The range of optical and thermal properties offered by Nd-doped phosphate glasses allows these materials to service a variety of laser applications. For example, the high extraction efficiency, low non-linear index and superb optical quality render Nd:phosphate glasses suitable for large-scale fusion laser technology. In this case laser efficiency as well as cost and glass yield issues are critical. As a consequence of the very low repetition rate ($LS 1/hour), however, issues surrounding thermal fracture during laser operation are not important. On the other hand, high and moderate-average power laser systems require that the active element performs well under substantial heat loading. Here, the most important issues involve the thermal properties of the medium, and design considerations suggest that it is worthwhile to have somewhat lower extraction efficiency if the material can be engineered to endure significantly more heat loading without thermal fracture. It has been observed that the Nd:phosphate composition space spans thermal figure-of-merit and emission cross section values exceeding a factor of two. It turns out, unfortunately, that improved thermal properties tend to be roughly correlated with inferior laser attributes. In addition to the laser and thermal properties many other property issues need to be addressed including devitrification, durability, and platinum solubility. The manner in which the glass constituents affect glass properties and the nature of the trade-offs that are encountered in engineering practical media are discussed.
展开▼
