基于光偏振调制器产生亚毫米波的研究

Research on the generation of submillimeter-wave based on optical polarization modulators

亚毫米波源是亚毫米波应用的最重要的器件之一,电域中产生亚毫米波信号的成本十分昂贵。光生亚毫米波信号可极大地降低成本,是目前国内外研究的热点课题。提出了一种采用两组并行光偏振调制器级联产生32倍频亚毫米波的方案,首先用两个由4个偏振调制器并联构成的子系统级联产生主要保留载波和±16阶边带的光信号,同时利用光移相器和光分束器抑制载波,最后通过合成光信号在光电探测器上的拍频,获得32倍频亚毫米波信号。理论分析了产生32倍频亚毫米波信号的原理,推导出±16阶边带信号的光边带抑制比为55.7 dB,32倍频亚毫米波信号的射频杂散抑制比为43.7 dB。采用光子模拟软件,设计了一个基于上述原理产生32倍频亚毫米波的系统,获得了光边带抑制比为54 dB,射频杂散抑制比为43 dB,与理论分析吻合。同时分析了相移量、调制指数和分光比偏离对抑制比的影响。

The submillimeter-wave source is one of the most crucial components in submillimeter-wave applications.However,it is expensive to produce submillimeter-wave signals within the electric domain.Photogenerated submillimeter-wave signal can reduce the cost significantly,which is widely researched at home and overseas.A scheme based on two cascaded sets of paralleled polarization modulators to generate 32-times frequency submillimeter-wave signals is proposed.Firstly,two subsystems of four paralleled polarization modulators are cascaded to produce optical signals which are mainly retained the optical signals of the carrier and±16 th-order sideband signal.Thirdly,the carrier can be suppressed by an optical phase shifter and an optical splitter.Finally,the submillimeter-wave signal with frequency 32-tupling is generated after signals are beaten by the photodetector.The principle of producing 32-times frequency submillimeter-wave signals is theoretically analyzed.The±16 th-order optical sideband suppression ratio is derived as 55.7 dB and the radio frequency stray suppression ratio obtained from the experiment is 43.7 dB.According to the above theory,a system was designed using photon-simulation software.The OSSR and RFSSR values are 54 dB and 43 dB respectively,which is consistent with the theoretical analysis.Meanwhile,the effects of phase offset and modulation index,and splitting ratio deviation on suppression ratio are analyzed.