Optical wave propagation in parity-time (PT) symmetric potentials
Final Report Abstract
In this research program we explored fundamental issues concerning the properties and behaviour of optical beams and waves in parity-time (PT) symmetric structures. For the experimental investigations we used iron-doped lithium niobate which allows for both tailoring of refractive index and gain/loss. As a continuation of the formerly investigated two-channel coupler or dimer, we concentrated our work on a trimer system. We first analysed all the relevant branches of regular solutions as well as bifurcations and instabilities thereof. We also examined the dynamics of unstable trimers, as well as those of the ghost states in the parametric regime where the latter are found to exist. Finally, we performed experiments in a related gain-loss-gain three-channel waveguide structure, which are in quite reasonable agreement with corresponding numerical solutions of the coupled wave equations of the PT trimer. During development of the project work it came out that there exist still some limitations that have to be overcome in order to realize more advanced PT symmetric optical settings when using the photorefractive effect of lithium niobate to provide optical gain. The high gain coefficients observed in melt-doped crystals could not be obtained in waveguide sample where Fe doping was realized by indiffusion. In the PT experiments performed so far, gain was further limited because of the requirements to keep input powers quite low in order to avoid any decoupling of excited channels due to nonlinear index changes. As nonreciprocal beam propagation and symmetry breaking is an intrinsic property of PT optics, we used the fabricated samples also to carefully analyse spontaneous symmetry breaking effects related to the existence of nonlinearity. In two channel couplers, we experimentally investigated nonlinearity-induced symmetrybreaking and the existence of a multi-stable regime. In another work spontaneous symmetry-breaking was investigated in a photonic lattice containing a single defect.
Publications
- Multistable regime and intermediate solutions in a nonlinear saturable coupler. Phys. Rev. A 87, 043837 (2013)
D. Guzman-Silva, C. Lou, U. Naether, C. E. Rüter, D. Kip, R. A. Vicencio
(See online at https://doi.org/10.1103/PhysRevA.87.043837) - Revisiting the PT-symmetric trimer: bifurcations, ghost states and associated dynamics. J. Phys. A: Math. Theor. 46, 375304 (2013)
K. Li, P. G. Kevrekidis, D. J. Frantzeskakis, C. E. Rüter, D. Kip
(See online at https://doi.org/10.1088/1751-8113/46/37/375304) - Spontaneous symmetry breaking of gap solitons in defect loaded uniform one-dimensional photonic lattices. Phys. Rev. A 88, 23858 (2013)
P. P. Belicev, I. Ilic, M. Stepic, L. Hadzievski, C. Lou, S. Suntsov, C. E. Rüter, D. Kip
(See online at https://doi.org/10.1103/PhysRevA.88.023858)
