Professor Juzo Kabuto's expedition within Mt. Fuji led him not only to Japanium but in the volcanic area, nuclear fission from the elements within Japanium gave rise to a new kind of energy. The professor researched this energy noting the large amount of photons and how it gave off no pollution. The professor managed to reverse engineer the nuclear fission process that brought in a new energy revolution, surpassing nuclear power. The professor dubbed the energy Photonic Energy.
With Dr. Hell's threat coming into fruition, Juzo continued his research developing the Photon Engine for the Mazinger Z's power supply. The photonic energy makes up most of the Mazinger's features such as Koshiryoku Beam photon cannons and photon propulsion rockets.