Fabrication of HOE using CGH technique and laser direct write lithography system

Sumio Nakahara
Kansai University, Japan
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Recently, the demand to the holographic optical element (HOE) is increasing with the developments in the laser or holographic display technology. In this research, the application of laser direct-write lithography (LDWL) system to the fabrication of HOEs is examined. We created a relative large HOE with same method of production of the diffractive-optical element (DOE) using the LDWL system that has the feature of high-resolution drawing, high-speed drawing, and a high accuracy positioning system. Although it is difficult to draw to a large-sized substrate with electron-beam lithography system, since the LDWL system makes it possible, production of the large HOE is expected. Furthermore, a binary phase-type HOE was easily produced by wet etching processing to the glass substrate, and in order to obtain a bright image, a comparison of the diffraction efficiency of the amplitude-type DOE and the phase-type one was examined on Fresnel zone plate (FZP). The diffraction efficiency is influenced by etching-depth of grating of a phase type hologram. Therefore, we manufactured a phase type HOE of a required grating depth with accuracy using a reactive ion etching (RIE) system.