Surface Plasmon-based Micro-structure Of The Metal Film

Surface plasmon polaritons is excited state of evanescent wave, which is localized in the surface of a metal by the interaction of free-electrons and photons. Through the subwavelength structure modulation in the surface in nanoscale, it can control wave field along the surface, particularly the control of its interaction with light. It has tremendous potential applications in the nanotechnology areas such as nano-photonic devices, integrated optoelectronic chips and so on in the future, thus it has attracted the broad attention. In this paper, the research focused on the one-dimensional linear metal thin film microstructure and transmission metallic gratings with very narrow and deep enough slits, including explorations in experiment.First according to principle of surface plasmon wave (SPW) , it can only propagate along the interface of two materials, and the amplitude decays exponentially with the perpendicular distance tothe interface. Based on the coupled wave propagate depth d_SP and propagate distance L_SP ofdifferent metal materials, the select criterion for device material has been presented and silver has the best characteristics and is the most suitable materials for subwavelength device.Through the finite difference time domain (FDTD) method, we simulated the propagation characteristic of light wave in sub-wavelength slit device surrounded by periodic grating corrugations for the p polarized Gaussian beam of wavelength 632.1nm as an example. It has been proved that transmission enhancement and self-collimation phenomena in such device can be achieved. Among them, the grating in incidence surface makes a contribution to the transmission enhancement, and that in exit surface affects on far-field distribution of intensity. The effect of the number of dented grooves in the grating on transmission enhancement is limited, and the relation between transmission intensity and sub-wavelength slit depth has periodicity. These structure parameters for design photonic devices are very important.Because of the effect of surface plasmons wave, slit with symmetric grating can realize symmetric diffraction, and asymmetric structure with special design can achieve off-angle beaming phenomenon. Through formula Derivation and Helmholtz reciprocity theorem, we can design devices for parallel beam of p polarized light. Gaussian beam is one of the most common used beam in practice, with the Gaussian beam's divergence and near-field distribution, the structural parameters of devices for Gaussian beam is shrinks by 12%. On the basis of optimizating some other structures parameters, we achieve the design of symmetric diffracted and off-angle beaming effect device for 632.1nm Gaussian beam.Simulated by the theory of rigorous coupled wave analysis(RCWA), the coupling between p-polarized incident wave and surface plasmon polaritons on the surface of transmission metallic gratings with very narrow and deep enough slits can lead to a extremely high transmission efficiency. The transmitted spectrum shift to longer wavelengths with the increasing of incident angle. There is also a linear relationship between them. In the comparison of metal gratings, the ranking transmission performance at the visible and infrared spectrum is: Ag>Au>Cu>Al.Modified structures base on high-duty cycle metal grating such as adding optical substrate can improve the transmission performance caused by SPPs resonance coupling. The transmission rate increase mainly by the increase in transmission distance and overlap of coupling resonance of SPPs with cavity resonance.Exploration in experiments of high-duty cycle of the metal grating has done, it is difficult to peel off the sedimentary material because of the hardness of the film, as well as the grating surface roughness also increase due to the high duty cycle, the optical properties of samples are not very good. At last, a summary of this paper is included and the prospect of this project is given together.