Researchers Demonstrate Reconfigurable Exciton-Polariton Canalization in Non-Hyperbolic CsPbBr3 Perovskite

Researchers are now demonstrating a new method for controlling the flow of light using exciton-polaritons, potentially revolutionising nanophotonic devices and photonic circuits. Jiahao Ren, Feng Jin and Hao Zheng, from Nanyang Technological University, alongside Olha Bahrova of the Institut Pascal and colleagues, have experimentally achieved reconfigurable polariton canalization within a non-hyperbolic CsPbBr3 perovskite crystal. This work overcomes previous limitations by operating without the need for specific crystal orientations or linear regimes, instead utilising a carefully designed microcavity to manipulate polariton behaviour. The ability to switch between collimated and divergent polariton flows via pump-spot size adjustment represents a significant advance, paving the way for all-polaritonic logic circuits and stabilised nonlinear interconnects.

Perovskite microcavity controls exciton-polariton flow for novel optical

Scientists have demonstrated optically reconfigurable canalization of exciton-polaritons in a non-hyperbolic perovskite crystal, representing a significant advance in nanophotonics and photonic circuitry. The research team achieved coherent, directional flow of these quasiparticles without relying on materials with intrinsic hyperbolic responses, a limitation of previous approaches. By carefully manipulating the interplay between cavity splitting and crystalline birefringence, the scientists engineered polaritonic isofrequency contours (IFCs) that evolve from hyperbolic to flat to parabolic shapes. This enhanced directionality is a key achievement, overcoming the inherent diffraction that typically limits wave propagation.

This switching induces a transition from divergent to collimating propagation behaviour, offering dynamic control over polariton flow. Experiments show that this novel approach circumvents the need for intrinsically hyperbolic materials, broadening the scope for scalable polaritonic devices. The anisotropic band geometry, achieved through the microcavity-perovskite combination, produces tilted Dirac points and a unique IFC evolution. This allows for precise tuning of polariton dispersion and directionality, enabling the creation of highly collimated flows. Quantitative analysis revealed a reconfigurable enhancement in polariton condensate collimation, ranging from 3.4 to 20.5times greater than that observed with arc-shaped IFCs.

This work establishes a distinct canalization framework for shaping nonlinear exciton-polariton condensate flows, opening opportunities for all-optical polaritonic logic circuits. The ability to create stabilized nonlinear interconnects based on these controlled flows promises advancements in energy-efficient photonic routing and manipulation at the nanoscale. The researchers anticipate that this reconfigurable canalization technique will facilitate the development of advanced nanophotonic devices and pave the way for complex, all-polaritonic circuits with unprecedented functionality.

Birefringent perovskite microcavity for polariton steering offers novel

Experiments at 2.323 eV (kkxx ≈ 4.30μm−1, hyperbolic) and 2.334 eV (kkxx ≈ 5.55μm−1, parabolic) were performed in situ, maintaining constant pump power while tuning excitation spot diameters to 2.0μm and 0.8μm respectively, as detailed in the methods section. S1 Stokes parameter maps confirmed the high-purity y-polarization of condensates propagating along the x direction. To quantitatively assess directional flow, the team extracted the evolution of real-space wave-packet width along x for hyperbolic, flat, and parabolic regimes. Linear fitting of beam-width evolution yielded lateral broadening rates of 0.102 ±0.020 (ΓΓhyperbolic), 0.064 ±0.007 (ΓΓflat), 0.381 ±0.035 (ΓΓparabolic), and 1.309 ±0.060 (ΓΓarc−shaped).

Further experiments with intermediate IFCs, termed weak-parabolic states at condensation energies of 2.328 eV, 2.330 eV, and 2.332 eV, yielded broadening rates of 0.076 ±0.011, 0.111 ±0.015, and 0.270 ±0.021. A collimation factor, defined as ΓΓarc−shaped/ΓΓregime, was calculated to quantitatively track directional collimation across the IFC transition, peaking near canalization at ξ≈1 with a value of 20.5 ±2.4. This approach enables continuous tuning of directional polariton collimation over a broad range, approaching one order of magnitude, simply by shifting the condensation energy across the hyperbolic-flat-parabolic sequence, opening avenues for all-polaritonic logic circuits.

Canalised polariton condensates via perovskite anisotropy offer novel

Quantitative analysis of lateral broadening dynamics revealed a reconfigurable enhancement in polariton condensate collimation ranging from 3.4 to 20.5times greater than the divergence induced by arc-shaped IFCs. This breakthrough delivers new opportunities for all-optical nonlinear polaritonic devices with controllable directional confinement. The research employed a CsPbBr3 perovskite with an orthorhombic structure as the active medium within a distributed Bragg reflector (DBR) cavity, leveraging its intrinsic birefringence and optical anisotropy. Diagonalization of the effective Hamiltonian yielded two eigenenergies associated with orthogonal linear polarizations, described by an equation incorporating TE, TM splitting and optical birefringence.

The resulting exciton-polariton dispersion was accurately captured by a coupled exciton, photon model, incorporating energy dependence of the exciton-polariton effective mass under a Rabi splitting ΩR. Three-dimensional band-view maps of the S1 Stokes parameter revealed anisotropic exciton-polariton dispersion, with the team calculating the curvature of the bands to understand diffraction behaviour. At a critical frequency, the polarization eigenmodes intersect at tilted Dirac points, where the two polarization modes are degenerate. The team determined that above these points, the solution with a negative curvature corresponds to a hyperbolic IFC, while a flat IFC emerges at a specific energy, marking the onset of canalization. Further energy increases lead to a parabolic profile dominated by isotropic curvature, demonstrating a complete evolution of IFC geometry.

Perovskite Microcavity Enables Polariton Flow Control for advanced

This study establishes a distinct framework for shaping nonlinear exciton-polariton condensate flows, offering potential for all-polaritonic logic circuits based on stabilized nonlinear interconnects. The team achieved over twenty times improvement in collimation relative to typical divergence, alongside nearly an order of magnitude of tunability in directional confinement by controlling the optical pump-spot size. Importantly, this canalization does not require specific crystal surfaces with intrinsic hyperbolic responses, broadening its applicability to various birefringent crystals. The authors acknowledge limitations related to the fabrication process and the complexity of fully characterizing the nonlinear interactions within the condensate. Future research could explore the integration of these canalized polariton condensates with other quantum fluids to further steer polariton flows, potentially leading to advancements in quantum-coherent information processing and neuromorphic computing.