Sergey A Magnitskiy

Observation and theory of X-ray mirages

The advent of X-ray lasers allowed the realization of compact coherent soft X-ray sources, thus opening the way to a wide range of applications. Here we report the observation of unexpected concentric rings in the far-field beam profile at the output of a two-stage plasma-based X-ray laser, which can be considered as the first manifestation of a mirage phenomenon in X-rays. We have developed a method of solving the Maxwell–Bloch equations for this problem, and find that the experimentally observed phenomenon is due to the emergence of X-ray mirages in the plasma amplifier, appearing as phase-matched coherent virtual point sources. The obtained results bring a new insight into the physical nature of amplification of X-ray radiation in laser-induced plasma amplifiers and open additional opportunities for X-ray plasma diagnostics and extreme ultraviolet lithography.

Characterization of polarization-angular spectrum of type-I SPDC in BBO crystal

We analyze the state of type-I SPDC polarization in nonlinear uniaxial crystals using a coordinate system connected with a pump beam. The entanglement loss due to the Migdall effect is examined. The analytical expressions for polarization components of the signal and idler waves for the frequency-degenerate regime are obtained. The numerical results for BBO crystal are also adduced.

Optical second harmonic generation from chiral nanostructures

Recent technological achievements provide unique possibilities for the composition of arrays of nanostructures with desired properties, nowadays referred to as metamaterials, that are perspective for various applications. A special place here belongs to chiral nanostructures that could compete with the natural materials both in efficiency and size of functional elements. For the case of metamaterials, optical activity originates from a special shape of the elements and their arrangement within an array. This research field has been actively developing over the last years and significant values of chirality effects were observed in the linear-optical response of metallic nanostructures [1]. Furthermore, chirality effects are more pronounced in the nonlinear-optical response of such structures [2, 3], the latter being governed to a great extent by the local field distribution inside the metal nanostructures. In this talk we will focus mostly on the recent results on the linear and nonlinear optical effects in planar arrays of chiral nanostructures with the shape of a flat spiral (G-shaped nanostructures).

Generation of phase-matched coherent point source in plasma media by propagated X-ray laser seeded beam

There is a significant interest in developing the coherent table-top X-ray lasers. Advent of plasma-based transient collisional excitation x-ray laser and particular, injection of coherent seeded beam, especially high-order harmonics, has tremendously improved the spatial coherence of such lasers, what allowed them to be the same widely used as synchrotron sources. Here we report experimental founding of unknown interference structure in a spatial profile of the output beam of the two-stage plasma X-ray laser. That allowed us experimental and theoretical discovering a new phenomenon consisted in a generation of phase-matched coherent point source in a laser plasma media by propagated X-ray laser seeded beam. This phenomenon could extend the applications of such x-ray lasers. For explanation of the observed phenomenon a new method of solving the standard system of Maxwell-Bloch equations has been developed. It was found that the interference pattern in the output laser beam was formed due to an emergence of phase-matched coherent virtual point source in the XRL amplifier and could be treated as the first observation of mirage phenomenon, analogous to the optical mirage, but in X-rays. The obtained results bring new comprehension into the physical nature of amplification of X-ray radiation in laser-induced plasma amplifiers and opening new opportunities for X-ray interferometry, holography and other applications, which requiring multiple rigidly phased sources of coherent radiation.

Source of single correlated photons at 1.06-mkm wavelength

We describe the source of correlated photon pairs at 1.06 micron wavelength based on spontaneous parametric down-conversion. The events corresponding to the photons in the pair are correlated with time accuracy better than 1 ns. Apart from wavelength, another distinctive feature of our set-up is that the “signal” photons can be delayed by passing the additional distance (up to 10 m) in the air.

Orientation of the AD-1 azo-dye molecules in solid nanostructured films upon the two-photon excitation

The orientation of the AD-1 azo-dye molecules in solid nanostructured films is studied upon the nonlinear excitation using femtosecond laser pulses. A significant dichroism resulting from the irradiation is due to the two-photon absorption. The optical anisotropy induced by the two-photon absorption is proven to be related only to the reorientation of the azo-dye molecules and is not caused by alternative effects (e.g., photobleaching).

Near-field 3D mapping of spiral light structures formed by a polymer nanocylinder

It is demonstrated that polymer nanocylinders can form spiral light structures. Spiral distributions of light intensity are observed at distances of 230–1100 nm above the nanocylinder with a diameter of 700 nm and a height of 1100 nm. The optical spirals are measured using a scanning near-field optical microscope that performs 3D scanning over planes when the nanocylinder is illuminated from the bottom with linearly polarized CW He-Ne-laser radiation at a wavelength of 632.8 nm. It is shown that the topology of the optical spirals significantly depends on the incident polarization.

Reflection Second-Harmonic Microscopy of Porous Silicon Structures

Scanning optical microscopy in reflection is used to quantity estimate effectiveness of second harmonic generation in porous silicon performed at various etching current density. We observe linear dependence of second harmonic signal on silicon porosity.