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We demonstrate a room temperature operation narrow pulse width Fe:ZnSe laser pumped by a gain-switched Ho,Pr:LLF laser emitting at 2.95 μm in this paper. The gain-switched Ho,Pr:LLF laser produced the 102 μJ maximum pulse energy and 33 ns minimum pulse width, corresponding to the peak power of about 3.1 kW. Using this gain-switched Ho,Pr:LLF laser as the pump source, the maximum energy of 6 μJ at around 4.47 µm and the pulse width of 5.5 ns was achieved in the room temperature Fe:ZnSe laser, corresponding to the peak power of 1.2 kW.

We demonstrate a single-longitudinal-mode Ho:GdVO4 continuous-wave (CW) laser at 2048.6 nm. We achieved excellent single-longitudinal-mode performance using a unidirectional ring cavity with an isolator and a half-wave plate. We obtain the maximum output power equal to 965 mW corresponding to a slope efficiency of 12.7%.

We demonstrated a 202 W Tm:YLF slab laser using a reflecting volume Bragg grating (VBG) as an output coupler at room temperature. Two kinds of active heat dissipation methods were used for the VBG to suppress the shift of wavelength caused by its increasing temperature. The maximum continuous wave (CW) output power of 202 W using the microchannel cooling was obtained under the total incident pump power of 553 W, the corresponding slope efficiency and optical-to-optical conversion efficiency were 39.7% and 36.5%, respectively. The central wavelength was 1908.5 nm with the linewidth (full width at half maximum) of 0.57 nm. Meanwhile, with the laser output increasing from 30 to 202 W, the total shift was about 1.0 nm, and the wavelength was limited to two water absorption lines near 1908 nm. The beam quality factors M2 were measured to be 2.3 and 4.0 in x and y directions at 202 W.

A single-longitudinal-mode Ho:YAG laser with a twisted-mode cavity under the continuous-wave and pulsed operation was demonstrated. The maximum continuous-wave single-longitudinal-mode output power of 0.76 W was obtained at the wavelength of 2097.46 nm, corresponding to a slope efficiency of 28.9%. The output wavelength was tuned from 2096.94 nm to 2098.48 nm by utilizing a 0.5-mm-thick etalon. Furthermore, the single-frequency pulsed operation of the twisted-mode Ho:YAG laser was realized by the electro-optic switch. For the 2 kHz pulse repetition frequency, the single-frequency pulse energy reached 0.2 mJ with the pulse width of 116.5 ns. The beam quality factors M2 of the pulsed twisted-mode Ho:YAG laser in the x and y directions were 1.15 and 1.10, respectively.

In this paper, we demonstrate a 570.0 MHz harmonically mode-locked all-polarization-maintaining Ho-doped fiber laser based on semiconductor saturable absorbed mirror. Firstly, the laser operates in the 15.4 MHz fundamental mode-locked soliton regime, emitting 2051.5 nm, 1.62 ps soliton pulse without Kelly sidebands. And then, the stable 37th-order harmonic mode-locked soliton with maximum repetition rate up to 570.0 MHz at 2053nm is generated. Moreover, colorful soliton rain behaviors are also discussed.

We demonstrated a 2.1 µm nanosecond laser pumped, 2.6 µm continuous-wave (CW) seed injected, cadmium selenide (CdSe) signal singly resonant optical parametric oscillator (OPO). A maximum average power of 1.05 W was obtained corresponding to a pulse energy of 1.05 mJ at the idler wavelength of 10.1 µm and optical-to-optical conversion efficiency of 4.69%, beam quality of M x 2 = 2.25 , M y 2 = 2.12 and pulse width of 24.4 ns. To the best of our knowledge, this is the first time to achieve 10–12 µm laser with watt-level average power using OPO technology.

In this paper, we have demonstrated an efficient intra-cavity pumped Ho:SSO laser based on a cascaded in-band pumping scheme for the first time. The laser diode at 1.6 µm was used to pump the Tm:YAG crystal. At an incident LD pump power of 18.7 W, dual end-pumped Tm:YAG laser provides the maximum output power of 9.7 W with a slope efficiency of 55.9%. With the same incident LD power, a maximum output power of 4.9 W at 2116.5 nm was achieved with a slope efficiency of 31.6% in the Ho:SSO laser intra-cavity pumped by a Tm:YAG laser. The beam quality factor of the Ho:SSO laser at maximum output level was measured to be 1.1 and 1.2 in the horizontal and vertical directions, respectively.

