Dongbin Jiang

Progress on developing a PW ultrashort laser facility with ns, ps, and fs outputting pulses

A petawatt laser facility with three beams for fast ignition research and strong-field physics applications has been designed and is being constructed. The first beam (referred as SILEX-I) is a Ti:sapphire femto-second laser which pulse width is 30 fs, and till now, output power has reached to 330 TW. The other two beams are Nd3+:glass lasers which output energy are larger than 1kJ and pulse width are about 1ps and 1ns respectively. By using the technology of OPA pumped by 800nm femtosecond laser and seeded by super-continuum spectrum white light, the three beams are synchronized with each other without jitter time. By using the seeds from OPA pumped by femtosecond laser, and by using the pre-amplification stage of OPCPA, the signal to noise ratio of the Nd3+:glass petawatt laser will reach to 108. Active methods are taken to control the gain narrowing effect of the Nd3+:glass amplifiers, giving the option to compress the chirped pulse to ultrashort pulse with width less than 400fs. Tiled multilayer dielectric coating gratings are used for the compressor of the PW beam, which has been successfully demonstrated on a 100J picosecond Nd3+:glass laser system.

Progress on the XG-III high-intensity laser facility with three synchronized beams

The paper presents the technical design and progress on a special high-power laser facility, i.e. XG-III, which is being used for high-field physics research and fast ignition research. The laser facility outputs synchronized nanosecond, picosecond and femtosecond beams with three wavelengths, i.e. 527 nm, 1053 nm and 800 nm respectively, and multiple combinations of the beams can be used for physics experiments. The commissioning of the laser facility was completed by the end of 2013. The measurement results show that the main parameters of the three beams are equal to or greater than the designed ones.

Temporal contrast enhancement for optical parametric chirped-pulse amplifiers by adopting cascaded second harmonic generation pump

Abstract. We report on a method to enhance the temporal contrast of optical parametric chirped-pulse amplifiers (OPCPAs) by smoothing pump noise. The instantaneous parametric gain in OPCPA couples the temporal modulation on the pump pulses to spectral variations of the intensity of the stretched signal pulses being amplified. In this way, pump noise significantly degrades the temporal contrast of the amplified pulses after recompression. Cascaded second harmonic generation (SHG) is adopted to smooth modulation on the pump pulses in the proposed method. Apparent reduction of modulation on the pump pulses is observed in the experiments. Numerical simulation reproduces the experimental results. Simulation results show that cascaded SHG with stable output 2 ω can enhance the temporal contrast for OPCPAs with four to five orders. It is believed that this new method can be widely adopted to build high-contrast OPCPA systems.

Design and optimization of the seed pulse generation scheme for precise beam synchronization in the Xingguang-III laser

Xingguang-III is a large hybrid optical parametric amplification/chirped pulse amplification laser that outputs synchronized femtosecond, picosecond, and nanosecond beams with three different wavelengths, i.e., 800, 1053, and 527 nm, respectively. We present here an in-house front-end system design that generates the 1053 nm seed laser for the ps/ns beam directly from the 800 nm femtosecond laser, which enables the three beams to have intrinsic synchronization. The results show that a seed laser of 140 μJ energy and 1053 nm central wavelength with 34 nm spectral width (FWHM) is generated and the shot-to-shot timing jitter (peak-to-valley) between the fs and the ps beam is less than 1.32 ps.

Novel front end design for synchronized output pulses with zero timing jitter in XG-III laser facility

XG-III laser facility is a petawatt laser which has a unique feature of three synchronized pulses output for various pump-probe experiments. To realize the synchronization with zero timing jitter, we have designed and implemented a novel front-end system based on super-continuum injected femtosecond optical parametric amplification (fs:OPA). Critical parameters of fs:OPA were optimized for the best conversion efficiency. Experimental results verified that major design specifications such as pulse energy, central wavelength and spectral width were fully accomplished and a high pulse contrast ratio was also achieved by the fs:OPA process.

Development of a sub-petawatt ultrashort laser facility

The paper presents the development of a sub-petawatt ultrashort laser facility, i.e. the upgraded super intense laser for experiment on the extremes (SILEX-I). The facility is a multi-stage Ti:sapphire chirped pulse amplification (CPA) laser system. Cross-polarized wave generation was used to improve the temporal contrast. An adaptive optical system was utilized to correct wavefront aberrations and to improve focusability before each shot. After upgrading, the maximum energy is 20.1 J, the recompressed pulse width is 26.8 fs and the peak power is up to 750 TW. The temporal contrast is around 109. The on-target focal spot size (full width at half maximum (FWHM)) is Φ6.5 μm and the focused intensity is greater than 4x1020 W/cm2.

Design and construction of a PW ultrashort laser facility with ns, ps, and fs outputting pulses

A petawatt laser facility with three beams for fast ignition research and strong-field physics applications has been designed and is being constructed. The first beam (referred as SILEX-I) is a Ti:sapphire femto-second laser which pulse width is 30 fs, and till now, output power has reached to 330 TW. The other two beams are Nd3+:glass lasers which output energy are larger than 1kJ and pulse width are about 1ps and 1ns respectively. By using the technology of OPA pumped by 800nm femtosecond laser and seeded by super-continuum white light (SWL), the three beams are synchronized with each other without jitter time. Tiled multilayer dielectric coating gratings are used for the compressor of the PW beam.

Study on active probe laser system used for laser plasma diagnostic

To measure the temperature and density of electronics in laser plasma accurately, two probe laser systems are built on XG-II laser facility. The one, called UV probe laser system, which can provide the UV laser pulse with duration of 30 ps by cascade Raman compressor after fourth harmonic conversion is used for density measurement of laser plasma. The other one, Thomson scattering system, which can provide the 4 ω laser pulse with energy of 3 - 5J, is now routinely operated for electronics temperature diagnostic in laser plasma. It is the first time that the density and temperature of laser plasma are measured directly by probe laser at the same shot.

Using the method of ray-tracing to allocate the stability requirements of fusion laser

A ray tracing software has been developed to allocate the stability requirements of a fusion laser facility. Using the developed software and by establishing a mathematical model of the layout of the fusion laser facility TIL, the task of analyzing the relations between the stability of any individual optical component and the position of the beam foci on the target has been fulfilled. Then, by adding random perturbation to the coordinate parameters of all optical components of the facility and calculating the possibility of the foci to locate in the sphere with radius of 30 μm (the target-shooting requirement of TIL), the stability requirements of the components of the facility has been acquired.