Tunable Optical And Faraday Magneto-optical Properties Of One-dimensional Photonic Crystals

Because photonic crystals have many properties such as photonic band gap, photonic localization, and so on, photonic crystals can be adopted to control the movement of photons. They can be used to make high-performance optoelectronic devices. Devices with photonic crystals have the advantages of high integration, high stability, high working speed, etc.. Researches on photonic devices will improve the development of the integration of optoelectronic devices and optical communications field. Because of the unique properties and potential applications of the photonic crystals, photonic crystals have drawn much attention recently. Many theoretical and experimental studies indicate that the optical and magneto-optical properties of photonic crystals have been strongly affected by the defect layers.Some magnetic materials are introduced as defects, the symmetric multi-defect structure are designed in this thesis. When one varies the structural parameters of the defects, the location of photonic crystal defect states and the position of the giant Faraday rotation can be changed. And under appropriate conditions, the optical Tamm states do appear at the interface of the photonic crystal and the inhomogeneous film. Since the nematic liquid crystals are easily influenced by the external environment, such as applied electric field, environmental temperature, the optical properties of the one-dimensional photonic crystal including the defects with nematic liquid crystals can be adjusted. Our study may become a theoretical guide for the related experiments and the designing of the device. The thesis is organized as follows: I. Independently tunable transmission-type magneto-optical isolatorsbased on symmetrical multilayers containing magnetic materials We investigate the magnetooptical (MO) properties of the one-dimensional photonic crystal containing several magnetic defects. Our numerical simulations show that each MO defect mode can be tuned independently by adjusting the structural parameters of magnetic materials. In addition, giant Faraday rotation can be obtained. Our results indicate that these symmetrical multilayers can be useful for the practical applications of independently tunable multichannel MO isolators.II. Temperature tunable optical properties of photonic crystal including a defect layer with nematic liquid crystalsWe theoretically demonstrate that temperature tunable photonic crystals (PCs) with nematic liquid crystals (NLCs) can be realized. We show that the environmental temperature may lead to red or blue shift of transmission peak. When the electric field is neither parallel nor perpendicular to direction of axis of NLC molecular, there will be two peaks in the transmittance spectra, resulting from the different resonant modes of linear polarization with electric field parallel and normal to the direction of NLCs. In addition, the rotation of polarization is greatly enhanced at the wavelength where the transmission peaks appear. Our calculations show that the right transmission peak is more sensitive to the variation of temperature. And the peaks of rotation are highly sensitive to the change of temperature when the temperature is nearby the transition temperature, above which the NLC will transition from nematic phase to isotropic state. This is very interesting from the point view of actual multipurpose device.III.Optical Tamm states in photonic structures containing inhomogeneous materials.We demonstrate the existence of a spectrally narrow localized surface state, the so-called optical Tamm state, at the interface between a photonic crystal and a film with non-uniform varied refractive index. The optical Tamm state is associated with a sharp transmission peak inside the band gap and strong localization of the electric field at the interface of the photonic crystal and the inhomogeneous film. The position of the optical Tamm state depends on the periodic constant of the inhomogeneous film and the thickness of the photonic crystal's first layer away from the interface. Moreover, the order of the inhomogeneous is of great significance for the occurrence of the optical Tamm state.