Transmission Gratings

A transmission grating offers a basic simplicity for optical designs that can be beneficial in fixed grating applications such as spectrographs (aka optical spectrometer). The incident light is dispersed on the opposite side of the grating at a fixed angle. Transmission gratings are very forgiving for certain types of grating alignment errors.

By necessity, a transmission grating requires relatively coarse groove spacings to maintain high efficiency. As the diffraction angles increase with finer spacing, the refractive properties of the materials used limit the transmission at the higher wavelengths and performance drops off. The grating dispersion characteristics, however, lend themselves to compact systems utilizing small detector arrays. The gratings are also relatively polarization insensitive.