We proposed an injection-seeded Q-switched Ho: YLF laser by a tunable single-longitudinal-mode Tm, Ho: YLF laser. The tunable single-longitudinal-mode seed laser was achieved by inserting two Fabry-Perot (F-P) etalons in the Tm, Ho: YLF laser resonant cavity and changing the cavity length through a piezoelectric transducer (PZT). The wavelength of single-longitudinal-mode Tm, Ho: YLF laser could be tuned from 2050.962 nm to 2051.000 nm finely. The single-longitudinal-mode output power of 76 mW from Tm, Ho: YLF seed laser was achieved at the CO2 absorption peak of 2050.967 nm. Single-frequency Q-switched Ho: YLF laser was achieved by injection seeding. The output energy of single-frequency Q-switched Ho: YLF pulse was 4.4 mJ, with a pulse width of 65 ns and a repetition frequency of 100 Hz. The beam quality factor M2 of Ho: YLF laser was 1.07, nearly diffraction limit. The full width at half maximum (FWHM) of single-frequency pulse Ho: YLF laser measured by a heterodyne technique was about 4.1 MHz with the simultaneously recorded pulse width of 132 ns.

A high power single crystal Ho:YAG laser was reported in this paper. With dual-end pump structure, maximum continuous wave power of 108W was achieved with slope efficiency of 63.2% and optical efficiency of 57.9%. With an acousto-optic Q-switch, maximum average output power of 106W at the pulse repetition frequency of 20kHz was achieved with pulse energy of 5.3mJ and pulse width of 21ns, corresponding to a peak power of approximately 252kW. The output wavelength was 2090.7nm with FWHM linewidth of 0.4nm. The beam quality factor of M2 was estimated to 1.6.

In this paper, output characteristics of single-longitudinal-mode Ho: YLF ring laser are firstly investigated in double corner cubes configuration. Single-longitudinal-mode laser output is realized by a faraday rotator and a half-wave plate, and an F-P etalon is inserted into the cavity to realize wavelength tuning. The principle of unidirectional operation of the Ho: YLF ring laser with double corner cubes is firstly analyzed with the method of optic matrix and transition matrix. A highest single-longitudinal-mode power of 733 mW at 2065.68 nm is achieved and the slope efficiency is 12%. The tunable range is about 238 GHz and M2 factor is 1.21. The results show that the single-longitudinal-mode Ho: YLF ring cavity with double corner cubes is a potential way to improve the misalignment sensitivity.

We report the acousto-optically Q-switched Ho:YAG laser with double anti-misalignment corner cubes pumped by a diode-pumped Tm:YLF laser. In the continuous-wave operation of Ho:YAG laser, the maximum s-polarized output power of 3.2 W at 2090.3 nm was obtained under the absorbed pump power of 12.9 W by rotating the fast axis of quarter-wave plate to change the output transmission of laser cavity. The corresponding optical-to-optical conversion efficiency was 24.8% and the slope efficiency was 55.7%. When one of the corner cubes was rotated to 11.8° around vertical direction or 6.7° around horizontal direction, the laser could still operate stably. For the Q-switched operation, the pulse energy of Ho:YAG laser was 9.9 mJ with a pulse width of 53 ns at the repetition rate of 100 Hz, resulting in a peak power of 186.8 kW. The beam quality factor M2 of Ho:YAG laser was 1.3.

In this paper, using two cadmium selenide (CdSe) crystals, we have demonstrated signal-resonant pulsed-nanosecond optical parametric oscillators (OPOs) in linear and rectangular ring cavity designs with output powers of up to 1.03 W at 10.15 μm (idler) and 1.18 W at 11 μm (idler) were obtained, respectively. A Q-switched Ho:YAG laser at 2.09 μm with a pulse repetition frequency of 1 kHz was used as the OPO pump source. At the maximum output power level of the idler at 10.15 μm, the corresponding slope efficiency and optical conversion efficiency were 5.22% and 2.33%, respectively, with a spatial beam quality of M2

A CdSe optical parametric oscillator (OPO) was demonstrated to operate at 12.07 µm with a maximum output power of 170 mW at a pulse repetition frequency of 1.2 kHz pumped at 2.09 µm with 14.64 W from an acousto-optic Q-switched Ho:YAG laser. To the best of our knowledge, 12.07 µm is the longest wavelength obtained with a 2-μm laser-pumped CdSe OPO. Besides, the angular tuning curve for type II CdSe was also investigated, and the idler wavelength from the OPO could be tuned from 10.24 to 12.07 µm.

