Towards a biosensor based on anti resonant reflecting optical waveguide fabricated from porous silicon

Abstract

Recently, we demonstrated that Anti Resonant Reflecting Optical Waveguide (ARROW) based on porous silicon (PS) material can be used as a transducer for the development of a new optical biosensor. Compared to a conventional biosensor waveguide based on evanescent waves, the ARROW structure is designed to allow a better overlap between the propagated optical field and the molecules infiltrated in the porous core layer and so to provide better molecular interactions sensitivity.The aim of this work is to investigate the operating mode of an optical biosensor using the ARROW structure. We reported here an extensive study where the antiresonance conditions were adjusted just before the grafting of the studied molecules for a given refractive index range.The interesting feature of the studied ARROW structure is that it is elaborated from the same material which is the porous silicon obtained via a single electrochemical anodization process.After oxidation and preparation of the inner surface of porous silicon by a chemical functionalization process, bovine serum albumin (BSA) molecules, were attached essentially in the upper layer. Simulation study indicates that the proposed sensor works at the refractive index values ranging from 1.3560 to 1.3655.The experimental optical detection of the biomolecules was obtained through the modification of the propagated optical field and losses. The results indicated that the optical attenuation decreases after biomolecules attachment, corresponding to a refractive index change ∆n c of the core. This reduction was of about 2 dB/cm and 3 dB/cm for Transverse Electric (TE) and 1 Electronic mail : mohamed-lazhar.haji@univ-rennes1.fr 2 Transverse Magnetic (TM) polarizations respectively. Moreover, at the detection step, the optical field was almost located inside the core layer. This result was in good agreement with the simulated near field profiles.

Buried anti resonant reflecting optical waveguide based on porous silicon material for an integrated Mach Zehnder structure

“…Recently, we have demonstrated the feasibility of a planar AntiResonant Reflecting Optical Waveguide (ARROW) based on porous silicon for detection purposes even if the refractive index contrast is rather low 15,16 compared to other materials. 17,18 The particular characteristic of this antiresonant waveguide is that the upper porous layer performs both the role of active and guiding layer supporting field propagation which ensures a more sensitive interaction between the propagated light and the infiltrated biological species.…”

“…After photolithography step, an electrochemical anodization process was performed through the mask apertures to create three distinct porous silicon layers with porosities and thicknesses satisfying the antiresonance conditions 21 to obtain the ARROW structures. 15,16 For this anodization process, we used an electrolyte composed of HF (50 %), ethanol and deionised water (at 18 M1) solution with ratios of 2-2-1 respectively. We applied successive current densities of 65, 2 and 19 mA.cm -2 respectively for the layers.…”

“…25 Using these, R was calculated 16 and plotted in Fig. 2 In the case of the TM mode, we note that the reflectivity is low and also that the difference between the maximum and minimum of reflectivity is lower than for the TE mode.…”

Study on the Formation of Au Nanoparticles on Fresh and Oxided Porous Silicon Microcavity Substrate

“…This improves low detection limit against other materials and high sensitivity could be obtained. Therefore, PS has been also used for transduction of recognition events into measurable optical signals using highly sensitive photonic structure, such as Bragg mirrors, optical waveguides, microcavities, and so on [5][6][7][8]. The most widely used PS-based photonic designs are due to the ease of preparation by periodically altering the etching time and etching current.…”

“…FESEM cross-sectional image of Au/PSM substrate and PSM structure following the (LH) 6 L c (HL)6 sequence.…”