Jiang Zhong-Hong

Efficient Fibre Amplifiers Based on a Highly Er3+/Yb3+ Codoped Phosphate Glass-Fibre

Highly Er3+/Yb3+-codoped single-mode phosphate glass fibre is fabricated by the rod-in-tube technique. The performances of high-concentration Er3+/Yb3+-codoped phosphate glass fibre amplifiers are investigated and discussed. An efficient optical fibre amplifier with a gain of 12.6 dB based on a 3.0 cm long Er3+/Yb3+-codoped phosphate glass fibre is demonstrated under a dual-pump configuration with two 976 nm fibre-pigtail laser diodes, which make it attractive for compact Er3+ -doped fibre amplifiers. The obtained noise figures of signal wavelength from 1525 to 1565 nm are less than 6.0 dB. Gain saturation behaviour at 1535 nm is also investigated, and the obtained saturation output power is larger than 10 dBm.

Tm3+-doped Ga2O3-GeO2-Bi2O3-PbO(PbF2) Glasses for 1.47-μm Optical Amplifications

We report the spectroscopic properties and thermal stability of Tm3+-doped Ga2O3–GeO2–Bi2O3–PbO(PbF2) glasses for 1.47-μm optical amplifications. Effects of PbF2 doping on the optical properties and thermal stability of Tm3+-doped gallate–germanium–bismuth–lead glass are investigated. The measured peak wavelength and full width at half-maximum of the fluorescence are 1465 nm and ~120 nm, respectively. Significant enhancement of the 1.47-μm emission and the lifetime of a 3H4 level with increasing PbF2 doping have been observed. The presence of GeO2 provides two potentials of increasing the thermal stability and shortening the ultraviolet cutoff band of host glasses.

Effect of network modifiers on spectroscopic properties of erbium-doped phosphate glasses

The integrated absorption cross section Σabs, peak emission cross section σemi, Judd-Ofeld intensity parameters Ωt (t=2,4,6), and spontaneous emission probability ArR of Er3+ ions were determined for Erbium doped alkali and alkaline earth phosphate glasses. It is found the compositional dependence of σemi is almost similar to that of Σabs, which is determined by the sum of Ωt(3Ω2 + 10Ω4 + 21Ω6). In addition, the compositional dependence of Ωt was studied in these glass systems. As a result, compared with Ω4 and Ω6, the Ω2 has a stronger compositional dependence on the ionic radius and content of modifiers. The covalency of Er-O bonds in phosphate glass is weaker than that in silicate glass, germanate glass, aluminate glass, and tellurate glass, since Ω6 of phosphate glass is relatively large. AR is affected by the covalency of the Er3+ ion sites and corresponds to the Ω6 value.

Laser Characteristics of Cladding-Pumped Short Er3+/Yb3+ Codoped Single Mode Phosphate Glass Fibre

We experimentally investigate the laser characteristics of a series of short pieces of newly-developed Er3+/Yb3+ codoped single mode phosphate glass fibres via the cladding pump of a 976nm multimode laser diode. A stable continuous-wave single transverse mode laser with over 85mW at 1553 nm is generated from a 5.5-cm-long active fibre. Single mode laser output power per unit length is up to 15mW/cm. Moreover, the slope efciency is 11.8% when the pump power is below 940mW and the 3dB linewidth is 0.06nm at the maximum pump power. The numerical simulation results show that the laser emission slope efficiency can exceed 20% by means of increasing the coupling efficiency of the pump to the fibre core further.

Broadband amplified spontaneous emission from Er3+-doped single-mode tellurite fibre

This paper reports on the fabrication and characterization of a newly erbium-doped single-mode tellurite glass-fibre applicable for 1.5-μm optical amplifiers. A very broad erbium amplified spontaneous emission in the range 1450–1650 nm from erbium-doped single-mode tellurite glass-fibre is obtained upon excitation of a 980-nm laser diode. The effects of the length of glass-fibre and the pumping power of laser diode on the amplified spontaneous emission are discussed. The result indicates that the tellurite glass-fibre is a promising candidate for designing fibre-optic amplifiers and lasers.

