Browsing by Author "Lin, Kung-Hsuan"

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Giant photothermal nonlinearity in a single silicon nanostructure
(2020-08-14)
Duh, Yi-Shiou
;
Nagasaki, Yusuke
;
Tang, Yu-Lung
;
Wu, Pang-Han
;
Cheng, Hao-Yu
Silicon photonics have attracted significant interest because of their potential in integrated photonics components and all-dielectric meta-optics elements. One major challenge is to achieve active control via strong photon-photon interactions, i.e. optical nonlinearity, which is intrinsically weak in silicon. To boost the nonlinear response, practical applications rely on resonant structures such as microring resonators or photonic crystals. Nevertheless, their typical footprints are larger than 10 mu m. Here, we show that 100nm silicon nano-resonators exhibit a giant photothermal nonlinearity, yielding 90% reversible and repeatable modulation from linear scattering response at low excitation intensities. The equivalent nonlinear index is five-orders larger compared with bulk, based on Mie resonance enhanced absorption and high-efficiency heating in thermally isolated nanostructures. Furthermore, the nanoscale thermal relaxation time reaches nanosecond. This large and fast nonlinearity leads to potential applications for GHz all-optical control at the nanoscale and super-resolution imaging of silicon.
[INVITED] Total-internal-reflection-based photomask for large-area photolithography
(2016-05)
Hung, Shao-Kang
;
Lin, Kung-Hsuan
;
Chen, Cheng-Lung
;
Chou, Chen-Hsun
;
Lin, You-Chuan
Photolithography has been widely implemented with a photomask in contact or in close proximity to the photoresist layer. The flatness of the substrates is a crucial factor to guarantee the quality of the entire patterned photoresist (PR) layer especially for large-area photolithography. However, some substrates, such as sapphire wafers, do not possess highly uniform thickness as silicon wafer does. In this work, we demonstrate that a flexible polydimethylsiloxane (PDMS) photomask with optical total-internal-reflection structure can effectively circumvent this problem for mass production. Different from conventional photomask that the light is blocked by the patterned reflective/absorbing materials, the distributions of light intensity on the PR is engineered by the geometric structure of the transparent PDMS photomask. We demonstrate that 4 in. patterned sapphire wafers can be successfully fabricated by using this PDMS photomask, which can be easily integrated into the present techniques in industry for mass production of substrates for GaN-based optoelectronic devices. (C) 2015 Elsevier Ltd. All rights reserved.
Protein Crosslinking and Immobilization in 3D Microfluidics through Multiphoton Absorption
(2020-01-12)
Lin, Chen-Feng
;
Su, Che-Fu
;
Lin, Kung-Hsuan
;
Hsieh, Yu-Shen
;
Cheng, Yun-Chien
This study used laser multiphoton absorption (MPA) to crosslink and immobilize protein in 3D microfluidics. MPA can be used to crosslink proteins to form smaller crosslinked-protein structures than those formed through single-photon absorption. However, studies on MPA protein crosslinking in 3D microfluidics are lacking. In this study, the MPA was implemented using pulse laser to induce bovine serum albumin (BSA) crosslinking. We also applied (3-glycidyloxypropyl)trimethoxysilane to increase the adhesion of crosslinked BSA. Also, the width of crosslinked-BSA structure was measured, and then curve-fitting and optical equation were used to predict heights of the crosslinked-BSA structures formed under various laser powers. At last, BSA structures were effectively crosslinked in the three-layered glass or polydimethylsiloxane microchannels. In contrast to studies on single-photon absorption in 3D microfluidics or MPA protein crosslinking in 2D microfluidics, we obtained relatively small crosslinked-BSA structures through MPA and immobilize BSA in 3D microfluidics. In the future, this method can be applied in monolithic 3D microfluidics for protein crosslinking to avoid misalignment and leakage in layer-by-layer 3D microchannels and form more compact 3D microfluidics. These features are conducive to enhance the diversity and convenience of microfluidics in biomedical testing.