Comment by momoschili

It's a really smart idea to try to leverage the inherent scalability of semiconductor photonics. I think the use of a linear optical resonator to amplify a weak optical nonlinearity is quite genius, and something the relatively small nonlinear photonics community has been trying to do forever. That they showed this kind of 'all-optical-ish' nonlinearity on a relatively mature process in a foundry is nothing to scoff at, and likely one of the biggest results in semiconductor photonics in a while. At the single device level I think it makes so much sense, but what concerns me in general is how well this scales from a few perspectives:

1. resonators and device-to-device variance: in general it's pretty hard to get these resonant effects to line up with each other from a production POV, especially with large arrays. Silicon photonics has come far, but I don't think it has approached the level of uniformity as electronics. They have demonstrated some level of electro-optic tunability, which is the traditional solution, but they still need to leverage that for their nonlinear effects too.

2. area and space: the 'minimum' trace size of these planar photonics circuits is still quite large (~200 nm minimum feature size typically for these waveguides). This is essentially due to a minimum size needed to confine light within a waveguide which depends generally on the waveguide's refractive index and target wavelength. These are currently all integrated on a planar manner, so each channel becomes quite large, especially if now you also need a relatively large ring resonator, which in this case is at least ~100 micrometers or so in diameter

3. the combination of 1 and 2: high device-to-device variation, along with a large planar footprint means that these things are quite expensive and difficult to manufacture, without some kind of miniaturization benefit that you would typically get with electronics (at least not yet). This effect appears to be more than the sum of 1 + 2.