Wang Yue-Zhu

High Efficiency Continuous-Wave Tm:Ho:GdVO4 Laser Pumped by a Diode

We report a high efficiency cw diode-pumped cryogenic Tm(5 at.%), Ho(0.5 at.%):GdVO4 laser. The pumping source is a fibre-coupled laser diode with fibre core diameter of 0.4 mm and numerical aperture of 0.3, supplying power 14.8 W at 793.6 nm. For input pump power of 13.6 W at 794.2 nm, the maximum output power of 4.2 W, optical-to-optical conversion efficiency of 31% and slope efficiency 38% have been attained at 2.0485 μm. To our knowledge, the operating performance is the best among the previously reported Tm:Ho:GdVO4 lasers. We also analyse the influence of pump wavelengths (from 792 nm to 794.2 nm) on the output power, the optical-to-optical conversion efficiency increases with the longer pump wavelength which is closer to the absorption peak of 797 nm in Tm,Ho:GdVO4.

All-Fiber Gain-Switched Thulium-Doped Fiber Laser Pumped by 1.558 μm Laser

We present an all-fiber gain-switched thulium (Tm) doped fiber laser operating in the eye-safe region at 1940 nm. The fibre Bragg gratings (FBGs) inscribed by phase mask technology are used as cavity mirrors, and the transmission spectra of FBGs are also measured. The output characteristics are studied at pulse repetition frequencies of 10, 20 and 30 kHz, and the maximum output powers of 28.9, 67.0 and 71.0 mW are achieved under incident pump powers of 122, 247 and 250 mW. The narrowest pulse width of 29 ns and shortest pulse built-time of 140 ns are obtained at 10 kHz. The relation between pulse built-time and cavity length are discussed.

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 bire-fringent 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.

A Single-Longitudinal-Mode Dual-Wavelength cw Tm, Ho:GdVO4 Microchip Laser

A liquid nitrogen cooled dual-wavelength Tm, Ho:GdVO4 microchip laser is reported. The output dual wavelengths are at 2038.9 nm and 2050.1 nm. At each wavelength, the laser has a single longitudinal mode. The threshold power is nearly 20mW and the slope efficiency is 18.7%. The single longitudinal mode output power reaches 98 mW, and the ratio of power is about 60% (2038.9 nm) and 40% (2050.1 nm).

Acousto-Optic Q-Switched Operation Ho:YAP Laser Pumped by a Tm-Doped Fiber Laser

We report on the acousto-optic Q-switched operation of a Ho:YAP laser double-passed pumped by an all-fiber Tm-doped fiber laser. The output characteristics of the Ho:YAP laser are studied at pulse repetition frequencies of 1, 2, 5 and 10 kHz. The shortest pulse width, the maximum pulse energy and the highest peak power are measured to be 17 ns, 1.71 mJ and 71.25 kW, respectively. The output wavelength is centered at 2115.96 nm with a bandwidth of about 1.5 nm. The beam quality factor M2 = 2.41 ± 0.03 at the output power of 3.54 W was measured by using the traveling knife-edge method.

A 2.048-μm Tm,Ho:GdVO4 Laser Pumped Doubly Resonant Optical Parametric Oscillator Based on Periodically Poled Lithium LiNbO3

A multi-grating periodically poled LiNbO3 (PPLN) doubly resonant optical parametric oscillator (DROPO) pumped by a 2-?m laser is demonstrated experimentally. Employing acousto-optically Q-switched Tm,Ho:GdVO4 laser with pump pulse of 25?ns and repetition rate of 10?kHz as pump sources firstly, the noncritically quasi-phase-matched (QPM) tunable mid-IR output in 3.87?4.43??m is produced. Wavelength tuning is achieved with crystal temperature tuning from 50?180?C. When the incident average pump power is 3?W at 2.048??m, the total OPO output power of 195?mW at wavelength 3.88??m is obtained, corresponding to optical-to-optical conversion efficiency up to 6.5%.

Diode Pumped Operation of Tm,Ho:YVO4 Microchip Laser

A cryogenic and room-temperature diode pumped Tm,Ho:YVO4 microchip laser with 0.5 mm crystal length lasing around 2 μm is demonstrated for the first time to our knowledge. Under cryogenic temperature of 77K, as much as 1.2 W output and slope efficiency of 35% with respect to absorbed pump power are obtained. At temperature of 5°C the maximum output power of 48mW is obtained at an absorbed pump power of 503 mW, representing a 9.5% optical to optical conversion efficiency. In addition, as much as 8 mW single-frequency output lasing at 2052.6 nm is achieved at room temperature of 15° C.

A Mid-IR 14.1 W ZnGeP2 Optical Parametric Oscillator Pumped by a Tm,Ho:GdVO4 Laser

We report a high power and high efficiency double resonant ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a Tm,Ho:GdVO4 laser. We employ a Tm,Ho:GdVO4 laser as the pump source operated at 2.049 μm with M2 = 1.1. The ZGP OPO can generate a total combined output power of 14.1 W at 3.80 μm signal and 4.45 μm idler under pumping power of 28.7 W. The slope efficiency reaches 61.8%, and M2 = 3.6 for OPO output is obtained.

LD-cladding-pumped 50 pm linewidth Tm 3+ -doped silica fiber laser

We report on a Tm(3+)-doped fiber laser source operating at 1936.4 nm with a very narrow linewidth (50 pm) laser output. Up to 2.4 W cw laser power was obtained from an 82 cm long Tm(3+)-doped multimode-core fiber cladding pumped by a 792 nm laser diode (LD). The fiber laser cavity included a high-reflective dichroic and a low-reflective FBG output coupler. The multimode fiber Bragg grating (FBG) transmission spectrum and output laser spectrum were measured. By adjusting the distance between the dichroic and the Tm(3+)-doped fiber end, the multipeak laser spectrum changed to a single-peak laser spectrum.

A Laser-Diode-Pumped Widely Tunable Single-Longitude-Mode Tm:YAP Laser at Room Temperature

A laser-diode-pumped widely tunable single-longitude-mode Tm:YAP laser in 2 μm eye-safe region is built. Continuous tunable range from 1899 nm to 2025 nm is achieved with the maximum laser output power of 225 mW at 1989 nm. In addition, the Tm:YAP laser operating under multimode and single-mode conditions is discussed.