Carbon-nanotube-based saturable absorbers for near infrared solid state lasers

We demonstrate the passive mode-locking of a diode-pumped Nd⁺³:YAG (central wavelength: 1.32 μm; pulse duration: 50 ps; output energy: up to 70 μJ) laser using a polymer film containing single-wall carbon nanotubes. The mode-locking regime is stable at a pump repetition rate of up to 1 kHz. We also investigate the temporal evolution of the light-induced absorption change of the polymer film containing carbon nanotubes in the spectral range of 1.3–1.5 μm by femtosecond time-resolved pump-probe measurements. The measurements reveal that light-induced transmission exhibits fast and slow components that last 280 fs and more than 10 ps, respectively. The third-order susceptibility of the polymer film containing single wall carbon nanotubes is as high as 10⁻¹¹ esu.     

Generation of a Polarization Sensitive Photocurrent in a CuSe/Se Nanocomposite Thin Film

JETP Letters - CuSe-based structures are widely used in various fields of photonics and optoelectronics. It has been shown for the first time that a photocurrent depending on the direction of the...     

The infrared absorption spectra of finely divided manganese borate

Journal of Applied Spectroscopy -     

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.     

Giant optical activity in quasi-two-dimensional planar nanostructures

We examine the spectral dependence in the visible frequency range of the polarization rotation of two-dimensional gratings consisting of chiral gold nanostructures with subwavelength features. The gratings, which do not diffract, are shown to exhibit giant specific rotation (approximately 10(4) degrees/mm) of polarization in direct transmission at normal incidence. The rotation is the same for light incident on the front and back sides of the sample. Such reciprocity indicates three dimensionality of the structure arising from the asymmetry of light-plasmon coupling at the air-metal and substrate-metal interfaces. The structures thus enable polarization control with quasi-two-dimensional planar objects. However, in contradiction with recently suggested interpretation of experiments on larger scale but otherwise similar structures, the observed polarization phenomena violate neither reciprocity nor time-reversal symmetry.     

Synthesis and Study of Acid-Basic Properties of Ti(IV) and Zr(IV) Phosphates Immobylized in the Matrix of Clinoptilolite

Abstract

By combination of the ionexchange and ionic-molecular layering methods [1], the synthesis of natural zeolite derivatives (clinoptilolite) containing in its composition nano-size fragments of Ti(IV) and Zr(IV) phosphates was performed. It was determined by the X-Ray method, that the phosphates of Ti(IV) and Zr(IV) replicate crystal lattice of zeolite, manifesting in enhancing the line's intensity on X-Ray patterns. The Brensted's and Lewis's spectra of acidic centers distributions were obtained by Hammett's indicator spectrophotometric method [2] in the interval of pK, values from -4.4 to 14.2, which have shown that P(V) of the derivatives is represented mainly by HPO₄- and H₂PO₄-groups, with predomination of these latter. It is shown that the force of Brensted's acidic centers, influenced by H₂PO₄-groups. remains at the level of H₂PO_(aq)-anion, and the force of the centers due to HPO₄-groups shifts into alkaline region, about 0,5 unit of pK. The strong acidic Lewis's centers were detected at the levels of pK, from 0 to -4.0. The spectra of Ti(IV) and Zr(IV) phosphates is presented in (1) and (2) respectively. A set of the acquired results makes possible a suggestion about using P(V)-containing derivatives in processes which are catalyzed both with Brensted's and Lewis's centers participation.     

Circular photocurrent in Ag/Pd resistive films upon excitation by femtosecond laser pulses

This paper presents the results of the experimental investigation of the generation of nanosecond photocurrent pulses in silver–palladium (Ag/Pd) resistive films under excitation by laser pulses with a duration of 120 fs at a wavelength of 795 nm. The photocurrent was detected in the direction perpendicular to the plane of incidence of the laser beam on the film. The 20-μm-thick films under investigation were a porous polycrystalline material consisting predominantly of nanocrystallites of the palladium oxide PdO and the Ag–Pd solid solution. The direction of the photocurrent observed in the films depends on the sign of the circular polarization of the incident radiation. It was found that the observed photocurrent depends on the angle of incidence in accordance with the odd law and consists of the circular and linear contributions, which are dependent on and independent of the sign of the circular polarization, respectively. It was shown that the circular photocurrent is significantly higher than the linear photocurrent. It was established that, for both the circular and linear polarizations, the photocurrent is directly proportional to the power of the excitation radiation. For the linearly polarized laser radiation, the photocurrent depends on the polarization angle in accordance with the odd law. The regularities revealed are consistent with the mechanism of the generation of transverse photocurrent with the photon drag effect.     

Femtosecond optical nonlinearity of metallic indium across the solid liquid transition

A very strong (~10(-8) esu) femtosecond cubic nonlinearity in metallic indium that increased sharply in magnitude as the temperature approached the melting point was observed.