While nano-imprint lithography (NIL) nears commercial viability for semiconductor applications, perhaps this is less true for nano-photonics. A preprint posted to the arXiv today outlines an apparently successful, albeit slow, demonstration of “three dimensional” NIL, starting from masters written by two-photon lithography. (Nanoscribe, for example, makes suitable equipment for this step.) The master has positive tone, while an intermediate replica of PDMS has negative tone. The latter is used to cast positive tone replicas on substrates.
The micrographs are quite impressive, revealing reproduction of even the sidewall texturing resulting from the two-photon lithography of the master.
Although the authors claim the technique could be used to print structures with overhangs, the examples shown are all strictly convex. For convex geometries, I see no advantage over electron-beam masters, except possibly capital outlay.
Reference: R Saive, C R Bukowsky, H A Atwater, “Three-dimensional nanoimprint lithography using two-photon lithography master samples”, arXiv:1702.04012