Self-Diffraction of Bessel Light Beams in a Nonlinear Medium

The phenomenon of self-diffraction of Bessel light beams (BLB) in a nonlinear liquid medium has been studied experimentally and theoretically for the first time. Diffraction maxima which do not correspond to integer orders for an induced periodic structure have been registered. It has been shown that the appearance of these maxima is due to the initial BLB modulation, which can be caused by the departure of the axicon refracting surface from the ideal conical surface, as well as by the imperfection of the form of the Gaussian beam incident on the axicon.     

Method for creating hollow light beams with local intensity minima and possibilities for their application

We propose and experimentally realize methods for forming light beams with local spatial intensity minima of different types (hollow light beams), based on application of specially shaped linear optics phase elements. The fields with local intensity minima, obtained as a result of phase conversion, are comparable with respect to transverse dimensions, power, and intensity gradient to the initial gaussian beam focused by means of a spherical lens. The optical layouts were assembled using photostable optical elements and therefore make it possible to create high-power laser fields suitable not only for manipulation of microparticles but also for laser machining of materials, in particular laser welding of metals. Using a phase element with planar symmetry, we can select the optimal laser beam profile that will ensure no burning on the line of contact between the ends of the parts to be welded for high penetration and will make it possible to achieve the maximum possible strength of the weld joint for a specified laser radiation power.     

Method for determining the efficacy of laser photophoresis

We used a laser scanning microscope to study the efficacy of laser photophoresis as a function of the type of biological tissue, the solvent for the agent to be introduced, and the wavelength of the laser radiation. We have observed that under optimal conditions, the penetration depth of the agent in the tissue at the half-concentration level and the total amount of the agent introduced when using laser radiation may exceed the analogous values with no irradiation by a factor of 1.76 and 1.55 respectively.     

Background noise suppression in wide-band lasers with a nonlinear mirror in the cavity

An effective method for suppressing free background generation is proposed. It is based on polarization separation of the narrow-band output radiation of a controlled laser with a nonlinear mirror in the cavity. An increase in the integral ratio between the energy of the narrow generation line and the integral value of the energy of the background over the entire gain band of a wide-band laser from 0.17 to 55.00 has been attained. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 169–171, March–April, 2000.     

Broad-Band Polarizing Light Beam Splitter Based on a Multilayer Thin-Film Coating

Journal of Applied Spectroscopy - A polarizing light beam splitter is created in the form of two Dove prisms of BK7 glass with a multilayer thin-fi lm coating made of two periodic substructures...     

Formation and Transformation of Non‐Bessel Multiring Light Beams

A method for forming multiring light beams (MRLB) on the basis of a biaxial crystal has been developed. The intensity distribution in output MRLBs depending on the parameters of the input light beam has been calculated. For the first time an optical scheme with three axicons for highefficiency transformation of the initial laser beam to a collimated light beam with wavefront dislocation is proposed. The method permits obtaining powerful laser MRLBs which can be used in data transfer and processing systems, in nanotechnologies for manipulating particles, for technological treatment of materials, for acting on organic cells and their components, and for investigating inhomogeneities of transparent media.     

A high-efficient method for generating radially and azimuthally polarized Bessel beams using biaxial crystals

As was shown previously, in propagation of a circularly polarized Bessel light beam along the optical axes of a biaxial crystal, there takes place the conversion of the order of Bessel function. In this paper, a new result is presented which is obtained by varying the polarization state of an input beam. Namely, a linearly polarized beam can be transformed into a beam with the radial or azimuthal polarization state. At that the order-transformation also occurs. The switching between radial and azimuthal polarization states of the output beam is performed by the proper switching between two orthogonal linear polarization states of the input beam. The efficiency of polarization conversion is high and can be practically full at an appropriate choice of the cone angle of the input beam or crystal length.     

Determination of the Quality Parameters of Higher-Order Bessel Light Beams

Journal of Applied Spectroscopy - A method is proposed for evaluating the quality of higher-order Bessel light beams (BLBn, order n > 0) by analyzing digital computer images of...     

Noninvasive optical method for determining the scattering coefficients and the specific volume of blood in biological tissue <Emphasis Type="Italic">in vivo</Emphasis>

We propose a method for determining the scattering coefficients of biological tissue and changes in the relative volume of blood. The method is based on the difference of the parameters of optical radiation that has passed through a biological tissue and the radiation scattered by it in the opposite direction. The obtained correlations between the ratio of the scattered light modulation coefficients at two wavelengths and the biotissue parameters permits determination of the tissue characteristics directly in the living organism. The scattering coefficients at different wavelengths and the values of the relative volume of blood for different anatomical zones and its changes during physiological loads have been calculated.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 119–123, January–February, 2005.