1. Temperature control of crystals
16th International Conference Laser Optics 2014
Temperature dependence of upconversion fluorescence intensity ratio of Er,Yb:YVO4 and Er,Yb:YGdVO4 crystals V.Aseev1, M. Khodasevich1,2, Y.Varaksa2, G. Sinitsyn2, N.Shereshovets2 1 ITMO University, Saint-Petersburg, Russia 2 Institute of Physics NAS Belarus, Minsk, Belarus 3 International Laser Center, Belarusian National Technical University, Minsk, Belarus
Abstract: Green upconversion fluorescence of Er,Yb:YVO4 and Er,Yb:YGdVO4 is studied in the spectral range of nm in the temperature range from room temperature to 150°С under 967 nm pumping. It is shown that the temperature measurement sensitivity of fluorescence intensity ratio sensors on the base of these crystals is about K-1 and is comparable with the corresponding values for Er-doped silica fiber
Upconversion fluorescence was demonstrated for most rare-earths and some other elements. Fluorescence intensity ratio of two spectral bands from closely spaced energy levels is temperature-dependent which allows implementation of optical fluorescence intensity ratio temperature sensors (FIR sensors). Such sensors are independent on pump power fluctuations and have larger sensitivity and more simple detection circuitry than fluorescence time-decay ones. They don’t create electromagnetic interference and can be used in harsh environment. Thus the study of fluorescence intensity ratio dependence on temperature for novel materials for application in FIR sensors is of particular interest.
The study is performed of temperature dependence of upconversion fluorescence spectra of Er- and Yb - codoped YVO4 and YGdVO4 crystals and the potential for temperature measurement by means of fluorescence intensity ratio in the crystals mentioned. Two crystals were used in the experiment with the Er concentration 0.6%. The fluorescence was registered from two temperature-related levels of Er ions 2H11/2 and 4S3/2 with 1 W diode-laser pumping at 967 nm.
Crystals:
Two crystals: YVO4 and YGdVO4
Er- and Yb-codoped
Er concentration 0.6%
Pump:
Laser diode radiation 967 nm
1 watt power
Luminescence
Upconversion luminescence (emitted wavelength is shorter than pump wavelength)
Upper luminescent levels 2H11/2 and 4S3/2
Two peaks:
552.6 nm and nm for YVO4
552.3 nm and nm for YGdVO4
Temperature control of crystals
PV10 furnace (Coversion Ltd, Great Britain)
Temperature controller TS-200 (Thorlabs, USA)
Precision about 0.1 ° C.
Figure 1 – Green upconversion fluorescence intensity spectra of YGdVO4
Figure 2 – Fluorescence intensity ratio for Er,Yb:YVO4 and Er,Yb:YGdVO4
An average sensitivity (relative variation of intensity ratio at temperature change 1°C)
about K-1 for YVO4
about K-1 for YGdVO4
Sensitivity is comparable to one of the Er-doped silica fiber
The potential exists for increasing sensitivity of FIR sensors by the proper choice of composition of crystal host as well as by varying the percentage of dopants