Research Of High Intensity Broadband Laser Frequency Tripling

This paper starts from the background of the requirement of ICF targeting, namely the uniformity radiation to the target. It mainly contains the research of broadband laser frequency tripling, and will give directions to ICF laser targeting experiment. We selected the orthogonal crystals cascade scheme for frequency tripling, and studied the characteristic of. harmonic generation process of high intensity broadband laser. We established the theory of frequency doubling and tripling with the results of near field, efficiency, bandwidth etc. We have considered the transverse diffraction and the absorption of the crystals in order to make the theory perfect. We have also optimized the parameters for "â… +â…¡+â…¡" scheme, and accomplished the broadband laser second harmonic generation experiment using KDP on LILEX-I laser devices to verify the frequency tripling theory indirectly. The results of efficiency and the spectrum are well accordance with the theory. This paper contains several parts below:1. Some phase match schemes for broadband laser frequency tripling, and get the reason for using the orthogonal crystals cascade scheme through comparison.2. Studied the theory of broadband laser frequency doubling and tripling in the orthogonal crystals cascade scheme, and analyzed the process of frequency coupling. We established the theory of broadband laser frequency doubling and tripling in the orthogonal crystals cascade scheme.3. We have accomplished the calculation of the theory, also optimized the crystals' parameters under the input bandwidth of 0.5nm, 1nm and 2nm. We present an optimized scheme for spectrum according to the spectrum change in broadband frequency doubling.4. We have studied the effects of fundamental temporal phase modulation on beam quality, and get the relationship between tripling efficiency and modulation depth.5. We accomplished the experiment of broadband chirped laser frequency doubling, the result accords theory well.This paper have analyzed the frequency doubling and tripling process in ICF broadband laser targeting, and established a well theory model, so can be taken as a direction for ICF.