In laser beam welding coalescence is produced by the heat obtained from the application of a concentrated coherent light beam impining upon the surface to be joined .

  It consists of a man-made cylindrical ruby crystal, around the outside of the

crystal is placed flash tube containing inert gas xenon and the capacitor bank.

When subjected to electrical discharge from the capacitors, xenon transforms a high proportion of the electrical energy into white light. As the ruby is exposed to the intense light flashes, the chromium atom of the crystal are excited and pumped to a high energy level. The effect is enhanced because the parallel ends of ruby rod are mirrored so that the red light that is produced reflects back and forth along the length of the crystal. Finally the total energy bursts over a threshold and escapes from the small hole in the mirror at one end of the ruby crystal, as the laser beam.