A. S. Gouveia-Neto

Upconversion fluorescence spectroscopy of Er3+/Yb3+-doped heavy metal Bi2O3–Na2O–Nb2O5–GeO2 glass

Upconversion fluorescence emission of Er3+/Yb3+-doped Bi2O3–Na2O–Nb2O5–GeO2 heavy metal glass samples excited at 1.06 μm is experimentally investigated. The results reveal the existence of intense emission bands centered around 520, 545, and 655 nm. The germano-niobate based host glass presents high transparency in the region of 400–2700 nm, the capability of incorporating high dopant concentrations, high melting temperature, and large resistance to atmospheric moisture. The observed intensity of the green fluorescence emission, suggested that the niobium based host glass material plays an important role in the efficiency of the upconversion process. Emission lines centered at 425, 483, 503, 608, and 628 nm were also observed.

Optical thermometry through infrared excited upconversion fluorescence emission in Er/sup 3+/- and Er/sup 3+/-Yb/sup 3+/-doped chalcogenide glasses

Optical thermometry based upon infrared excited upconversion fluorescence emission in Er/sup 3+/- and Er/sup 3+/-Yb/sup 3+/- doped Ga/sub 2/S/sub 3/-La/sub 2/O/sub 3/ chalcogenide glasses excited at 1.54 and 1.06 /spl mu/m, respectively, is presented. Temperature sensing in the region of 20/spl deg/C-220/spl deg/C with 0.3/spl deg/C accuracy using excitation powers readily obtainable from commercially available semiconductor lasers was achieved. The temperature sensing approach is independent of fluctuations in excitation intensity and transmission and requires a simple and low-cost signal detection and processing system. The results also indicate that the glassy host material plays a major role in the performance of the sensing system.

Red–green–blue upconversion emission and energy-transfer between Tm3+ and Er3+ ions in tellurite glasses excited at 1.064 μm

Red, green, and blue emission through frequency upconversion and energy-transfer processes in tellurite glasses doped with Tm 3+ and Er 3+ excited at 1.064 μm is investigated. The Tm 3+ /Er 3+ -codoped samples produced intense upconversion emission signals at around 480, 530, 550 and 660 nm. The 480 nm blue emission was originated from the 1 G 4 → 3 H 6 transition of the Tm 3+ ions excited by a multiphoton stepwise phonon-assisted excited-state absorption process. The 530, 550 nm green and 660 nm red upconversion luminescences were identified as originating from the 2 H 11/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of the Er 3+ ions, respectively, populated via efficient cross-relaxation processes and excited-state absorption. White light generation employing a single infrared excitation source is also examined.

Structural and spectroscopic study of oxyfluoride glasses and glass-ceramics using europium ion as a structural probe

Universidade Federal Rural de Pernambuco (UFRPE), Dept Fis, Lab Foton, BR-52171900 Recife, PE, Brazil

Twentyfold blue upconversion emission enhancement through thermal effects in Pr3+/Yb3+-codoped fluoroindate glasses excited at 1.064 μm

Infrared-to-visible upconversion emission enhancement through thermal effects in Yb3+-sensitized Pr3+-doped fluoroindate glasses excited at 1.064 μm is investigated. A twentyfold increase in the 485 nm blue emission intensity as the sample temperature was varied from 20 to 260 °C was observed. The visible upconversion fluorescence enhancement is ascribed to the temperature dependent multiphonon-assisted anti-Stokes excitation of the ytterbium sensitizer and excited-state absorption of the praseodymium acceptor. A model based upon conventional rate equations considering a temperature dependent effective absorption cross section for the 2F7/2→2F5/2 transition of the Yb3+ and 1G4→3P0 excited-state absorption of the Pr3+, agrees very well with the experimental results.

