An alternative heat source for an internal combustion engine with an elongated compartment with first and second ends, a directed energy device capable of sending a pulse of photonic energy to a focal point within the first end of the compartment, an intake allowing for the entry of a gas into the the elongated compartment, an exhaust allowing for the exit of the gas from the elongated compartment, and a piston capable of moving within the elongated compartment between the first and second ends. The pulse of photonic energy at the focal point heats the gas and causes a corresponding expansion of the gas in the elongated compartment, driving the piston toward the second end of the elongated compartment, where the piston movement can be translated into motive force. The same principle can work with a rotary chamber, or a dual chambered linear system.