Several Optical Properties And Devices Of Periodic Subwavelength Structure

With the development of laser manufacturing technology,it is able to manufacture material at nanometer scale with a considerable accuracy.It has provided conditions for investigating the optical properties of subwavelength structures.Meanwhile,subwavelength structures have been attracted many attentions due to their novel optical properties.In the first chapter of this thesis,the research progress of subwavelength metallic structure and subwavelength dielectric structure has been introduced,and the properties of surface plasmons have also been discussed.In the second chapter of this thesis,the near field optical properties and the dependence of dark hollow optical field modes on structure parameters have been discussed.Then,van der Waals potential and spontaneous emission of the atom has been discussed in order to evaluate the stability of trapping atoms.In the third chapter,an ultra board band mirror with extreme high reflectivity based on subwavelength trapzoid media grating has been proposed.Then the dependence of reflective band on structure parameters has been discussed.Finally,a reflective focusing mirror based on aperiodic subwavelength grating has been proposed.The dependence of reflective phase at grating on structure parameters has been discussed.In chapter ?,we propose a 2D optical lattice for ultra cold atom by the 2D metallic cylinder array.The light intensity distribution of Surface Plasmons with near field coupling is investigated by Finite Elements Methods(FEM).Optical potential and Van der Waals potential of cold atoms as well as the dependence of distribution of total potential and the height of center of the trap are investigated.We derive a dark hollow area with 350 nm length,350 nm width,60 nm height located above the middle of four metal cylinders.It is convenient to manipulate and control cold atoms by adjusting different spatial structures.In addition,the spontaneous emitting,Rayleigh scattering and Raman scattering of atoms trapped in our optical lattice are investigated.Our research provides a new method for further research of periodic atomic optical device with an ability of breaking diffraction limit.In chapter ?,we propose an ultra-broad band mirror with a wide spectral band and a high reflectivity by the novel subwavelength trapezoid grating.The reflectivecharacteristics of the plane wave on the trapezoid subwavelength grating are investigated,and the analytic research is studied by the Rigorous coupled wave analysis method as well as the numerical simulation is studied by the finite element method,and results from both methods are almost consistent.By optimizing the structural dimensions,we derive a spectral band of 345 nm with a reflectivity above 99.9%(??/?22%) at the center wavelength around 1550 nm.In addition,a spectral band of 482 nm for a reflectivity above 99% as well as 80 nm for a reflectivity above 99.99% are also obtained.The normalized mode distribution including the standing wave in the grating direction is analyzed for the large spectral band.In chapter ?,a reflective focusing mirror based on aperiodic subwavelength dielectric grating has been proposed.Finite Elements Methods has been used to study the optical properties.As L=700 nm,l1 = 525 nm,d = 600 nm and the height of grating cell fits with a quadratic function,the magnetic field intensity at focusing point is more than 5times higher than the magnetic field intensity of the surrounding.It has shown that the reflective phase at grating is closely related to focusing intensity,and the dependency of the reflective phase at grating on structure parameters has also been discussed.