Dual-band switched unidirectional Ho:YLF ring laser with wavelength tunability.

Tunable single-longitudinal-mode (SLM) ring Ho:YLF laser with intra-cavity isolator is investigated for 2.05 µm and 2.06 µm band based on single resonator, which is realized dual-band SLM laser conversion by a polarizer. Up to 548 mW SLM power with beam quality factor M2 of 1.1 is achieved at wavelength of 2064.63 nm, and the corresponding slope efficiency is 26.7%. Wavelength tuning ranges from 2063.91 nm to 2065.71 nm and 2050.65nm to 2053.15nm can be demonstrated. The highest SLM power around P12 and R30 CO2 absorption peak of 2064.41 nm and 2050.96 nm are 540 mW and 500 mW, respectively. The power instability within 30 minutes is around 0.14%. As we know, dual-band switched Ho:YLF laser operation at SLM with wavelength tunability is reported for the first time for the potential application of CO2 differential absorption lidar.

161 W middle infrared ZnGeP2 MOPA system pumped by 300 W-class Ho:YAG MOPA system.

We demonstrated a high-power Q-switched two-stage Ho:YAG master-oscillator power-amplifier (MOPA) system dual-end pumped by Tm:YLF lasers. A new method was introduced by rotating and swapping spatial axial directions of pump beams to improve the beam quality of the Ho:YAG oscillator and first-stage amplifier. Two parallel second-stage Ho:YAG amplifiers were employed to output high power. A total maximum average output power of 332 W at 2091 nm with pulse repetition frequency of 20 kHz was achieved. Then a ZnGeP2 MOPA system was demonstrated using the Ho:YAG MOPA as the pump source. A maximum average output power of 161 W at 3-5 µm was obtained with 290 W incident Ho pump power, corresponding to beam quality factors M2 of 3.42 and 3.83 for horizontal and vertical directions, respectively.

Tunable twisted-mode Ho:YAG laser at continuous-wave and pulsed operation.

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.

11 µm, high beam quality idler-resonant CdSe optical parametric oscillator with continuous-wave injection-seeded at 2.58 µm.

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.

Continuously tunable high-power single-longitudinal-mode Ho:YLF laser around the P12 CO2 absorption line.

A continuously tuned single-longitudinal-mode (SLM) Ho:YLF laser around the P12 CO2 absorption line was demonstrated. The continuous tuning range of 5.75 pm within one longitudinal mode spacing of the Ho:YLF resonator was realized by using a novel intra-cavity wedge prism device fixed on the piezoelectric transducer (PZT) as the cavity length controller. High SLM power of 11.3 W was obtained from a Ho:YLF amplifier with three crystals at the pump power of 31.8 W and master oscillator power of 323 mW, corresponding to a gain of 15.44 dB and an optical-to-optical conversion efficiency of 34.5%. The beam quality factors M2 of the SLM Ho:YLF amplifier in the x and y directions were estimated to be 1.04 and 1.05, respectively.

1 W, 10.1 µm, CdSe optical parametric oscillator with continuous-wave seed injection.

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 $M_x^2={2.25}$Mx2=2.25, $M_y^2={2.12}$My2=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.

Broadband second-harmonic and sum-frequency generation with a long-wave infrared laser in AgGaGe5Se12.

Using an 8 µm long-wave infrared laser as the fundamental wave, we achieved second-harmonic generation (SHG) and sum-frequency generation simultaneously in AgGaGe5Se12 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 (LδT) (FWHM) was 50 K·cm; the angular acceptance bandwidth (Lδθ) (FWHM) was 13.3 mrad·cm; and the average absorption coefficient in the wavelength range of 0.86-11.30 µm was 0.07cm-1. In addition, the spectral acceptance bandwidth (Lδλ) of fundamental wave in AgGaGe5Se12 SHG and the spectral gain bandwidth of frequency downconversion in AgGaGe5Se12 were calculated. In view of the small absorption coefficient, the large temperature acceptance bandwidth, and the large spectral gain bandwidth, we conclude that AgGaGe5Se12 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 AgGaGe5Se12 lasers.

Dual-wavelength injection-seeded Q-switched Ho:YLF laser for CO2 differential absorption lidar application.

