Acousto-optic reconfigurable filter based on vector mode fusion in dispersion-compensating fiber.

An acousto-optic reconfigurable filter (AORF) is proposed and demonstrated based on vector mode fusion in dispersion-compensating fiber (DCF). With multiple acoustic driving frequencies, the resonance peaks of different vector modes in the same scalar mode group can be effectively fused into a single peak, which is utilized to obtain arbitrary reconfiguration of the proposed filter. In the experiment, the bandwidth of the AORF can be electrically tuned from 5 nm to 18 nm with superposition of different driving frequencies.

Ultra-narrow linewidth vertical-cavity surface-emitting laser based on external-cavity weak distributed feedback.

We demonstrate an ultra-narrow linewidth vertical-cavity surface-emitting laser (VCSEL) based on external-cavity weak distributed feedback from Rayleigh backscattering (RBS). A single longitudinal mode VCSEL with the linewidth as narrow as 435 Hz and a contrast of 55 dB are experimentally achieved by RBS fiber with a feedback level of RBS signal of -27.6 dB.

Tens of hertz ultra-narrow linewidth fiber ring laser based on external weak distributed feedback.

We suggest and demonstrate a single-frequency fiber ring laser with an ultra-narrow linewidth based on an external weak distributed feedback. A π phase-shifted fiber Bragg grating (PSFBG) is used to improve mode selection and enable single-longitudinal mode (SLM) laser operation. The linewidth is then further strongly compressed using a signal generated by a weak distributed feedback structure (WDFS) and injected into the main laser cavity to suppress spontaneous emission.

Ultra-narrow-linewidth DFB laser array based on dual-cavity feedback.

Herein, we propose a structure to simultaneously compress the distributed feedback (DFB) laser array's linewidth. The proposed structure is meticulously designed to ensure single longitudinal mode operation via the interference phenomenon between the laser's primary cavity and the dual-cavity feedback. Given the weak feedback effect for each wavelength in the laser array, the proposed structure could realize the intense compression of the laser linewidths.

Control of polarization switching in a VCSEL via resonant feedback from a whispering-gallery-mode cavity.

We report a method for flexibly switching the dominant polarization of a vertical-cavity surface-emitting laser (VCSEL) by introducing polarization-resolved resonant optical feedback from a whispering-gallery-mode (WGM) cavity to the lasing cavity. Switching between the originally dominant mode and a side mode is experimentally demonstrated under different bias currents once one of them is locked to the resonance mode of the WGM cavity. In addition to a controllable polarization state, the reported VCSEL also demonstrates a linewidth as narrow as tens of kilohertz, which is highly desirable for many applications, including high-speed data communication, light detection and ranging (lidar), and absorption spectroscopy.

Simultaneous self-injection locking of two VCSELs to a single whispering-gallery-mode microcavity.

Simultaneous self-injection locking of two vertical-cavity surface-emitting lasers (VCSELs) to a single whispering-gallery-mode (WGM) microcavity is experimentally demonstrated. The linewidths of the two VCSELs are compressed from 3.5 MHz and 5 MHz to 20.