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This paper discusses the use of dispersive optical elements as control devices for the wavelength of alexandrite laser. Some types of selective resonators are considered. The losses in the resonators with dispersive elements are described. The results of a dual-wavelength alexandrite lasing with an installed birefringent filter are presented.

This paper shows the possibility of the use of a solid-state alexandrite laser as a radiation source for the method of spin-exchange optical pumping of noble gases (xenon, krypton). The use of dispersive optical elements in the laser cavity will allows the adjusting of the radiation wavelength exactly in the rubidium spectral absorption lines 794.7 nm and 780 nm. To obtain a hyperpolarized state of noble gases, it is necessary to excite rubidium atoms for further spin-exchange process with the noble gas nuclei. This fact will allow the increasing of the magnetic resonance imaging contrast in the field of diagnosis of respiratory organs diseases.Magnetic resonance imaging (MRI) is used to diagnose respiratory diseases, as one of the safest and most effective medical methods. Currently, MRI is based on measuring of the electromagnetic response of the hydrogen atoms nuclei, i.e. tomographic images are obtained through the use of the phenomenon of nuclear magnetic resonance (NMR). With this approach, it is difficult to visualize all human organs, such as the lungs and brain. One of the promising ways for the development of MRI is using hyperpolarized noble gases Xe, Kr, which, when inhaled by a person, increase the resolution of this diagnostic method. The nuclear polarization degree of noble gas atoms increases due to spin-exchange optical pumping (SEOP) of alkali metal vapour, which makes it possible to increase the contrast of the obtained NMR images by 5-10 times [1].This method is based on the phenomenon of spin exchange between the valence electron of an alkali metal atom in the gas phase and the nucleus of a noble gas due to collisions or the formation of Van-der-Waals interactions (Fig. 1). As the alkali metal, Rb is usually used, which has an absorption spectrum in the near infrared region. [2] Rb atoms have two transitions, D1 and D2 (Fig. 1b), when the laser is absorbed at wavelengths of 794.7 nm and 780 nm [3].To pump the Rb atomspowerful laser diodes and Ti:Sa lasers emitting at a wavelength of 794.7 nm are used. Ti:Sa lasers are capable of generating narrow-band radiation with a high pulse repetition rate, but they are large, high cost at a low average radiation power in practical applications in SEOP. Powerful laser diodes are compact source of radiation.

This article is devoted to the process of remote exposure to the radiation of fiber laser on metal shell explosive objects. The advantages of fiber lasers that allow their use in demining complexes are described. The paper presents an experimental study of the effect of fiber laser radiation profiled and non-profiled pulses on metal simulators of explosive objects. It is established that the effect of profiled pulses compared to the non-profiled allows to significantly reduce the melting time of the sheath and to decrease the required laser energy.