i'm doing some readonly stuff right now and clicked this thread!
   [1]https://www.osapublishing.org/optica/fulltext.cfm?uri=optica-8-11-13
   65&id=462661
   I only skimmed it quick.  this involves reading sentences from the
   middle of the abstract, from materials and methods, and from the
   conclusion.  here are fun points regarding this random article:
   - presently described using research-grade femtosecond lasers, optics,
   etc, because their setup is organised for comparison of approaches, not
   uses
   - similarly their paper reportedish 1-200 K/s write speed 1-100 b/s
   read speed, with pointers for how to develop new setups with MB/s
   speed.
   - high density due to 5 degrees of freedom to the artefact written to
   the transparent medium
   - other uses in shaping detailed nanomaterials

References

   1. https://www.osapublishing.org/optica/fulltext.cfm?uri=optica-8-11-1365&id=462661