time resolution in the future. [ABSTRACT FROM AUTHOR]

In the realm of biological experimental research, bacterial deposition on scientific instruments' surfaces can compromise the integrity of experimental outcomes. Prolonged bacterial accumulation may even result in diminished instrument functionality, rendering them incapable of normal operation. Traditional chemical cleaning methods carry the risk of secondary contamination and are unsuitable for decontaminating precision optical or electronic instruments. Therefore, it is imperative to develop novel non-contact, waterless, contamination-free, and non-destructive decontamination methods. This paper introduces an innovative two-dimensional high-speed scanning sterilization technique based on high repetition rate laser-induced quasi-continuous plasmas. The experiment targeted Escherichia coli and Bacillus subtilis for decontamination, investigating the impact of laser energy, repetition rate, scanning rate, repetition scanning times, and focal distance on the inactivation rate. The results indicate that at a laser repetition rate of 15 kHz, an energy of 680 μJ/pulse, a repetition scanning of 10 times, and a focal distance of −50 mm, the decontamination efficiency reaches 26.7 mm2/min, with an inactivation rate exceeding 98 %, achieving rapid and efficient decontamination of bacteria adhering to the carrier. Furthermore, the paper explores the decontamination mechanism of laser-induced plasma, demonstrating that the primary mechanism of bacterial inactivation using this technique is the action of the plasma rather than the thermal ablation effect of laser irradiation. The proposed laser-based bacterial decontamination device is characterized by its compact design, integrability, ease of operation, and high inactivation effectiveness. This makes it a promising solution with broad applications in the fields of biological science, precision optoelectronics, medical devices, food processing, and more. Moreover, it integrates with LIBS technology to achieve the integrated development of identification and disinfection. [ABSTRACT FROM AUTHOR]

• Laser performance of neodymium-doped gadolinium scandium aluminum garnet (Nd:GSAG) crystals at 1.3 μm was investigated for the first time, to the best of our knowledge. • An efficient continuous-wavelaser at 1336 nm and on output power of up to 2.01 W was obtained under an absorbed pump power of 4.89 W with slope and optical-to-optical efficiencies of 43.4 % and 41.1 %, respectively. • A passively Q-switched laser with a Co:MgAl2O4 crystal serving as a saturable absorber was examined and a maximum average output power of 0.2 W was obtained with a pulse width, pulse energy, and peak power of 34.4 ns, 22.2 µJ, and 645 W, respectively. • Our results indicated that Nd:GSAG crystals are promising for producing high-efficiency CW lasers and effective PQS lasers at 1336 nm. We report on the laser performance of neodymium-doped gadolinium scandium aluminum garnet (Nd:GSAG) crystals at 1.3 μm for the first time, to the best of our knowledge. An efficient continuous-wave (CW) laser at 1336 nm and on output power of up to 2.01 W was obtained under an absorbed pump power of 4.89 W with slope and optical-to-optical efficiencies of 43.4 % and 41.1 %, respectively. Furthermore, a passively Q-switched (PQS) laser with a Co:MgAl 2 O 4 crystal serving as a saturable absorber in a compact plano-plano resonator cavity was examined. A maximum average output power of 0.2 W was obtained with a pulse width, pulse energy, and peak power of 34.4 ns, 22.2 µJ, and 645 W, respectively. Our results indicated that Nd:GSAG crystals are promising for producing high-efficiency CW lasers and effective PQS lasers at 1336 nm. [ABSTRACT FROM AUTHOR]

The growing field of photonics has seen significant developments in optical pulse fiber-based sensing technologies. In this research, a novel fiber Bragg grating using a Q-switched erbium-doped fiber laser source and innovative spider silk as a base material is presented, specifically designed for the detection of adulteration in pure kelulut honey. Kelulut honey has attracted much attention from Malaysian researchers as it is a highly prized, versatile local health remedy. During the experimental setup, concentrations of the adulterant isoglucose ranging from 0 % to 8 % and 10–50 % were intentionally added to the pure kelulut honey. The sensor showed remarkable sensitivity and detected subtle shifts in both the wavelength and radio frequency spectrum. The experimental results obtained emphasize the effectiveness of the proposed sensor and demonstrate its exceptional sensitivity in detecting adulteration in pure kelulut honey. This inherent property makes the derived pulse fiber laser sensor a promising tool for various applications in clinical detection and diagnosis as well as in the food industry. The results presented here not only contribute to the field of photonics but also have the potential to advance the quality control and authenticity assessment of kelulut honey in various fields. [Display omitted] • Developed a highly sensitive FBG sensor using a spider silk saturable absorber for adulteration detection in kelulut honey. • Demonstrated the effectiveness of a Q-switched pulse erbium-doped fiber laser in enhancing the detection sensitivity. • The sensor shows exceptional sensitivity in detecting kelulut honey adulteration, promising for clinical, diagnostic, and food industry applications. [ABSTRACT FROM AUTHOR]

