Patent ID: 7545513

Claim:
A method of using an optical cavity that is operable to provide output light in one or more modes; when providing output light in one of the modes with analyte absent, the optical cavity providing the output light with a respective unencoded intensity function; the method comprising: positioning an analyte in the optical cavity, the analyte having a respective optical absorption characteristic; and while the analyte is positioned in the optical cavity, providing analyte-affected output light in at least one of the modes; the analyte-affected output light from each mode having a respective encoded intensity function that is different than its unencoded intensity function; the difference indicating the analyte's optical absorption characteristic; each mode's encoded and unencoded intensity functions having a respective difference that includes at least one of: a difference between maximum intensities of the mode's encoded and unencoded intensity functions; a difference between contrasts of the mode's encoded and unencoded intensity functions; and a difference between intermediate intensity widths of the mode's encoded and unencoded intensity functions.