Sensitivity enhancement in photonic crystal slab biosensors. Opt Express

The Edward S Rogers Sr Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
Optics Express (Impact Factor: 3.49). 10/2010; 18(22):22702-14. DOI: 10.1364/OE.18.022702
Source: PubMed


Refractive index sensitivity of guided resonances in photonic crystal slabs is analyzed. We show that modal properties of guided resonances strongly affect spectral sensitivity and quality factors, resulting in substantial enhancement of refractive index sensitivity. A three-fold spectral sensitivity enhancement is demonstrated for suspended slab designs, in contrast to designs with a slab resting over a substrate. Spectral sensitivity values are additionally shown to be unaffected by quality factor reductions, which are common to fabricated photonic crystal nano-structures. Finally, we determine that proper selection of photonic crystal slab design parameters permits biosensing of a wide range of analytes, including proteins, antigens, and cells. These photonic crystals are compatible with large-area biosensor designs, permitting direct access to externally incident optical beams in a microfluidic device.

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Available from: Mohamed El Beheiry, Dec 26, 2013
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    • "In the last years photonic crystal (PhC)-based label-free biosensors have been also investigated in different configurations, such as cavity [15]–[18], line-defect [19] and slab [20]. Photonic crystals [21], [22] are structures composed by a periodic arrangement of materials with different refractive indexes ðnÞ and able to transmit or reflect well determined electromagnetic wavelength ranges by tuning their geometrical parameters such as the periodicity p or the radius r . "
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    • "It is well-known for 2D PCs that the air holes in the dielectric substrate highly favor the TE mode and the dielectric rods in the air medium highly favor the TM mode. In most of previous woks [11] [12] [13] [14] [15] [16] [17] [18], studies on 2D PCs biosensors were focused on air-hole type and only TE polarization was considered. Compared with conventional 2D PCs, 2D APCs can well support both TE and TM modes because they are actually a combination of air-hole type and dielectric-rod type PCs. "
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    ABSTRACT: To promote the development of two-dimensional (2D) photonic crystals (PCs) based refractive-index (RI) biosensors, there is an urgent requirement of an effective approach to improve the RI sensitivity of 2D PCs (usually less than 500 nm/RIU). In this work, the photonic band gap (PBG) feature and the corresponding RI sensitivity of the air-ring type 2D annular PCs (APCs) have been studied in detail. Such type of 2D PCs can easily and apparently improve the RI sensitivity in comparison with conventional air-hole type 2D PCs that have been widely studied in previous works. This is because the APCs can naturally exhibit suppressed up edge of PBG that can strongly affect the final RI sensitivity. In general, an enhanced sensing performance of as high as up to 2-3 times RI sensitivity can be obtained from pure 2D APCs. Such high RI sensitivity is also available in three typical waveguides developed from pure 2D APCs. Furthermore, a new conception of dual-polarization RI biosensors has been proposed by defining the RI sensitivity as the difference of crossing relative sensitivity of up-edge PBG between different polarizations. Based on pure 2D APCs, a dual-polarization RI biosensor with high RI sensitivity of around 1190 nm/RIU in infrared range was also presented as an example.
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    ABSTRACT: The extraordinary spectral sensitivity of surface plasmon resonance (SPR) sensors is commonly attributed to the modal overlap or unique dispersion of surface plasmons. In contrast to this belief, we show that such high sensitivity is due to the multi-mode nature of the sensing scheme. This concept of multi-mode sensing can be applied to dielectric systems as well in order to achieve similar extraordinary spectral sensitivity. We also show that there is a fundamental constraint between the spectral sensitivity and quality factor in such multi-mode sensing approach.
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