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

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.