Abstract: Radiant energy such as solar energy is utilized to form a vapor from a liquid state of a material. Concentrated radiant energy is directed through a liquid lens to a target for absorption of the radiation. The target in this way is heated to a high temperature and produces steam or other vapor at high pressure. High efficiency at low over-all cost is achieved by (1) the direct vaporization of a liquid within a collector enclosing the target structure; (2) the recovery of energy absorbed by the liquid lens; (3) the reduction in conductive and convective heat losses in the solar collector by special enclosure of the target within the collector; (4) recovery of heat as blackbody radiation from the target by using reflective walls within the enclosure and/or permitting absorption of the blackbody radiation by the liquid lens; and (5) an optional use of a heat pump effect for increasing the output of the collector.