White light cavity formation and superluminal lasing near exceptional points

Area of Science:

• Quantum optics
• Laser physics
• Photonics

Background:

• Coupled micro-resonator systems offer unique optical properties.
• Parity-time symmetry (PT symmetry) in optical systems leads to novel phenomena at exceptional points (EP).
• Superluminal propagation, characterized by a negative group index, has been theoretically explored but experimentally challenging.

Purpose of the Study:

• To theoretically investigate superluminal lasing in a coupled micro-resonator system.
• To establish the connection between the white light cavity (WLC) condition, PT symmetry, and superluminal lasing.
• To explore the potential applications of this superluminal lasing regime.

Main Methods:

• Theoretical analysis of coupled active and passive micro-resonators.
• Investigation of the system's behavior under the white light cavity (WLC) condition.
• Examination of PT-symmetric properties at the exceptional point (EP).

Main Results:

• The system satisfies the white light cavity (WLC) condition, exhibiting zero group index.
• The WLC condition coincides with the formation of a PT-symmetric system (PTSS) at its exceptional point (EP).
• Superluminal lasing is observed slightly above the lasing threshold in the broken symmetry regime near the EP.

Conclusions:

• The study theoretically confirms superluminal lasing in PT-symmetric coupled micro-resonators.
• This superluminal lasing regime, occurring near the EP, is highly attractive for sensing and precision metrology.
• Existing experimental studies on PTSSs may have indirectly observed this superluminal lasing phenomenon.