More boring stuff. The average frequency of the Gamma Photon is 1picosecond. Typically, a laser can damage a material by exciting electrons and through collisions and avalanche ionization; eventually excite electrons across the energy bandgap, Eg, resulting in material breakdown. This is illustrated as single photon absorption in Figure 1. The greater peak power of ultrashort pulses means it is possible for an electron to absorb several photons in multiphoton absorption mechanisms [7]. This absorption mechanism is dependent on the intensity of the laser pulses so this effect is more pronounced with ultrafast pulses. Using picosecond pulses combined with a small spotsize 1 TW/cm-2), which allow enhanced absorption of the incident laser light. This greater absorption is reflected in improved laser micromachining quality. A short wavelength is also important so that the individual photons have enough photon energy so that fewer photons are required to excite individual electrons across the bandgap.
Posted on: Wed, 07 Aug 2013 11:31:45 +0000
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