Reposting in each OPT Yellow Thread for INFO Purposes: For those whose 565/575 nm yellow has died/ lost power:
After reading paper after paper... YB:SVAP has some bad habits to be solved.
Turns out the dopant metal has a habit of A. Migrating, and B. forming micro-clusters of raw metal in the crystal, and C. forming F Centers of high adsorption. . If your yellow is dying, as in really dead, move the crystal sideways in the laser and retune the pump diode focus and crystal angle. See if it lives. Your pump diode needs to be on wavelength within +/- a nanometer and a half or so, as well for peak power.
The pump diode moves around 0.2 nm /'C . Pump is near 796 nm, although other bands can be used. Wear Laser Safety Glasses when doing this, a Watt of 796 nm pump light can easily blind you..
Steve