From https://news.ycombinator.com/item?id=45282604 re: spiking neuromorphics:

> What are the ways to get spiking behavior out of integrated nanophotonics?

> Saturable Absorption (excitable semiconductor lasers, graphene laser cavity ,), NDR Negative Differential Resistance (RTD Resonant Tunneling Diodes,), PCM: Phase-change materials (DVD-RW,),

> Metamaterials and metasurfaces are probably useful for extreme nonlinear spiking neuromorphic computing with integrated nanophotonics.

Some optical metamaterials have picosecond phase change latency