New ultraviolet lasers for material processing in industrial applications

Abstract

Ultraviolet (UV) lasers are in many ways ideal industrial processing tools. They offer a noncontact method of producing fine microstructures on many substances, with minimal effect on surrounding material. The most important type of high power UV laser for industrial applications is the excimer laser. Available wavelengths include 351, 308, 248, 193, and 157 nm. The largest commercially available excimer lasers generate up to 200 W stabilized average power and up to 700 mJ pulse energy at 308 nm. Nd:yttrium aluminum garnet (YAG) lasers that utilize nonlinear crystals to transform the 1.06 μm output to its third (355 nm), fourth (266 nm), or fifth (213 nm) harmonic are also an important industrial UV source. More and more diode-pumped, frequency multiplied Nd:YAG lasers greatly impact the industrial processing market. The advantage of this laser is that it is physically compact, highly reliable, and mechanically rugged. Coupled with advantages of short wavelength output, recent improvements in laser reliability, cost of ownership, and performance are enabling UV lasers to be employed in an expanding range of applications. This article will briefly review those applications and their main laser requirements, and then present the most current advances in UV laser technology which address those needs.

Inactivation of Bacillus subtilis spores on packaging surfaces by u.v. excimer laser irradiation

“…Although problems still exist with regard to removing spores possibly located deep within the crevices/pores, they could be overcome by optimizing optical delivery systems. Although the cost of lasers is relatively high compared with germicidal lamps, recent technological advances ( Endert et al . 1999 ) should enable laser‐based systems to be commercially viable in the near future.…”

“…Unlike other high intensity light systems, lasers produce pulses of monochromatic light and therefore, may be considered as more efficient at inactivating spores ( Jones 1996). Excimer u.v.‐lasers have mainly been used for microfabrication purposes, where the low heat generated is advantageous ( Endert et al . 1999 ).…”

Removal of enamel from ultrafine monofilamentary wires

“…14 The technique is being used at an industrial level to strip insulation from very fine ͑Ͻ100 m diameter͒ wires in ͑for example͒ hard-disk heads. 15 The main impediment to the use of this method in the laboratory is the high cost of the apparatus, as well as its size. ͑Mainly for these reasons, we have not yet used this technique in our own work.͒ However, both of these constraints are likely to diminish, and eventually the photoablative technique may become the method of choice for stripping very fine wires in a laboratory environment as well.…”

Wafer-scale crack-free AlGaN on GaN through two-step selective-area growth for optically pumped stimulated emission

“…Especially, AlGaN has been considered as a promising material for the ultraviolet (UV) lighting devices which were applied to the industrial, medical, and germicidal applications [7][8][9][10]. However, the development has been limited due to the poor crystal quality of AlGaN epilayer, where the lattice mismatch and tensile stress of the AlGaN on GaN template generated many number of dislocations and cracks on the surface [11,12].…”