Stopped because there is no market for yellow other then lab and a very small amount of medical. Lab folks are happy with 561, and medical buys OPSL right now because of the use of Dye for years means they only want 578, or they have to spend a decade doing a study to prove the new wavelength works on humans.
Oxygen free crystal growth at 1500'C.. Ouch... Molten Fluoride salts is not a winner to work with outside of a lab.
Sorry, but the economy is against us. Again, 30,000 to 100,000 USD to grow a useful Boule.
There are two marketable wavelengths in the yellow and orange, and only two. 578 for medical, the small markets for Ophthalmic and Dermal. The second is 589 sodium line, but must be very precisely overlaying the atomic Sodium line. Even then the 589 market is lab chemistry /astronomy only, and that market right now is well covered by Toptica.
To gain the medical market you need the beam quality of a good HENE and three to five watts of proven power that will work untouched/no adjustments for three to five years.
A patent in the US is locking up OPSL for 578 Medical, and the skin doctors very much like disposable dye cartridges running off 20 Hz picosecond Green Yags. Those short pulse dyes use a solid polymer host, and they throw them away after 10K shots. The handpiece is a lump of very expensive dyed optical polymer with a transmit 532 reflect 578 mirror and a output coupler. It screws on to the green laser's delivery arm. Looks like a 14 cm length of 22 mm pipe. 1 Joule of fat beam yellow does a great job on just about any skin condition in a few shots.
Right now there is no hesitation to pay 40-60K for an ophthalmic yellow, after all they had been paying twice that for decades for Argon pumped Liquid Dye.
Yellow is easily obtained for video projectors from a blue pumped yellow phosphor, but no one wants to pay to develop laser to obtain 10-20 percent more color Gamut, unless its watts or tens of watts and off the shelf. How many of those Necsel Video yellows show up on Ebay? Answer, very few, too expensive and no demand in the initial market. "RGB" is good enough!.
Find a massive industrial market that 578 does better then 532 and you'd have your laser off the shelf. Right now, no such major market exists. 5-10 mW of 561 or 578 is all the lab market needs, there is no scientific demand in cell sorting, optogenetics, or microscopy for more then 10-20 mW. We have 561 in a Confocal Microscope at work, and in the scheme of things, 10K for the Yellow Option in a 1.2 Million Dollar microscope is nothing.
Steve
ATS-405