6 W, 5 mJ amplification with a 28 efficient, kHz, Ti:sapphire regenerative amplifier

摘要

The laser design methodology provides the highest energy from a regenerative amplifier possible with a modern pump laser (Quantronix 527 DQ) and minimizes the spectral and phase distortion for a regeneratively amplified ultrafast pulse. In most high-power laser systems, the regenerative amplifier is only a preamplifier that is followed by a multipass amplifier to increase the pulse energy to the several millijoule level. Our regenerative amplifier, however, produces 6 watts of average power at 2 kHz or 5 mJ of pulse energy at 1 kHz. We are aware of no previous Ti:sapphire regenerative amplifier whose average power exceeds 1.5 watts. The regenerative amplifier is a symmetric, two-rod, ring cavity that is stable with pump powers from 0 watts (single shot) to >28 watts. Examine in Fig. 1 the low variance of the cavity mode size at the Ti:sapphire rod and Pockels cell positions as the thermal lens (load) in the gain medium varies. The net input/output energy conversion efficiency for the amplifier is 28±2%. This corresponds to a rod conversion efficiency >34% before losses. Based on our current results and modeling, we believe the laser will produce 8 watts of amplified energy with 28 watts of pump energy. Since the ring cavity amplifies a travelling wave, no amplified pulse energy is sent back to the oscillator. Furthermore, stray reflections in the cavity contribute "postpulse" rather than "prepulse" to the output pulse as required for laser plasma studies. Focusing tests show excellent agreement between a diffraction limited TEM_(00) mode and the amplified spatial mode (see Fig. 2). The high mode quality is ideal for high intensity physics studies.