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A multidisciplinary approach for the production and characterization of a series of high concentration Er3+ activated SrLaGa3O7 (abbreviated as Er:SLGO) crystal fibers is shown to have a great promise for implementation in mid-infrared laser applications. The current approach includes the design and formation of unique layered tetrahedral network structures with several kinds of rare earth (RE) ions including Er ions distributing statistically between layers, such as Er:SLGO, Er,Nd:SLGO,Er,Yb, Ho: SLGO,Er,Eu:SLGO and Er,Ho:SLGO. Five kinds of Er:SLGO crystal fibers were designed to grow via a micro-pulling down method. Spectroscopic analyses show that Er,Yb,Ho:SLGO and Nd,Er:SLGO crystal fibers were superiorly endowed with inhomogeneous broadening absorption and strong emission. The unique structural components design enables the generation of improved absorption and emission recombination, and the inhibition of self-termination as well. Generally, the use of structural components design may warrant high-efficiency emissions in RE-doped crystal fibers.

We report on an Er:Y2O3 ceramic channel waveguide laser operating at continuous-wave and passively Q-switched regimes, for the first time to the best of our knowledge. The Er:Y2O3 ceramic channel waveguide has been fabricated by a femtosecond laser direct-writing technique. The maximum output power reached 123.5 mW in continuous-wave mode with a slope efficiency of about 21%, and the lasing behavior has been found simultaneously at 2710.28, 2716.76, and 2723.18 nm. We have further fabricated an MXene Ti3C2Tx saturable absorber mirror to operate the Er:Y2O3 waveguide in passively Q-switched regime. At the same time, property of the MXene Ti3C2Tx saturable absorber has been characterized, and nonlinear saturable absorption of the saturable absorber has also been measured. The average output power is about 67.6 mW, and the shortest pulse width is about 58.1 ns. This work indicates that femtosecond laser direct writing is a reliable technique for processing mid-infrared ceramic waveguides, and MXene Ti3C2Tx is promising for operating pulsed mid-infrared lasers.

The development of intense ultrashort laser sources in the mid-infrared (mid-IR, 2-8 μm) and long-wave infrared (LWIR, 8-15 μm) is of great interest in various important research directions, including vibrational spectroscopy of the absorption lines of gases localized in the "fingerprint" wavelength region (2-20 μm), remote sensing and chemically sensitive LIDAR measurements, utilizing the atmosphere transparency windows (3–5 μm, and 8-15 μm), and fundamental sciences, such as laser particle acceleration, attoscecond pulse generation, and strong-field physics. For those applications, the use of fiber lasers provides the advantages such as low cost, compactness, maintenance-free operation, and diffraction-limited beam output, competing with other solid state laser sources. Fluoride fibers are used instead of silica fibers to build mid-IR lasers, benefiting from the much broader transmission window reaching 4 μm. Reaching LWIR using mid-IR lasers has the intrinsic advantage of smaller quantum defect compared with near-IR lasers, and thus potentially higher conversion efficiency, consequently leading to the generation of higher energy/power LWIR signals. In this thesis, key aspects for the development of the pump and signal laser sources of a LWIR OPCPA system are presented, which is recognized as a promising pathway for efficient intense few-cycle pulse generation in LWIR. First, ultrashort pulses centering at 2.8 μm were generated from an Erbium-doped fluoride fiber mode-locked oscillator. Its performance was characterized experimentally, and its mode-locking mechanism was numerically investigated. Second, these pulses were amplified and simultaneously compressed in an Erbium-doped fluoride fiber nonlinear pre-amplifier, without using any external dispersion management arrangements. Its characteristics were investigated, and the physics of its operation was thoroughly studied via numerical simulations. The combination of the first two experiments constitutes the front end for seeding both pump and signal pathways of the LWIR OPCPA system. Third, mid-IR soliton pulses, tunable from 2.8 μm to beyond 4 μm were generated, using Raman-induced soliton self-frequency shift (SSFS). This experiment was also analyzed via numerical simulations. This process has high conversion efficiency and stability, and was implemented as a compact and practical laser system. Fourth, ultrashort LWIR pulses were generated by difference frequency generation (DFG), using mid-IR lasers as pump and signal sources (2.8 μm and 4 μm) for the first time. Lastly, a novel phase stabilization technique for mode-locked pulses using a Gires-Tournois interferometer was demonstrated. It has the potential to be used for the phase stabilization of the LWIR OPCPA system. To summarize, ultrashort LWIR pulses were generated, using DFG pumped and seeded with mid-IR fluoride fiber lasers for the first time. This research is the first step in the proof-of-principle demonstration of the signal source for a LWIR OPCPA system. It also provides with a seed source for the high-energy large-core Er:ZBLAN fiber based CPA system, which is currently being developed. This mid-IR fiber CPA will serve as the OPCPA pump source. This thesis research opens new paths for developing intense mid-IR and LWIR ultrashort pulse sources, useful for a wide range of potential applications.

