Frequency tripling of convergent beam employing crystals tiling in large-aperture high-energy laser facilities

Abstract In inertial confinement fusion, ultraviolet laser damage of the fused silica lens is an important limiting factor for load capability of the laser driver. To solve this problem, a new configuration of frequency tripling is proposed in this paper. The frequency tripling crystal is placed on downstream of the focusing lens, thus sum frequency generation of fundamental frequency light and doubling frequency light occurs in the beam convergence path. The focusing lens is only irradiated by fundamental light and doubling frequency lights. Thus, its damage threshold will increase. LiB3O5 (LBO) crystals are employed as frequency tripling crystals for its larger acceptance angle and higher damage threshold than KDP/DKDP crystals’. With the limitation of acceptance angle and crystal growth size are taken into account, the tiling scheme of LBO crystals is proposed and designed optimally to adopt to the total convergence angle of 36.0 mrad. Theoretical results indicate that 3 LBO crystals titling with different cutting angles in θ direction can meet the phase matching condition. Compared with frequency tripling of parallel beam using one LBO crystal, 83.8% (93.1% with 5 LBO crystals tiling) of the frequency tripling conversion efficiency can be obtained employing this new configuration. The results of a principle experiment also support this scheme. By employing this new design, not only the load capacity of a laser driver will be significantly improved, but also the fused silica lens can be changed to K9 glass lens which has the mature technology and low cost.

[1]  E. R. Dobrovinskaya,et al.  Sapphire: Material, Manufacturing, Applications , 2009 .

[2]  Albert F. Slomba,et al.  Combined advanced finishing and UV-laser conditioning for producing UV-damage-resistant fused-silica optics , 2002, SPIE Laser Damage.

[3]  J. Chen,et al.  Noncollinear third-harmonic generation with large angular acceptance by noncritical phase matching in KDP crystal. , 2015, Optics letters.

[4]  R. S. Craxton,et al.  High efficiency frequency tripling schemes for high-power Nd: Glass lasers , 1981 .

[5]  H. Smith.  Optical‐Contact Bonding , 1965 .

[6]  Mark S. Akselrod,et al.  Modern trends in crystal growth and new applications of sapphire , 2012 .

[7]  Philip Rabinowitz,et al.  Methods of Numerical Integration , 1985 .

[8]  Baoqiang Zhu,et al.  Noncritically phase-matched fourth-harmonic generation of Nd:glass lasers and design of final optics assembly. , 2016, Applied optics.

[9]  Mike Dunne,et al.  A high-power laser fusion facility for Europe , 2006 .

[10]  D. Speck,et al.  Large aperture harmonic conversion experiments at Lawrence Livermore National Laboratory , 1981, IEEE Journal of Quantum Electronics.

[11]  Jin Huang,et al.  Subsurface defects characterization and laser damage performance of fused silica optics during HF-etched process , 2014 .

[12]  Gang Chen,et al.  Stability of Target Area Support System for SG-III Facility , 2012 .

[14]  Frequency tripling for next generation high energy lasers , 2011 .

[15]  N. Chen,et al.  Highly efficient ultraviolet generation at 355 nm in LiB(3)O(5). , 1989, Optics letters.