A laser remote sensing apparatus comprises a laser to provide collimated
excitation light at a wavelength; a sensing optic, comprising at least
one optical element having a front receiving surface to focus the
received excitation light onto a back surface comprising a target sample
and wherein the target sample emits a return light signal that is
recollimated by the front receiving surface; a telescope for collecting
the recollimated return light signal from the sensing optic; and a
detector for detecting and spectrally resolving the return light signal.
The back surface further can comprise a substrate that absorbs the target
sample from an environment. For example the substrate can be a SERS
substrate comprising a roughened metal surface. The return light signal
can be a surface-enhanced Raman signal or laser-induced fluorescence
signal. For fluorescence applications, the return signal can be enhanced
by about 10.sup.5, solely due to recollimation of the fluorescence return
signal. For SERS applications, the return signal can be enhanced by
10.sup.9 or more, due both to recollimation and to structuring of the
SERS substrate so that the incident laser and Raman scattered fields are
in resonance with the surface plasmons of the SERS substrate.