• DCBB crystal was grown by solvent evaporation and it confirms monoclinic crystal system. • The band gap value is 3.84 eV. • Thermal stability was 125°C and it belongs to soft material category. • Z-scan shows reverse saturable absorption induces optical limiting behavior. New organic 2,4-dichlorobenzoic acid benzamide co-crystal (DCBB) was successfully grown using slow evaporation solution growth technique. The formation of new DCBB co-crystals was taken and their structure and crystallinity were analyzed by single crystal and powder X-ray diffraction analyses. It shows that DCBB material in monoclinic structure with centrosymmetric space group of P21/c. The different vibrations, chemical bonding and chemical configuration of the co-crystal was studied through FTIR, Raman and 1H NMR spectroscopy. Optical transmittance is the basic requirement for the nonlinear optical application with a lower cutoff wavelength of about 320 nm as well as optical band gap value E g is 3.84 eV. Photoluminescence spectrum showing two emission peaks of 403 and 550 nm by means of an excitation wavelength of 290 nm. The compound's thermal stability was up to 125 °C was analyzed by the thermal analysis. Vickers's micro hardness test was used for evaluating mechanical properties of DCBB, and the results showed that the material was classified as soft category (n = 2.54). Nonlinear optical characteristics of the sample under pulsed laser stimulation by Q-switched Nd:YAG laser with 532 nm wavelength. The presence of reverse saturable absorption peak exhibits 2-photon absorption process was confirmed by varying its intensity shows saturation intensity I S), nonlinear absorption coefficient (β) under pulse laser excitation. The optical limiting threshold determined by three different intensities were found to be 3.02×1012 (W/m2), 2.85×1012 (W/m2) and 1.44×1012 (W/m2) respectively. Theoretical investigations like density functional theory using B3LYP to calculate as well as determining non-linear optical characteristics of the DCBB complex. [Display omitted] [ABSTRACT FROM AUTHOR]

• Breathing dynamics of dissipative soliton in fiber laser is experimentally observed. • Numerical simulations are employed to generate similar breathing dynamics within the context of a model that combines equations describing the population inversion. • These results provide confirmation that the Q-switching instability is responsible for the initiation of breathing dynamics. The occurrence of periodically oscillatory behaviors in various nonlinear dissipative systems is known as breathing dynamics, which holds potential applications in spectroscopy. Herein, we have employed both experimental and numerical methods to investigate the breathing dynamics of dissipative soliton induced by Q-switched modulation in a mode-locked fiber laser. The findings indicate that the dynamics of breathing significantly influences the buildup stage of both stationary and breathing dissipative solitons. The breathing rate, breathing duration and breathing period are quite sensitive to the pump power. Numerical simulations are employed to generate similar breathing dynamics within the context of a model that combines equations describing the population inversion in a mode-locked laser. These obtained results provide confirmation that the Q-switching modulation is responsible for the initiation of breathing oscillations, and present novel prospects for the development of different operational frameworks for ultrafast lasers. [ABSTRACT FROM AUTHOR]

This paper presents the first demonstration of a Q-switched Thulium-doped fiber laser (TDFL) utilizing our newly developed Thulium-doped fiber (TDF) and a MXene niobium carbide - polyethylene oxide (Nb 2 CT x -PEO) thin film as a gain medium and saturable absorber (SA), respectively. The TDF core glass contains 6.15 wt% Al 2 O 3 , 2.2 wt% Y 2 O 3 , 0.47 wt% Tm 2 O 3 , 2.12 wt% GeO 2 , 1.57 wt% HfO 2 and 0.05 wt% Bi 2 O 3 with the absorption of 30 dB/m at 1550 nm. The outcome was the realization of a stable pulsed laser operating at a central wavelength of 1888.3 nm. The Q-switched pulses exhibited a maximum repetition rate of 46.7 kHz and a minimum pulse width of 1.995 µs at a pump power of 731.41 mW. The Q-switched operation maintained a signal-to-noise ratio (SNR) of 45 dB, confirming its stability. This breakthrough highlights the laser system's potential for diverse applications, including free-space optical communication, spectroscopy, and medical fields. [ABSTRACT FROM AUTHOR]

The light field uniformity (LFU) in lithography system is a key factor in defining the resolution across the entire micro/nano structures. In this work, a cost-effective and straightforward method based on the focused laser marking on heat-mode resist is proposed for measuring and optimizing the LFU. The factors affecting the LFU are analyzed from the perspectives of optical system aberrations and mechanical assembly error. Subsequently, marking patterns with special structures are designed based on the properties of the heat-mode resist. By analyzing the marked patterns, the LFU of the system is obtained with uniformity coefficient is 42.24%. After optimization achieved by dynamic laser power adjustment, the uniformity coefficient was notably enhanced to 96.11%. This work provides an effective method for measuring and optimizing the LFU in dual-galvanometer laser scanning lithography system. • Propose a cost-effective method to measure light field uniformity of dual-galvanometer laser scanning lithography. • The factors influencing light field uniformity are analyzed: mainly optical aberrations and mechanical assembly error. • Optimization enhanced light field uniformity from 42.24% to 96.11% and significantly reduced feature size error to 35 nm. [ABSTRACT FROM AUTHOR]

