(Laser Produced Plasma) Relates to plasma produced by laser irradiation of a substance. Generally created by directing a laser at a target composed of a liquid, a solid, or a partially condensed gas. As the substance absorbs the high energy, energetic disassociation of the substance creates an ionized atmosphere (plasma). Depending on the power, frequency and the substance irradiated, the plasma can produce a wide range of energetic EUV photons. Two disadvantages of an LPP source is that the conversion of electrical energy into plasma is through an intermediate stage (the laser). LPP was the first EUV light source developed for the EUVL project in the United States at the end of the 90s. The conversion efficiency from laser power to EUV emission power is high but the system wide efficiency is poor, when the rather small efficiency of electrical to laser power is taken into consideration.