Unidirectional single-mode lasing realization and temperature-induced mode switching in asymmetric GaN coupled...

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Semiconductor microlasers are crucial for optical interconnects, on-chip communication, and biosensors.
• Effective control over lasing modes and unidirectional coupling is essential for enhancing microlaser performance and applications.

Purpose of the Study:

• To design and fabricate Gallium Nitride (GaN) floating microdisks and coupled cavities utilizing the Vernier effect for controlled lasing.
• To investigate the lasing properties, including mode characteristics, threshold, radiation direction, and mode switching mechanisms.
• To demonstrate directional control of lasing output and dynamic mode switching in GaN microdisk structures.

Main Methods:

• Design of symmetric and asymmetric GaN floating microdisks and coupled cavities based on the Vernier effect.
• Fabrication using electron beam lithography, dry-etching of GaN, and isotropic wet-etching of silicon (Si) support.
• Experimental and simulated analysis of optical field distributions and lasing properties.

Main Results:

• Asymmetric GaN microdisk structures allow for controlled lasing outgoing direction, unlike their symmetrical counterparts.
• Whispering gallery mode (WGM) lasing was achieved, showing quasi-single-mode lasing at 374.36 nm and dual-mode lasing at 372.36 nm and 373.64 nm in coupled cavities.
• Dynamic switching between dual-mode and single-mode lasing was successfully demonstrated through thermally induced mode shifting.

Conclusions:

• Asymmetric GaN microdisks offer a pathway to directional control of laser emission.
• The Vernier effect-based design enables tunable and switchable multi-mode lasing in coupled cavities.
• These findings pave the way for advanced semiconductor microlasers with tailored optical output for integrated photonic applications.