Picric acid (PA) – polymethyl methacrylate (PMMA) nanofibers were synthesised using electrospinning technique by optimising all the required parameters. The nonlinear optical behaviour of the synthesised nanofibers was investigated along with their preliminary characterisations like morphological, structural, thermal, mechanical, dielectric and linear optical studies. The nanofibers with average diameter around ∼800 nm, were found to crystallise in Pca2 1 space group under the orthorhombic crystal system. The incorporation of Picric acid nanocrystals inside the PMMA nanofibers enhanced their tensile strength. Second harmonic generation imaging of picric acid embedded PMMA nanofibers was done by nonlinear microscopy and the emission was confirmed by power dependence as well as Kurtz – Perry powder technique. Nonlinear absorption studies by Z – scan technique were conducted with a Q – switched Nd: YAG laser and the nanofibers exhibited reverse saturable absorption nature at all the input intensities (0.616 × 1012 W/m2, 1.23 × 1012 W/m2 and 2.46 × 1012 W/m2) and the value of the nonlinear absorption coefficient increased corresponding to an increase in input intensity (0.98 × 10−10 m/W, 1.39 × 10−10 m/W and 1.61 × 10−10 m/W) owing to a sequential two photon absorption. Using the transmittance data optical limiting properties of the nanofibers were also analysed and the limiting threshold values (1.92 × 1012 W/m2, 1.80 × 1012 W/m2 and 1.54 × 1012 W/m2) at respective intensities were extracted. The low optical limiting threshold obtained in the present case confirms that picric acid – PMMA nanofibers can be an assured contender as optical limiters in laser safety devices. • Synthesis of Picric acid (PA) - PMMA nanofibers by electrospinning technique. • Enhancement in the tensile strength of the nanofibers due to PA incorporation. • Confirmation of SHG emission by nonlinear microscopy and Kurtz Perry technique. • Z-scan technique was used to investigate its nonlinear absorption properties. • Sample showed RSA behaviour, thus can be used for optical limiting applications. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (TMDs) with remarkable nonlinear properties, like MoS 2 /WS 2 and the ternary compound Mo 0.5 W 0.5 S 2 , have attracted a lot of attention. The field has made use of the nonlinear characteristics of all-solid-state lasers. The liquid-phase exfoliation method was used in this work to create Mo 0.5 W 0.5 S 2 nanosheets. At 2 μm, the nonlinear absorption characteristics of Mo 0.5 W 0.5 S 2 were examined and the results showed a saturation intensity of 1.56 MW/cm2 and a modulation depth of 5.2%. A high-power passively Q-switched Tm:YAP laser with an average output power of 3.20 W and a brief pulse width of 633 ns was produced using the Mo 0.5 W 0.5 S 2 nanosheet as a saturable absorber. According to the results, Mo 0.5 W 0.5 S 2 has the potential to produce pulsed lasers with high peak and average powers that operate at about 2 μm. • The Mo 0.5 W 0.5 S 2 -based SA showed a modulation depth of 5.2 % and a saturation intensity of 1.56 MW/cm2. • When T oc = 2 %, the laser with the highest average power of 3.55 W and the central wavelength of 1936 nm were obtained. • The passively Q-switched laser with maximum peak power of 34.43 W and pulse width of 633 ns were achieved. [ABSTRACT FROM AUTHOR]

• Efficient 100W s-polarized Ho:YAG oscillator demonstrated, pumped by high-power Tm:YLF laser. • Orthogonal cylindrical lenses optimized 1.9 μm laser beam distribution within Rayleigh length. At maximum output, the beam quality factor was less than 1.6. A hundred-watt, linearly-polarized Ho:YAG oscillator, pumped by a 200 W, home-made and s- polarized Tm:YLF laser, was demonstrated. By utilizing a combination of a half-wave plate (HWP) and a thin-film polarizer (TFP), the Tm:YLF laser was split into two orthogonally polarized parts. Each part was significantly reshaped by a system of orthogonally arranged cylindrical lenses and subsequently used to dual-end pump the oscillator. With a total incident pump power of 183 W, a continuous wave (CW) output power of 101 W at 2.1 μm was achieved, with corresponding slope efficiency and optical-to-optical conversion efficiency (OOCE) of 61.6 % and 55.2 %, respectively. Additionally, the beam quality factors, measured in the x and y directions, were 1.59 and 1.35, respectively. Finally, under Q-switched operation at a repetition rate of 20 kHz, a maximum output power of 97 W was achieved, with a corresponding pulse width of less than 34 ns. The central wavelength of the laser was measured to be 2090.2 nm. [ABSTRACT FROM AUTHOR]

