Cavity-enhanced resonant photoacoustic and Raman spectroscopy for trace gas analysis and high-resolution spectroscopy

We introduce two new spectroscopic techniques which have been developed recently in Sheffield, cavity-enhanced resonant photoacoustic spectroscopy (CERPAS) [1] and cavity-enhanced Raman spectroscopy (CERS) [2]. In these techniques, diode laser light is coupled into an optical cavity composed of two highly reflective mirrors, and is stabilized to this cavity by optical feedback. Inside the cavity, a build up of laser power by a factor of 8000 occurs. In CERPAS, absorbing species are detected by resonant photoacoustic detection, achieving very high sensitivities in a "zero-background" method. In CERS, Raman scattering is excited by a visible diode laser and amplified in an optical cavity with detection limits in the ppm and sub-ppm range for Raman gas phase spectroscopy. Both CERPAS and CERS have great potential for analytical applications and for fundamental studies with high-resolution laser spectroscopy.

[1] M. Hippler, C. Mohr, K. Keen, E. McNaghten, J. Chem. Phys., 133 (2010), 044308.
[2] R. Salter, J. Chu, M. Hippler, Analyst 137 (2012), 4669.