Advances in the design and applications of complex volume Bragg gratings

Recent work has advanced volume Bragg gratings (VBGs) by enabling compact, versatile devices for spectroscopy, light-field synthesis, and filtering. The X-CBG multiplexes two orthogonal rotated chirped VBGs (r-CBGs) in a single volume, achieving dual-band, high-resolution spectral analysis in a compact footprint. Each channel is independently tunable, supporting visible and NIR bands simultaneously, ideal for portable spectroscopy. A second innovation uses cascaded r-CBGs with a phase plate to synthesize space–time wave packets (STWPs). This ultra-compact (25×25×8 mm³) system replaces bulky diffraction-grating setups, producing diffraction-free, tunable STWPs efficiently. Finally, phase-shifted chirped VBGs (PS-CBGs) were realized in bulk glass, combining chirp and a π-phase shift to yield ultra-narrowband (