Dynamically encircling an exceptional point for asymmetric mode switching.

Area of Science:

• Physics
• Quantum Mechanics
• Waveguide Technology

Background:

• Physical systems with loss or gain exhibit resonant modes with exponential decay or growth.
• Exceptional points (EPs) arise when two such modes coalesce in frequency and decay/growth rate, leading to non-intuitive phenomena.
• Previous studies explored EP topology, but full dynamical encircling and adiabaticity breakdown remained experimentally challenging.

Purpose of the Study:

• To demonstrate the dynamical encircling of an exceptional point.
• To investigate the analogy between EP encircling and wave scattering in a two-mode waveguide.
• To realize a robust and asymmetric switch for waveguide modes.

Main Methods:

• Developed a two-mode waveguide structure with tailored boundaries and losses.
• Experimentally steered incoming waves around an exceptional point during transmission.
• Analyzed the induced mode transitions and switching behavior.

Main Results:

• Successfully demonstrated the dynamical encircling of an exceptional point via wave scattering.
• Observed mode transitions that function as an asymmetric switch.
• Validated the analogy between EP encircling and waveguide scattering.

Conclusions:

• Exceptional point encircling can be achieved through waveguide scattering.
• The developed waveguide structure acts as a robust asymmetric switch.
• This work facilitates exploration of EP physics for quantum system control and state transfer.