Statistical PT-symmetric lasing in an optical fiber network

Abstract

PT-symmetry in optics is a condition whereby the real and imaginary parts of the refractive index across a photonic structure are deliberately balanced. This balance can lead to a host of novel optical phenomena, such as unidirectional invisibility, loss-induced lasing, single-mode lasing from multimode resonators, and non-reciprocal effects in conjunction with nonlinearities. Because PT-symmetry has been thought of as fragile, experimental realizations to date have been usually restricted to on-chip micro-devices. Here, we demonstrate that certain features of PT-symmetry are sufficiently robust to survive the statistical fluctuations associated with a macroscopic optical cavity. We construct optical-fiber-based coupled-cavities in excess of a kilometer in length (the free spectral range is less than 0.8 fm) with balanced gain and loss in two sub-cavities and examine the lasing dynamics. In such a macroscopic system, fluctuations can lead to a cavity-detuning exceeding the free spectral range. Nevertheless, by varying the gain-loss contrast, we observe that both the lasing threshold and the growth of the laser power follow the predicted behavior of a stable PT-symmetric structure. Furthermore, a statistical symmetry-breaking point is observed upon varying the cavity loss. These findings indicate that PT-symmetry is a more robust optical phenomenon than previously expected, and points to potential applications in optical fiber networks and fiber lasers.

Submitted to Nature Communications, Pages 1-19: Main manuscript; Pages 20-38: Supplementary materials

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Cited by in corpus (8)

• Parity-Time Symmetry in Non-Hermitian Complex Optical Media
• Non-Hermitian Photonic Lattices: tutorial
• PT-symmetry entails pseudo-Hermiticity regardless of diagonalizability
• Spectral Signatures of Exceptional Points and Bifurcations in the Fundamental Active Photonic Dimer
• Activating non-Hermitian skin modes by parity-time symmetry breaking
• Holonomic Gates in Pseudo-Hermitian Quantum Systems
• Anomalous spontaneous emission dynamics at chiral exceptional points
• Nonlinear transition between PT-symmetric and PT-broken modes in coupled fiber lasers