We proposed a Ho:GdVO4 laser operating at 2.05 mu m in-band directly pumped by the 1.94 mu m fiber-coupled laser diode, which electro-optically Q-switched by an LGS(La3Ga5SiO14) crystal. Adopting 1.0 at.%-doped Ho:GdVO4 crystal as the gain medium, a maximum output power of 6.5 W at 2047.9 nm with the absorbed pump power of 28 W was obtained in the continuous-wave mode, corresponding to a slope efficiency of 37.6 %. At a pulse repetition frequency of 1 kHz, the highest pulse energy of 3.25 mJ with a pulse width of 4.2 ns was achieved, corresponding to a peak power of 773.8 kW. In addition, the beam quality factor M2 was measured to be 1.9 at the maximum output level by the 90/10 knife-edge method. TEM00 propagation has been verified by a camera. To the best of our knowledge, this is the first demonstration of high peak power electro-optically Q-switched Ho: GdVO4 laser directly pumped by the 1.94 mu m laser diode.

In this paper, a ring cavity of Er:YAG laser with a single corner cube prism is investigated. Due to the depolarization effect of the corner cube, the tunable output coupling ratio was 0.25% to 72.67% by changing the angle of the lambda/4 plate according to the calculation results of Jones matrix. An experiment for checking the anti-detuning performances of the single corner cube cavity was also carried out. The results indicated that the output power was stable at the rotating angles of <3.06 deg and 1.637 deg along the vertical and horizontal directions, respectively. Under continuous wave operation, a 5.4 W vertically-polarized laser of 1645.1 nm was acquired through double polarizers with the beam quality factors (M-2) of 1.17 in the x direction and 1.42 in the y direction, and the slope efficiency was 45.47%. Additionally, under the condition of a pulse-repetition-frequency (PRF) of 200 Hz, the pump power of 29.04W, a maximum pulse energy of 2.2 mJ was realized, and the minimum pulse width was 86 ns, leading to a peak power of 25.58 KW. (c) 2023 Society of Photo-Optical Instrumentation Engineers (SPIE)

This paper demonstrates a single-frequency injection-seeded laser with a Q-switched Ho:YAG laser consisting of two corner cube reflectors. As a seed laser, the Ho:YAG NPRO has an available output power of 1.8 W and operates at 2090.6964 nm. The single-frequency pulse energy obtained in the case of injection-seeded is 6.8 mJ, the pulse width is 166 ns, and the Q-switched Ho:YAG laser operates at a repetition rate of 100 Hz. The Ho:YAG single-pass amplifier scales single-frequency energy from 6.8 mJ to 32.3 mJ. The pulsed spectrum has a half-width of 2.84 MHz. The Ho:YAG amplifier has a beam quality of 1.1 and 1.17 in the x and y axes.

We demonstrate a continuously operating Er:YAG single-longitudinal-mode laser and its amplifier with a corner cube retroreflector based on the Faraday effect. A maximum power of 1.02 W, the central wavelength of 1645.46 nm, Er:YAG single-longitudinal-mode laser with a line-width of 204 kHz has been realized. The slope efficiency is 9.38% and the beam quality factors M2 are 1.16, 1.05 in the x and y directions. Additionally, the singlelongitudinal-mode laser is amplified to 1.86 W by the double-pass amplifier. The results indicate that the unidirectional operation ring laser in combination with the corner cube prism provides a 1.6 & mu;m continuous-wave single-longitudinal-mode laser with high-power and stability.

In this letter, a non-critical phase-matching (NCPM) BaGa4Se7 (BGSe) optical parametric oscillator (OPO) was demonstrated with a home-made acousto-optic (AO) Q-switched Ho:YLF laser as the pump source. The idler wavelength tunability was recorded to be 9393.3 to 10627.4 nm with BGSe crystal temperature varying from 45 to 5 Celsius (C), corresponding to an average wavelength adjustment of 30.85 nm/C. Up to 200 mW of idler average output power at 10219 nm was obtained with pulse repetition frequency (PRF) at 200 Hz, the slope efficiency and pump-to-idler efficiency are 8.04 % and 5 %, respectively. In addition, in the angle tuning experiment, a refined Sellmeier Equation (S-E) was derived based on the discrepancy between the experimental data and the theoretical calculations based on the existing S-Es. However, it was found that the deviations between experimental measurement data and theoretical calculations in NCPM experiment were still too large to be ignored after using the refined S-E. Probably, the phenomenon was caused by the thermo-optic dispersion formula dn/dT provided by references were not precise enough for describing NCPM BGSe crystal in waveband similar to 10 mu m.

