A. V. Khokhlov

Processing large blanks of anisotropic single-mode lightguides with elliptical cladding

This paper discusses the possibility of increasing the diameter of blanks for drawing anisotropic single-mode quartz fiber lightguides by fusing the preblank with a tube, the gap between which, is filled with quartz grits. It is shown that the polarization stability of such lightguides increases as the diameter of the light-fiber increases.

Cross-phase-modulation-controlled spectral transformations of ultrashort pulses in photonic-crystal fibres

Cross-phase modulation provides an efficient means to control spectral transformations of femtosecond laser pulses in photonic-crystal fibres with a specially designed dispersion profile. Femtosecond pulses of fundamental radiation of a Cr?:?forsterite laser are shown to induce an asymmetric spectral broadening of the anti-Stokes signal generated in a photonic-crystal fibre by the pulses of second-harmonic radiation of the same laser. Cross-phase-modulation-induced phase shifts control the efficiency of anti-Stokes generation in a photonic-crystal fibre, suggesting a method of switching the anti-Stokes signal on and off by varying the intensity of the control laser pulse.

How the pitch of a holey optical fiber affects its lightguide properties

This paper discusses how scaling (increasing) the transverse dimensions of a holey optical quartz fiber affects its lightguide properties. It is established that a limiting pitch exists, and that, when this is exceeded, the lightguide properties of a holey optical fiber are weakened.

7- and 19-Element-Core Bend-Resistant Microstructured Fibers

The conception of main role of the lattice pitch value in bend-induced short-wavelength optical losses is presented. There is shown that creation of the fiber core by substitution with seven or nineteen central elements leads to the essential expansion of spectral working range in microstructured large core optical fibers.

Microstructured lightguides with a quartz core for obtaining a spectral supercontinuum in the femtosecond range

Quartz fiber lightguides with a core (diameter 1-5 µm) surrounded by a hexagonal system of holes and having high numerical aperture have been developed and implemented for the spectral conversion of ultrashort laser pulses into broad-band radiation (a supercontinuum). It is shown that the spectral range from 400 to 1000 nm can be covered when the radiation of a Ti-sapphire laser is used.

Anisotropic single-mode lightguide with an elliptical germanium silicate core and depressed cladding

The properties of anisotropic single-mode fiber lightguides with an elliptical highly doped germanium core and elliptical fluorine-doped cladding have been investigated. When the difference of the refractive indices of the core and the cladding equals 0.033 and the ratio of the axes of the core is about 2, the birefringence is about 0.00037. The fabricated lightguides, despite the differential optical losses of the orthogonal modes to radiation leakage, are distinguished by a low level of polarization stability. The degree to which the radiation remains polarized in them (≈0.003  m−1) is two orders of magnitude worse than in commercially produced lightguides. This is probably caused by local microstrain of the low-viscosity glass of the core.

Pulse-shaping control of spectral transformations of ultrashort pulses in photonic-crystal fibers

We experimentally demonstrate that the initial pulse width and spectral phase of ultrashort laser pulses may significantly influence the solition dynamics of such pulses in a photonic-crystal fiber. These findings suggest new solutions for the transmission, shaping, stretching, amplification, and spectral transformation of ultrashort pulses in all-fiber laser technologies.

Bimodal character of the strength statistics of lightguides made from quartz glass

This paper shows that the bimodal character of the strength statistics of quartz lightguides is determined by the oxidation-reduction conditions of their fabrication and is caused by the physicochemical state of microimpurities. Impurities that are soluble and insoluble in glass determine, respectively, the high-strength and low-strength states of glass fiber.

Holey lightguides with a quartz core for nonlinear-optical conversion of laser-emission pulses

Holey lightguides based on quartz glass with a solid core 1-5 µm in diameter, surrounded by a hexagonal system of openings with a number of cycles from one to four, have been developed for converting ultrashort laser pulses into a spectral supercontinuum. It has been shown that the wavelength range from 400 to 1300 nm can be overlapped when the radiation of a Ti-sapphire laser is used.

Cross-phase-modulation-induced instabilities and frequency shifts of ultrashort laser pulses in a photonic-crystal fiber

This work shows that a second input laser field spectrally separated from the first laser pulse can serve as a convenient control knob for spectral transformations of ultrashort laser pulses in photonic crystal fibers (PCFs). This study also explores the potential of cross-phase modulation (XPM) and XPM-induced instability as physical mechanisms behind this control. Results show that the capability of PCFs to radically enhance nonlinear-optical processes, suggests the ways to extend XPM-based short-pulse control techniques to lower energy pulses and substantially shorter fibers, allowing, in particular, efficient frequency tuning of femtosecond probe pulses within a broad spectral range by using a low-energy pump field, launched into a PCF with a variable delay time. Group delay between the pump and probe pulses leads to an XPM-induced frequency shift of the probe field, allowing its frequency to be smoothly tuned by varying the delay time between the pulses at the input of the fiber.