R. G. Zonov

Giant optical rectification effect in nanocarbon films

We present observations of the optical rectification effect in the nanocarbon film, which is excited by nanosecond pulses of a Nd:YAG laser in the absence of an external electric field. Effective second order susceptibility of the film material is found to be 10−6 CGSE, which is higher than that of conventional noncentrosymmetric crystals. The measured ratio of the dc voltage to the laser power is 500 and 650 mV/MW at the wavelengths of 1064 and 532 nm, respectively. This makes the nanocarbon materials a promising alternative to conventional semiconductor-based terahertz radiation sources.

Photon-Drag Effect in Single-Walled Carbon Nanotube Films

We observed an interaction of single-walled carbon nanotube films with obliquely incident nanosecond laser radiation in visible and infrared regions generating unipolar voltage pulses replicating the shape of the laser pulses. The photoelectric signal significantly depends on the laser polarization and has maximum value at the laser beam incidence angle of ±65° and at the film thickness of 350 nm. The results are explained in the framework of the photon-drag effect.

Light-induced EMF in silver-palladium film resistors

We have studied the generation of nanosecond emf pulses in silver-palladium film resistors under the action of radiation of a Q-switched laser. The samples were fabricated using the technology of thick film resistors on dielectric substrates, based on fusing a resistive paste that contains palladium, silver oxide, glass, and an organic binder into the substrate at 880 K. The amplitude of detected pulses exhibits linear growth with the power of incident laser radiation, depends on the angle of light incidence (vanishes at the normal incidence) onto the film and the angle of film rotation about the normal to its surface, and changes its sign with that of the incidence angle. The duration of the generated emf pulses is several times that of the incident laser pulses. The signal is not of a thermoelectric nature and can be related to the current generation by means of the surface photogalvanic effect and the photon quasi-momentum transfer to charge carriers during light absorption by the film material.

Quick-Response Film Photodetector of High-Power Laser Radiation Based on the Optical Rectification Effect

The efficiency of conversion of high-power laser radiation to an electric signal based on the optical rectification effect in nanographite films is studied experimentally. The amplitude of the signal is found to significantly depend on the size of the film, as well as on the length and arrangement of measuring electrodes. The maximal sensitivity of the photodetector (above 500 mV/MW at a wavelength of 1064 nm) consisting of the film with electrodes and operating without an external power supply and add-on components is shown to be achieved when the size of the film is comparable to the laser beam diameter. The sensitivity of the photodetector is studied under the condition when a nanosecond beam from a pulsed laser scans the surface of the film in two mutually perpendicular directions. The local sensitivity increases near the free ends of the photodetector. It is shown that the nanographite detector and a similar photodetector made of a polished silicon wafer have radically different parameters.

Effect of the burning temperature on the phase composition, photovoltaic response, and electrical properties of Ag/Pd resistive films

Silver-palladium (Ag/Pd) films were grown by thick-film technology using a resistive paste consisting of Pd, Ag2O, and glass on ceramic substrates at burning temperatures of 878, 1013, and 1113 K. The effect of the burning temperature and Pd content in the initial paste on the phase composition, resistivity, photovoltaic properties of films, free carrier concentration, and mobility was studied. It was found that the films grown at a burning temperature of 878 K have the greatest factor of conversion of the pulsed laser power to the photovoltaic signal, which depends on the direction of the incident radiation wave vector. Using X-ray diffraction, X-ray photoelectron spectroscopy, and thermodynamic modeling, it was shown that the AgPd alloy and PdO oxide are the main components of the Ag/Pd film with photovoltaic properties.

