A device may include a rotated volume Bragg grating (r-VBG) formed as planes of refractive index variation with periodicity along parallel grating vectors, where periods are chirped to vary along the respective grating vectors. The device may include a mirror spatially separated from the r-VBG along a separation direction at a non-zero angle relative to the grating vectors, and a phase modulator between the r-VBG and mirror with a spatially non-uniform phase distribution orthogonal to the separation direction. The r-VBG may reflect portions of input light propagating along an incidence direction satisfying a Bragg condition into the separation direction as a spectrally-spread beam, where the Bragg condition is satisfied for different wavelengths at different locations along the incidence direction. The mirror may retroreflect the spectrally-spread beam back through the phase modulator to the r-VBG, which reflects portions satisfying the Bragg condition to spectrally recombine into an output beam.