• Continuous and passively Q-switched dual-wavelength lasers were achieved. • Nd:YVO 4 crystal and Nd:CTGAS crystal were used as the composite gain medium. • The effect of temperature on wavelength was studied. LD pumped dual-wavelength lasers have great application potential in scientific and technical scopes. In this paper, we reported a novel dual-wavelength laser by combining Nd:YVO 4 and Nd:CTGAS crystals. For 1064 nm and 1068 nm dual-wavelength laser operation, the maximum continuous-wave output power was 929 mW, corresponding to an optical conversion efficiency of 38.7 %. With a Cr:YAG crystal as the saturable absorber, the maximum passively Q-switched output power was 239 mW, giving a shortest pulse width of 20.8 ns and an optical conversion efficiency of 17.1 %. [ABSTRACT FROM AUTHOR]

• A high-performance Q-switched vortex laser has been realized on a waveguide platform. • The pulse width (28 ns) is the shortest ever reported for Q-switched vortex laser. • The near-field distributions of nanoparticles arrays have been simulated. Vortex beam, particularly pulsed vortex laser, has expanded the potential applications in optics due to their unique wave-front phase structure and the determined photon orbital angular momentum. In this study, we present a novel approach including the integration of fused silica embedded with silver nanoparticles (Ag:SiO 2) into the Nd:YAG waveguide platform for achieving nanosecond vortex pulses. Using a spiral phase plate for in-cavity phase modulation, we successfully demonstrate a Q-switched vortex laser with a high repetition rate in the megahertz range and short pulse width in the nanosecond regime. Additionally, we conduct a comprehensive analysis of the near-field distributions of Ag nanoparticles with varying sizes and distributions using COMSOL simulation. This study exemplifies the integration of silica-based photonic elements for realizing a high-stability and cost-effective nanosecond vortex laser system. [ABSTRACT FROM AUTHOR]

• The approach optimizes the laser cladding model by considering both temperature characteristics and residual stress distribution during thermo-mechanical coupling. • Model accuracy is validated with experimental data, showing close agreement with melt pool characteristics and residual stresses. • Longitudinal residual stresses show a "tension first, compression later" pattern, with tensile stresses near the clad layer. • The method predicts residual stresses in titanium alloy laser cladding, offering insights to improve quality and performance. Laser cladding is a cutting-edge technology widely used in additive manufacturing and surface modification. This process entails rapid melting and solidification driven by laser heating, which induces residual stress within the material. This study presents a data-driven approach to refine the numerical model of laser cladding, simultaneously emphasizing both the temperature characteristics and residual stress distribution within the thermomechanical coupling process. After integrating the residual stress distribution data obtained through the contour method with the molten pool morphology shaped by the thermal effects of laser cladding, a Levenberg-Marquardt optimization algorithm based finite element model updating scheme is proposed to efficiently identify the parameters of double ellipsoid heat source model, which employs parallel computing to reduce the computational time for iterations. The effectiveness of the proposed method is validated using experimental data. Moreover, this approach is adaptable, unaffected by the specimen size and shape, and can accurately predict the residual stress distribution characteristics. Therefore, it offers a robust framework for simulating the mechanisms of residual stress generation in titanium alloy laser cladding. [ABSTRACT FROM AUTHOR]

We show that a passive Q-switch nanosecond Tm:Yap laser operating at 1. 940 μ m is a promising candidate for conducting ablation process at the surface of silicon wafers. By modulating the fluence intensity of the lasing source, we can engrave the surface with a short series of pulses and obtain sharp and regular craters with a high level of repeatability. Our results show that we can get highly repeatable craters of diameters ranging from D = 10. 0 μ m up to D = 40. 0 μ m with a laser operating We easily manage the hole depth by choosing the correct fluence repetition rate between pulses, reducing the waste deposition on the borders of the holes. For fluences greater than 3. 8 J/cm 2 , third-order nonlinear effects, such as the lens converging Kerr n 2 and the two-photon absorption β T P A effects, turn the silicon into an absorbing medium, improving the ablation process. At a room temperature of 300 ° K , n 2 = 12. 0 × 1 0 − 5 ± 2. 0 × 1 0 − 5 cm 2 / GW and β T P A = 0. 56 ± 0. 02 cm/GW , the resulting nonlinear factor of merit N F O M = 2. 1 ± 2. 0 is very large; conferring a self-focusing lensing action on the silicon. We also observe that these latter nonlinear effects modify the regular linear regression relating the ablated surface to the logarithm of the fluence, enhancing the efficiency of the ablation process at higher fluences due to these effects. • A Passive Q-switched, mJ level, Tm:YAP 2 μ m wavelength laser enhances silicon ablation. • In the SWIR domain, silicon is transparent at low fluence, but third-order nonlinear effects make it highly absorptive. • Silicon ablation is further enhanced by the high nonlinear factor of merit, promoting the self-focusing Optical Kerr effect, thereby controlling the heat- affected zone (HAZ). [ABSTRACT FROM AUTHOR]

