Mikhail N. Libenson

Surface electromagnetic waves in optics

The basic concepts of surface electromagnetic waves (SEWs) in the optical band, the unique features of their excitation by light at the boundary of condensed media, and the participation of SEWs in the formation of periodic structures and other photophysical processes that occur on surfaces due to the influence of high-intensity laser radiation are presented. The use of middle infrared SEW for measuring optical characteristics of materials is considered. A method, developed by the authors, for measuring the real part of the SEW wave vector to obtain metal plasma frequency directly, is presented.

Laser heating of near-field tips

Abstract The problem of heating of a near-field probe by laser radiation passing through it is considered. The stationary distribution of temperature along the probe and its dependence on geometrical parameters of the probe and on distribution of the absorbed light power are found. The threshold light power causing melting of the probe is estimated.

Surface polaritons propagation along micropipettes

Abstract The choice of the type of micropipette that can provide good field localization as well as energy efficiency is the problem of current interest. Up till now, exact analysis of cylindrical modes has been carried out only for waveguides with dielectric cores. In this paper the characteristics of the metal core cylindrical modes are investigated theoretically in comparison with the metal cladding modes at the core radius tending to zero. It is shown that the metal core can be promising for improving the micropipette energy efficiency because of unique localization properties of the cylindrical surface polaritons (CSP) propagation along the metal core.

Surface periodic structures under the optical damage of transparent dielectrics

Experimental studies of the laser elements radiation strength show that optical damage of transparent dielectrics may be accompanied by the formation of surface periodic structures (SPS). SPS with ripples oriented normally to the strength vector of the incident electric field were found on the output surface of a dielectric plate (alkali- halide crystal) under focusing near or middle IR laser radiations of a microsecond duration. This relief was assumed to arise from heating caused by interference between the incident light and the wave scattered from the surface defects on the assumption that scattered wave represents a rapidly decreasing field of the Coulomb type. More correct SPS model developed by V. S. Makin proposes participation of surface electromagnetic waves (SEW). As known, optical damage is accompanied by the development of plasma flash. When emission of electronics from solid surface is strong, the plasma dielectric constant runs out to be negative with its modulus exceeding the dielectric constant of the transparent medium. This causes the generation conditions for SEW to be fulfield on the dielectric-plasma boundary, which results in interference between the incident light and SEW, thus leading to formation of SPS. The model explains reasonably well, why these SPS can be observed only on the output surface when developing plasma produces no screening effect on the surface. For CO2 laser irradiation, the necessary electronic concentration is high but reasonable value and amounts about 1019 cm-. However, SPS formed by the short-wavelengths radiation cannot find correct explanation in the framework of this model, since electronic concentration at the wavelengths (lambda) equals micrometers should be no less than 1021 cm-3 in this case.

Electrodynamic instability as a reason for bulk and surface optical damage of transparent media and thin films

Electromagnetic field instability in nonabsorbing dielectric nonhomogeneity is considered to be one of possible mechanisms of field localization and abrupt amplitude increasing in transparent dielectric materials. Instability threshold estimates and some parametric dependences of the threshold amplitude are obtained making use of model of field instability in dielectric sphere. It is discussed using of the model for analysis of optical breakdown processes in transparent media.

Laser heat-up of near-field probe tip

The work includes theoretical analysis of heat-up of an optical near- field probe with laser radiation passing through it. Stationary solution is found regarding the probe heating due to partial absorption of the radiation by the metal film and linear heat exchange between the probe and its environment. Temperature space distribution down the tapered part of the probe is found. The threshold power of continuous radiation leading to melting of the probe is estimated.

Laser-pulse microstructuring of a silicon surface*

Laser microstructuring of a silicon surface usually results from the development of instabilities and the effects of self-organization. This paper shows that this is a multistage process, consisting of successive rapid transitions of the system from some quasi-stationary states into others. The following classification of the observed changes is proposed:

Nonlinear self-depolarization effect of high-intensity tightly focused laser beams in transparent isotropic dielectric

There are presented results of theoretical investigation of nonlinear self-depolarization effect resulting in variation of space distribution of polarization-ellipse parameters of monochromatic high-intensity focused laser beam. Both qualitative consideration of symmetry properties and numerical calculations for Gaussian beams of low order (TE00, TE01, TE10 and TE11) show that linear and circular initial polarizations change and turn into elliptic polarization with inhomogeneous distribution of polarization-ellipse parameters in focal area. Bearing in mind obtained results, we discuss specific symmetry structure of self-depolarization effect allowing experimental checking of described phenomenon. There are analyzed and estimated other contributions to depolarization effect resulting from low-intensity diffraction. Obtained results are generalized for the case of laser pulses and other types of nonlinear optical response of isotropic dielectric.

Propagation of high-power tightly focused laser beams and self-depolarization effect

There are presented results of theoretical investigation of self- depolarization effect in transparent isotropic materials resulting in variation of initial space distribution of polarization-ellipse parameters of focused high-power laser beam. Qualitative results are obtained within non-paraxial approximation while detailed calculations are done within paraxial approximation. In particular, both linear and circular initial polarizations are shown to change and turn into elliptic polarization with inhomogeneous distribution of polarization ellipses in focal area. Detailed calculations are presented for particular case of low-order Gaussian beams (TE00, TE01, TE10 and TE11). Bearing in mind obtained results, we discuss specific symmetry structures of self- depolarization effect allowing experimental checking of described phenomenon.

Laser-induced instabilities in optical materials induced by low-absorbing microinclusion and laser-induced damage

There are reviewed and summarized several theoretical models describing various mechanisms of developing of laser-induced temperature and field instabilities in both absorbing and nonabsorbing microinclusions. Most attention is paid to application of the models to investigation of laser-induced damage. General criterion for evaluation of damage threshold is deduced from presented models and discussed.