Laser spectrum of a high power Tm,Ho:GdVO<Subscript>4</Subscript> laser

In this paper, we report a 18.8 W continuous wave and 18.4 W Q-switched diode-pumped cryogenic Tm(5 at %), Ho(0.5 at %):GdVO₄ laser. The pumping source of Tm, Ho:GdVO₄ laser is a fiber-coupled laser diode with fiber core diameter of 0.4 mm, supplying 42 W power at 802.5 nm. For input pump power of 41.9 W at 802.4 nm, the output power of 18.8 W in CW operation, optical-to-optical conversion efficiency of 45% at 2.05 μm and the average output power of 18.4 W in Q-switched operation, optical-to-optical conversion efficiency of 44% at 2.04 and 2.05 μm have been attained. The emission wavelengths of the Tm(5 at %), Ho(0.5 at %):GdVO₄ laser were firstly compared when it worked in CW mode and Q-switched mode.     

A high power CW Ho,Tm:GdVO<Subscript>4</Subscript> laser

In this paper, we report a 22.7 W continuous wave (CW) diode-pumped cryogenic Ho( at %), Tm(3 at %):GdVO₄ laser. The pumping sources of Ho,Tm:GdVO₄ laser are two fiber-coupled laser diodes with fiber core diameter of 0.4 mm, both of them can supply 42 W power laser operating near 802 nm. For input pump power of 64.7 W at 802.5 nm, the output power of 22.7 W in CW operation, optical-to-optical conversion efficiency of 35.1% at 2.05 μm has been attained. The M ² factor was found to be 2.0 under an output power of 16.5 W.     

8.30 μm singly resonant ZnGeP2 optical parametric oscillators pumped by a Tm,Ho:GdVO4 laser

A single resonator 8.30 μm ZnGeP₂ (ZGP) optical parametric oscillators (OPO) was reported in the paper. The OPO was pumped by a 10.2-W Tm,Ho:GdVO₄ laser at 8 kHz in a Q-switch mode, a 170-mW idler was obtained at 8.30 μm, and the output power of the idler and signal wave was 1.0 W, corresponding to an optical-optical conversion efficiency of 10.3% and a slope efficiency of 20.9%. Tm,Ho:GdVO₄ laser was pumped by a 30-W fiber-coupled laser diode (LD) at the center wavelength of 801 nm. The output wavelength of Tm,Ho:GdVO₄ laser was at 2.05 μm, and the energy per pulse of 1.28 mJ in 18 ns was achieved at 8 kHz with the peak power of 71.1 kW.     

Effect of resonator length on ZnGeP<Subscript>2</Subscript> doubly resonant optical parametric oscillator pumped by a Tm,Ho:GdVO<Subscript>4</Subscript> laser

The effect of resonator length on ZnGeP₂ doubly resonant optical parametric oscillator was reported in this letter. With the employment of a Tm,Ho:GdVO₄ laser as the pump source at 2.05 μm, we have found that there are obvious peaks of the output power when the resonator lengths are matched to the length of the pump source. The ZGP OPO can generate a maximum output power of 4.27 W at 3.80 μm signal and 4.45 μm idler when the resonator length matches that of the pump source.     

A comparative study on diode-pumped continuous wave Tm:Ho:YVO<Subscript>4</Subscript> and Tm:Ho:GdVO<Subscript>4</Subscript> lasers

In this paper, we presented experimental results concerning on the laser characteristics of two microchip lasers emitting in the 2 μm range, Tm:Ho:YVO₄ microchip laser and Tm:Ho:GdVO₄ microchip laser. At a heat sink temperature of 283 K, the maximum output power of Tm:Ho:YVO₄ laser and Tm:Ho:GdVO₄ laser is 47 and 34 mW under absorbed pump power of 912 mW, respectively. High efficiency can be achieved for both lasers at room temperature. Nevertheless, compared with Tm:Ho:GdVO₄ laser, Tm:Ho:YVO₄ laser can operate on single frequency with high power easily. At the heat sink temperature of 288 K, as much as 16.5 mW of 2052.3 nm single-longitudinal-mode (SLM) laser was achieved for Tm:Ho:YVO₄ laser. Under the same condition, only 8 mW of 2048.5 nm SLM laser was achieved for Tm:Ho:GdVO₄ laser.     

