A FLAT-FIELD BROAD-BAND SPECTROGRAPH DESIGN

A planar spectrograph design is described that features a flat-field o utput and operates over a remarkably broad range of wavelengths. The g rating facet positions are described by an iterative algorithm that en sures that light will arrive in phase at the focal point. There are no aberrations of any order at the design wavelength and aberrations nea r the design wavelength are simultaneously minimized. The peak intensi ty of the output varies less than 3 dB over a wavelength range of 1.46 to 1.64 mum. The spectrograph may be used as a demultiplexer in photo nics systems using wavelength division multiplexing. The design easily accommodates hybrid integration of a linear detector array at the out put.