Self-organized Voids Revisited: Experimental Verification of the   Formation Mechanism*
  In this paper, several experiments were conducted to further clarify the formation mechanism of self organized void array induced by a single laser beam, including energy-related experiments, refractive-index-contrast-related experiments, depth-related experiments and effective-numerical-aperture experiment. These experiments indicate that the interface spherical aberration is indeed responsible for the formation of void arrays. 
Juan Song, Junyi Ye, Mengdi Qian, Fangfang Luo, Xian Li, Huadong Bian,   Ye Dai, Guo-hong Ma, Qingxi Chen, Yan Jiang, Quanzh...
physics.optics