Andrey Konyukhov

Nonlinear optical response and heating of chalcogenide glasses upon irradiation by the ultrashort laser pulses

Abstract. Large third-order nonlinearity and transparency in the mid-infrared region are the basic motivations for prospective applications of chalcogenide glasses in nonlinear photonics and laser technologies. We present the state-of-the-art and our recent results of measurement and evaluation of the nonlinear optical constants, plasma dynamics, and thermal regimes upon irradiation of As-S-Se samples using 40-fs pulses at 790-nm wavelength.

Soliton fission management by dispersion oscillating fiber.

We report the experimental observation of the fission of picosecond solitons in a fiber with sine-wave variation of the core diameter along the longitudinal direction of propagation. The experimental pulse dynamics is reproduced by numerical simulations. The fission of high-intensity solitons caused by both the variation of the fiber dispersion and stimulated Raman scattering is demonstrated. The number of output pulses and their frequencies can be managed by periodical modulation of the fiber dispersion even under the strong effect of the Raman scattering.

Generation of Picosecond Pulse Train With Alternate Carrier Frequencies Using Dispersion Oscillating Fiber

The train of picosecond pulse pairs with alternate carrier frequencies was observed when the train of picosecond pulses was launched into the fiber with sine-wave variation of the core diameter. The effect occurs due to dispersion oscillations along the fiber length, which result in splitting high-order solitons. In the experiments, the splitting of second-order soliton was observed. The separation between carrier frequencies of output pulses depends on the phase of periodical oscillation of the fiber dispersion. Numerical simulations were made and show good agreement with the experimental results.

The optical properties of chalcogenide glasses: From measurement to electromagnetic simulation tools

Chalcogenide glasses are promising candidate materials for a wide range of photonics applications. The design and realisation of optical components based on these materials requires detailed information on their optical properties, frequently over a range of wavelengths. In this paper we review experimental refractive index data for three chalcogenide glass compositions, and discuss how various numerical fits to the data prove useful within electromagnetic simulation tools.

Chalcogenide glasses as a medium for controlling ultrashort IR pulses: Part I

Chalcogenide glasses are ideal materials for developing fiber lasers and amplifiers, remote sensors, high-speed switches, and other devices that operate in the IR range of 1–10 μm. The nonlinear refractive index of chalcogenide glasses may exceed that of quartz glass by a factor of 100–1200 or even more. The data on the dispersion properties of some chalcogenide glass compositions in the IR range are presented. The possibility of forming waveguide structures with specified dispersion properties (in particular with a fixed wavelength at which the group velocity dispersion is zero) from these glasses is numerically investigated. It is shown by the example of completely glassy periodic waveguide structures with planar geometry that the use of photonic band gap modes makes it possible the change the position of zero dispersion in a wide wavelength range. In the calculations the contrast of waveguide structures was varied using parameters of glasses of different composition.

Femtosecond Laser Processing as an Advantageous 3-D Technology for the Fabrication of Highly Nonlinear Chip-Scale Photonic Devices

The properties of highly nonlinear glasses for photonic devices and the advantages of processing these materials using femtosecond laser pulses are discussed in a brief review. A novel approach is proposed for the optimization of the modification process that takes into account the dispersion of the nonlinear coefficients of refraction and absorption. Numerical modeling of the pulse energy deposition into a sample of chalcogenide glass shows that the shapes and dimensions of the modified regions depend on the nonlinear coefficients.

Inelastic collision and fusion of optical solitons in dispersion oscillating fiber

We show through numerical simulations that dispersion oscillating fibers can be used for the fusion of fundamental solitons into high-intensity pulse. Three particular cases are considered: fusion of two co-propagating fundamental solitons, fusion of three co-propagating fundamental solitons and merge of two colliding solitons into breather bound state. Generation of high-intensity pulse is associated with the formation of distinct high-amplitude soliton.

Dynamics of Optical Pulses Propagating in Fibers with Variable Dispersion

The book chapter describes recent progress in the management of laser pulses by means of optical fibers with smoothly variable dispersion. Nonlinear Schrodinger equation based numerical simulations give powerful mathematics for optimizing of fiber dispersion for given task. In the book chapter we use numerical simulations to describe and analyse soliton and pulse dynamics in three kind of fibers with variable dispersion: i) dispersion oscillating fiber; ii) negative dispersion decreasing fiber. Optical pulse compression techniques are important for the generation of subpicosecond and femtosecond optical pulses. Dispersion decreasing fibers are useful for high quality, pedestal-free optical pulse compression. The classical soliton concept was developed for nonlinear and dispersive systems that have been autonomous; namely, propagation distance has only played the role of the independent variable and has not appeared explicitly in the nonlinear Schrodinger equation (NLSE) (Ablowitz et al., 1981; Agraval, 2001; Akhmanov et al., 1991). Under condition of harmonical dispersion and nonlinearity nonautonomous solitons interact elastically and generally move with varying amplitudes, speeds, and spectra (Serkin et al., 2007). High-order soliton propagating in a fiber with fixed dispersion and nonlinearity is reshaped periodically after propagation distance equal to the soliton period 0.16π|β2| −1T2 FWHM (Agraval, 2001; Akhmanov et al., 1991), where β2 is second order dispersion coefficient, TFWHM is the full-width at half-maximum (FWHM) pulse duration. In a fiber with periodically modulated core diameter, the dispersion oscillates periodically along the fiber length. When the oscillation period approaches the soliton period, the soliton splits into few pulses. Simulations show that second-order soliton splits into two pulses, which carrier frequencies are located symmetrically with respect to the initial pulse frequency (Bauer et al., 1995; Hasegava et al., 1991). A sequence of second-order solitons transmitted through dispersion oscillating fiber (DOF) will produce a pulse train with alternate carrier frequency. Nonlinear pulse propagation in periodic transmission lines with multisegmented fibers was investigated extensively. The dispersionmanaged soliton (Malomed, 2006; Smith et al., 1996), split-step soliton (Driben et al., 2000), and stationary rescaled pulse (Inoue et al., 2005) have been discovered. The studies were focused mainly on the stability of solitons. 13

Thermal diffusion in chalcogenide glass irradiated by a train of femtosecond laser pulses

Local heating of chalcogenide glass sample by a train of high-intensity femtosecond laser pulses depending on non-linear and thermal properties of the glass is studied in a theoretical model and in experiments on photo-induced glass modification.

Non-linear chalcogenide glasses and technologies for the development of ultra-fast chip-scale optical devices

Chalcogenide glasses are novel highly non-linear materials for photonics. Modification of optical glasses by high-intensity femtosecond pulses is a novel fast developing technology based on non-linear effects. In this paper, the advantages of using the method of femtosecond modifications for the fabrication of highly non-linear 3D photonic structures in bulk chalcogenide glasses are overviewed. Design and modelling of chip-scale highly non-linear structures for all-optical signal processing are discussed.