Anti-parity-time-symmetry optics in an atomic vapor

Zhaoyang Zhang, Yiqi Zhang, Jiteng Sheng +3 more

Frost Mengmeng Xu, Hao Song, Jian Xu +1 more

In optical parity-time symmetry, the electric permittivity of an electromagnetic structure should have a real part, which is an even function of spatial coordinates, and an imaginary part, which is an odd function of coordinates. Since a Vee- and a Lambda-configuration three-level atomic vapor can be driven by both control and probe beams, and can exhibit both frequency-sensitive and field-controlling optical responses, the dielectric “constants” of these two atomic vapors can be tuned by manipulating the applied external control fields. The requirement for realizing optical parity-time symmetry can be fulfilled in quantum-coherent multilevel atomic vapors. A design based on Vee- and Lambda-configuration three-level atomic vapors for achieving optical parity-time symmetric interface is suggested in this paper. Under certain parameter conditions, an optical parity-time symmetric interface can possibly be fabricated in the present scenario of quantum-coherent multilevel atomic vapors.

James J. Wynne, P. P. Sorokin

Runrun Li, Hengfei Zhang, Jinpeng Yuan +3 more

Non-Hermitian systems based on anti-parity-time (PT) symmetry reveal rich physics beyond the Hermitian regime. Here, the anti-PT-symmetric photonic lattice is effectively achieved in a four-level inverted Y-type 85 Rb atomic vapor. Such instantaneously reconfigurable anti-PT-symmetric photonic lattice possessing susceptibility of 𝜒 ⁡ ( 𝑥 ) = − 𝜒 ∗ ⁡ ( − 𝑥 ) , is established by a one-dimensional standing-wave coupling field under the assist of a standing-wave driving field. The input probe beam experiences a periodic refractive index modulation when traveling through the photonic lattice, the evolution of output diffraction patterns with symmetric, asymmetric, and lopsided intensity distribution is obtained by adjusting the relevant parameters of constructed non-Hermitian system. Moreover, the anti-PT symmetry in two-dimensional case of both square and hexagonal lattices are correspondingly realized. Our work promotes the development of non-Hermitian devices, and also has some important applications in quantum simulation .

Stephan Wielandy

Yue Jiang, Yefeng Mei, Ying Zuo +4 more

Non-Hermitian optical systems with parity-time (PT) symmetry have recently revealed many intriguing prospects that outperform conservative structures. The previous works are mostly rooted in complex arrangements with controlled gain-loss interplay. Here, we demonstrate anti-PT symmetry inherent in the nonlinear optical interaction based upon forward optical four-wave mixing in a laser-cooled atomic ensemble with negligible linear gain and loss. We observe that the pair of frequency modes undergo a nontrivial anti-PT phase transition between coherent power oscillation and optical parametric amplification in presence of a large phase mismatch.