Highly tunable low-threshold optical parametric oscillation in radially poled whispering gallery resonators

Area of Science:

• Nonlinear Optics
• Photonics
• Materials Science

Background:

• Whispering-gallery resonators (WGRs) offer high quality factors for efficient light-matter interactions.
• Their potential for broadband or tunable electromagnetic radiation generation is significant.
• Lithium niobate is a key material for nonlinear optical applications.

Purpose of the Study:

• To experimentally and theoretically investigate the tunability of optical parametric oscillation (OPO).
• To explore OPO in a radially structured lithium niobate WGR.
• To assess the impact of structural modifications on tuning capabilities.

Main Methods:

• Utilized a radially structured lithium niobate whispering-gallery resonator.
• Employed a 1.04 μm pump wave for optical parametric oscillation.
• Varied temperature from 20 to 62 °C to tune signal and idler waves.
• Investigated the effect of slight off-centering in the radial domain structure.

Main Results:

• Achieved tunable signal and idler waves from 1.78 to 2.5 μm, covering the degeneracy point.
• Demonstrated tuning by temperature variation.
• Showed that slight off-centering of the radial domain structure significantly enhances tuning capabilities.
• Observed a low oscillation threshold in the milliwatt power range.

Conclusions:

• Radially structured lithium niobate WGRs are effective for tunable optical parametric oscillation.
• Temperature tuning provides a viable method for controlling output wavelengths.
• Structural modifications offer further enhancement of tuning range, paving the way for versatile light sources.