Systems, devices, and methods for eyebox expansion in wearable heads-up display are described. The eyebox of a wearable heads-up display may be expanded by increasing the bandwidth of the hologram comprising the holographic combiner of the wearable heads-up display. The bandwidth of the hologram may be increased by physically coupling a donor film to a hologram film, causing donor material to diffuse into the hologram film and then fixing the donor material in place. Diffusion of donor material into the hologram film causes a change in the slant angle and/or the spacing of at least a portion of the hologram fringes of the hologram film, broadening the bandwidth of the hologram.