Ho:Lu3Al5O12(LuAG) transparent ceramics are potential 2 μm eye-safe laser materials. Polycrystalline 0.8 at.% Ho:LuAG ceramics with high optical quality were successfully fabricated by solid-state reactive sintering of high-purity oxide powders. The microstructure, the optical transmission, the spectrum characteristic, and the laser performance were investigated in this paper. The average grain size of Ho:LuAG ceramics vacuum sintered at 1830°C for 30 hour is about 14 μm. The in-line transmittance of the sample is measured to be 81.7% and 82.0% at 1000 and 2250 nm, respectively. The absorption and the emission cross sections are calculated to be 0.88 × 10−20 cm2 at 1906 nm and 1.26 × 10−20 cm2 at 2094 nm. Using a thulium-doped yttrium-lithium-fluoride (Tm:YLF) laser with the central wavelength of 1907.5 nm as the pump source, 2.67 W continuous wave (CW) laser operation at 2100.74 nm was obtained with a slope efficiency of 26.5%. The beam quality factor M2 was calculated to be 1.1, which indicated nearly diffraction-limited beam propagation and the laser was the fundamental TEM00 Gaussian mode.

A single-frequency pulsed holmium-doped yttrium lithium fluoride (Ho:YLF) amplifier pumped by a Tm-doped fiber laser was demonstrated. The seed was an injection-seeded Q-switched Ho:YLF laser. The output energy from the single-frequency pulsed amplifier was 24.2 mJ, with a pulse width of 250 ns at a pulse repetition frequency (PRF) of 100 Hz. The energy stability during 30 min was improved to 1% after the single-frequency pulsed Ho:YLF laser was amplified. The line width of the single-frequency pulsed spectrum of the Ho:YLF amplifier was 2.81 MHz. The single-frequency pulsed Ho:YLF amplifier can be applied to differential absorption lidar (DIAL), since its output spectrum is around the P12 CO2 absorption line.

Pumped by a 100 W Q-switched Ho:YAG laser at 2090.7 nm with pulse repetition frequency of 10 kHz, four types of high-power long-wave infrared ZnGeP2 (ZGP) subsequent optical parametric amplifier (OPA) based on optical parametric oscillator (OPO) with different types of phase matching (PM) of ZGP crystals were demonstrated. For the results of 8.2 µm output characteristics at the full incident pump power, Type-II PM ZGP OPO with Type-II PM ZGP OPA had the best M2 of 1.8 and lowest average output power of 9.2 W with the narrowest linewidth of 77 nm, while Type-I PM ZGP OPO with Type-I PM ZGP OPA had the worst M2 of 2.2 and the widest linewidth of 122 nm, and Type-II PM ZGP OPO with Type-I PM ZGP OPA had the highest average output power of 12.6 W, corresponding to overall optical conversion efficiency of 12.6% from Ho to long-wave infrared laser system.

In this paper, we demonstrate 1-kHz-repetition-rate laser ultrasound in carbon-fiber-reinforced plastics (CFRPs). A ZGP master oscillator and power amplifier (MOPA) system was used to generate high-repetition-rate laser radiation in the spectral range 3.2–3.4 μm. At the output wavelength of 3.4 μm, the maximum output energy of the ZGP MOPA system is 5.62 mJ with a pulse width of 24 ns, corresponding to a peak power of approximately 233.9 kW. The ultrasound was generated by the laser converted from 3.2 to 3.4 μm in the graphite/epoxy composite. The maximum ultrasonic signal amplitude in the CFRP sample was 36.2 mV in the condition of thermoelastic excitation at 3.4 μm. Ablation occurred in the CFRP sample when the energy fluence was over 90 mJ/cm2. Compared in different samples, laser-ultrasound generation was influenced by the wavelength of the laser.

We reported an acousto-optic mode-locked Tm:LuAG laser pumped by a 786 nm laser diode and realized continuous-wave mode-locked operation. At the pump power of 8.2 W, the output average power was 335 mW with the wavelength of 2023.2 nm. The pulse width was 240 ps at the pulse repetition frequency of 81.60 MHz, and the beam quality factor M2 was 1.04. The output wavelength was tuned from 2022.6 to 2025.3 nm, corresponding to the output average power of 310 to 353 mW. In addition, the self-mode-locking phenomenon was found.

