Z. M. Yang

An efficient compact 300 mW narrow-linewidth single frequency fiber laser at 1.5 μm

An efficient single frequency fiber laser by using a newly-developed Er(3+)/Yb(3+) co-doped single mode phosphate glass fiber with the net gain coefficient of 5.2 dB/cm and propagation loss coefficient of 0.04 dB/cm has been demonstrated. Over 300 mW stable continuous -wave single transverse and longitudinal mode seed lasering at 1.5 microm has been achieved from a 2.0 cm-long active fiber. The measured slope efficiency and the calculated quantum efficiency of laser emission are found to be 30.9% and 0.938 +/- 0.081, respectively. It is found that the linewidth of the fiber laser is less than 2 kHz, and the measured relative intensity noise (RIN) is around -120 dB/Hz in the frequency range of 50 to 500 kHz.

Enhanced 2.0 μm emission and gain coefficient of transparent glass ceramic containing BaF 2 : Ho 3+ ,Tm 3+ nanocrystals

Transparent glass ceramic containing BaF(2):Ho(3+),Tm(3+) nanocrystals has been prepared by melt quenching and subsequent thermal treatment. The precipitation of BaF(2) nanocrystals was confirmed by X-ray diffraction and high-resolution transmission electron microscopy. Intense 2.0 microm fluorescence originating from Ho(3+): (5)I(7) --> (5)I(8) transition was achieved upon excitation with 808 nm laser diode. A large ratio of forward Tm(3+) --> Ho(3+) energy transfer constant to that of backward process indicated high efficient energy transfer from Tm(3+)((3)F(4)) to Ho(3+)((5)I(7)), benefited from the reduced ionic distances of Tm(3+)-Tm(3+) and Tm(3+)-Ho(3+) pairs and low phonon energy environment with the incorporation of rare-earth ions into the precipitated BaF(2) nanocrystals. The results indicate that glass ceramic is a promising candidate material for 2.0 microm laser.

Thermal stability and spectroscopic properties of Er3+-doped antimony-borosilicate glasses

This paper reports on the optical spectroscopic properties and thermal stability of Er3+-doped antimony-borosilicate glasses for developing 1.5 microm optical amplifiers. Upon excitation at 980 nm laser diode, an intense 1.5 microm infrared fluorescence has been observed with the maximum full width at half maximum (FWHM) of 90 nm for Er3+-doped antimony-borosilicate glasses. The emission cross-section and the lifetime of the 4I13/2 level of Er3+ ions are 6.3 x 10(-21) cm2 and 0.30 ms, respectively. It is noted that the product of the emission cross-section and FWHM of the glass studied is as great as 567 x 10(-21) cm2 nm, which is comparable or higher than that of bismuthate and tellurite glasses.

3-Dimensional heat analysis in short-length Er 3+ /Yb 3+ co-doped phosphate fiber laser with upconversion

A 3-dimenstional (3D) heat flow model of laser diode (LD) pumped short-length Er(3+)/Yb(3+) heavily co-doped phosphate fiber laser that includes the energy-transfer upconversion (ETU) effects has been developed. The fully 3D analytical solution with the consideration of longitudinal heat flow has been given to describe the temperature distribution in phosphate fiber. The calculated results show that both ETU processes and longitudinal heat conduction have a great influence on the fiber laser performance. Finally, we have validated the analytical expression by measuring the temperature distribution of an end-pumped short-length Er(3+)/Yb(3+) co-doped fiber laser, which was placed into the copper tube.

