Laser induced backside wet etching: Mechanisms and fabrication of micro-optical elements

A novel method for the fabrication of complex 3 dimensional structures, such as plano-convex. microlens arrays in quartz, is presented. This technique is applied for precise micromachining of UV transparent materials, e.g. quartz, by using a conventional XeCl excimer laser and an organic solution which is in contact with the substrate. Strong absorption of the intense laser light results in the formation of the high pressure and temperature jumps at the quartz-liquid interface, which are the key elements in this process. A combination of laser assisted wet etching with the projection of a Diffractive Gray Tone Phase Mask is applied to fabricate diffractive and refractive micro-lens arrays in quartz. A quartz micro-lens array, which consists of 10 x 10 plano-convex microlenses is tested as a beam homogenizer for the quadrupled Nd:YAG laser.