Compensating for frequency shifts in modulation transfer spectroscopy caused by residual amplitude modulation |
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Authors: | Esa Jaatinen David J. Hopper |
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Affiliation: | aApplied Optics Program, School of Physical and Chemical Sciences, Queensland University of Technology, P.O. Box 2434, Brisbane, Qld 4001, Australia |
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Abstract: | Residual amplitude modulation (RAM) distorts saturated absorption signals, limiting the accuracy of optical frequency references based on modulation transfer spectroscopy (MTS). Described here are two independent means by which RAM is produced in these references: (1) by the modulator and (2) when the overlap of the optical fields in the saturable absorber is asymmetric. Methods to vary RAM generated by either mechanism will be outlined and these will be used to show how RAM arising from one effect can be cancelled by the other. A theoretical treatment of MTS signals in references containing RAM is given and used to evaluate the level of signal distortion allowing the conditions for RAM cancellation to be determined. This technique is applied to improve the frequency accuracy of a reference by an order of magnitude. |
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Keywords: | Modulation transfer spectroscopy Optical frequency references |
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