Is there any way to convert short wavelength (visible light/near infrared) electromagnetic waves into multiple long wavelength waves (microwave) of near equal total energy?
Heating a blackbody with short wavelength light and letting it emit its energy in longer wavelengths is the best way I can imagine doing this. But, if I'm correct, most of the energy emitted by blackbodies is <20μm above room temperature. Is there anything that will emit most of its energy at >300μm? Can this be done with some kind of multiple photon emission from a single electron transition?