Charged Particle Sources
Did You know?
Laser micromachining covers a wide range of scribing and drilling techniques that are based on both thermal and non-thermal modes of laser processing. Non-thermal mechanisms involve breaking chemical bonds using ultraviolet pulsed lasers. Since the pulse durations are on the order of femtoseconds (10^−15 s), collisions between material particles (10^−12–10^−14s) will not be triggered, and hence the mechanisms of interaction do not follow the laws of thermal conduction. Thermal laser machining is based on laser heating effects, and the required power density is typically 10^4 W/mm^2 for melting and 10^6 W/mm^2 for vaporization-dominated mechanisms. The corresponding beam interaction times lie around 10^−6 to 10^−8 s. Most classes of engineering materials can be machined using an appropriate laser beam: high energy, short wavelength visible and ultraviolet output from pulsed copper vapor and frequency-multiplied Nd:YAG lasers for metals, alloys and many ceramics; or the lower energy, longer wavelength radiation of pulsed red ruby far infrared CO2 lasers for some ceramics, glasses and polymers.