Optical microspectrometers are potentially important components for improving the functionality of lab-on-a-chip systems used for detection and identification of cells and other biological material. For disposable and portable applications, monolithic integration of the microfluidic channels, optical waveguides and diffraction grating is desirable. This paper presents the design and simulation of a transmission grating that can be integrated with microfluidic channels for on-chip fluorescence detection. The grating design features two stigmatic points and large facet sizes that can be easily fabricated in low-cost polymers. Scalar simulations predict grating efficiencies greater than 74% for wavelengths from 500 nm to 700 nm in the -2 diffraction order.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.