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Authors: S. Kumar, N. Le Thomas
Title: On-chip photonic crystal cavity designs for nanoparticle characterization
Format: International Conference Poster
Publication date: 4/2014
Journal/Conference/Book: Taking Detection to the Limit: Biosensing with Optical Microcavities.
Location: Bad Honnef, Germany
Citations: Look up on Google Scholar
Download: Download this Publication (195KB) (195KB)


Planar Photonic Crystal (PhC) cavities are unique optical resonators that can confine modes in a sub-wavelength volume V and have a high-quality factor Q. Decreasing V enhances light-matter interaction in the mode volume, whereas increasing Q improves the detection limit of any frequency shift induced by a perturbation of the cavity mode. As a result, such cavities are promising refractive index sensors to detect biomolecules as small as proteins.
Such cavities are defined by introducing a lattice defect in a two-dimensional periodic array of low-index holes that are etched in thin planar waveguides of high-index material. Being integrated photonic structures, they can benefit from a complete on-chip signal processing.
We investigate here new designs to probe with a highdetection limit the frequency shifts induced by a nanoparticle in the core of a hollow core PhC cavity.The hollow-core PhC cavity that allows nanoparticles to interact with the maximum of the cavity field is created from a slight modulation of the width of a low-index slot that replaces a line of holes in the PhC pattern. A second cavity formed by three in-line missing holes, commonly called L3 cavity, is used to probe the frequency fluctuations of the hollow-core cavity. Various adaptations of such a design are being processed on Silicon-on-Insulator (SOI) substrate using deep ultraviolet (UV) lithography by the ePIXfab platform.
We will present the design methodology that was based on guided-mode expansion method and demonstrate the high performance of the proposed concept to extract information about the size and the shape of different nanoparticles.

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