An extensive study of a novel room-temperature mid-infrared Ce3+-doped Ge20Sb10Ga5Se65 glass laser is reported. An influence of output-coupler transmission on laser efficiency and emission spectra is investigated. Pumped by a pulsed Fe:ZnSe laser at 4.1 µm, a maximum output energy of 35 mJ is demonstrated at 5.2 µm, with a laser threshold of about 60 mJ and a slope efficiency of 21%. The tuning range of a mid-infrared Ce:glass laser is reported for the first time: with an intracavity prism, the laser is continuously tunable in the spectral range of 4.5–5.6 µm. The internal losses are determined to be below 9% per roundtrip.

International audience; We report here on a spectroscopic study of Dy3+-doped and Tm3+-Dy3+ doped CaF2 as promising candidates to develop crystalline waveguide laser sources around 3 μm. The advantages of Tm3+ ions as sensitizers to improve the excitation of Dy3+ ions in CaF2 is demonstrated: an energy transfer efficiency from Tm3+ to Dy3+ ions of 99.6% has been reached for Dy3+ concentration as high as 2 at.%, by considering a Tm3+ ratio set at 5 at.%. Moreover, the behavior of such doped crystals in a laser waveguide configuration has been modeled and the modeling results show that it seems possible to achieve promising laser perspectives around 3 μm, with laser thresholds in the watt level for singly doped Dy3+:CaF2 and around 0.2–0.3 W for codoped Tm3+-Dy3+:CaF2, presenting both laser efficiencies in the order of 30%. Finally, the saturation of the absorption which is observed in the modeling for such codoped Tm3+-Dy3+:CaF2 waveguide at Dy3+ concentration below 1% is discussed and its origin is explained.

We demonstrate advanced experimental approaches to photoacoustic gas detection with tunable mid-infrared (mid-IR) laser sources of different types. A gas analyzer for registration of various gas components based on a tunable narrow-linewidth optical parametric oscillator (OPO) was designed and investigated. Using this OPO, the possibility of measuring the trace concentration (~2÷3 ppm) of methane (CH4) in air was experimentally shown. The gas detection capability was enhanced by introducing injection seeding into the OPO. Another gas analyzer was based on a quantum cascade laser (tunable within the range ~7.6 ÷7.7 μm) and a resonant differential photoacoustic detector. Detection of the ultra-low concentration (~0.3 ppm) of methane in air was achieved (the standard dispersion was (1σ) ≈ (10–11) ppb with an integration time of 10 s). We compare the presented approaches and outline their further development. © 2021 Institute of Physics Publishing. All rights reserved. This work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (grant FSUS-2020-0036). The Fan-out MgO: PPLN chip was prepared by A.A. and V.S with support from Russian Foundation for Basic Research (grant RFBR-mk-18-29-20077). The CH4 spectroscopic experiments were funded by RFBR, project number 19-32-60055.

We demonstrated a high-power laser diode (LD) side-pumped two-rod Er:YSGG mid-infrared laser by optimizing the location of the two laser heads in resonator based on the matrix formalism A maximum output power of 61.02 W was achieved at repetition rate of 100Hz and pulse width of 750 μ s , corresponding to optical–optical efficiency of 12.6%. The experimental results illustrated that the technology of double rods in series can effectively improve the output power of the LD side-pumped Er:YSGG laser.

Compact and portable diode-pumped solid-state MIR lasers with active and passive Q-switching based on Er:YAG, Er,Cr:YSGG and Ho,Yb,Cr:YSGG crystals have been designed and investigated. Those lasers provided the following parameters: pulse width 60 ns, peak power up to 1 MW and repetition rate 50 Hz. Geometrical sizes our lasers were just 75 mm diameter and 200 mm length. The Fe2+:ZnSe(ZnS) crystals pumping by radiation of designed lasers with the optical conversion efficiency near 40% was demonstrated

Extra-cavity type II NCPM KTA OPO-based oscillator pumped by Q-switched Nd:YAG laser is developed for laser radars operating in the mid-infrared. The laser operates in the 3.0-4.5 um range with a linewidth of 0.5 nm.

We report the first wavelength stabilized all-fibre ultrafast mid-infrared laser using MXene as a novel saturable absorber. This all-integrated pulsed laser is a promising tool for a broad range of applications in the mid-infrared regime.

