飞秒激光在透明介质中诱导光学微腔的实验研究

鉴于飞秒激光脉冲持续时间极短且峰值功率极高，将其紧聚焦到透明介质体内部时，易引发双光子效应、碰撞电离、雪崩击穿等一系列非线性过程，在焦点处产生微爆，从而形成微腔结构。提出采用25fs的激光脉冲在透明介质内部诱导形成微腔结构。分析了微腔的能量阈值。结合三维精密位移台，制备了三维微腔点阵。探讨了超短激光脉冲在透明介质内部形成微腔结构的方法与基本实验参数。试验发现：采用更短脉宽的飞秒脉冲时可以降低微腔形成的能量阈值；通过调整飞秒激光功率、脉冲作用次数和光束聚焦情况等因素，可以有效改变微腔的纵深比；在数值孔径较低时因无法实现紧聚焦，故不能形成微腔。

Experiment research on femtosecond-laser-induced optical micro-cavity in transparent materials

Femtosecond laser pulses have the characteristics of ultra-short duration and ultrahigh power. A series of nonlinear processes such as double photons effect, collision ionization and avalanche breakthrough will be induced, micro-explosions will happen and micro-cavities will be formed at the focus in transparent materials when femtosecond laser is tightly focused into transparent materials. The micro-cavity structure induced by 25 fs laser pulse in the interior of transparent materials is proposed. The energy threshold of the micro-cavity is analyzed. Three-dimensional micro-cavity dot-matrix was prepared with a three dimensional precision displacement instrument. The experiments indicate that the energy threshold for generating micro-cavity can be decreased by use of femtosecond pulse with shorter pulse width, the penetration depth of the micro-cavity can be improved by adjusting the power of femtosecond laser, the number of pulses and the beam focus, but the micro-cavity can not be formed if numerical aperture is too small because the tight focus can not be achieved.