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As an innovative propulsion technique, laser augmented chemical propulsion (LACP) seems superior to the traditional ones. However, the corresponding combustion theories have still to be ascertained for LACP. Burning rate of 5-aminotetrazole (5-ATZ) propellant has been studied by testing pressed samples under different combustor pressures and laser powers. Based on micro computed tomography (MicroCT), an advanced thickness-over-time (TOT) method to characterize the regression of the produced non-planar burning surface is established. Because of a shell structure covering the combustion surface, the burning rate of the implemented 5-ATZ propellant is not constant during laser ablation. Resorting to functional fitting, a new law of non-constant burning including the effect of the observed unique burning surface structures is proposed. Accordingly, applicable combustion conditions of 5-ATZ based propellants have been preliminarily speculated for future research activities.

BACKGROUND The search for aesthetic non-surgical procedures is growing. The use of polymethylmethacrylate (PMMA) as a filling material in the nose represents one of the many options among these aesthetic procedures. Its use, however, can lead to complications. The treatment of these complications is often challenging. METHODS We performed a retrospective clinical analysis of the medical records of patients undergoing treatment of PMMA granulomas of the nose at a private clinic from January, 2015, to January, 2021. A short-pulsed neodymium-YAG (Nd:YAG) laser was applied intranasally or directly by cutaneous incision in the granulomas. Laser-tissue interaction heats the alloplastic material, fragments the product and creates cleavage paths, thereby facilitating the removal of PMMA, either by intercartilaginous removal or aspiration. RESULTS Twenty-seven patients were included in the study. All had a history of PMMA injection in the nose. All patients were treated with an intralesional pulsed 1064nm Nd:YAG laser. The material removed after laser-tissue interaction was sent for histopathological examination; this showed the presence of microparticles of exogenous material compatible with PMMA. The partial removal of the alloplastic material was shown to be effective in all cases. One patient developed a small blister in the nasal dorsum. Follow-up ranged from six to 47 months. CONCLUSIONS The use of intralesional Nd:YAG laser for the treatment of PMMA granulomas on the nose proved to be an effective and safe procedure with improvement of nasal shape, without compromising respiratory function. This technical option represents yet another alternative in the treatment of PMMA granuloma complications. J Drugs Dermatol. 2021;20(11): 1161-1166. doi:10.36849/JDD.6550.

In laser powder bed fusion (LPBF) additive manufacturing, the melt pool (MP) characteristics are key indicators for process and part defects. For example, the laser scan location on the build plate...

Measuring displacements in model tests typically involves contact-based sensors such as linear potentiometers, where contact between two moving parts occurs at the sensing point. The sensor's finite mass, the limited stiffness of the beams and the clamping mechanism, and the slippage and hinging of the sensor body could affect the object's response and lead to measurement errors. Also, the physical mounting rack required to hold these sensors often obstructs the view and makes significant areas unavailable for conducting some other essential investigations. The advancement in high-speed, high-resolution and reasonably priced rugged cameras makes it feasible to obtain better displacement measurements by image analysis. This paper introduces a non-contact method that works by video recording the projection of laser lines on a test object to measure static and dynamic vertical displacements. The technique produces a continuous settlement distribution along the laser line passing through multiple objects of interest. This paper presents the theory for converting laser line images to displacements. The new method's validity is demonstrated by comparing the results from other measurement techniques: hand measurements, linear potentiometers and three-dimensional stereophotogrammetry.

One of the most important industrial applications of lasers is the treatment of materials. In this work pulsed Nd:YAG laser of wavelength (1064 nm) was used to precipitate the prepared solution of CuO nanoparticles in the form of thin films using energies (300, 400, 500 and 600 mJ) at a distance (10 cm) and for an irradiation period (20 s) for each energy. The optical properties of the material were examined, which include transmittance, absorbance and some other optical constants, in addition to calculating the optical energy gap and knowing the effect of increasing the laser energy on its values.

CdSe, Cu2Se and CdSe:Cu2Se nanocrystal (NC) thin films were synthesized using vacuum deposition technique. The open aperture Z-scan measurements carried out using 7 ns pulses at 532 nm revealed that the CdSe and Cu2Se samples exhibited saturable absorption (SA) at 30 µJ. A nonlinear optical switching from saturable absorption (SA) to reverse saturable absorption (RSA) is observed by increasing the laser input intensity.

A novel tribologic system was developed in which volatile lubricants (carbon dioxide-CO2 or nitrogen-N2) were used as a substitute for mineral oil-based lubricants in deep drawing processes. This process allows an intermediate medium to be introduced into the tool contact surfaces under high pressure by flow-optimized, laser-drilled microholes. This eliminates the need for subsequent cost-intensive cleaning processes as volatile lubricants evaporate while expanding to ambient pressure without leaving any residue. This article gives an overview of the current findings to enable and characterize the novel tribologic system. The areas of microhole laser drilling by ultrashort pulsed laser radiation, characterization of the novel tribologic system and realization of the system using a prototype tool will be described., Deutsche Forschungsgemeinschaft, Projekt DEAL

Background Observational studies have shown promising therapeutic effects of long-pulsed neodymium-doped yttrium aluminum garnet (LP-Nd:YAG) laser on warts. Objective To evaluate whether LP-Nd:YAG laser was superior to cryotherapy for cutaneous warts. Methods In this study, 150 adult patients with warts were randomized equally to receive laser or cryotherapy every 3–4 weeks, a maximum of 4 sessions. The primary outcomes were cure rate at 16 weeks and 6 months; secondary outcomes included time to clearance of warts and treatment-related adverse effects. Results There was no difference in the cure rate for laser versus cryotherapy at 16 weeks (54.1% vs. 46.7%) and 6 months (59.5% vs. 57.3%). However, time to clearance of warts, up to 16 weeks and 6 months, tended to be shorter for laser versus cryotherapy ( P = .04 and .08, respectively). Post-hoc analyses showed a significantly higher cure rate for laser versus cryotherapy in 3 subgroups of HPV 2/27/57-induced recalcitrant warts, but not in their counterpart subgroups. Laser had more mild adverse effects. Limitations Single-center. Conclusions The overall therapeutic effects of LP-Nd:YAG laser were similar to cryotherapy, but laser may be more effective to relatively recalcitrant warts and may associate with shorter time to clearance of warts.