In this paper, a high-power and high-efficiency 4.3 µm mid-infrared (MIR) optical parametric oscillator (OPO) based on ZnGeP2 (ZGP) crystal is demonstrated. An acousto-optically Q-switched Ho:Y3Al5O12 laser operating at 2.1 µm with a maximum average output power of 35 W and pulse width of 38 ns at a repetition rate of 15 kHz is established and employed as the pump source. A doubly resonant OPO is designed and realized with the total MIR output power of 13.27 W, including the signal and idler output power of 2.65 W at 4.07 µm and 10.62 W at 4.3 µm. The corresponding total optical-to-optical and slope efficiencies are 37.9% and 67.1%, respectively. The shortest pulse width, beam quality factor, and output power instability are measured to be 36 ns, Mx2=1.8, My2=2.0, and RMS

We demonstrate a stable and efficient passively Q-switched 2.8 μm Er3+-doped ZBLAN fiber laser with a broadband semiconductor saturable absorber mirror. Enabled by the broadband optical modulator, the stable Q-switched fiber laser can deliver a maximum average power over 700 mW with corresponding per-pulse energy of 8.19 μJ and a pulse width of 1.3 μs at a repetition rate of 88.6 kHz under an incident pump power of 3.8 W. In addition, the slope efficiency can reach 22.5%. To the best of our knowledge, this is the highest reported slope efficiency for the passively Q-switched Er3+-doped ZBLAN fiber laser.

An efficient enhancement of 2.78 μm emission from the transition of Er3+: 4I11/2 → 4I13/2 by Tm3+ introduction in the Er/Tm: PbF2 crystal was grown by the Bridgman technique for the first time. The spectroscopic properties, energy transfer mechanism, and first-principles calculations of as-grown crystals were investigated in detail. The co-doped Tm3+ ion can offer an appropriate sensitization and deactivation effect for Er3+ ion at the same time in PbF2 crystal under the pump of conventional 800 nm laser diodes (LDs). With the introduction of Tm3+ ion into the Er3+: PbF2 crystal, the Er/Tm: PbF2 crystal exhibited an enhancing 2.78 μm mid-infrared (MIR) emission. Furthermore, the cyclic energy transfer mechanism that contains several energy transfer processes and cross-relaxation processes was proposed, which would well achieve the population inversion between the Er3+: 4I11/2 and Er3+: 4I13/2 levels. First-principles calculations were performed to find that good performance originates from the uniform distribution of Er3+ and Tm3+ ions in PbF2 crystal. This work will provide an avenue to design MIR laser materials with good performance.

A novel mid-infrared (MIR) laser crystal C o / E r : P b F 2 was successfully grown. The use of E r 3 + ion co-doping to sensitize a C o 2 + ion and enhance the 2.1–4.2 µm broadband MIR emission of the C o 2 + ion in a P b F 2 crystal was studied for the first time, to the best of our knowledge. The E r 3 + ion was demonstrated to be an effective sensitizer of the C o 2 + ion, making the C o / E r : P b F 2 crystal propitious to be pumped by commercialized laser diodes. Furthermore, with E r 3 + ion co-doping, the local symmetry of C o 2 + and E r 3 + ions was seriously distorted, thereby enhancing the 2.1–4.2 µm MIR emissions. This study provides a path for designing MIR laser materials with optimal performance.

In this work, we investigate GaSb / InAs 1 − x N x T-shaped quantum wire active region in mid-infrared laser. Multi-band k.p model and variational formalism are applied to find the confinement energies, the band structures, and optical gain. We then present a method of numerical calculation that is suited to any T-shaped quantum wire. By tuning the quantum wire thickness, the TE- and TM-polarized optical gain up to 21 × 10 3 cm − 1 can be obtained for λ = 3.11 μm at room temperature (RT), which is very promising to serve as an alternative active region for high-efficiency mid-infrared laser applications.

Inertia-less optical scanners are an essential building block for many systems, including remote sensing, spectroscopy, and optronics. Although many solutions provide efficient scanning devices in the visible to near-infrared spectral range today, none of these devices offers good performances in longer wavelengths like in the mid-IR range. The new rationale that is described in this paper is to take advantage of existing and well-proven steering techniques in the near IR and to reach mid-IR by frequency conversion in a specifically designed Fourier transform optical parametric oscillator.

A compact passively Q-switched YVO4/Nd:YVO4/KTA intracavity optical parametric oscillator (OPO) is realized. With an end-pumping diode power of 16.6 W, output signal power of 932 mW and idler power of 415 mW are obtained at a pulse repetition rate of 101 kHz. The pulse widths and the beam quality factors are also analyzed for both signal and idler lasers.

