Design and Fabrication of Diffractive Light-Collecting Microoptical Device with 1D and 2D Lamellar Grating Structures

Chabum Lee

doi:10.1155/2014/101823

Abstract

This paper presents the optimal design method of diffractive light-collecting microoptical device and its fabrication method by E-beam lithography, fast atom beam etching, and hot-embossing processes. The light-collecting device proposed in the paper is comprised of 9 (3 × 3) blocks of optical elements: 4 blocks of 1D lamellar grating structures, 4 blocks of 2D lamellar grating structures, and a single block of nonpatterned element at the center, which acts for lens to be able to collect the diffracted and transmitted lights from the lamellar grating structures into the focus area. The overall size of the light-collecting device is 300 × 300 μm2, and the size of each block was practically designed as 100 × 100 μm2. The performance of 1D and 2D lamellar grating structures was characterized in terms of diffraction efficiency and diffraction angle using a rigorous coupled-wave analysis (RCWA) method, and those geometric parameters, depth, pitch, and orientation, were optimized to achieve a high light-collecting efficiency. The master molds for the optimized structures were fabricated on Si substrate by E-beam lithography and fast atom beam etching processes. The 100 μm thick patterned polymethyl methacrylate (PMMA) film was then replicated by a hot-embossing process. As a result, the patterned PMMA film collected 63.0% more incident light than a nonpatterned one.

Highlights

Microoptical devices or hybrid integrated optical devices have been very important in the field of optical application systems such as optical communication systems, optical information processing systems, and optical sensing systems to achieve compactness and high performance [1,2,3,4]
The light source transmits through optical fibers in many cases; the output beam emitting from the source has far-field radiation angles that need an external lens such as a collimating lens or a focusing lens
The Laser diodes (LD) (λ = 0.65 μm, Neoark) was used as the light source with a Gaussian intensity distribution, and the optical fiber was used to deliver the light from the LD

Summary

Introduction

Microoptical devices or hybrid integrated optical devices have been very important in the field of optical application systems such as optical communication systems, optical information processing systems, and optical sensing systems to achieve compactness and high performance [1,2,3,4]. The light source transmits through optical fibers in many cases; the output beam emitting from the source has far-field radiation angles that need an external lens such as a collimating lens or a focusing lens These lenses are so bulky that it is difficult to compact collimated or focus light sources for microoptical applications [3,4,5]. International Journal of Manufacturing Engineering ultraprecision machining-based fabrication methods rely on more complicated mechanisms depending on the degree of the size effect due to small ratio of depth of cut to the tool edge radius. There is little work regarding thin film-type Fresnel lens for microoptics light-collecting applications

Methods

Results

Conclusion