Microspectrometers fabricated in silicon using microelectromechanical systems technologies are versatile microinstruments: small, lightweight, and featuring a demonstrated capability for spectral analysis. When realized using silicon process compatible technologies, low-cost batch fabrication of an intelligent optoelectronic system-on-a-chip is feasible by cointegration of optics with microelectronic circuits. However, the spectral resolution of devices presented so far has been limited to about R=15, which does restrict application. This paper provides an overview of microspectrometers operating in the visible and infrared spectral range. Moreover, it is demonstrated that the resolution is primarily limited due to the short optical path that is inherent to a microsystem, optical properties of silicon IC-process compatible materials, and lack of adequate optical signal conditioning.

In this paper the concept of a microspectrometer based on a Linear Variable Optical Filter (LVOF) for operation in the visible spectrum is presented and used in two different designs: the first is for the narrow spectral band between 610 nm and 680 nm, whereas the other is for the wider spectral band between 570 nm and 740 nm. Design considerations, fabrication and measurement results of the LVOF are presented. An iterative signal processing algorithm based on an initial calibration has been implemented to enhance the spectral resolution. Experimental validation is based on the spectrum of a Neon lamp. The results of measurements have been used to analyze the operating limits of the concept and to explain the sources of error in the algorithm. It is shown that the main benefits of a LVOF-based microspectrometer are in case of implementation in a narrowband application. The realized LVOF microspectrometers show a spectral resolution of 2.2 nm in the wideband design and 0.7 nm in the narrowband design.