A Robust and Tunable Add-Drop Filter Using Whispering Gallery Mode Microtoroid Resonator

TL;DR

This paper presents a robust, tunable add-drop filter based on a high-Q whispering gallery mode microtoroid resonator, featuring improved mechanical stability and thermal tuning capabilities for precise wavelength filtering.

Contribution

The study introduces a novel device design with silica side walls that enhances stability and allows on-plane fiber coupling, enabling efficient thermal tuning without compromising drop efficiency.

Findings

Achieved a drop efficiency of approximately 57%.

Demonstrated thermal tuning of the filter to target specific wavelengths.

Enhanced mechanical stability compared to previous designs.

Abstract

We fabricated and theoretically investigated an add-drop filter using an on-chip whispering gallery mode (WGM) microtoroid resonator with ultra-high quality factor (Q) side coupled to two taper fibers, forming the bus and drop waveguides. The new device design incorporates silica side walls close to the microresonators which not only enable placing the coupling fibers on the same plane with respect to the microtoroid resonator but also provides mechanical stability, leading to an add-drop filter with high drop efficiency and improved robustness to environmental perturbations. We show that this new device can be thermally tuned to drop desired wavelengths from the bus without significantly affecting the drop efficiency, which is around 57%