In this paper, we demonstrate a langasite (LGS) electro-optic Ho:YAG cavity-dumped laser that suppresses the gain dependence of pulse duration in Q-switched lasers. A constant pulse duration of 7.2 ns was achieved at a repetition rate of 100 kHz. Benefiting from the LGS crystal has no significant reverse piezoelectric ring effect and thermally induced depolarization, a stable pulse train was achieved at an output power of 43 W. For the first time, the application of cavity-dumped laser in mid-infrared (mid-IR) ZnGeP2 (ZGP) optical parametric oscillator (OPO) has been realized, providing a reliable way to achieve high repetition rates and short nanosecond pulse times for high-power mid-infrared ZGP OPOs. The average output power was 15 W, corresponding to a pulse duration of 4.9 ns and a repetition rate of 100 kHz.

In this paper we report on a continuous-wave and electro-optically (EO) Q-switched Ho-doped lutetium vanadate (Ho:LuVO4) laser dual end-pumped by two laser diodes at 1.94 mu m. Under continuous-wave regime, a maximum output power of 18.8 W at 2058.1 nm was achieved with absorbed pump power of 44.7 W, corresponding to a slope efficiency of 54.1 % with respect to the absorbed pump power. By using a langasite (La3Ga5SiO14, LGS) crystal as the EO Q-switch, at a pulse repetition frequency of 3 kHz, the EO Q-switched Ho:LuVO4 laser produced a maximum pulse energy of 3.2 mJ and a minimum pulse width of 8.9 ns, resulting in a peak power of 358.8 kW.

We demonstrated an efficient, high-power Ho:YAG master-oscillator power amplifier (MOPA) system and investigated its thermal-birefringence-induced depolarization. The maximum output power was 450 W with a depolarized power of 32.1 W and depolarization of 0.071 via three power amplifiers. To our knowledge, this is the highest average power generated from a Ho:YAG MOPA system. In theory, a simplified model was built to calculate the depolarization in the amplifier, and the theoretical results agreed with the actual value well. Moreover, the overall optical-to-optical efficiency of the MOPA system was near 60%, and the beam quality M2 factors of s-polarized laser were measured to be ∼ 1.8 at 400 W. In pulse operation, the per pulse energy was ∼ 11 mJ at the pulse repetition frequency of 40 kHz with the corresponding peak power of 220 kW.

High-energy linearly polarized Q-switched lasers are realized using a 1940 nm Tm-doped fiber laser to in-band pump a compact U-type Ho:YLF oscillator. When absorbing 44 W pump power, the laser output power under continuous-wave (cw) operation is 9.7 W, and the center laser wavelength is 2051.7 nm. Corresponding to 22% optical-to-optical conversion efficiency and up to 77.9% slope efficiency. The Q-switched Ho:YLF oscillator has a maximum single pulse energy of 39.6 mJ under a repetition rates of 100 Hz and absorption of 42.4 W pumping, and the pulsewidth is 47 ns. The beam quality M 2 factors in the horizontal and vertical directions are 1.17 and 1.07, respectively.

We demonstrated a high optical-to-optical efficiency, compact Ho:YLF MOPA system operating at room tem-perature. The pump source was a 1937.8 nm linearly polarized Tm:YAP slab laser. At the PRF of 10 kHz, the maximum average output power of the oscillator and the amplifier were 51.1 W and 61.1 W, with the incident pump power of 97.3 W, respectively. The optical-to-optical efficiency of the MOPA system was up to 62.8%. As far as we know, it is the most efficient Ho:YLF MOPA system with a compact structure. The highest per pulse energy was 6.1 mJ with a pulse width of 22.5 ns, corresponding to a peak power of 265.2 kW. Besides, the beam quality was excellent with the M-2 factor of similar to 1.1.

For the first time, to the best of our knowledge, we demonstrate an efficient continuous-wave Ho : LSO laser dual-end-pumped by a fiber-coupled laser diode at 1.94 μm. We show that the elaborated Ho : LSO laser produces 5.8 W output power at 2106.55 nm, corresponding to a slope efficiency of 37.7% with respect to the absorbed pump power. In addition, the beam quality factors M2 are 1.5 and 1.7 in the horizontal and vertical directions, respectively, at the maximum output power.

A Ho3+:BSO crystal was grown using the Bridgman method. The 2.1 μm CW laser of the crystal was demonstrated.

We demonstrated a high-peak-power acousto-optically Q-switched Ho:GdVO4 laser pumped by a linear polarized Tm:YAP solid laser. Adopting 0.5 at. % Ho:GdVO4 crystals as the gain medium, the maximum continuous-wave output power was 16.6 W at 2048.5 nm with the incident pump power of 97.3 W, corresponding to a slope efficiency of 51.5%. When the pulse repetition frequency was 1 kHz, the maximum pulse energy of 10.7 mJ with a pulse width of 6.9 ns was obtained, corresponding to a peak power of 1.5 MW. To the best of our knowledge, this is the first demonstration of a Q-switched Ho:GdVO4 laser with pulse energy exceeding 10 mJ, and the peak power reached a million-watt level.

