Energy transfer in Tm,Ho:KYW crystal and diode-pumped microchip laser operation

An investigation of Tm-Ho energy transfer in Tm(5at.%), Ho(0.4at.%):KYW single crystal by two independent techiques was performed. Based on fluorescence dynamics measurements, energy transfer parameters P71 and P28 for direct (Tm→Ho) and back (Ho→Tm) transfers, respectively, as well as equilibrium constant Θ were evaluated. The obtained results were supported by calculation of microscopic interaction parameters according to the Förster-Dexter theory for a dipoledipole interaction. Diode-pumped continuous-wave operation of Tm,Ho:KYW microchip laser was demonstrated, for the first time to our knowledge. Maximum output power of 77 mW at 2070 nm was achieved at the fundamental TEM00 mode

ПРИМЕНЕНИЕ МЕТОДОВ ФЮХТБАУЭРА–ЛАДЕНБУРГА И СООТВЕТСТВИЯ ДЛЯ ОПРЕДЕЛЕНИЯ СПЕКТРОВ СЕЧЕНИЙ СТИМУЛИРОВАННОГО ИСПУСКАНИЯ НЕОДИМОВЫХ ЛАЗЕРНЫХ СРЕД

Rare-earth doped crystals with broad bands of gain spectra are attractive for femtosecond laser applications. Therefore, for this purposes crystals with disordered structure are of great interest. In this article we investigate laser-related spectroscopic properties of new trigonal crystals Nd3+:Ca10K(VO4 )7 (Nd:CKV), Nd3+:Ca9 La(VO4 )7 (Nd:CLaV) и Nd3+:Ca10Li(VO4 )7 (Nd:CLiV). The Füchtbauer-Ladenburg equation and the integral reciprocity method were applied for determination of stimulated emission cross section spectra for Nd3+ ions. The maximum values of emission cross sections and bandwidth (FWHM) near λ = 1,07 μm are 9,33·10 -20cm2 (σ – polarization, Nd:CKV) and 30 nm (π – polarization, Nd:CKV), near λ = 1,35 μm – 1,55·1020cm2 and 50 nm (π – polarization, Nd:CKV). The broad and smooth bands of the gain spectra in the regions near 1,07 and 1,35 μm make it possible to generate ultra short light pulses with duration of about 60 fs (1,07 µm) and 45 fs (1,35  µm) in the mode-locking regime. Для создания лазеров, генерирующих импульсы ультракороткой длительности, представляют большой интерес лазерные материалы с широкими полосами усиления. В этой связи значительный интерес представляют структурно разупорядоченные материалы, в частности новые кристаллические среды, принадлежащие тригональной сингонии Nd3+:Ca10K(VO4 )7 (Nd:CKV), Nd3+:Ca9 La(VO4 )7 (Nd:CLaV) и Nd3+:Ca10Li(VO4 )7 (Nd:CLiV). В данной работе формула Фюхтбауэра-Ладенбурга и интегральный метод соответствия применены для определения спектров сечений стимулированного испускания указанных выше кристаллов на переходах 4 F3/2 → 4 I9/2, 4 F3/2 → 4 I11/2, и 4 F3/2 → 4 I13/2 иона неодима. Максимальные пиковые значения сечений стимулированного испускания и наибольшие спектральные ширины полос в области 1,07 мкм составляют 9,33·10-20 см2 (σ-поляризация, Nd:CKV) и 30 нм (π-поляризация,  Nd:CKV), в области 1,35 мкм – 1,55·10-20 см2 и 50 нм (π-поляризация, Nd:CKV). Полосы стимулированного испускания, а следовательно, и усиления в областях спектра 1,07 и 1,35 мкм являются гладкими и бесструктурными с ширинами, позволяющими получать ультракороткие импульсы света с длительностью  ≈  60 фс (1,07 мкм), ≈ 45 фс (1,35 мкм) в лазерах на исследованных лазерных средах, работающих в режиме синхронизации мод.

Temperature dependence of green upconversion fluorescence of fluorophosphate and tellurite-barium glasses for application in temperature sensors

Temperature dependences are studied of green upconversion fluorescence of the five erbium- and ytterbium-doped glasses (three fluorophosphate glasses, one of which is additionally doped with Tm, and two tellurite-baruim ones) in the temperature range from 30°C to 150°C. The ratio of intensities is determined of two fluorescence bands at about 515-525 nm and 540-560 nm versus the specimen temperature. The sensitivity of temperature measurement is found and a comparison of the glasses is performed according to this characteristic

APPLICATION OF FÜCHTBAUER–LADENBURG EQUATION AND RECIPROCITY METHOD FOR DETERMINATION OF EMISSION CROSS SECTIONS OF ND-DOPED LASER MEDIA

