Solid-state Laser Driver Research Articles

High-energy parametric amplification of spectrally incoherent broadband pulses.

We study and demonstrate the efficient parametric amplification of spectrally incoherent broadband nanosecond pulses to high energies. Signals composed of mutually incoherent monochromatic lines or amplified spontaneous emission are amplified in a sequence of optical parametric amplifiers pumped at 526.5 nm, with the last amplifier set in a collinear geometry. This configuration results in 70% conversion efficiency from the pump to the combined signal and idler, with a combined energy reaching 400 mJ and an optical spectrum extending over 60 nm around 1053 nm. The spatial, spectral, and temporal properties of the amplified waves are investigated. The demonstrated high conversion efficiency, spectral incoherence, and large bandwidth open the way to a new generation of high-energy, solid-state laser drivers that mitigate laser-plasma instabilities and laser-beam imprint via enhanced spectral bandwidth.

欧洲HiPER项目激光驱动器概念设计研究现状

欧洲HiPER项目激光驱动器概念设计研究现状

美国LIFE计划激光驱动器概念设计研究现状

美国LIFE计划激光驱动器概念设计研究现状

高功率固体激光驱动器污染控制及片状放大器洁净度改进

The contamination control method covering the whole process of laser driver construction is proposed to ensure the safe operation of high-power solid-state laser driver. The technical means for improving cleanliness level including high pressure washing, cleanliness detection and protection are described, and a technical approach is proposed for improving cleanliness of the slab amplifiers of SG-Ⅲ laser driver. The illuminating cleaning experiment by flashlamp light is introduced. The results indicate that the cleanliness of SG-Ⅲ laser driver is close to NIF, and better than other similar devices.

Experimental research on smoothing by spectral dispersion based on wave-guide phase modulator

Precise physical experiments place strict requirements on target illumination uniformity in inertial confinement fusion. Currently, the main stream of beam smoothing technology adopted in solid-state laser driver is smoothing by spectral dispersion (SSD). The SSD based on wave-guide phase modulator is experimentally studied here. The experimental results indicate that this phase modulator can easily broaden the narrow-band light generated from a DFB laser to 0.1 nm to 1.5 nm bandwidth. The far-field analysis indicates the experimental results are in good accordance with the simulation results. In the meantime, nearfield modulation around 100 μm after the dispersion grating could be smoothed significantly. The research lays experimental basis for the optimization of beam smoothing in high-power laser facility.

Experimental study on smoothing by spectral dispersion using linear frequency-modulated pulse

Precise physical experiments place strict requirements on target illumination uniformity in inertial confinement fusion research. Currently, the main stream of beam smoothing technology adopted in solid-state laser driver combines smoothing by spectral dispersion （SSD）, phase plate and beam overlapping. A new smoothing method aimed at indirect-drive laser fusion is studied here, which uses linearly modulated light and angular spectral dispersion. After using this technique, high frequency modulations on the far field could be smoothed. In the meantime, near field after the dispersion grating could be smoothed too. Experimental results show that the measured spectrum is similar to the simulated one. Phase modulator is not necessary in this method, while it is a crucial element in traditional SSD method.

高功率固体激光器光路自动准直算法与流程优化

高功率固体激光器光路自动准直算法与流程优化

A key issue for next generation diode pumped solid state laser drivers for IFE: amplified spontaneous emission in large size, high gain Yb:YAG slabs

Amplified Spontaneous Emission (ASE) is one of the key issues to be addressed when designing a diode pumped laser with a large transverse size / high gain amplifier. A 3D model using the Monte-Carlo method computing the effect of ASE in the quasi-three-level system of Yb3+:YAG is actually under development for the Lucia-project. This work is performed within the Lucia project [1].

惯性聚变能领域的激光二极管抽运固体激光装置

惯性聚变能领域的激光二极管抽运固体激光装置

Study of small-scale self-focusing in laser beams by high-order contrast

In this paper, high_order contrast is brought forward for studying small_scale self_focusing phenomenon in high_power solid state laser drivers. Based on the properties of semi_invariant, we obtain the analytic expressions of high_order contrast of near field of beams. Finally, we study the propagation of plane waves with PSD phase noise and obtain the evolution of fill factor, modulation, contra st, third_order contrast and fourth_order contrast with Bintegral value. C omparing the results of numerical simulation, we find that third_order contrast and fourth_order contrast are good parameters for characterizing the small_scale self_focusing phenomenon.

Cost of electricity difference for direct and indirect drive targets for inertial fusion energy using a diode pumped solid state laser driver

A detailed systems analysis code has been used to compare the projected cost of electricity (COE) for inertial fusion energy for direct drive (DD) and indirect drive (ID) target scenarios, based on a diodepumped solid state laser driver with Yb:S-FAP (Yb doped Sr5(PO4)3F) gain media.Previously published target gain curves which resulted in a target gain at the optimal DD operating point that is 30% higher than that for the ID scenario have been used. This gain advantage for DD is offset by a requirement for improved beam smoothing, which was obtained via smoothing by spectral dispersion (SSD) with a 1 THz bandwidth at 349 nm. Such a large SSD bandwidth has a number of effects on laser performance, including greater risk of optics damage from non-linear effects, lowered harmonic conversion efficiency, altered extraction parameters and higher front-end costs. The non-linear effects, which contribute to optical component damage by amplification of intensity non-uniformities, were parameterized through a constraint on the maximum allowable B integral (i.e. the total average phase retardation due to the non-linear indices of all materials traversed by the beam). If we constrain B to be no larger than 1.8 rad, which is the presently accepted safe value based on observations in single shot glass laser facilities, the COEs for DD and ID are predicted to be the same within the uncertainties. If technology permits the B limit to be raised, the optimized COE for DD is predicted to decrease relative to that for ID.

