The frequency domain optical parametric amplification technology, as a new technology reserve for ultra-strong ultrashort pulses of 10 PW or even EW-level OPCPA systems, has many advantages in achieving high-energy ultra-wideband OPCPA. It can take the large gain bandwidth into consideration while enlarging the energy of ultra-short pulses, does not need stretcher and compressor, and is not restricted by materials such as crystal growth and grating damage threshold. In this thesis, the theoretical analysis and numerical simulation of frequency-domain chirped-pulse parametric amplification (FOPA) are mainly performed to complete the entire system design and experimental verification. Based on the picosecond laser system in the laboratory, the experimental verification of the frequency-domain optical parametric chirped-pulse amplification technology with a center wavelength of 800 nm and a gain bandwidth of nearly 100 nm has been completed.
A preliminary concept design of a diode pump solid-state Nd: glass laser amplifier based on helium-cooled multi-slab geometry is presented. The laser amplifier is designed to obtain an output of 100 J/10 Hz. The gain slabs applied in the laser amplifier can lead to low thermally induced wavefront distortion, which are based on heating the edge by the cladding layer. In addition, we also develop a comprehensive numerical model for study effect of amplifier spontaneous emission on the stored energy and thermo-optic effects in the Nd: glass laser amplifier. The results of simulations show that energy storage efficiency of 48% and the average volume density of the stored energy greater than 0.55 J/cm3 are obtained for the laser amplifier. The wavefront distortion can be decreased to 0.78 λ for a gain slab in the laser amplifier.
This study presents the hydrodynamic simulation for high energy large-size Nd:YAG liquid-cooled laser amplifier. Based on hydrodynamic equations, the heat transfer coefficient as a function of cooling fluid velocity is derived. The velocity of cooling fluid could be chosen as 0.8m/s by considering critical Reynolds numbers for laminar and turbulent flows. In order to assess the uniformity of the cooling fluid, a four-channel fluid model is established. The uniformity of four D2O fluid channel in gain region are 98.5%, 98.7%, 98.5%, 98.6%, respectively. Besides, A simple Nd:YAG heat transfer model is built for assessing the cooling capacity of fluid, which is based on the calculation of heat transfer coefficients equation. The temperature differences of central and marginal gain medium planes is 3.451K and 1.951K, respectively, which is close to 3.255K and 1.778K calculated in the heat-fluid-solid coupling model. Based on the heat fluid-solid coupling model, the total wavefront aberration is 0.266λ cooled by D2O. Finally, another cooling fluid FC770 has been compared with D2O. In terms of fluid uniformity, the uniformity of four FC770 fluid channels in the gain region are 98.5%, 98.7%, 98.5%, 98.6%, respectively, which is close to D2O. In terms of heat effect, the heat transfer coefficients of D2O is larger than FC770. And total wavefront aberration of Nd:YAG cooled by FC770 is 0.840λ, which is larger than D2O. Eventually, the thermally induced wavefront aberrations of D2O and FC770 are 0.0475λ and 0.6092λ, respectively. The calculated results showed that D2O is a better cooling fluid than FC770.
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