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Adaptive optics is a real-time compensation technique using high speed support system for wavefront errors caused by atmospheric turbulence. However, the randomness and instantaneity of atmospheric changing introduce great difficulties to the design of adaptive optical systems. A large number of complex real-time operations lead to large delay, which is an insurmountable problem. To solve this problem, hardware operation and parallel processing strategy are proposed, and a high-speed adaptive optical control system based on DSP is developed. The hardware counter is used to check the system. The results show that the system can complete a closed loop control in 7.1ms, and improve the controlling bandwidth of the adaptive optical system. Using this system, the wavefront measurement and closed loop experiment are carried out, and obtain the good results.

The laser pulse should be shaped to satisfy the ICF physical requirement and the profile should be flattened to increase the extraction efficiency of the disk amplifiers and to ensure system safety in ICF laser facility. The spatial-temporal distribution of the laser pulse is affected by the gain saturation, uniformity gain profile of the amplifiers, and the frequency conversion process. The pulse spatial-temporal distribution can’t be described by simply analytic expression, so new iteration algorithms are needed. We propose new inversion method and iteration algorithms in this paper. All of these algorithms have been integrated in SG99 software and the validity has been demonstrated. The result could guide the design of the ICF laser facility in the future.

Integration-Test-Bed(ITB) is China's first laser devices with single-beam ten-thousand joules output for Inertial Confinement Fusion (ICF) research. In this paper we describe the development of single-segment slab amplifiers for Integration-Test-Bed (ITB) with 400mm× 400mm aperture. The experiment results shows that the average small signal gain coefficient in 400mm×400mm aperture reach 5.28%/cm with the gain uniformity is about 1.09:1(maximum value/ average value), and up to 1.063:1 (maximum value/ average value) in 360mm×360mm beam-diameter clear aperture. The storage efficiency of system is about 1.47%. The pump-induced wave-front distortion is 5.3λ for the laser beams, which within the correction range of deformable mirror; the thermal recovery time was less than 4 hours. All of this guaranteed the output of 19.6kJ/5ns with wavelength of 1053nm from the Integration-Test-Bed (ITB) device.

Large-aperture electro-optical switch based on plasma Pockels cell (PPC) is one of important components for inertial confinement fusion (ICF) laser facility. We have demonstrated a single-pulse driven 4×1 PPC with 400mm×400mm aperture for SGIII laser facility. And four 2×1 PPCs modules with 350mm×350mm aperture have been operated in SGII update laser facility. It is different to the PPC of NIF and LMJ for its simple operation to perform Pockels effect. With optimized operation parameters, the PPCs meet the SGII-U laser requirement of four-pass amplification control. Only driven by one high voltage pulser, the simplified PPC system would be provided with less associated diagnostics, and higher reliability. To farther reduce the insert loss of the PPC, research on the large-aperture PPC based on DKDP crystal driven by one pulse is developed. And several single-pulse driven PPCs with 80mm×80mm DKDP crystal have been manufactured and operated in laser facilities.

We demonstrate the design and performance of an optical switch that has been constructed for the SG-II upgrading facility. The device is a longitudinal, potassium di-hydrogen phosphate (KDP), 360 mm×360 mm aperture, and 2×1 array electro-optical switch driven by a 20 kV output switching-voltage pulse generator through two plasma electrodes produced at the rise edge of the switching-voltage pulse. The results show that the temporal responses and the spatial performance of the optical switch fulfill the operation requirements of the SG-II upgrading facility.

The Integration Test Bed (ITB) is a large-aperture single-beam Nd:glass laser system, built to demonstrate the key technology and performance of the laser drivers. It uses two multipass slab amplifiers. There are four passes through the main amplifier and three passes through the booster amplifier. The output beam size is 360mm by 360mm, at the level of 1% of the top fluence. The designed output energy of ITB at 1053nm is 15kJ in a 5ns flat-in-time (FIT) pulse, the third harmonic conversion efficiency is higher than 70%. The first phase of the ITB has been completed in July 2013. A series of experiments demonstrated that laser performance meets or exceeds original design requirements. It has achieved maximum energies at 1053nm of 19.6kJ at 5ns and 21.5kJ at 10ns. Based on a pair of split third harmonic generation KDP crystals, the third harmonic conversion efficiency of about 70% and 3ω mean fluences as high as 8.4 J/cm 2 have been obtained with 5ns FIT pulse.

optical propagation simulation by SG99 code and invert algorithm has been made for two typical laser architecture, namely the National Ignition Facility (model A) and SG-III laser facility (model B) based on measured 400mm aperture Nd:glass slab gain distribution data on ITB system. When the gain nonuniformity is about 5%, 7%, and 9% respectively within 395x395mm 2 aperture and output beam aperture is 360x360mm 2 , and output energy is about 16kJ/5ns(square) with B-integral limited, 1ω(1053nm) nearfield modulation is about 1.10, 1.15, and 1.30 respectively for model A (11+7 slab configuration), and 1.07, 1.08, and 1.17 respectively for model B (9+9 slab configuration) without spatial gain compensation. With the above three gain nonuniformity and slab configuration unchanged, to achieve flat-in-top output near field, the compensation depth of the input near field is about 1.5:1, 2.0:1, and 6.0:1 respectively for model A, and 1.3:1, 1.4:1, and 3.5:1 respectively for model B. Compared with model A (the beam aperture unchanged in multi-pass amplification), the influence of slab gain nonuniformity on model B (beam aperture changed) is smaller. All the above simulation results deserve further experiment study in the future.

Plasma Pockels cell (PPC), which can use a thin crystal to perform the uniform electro-optical effect, is ideal component as average-power optical switch with large aperture. In this paper, by reformative design and employing a capacity to share the gas discharge voltage, the DKDP PPC driven by one pulse is realized. As gas breakdown delay time is stable, and discharge plasma is uniformly filled the full aperture, it meets the demand of plasma electrode for the repetition-rate PPC with DKDP crystal. A rep-rate plasma Pockels cell (PPC) with Φ30mm aperture has been fabricated. It is optimized with the limited space of repetition rate diode pumped laser. The specification of the PPC is: static transition of 97.2%, switching efficiency of 99.8%, the switch rising time of 8.6ns. In the LD pumped Yb:YAG plate laser system, the PPC can steadily work on 10Hz repetition rate performed as Q-switch. The key problems in PPC are analyzed for repetition-rate application, and thermo-optical effects are simulated by means of numerical modeling when average power laser is loaded on the electro-optical crystal. Furthermore, the principium design of rep-rate PPC with longitudinally conductive cooled structure is described in this paper. It will efficiently abate the thermo-optical effects under repetition rate application.

Large-aperture plasma Pockels cell is one of important components for inertial confinement fusion laser facility. We demonstrate a single-pulse driven PPC with 350mm×350mm aperture. It is different to the PPC of NIF and LMJ for its simple operation to perform Pockels effect. With optimized operation parameters, the PPC meets the optical switching requirement of SGII update laser facility. Only driven by one high voltage pulser, the simplified PPC system would be provided with less associated diagnostics, less the maintenance, and higher reliability.