In a traditional Fourier holographic projection, a clear reconstructed image is formed only in the focal plane of the Fourier lens. In this paper, we propose a novel method to form simultaneously holographic reconstructed images in good focus located at different continuous planes. The phase profile of the hologram is superimposed with the phase of diffractive axilens to obtain a new diffractive phase element (DPE). We use laser direct write lithography system to fabricate the desired DPE with smaller feature sizes of pixels. A comparative experiment is carried out to observe reconstructed images of superposition of the axilens phase and Fresnel lens phase on the phase hologram, respectively. Finally, the DPEs are drawn in a photoresist of glass substrate by laser direct write lithography technology, in which only a limited number of quantized phase levels m are achieved (e.g., m=2 , m=4 ). Our experiment results revealed that the approximate clear holographic images can be observed simultaneously on multiple planes by using the DPE, which is in good agreement with the simulations.
The optical properties of conventional optical components vary with wavelength. This leads to chromatic aberrations of optical components, and affects the accuracy and effectiveness of optical systems operating in wideband severely, especially in the visible band. The traditional optical design achieves achromatic result by bonding a plurality of lenses of different dispersion properties. The diffractive optical element (DOE) is characterized by miniaturization and light weight, which can realize functions such as array, integration, and arbitrary wave-front conversion. However, it is difficult to perform in conventional optical devices. In this paper, we can use diffractive lenses to achieve achromatic effects. A method of designing multi-wavelength achromatic lenses by using genetic algorithms combined with scalar diffraction theory is proposed. We use the focusing performance of different light wavelengths in the focal plane as the optimization condition. After several iterations, we finally get the optimal lens structure, and use this lens to do the simulation focusing experiment based on RGB three-color light. The simulation results show that the achromatic lens can focus the red, green and blue light to a point in space. In addition, the achromatic lens can be on the order of microns in diameter. Therefore, such a lens has a smaller volume, which is difficult to achieve with conventional lenses.
A deep sub-wavelength metal grating is used to replace the top electrode of liquid crystal on silicon (LCOS) to form a new structure of liquid crystal (LC) phase spatial light modulator (SLM), which to meet large spatial bandwidth product of dynamic holographic video display. Although the structure of this (gold) deep sub-wavelength grating-LC-metal electrode is similar to the geometry of the current LCOS, the physical mechanism is completely different, which we called it G-LCOS. In order to study the feasibility of the new G-LCOS for phase modulation of digital holographic display, based on previous calculation and simulation, we fabricate deep sub-wavelength gratings by using EBL and obtain a conceptual verification device by referring to the traditional LCOS process flow. In this paper, we present experimental investigations based on Michelson's interference principle on the phase modulation performance of this proof-of-concept device. The results show that the phase modulation of the structure can reach 1.2π. The slight disagreement between the theoretically predicted and the experimentally measured values for the G-LCOS phase modulation could be caused by the errors in the preparation process and measurement.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.