Infrared-to-visible frequency upconversion in Pr3+/Yb3+- and Er3+/Yb3+-codoped tellurite glasses

Abstract Upconversion luminescence and thermal effects in Pr 3+ /Yb 3+ - and Er 3+ /Yb 3+ -codoped 60TeO 2 –10GeO 2 –10K 2 O–10Li 2 O–10Nb 2 O 5 tellurite glasses excited by CW infrared radiation at 1.064 μm is reported. Generation of intense green and red fluorescence emission in Er 3+ /Yb 3+ -codoped samples and appreciable upconversion luminescence in the wavelength region of 450–680 nm in Pr 3+ /Yb 3+ -codoped samples is observed. Temperature-induced enhancement of ×12 in the upconversion efficiency in Er 3+ /Yb 3+ - and ×10 in the Pr 3+ /Yb 3+ -doped samples is demonstrated.

Blue cooperative luminescence in Yb3+-doped tellurite glasses excited at 1.064 μm

Blue luminescence emission around 480 nm through cooperative upconversion from pairs of Yb3+ ions implanted into 60TeO2–10GeO2–10K2O–10Li2O–10Nb2O5 tellurite glasses and excited by a cw laser at 1.064 μm is demonstrated. Cooperative luminescence emission enhancement owing to the temperature dependent multiphonon-assisted anti-Stokes excitation process of the ytterbium ions is also observed. The experimental results revealed a fourfold enhancement in the cooperative luminescence emission when the sample was heated in the temperature range of 20 °C–260 °C. The thermally induced enhancement is assigned to the effective absorption cross-section for the ytterbium ions which is an increasing function of the medium temperature.

Energy upconversion luminescence in neodymium-doped tellurite glass

Abstract Infrared-to-visible upconversion luminescence emission in Nd 3+ -doped 60TeO 2 –10GeO 2 –10K 2 O–10Li 2 O–10Nb 2 O 5 tellurite glasses under cw excitation around 800 nm is investigated. Blue (430, and 475 nm), green (530 nm) and yellow-orange (590 nm) energy upconversion emission owing to the 2 P 1/2 → 4 I j ( j =9/2, 11/2, 13/2 and 15/2) transitions of the Nd 3+ ions, respectively, was recorded. The dependence of the upconversion intensity upon the excitation wavelength and pump power is also studied. The upconversion excitation mechanism responsible for the observed emission signals is attributed to stepwise multiphoton absorption.

All optical integrated upconversion fluorescence-based point temperature sensing system using Er3+-doped silica-on-silicon waveguides

In this work an optically integrated and compact point temperature sensor based upon upconversion fluorescence emission in an Er3+-doped silica-on-silicon waveguide is proposed. The sensing system relies upon the temperature information residing in the intensity ratio of two thermally coupled upconversion excited fluorescence emission signals around 530 and 550 nm due to the Er3+ transitions 2H11/2→4I15/2 and 4S3/2→4I15/2, respectively. The system was tested in the range of temperature from 20 °C to 140 °C. Under this circumstance the system have shown sensitivity close to 9.0×10−3/°C with a coupled pump power around 800 nm as low as 7 mW and a maximum sensitivity of 0.010/°C is expected at 250 °C.

Efficient energy upconversion emission in Tm3+/Yb3+-codoped TeO2-based optical glasses excited at 1.064 μm

Efficient energy upconversion of cw radiation at 1.064 μm into blue, red, and near infrared emission in Tm3+-doped Yb3+-sensitized 60TeO2-10GeO2-10K2O-10Li2O-10Nb2O5 glasses is reported. Intense blue upconversion luminescence at 485 nm corresponding to the Tm3+ 1G4→3H6 transition with a measured absolute power of 0.1 μW for 800 mW excitation power at room temperature is observed. The experimental results also revealed a sevenfold enhancement in the upconversion efficiency when the sample was heated from room temperature to 235 °C yielding 0.7 μW of blue absolute fluorescence power for 800 mW pump power. High brightness emission around 800 nm (3F4→3H6) in addition to a less intense 655 nm (1G4→3H4 and 3F2,3→3H6) fluorescence is also recorded. The energy upconversion excitation mechanism for thulium emitting levels is assigned to multiphonon-assisted anti-Stokes excitation of the ytterbium-sensitizer followed by multiphonon-assisted sequential energy-transfer processes.