Active 3D thermography combines 3D shape and active thermography. Thus, it enables the provision of the intuitive thermographic inspection results for composite parts with a complex geometry. However, conventional 3D thermography acquires thermographic information and 3D shape through at least two independent sensors and requires complex cross-modal image registration algorithm based on the keypoint detection and matching. In this paper, an active 3D thermography system is proposed using only one thermal camera for moving objects. This system does not require an independent 3D sensor while the thermal camera acts as the 3D sensor. Nature behind that is that a mathematical model is proposed to unify the line scanning thermography and laser triangulation in the dynamic scanning process, taking a line laser as both heat excitation for active thermography and spatial coding for 3D reconstruction. Furthermore, the model enables the feature-free registration of thermogram sequence and 3D shape, so that the registration is fast and robust without keypoint features. The experiments on standard height specimens, 3D printing glass fiber composites, and carbon fiber intake tube have shown the error is calibrated within 0.25 mm in the range of 1 mm to 150 mm and evidenced the capability for sub-surface defects detection.

Statement of problem The anatomic complexity of the ear challenges conventional maxillofacial prosthetic rehabilitation. The introduction of specialized scanning hardware integrated into computer-aided design and computer-aided manufacturing (CAD-CAM) workflows has mitigated these challenges. Currently, the scanning hardware required for digital data acquisition is expensive and not readily available for prosthodontists in developing regions. Purpose The purpose of this virtual analysis study was to compare the accuracy and precision of 3-dimensional (3D) ear models generated by scanning gypsum casts with a smartphone camera and a desktop laser scanner. Material and methods Six ear casts were fabricated from green dental gypsum and scanned with a laser scanner. The resultant 3D models were exported as standard tessellation language (STL) files. A stereophotogrammetry system was fabricated by using a motorized turntable and an automated microcontroller photograph capturing interface. A total of 48 images were captured from 2 angles on the arc (20 degrees and 40 degrees from the base of the turntable) with an image overlap of 15 degrees, controlled by a stepper motor. Ear 1 was placed on the turntable and captured 5 times with smartphone 1 and tested for precision. Then, ears 1 to 6 were scanned once with a laser scanner and with smartphones 1 and 2. The images were converted into 3D casts and compared for accuracy against their laser scanned counterparts for surface area, volume, interpoint mismatches, and spatial overlap. Acceptability thresholds were set at 0.70 for spatial overlap. Results The test for smartphone precision in comparison with that of the laser scanner showed a difference in surface area of 774.22 ±295.27 mm2 (6.9% less area) and in volume of 4228.60 ±2276.89 mm3 (13.4% more volume). Both acceptability thresholds were also met. The test for accuracy among smartphones 1, 2, and the laser scanner showed no statistically significant differences (P>.05) in all 4 parameters among the groups while also meeting both acceptability thresholds. Conclusions Smartphone cameras used to capture 48 overlapping gypsum cast ear images in a controlled environment generated 3D models parametrically similar to those produced by standard laser scanners.

The laser welding (LW) process of highly reflective materials presents low thermal efficiency and poor stability. To solve the problem, the effects of subatmospheric environment on LW process, technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were explored. The AZ31 magnesium (Mg) alloy was used as the test materials. The test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal pressure. After the keyhole depth greatly rises, significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole depth. Eventually, the hump-shaped surface morphology of the welded seam is formed; moreover, the weld width in local zones in the lower part of the welded seam remarkably grows. During LW in subatmospheric environment, the weld penetration can be further greatly increased through power modulation. Besides, power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment, thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded seams. Finally, the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was illustrated. This was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.

The optoelectronic application of gold nanoparticles is majorly influenced by certain unique features they exhibit, like surface plasmon resonance, ready functionalization and ease of conjugation with bio-analytes etc. Production of gold nanoparticles through laser ablation is the simplest method with the advantage of obtaining high purity particles. In this work, the saturation and reverse saturation behaviour during ultrafast absorption in laser ablated gold nanoparticles is studied using the Z-scan technique. The Z-scan experiment is conducted using 800 nm, 84 MHz and 120 fs intense laser pulses at different excitation intensities from 6.23 GW/cm2 to 23.37 GW/cm2. The open aperture Z-scan measurements show distinct positive region till an excitation of 17 GW/cm2 after which there is a clear cross-over into negative trend. The strength of this negative wing increases with the excitation intensity, which is featured by the nonlinear absorption due to the two-photon and three-photon absorption contributions with their respective coefficients in the range of 10-3. The optical limiting nature of these gold nanoparticles is demonstrated. An understanding of these nonlinear optical properties provides better insight in their application towards biomedical diagnostics and optical switching and limiting.

