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History of research in optics and acoustics

At the laboratory of optics and acoustics much attention was drawn on the experimental study of thermal fluctuations in crystals, especially in the vicinity of second order phase transitions when the latent heat threshold between the phases vanishes and fluctuations rise. As one of the most appropriate methods, the investigations of intensity and spectra of molecular light scattering were choosen. In this way the new phenomenon of optical opalescence was discovered near the border of the a and b phases in silica, NH Cl and other crystals (T.S.Velichkina, I.A.Yakovlev, O.A.Schustin) [1-4]. The results of these investigations with those by other authors were later collected in the volume "Light scattering near phase transitions" (North Holland 1983). In recent years the Mandelstam- Brillouin spectra of the scattered light were studied. These investigations have given a first hand information on the propagation of hypersonic (h.s.) incoherent waves in the volume and on the surface of crystals in thermal equilibrium and also provided information on the phonon spectra of solids. Electron- phonon interactions in semiconductor piezoelectrics were studied by the same method [5 - 7]. In order to study natural relaxation processes in crystals in the vicinity of their second order phase transitions the absorption of sound was investigated [9]. Simultaneously to the study of natural hypersound propagation in crystals much attention was given to the generation of coherent hypersound (10 -10 Hz) in crystals in order to overcome the traditional frequency limit for ultrasound. In 1957 K.N.Baransky developed a new nonresonance method of surface generation of hypersound (h.s.) in large piezocrystals freely placed in e.m. cavity [8], giving also an opportunity for hypersound to transfer, if needed, to neighboring media. Using this method of h.s. generation Bragg light diffraction in quartz was studied for frequencies up to 2.10 Hz [12]. This method is now used as the foundation of modern h.s. acoustics, acoustooptics and magnetoacoustics. Later the authour of the method used a wide range of frequencies to determine the velocity and absorption of sound up to 9,4.10 Hz in crystals [10], liquids [9] and thin metal and piezosemiconductor layers [12]. The natural relaxation phenomena in these media, coupled with h.s. propagation, were also studied. Based on the detalied electrodynamic analysis of the propagation of elastic waves in piezocrystals, the method of volume generation of both piezoactive and nonpiezoactive waves in piezocrystals by vortex e.m. field in induction coils was developed [13]. The holographic method for the investigation of diffusion processes in liquids has been elaborated at the Laboratory in 1975 [14] .

References:

1. T.S.Velichkina, L.F. Mikheeva, I.A.Yakovlev. Molecular scattering of light and the ^^86 to ^^87 transion in qutz, Kristallographia, 1(1956) 123
2. O.A.Shustin. Light scattering in ammonium chloride at the vicinity of the phase transition, Pis'ma v ZhETF, 12(1966), 491
3. O.A.Shustin, T.S.Velichkina, I.A.Yakovlev et al. Light scattering in KH PO crystal undergoing a high-temperature phase transition, Pis'ma v Zh.ETF, 18 (1973), 632
4. O.A.Shustin,T.G.Chernervich, I.A.Yakovlev. Optical examination of inhomogeneities of quartz crystals in the vicinity of the phase transition, Solid State Comm., 37(1981),65
5. V.V.Alexandrov, T.S.Velichkina, I.A.Yakovlev, et al, New Mandelstam- Brillouin components observation in the ZnO crystal spectrum of light scattering under constant electric field, Pis'ma v ZhETF- ,37(1983), 481
6. V.V.Alexandrov, T.S.Velichkina, I.A.Yakovlev, et al, Mandelstam - Brillouin spectra of acousto- electron interaction in CdS single crystal, FTT (Solid State Phys), 28(1988), 55
7. T.S.Velichkina, I.A.Yakovlev, Nonequilibrium molecular scattering of light in piezo-semiconductotrs, in book "Problems of Crystallography, Nauka, Moscow, 1987, 335
8. N.K.Baranskii, Exitation of hypersound oscillations in the quartz, Kristallographia, 2(1957),299
9. K.N.Baranskii, G.A.Sever, T.S.Velichkina, Propagation of transversal hypersound waves in viscosity liquids, Pis'ma v Zh.ETF, 13(1971), 52
10. G.A.Sever, K.N.Baranskii, Selection of exitation of hypersound impulses, Izv. AN USSR, 35(1971), 935
11. K.N.Baranskii, Z.A.Magomedov, G.A.Sever, et al, Generation and absorption of hypersound in ZnSe thin films, Microelectronica, 11(1982), 418
12. K.N.Baranskii, G.A.Sever, et al, Piezoelectric trancducers of bulk waves on AlN crystal, Pis'ma v ZhETF, 6 (1980),1112
13. K.N.Baransky, M.B.Zubareva, I.A.Yakovlev. Ectitation and detection of elastic vibrations in piezoelectric crystals by a vortex electric field of an induction coil. JETP Letters, 1988, v.47, pp.291-294
14. T.S.Velichkina, T.G.Chernevich, O.A.Shustin I.A.Yakovlev et al. Propagation of a coherent light beam through a fluids. Pis'ma Zh.ETF, 24(1976), 174-79

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