Laser cooling with optical temperature sensing in Er3+-doped tellurite-germanate glasses

A novel optical cooling route based on anti-Stokes fluorescence of ²H_11/2 state in Er³⁺-doped materials was proposed. The target temperature of the cooled solid could be monitored simultaneously via spectral inspection of the two green emissions from ²H_11/2 and ⁴S_3/2 excited states of Er³⁺. Here Er³⁺-doped tellurite-germanate glasses with various compositions were prepared. The temperature sensing properties and cooling abilities were systematically analyzed. It was found that all of the samples exhibit good temperature sensing performance and the net cooling could be achieved by properly choosing host materials and pumping wavelength estimated by the spectral measurements.