Abstract
In this paper, we report the generation of an ultra-sharp asymmetric resonance spectrum through Fano-like interference. This generation is accomplished by weakly coupling a high-quality factor (Q factor) Fabry-Pérot (FP) cavity and a low-Q factor FP cavity through evanescent waves. The high-Q FP cavity is formed by Sagnac loop mirrors, whilst the low-Q one is built by partially transmitting Sagnac loop reflectors. The working principle has been analytically established and numerically modelled by using temporal coupled-mode-theory (CMT), and verified using a prototype device fabricated on the 340 nm silicon-on-insulator (SOI) platform, patterned by deep ultraviolet (DUV) lithography. Pronounced asymmetric resonances with slopes up to 0.77 dB/pm have been successfully measured, which, to the best of our knowledge, is higher than the results reported in state-of-the-art devices in on-chip integrated Si photonic studies. The established theoretical analysis method can provide excellent design guidelines for devices with Fano-like resonances. The design principle can be applied to ultra-sensitive sensing, ultra-high extinction ratio switching, and more applications.
Highlights
Fano resonance is a phenomenon describing resonant scattering, involving interference between a discrete quantum state and a continuum state [1,2], which results in asymmetric resonances
It is highly desirable to demonstrate the fabrication of devices with Fano-like resonances using CMOS compatible processes, namely deep ultraviolet (DUV) lithography, to enable these devices to be fabricated in silicon photonics foundries
We investigate a Fano-like resonance generation mechanism with ultra-sharp resonance line shape based on on-chip integrated silicon photonic devices, in which a high-Q cavity and a low-Q cavity are weakly coupled together through evanescent waves
Summary
Fano resonance is a phenomenon describing resonant scattering, involving interference between a discrete quantum state and a continuum state [1,2], which results in asymmetric resonances. The guidelines to design devices with Fano-like resonances are highly desirable, they are not sufficient in the published studies. We investigate a Fano-like resonance generation mechanism with ultra-sharp resonance line shape based on on-chip integrated silicon photonic devices, in which a high-Q cavity and a low-Q cavity are weakly coupled together through evanescent waves.
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