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We present a thulium-doped fiber laser mode-locked by a carboxymetylcellulose high-optical quality film with dispersed single-walled carbon nanotubes. Laser system based on the nonlinear amplifying loop mirror generates the shortest pulses earlier obtained in SWCNT mode-locked thulium-doped fiber lasers with a duration of 450 fs and 18 mW maximum average power at 1870 nm.

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We report on the stable picosecond and femtosecond pulse generation from the bidirectional erbium-doped all-fiber ring laser hybridly mode-locked with a coaction of a single-walled carbon nanotube-based saturable absorber and nonlinear polarization evolution that was introduced through the insertion of the short-segment polarizing fiber. Depending on the total intracavity dispersion value, the laser emits conservative solitons, transform-limited Gaussian pulses, or highly chirped stretched pulses with almost 20 nm wide parabolic spectrum in both clockwise (CW) and counterclockwise (CCW) directions of the ring. Owing to the polarizing action in the cavity, we have demonstrated for the first time, to the best of our knowledge, an efficient tuning of soliton pulse characteristics for both CW and CCW channels via an appropriate polarization control. We believe that the bidirectional laser presented may be highly promising for gyroscopic and other dual-channel applications.

We demonstrate an erbium doped fiber ring laser mode-locked with a carboxymetylcellulose high-optical quality film with dispersed single-walled carbon nanotubes (SWCNT). The laser with large normal net cavity dispersion generates near bandwidth-limited picosecond inverse modified soliton pulses at 1.56 µm.

Structural modifications of tetrahedral amorphous carbon (ta-C) films, caused by single-pulse laser irradiation, were investigated. Graphitization of the films, content and size of sp 2 carbon clusters were analyzed by means of Raman spectroscopy. It has been shown that pulse duration, as well as laser fluence and wavelength of irradiation, strongly influence the processes of graphitization and ablation of the ta-C films. In particular, heating of the films by the laser beam leads to formation of sp 2 carbon clusters and their enlargement up to the size of several nanometers. Material transformation to graphitized fraction is much more efficient in case of ns pulse duration. In case of fs pulse duration, such factors as multiphoton absorption and evaporation of over-heated material from the surface at high laser fluence, shorter time of irradiation, and heat transfer to the inner layers of the film lead to relatively weak graphitization characterized by the maximum size of the sp 2 carbon clusters of about 1 nm.

Laser surface micropatterning (texturing) of hard materials and coatings is an effective technique to improve tribological systems. In the paper, we have investigated the laser-induced surface modifications and micropatterning of diamond-like nanocomposite (DLN) films (a-C:H,Si:O) using IR and visible femtosecond (fs) lasers, focusing on the improvement of frictional properties of laser-patterned films on the micro and macroscale. The IR and visible fs-lasers, operating at λ = 1030 nm and λ = 515 nm wavelengths (pulse duration 320 fs and pulse repetition rate 101 kHz), are used to fabricate different patterns for subsequent friction tests. The IR fs-laser is applied to produce hill-like micropatterns under conditions of surface graphitization and incipient ablation, and the visible fs-laser is used for making microgroove patterns in DLN films under ablation conditions. Regimes of irradiation with low-energy IR laser pulses are chosen to produce graphitized micropatterns. For these regimes, results of numerical calculations of the temperature and graphitized layer growth are presented to show good correlation with surface relief modifications, and the features of fs-laser graphitization are discussed based on Raman spectroscopy analysis. Using lateral force microscopy, the role of surface modifications (graphitization, nanostructuring) in the improved microfriction properties is investigated. New data of the influence of capillary forces on friction forces, which strongly changes the microscale friction behaviour, are presented for a wide range of loads (from nN to μN) applied to Si tips. In macroscopic ball-on-disk tests, a pair-dependent friction behaviour of laser-patterned films is observed. The first experimental data of the improved friction properties of laser-micropatterned DLN films under boundary lubricated sliding conditions are presented. The obtained results show the DLN films as an interesting coating material suitable for laser patterning applications in tribology.

The temperature-induced changes in Raman spectra of two BN-based materials: a hexagonal boron nitride and soot with single-wall BN nanotubes, have been measured in temperature range 77 -600 K in course of heating in the oven/cryostat cell. A nonlinear temperature dependence of the tangential Raman mode position (being at 1366 cm -1 at room temperature) has been observed for both materials. In the temperature range 350 -600 K a linear approximation of the tangential Raman mode shifting was applicable. The measured rates were -0.014 cm -1 /K (for h-BN) and -0.027 cm -1 /K (for the nanotube-containing sample). The effects of the oven and laser heating have been compared. Under the laser heating with the same power density the nanotube-containing soot demonstrated much bigger shifts (up to 30 cm -1 ) than h-BN. The data obtained are useful for in-situ diagnostics of different BN-based phases in course of synthesis.