I have the later papers in front of me, so I have a bit of advantage. SVAP is the only published material so far that has the full 46 nm tunable range we see on these devices, with the 565/575 yellow. and the occasional flash of short wavelength green during warmup on mine is at the other end of the tuning range.
SVAP is the one that dies slowly, but the IEEE web site is still messed up regarding accessing the relevaent paper, so I cannot see what the mechanism is.
Look at the date on the DTIC mil link. It is very early in the career of YB, which really has just sprung on the market in the past 5-6 years.
The point is these crystals need X-ray orienting before cutting and coating so they will both lase and frequency double. The yield loss during production will be large because of this. They are also a three level laser, and lasing in the IR where "yellow" occurs depopulates the lower level often, so they tend to jump around in wavelength, resulting in power instability. This makes this a tricky device to make as a thin monolithic laser. BTW< The tolerance on the pump diode laser wavelength is tight for this class of materials, about +/- 1.5 nanometers around 796 or your not lasing well.
In a laser with a large thick crystal, and external optics, this material would probably be fine. It does have the disadvantage of being strongly adsorptive at the pump wavelength, making very long crystals impractical unless you side pump.
Remember, once this crystal is cut, your stuck with what you have. This is not like a dual crystal laser ( ND:Vandate + KTP), where you can change the angle or temperature of the doubler for peak power. Ie No angle tuning for best power, and a very limited range, if at all, for temperature tuning.
Steve