We describe comparatively cryogenically cooled Tm, Ho: GdVO4 lasers with an emission wavelength of 2.05 μm under continuous wave and pulse operating mode. By varying the transmittance of output couplers to be 0.40 for a continuous wave laser, the maximum output power of 7.4 W was generated with a slope efficiency of 43.3% when the absorbed pump power was increased to 18.7 W. For passively Q-switched lasers, the output characteristics were researched through altering pump mode radius. When the pump mode radius focused into the Tm, Ho: GdVO4 center equaled near 600 μm, the peak power was increased to be the maximum value of 9.9 kW at the absorbed pump power of 11.8 W. The pulse energy of 0.39 mJ was achieved at the same absorbed pump power with repetition of 5.7 kHz.

We demonstrated a high power and good beam quality continuous-wave (CW) Tm:YAP slab laser operating at room temperature. Two fiber-coupled laser diodes were used as pump source, the maximum output power of 105 W at 1936.4 nm was achieved with the total incident pump power of 308 W, corresponding to the slope efficiency and optical-to-optical efficiency were 41.4% and 34.1% with respect to the incident pump power, respectively. At the maximum output power, the beam quality factors M2 were 2.76 and 2.78 in the x and y directions, respectively. Besides, a theoretical model was presented to predict the temperature distribution, thermal induced stress and laser performance of the Tm:YAP slab laser, and the experimental results were consistent with the theoretical simulation results which indicated that this model could simulate hundred-watt-level Tm:YAP lasers well.

We demonstrate a comparative analysis of directly diode-pumped Tm3+-doped all-fibre laser operating at 1908 nm with different structure at fibre end facets. The feedback arising from parasitic oscillations and amplified spontaneous emission can be suppressed by coating an anti-reflection on the forward end facet and cleaving an angle on the backward end facet. 44.1 W laser power on forward end at the pumped power of 120 W was achieved. The forward laser slope efficiency was 39.3%, corresponding to the backward laser slope efficiency of 3.0%. The beam quality factor of M2 was 1.4.

We demonstrate a single-longitudinal-mode Ho3+:YVO4 unidirectional ring laser based on the acousto-optic effect, utilizing the features of the acousto-optical Q switch and half-wave plate to achieve unidirectional operation. The maximum power achieved in the single-longitudinal-mode at 2053.9 nm is 941 mW when the absorbed power is set as 4.4 W, yielding a nearly 50% slope efficiency. The M2 factor is 1.1. The results show that such a technique offers a potentially promising new method for achieving a high power and narrow linewidth 2 μm single-longitudinal-mode laser.

We demonstrate a gain-switched laser pumped by a high energy Ho : YAG laser. The maximum output power of in the spectrum range from to is obtained at a pulse repetition rate of , corresponding to a pulse energy of . With a volume Bragg grating (VBG) for compressing the linewidth, a output power with a narrow linewidth is obtained at . The pulse shapes obtained at different pump energies are also studied and analysed. A minimum pulse width of is achieved at a pump energy of , corresponding to a peak power of .

We present a 2.09 μm single-longitudinal-mode sandwich-type YAG/Ho:YAG/YAG ceramic laser pumped by a Tm-doped fiber laser for the first time. A pair of F-P etalons was used to achieve tunable single-longitudinal-mode operation. The maximum single-longitudinal-mode output power of 530 mW at 2091.4 nm was obtained with an absorbed pump power of 8.06 W, corresponding to an optical conversion efficiency of 6.6% and a slope efficiency of 12.7%. Wavelength tunable was achieved by tuning the angle of etalons and the wavelength could be tuned from 2091.1 nm to 2092.1 nm, corresponding to a tuning frequency of 68 GHz. The M2 factor was measured to be 1.23.

We report a high peak power, narrow linewidth, stable pulsed Ho:GdVO4 amplifier based on thuliumdoped fiber, which produces 6.65 W average output power at 2,048 nm and 56.8 kW peak power with 11.7 ns pulse width at 10 kHz repetition rate. We use a simple Q-switched Ho:GdVO4 laser as a seed laser and a thulium-doped fiber pumped by a 792 nm laser diode as an amplifier. The fiber amplifier provided 6.5 dB gain to the input signal. The spectral linewidth of the Ho:GdVO4 amplifier remains < 0.5 nm with an M2 beam quality of 1.36.

