We have used FM spectroscopy to detect the stimulated Raman gain effect in deuterium, demonstrating for the first reported time the quantum-noise-limited performance of this technique.
We demonstrate that the large FM noise of a semiconductor laser can be combined with a squeezed AM noise spectrum to make a sub-shot-noise, FM-noise-based spectroscopic measurement. In particular, we probe the spectrum of magneto-optically trapped and cooled rubidium atoms using the FM noise on squeezed AM background noise. The natural absorption line as well as a stimulated Raman transition are clearly visible in the FM-to-AM converted noise even though the signal is below the classical shot-noise level.
Stimulated Raman spectroscopy has become a powerful tool to study the spatio-dynamics of molecular bonds with high sensitivity, resolution, and speed. However, the sensitivity and speed of stimulated Raman spectroscopy are ultimately limited by the shot-noise of the light beam probing the Raman process. Here, we demonstrate an enhancement of the sensitivity of stimulated Raman spectroscopy by reducing the noise below the shot-noise limit by means of squeezed states of light. Our demonstration constitutes the first step towards a new generation of quantum-enhanced Raman microscopes.
Stimulated Raman spectroscopy has become a powerful tool to study the spatiodynamics of molecular bonds with high sensitivity, resolution, and speed. However, the sensitivity and speed of state-of-the-art stimulated Raman scattering spectroscopy are currently limited by the shot-noise of the light beam probing the Raman process. Here, we demonstrate in a proof-of-principle experiment an enhancement of the sensitivity of continuous-wave stimulated Raman spectroscopy by reducing the quantum noise of the probing light below the shot-noise limit by means of amplitude squeezed states of light. Probing polymer samples with Raman shifts around 2950 c m − 1 with squeezed states, we demonstrate a quantum enhancement of the stimulated Raman signal-to-noise ratio (SNR) of 3.60 dB relative to the shot-noise limited SNR. Our proof-of-concept demonstration of quantum-enhanced continuous-wave Raman spectroscopy paves the way for more elaborate demonstrations using state-of-the-art stimulated Raman scattering microscopes, and thus constitutes the very first step towards a new generation of Raman microscopes, where weak Raman transitions can be imaged without the use of markers or an increase in the total optical power.