Development of nano-crystalline ceramic laser materials and high power diode pumped ceramic lasers
Tang, Ding Yuan.
Date of Issue2008
School of Electrical and Electronic Engineering
Solid-state lasers have been utilized for micromachining in the semiconductor industry; for welding, cutting, and drilling in the automotive, heavy machinery, and steel industry; for X-ray and laser-beam generation in medical applications [1, 2], and as a light source in nuclear fusion . The applications of solid-state lasers and the laser market are rapidly growing. Solid-state lasers can be classified into crystal lasers and glass lasers . The essential requirements on the media used as gain host in solid-state lasers are high thermal conductivity, chemical stability, and ease of machining, in addition, (a) a large product of σ (cross section of stimulated emission) and τ (fluorescence lifetime), (b) lower lasing threshold and stable operation at both continuous and pulse oscillation modes, and (c) excellence in laser energy-conversion efficiency are also critical and indispensable factors. However, glasses have poor chemical stability, low melting point and are easy to deliquesce. The thermal conductivity of glasses is about one order of magnitude lower than that of single crystals, which makes it seldom used in high power industrial lasers. On the other hand, YAG single crystals satisfy all these requirements, and are the main host of solid-state lasers. However, The growth of large Nd:YAG single crystal takes 30-40 days, and <25% of the grown ingot can be used as laser media. Also, the solubility of Nd is limited to 1 at% in YAG single crystals during growth. Thus, efficient absorption of the excitation light is limited. Therefore, it is difficult to construct a laser of compact size and high efficiency.
DRNTU::Engineering::Electrical and electronic engineering::Nanoelectronics