Fan Zhiqiang, Zhang Weifeng, Qiu Qi, Yao Jianping
Opt Lett. 2020 Feb 15;45(4):1027-1030. doi: 10.1364/OL.381106.
A wavelength-tunable single-mode laser with a sub-kilohertz linewidth based on parity-time (PT)-symmetry is proposed and experimentally demonstrated. The proposed PT-symmetric laser is implemented based on a hybrid use of an optical fiber loop and a thermally tunable integrated microdisk resonator (MDR). The MDR, implemented based on the silicon-on-insulator, operates with the optical fiber loop to form two mutually coupled cavities with an identical geometry. By controlling two light waves passing through the two cavities, with one having a gain coefficient and the other a loss coefficient but with an identical magnitude, a PT-symmetric laser is implemented. Thanks to an ultranarrow passband of the cavity due to PT-symmetry, single-longitudinal mode lasing is achieved. The tuning of the wavelength is implemented by thermally tuning the MDR. The proposed PT-symmetric laser is demonstrated experimentally. Single-longitudinal mode lasing at a wavelength of around 1555 nm with a sub-kilohertz linewidth of 433 Hz is implemented. The lasing wavelength is continuously tunable from 1555.135 to 1555.887 nm with a tuning slope of 75.24 pm/°C.
提出并通过实验证明了一种基于宇称时间（PT）对称的线宽低于千赫兹的波长可调谐单模激光器。所提出的PT对称激光器基于光纤环和热可调集成微盘谐振器（MDR）的混合使用来实现。基于绝缘体上硅实现的MDR与光纤环一起工作，形成两个几何形状相同的相互耦合的腔。通过控制穿过两个腔的两束光波，一束具有增益系数，另一束具有损耗系数但幅度相同，实现了PT对称激光器。由于PT对称导致腔具有超窄通带，实现了单纵模激光振荡。波长调谐通过对MDR进行热调谐来实现。对所提出的PT对称激光器进行了实验演示。实现了波长约为1555 nm、线宽为433 Hz的亚千赫兹单纵模激光振荡。激光波长在1555.135至1555.887 nm之间连续可调，调谐斜率为75.24 pm/°C。
