Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Mitigation scratch on fused silica optics using CO2 laser

Liu C.-M., Yan Z.-H., Yang L., Jiang Y., Zu X.-T., Wang H.-J., Liao W., Yuan X.-D., Zheng W.-G.

Optica Applicata

2016

Vol. 46, nr 3

387--397

The scratch on a fused silica surface was treated as a chain of connected damage sites and mitigated one after another using CO2 laser irradiation. The optical microscopy image shows that a scratch with the width of about 30 μm and length of several millimeters can be completely mitigated without the formation of debris and bubbles. The mitigated scratch can survive under raster scan laser irradiation with the fluency increased up to 11.0J/cm2 at 3ns and 351nm. On the contrary, the substrate without CO2 laser mitigation is seriously damaged under this irradiation. The light modulation induced by mitigation is much smaller when the scratch is mitigated before being damaged. The light modulation is about 2 when the distance to the mitigated sample is larger than 20cm. The birefringence induced by residual stress in the mitigated scratch is measured. The retardance of the mitigated scratch before being damaged is not visible. Therefore, residual stress in this mitigated scratch before being damaged should be not a critical potential risk in laser damage.

Will Czochralski Growth of Sapphire Once Again Prevail?

Bruni F. J., Liu C.-M., Stone-Sundberg J.

Zeszyty Historyczne Politechniki Warszawskiej

2014

z. 16

93--98

In the past decade there has been an explosive growth in the consumption of sapphire driven by the demands of the next generation of energy effcient general lighting based on GaN LEDs. This application requires orienting these rhombohedral corundum crystals such that the substrate surface is the c-plane; a basal plane defined using hexagonal axes. Sapphire crystals form a strong facet on the c-plane, and growth in that direction generally results in crystals with high defect densities, particularly dislocations, and low angle grain boundaries. To overcome this drawback, the usual methodology is to grow the crystal in the a-direction and then core drill rods perpendicularly which are then sliced into c-plane substrates. For all crystal growth techniques commonly employed for sapphire, this approach suffers from poor material utilization. Although this has generally been viewed as an acceptable trade-off in the manufacturing process as long as 200 substrates were the dominant market, as substrate diameters have increased towards 150 mm and larger, this compromise is no longer seen as a viable alternative because of the low material utilization and the high energy consumption of the growth process. This has led to a renewed look at the Czochralski process for more effcient c-axis substrate production.