This proposal describes a research plan to develop novel solid-state semiconductor photoreceivers for operation in the combination region of the near infrared spectrum. These receivers are necessary to improve spectral quality for noninvasive measurements of blood glucose. Data is provided to show that glucose can be measured selectively in complex biological matrices (undiluted human serum and mammalian cell culture media) for near infrared spectra collected over the combination spectral region (2.08 to 2.38). Noninvasive human spectra collected over this wavelength range lack sufficient signal-to-noise to permit accurate blood glucose measurements. Analysis of the instrumentation reveals that detector performance currently limits our progress area. Hence, we propose to develop low-noise, high responsivity detectors specifically designed for this application and this spectral range. Specifically the alloy InGaAsSb will be used to fabricate semiconductor detectors for wavelengths between 2.08 and 2.38 microns. This semiconductor material provides an ideal bandgap for this spectral range which will maximize responsivity. Furthermore, this alloy can be lattice matched to commercially available GaSb substrates that will minimize dark currents. Coupling these novel photodetectors directly with custom-designed transimpedance amplifier circuits will reduce noise. The resulting photoreceivers will provide excellent signal-to-noise ratios for spectra collected between 2.08 to 2.38 microns. This proposal details the fabrication and characterization of a first generation of receivers. Subsequent generations will be constructed on the basis of photonic, electronic and spectroscopic performance.
