A CO2 laser and xenon lamp were used to monitor the temperature rise in lithium niobate, a transparent dielectric. The CO2 laser was used to heat the sample while the xenon lamp was used to monitor the energy absorption at the band gap where the absorption is exponentially dependent upon the temperature. This technique provides a means of determining temperature rise at the laser spot with both spatial and temporal resolution. In addition, it should be applicable to many transparent dielectrics. © 1998 American Institute of Physics.