Blue upconversion laser based on thulium-doped silica microcavity.

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Laser Physics

Background:

• Whispering gallery mode optical resonant cavities (WGMs) using rare-earth-doped silica glasses have achieved lasing across visible and near-infrared spectra.
• Lasing in the blue spectrum from these cavities has remained a significant challenge.

Purpose of the Study:

• To achieve blue lasing in optical microcavities.
• To investigate thulium-doped silica films for microcavity fabrication.
• To explore upconversion mechanisms in high-intensity optical microcavities.

Main Methods:

• Synthesis of thulium-doped silica films.
• Fabrication of toroidal optical microcavities with quality factors exceeding 10 million.
• Characterization of lasing emission and threshold powers.

Main Results:

• Thulium-doped silica microcavities demonstrated lasing in the blue and near-infrared regions.
• Microwatt threshold powers were achieved, indicating efficient lasing.
• Lasing intensity scaled linearly with thulium concentration.
• High circulating optical intensities facilitated thulium upconversion despite silica's high phonon energy.

Conclusions:

• Thulium-doped silica toroidal microcavities are capable of producing blue lasing.
• High optical intensities within microcavities are key to overcoming material limitations for upconversion.
• This work paves the way for blue light generation using rare-earth-doped silica microcavities.