Saturday, June 11, 2016

Recent progress on high-energy ultrafast laser systems in RIKEN

Seminar Yuxi FU- in PSB 160/161 @ 1:30 pm Monday June 13

Recent progress on high-energy ultrafast laser systems in RIKEN

Yuxi FU
RIKEN Center for Advanced Photonics, Japan

In this seminar, two of our recent work will be presented. The first one is developing high-energy infrared fs laser using a dual-chirped optical parametric amplification (DC-OPA) scheme. In the DC-OPA scheme, a high-energy fs laser pulse is temporally stretched by introducing an amount of temporal chirp and is used as a pump for an OPA system. In this way, the pump energy can be scaled up without damaging nonlinear crystals. Simultaneously, the seed pulse of the OPA is also temporally broadened to achieve good conversion efficiency. Because both of the pump and seed pulses are temporally chirped, the method is dubbed as dual-chirped OPA. In this novel method, it is important not only to optimize the chirp value but also to use the same chirp sign. By using the DC-OPA method, we successfully demonstrated its excellent energy scaling ability and obtained more than 100 mJ output (signal + idler) energy. To the best of our knowledge, this is the first time for an ultrafast infrared laser to reach the 100 mJ class. Such a high-energy infrared fs laser is very useful for energy scaling of sub-keV high harmonics generation and intense isolated attosecond pulse generation by infrared two color gating (IR-TCG) method.

The other one is carrier-envelope phase (CEP) stabilization of a high-energy, low-repetition rate laser. A high-repetition rate reference pulse, which copropagates with the high-energy pulse though the power amplifier and compressor, is employed to characterize and stabilize its CEP. CEPs of the high-energy pulses are indirectly stabilized to below 600 mrad RMS level under an out-of-loop measurement (single-shot). What’s more, we experimentally investigated CEP stabilization affected by energy fluctuation, sampling/feedback frequency and thermal effect. The method can be employed to stabilize CEPs of 100-TW or even PW class lasers.

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