Coherent sources of picosecond pulses that are tunable in the near infrared are interesting for many applications and more significantly for fundamental and applied research in nonlinear optics and telecommunications.Optical fiber and waveguide components usually require relatively low-peak-power optical sources for diagnosis or excitation

thus making high-repetition-rate synchronously pumped optical parametric oscillator(OPO)an attractive solution for this application.Quasi-phase-matched OPO based on periodically poled lithium niobate(PPLN)offer a high nonlinear coefficient

low loss

a broad operating range

versatility and large nonlinear optical coefficient(

d

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~25.2pm/V at 1.064nm)in fabrication techniques.Recently many efforts were devoted to fabricating a periodically poled structure in 5%(mol fraction)MgO-doped LiNbO

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(MgO:LN)because of its higher resistance to photorefractive damage and lower coercive field of ~4.5 kV/mm at room temperature(RT)than that of LN

as well as its large nonlinear coefficient

comparable with that of LN.Temperature tuning is a unique feature of OPO

which makes its application scope enlarged.Temperature tuning feature of OPO based upon PPLN is the result that the operating temperature fluctuation of PPLN causes output wavelength shifts due to the changes of the length of PPLN and the refractive index of material.The width of PPLN grating period will change because of the expansion coefficient of material when the operating temperature fluctuates.By using short-pulse field

the periodically poled grating(Λ=30.0μm)was successfully fabricated in 1.0mm thick MgO:LiNbO

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(doped 5% MgO).A high-repetition-rate optical parametric oscillator(OPO)based on PPMgLN pumped by a 1.064nm acousto-optically Q-switched Nd:YAG laser.The threshold is 45 mW with pulses repetition rate 1 kHz at room temperature.Under the condition of 225mW of input pump power and at 20℃

36mW of output signal power was obtained

and the conversion efficiency is 16.0%.Furthermore a tunable infrared(IR)output from 1503~1550nm was obtained by tuning the temperature of PPMgLN from 20℃ to 180℃.