Experimental studies and analysis of acousto-optic diffraction in alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are given. Ultrasonic wave velocity, elastic compliance and stiffness coefficients, and piezo-optic and photoelastic coefficients of alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are determined. The acousto-optic figure of merit has been estimated for different possible geometries of acousto-optic interaction. It is shown that the acousto-optic figures of merit for alpha-BaB(2)O(4) crystals reach the value M(2)=(270 +/- 70) x 10(-15) s(3)/kg for the case of interaction with the slowest ultrasonic wave. The directions of propagation and polarization of those acoustic waves are obtained on the basis of construction of acoustic slowness surfaces. The acousto-optic diffraction is experimentally studied for alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals.

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Abstract. Currently optically pumped mirrorless lasing is represented by three distinct branches, which concern lasing in different types of the gain media: optically random and photonic media, and microcavities. This article is a first part of our review on optically pumped mirrorless lasing, with the random lasing in scattering media being a main subject. The other mirrorless lasing mechanisms will be addressed in the second part. Considering light localization as a key function of the feedback, we discuss possible mechanisms for the light localization in the scattering media. Special attention is paid to the Anderson light localization. The other mechanisms of the light localization in the scattering media concern high Q-resonances in local microresonators, which exist due to structural inhomogeneities in the scattered media. Applications of the random lasers are shortly reviewed.

Optically pumped light emissions in imperfectly aligned dye-doped cholesteric cells with glance and frosted glass substrates of three different cell gap thicknesses are experimentally studied. Alignment imperfections show up in emission spectra by a broadening of the photonic bandgap (PhBG) lasing (allowed) lines at short- and long-wavelength PhBG edges and by an additional (forbidden) emission line inside the PhBG. Forbidden and allowed lines differ distinctively by their stability in the course of pumping. The origin of the forbidden line is discussed.

Abstract. This article is a second part of the review on optically pumped mirrorless lasing. Consideration of random lasing presented in the first part [Nastishin Yu A and Dudok T H, 2013. Ukr. J. Phys. Opt.] is now followed by analysis of the literature on the lasing in photonic structures, which is mainly focussed on dye-doped cholesteric liquid crystals and microcavities, including liquid-crystal microdroplets.