A dual-wavelength injection-seeded Q-switched Ho:YLF laser for CO2 differential absorption lidar pumped by the thulium-doped fiber laser was demonstrated. The single-frequency Ho:YLF seed laser was achieved by a pair of highly anti-misalignment corner cubes. The wavelength of an online seed laser was corrected to the P12 CO2 absorption line at 2064.414 nm by using a CO2 absorption cell. At the pulse repetition frequency of 100 Hz, the single-frequency pulsed energy was 16.1 mJ with the pulse width of 221.3 ns after a single-pass amplifier. The full width at half-maximum of a single-frequency pulsed spectrum was about 3.87 MHz, and the fluctuation of center frequency was 2.8 MHz in 30 min.

High repetition rate 102 W middle infrared ZnGeP2 master oscillator power amplifier system with thermal lens compensation.

We demonstrate a 102 W middle infrared ZnGeP2 (ZGP) optical parametric amplifier (OPA) pumped by a 2097-nm Q-switched Ho:YAG laser at a pulse repetition frequency of 10 kHz. The seed middle infrared laser was produced by a ZGP optical parametric oscillator. Its average power was 28.4 W pumped by a 50 W 2097-nm laser. By thermal lens compensation, the beam factor M2 reduced from 3.1 to 2.1. When the incident Ho pump power was 120 W, the middle infrared ZGP OPA yielded the maximum average output power of 102 W and slope efficiency of 61.7%. The overall optical conversion efficiency of 60% from Ho to middle infrared was obtained for the whole middle infrared laser system. In addition, at the maximum average output power, the beam quality factors of the middle infrared ZGP OPA were measured to be about 2.7 and 2.8 for horizontal and vertical directions, respectively.

110.4 mJ, 1 kHz repetition rate, Ho:YAG master oscillator power amplifier.

We reported a high-energy, high-pulse-repetition-frequency Ho:YAG master oscillator and power amplifier (MOPA), which was resonantly dual-end pumped by Tm:YLF lasers at room temperature. At a pulse repetition frequency of 1 kHz, the Ho:YAG MOPA laser system produced a maximum pulse energy of 110.4 mJ with a 28 ns pulse width, corresponding to a peak power of approximately 3.94 MW. The output wavelength of the Ho:YAG MOPA laser system was 2090.9 nm. In addition, a beam quality factor M2 of about 1.7 was achieved at maximum output level.

11.4 W long-wave infrared source based on ZnGeP2 optical parametric amplifier.

In this paper we present a high power long-wave infrared ZnGeP2 (ZGP) optical parametric amplifier (OPA) pumped by a 2097-nm Q-switched Ho:YAG laser with pulse repetition frequency of 20 kHz. When the incident Ho pump power was 116.0 W, the maximum average output power of 11.4 W at 8.3 µm was achieved in the ZGP OPA. The optical conversion efficiency from Ho to long-wave infrared was about 9.8%. The ZGP OPA produced 30.4 ns long-wave infrared laser pulse. The beam quality factor (M2) of ZGP OPA was measured to be about 2.9 at the maximum average output power.

1.5 W high efficiency and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect.

We demonstrated an efficient and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect for application to measure atmospheric carbon dioxide (CO2). Single-longitudinal-mode power at 2051.65 nm achieved 528 mW with the slope efficiency of 39.5% and the M2 factor of 1.07, and the tunable range of about 178 GHz was obtained by inserting a Fabry-Perot (F-P) etalon with the thickness of 0.5 mm. In addition, the maximum single-longitudinal-mode power reached 1.5 W with the injected power of 528 mW at 2051.65 nm by master oscillator power amplifier (MOPA) technique. High efficiency and tunable single-longitudinal-mode based on Faraday effect around 2 µm has not been reported yet to the best of our knowledge.

Diode-pumped tape casting planar waveguide YAG/Tm:YAG/YAG ceramic laser at 2013.76 nm.

We demonstrated the efficient guided laser action in a diode-pumped YAG/Tm:YAG/YAG ceramic planar waveguide fabricated by nonaqueous tape casting and solid-state reactive sintering technology for the first time, to the best of our knowledge. In the experiment, a maximum output power of 173 mW at a center wavelength of 2013.76 nm was obtained under an incident pump power of 10.3 W, corresponding to a slope efficiency of 3.0%. The beam quality M2=1.5 in a horizontal direction was measured at the highest output power.

Electro-optically cavity-dumped 3 ns Tm:LuAG laser.

