将调制频率为1 GHz的正弦波光信号的高阶谐波分量注入直调激光器,信号的光场强度和载流子浓度相互作用形成光电流,光电流经过直调激光器的射频(RF)端口形成微波倍频信号。实验通过检测RF端口的倍频信号功率变化,反馈控制直调激光器的波长,完成直调激光器的自动锁定,产生无光电探测器的10 GHz、12 GHz微波倍频信号。对比无自动锁定回路的注入锁定方案,自动锁定产生的微波倍频信号更稳定,其功率波动在10 min内稳定在2 dB,10 kHz处的相位噪声恶化程度控制在2.2 dB。微波倍频信号的最高倍频数取决于直调激光器的最高调制速率。

The high-order harmonic component of a 1 GHz modulated sinusoidal wave optical signal is injected into the directly modulated laser, and the interaction between the intensity of the light field and the carrier concentration forms the photocurrent. The photocurrent is then converted into a microwave frequency multiplication signal at the radio frequency (RF) port of this directly modulated laser. In the experiment, the feedback control the directly modulated laser wavelength and thus the automatic locking of the laser are realized by the powe rvariance of the frequency multiplication signal detected at the RF port. The microwave frequency multiplication signals at 10 GHz and 12 GHz are generated without photodetectors. Compared with those by the injection locking scheme without an automatic locking loop, the microwave frequency multiplication signals by automatic locking are more stable. The power fluctuation is stable at 2 dB within 10 min, and the phase noise deterioration at 10 kHz is as little as 2.2 dB. The produced largest frequency doubling number of microwave frequency multiplication signals depends on the maximum modulation rate of the directly modulated laser.