Fei Zhou, Zhiyuan Yang, Jingtao Huang, Xueping Zheng, Xianhua Wei, Bo Dai
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Self-trapped exciton-phonon resonance enhanced nonlinear susceptibility in 2D KNbO2
Strong second harmonic generation (SHG) was observed when the two-photon energy matches to the self-trapped exciton resonance states in the lattice inversion symmetric system of two-dimensional (2D) KNbO2 crystals. It is ascribed to the symmetry broken induced by the bending distortion of O−Nb−O in individual octahedrons (low frequency T2g modes) that coupling to the two-photon frequency. The quantum confinement SHG response with more than one orders of enhancement is obtained due to the phonon-exciton-photon interaction with dimension reduction. In addition, the exciton-phonon interaction couples SHG photons to a non-equilibrium energy with a Stokes or anti-Stokes energy splitting of ∼18–21 meV, which is corresponding to the Raman shift of T2g modes.
期刊介绍:
Applied Physics Letters (APL) features concise, up-to-date reports on significant new findings in applied physics. Emphasizing rapid dissemination of key data and new physical insights, APL offers prompt publication of new experimental and theoretical papers reporting applications of physics phenomena to all branches of science, engineering, and modern technology.
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