Thermal-birefringence-induced depolarization in a 450 W Ho:YAG MOPA system.

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.

113 W Ho:YLF oscillator with good beam quality efficiently pumped by a Tm:YAP laser.

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.

High-power actively Q-switched Ho-doped gadolinium tantalate laser.

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.

Tm3+: Bi4Si3O12 crystal as a promising laser material near 2 µm: growth, spectroscopic properties and laser performance.

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 of 3F4 upper 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.

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.

Design and synthesis of novel substituted benzyl pyrrolopyrimidine derivatives as selective BTK inhibitors for treating mantle cell lymphoma.

Ibrutinib, a potent irreversible Bruton's tyrosine kinase (BTK) inhibitor, was approved by the FDA for treating mantle cell lymphoma (MCL). Although ibrutinib exhibited excellent antitumor activity, it was associated with certain adverse reactions, with off-target effects against EGFR, Itk and Src family kinases. Our studies yielded a novel series of substituted benzyl pyrrolopyrimidine derivatives capable of potent inhibition of BTK. Compared with ibrutinib, compound 15c exhibited potent BTK inhibitory activity and enhanced antiproliferative activity, a 12-24-fold increase, against MCL cell lines, with IC50 values lower than 1 µM. Low micromolar doses of 15c inhibited the BCR signaling pathway and strongly induced the apoptosis of Z138 cells. Ibrutinib and 15c induced autophagy in a dose-dependent manner in Z138 cells. Moreover, compound 15c induced the production of reactive oxygen species (ROS), which may be a reason for its potent antiproliferative activity. Importantly, compound 15c showed greater BTK selectivity than ibrutinib, indicating a potentially safer treatment of MCL.

Passively Q-switched Tm:YAP laser with a lead zirconate titanate saturable absorber.

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.

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.

570†MHz harmonic mode-locking in an all polarization-maintaining Ho-doped fiber laser.

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.

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.

Research on performance improvement technology of a BaGa4Se7 mid-infrared optical parametric oscillator.

In this Letter, we demonstrate an average output power of 5.12 W at 3-5 µm from a type-I phase-matching BaGa4Se7 (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 M2 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.

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.

High-beam-quality 2.1 µm pumped mid-infrared type-II phase-matching BaGa4Se7 optical parametric oscillator with a ZnGeP2 amplifier.

We firstly demonstrated a tunable 2.1 µm pumped mid-infrared type-II phase-matching BaGa4Se7 (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 ZnGeP2 (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 M2 of the whole system is ∼2.3, which is over a 50% promotion on the previous M2 results of single BGSe OPO.

3.5 W long-wave infrared ZnGeP2 optical parametric oscillator at 9.8 µm.

We demonstrated a high-power long-wave infrared optical parametric oscillator at 9.8 µm based on a type-I phase-matching ${{\rm ZnGeP}_2}$ZnGeP2 crystal. By using a ${Q}$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 ${M^2}$M2 was measured to be ${\sim}{2.2}$∼2.2.

Measurement of optical homogeneity of ZnGeP2 crystal using a 2.02 µm single-longitudinal-mode Tm:LuAG ring laser.

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 ZnGeP2 (ZGP) crystal. The maximum single-longitudinal-mode power was 511 mW at 2022.4 nm, with a slope efficiency of 9.7%, and the M2 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.

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.

High efficiency single-longitudinal-mode resonantly-pumped Ho:GdTaO4 laser at 2068nm.

Based on Faraday effect we demonstrate a thulium fiber pumped continuous-wave single-longitudinal-mode laser with a new Ho:GdTaO4 crystal. By inserting a faraday rotator and a half-wave plate into the laser cavity, the single-longitudinal-mode output power of 392 mW at wavelength of 2068.33 nm was obtained in unidirectional Ho:GdTaO4 ring laser, corresponding to a slope efficiency of 60.2% respect to the absorbed pump power. Furthermore, utilizing the Ho:GdTaO4 power amplifier, the maximum single-longitudinal- mode output power of 1.02 W was achieved.

Single-longitudinal-mode Ho:YVO4 MOPA system with a passively Q-switched unidirectional ring oscillator.

A 2052.96 nm single-longitudinal-mode pulsed Ho:YVO4 MOPA system was demonstrated for the first time. The pulsed Ho:YVO4 MOPA system consisted of a unidirectional ring passively Q-switched oscillator and a single-pass amplifier. By inserting an isolator, a half-wave plate and a Cr2+:ZnS plate into the ring Ho:YVO4 oscillator cavity, the single-longitudinal-mode pulsed laser was achieved with an average output power of 1.02 W with pulse width of 910 ns and pulse repetition frequency (PRF) of 67 kHz. Using the residual (non-absorbed) pump power of the oscillator as pump, the single-pass pulsed Ho:YVO4 amplifier obtained an average output power of 1.67 W. The total optical-to-optical efficiency of the pulsed Ho:YVO4 MOPA system was 14.3%. Single-longitudinal-mode pulsed MOPA system based on isolator and Cr2+:ZnS around 2 µm has not been reported yet to the best of our knowledge.

Resonantly pumped high efficiency Ho:GdTaO4 laser: erratum.

An erratum is presented to correct the wrong picture in our paper.