Two-frequency acousto-optic modulator driver to improve the beam pointing stability during intensity ramps
Year: 2007
Authors: Fröhlich B., Lahaye T., Kaltenhäuser B., Kübler H., Müller S., Koch T., Fattori M., Pfau T.
Autors Affiliation: 5. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
Abstract: We report on a scheme to improve the pointing stability of the first order beam diffracted by an acousto-optic modulator (AOM). Due to thermal effects inside the crystal, the angular position of the beam can change by as much as 1 mrad when the radio-frequency power in the AOM is reduced to decrease the first order beam intensity. This is done, for example, to perform forced evaporative cooling in ultracold atom experiments using far-off-resonant optical traps. We solve this problem by driving the AOM with two radio frequencies f1 and f2. The power of f2 is adjusted relative to the power of f1 to keep the total power constant. Using this, the beam displacement is decreased by a factor of 20. The method is simple to implement in existing experimental setups, without any modification of the optics.
Journal/Review: REVIEW OF SCIENTIFIC INSTRUMENTS
Volume: 78 (4) Pages from: 043101 to: 043101
More Information: The authors thank C. S. Adams for useful discussions and W. Möhrle for the design of the digital control box. The authors gratefully acknowledge the support of the German Science Foundation (DFG) (SFB/TR 21) and the Landesstiftung Baden-Württemberg. One of the authors (T.L.) acknowledges support from the European Marie Curie Grant MEIF-CT-2006-038959.KeyWords: Evaporative cooling systems; Optics; Problem oriented languages, Beam pointing stability; Optical traps; Power constant; Ultracold atom, Bragg cellsDOI: 10.1063/1.2720725