Ying-Jie Shen

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.

A 41-W ZnGeP 2 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%.

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.

Single-frequency, Q-switched Ho:YAG laser at room temperature injection-seeded by two F–P etalons-restricted Tm, Ho:YAG laser

We demonstrated a 1.91 μm pumped, injection-seeded Q-switched Ho:YAG laser operating at room temperature. By inserting two Fabry-Perot etalons into the laser cavity, single-frequency Tm, Ho:YAG seed lasing was achieved at a wavelength of 2090.9 nm, with a typical output power of 60 mW. Single-frequency, nearly transform-limited Q-switched operation of the Ho:YAG laser was achieved by injection seeding. The output energy of the single-frequency Q-switched pulse is 7.6 mJ, with a pulse width of 132 ns and a repetition rate of 100 Hz. We measured the pulse spectrum, half-width of which was 3.5 MHz, by a heterodyne technique.

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.

Resonantly pumped room temperature Ho:LuVO 4 laser

Spectroscopic characterization of a Ho:LuVO4 crystal grown by the Czochralski method has been performed, including the absorption and emission spectra. We demonstrate a 2 μm room temperature Ho:LuVO4 laser, resonantly pumped by a 1.94 μm Tm:YAP laser. By use of an output coupler with T=10% transmission, the Ho:LuVO4 laser generated continuous-wave output power of 2.5 W at 2074.18 nm, with a beam quality factor of Mx2=My2=1.3, for a total incident pump power of 19.4 W. The slope efficiency with respect to the pump power was 17.6%, and the optical-to-optical efficiency was 12.9%. Moreover, we obtained a Ho:LuVO4 laser that operated at 2073.77 and 2055.27 nm, by using different output couplers with transmissions of T=15 and 30%.

High-power and efficiency continuous-wave operation of a -cut Ho:YAP laser at room temperature

We report the continuous-wave (CW) operation of a room-temperature a-cut Ho:YAP laser resonantly end-pumped by a diode-pumped Tm:YLF laser at 1.91 μm. A maximum CW output power of 14.6 W at 2118.7 nm for a-oriented Ho:YAP was obtained, corresponding to the slope efficiency of 69.35% and optical-to-optical conversion efficiency of 63.04% with respect to absorbed pump power. The laser operated at a single mode (TEM00) with the beam quality factor of M2 ∼ 1.51.

The output characteristics of double-end-pumped Ho:LuAG laser at room temperature

Continuous-wave (CW) and Q-switched operation of a room-temperature Ho:LuAG laser was resonantly double-end-pumped by a diode-pumped Tm:YLF laser at 1.91 μm. The CW Ho: LuAG laser generated 24.5 W of linearly output at 2094.4 nm with beam quality factor of M2 = 1.11 ± 0.02 for an absorbed pump power of 44.0 W, corresponding to optical-to-optical conversion efficiency of 55.7% and slope efficiency of 60.5%. Under Q-switched operation, a maximum output power of 24.1 W with a slope efficiency of 58.1% at 12 kHz was obtained. Also, the minimum pulse width of 32 ns was achieved, corresponding to the peak power was 37.7 kW.

Continuous-wave and Q-switched operation of a Ho:YAG ring laser in-band pumped at 1908 nm

We demonstrated continuous-wave (CW) and Q-switched operation of a Ho:YAG ring laser in-band pumped at 1908 nm. A maximum CW output power of 2.2 W at 2122.35 nm was obtained under an incident pump power of 13.2 W, corresponding to a slope efficiency of 26%. For the Q-switched regime a maximum output energy of 5.2 mJ at a repetition rate of 100 Hz was achieved. A shortest pulse width of 200 ns was achieved, corresponding to a peak power of 26 kW.

A room temperature a-cut Ho:YVO4 laser in-band pumped using a 1.91 μm laser

We present a room temperature singly doped Ho:YVO4 laser in-band pumped using a 1.91??m Tm:YLF laser in this paper. By using different output transmittances of 2%, 5%, and 11%, we have investigated the continuous wave laser performance of a-cut Ho:YVO4 crystal. With the output transmittance of 5%, a maximal output power of 0.54?W at 2067?nm is obtained with the slope efficiency of 20.0%. With the output transmittances of 2% and 11%, the slope efficiencies are 16.6% and 8.5%, respectively.