End-fire injection of guided light into optical microcavity

TL;DR

This paper introduces a robust end-fire injection method for coupling light into optical microcavities, achieving high efficiency and reduced environmental sensitivity, with potential applications in resonant filters and sensors.

Contribution

The study presents a novel direct coupling mechanism called end-fire injection, demonstrating high efficiency and robustness compared to traditional methods.

Findings

Coupling efficiency up to 0.75 at resonance

Constructive interference enhances coupling

Applicable to low refractive index resonances

Abstract

Coupling light into microdisk plays a key role in a number of applications such as resonant filters and optical sensors. While several approaches have successfully coupled light into microdisk efficiently, most of them suffer from the ultrahigh sensitivity to the environmental vibration. Here we demonstrate a robust mechanism, which is termed as end-fire injection. By connecting an input waveguide to a circular microdisk directly, the mechanism shows that light can be efficiently coupled into optical microcavity. The coupling efficiency can be as high as 0.75 when the input signals are on resonances. Our numerical results reveal that the high coupling efficiency is attributed to the constructive interference between the whispering gallery modes and the input signals. We have also shown that the end-fire injection can be further extended to the long-lived resonances with low refractive index such as n = 1.45. We believe our results will shed light on the applications of optical microcavities.