Mode localization and the Q-factor of a cylindrical microresonator

Area of Science:

• Optics
• Photonics
• Condensed Matter Physics

Background:

• Whispering gallery modes (WGMs) in spherical/spheroidal microresonators are well-studied but delocalized in long cylinders.
• Light coupling into cylinders typically radiates axially after total internal reflection.

Purpose of the Study:

• To investigate the axial localization of resonant modes in long cylindrical microresonators.
• To analyze the characteristics and potential of these localized modes.

Main Methods:

• Theoretical analysis of light propagation and self-interference within a cylindrical waveguide.
• Derivation of mode characteristic width based on material attenuation and propagation constants.
• Comparison of Q-factors with existing microresonator modes.

Main Results:

• A novel resonant mode, localized along the cylinder axis, is predicted.
• The mode's characteristic width is determined by (alphabeta)(-1/2), where alpha and beta are material constants.
• The Q-factor of this localized mode approaches that of spheroidal microresonator modes.

Conclusions:

• Axial self-interference can overcome the inherent delocalization of WGMs in long cylinders.
• This localized axial mode offers potential for high-Q factor optical devices.
• The findings open new avenues for designing resonant structures in cylindrical geometries.