LUMINESCENCE INDUCED BY IRFEL ABLATION OF SOLID SAMPLES

An intense infrared free electron laser (IRFEL) causes laser ablation with an emission of visible luminescence from solids samples. In the c ase of zinc selenide crystals (ZnSe), the focused IRFEL pulse induces the ablation on the surface because of its high peak power density, de spite ZnSe being normally transparent to infrared light. The pulsed IR FELs are at 9.2- and 10.2-mu m in wavelength and of several GW/cm(2) i n power density. The luminescent lines can be identified as the neutra l atomic lines originating from the target zinc atoms. The pulsed lumi nescence from ZnSe is short in width and synchronized with the irradia ted IRFEL pulses, which is operated at 22.3 MHz. From the relation of the 9.2-mu m FEL fluence and luminescent intensity, the threshold of t he ZnSe luminescent emission is found to be similar to 13 mJ/cm(2) at 9.2-mu m IRFEL irradiation. (C) 1998 Elsevier Science B.V. All rights reserved.