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Polarization-Independent, Narrowband, Near-IR Spectral Filters via Guided Mode Resonances in Ultrathin a-Si Nanopillar Arrays

Ng, Ryan C. and Garcia, Juan C. and Greer, Julia R. and Fountaine, Katherine T. (2019) Polarization-Independent, Narrowband, Near-IR Spectral Filters via Guided Mode Resonances in Ultrathin a-Si Nanopillar Arrays. ACS Photonics, 6 (2). pp. 265-271. ISSN 2330-4022.

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We report the optical properties obtained through experiments, simulation, and theory of ultrathin (<0.1λ), amorphous Si nanopillar arrays embedded in a thin film of SiO_2 designed for narrowband filtering for multi- and hyperspectral imaging in the near-infrared. The fabricated nanopillar arrays are square-packed with subwavelength periodicity, heights of ∼100 nm, and a radius-to-spacing ratio, r/a, of ∼0.2. Specular reflection measurements at normal incidence demonstrate that these arrays behave as narrow stopband filters in the near-infrared (λ = 1300–1700 nm) and attain ∼90% reflectivity in band and a full width at half-maximum as low as 20 nm. Using a combination of full-wave simulations and theory, we demonstrate that these narrowband filtering properties arise from efficient grating coupling of light into guided modes of the array because the nanopillar arrays serve as photonic crystal slabs. This phenomenon is known as a guided mode resonance. We discover that the spectral location of these resonances is passively tunable by modifying array geometry and is most sensitive to nanopillar spacing. Theoretical photonic crystal slab band diagrams accurately predict the spectral locations of the observed resonance and provide physical insights into and support the guided mode resonance formulation. This work demonstrates that these ultrathin all-dielectric nanopillar arrays have advantages over existing hyperspectral filter designs because they are polarization independent, do not suffer from material absorption loss, and have significant implications for minimizing imaging device size.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Ng, Ryan C.0000-0002-0527-9130
Greer, Julia R.0000-0002-9675-1508
Fountaine, Katherine T.0000-0002-0414-8227
Additional Information:© 2019 American Chemical Society. Received: September 6, 2018; Published: January 7, 2019. The authors gratefully acknowledge the financial support of Department of Defense through J.R.G.’s Vannevar-Bush Faculty Fellowship and the critical support and infrastructure provided by the Kavli Nanoscience Institute at Caltech. The authors also thank Harry Atwater for computational resources used to calculated a portion of these results. The authors declare no competing financial interest.
Group:Kavli Nanoscience Institute
Funding AgencyGrant Number
Vannever Bush Faculty FellowshipUNSPECIFIED
Subject Keywords:hyperspectral, guided mode resonance, nanopillar array
Issue or Number:2
Record Number:CaltechAUTHORS:20190114-082742867
Persistent URL:
Official Citation:Polarization-Independent, Narrowband, Near-IR Spectral Filters via Guided Mode Resonances in Ultrathin a-Si Nanopillar Arrays. Ryan C. Ng, Juan C. Garcia, Julia R. Greer, and Katherine T. Fountaine. ACS Photonics 2019 6 (2), 265-271. DOI: 10.1021/acsphotonics.8b01253
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92240
Deposited By: Tony Diaz
Deposited On:14 Jan 2019 20:58
Last Modified:03 Oct 2019 20:42

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