In this paper, recent results regarding rare earth element doped with chalcogenide glasses for optical gain media such as amplifiers and lasers are reviewed. Rare earth Chalcogenide glasses are formed when chalcogen elements (S, Se, Te etc.) are mixed with new additive elements (Ge, Ga, Sb, As etc.) and also with rare earth elements (Er, Dy, Pd, Pr etc.) from periodic table and prepared by melt quench technique (MQT). Rare earth element doped with chalcogenide glasses has been emerged as a suitable candidate for applications in the numeral passive and active. Among various materials, chalcogenide glasses show significant improvement in their emission properties in the optical communication range and spectroscopic properties. Finally, rare earth doped chalcogenide and optical fibers show potential for high power mid-infrared gain medium and their spectroscopic properties as well.

In this paper, a novel optical rotary sensor based on laser self-mixing interferometry is developed for the full-circle rotation measurement. The proposed sensor is convenient to use for it does not need any contact with the target or a cooperative mirror. A prototype is fabricated and tested. The measured results demonstrate a good performance compared with other optical rotary sensors, in terms of the 0.1 μrad resolution, the 2.33×10-4 linearity and 2 μrad stability over one hour. Additionally, the repeatability error is below 14.66 mrad under 9-group full-circle tests, which exhibits the potential to be instrumentalized reliably. Error analysis and limitation discussion have been also carried out. Although the accuracy needs further improvement compared with the best rotary sensor, this method has its unique advantages of high resolution, non-cooperative target sensing and electromagnetic immunity. Hence, the proposed optical rotary sensor provides a promising alternative in precise rotation measurement, tremor tracing and nano-motion monitoring.In this paper, a novel optical rotary sensor based on laser self-mixing interferometry is developed for the full-circle rotation measurement. The proposed sensor is convenient to use for it does not need any contact with the target or a cooperative mirror. A prototype is fabricated and tested. The measured results demonstrate a good performance compared with other optical rotary sensors, in terms of the 0.1 μrad resolution, the 2.33×10-4 linearity and 2 μrad stability over one hour. Additionally, the repeatability error is below 14.66 mrad under 9-group full-circle tests, which exhibits the potential to be instrumentalized reliably. Error analysis and limitation discussion have been also carried out. Although the accuracy needs further improvement compared with the best rotary sensor, this method has its unique advantages of high resolution, non-cooperative target sensing and electromagnetic immunity. Hence, the proposed optical rotary sensor provides a promising alternative in precise rotation measurement, tremor tracing and nano-motion monitoring.

PURPOSE To examine the three-dimensional foveal cone photoreceptor structure in a patient who had suffered laser pointer induced retinal injury. METHODS Patient underwent standard fundus photography and clinical spectral domain optical coherence tomography (SD-OCT) imaging. High-resolution imaging was performed using an Adaptive Optics-OCT-Scanning Laser Ophthalmoscope (AO-OCT-SLO). RESULTS AO imaging revealed loss of inner and outer segments of cone photoreceptors while the anterior retinal layers appeared healthy. Analysis of cone topology showed an increase in Voronoi domain area and a less regular hexagonal packing structure closer to the lesion site. CONCLUSION Exposure to laser pointer radiation, however brief, can result in damage to the retina. Here, repeated imaging nine months later showed a decrease in the size of the lesions (ranging from 3.7 to 23.9%) compared to the first time point. However, the longer-term prognosis is likely permanent scarring.

Laser powder bed fusion (LPBF) is a promising technology that requires further work to improve productivity to be adopted more widely. One possible approach is to increase the laser power and scan ...

A line laser with high power as the background light source for the design of a new photoelectric detection target is proposed in this paper, aiming to improve the detection ability of the traditional photoelectric detection target under low background illumination. The laser emitted pulse waveform function and the laser echo pulse response function were used to establish the mathematical model of the reflected echo power of projectile in the detection area and derive the calculation function of minimum detectable echo power in the line laser detection screen, according to information of the line laser emitted power, incident angle of projectile, duration time and detection distance of projectile passing through the line laser detection screen. Calculations and experimental results showed that the design method of line laser detection screen and calculation model of laser echo power are reasonable, and the detection ability of line laser detection screen is obviously higher than that of traditional photoelectric detection screen, especially in low background illumination; at the same time, the designed line laser detection screen was used to combine a six line laser detection screen intersection test system, based on live ammunition for shooting. The test system is stable and able to obtain the dynamic parameters of the flying projectile, verifying that the design of the line laser detection screen in new photoelectric detection target can be suitable for shooting range test applications.

To evaluate the visual and refractive outcomes of laser corneal enhancement after trifocal intraocular lens (IOL) implantation in eyes previously treated with myopic/hyperopic laser corneal refractive surgery (LCRS).Clinica Baviera-AIER-Eye Group, Spain.Retrospective comparative case series.Patients were divided by primary LCRS into myopic and hyperopic groups. The outcomes evaluated were uncorrected distance (UDVA), corrected distance (CDVA), uncorrected intermediate (UIVA), and uncorrected near visual acuity (UNVA), and predictability, safety, efficacy, and satisfaction after implantation of 2 trifocal IOL models (Physiol-FineVision and Zeiss-ATLisa 839) and subsequent laser enhancement.186 eyes (89 myopic and 97 hyperopic eyes) from 146 patients were assessed. At the last visit, refractive outcomes were better in myopic than those in hyperopic eyes, with statistically significant differences for sphere ( P.001), cylinder ( P.001), manifest refraction spherical equivalent (MRSE) ( P = .003), CDVA ( P = .005), UDVA ( P = .047), and UNVA ( P = .003) but not for UIVA ( P = .580), binocular UIVA ( P = .660), or binocular UNVA ( P = .836). Predictability differences were nonsignificant between groups for a final MRSE of ±0.5 diopters (D) and ±1.0 D (P = .167 and .502, respectively). Efficacy and safety were similar in both groups ( P = .235 and P = .080). A greater myopic MRSE was present after trifocal implantation in myopic than in hyperopic eyes (MRSE = -0.93 vs -0.69 D, P = .013), and the statistically significant differences were maintained after enhancement between both groups (MRSE -0.00 vs 0.00 D, P = .003). Overall satisfaction was similar in both groups ( P.05 all items).Corneal laser enhancement after implantation of a trifocal IOL in eyes previously treated for myopia or hyperopia with LCRS was safe, effective, predictable, and highly satisfactory.

