Anti-Parity-Time Symmetry in Passive Nanophotonics

Abstract

Parity-time (PT) symmetry in non-Hermitian optical systems promises distinct optical effects and applications not found in conservative optics. Its counterpart, anti-PT symmetry, subscribes another class of intriguing optical phenomena and implies complementary techniques for exotic light manipulation. Despite exciting progress, so far anti-PT symmetry has only been realized in bulky systems or with optical gain. Here, we report an on-chip realization of non-Hermitian optics with anti-PT symmetry, by using a fully-passive, nanophotonic platform consisting of three evanescently coupled waveguides. By depositing a metal film on the center waveguide to introduce strong loss, an anti-PT system is realized. Using microheaters to tune the waveguides' refractive indices, striking behaviors are observed such as equal power splitting, synchronized amplitude modulation, phase-controlled dissipation, and transition from anti-PT symmetry to its broken phase. Our results highlight exotic anti-Hermitian nanophotonics to be consolidated with conventional circuits on the same chip, whereby valuable chip devices can be created for quantum optics studies and scalable information processing.

Liouvillian exceptional points of any order in dissipative linear bosonic systems: Coherence functions and switching between PT and anti- PT symmetries

“…[67,84]. We stress that the possibility to witness different symmetries of the system by considering different operators offers great flexibility to explore different dynamical regimes and various kinds of nontrivial light behavior in this system in the semiclassical regime [67][68][69]. Moreover, we have explained that one can witness not only the PT and anti-PT symmetries, but also can physically switch between them by transforming the system two-mode output fields with an additional tunable linear coupler, e.g., a tunable beam splitter in optical implementations of the general model discussed.…”

“…Incoherent mode coupling can be produced in various ways. These have been already realized, e.g., in anti-PT -symmetrical classical systems, which include: nonlinear Brillouin scattering in a single microcavity [67], two passive waveguides, separated by a metallic film [68], countermoving media with heat exchange [69] or resistively coupled electric resonators [70]; and, in quantum systems, through a coherent transport of flying atoms [71]. Nevertheless, in all these works, when studying EPs, a phenomenological approach has been utilized based exclusively on effective NHHs, thus ignoring quantum-jump effects.…”

Single-cavity bi-color laser enabled by optical anti-parity-time symmetry

“…An APT symmetric Hamiltonian can be obtained from a PT symmetric one by multiplying the unit imaginary number i, H ˆ (APT) = iH ˆ (PT) . Such close connection between APT and PT symmetric systems has attracted great interest in investigating the physics of APT symmetry in various configurations in atomic [19], thermal [20], electrical [21] and optical [22][23][24] systems. However, how to exploit this new quantum symmetry into practical laser applications is still yet to be discussed.…”

Generating high-order quantum exceptional points in synthetic dimensions

“…As an example, we implement our method for the U (1)-symmetric quadratic Liouvillian that describes a two-mode optical cavity with incoherent mode coupling. This model is also characterized by the anti-PT -symmetry [63][64][65][66][67][68], as defined in Eq. (20).…”