an apparatus for applying and fusing a powder coating to substrates of various composition uses two lasers to accurately heat the coating to the optimum temperature . a second laser has less power and heats a smaller area than the first laser . temperature control is enhanced by the ability to superheterodyne two lasers at separate frequencies . this allows for better absorption of certain materials being fused by the laser . another common problem associated with laser processing occurs as the polymer heats up . during the heating process the spectral lines are doppler broadened and slightly shifted . this can affect the absorption of a laser of a fixed wavelength . with the present invention , the optimum laser frequency can be turned to a more optimum frequency for absorption still with sufficient power for fast efficient thermal processing .