Compact Spectrometer Design as WDM-Element in POF-Communication

Optical simulation software, which is based on the ray tracing method, offers fast results in the imaging optics. This simulation method can also be applied in other fields of light propagation, such as non-imaging optics for design of optical sensor or metrology elements. In this paper a design approach of a fully integrated miniature spectrometer by means of ray tracing simulation software is demonstrated. The basis of the presented element is a Rowland spectrometer that is optimized in crucial points, e.g. shape of mirror and grating, to guide the maximum of light. The classical Rowland spectrometers exhibit a flat design in one dimension, leading to a bad signal-to-noise ratio especially for high numerical aperture sources. Therefore, this spectrometer is designed to guide the complete light in the sagittal and tangential plane. Further on, a monolithic approach is presented with a blazed grating based on an aspheric mirror to spectrally separate and focus light on the image layer. The aspheric mirror is designed in a way that most of the aberrations are suppressed. In general, the element should be designed in a way that it can be produced with a mass production technology like injection molding in order to offer a reasonable price. The paper will introduce the application fields of miniature spectrometers and will step by step describe the development of this fully integrated monolithic miniature spectrometer by means of ray tracing simulation.