Devices for temperature measurement and laser profile analysis using YBa2Cu3O7-δ atomic layer thermopiles

We report on the application of the atomic layer thermopile for the determination of both the temperature profile near a heated surface and the radiation profile of laser radiation. As thermopile we used a YBa₂Cu₃O_7-δ (YBCO) film grown epitaxially on a substrate with the crystal c-axis tilted away from the substrate normal. Irradiating the film (at room temperature) leads to a temperature gradient in the film, resulting in a voltage signal parallel to the film surface. The origin of the signal is due to the transverse Seebeck effect, which is a consequence of the anisotropy of YBCO. We made use of this effect for developing several devices. For fast non-contact temperature measurement we prepared a small sensor (response time less than 30 ns). For profile analysis of laser radiation we developed two complete systems. One is suitable for cw lasers, in particular for CO₂ lasers. The cross-section of the laser beam is scanned by a rotating aperture facility. For the analysis of pulsed laser radiation we built an array of atomic layer thermopiles, which is moved stepwise across the laser beam. This system is suitable for the determination of radiation profiles of pulsed lasers from the UV to the FIR. Finally, we are developing the detector head of a third system. It consists of 100 small atomic layer thermopile pixels for fast online profile analysis of cw lasers