Overview
This research investigates multimode exciton-photon coupling within planar waveguides. Both conventional multimode strong coupling and a superstrong coupling regime were explored, where the Rabi splitting approximates the spacing between adjacent photonic modes. The study demonstrates exciton-tunable phase control and modal switching capabilities, suggesting applications in integrated photonic architectures.
Research Context
Strong light-matter coupling in optical waveguides serves as a platform for engineering hybrid polaritonic modes and their dispersion. The work focuses on visible semiconductor waveguides that support multiple transverse electric modes. Engineering the photonic band structure across different coupling regimes was a central theme.
Approach
The investigation utilized rigorous coupled-wave analysis in conjunction with a coupled-oscillator model. This combined approach allowed for the analysis of multimode exciton-photon coupling and the engineering of the photonic band structure. The study explored conditions under which hybridization between orthogonal electromagnetic modes occurs, specifically by confining the active material to a subregion of the mode volume where photonic modes exhibit significant mutual overlap.
Findings
- The photonic band structure can be engineered to cover a range of regimes, from conventional multimode strong coupling to a superstrong coupling regime.
- In the superstrong coupling regime, the Rabi splitting becomes comparable to the spacing between adjacent photonic modes.
- Hybridization between orthogonal electromagnetic modes is facilitated by restricting the active material to a subregion of the mode volume where photonic modes have strong mutual overlap.
- This hybridization leads to polaritonic branches whose composition can be tuned across several photonic modes and the exciton.
- Small shifts in the exciton resonance produce pronounced changes in the propagation constants of different polariton branches.
- Exciton-controlled phase modulation is enabled through modal interference.
- In the superstrong coupling regime, direct modal switching is observed across a continuous S-shaped dispersion.
- Figures of merit predict $\pi$ phase shifts for exciton energy shifts of a few meV over propagation lengths of tens of micrometers.
- Larger exciton energy shifts are required for mode switching.
Why This Matters
The findings establish multimode waveguide polaritons as a versatile platform capable of spanning multiple coupling regimes. This versatility supports compact phase and intensity control in integrated photonic architectures.