Применение метода отклонения лазерного пучка для определения термооптических коэффициентов в кристалле гадолиний-иттриевого ортосиликата, легированного ионами эрбия

Results of use of the laser beam deflection technique for determination of thermo-optic coefficients (TOCs) of the Er3+-doped gadolinium-yttrium oxyorthosilicate crystal (Er3+:(GdY) SiO– Er:GYSO) are presented. A 0.1 at.% Er-doped gadolinium-yttrium oxyorthosilicate crystal was grown by the Czochralski method under nitrogen atmosphere. Raw materials such as Er2O3, Gd2O3, Y2O3, and SiO2 were weighed according to the formula (Er0.001Gd0.8995Y0.0995)2SiO5. Optical properties of the biaxial Er:GYSO crystal are described within the frame of the optical indicatrix with orthogonal principal axes Np , Nm , and Ng . To characterize the anisotropy of the TOCs a sample from the grown Er:GYSO crystal was prepared in a shape of a rectangular parallelepiped with dimensions of 7.0 (Np ) × 8.0 (Nm ) × 8.5 (Ng ) mm3. Each face of the sample is perpendicular to one of the optical indicatrix axes Np , Nm and Ng . For determination of the TOCs the laser beam deflection technique for a material with a linear temperature gradient is used. Measurements are performed at the wavelength of 632.8 nm. The thermal coefficient of the optical path (TCOP) for the Er:GYSO crystal measured at the wavelength of 632.8 nm at different light polarization E and propagation direction k were obtained. The TCOP values are positive for all directions of the light propagation k // Np , Nm , Ng . This means that the sign of the thermal lens which is directly related to the TCOP value will also be positive, and the positive thermal lens is then expected for Np Nm-, and Ng -cut Er:GYSO. Applying an analysis of the thermal lensing the dn /dT value for Yb:GYSO is estimated to be 6.5×10–6 K–1.  В статье представлены результаты использования метода отклонения лазерного пучка для определения величин термооптических коэффициентов (ТОК) в кристалле гадолиний-иттриевого ортосиликата, легированного ионами эрбия Er3+ (Er3+:(GdY)2SiO5– Er:GYSO). Кристалл Er:GYSO, легированный ионами эрбия в количестве 0,1 ат.%, выращен методом Чохральского в атмосфере азота. Шихта состояла из оксидов Er2O3, Gd2O3, Y2O3 и SiO2 в пропорции, соответствующей формуле (Er0.001Gd0.8995Y0.0995)2SiO5. Оптические свойства кристалла Er:GYSO описываются на основе оптической индикатрисы с тремя ортогональными главными осями Np , Nm  и Ng . Для характеризации TOК использовался образец кристалла Er:GYSO в форме прямоугольного параллелепипеда размером 7,0 (Np) × 8,0 (Nm ) × 8,5 (Ng ) мм3. Грани образца перпендикулярны осям оптической индикатрисы Np , Nm  и Ng . Метод отклонения лазерного пучка в результате распространения через исследуемый материал, в котором создан линейный градиент температуры, использован для определения TOК. Измерения проведены на длине волны 632,8 нм. Установлены также термические коэффициенты оптического пути (TКOП) для кристалла Er:GYSO на длине волны 632,8 нм для различных поляризаций света E и волнового вектора k. Величины TКOП являются положительными для всех направлений распространения света k // Np , Nm , Ng . Это означает, что знак термической линзы, которая непосредственно связана с величиной TКOП, будет также положительным и, следовательно, положительная термическая линза будет наблюдаться в кристалле Er:GYSO, вырезанном вдоль направлений Np , Nm  и Ng . Из анализа значений термической линзы величина dn/dT в кристалле Yb:GYSO оценена как 6,5×10–6 K–1

All-space existence and dispersion of athermal directions in monoclinic KY(WO4)2

The analytical expressions for thermo-optic coefficients, dn/dT, for “fast” and “slow” light waves propagating along the arbitrary direction in a biaxial crystal are derived. On the basis of these expressions, the all-space analysis of existence of athermal directions is performed for monoclinic and biaxial KY(WO4)2 at 1.03 μm. The calculations are performed for an arbitrary light propagation direction and polarization (not restricted to the principal planes). The appearance of directions that can be athermal for both “fast” and “slow” waves is predicted. The dispersion of athermal directions is analyzed for visible and near-IR. The existence of upper and lower dispersion limits for athermal behavior of KY(WO4)2 is shown. It is shown that the optical indicatrix axes can be athermal itself at some light wavelengths. Wavelength- and temperature-dependent position of the optical axes of KY(WO4)2 is also determined

Use of the Laser Beam Deflection Technique for Thermo-Optic Coefficients Study in Gadolinium-Yttrium Oxyorthosilicate Doped with Erbium Ions

