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) crysal 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 50kHz and the pulse width of the pump source is 80ns, the maximum average total output power of the single-pass PPLN OPG is about 1.9 W, which includes 1.322 W of 1.536μm signal radiation. The length of the PPLN crystal is only 38.7mm (at room temperature) with a grating period of 28.93μm (at room temperature). The 1.502-1.536μm signal radiation and 3.652-3.465μm idler radiation are obtained by adjusting the PPLN crystal temperature from 155℃ to 250℃.     

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 18.7mm long and has a grating period of 28.93tzm at room temperature, is inserted in a diode-end-pumped Nd：YV04 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 280mW has been achieved. The signal pulse duration is approximately 85 ns. By changing the crystal temperature from 120℃ to 250℃, the signal wavelength can be tuned from 1.493μm to 1.538μm.     

Violet to Infraned Multiwavelength Generation in Periodically Poled Lithium Niobate Pumped by a Q—Switched Nd：YVO4 Laser

Six output wavelengths from violet to infrared have been observed simultaneously from an all-solid-state laser pumped optical parametric oscillator in a periodically poled lithium niobate crystal.The output wavelengths can be tuned by varying the quasi-phase matched period and/or temperature.The pump laser is a diode-pumped pasive Q-switched Nd:YVO4 laser operated at 1064nm.Using a crystal with a 29.9μm grating period,we measured six wavelengths at 448,515,532,630,773 and 1546nm and obtained efficient output.We explain the multiwavelength generation by multiwave coupling theory.This phenomenon may have novel applications in photonic devices.     

Wavelength Converter Based on Linearly Chirped Gratings in Lithium Niobate Through Cascaded Second—Order Processes

We report a wavelength converter based on linearly chirped gratings in a lithium niobate crystal through cascaded second-order nonlinear processes. The influence of the chirp coetficient on the conversion bandwidth and the efficiency is analysed. The exact phase matching point is optimized at the 0.33 times of the waveguide total length. When the waveguide length is 3 cm, the bandwidth of the linearly chirped grating increases 42% with the etficiency penalty of 1.7dB compared with the periodic grating. At the same mean conversion etficiency of- 1.4 dB via adjusting the waveguide total lengths, the bandwidth of the linearly chirped grating is 36% broader than the periodic grating.     

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

A multi-grating periodically poled LiNb03 （PPLN） doubly resonant optical parametric oscillator （DROPO） pumped by a 2-ttm laser is demonstrated experimentally. Employing acousto-optically Q-switched Tm,Ho：GdV04 laser with pump pulse of 25ns and repetition rate of lOkHz as pump sources firstly, the noncritically quasi- phase-matched （QPM） tunable mid-IR output in 3.87-4.43 μm is produced. Wavelength tuning is achieved with crystal temperature tuning from 50-180^o C. When the incident average pump power is 3 W at 2.048μm, the total OPO output power of 195mW at wavelength 3.88μm is obtained, corresponding to optical-to-optical conversion efficiency up to 6.5%.