A 1.94 μm Tm-doped fiber laser pumped tunable single-longitudinal-mode Ho:YLF laser with double etalons was reported for the first time. The maximum single-longitudinal-mode output power of 345 mW at 2051.6 nm was achieved at the absorbed pump power of 11.9 W, corresponding to a slope efficiency of 5.5% and an optical conversion efficiency of 2.9%. By regulating the angle of the F–P etalons, the output wavelength of the laser can be tuned from 2051.6 nm to 2063.3 nm. The single-longitude-mode Ho:YLF laser operating at 2 μm can be used as the seed laser source of coherent Doppler lidar, differential absorption lidar and so on.

We report a continuous wave Tm:YAP laser resonantly pumped Ho:YAP laser in CW mode and passive Q-switched mode. Multilayer Cr:ZnS is used as the saturable absorber for the Q-switched operation. The maximum continuous wave output power of 6.36 W at 2118.67 nm was obtained, corresponding to a slope efficiency of 25.2% and the overall optical-to-optical conversion efficiency of 19.8%. The maximum pulse repetition frequency reached 41.25 kHz and the minimum pulse width of 382 ns was obtained at average output power of 5.24 W. Meanwhile, the output beam spatial profile was close to fundamental TEM 00 mode and the beam quality factor M 2 was 1.4.

We demonstrate a compact and efficient passively Q -switched (PQS) Ho:YLF laser pumped by a self-made all-fiber laser. Firstly, we design and make an all-fiber laser operating at 1940 nm with a slope efficiency of 40.6%. Then, the all-fiber laser was used to pump Ho:YLF laser directly. In the CW (continues-wave) operation Ho:YLF laser, the maximum output power was 7.79 W, corresponding to the slope efficiency of 55.2%. Using Cr 2+ :ZnS as the saturable absorber, the average power of 6.03 W was achieved with the slope efficiency of 45.9%. The shortest pulse duration was 15.6 ns and the pulse repetition frequency was 2.3 kHz at the pump power of 20.4 W. The pulse energy was a constant as 2.7 mJ when the pump power exceeded 15 W. The beam quality factor of M 2 was 1.05, indicating nearly diffraction limited beam propagation.

A passively Q-switched Ho:LuAG solid-state laser using a graphene saturable absorber pumped by a continuous-wave diode-pumped Tm:YLF laser was first reported in this letter. Single layer graphene grown by chemical vapor deposition and transferred onto a thin quartz plate was fabricated as the SA. For the continuous-wave mode, a maximum output power of 0.87 W at 2100.7 nm was obtained under the output coupler T = 10%, corresponding to the slope efficiency of 30.8% and the optical conversion efficiency of 18.9%. For the passively Q-switched mode, a stable PQS Ho:LuAG laser under the highest incident pump power of 4.3 W was obtained, corresponding to the maximum average output power, the maximum repetition frequency and the minimum pulse width being 0.37 W, 48.8 kHz and 752.2 ns, respectively. Our results illustrate that graphene can be used well as a saturable absorber in a Ho-doped solid-state laser at 2 μm wavelength.

We have demonstrated an acousto-optical cavity dumping Tm:YAG ceramic laser at a wavelength of 2012.6 nm. The pulses were coupled out of the cavity by the lateral surface when radio frequency was added into the acousto-optical modulator. The minimum pulse width of the cavity dumped Tm:YAG ceramic laser is 31 ns, corresponded with an output power of 180 mW and a repetition rate of 200 kHz. In addition, the unsmooth pulse shape of the cavity dumped Tm:YAG ceramic laser was numerically calculated.

In this Letter, we demonstrate an average output power of 5.12 W at 3–5 µm from a type-I phase-matching B a G a 4 S e 7 (BGSe) optical parametric oscillator (OPO), which is pumped by a 2090 nm Q -switched Ho:YAG laser with pulse repetition frequency of 1 kHz. At maximum output level, the corresponding slope efficiency and optical-to-optical conversion efficiency are 30.0% and 18.3%, respectively. Moreover, under ring cavity conditions, the BGSe OPO produced a 3.04 W mid-infrared laser with high beam quality factors M 2 of 1.47 in the horizontal direction and 1.51 in the vertical direction. Besides, the wavelength-tuning curve for type-I BGSe was also investigated, corresponding to an idler wavelength-tuning range of 4.5–5.3 µm, and the signal light wavelength was 4.5 to 4.1 µm.

