12 Sep 2003
Scientists say they have produced a 33 fs pulse with a record-breaking peak power of 0.85 PW.
Researchers in Japan claim to have produced the highest peak-power pulse from any Ti:Sapphire chirped-pulse amplification system. The record-breaking 800-nm pulse had a peak power of 0.85 PW and a duration of just 33 femtoseconds. (Optics Letters 28 1594)
Chirped-pulse amplification (CPA) involves stretching an ultrashort pulse to a few nanoseconds in length, amplifying it and then compressing it again. Since the advent of this technique, high-peak power, ultrashort-pulse lasers have generally come in two forms.
The first is an Nd:glass-based CPA system, the approach taken at facilities such as VULCAN in the UK and NIF in the US. To date, pulses as short as 450 fs with 1.5 PW peak-power have been generated using these large-scale lasers. Systems using this method tend to produce extremely high-energy pulses with relatively longer pulse durations and at a lower repetition rate.
The alternative is a Ti:Sapphire CPA laser system, which produces shorter but less powerful pulses. Until now, the record here was a 75 fs pulses with a peak-power of 200 TW were generated from a Ti:Sapphire disk amplifier system.
“Using different approaches to efficient amplification and by shortening the pulse duration, we have developed a laboratory-scaled petawatt Ti:Sapphire laser system,” say the team from the Japan Atomic Energy Research Institute. The researchers add that their laser can produce several shots per hour and the laser parameters are easy to modify.
The system initially stretches 10 fs seed pulses to 1.5 ns. These are then amplified by the team’s existing 100-TW Ti:Sapphire arrangement. The key to producing a pulse with a peak power approaching 1 petawatt was to add a Ti:Sapphire disk booster amplifier on to the team’s 100-TW system. The final stage involves passing the amplified pulses into a compressor.
The authors say that their Ti:Sapphire petawatt laser system has smaller beam sizes than its Nd:glass counterparts. “With an f/1 parabolic mirror, the laser pulses can be expected to realize a focused intensity of 3.8 x 1021 W/cm2 with this beam quality,” report the authors. They add that using deformable mirrors could result in focused intensities greater than 1022 W/cm2.