A clean 50-µm hole drilled in stainless steel demonstrates the high-quality performance of copper-vapor lasers (CVLs) in recent industrial material-processing trials conducted by Oxford Lasers Ltd. (Abingdon, England). The company has developed CVL-based techniques for microdrilling ink jets used in computer printers, fuel-injector nozzles, and similar components.
Fabrication of micromechanical and electrical devices seems set to become a growth area for these lasers. Copper-vapor lasers combine high precision with high tolerance and allow direct drilling of holes to less than 2-µm diameter; cutting with a kerf width below 5 µm is also possible, as is working with high-aspect-ratio features, with greater than 50:1 already realized.
The properties that make CVLs attractive for material processing include their ability to deliver a combination of very short pulses (approximately 40 ns) with high repetition rates (typically 5 to 20 kHz), high peak powers (50 to 500 kW), and good beam quality. Thus, ablative material removal at fast process speeds is possible with minimal thermal effects. Most existing laser-based material-processing techniques use IR output from CO2 or Nd:YAG lasers, although UV excimer lasers have recently found some niches. Both the green (511 nm) and yellow (578 nm) outputs of CVLs, though, have advantages over IR; absorption coefficients are higher in some key materials, and the laser beams can be focused to a smaller spot size.
Materials that respond well to CVL processing include ceramics, diamond, and many metals previously considered difficult to process with lasers. Tests with copper, aluminum, silicon, and stainless steel have all been successful, as have those conducted with multilayered materials. Richard Foster-Turner, sales manager at Oxford Lasers, is optimistic about the future of CVL-based material processing. He comments, "We have seen spectacular growth over the past year, with CVLs now used in a wide variety of manufacturing applications."