• Report a novel laser array with one lamp pumping six Nd:YAG rods for programmable laser reconstruction in space-power-time domains. • Only one xenon flash lamp, with advantageously cylindrical pumping characteristics comparing with LD pumping source, is introduced to structure a high-out laser array which reduces complicated power supplies and liquid cooling system and has a potential of laser miniaturization. • The laser array has a total output energy of 1.53 J at an electrical input of 93.3 J, corresponding to an overall electro-optical conversion efficiency of 1.64 % and an electro-optical slope efficiency of 3.17 %. • Laser array with controllable space-power combination and an accurate time code modulated in the space-power-time domains are achieved. We report a novel laser array with one lamp pumping six Nd:YAG rods for programmable laser reconstruction in space-power-time domains. A sextuple ellipse pump cavity is proposed, and this scheme permits one xenon flash lamp with advantageously cylindrical pumping characteristics to simultaneously efficiently pump multiple Nd:YAG lasers in a laser system. The experimental setup was designed, and further experiments were carried out. The laser array can stably operate at a pumping rate of 1 Hz-10 Hz. Each laser beam of the six laser outputs has a divergence angle of less than 1.7 mrad, an output pulse of greater than 208 mJ, and a pulse width of approximately 10 ns, corresponding to a pulse peak power of approximately 20 MW. The laser array has a total output energy of 1.53 J at an electrical input of 93.3 J, corresponding to an overall electro-optical conversion efficiency of 1.64 % and an electro-optical slope efficiency of 3.17 %. Finally, laser array output pulses coded modulation in the space-power-time domains are achieved by electro-optical Q-switching. Therefore, the laser array provides the capability for programmable laser reconstruction in the space-power-time domains in a laser system for multipurpose applications, such as energy-tailored material processing, coded pulse laser ranging for improved signal-to-noise ratio (SNR), active optical remote sensing and scientific research. [ABSTRACT FROM AUTHOR]

The Kahramanmaraş seismic sequence of February 6th, 2023, caused extreme damage and a significant number of casualties across a large region of Turkey and Syria. The paper reports on the survey activities carried out by the authors in the city of Gölbaşı, where extensive liquefaction took place. The damage to the built environment caused by liquefaction differs from that caused by typical inertial seismic actions, with quasi-rigid body displacement mechanisms, resulting in extreme settlements, tilts, and, in some cases, complete overturning. After a brief introduction to the geological features of the Gölbaşı area and a discussion of the seismic effects on the area, the paper reports and comments on the damage observed in one part of the city and provides some statistical interpretations. • For the Gölbaşı district, the proposed seismic motion estimation methodology yields a max = 0.25 g for the Mw = 7.8 event. • The w/B and q values from the maximum deformation curve indicate significant liquefaction in Gölbaşı. • Taller buildings suffered the most due to higher load transfer and lower initial bearing capacity safety factors. • Larger foundation areas resulted in lower damage for a given number of floors. [ABSTRACT FROM AUTHOR]

• Irradiation of monolayer graphene on Nd:YAG channel waveguides with 7.5 MeV carbon ions. • Presentation of the polarization dependency of guiding properties and Raman effect in channel waveguides. • Achievement of efficient pulsed waveguide lasers Q-switched by ion-irradiated monolayer graphene. • Demonstration of the shortest pulse duration of 38.7 ns in a larger cross-section waveguide. • Tailoring lasing performance of pulsed lasers by adjusting the TE or TM polarization of the pump laser. The transfer of two-dimensional (2D) nanomaterials as saturable absorbers to the surface of optical waveguides is extremely attractive for increasing the laser damage threshold of 2D nanomaterials and the laser power of pulsed waveguide lasers. We report on the design and fabrication of passively Q-switched waveguide lasers based on monolayer graphene covered on the surface of neodymium-doped yttrium aluminum garnet (Nd:YAG) cladding waveguides under high-energy carbon ion irradiation. The monolayer graphene is forced into close contact with the waveguide surface by energetic carbon ions, which leads to an excellent coupling of the evanescent wave with graphene. As a result, highly efficient Q-switched pulsed waveguide lasers with high output power, short pulse duration, and high repetition rate are realized under both TE and TM polarized optical pumping. Among all lasers in this experiment, the shortest pulse duration of 38.7 ns is provided by the ion-irradiated larger waveguide system under TE optical pumping. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comparative study on disc laser welding and coaxial laser plasma hybrid welding of thin titanium alloys. • The molten pool flow model illuminate the coupling effect which makes the weld reinforcement from steep ridge to gentle at high welding speed. • The composite heat source of plasma arc and laser can effectively inhibit the formation of undercut defects and obtain better bridging ability under certain gap. • The tensile failure mechanism was changed from the rapid failure to plastic fracture due to the effective suppression of the undercut defect. The coaxial laser-plasma hybrid welding for thin titanium alloy sheets with reserved gaps and without filler at high welding speed was carried out. Laser welding under the same condition was studied as a comparative experiment. Inhibition of undercut defect and its effect on tensile failure mechanism was studied by analysis of the joints' appearance, microstructure and mechanical properties. The molten pool flow model illustrated the reinforcement of the weld turns to be gentle from a steep ridge due to the addition of plasma changing the heat distribution of the heat source own to the coupling effect. It is revealed that the composite heat source of the composite of plasma arc and laser can effectively inhibit the formation of undercut defects and obtain better bridging ability under certain gaps. Results show that grain refinement of acicular α' martensite, fine α g particles and higher misorientation angle between grain boundaries in the weld zone contributed to an increase in hardness, tensile strength of the hybrid welded joint of Ti6Al4V. The tensile failure mechanism was changed from the rapid failure caused by strain concentration to plastic fracture with dispersed strain as the effective suppression of the undercut defect. This work provides a well-formed and high-quality welding method at high welding speed, which provides a theoretical basis for the application of this welding method in thin titanium alloy. [ABSTRACT FROM AUTHOR]