The optical and thermal properties of a new class of fluoroindate glass with different erbium contents were investigated via Raman, transmission, and fluorescence spectroscopies, fluorescence decay curve analysis, and differential scanning calorimetry. The strength parameters of the samples were calculated using the Judd–Ofelt theory. The mid-infrared luminescence properties of erbium-doped fluoroindate glasses were studied, and a strong emission at 2.7 μm was obtained. Compared with the traditional ZBLAN glass, this glass has excellent emission properties, especially a longer fluorescence lifetime (7.09 ms) and larger emission cross-section (6.95 × 10−21 cm2) at 2.7 μm. The results indicate that fluoroindate glass is an attractive host for mid-infrared lasers and as a gain medium for optical amplifier applications.

Purpose To measure the retrieval force required to remove 1.5-mm-thick CAD/CAM zirconia copings cemented on zirconia (Zr) and titanium (Ti) stock implant abutments after a single application of erbium-doped yttrium scandium gallium garnet (Er:YSGG) laser. Materials and methods A total of 60 monolithic Zr copings were cemented on Zr and Ti implant abutments with either a resin-modified glass-ionomer (RelyX Luting Plus Cement, 3M ESPE; Rx) or a zinc oxide eugenol cement (Temp-Bond, Kerr; Tb). These abutment-coping specimens were randomly divided into 12 groups based on laser application (vs control [C]), abutment type (Zr vs Ti), cement (Rx vs Tb), and storage condition (dry [D] vs saline water [W]). Er:YSGG laser was applied at 6 W, 30% water-60% air, and 20 Hz (300 mJ/pulse energy) postcementation following a defined pattern. The force required to remove all the cemented copings from their abutments was measured on a universal testing machine (Instron model 4204). Descriptive statistics, multi-factor analysis of variance, and post hoc Tukey honest significant difference tests (α = .05) were performed. Results The mean peak force values at removal of the Zr abutment groups were 470.3 ± 151.33 N (ZrRxC), 161.7 ± 19.29 N (ZrRxD), 316.03 ± 95.24 N (ZrRxW), 103.27 ± 24.53 N (ZrTbC), 39.33 ± 6.21 N (ZrTbD), and 20.33 ± 6.45 N (ZrTbW); and for the Ti abutment groups were 349.80 ± 106.82 N (TiRxC), 84.63 ± 14.02 N (TiRxD), 177 ± 62.57 N (TiRxW), 54.77 ± 9.10 N (TiTbC), 22.67 ± 4.32 N (TiTbD), and 11.57 ± 2.30 N (TiTbW). Conclusion Within the limitations of this study, it can be concluded that Er:YSGG laser allows for easier removal of cemented Zr copings with lower removal forces, with Ti abutment groups requiring lower forces than Zr abutment specimens. No significant difference was seen between laser and control groups for Tb compared to Rx. Er:YSGG laser shows great clinical promise for predictable retrievability of cemented, monolithic Zr implant crowns, especially with stronger resin-based cement such as Rx. With further clinical evidence, this could be very useful for clinicians managing cement-retained implant crown complications.

We study the quantum interference between the excitation pathways in a three-level $\Lambda$-type atom interacting with two short laser pulse trains under the conditions of electromagnetically induced transparency. The probability amplitude equations which describe the interaction of a three-level $\Lambda$-type atom with two laser pulse trains are numerically solved. We derive analytical expressions for the population of the upper excited state for resonant laser pulse trains with a rectangular temporal profile. By varying the parameters of the laser pulse trains such as area of a single pulse, detuning, repetition period, and number of individual pulses, we analyze the quantum interference between the excitation pathways in terms of the upper excited state population.

Laser ultrasonic techniques (LUTs) are becoming widely used for damage detection based on full-field ultrasonic data. In general, LUTs provide threedimensional (3-D) ultrasonic signals from which significant informative features may be extracted about the health condition of a structure. In this paper, statistical convariance method is proposed to investigate 3-D ultrasonic features. A laser ultrasonic interrogation method based on a Q-switched laser scanning system was used to interrogate 3-D ultrasonic signals in to a 2 mm aluminum plate. The ultrasonic signals in three-dimensional (3-D) space were generated, indexed by spatial N (xdirection), spatial M (y-direction), and temporal K (t-direction) samples, respectively. Then, two sets of covariance matrices were obtained based on the vector variables in x-direction and y-direction respectively for all k time samples respectively. The covariance imaging and the corresponding variance map were obtained. The wavelength and group velocity of S0 and A0 modes were able estimated from the variance map. The wavelength of the S0 and A0 modes were estimated with the deviation error of 2.3% and 11% respectively. The group velocities of S0 and A0 modes were estimated with the deviation error of 1.8% and 0.9%. The analysis will be further performed to develop group velocity curves for a range of frequency in metal and composite plates.

