The flash lamp’s spectral output characteristics should match the absorption spectrum of the laser material as closely as possible. The graph below shows the absorption spectrum of Nd:YAG – one of the most widely used solid state lasing media.
A continuum of radiation accounts for a large proportion of the total spectral output of a flash lamp. This is especially evident when the lamp is driven at high power densities. The continuum is a result of radiation generated by free-bound transitions (ions recombining with free electrons) and free-free transitions (electrons and ions decelerating upon collision). Line spectra in the near-infrared are more dominant at lower power densities of around 2500Wcm-2, where bound-bound transitions (transitions between bound energy levels of atoms and ions) dominate. Examples of these phenomena are shown in the figure below.
Spectral outputs of gas-filled flash lamps and absorption spectrum of Nd:YAG
Infrared heaters from Heraeus
