Optically detected thermal effects in rare-earth doped materials for host characterization, thermometric devices, nanothermometry and biothermometry

Abstract

We present a review of recent works on optically investigated thermal effects in crystalline and amorphous materials doped with trivalent rare-earth (RE) ions. The paper describes how the frequency upconversion (UC) photoluminescence (PL) technique is used to investigate the thermal behavior of samples and how to perform optical measurements of temperature. The UC technique is based on the sequential multiphoton absorption phenomenon that leads to anti-Stokes type emission. By measuring the relative intensity between UC emissions from thermally coupled RE energy levels, the absolute temperature of a sample can be determined. Research in this area is motivated by the possible uses of UC for basic characterization of materials and for noncontact thermometry using nanoscale devices as well as for biological and medical studies. Examples based on the application of bulk materials and nanopowders doped with several RE ions are presented.