In this paper, the thermal lens effect of dual-end-pumped Ho:YAG ceramic laser was studied experimentally and numerically. The thermal lens magnitude of Ho:YAG ceramic was obtained by beam quality inverse method. When the pump power increased from 9 to 88 W and the according pump radius increased from 0.2 to 0.25 mm, the thermal focal lengths in X and Y directions were decreased from 102 to 65 mm and 140 to 68 mm, respectively. Considering of the thermal lens, we further optimized the laser resonator with a concave-convex cavity and the slope efficiency was increased by 11.6 percent compared to the plane-concave cavity.

We firstly demonstrated a tunable 2.1 µm pumped mid-infrared type-II phase-matching B a G a 4 S e 7 (BGSe) optical parametric oscillator (OPO). A signal tuning range of 3.82–3.99 µm was achieved. With a signal light produced by the BGSe OPO serving as seed, the Z n G e P 2 (ZGP) optical parametric amplifier (OPA) was first introduced. A 4.35 W mid-infrared laser was obtained in the novel type-II BGSe OPO with a ZGP OPA system, which was pumped by a 24 W 1 kHz Q -switched Ho:YAG laser. The beam quality factor M 2 of the whole system is ∼ 2.3 , which is over a 50% promotion on the previous M 2 results of single BGSe OPO.

We demonstrate a single-longitudinal-mode Tm:LuAG unidirectional ring laser based on the Faraday effect and its application in measuring the optical homogeneity of Z n G e P 2 (ZGP) crystal. The maximum single-longitudinal-mode power was 511 mW at 2022.4 nm, with a slope efficiency of 9.7%, and the M 2 factors were 1.13 and 1.23 in the x and y directions, respectively. The laser was s polarized with a polarization degree of 30 dB. Also, the optical homogeneity of ZGP crystal was measured by the Mach–Zehnder interference method, which adopts the single-longitudinal-mode laser as the monochrome source. According to the interference fringes, the quantitative calculation or qualitative analysis of the optical homogeneity of ZGP crystal was achieved, which could quickly and conveniently judge the quality of ZGP crystal, and provided high-quality crystals for high-power mid-infrared lasers. To our knowledge, it is the first report of the optical homogeneity measurement of ZGP crystal by a 2 µm single-longitudinal-mode laser.

Using an 8 µm long-wave infrared laser as the fundamental wave, we achieved second-harmonic generation (SHG) and sum-frequency generation simultaneously in A g G a G e 5 S e 12 and obtained a 4 µm laser output. Among them, SHG was achieved in the 173 nm spectral range of the fundamental wave, which was consistent with theoretical calculations. The average power of the obtained 4 µm laser was 41 mW, corresponding to an optical-to-optical conversion efficiency of 3.2%. The measured temperature acceptance bandwidth ( L δ T ) (FWHM) was 50 K·cm; the angular acceptance bandwidth ( L δ θ ) (FWHM) was 13.3 mrad·cm; and the average absorption coefficient in the wavelength range of 0.86–11.30 µm was 0.07 c m − 1 . In addition, the spectral acceptance bandwidth ( L δ λ ) of fundamental wave in A g G a G e 5 S e 12 SHG and the spectral gain bandwidth of frequency downconversion in A g G a G e 5 S e 12 were calculated. In view of the small absorption coefficient, the large temperature acceptance bandwidth, and the large spectral gain bandwidth, we conclude that A g G a G e 5 S e 12 is a suitable nonlinear crystal for high-power short/mid/long-wave infrared lasers and frequency conversions of nanosecond-femtosecond infrared lasers. These results are conducive to the further development of A g G a G e 5 S e 12 lasers.

