High Q-factor distributed bragg reflector resonators with reflectors of arbitrary thickness

Area of Science:

• Electromagnetics and Applied Physics
• Materials Science and Engineering

Background:

• The Bragg reflection technique enhances resonator Q-factor by minimizing conductor and dielectric losses using a low-loss resonant core and distributed Bragg reflector layers.
• Existing models often require Bragg reflectors to be precisely lambda/4 thick, limiting design flexibility.

Discussion:

• A novel, simple non-Maxwellian model was developed to design cylindrical Bragg resonators with arbitrary dielectric reflector thicknesses.
• The model accommodates higher-order field variations in both resonant and anti-resonant regions, enabling versatile resonator designs.
• Three distinct resonators were fabricated using single-crystal sapphire, varying only the cavity dimensions.

Key Insights:

• An unloaded Q-factor of 234,000 at 9.7 GHz was experimentally achieved for the fundamental mode.
• The Bragg resonator demonstrated a higher Q-factor than conventional whispering gallery mode resonators.
• Significantly reduced spurious mode density was observed compared to overmoded whispering gallery resonators.

Outlook:

• This work provides a simplified yet effective modeling approach for designing high-performance Bragg resonators.
• The demonstrated high Q-factor and low spurious modes suggest potential applications in sensitive microwave and millimeter-wave devices.
• Further research could explore different dielectric materials and resonator geometries to optimize performance for specific frequency ranges.