Spectrometer with rotated volume bragg grating

A method comprising:

• directing input light through an input face of a material including a rotated chirped volume Bragg grating (r-VBG) within a volume of the material, wherein the r-VBG is formed as planes of refractive index variation with periodicity along a grating vector at a non-zero angle relative to a normal vector of the input face, wherein the r-VBG reflects portions of input light propagating along an incidence vector through the input face that satisfies a Bragg condition for wavelengths within a spectral band, wherein a period of the r-VBG along the grating vector is chirped to vary along the grating vector to provide that the Bragg condition is satisfied for different depths, wherein the reflected portions of the input light by the r-VBG are spatially resolved in the reflected portions of the input light by the r-VBG;
• and
• capturing the reflected portions of the input light from the output face with a multi-pixel detector;
• determining a spectrum of the input light within the spectral band based on output spectral data from the multi-pixel detector.