Low-noise local oscillators are very important in modern communication systems. To realize a stable solution with a limited size, symmetric multimode multi-section semiconductor laser pairs are reported in this article for building a chip-level RF synthesizer. The symmetric laser structure utilizes a shared distributed Bragg reflector (DBR) and counterpropagating laser output with the help of an external feedback circuit to achieve self-mode-locking. The achieved phase noise performance is −92 dBc/Hz at a 10 kHz offset frequency for intermodal operation at 26.4 GHz using 5 locked modes, which is a 57 dB improvement compared to the free-running case. Moreover, an RF synthesizer covering frequencies of 11–13 GHz is realized based on the achieved mode-locked system using current tuning. The related phase noise of the laser pair beat-note output is −100 dBc/Hz at a 10 kHz offset of carrier frequencies of 11–13 GHz, which is 58 dB better than the phase noise of the beat-note output without mode-locking over 11–13 GHz.

中文翻译：

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基于自锁模多模激光器的射频频率合成器

低噪声本地振荡器在现代通信系统中非常重要。为了实现尺寸有限的稳定解决方案，本文报道了对称多模多节半导体激光器对，用于构建芯片级射频合成器。对称激光器结构利用共享分布式布拉格反射器 (DBR) 和反向传播激光输出，借助外部反馈电路实现自锁模。对于使用 5 种锁定模式的 26.4 GHz 联运操作，在 10 kHz 偏移频率下实现的相位噪声性能为 −92 dBc/Hz，与自由运行情况相比提高了 57 dB。此外，基于使用电流调谐实现的锁模系统，实现了覆盖 11-13 GHz 频率的射频合成器。