Optical isolator based on volume Bragg gratings

An optical isolator comprising:

• one or more rotated volume Bragg gratings (r-VBGs) within a volume of a material having an input face, wherein each of the r-VBGs is formed as planes of refractive index variation with periodicity along a grating vector at a non-zero angle relative to a normal vector of the input face, wherein each of the r-VBGs reflects along a common reflection path portions of input light propagating along an incidence vector through the input face that satisfies a Bragg condition for one or more selected wavelengths and has a polarization orthogonal to a diffraction plane formed by the associated grating vector and the incidence vector, wherein each of the r-VBGs transmits remaining portions of the input light as transmitted light along a transmission path;
• and
• one or more polarization-controlling optics located along the common reflection path of the one or more r-VBGs configured to rotate a polarization of retroreflected light propagating back along the common reflection path towards the one or more r-VBGs by 90 degrees, wherein the one or more r-VBGs transmit the retroreflected light.