The search for high efficient types of light sources, suited to the indoor use, is in growth because this market is nowadays supplied mainly with fluorescent lamps (~80 lm/W ) although they contain pollutants. Alternatives based on sulfur vapor are currently in development in a number of countries. At high temperature, this vapor radiates a continuous spectrum that fits well onto the eye’s sensitivity range. The first commercialized sulfur lamp, the Solar-1000, outputs 110 lm/W at 1400 W in input. The attempt to launch a large commercialization failed for a lack of technical maturity: the bulb is hold in rotation, at 2500 t/min. We have succeeded to avoid any mechanical motion as well as to reduce the nominal power without degrading strongly the efficiency. The innovation consists in fitting the power supply with a radiofrequency modulator. The system is designed to make vibrate the plasma in order to create an ultrasonic wave inside the bulb. At the frequency where the acoustic absorption is maximal, the diatomic molecules are maintained out of thermodynamics equilibrium, and as a result, the luminous efficiency is increased. The experimental tests are positive. The efficiency of a static bulb has passed from 41 lm/W to 86 lm/W at 650 W in input of the magnetron. Furthermore, 68 lm/W has been reached at 490 W by scaling down the size of the bulb. If the magnetron had a cold cathode, a known technology, it would have been 91 lm/W at 610 W and 73 lm/W at 460 W.