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Flat-focal-field integrated spectrometer using a field-flattening lens

Integrated spectrometers are usually of the Rowland mounting type [1]. For applications in which a continuous output spectrum needs to be imaged directly onto a linear detector array, the curved image plane of the Rowland mounting would result in additional losses and aberrations at the outer detector channels. Therefore, a flat-focal-field spectrometer would be highly desirable for such applications. Different methods have been proposed for the design of a flat-focal-field spectrometer [2,3], with limited success. In this work, an alternative way of designing a flat-focal-field arrayed-waveguide grating (AWG) [4] using an integrated field-flattening lens is presented.