A photonic warhead was a type of warhead technology utilized by the Vissians in the 22nd century.
According to Veylo, a Vissian tactical officer, the torpedoes utilized by Starfleet in 2153 were "antiquated." (ENT: "Cogenitor")
In 2376, Tuvok was able to dismantle a photonic warhead in less than thirty seconds. (VOY: "Riddles")