High efficient double end-pumped <Emphasis Type="Italic">b</Emphasis>-cut Tm,Ho:YAlO<Subscript>3</Subscript> laser

High efficient continuous wave (CW) and acousto-optical (AO) Q-switched operation of a b-cut Tm,Ho:YAlO₃ (Tm,Ho:YAP) laser are reported in the paper. The Tm,Ho:YAP crystal was cooled by liquid nitrogen and pumped by a fiber-coupled laser diode (LD). Different pump wavelengths were tried in the experiment. An 8.36-W output power was acquired at 2.12 μm in the CW operation with an optical-optical conversion efficiency of 33.3%, and an 8.14-W average power was obtained at the pulse repetition frequency (PRF) of 10 kHz with an optical-optical conversion efficiency of 32.4%.     

RTP Q-switched 2 μm Tm,Ho:GdVO<Subscript>4</Subscript> Laser

In this paper, we report the performance of a diode-pumped cryogenic Tm (5 at %), Ho (0.5 at %):GdVO₄ laser with an RTP pockel cell Q-switch at different pulse repetition rate including 300 Hz, 500 Hz, 1 kHz, and 10 kHz. At the pump power of 6.96 W, the maximum output of 1.7 mJ with a pulse width of 28 ns was achieved under 300 Hz repetition rate, corresponding to a peak power of 61 kW. To the best of our knowledge, this is the first time that RTP was used as a Q-switch generator in the 2 μm Tm,Ho:GdVO₄ laser.     

Actively Q-switched intracavity frequency-doubled Nd:LuVO<Subscript>4</Subscript>/LBO green laser with an acousto-optic modulator

This work presents experimental results concerning an actively Q-switched intracavity frequency-doubled Nd:LuVO₄/LBO green laser with an acousto-optic modulator operated at the wavelength of 0.53 μm. The green average output power of 2.8 W was obtained at a pump power of 16.3 W and a pulse repetition rate of 20 kHz, resulting in an optical conversion efficiency of 17%. When the pulse repetition rate is operated at 5 kHz, the shortest pulse width and the highest peak power at 0.53 μm were measured to be 26.5 ns and 8.43 kW, respectively.     

High-power,high-quality ZGP OPO pumped by a Tm,Ho:GdVO<Subscript>4</Subscript> laser

We report a ZGP OPO system capable of producing >6 W at a signal wavelength of 3.80 μm and an idler wavelength of 4.45 μm. The pumping source is the Tm,Ho:GdVO₄ laser operated at 2.049 μm with an M ² of 1.07. The ZGP OPO generated a total combined output power of 6.1 W at signal wavelength and idler wavelength under pumping power of 18.3 W, and an M ² of 1.7 for OPO output was obtained.     

Comparison of RTP electro-optic Q-switch and acousto-optic Q-switch in Tm,Ho:GdVO<Subscript>4</Subscript> laser

We demonstrate a tunable, narrow linewidth, linearly polarized and gain-switched Cr²⁺:ZnSe laser pumped by a Tm, Ho:YVO₄ laser at 10 kHz pulse repetition frequency. By setting a quartz birefringent filter with a Brewster angle in the cavity, the linearly polarized Cr²⁺:ZnSe laser can be continuously tuned from 2.45 to 2.50 μm, and the output power was almost not changed. In addition, the linewidth was compressed to about 5 nm. At the incident pump power to the crystal of 14 W, the maximum output power of 2.84 W was obtained, corresponding to a slope efficiency of 20.4%.     

High efficiency 2.05-μm CW and AO Q-switched operation of diode end-pumped Tm,Ho:GdVO4 laser

The continuous-wave (CW) and acoustooptically (AO) Q-switched operation of a Tm (4 at %), Ho (0.4 at %):GdVO₄ laser at a 2.05-μm wavelength were reported in this paper. The Tm,Ho:GdVO₄ crystal was cooled by liquid nitrogen and end pumped by a 29.8-W fiber-coupled laser diode at 801 nm. A conversion efficiency of 41% and a slope efficiency of 46% were acquired with a continuous-wave output power of 12.2 W. An average power of 11.6 W was obtained at a pulse repetition frequency (PRF) of 10 kHz, corresponding to an optical-to-optical conversion efficiency of 38.9% and a slope efficiency of 41.4%. The energy per pulse of 1.8 mJ in 14 ns was achieved at 5 kHz with a peak power of 130 kW.     

Q-switched Ho:YAlO<Subscript>3</Subscript> laser pumped by Tm:YLF laser at room temperature

A Q-switched high efficient Ho:YAlO₃ (Ho:YAP) laser pumped by a diode-pumped Tm:YLF laser at room-temperature is realized. The maximum output energy reaches 1.58 mJ under the repetition frequency of 5 kHz, when the incident pump power is 15.6 W. The pulse width is 22 ns. The wavelength is 2118 nm when the transmission of output coupler is 30%. The beam quality factor is M ² ∼ 1.39 measured by the traveling knife-edge method.     

