# A compact structure for realizing Lorentzian, Fano and EIT resonance lineshapes in a microring resonator

## TL;DR

This paper introduces a compact microring resonator structure that can reliably generate tunable Lorentzian, Fano, and EIT resonance lineshapes by integrating a Fabry-Perot cavity with adjustable parameters, enhancing device performance.

## Contribution

A novel microring design with side-coupled air-holes that enables flexible and reliable tuning of resonance lineshapes through simple structural modifications.

## Key findings

- Achieved Fano lineshapes with about 20 dB extinction ratio
- Demonstrated slope rates over 280 dB/nm
- Verified theoretical analysis with experimental results

## Abstract

Microring resonators, as a fundamental building block of photonic integrated circuits, have been well developed into numerous functional devices, whose performances are strongly determined by microring's resonance lineshapes. We propose a compact structure to reliably realize Lorentzian, Fano, and electromagnetically induced transparency (EIT) resonance lineshapes in a microring. By simply inserting two air-holes in the side-coupled waveguide of a microring, a Fabry-Perot (FP) resonance is involved to couple with microring's resonant modes, showing Lorentzian, Fano, and EIT lineshapes over one free spectral range of the FP resonance. The quality factors, extinction ratios, and slope rates in different lineshapes are discussed. At microring's specific resonant wavelength, the lineshape could be tuned among these three types by controlling the FP cavity's length. Experiment results verify the theoretical analysis well and represent Fano lineshapes with extinction ratios of about 20 dB and slope rates over 280 dB/nm. The reliably and flexibly tunable lineshapes in the compact structure have potentials to improve microring-based devices and expand their application scopes.