Bosonic Condensation And Photon Spin-orbit Coupling In Organic Single Microcavities

Due to the high exciton binding energy and large oscillator strength of Frenkel excitons in organic single crystal materials,they can achieve strong coupling between exciton and photons with Rabi splitting greater than 150 me V at room temperature compared to inorganic semiconductors.And because of the easy tailoring of organic molecules,polariton condensation across the entire visible light spectrum is easily achieved.In addition,the highly ordered molecular arrangement of organic single crystals makes its absorption and emission have strongly anisotropy.The above characteristics directly lay the foundation for the study of polariton condensation.And due to the strongly anisotropy（linear birefringence）of the organic crystal,the transverse electric and transverse magnetic（TE-TM）mode can be split at the wavevector6)=0,which can used as the fundamentals of photon spin-orbit coupling and topological photonics research.Therefore,this paper realizes the bosonic condensation and spin-orbit coupling of photons by preparing a classic sandwich organic microcavity structure.The main research contents are as follows:（1）The highly ordered molecular arrangement in organic single crystals makes it have strongly anisotropic,especially in its absorption and emission spectrum.We demonstrate strongly polarization-dependent exciton polariton in a microcavity consisting of an H-aggregate organic single-crystalline microbelt（DPAVBi）sandwiched between two silver reflectors.Benefitting from the advantages of vibronic coupling in H-aggregates and heavy exciton-like polaritons under positive detuning,both macroscopic coherent exciton polariton ground-state population and high-energy quantized modes are observed.The ease of fabrication of microcavity and the observation of low threshold polariton condensation make microcrystals of organic semiconductors attractive candidates for electrically pumped functional photonic polariton circuits and continuous wave pumped and organic polariton lasers,operating at room temperature.（2）By integrating optically anisotropic organic crystallites（α-phase perylene）into a Fabry-Pérot（FP）microcavity,due to the coexistence of the three polarization splitting effects of the overrall optical rotation of the microcavity,the TE-TM cavity mode splitting and the linear birefringence of the materials,and the combination constitutes an equivalent photon gauge field.The microcavity photon undergoes spin-orbit coupling under the action of the gauge field,and the photon energy band is anti-crossed at a spectric wave vector and an open Dirac cone point emerges,realizing the local topogical nontrivial geometry of the photonic energy band of the mocrocavity.Because no external magnetic field and other factors are introduced during the whole experiment,the time-reversal symmtery is preserved and the topological energy bands are trival as a whole.In this work,we report a direct measurement of the Berry curvature and quantum metric of the photonic modes of a planar cavity.This experiment is carried out at room temperature and visible wavelength,without external magnetic field and does not depend on photonic lattice structure,which provides a new method for further realization of spin and energy valley Hall effect,spin orbit coupling manipulation on photonic chip.（3）The ability to control the spin-orbit interaction（SOI）of photons in optical microcavities is critical for future photonics.Organic crystallites play a crucial role in spin optics and topological photonics due to their enormous optical anisotropy.Here,we constructed an optical microcavity filled with organic crystals（β-phase perylene）,due to the strongly anisotropic exciton response inβ-phase perylene crystals,the vertical polarization（V）of the cavity modes interact strongly with excitons and resulting in a flattened cavity mode curvature,while the horizontal polarization（H）of the cavity modes in not affected,so the H and V cavity modes with different pairty can occur spin-orbit coupling at a larger wave vector,so that the energy band is split and an open Dirac cone point appears.And at the wave vector k=0,orthogonally polarized cavity modes of different parity can occur Rashba-Dresselhaus spin-orbit interaction.We artificially design spin-orbit coupling through exciton-photon interactions,in addition to its fundamental effects,it is also expected to be applied to spin-controlled on-chip integrated nanophotonic elements to develop non-magnetic and low-cost spin photonic devices.