Authentication labels based on guided-mode resonant filters

Mount Learn Wu, Che Lung Hsu, Hsiao Chin Lan, Hung I. Huang, Yung Chih Liu, Zong Ru Tu, Chien Chieh Lee, Jian Shian Lin, Chih Chieh Su, Jenq Yang Chang

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

A guided-mode resonance (GMR) filter with wide angular tolerances is experimentally demonstrated as an authentication label illuminated with unpolarized white light. The proposed filter, based on a free-standing silicon nitride membrane suspended on a silicon substrate, is fabricated by using anisotropic wet etching to remove the substrate beneath the silicon nitride layer. Both grating and waveguide structures without a lower cladding layer, i.e., a substrate, are fabricated simultaneously on a silicon nitride membrane. Since the silicon nitride is transparent within the spectra of visible and infrared light, such suspended-membranetype GMR filters are well suited for applications within the visible spectrum. Moreover, the high refractive index of silicon nitride allows the proposed filters to have strongly modulated gratings and an immunity to high angular deviation. The measured reflection resonance has an angular tolerance up to ±5° under normal incidence for the wavelength of 629.5 nm.

Original languageEnglish
Pages (from-to)1614-1616
Number of pages3
JournalOptics Letters
Volume32
Issue number12
DOIs
StatePublished - 15 Jun 2007

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