Related Experiment Video
Updated: Jun 22, 2026

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
Published on: June 28, 2016
Finesse and sensitivity gain in cavity-enhanced absorption spectroscopy of biomolecules in solution
Timothy McGarvey1, André Conjusteau, Hideo Mabuchi
1Mail Code 266-33, California Institute of Technology, Pasadena, CA 91125, USA. mcgarvey@caltech.edu
Abstract:
We describe a 'wet mirror' apparatus for cw cavity-enhanced absorption measurements with Bacteriochlorophyll a (BChla) in solution and show that it achieves the full sensitivity gain ( approximately 2.3 x 10(4)) afforded by the finesse (3.4 x 10(4)) and loss distribution of our optical resonator. This result provides an important proof-of-principle demonstration for solution-phase cavity-enhanced spectroscopy; straightforward extrapolation to a system with state-of-the-art low-loss mirrors and shot-noise-limited performance indicates that single molecule sensitivity in liquids is within reach of current technology. With the probe laser locked to the cavity resonance, our instrument achieves a sensitivity approximately 3.4 x 10(-8)/ radicalHz (for a sample of length 1.75 mm) with 100 kHz bandwidth and can reliably detect sub-nM concentrations of BChla with 1 ms integration time.
Related Concept Videos
NMR Spectrometers: Resolution and Error Correction
¹H NMR: Interpreting Distorted and Overlapping Signals
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
Molecular Spectroscopy: Absorption and Emission