What is the nature of glassy state

Glasses, non-crystalline solids, and amorphous materials are presently playing increasingly important roles in modern technology. In addition to conventional glass, which is an indispensable material in the current economy in architecture, transport, lighting, and environmental control, a wide variety of glasses and amorphous materials are used in increasingly sophisticated applications in optics, electronics, optoelectronics, energy science and biotechnologies. Glass is considered a vitreous supercooled liquid that is in a thermodynamically metastable state between the molten liquid state and the crystalline state. This unique property of glass is different from the solid, liquid, and gaseous states observed for other elements. The vitrification of a liquid to form a glass is often related to glass transition. This process is a complex dynamic system with multi-body interactions, and hence glass transition is still an unsolved problem in condensed matter physics up to the present time. The formation of glasses is an extremely interesting phenomenon. In terms of thermodynamic phase equilibrium, no substance should persist in the glassy state because glass is a metastable state. However, in terms of kinetics, any material can form a glassy state as long as the cooling rate and the melting viscosity are sufficiently high to prevent crystallization. A comprehensive understanding of the nature of glass formation and the factors that predominantly dominate the glass-forming ability and glass-forming regions of materials is of fundamental importance for advancing the technological applications of glasses. Glass structure is another essential question in glass science. Great efforts have been invested to develop a universal model to represent all glass structures. However, the concept of a universal structure model is incompatible with the fact that the vitreous state is in a thermodynamically metastable state because a specific structure can only arise in a thermodynamically stable state. To date, theories proposed on glass structures are based on various models rather than on the variability and diversity of glass structures in thermodynamically metastable states. The controversy surrounding the glass structure hypotheses lies in the estimation of the degree of order or disorder. While whether or not glass is an ordered state has long been a topic of debate, the structure-properties relationships are not much addressed. Understanding the nature of the glassy state is the key to the development of new glasses with improved properties and manufacturability for various engineering applications. In 2005, the question of “What is the nature of glassy state” was suggested one of the greatest scientific conundrum for science’s 125th anniversary. Herein, the present review strives to provide a comprehensive review of the recent progress made in understanding glassy state and describes the technological developments driven by this new information, especially on the basic scientific problems of glass transition, physical mechanism and theoretical prediction of glass formation, and glass structure hypotheses and technological developments. Finally, we discussed the current progress and the challenges on the nature of glassy state, and suggested possible research directions.

Recent advances in rare-earth-doped photonic glasses for near- and mid-infrared lasers

Rare-earth (RE) doped photonic glasses exhibit potential applications in the area of optical communication, laser lidar, remote sensing, infrared detection, and biomedical. Up to now, the widely used silica based photonic glasses encounted intrinsic limitations such as lower rare-earth doping concentration, narrower emission band, larger phonon energy, and lower gain coefficients. Therefore, it is necessary to study and develop novel photonic glasses and fibers to meet the needs of new wavelength bands, especially the near-and mid-infrared materials and devices. In this paper, the important applications of RE doped photonic glasses in optical fiber amplifiers and fiber lasers are briefly described. The basic requirements for realizing near-and mid-infrared luminescence and laser are summarized. The latest research progress in RE doped photonic glasses, fibers, and devices are reviewed with special emphasis on 1.0, 1.5, 2.0 and 3.0 μm wavelength bands. In addition, challenges, applications, and future advances of the near-and mid-infrared luminescence and laser in RE doped photonic glasses have also been dealt with.

Laser-diode excited intense upconversion luminescenceof Er3+ in bismuth–lead–germanate glasses

We have investigated infrared-to-visible upconversion luminescence of Er3+ in bismuth–lead–germanate glasses. The UV cutoff wavelength is shortened while its lifetime is increased almost linearly, with PbF2 substituting for PbO in the bismuth–lead–germanate glasses. Three emissions centred at around 529, 545 and 657 nm are clearly observed, which are identified as originating from the 2H11/2→4I15/2,4S3/2→4I15/2 and 4F9/2→4I15/2 transitions, respectively. It is noted that all the upconversion emission intensities increase with PbF2 concentration increasing. The ratio between the intensities of red and green emissions increases with the increasing of PbF2 content. Energy transfer processes and nonradiative phonon-assisted decays account for the populations of the 2H11/2,4S3/2 and 4F9/2 levels. The quadratic dependence of fluorescence on excitation laser power confirms a two-photon process to contribute to the upconversion emissions.

Structural and Luminescence Properties of Transparent Nanocrystalline ZrO2:Er3+ Films

The structural and luminescence properties of nanocrystalline ZrO2:Er3+ films are reported. Transparent nano-ZrO2 crystalline films doped with Er3+ have been prepared using a wet chemistry process. An intense room-temperature emission at 1527 nm with a full width at half-maximum of 46 nm has been observed, which is assigned to the 4I13/2 → 4I15/2 intra-4fn electric transition of Er3+. Correlations between the luminescence properties and structures of the nanocrystalline ZrO2:Er3+ films have been investigated. Infrared-to-visible upconversion occurs simultaneously upon excitation of a commercially available 980-nm laser diode and the involved mechanisms have also been explained. The results indicate that the nanocrystalline ZrO2:Er3+ films might be suggested as promising materials for achieving broadband Er3+-doped waveguide amplifiers and upconversion waveguide lasers.