It is reported in this paper that a cavity-dumped electro-optically Q-switched Tm:LuAG oscillator offers a unique combination of high power, constant short pulse duration, and high repetition rate at a wavelength of 2012.7 nm. The constant short pulse durations of 3 ns were achieved by the cavity-dumped technology at different repetition rates from 60 to 100 kHz. An average power of 1.22 W and a peak power of 4.1 kW were obtained at a repetition rate of 100 kHz and an incident pump power of 42.3 W, corresponding to the slope efficiency of 6% and beam quality factor of M2∼1.4. In addition, the accumulation time of intracavity photons from 500 to 1000 ns was studied for the performance of the output characteristic.

Diode-end-pumped single-longitudinal-mode Er:LuAG laser with intracavity etalons at 1.6 µm.

We present a laser-diode-pumped 1.6 µm single-longitudinal-mode Er:LuAG laser. The intracavity etalons were used as mode selectors for the single-longitudinal-mode operation. The maximum single-longitudinal-mode output power was 153 mW with the wavelength of 1650.2 nm at the pump power of 9.18 W, corresponding to a slope efficiency of 4.3%. The M2 factor was measured to be 1.07. In addition, by changing the thickness of the etalons, a maximum single-longitudinal-mode output power of 114 mW at 1628.1 nm with a slope efficiency of 3.5% was also achieved. To our knowledge, the intracavity etalons Er:LuAG laser operated at single-longitudinal-mode is being reported for the first time.

Acousto-optically cavity dumped Tm:YAG laser with 54 ns pulses at 200 kHz repetition rate.

In this paper, a cavity dumped Tm:YAG laser was obtained for the first time, whose output pulse width was constant at 54 ns. Maximum repetition rate was 200 kHz, and wavelength was 2013 nm. Its average output power was 595 mW. The laser cavity length was 208 mm with an inserted acousto-optic modulator. Pulses were coupled out of the lateral surface of the cavity when Radio Frequency was added into the modulator. And lens was used to compensate the thermal focal length of Tm:YAG crystal. Numerical calculation of pulse was done.

A 41-W ZnGeP2 optical parametric oscillator pumped by a Q-switched Ho:YAG laser.

We reported a high-power ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a Q-switched Ho:YAG laser. The maximum output power of the ZGP OPO was 41.2 W at 107.0 W incident Ho pump power, corresponding to a slope efficiency of 44.6%. The ZGP OPO produced 16-ns mid-IR pulse laser in the 3.74-3.98 µm and 4.38-4.76 µm spectral regions simultaneously. The beam quality was measured to be M²<4.37. The continuous wave maximum average output power of the Ho:YAG laser was 128 W, corresponding to a slope efficiency of 65.8%.

Diode-pumped acousto-optical cavity-dumped Tm:YAP laser at 1989 nm.

In this paper, we demonstrated a diode-pumped acousto-optical cavity-dumped Tm:YAP laser for the first time. The pulses were coupled out of the lateral surface of the cavity when radio frequency signal was loaded on the acousto-optical modulator. A maximum output power of 1.28 W was obtained with pump power of 40.3 W at a repetition rate of 200 kHz, corresponding to a slope efficiency of 4.7%. The output pulse width of the cavity-dumped Tm:YAP laser was constant at 43 ns, and the wavelength was 1989.8 nm.

Cr:ZnS saturable absorber passively Q-switched Tm,Ho:GdVO4 laser.

A passively Q-switched Tm,Ho:GdVO4 laser operating at cryogenic temperature with a Cr(2+):ZnS saturable absorber pumped with continuous wave LDs was demonstrated. The performance of the laser was investigated through changing the distance between Cr(2+):ZnS and output coupler. The maximum pulse energy of 70.5 µJ was obtained at 10 W input power. The maximum average output power of PQS laser was up to 3.2 W at the pump power of 22.8 W, corresponding to CW output power of 7.4 W, pulse repetition frequency of 52 kHz, and a pulse width of 389 ns. The M(2) factor measured by the traveling knife-edge method was ~1.1 in x and y directions with near-diffraction limited beam quality.

103 W in-band dual-end-pumped Ho:YAG laser.

An efficient 2 µm in-band pumped Ho:YAG laser was demonstrated. The resonator involves two Ho:YAG crystals, each of which was dual-end-pumped by two orthogonally polarized diode-pumped Tm:YLF lasers. The maximum continuous wave output power of 103 W was achieved, corresponding to a slope efficiency of 67.8% with respect to the incident pump power and an optical-to-optical conversion efficiency of 63.5%. Under Q-switched mode, we obtained 101 W laser output at 30 kHz, corresponding to a slope efficiency of 66.2%. The beam quality or M2 factor was found to be less than 2.