State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
Opt Lett. 2013 Sep 1;38(17):3441-4. doi: 10.1364/OL.38.003441.
We present a novel photonic approach to generating widely tunable and background-free binary phase-coded radio-frequency (RF) pulses by cascading a polarization modulator (PolM) and a phase modulator (PM). The PolM is used to produce an optical carrier and two sidebands with orthogonal polarization states. The phase shift θ between the optical carrier and the sidebands is controlled by the electrical driving signal applied to the PM. For θ>π/2 or <π/2, the phase of the detected RF signal is 0 or π, respectively. For θ=π/2, there is no RF signal recovered in the photodiode (PD). In this way, binary phase-coded RF pulses can be generated, while the optical power launched to the PD keeps constant. The proposed technique is therefore background free by eliminating the baseband frequency components. Moreover, the carrier frequency of the RF pulses is widely tunable and the π phase shift of the RF signal is independent of the amplitude of the electrical driving signal. The proposed scheme is theoretically analyzed and experimentally verified.
我们提出了一种新颖的光子学方法，通过级联偏振调制器（PolM）和相位调制器（PM）来产生宽带可调且无背景的二进制相位编码射频（RF）脉冲。PolM 用于产生具有正交偏振态的光载波和两个边带。施加到 PM 的电驱动信号控制光载波和边带之间的相位差θ。对于θ>π/2 或<π/2，检测到的 RF 信号的相位分别为 0 或π。对于θ=π/2，光电二极管（PD）中没有恢复 RF 信号。通过这种方式，可以产生二进制相位编码的 RF 脉冲，同时向 PD 发射的光功率保持恒定。因此，通过消除基带频率分量，该技术是无背景的。此外，RF 脉冲的载波频率可宽范围调谐，并且 RF 信号的π相移与电驱动信号的幅度无关。该方案在理论上进行了分析，并通过实验得到了验证。
