Jinhe Yuan

High-power Cr 2+ :ZnS saturable absorber passively Q-switched Ho:YAG ceramic laser and its application to pumping of a mid-IR OPO

We used the Cr2+:ZnS as a saturable absorber to obtain a passively Q-switched Ho:YAG ceramic laser operating near 2.1 μm. The maximum average output power of 14.8 W and a shortest pulse width of 29 ns were obtained, and to our knowledge, this is the best report for the PQS Ho:YAG ceramic laser. A maximum energy per pulse of 0.6 mJ with a maximum pulse repetition frequency of 24.4 kHz was achieved, which corresponded to a peak power of 20 kW. We first used the PQS laser as the pump source of optical parametric oscillator to obtain the mid-infrared laser. A maximum average output power of 4.4 W was achieved from the ZnGeP2 parametric oscillator, corresponding to a slope efficiency of 49.5% with respect to the incident pump power.

High power, tunable mid-infrared BaGa 4 Se 7 optical parametric oscillator pumped by a 2.1 μm Ho:YAG laser

We, for the first time, demonstrate a tunable mid-infrared BaGa4Se7-based optical parametric oscillator pumped by a acousto-optical Q-switched Ho:YAG laser at 2090.6 nm. Up to 1.55 W of average power was generated in the 3-5 μm range, corresponding to an optical-to-optical conversion efficiency of 14.4% and a slope efficiency of 19.9%. The mid-IR radiation spectra were also seriously researched at different phase-matched angles. The tunable range was 3.49-4.13 μm for the signal, and 5.19-4.34 μm for the idler.

Output characteristics of actively Q-switched Ho:LuVO 4 laser at room temperature

A compact continuous wave (CW) and actively Q-switched (AQS) Ho:LuVO4 laser pumped by a 1.94 μm Tm: YAP laser is demonstrated. The performance of the laser was investigated by changing the output coupler. The maximum output power of 4.1 W at 2058.43 nm in CW regime is obtained at the maximum absorbed pump power of 12.3 W. The minimum pulse width of 29.3 ns was obtained at Pulse Repetition Frequency (PRF) of 20 kHz with the same output coupler corresponding to a peak power of 6.9 kW. The maximal output power is 4.1 W with center wavelength of 2058.43 nm at PRF of 40 kHz, corresponding to slope efficiency of 43.0% with respect to absorbed pump power. The M2 factors measured by the traveling knife-edge method are 1.04 in parallel a-axis and 1.08 in parallel c-axis with diffraction limited beam quality.

Resonantly pumped actively mode-locked Ho:YAG ceramic laser at 2122.1 nm

We discuss what we believe is the first continuous-wave mode-locked Ho:YAG ceramic laser. We produced a mode-locked pulse using an acousto-optic modulator. We used a 1.91 μm Tm-fiber laser as the pump source. At the incident pump power of 11.4 W, we achieved the maximum output power of 1.84 W at 2122.1 nm in a continuous-wave mode-locked regime. We obtained a short-duration pulse of 241.5 ps at a repetition frequency of 82.15 MHz and achieved the beam quality factor M² of 1.2. In addition, the maximum single pulse energy was 22.4 nJ.

Doubly Q-switched Ho:LuAG laser with acoustic-optic modulator and Cr 2+ :ZnS saturable absorber

A doubly Q-switched (DQS) Ho:LuAG laser resonantly pumped by a 1.91-μm laser was first presented with an acoustic-optic modulator (AOM) and a Cr2+:ZnS saturable absorber. A comparison among the active Q-switched (AQS), passively Q-switched (PQS), and DQS laser performances was carried out. The maximum continuous wave (CW) output power of 6 W with the central wavelength of 2100.65 nm was obtained at an incident pump power of 35.2 W. Compared with CW laser, the AQS, PQS, and DQS lasers shared the same central wavelength of 2098.34 nm under the same incident pump power. The central wavelength of the AQS and DQS lasers remained constant with the change of AOM repetition frequency (RF). When the incident pump power was 35.2 W and the AOM RF was 15 kHz, the DQS Ho:LuAG laser at a maximum RF of 2.13 kHz achieved the maximum average output power of 4.95 W. At the AOM RF of 10 kHz, the DQS Ho:LuAG laser achieved the shortest pulse width of 40.4 ns with the highest peak power of 61.5 kW. At an incident pump power of 35.2 W, the PQS Ho:LuAG laser obtained the shortest pulse width of 46.1 ns, corresponding to the RF of 2.25 kHz. Experiment results showed that the pulse width could be compressed effectively with a significant increase of peak power for a 2-μm DQS laser.

10 W mid-IR optical parametric oscillator pumped by a passively Q-switched Ho:YAG ceramic laser

We report on a ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a Cr2+:ZnS saturable absorbed passively Q-switched (PQS) Ho:YAG ceramic laser. The maximum output power of the ZGP OPO was 10 W at a 27.4 W incident PQS Ho:YAG ceramic laser, corresponding to a slope efficiency of 41.3% with respect to the incident pump power. The minimum mid-IR pulse width of 21 ns in 3.8 and 4.6 μm was obtained from the ZGP OPO. The beam quality was measured to be M 2 < 3.22.

Experimental study on the actively Q-switched performance of Ho : LuVO4 laser

Abstract. A compact continuous-wave and actively Q-switched Ho:LuVO4 laser pumped by a 1.94  μm Tm:YAP laser is demonstrated. The maximum output power of 6.7 W at 2058.13 nm in continuous-wave regime is obtained at an absorbed pump power of 17.8 W, corresponding to a slope efficiency of 48.4%. For Q-switched operation, average output power of 6.65 W and pulse width of 22.3 ns are obtained with a repetition frequency of 20 kHz, corresponding to a central wavelength of 2058.13 nm. In addition, different Q-switched pulses at repetition frequencies of 20, 30, 40, 50, and 60 kHz are investigated comparatively.

Repetition-frequency-controllable double Q-switched Ho:LuAG laser with acousto-optic modulator and Cr2+:ZnS saturable absorber

A repetition-frequency-controllable double Q-switched (DQS) Ho:LuAG laser at 2098.34 nm with acousto-optic modulator (AOM) and Cr2+:ZnS saturable absorber (SA) was investigated. The maximum output power of 5.3 W was obtained at the AOM repetition frequency (RF) of 3.72 kHz, corresponding to the slope efficiency of 29.8%. The largest pulse energy of 2.8 mJ with the shortest pulse width of 54.2 ns was observed at the AOM RF of 2.64 kHz. Compared with the passively Q-switched Ho: LuAG laser, the DQS Ho: LuAG laser could generate shorter pulse width and larger pulse energy, and its RF could be controlled by the AOM RF

Investigation of high-power diode-end-pumped Tm:YLF laser in slab geometry

Comparative investigations of high-power diode-end-pumped Tm:YLF laser with a-cut and c-cut slab crystals were demonstrated. A maximum output power of 87.5 W of 1907.8 nm Tm:YLF laser with two slab crystals was achieved, corresponding to a slope efficiency of 35.9% and an optical-to-optical efficiency of 32.1% with respect to the pump power. The c-cut slab Tm:YLF laser operated at 1907.8 nm with a beam quality factor of M2∼1.79 at the output power level of 71.0 W.

Investigation of a gain-switched laser pumped by an acousto-optic -switched Ho : YAG 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 .