Spatial resolution and refractive index contrast of resonant photonic crystal surfaces for biosensing

TY - JOUR

T1 - Spatial resolution and refractive index contrast of resonant photonic crystal surfaces for biosensing

AU - Triggs, G. J.

AU - Fischer, M.

AU - Stellinga, D.

AU - Scullion, M. G.

AU - Evans, G. J O

AU - Krauss, T. F.

N1 - (c) 2015 IEEE. This content is made available by the publisher under a Creative Commons CC-BY Licence

PY - 2015/6/1

Y1 - 2015/6/1

N2 - By depositing a resolution test pattern on top of a Si3N4 photonic crystal resonant surface, we have measured the dependence of spatial resolution on refractive index contrast \Delta n. Our experimental results and finite-difference time-domain (FDTD) simulations at different refractive index contrasts show that the spatial resolution of our device reduces with reduced contrast, which is an important consideration in biosensing, where the contrast may be of order 10{-2} . We also compare 1-D and 2-D gratings, taking into account different incidence polarizations, leading to a better understanding of the excitation and propagation of the resonant modes in these structures, as well as how this contributes to the spatial resolution. At \Delta n = 0.077, we observe resolutions of 2 and 6 \mu\hbox{m} parallel to and perpendicular to the grooves of a 1-D grating, respectively, and show that for polarized illumination of a 2-D grating, resolution remains asymmetrical. Illumination of a 2-D grating at 45 ^{\circ} results in symmetric resolution. At very low index contrast, the resolution worsens dramatically, particularly for \Delta n\ <\ 0.01, where we observe a resolution exceeding 10 \mu\hbox{m} for our device. In addition, we measure a reduction in the resonance linewidth as the index contrast becomes lower, corresponding to a longer resonant mode propagation length in the structure and contributing to the change in spatial resolution.

AB - By depositing a resolution test pattern on top of a Si3N4 photonic crystal resonant surface, we have measured the dependence of spatial resolution on refractive index contrast \Delta n. Our experimental results and finite-difference time-domain (FDTD) simulations at different refractive index contrasts show that the spatial resolution of our device reduces with reduced contrast, which is an important consideration in biosensing, where the contrast may be of order 10{-2} . We also compare 1-D and 2-D gratings, taking into account different incidence polarizations, leading to a better understanding of the excitation and propagation of the resonant modes in these structures, as well as how this contributes to the spatial resolution. At \Delta n = 0.077, we observe resolutions of 2 and 6 \mu\hbox{m} parallel to and perpendicular to the grooves of a 1-D grating, respectively, and show that for polarized illumination of a 2-D grating, resolution remains asymmetrical. Illumination of a 2-D grating at 45 ^{\circ} results in symmetric resolution. At very low index contrast, the resolution worsens dramatically, particularly for \Delta n\ <\ 0.01, where we observe a resolution exceeding 10 \mu\hbox{m} for our device. In addition, we measure a reduction in the resonance linewidth as the index contrast becomes lower, corresponding to a longer resonant mode propagation length in the structure and contributing to the change in spatial resolution.

KW - biosensor

KW - grating

KW - photonic crystal

KW - polarisation

KW - refractive index contrast

KW - Resonant surface

KW - spatial resolution

UR - http://www.scopus.com/inward/record.url?scp=84930958506&partnerID=8YFLogxK

U2 - 10.1109/JPHOT.2015.2435699

DO - 10.1109/JPHOT.2015.2435699

M3 - Article

AN - SCOPUS:84930958506

SN - 1943-0655

VL - 7

JO - Ieee photonics journal

JF - Ieee photonics journal

IS - 3

M1 - 6801810

ER -