Optical coherence tomography (OCT) is a novel imaging modality that provides volumetric in-vivo high-resolution (1-15μm) images in real-time. Multi-channel OCT (MOCT) imaging utilizes many imaging channels simultaneously yielding several advantages over single-channel OCT. The benefits of MOCT are at the cost of the added requirement of several imaging beams, which demands high power output from the laser source. Dual-core Ytterbium (Yb) doped fiber was used in two configurations to demonstrate its use as a MOCT light source gain medium: 1) within a ring cavity resonator and 2) in a post-amplification regime with a low powered seed-laser. The amplification wavelength range was tailored to be centered at ~1060nm, where light absorption and scattering is at a minimum in water. In the post-amplification configuration, the output power was increased from 5mW to >200mW, with the axial resolution reducing from 10μm to 12μm. We also present initial in-vivo MOCT imaging of a tadpole.

Surface hardening and compressive residual stresses are keys to superior part performance in numerous applications. In this context the development of advanced laser surface treatments for new materials and complex sample shapes is a time consuming process. Eventually, determination of residual stress states by means of X-ray diffraction in the whole surface and subsurface region, respectively, is one of the main time consuming facors in terms of characterization. In many applications the provision of an adequate distribution of compressive residual stresses, however, is needed for approval of parts. In the present work it is shown that micrograph analysis can be used to provide the zero transition zone of residual stresses revealing the relevant penetration depth of the laser treatment conducted. One single surface stress scan employing standard techniques only is needed to verify the sign of residual stresses induced by the treatment. In fact, the screening approach introduced in this study enables time- and cost-efficent development processes for studying new sets of laser hardening parameters.

Laser surface hardening provides for many advantages in terms of flexible production due to very localized and controlled energy input into the material. Laser processing offers the possibility to treat surfaces in order to locally strengthen the areas that are prone to fatigue cracking. It is well known that laser energy absorption depends on many parameters, e.g., the surface structure and the surface orientation. The incident angle of the laser beam plays a key role in this regard. When complex geometries like crankshaft fillets are treated, the surface cannot be considered a series of flat surfaces. Obviously, this leads to locally varying degrees of energy absorption. In the present work, curved surface structures were chosen in order to analyze the impact of the geometrical characteristics on surface and subsurface material properties after laser treatment. Microstructure evolution generally was found to be similar for flat and curved geometries. However, even if higher absorption in the groove due to the illumination at larger incident angles was expected, the outer parts of the curved geometry were not fully hardened. Thus, the increased effective length of the complex geometry-treated and the larger heat-affected volume are expected to have a more dominant influence on the final appearance of the subsurface microstructure. Eventually, for austenitization of the complete illuminated surface volume, the energy density needs to be increased.

Coherent light-matter interaction of molecular media in infrared (IR) cavities is a promising tool for manipulating and controlling chemical reactivity and light emission. We study the wavepacket dynamics of a single hydrogen fluoride (HF) molecule in electromagnetic environment, using the multiconfiguration time-dependent Hartree (MCTDH) method. We show that in the absence of additional thermal or coherent external sources, a single-mode cavity vacuum can efficiently dissociate a HF bond that is suddenly prepared in the vibrational ground level. We predict dissociation probabilities of up to 20% in less than 200 fs for a bare vacuum field that is resonant with the fundamental vibration frequency at the onset of the ultrastrong coupling regime. Additional enhancements of the dissociation probability can be expected for cavity with thermal excitations and multimode cavities. The results are understood analytically as the result of a Bloch-Siegert shift by using the extended-multi-level quantum Rabi model in a polaron frame that highlights the influence of the permanent dipole moments in the light-matter dynamics. Our work highlights the fundamental differences that can be expected for reactive dynamical processes inside infrared cavities and plasmonic nanostructures relative to free space.

This paper describes the interdependence of additive and subtractive manufacturing processes using the production of test components made from S Al 5356. To achieve the best possible part accuracy and a preferably small wall thickness already within the additive process, a closed loop process control was developed and applied. Subsequent machining processes were nonetheless required to give the components their final shape, but the amount of material in need of removal was minimised. The effort of minimising material removal strongly depended on the initial state of the component (wall thickness, wall thickness constancy, microstructure of the material and others) which was determined by the additive process. For this reason, knowledge of the correlations between generative parameters and component properties, as well as of the interdependency between the additive process and the subsequent machining process to tune the former to the latter was essential. To ascertain this behaviour, a suitable test part was designed to perform both additive processes using laser metal wire deposition with a closed loop control of the track height and subtractive processes using external and internal longitudinal turning with varied parameters. The so manufactured test parts were then used to qualify the material deposition and turning process by criteria like shape accuracy and surface quality., Ministry of Science, Research and Arts of the Federal State of Baden-Württemberg, Projekt DEAL

A high-precision tunable single-frequency fiber laser (T-SFFL) at 1.5 μm based on self-injection locking is experimentally demonstrated. By virtue of an effective filtering and self-injection locking scheme, a stable single-longitudinal-mode operation of the fiber laser is obtained. The fine wavelength tunability is implemented by stretching a uniform fiber Bragg grating in the self-injection loop, and the laser wavelength is tuned from 1550.28 to 1560.40 nm with a tuning accuracy of less than 54 pm. In the whole tuning range of 10.12 nm, an output power of approximately 5 mW and an optical signal-to-noise ratio of 71 dB are synchronously obtained with this laser system. Additionally, the measured laser linewidth is less than 630 Hz and the relative intensity noise is lower than -149 dB/Hz at frequencies from 0.4 to 7.5 MHz. It is believed that this 1.5 μm high-precision T-SFFL can be a promising candidate for the optical communications system applications.

