Abstract: The photonic crystal material has a 3-D periodic structure with a periodicity that varies on a length scale comparable to the wavelength of electromagnetic radiation. The 3-D periodic structure is produced by irradiating photosensitive material with electromagnetic radiation such that interference between radiation propagating in different directions within the sample gives rise to a 3-D periodic variation in intensity within the sample. Thereafter the irradiated material is developed to remove the less or more irradiated regions of the material to produce a structure having 3-D periodicity in the refractive index of the composite material. 3-D photonic material is particularly suited to use as low-loss waveguides and as a control with lasers to limit the number of modes into which a laser may emit radiation.