Abstract: A spectrophotometer comprising a monolithic semiconductor substrate, one or more wavelength dispersing means, and one or more wavelength detecting means, wherein the monolithic substrate (1) has waveguide means (2) and one or more resonators (3-14) acting as detectors of particular light wavelengths and disposed in proximity to the waveguide means in such a way that evanescent light coupling can occur for said light wavelengths.

Abstract: A spectrophotometer has a first photodetector (24) and a second photodetector (25) which is displaced spatially from the first photodetector in the direction of increasing wavelength in the spectrum. At any given time the second photodetector receives light at a wavelength which is substantially greater than that being received simultaneously by the first photodetector at that time. The first photodetector has first range of wavelengths over which it is operable and a first upper operating limit, and the second photodetector has a second range of wavelengths over which it is operable and a second upper operating limit, the second range overlapping the first range and the second upper operating limit being greater than the first upper operating limit. Thus the range of operation is extended, and data in two different ranges is processed simultaneously.