A 2047.9-nm acousto-optically Q-switched Ho:GdVO4 laser pumped by two laser diodes at 1.94 mu m was demonstrated in this paper. By using a 1.0 at.%-doped Ho:GdVO4 crystal as the gain medium, a maximum output power of 8.08 W was obtained with the absorbed pump power of 28.12 W in the continuous-wave mode, corresponding to a slope efficiency of 45.7 %. In Q-switch mode, the highest pulse energy of 1.29 mJ with a pulse width of 4.3 ns was achieved at pulse repetition frequency of 5 kHz, corresponding to a peak power of 300.5 kW. Moreover, the beam quality factor (M-2) of 1.6 was estimated by the 90/10 knife-edge method at maximum output level. As far as we know, this is first operation of acousto-optically Q-switched Ho:GdVO4 laser directly pumped by laser diode.

We demonstrate a linearly polarized Tm:YAP slab laser pumped by fiber-coupled laser diodes. The maximum output power is 202 W at 1937.5 nm with a slope efficiency of 47.4% and an optical-to-optical efficiency of 35.6%. The beam quality M2 factors are 10.1 and 8.33 in x and y directions, respectively. Using the Tm:YAP laser as the pump source, the maximum power of the Ho:YLF oscillator is 113 W at 2063.3 nm, corresponding to an optical-to-optical efficiency of 55.9%. In addition, the beam quality factors of the Ho:YLF laser are ∼1.5 at maximum power.

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.

In this paper, we present the acousto-optical (AO) Q-switched performance of a holmium (Ho):gadolinium tantalate (GdTaO4) (Ho:GTO) laser pumped by a thulium (Tm)-fiber laser emitting at 1.94 µm. In the efficient continuous wave (CW) regime, a maximum output power of 30.5 W at 2068.8 nm was achieved, corresponding to a slope efficiency of 74.9% with respect to the absorbed pump power. In the Q-switching regime, pulse energies of 2.4 mJ, 1.2 mJ, and 0.9 mJ were obtained with pulse repetition frequencies of 10 kHz, 20 kHz, and 30 kHz, respectively. The minimum pulse widths were 18 ns, 23 ns, and 26 ns, corresponding to peak powers of approximately 133.3 kW, 52.2 kW, and 34.6 kW, respectively.

In the paper, we prepare a lead zirconate titanate saturable absorber, which is used to demonstrate a passively Q-switched (PQS) Tm:YAP laser. In the PQS mode, an average output power of 0.81 W and pulse width of 1.69 µs at 175 kHz are obtained at 1991.9 nm with a pump power of 12.76 W, corresponding to an optical-optical conversion efficiency of 6.35%. In addition, the beam quality factors M2 of the PQS Tm:YAP laser in the x and y directions are 1.17 and 1.15, respectively.

We report on the crystal growth, spectroscopic properties and laser performance of Tm3+-doped Bi4Si3O12(BSO) crystal. The crystal was grown by the vertical Bridgeman method. The spectroscopic properties are investigated based on absorption and luminescence spectroscopy. Judd - Ofelt (JO) analysis is performed to calculate the spontaneous emission probabilities, branching ratio and the radiative lifetimes. The absorption spectrum, emission spectrum and gain cross-section spectra of Tm3+: BSO crystal are determined for the 2 μm transition. Luminescence decay kinetic of3F4upper level was analysed in detail. The continuous-wave 2 μm laser with a maximum output power of 650 mW and a slope efficiency of 29.7% is demonstrated for the first time. The beam quality factor (M2) of Tm3+: BSO laser was about 1.03 at the maximum output level.

In this paper, a dispersion solution of rhenium diselenide (ReSe2) was prepared using an ultrasonic decomposition method and prepared for use as a saturable absorber (SA) mirror by spin-coating. The optical characteristics of the ReSe2 SA were characterized to acquire those parameters which were saturated at 2 mu m. A passively mode-locked (PML) Tm:YAG laser with an ReSe2 SA was first demonstrated in an experiment. Under a continuous wave (CW) regime, a 1940-mW output power was achieved at 2013.8 nm with a pump power of 22.4 W. In PML mode, a 320-mW average output power and a 580.5-ps pulse duration at 203.1 MHz were acquired from the PML Tm:YAG laser with an output wavelength of 2012.6 nm, corresponding to a pulse energy of 1.58 nJ and an optical-optical conversion efficiency of 2.2%.