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.     

Research of Tm (5.5 at %), Ho (0.55 at %):GdVO<Subscript>4</Subscript> laser pumped by diode laser at 800 nm

In this paper, we report a Tm (5.5 at %), Ho (0.55 at %):GdVO₄ laser pumped by diode laser at 800 nm. To our best knowledge, it is the first time that the use of Tm (5.5 at %), Ho (0.55 at %):GdVO₄ crystal among the similar experiments. We observed the influences of LD working temperature i.e. pump wavelength to 2 μm laser conversion efficiency. In the conditions of the continuous wave and 10 kHz acousto-optic Q-switch, high efficiency output of 2.05 μm laser was obtained. With the maximum pump power of 34.6, 13.9, and 13.6 W at 2.05 μm laser output was achieved respectively. Single laser pulse width was 25.6 ns in 10 kHz acousto-optic Q-switched condition.     

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.     

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.     

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.     

Efficient Cr:ZnSe laser with a volume Bragg grating

An efficient and narrow linewidth Cr:ZnSe laser pumped by Tm,Ho:GdVO₄ laser with a volume Bragg grating (VBG) is reported. The Cr:ZnSe laser operated at 2580 nm with emitting linewidth (FWHM) about 0.8 nm. Using the volume Bragg grating, 3.57 W of output was achieved under total incident pump power of 13.1 W, corresponding to optical-to-optical conversion efficiency of 27.3%. By use of conventional mirror, 4.11 W of output was achieved the same incident pump power and the optical-to-optical conversion efficiency is 31.4%.     

A high efficiency Ho:YAlO<Subscript>3</Subscript> laser pumped by Tm:YLF laser with a Volume Bragg Grating

We report a CW Ho:YAlO₃ (Ho:YAP) laser at room temperature pumped by a Tm:YLF laser with a Volume Bragg Grating (VBG) instead of the conventional mirror. The Ho:YAP laser operated at 2117.9 nm with output power 9.12 W. The optical-to-optical conversion efficiency is 60.4% and slope efficiency is 71.2%. The Ho:YAP output wavelength is centered at 2117.9 nm with bandwidth of about 1 nm. The beam quality factor is M ² ∼ 1.29 measured by the traveling knife-edge method.     

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.     

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.     

Q-switched operation of <Emphasis Type="Italic">a</Emphasis>-cut Ho:YAlO<Subscript>3</Subscript> laser pumped by a diode-pumped 1.91 μm thulium laser

Q-switched operation of a room temperature Ho:YAP laser was resonantly end-pumped by a diode-pumped Tm:YLF laser at 1.91 μm. The CW Ho:YAP laser generated 9.9 W of linearly output at 2119.03 nm with beam quality factor of M ² ∼1.46 with respect to absorbed pump power of 19.16 W, corresponding to an optical-to-optical conversion efficiency of 51.7% and slope efficiency of 60.6%. Under Q-switched operation, the maximum output power of 9.8 W in relation to 10 kHz pulse repetition frequency (PRF) was obtained, however, the maximum peak power of 60 kW at the PRF of 5 kHz was demonstrated. At 5 kHz pulse energies of 1.92 mJ with pulse width of 32 ns was achieved.     

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%.     

Single-longitudinal-mode lasing of Tm,Ho:GdVO<Subscript>4</Subscript> using a filter of Fabry-Perot etalon and volume Bragg grating

In this letter, we report a diodepumped CW Tm, Ho:GdVO₄ laser at 77 K with a volume Bragg grating (VBG) instead of the conventional mirror. Inserting a Fabry-Perot etalon into the cavity, a singlelon-gitudinal-mode of Tm, Ho:GdVO₄ laser which I s operating at 2038.387 nm with output power 64 mW is obtained. The slope efficiency of 4.68% and a narrow linewidth about 45 pm FWHM are achieved. And appropriate cavity length is about 75 ± 5 mm.     

Study of LD pumped Q-switched Nd:Y<Subscript>0.5</Subscript>Lu<Subscript>0.5</Subscript>VO<Subscript>4</Subscript> laser with acousto-optic modulator

A laser-diode (LD) pumped Q-switched Nd:Y_0.5Lu_0.5VO₄ crystal laser with an acousto-optic (AO) modulator is presented in this paper. The maximum continuous wave (CW) output power of 5.53 W is achieved at the incident pump power of 14.09 W with the transmission of 10% for the output coupler, resulting in an optical-to-optical conversion efficiency of 39.2%. For Q-switching operation, the shortest pulse width of 8.3 ns and the highest peak power of 259 kW are generated under the incident pump power of 14.09 W at 1 kHz.     

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.     