The frequent replacement of worn rails on tracks brings an immense economic burden on the railroad industry, and also causes significant interruptions to railroad operation. Restoration of worn rails via laser powder deposition (LPD) can considerably reduce the associated maintenance costs. This study was focused on the use of LPD to repair the worn profile of a standard U.S. rail. The microstructure of the 304L stainless steel deposits with a minimum hardness of 85 HRB was composed of austenite, δ-ferrite, and sigma. Micropores were dispersed throughout the deposit, and microcracks were found at the rail-deposition interface. The pearlitic rail substrate showed a moderate hardness of 94 HRB. The fine-grain, pearlitic-ferritic heat affected zone had the maximum hardness of 96 HRB, which was still below the minimum required hardness of 97 HRB for a typical rail. To increase the hardness to or above 97 HRB and to mitigate the microstructural defects, the as-repaired rail went through a heat treatment process. The average hardness of the as-treated rail was increased significantly, i.e., to 103 HRB. Besides, the porous and coarse-grain deposition materials were transformed into an impermeable and fine-grain microstructure. However, heat treatment intensified the microcracks at the rail-deposition interface and also led to the formation of martensite and augmentation of the micropores in the parent rail. Isolation of the base rail during heat treatment and preheating were suggested as solutions for the problematic results. The LPD process ultimately was found to be a promising technique for repairing rails.

This article presents the spatial and temporal dynamics of high-power Gaussian laser pulse in relativistic plasma. At higher intensities, the self-focusing and self-compression of laser pulse take place due to the variation in the mass of plasma electrons moving with speed comparable to the speed of light. The two non-linear coupled differential equations for spatial and temporal pulsewidth parameters have been obtained using the moment theory approach. These equations have been solved numerically using the Runga-Kutta method. The variation in the spatial and temporal pulsewidth parameters with the distance of propagation is then used to calculate the energy gained by the electrons, which are trapped by the excited electron plasma wave during laser-plasma interaction. It is observed that spatio-temporal dynamics play an important role in electron acceleration in relativistic plasma.

In principle, this paper suggests powerful laser technology as a promising instrument that can be experimentally useful to control the lifetime and branching ratio for an unstable particle decay. In a recent paper [ arXiv:2101.00224 ], we calculated theoretically the W − -boson leptonic decay ( W − → l − ν l ) in the presence of a circularly polarized laser and we showed that the laser significantly contributed to the diminution of the leptonic decay rate. In this paper, as a continuation of the previous one, we mainly deal with the theoretical calculation of the W − -boson hadronic decay ( W − → q q ′ ) and we combine the analytical results obtained in both papers to examine the effect of an intense laser, in terms of its field strength and frequency, on the three measurable quantities in W − -boson decay (total decay rate, lifetime and branching ratios). It was found that the laser has notably contributed to the reduction of the total decay rate leading to a longer lifetime. Most importantly, the two branching ratios (one for leptons and the other for hadrons) are affected (increased or decreased) by the presence of a strong external electromagnetic field. Combined together, these two complementary works may provide an in-depth and comprehensive study that would be useful for any experimental investigation in the future.

We report laser cladding of pure titanium on a CoCrMo alloy using directed energy deposition. Using electron microscopy, the microstructural evolution upon varying the process parameters, especially laser power and powder feed rate, was investigated in relation with crack formation. Cladding layers showing dilution rates of more than 5% contained cracks due to the formation of the brittle Co2Ti intermetallic phase. The observed cracks could be ascribed to a mismatch in thermal expansion and a resulting stress of more than 440 MPa acting on the Co2Ti phase, as determined by density functional theory and nanoindentation. Furthermore, an excess laser energy caused chemical inhomogeneity and unmelted Ti powder particles, while a deficient laser energy resulted in lack of fusion. Neither cracks nor partially melted powders were observed for a powder feed rate of 3 g/min and a laser power of 225-300 W, for which the dilution rate was minimized to less than 5%. For such samples the cladding layers comprised pure α-Ti and a uniform CoTi interface with Co2Ti islands.

Combining treatment and diagnosis, called theranostics, which is achieved within single nanoparticle is an ultimate goal of many studies. Herein, we developed a new nanotheranostic agent − Nd3+-sensitized upconversion nanoparticles core for dual modal imaging (i.e., upconversion luminescence imaging and magnetic resonance imaging) and antimony nanoshell for photothermal therapy (PTT). The core-shell-shell upconversion nanoparticles (NaYF4:Yb,Er@NaYF4:Yb,Nd@NaGdF4:Nd, named as UCNP) were firstly synthesized using thermal decomposition method and then were coated by antimony shell over the surface of UCNP using simple cost and time effective new method. Furthermore, the surface of UCNP@Sb nanostructures was modified with DSPE-PEG in order to enhance the water solubility and biocompatibility. The final nanotheranostic agent, named as UCNP@Sb-PEG, exhibits very low toxicity, good biocompatibility, very good photothermal therapeutic effect, and efficient upconversion luminescence (UCL) imaging of HeLa cells under only one laser (808 nm) irradiation. The antimony shell is quenching the upconversion emission in pristine nanotheranostic agent, but interestingly, the UCL intensity of the agent recovers progressively under 808 nm laser irradiation due to light induced degradability of antimony shell. Besides, high longitudinal relaxivity (r1) obtained from the experiment approves excellent potential of the nanotheranostic agent for T1-weighted magnetic resonance imaging application.

