Linewidth narrowing and wideband frequency modulation of a DBR laser

Abstract: We present a scheme to phase-lock a 240 mW, 852 nm distributed Bragg reflector (DBR) laser to a fixed-frequency narrow-linewidth laser with a rapidly tunable frequency offset near 9 GHz. The phase-lock is accomplished by electronic feedback on the beatnote between the two lasers. The frequency offset can be swept 200 MHz in 300 us, limited by the feedback loop bandwidth, allowing for its use in complex cooling and state preparation schemes needed in atomic physics experiments. Additionally, we find that the phase-lock reduces the linewidth of the DBR laser below its natural linewidth of ~400 kHz to ~100 kHz.