Abstract
We exploit the properties of surface electromagnetic waves propagating at the surface of finite one dimensional photonic crystals to improve the performance of optical biosensors with respect to the standard surface plasmon resonance approach. We demonstrate that the hydrogenated amorphous silicon nitride technology is a versatile platform for fabricating one dimensional photonic crystals with any desirable design and operating in a wide wavelength range, from the visible to the near infrared. We prepared sensors based on photonic crystals sustaining either guided modes or surface electromagnetic waves, also known as Bloch surface waves. We carried out for the first time a direct experimental comparison of their sensitivity and figure of merit with surface plasmon polaritons on metal layers, by making use of a commercial surface plasmon resonance instrument that was slightly adapted for the experiments. Our measurements demonstrate that the Bloch surface waves on silicon nitride photonic crystals outperform surface plasmon polaritons by a factor 1.3 in terms of figure of merit.
Highlights
In the wide range of bio-sensing techniques, surface plasmon resonance (SPR) optical biosensors [1] have become a mature technology for simple and fast label free bio-detection [2]
We report experimental results obtained for three different optical biosensors: a standard gold surface plasmon polaritons (SPP) chip and two chips based on a-SixNy:H 1DPC, the first one supporting a guided mode (GM), and the second one a Bloch surface mode (BSW)
We note that the measured width of the BSW resonances (BSWR) is larger than that expected from numerical simulations carried out by the transfer matrix method at a single wavelength (804 nm)
Summary
In the wide range of bio-sensing techniques, surface plasmon resonance (SPR) optical biosensors [1] have become a mature technology for simple and fast label free bio-detection [2] Due their surface-bound nature, surface plasmon polaritons (SPP) are used to sense the refractive index changes in a very narrow region in close proximity of the sensor surface, mainly in real-time conditions. A possible solution [3,4,5] to improve the performances of optical biosensors is to exploit another kind of surface localized electromagnetic waves: e.g. Bloch Surface Waves (BSW) on dielectric multilayers Such electromagnetic modes can propagate at the interface between a finite one-dimensional photonic crystal (1DPC) and a homogeneous external medium [6]. Dielectrics exhibit much lower extinction coefficients than metals and the BSW resonances (BSWR) appear much narrower than the SPR [7], with an expected increase of sensor performances
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