Tunable parity-time symmetry vortex laser from a phase change material-based microcavity.

Area of Science:

• Photonics and Optics
• Materials Science
• Quantum Information

Background:

• Traditional light sources lack orbital angular momentum (OAM) emission, limiting optical applications.
• Existing OAM lasers based on micro/nanostructures have fixed parameters, hindering dynamic tuning.

Purpose of the Study:

• To propose and demonstrate a tunable vortex laser using a phase change material for dynamic OAM emission.
• To achieve wavelength tunability in OAM lasers without altering microring geometry.

Main Methods:

• Integration of Ge2Sb2Te5 (GST225), a phase change material, into a microring cavity.
• Utilizing exceptional points (EPs) to break mode degeneracy and impart artificial angular momentum.
• Employing grating scatter for efficient vertical radiation of vortex beams.
• Constructing an electric-thermal model to simulate wavelength tuning.

Main Results:

• Demonstrated tunable vortex lasing by switching GST225 between amorphous and crystalline states.
• Achieved dynamic wavelength tuning of the vortex laser from 1544.5 to 1565.9 nm in approximately 25 ns.
• Successfully imparted well-defined orbital angular momentum (OAM) to emitted vortex beams.

Conclusions:

• The developed GST225/InGaAsP dual-layered microring cavity offers high-speed, tunable vortex laser emission.
• This technology facilitates next-generation integrated optoelectronic devices for optical computing and communications.
• The tunable PT-symmetry vortex laser is crucial for advancements in classical and quantum information processing.