High-Resolution Two-Grating Spectrometer for Dual Wavelength Spectral Imaging

Abstract

A two-grating high-resolution spectrometer for dual wavelength imaging is demonstrated based on the standard Czerny–Turner mounting with an auxiliary grating and a mirror. A two-dimensional charge-coupled device (CCD) detector in the spectrometer focal plane allows simultaneous detection of two spectral intervals. Each spectrometer grating is driven by a high-precision stepper motor interfaced to a computer via home-made software. The software allows fast tuning of the gratings to a desirable spectral interval anywhere between 200 nm and 800 nm. The spectral interval widths are 2–3 nm for a “high-resolution” (2400 grooves/mm) grating and 4–5 nm for a “low-resolution” (1200 grooves/mm) grating. The resolution varies between 0.01 nm and 0.02 nm depending on the grating used. The performance of the spectrometer is demonstrated by detecting spectrally resolved images from a back-illuminated template and from a laser-induced plasma. The spectrometer can be useful for two-line spectroscopic diagnostics or can be expanded for multi-element spectral analysis.