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Journal of Undergraduate Research

Keywords

diode laser, anti-reflective coatings, scan range, atomic clock

College

Physical and Mathematical Sciences

Department

Physics and Astronomy

Abstract

Over the course of this grant, we have made considerable progress on our laser. We tested an anti-reflection coated diode in our setup, and although the anti-reflective coatings appear to be good, we did not see considerable improvement in scan range. However by experimenting with the geometry of the laser and implementing current feed-forward we were able to improve the scan range from about 9 GHz to greater than 50 GHz, more than sufficient for use in our atomic clock. We found a regular mode hop when attempting to scan over 50 GHz. We considered various etalons inside the cavity which could have caused this phenomenon (collimating lens, quarter wave plate, and other optics) but through extensive testing have found that the 50 GHz mode hop is due to the free spectral range of the laser diode. We could not find a way to eliminate this mode-hop, even with the use of an expensive anti-reflection coated laser diode. We spoke to the head of a company specializing in diode laser systems and found that this is a common problem even with the best anti-reflective coatings.

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