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Updated: Jun 2, 2025

Multiplex Chemical Imaging Based on Broadband Stimulated Raman Scattering Microscopy
Published on: July 25, 2022
Squeezed dual-comb spectroscopy
Daniel I Herman1, Mathieu Walsh2, Molly Kate Kreider1,3
1Department of Electrical, Computer and Energy Engineering, University of Colorado Boulder, Boulder, CO, USA.
Abstract:
Optical frequency combs have enabled distinct advantages in broadband, high-resolution spectroscopy and precision interferometry. However, quantum mechanics ultimately limits the metrological precision achievable with laser frequency combs. Quantum squeezing has led to substantial measurement improvements with continuous wave lasers, but experiments demonstrating metrological advantage with squeezed combs are less developed. Using the Kerr effect in nonlinear optical fiber, a 1-gigahertz frequency comb centered at 1560 nanometers is amplitude-squeezed by >3 decibels (dB) over a 2.5-terahertz bandwidth. Dual-comb interferometry yields mode-resolved spectroscopy of hydrogen sulfide gas with a signal-to-noise ratio nearly 3 dB beyond the shot-noise limit. The quantum noise reduction leads to a twofold quantum speedup in the determination of gas concentration, with implications for high-speed measurements of multiple species in dynamic chemical environments.
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