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A Hollow‐Core Optical Cavity Built in a Three‐Layer Silicon Photonic Crystal
Author(s) -
Wang Jian,
Ouyang Jing,
Varghese Leo T.,
Fan Li,
Xuan Yi,
Qi Minghao
Publication year - 2013
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.201300208
Subject(s) - materials science , photonic crystal , optoelectronics , lasing threshold , fabrication , refractive index , dielectric , silicon , optics , core (optical fiber) , silicon photonics , photonics , wavelength , medicine , alternative medicine , physics , pathology , composite material
Hollow‐core (HC) optical microcavities differ from conventional ones in that they can strongly confine light in air. HC cavities simultaneously possessing high air–energy ratios (α air ), high quality factors ( Q ), and small mode volumes ( V eff ) may enable on‐chip low‐concentration molecular sensing, high optical power delivery or storage, and low‐threshold optical oscillation or lasing when filled with materials of desirable nonlinearities. However, designing and fabricating such cavities has been challenging, especially when using only a small number of layers. Here, the design and fabrication of such an HC cavity in a three‐layer silicon photonic crystal (PhC) is reported. It supports a transverse magnetic (TM) cavity mode with α air ≈ 67% and Q ≈ 1.7 × 10 5 in the 1550 nm wavelength range. The in‐plane confinement is provided by the 2D photonic bandgap (PBG) of a dielectric rod array, while a pair of capping slabs with air–hole PhC patterns confine light in air in the vertical direction. The cavity allows detection of low‐concentration substances that induce refractive index changes as small as around 8.8 × 10 −6 . The proposed cavity design and its fabrication provide a new approach to three‐dimensional photonic confinement using a structure consisting of only a few layers.