A cryocatheter for treating cardiac arrhythmias comprises a miniature refrigeration system powered by electromagnetic radiation. The miniature refrigeration system is disposed at the tip of the catheter and electromagnetic radiation is delivered to the refrigeration system by a waveguide. The miniature refrigeration system includes an engine that converts the electromagnetic radiation into mechanical work. The engine compresses refrigerant for circulation through microchannels in the refrigeration system. Such compression is achieved by using the electromagnetic radiation to superheat a portion of a liquid mass. The superheating causes explosive boiling in the liquid to propel the mass and compress the refrigerant. While particularly advantageous in a miniature refrigeration system, the engine may also be applied to other types of devices.