ИСТИНА

Picosecond lasers with single pulse energy of a few millijoules, controllable repetition rates within kilohertz, in a compact and reliable design, are claimed in satellite and lunar laser ranging, remote 3d-imaging, time-resolved laser spectroscopy, material processing, driving photoinjectors etc. Advanced pulse-diode-pumped lasers generating ultrashort, mainly picosecond, pulses may utilize dynamical operation control schemes based on active and passive mode-locking, negative feedback and adjustable loss level in the oscillator cavity [1]. Such lasers providing high energy and peak power levels just at the laser output, radiation stability, reasonably low optical jitter [2], enhanced tolerance to environmental conditions, can be easily power scaled and integrated into complicated measuring systems and technological complexes. In the present paper we demonstrate picosecond pulse-diode-pumped Nd:YAG laser with one amplifier stage operating at repetition rate up to 400 Hz and providing output single pulse energy up to 3 mJ. Both laser and amplifier use diode end-pumping by means fiber coupled laser diode arrays. At high repetition rates generation conditions strongly depend on thermal lens induced in the laser crystal [3]. Increase of average pump power at longitudinal geometry may result in aberrational lens formation and increasing radiation losses. To provide operation at high repetition frequencies, special efforts should be paid to compensate spherical part of the thermal lens and to minimize the aberrational one. Using removable Fabry-Perot etalons inside oscillator cavity allows varying output pulse width which can take several different values from 25 and up to 280 ps. Similar schemes were realized with Nd:YLF lasers providing shorter pulse width within 15 ps. To describe evolution of time pulse profile a universal model specially aimed at numerical calculation of generation process in advanced pulse-periodic high-peak-power picosecond lasers [4] is used. The model describes pulse formation governed with active and passive mode locking, negative feedback, adjustable loss level in the resonator, and also taking into account the pulse profile modifying due to amplification. Further development of the model is presented. [1] M.V.Gorbunkov, A.V.Konyashkin, P.V.Kostryukov, V.B.Morozov, A.N.Olenin, V.A.Rusov, L.S.Telegin, V.G.Tunkin, Yu.V.Shabalin, D.V.Yakovlev. Pulsed-diode-pumped, all-solid-state, electro-optically controlled picosecond Nd:YAG lasers. Quantum Electron., 35 (1), 2-6 (2005). [2] A.A.Karnaukhov, V.B.Morozov, A.N.Olenin and D.V.Yakovlev. J. Phys.: Conf. Ser. 414, 012027 (2013). [3] V.B.Morozov, A.N.Olenin, V.G.Tunkin, D.V.Yakovlev. Operation conditions for a picosecond laser with an aberration thermal lens under longitudinal pulsed diode pumping. Quantum Electron., 41 (6), 508–514 (2011). [4] N.G.Mikheev, V.B.Morozov, A.N.Olenin, D.V.Yakovlev. Picosecond lasers with the dynamical operation control. Proc.of SPIE, 9917, 99170A1-9 (2016).