krazer,
This project involves several different and simultaneous parts. There is the basic design philosophy, the optical layout and components, the procurement, the electrical drivers and control as well as the support deck/case. The design choices are still being made, but they are more like good, better, best. And because money is an object ,the cost as well as repeatable/reliable sources influence the design along with performance and this has to be done at the same time. Although not certain, end pumping is likely going to be the choice because M2 is pretty important. And $500, while not cheap it is not too bad for a very symmetric and efficiently mode coupled 7W.
I am still not sure I understand the pump diode polarization problem. In all of the papers that we have referenced to date the fiber pumps are not specified, but I suspect the the higher powered pumps are using fiber bundles which will scramble polarization pretty quickly. The differential absorption coefficient for the favorable vs. the unfavorable polarization at 808nm is roughly a factor of two while the absorption coefficient at 888 although nearly equal for both polarizations is 20 times lower. The result is greater penetration depth. Greater penetration depth should produce less localized surface heating and the small increase in absorption depth should not require a longer crystal as long as we stay at 808nm. Diffusion bonding, Gd and dual end pumping are all options to mitigate this lensing and we are looking at all of these.
I have always been fascinated with running these things at low temps. Are you doing work similar to what Snake Creak has published with Yb and 941nm pumps?
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Originally Posted by ArcDevilz
