Optical Creation of Radiophotoluminescence Centres in Dosemeter Glass By Two-Photon Absorption

In recent years considerable progress has been achieved in the field of phosphate glass dosimetry through the evolution of improved glass material with good batch uniformity, newly designed dosemeter encapsulation and automatic readout techniques based on pulsed UV laser excitation. The peak intensity of the laser pulses exceeds the range of intensity available with conventional UV light sources. This paper reports on effects that may occur when an intense light source is used for RPL readout. In a specially designed reader unirradiated flat RPL glasses and a scanning focused laser beam for RPL readout were used. The influence of intense UV laser excitation on RPL readout intensity has been studied for dependence on the intensity and duration of excitation. The experimental arrangement, the scanning procedure for laser excitation, the dosemeter glass handling and the method of RPL readout are described. The observed RPL intensity is attributed to the optical creation of RPL centres by two-photon absorption in the focal region of the laser beam. By means of beam profile and power measurements an estimation of the lower limit of excitation intensity is given where two-photon absorption becomes important.