<title>High-power picosecond laser on Nd:glass based on a passively modelocked oscillator with negative feedback</title>

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St.able pulses with a duration of 2ps derived from a special designed pulsed Nd:glass oscillator with negative feedback were amplified by the injection seeding of Q-swit.cned laser. Amplification fact.or of ~ 10• was achieved in this scheme. Chirped pulses amplification technique is used in further amplification in many staged laser system. In the works of recent. years to advance in the region of high power light. fields the Nd:glass lasers were suicessfully used and tfie highest J<OWer densities al. nearly 1020 W/cm level have been obt. ained1 • . Two problems would be solved for the beginning when such high PQwer picosecond laser system is creating.The first is the designing of J<icosecond oscillator with performed parameters. Compared witfi cw-raser system, pulsed mode-locked solia state laser offer the advantages of the increased out.put energy and short.er pulses. To overcome the shortcomings of a passive mode-locking concept the idea of feedback controllea generation was _proP.osed by many authors. N~at.ive feedback operation results in armost. 100% inode-Iocking and highly contrast. pulses at the out.put. due to controlled prolongation of the nonlinear stage of generation process. One of the main feature is that the pulse intensity in the cavity mar be maintained by negative feecffiack on the level when considerab e pulse shortening would occur. In this way, pulse duration which is close to the theoretical limit set. by the fluorescence linewidth of the laser material may be obtained. Generation of reproducible subpicosecond li~ht pulses in pulsed Nd: glass oscillator was perfectly realized in ' 4 • Second problem is concerned with the efficient preamplificat.ion of relatively weak pulse from the oscillator out.put.. One of the widely used method in preient is the ul t.rashort. pulses amplification in regenerative amplifier . However, one have to satisfy in this case to sufficiently severe reqqirement.s for the cavities length detuning Ct.o within 0.001- 0.01YJ bet.ween the oscillator and regenerative amplifier.