Researchers at the University of South Florida have developed a new invention that is comprised of an ultra-sensitive Raman chemical sensor based on enhanced spontaneous emission as a result of cavity quantum electrodynamic effects.
In prior art, flat/flat resonators with cavity spacing less than a wavelength were used. This was necessary because the flat/flat resonator is only stable for infinitely wide beams and its effective finesse decreases with increasing cavity length for real laser beams with finite widths, and because the double resonance was achieved through an off-axis orientation of the excitation beam. This type of geometry is incompatible with the free flow of analytes through the cavity. In the present invention the microcavity is highly stable by using one or two concave micromirrors, so that cavity spacing can be much longer.
Specifically, the device makes use of a double resonance of a microcavity with both the excitation laser frequency and the Raman frequency. Because the Raman frequency directly depends on the excitation laser frequency, this virtually guarantees that resonance with the Raman frequency is also satisfied, provided that the Raman linewidth is larger than the cavity linewidth.