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Register a new userDifferential wavefront sensing and control using radio-frequency optical demodulation
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Differential wavefront sensing is an essential technique for optimising the performance of many precision interferometric experiments. Perhaps the most extensive application of this is for alignment sensing using radio-frequency beats measured with quadrant photodiodes. Here we present a new technique that uses optical demodulation to measure such optical beats at significantly higher resolutions using commercial laboratory equipment. We experimentally demonstrate that the images captured can be digitally processed to generate wavefront error signals and use these in a closed loop control system for correct wavefront errors for alignment and mode-matching a beam into an optical cavity to 99.9%. This experiment paves the way for the correction of even higher order errors when paired with higher order wavefront actuators. Such a sensing scheme could find use in optimizing complex interferometers consisting of coupled cavities, such as those found in gravitational wave detectors, or simply just for sensing higher order wavefront errors in heterodyne interferometric table-top experiments.
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We report on the realization of a novel fiber-optic radio frequency (RF) transfer scheme with the bidirectional frequency division multiplexing (FDM) dissemination technique. Here, the proper bidirectional frequency map used in the forward and backward directions for suppressing the backscattering noise and ensuring the symmetry of the bidirectional transfer RF signals within one telecommunication channel. We experimentally demonstrated a 0.9 GHz signal transfer over a 120 km optical link with the relative frequency stabilities of 2.2E-14 at 1 s and 4.6E-17 at 20,000 s. The implementation of phase noise compensation at the remote site has the capability to perform RF transfer over a branching fiber network with the proposed technique as needed by large-scale scientific experiments.
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