LiTaO_3相位调制器扩频特性的研究

Study of Spectrum Broadening Characters with LiTaO_3 Phase Modulators

介绍一种利用开关微波信号调制LiTaO3 电光晶体,实现对输入光扩频的方法。研究了LiTaO3 相位调制器的理论模型,并给出了相应的计算公式。利用公式模拟、计算得到在一定微波功率调制下相位调制器输出的扩频光谱。给出了实际系统的框图,并对实际系统的输出光谱进行测量,得到在不同微波调制功率下的光谱图。对理论计算所得的输出光谱与实际系统的输出光谱进行分析,发现谱线情况较一致,仅对应的微波输入功率有差异,原因是实际系统中微波传输线阻抗不匹配,所需的实际微波功率比理论值大。该系统的电光晶体为 LiTaO3,激光器工作波长为1053 nm,微波频率为4. 3 GHz,开关信号是重复频率为1 kHz,占空比为4∶6的方波。使90%的光功率分散于主峰以及一、二次边频,且一、二次边频的功率近似相等。

A novel method of broadening spectrum with LiTaO3 crystal by switching microwave signal modulation is presented in this paper. The theory model of phase modulation is illustrated, with the according formulae in details. The output result of broading spectrum in a certain microwave power is computed and simulated by the formulae. Furthermore, from a practical microwave phase modulator system framed in this paper, the actual spectrum is measured corresponding to variant level of modulating microwave power. The spectrum calculated by theory agrees with the spectrum of real system in shape, except for the disaccord of the level due to the impedance mismatch in practical transmission. Using the integrated waveguide eletrooplic phase modulator made of LiTaO3, the input light at 1053 nm is modulated by a 4.3 GHz microwave frequency, whose switching signal is 1 kHz repetition frequency and square-wave of 4:6 duty cycle. The 90 percent of input power is broadened to the fundamental frequency, first and second side frequency. The both side powers are nearly same.