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arXiv · 1610.01631

Simple High-Bandwidth Sideband Locking with Heterodyne Readout

Christoph Reinhardt·Tina Müller·Jack C. Sankey
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Abstract

We present a robust sideband laser locking technique that is ideally suited for applications requiring low probe power and heterodyne readout. By feeding back to a high-bandwidth voltage controlled oscillator, we lock a first-order phase-modulation sideband to a table-top high-finesse Fabry-Perot cavity, achieving a feedback bandwidth of 3.5 MHz with a single integrator, limited fundamentally by the signal delay. The directly measured transfer function of the closed feedback loop agrees with a model assuming ideal system components, and from this we suggest a modified design that should realistically achieve a bandwidth exceeding 6 MHz with a near-causally limited feedback gain of $4\times 10^7$ at 1 kHz. The off-resonance optical carrier is used for alignment-free heterodyne readout, alleviating the need for a second laser or additional optical modulators.

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Christoph Reinhardt, Tina Müller, Jack C. Sankey. 2016-10-05. Simple High-Bandwidth Sideband Locking with Heterodyne Readout. https://doi.org/10.1364/oe.25.001582

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