Zhang Tie-Li

High-Average-Power Nanosecond Quasi-Phase-Matched Single-Pass Optical Parametric Generator in Periodically Poled Lithium Niobate

A pulsed nanosecond optical parametric generator (OPG) in periodically poled lithium niobate (PPLN) crystal is presented. The pump laser is an acousto-optically Q-switched Nd:YVO4 laser with the maximum average power of 6.58 W. When the repetition rate is 50 kHz and the pulse width of the pump source is 80 ns, the maximum average total output power of the single-pass PPLN OPG is about 1.9 W, which includes 1.322 W of 1.536 μm signal radiation. The length of the PPLN crystal is only 38.7 mm (at room temperature) with a grating period of 28.93 μm (at room temperature). The 1.502–1.536 μm signal radiation and 3.652–3.465 μm idler radiation are obtained by adjusting the PPLN crystal temperature from 155 degrees C to 250 degrees C.

Experimental 511 W Composite Nd:YAG Ceramic Laser

We demonstrate a 511 W laser diode pumped composite Nd:YAG ceramic laser. The optical pumping system is consisted of five laser diode stacked arrays arranged in a pentagonal shape around the ceramic rod whose size is Φ6.35×144 mm. When the pumping power is 1600 W, the cw laser output up to 511 W at 1064 nm can be obtained with a linear plano–plano cavity, and the optical-to-optical efficiency is 31.9%. To our knowledge, this is the highest value of laser output by using a newly invented composite Nd:YAG ceramic rod as the gain medium.

High-efficiency single-pass cw quasi-phase-matched frequency doubling based on PP-MgO:SLT

We demonstrate a single-pass cw quasi-phase-matched (QPM) frequency doubling based on periodically poled MgO-doped stoichiometric lithium tantalate (PP-MgO:SLT) with crystal length of 20mm. For the maximum 1064nm fundamental power of 7.69W, the maximum conversion efficiency and the maximum output second-harmonic power are 11.8% and 905mW, respectively. In the experiment we found that the optimum temperature of the oven for PP-MgO:SLT should be adjusted with the change of the fundamental power and the focal length. In addition, angular acceptance bandwidth and temperature acceptance bandwidth are studied. Their experimental results are in good agreement with the theoretical calculations.

High power output quasi-continuous-wave nanosecond optical parametric generator based on periodically poled lithium niobate

We report on a high power output quasi-continuous-wave nanosecond optical parametric generator (OPG) of congruent periodically poled lithium niobate (PPLN) pumped by a 1064 nm acousto-opticallyQ-switched Nd: YVO4 laser (duration: 70 ns, repetition rate: 45 kHz, spatial beam qualityM2< 1.3). The OPG consists of a 38.7 mm long PPLN crystal with a domain period of 28.93 μ. With 5.43 W of average pump power the maximum average output power is 991 mW at 1517.1 nm signal wave of the PPLN OPG.

Bend-Induced Distortion in Large Mode Area Holey Fibre

A simplified scheme of bend-induced mode distortion is introduced into bent holey fibres, the distorted mode distribution and mode effective area reduction are investigated using the finite difference method. Numerical results show that the modes of bent holey fibres with small bend radius shift away from the core and are deformed greatly, and the mode areas drop significantly as the bend radius decreases, which severely affects the fibre laser performance. The propagation characteristics of bent holey fibres at given wavelength are determined by fill factor and normalized bend radius. Finally, the transition normalized bend radius that represents the location of the mode area beginning to fall off is obtained.

Compact efficient optical parametric generator internal to a Q-switched Nd ： YVO4 laser with periodically poled MgO：LiNbO3

This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVO4 laser with periodically poled MgO:LiNbO3(PPMgLN). With the Q-switch set at a repetition rate of 25kHz and the PPMgLN crystal operated at room temperature (25°C), the intracavity optical parametric generator threshold was reached as a diode pump power of 0.9 W. A maximum signal output power of 0.34 W with a pulse width of 25 ns and a beam quality factor of 1.4 was obtained at an incident diode power of 3.4 W, leading to a conversion efficiency of 10% with a slope efficiency of 14.4%. By varying the crystal temperature from 25 to 200°C, the output signal wavelengths were tuned in range of 1506-1565 nm. Over a 30-minutes interval, the instability of the signal power was measured to be less than 1%. In addition, the threshold pump intensity for the intracavity optical parametric generator is theoretically investigated, and the obtained result is in good agreement with the experimental results.

1-W, high-repetition-rate room temperature operation of mid-infrared optical parametric oscillator based on periodically poled MgO-doped LiNbO

In this paper a high-repetition-rate mid-infrared (mid-IR) optical parametric oscillator based on periodically poled MgO-doped LiNbO3 (PPMgLN) at room temperature was demonstrated. The maximum average mid-IR output power at 3.63μm was 1.02 W with the repetition rate of 60kHz and corresponding efficiency from the pump to the idler was 26.7%. The temperature tuning and the period tuning characteristics were also discussed.

Efficient Nanosecond Dual-Signal Optical Parametric Generator with a Periodically Phase Reversed PPMgLN

We report an efficient nanosecond optical parametric generator (OPG) with a periodically-phase-reversed periodically poled MgO:LiNbO3(ppr-PPMgLN), which produces two pairs of signal and idler waves. The OPG is pumped by a 1.064 μm Q-switched Nd:YVO4 laser. When the repetition rate is set at 10 kHz, the maximum average total output power of 570 mW is achieved, including 410 mW of dual-signal radiations and 160 mW of dual-idler radiations. The total conversion efficiency is 32.5%. The tunable dual-signal wavelengths in the range of 1.474–1.518 μm and 1.490–1.539 μm and the dual-idler of 3.826–3.558 μm and 3.726–3.451 μm are obtained by changing the crystal temperature from 30°C to 200°C.

A Low-Pump-Threshold High-Repetition-Rate Intracavity Optical Parametric Generator Based on Periodically Poled Lithium Niobate

A low-pump-threshold high-repetition-rate intracavity optical parametric generator (IOPG) by using a periodically poled lithium niobate (PPLN) is reported. The PPLN, which is 18.7 mm long and has a grating period of 28.93 μm at room temperature, is inserted in a diode-end-pumped Nd:YVO4 laser with an acousto-optic Q switch. The parametric generation threshold is 1.3 W (diode laser power) at a Q-switch repetition rate of 19 kHz. At an incident diode pump power of 5 W, an average signal output power of 280 mW has been achieved. The signal pulse duration is approximately 85 ns. By changing the crystal temperature from 120°C to 250°C, the signal wavelength can be tuned from 1.493 μm to 1.538 μm.