Isolator and Circulator

Abstract

Isolators and circulators are nonreciprocal devices, whose transmission characteristics change depending on the propagation direction. An ideal isolator transmits incident lightwave with no attenuation in a forward direction, while it completely attenuates backward reflections. The optical circulator is used to construct optical functional devices and/or subsystems. The rare earth iron garnet is grown by liquid phase epitaxy (LPE), sputter epitaxy, and flux method. The LPE of rare earth iron garnet was initially developed for growing a thin crystal layer. A fiber-in-line type optical isolator has high connectivity with other fiber optic components. In the fiber-in-line isolator, the components needed for isolator operation are micro-optic devices and installed in-between input and output fibers. In the waveguide isolator, the propagation of eigen mode, which is classified into quasi transverse electric and transverse magnetic modes in a channel waveguide, is strongly dependent on the waveguide structure. The waveguide isolators are classified into mode conversion type and phase shifter type.