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Of the many emerging applications of laser systems, one of the most intriguing is three-dimensional (3D) printing. That is, rather than manufacturing a component by starting with a bar or rod and removing material, 3D printing starts with fine grains of material and builds up layers by using the heat from absorbed laser light to thermally fuse the grains together (Fig. 2.1). Such laser additive manufacturing (LAM) allows complexity not readily available using material removal - lattice structures in the axles of high-performance racecars requiring low weight and high strength, for example. While there are still a number of details being worked out - design rules, material strength, process reliability, manufacturing throughput, etc. - at this point are that the benefits of LAM exceed the costs for some low-volume applications.
Another approach to manufacturing parts of increasing complexity and precision is to improve on the “material removal” model by using USP lasers for micromachining of very fine features that are otherwise obtainable only at high cost or insufficient quality. An example is the use of USPs for the cost-effective manufacture of flow injectors for regulating fuel consumption in diesel engines - thus improving fuel efficiency and reducing carbon emissions. The type of laser that allows this type of manufacturing is also used for a number of other applications, ranging from laser eye surgery - which is not yet additive - to the trade show demonstration of scribing a customer’s name in the interior of a block of plastic.
The purpose of this chapter is to review the various types of lasers that might be useful for given system requirements such as LAM or material removal. As part of this, we first identify in Section 2.1 laser specifications such as average power, peak power, linewidth, pulse repetition frequency, etc., that are unique to specific applications such as manufacturing, biomedical systems, laser radar, laser communications, laser displays, directed energy, and so on. We then review in Section 2.2 the various types of lasers, classified as semiconductor, solid-state, fiber, and gas. Finally, Section 2.3 pulls everything together from the perspective of laser selection to meet overall system requirements. The emphasis is on commercially available lasers that can be used for most applications; we do not include “hero” experiments or rarely used lasers such as dye, chemical, free-electron, or x-ray.
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