The inverse gradient-grained CoCrFeMnNi high-entropy alloy with a desirable mechanical property that evades the strength-ductility trade-off is fabricated by the process of cold rolling and subsequent laser surface heat-treatment. Due to the gradually decayed thermal effect along with the thickness, the grain size increases from the hard core to the soft surface in terms of the inverse gradient-grained sample, which is in good consistent with the microhardness profiles. The hetero-deformation induced strengthening and strain hardening which caused by the inverse gradient-grained structure improve the strength-ductility combination, as well as the high-order hierarchal nanotwins due to the enhanced interaction with dislocations. For the laser surface heat-treatment technique, the strength and ductility are significantly increased by enlarging the microhardness difference and decreasing the thermal stress. Considering the high volume fraction of gradient-grained layer and a great deal of high-order hierarchal nanotwins in the central region, the laser surface heat-treatment technique is a promising way to produce the gradient-structured materials without thickness limitation.

In the centre of mass frame, we have studied theoretically the Z -boson resonant production in the presence of an intense laser field via the weak process e + e − → μ + μ − . Dressing the incident particles by a Circularly Polarized laser field (CP-laser field), at the first step, shows that for a given laser field’s parameters, the Z - boson cross section decreases by several orders of magnitude. We have compared the Total Cross Section (TCS) obtained by using the scattering matrix method with that given by the Breit-Wigner approach in the presence of a CP-laser field and the results are found to be very consistent. This result indicates that Breit-Wigner formula is valid not only for the laser-free process but also in the presence of a CP-laser field. The dependence of the laser-assisted differential cross section on the Centre of Mass Energy (CME) for different scattering angles proves that it reaches its maximum for small and high scattering angles. At the next step and by dressing both incident and scattered particles, we have shown that the CP-laser field largely affects the TCS, especially when its strength reaches 1 0 9 V . c m − 1 . This result is interpreted by the fact that heavy interacting particles require high laser field intensities to affect the collision’s cross section.

In this paper, we study optical bistability (OB) and optical multistability (OM) in a defect medium with a monolayer of graphene quantum system. The graphene quantum system interacts with two weak probe laser fields and an elliptical polarized coupling beam for adjusting the linear and nonlinear optical properties of defect layer. We find that by controlling the relative phase between applied lights and elliptical parameter of the coupling light, the enhanced Kerr nonlinearity with probe amplification can be obtained in resonance of probe light. Then we study the transmission and reflection coefficients of the incident lights for controlling the OB and OM features of transmitted and reflected light beams, respectively. Also, we discuss the thickness effect of the defect layer on the OB and OM properties and find that the switching from OB to OM or vice versa is possible. Moreover, we realize that by modifying the nonlinear properties of the defect medium, one can control the behaviors of the OB and OM, respectively.

The thermochemical processes in a TiN coating deposited on a steel substrate under cyclic irradiation with laser pulses are investigated. It has been established that the combustion of the coating in the irradiated regions occurs spatially inhomogeneously due to the uneven distribution of microregions in the coating, consisting of titanium nitride compounds with different stoichiometry. It is shown that dissociation reactions of various titanium nitride compounds with the release of free nitrogen occur inside the coating. As a result, the ratio of the mass fractions of titanium nitride compounds with different stoichiometry changes in comparison with the original coating. Diffusion of nitrogen into the steel substrate results in the formation of iron nitride.

A review of experimental investigations of changes in the structure and properties of the surface and near-surface layers of various materials (steels, metal alloys, ceramics and graphite) in the area of a barcode applied by continuous laser radiation and short (nanosecond) and ultrashort (femto- and picosecond) laser pulses.

The results of experiments on ablation of targets made of stainless steel and aluminum by a scanning beam of nanosecond pulses at intensity up to 109 W/cm2 are presented. It was found that the overlap of the impact zones during irradiating leads to an increase in the ablation depth in proportion to the area of overlap of the irradiation spots. This is due to increase in overlap irradiation spots degree, zones with a large number of pulse effects are formed on surface, which increases the depth of the melt bath and leads to the ejection of larger particles. An increase in ablation depth of aluminum increase with increase of the interval between pulses up to 10 ms and overlapping of the irradiation spots. The shape of the ejected particles changes from spherical, when formed from a melt, to an irregular shape, when the target is mechanically destroyed by an internal shock wave. The size and velocity distribution of the ejected particles was determined, and on the basis of these data, the laser radiation shielding coefficients were calculated depending on the degree of overlapping of the irradiation spots. It was found that the main mechanism for the decrease in the efficiency of ablation by a scanning beam of radiation is the backflow of microparticles deposited on the target surface. The analysis of the energy balance of the aluminum ablation process is carried out.