Lasers operating in mid-infrared spectral region specifically with 3 μm wavelength attract a lot of attention due to their various applications in atmospheric monitoring, medical surgery, remote sensing and scientific research. Such laser can be used as an efficient and high-quality radiation source for optical parametric oscillators and converters to longer IR wavelengths.

We experimentally observe the resonant radiation (RR) of mid-infrared laser filaments in YAG, pumped by 2.4 µm, 220 fs Cr: ZnSe laser pulses in anomalous dispersion regime, and numerically investigate the phase matching of RR.

We report the first LiGaS2-based mid-IR OPCPA, delivering 13.8µJ, 10kHz, 145fs, 9µm pulses. A 5-mm thick KrS5 crystal is employed to further compress the pulse to the 45fs (1.5 cycle) pulse duration.

The interpretation of experimental data from novel mid-infrared few-cycle laser sources requires an understanding of ionization mechanisms and knowledge about related ion yields. Experimental studies have indicated sequential double ionization as the dominant process above 1014 W cm−2. These results contradict a recent prediction that in this spectral region, non-sequential processes dominate the double ionization of xenon up to intensities of about 1015 W cm−2. In either case, the ratio of doubly to singly charged xenon yield reported in previous studies has been limited to a few percent, indicating a regime well below the onset of saturation of the double ionization process. We present an experimental study of double ionization of xenon and krypton atoms exposed to intense near four-cycle pulses at 3.2 μm. Our experiments rely on the ion microscopy technique, which facilitates the detection of ions originating from a restricted region within the interaction volume, thereby reducing the impact of focal averaging. Our measurements suggest that at intensities of close to 1.2 × 1014 W cm−2, double ionization of xenon and krypton is already significantly saturated. In particular, we find a doubly to singly charged yield ratio of about 75 percent for xenon and 25 percent for krypton. We compare our results with the predictions of different models accounting for the effects of volume averaging and focal geometry. We find that in the deeply saturated regime of our experiment, the Perelomov–Popov–Terentyev theory significantly underestimates the observed double ionization yield.

Highly doped erbium crystals have complex fine energy levels, which can be used to emit lasers of different wavelengths under different conditions. The mid-infrared multi-wavelength laser of erbium ions has not yet achieved stable laser emission. In this study, the rate equation is used, with consideration of mode competition, to design a mid-infrared Er:YAG pulsed laser that emits four wavelengths at room temperature. The gain of the multi-wavelength erbium laser is related to the Boltzmann distribution coefficient. Based on this, the conditions for multi-wavelength output have been calculated and verified in experiments. A four-wavelength stable output mid-infrared pulsed laser based on Er:YAG was produced. This laser may be applied to remote sensing or gas detection.

A new laser crystal, Cr/Er/Pr:CaLu0.2La0.8Ga3O7 (Cr/Er/Pr:LuCLGO), was successfully grown by the Czochralski method for the first time. The structural parameters of Cr/Er/Pr:LuCLGO crystal were determined by the x-ray Rietveld refinement method. Optical absorption, fluorescence spectra and lifetime decay profiles were measured for the crystal. The co-doped Cr3+ ion expands the absorption cross-section considerably for 400–700 nm bands, which is beneficial for xenon lamp pumping. Also the co-doped Pr3+ ions decrease the population of the Er3+:4I13/2 energy state effectively. The energy transfer efficiencies of the Er3+:4I11/2 → Pr3+:1G4 and Er3+:4I13/2 → Pr3+:3F4 processes were calculated, showing that Pr3+ ions can play an important role as deactivators for Er3+ ions. Furthermore, the energy transfer mechanisms among Cr3+, Er3+ and Pr3+ ions were studied. The results suggest that Cr/Er/Pr:LuCLGO crystal is a new promising laser medium for 2.7 μm xenon lamp pumping solid-state lasers.

In this paper, we propose a gas analyzer that uses a quantum cascade laser (QCL) and achieves high sensitivity and gas selectivity with simple configuration and signal processing. Feature quantities are extracted from an absorption-modulated signal, which is obtained by the logarithmic conversion of a detector signal receiving a wavelength-modulated laser light. The extracted feature quantities are used for the determination of target and interfering gas concentration with simple simultaneous linear equations. As a result of the demonstration of CO gas measurement with a gas analyzer consisting of a 4.6 μm pulsed QCL, a small-volume Herriott cell with a path length of 5 m and a thermopile as a photodetector, it is shown that the limit of detection is 2.0 ppb at the integration time of 1 s and that interference by N2O can be eliminated. It is also shown that various disturbances such as spectral shift due to laser wavelength drift and spectral broadening due to partial pressure change of coexisting gases can be corrected by extracting appropriate additional feature quantities.

