A tellurite glass optical microbubble resonator

Area of Science:

• Photonics and optical materials science
• Micro- and nanofabrication technologies
• Glass science and engineering

Background:

• Whispering gallery resonators (WGRs) are crucial for various photonic applications.
• Soft glasses, like tellurite, offer unique thermo-optical and optomechanical properties.
• Fabricating microscale WGRs with high quality factors from soft glasses presents challenges.

Purpose of the Study:

• To develop a novel method for fabricating microbubble whispering gallery resonators (WGRs) from tellurite glass.
• To investigate the optical characteristics and sensitivities of tellurite microbubble WGRs to temperature and air pressure.
• To demonstrate lasing capabilities and explore potential applications in sensing and integrated photonics.

Main Methods:

• Utilized a CO2 laser for precise fabrication of microbubble WGRs from tellurite glass.
• Characterized passive and active (Yb3+-Er3+ co-doped) tellurite microbubbles.
• Measured optical properties, including quality factors, temperature sensitivity, and air pressure sensitivity.
• Analyzed microbubble morphology using electron microscopy and optical spectra.

Main Results:

• Achieved loaded quality factors as high as 2.3 × 10^6.
• Measured temperature sensitivity of 4.9 GHz/K and air pressure sensitivity of 7.1 GHz/bar for passive microbubbles.
• Demonstrated C-band single-mode lasing in active microbubbles with a low threshold of 1.66 mW.
• Observed a laser output frequency sensitivity to pressure changes of 6.5 GHz/bar.
• Fabricated microbubbles exhibited low eccentricity and uniform wall thickness.

Conclusions:

• The CO2 laser fabrication method enables high-quality microbubble WGRs from low-melting-point soft glasses.
• Tellurite microbubbles possess excellent optical properties and high sensitivities, making them suitable for sensing applications.
• Active tellurite microbubbles can function as tunable microcavity lasers.
• These microbubbles hold significant potential for integrated photonics, nonlinear optics, and advanced sensing platforms.