We report an idler-resonant, continuous-wave (CW) seed injected, optical parametric oscillator (OPO) based on cadmium selenide (CdSe). The CdSe OPO was pumped by a 2.09 µm ns-pulsed laser and injection-seeded by a 2.58 µm CW laser. The idler-resonant oscillator was designed to maximize the optical-to-optical conversion efficiency and optimize the beam quality. The injected seed laser was designed to reduce the pump threshold. With this setup, the average idler output power of 802 mW was obtained corresponding to a pulse energy of 0.8 mJ at the wavelength of 11.01 µm and linewidth (FWHM) of 0.6 cm−1, optical-to-optical conversion efficiency of 4.4%, quantum conversion efficiency of 23.3%, beam quality of M2x = 1.23, M2y = 1.12, and pulse width of 21 ns. In addition, by turning the angle of the CdSe, wavelength tuning of 10.55-11.98 µm was achieved.

We demonstrated a high-power long-wave infrared optical parametric oscillator at 9.8 µm based on a type-I phase-matching Z n G e P 2 crystal. By using a Q -switched 2091 nm Ho:YAG laser with pulse repetition frequency of 10 kHz as the pump source, the maximum average output power of 3.51 W at 9.8 µm was achieved with incident pump power of 90 W, corresponding to a slope efficiency of 4.81% and conversion efficiency at maximum pump power of 3.9%. The pulse width of 19.6 ns and linewidth of 142 nm were obtained at maximum output level. In addition, the beam quality factor M 2 was measured to be ∼ 2.2 .

We describe a pulsed Ho:YAG laser with double anti-misalignment corner cubes that uses an RbTiOPO4 crystal as the electro-optic Q-switch. Two polarizers coated with high reflectivity coatings for the s-polarized light at the laser wavelength were employed to achieve linearly polarized laser output. The maximum s-polarized output power of 2.95 W at 2091.3 nm was obtained under the absorbed pump power of 12.9 W by increasing the voltage applied on RbTiOPO4 electro-optic crystal to 1000 V. The corresponding optical-to-optical conversion efficiency was 22.9% and the slope efficiency was 67.9%. For the Q-switched operation, the pulse energy of Ho:YAG laser was 7.8 mJ with a pulse width of 57 ns at the repetition rate of 100 Hz, resulting in a peak power of 136.8 kW. The beam quality factor M2 of Ho:YAG laser was 1.33.

We demonstrated a first continuous-wave and acousto-optical Q-switched Ho:YAP laser pumped by fiber-coupled laser diode at 1.91 µm. With a dual-end wing-pumping scheme, a maximum continuous-wave output power of 10.5 W at 2.1 µm and a slope efficiency of 53.2% were obtained when the incident LD power was 25.6 W, while diode-to-Ho conversion efficiency reached up to 41.0%. The Q-switched Ho:YAP laser was investigated for different pulse repetition frequencies from 3 to 20 kHz. The maximum average output power of 9.8 W and maximum pulse energy of 2.7 mJ were achieved at pulse repetition frequencies of 20 and 3 kHz, respectively. In addition, we demonstrated an efficient mid-infrared laser based on a diode-Ho-ZGP architecture for the first time. With a pulse repetition frequency of 3 kHz and an incident Ho pump power of 8.2 W, the average output power of 4.8 W and slope efficiency of 61.0% were reached in mid-infrared ZGP-OPO.

We demonstrated a high power acousto-optical Q-switched Ho:YAG ceramic laser operating at 2090.5 nm that was pumped at 1908 nm by a Tm:YLF laser. A maximum continuous wave power of 22.6 W was obtained, which corresponds to a slope efficiency of 50.6% and an optical-to-optical efficiency of 47.6% with respect to the absorbed pump power. For the Q-switched mode, to our best knowledge, the maximum average output power of 21.2 W was achieved with a minimum pulse width of 20 ns at a pulse repetition frequency of 10 kHz, corresponding to an energy of 2.12 mJ per pulse and a peak power of 106 kW.

We report a monolithic Tm:YLF micro laser in this Letter. In order to improve the relaxation oscillation of the laser, both ends of the crystal are coated, making the Tm:YLF crystal itself a resonant cavity. The micro laser is pumped by a 792 nm laser diode operated in the continuous wave (CW) mode. We obtain maximum output powers of 7.78 and 10.4 W at the total incident power of 43.6 W with focus lenses of 37.5 and 40 mm, respectively, corresponding to the slope efficiencies of 25.6% and 40.0% and the optical–optical conversion efficiencies of 17.8% and 23.8%. It is clear that the amplitude of the relaxation oscillation is smaller and the beam quality is better with the focus length of 37.5 mm; however, the laser with the focus length of 40 mm produces a higher output power and a more stable wavelength centering at 1878.44 nm.

