COMPOUND PARABOLIC CONCENTRATOR PROBE FOR EFFICIENT LIGHT COLLECTION IN SPECTROSCOPY OF BIOLOGICAL TISSUE

We describe a compound parabolic concentrator (CPC)-based probe for en hanced signal collection in the spectroscopy of biological tissues. Th eoretical considerations governing signal enhancement compared with co nventional collection methods are given. A ray-tracing program was use d to analyze the throughput of CPC's with shape deviations and surface imperfections. A modified CPC shape with 99% throughput was discovere d. A 4.4-mm-long CPC was manufactured and incorporated into an optical fiber-based near-infrared Raman spectrometer system. For human tissue samples, light collection was enhanced by a factor of 7 compared with collection with 0.29-NA optical fibers. (C) 1996 Optical Society of A merica