Sapphire Concave Microlens Arrays for High-Fluence Pulsed Laser Homogenization

Microlens array has been demonstrated to be an effective method for laser beam homogenization. However, the homogenization of high-fluence laser beam is still a great challenge due to the serious damage to the microlens-array-based homogenizer. Here, an ultra-smooth sapphire concave microlens-array-based homogenizer, which is fabricated by dry-etching-assisted femtosecond laser machining, is proposed for shaping high-fluence pulsed laser beam to a flat-top profile intensity distribution. By taking advantages of high transmittance (>70%) and low surface roughness (1.1 nm), high-fluence (5 J/cm ² ) and wide-band (266 nm, 532 nm and 808 nm) laser beams homogenization is successfully realized by the sapphire concave microlens arrays.