Accelerated exceptional point encirclement in anti-parity-time symmetric systems for ultra-compact chiral mode switching

Anti-parity-time (anti-PT) symmetric systems have emerged as promising tools in optical design, offering unique advantages over parity-time (PT) symmetric systems. These systems leverage symmetry-broken modes, which play a crucial role in enabling chiral mode switching—a key functionality for integrated photonic devices. However, achieving such switching typically requires maintaining low adiabaticity through slow parameter variation, often leading to larger device footprints. In this paper, we present a novel anti-PT symmetric system that introduces parameter evolution via loss and width variations in waveguides, offering an innovative design approach. Through theoretical analysis of the Hamiltonian parameter space, we evaluate the degree of adiabaticity and optimize parameter evolution along the boundary of the Reimann surface. This strategy achieves chiral mode switching while maintaining low adiabaticity. In addition, the simultaneous modulation of loss and width significantly reduces the device footprint to just 30 μm, which is less than half the length of conventional anti-PT symmetric systems. The proposed system not only facilitates efficient chiral mode switching via exceptional point (EP) encircling but also enhances device compactness, paving the way for higher integration density in photonic devices.