<p>The resolution optimization and sampling strategies in practical digital in-line holography (DIH) with spherical wave illumination are analytically studied by optimizing system parameters. Optimal parameters of holographic recording, including illumination wavelength, numerical aperture of the spherical illumination wave, source-sensor distance, object–sensor distance, and sampling parameters of the sensor, for achievable resolution are worked out. A formula is derived to guide the DIH system design in general cases. Different sampling strategies associated with corresponding reconstruction waves (plane wave and spherical waves with various curvatures) are analyzed. The reason why recording with spherical wave and reconstructing with plane wave works well in practice is explained in detail. We also present how to determine the reconstruction distance and magnification to reconcile the curvature difference. The analysis is carried out mathematically and verified by simulated holograms. Optical experiments with U.S. Air Force resolution target are carried out based on the analysis for further verification.</p>
Metasurface is used to manipulate the optical field recently. In holography, the complex amplitude computer generated hologram can improve the quality of the reconstructed image. However, the current devices limit the application of complex amplitude modulation. Several works have been done for complex amplitude modulation by metasurface. In this work, a novel metasurface structure has been proposed to realize complex amplitude modulation. This kind of metasurface can modulate arbitrary complex amplitude. Furthermore, it has a thinner thickness, making it easier to fabricate.
The photonic crystals possess complex dispersion relation and the unusual dispersion leads to negative refraction. Based on negative refraction, three main physical phenomena, negative Goos–Hänchen displacement, inverse Doppler effect and abnormal Cherenkov radiation have been proposed. In this work, two abnormal physical phenomena are discussed. Firstly, the negative Goos–Hänchen shift displacement is simulated by using common FDTD method. The negative displacement is measured experimentally at the wavelength of 10.6 μm. Secondly, a novel phenomenon, the dual Doppler effect, in the simultaneous occurrence of both normal and inverse Doppler effect in one moving two-dimensional wedge-type photonic crystal with negative index is investigated by using spatial Fourier Transformation. This phenomenon is also simulated by an improved FDTD method. The results have potential applications in precision measurement, cloaking, sensor, radar deception and so on.