Abstract
Engineered non-Hermitian systems featuring exceptional points (EPs) can lead to a host of extraordinary phenomena in diverse fields ranging from photonics, acoustics, opto-mechanics, and electronics to atomic physics. In optics, non-Hermitian dynamics are typically realized using dissipation and phase-insensitive gain accompanied by unavoidable fluctuations. Here, we introduce non-Hermitian dynamics of coupled optical parametric oscillators (OPOs) arising from phase-sensitive amplification and de-amplification, and show their distinct advantages over conventional non-Hermitian systems relying on laser gain and loss. OPO-based non-Hermitian systems can benefit from the instantaneous nature of the parametric gain, noiseless phase-sensitive amplification, and rich quantum and classical nonlinear dynamics. We show that two coupled OPOs can exhibit spectral anti-parity-time (anti-PT) symmetry and a EP between its degenerate and nondegenerate operation regimes. To demonstrate the distinct potentials of the coupled OPO system compared to conventional non-Hermitian systems, we present higher-order EPs with two OPOs, tunable Floquet EPs in a reconfigurable dynamic non-Hermitian system, and the generation of a squeezed vacuum around EPs, all of which are not easy to realize in other non-Hermitian platforms. We believe our results show that coupled OPOs are an outstanding non-Hermitian setting with unprecedented opportunities to realize nonlinear dynamical systems for enhanced sensing and quantum information processing.
Highlights
Non-Hermitian systems with engineered gain and dissipation have attracted a lot of attention thanks to remarkable properties and functionalities that are absent in their counterparts based on closed Hermitian setups [1,2]
We explore the possibility of reduced uncertainty of fluctuations manifested in the form of squeezed noise in the vicinity of parametric exceptional points (EPs) to leverage the high sensitivity of EP in the pursuit to obtain a high signal-to-noise ratio (SNR)
The threshold for parametric oscillation in the coupled optical parametric oscillators (OPOs) is determined by the linear eigenvalues, with oscillation occurring for λI > 0
Summary
Non-Hermitian systems with engineered gain and dissipation have attracted a lot of attention thanks to remarkable properties and functionalities that are absent in their counterparts based on closed Hermitian setups [1,2]. Parametric non-Hermitian systems can extend beyond the spectral coverage of laser gain [17], and the instantaneous nature of parametric gain enables the realization of tunable/reconfigurable non-Hermitian systems that are otherwise difficult to achieve in conventional optics-based nonHermitian setups. The noiseless nature of phase-sensitive degenerate parametric amplification motivates studying non-Hermitian dynamics of coupled OPOs for sensing. In this regard, we explore the possibility of reduced uncertainty of fluctuations manifested in the form of squeezed noise in the vicinity of parametric EP to leverage the high sensitivity of EP in the pursuit to obtain a high SNR. These behaviors may be extended to the non-Gaussian regime [34]
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