Within the vast range of laser materials processing applications, every type of successful commercial laser has been
driven by a major industrial process. For high average power, high peak power, nanosecond pulse duration Nd:YAG
DPSS lasers, the enabling process is high speed surface engineering. This includes applications such as thin film
patterning and selective coating removal in markets such as the flat panel displays (FPD), solar and automotive
industries. Applications such as these tend to require working spots that have uniform intensity distribution using
specific shapes and dimensions, so a range of innovative beam delivery systems have been developed that convert the
gaussian beam shape produced by the laser into a range of rectangular and/or shaped spots, as required by demands of
each project. In this paper the authors will discuss the key parameters of this type of laser and examine why they are
important for high speed surface engineering projects, and how they affect the underlying laser-material interaction and
the removal mechanism. Several case studies will be considered in the FPD and solar markets, exploring the close link
between the application, the key laser characteristics and the beam delivery system that link these together.
Laser milling of diverse materials has been demonstrated with short pulse lasers ranging from microsecond to femtosecond pulse durations, and with wavelengths from the far infrared to vacuum ultra-violet. In all cases a balance between quality, throughput and cost of ownership must be struck in order to determine commercial relevance. Latest generation Q-switched Diode Pumped Solid State Lasers offer the potential to enable the industrial uptake of laser milling for a wide variety of materials including aerospace alloys, thermal barrier coatings, tool steels, diamond and diamond substitutes. This paper will investigate these practical applications of laser milling with reference to comparative laser and non-laser processes.
Laser milling of a variety of substrates is investigated with the intention of achieving high quality material removal to create three-dimensional shapes in the material. A high power Q-switched Diode Pumped Solid State Nd:YAG Laser at 1064nm is used in all cases. Materials investigated include Nickel Superalloys, Thermal Barrier Coatings, Steels, Tungsten Carbide and Polycrystalline Diamond. Multi-layer substrates are also considered. The effects of laser intensity, plasma formation, pulse duration, material properties, and resulting removal rate, recast and surface finish are explored for this process. This paper defines the findings of this study within the context of commercial imperatives.
Electrical to EUV conversion efficiency is a key parameter for systems scaled to EUV emission in the 100W regime. Improvement in efficiency of conversion from laser radiation at the EUV source, reduces the required laser power and as such can lend itself to reduced heat load and debris emission. Also, improvement in the electrical to laser conversion efficiency results in a direct reduction in cost of ownership. Laser solutions optimised for efficient conversion to high M<SUP>2</SUP> CW laser radiation are not optimised in design for efficient short-pulsed operation; the mode of operation required for EUV generation. Aspects of both EUV source and laser design are discussed, with a view to optimising conversion efficiency for scalable EUV solutions.