Ultrashort Pulse Laser Processing of Transparent Materials

Ultrashort pulse lasers can generate extremely high peak power with a modest average power. For example, a 1-W average power laser can produce pulses with a peak power of 20 MW (500 fs, 100 kHz). Focusing this extremely high peak power laser beam enables a range of material modifications in and on transparent materials. Fiber lasers can produce micro Joule pulses at repetition rates from the 100s of kHz to the MHz range. Sub-surface optical waveguides written by ultrashort pulse lasers in a range of transparent materials have been reported on in the past. By adjusting the focusing conditions, pulse energy and other laser processing parameters, it is possible to create well-defined material modifications or even cracks below the surface. These features can be used to produce different types of marks and icons. By properly controlling the processing conditions, it is possible to produce features that are relatively difficult to see under normal, ambient lighting, but clearly visible when illuminated from the edge - the Visibility Trade-Off.