Abstract
An ultra-compact one-dimensional topological photonic crystal (1D-TPC) is designed in a single mode silicon bus-waveguide to generate the Fano resonance lineshape. The Fano resonance comes from the interference between the discrete topological boundary state of the 1D-TPC and the continuum high-order leaky mode of the bus-waveguide. Standalone asymmetric Fano resonance lineshapes are obtained experimentally in the waveguide transmission spectrum with a maximum extinction ratio of 33 dB and a slope ratio of 10 dB/nm over a broadband flat background.
Highlights
Constructive and destructive interferences between the localized discrete state and the continuum state usually give rise to asymmetric spectra, which is known as Fano resonance.1 The asymmetric lineshape of Fano resonance exhibits an ultra-sharp variation from the minimum to the maximum compared to the symmetric Lorenzian lineshape with an approximative quality (Q) factor.2 This steeper resonant peak provides great advantages for chip-scale integrated applications, such as low-threshold lasing,3,4 high-sensitivity optical sensing,5–7 and low-power all-optical switching.2,8–10 Due to the maturity and rapid development of planar processing technology, a large number of structures, such as microring resonators,11–15 microdisks,16 and photonic crystal (PC) nano-cavities,2,4,8–10 have been proposed to generate the Fano resonance
Photonic analogs of topological quantum systems can be realized via PC or microring arrays,17–19 which promise a new generation of compact chip-scale photonic devices
We demonstrate the generation of Fano resonance through an ultra-compact 1D-TPC structure embedded in a single mode bus-waveguide
Summary
Constructive and destructive interferences between the localized discrete state and the continuum state usually give rise to asymmetric spectra, which is known as Fano resonance. The asymmetric lineshape of Fano resonance exhibits an ultra-sharp variation from the minimum to the maximum compared to the symmetric Lorenzian lineshape with an approximative quality (Q) factor. This steeper resonant peak provides great advantages for chip-scale integrated applications, such as low-threshold lasing, high-sensitivity optical sensing, and low-power all-optical switching. Due to the maturity and rapid development of planar processing technology, a large number of structures, such as microring resonators, microdisks, and photonic crystal (PC) nano-cavities, have been proposed to generate the Fano resonance. The asymmetric lineshape of Fano resonance exhibits an ultra-sharp variation from the minimum to the maximum compared to the symmetric Lorenzian lineshape with an approximative quality (Q) factor.2 This steeper resonant peak provides great advantages for chip-scale integrated applications, such as low-threshold lasing, high-sensitivity optical sensing, and low-power all-optical switching.. By coupling a Fabry–Perot cavity mode with a topological edge mode, it is possible to construct a high Q Fano resonance in a compact one-dimensional topological photonic crystal (1D-TPC) heterostructure.. By coupling the valley-dependent topological edge states with a double-degenerate cavity, the immune property to system impurities has been verified on the two-dimensional photonic valley Hall insulators These efforts pave a way for the topologically protected robust Fano devices with ultra-compact sizes, such as optical switches, low-threshold nanolasers, and ultra-sensitive optical sensors. The results are further verified by experimentally fabricating the devices in a silicon slab
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