Use Of Laser Direct Writing To Produce Gray-scale Mask Technique

In some application field, miniaturizating, high efficiency and arrayed diffractive optics element (DOE) is needed. DOE' s fabrication technologies such as conventional machining, binary optics and direct write technology have some disadvantages. Gray-scale mask(GSM) is a kind of new fabrication technology of DOE and developed from middle of 90' s. This technology has many good characteristics and is a kind of promising DOE fabrication technology compared with other fabrication technologies.Analyzing DOE using scalar diffraction theory is effective when the size of DOE is much bigger than wavelength. In this paper, we studied GSM technology detailedly around diffractive efficiency based on scalar diffraction theory. The contents as follow:1. Based on the actual parameter of laser direct writing system in our laboratory, designed a Fresnel lens.2. How to choice the writing step length was discussed when considering both the writing speed and the fabricated DOE ' s capability.3. We simulated the light exposure distribution of the mask and structure of the Fresnel lens in computer.4. The influence of etching depth errors to diffractive efficiency was analyzed.5. Two kinds of line width errors model were set up and the influence of the errors on diffractive efficiency were discussed for each one.6. The influences of tilt errors to diffractive efficiency were estimated.