Diode-end-pumped Tm,Ho:YVO<Subscript>4</Subscript> microchip laser at room temperature

Room temperature Tm, Ho:YVO₄ microchip laser operated around 2 μm was demonstrated for the first time to our knowledge. At a heat sink temperature of 283 K, a maximum output power of 47 mW was obtained by using a 0.25 mm length crystal at an absorbed pump power of 912 mW, corresponding to a slope efficiency of 9.1%. Increasing the temperature to 288 K, as much as 16.5 mW 2052.3 nm single-longitudinal-mode laser was achieved. The M ² factor was measured to be 1.4.     

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 M ² = 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.     

Diode single-end-pumped AO Q-switched Nd:GdVO<Subscript>4</Subscript> 266 nm laser

By simple extra-cavity frequency conversion, the performance of a diode single-end-pumped AO Q-switched Nd:GdVO₄/KTP/BBO 266 nm laser was demonstrated. Under the incident pump power of 14.32 W, the maximum average output power at 266 nm was 374 mW at the repetition of 20 kHz; the opticaloptical conversion efficiency was 2.6%. The corresponding pulse width was 5 ns, with the single-pulse energy and peak power calculated to be 18.7 μJ and 3.74 kW, respectively. The dependence of the operational parameters on the pump power was also investigated experimentally.     

High-power and efficiency continuous-wave operation of <Emphasis Type="Italic">a</Emphasis>-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 M ² ∼ 1.51.     

High repetition rate passive Q-switching of diode-pumped Nd:GdVO<Subscript>4</Subscript> laser at 912 nm with V<Superscript>3+</Superscript>:YAG as the saturable absorber

The character of a diode-pumped passively Q-switched Nd:GdVO₄/V³⁺:YAG 912 nm laser was demonstrated for the first time to our knowledge. With an absorbed pump power of 7.4 W, an average output power of 360 mW with a Q-switched pulse width of 328 ns at a pulse repetition rate of 163 kHz was obtained. The Q-switching efficiency was found to be 32.7%. Our work further indicated V³⁺:YAG could be an effective fast passive Q-switch for 0.9 μm radiation.     

Continuous wave operation of singly-doped Ho:LSO laser at room temperature

We present the room-temperature continuous-wave Ho:LSO laser single-pass-end-pumped by a diode-pumped Tm:YLF laser at 1.91 μm in this paper. Under different output couplers of 2.4, 5.0, and 14.0%, the laser output power and output spectrum of Ho:LSO laser operating at room temperature are investigated. The output wavelength of Ho:LSO laser was centered at 2106.5 nm with linewidth (FWHM) of about 3.2 nm. With T = 5.0%, the maximum output power of 2.4 W was achieved under the absorbed pump power of 11.1 W, corresponding to a slope efficiency of 38.0%.     

Comparative investigation of long-wave infrared generation based on ZnGeP2 and CdSe optical parametric oscillators

Long-wave infrared (IR) generation based on type-II (o→e+o) phase matching ZnGeP₂ (ZGP) and CdSe optical parametric oscillators (OPOs) pumped by a 2.05 μm Tm,Ho:GdVO₄ laser is reported. The comparisons of the birefringent walk-off effect and the oscillation threshold between ZGP and CdSe OPOs are performed theoretically and experimentally. For the ZGP OPO, up to 419 mW output at 8.04 μm is obtained at the 8 kHz pump pulse repetition frequency (PRF) with a slope efficiency of 7.6%. This ZGP OPO can be continuously tuned from 7.8 to 8.5 μm. For the CdSe OPO, we demonstrate a 64 mW output at 8.9 μm with a single crystal 28 mm in length.     

Efficient continuous wave and Q-switched operation of a dual-end-pumped <Emphasis Type="Italic">c</Emphasis>-cut Tm:YAP laser

An efficient continuous wave (CW) and Q-switched c-cut Tm:YAP laser is reported in this letter. With the dual-end-pumped convex-concave resonator, CW output power up to 13.6 W at 1.99 μm was obtained under a total incident pump power of 50 W. The corresponding slope efficiency was 34.3% and conversion efficiency was 27.2%. The active Q-switched operation of the laser had an average output power of 12.5 W at 10 kHz pulse repetition frequency, with a minimum pulse width of 126 ns. With 6 kHz pulse repetition frequency, the maximum pulse energy of 1.6 mJ was obtained. In addition, using the Tm:YAP laser as a pumping source for gain-switched Cr:ZnSe laser, as much as 4 W output power in the wavelength range of 2.5–2.6 μm was obtained.