Two-photon absorption is a fascinating property: some molecules can simultaneously absorb two photons and then emit a photon of higher energy than absorbed ones.
This has found numerous uses:
As a result, it is very important to find materials with stronger two-photon absorption. We have developed an interpretable machine learning approach based on experimental data which predicts two-photon absorption strength instantaneously with accuracy comparable to DFT.
You can easily do such simulations online with MLatom on the XACS cloud as described in our tutorial.