Wideband laser locking to an atomic reference with modulation transfer spectroscopy

TL;DR

This paper enhances conventional modulation transfer spectroscopy for laser frequency stabilization by achieving a wideband lock with 100 kHz bandwidth, significantly reducing frequency noise and linewidth, using an acousto-optic modulator.

Contribution

It introduces a method to attain wideband laser locking with deep noise suppression using standard apparatus and acousto-optic modulation.

Findings

Achieved 100 kHz feedback bandwidth in laser locking.

Reduced frequency noise by 30 dB across the acoustic range.

Narrowed laser linewidth by a factor of five.

Abstract

We demonstrate that conventional modulated spectroscopy apparatus, used for laser frequency stabilization in many atomic physics laboratories, can be enhanced to provide a wideband lock delivering deep suppression of frequency noise across the acoustic range. Using an acousto-optic modulator driven with an agile oscillator, we show that wideband frequency modulation of the pump laser in modulation transfer spectroscopy produces the unique single lock-point spectrum previously demonstrated with electro-optic phase modulation. We achieve a laser lock with 100 kHz feedback bandwidth, limited by our laser control electronics. This bandwidth is sufficient to reduce frequency noise by 30 dB across the acoustic range and narrows the imputed linewidth by a factor of five.