Digital stabilization of an IQ modulator in the carrier suppressed single side-band (CS-SSB) mode for atom interferometry

We present an all-digital method for stabilising the phase biases in an electro-optic I/Q modulator for carrier-suppressed single-sideband modulation. Building on the method presented in S. Wald \ea, Appl. Opt. \textbf{62}, 1-7 (2023), we use the Red Pitaya STEMlab 125-14 platform to digitally gener...

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Bibliographic Details
Published in:arXiv.org 2024-10
Main Authors: Ullah, Arif, Legge, Samuel, Close, John D, Haine, Simon A, Thomas, Ryan J
Format: Article
Language:English
Subjects:
Atom interferometry
Bias
Couplings
Error signals
Feedback control
Modulators
Phase stability
Single sideband transmission
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Summary:We present an all-digital method for stabilising the phase biases in an electro-optic I/Q modulator for carrier-suppressed single-sideband modulation. Building on the method presented in S. Wald \ea, Appl. Opt. \textbf{62}, 1-7 (2023), we use the Red Pitaya STEMlab 125-14 platform to digitally generate and demodulate an auxiliary radio-frequency tone whose beat with the optical carrier probes the I/Q modulator's phase imbalances. We implement a multiple-input, multiple-output integral feedback controller which accounts for unavoidable cross-couplings in the phase biases to lock the error signals at exactly zero where optical power fluctuations have no impact on phase stability. We demonstrate \(>23\,\rm dB\) suppression of the optical carrier relative to the desired sideband at \(+3.4\,\rm GHz\) over a period of \(15\) hours and over temperature variations of \(20^\circ\rm C\).
ISSN:2331-8422
DOI:10.48550/arxiv.2408.16678