We present numerical investigations to evaluate the performance of the second-harmonic generation (SHG) for a 100 J, 1 Hz Nd:glass laser operating at 1053 nm under different phase-matching conditions in a large-aperture DKDP crystal. Steady state temperature maps for different crystal length, as well as temperature bandwidth analysis under different phase-matching conditions are presented. Studies show that the SHG efficiency drops due to thermal dephasing for the type-I and type-II configurations are 14.6 % and 3.6 %, respectively. Since the type-I SHG implementation is more straightforward and cost-effective in the laser facility, we focused on how to improve its performance in the present work. Besides some existing routines, we proposed here a new approach to mitigate the thermal dephasing issue, by pre-detuning the phase-matching angle for the DKDP crystal. The results show that performance of type-I SHG can be greatly improved by this new approach, with the efficiency drop being reduced from 14.6 % to 3.9 %. We believe that our findings would be beneficial to the construction of ultra-short, ultra-intense laser drivers with reliability, cost-effectiveness and fewer number of large optics.
A ultrashort pulse Nd:YAG rod gain medium regenerative amplifier side-pumped by A laser diode array was studied. The SESAM mode locking fiber seed pulses with 10ps pulse duration 1nJ single pulse energy 50 MHz repetition-rate and the wavelength of 1064 nm, was amplified to 1 mJ at 1 kHz by our regenerative amplifier, corresponding to a peak power of 0.1 GW, with the maximum amplification about 3.3×106 . And when the repetition rate changed to 10 kHz, an average power of 6 W was obtained, corresponding to an amplification of 2×106 . The repetition-rate to period doubling of regenerative amplifier pulse was experimentally studied.
We demonstrate a short pulsed Yb-doped fiber laser system comprising two coherently combined fibers with 15ps pulse width and 20MHz repetition rate. The system delivers an average laser power of 6.6mW, of which the RMS error is only 0.13%. The stability is optimal for a coherent beam combining system with multiple combining stages, thanks to an active feedback control loop implemented in the system. The feedback control loop constantly checks the system output power, automatically maximizing and stabilizing it. Implementation of the active feedback control loop is simple, robust, and versatile.
The grating tiling technology is one of the most effective means to increase the aperture of the gratings. The line-density error (LDE) between sub-gratings will degrade the performance of the tiling gratings, high accuracy measurement and compensation of the LDE are of significance to improve the output pulses characteristics of the tiled-grating compressor. In this paper, the influence of LDE on the output pulses of the tiled-grating compressor is quantitatively analyzed by means of numerical simulation, the output beams drift and output pulses broadening resulting from the LDE are presented. Based on the numerical results we propose a compensation method to reduce the degradations of the tiled grating compressor by applying angular tilt error and longitudinal piston error at the same time. Moreover, a monitoring system is setup to measure the LDE between sub-gratings accurately and the dispersion variation due to the LDE is also demonstrated based on spatial-spectral interference. In this way, we can realize high-accuracy measurement and compensation of the LDE, and this would provide an efficient way to guide the adjustment of the tiling gratings.
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.
A spectral shaping method during the optical parametric chirped pulse amplification is presented. The relationship between the temporal shape of the signal pulse and the pump pulse is analyzed theoretically, which shows that the temporal shape of the signal pulse can be modulated through modulation of the pump pulse. This is proven by our verification experiment. And we have successfully used this method in the pre-amplifier of the XG-III laser facility to modulate the signal spectrum to match the requirements of the main amplifier.
KEYWORDS: Sensors, High power lasers, Coherent beam combination, Signal detection, Research facilities, Numerical simulations, Beam splitters, Automatic control, Process control, Calibration
Array element tiling is one of the key technologies for the coherent beam combination in a high-power laser facility. In this paper, we proposed a method of the array element auto-tiling based on capacitive displacement sensor. The method was verified on a double-pass tiled-grating compressor in XG-III laser facility. The research showed that the method is an effective way to control the misalignment errors automatically, with high precision and long-term stability.
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.
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