Pulse infrared laser induced visible luminescence

Crystals of saccharin doped with p-toluenesulfonamide, courmarin, NaCl, and KCl are found to emit in the visible, following a 20 nsec pulse of high intensity 1060 nm radiation. The pulses were 0.5 to 4 J/sq.cm. in energy, corresponding to up to 200 MW peak power. The emissions in the first two cases are from molecular excited states, but with differences in detail from those induced by photoexcitation or found in triboluminescence. NaCl and KCl show neither photoemission or relevant triboluminescence, and the laser induced emission is essentially that found thermally or by mechanically stressing x- or gamma-ray irradiated crystals. It is attributed to electron-hole recombination. The mechanism of the laser induced emission may thus involve some combination of mechanical shock wave and of plasma ionization. The trivial explanations of photoexcitation by higher harmonics of the 1060 nm fundamental or through successive multiple photon processes can be ruled out.