S K Vartapetov

Saturable absorption of film composites with single-walled carbon nanotubes and graphene

Saturable absorption of polymer film composites with single-walled carbon nanotubes (SWNTs) and multilayer graphene (GR) were studied by Z- and P-scan methods with femtosecond probing pulses at a wavelength of 1.06 μm. As a matrix for the composite film, a polymer carboxymethylcellulose (CMC) was used. For these composites, the dependence of transmittance on peak intensity of a probe pulse was shown. The values of saturation intensities for the GR-CMC and SWNT-CMC composites were determined by the different methods. The intensities at which optical damage of the composites occurs were estimated.

Femtosecond laser fabrication of linear graphitized microstructures in a bulk of polycarbonate samples

We have fabricated high aspect ratio straight and curved graphitized lines inside of polycarbonate samples by using a femtosecond laser. Use of a spherical lens with high NA to focusing femtosecond pulse in the bulk of material leads to self-diffraction of laser beam and formation a filamentary structure. We fabricated two kinds of graphitized lines. The first type is a straight line extended in the direction of the laser beam. This type of lines was created by femtosecond laser scanning without pulse overlapping. The second type of graphitized lines is curved lines, which was created by scanning with a significant overlapping of focal spot. We determined conditions of the formation of straight graphitized lines by one femtosecond pulse with diameter about 2 pm and length greater than 1 mm in polycarbonate samples. Mechanism of formation and potential applications of these structures are also discussed.

Techniques of surface optical breakdown prevention for low-depths femtosecond waveguides writing

We demonstrated technique of direct femtosecond waveguide writing at record low depth (2-15 μm) under surface of lithium niobate, that play a key role in design of electrooptical modulators with low operating voltage. To prevent optical breakdown of crystal surface we used high numerical aperture objectives for focusing of light and non-thermal regime of inscription in contrast to widespread femtosecond writing technique at depths of tens micrometers or higher. Surface optical breakdown threshold was measured for both x- and z- cut crystals. Inscribed waveguides were examined for intrinsic microstructure. It also reported sharp narrowing of operating pulses energy range with writing depth under the surface of crystal, that should be taken in account when near-surface waveguides design. Novelty of the results consists in reduction of inscription depth under the surface of crystals that broadens applications of direct femtosecond writing technique to full formation of near-surface waveguides and postproduction precise geometry correction of near-surfaces optical integrated circuits produced with proton-exchanged technique.

Managing of spatial characteristics of internal modifications by means of optical delay in cases of femtosecond micromachining of materials

Presents the results of direct managing of spatial characteristics of the modifications in the case of focusing of femtosecond laser pulses in a bulk of material. Managing performed by inserting optical delay into different parts of the focused beam.

Study of the formation of a microrelief on ZnSe- and CdSe-crystal surfaces ablated by excimer KrF-laser radiaton

One-dimensional gratings with a period of are formed on the surfaces of CdSe and ZnSe crystals ablated by two interfering radiation beams of a nanosecond excimer KrF laser. Investigated are the dependences of the shape and depth of gratings on the energy density under irradiation by a single pulse, and on the number of pulses at a given energy density. The maximum grating depth is estimated as of the period. By forming a one-dimensional grating with a period of and a depth of on the CdSe-crystal surface, this surface becomes antireflective at a wavelength of . The surface reflectivity is reduced by 88 %. A possibility of forming two-dimensional gratings having periods of 1 and is demonstrated.

Picosecond Laser System 193 nm Based On Solid State Nd:YAG Laser, Parametric Oscillator And ArF Amplifier.

Realized method of producing high-power picosecond UV pulses at a wavelength of 193 nm. Nd: YAG laser is used, followed by radiation and nonlinear transformations in the excimer gain medium to an energy of 10 mJ, a wavelength of 193 nm.

Light driven self-ordering in fused quartz

Theoretical and experimental investigation of self-ordering in a fused quartz under strong light pumping is presented. It is shown that uniform radiation drives a self-organization process in a random medium and macroscopic spatially ordered structure is formed.

Excimer laser micromachining

Wavelength, pulse energy, repetition rate of excimer lasers as well as beam profile and beam delivery system are highly important parameters for precision machining. In this paper we report features of our excimer lasers and excimer laser systems that have been designed for micromachining. The examples of treatment of different materials are presented. In particular, we provide some new results of microstructuring of the surface of fused silica and also formation of up to 10 mm long microchannels with extremely high aspect ratio. We discovered some liquid forming under certain circumstances due to drilling of microchannels in PMMA. This liquid remains unchanged in the microchannels after the treatment.

Photosensitivity and induced losses in phosphosilicate fibers exposed to 157 and 193 nm irradiation

Photosensitivity and induced losses in phosphosilicate fibers depend on irradiation wavelength. The best induced index/loss relation has been obtained for H2-loaded samples at 157 nm irradiation. Pre-exposure procedure failed to decrease the induced losses.

High photosensitivity of Al2O3-doped fibers to 193 nm and 157 nm excimer laser irradiation

Significant photosensitivity of aluminosilicate fibers (with and without Er codoping) was observed. Effect of photosensitization was demonstrated for the first time for such fibers. Potential to write gratings directly in Er-doped aluminosilicate fibers was demonstrated.