In this paper, we propose a dielectric cylindrical lens and a dielectric spherical lens with dual polarity operating at visible frequencies. Composed of an array of nanofins with high aspect ratio as phase shifting elements, the designed dielectric dual-polarity lens have higher scattering efficiency and polarization conversion power than plasmonic dualpolarity lens. The phase variation from 0 to 2π is determined by adjusting the orientation angle of the individual nanofins according to the PB phase. By controlling the helicity of the incident circularly polarized light, the positive and negative polarity are interchangeable in one designed metalens. We demonstrate the broadband metalens possess a wavelength controllable focal length with incident wavelength from 488 to 740 nm. The dielectric dual-polarity metalens may open a new avenue for advanced research and applications in focusing and imaging devices, angular-momentum-based quantum information processing and integrated nano-optoelectronics.
A new kind of birefringence is found in a two-dimensional (2D) flat perfect photonic crystal (PhC). It is different from
the one in the normal biaxial crystal, but qualitative, and comes from the positive and negative refraction in the 2D flat
perfect PhC. The quantitative relationship between the refractive index and the incident angle are plotted, by the analysis
of the equal-frequent surface (EFS) of the perfect PhC. The plot is consisted of three branches---the main across 0° to
45.53° of the incident angle, the upper across 33.3° to 38.53° and the lower across 38.53° to 45.53°. The upper reveals the
positive refraction; the lower and the main reveal the negative ones. The finite-difference time-domain (FDTD)
simulations are performed, and the relevantly quantitative measurement validates the quantitative relationship by the
analysis of the EFS, but a 2.67° shift to the bigger incident angle.
A novel beam guiding is observed, which is resulted not from the guiding in a defect photonic crystal (PhC) but from the
negative refraction in a two-dimensional (2D) flat perfect PhC slab.
Readout optical technique is very important for the multilayered waveguide optical memory, which is based on an optical waveguide principle and a promising subject in the optical storage field compared to other 3D optical memory techniques. In this paper, the readout illumination system is designed by geometrical optical method and the experiment shows that the system works well.
The waveguide multilayer optical memory is a novel and promising subject in the optical storage field compared with other 3D optical memory techniques. To our certain knowledge, how to establish the information scattering model of the single-layer waveguide optical memory is not found. In this paper, the Lippman-Schwinger equation and dyadic Green's function are used to compute an exact solution of the wave equation about the single-layer plane waveguide with information recorded. Then, the constructing method of the dyadic green function of the perfect plane waveguide with three layered structures is presented. Among the numerical calculations, a method about double integration of rapidly oscillatory function is introduced in detail. Based on the above method, the information scattering model of the waveguide single-layer optical memory will be constructed. According this theoretic model, with the computer simulation, the scattered light intensity distribution on the detector plane is showed. The scattering light intensity of the single information pit that is on behalf of information is also given.
The diffraction of volume holographic gratings follows the Bragg law, and narrow wavelength selectivity and angle selectivity can be achieved with certain thickness of hologram. Multiple volume holographic gratings formed in Fe : LiNbO3 have high diffraction efficient and stability performance, which can be used for compact dense multiplexer/demultiplexer (MUX/DMUX). In this paper, we identify that it is feasible to record 16 volume holographic gratings by a special recording ways. The calculated results show the insertion losses and crosstalk at 1 .55µm waveband with channel separation 0.8nm is 0.66dB and —26dB respectively.