Diffraction efficiency

About: Diffraction efficiency is a research topic. Over the lifetime, 10320 publications have been published within this topic receiving 158298 citations.

Analysis of Bloch-surface-wave assisted diffraction-based biosensors

Abstract: A systematic study of Bloch surface wave (BSW) properties and applications in diffraction-based biosensors is presented. The design of such devices starts with the calculation of the BSW dispersion relation for a semi-infinite one-dimensional photonic crystal. We propose an approach in which polarization and 1DPC termination effects are simply described. Since in a realistic device the number of periods is limited, we investigate the issues arising from finite size effects and the choice of a structure substrate. Diffraction efficiency is studied as a function index contrast, multilayer termination, grating thickness, and number of periods. Numerical examples for Si/SiO2 and a-Si1−xNx:H periodic dielectric stacks are presented, showing that BSW can be exploited for the realization of efficient diffraction-based biosensors from the infrared to the visible range.

Waveguiding in blazed-binary diffractive elements

Abstract: Recent experimental and numerical results clearly show that blazed-binary diffractive elements outperform their standard blazed-echelette counterparts in the resonance domain. A theoretical study of one-dimensional blazed-binary gratings shows that the reason for this high efficiency is a waveguiding effect. The electromagnetic study supports the idea that, through waveguiding, a reduction of the shadowing zone is achieved, and thus the efficiency is increased. This is intrinsic to high-frequency binary structures and cannot be achieved with standard echelette diffractive elements.

Structured illumination in total internal reflection fluorescence microscopy using a spatial light modulator.

Abstract: In wide-field fluorescence microscopy, illuminating the specimen with evanescent standing waves increases lateral resolution more than twofold. We report a versatile setup for standing-wave illumination in total internal reflection fluorescence microscopy. An adjustable diffraction grating written on a phase-only spatial light modulator controls the illumination field. Selecting appropriate diffraction orders and displaying a sheared (tilted) diffraction grating allows one to tune the penetration depth in very fine steps. The setup achieves 91 nm lateral resolution for green emission.

Modern Classical Optics

Abstract: 1. Electromagnetism and basic optics 2. Fourier series and Fourier transforms 3. Diffraction 4. Diffraction gratings 5. The Fabry-Perot 6. Thin films 7. Ray matrices and Gaussian beams 8. Optical cavities 9. Coherence: qualitative 10. Coherence: correlation functions 11. Optical practicalities: etendue, interferometry, fringe localization 12. Image formation: diffraction theory 13. Holography 14. Optical fibres 15. Polarization 16. Two modern optical devices

Wide-angle nonmechanical beam steering using thin liquid crystal polarization gratings

Abstract: We introduce and demonstrate a compact, nonmechanical beam steering device based on liquid Crystal (LC) Polarization Gratings (PGs). Directional control of collimated light is essential for free-space optical communications, remote sensing, and related technologies. However, current beam steering methods often require moving parts, or are limited to small angle operation, offer low optical throughput, and are constrained by size and weight. We employ multiple layers of LCPGs to achieve wide-angle (> ±40°), coarse beam steering of 1550 nm light in a remarkably thin package. LCPGs can be made in switchable or polymer materials, and possess a continuous periodic birefringence profile, that renders several compelling properties (experimentally realized): ~ 100% experimental diffraction efficiency into a single order, high polarization sensitivity, and very low scattering. Light may be controlled within and between the zero- and first-diffraction orders by the handedness of the incident light and potentially by voltage applied to the PG itself. We implement a coarse steering device with several LCPGs matched with active halfwave LC variable retarders. Here, we present the preliminary experimental results and discuss the unique capability of this wide-angle steering.