The BTC661E is a high-resolution and high-sensitivity compact spectrometer for Raman spectroscopy. The spectrometer is designed with a unique folded dual pass optical system for high photon throughput and features an extremely low dark noise, back-thinned CCD array that can be thermoelectrically cooled to -20° C. The narrow pixel width of the array supports high spectral resolution. The BTC661E is an ideal building block for OEM manufacturers and bench top end users alike. Four different models are offered for use with excitation lasers of 532 nm or 785 nm and in either wide range or high resolution configurations. The BTC661 is supplied with BWSpec software that includes a user interface for directly measuring Raman spectra as well as drivers for Thermo GRAMS/AI and LabView.