Energy transfer between Yb3+ and Er3+ in barium gallogermanate glass

Spectroscopic properties of Er3+/Yb3+ codoped barium gallogermanate glass demonstrate that an efficient energy transfer from Yb3+ to Er3+ ions occurs while the back energy transfer from Er3+ to Yb3+ ions cannot be ignored. Based on the rate equations of electron transitions, the forward energy transfer Yb3+(F25/2)+Er3+(I415/2)→Yb3+(F27/2)+Er3+(I411/2) and the back transfer Er3+(I411/2)+Yb3+(F27/2)→Er3+(I415/2)+Yb3+(F25/2) coefficients were calculated to be 9.2×10−17 cm3 s−1 and 1.1×10−17 cm3 s−1, respectively. Also the energy transfer upconversion coefficient Yb3+(F25/2)+Er3+(I411/2)→Yb3+(F27/2)+Er3+(F27/2) was determined to be 1.1×10−16 cm3 s−1. The calculated results show that a population inversion between the I413/2 and I415/2 levels can be attained at a low pumping flux of around 1.7×1022 cm−2 s−1, while the inversion threshold between the S43/2 and I415/2 levels is about 30 times higher when pumped by 980 nm laser diode. With increasing pump flux the back energy transfer probability becomes larger a...

Synthesis and optical properties of two novel stilbene derivatives containing 1,3,4-oxadiazole moiety.

Two novel stilbene derivatives containing 1,3,4-oxadiazole moiety were synthesized and characterized by elemental analyses, (1)H NMR, MS. The photophysical processes of the title compounds were investigated by UV-vis absorption and fluorescence emission spectra in different solutions. The fluorescence quantum yield (Phi) of 1a and 1b in THF is 0.65 and 0.69, respectively. The influence of the solution on the fluorescence intensities was also discussed. Under ultraviolet light excitation, the two compounds exhibit strong blue fluorescence emission. They may serve as potential applications in organic electroluminescent materials.

Enhanced broadband near-infrared emission from Bi-doped glasses by codoping with metal oxides

An intense broadband and flat 1.3 μm emission from Bi-doped germanate glass has been measured upon excitation with a commercial laser diode, which makes the glasses more attractive for their use in broadband optical fiber amplifiers. The 1.3 μm emission exhibits a distinctive fine luminescence shape with four bands centered at 1225, 1320, 1370, and 1390 nm, respectively. It is noted that the addition of CeO2 (2 mol %), As2O5 (2 mol %), or Y2O3 (1 mol %) into Bi-doped glasses could remarkably enhance the luminescence intensity by a factor of 4, 12, and 23, respectively. Whereas, no luminescence has been observed for the glass prepared under a controlled redox condition. The optical properties of the Bi-doped glasses and the possible mechanism involved have been explained.

Ultrabroadband sensitization of near infrared emission through energy transfer from Pb to Yb ions in LiYbMo2O8:Pb

Ultrabroadband sensitization of near infrared emission through energy transfer from Pb to Yb ions in LiYbMo2O8:Pb has been achieved upon ultraviolet (UV)-blue light excitation varying from 300 to 450 nm. The excitation band at 300–370 nm can be assigned to the charge transfer state of MoO42− groups, while the band at 370–450 nm could be mainly ascribed to charge transfer from Pb2+ to Yb3+ with a possible additional partial absorption contribution of Pb3+. Application of these phosphors in silicon-based solar cells might enhance its UV-blue response via spectrum modification.

Near-infrared quantum splitting in Ho 3+ :LaF 3 nanocrystals embedded germanate glass ceramic

We report on a sequential two-step near-infrared quantum splitting in Ho3+-doped germanate glass ceramics (GC). The formation of LaF3 nanocrystals is confirmed by X-ray diffraction and transmission electron microscopy analysis. Emission of two NIR photons at 1013 and 1190 nm for one incident photon absorption within the 300-560 nm region has been demonstrated by static and dynamic photoemission and excitation spectroscopy. Using the spectroscopic parameters calculated from Judd-Ofelt theory, the quantum efficiency of Ho3+ in GC sample is estimated to be approximately 110%.

Analytical investigation on transient thermal effects in pulse end-pumped short-length fiber laser

The transient heat conduction and thermal effects in pulse end-pumped fiber laser are modeled and analytically solved. For the arbitrary temporal shape of pump pulse, a three-dimensional (3D) temperature expression is derived via an integral transform method, and the thermal stress field is deduced through solving the Navier displacement equations. The results show that pulse shape has an important influence on the peak thermal stress and transient phase shift induced by heating of the fiber. Reasonable design for pulse duration and period can reduce thermal effects and optimize the performance of high-power fiber laser.