Just to show Mr. Klompen that this board is able to discuss also possible threats to the POET technology:
One issue came to my mind: Many SI-fabs, also the "old" ones working on 40nm node or bigger, are working with 300 mm wafers, some with 400 or 450 mm.
So swithing them to POET could have one major problem: The supply with GaAs-Wafers. As far as I know the maximum size on the market is 200mm GaAs-wafers, most common is 100 or 150mm.
The same for the MBE-Tools:
The biggest Molecular beam Epitaxy tools can accept 200mm wafers, as an example RIBER MBE7000:
Riber is a French company and seems to sell leading edge tools. This is their premium MBE, but it can take "only" 3x 8'' wafers.
Can we estimate which fabs can work with 200 mm, or can a 300mm fab run with 200mm wafers?