Narrow-linewidth 852-nm DBR-LD with self-injection lock based on high-fineness optical cavity filtering

TL;DR

This paper demonstrates a narrow-linewidth 852-nm DBR laser diode achieved through self-injection locking with a high-finesse optical cavity, significantly reducing phase noise and linewidth for applications in quantum and precision measurement.

Contribution

It introduces a self-injection locking technique using a high-finesse Fabry-Perot cavity to substantially narrow the laser linewidth and suppress phase noise in 852-nm DBR-LDs.

Findings

Laser linewidth reduced to 263 Hz via self-injection locking.

Phase noise suppressed by over 30 dB at 100 kHz.

Effective linewidth narrowing enhances laser spectral purity.

Abstract

Narrow-linewidth lasers have high spectral purity, long coherent length and low phase noise, so they have important applications in cold atom physics, quantum communication, quantum information processing and optical precision measurement. We inject transmitted laser from a narrow-linewidth (15 kHz) flat-concave Fabry-Perot (F-P) cavity made of ultra-low expansion (ULE) optical glass into 852-nm distributed-Bragg-reflector type laser diode (DBR-LD), of which the comprehensive linewidth of 1.67 MHz for the free running case. With the increase of self-injection power, the laser linewidth is gradually narrowed, and the inject-locking current range is gradually increased. The narrowest linewidth measured by the delayed frequency-shifted self-heterodyne (DFSSH) method is 263 Hz. Moreover, to characterize the laser phase noise, we use a detuned F-P cavity to measure the conversion signal from laser phase noise to intensity noise for both the free running case and self-injection lock case. Laser phase noise for the self-injection lock case is significantly suppressed in the analysis frequency range of 0.1-10 MHz compared to the free running case. Especially, the phase noise is suppressed by more than 30dB at the analysis frequency of 100 kHz.