Purpose. To evaluate the incidence of laser enhancement following cataract surgery and refractive lens exchange (RLE) with FineVision Micro F trifocal lens implantation (PhysIOL, Liege, Belgium). Methods. Retrospective study of patients who had undergone cataract or RLE surgery and had received a FineVision Micro F intraocular lens. Laser enhancement of residual refractive error was determined. Visual acuity (VA) assessments were performed before and after surgery: uncorrected distance VA (UCDVA), best-corrected distance VA (BCDVA), uncorrected near VA (UCNVA), plus preoperative and postoperative spherical equivalent (SE) assessments. Results. Of the 1129 eyes from 596 patients, 61 (5.4%) required laser enhancement to correct residual refractive error (by group: 30/679 eyes [4.4%] cataract; 31/450 eyes [6.9%] RLE). Eleven eyes received FemtoLASIK; 50 eyes received PRK. Mean UCDVA before laser enhancement was 0.26±0.19 logMAR and 0.24±0.14 in the FemtoLASIK and PRK groups, respectively. After laser enhancement, these were 0.04±0.05 logMAR and 0.13±0.19, respectively; BCDVA values were 0.00±0.00 logMAR in the FemtoLASIK group and 0.06±0.11 in the PRK group. Laser enhancement improved UCNVA (Jaeger) from 2-3 to 1-2 in both groups. Enhancement reduced preoperative SE of -0.39±0.99 D and -0.53±0.58 D (FemtoLASIK and PRK groups, respectively) to 0.24±0.36 D and 0.04±0.47 D. Conclusions. The FineVision Micro F trifocal lens is an effective solution for gaining increased spectacle independence. The incidence of residual refractive error requiring laser enhancement is low, and laser procedures are a safe and effective solution for improving the quality of vision and patient satisfaction. Synopsis. Laser enhancement rates and outcomes were determined following cataract / refractive lens exchange surgery that used a trifocal IOL. Enhancement was safe and effective and rates were low (5.4%).

In this paper, we present the design, development, and characteristics of the novel aerosol mass spectrometer ERICA (ERC Instrument for Chemical composition of Aerosols; ERC – European Research Council) and selected results from the first airborne field deployment. The instrument combines two well-established methods of real-time in situ measurements of fine particle chemical composition. The first method is the laser desorption and ionization technique, or laser ablation technique, for single-particle mass spectrometry (here with a frequency-quadrupled Nd:YAG laser at λ = 266 nm). The second method is a combination of thermal particle desorption, also called flash vaporization, and electron impact ionization (like the Aerodyne aerosol mass spectrometer). The same aerosol sample flow is analyzed using both methods simultaneously, each using time-of-flight mass spectrometry. By means of the laser ablation, single particles are qualitatively analyzed (including the refractory components), while the flash vaporization and electron impact ionization technique provides quantitative information on the non-refractory components (i.e., particulate sulfate, nitrate, ammonia, organics, and chloride) of small particle ensembles. These techniques are implemented in two consecutive instrument stages within a common sample inlet and a common vacuum chamber. At its front end, the sample air containing the aerosol particles is continuously injected via an aerodynamic lens. All particles which are not ablated by the Nd:YAG laser in the first instrument stage continue their flight until they reach the second instrument stage and impact on the vaporizer surface (operated at 600 ∘C). The ERICA is capable of detecting single particles with vacuum aerodynamic diameters (dva) between ∼ 180 and 3170 nm (d50 cutoff). The chemical characterization of single particles is achieved by recording cations and anions with a bipolar time-of-flight mass spectrometer. For the measurement of non-refractory components, the particle size range extends from approximately 120 to 3500 nm (d50 cutoff; dva), and the cations are detected with a time-of-flight mass spectrometer. The compact dimensions of the instrument are such that the ERICA can be deployed on aircraft, at ground stations, or in mobile laboratories. To characterize the focused detection lasers, the ablation laser, and the particle beam, comprehensive laboratory experiments were conducted. During its first deployments the instrument was fully automated and operated during 11 research flights on the Russian high-altitude research aircraft M-55 Geophysica from ground pressure and temperature to 20 km altitude at 55 hPa and ambient temperatures as low as −86 ∘C. In this paper, we show that the ERICA is capable of measuring reliably under such conditions.

OBJETIVES: To assess the effect of various factors on laser fiber tip degradation with the Thulium Fiber Laser (Tm-fiber): fiber stripping, adjustable laser settings (energy, frequency, peak power)...

Annotation In connection with the possible use of laser technological equipment in space the impact of nanosecond UV laser on copper and its alloys was investigated. At the pre-threshold mode, in the absence of obvious traces of melting, at an energy density of E = 0.1–1.0 J/cm2, the metal in the irradiated zone swelled up and traces of plastic deformation were found. The uplift arised as a result of the formation of an excessive number of point defects. With an increase of the number of impacting pulses, accumulation of damage occurred, despite the fact that the surface completely cools down during the time between pulses. The height of the resulting uplift reached 1 μm, and sometimes even slightly more. Sliding and cracking along grain boundaries occurred, as well as crystallographic slipping. The discovered effect of the impact of laser pulse on the metal surface, associated with the occurrence of uplift and the presence of plastic deformation, is similar to the well-known acoustoplastic, electroplastic, and magnetoplastic effects. The discovered effect was called optoplastic. Exceeding the laser damage threshold (E ∼ 1.0 J/cm2) leads to melting and evaporation of the metal with the formation of a crater. This is oppositely directed process, which suppresses the manifestations of the optoplastic effect.

In this paper we demonstrate a high wall-plug efficiency and low threshold current for heterogeneously integrated III-V-on-Silicon distributed feedback (DFB) lasers. Above 12% wall plug efficiency is achieved for a 200 µm long DFB laser diode at 25 °C. Up to two times 6 mW of optical power is coupled into the silicon waveguide and more than 40 dB side-mode suppression ratio is obtained. We also discuss the non-return-to-zero on-off keying modulation at 20 Gb/s and the transmission over a 2 km long optical fiber.