高脉冲重复频率调Q Tm,Ho:GdVO4激光器

报道了一个高效率连续波和调Q高重频两种运行方式的Tm,HoGdVO4激光器.Tm,HoGdVO4晶体尺寸4 mm×4 mm×7 mm,a轴通光,液氮制冷到100 K,由发射中心波长为793 nm的光纤耦合激光二极管端面泵浦.Tm,HoGdVO4激光连续波输出功率4.0 W,光光转换效率26%.声光调Q条件下输出平均高功率3.9 W,脉冲重复频率10 kHz,脉冲宽度50 ns. 通过减小声光Q开关的开启时间,激光脉冲宽度由50 ns减小至23 ns.在10 kHz重频下,测量最大脉冲能量0.39 mJ , 峰值功率7.8 kW.     

2041.3 nm/2054.6 nm simultaneous dual-wavelength single-longitudinal-mode Tm,Ho:YVO<Subscript>4</Subscript> microchip laser

We report a single-longitudinal-mode CW diode-pumped Tm, Ho: YVO₄ microchip laser emitting at both 2041.3 and 2054.6 nm. At each wavelength, the laser has a single longitudinal mode. The total single-longitudinal-mode output power reaches 185 mW with 20.4% optical conversion efficiency at 905 mW incident pump power.     

A comparison of resonantly pumped Ho:YLF and Ho:LLF lasers in CW and Q-switched operation under identical pump conditions

Singly 0.5 at.% Ho doped crystals of YLiF₄ (YLF) and LuLiF₄ (LLF) are studied under identical pump conditions in continuous-wave (CW) and Q-switched operation. Longitudinal end-pumped CW laser performance shows Ho:LLF to have a slightly lower threshold and a slightly higher slope efficiency with respect to absorbed pump power than Ho:YLF. Both lasers were operated on π-polarization. At a cavity output coupling of 20% and a crystal length of 30 mm, the Ho:LLF (Ho:YLF) laser yielded 18.8 W (18 W) of CW output at a wavelength of 2067.8 nm (2064.0 nm) for 41.4 W (42.2 W) of absorbed pump power with a slope efficiency of 67.1% (65.6%) and an optical-to-optical efficiency of 45.4% (42.6%) with respect to absorbed pump power. With the same output coupling and a crystal length of 40 mm, the Ho:LLF (Ho:YLF) laser yielded 20.5 W (18.1 W) of CW output at a wavelength of 2067.7 nm (2064.3 nm) for 51.5 W (50.0 W) of absorbed pump power with a slope efficiency of 58.4% (55.4%) and an optical-to-optical efficiency of 39.8 (36.1%) with respect to absorbed pump power. The influence of the temperature of the cooling mount on CW laser performance was studied and showed very similar results for both laser materials. At full pump power, a slope of −155 mW/°C (−149 mW/°C) was observed for the Ho:LLF (Ho:YLF) laser with a crystal length of 30 mm. In Q-switched operation, the Ho:LLF (Ho:YLF) laser produced 37 mJ (38.5 mJ) at a repetition rate of 100 Hz with a pulse duration of 38 ns (35 ns) at a wavelength of 2053.1 nm (2050.2 nm) with a slope efficiency of 30.3% (31%) and an optical-to-optical efficiency of 14.2% (13.9%) with respect to absorbed pump power. The beam quality was nearly diffraction limited (M ²<1.1).     

A single-longitudinal-mode CW 0.25 mm Tm,Ho:GdVO<Subscript>4</Subscript> Microchip Laser

A single-longitudinal-mode of 0.25 mm Tm,Ho:GdVO₄ Microchip Laser was reported. The maximal continuous wave (CW) output power was 26.4 mW and the threshold of 118 mW. The Tm,Ho:GdVO₄ Microchip Laser output wavelength was centered at 2039.7598 nm with bandwidth of about 57.1 pm. The beam quality factor was M ² ∼ 1.52 ± 0.03 measured by knife-edge method. The Longitudinal-Mode was scanned by a FPI and the transverse mode was monitored by an infrared vidicon camera.     

All-solid-state CW frequency-doubling Nd:LuVO<Subscript>4</Subscript>/KTP laser with 2.3 W output power at 545 nm

Efficient and compact green-yellow laser output at 545 nm is generated by intracavity frequency doubling of a continuous-wave (CW) diode-pumped Nd:LuVO₄ laser at 1089 nm under the condition of suppressing the higher gain transition near 1066 nm. With 18.7 W of diode pump power and the frequency-doubling crystal KTiOPO₄(KTP), as high as 2.3 W of CW output power at 545 nm is achieved, corresponding to an optical-to-optical conversion efficiency of 12.3%; the output power stability over 4 h is better than 5.4%.     

CW Nd:LuVO<Subscript>4</Subscript>-GdCa<Subscript>4</Subscript>O(BO<Subscript>3</Subscript>)<Subscript>3</Subscript> red laser under direct 888 nm pumping

We report a red laser at 672 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1343 nm Nd:LuVO₄ laser under in-band diode pumping at 888 nm. An GdCa₄O(BO₃)₃ (GdCOB) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 17.8 W, as high as 1.73 W of CW output power at 672 nm is achieved. The optical-to-optical conversion efficiency is up to 9.7%, and the fluctuation of the red output power was better than 3.3% in the given 30 min.