A compact and rugged tunable external cavity diode laser with Littman-Metcalf configuration

An external cavity diode laser (ECDL) with Littman-Metcalf configuration is constructed in this paper. The ECDL adopts a compact structure with a star-flexure hinge as the tuning mechanism. Its mechanical characteristics and design are analyzed and optimized by finite element calculations. The first order resonance frequency of tuning arm is measured as 3.7 kHz. The laser cavity structure parameters are designed according to the mode-hop-free tuning condition, and the performance of the ECDL is obviously improved, showing single-mode operation with mode-hopping free tuning range over 80 GHz at 780 nm. The device has been operating stably without realignment for more than one year, indicating its good ruggedness. The frequency of ECDL can be locked at 87Rb (F=2→F′=2, 3) transitions. The linewidth of 200 kHz and temperature stability of 35 MHz/°C are measured, and the Allen deviation reaches 3.5×10-11 in 3-s integration time. Its output power is continuously monitored with fluctuation below 0.75% for 24 h, showing with good stability.