Experiments using a 150-terawatt peak power laser system are reported. The relativistic interactions of ultra-high-intensity light with matter are studied with the Diocles laser, currently in operation at the University of Nebraska, Lincoln. Bright pulses of energetic (keV - MeV) x-rays and charged-particle beams are also generated in ultrashort (femtosecond) duration pulses. A study of the damage to various diffraction gratings by ultrashort laser pulses (30 femtoseconds in duration) is also discussed; these results are relevant to the operation of the laser at a repetition rate of 10 Hz, and its planned upgrade to the 1-petawatt (PW) peak power level. Also covered are applications of these unique radiation sources in the physical sciences, biomedicine, defense and homeland security.