Diode pumping efficiently produces tunable picosecond pulses
Researchers at the Université de Paris-Sud (Orsay, France) have used diode pumping to improve the electrical-to-optical efficiency of a compact, high-energy, picosecond laser system created by injection-seeding a solid-state amplifier with an ultrafast diode laser--an arrangement that is potentially useful for reducing the size of high-energy ultrafast lasers. The setu¥consisted of a gain-switched, picosecond diode-laser stripe driven by a pulse generator. The 22-pJ diode-laser output pulses were 200 ps wide with a range of longitudinal modes from 800 to 840 nm and a peak at 812 nm. These pulses entered a regenerative amplifier consisting of a 13-mm-long Ti:sapphire crystal, a Pockels cell, a polarizer, and a prism to select the optical wavelength--all within a classical L-shaped cavity.
The regenerative amplifier was pumped by 40-ns, 40-µJ pulses at 10 kH¥from a Q-switched, frequency-doubled Nd:YVO4 laser driven by a single 808-nm, 4-W laser diode. Pulse jitter in the amplifier output was measured to be less than 30 ps for pulsewidths less than 100 ps. Two lithium triborate crystals produced second and third harmonics of the amplified pulses, with average powers of 11 mW at 406 nm (30-nm tuning range) and 4 mW at 271 nm (12-nm tuning range). The researchers say that the system will be particularly useful for time-resolved spectroscopy applications.