A hybrid laser comprising a semiconductor pump laser and small-cavity rare
earth fiber laser where laser cavities of both lasers are butt coupled or
otherwise optically coupled to form a plurality of laser cavities that
produce a plurality of emission wavelengths, one which may be the pump
laser emission wavelength at the output of the fiber laser thereby
forming a multi-wavelength combined output. The wavelengths in such an
output may substantially match distinguishing spectral characteristic
features along at least a portion of a characteristic optical spectrum of
the analyte under examination providing a method of determining the
concentration of an analyte in a specimen undergoing examination.