The study numerically investigates the melting of phase change material in a two-dimensional rectangular region with an aspect ratio of 10/7 under sidewall heating conditions, utilizing the enthalpy method. It comprehensively examines the effects of varying Rayleigh numbers (4 × 10 2 ≤ R a ≤ 4 × 10 6), Prandtl numbers (0.01 ≤ P r ≤ 100), and Stefan numbers (0.01 ≤ S t e ≤ 1), corresponding to different material properties and operating conditions. The results regarding the melting rate and pattern, characteristic melting time and heat transfer properties reveal that both Ra and Ste exert more pronounced effects on the phase change process compared to Pr , with Pr demonstrating significance only for P r ≤ 0.1. It is important to note that convective effects ultimately manifest unless Ra is sufficiently small to yield nearly stationary flow, leading to deviations in the mean interface evolution from one-dimensional conduction-only results. Additionally, it can be shown that the non-dimensionalized stored energy q (τ) is approximately proportional to the mean interface position s (τ) as q (τ) ≈ (1 / 2 + 1 / S t e) s (τ) , which is consistent with the simulation results. Although, the maximum stored energy q m a x is solely dependent on Ste , the average energy storage rate increases with Ra and decreases with Ste. Our investigations provide valuable insights into the selection of phase change materials and operating conditions for energy storage systems that involve solid-liquid phase change. • Systematically investigate the effects of various dimensionless parameters on flow characteristics and heat transfer. • Derive and validate the perturbation solutions of a one-dimensional melting system. • Derive a quantitative relationship between the non-dimensionalized stored energy and the mean interface position. [ABSTRACT FROM AUTHOR]

In this experiment, stable dual-wavelength Q-switched pulses and bright-dark pulses pairs are achieved in an erbium-doped fiber laser based on NbS 2 under saturable absorber. At pump powers of 172 mW–322 mW, stable dual-wavelength Q-switched pulses with center wavelengths of 1531.9 nm and 1557.05 nm were obtained with a signal-to-noise ratio (SNR) as high as 43 dB. The repetition frequency was increased from 14.3 kHz to 22.7 kHz as the pump power was increased. When the pump power was increased to 340 mW, we found stable bright-dark pulses with center wavelengths of 1559.7 nm and 1560.12 nm, respectively, and a repetition frequency of 3.44 MHz with an SNR of 52 dB. The experimental results show that NbS 2 can be used as an excellent SA for fiber lasers and demonstrate that NbS 2 can be used to study dual-wave Q-switched pulses and bright-dark soliton pairs. • NbS 2 was prepared as a saturable absorber for generating passively mode-locked in an Er-doped fiber laser. • For the first time, dual-wavelength Q-switched pulses and bright-dark pulse operation of the base with NbS 2 SA has been realized. (with reference to current literature). [ABSTRACT FROM AUTHOR]

In this work, a unique pentagonal TMD material, palladium disulfide (PdS 2) nanosheets were fabricated by the liquid-phase exfoliation (LPE) process, and the physical characteristics were also investigated. The nonlinear transmittance is measured by the power scanning method and the modulation depth is fitted to be 15.3%. Based on the transmittance curve, the saturable absorption parameters of PdS 2 are calculated, including 5.85 × 10−19 cm2 ground-state absorption cross-section, 1.63 × 10−19 cm2 excited-state absorption cross-section, and 683.5 μs excited-state lifetime. By employing both PdS 2 as a saturable absorber (SA) and an acousto-optic modulator (AOM), a doubly Q-switched and mode-locked (QML) laser-pumped intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) was realized. The pulse energy and the pulse width of the Q-switched envelope for signal wave have been measured. At higher pump power, the high-peak-power low-repetition-rate sub-nanosecond mode-locking pulse of signal wave is generated, in which there is only one mode-locked pulse underneath a Q-switched envelope. The measured shortest signal pulse duration is 530 ps, corresponding to a peak power of 337 kW, at an incident pump power of 9.81 W and an acousto-optic modulator (AOM) repetition rate of 1 kHz. In addition, by considering the Gauss distribution of intracavity photon density, a set of coupled rate equations for a doubly QML laser-pumped intracavity OPO was given and the numerical simulations agreed with the experimental results. These results indicate that PdS 2 is a promising nonlinear optical material for optical applications in the near-infrared (NIR) region. • The PdS 2 nanoflakes was fabricated by liquid-phase exfoliation and characterized. • Palladium disulfide nanomaterials performed well for pulsed laser generation. • Applying the PdS 2 SA, a dual-loss-modulated QML IOPO was realized. • The rate equations for IOPO with PdS 2 were numerically solved. [ABSTRACT FROM AUTHOR]

