Two-photon luminescence thermometry: towards 3D high-resolution thermal imaging of waveguides

We report on the use of the Erbium-based luminescence thermometry to realize high resolution, three dimensional thermal imaging of optical waveguides. Proof of concept is demonstrated in a 980-nm laser pumped ultrafast laser inscribed waveguide in Er:Yb phosphate glass. Multi-photon microscopy images revealed the existence of well confined intra-waveguide temperature increments as large as 200 °C for moderate 980-nm pump powers of 120 mW. Numerical simulations and experimental data reveal that thermal loading can be substantially reduced if pump events are separated more than the characteristic thermal time that for the waveguides investigated is in the ms time scale.