Patent ID: 8330956

Claim:
A device for spectroscopy comprising: a coupled-cavity comprising a first mirror, a second mirror, and a third mirror configured in parallel, wherein the first mirror and the second mirror form a Fabry Perot (FP) cavity, and the second mirror and the third mirror form a sample cavity configured to contain a sample; and a radiation source configured to generate a radiation beam to pass through both the FP cavity and the sample cavity, wherein the FP cavity is configured to tune a wavelength of the radiation beam passing through the FP cavity such that the tuned wavelength coincides with an absorption feature of the sample contained in the sample cavity, wherein each of the first mirror and the second mirror has a same reflectivity R 0 , wherein R 0 >1−√{square root over (8αL)}; α is the sample's absorption coefficient; and L is the sample cavity's length.