Spectral dependence of circular photocurrent in silver-palladium resistive films

The exposure of silver-palladium (Ag-Pd) resistive films to obliquely incident nanosecond pulsed laser radiation with wavelengths of 1064, 532, 354.7, and 266 nm leads to the appearance of a photo-current dependent on the sign of the circular polarization of incident radiation (circular photocurrent). The photocurrent was determined by measuring pulsed photo-emf in a longitudinal geometry for which the plane of laser-radiation incidence onto the film was parallel to the electrodes. It is established that the response signal changes its sign with that of the angle of incidence, significantly decreases with the laser-radiation frequency, and consists of linear and circular contributions. The ratio of the circular to linear signal components significantly decreases with decreasing radiation wavelength. The obtained results can be used for the creation and development of a device capable of determining the sign of polarization of laser radiation.

Optical rectification effect in nanocarbon films

When a nanocarbon film obtained by plasmachemical deposition is fixed between two parallel electrodes and exposed to the pulsed radiation of a Q-switched neodymium laser, a pulsed electric voltage appears between the electrodes, with the pulse shape repeating the laser pulse envelope. It is shown that the amplitude and polarity of the pulsed voltage strongly depend on the angle of incidence and polarization of laser beam and on the spatial orientation of a carbon film with electrodes relative to the laser beam. The observed phenomenon exhibits all features characteristic of the optical rectification effect. For the optimum spatial orientation of a film, the factor of conversion of the laser pulse power into electric voltage amounted to 500 mV/MW, which is many times greater than the values observed in the case of optical rectification in well-known dielectric nonlinear optical crystals.

Optical rectification effect in nanostructured carbon films

Electrically conducting nanostructured carbon films obtained by chemical vapor deposition and composed of nanodimensional graphite crystals exhibit the effect of optical rectification on exposure to nanosecond pulsed laser radiation. Experiments show that the amplitude and polarity of the pulsed voltage strongly depend on the angle of incidence and polarization of the laser radiation and on the spatial orientation of a carbon film with electrodes relative to the laser beam. Under the optimum conditions corresponding to maximum amplitude of the response signal, the factor of conversion of the laser pulse power into electric voltage was about 500 and 650 mV/MW at a laser wavelength of 1064 and 532 nm, respectively.

Anisotropic Laser-Induced Evaporation of Graphite Films

An experimental investigation of the effect of linearly polarized high-energy pulsed laser light, normally incident on a carbon thin film, is reported. The material under study consists of platelike graphite crystallites with basal crystallographic planes mostly oriented perpendicular to the substrate surface. An increase is revealed in the fraction of the graphite crystallites oriented perpendicular to the polarization plane. Laser light is found to cause significant anisotropy in diffuse scattering by the film surface. Experimental observations are explained by a model of anisotropic evaporation of graphite-like carbon material due to polarization dependence of the absorption and reflection coefficients for a rough surface.

Photon-drag in single-walled carbon nanotube and silver-palladium films: The effect of polarization

Abstract. Polarization influence on the photovoltaic current raised due to the photon-drag effect in the single-walled carbon nanotube (SWNT) films and nanostructured silver-palladium (Ag/Pd) resistive films is examined at the wavelengths of 532 and 1064 nm of nanosecond laser pulses. The SWNT films were synthesized by the aerosol chemical vapor deposition technique. Ag/Pd films, consisting of AgPd alloy and palladium oxide (PdO), were prepared by burning a special paste on a ceramic substrate. The films obtained were characterized by Raman spectroscopy. It is shown that the Ag/Pd films Raman spectra consist of PdO peak that moves from 650  cm−1 to 628  cm−1 as the excitation He-Ne laser power increases. The photocurrent was measured at the oblique incidence of the laser beam on the film in the direction perpendicular to the plane of incidence. It is found that the transverse photocurrent in the SWNT films at circular polarization is absent and does not depend on the direction of the electric field vector rotation (the sign of the circular polarization) of the incident irradiation. The photocurrent in the Ag/Pd films at circular polarized irradiation is significant and depends on the circular polarization sign. The results obtained demonstrate the potential applications of the Ag/Pd resistive films as a sensor of the circular polarization sign of the incident light pulse in a wide wavelength range.