Ultracompact biochemical sensor built with two-dimensional photonic crystal microcavity

Abstract

We report an experimental demonstration of an ultracompact biochemical sensor based on a two-dimensional photonic crystal microcavity. The microcavity, fabricated on a silicon-on-insulator substrate, is designed to have a resonant wavelength (lambda) near 1.5 microm. The transmission spectrum of the sensor is measured with different ambient refractive indices ranging from n = 1.0 to n = 1.5. From observation of the shift in resonant wavelength, a change in ambient refractive index of delta(n) = 0.002 is readily apparent. The correspondence between absolute refractive index and resonant wavelength agrees with numerical calculation to within 4% accuracy. The evaporation of water in a 5% glycerol mixture is also used to demonstrate the capability for in situ time-resolved sensing.

Silicon photonic crystal nanostructures for refractive index sensing

“…Other groups used evanescent coupling from ridge waveguides ͑WGs͒ to a silicon PhC nanocavity in a serial geometry, achieving sensitivities of ⌬n / n = 0.002. 9,10 Sensors based on measuring the transmission properties of PhC-WGs were investigated by Erickson et al 11 and Skivesen et al 12 Cunningham et al 13 utilized an alternative approach based on detecting the RI from a two-dimensional Bragg grating. However, as for SPR and interferometric methods this approach is nonlocal and requires a large analyte volume.…”

“…Unlike previously reported PhC sensors that rely on direct coupling from a WG to the PhC cavity, [8][9][10]12 we employ a drop filter consisting of a resonant cavity between two spatially separated PhC-WGs. This allows many detectors to be selectively addressed in parallel via the resonant frequency and readily lends itself to operation in a liquid flow cell.…”

Optical sensing with Anderson-localised light

“…Our devices show shift/linewidth ratios of the optical resonances that even exceed values reported for state-of-the-art optimised sensors based on photonic crystal cavities 18 . Given the volatility of the alcohol used at ambient temperature and pressure, the shift of the spectral position of the optical resonance varies as a function of time after deposition (see Fig.…”

Optofluidic waveguides: II. Fabrication and structures

“…Light can be coupled into and out of these photonic crystal waveguides through TIR based ridge waveguides etched into silicon. Researchers have been able to fill the etched voids of the photonic crystals with fluids and use them as fluidic sensors (Chow et al 2004;Skivesen et al 2007) as well as fluidic controlled photonic devices (Erickson et al 2006). To selectively control the flow of fluids over the photonic crystal structures, silicone molds containing fluid channels are aligned and attached to the silicon substrate.…”