Study Of Nonreciprocal Optical Propagation Phenomena And Optical Devices In Optical System

Nonreciprocal optical devices(NODs) are indispensable components in optical systems, including optical isolators, optical circulators, optical diodes, and et al., to realize the directional transmissions and controls of light. With the emerging of integrated of optical systems, minimization of optical components is needed. Thus, the researchs about integratable micro- and nano-scale NODs are very important than ever.Based on the breaking of time-reversal symmetry, this thesis will concern about the mechanism of nonreciprocal propagation of light, and about the designs of several NODs with simple structures.The works in this thesis is surported by the Key Project of Chinese Ministry of Education and National Natural Science Foundation of China. The detailed research contents are as follows:1. Study of unidirectional waveguide in Magneto-Optical Photonic Crysatals(MOPC). 1) Design a unidirectional waveguide based on MOPCs. Electro-magnetic wave with special frequencies can only propagate along one direction in this waveguide, while the reverted directional propagation is suppressed.2) With the help of dispersion relation analysis, t he origin of this unidirectional mode is the special gaps induced by external magnetic field into the band diagrams.3) The extraordinary couplings of electro-magnetic wave into this unidirectional waveguide are discussed.2. Study of the unidirectional boundary mold along magnetic domain-wall(MDW) in magneto-optical(MO) medium. 1) Using the breaking of time-reversal symmetry induced by MO medium, a kind of unidirectional boundary mold along MDW is proposed. The existing conditions, original reasons and the special characteristics of the unidirectional mode are also discussed.2) Based on this unidirectional mode, a new kind of isolator with simple structure is proposed, which can work in broadband. The performance of this isolator is also concerned.3. Study of isolator based on nonreciprocal micro-ring resonator(NMRR). 1) A new kind of nonreciprocal waveguide is proposed basing on the unidirectional boundary mode along MDW. The nonreciprocal dispersion relation of this waveguide is also calculated.2) Using this nonreciprocal waveguide, a NMRR is suggested, and a isolator is also proposed. Numerical results reveal an optical isolation of 20 d B in optical regium.4. Study of sharp waveguide bends with high transmission. 1) A new kind of nonreciprocal waveguide in microwave regium is proposed, basing the unidirectional mold along MDW.2) The posiblity of sharp waveguide bend with high transmission, using this nonreciprocal waveguide is discussed. With the help of curve corner, high transmissions can be achieved. Numerical results show the waveguide bend have three special characteristics such as broadband high transmission, compact structure, and minimized distortion in the guided mode.5. Study of nonreciprocal extraordinary optical transmission(NEOT). 1) A kind of double grating structure is proposed, which can performe NEOT in near-IR frequency range. 2) Dependances of NEOT on difference incidence angle and on difference thickness of MO substrate are discussed. When the incidence angle is 27 degree, and the thickness of the MO substrate is 290 nm, the nonreciprocity of transmissions can achieve 57.6%.