Browsing by Author "Choi, Kyung-Hak"
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Item Innovative SU-8 Lithography Techniques and Their ApplicationsLee, Jeong Bong; Choi, Kyung-Hak; Yoo, KoangkiSU-8 has been widely used in a variety of applications for creating structures in micro-scale as well as sub-micron scales for more than 15 years. One of the most common structures made of SU-8 is tall (up to millimeters) high-aspect-ratio (up to 100: 1) 3D microstructure, which is far better than that made of any other photoresists. There has been a great deal of efforts in developing innovative unconventional lithography techniques to fully utilize the thick high aspect ratio nature of the SU-8 photoresist. Those unconventional lithography techniques include inclined ultraviolet (UV) exposure, back-side UV exposure, drawing lithography, and moving-mask UV lithography. In addition, since SU-8 is a negative-tone photoresist, it has been a popular choice of material for multiple-photon interference lithography for the periodic structure in scales down to deep sub-microns such as photonic crystals. These innovative lithography techniques for SU-8 have led to a lot of unprecedented capabilities for creating unique micro-and nano-structures. This paper reviews such innovative lithography techniques developed in the past 15 years or so.Item One-Step Combined-Nanolithography-And-Photolithography for a 2d Photonic Crystal TM Polarizer(MDPI AG) Choi, Kyung-Hak; Huh, J.; Cui, Yonghao; Trivedi, Krutarth; Hu, Walter; Ju, B. -K; Lee, Jeong-BongPhotonic crystals have been widely investigated since they have great potential to manipulate the flow of light in an ultra-compact-scale and enable numerous innovative applications. 2D slab photonic crystals for the telecommunication C band at around 1550 nm have multi-scale structures that are typically micron-scale waveguides and deep sub-micron-scale air hole arrays. Several steps of nanolithography and photolithography are usually used for the fabrication of multi-scale photonic crystals. In this work, we report a one-step lithography process to pattern both micron and deep sub-micron features simultaneously for the 2D slab photonic crystal using combined-nanoimprint-andphotolithography. As a demonstrator, a 2D silicon photonic crystal transverse magnetic (TM) polarizer was fabricated, and the operation was successfully demonstrated.