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Silicon Nitride based Medium Contrast Gratings for Doubly Resonant Fluorescence Enhancement

Menon, Sruti Hemachandran Geetha and Krishna, Lal A S and Raghunathan, Varun (2019) Silicon Nitride based Medium Contrast Gratings for Doubly Resonant Fluorescence Enhancement. In: IEEE PHOTONICS JOURNAL, 11 (4).

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Official URL: https://dx.doi.org/10.1109/JPHOT.2019.2909794


We present the design, fabrication, and experimental characterization of silicon nitride based medium-index contrast gratings on glass substrate for fluorescence enhancement in the yellow to red spectral range with resonances for both incident excitation and fluorescence emission wavelengths under surface normal incidence. A comparison of the design space to realize resonant field enhancement in high-index contrast silicon and medium-index contrast silicon nitride grating structures is presented. The one-dimensional sub-wavelength grating structures studied here are designed with large duty cycle (similar to 80%) to account for the medium refractive index contrast (Delta n similar to 0.5) between silicon nitride and the glass substrate to ensure that the device operates in the two-mode regime. The resonant enhancement of fluorescence is experimentally verified using rhodamine-B isothiocyanate dye as the fluorophore of interest. A resonant enhancement of 10.8 times is demonstrated in this sample when compared to un-patterned film for transverse electric-transverse magnetic (TE-TM) polarization combination. We have also performed simulation study with plane wave excitation and incoherent dipole array emission to model the resonant excitation and emission processes, respectively. The simulations corroborate well with the best observed experimental results for the doubly resonant fluorescence configuration. Silicon nitride based medium contrast gratings are a promising platform to fabricate scalable structures for resonant enhancement of light-matter interaction with potential applications in high-sensitivity biological fluorescence assays and as a platform for polarization selective interrogation of light emission from nanoscale emitters attached to the grating.

Item Type: Journal Article
Additional Information: copyright for this article belongs to IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Keywords: Subwavelength gratings; guided-mode resonance; fluorescence; optical resonance
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 22 Aug 2019 06:02
Last Modified: 22 Aug 2019 06:02
URI: http://eprints.iisc.ac.in/id/eprint/63251

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