Xiang Hua Zhang

Low loss optical fibres of the tellurium halide-based glasses, the TeX glasses

Abstract The TeX glasses based on the glass-forming ability of the TeX (X = Cl, Br, I) systems have potential low losses in the 8–12 μm region. Different glass compositions in the TeSeI and TeSeAsI systems have been chosen for fibre drawing. High purity glasses can be obtained by using special purification techniques. Fibres having a minimum attenuation as low as 0.4 dB/m have been drawn and the losses of these fibres are

Dy3+-doped stabilized GeGaS glasses for 1.3 μm optical fiber amplifiers

Abstract Dy 3+ -doped stabilized-GeGaS sulfide glasses are synthesized and characterized. When antimony is added to GeGaS, the glass shows very weak crystallization upon heating as compared to standard compositions. Because of the low phonon energy inherent in sulfide glasses, the 1.3 μm emission of Dy 3+ ions can be observed. This transition is characterized in terms of emission cross-section and quantum efficiency.

Telluride Glass Step Index Fiber for the far Infrared

Nulling interferometry is an important technique under development for the DARWIN planet finding mission which enables the detection of the weak infrared emission lines of an orbiting planet. This technique requires the use of single mode optical fibers transmitting light as far as possible in the infrared. Tellurium based glasses transmit infrared light far beyond the second atmospheric window but are usually not stable enough toward crystallisation to be drawn into optical fiber. It was recently shown that the GeTe4 initial glass composition could be stabilized by the introduction of few percents of Se. In this paper, we report the development and the optical characterisation of far-infrared transmitting step index optical. The evolution of the refractive index of the glass versus the ratio Se/Te was measured in order to design a multi mode step index fiber. Its core diameter was 200 μm therefore permitting to easily characterise its optical properties. This multimode fiber transmitted light from 4 to about 15 μ m with losses near 20 dB.m-1. Despite these significant losses, the fiber was efficiently used to detect the broad absorption band of the CO2 located at 15 μm. These results are very promising in the context of the DARWIN mission of the European Space Agency.

Relaxation near room temperature in tellurium chalcohalide glasses

Structural relaxation during sub-T g annealing was monitored by DSC for three chalcohalide glasses with low glass transition temperatures: Te 3 I 3 Se 4 (T g =49°C), Te 3 Se 5 Br 2 (T g =71°C) and As 4 Se 3 Te 2 I (T g =118°C). On annealing at room temperature, the glass with the lowest T g relaxed to equilibrium within a few days, the glass with the intermediate T g showed substantial relaxation but did not fully equilibrate over a period of months, and the glass with the highest T g showed no relaxation in a two month period

Te-based chalcohalide glasses for far-infrared optical fiber

Tellurium based glasses have been studied for their optical properties in the far infrared region. New glasses, in the system Ge-Te-AgI, present a very good thermal stability. Indeed, for the first time, no obvious crystallization peak is observed in tellurium based glasses. Then, fibers have been drawn showing interesting optical losses and quite large transmission in the mid-infrared. So, these glasses are good candidates for the elaboration of single mode fibers able to detect the CO2 signature at 15µm for the ESA Darwin project.

Ga–Ge–Sb–Se based glasses and influence of alkaline halide addition

The quaternary Ga–Ge–Sb–Se system has been systematically studied and the glass-forming region has been determined. It has been found that there is a domain in which glasses do not crystallise when heated at a rate of 10°C/min. Optical properties of these glasses have been determined, showing transmission from 0.9 to 15 μm. The refractive index for the Ga5Sb10Ge25Se60 glass is 2.6709±0.0001 at 2 μm and 2.6198±0.00025 at 12 μm. Some attempts have been made to increase the band-gap by introducing 5–30 wt% of electronegative elements such as Cl2, Br2 or I2 in the form of alkaline halides. Refractive indices, optical transmission and chemical durability towards air and hot water of these new glasses have been measured. Results have been obtained with CsI addition and stable red coloured glasses have been synthesised, which are transparent to 14 μm.

Evaluation of glass fibers from the Ga–Ge–Sb–Se system for infrared applications

Abstract The overall properties of the Ga5Sb10Ge25Se60 glass fiber have been compared to the Te20As30Se40I10 glass fiber, which has been intensively studied for infrared applications. The first has a significantly higher glass transition temperature and better thermal mechanical properties, leading to stronger fibers. The second glass is transparent further in the infrared region. The infrared transmission cut-off is about 15 μm for the Ga5Sb10Ge25Se60 glass and 18 μm for the Te20As30Se40I10 glass. CO2 laser power delivery has been performed with these two fibers. Even with a significantly higher absorption, the Ga5Sb10Ge25Se60 glass fiber can withstand the same power level as the Te20As30Se40I10 glass fiber.

Optical microfabrication of tapers in low-loss chalcogenide fibers

We demonstrate the use of photoinduced fluidity in low-loss chalcogenide fibers for producing tapers with fine control of the diameter and geometry. The tapers produced this way act as sensing zones along chalcogenide glass fibers used for evanescent wave spectroscopy. The optical microfabrication method consists in irradiating the chalcogenide fiber with sub-bandgap laser light under a tensile stress. The resulting athermal photoinduced fluidity permits to produce tapers with good control over the geometry without altering the optical properties of the fiber. Gains in detection sensitivity greater than 1 order of magnitude are measured using these tapers.

Tellurium halide glass fibers : preparation and applications

Abstract Tellurium halide (TeX) glasses were prepared from high-purity raw materials which were purified in a silica set-up in order to eliminate the surface oxides. All the starting elements were then distilled. The rod in tube method was used to obtain TeX glass fibers having a core-cladding structure. The fiber attenuation was measured by using a Fourier-transform infrared (FTIR) spectrometer. The fiber losses, regularly obtained, were

Nonlinear characterization of GeS2–Sb2S3–CsI glass system

We present the results of Z-scan measurements (1064 nm, 17 ps) of nonlinear refractive indices and nonlinear absorption coefficients for different compositions of chalcogenide glasses in GeS2–Sb2S3–CsI system. We show that the simple well known Boling, Glass, and Owyoung model based on the theory of the semiclassical harmonic oscillator can be a useful tool for theoretical predictions of the nonlinear refractive index in these infrared glasses. A quasi-linear behavior is observed relating the nonlinear index and the linear one. Some of the compositions reveal properties potentially useful for all optical switching applications.