Publication Date

Spring 2014

Degree Type


Degree Name

Master of Science (MS)


Physics and Astronomy


Peter Beyersdorf


Error signal, Frequency locking of laser, Littrow configuration, Loop filter circuit, Rubidium Spectroscopy, Tunable laser diode

Subject Areas

Physics; Optics


A laser diode emits a narrow range of frequencies. However, drifts in

frequency occur over time due to many factors like changes in laser temperature, current, mechanical vibrations in the apparatus, etc. These frequency drifts make the laser unsuitable for experiments that require high frequency stability. We have used an atomic transition in rubidium as a frequency reference and used Doppler

free saturated spectroscopy to observe the reference peak.

We have designed an electronic locking circuit that operates the diode laser at a specific frequency. It keeps the laser at that frequency for a long period of time with very few or no drifts.

We have constructed and characterized an extended cavity diode laser that costs significantly less than a commercial unit. It is much more compact with performance comparable to that of a commercial unit. It can be used in undergraduate and graduate optics laboratories where commercial units are cost prohibitive. The various components of the set-up are discussed, and the basic

principles behind the function and operation of this versatile device are explained. We designed a servo loop filter circuit, which is used to stabilize the frequency of the laser to an atomic reference frequency. We also generated an error signal using a technique similar to the Pound Hall Drever technique and then feedback the error signal in the loop filter circuit.