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Locking the frequency of a laser using an acoustic-optic modulator

Students Jake Lampen and Margeaux Carter

Tuesday, November 5, at 3:45 p.m. in SB110.

In order to implement a magneto-optical trap (MOT) for argon atoms, we needed a laser that was frequency-tuned precisely to the atomic transition at 811 nm. To build a “laser-frequency lock” we used an acousto-optic modulator to separate a laser beam into two beams exhibiting a specific frequency difference. After both beams were sent through a sample of argon gas, the absorption signal of one was subtracted from the other.  This resulted in an electronic “zero-crossing”—and therefore a locking point—at the midpoint between frequencies of the beams. We used the lock in order to implement a MOT for argon atoms, but it was not stable for more than a few seconds at a time, so it will have to be improved.





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