## 1 Introduction  
The interaction of laser radiation with medium in a condensed state has recently been studied; see, for example, recent works [1; 2; 3; 4]. Local thermal and thermo-elastic effects are shown in this work. These effects can be used in surgical practice. In this connection, laser technologies are widely used in ophthalmic surgery. The optically transparent structures of the eye, i.e., cornea, lens and vitreous body, make the delivery of laser pulse energy in the visible and near infrared spectral range much easier than in other tissues, thereby allowing surgical operations to be performed without destroying the areas, which are sensitive to light, e.g., the retina. Radiation with different wavelengths, pulse durations and intensities interacts with the tissues of the eye in different ways. For example, continuous-wave green light is used for the local thermal pinpoint coagulation of the retina, while nanosecond pulses in the ultraviolet region of the spectrum are used for high-precision superficial tissue ablation, for example, to change the shape of the corneal surface; see reviews [5; 6] for more details. The first type of pulsed laser that was successfully used in ophthalmology was the YAG:Nd\({}^{3+}\) laser, emitting at wavelength of \(\lambda\) = 1064 nm. The cornea, lens and vitreous are transparent at this wavelength. Nanosecond pulses at this wavelength are widely used in ophthalmologic operations; the energies of these pulses typically lie in the range of 0.3-10 mJ [7]. In the case where YAG:Nd\({}^{3+}\) laser pulses are tightly focused inside the eye up to a size of several microns, the pulses of nanosecond duration produce an intensity of about 10\({}^{11}\)-10\({}^{12}\) W/cm\({}^{2}\) at the focal area of the lens. Under these conditions, a phenomenon called \"optical breakdown\" occurs. This effect is characterized by a sufficiently bright flash of light, which is visible to the naked eye. The reason for the appearance of such a flash consists in rapidly increasing electron density in the liquid bulk. When this density exceeds approximately 10\({}^{20}\) cm\({}^{-3}\), a plasma flash in the focal area of the lens is formed [6]. At such intensities, a macroscopic cavitation bubble appears in water; this process is accompanied by the generation of a shock wave and tissue destruction [8]. The cavitation bubble makes several pulsations and eventually collapses, which leads to the generation of another shock wave [6]. All these effects are often referred to as the \"photodegradation\" of tissue. The radii of cavitation bubbles belong to the range of 1-2 mm, and at typical pulse energies of the YAG:Nd\({}^{3+}\) laser the amplitudes of shock waves at a distance of 1 mm from the focus reach up to 100-500 bar [9]. These harmful side effects limit the use of nanosecond laser pulses in ophthalmology. When lasers with picosecond pulses became available, their mechanical side effects appeared less, but were still too great for many ophthalmic applications. This limits the use of nanosecond and picosecond pulses in clinical ophthalmology [10]. Recently, femtosecond laser pulses have been used in ophthalmology. The reason for that is the rather low energy of the femtosecond laser pulse, which leads to a sharp decrease in mechanical side effects. For example, if we are dealing with 300 fs pulses with an energy of 0.75 \(\upmu\)J, the generated cavitation bubbles have a radius of only 45 \(\upmu\)m, which is almost two orders of magnitude less than for nanosecond pulses with energies, which amounts to several mJ, see Ref. [11]. In addition, for femtosecond pulses, the pressure waves arising during optical breakdown are much weaker, and reach about 1-5 bar at a distance of 1 mm from the breakdown area [12]. Finally, the thermal effects of femtosecond pulses in living tissues are negligible [6]. Note that in all works on optical breakdown in pure water, the breakdown threshold was determined by the onset of a breakdown flash.