Locking a microsphere whispering-gallery mode to a laser.

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Technology

Background:

• Whispering-gallery mode resonators are sensitive to environmental changes.
• Stable and tunable optical resonances are crucial for various photonic applications.
• Previous methods for tuning microsphere resonances had limitations in range and speed.

Purpose of the Study:

• To achieve stable locking of a whispering-gallery resonance to a frequency-scanning laser.
• To demonstrate a wide tracking range for the locked resonance.
• To investigate the performance of an improved compression tuner for microsphere resonance modulation.

Main Methods:

• Utilized a fused-silica microsphere to support whispering-gallery resonances.
• Employed a frequency-scanning laser at 1570 nm or 830 nm for resonance locking.
• Implemented phase-sensitive detection of fiber-coupled optical throughput for feedback control.
• Used an improved compression tuner for axial modulation of the microsphere.

Main Results:

• Successfully locked the whispering-gallery resonance to the laser.
• Demonstrated a locked tracking range exceeding 30 GHz.
• Achieved coarse tuning over 1 THz and piezoelectric tuning over 80 GHz with the new tuner.
• Obtained compression modulation rates up to 13 kHz.

Conclusions:

• The developed system enables robust locking and wide-range tracking of microsphere resonances.
• The improved compression tuner significantly enhances tuning capabilities and modulation speed.
• This work paves the way for advanced applications in optical sensing, communication, and metrology.