Title: Resonant Mode Engineering of Photonic Crystal Sensors Clad with Ultralow Refractive Index Porous Silicon Dioxide

Abstract

Porous SiO₂ (PSiO₂) with ultralow refractive index ($$n$$ = 1.09) is incorporated as the cladding of a photonic crystal (PC) refractive index sensor with enhanced sensitivity through the establishment of resonant modes that principally reside in the liquid medium covering the PC surface. PSiO₂, obtained by thermal oxidation of porous Si that has been transferred to a transparent substrate, is transparent at visible and near infrared wavelengths with a refractive index determined by its porosity. The PSiO₂ periodic grating structure ($$Λ$$ = 590 nm) is patterned by nanoimprint lithography and reactive ion etching, then conformally coated by sputtering high refractive index TiO₂ to seal the pores from liquid infiltration. With the refractive index of PSiO₂ much lower than that of water, the resonant mode “flips” its spatial distribution from within the solid dielectric regions of the photonic crystal to reside mainly in the water media covering the PC, resulting in 4× greater resonant wavelength shift for a fixed refractive index change. This study demonstrates design, fabrication, and testing of the sensor as a refractometer, supported by electromagnetic simulations of the resonant mode spatial distribution, in which porous PC sensors are compared to nonporous PC sensors.

Authors:

Wan, Yuhang  ^[1];

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Krueger, Neil A. ^[2]; Ocier, Christian R. ^[2]; Su, Patrick ^[3]; Braun, Paul V. ^[2]; Cunningham, Brian T. ^[4]

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+ Show Author Affiliations

1. Univ. of Illinois at Urbana-Champaign, IL (United States). Dept. of Electrical and Computer Engineering; Beihang Univ., Beijing (China). School of Electronic and Information Engineering
2. Univ. of Illinois at Urbana-Champaign, IL (United States). Dept. of Materials Science and Engineering
3. Univ. of Illinois at Urbana-Champaign, IL (United States). Dept. of Electrical and Computer Engineering, Micro and Nanotechnology Lab.
4. Univ. of Illinois at Urbana-Champaign, IL (United States). Dept. of Electrical and Computer Engineering, Micro and Nanotechnology Lab., and Dept. of Bioengineering

Publication Date:

2017-09-01

Research Org.:

Energy Frontier Research Centers (EFRC) (United States). Light-Material Interactions in Energy Conversion (LMI)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1470416

Alternate Identifier(s):

OSTI ID: 1378114

Grant/Contract Number:  

SC0001293; DE‐SC0001293

Resource Type:

Accepted Manuscript

Journal Name:

Advanced Optical Materials

Additional Journal Information:

Journal Volume: 5; Journal Issue: 21; Related Information: LMI partners with California Institute of Technology (lead); Harvard University; University of Illinois, Urbana-Champaign; Lawrence Berkeley National Laboratory; Journal ID: ISSN 2195-1071

Publisher:

Wiley

Country of Publication:

United States

Language:

English

Subject:

14 SOLAR ENERGY; 36 MATERIALS SCIENCE; 42 ENGINEERING; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; solar (photovoltaic); solid state lighting; phonons; thermal conductivity; electrodes - solar; materials and chemistry by design; optics; synthesis (novel materials); synthesis (self-assembly)