RESUMEN
Partially temporal coherent light (PTCL) has been applied to holographic reconstruction to reduce speckle noise in display systems, while the encoding methods of computer-generated hologram (CGH), based on PTCL, have not been reported. We propose a novel method to encoding CGH, in which a PTCL with a broadband continuous spectrum is used to illuminate the object image. The continuous spectrum is discretized into different wavelengths and a weight value associated with PTCL power spectrum is assigned to each wavelength. The diffractive transmission is based on Fresnel diffraction theory. The phase distribution of the encoded CGH is obtained using the sum of multiplying the different CGH phase distributions of corresponding discrete wavelengths by the corresponding weight values. The modulation results without iteration are performed to verify the feasibility of the proposed method and the iterative algorithm is introduced to improve the quality of the modulation. The reconstructed images from the proposed encoding method exhibit high quality as compared with that obtained from the encoding method based on ideal temporal coherent light. Numerical simulations and optical experiments are good consistent with each other. The proposed method can provide a reference for various wave-front modulations.
RESUMEN
A curved multiplexing method based on the curved computer-generated hologram (CCGH) is proposed theoretically and demonstrated experimentally to increase field of view (FOV) and spatial bandwidth. Point source method is used to calculate the CCGH. Curved multiplexing method can be used to reconstruct different 3D objects at the same position by bending a composed hologram which is synthesized of several CCGHs with different central angles. Numerical simulations and optical experiments demonstrate that the method is feasible. It could have a good prospect by combining with the curved display screen and flexible display materials.
RESUMEN
Computer generated hologram (CGH) should be obtained with high accuracy and high speed in 3D holographic display, and most researches focus on the high speed. In this paper, a simple and effective computation method for CGH is proposed based on Fresnel diffraction theory and look up table. Numerical simulations and optical experiments are performed to demonstrate its feasibility. The proposed method can obtain more accurate reconstructed images with lower memory usage compared with split look up table method and compressed look up table method without sacrificing the computational speed in holograms generation, so it is called accurate compressed look up table method (AC-LUT). It is believed that AC-LUT method is an effective method to calculate the CGH of 3D objects for real-time 3D holographic display where the huge information data is required, and it could provide fast and accurate digital transmission in various dynamic optical fields in the future.
RESUMEN
The multiplexing encoding method is proposed and demonstrated for reconstructing colorful images accurately by using single phase-only spatial light modulator (SLM). It will encode the light waves at different wavelengths into one pure-phase hologram at the same time based on the analytic formulas. The three-dimensional (3D) images can be reconstructed clearly when the light waves at different wavelengths are incident into the encoding hologram. Numerical simulations and optical experiments for 2D and 3D colorful images are performed. The results show that the colorful reconstructed images with high quality are achieved successfully. The proposed multiplexing method is a simple and fast encoding approach and the size of the system is small and compact. It is expected to be used for realizing full-color 3D holographic display in future.
RESUMEN
Holography has extremely extensive applications in conventional optical instruments spanning optical microscopy and imaging, three-dimensional displays and metrology. To integrate holography with modern low-dimensional electronic devices, holograms need to be thinned to a nanometric scale. However, to keep a pronounced phase shift modulation, the thickness of holograms has been generally limited to the optical wavelength scale, which hinders their integration with ultrathin electronic devices. Here, we break this limit and achieve 60 nm holograms using a topological insulator material. We discover that nanometric topological insulator thin films act as an intrinsic optical resonant cavity due to the unequal refractive indices in their metallic surfaces and bulk. The resonant cavity leads to enhancement of phase shifts and thus the holographic imaging. Our work paves a way towards integrating holography with flat electronic devices for optical imaging, data storage and information security.
RESUMEN
The emerging graphene-based material, an atomic layer of aromatic carbon atoms with exceptional electronic and optical properties, has offered unprecedented prospects for developing flat two-dimensional displaying systems. Here, we show that reduced graphene oxide enabled write-once holograms for wide-angle and full-colour three-dimensional images. This is achieved through the discovery of subwavelength-scale multilevel optical index modulation of athermally reduced graphene oxides by a single femtosecond pulsed beam. This new feature allows for static three-dimensional holographic images with a wide viewing angle up to 52 degrees. In addition, the spectrally flat optical index modulation in reduced graphene oxides enables wavelength-multiplexed holograms for full-colour images. The large and polarization-insensitive phase modulation over π in reduced graphene oxide composites enables to restore vectorial wavefronts of polarization discernible images through the vectorial diffraction of a reconstruction beam. Therefore, our technique can be leveraged to achieve compact and versatile holographic components for controlling light.