Hi there, I was looking into two photon fluorescence microscopy and was amazed at the light intensity required for the simultaneous two photon absorption to take effect; as it is, the setup is prohibitively expensive, the laser source is particularly problematic. Are there any compounds that you know of capable of generating shorter wavelengths from visible or infrared? I researched this stuff a bit and I've only come across a definition for this sort of phenomena (the titular UF) and various Jablonski diagrams with metastable states, which are a bit beyond my expertise. I would also like to know if you reckon they can be tailored to fluorescence only under simultaneous stimulation by two different wavelengths. That would open up a lot of possibilities... Thanks in advance!