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We demonstrate the enhanced second-harmonic generation (SHG) in single ZnS nanowires (NWs) attached with gold nanoparticles (Au NPs). The hybrid Au/ZnS NWs with different densities of the attached Au NPs were prepared by a simple solution impregnation method. By comparing with bare ZnS NWs, ∼1.3, ∼6.6, ∼7 and ∼2 times enhancement of SH intensity was achieved in the hybrid Au/ZnS NWs with low, moderate, high and ultrahigh densities of the attached Au NPs, respectively. The enhanced SHG in the hybrid Au/ZnS NWs is attributed to the strong local-fields from the Au cluster under the near-resonant condition, which is supported by the related dark-field scattering spectra. This hybrid Au/ZnS NWs provide a simple platform for enhancing nonlinear optical responses, which have potential applications in nano-probing and nano-sensing. [ABSTRACT FROM AUTHOR]

Abstract: By performing Z-scan method with a femtosecond laser (800nm, 50fs, 1kHz), we investigated the third-order optical nonlinearities of a cuprous oxide (Cu2O) film. Single-phase Cu2O film deposited on a quartz substrate was obtained using the pulsed laser deposition technique. The structure properties, surface morphology and optical transmission spectrum were characterized by X-ray diffraction, scanning electron microscopy and double beam spectrophotometer, respectively. The Z-scan results show that the Cu2O film exhibits large nonlinear refractive index, n2 =3×10−3 cm2/GW, while the two-photon absorption coefficient, α 2 =40cm/GW, is relatively small. It implies that the Cu2O film is a promising candidate for nonlinear photonic devices. [Copyright &y& Elsevier]

By controlling the oxygen pressure, single-phase CuO and CuO thin films have been obtained on quartz substrates using a pulsed laser deposition technique. The structure properties and linear optical absorption of the films were characterized by X-ray diffraction and UV-VIS spectroscopy. By performing z-scan measurements using a femtosecond laser (800 nm, 50 fs), the real and imaginary parts of the third-order nonlinear susceptibility, Re χ and Im χ, of the films were determined. Both CuO and CuO films exhibited large optical nonlinearities, which is comparable to those in some representative semiconductor films such as ZnO and GaN films using femtosecond laser excitation. Compared with CuO films, the CuO films showed larger third-order nonlinear optical effects under off-resonance excitation. Furthermore, the mechanisms of the optical nonlinearities in CuO and CuO films are explained in the main text. It was suggested that the reasons of the difference in their nonlinear refractive effects may be related to the different electronic structure in CuO and CuO materials. [ABSTRACT FROM AUTHOR]

Abstract: We present the experimental and theoretical study of colored conical emission (CCE) during intense femtosecond pulses propagating in a β-barium borate (BBO) crystal. CCE revealed special nonlinear dynamics of the strong coupling between the fundamental and second harmonic pulses due to the spatiotemporal modulation instability (MI). The underlying physics of CCE involve three three-photon processes, according to which the beam angular spectra was calculated on the phase-matching conditions and accords with the experimental observation. [ABSTRACT FROM AUTHOR]

We theoretically investigate the UV-assisted high-order harmonic generation (HHG) process in a mid-infrared polarization gating (PG) field. The ionization and recombination steps of the HHG process can be controlled simultaneously by the UV and PG pulses. The influences of the delay between the UV and PG pulses on the phase-locking degree and the intensity of the harmonics are presented quantitatively. The results show that the harmonics are phase-locked as well as the intensity is significantly enhanced by 3 or 4 orders at a proper delay. Then a phase-locked ultra-broadband supercontinuum with a bandwidth of 240 eV is produced efficiently, supporting the generation of a Fourier-transform-limited pulse duration below one atomic unit of time. In addition, efficient isolated 110 as pulses with tunable central wavelengths can be obtained directly by selecting a different range of the supercontinuum. [ABSTRACT FROM AUTHOR]

Abstract: Titanium dioxide (TiO2) films have been fabricated on fused quartz and Si(001) substrates by pulsed laser deposition technique and the single-phase anatase and rutile films were obtained under the optimal conditions. The surface images and optical transmission spectra were investigated by scanning electron microscopy and double beam spectrophotometer, respectively. The values of optical band-gap and linear refractive index of the anatase and rutile films were determined. The optical nonlinearities of the films were measured by Z-scan method using a femtosecond laser (50 fs) at the wavelength of 800 nm. Through the open-aperture and closed-aperture Z-scan measurements, the real and imaginary parts of the third-order nonlinear optical susceptibility were calculated and the results show that the anatase phase TiO2 films exhibit larger nonlinear refractive effects compared with rutile phase. The figure of merit, T, defined by T = βλ/n 2, was calculated to be 0.8 for anatase films, meeting the requirement of T <1 and showing potential applications in all-optical switching devices. [Copyright &y& Elsevier]

Abstract: In this work we investigate the third-order optical nonlinearities in CuO films by Z-scan method using a femtosecond laser (800 nm, 50 fs, 200 Hz). Single-phase CuO thin films have been obtained using pulsed laser deposition technique. The structure properties, surface image, optical transmittance and reflectance of the films were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and UV–vis spectroscopy. The Z-scan results show that laser-deposited CuO films exhibit large nonlinear refractive coefficient, n 2 =−3.96×10−17 m2/W, and nonlinear absorption coefficient, β =−1.69×10−10 m/W, respectively. [Copyright &y& Elsevier]

Herein, a 20‐fold enhancement of the optical second harmonic generation (SHG) from WS2 monolayers by cooperating with SiO2 dielectric microspheres (MSs) is reported. Detailed experiment and simulation studies indicate that the SHG enhancement is dominantly originated by the enhanced excitation intensity and enlarged collection efficiency produced by the SiO2 MSs. The size effect of the SiO2 MS on the SHG enhancement is also systematically investigated. Moreover, the SHG enhancement is found to be very sensitive to the surrounding refractive index of the SiO2 MS, which advocates great promise for the photonic sensing applications. This work provides a low‐cost and efficient approach to enhancing the SHG emission, and demonstrates great potential for functional nanodevices based on hybrid dielectric structures. A 20‐fold enhancement of the optical second harmonic generation (SHG) from WS2 monolayers by cooperating with SiO2 dielectric microspheres (MSs) is reported. The SHG enhancement is attributed to the increased excitation intensity and enlarged collection efficiency produced by the SiO2 MSs. Moreover, a proof‐of‐concept photonic sensing application based on SHG is demonstrated. [ABSTRACT FROM AUTHOR]