Broadband second harmonic generation from ZnO nano-tetrapods

Second harmonic generation (SHG) from ZnO bulk single crystal and nano-tetrapods were comparatively studied at room temperature for a wide wavelength range of 710–930 nm by using femtosecond broadband near-infrared laser as the excitation source. Strong enhancement of SHG was interestingly observed in the tetrapods, especially for the excitation photon energy less than the half band gap of ZnO. Broadband efficient SHG of the tetrapods is attributed to the structural symmetry breaking in the surface area of tetrapods with four long arms.