Novel Nano-Photoic Structures And Devices: Design And Optical Propagation Properties

Photonics nowadays is one of the most rapidly developing areas of modern physics. Photonics, which traditionally covers lasing cavities, waveguides, optical fibers and so on, is now expanding to new research directions such as photonic crystals (PhCs), plasmonics and nanophotonics that aimed at establishing and using the peculiar properties of light and light-matter interaction in various nanostructures to guide and manipulate light at nanoscale. In the above background, we have carried out some related research work.This thesis mainly studies the optical properties of the photonic crystals and plasmonic based periodic structures and the applications in photonic devices. The physical mechanisms and technological applications of the periodic structures in integrated optics and thin film solar cells are numerically analyzed. The primary research and achievement are as follows:(1) The abnormal dispersion properties of PhCs have been studied by plane wave expansion (PWE) method, especially self-collimation, directional emission and co-directional coupling phenomena. Based on self-collimation and co-directional coupling mechanism, one arbitrarily bent beam splitter has been designed and verified by FDTD method. Through the modification of the input and output surface of self-collimation region, even the optical source is put 15a way, the output beam can also propagate a long distance with small diverse angle. Optical interconnections using self-collimation, directional emission and co-directional coupling have been proposed and analyzed.(2) Plasmonic structures is the "state of the art" of nano-photonics. Surface plasmons (SPs), the electromagnetic modes localized at metal-dielectric interfaces and metallic nanoparticles, bring in new unprecedented opportunities of guiding and manipulating light beyond the diffraction limit. Plamonic nanolens which can render focused spot at a few times of wavelength from the substrate that is difficult to be achieved by the traditional convex lens system have been designed, two different proposals have been demonstrated and the methods used to modify focusing length and the full-width at half-maximum (FWHM) of the spot have been discussed.(3) Within the researches in the next generation thin film solar cells (TFSC), micro and nano photonics are one promising and exciting direction. To introduce photonic periodic structures into thin film solar cells, the optical path length of incident photons will be increased which is very helpful for light trapping and result in high efficiency of TFSC. Subwavelength grating is one of the structures mostly used, after using the metallic grating and one dimensional photonic crystals at the bottom of the TFSC, the incident photons will return back into absorbing region because of diffraction, scattering and reflection.(4) The nanoimprint lithography (NIL) method was introduced to fabricate periodic metallic nano structures. High aspect ration gratings were fabricated using NIL, sputtering together with reactive ion etching (RIE) method. The grating with the aspect ration of 24 with 10 micrometers period was fabricated successfully. The absorption of the grating was measured by FTIR in RIKEN. The results show that when the incident light is p-polarized, the absorption spectra present some peaks, the fabricated grating shows large reflection for s-polarized light. This kind of special metallic grating can be used to increase the sensitivity of surface plasmon resonance sensors through planar metallic film coupled to nano-gratings and use grating period to adjust the wavelength of resonance reflection.