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22 March 2007 Rb-saturated absorption profile-based enhancement of semiconductor laser frequency stability
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Laser interferometers detect gravitational waves with a degree of accuracy and efficiency unimaginable even a few years ago. The semiconductor lasers that are the primary light source for these devices are small, lightweight, durable and energy-efficient. On the downside, the devices currently available are still marked by broad oscillation spectra, and heightened sensitivity to fluctuations in injection current and /or ambient temperature. By applying a small sine wave to the injection current, we modulate the oscillation frequency. This frequency-modulated beam is introduced to the Avalanche photo diode through the Rb cell in the saturated absorption optical setup. The resulting signal and a reference signal are detected simultaneously and combined, to produce an error signal, which, when fed back to the injection current, stabilizes the diode's oscillation frequency at 2.12x10-12 ⩽ &sgr;(2,τ) ⩽ 5.88x10-11 in the averaging time between 0.4s to 65s. An optical feedback method, which introduces the laser beam reflected by a mirror or a grating to the semiconductor laser itself, is reported to narrow oscillation linewidth and improve frequency stability. We are now combining these two techniques to further improve frequency stability.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
K. Nakano, S. Maehara, M. Yanagisawa, Y. Sekiya, T. Sato, M. Ohkawa, T. Maruyama, and S. Kawamura "Rb-saturated absorption profile-based enhancement of semiconductor laser frequency stability", Proc. SPIE 6468, Physics and Simulation of Optoelectronic Devices XV, 64680C (22 March 2007);

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