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Demonstrations of CW and pulsed microchip lasing in Cr 2þ : ZnS and Cr 2þ : ZnSe crystals are reported. Slope efficiencies up to 53% with output power up to 150 mW for CW and energy up to 1 mJ for pulsed pumping were achieved. Two compact diode and Er fibre laser directly pumped external cavity Cr 2þ : ZnS lasers are also described. Crystal preparationBulk Cr 2þ : ZnS crystals can be obtained from melt [14] or vapour growth techniques [14] by including the dopant in the starting charge. Under atmospheric pressure ZnS is sublimed at a temperature higher than about 1180 8C before melting [15]. Therefore for melt growth, in addition to high temperature (1950 8C), it is necessary to apply high q IEE, 2003

We report purely active mode-locking of Cr 2+ :ZnSe laser with 15-30 ps pulses as well as acousto-optically initiated passive mode-locking with ~4ps pulses at up to 400 mW of output power. Pulse-break-up is observed at intracavity peak-powers exceeding ^50 kW.

Nonlinear optical phenomena in silicon such as self-focusing and multi-photon absorption are strongly dependent on the wavelength, energy, and duration of the exciting pulse, especially for wavelengths >2 µm. We investigate the sub-surface modification of silicon using ultra-short pulsed lasers at wavelengths in the range of 1950-2400 nm, at a pulse duration between 2 and 10 ps and pulse energy varying from 1 µJ to 1 mJ. We perform numerical simulations and experiments using fiber-based lasers built in-house that operate in this wavelength range for the surface and sub-surface processing of Si-wafers. The results are compared to the literature data at 1550 nm. Due to a dip in the nonlinear absorption spectrum and a peak in the spectrum of the third-order nonlinearity, the wavelengths between 2000 and 2200 nm prove to be more favorable for creating sub-surface modifications in silicon. This is the case even though those wavelengths do not allow as tight focusing as those at 1550 nm. This is compensated for by an increased self-focusing due to the nonlinear Kerr-effect around 2100 nm at high light intensities, characteristic for ultra-short pulses.

We report and compare three configurations of the SESAM mode-locked, linear cavity femtosecond all-fiber MOPA based on a highly Ge-doped Thulium-doped normal dispersion fibers. We have studied the performance of the system and have obtained stable mode-locking in a wide cavity dispersion range around 1.88 μm. In this article we focus our attention on three mode-locking regimes: laser operating in the anomalous, nearly zero and normal cavity dispersion regimes without the use of the additional dispersion compensating elements. For the nearly zero and normal cavity dispersion regimes the femtosecond pulses with several nanojoule energy could be obtained. The pulses were further compressed down to 630 fs using a simple fiber compressor consisting of a piece of the conventional telecommunication fiber, making the laser design particularly simple and cost effective.