title: Laser ablation of silicon using a Bessel-like beam generated by a subwavelength annular aperture structure.
abstract: Using a femtosecond laser incident to an oxide-metal-oxide film engraved with a subwavelength annular aperture (SAA) structure, we generated a Bessel-like beam to ablate silicon. Experimental results show that the silicon can be ablated with a 0.05 J/cm(2) input ablation threshold at 120 fs pulse duration. We obtained a surface hole possessing a diameter less than 1 μm. Optical performance, including depth-of-focus and focal spot of the SAA structure, were simulated using finite-different time-domain calculations. We found that a far-field laser beam propagating through a SAA structure possesses a submicrometer focal spot and high focus intensity. Our method can be easily adopted for surface machining in microfabrication applications.
authors.affiliation: Institute of Applied Mechanics, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Yuh-Yan
authors.initials: YY
authors.lastname: Yu
authors.forename: Chin-Kai
authors.initials: CK
authors.lastname: Chang
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Lai
authors.forename: Long-Sun
authors.initials: LS
authors.lastname: Huang
authors.forename: Chih-Kung
authors.initials: CK
authors.lastname: Lee