实验研究了周期域反转铌酸锂光波导级联和频与差频二阶非线性效应(cSFG/DFG)皮秒脉冲间的可调谐波长转换。信号光采用重复频率为40 GHz,脉宽为1.57 ps的脉冲信号。当输入信号光和第一个控制光波长分别为1554.4 nm和1532.5 nm时,通过调节第二个控制光波长由1550.5 nm到1541.0 nm,输出信号光波长可从1536.0 nm调谐至1545.2 nm。当输入信号光波长改变时,通过改变第一个控制光波长以满足和频过程的准相位匹配条件,同时调节第二个控制光波长可以实现输出信号光波长的可调谐。实验中利用两个窄带可调谐滤波器有效抑制了掺铒光纤放大器引入的放大自发辐射噪声,同时观察到了波长下转换和波长上转换。

A tunable wavelength conversion between picosecond pulses is experimentally demonstrated by using the cascaded sum and difference-frequency generation (cSFG/DFG) in a periodically poled LiNbO3 (PPLN) waveguide. The pulsed signal with 40 GHz repetition rate and 1.57 ps pulse width is adopted. When the input signal and the first control wavelengths are kept at 1554.2 nm and 1532.5 nm, respectively, the output signal wavelength can be tuned from 1536.0 nm to 1545.2 nm as the second control wavelength is varied from 1550.5 nm to 1541.0 nm. By varying the first control wavelength to satisfy the quasiphase matching (QPM) condition for the sumfrequency generation (SFG), and simultaneously adjusting the second control wavelength, the tunable output signal wavelength can be also obtained when the input signal wavelength is changed. In the experiment, the amplified spontaneous emission (ASE) noise from the erbium-doped fiber amplifier (EDFA) is effectively suppressed by employing two narrow band tunable filters. Therefore, the wavelength down and upconversions are simultaneously observed.