用于产生ps量级双脉冲的光纤光栅

Fiber Bragg Grating for Generation of Pico-second Doubled Optical Pulses

设计了一种用于ps级单脉冲变换到双脉冲的光纤光栅(FBG)。依据傅立叶光学理论,数值模拟了光脉冲经不同强度光栅反射后的输出光脉冲的特性,随着光栅强度的增加,输出脉冲间的强度差别变大,但输出光脉冲具有与输入光脉冲相同的谱形和脉宽。设计出的FBG折射率调制函数是sinc函数的叠加。当FBG是弱光栅满足一阶波恩近似时,光脉冲经光栅反射后的输出双脉冲具有相同的强度,且谱形和脉宽与输入脉冲相同。在强光栅情况下,改变光栅折射率调制sinc函数的相对强度,仍然可以使输出双脉冲具有相同的强度。

A fiber Bragg grating (FBG) which could transform a single pico-second optical pulse to a doubled optical pulse pair was designed by using Fourier transformation method. The designed FBG consists of a grating with index modulation distribution as a pair of sine function. The characteristics of the reflected pulses from the designed FBGs with different reflectivity were examined by numerical calculation. The intensity difference between two output pulses was increased with increasing of the FBG reflectivity, while the output pulses would have the same shape of the input pulse. When the FBG is weak, i.e. with lower reflectivity, the output doubled pulses will have the same amplitude, same pulse shape and same pulse width with the input pulse. When the FBG becomes strong, the amplitudes to the two output pulses will be different. They can have the same amplitude if the FBG is made of a pair of sine function with different amplitudes.