High isolation optical switch, isolator or circulator having thin film polarizing beam-splitters

A method of controlling the flow of light, comprising the steps of splitting a light beam incident at a first port into a reflected p-polarized beam and a transmitted s-polarized beam with a first polarizing device, passing the p-polarized and s-polarized beams through respective polarization-rotating devices, and combining beams emerging from said polarization rotating devices into an output beam at a second port with a second polarizing device, each of said first and second polarizing devices employing total internal reflection and thin film interference in a stack of alternate high and low refractive thin film layers sandwiched between two high refractive index substrates to reflect p-polarized light and transmit s-polarized light, the thickness of the thin film layers in each of said polarizing devices being such that an equivalent optical admittance of the thin film layers for s-polarized light is substantially the same as an optical admittance of the substrates for s-polarized light for a range of angles of incidence and a band of wavelengths when incident light is incident upon the low refractive index layers at an angle greater then the critical angle whereby substantially all the s-polarized light is transmitted, and the thin film layers having an equivalent optical admittance for p-polarized light that is substantially different from the optical admittance of the substrates for p-polarized light for a range of angles of incidence and a band of wavelengths, whereby substantially all the p-polarized light is reflected.