We derive an expression describing pre-compensation of pulse-distortion due to saturation effects in short pulse laser-amplifiers. The analytical solution determines the optimum input pulse-shape required to obtain any arbitrary target pulse-shape at the output of the saturated laser-amplifier. The relation is experimentally verified using an all-fiber amplifier chain that is seeded by a directly modulated laser-diode. The method will prove useful in applications of high power, high energy laser-amplifier systems that need particular pulse-shapes to be efficient, e.g. micromachining and scientific laser-matter-interactions.
An efficient and simple approach for converting pulsed near-IR laser radiation into visible and mid-IR light by exploiting degenerate four-wave-mixing in an endlessly single-mode, large-mode-area photonic-crystal fiber is presented. Coupling a 1 MHz, 200 ps, 8 W average power pulsed source emitting at 1064 nm into this fiber results in average powers of 3 W at 673 nm signal wavelength and of 450 mW at 2539 nm idler wavelength, respectively. The excellent pulse energy conversion efficiencies of 35% for the signal and 6% for the idler wavelength are due to the unique combination of characteristics of this type of fiber.
We report on the suppression of stimulated Raman scattering (SRS) in a double-clad fiber amplifier using long-period gratings (LPGs). The LPGs, fabricated with a CO(2) laser, achieve SRS suppression by coupling the Stokes wavelength from the active core into the cladding. With only three LPGs inserted into a fiber pulse amplifier, the extractable Raman-free output power was nearly doubled. A numerical simulation of the setup shows good agreement with the experimental results.
We present passively Q-switched microchip lasers with items bonded by spin-on-glass glue. Passive Q-switching is obtained by a semiconductor saturable absorber mirror. The laser medium is a Nd:YVO(4) crystal. These lasers generate pulse peak powers up to 20 kW at a pulse duration as short as 50 ps and pulse repetition rates of 166 kHz. At 1064 nm, a linear polarized transversal and longitudinal single-mode beam is emitted. To the best of our knowledge, these are the shortest pulses in the 1 microJ energy range ever obtained with passively Q-switched microchip lasers. The quasi-monolithic setup ensures stable and reliable performance.
We report on the simulation of stimulated Raman scattering inhibition by lumped spectral filters both in passive optical transport fibers and in fiber amplifiers. The paper includes a detailed theoretical study that reveals the parameters that have the strongest influence on the suppression of the Raman scattering, such as the filter distribution and the insertion losses at the signal wavelength. This study provides guidelines for the use of spectral filtering elements, such as long period gratings, for Raman scattering inhibition in real-world high power fiber amplifiers.
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