Suppression of Transverse Parasitic Oscillation in Fe:ZnSe and Fe:ZnS Lasers Based on Polycrystalline Active Elements: A
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ASER RADIATION AND ITS APPLICATION
Suppression of Transverse Parasitic Oscillation in Fe:ZnSe and Fe:ZnS Lasers Based on Polycrystalline Active Elements: A Review A. E. Dormidonova, K. N. Firsova, *, E. M. Gavrishchukb, V. B. Ikonnikovb, I. G. Kononova, S. V. Kurashkinb, S. V. Podlesnykha, and D. V. Savinb aProkhorov
General Physics Institute of the Russian Academy of Sciences, Moscow, 119991 Russia Devyatykh Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhny Novgorod, 603951 Russia *e-mail: [email protected]
b
Received February 11, 2020; revised February 26, 2020; accepted March 16, 2020
Abstract—The methods for suppressing transverse parasitic oscillation (TPO) at room temperature in Fe:ZnSe and Fe:ZnS lasers based on polycrystals doped using high-temperature diffusion have been considered. When active elements of this type are used, the development of TPO at large pump spots is due to the high dopant concentration on the surface of element end face and small length of the active medium as a whole (i.e., typical disk laser geometry). The TPO suppression methods under consideration are based on the fact that undoped Fe:ZnSe and Fe:ZnS exhibit significant absorption at the corresponding lasing wavelengths. Thus, the TPO development can be excluded by simple increase in the transverse size of active element and growth of active elements with several inner doped layers or an inner doped layer (layers) in the form of a meniscus. The problems of damage of active elements at large pump spots are discussed, and the potential of further increase in the radiation energy of Fe:ZnSe and Fe:ZnS lasers with room-temperature active elements is predicted. DOI: 10.3103/S1541308X20030073
1. INTRODUCTION Lasers based on Fe:ZnSe and Fe:ZnS crystals (Fe:ZnSe(S) lasers), operating in the mid-IR wavelength range (which is important for a variety of practical applications), have been actively investigated in the last two decades [1–36]. The studies in this field were reviewed relatively recently in [32]. To date, the highest values of pulse energy [20, 21, 27] and average radiation power [20] for Fe:ZnSe(S) lasers with active elements operating at room temperature were reached when pumping crystals by short pulses of electric-discharge HF laser [see 37, 38, and references therein]. Since the pulse energy of HF lasers is high [17, 21, 27] in comparison with the lasing energy of solid-state Q-switched lasers operating in the same spectral range, the pump energy (and, correspondingly, the lasing energy of Fe:ZnSe(S) lasers at room temperature) can be enhanced by a simple increase in the pump-spot area on the surface of active element (at the pump energy density determined by the surfacedamage threshold). However, the possibilities of this simple method for scaling the energy characteristics of lasers are limited by the occurrence of transverse parasitic oscillation (TPO) with an increase in the pumpspot size. This limitation is especially pronounced when laser active elements are polycrystals doped
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