Photorefractive Surface Waves And Their Applications In The Long Distance Propagation Of Surface Plasmon Polaritons

The photorefractive surface waves (PR SWs) are a kind of self-induced nonlinear surface waves which can propagate along the surface of the photorefractive materials. The interaction of reflaction of light at the interface and nonliearity of photorefractive crystal restricts the light energy is a narrow layer near the surface. The most attractive feature of PR SWs is that the concentration of beam energy with high intensity in the narrow surface layer, which ensures various nonlinear surface optical effects to be enhanced. So PR SWs are potentially usefully for waveguide fabrication, harmonic generation, integrated optics technique, and so on.Surface plasmon polaritons (SPPs) are propagating electromagnetic surface waves that may exist at a metal-dielectric interface. Their strong surface confinement, extremely sensitivity to the dielectric constant of the medium near the metal surface and sub-wavelength character make them attractive and being widely applied in many fields. However, the intrinsic damping due to the ohmic loss in metal film limits the propagation distance of SPP (about ten micrometers in the optical frequency range). This severely limits the application of SPPs.Researchers have proposed various methods to improve the propagation distance of SPPs which has already reached the order of centimeter. However, for a fixed scheme in previous methods, the SPP mode and its propagation length is fixed. In this dissertation, we take advantage of the photorefractive surface wave (PR SW) in attempt to lengthen the propagation length of SPP, and we get a configuration in which long-range surface plasmon polaritons whose modes and propagation distances are tunable can propagate. Unlike SPP, PR SW has no energy dissipation and could propagate without decay. The SPP and the PR SW will couple with each other during propagation, PR SW equal to an energy storage facility for SPP and then the propagation distance of SPP will be improved. Moreover, due to the photorefractive nonlinearity, a waveguide forms in accordance with the formation and propagation of PR SW. So the PRC is equivalent to a tunable waveguide and the excitation condition of SPP was extended, then it will come true that to excite various SPP modes in a fixed scheme.Firstly, in this dissertation, we deduce the nonlinear wave equations of PRC from band transport model and numerically calculate the steady solutions of PR SW on the interface of PRC and air under diffusition mecanism. Then we analyze the influences of propagation constant, dark irradiance and background light on the PR SW modes. We also analyze the coupling of TE mode and TM mode. When both TE and TM modes PR SW are present, they will be coupled drastically, the PR SW cannot remain decay, and the light energy can not be confined near the surface steadily.Secondly, a spatial-partition fast-Fourier-transformation beam propagation method (SP FFT-BPM) is presented, which can accurately simulate the propagation of light in media with large index variation while the conventional FFT-BPM can not. Then we use this SP FFT-BPM method to analyze the stability of PR SW under diffusion mechanism and get the same conclusion with the linear stability analysis that the PR SW under diffusion mechanism can propagate steadily.Thirdly, we present an improved Kretschmann configuration (linear-dielectric/ metal/nonlinear-dielectric) with nonlinear dielectric as substrate, in which long-range surface plasmon polaritons (SPPs) may appear with tunable modes and propagation lengths. We numerically simulate the solutions of SPP modes and their propagations. The results show that the SPP propagation length can range from tens of micrometers to tens of centimeters or even longer. The configuration proposed in this dissertation makes a breakthrough of the intrinsic restriction in conventional Kretschmann configuration and there exist the continuous steady SPP modes also in the range of k0ε31/2>β>k0ε11/2.Finally, the light transmission properties in one-dimensional metal-dielectric photonic crystals are studied theoretically by transfer-matrix method. Through numerical calculation, we obtain subwavelength discrete soliton in one-dimensional metal-dielectric photonic crystals. And on the interface of a one-dimensional metal-nonlinear dielectric photonic crystals and nonlinear dielectric, subwavelength surface discrete soliton is also obtained.The innovative points in this dissertation are as follows: 1. We theoretically study the TM mode PR SW and the coupling of TE mode and TM mode PR SWs for the first time, and analyze the factors affect the coupling. Then we present a spatial-partition fast-Fourier-transformation beam propagation method and simulate the propagation of PR SW by this method.2. A linear-dielectric/metal/nonlinear-dielectric configuration in which SPPs whose modes and propagation lengths are tunable can be exicted and propagate is presented.3. Through numerical simulation, we obtain the subwavelength surface discrete soliton on the interface of a one-dimensional metal-nonlinear dielectric photonic crystal and a semi-infinite nonlinear dielectric.Surface Plasmon polariton has a profound influence on the development of nano-optics and the miniaturization of photonic devices. Long-range surface plasmon polaritons whose modes and propagation distances are tunable will make SPP application more flexible in practice especially in the realization of optical integrated circuits.