A self-injection locked DBR laser for laser cooling of beryllium ions

TL;DR

This paper introduces a simple, stable, narrow-linewidth laser system for cooling beryllium ions, achieved through self-injection locking and frequency stabilization techniques, eliminating complex feedback requirements.

Contribution

It demonstrates a novel self-injection locking method for a DBR laser at 626 nm, providing high stability and narrow linewidth suitable for ion cooling applications.

Findings

Laser instability reduced from MHz to 20 kHz

Long-term frequency stability achieved with feedback to cavity length

Automatic relocking algorithms maintain stable operation

Abstract

We present a simple, robust, narrow-linewidth, frequency-doubled semiconductor laser source suitable for laser cooling and repumping of $^9$Be$^+$ ions. A distributed Bragg reflector (DBR) laser diode operating at 626 nm is self-injection-locked to a frequency doubling cavity via phase-stabilised optical feedback when the laser is resonant with the cavity mode. The short-term laser instability is reduced from the MHz-level to approximately 20 kHz by the injection process, thus eliminating the need for a high-bandwidth feedback loop to suppress the otherwise troublesome high-frequency laser noise. Long-term stability of the laser frequency is achieved by feeding back to the length of the enhancement cavity utilising an electro-optic frequency comb generator to produce a beatnote with a laser that is detuned by 98 GHz. Long-term injection locking and frequency stabilisation via a wavemeter are ensured using automatic relocking algorithms.