Research Index / Ultrafast Optics / Yb-Doped Lasers
In collaboration with Patrick George and Frederic Druon at the Institute d'Optic, in France, a regenerative amplifier was demonstrated using Yb-doped GdCOB. This laser material has a thermal conductivity 3 times higher than that of Yb-doped phosphate glass and an emission cross-section of a similar value. The chirped pulse amplifier produced 12 mJ pulses compressed to 30 fs.
Yb-doped KYW is a laser crystal that exhibits an emission cross-section considerably larger than the Yb-phosphate glass and the GdCOB used in previous experiments. Furthermore, by using a minor axis for pumping and lasing a broader, smoother spectrum can be made to lase. In an end-pumped configuration, the KYW crystal produced a slope efficiency of 40% and a cw output of 680 mW from an incident pump of 2.8 W. As a regenerative amplifier this laser produced 50 µJ pulses at 2 kHz repetition rate. Compressed, 40 mJ pulses measured 400 fs in duration. Using the same pumping configuration and reconfiguring the cavity to include dispersion compensation, Kerr-lens mode-locking laser was obtained. This is the first diode-pumped rare-earth laser to be mod-locked without a semiconductor saturable absorber. It displays a pulse duration ranging from 71 to 105 fs.
65-µJ pulses were obtained from a side-pumped version of this laser at 2 kHz using a 20 W diode bar. Autocorrelation indicates these pulses have 460-fs duration. In similar experiments Yb-doped KGW was used as a gain material in a regenerative amplifier, but with the primary axis being excited (E//a). In this laser a 43% slope efficiency was seen in cw operation and 43 µJ pulses were obtained at a repetition rate of 1 kHz. Raman activity was also observed in this system. Finally, a high-energy regenerative chirped-pulse amplifier was demonstrated using a flashlamp-pumped Ti:sapphire laser as a source to simulate diode pumping with up to 1.2 J. The slope efficiency of the laser was as high as 72% in free-running mode, without polarizer or electro-optic cell. As a chirped-pulse amplifier, the laser produces 25 mJ compressed to 1.4 ps pulse limited by gain narrowing. The following table summarizes the characteristics of several Yb-doped lasers demonstrated during the last two years at CUOS.
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