Rare-earth doped crystals with broad bands of gain spectra are attractive for femtosecond laser applications. Therefore, for this purposes crystals with disordered structure are of great interest. In this article we investigate laser-related spectroscopic properties of new trigonal crystals Nd3+:Ca10K(VO4 )7 (Nd:CKV), Nd3+:Ca9 La(VO4 )7 (Nd:CLaV) и Nd3+:Ca10Li(VO4 )7 (Nd:CLiV). The Füchtbauer-Ladenburg equation and the integral reciprocity method were applied for determination of stimulated emission cross section spectra for Nd3+ ions. The maximum values of emission cross sections and bandwidth (FWHM) near λ = 1,07 μm are 9,33·10 -20cm2 (σ – polarization, Nd:CKV) and 30 nm (π – polarization, Nd:CKV), near λ = 1,35 μm – 1,55·1020cm2 and 50 nm (π – polarization, Nd:CKV). The broad and smooth bands of the gain spectra in the regions near 1,07 and 1,35 μm make it possible to generate ultra short light pulses with duration of about 60 fs (1,07 µm) and 45 fs (1,35  µm) in the mode-locking regime

Energy transfer in Tm,Ho:KYW crystal and diode-pumped microchip laser operation

An investigation of Tm-Ho energy transfer in Tm(5at.%), Ho(0.4at.%):KYW single crystal by two independent techiques was performed. Based on fluorescence dynamics measurements, energy transfer parameters P71 and P28 for direct (Tm→Ho) and back (Ho→Tm) transfers, respectively, as well as equilibrium constant Θ were evaluated. The obtained results were supported by calculation of microscopic interaction parameters according to the Förster-Dexter theory for a dipoledipole interaction. Diode-pumped continuous-wave operation of Tm,Ho:KYW microchip laser was demonstrated, for the first time to our knowledge. Maximum output power of 77 mW at 2070 nm was achieved at the fundamental TEM00 mod

Growth and spectroscopic properties of Sm3+:KY(WO4)2 crystal

A Sm3+:KY(WO4)2 crystal was grown by the modified Czochralski technique. Polarized absorption and fluorescence spectra, as well as a fluorescence decay curve, were recorded at room temperature. Radiative properties such as emission probabilities, branching ratios and radiative lifetimes were investigated within the framework of the Judd-Ofelt theory as well as the theory of f-f transition intensities which takes into account the influence of the excited configurations. Emission cross section spectra were determined. 4G5/2 fluorescence decay was analyzed within the framework of the Inokuti-Hirayama model. The spectroscopic properties of Sm:KYW crystal were compared with those of other Sm3+-doped materials

Ca10Li(VO4)7:Nd3+\mathrm{Ca_{10}Li(VO_{4})_{7}:Nd^{3+}}, a promising laser material: growth, structure and spectral characteristics of a Czochralski-grown single crystal

Pure and Nd-doped Ca$_{10}$Li(VO$_{4}$)$_{7}$ single crystals were grown by the Czochralski method. The structure of Ca$_{10}$Li(VO$_{4}$)$_{7}$ single crystal was refined starting from a model of Ca$_{10}$K(VO$_{4}$)$_{7}$ using the powder diffraction data collected at a laboratory high-resolution diffractometer. The defect structure of the single crystal was studied with the use of both, high-resolution diffraction using a laboratory instrument and X-ray topographic techniques employing synchrotron radiation at the Hasylab laboratory (Hamburg). Polarized absorption and luminescence spectra of Nd-doped Ca$_{10}$Li(VO$_{4}$)$_{7}$ crystal were investigated in details. The laser oscillation was obtained under flash lamp pumping and the slope efficiency of 0.87% was achieved in the free-running mode. Preliminary examination of lasing properties points that Ca$_{10}$Li(VO$_{4}$)$_{7}$:Nd crystal can be a highly efficient solid state laser medium. Crystals of this kind are expected to be suitable for application as efficient non-linear optics materials

Growth, spectroscopic and thermal properties of ND-doped disordered CA 9 (LA/Y) (VO4) 7 and CA10 (LI/K) (VO 4)7 crystals

Pure and Nd-doped disordered calcium vanadate Ca10K (VO4)7, Ca10Li(VO4)7, Ca9La(VO4)7 and Ca9Y(VO4)7 single crystals with high optical quality were grown by Czochralsky technique in inert atmosphere. Their polarized absorption spectra were investigated in details. Spectroscopic parameters for Nd3+ ion were determined with Judd– Ofelt theory (J–O) and theory of f–f transition intensities for systems with intermediate or anomalously strong configuration interaction (ICI or ASCI approximation). Spectral and temporal characteristics of luminescence associated with 4F3/2→4I9/2, 4I11/2 and 4I13/2 transitions were analyzed, luminescence branching ratios and radiative lifetimes were calculated. Thermal expansion coefficients were determined for Ca9La(VO4)7 and Ca9Y(VO4)7 crystals in the directions of a and c crystallographic axes. Principal thermo-optic coefficients dno/dT and dne/dT were measured for Ca9La(VO4)7 crystal in the spectral range of 0.4–1.1 μm