Synthetic FM triplet for AM-free precision laser stabilization and spectroscopy

Abstract

The Pound-Drever-Hall (PDH) cavity-locking scheme has found prevalent uses in precision optical interferometry and laser frequency stabilization. A form of frequency modulation spectroscopy, PDH enjoys superior signal-to-noise recovery, large acquisition dynamic range, wide servo bandwidth, and robust rejection of spurious effects. However, residual amplitude modulation at the signal frequency, while significantly suppressed, still presents an important concern for further advancing the state-of-the-art performances. Here we present a simplified and improved scheme for PDH using an acousto-optic modulator to generate digital phase reference sidebands instead of the traditionally used electro-optic modulator approach. We demonstrate four key advantages: (1) the carrier and two modulation tones are individually synthesized and easily reconfigured, (2) robust and orthogonal control of the modulated optical field is applied directly to the amplitude and phase quadratures, (3) modulation synthesis, demodulation, and feedback are implemented in a self-contained and easily reproducible electronic unit, and (4) superior active and passive control of residual amplitude modulation is achieved, especially when the carrier power is vanishingly low. These distinct merits stimulate new ideas on how we optimally enact PDH for a wide range of applications.

References in corpus (7)

• Advanced Virgo: a 2nd generation interferometric gravitational wave detector
• Advanced LIGO
• Exploring the Sensitivity of Next Generation Gravitational Wave Detectors
• An ultrastable silicon cavity in a continuously operating closed-cycle cryostat at 4 K
• Excess noise and photo-induced effects in highly reflective crystalline mirror coatings
• Residual amplitude modulation at the $10^{-7}$ level for ultra-stable lasers
• Laser-cavity locking at the $10^{-7}$ instability scale utilizing beam elipticity

Cited by in corpus (5)

• 300 μs optical cavity storage time and $10^{-7}$ active RAM cancellation for $10^{-19}$ laser frequency stabilisation
• A laser with instability reaching $4\times 10^{-17}$ based on a 10-cm-long silicon cavity at sub-5-K temperatures
• Ultrastable lasers: investigations of crystalline mirrors and closed cycle cooling at 124 K
• Hänsch-Couillaud locking of a large Sagnac interferometer: advancing below the flicker floor
• Errors in PDH offset locking due to spurious spectral features