Residual amplitude modulation at the $10^{-7}$ level for ultra-stable lasers

Abstract

The stabilization of lasers on ultra-stable optical cavities by the Pound-Drever-Hall (PDH) technique is a widely used method. The PDH method relies on the phase-modulation of the laser, which is usually performed by an electro-optic modulator (EOM). When approaching the $10^{-16}$ level, this technology requires an active control of the residual amplitude modulation (RAM) generated by the EOM in order to bring the frequency stability of the laser down to the thermal noise limit of the ultra-stable cavity. In this article, we report on the development of an active system of RAM reduction based on a free space EOM, which is used to perform PDH-stabilization of a laser on a cryogenic silicon cavity. A RAM stability of $1.4\times 10^{-7}$ is obtained by employing a digital servo that stabilizes the EOM DC electric field, the crystal temperature and the laser power. Considering an ultra-stable cavity with a finesse of $2.5\times 10^5$, this RAM level would contribute to the fractional frequency instability at the level of about $5\times 10^{-19}$, well below the state of the art thermal noise limit of a few $10^{-17}$.

arXiv comment6 pages, 4 figures

References in corpus (9)

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• Compact, thermal-noise-limited optical cavity for diode laser stabilization at 1 x 10-15
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Cited by in corpus (4)

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• 300 μs optical cavity storage time and $10^{-7}$ active RAM cancellation for $10^{-19}$ laser frequency stabilisation
• Influence of a magnetic field on the frequency of a laser stabilized to molecular iodine
• Development of a laser stabilized on an ultra-stable silicon cryogenic Fabry-Perot cavity for dark matter detection