Microcavity-Enhanced Raman Scattering for Chemical Sensing

Raman scattering stands out as a unique process for true noninvasive molecular fingerprinting of chemical species, with applications in defense, air quality control, and metrology.  However, due to free-space scattering cross-sections of order ~10^-31 cm^2/sr-molecule (for gases) a compact and inexpensive Raman sensor for trace detection has not been demonstrated yet, despite a long history of research in enhancement methods, most notably surface enhanced Raman scattering (SERS) by which single molecules adsorbed to nanoparticles have been detected.  In this talk I will describe an enhancement method that uses optical microcavities and a quantum mechanical process — the Purcell effect — to provide sizable enhancement of Raman scattering at a miniature (~ 10 micron) scale.  This Purcell enhanced Raman scattering (PERS), makes use of ultrahigh finesse microcavity technology and a double-resonance configuration which can potentially lead to handheld gas Raman devices with order parts-per-million sensitivity.  I will present our most recent experimental efforts which include isotopically-resolved PERS in carbon dioxide gas.  In addition, I will show how the optimization of the PERS process involves surprising physical phenomena, such as the spontaneous generation of self-sustained thermomechanical oscillations of the intracavity circulating power.

All Faculty, staff and students are invited
Coffee will be served in the Department of Physics
SP-367-11 at 2:30  PM
Information: 514 848-2424 ext. 3270