I think we should work on the process using an existing fab with existing machines, as it is
hard work to do.
So let alone the optics (dispersion, wavelength) of a photo lithography machine. If you get to structure widths that are
in the range of the wavelength of the light being used things become difficult as there are
interference patterns which are formed with the mask and the light which forces the user
to generate special masks that compensate the effects of interference like it is used in holographic technology.
Or go for a shorter wave length and use UV lasers for the lithography which are now available.
In times where the 1000nm processes were made UV lasers were not commonly available to my knowledge,
but just using another laser with an old machine might be a problem because the optics were made for a different
wave length but maybe, this can be adjusted by changing the distance of the optics to the waver and/or mask thus
forcing major changes to the machine.
It is not that easy, one thing after the other.
Cheers,
Ludwig