M. Diaf

Anti-stokes emissions and determination of stark sub-level diagram of Er3+ ions in KY3F10

We are interested, in this work, in determining the Stark sub-level of Er3+ ions doping a KY3F10 single crystal with a molar concentration of 1%. We have used a new method of measurement of energies of the ground level and emitting levels from excitation and anti-Stokes emission spectra recorded at liquid nitrogen temperature. This technique is based on a spectral analysis of the anti-Stokes emissions recorded after selective excitation with a red dye tunable laser. Thus, we could determine the Stark sub-levels of the ground and the principal emitting levels in the infrared, visible and near-UV ranges with a very good precision.

Crystal growth and spectroscopic properties of Er3+ ions doped CdF2 single crystals

Single crystals of Er3+:CdF2 with good optical quality were grown by a Bridgman technique after purification of the starting materials. Absorption and emission spectra are recorded at room temperature. The Judd–Ofelt (JO) analysis was applied to obtain the three phenomenological intensity parameters and the transition strengths. These JO parameters are used to calculate the radiative transition probabilities, the radiation lifetimes and the branching ratios. The results obtained are in good agreement with those of other fluoride laser materials. We also carried out luminescence measurements for red and green emission. The studied host may offer infrared and visible laser emissions.

Upconversion emission investigation of Tb3+/Yb3+ codoped CdF2 single crystals under infrared laser pump

Tb3+/Yb3+ co-doped CdF2 single crystals were successfully fabricated by the Bridgman technique from a vacuum furnace in fluoride atmosphere. The structural and luminescent properties were investigated by X-ray diffraction, optical absorption and luminescence techniques at room temperature. The emission spectra exhibit a weak blue and green emission under 350 nm excitation and a strong emission under 975 nm in the spectral range 450 – 510 nm and 510 – 570 nm which are assigned to 5D4 → 7F6 and 5D4 → 7F5 transitions of Tb3+ ions, respectively. Furthermore, the time resolved decay time spectra are also obtained using pulse laser. The obtained upconversion spectra under 940 nm diode laser excitation at different powers showed the two-photon absorption process responsible of blue, green and red emissions.

Temperature sensor for scanning thermal microscopy based on photoluminescence of microcrystal

A new sensor is developed for measuring local temperatures. This sensor is based on a thermal-resistive probe and on photoluminescence of crystal. The final purpose is to develop a device calibrated in temperature and capable of acquiring images of local temperature at sub-micrometric scale. Indeed, the sensor temperature can be obtained in two distinct ways: one from the thermal probe parameters and the other from the green photoluminescence generated in the anti- Stokes mode by the Er ions directly excited by a red laser. The thermal probe is in Wollaston wire whose thermal-resistive element is in platinum/rhodium. Its temperature is estimated from the probe electrical characteristics and a modelling. A microcrystal of Cd0.7Sr0.3F2: Er3+(4%)-Yb3+(6%) about 25μm in diameter is glued at the probe extremity. This luminescent material has the particularity to give an emission spectrum with intensities sensitive to small temperature variations. The crystal temperature is estimated from the intensity measurements at 522, 540 and 549 nm by taking advantage of particular optical properties due to the crystalline nature of Cd0.7Sr0.3F2: Er3+-Yb3+. The temperature of probe microcrystal is then assessed as a function of electric current in the thermal probe by applying the Boltzmanns equations. The first results will be presented and discussed.