Continuous-wave upconversion lasing with a sub-10 W cm^-2 threshold enabled by atomic disorder in the host matrix.

Area of Science:

• Photonics and Nanotechnology
• Materials Science

Background:

• Microscale lasers are crucial for applications like intracellular biosensors and microprocessors.
• Upconversion microlasers offer large anti-Stokes shifts but require high pump power.

Purpose of the Study:

• To demonstrate continuous-wave upconversion lasing at an ultralow threshold.
• To overcome the high pump power limitations of previous upconversion microlasers.

Main Methods:

• Synthesized monolithic whispering-gallery-mode microspheres using laser-induced liquefaction and rapid quenching ('liquid-quenching').
• Integrated upconversion nanoparticles for enhanced pump-to-gain interaction and reduced intracavity losses.
• Utilized atomic-scale disorder in the host matrix to suppress energy back transfer.

Main Results:

• Achieved continuous-wave upconversion lasing with an ultralow threshold of 4.7 W cm⁻².
• Demonstrated wavelength tunability of up to 3.56 nm via pump power and temperature adjustments.
• Developed a narrow-linewidth anti-Stokes shift microlaser competitive with state-of-the-art Stokes-shift microlasers.

Conclusions:

• The liquid-quenching method enables highly efficient upconversion microlasers.
• This technology paves the way for advancements in atomic spectroscopy, biomedical imaging, and optical communication.