We report the visible up-conversion, near to middle infrared luminescence, and energy transfer mechanism of Er 3+ /Ho 3+ co-doped barium gallo-germanate glasses under 980 and 1550 nm excitations, respectively. The 2.0 μm emission lifetime of the present glass is as high as 5.67 ms with the corresponding energy transfer efficiency of 70.0% from Er 3+ : 4 I 13/2 to Ho 3+ : 5 I 7 when pumped by 980 nm laser diode. In addition, the enhanced 2.0 μm emission is also obtained upon excitation of 1550 nm due to the efficient energy transfer from Er 3+ to Ho 3+ . Meanwhile, the calculated maximum gain is 2.13 cm −1 at 2024 nm. These results suggest that Er 3+ /Ho 3+ co-doped barium gallo-germanate glasses is a potential material for 2.0 μm fiber laser.

为了研究石墨烯器件在中红外波段的光限幅机理，采用化学气相沉积法制备出层数可控的石墨烯薄膜CaF2镜片，并基于MgO∶PPLN周期极化晶体搭建了全固态中红外光学参量振荡器，利用3 m~5 m波长可调谐的闲频光开展了石墨烯薄膜散射实验，测量了石墨烯薄膜的散射信号与入射光强度变化的归一化曲线。当闲频光能量超过1 J/cm2时，石墨烯被迅速汽化，电离形成的微小等离子体和石墨烯微片对入射闲频光产生多重非线性散射，散射能量信号呈现出快速非线性增长趋势，并且散射能量信号值的增长率与闲频光的入射波长成反比，与石墨烯的层数成正比关系，从而验证了石墨烯对中红外波段激光较强的非线性散射使其具有光限幅效应。

Ho3+-doped low-hydroxyl (OH-) ZnF2 based fluoride glasses were prepared by using the conventional melt-quenching method in a glove box. The glasses have a composition of ZnF2-BaF2-SrF2-YF3-HoF3 (ZBSY-H), and the absorption coefficient of OH- in the ZBSY-H glasses was calculated to be only ∼0.003 cm−1 at 2.86 µm. Under the excitation of an 1120 nm laser, efficient 2.86 µm emissions were observed in the ZBSY-H glasses. The emission cross section of the ZBSY-H glasses was also calculated, and the corresponding value was ∼7.19 × 10−21 cm2. These results indicated that the ZBSY-H glasses were potential candidate for 2.86 µm laser applications.

In this paper, a reflective methane (CH4) gas telemetry system has been developed based on the direct optical absorption spectroscopy technique for an open light path. It can realize the real-time in-situ monitoring of CH4 gas within a range of 150 m. Considering the potential cross-interference effects of hydrocarbon gases in ambient air, a diode laser operating at a specific wavelength of 1653.7 nm is employed to target the strong CH4 absorption line in near-infrared region and therefore avoid the interference of water vapor absorption simultaneously. A measurement precision of 0.02 ppm within 40 m open optical path has been achieved over 30 h of continuous monitoring, indicating the excellent measuring sensitivity and stability of our telemetry system. Through the field test of leaked CH4 gas with a 150 m one-way open optical path, the developed CH4 telemetry system has proved to have great potential and reliability for environmental monitoring and remote gas detection in various industries.

BaGa4Se7(硒镓钡，简称BGSe)与KTiOAsO4(砷酸氧钛钾，简称KTA)均可在1.06 μm激光泵浦下产生中红外激光。首先仿真计算出两种非线性晶体的相位匹配曲线，结果显示：切割角为(56.3°, 0°)的BGSe晶体在I类相位匹配条件下和切割角为(90°, 0°)的KTA在II-A类相位匹配条件下均可产生~3.5 μm的闲频光。然后理论计算出BGSe (56.3°, 0°, I类)的有效非线性系数为−11.9 pm/V，KTA(90°, 0°，II-A类)的有效非线性系数为−3.2 pm/V；在其他条件相同的情况下，15 mm长BGSe (56.3°, 0°, I类) 的OPO振荡阈值是20 mm长KTA (90°, 0°, II-A类) OPO振荡阈值的35.11%。最后通过实验验证BGSe (56.3°, 0°, I类, 15 mm) 的振荡阈值小于KTA(90°, 0°, II-A类, 20 mm)，输出的中红外激光能量大于KTA。因此，BGSe是一种极具应用前景的中红外非线性晶体。