2D high power laser diode arrays for solid-state laser driver inertial fusion energy project

2D arrays of laser diodes were developed and investigated under QCW operating conditions. Output power and energy density up to 1 kW/cm2 and 0.45 J/cm2 (at pulse duration 0.5 ms) were measured at the wavelength 810 nm. The spectral composition of radiation, shape of the output pulses, and far-field and near-field radiation zones were examined under various pumping parameters. The kinetics of the temperature profiles in monolithic QCW AlGaAs/GaAs linear bars and 2D arrays, emitting at the wavelength 810 nm was modeled numerically. Quasi-CW and CW operation under various pump parameters were considered as a function of a heat sink design. A calculation model was used to interpret the experimental dependences of the output parameters of the arrays on the pump conditions for application in the solid-state laser driver project. The limit of total power conversion efficiency of diode lasers was analyzed in respect of the threshold current density, series resistance and external differential quantum efficiency. The estimated maximum value of 75% was obtained for the present technological level of the diode lasers production. The corresponding limit of the output optical power density of 2D laser array was defined around 10 kW/cm2.

A diode pumped solid state laser driver for inertial fusion energy

A comprehensive conceptual design for a diode pumped solid state laser (DPSSL) as a driver for an inertial fusion energy (IFE) power plant is presented. This design is based on recent technical advances that offer potential solutions to difficulties previously associated with the use of a laser for IFE applications. The design was selected by using a systems analysis code that optimizes a DPSSL configuration by minimizing the calculated cost of electricity (COE). The code contains the significant physics relevant to the DPSSL driver, but treats the target chamber and balance of plant costs generically using scaling relations published for the Sombrero KrF laser concept. The authors describe the physics incorporated in the code, predict DPSSL performance and its variations with changes in the major parameters, discuss IFE economics and technical risk, and identify the high leverage development efforts that can make DPSSL driven IFE plants more economically competitive. It is believed that this study is a significant advance over previous conceptual studies of DPSSLs for IFE because it incorporates a new cost effective gain medium, applies a potential solution to the `final optics` problem, and considers the laser physics in substantially greater detail. The result is the introduction of an option for an IFE driver that has relatively low development costs and that builds upon the mature laser technology base already developed for Nova and being developed for the proposed National Ignition Facility. The baseline design of the paper has a product of laser efficiency and target gain of ηG~6.6 and a COE of 8.6 cents/kW.h for a 1 GW(e) plant with a target gain of 76 at 3.7 MJ. Higher ηG(≳11) and lower COEs (≲6.6 cents/kW.h) can be achieved with target gains twice as high

High-laser-damage-threshold potassium dihydrogen phosphate crystals

Development of solid-state laser drivers of higher operating fluence is dependent upon the damage resistance of the frequency conversion crystals. We have demonstrated the correlation between the purity of the crystal growth solution and the laser damage threshold of single-crystal potassium dihydrogen phosphate (KDP). Impurities introduced in the growth process can be atomic species, inorganic or organic compounds (dissolved or particulate), or bacteria. We have developed a purification process for KDP that minimizes contamination: initial recrystallization of bulk KDP followed by ozonation to remove oxidizable material, ultrafiltration to remove nonoxidized particles, and UV-light exposure to suppress bacterial growth. We have also developed a crystal growth method that excludes load-bearing surfaces, which are a potential source of particulate contamination, from the growth environment. The method, which incorporates continuous filtration and continuous flow of the growth solution has yielded crystals with damage thresholds of 28.6 J/cm2 at 355 nm and greater than 64 J/cm2 at 1064 nm (10-ns pulse length).

Solid State Laser Driver for an ICF Reactor

A conceptual design is presented of the main power amplifier of a multi-beamline, multi-megawatt solid state ICF reactor driver. Simultaneous achievement of useful beam quality and high average pow...

Laser diode pumped solid state laser for laser fusion reactor driver.

The most promising alternative to flashlamp pumping of high power solid-state laser driver for inertial confinement fusion reactor is the rapidly growing semiconductor laser (also called laser diode). It has inherently high efficiency, long lifetime (over three years at 10 Hz) and small thermal load to the laser material. The latter will enable an increase in pulse repetition frequency. It is shown that for laser fusion reactor driver a LD pumped MJ 0.35 p m regenerative solid-state laser with an overall efficiency of 10 % can be designed. It may be capable to operate at 4 Hz and 10 Hz with the laser material of Nd : glass and Nd SiO2 (or Nd : YAG), respectively.