Ultrahigh intensity lasers have been excellent tools in exploring the physics of superintense laser-matter interactions. The laser power has increased steadily to a multi-PW level by implementing the chirped pulse amplification (CPA) technique. Such a laser power can be further enhanced through a pulse shortening without additional the amplifiers. To enhance a peak power of a high energy femtosecond laser, the pulse shortening was investigated through a post-compression by installing a post-compression stage of a 100-TW CPA laser. The laser spectrum was broadened by the self-phase modulation (SPM) in thin fused silica plates and an induced dispersion was compensated by a set of chirped mirrors. The laser beam was post-compressed from 23 fs to 9.7 fs, corresponding to the peak-power enhancement by a factor of 2.1.
To realize the ultrahigh intensity over 10^23 W/cm^2, we carried out the wavefront correction and tight focusing of the CoReLS petawatt laser. By the wavefront correction and tight focusing of the CoReLS petawatt laser with two-stage adaptive optics systems and an f/1.1 (f=300 mm) off-axis parabolic mirror, we obtained a near-diffraction-limited focal spot. The measured peak intensity was (1.1±0.1)×10^23 W/cm2, the first realization of the laser intensity over 10^23 W/cm^2. With the PW laser of intensity over 10^23 W/cm^2, we plan to explore strong field QED phenomena and proton/ion acceleration dominated by the RPA mechanism.
The beam combination method using stimulated Brillouin scattering phase conjugate mirrors is a promising technique
for solid state lasers of high power/energy operating with high repetition rate. The key technology of this method is the
phase control of the SBS waves. In the previous works, the principle of this phase control technique was demonstrated experimentally. As a next step, in this work, amplifiers have been added to the beam combination system. Inserting the amplifiers, a stabilized phase difference has been obtained with a fluctuation less than λ/50 at 44 mJ total output energy and 10 Hz repetition rate.
The beam combination technique using stimulated Brillouin scattering phase conjugate mirrors (SBS-PCMs) is one of
the most promising technology to realize high energy/ high power/ high repetition rate. The beam combination technique
using SBS-PCM can compensate any optical distortions occurred in the amplifier chain because it gives the phase
conjugated wave for the good beam quality. In this paper we will introduce the cross type amplifier as a basic unit of the
proposed beam combination system and show essential technology for realization of the beam combination system, such
as the new SBS phase control technique proposed by the authors. These new techniques are the most simple among the
phase locking techniques developed previously, and furthermore it is possible not only to lock but also to control the
phases of the SBS waves very accurately.
The beam combination technique using stimulated Brillouin scattering (SBS) phase conjugate mirrors (PCMs)
proposed by one of the authors, H. J. Kong, is a promising one for realization of high energy/power laser system with
high repetition rate. However, phase controlling of the SBS waves is essentially required for beam combination system,
since the SBS-PCM generates the random phase. Recently, we have achieved successful results for phase locking by the
self-generated density modulation method. But it showed a long-term phase fluctuation due to the long-term fluctuation
of the density of the liquid SBS medium. To compensate this long-term phase fluctuation, we have designed new phase
stabilization system. In this paper, we will introduce this system and show successful experimental results.
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