Zhang Qin-Yuan

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.

A Compact Low Noise Single Frequency Linearly Polarized DBR Fiber Laser at 1550 nm

A compact low noise single frequency linearly polarized distributed Bragg reflector (DBR) fiber laser based on a 1.4-cm-long homemade Er3+/Yb3+ -codoped phosphate single mode glass fiber has been demonstrated. An over 50 mW stable single frequency linearly polarized fiber laser was achieved. The measured slope efficiency is more than 21.6%, and the signal-to-noise ratio (SNR) is higher than 65 dB and the laser linewidth is less than 2.0kHz. The laser RIN is measured to be less than −150 dB/Hz at the frequencies over 2.0MHz, and the obtained linear polarization extinction ratio (LPER) is more than 30 dB.

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.

Gain Characteristics of Er3+-Doped Phosphate Glass Fibres

An erbium-doped phosphate glass fibre has been drawn by the rod-in-tube technique in our laboratory. The gain for the Er3+-doped phosphate glass fibre with different pump powers and with different input signal wavelengths is investigated. The 2.2-cm-long fibre, pumped by a single-mode 980-nm fibre-pigtailed laser diode, can provide a net gain per unit length greater than 1.8 dB/cm. The pump threshold is about 50 mW at the wavelength of 1534 nm, and below 70 mW at 1550 nm. The gain linewidth of the Er3+-doped phosphate glass fibre is greater than 34 nm and can cover the C band in optical communication networks.

Er3+/Yb3+ Codoped Phosphate Glass Fibre with Gain per Unit Length Greater Than 3.0 dB/cm

We experimentally study a novel fibre with high gain per unit length based on the homemade erbium–ytterbium codoped phosphate glass. The gain and noise characterizations with different pump powers at different wavelengths are investigated. The 1.8-cm-long fibre, dual-pumped by two single mode 980-nm fibre-pigtailed laser diodes, provides a gain per unit length greater than 3.0 dB/cm and a noise figure less than 6.5 dB. The gain saturation behaviour at 1535 nm is obtained and the saturation output power (3 dB compression) is greater than 5 dBm.

Spectroscopic properties and thermal stability of Er3+/Yb3+-codoped fluorophosphate glasses

A comprehensive study on the thermal stability and spectroscopic properties of Er3+/Yb3+-codoped Al(PO3)3-based fluorophosphate glasses is reported of the 1.5μm fibre amplifiers in this paper. From optical absorption spectra, the Judd–Ofelt parameters of Er3+ in the glasses and several important optical properties, such as the radiative transition probability, the branching ratio and the spontaneous emission probability, have been calculated by using Judd–Ofelt theory. The fluorophosphate glass exhibits broadband near-infrared emission at 1.53 μm with a full width at half-maximum over 63nm and a large calculated stimulated-emission cross-section of 6.85×10−21cm2.

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.