• We have compared the crystal characteristics and laser performances of Er3+-doped YAG and LuAG substrates, in the cavity with a pair of corner-cube prisms. • The maximum pulsed energy of 4.7 mJ for Er:LuAG, and 5.1 mJ for Er:YAG crystals, has been achieved, with corresponding pulse durations of 237 ns and 276 ns, respectively. • The anti-misalignment of YAG and LuAG in a double corner-cube-prisms resonator was studied. The thermal focal lengths, absorption efficiencies, and laser performances of Er:YAG and Er:LuAG crystals are systematically demonstrated within an anti-misalignment double corner-cube-prisms resonator. The maximum continuous-wave output power of 5.12 W at 1645.39 nm and 6.43 W at 1650.33 nm are obtained, with slope efficiencies of 16.29 % and 36.78 %. In pulsed operation, Er:YAG yielded a maximum pulse energy of 5.1 mJ, and Er:LuAG delivered 4.7 mJ, both at the pulse repetition rate of 200 Hz. The beam qualities, represented by M2 factors, are measured at 1.52 for Er:YAG and 1.44 for Er:LuAG. [ABSTRACT FROM AUTHOR]

• We demonstrate a wavelength-locked nanosecond Yb:YAG/V:YAG solid-state laser with inhomogeneous polarization output. • The Yb:YAG/V:YAGlaser can deliver nanosecond wavelength-locked cylindrical vector beam with spectral linewidth 0.13 nm. • The Yb:YAG/V:YAG solid-state laser can deliver switchable radially and azimuthally polarized beams with high mode purity. We demonstrate a compact self-starting wavelength-locked nanosecond Yb:YAG/V:YAG solid-state laser with switchable cylindrical vector beam output experimentally. With the help of the pancharatnam-berry phase optical element S-waveplate and the birefringent filter, the Yb:YAG/V:YAG solid-state laser can deliver wavelength-locked radially and azimuthally polarized beam centered at 1030.3 nm with spectral linewidth 0.13 nm. Under the maximum pump power, the stable pulse with minimum pulse width 46 ns at the repetition rate of 3.8 kHz can be delivered from the Q-switched laser. In addition, the switchable radially and azimuthally polarized beams can be realized with mode purity of 94.3 % and 94.9 %, respectively. The experimental results can provide a reliable compact nanosecond laser source with inhomogeneous polarization output for the optoelectronic applications. [ABSTRACT FROM AUTHOR]

• An organic-inorganic hybridized CH 3 NH 3 PbBr 3 saturable absorberwas used in a passively Q-switched Tm:YAP solid-state laser, achieving pulsed laser output successfully. • A maximum output power of 0.68 Wwas achieved at the continuous wave lof 1989.9 nm. • In passively Q-switched mode, the maximum average output power of 203 mW and a maximum peak power of 3.9 W were achieved. The beam quality factors (the horizontal and vertical directions) were M2 x = 1.1 and M2 y = 1.39. Perovskite materials are used in the field of lasers and can achieved good results. In this paper, we prepared an organic–inorganic hybridized CH 3 NH 3 PbBr 3 saturable absorber (SA). Continuous wave (CW) Tm:YAP solid-state lasers with CH 3 NH 3 PbBr 3 -SA successfully obtained pulsed lasing at 1987.5 nm after continuous tuning. In CW mode, the maximum absorbed pump power by the laser was 19.42 W, which corresponds to 0.68 W output power. The central output wavelength of the continuous wave laser was 1989.9 nm. In PQS mode, the output power of laser was 203 mW. Under the condition of maximum repetition frequency of 45 kHz, the narrowest pulse width of the PQS laser were 1.16 μs. Meanwhile, the laser produced a maximum single-pulse energy (4.5 μJ) and a maximum peak power (3.9 W). The beam quality factors (the horizontal/vertical directions) were M2 x = 1.1 and M2 y = 1.39. The CH 3 NH 3 PbBr 3 was an excellent SA for infrared PQS solid-state lasers, which had a large potential for development applications in the field of lasers. [ABSTRACT FROM AUTHOR]

