Spherical silicon optical resonators: Possible applications to biosensing
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We observed whispering gallery modes in the 90∘ elastic light scattering and 0∘ transmission spectra of a 500 μm silicon microsphere in the near-infrared telecommunication wavelengths. The whispering gallery modes have quality factors on the order of 105. An autocorrelation function analysis of the 90∘ elastic light scattering and 0∘ transmission spectra is performed. The differential autocorrelation of the 90∘ elastic light scattering and 0∘ transmission spectra reveal a spectral mode spacing 0.23 nm of the whispering gallery modes, which can be used for spectral calibration as well as the calibration of the microsphere size. The spectral shift of the whispering gallery modes can be measured for biosensing applications. An estimation analysis is performed for the adsorption of 30 DNA base pairs on the microsphere results in a wavelength shift of 0.57 nm, which is approximately 40 times the linewidth of the whispering gallery modes. This high sensitivity heralds silicon microspheres as possible candidates for biosensing applications.
KeywordsTransmission Spectrum Elastic Scattering European Physical Journal Special Topic Wavelength Shift Mode Spacing
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