Results of use of the laser beam deflection technique for determination of thermo-optic coefficients (TOCs) of the Er3+-doped gadolinium-yttrium oxyorthosilicate crystal (Er3+:(GdY)2SiO5 – Er:GYSO) are presented. A 0.1 at.% Er-doped gadolinium-yttrium oxyorthosilicate crystal was grown by the Czochralski method under nitrogen atmosphere. Raw materials such as Er2O3, Gd2O3, Y2O3, and SiO2 were weighed according to the formula (Er0.001Gd0.8995Y0.0995)2SiO5. Optical properties of the biaxial Er:GYSO crystal are described within the frame of the optical indicatrix with orthogonal principal axes Np , Nm , and Ng . To characterize the anisotropy of the TOCs a sample from the grown Er:GYSO crystal was prepared in a shape of a rectangular parallelepiped with dimensions of 7.0 (Np ) × 8.0 (Nm ) × 8.5 (Ng ) mm3. Each face of the sample is perpendicular to one of the optical indicatrix axes Np , Nm and Ng . For determination of the TOCs the laser beam deflection technique for a material with a linear temperature gradient is used. Measurements are performed at the wavelength of 632.8 nm. The thermal coefficient of the optical path (TCOP) for the Er:GYSO crystal measured at the wavelength of 632.8 nm at different light polarization E and propagation direction k were obtained. The TCOP values are positive for all directions of the light propagation k // Np , Nm , Ng . This means that the sign of the thermal lens which is directly related to the TCOP value will also be positive, and the positive thermal lens is then expected for Np - Nm-, and Ng -cut Er:GYSO. Applying an analysis of the thermal lensing the dn /dT value for Yb:GYSO is estimated to be 6.5×10–6 K–1

Thermo-optic coefficients of monoclinic Er3+:(GdY)2SiO5 crystal

Thermo-optic coefficients of the Er3+-doped gadolinium-yttrium oxyorthosilicate crystal Er3+:GdYSO are determined at a wavelength of 632.8 nm for light polarizations E // Np, Nm and Ng. Linear thermal expansion coefficients are estimated for this crystal in the directions of the optical indicatrix axes Nm and Ng

Anisotropy of the photo-elastic effect in Nd : KGd(WO4) 2 laser crystals

The anisotropy of thermal lensing and the photo-elastic effect is characterized for diodepumped Nd : KGd(WO4)2 crystals cut along the Np and Ng optical indicatrix axes and along its optical axis, O = Ng + 43°, at a laser wavelength of 1067 nm. Distortions in the spatial profile of the output laser beam are analyzed. The thermal lens is astigmatic; the orientation of its principal meridional planes, A and B, is determined by the anisotropy of photo-elastic effect. The thermal lens has opposite signs for rays lying in the principal meridional planes for Np- and O-cut crystals; it is positive for an Ng-cut crystal. The increase of thermal lens optical power after absorption of 1 W of pump power, i.e. the thermal lens sensitivity factors MA(B), and astigmatism degree S = |MA–MB| are determined. The photo-elastic effect was found to increase the optical power of the thermal lens and was significant for all studied crystal orientations

Luminescence of oxyfluoride glasses containing YB3+–RE3+ ions

The optical absorption and up-conversion luminescence of oxyfluoride glasses in the system SiO2–PbO–PbF2–CdF2 coactivated by Yb3+–RE3+ ions (where RE = Er, Tm, Ho, Dy, Pr, or Tb) are investigated. Excitation with a laser diode in the IR range (960 nm) gives intense green, blue, and red luminescence. The color characteristics of the up-conversion luminescence in the CIE 1931 system are determined. The efficiency of energy transfer from the Yb3+ to the RE3+ ions is found to be 70% for RE = Er, Tm, and Ho. The efficiency of cooperative energy transfer reaches 10% for glass with Yb–Tb ions

Stokes and anti-Stokes luminescence from cubic elpasolite Cs2NaYF6 crystals doped with Er3+and Yb3+ ions

Er3þ and Yb3þ doped cubic elpasolite Cs2NaYF6 crystals including stoichiometric compositions Cs2NaErF6 and Cs2NaYbF6 have been synthesized under hydrothermal conditions. Absorption, stimulated-emission and gain cross-sections spectra have been determined for the 2F5/2-2F7/2 (Yb3þ) and 4I13/2-4I15/2 (Er3þ) transitions at room-temperature. The maximum σSE values are 1.8 10 21 cm2 at 993 nm (Yb3þ) and 3.8 10 21 cm2 at 1535 nm (Er3þ). Elpasolite crystals provide exceptionally long radiative lifetimes of the excited-states for both ions, namely τ(2F5/2)¼6.3 ms and τ(4I13/2) 32 ms for 10 at% Yb3þ:Cs2NaYF6 and 10 at% Er3þ:Cs2NaYF6 which can be used in high pulse energy Q-switched lasers. Up-conversion luminescence has been studied for Er3þ doped and Er3þ, Yb3þ codoped Cs2NaYF6 crystals