In most laser micro-machining applications using copper vapour lasers, the system is configured for near-diffraction limited beam quality. This enables the beam to be tightly focussed to very small spot sizes and can be used for drilling very small holes or trepanning larger ones. The focused spot has a gaussian-like profile. In this paper a new laser system is presented that has a flat-top beam when focused. This has many advantages over gaussian beams when applied to percussion drilling and certain other applications. This system has demonstrated high speed percussion drilling of high quality 100 micron diameter holes in metals. We also report high speed (>200 holes/sec) percussion drilling in green sheet ceramic. The new laser system is a compact copper vapour laser (CVL) master-oscillator power-amplifier (MOPA) incorporating telescopic beam expansion in a high-gain double-pass amplifier. By configuring an oscillator for low coherence output and using a multimode optical fibre between the oscillator and a double-pass amplifier, high power (up to 34W) low divergence output beams having well defined flat-top far field beam profiles have been produced. This scheme generates a flat-top far-field beam profile by control of the spatial coherence of a flat-top near-field beam rather than the usual techniques of producing flattened gaussian beams from coherent gaussian beams. The output of such a MOPA has also demonstrated high power (34W average power, 80kW peak power) damage-free transmission through 100 micron core diameter optical fibres. This is of significant interest to system integrators and for certain applications.
|Title of host publication||Proceedings of the Laser Institute of America|
|Subtitle of host publication||Laser Microfabrication Conference|
|Editors||Eckhard Beyer, Rajesh Patel|
|Place of Publication||Orlando, USA|
|Publisher||Laser Institute of America|
|Number of pages||10|
|ISBN (Print)||0912035722, 9780912035727|
|Publication status||Published - 2002|
|Event||ICALEO 2002 - 21st International Congress on Applications of Laser and Electro-Optics - Scottsdale, AZ, United States|
Duration: 14 Oct 2002 → 17 Oct 2002
|Other||ICALEO 2002 - 21st International Congress on Applications of Laser and Electro-Optics|
|Period||14/10/02 → 17/10/02|
Coutts, D. W., Withford, M. J., Piper, J. A., Rutterford, G., Bell, A. I., & Knowles, M. R. H. (2002). Generation of flat-top focussed beams for percussion drilling of ceramic and metal. In E. Beyer, & R. Patel (Eds.), Proceedings of the Laser Institute of America: Laser Microfabrication Conference (pp. 1-10). Orlando, USA: Laser Institute of America.