Holographic gratings with asymmetric structure are widely used to couple light into and out of waveguides due to
their high diffraction efficiencies and planar packaging. In this paper, a holographic grating coupler based on the
photopolymer has been designed and experimentally demonstrated at wavelength of 405nm. To achieve the high
diffraction efficiencies in the structure, we investigated the optical properties of the coupler according to the
exposure energy at the 405nm wavelength. In the holographic recording for the asymmetrical geometry, we
researched the optical characteristics of the Dupont photopolymer HRF150-38 as the correction of the Bragg angles
shift because of shrinkage factor and the diffraction efficiency. The performance and the optical characteristics of
the coupler using volume holographic grating will discussed in detail.
In this paper, we design a subwavelength binary grating working as a diffractive polarizing beamsplitter. The polarizing beamsplitter is then optimized by using a genetic algorithm to increase its extinction ratios up to as high as 238 and 82. We use the rigorous coupled-wave analysis method to calculate the parameters of the beamsplitter during the optimizing process.
Holographic transmission gratings with 0o;-Bragg angle are widely used to couple light into and out of waveguides due to their high diffraction efficiencies and planar packaging. In this paper, a holographic grating coupler based on the photopolymer has been designed and experimentally demonstrated. To achieve the high diffraction efficiencies, we investigate the optical properties of the coupler according to the exposure energy at the 405 nm wavelength. For the asymmetrical geometry with 72othe correction of the Bragg angles shift of about 0.95o; and 3.45o;, which are induced by the 7.86% shrinkage factor, is successfully demonstrated. The performance and the optical characteristics of the coupler using volume holographic grating are discussed in detail.
A new structure of polarization-selective elements consisting of two holographic gratings and a dove prism coupler is proposed. The absence of a multi-stage wave-guide, compact size, and lightweight volume are the outstanding features of the new structure. Based on the coupled-wave theory, the analysis and design of the structure are discussed in detail to calculate the required index modulation. Several parameters such as the recording intensity, the exposure time, and the recording angles for the fabrication of the proposed element are determined. Under the conditions the element is fabricated in Dupont photopolymer HRF-150-38 material and with the operating wavelength of 532nm. A simplified pick-up head is constructed to evaluate the performance of the fabricated element.
A polymer focusing waveguide grating coupler(FGC) was implemented by UV nanoimprinting method. The size of this focusing grating is 1 mm X 1 mm and the total device size is 8 mm X 2 mm. We use the UV sensible polymer which is coated by spin coating method. After nanoimprinting the device, the residual thickness on the slab waveguide is about 10 nm ~ 30 nm. The spot size of this polymer FGC is 347 nm for blue laser and the coupling efficiency is 28.2%.
A focusing grating coupler (FGC) using a blue laser of a wavelength of 400 nm as a light source was fabricated for the first time. The FGC was designed to have a numerical aperture of 0.48 and a focusing angle of zero. The focal length and the grating area were 900 μm and 1×1mm2, respectively. Grating pattern of a minimum period of 0.2μm was fabricated on a single mode waveguide based on the boron phosphor silicate glass (BPSG) material by electron-beam lithography process using the vector scan method. The spot size at the full width (1/e2) was measured at 0.85 and 0.92μM in x and y direction, respectively, and these values are nearly same as the diffraction limited size.
A micro-optical pickup has been implemented by using a focusing waveguide grating coupler. The grating coupler was designed and fabricated on a single mode BPSG (boron phosphor silica glass) waveguide layer. The coupling area was 1×1mm2 containing more than 1,500 grating lines, where the maximum and minimum grating pitch were 296nm and 811nm, respectively. The focal length and the numerical aperture of the present grating coupler were 530 μm and 0.68 with 632.8nm He-Ne red laser. The full width half maximum diameter of the focal spot was measured to be 450 nm and 510 nm in x and y direction.
A new beam steering scheme using computer-generated holograms(CGHs) is proposed. The steering devices in order to control the reference and object wave are necessary in various holographic multiplexing methods. The beam steering device using CGHs can be simultaneously processed the coarse address function controlling the beam up or down so as to select slice and the fine address function adjusting to the particular holographic page within the chosen layer. From the experimental results, we show that the beam steering can be easily implemented and so powerful to generate the electrically addressed reference wave in digital holographic memory system.