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Comment by anigbrowl | Hacker News Reader

I found this article extremely hard to understand, and the linked abstract was not much more help. My impression is that the device can take light coming into one of several input ports and through some magic of nonlinear optics, ensure that it all ends up at a single output port, something like a funnel. I was unable to determine anything about what this routing mechanism is (heating a substrate, maybe?), if the routing is dynamically changeable, or it works in reverse, eg light coming in can be routed to one of several output ports. The latter would seem like a breakthrough, but my impression is that what's described here is more proof-of-concept than prototype.

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>what this routing mechanism is (heating a substrate, maybe?)

You can engineer a waveguide if you understand the nonlinear theory they propose. There's no heat exchange involved, which is easy to get confused on because the writing in the article does not really understand "optical thermodynamics".

>if the routing is dynamically changeable

At this point probably not, it requires a finely engineered waveguide which has a well-defined "ground state"

>it works in reverse, eg light coming in can be routed to one of several output ports

In theory it works in reverse, as everything in this system is time-reversible (i.e., the "optical thermodynamics" is just an analogy and not real thermodynamics, which would break time reversibility). This is demonstrated via a simulation in the SI, but experimentally they did not achieve this (it may be difficult, I am not an experimentalist so cannot comment).

As best I can understand (which is barely, and poorly!), it seems that this new, and interesting, field of optical thermodynamics allows the behavior of non-linear optical systems to be predicted, in this case allowing them to design a "photonic lattice" - some sort of system of waveguides - so that light behaves in a predictable way and can effectively be steered without having to use any active switching components.

What is even less clear than the above is how is this being used.. Presumably it's not just about routing light to some fixed location, but rather allowing it to be switched, so perhaps(?!) the phototic lattice has multiple inputs that interact resulting in light being steered to one of many outputs? Light being used to switch light?

I dunno - it was clear as mud. I'm basically just guessing here.

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