Where is the source? Tantalo does not produce photons, it is not like GaAs that you can pump and get stimulated emission. The Nature paper does not have laser in the title.
its purpose isn't to produce photons, neither is the lithium niobate. The purpose is act as a material to mediate the nonlinear interactions between photons to achieve fun things like supercontinuums, frequency comb generation, etc.
Think of it like the phosphor on your white LED - it produces no photons by itself, but it takes in the blue photons and remits them in a different spectrum. Obviously different physics, but still a similar concept.
Think of it like the phosphor on your white LED - it produces no photons by itself, but it takes in the blue photons and remits them in a different spectrum. Obviously different physics, but still a similar concept.