Estimating surface-roughness loss and output coupling in microdisk resonators

Area of Science:

• Photonics and optical engineering
• Materials science
• Electromagnetism

Background:

• Microdisk and ring resonators are key components in integrated photonics.
• Scattering losses limit device performance and are crucial to understand for miniaturization.
• Surface roughness and boundary corrugations are inherent imperfections in fabricated devices.

Purpose of the Study:

• To analytically estimate scattering losses in microdisk and ring resonators.
• To identify the primary mechanisms responsible for radiation losses due to boundary imperfections.
• To investigate the influence of device geometry and material properties on loss.

Main Methods:

• Utilizing the volume current method for analytical estimation of scattering losses.
• Analyzing harmonic components of boundary imperfections.
• Differentiating between phase-matched radiation and tunneling radiation.

Main Results:

• The volume current method effectively estimates scattering losses from boundary corrugations and surface roughness.
• Harmonic components of imperfections can lead to phase-matched radiation or tunneling radiation.
• Phase-matched radiation is a significant loss contributor, minimally dependent on resonator radius.
• The longitudinal electric field component dominates radiation losses in high-index contrast devices.

Conclusions:

• Scattering losses in microdisk and ring resonators are analytically predictable.
• Understanding the role of boundary imperfections and electric field components is vital for designing efficient optical resonators.
• The findings are particularly relevant for high-index contrast photonic integrated circuits.