In this paper, we present novel approaches to multi-attribute decision-making problems using q -rung normal fuzzy numbers. The q -rung normal fuzzy sets are an important way to express uncertain information, and they are superior to the intuitionistic fuzzy sets, Pythagorean fuzzy sets and normal Pythagorean fuzzy sets. A combination of the q -rung fuzzy number and the normal fuzzy number becomes q -rung normal fuzzy numbers. The new averaging and geometric operations of q -rung normal fuzzy numbers are studied using the general aggregation function. There are both commutative, associative, idempotent and boundedness compatible using q -rung normal fuzzy numbers. There are four new aggregating operators presented such as q -rung normal fuzzy interaction weighted averaging, q -rung normal fuzzy interaction weighted geometric, q -rung generalized normal fuzzy interaction weighted averaging and q -rung generalized normal fuzzy interaction weighted geometric. Usually, the aggregation functions are taken to be the Euclidean distance and Hamming distance. The existence of these operators enables the development of algorithms that solve multi-attribute decision-making problems. We demonstrate the application of enhanced Euclidean and Hamming distances to problems arising in real-world situations. An important component of a robot sensor is computer science and machine tool technology. There are four factors that can be used to evaluate robotics systems: resolution, sensitivity, error and accuracy. In order to determine the best alternative, expert opinions should be compared to the criteria. The accuracy of these models is better and they are closer to q. Finally, we used some practical examples to illustrate the validity and superiority of the proposed method by comparing with other existing methods. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a passively Q -switched thulium-doped YAlO 3 (Tm:YAP) laser based on the Cr2+:ZnSe (Chromium, Zinc Selenide) and Cr2+:ZnS (Zinc Sulfide) crystals. Wavelength tuning for 1.87 μm, 1.90 μm, and 1.94 μm operations was achieved by employing a birefringent plate. The impact of varying doping concentrations of Cr2+:ZnS crystals and a Cr2+:ZnSe crystal on the laser output was investigated. During the analysis, the passively Q -switched Tm:YAP laser achieved a pulse with the highest peak power of 107.5 kW and the narrowest pulse width of ∼6 ns, utilizing a Cr2+:ZnSe crystal as the saturable absorber (SA) with a modulation depth (ΔR) of 14 %. [ABSTRACT FROM AUTHOR]

• A novel 2D Bi 2 O 3 has been fabricated by the chemical reaction assisted vertical micro sublimation method (CVMS) for the first time. • The 2D Bi 2 O 3 has been first used as a saturable absorber. • A 358 ns-Q-switching operation was achieved on the disordered Nd: GYAP crystal using the 2D Bi 2 O 3 saturable absorber. • The Q-switched mode-locked laser was achieved on the disordered Nd: GYAP crystal for the first time with the Bi 2 O 3 saturable absorber. With a newly fabricated Bi 2 O 3 saturable absorber, the passive Q-switched and Q-switched mode-locked laser operations were experimentally demonstrated on a novel Nd: GYAP (Nd: Gd 0.1 Y 0.9 AlO 3) disordered crystal. For the Q-switched operation, a 358 ns pulse was achieved with a short cavity laser, and a maximum output power of 0.203 W with a slope efficiency of 3.1% was realized. For the Q-switched mode-locked operation, the laser of a maximum output power of 0.264 W and a spectrum of 1.062 nm (FWHM) was also achieved on a 1.78 m Z-folded cavity. The mode-locked pulse has a calculated pulse width of sub-1000 ps and a repetition rate of 90.09 MHz. The research results will open up applications of 2D Bi 2 O 3 saturable absorber and the Nd: GYAP crystal in the field of ultrafast lasers. [ABSTRACT FROM AUTHOR]

The present work investigates the switching dynamics of conventional fiber Bragg gratings (FBGs) with saturable coupling and parity-time (PT)-symmetric fiber Bragg gratings (PTFBGs) with saturable coupling (SC) and saturable gain-loss (SGL) in the presence of Kerr nonlinearity (KNL) [model - I] and saturable nonlinearity (SNL) [model - II]. Both system models can generate distinct optical multistability (OM) and bistability (OB) curves, including S-shaped, ramp-like, and mixed OM curves in both unbroken and broken PT -symmetric regimes. The impact of each control parameter on controlling switching intensities, hysteresis width, and the number of stable states is thoroughly examined for both of these system models. The direction of right light incidence enables a significant reduction in the switching intensities to below 100 W / c m 2 , the lowest critical power ever reported in the literature of PTFBGs, thanks to the concept of both saturable coupling, gain and loss. • The role of saturable coupling, gain and loss on switching is reported in diverse regimes. • The system includes two different models of PT -symmetric Bragg structures. • This intriguing study yields diverse multistability curves namely S-shaped, ramp-like, and mixed ones. • Frequency detuning has dual functions: alters multistable state and reduces switching intensities. • Parameter tuning achieves switching at 0.1 M W / c m 2 , the lowest power reported for Bragg structures. [ABSTRACT FROM AUTHOR]