大尺寸KDP/DKDP晶体的非线性吸收研究

Research on Nonlinear Optical Absorption of Large-aperture KDP /DKDP Crystals

大口径KDP/DKDP晶体可用作激光约束核聚变（ICF）中Pockels盒和倍频器件的晶体材料。但是在强激光脉冲下,非线性光吸收限制了激光输出的能量密度和晶体的应用。本文利用Z-扫描技术,测量了大口径KDP和DKDP（70%氘含量）晶体样品在皮秒激光波长λ=1064 nm,532 nm下的非线性吸收曲线,获得相应的非线性吸收系数β。研究表明,在λ=532 nm时,KDP晶体的非线性吸收系数β介于0.0124-0.1591 cm/GW之间,I类DKDP（70%氘含量）的非线性吸收系数β为0.0920 cm/GW;当λ=1064 nm时,KDP和DKDP（70%氘含量）都未测量到非线性吸收。晶体的非线性吸收可能与波长、晶体的切向等有关。

Large-aperture KDP /DKDP crystals are available as the Pockels cells and frequency-doubling devices used in inertial confinement fusion（ ICF）. But the nonlinear optical absorption of KDP /DKDP crystals limit the laser output energy density and application of the crystals under the powerful laser pulses.The nonlinear optical absorption curves of KDP and DKDP（ 70% Deuteration level） were meassured underλ =1064 nm and 532 nm using Z-scan technique,nonlinear absorption coefficients β were calculated. The results show that nonlinear absorption coefficients β for KDP fall in between 0. 0124 and 0. 1591 cm /GW and the β of I-DKDP（ 70% Deuteration level） equals 0. 0920 cm /GW at λ = 532 nm. However,no nonlinear absorption at λ = 1064 nm are observed in KDP and DKDP（ 70% Deuteration level）. Nonlinear absorption may be associated with wavelength,the direction of crystals and so on.