Quasi-achromatic optical isolators and circulators using prisms with total internal fresnel reflection

摘要

A quasi-achromatic configuration of two nonreciprocal optical rotators (25, 27) coupled by linear retardation elements (26, 28) based on total internal Fresnel reflec­tion, such that wavelength or temperature effects on the optical rotator elements compensate one another to give quasi-achromatic isolation and/or temperature stability when this optical configuration is incorporated into an optical isolator or circulator. A quasi-achromatic optical isolator through which a light beam within a wavelength range about a nominal wavelength may propagate is made from a sequence of elements having a first plane polarizer (24) accepting said light beam as an input, said light beam then passing through in sequence, a first Faraday rotator (25), a first wave-­length independent linear retardation element (26), a second Faraday rotator (27), a second wavelength independent linear retardation element (28), and said light beam exiting said isolator undiminished in intensity through a second plane polarizer (29). A quasi-achromatic optical circulator having first, second, third and fourth ports is provided such that said circulator may accept a light beam within a wavelength range about a nominal wavelength and direct it to a succeeding port. A light beam enters said circulator through a first polarizing beam splitter (44) adjacent to said first and third ports and passes through sequentially a first Faraday rotator (25), a first wavelength independent linear retardation element (26), a second Faraday rotator (27), a second wavelength independent linear retardation element (28) and a second polarizing beam splitter (49) adjacent to said second and fourth ports of said circulator, whereby said light beam is transmitted undiminished in intensity to the next succeeding port.