Circular photocurrent in the carbon nanowall film.

We report the helicity-dependent photocurrent in the carbon nanowall film synthesized on the silicon substrates by the chemical vapor deposition technique. The film is composed of multilayer graphene flakes grown along the substrate normal. We measured the transverse photocurrent generated in the film under irradiation with nanosecond laser pulses by depositing two conductive electrodes along the plane of incidence. The measurements were performed by using elliptically polarized fundamental, second-, third-, and fourth-harmonics beams of the Nd:YAG laser. We revealed that the shorter the excitation wavelength, the higher the magnitude of the helicity-dependent transverse photocurrent generated in the film. In particular, at wavelengths of 266 and 355 nm, the photocurrent strongly depends on the degree of the circular polarization of the laser beam while, at the wavelength of 1064 nm, the transverse photocurrent is almost helicity independent.

Interplay of the photon drag and the surface photogalvanic effects in the metal-semiconductor nanocomposite.

Photon drag effect (PDE) and surface photogalvanic effect (SPGE) can be observed in centrosymmetric media and manifest themselves in photocurrents, the magnitude and polarity of which depend on wavevector and polarization of the excitation laser beam. PDE photocurrent originates from the transfer of the photon momentum to a free charge carrier, while SPGE photocurrent is due to diffuse scattering of the photoexcited carriers in the subsurface layer. However, despite the different underlying physical mechanisms, these photocurrents have almost indistinguishable dependencies on the polarization and the angle of incidence of the excitation laser beam. In this paper, we observe for the first time a competition between PDE and SPGE in the film containing metal (Ag-Pd) and semiconductor (PdO) nanocrystallites. We show that, depending on the angle of incidence, polarization azimuth and wavelength of the excitation laser beam, the interplay of the PDE and SPGE leads to the generation of either monopolar or bipolar nanosecond current pulses. The experiments performed allow us to visualize the contributions both these effects and obtain light-to-current conversion efficiency in a wide spectral range. Our experimental findings can be employed to control the magnitude and polarity of the light-induced current by polarization of the excitation laser beam.

Revealing the nanoparticles aspect ratio in the glass-metal nanocomposites irradiated with femtosecond laser.

We studied a femtosecond laser shaping of silver nanoparticles embedded in soda-lime glass. Comparing experimental absorption spectra with the modeling based on Maxwell Garnett approximation modified for spheroidal inclusions, we obtained the mean aspect ratio of the re-shaped silver nanoparticles as a function of the laser fluence. We demonstrated that under our experimental conditions the spherical shape of silver nanoparticles changed to a prolate spheroid with the aspect ratio as high as 3.5 at the laser fluence of 0.6 J/cm2. The developed approach can be employed to control the anisotropy of the glass-metal composites.

Electric field imprinting of sub-micron patterns in glass-metal nanocomposites.

We demonstrate that the dissolution of 10 nm metal nanoparticles localized in the subsurface layer of silicate glass by static electric field can be employed to alter the optical density and surface profile of the glass-metal composite with spatial resolution of 200 nm. The developed technique, which can be referred to as electric field imprinting (EFI), offers an attractive alternative to conventional micro- and nano-pattering techniques.

Femtosecond absorption dynamics in glass-metal nanocomposites.

We report strong optical nonlinearity of glasses embedded with copper and silver nanoparticles. In pump-probe experiments with copper-doped glasses, the observed absorption bleaching with picosecond relaxation time is as high as 22%. Transmission femtosecond measurementsreveal the reverse saturable absorption with nonlinear absorption coefficient of 10(-10)cm/W in both copper- and silver-doped nanocomposites.

Efficient two-photon light amplification by a coherent biexciton wave.

A reversible coupling between photon pair states and a long-lived, highly coherent biexciton wave in CuCl allows efficient phase-sensitive two-photon amplification or attenuation of ultrashort light pulses. We demonstrate a gain of 350 cm(-1) for a pump intensity of 1 MW/cm(2), nearly 2 orders of magnitude higher than that achievable with conventional parametric crystal amplifiers. We develop a theoretical model that describes this new type of parametric converter where the light pump is replaced by a coherent biexciton wave and show that it is well suited for the generation of entangled photons and the squeezing of an optical beam with ultrafast time gating.