POWER CHANGES IN DIFFERENT-TYPE LIGHT BEAMS AFTER PASSING THROUGH THE LAYERS OF DIFFERENT-THICKNESS SCATTERING MEDIUM

Laser radiation is extensively used for optical diagnostics of various scattering media. In most cases, laser beams having a Gaussian profile are applied for this task. At the same time, other-type light beams have some features that can be used to obtain additional information about investigated objects. In this context, a relevant task is to reveal the penetrability of different-type light beams in a scattering medium with their subsequent application for the nondestructive testing of various objects, including biological tissues. In this article, a comparative analysis is carried out for four different configurations of laser light beams (Gaussian, Laguerre-Gaussian, and zero- and first-order Bessel light beams) in relation to the power stored by them after passing through a scattering medium layer. To form the light beams we used helium-neon laser emitting at a wavelength of 0.633 micrometers, and a modular optical system. This system makes it possible to change the light beam profile by the inclusion / exclusion of the corresponding modules from the light path. As the scattering medium we used plane-parallel layers of semi-transparent silastic with the thickness ranging from 0.17 to 6.61 mm. It is investigated experimentally how the power of the light beam passing through the scattering medium layer depends on the layer thickness. According to the obtained results, the approximating curves are plotted in the form I = exp (–Dx) where D is the attenuation coefficient, I is the total power of the beam, x is the layer thickness. The values of the coefficient D for different-type beams are calculated. The D values for different-type beams scarcely differ (within the standard error) from each other. It means that the beam type in the optical system configuration has almost no effect on the penetration properties of the light beam, and on the total energy of the light passing through the scattering medium layer.

Gaussian light beam, Laguerre-Gaussian light beam, zero-and first-order Bessel light beam, first-order Bessel light beam, scattering media

1. Goncharenko A. M. Gauss Light Beam. Minsk, Nauka i Tekhnica Publ., 1977. 144 p. (in Russian).

2. Rohrbach A. Artifacts resulting from imaging in scattering media: a theoretical prediction. Optical Letters, 2009, vol. 34, no. 19, pp. 3041–3043. Doi: 10.1364/OL.34.003041

3. Katsev I. L., Prikhach A. S., Kazak N. S., Kroening M. Peculiarities of propagation of quasi-diffraction-free light beams in strongly scattering absorbing media. Quantum Electronics, 2006, vol. 36, no. 4, pp. 357–362. Doi: 10.1070/qe2006v-036n04abeh013151

4. Kulikov K. Laser Interaction with Biological Material. Biological and Medical Physics, Biomedical Engineering. Springer International Publishing Switzerland, 2014. 155 p. Doi: 10.1007/978-3-319-01739-6

5. Kazak N. S. Katranzhi E. G., Ryzhevich A. A. Formation and Transformation of Non-Bessel Multiring Light Beams. Journal of Applied Spectroscopy, 2002, vol. 69, no. 2, pp. 279–285. Doi: 10.1023/A:1016105706082

6. Durnin J., Miceli J. J. Jr., Eberly J. H. Diffraction-Free Beams. Physics Review Letters, 1987, vol. 58, no. 15, pp. 1499– 1501. Doi: 10.1103/physrevlett.58.1499

7. King T. A. Hogervorst W., Kazak N. S., Khilo N. A., Ryzhevich A. A. Formation of higher-order Bessel light beams in biaxial crystals. Optics Communications, 2001, vol. 187, no. 4/6, pp. 407–414. Doi: 10.1016/s0030-4018(00)01124-x