Compact fiber-ring resonator for blue external cavity diode laser stabilization

We demonstrate a compact and low-cost all-fiber-based locking setup for frequency-noise suppression of a 420 nm external-cavity diode laser. Frequency noise reduction in the 100 Hz to 800 kHz range is demonstrated up to 40 dB associated with a linewidth narrowing from 850 kHz to 20 kHz for 10 ms integration time. This simple locking scheme might be implemented for a large range of wavelengths and can be integrated on a small footprint for embedded applications requiring narrow linewidth blue laser diodes.