Browsing by Subject "Exceptional points"

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Embargo
Giant ultrafast all-optical modulation based on exceptional points in exciton–polariton perovskite metasurfaces
(American Chemical Society, 2024-01-22) Masharin, Mikhail A.; Oskolkova, Tatiana; Işık, Furkan; Demir, Hilmi Volkan; Samusev, A. K.; Makarov, S .V.
Ultrafast all-optical modulation with optically resonant nanostructures is an essential technology for high-speed signal processing on a compact optical chip. Key challenges that exist in this field are relatively low and slow modulations in the visible range as well as the use of expensive materials. Here we develop an ultrafast all-optical modulator based on MAPbBr3 perovskite metasurface supporting exciton–polariton states with exceptional points. The additional angular and spectral filtering of the modulated light transmitted through the designed metasurface allows us to achieve 2500% optical signal modulation with the shortest modulation time of 440 fs at the pump fluence of ∼40 μJ/cm2. Such a value of the modulation depth is record-high among the existing modulators in the visible range, while the main physical effect behind it is polariton condensation. Scalable and cheap metasurface fabrication via nanoimprint lithography along with the simplicity of perovskite synthesis and deposition make the developed approach promising for real-life applications.
Open Access
Optomechanically induced transparency in a PT symmetric system
(2020-08) Sütlüoğlu, Beyza
Optomechanical systems have attracted attention recently in various areas of physics, and are widely used with the purpose of laser cooling, gravitational wave detection, preparation of entangled states, cooling of mechanical mode to its ground state of motion. Some associated remarkable phenomena are optomechanically induced transparency and slow light. Here, we investigate these features in the context of parity-time (PT ) symmetry. For that purpose, we analyze a system composed of a cavity coupled to pair of PT symmetric mechanical resonators, and investigate the first-order sidebands induced by the radiation pressure on the cavity end-mirror. System is driven by a strong control field and a weak probe field. Using a perturbative method in resolved sideband regime, we observe the transmission of the probe field and slow light around the exceptional point. System exhibits different behaviors in PT broken and PT unbroken phases. In addition to these, we apply polaron transformation, and compare our results with the previous approach. Finally, we offer a preliminary exposition of phase relations for a ternary coupled PT symmetric system, where both mechanical resonators are coupled to the electromagnetic cavity which exemplifies higher-order exceptional points. Predominantly, our results highlight the effects of PT symmetry and exceptional points on the optomechanically induced transparency.
Open Access
Room-temperature exceptional-point-driven polariton lasing from perovskite metasurface
(John Wiley and Sons Inc, 2023-05-25) Masharin, Mikhail A.; Samusev, A. K.; Bogdanov, A. A.; Iorsh, I. V.; Demir, Hilmi Volkan; Makarov, S. V.
Excitons in lead bromide perovskites exhibit high binding energy and high oscillator strength, allowing for a strong light-matter coupling regime in the perovskite-based cavities localizing photons at the nanoscale. This opens up the way for the realization of exciton-polariton Bose–Einstein condensation and polariton lasing at room temperature – the inversion-free low-threshold stimulated emission. However, polariton lasing in perovskite planar photon cavities without Bragg mirrors has not yet been observed and proved experimentally. In this study, perovskite metasurface is employed, fabricated with nanoimprint lithography, supporting so-called exceptional points to demonstrate the room-temperature polariton lasing. The exceptional points in exciton-polariton dispersion of the metasurface appear upon optically pumping in the nonlinear regime in the spectral vicinity of a symmetry-protected bound state in the continuum providing high mode confinement with the enhanced local density of states beneficial for polariton condensation. The observed lasing emission possesses high directivity with a divergence angle of 1° over one axis. The employed nanoimprinting approach for solution-processable large-scale polariton lasers is compatible with various planar photonic platforms suitable for on-chip integration.