We demonstrate a diode-pump Tm3+-doped all-fiber laser operating at 1908 nm based on a master oscillator power amplifier (MOPA) configuration. In our work, 152 W of laser output power is generated by a total incident pump power of 434 W at 790 nm, corresponding to the total optical efficiency of 35%. The laser wavelength is 1908.29 nm. To the best of our knowledge, it is the highest output power reached around 1908 nm with such a narrow linewidth of 0.18 nm based on a MOPA configuration.

Actively mode-locked Ho:LuAG laser pumped by a 1.91-μm Tm3+ fiber laser was demonstrated. To our best knowledge, it was the first time to report an actively mode-locked Ho:LuAG laser. The maximum output power of 2.7 W at 2010.4 nm in continuous-wave mode-locked regime was obtained at the maximum incident pump power of 11.4 W. The mode-locked pulse width of 333.4 ps was obtained at a pulse repetition frequency of 82.48 MHz with the same incident pump power of 11.4 W, corresponding to single-pulse energy of 32.7 nJ. Furthermore, the M 2 factor of the Ho:LuAG laser was calculated to be 1.1.

A high-power single-longitudinal-mode Ho:YAG laser operating at 2090.8 nm was demonstrated by using a dual-crystal, double-pass MOPA architecture. 6.2 W single-longitudinal-mode laser was extracted from the amplifier at the pump power of 22 W combined with around 23 mW injected seed laser, corresponding to an optical-to-optical efficiency of 28.2 % and a slope efficiency of 36.2 % for the double-pass Ho:YAG MOPA laser system. The maximum small-signal gain of 26.2 dB was obtained with around 10 mW input seed laser. The beam quality factor was measured as M2 ~ 1.27.

We have demonstrated a high repetition frequency passively Q-switched Ho:YVO 4 laser with a Cr 2+ :ZnS saturable absorber pumped by a 1.94 μm Tm-fiber laser, for the first time to our knowledge, in this Letter. The maximum average output power of 8.1 W was achieved at the absorbed pump power of 30.4 W, corresponding to the minimum pulse width of 161.6 ns, pulse energy of 70.3 μJ and pulse repetition frequency of 114.6 kHz. In addition, the laser had beam quality factor of M x 2 ∼ 1.15 and M y 2 ∼ 1.09 at the output power of 5 W.

We demonstrated a high-power dual-end-pumped passively Q-switched Ho:YAG ceramic laser with a Cr2+:ZnS saturable absorber (SA). The influence of the beam diameter on SA on the Q-switched laser performance was investigated. Up to 30.3 W average output power was obtained, to our best knowledge, which is the highest average output power obtained in a Ho-doped passively Q-switched laser. The maximum pulse energy and peak power of 0.94 mJ and 33.5 kW were achieved, when the Cr2+:ZnS SA was placed far from the laser beam waist, corresponding to a pulse width of 28 ns and a pulse repetition frequency of 28.8 kHz. In addition, we achieved the highest output power of 40.4 W from continuous-wave Ho:YAG ceramic laser.

Continuous-wave Tm:YLF laser with two slab crystals was double end pumped by four fiber-coupled laser diodes at room temperature. A maximum continuous wave output power of 108 W for the slab Tm:YLF laser was generated, corresponding to a slope efficiency of 39.0 % and an optical-to-optical conversion efficiency of 35.5 % with respect to the incident pump power. The laser operated at 1,908.1 nm with a beam quality factor of M 2 ~ 2.9 at the highest output power.

In this Letter, we demonstrate a diode-pumped electro-optical cavity-dumped Tm:YAP laser for the first time to our knowledge. A pulse width of 7.1 ns is achieved at a wavelength of 1996.9 nm. A maximum output power of 3.02 W is obtained with a pump power of 58.8 W at a repetition rate of 100 kHz and a high-voltage time of 1000 ns, corresponding to an overall optical-to-optical conversion efficiency of 5.2%. In addition, we study the effect of repetition rate and high-voltage time on the output power characteristics of a cavity-dumped Tm:YAP laser.

A diode-end-pumped tunable twisted-mode cavity Tm, Ho:YAG laser with single-longitudinal-mode (SLM) operation is demonstrated in this Letter. The maximal SLM output power is 106 mW with a slope efficiency of 4.86%. The wavelength can be changed from 2090.38 to 2097.32 nm by tuning the angle of an etalon.