Lasing condition for trapped modes in subwavelength-wired PT-symmetric resonators

Area of Science:

• Optoelectronics
• Plasmonics
• Materials Science

Background:

• Controlling laser modes in subwavelength resonators is crucial for modern optoelectronics.
• PT-symmetric systems offer unique optical properties due to balanced gain and loss.
• Graphene integration enables novel functionalities in nanoscale optical structures.

Purpose of the Study:

• To theoretically investigate the optical properties of a PT-symmetric nano-scaled dimer composed of dielectric wires with gain and loss, wrapped in graphene.
• To demonstrate the transformation of non-radiating trapped modes into radiating modes by tuning the gain-loss parameter.
• To achieve lasing conditions and ultra-high quality factors in the designed structure.

Main Methods:

• Theoretical analysis of optical properties.
• Utilizing a PT-symmetric dimer model with gain and loss elements.
• Employing graphene sheets for enhanced optical response.
• Investigating mode transformation and lasing conditions via parameter variation.
• Developing an approximated analytical method.

Main Results:

• Existence of two non-radiating trapped modes that transition to radiating modes with increased gain-loss.
• Lasing condition achieved for specific gain-loss parameters, resulting in ultra-high quality factors.
• Gain-loss parameter variation modulates the phase difference of induced dipole moments without significantly altering their magnitude.
• An approximated method accurately reproduces key findings from rigorous calculations.

Conclusions:

• The study demonstrates a novel mechanism for controlling trapped and radiating modes in PT-symmetric nano-resonators.
• The findings pave the way for developing advanced optoelectronic devices with tunable functionalities.
• The use of graphene in balanced gain-loss structures offers a promising route for enhanced optical performance.