K. V. Dukel’skii

Nanostructure of optical fluoride ceramics

The real structure of samples of optical fluoride ceramics is studied by atomic force, scanning electron, and transmission electron microscopy. It is shown that the optical ceramic samples based on CaF2 have a lamellar structure, and the distance between lamellae is 25–50 nm. Most likely, lamellae have a twin nature. For BaF2 ceramic, lamellae are not typical, and they are concentrated near grain boundaries.

The mode structure and spectral properties of supercontinuum emission from microstructure fibers

The mode structure and spectral properties of supercontinuum emission generated by femtosecond pulses of Ti: sapphire laser radiation in microstructure fibers are studied. The long-wavelength (720–900 nm) and visible (400–600 nm) parts of supercontinuum emission are shown to be spatially separated in microstructure-fiber modes, which can be isolated with an appropriate spectral filtering. The spatial modes thus isolated in spectrally sliced supercontinuum emission possess a spatial quality sufficient for further efficient frequency conversion. The possibility of achieving a high spectral quality of supercontinuum emission is also demonstrated. We explore the ways to control the spectrum of supercontinuum emission by matching parameters of the pump pulse with the parameters of a microstructure fiber and by tuning the initial chirp of the pump pulse. The results of our studies show that supercontinua produced in microstructure fibers offer new approaches to designing a new generation of optical parametric amplifiers and broadband radiation sources for spectroscopic, metrological, and biomedical applications.

Additive Coloring of CaF 2 Optical Ceramic

The specificity of additive coloring of CaF2 optical ceramic (formation of color centers in it and photothermochemical transformation of these centers in colored ceramic samples) has been considered. Under the same coloring conditions, this process occurs more slowly in ceramics rather than in crystals; at the same time, the limiting concentration of color centers that can be introduced into ceramics is much higher. The photothermochemical transformations of color centers in crystals and ceramics, which occur under illumination at different wavelengths and upon heating, have been studied. The specific features of introduction of color centers into ceramic and their transformation under illumination and heating are likely to be related to the mass twinning of ceramic grains.

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.