Systems, devices, and methods for beam combining are described. A monolithic beam combiner includes a solid volume of optically transparent material having a planar input surface, an output surface, a planar reflector physically coupled to the solid volume, and at least a first planar dichroic reflector within the solid volume. Multiple light sources input light into the solid volume through the planar input surface such that each light beam from a respective source is initially incident on one of the planar reflector and the at least a first planar dichroic reflector. The light is reflected by and transmitted through the reflectors and an aggregate beam is created. Because the reflectors are within an optically transparent material the beam combiner can be made more compact than a conventional beam combiner. This monolithic beam combiner is particularly well suited for use laser projectors and in wearable heads-up displays that employ laser projectors.