Tongyu Dai

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.

Efficient Q-switched Ho:GdVO 4 laser resonantly pumped at 1942 nm

An efficient 2 μm room-temperature Q-switched Ho:GdVO4 laser end-pumped by a 1942 nm Tm-fiber laser is demonstrated. To our knowledge, this is the first report of Q-switched performance of Ho:GdVO4 crystal. A maximum CW output power of 6.85 W under the absorbed pump power of 24.1 W was obtained with a slope efficiency of 39.5% at a temperature of 17°C. With the same absorbed pump power, a maximum output energy per pulse of about 0.9 mJ and minimum pulse width of 4.7 ns were obtained at the pulsed repetition frequency (PRF) of 5 kHz, corresponding to a peak power of approximately 187.2 kW.

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.

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.

Tunable single-longitudinal-mode Er:YAG laser using a twisted-mode technique at 1.6 μm

We demonstrated a diode-pumped tunable single-longitudinal-mode Er:YAG laser using a twisted-mode technique at 1.6 μm. The maximum single-longitudinal-mode output power of 315 mW was obtained at 1645.3 nm, corresponding to a slope efficiency of 7.7%. The single-longitudinal-mode laser has a beam quality factor of M2 ~ 1.07. The output wavelength can be tuned from 1644.8 to 1646.1 nm by changing the etalon angle. In addition, by changing an output coupler, a maximum single-longitudinal-mode output power of 130 mW at 1617.2 nm with a slope efficiency of 3.3% was also achieved. The output wavelength can be tuned from 1616.9 to 1617.4 nm by changing the etalon angle. The twisted-mode Er:YAG laser operated at single-longitudinal mode is being reported for the first time to the best of our knowledge.

An actively mode-locked Ho: YAG solid laser pumped by a Tm: YLF laser

A continuous wave mode-locked (CWML) Ho: YAG laser based on an acousto-optic modulator (AOM) pumped by a 1.9 μm Tm: YLF laser is demonstrated. This is the first time a report on an active CWML Ho: YAG laser has been published. A maximum output power of 1.04 W at 2097.25 nm in the CWML regime is obtained at a pump power of 13.2 W, corresponding to a slope efficiency of 13.3%. The mode-locked pulse repetition frequency is 82.76 MHz and the single pulse energy is 12.57 nJ. The mode-locked pulse width is 102 ps measured through a no-background second harmonic autocorrelation with KTP as the nonlinear crystal. Furthermore, the M2 factor is calculated to be 1.146.

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.