Nanoscale Single-Element Color Filters

본 연구는 나노막대를 이용한 극소 나노 무기물 color filter 의 제조에 관한 것이다. 기존의 나노단위의 color filter는 금속 격자를 사용하였기 때문에 크기가 제한적이었던 반면 본 연구에서는 단일 나노막대만을 사용함으로써 크기가 수백 나노 정도로 훨씬 작은 광학 filter를 구현할 수 있었다. 은으로 둘러싸인 ZnO 나노막대를 사용하여 크기에 따라서 투과되는 빛의 파장이 달라짐을 확인할 수 있었다. 이 연구를 통해 초고해상도 디스플레이 픽셀의 구현, 나노광회로에서의 band pass filter의 제조와 같은 일들이 가능해 질 것으로 기대된다.

Visible-light filters constructed from nanostructured materials typically consist of a metallic grating and rely on the excitation of surface plasmon polaritons (SPPs). In order to operate at full efficiency, the number of grating elements needs to be maximized such that light can couple more efficiently to the SPPs through improved diffraction. Such conditions impose a limitation on the compactness of the filter since a larger number of grating elements represents a larger effective size. For emerging applications involving nanoscale transmitters or receivers, a device that can filter localized excitations is highly anticipated but is challenging to realize through grating-type filters. In this work, we present the design of an optical filter operating with a single element, marking a departure from diffractive plasmonic coupling. Our device consists of a ZnO nanorod enclosed by two layers of Ag film. For diffraction-limited light focused on the nanorod, narrow passbands can be realized and tuned via variation of the nanorod diameter across the visible spectrum. The spectral and spatial filtering originates from scattering cancellation localized at the nanorod due to the cavity and nanorod exhibiting opposite effective dipole moments. This ability to realize high-performance optical filtering at the ultimate size introduces intriguing possibilities for nanoscale near-field communication or ultrahigh resolution imaging pixels.

Authors: Jerome K. Hyun, Taehee Kang, Hyeonjun Baek, Dai-sik Kim, and Gyu-chul Yi

Nano Lett., Article ASAP
DOI: 10.1021/acs.nanolett.5b02049

Publication Date (Web): August 3, 2015