Stability enhancement of a wide tunability Littrow-type external cavity diode laser using a non-collimating cavity

The traditional Littrow-type external cavity diode laser (ECDL) has a collimating cavity that is sensitive to external vibration. To solve this problem, we demonstrate a high-stability Littrow-type ECDL using a non-collimating cavity. The laser has a maximum output power of 30.2 mW at 420 mA drive current. The 3 dB tuning range of the laser is more than 100 nm covering all of the C-band. Compared to the ECDL using a collimating cavity, the root mean square (RMS) power stability is improved from 0.52% to 0.02% and the peak-to-peak power stability is improved from 3.6% to 0.1%. The integral linewidth is suppressed from 70 to 15.4 kHz and the intrinsic linewidth is 2.2 kHz with a 75 mm cavity length. By prolonging the cavity length, the intrinsic linewidth can be reduced to 31 Hz. This study presents a simple structure to substantially improve the power stability of ECDLs and reduce the linewidth to the Hz level.