Ultraviolet laser excited luminescence of Ti-sapphire

Abstract

The photoluminescence of Ti-doped sapphire (Ti:Al₂O₃) crystals excited using the second (532 nm) and fourth (266 nm) harmonics of a high power pulsed Nd:YAG laser has been investigated. Excitation at 532 nm into the crystal field band of Ti³⁺ produces the well known broad infrared emission band corresponding to the e_g to t_2g transition in the octahedral field approximation. However, this emission can also be excited with ultraviolet light together with an additional blue emission via a two-photon excitation process. This has two lifetime components of 600 and 21 mu s. The mechanism of excitation for the infrared emission band when it is excited via ultraviolet radiation has been studied: it is shown that the excited state of the Ti³⁺ ions is populated via an intermediate state (labelled as X) which clearly correlates with the shortest lifetime component of the blue emission.