激光经电光相位调制后,由于剩余幅度调制的存在造成调制边带幅度不相等。利用法布里珀罗腔的透射特性和Pound-Drever-Hall技术对通过法布里珀罗腔的调制光正、负一级边带的幅度产生不同的衰减,使得调制边带的幅度相等,从而实现对电光相位调制中剩余幅度调制的抑制。采用该方法,理论上计算了调制光经法布里珀罗腔后的光外差光谱信号,获得锁定法布里珀罗腔后调制边带幅度的不对称度较腔锁定前减小四个数量级。实验研究了调制光经法布里珀罗腔透射的光外差光谱,结果表明将法布里珀罗腔锁定于该透射光外差光谱中心零位时,对剩余幅度调制的抑制程度可达45 dB。

Residual amplitude modulation (RAM) in electro-optical phase modulators (EOM) results in unequal amplitude of modulation sidebands. Different amplitude attenuation of the first-order sidebands is undergone by means of transmission characteristic of Fabry-Pérot cavity and the Pound-Drever-Hall technique. Thus the amplitude of modulation sidebands is equal and the residual amplitude modulation can be suppressed. The beat signal between carrier and modulation sidebands is calculated theoretically after transmitting the Fabry-Pérot cavity, and the asymmetry of sidebands is reduced by four orders of magnitude once the Fabry-Pérot cavity is locked properly. Finally in experiment, the optical heterodyne spectrum is obtained after the modulated laser beam transmitted the Fabry-Pérot cavity. The result shows that the suppression of the residual amplitude modulation in electro-optical phase modulators is about 45 dB when the Fabry-Pérot cavity is locked to the central zero point of optical heterodyne spectrum.