Low-loss compact chalcogenide microresonators for efficient stimulated Brillouin lasers

Area of Science:

• Photonics
• Materials Science
• Optoelectronics

Background:

• Chalcogenide glasses (ChGs) offer high elasto-optic coefficients, suitable for microwave photonics and stimulated Brillouin scattering (SBS) lasers.
• Existing As2S3-based integrated devices exhibit poor stability and low laser-induced damage thresholds, while planar ChG devices have limited quality factors.

Purpose of the Study:

• To propose and demonstrate a high-quality integrated Germanium-Antimony-Sulfur (GeSbS) chalcogenide glass (ChG) Brillouin photonic device.
• To overcome limitations of existing ChG devices, improving stability, damage threshold, and quality factors for enhanced SBS applications.

Main Methods:

• Fabrication of a finger-shaped GeSbS microresonator incorporating Euler bending structures.
• Suppression of high-order optical modes and reduction of propagation losses within the microresonator.
• Characterization of the device's quality factor, Brillouin gain, laser threshold, linewidth, and cascaded SBS generation.

Main Results:

• Achieved a compact footprint of 3.8 mm² and a high intrinsic quality factor of 5.19 × 10⁶.
• Demonstrated stimulated Brillouin lasers with a low threshold of 0.96 mW and a fundamental linewidth of 58 Hz.
• Successfully realized cascaded stimulated Brillouin lasers up to the seventh order, producing microwave beat frequencies up to 40 GHz.

Conclusions:

• The developed GeSbS ChG Brillouin photonic device offers superior performance compared to existing technologies.
• The device's high quality factor and material gain enable efficient SBS laser generation and high-frequency microwave signal production.
• This work paves the way for advanced integrated photonic devices in microwave photonics and laser applications.