Compact broadband high-resolution infrared spectrometer with a dihedral reflector.

We demonstrate a compact broadband high-resolution spectrometer approach. A dihedral reflector is used to reflect the dispersed light back to the grating for a second diffraction, folding the light path in a compact space, and enhancing the spectral resolution. The theoretical formulas for the system are strictly derived. In addition, a prototype of this spectrometer for fiber communication in the infrared wavelength range has been built. The optics can fit inside a volume of 12 cm × 14 cm × 5 cm and its spectral resolution is 57 pm over a wide wavelength range from 1250 nm to 1650 nm.