Development and Infrared Applications of Chalcogenide Glass Optical Fibers

Chalcogenide glass fibers based on sulphide, selenide, telluride, and their rare earth doped compositions are being actively pursued both at the Naval Research Laboratory in Washington, D.C. (NRL) and worldwide. Great strides have been made in reducing optical losses using improved chem ical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite this, current singlemode and multimode chalcogenide glass fibers are enabling numerous applications. Some of these applications include laser power delivery, chemical sensing, imaging, scanning near field microscopy spectroscopy, fiber infrared (IR) sources lasers, amplifiers, and optical switches. The authors assert that the research and development of chalcogenide glasses will grow in the foreseeable future, especially with respect to improvements the optical quality of the fibers and the performance of the fibers in existing future applications.     

Middle-infrared chalcogenide glass fibers with losses lower than 100 db km−1

Optical losses and mechanical strength of chalcogenide glass fibers prepared by crucible technique are reported. Mechanisms of optical losses in the high-transparancy region of chalcogenide glasses are discussed.     

Measurement of impurity concentration in chalcogenide glasses using optical principle

Owing to impurity concentration, is important in chalcogenide glass to study various commercial applications, this paper presents a novel technique to measure the impurity concentration in chalcogenide glass at wavelength of 633 nm and 1500 nm using optical principle. Here both reflection and absorption losses are considered to estimate the same impurities. Reflectance is found using plane wave expansion method, where absorption factor is determined using Maxwell's curl equations. Simulation result reveals that reflectance, absorption factor and transmitted intensity vary linearly with respect to different impurity concentrations. The excellent linear variation of transmitted intensity gives an accurate measurement of impurity concentration in chalcogenide at aforementioned wavelength.     

Chalcogenide Fibers: An Overview of Selected Applications

Chalcogenide glass fibers have many unique properties that make them attractive for applications that are not possible with silica fibers. Selected applications of chalcogenide fibers in research, commerce, and the military are reviewed.     

Freely adjusted properties in Ge–S based chalcogenide glasses with iodine incorporation

In this study, we examined the function of halogen iodine acting as a glass network modifier in green chalcogenide glasses based on the Ge–S system. We obtained a series of Ge–S–I glasses and determined their glass-forming region. We then recorded the physical, thermal, and optical properties and studied the effect of halogen iodine on Ge–S–I glasses. Results show that these glasses have relatively wide optical transmission window for infrared (IR) applications. The softening temperature of Ge–S–I glasses varies from 210.54 °C to 321.63 °C, this temperature fits well with some kinds of high-temperature polymers, such as PES and PEI, the polymers serve as protective layers with high strength and flexibility, thus simplifying the fabrication processes of IR chalcogenide glass fiber. Finally, we performed a purification process to eliminate impurities and to improve optical spectra.     

Te基远红外硫系玻璃光纤的制备及性能分析

随着光学技术由可见向中、远红外等长波长领域的发展,可透远红外的玻璃光纤研究成为近年来光学领域的发展热点之一.传统含Se的Te基硫系光纤无法工作于12μm以上的远红外.本文研究了新型GeTe-AgI硫系玻璃体系的提纯制备,利用挤压技术,制备了阶跃型GeTe-AgI远红外光纤,其光学损耗为:15.6 dB/m@10.6μm,整体低于24 dB/m@8—15μm.在实验过程中,首先采用传统的熔融-淬冷法和蒸馏纯化工艺制备了GeTe-AgI高纯玻璃样品.利用差示扫描量热仪、红外椭偏仪、红外光谱仪等测试了玻璃的物理性质和红外透过性能,分析了提纯工艺、AgI原料纯度对玻璃形成以及透过的影响,最后采用分步挤压法制备了芯包结构光纤.实验结果表明:蒸馏提纯和AgI原料纯度对玻璃的透过性能有着决定性的影响,同时Te含量的增加影响了玻璃的抗析晶能力,但新型挤压制备工艺和有效提纯技术共同保障了较低损耗Te基光纤的制备,所获得的GeTe-AgI光纤具有远红外宽谱应用的潜能(工作波段5.5—15μm)并且绿色环保,可以满足CO_2激光的能量传输和远红外传感应用.     

新型单模大模场红外硫系玻璃光子晶体光纤设计研究

大模场光子晶体光纤在高功率激光传输、光纤放大器、光纤激光器中的广泛应用, 使其受到研究者的广泛关注.硫系玻璃在红外波段(1–20μm)具有优良透过性能, 且具有折射率高(2.0–3.5)、声子能量低(小于350 cm^-1)、 组分可调等特性, 成为制备红外光纤的理想材料. 本文设计一种基于Ge₂₀Sb₁₅Se₆₅硫系玻璃基质的新型单模传输、低损耗、超大模场面积光子晶体光纤结构, 经理论验证其在λ =10.6 μm处基模限制损耗远低于0.1 dB/m, 高阶限制模损耗大于2 dB/m, 模场面积约为13333 μm². 关键词： 硫系玻璃 大模场面积 红外光子晶体光纤 结构设计     

Gallium Lanthanum Sulphide Fibers for Infrared Transmission

Gallium lanthanum sulphide (GLS) glass and fiber have potential for use in both active and passive infrared applications. In this paper the optical, thermal, and other key properties, which are essential for understanding the applications and crucial in the quest for practical fibres, are discussed. Glass preparation by melt-quenchingand subsequent fibre fabrication is described using both rod-in-tube and extruded preforms. Absorptive and scattering losses are explored as they could represent a fundamental limitation to successful device fabrication. Potential passive and active applications are reported and the prospects for a future generation of sulphide fiber-based devices examined.     

All-optical switching based on inverse Raman scattering in liquid-core optical fibers

We report on a new platform for all-optical switching based on inverse Raman scattering in liquids. Narrowband switching, which could be suitable for wavelength-division-multiplexed applications, is demonstrated using integrated liquid-core optical fiber infiltrated with both neat liquids (CCl(4) and CS(2)) as well as an organic chromophore (β-carotene) dissolved in CCl(4). Compared to standard glass optical fibers, these liquids have much larger Raman loss coefficients, which help reduce the pump power by at least an order of magnitude. Further improvements can be expected with the development of highly soluble organic compounds possessing large Raman cross sections.     

Strong self-phase modulation in planar chalcogenide glass waveguides

Single-mode planar waveguides were fabricated from chalcogenide glass compounds with large Kerr nonlinearities. Strong self-phase modulation of subpicosecond pulses along with low linear and nonlinear absorption losses demonstrates the potential for ultrafast, low-power, all-optical processing applications.     

高激光损伤阈值Ge-As-S硫系玻璃光纤及中红外超连续谱产生

测量了Ge-As-S系列硫系玻璃在中红外波段的飞秒激光损伤阈值,研究了它与玻璃化学组成的关系.基于优化的玻璃组成,采用棒管法制备了芯径为15μm的阶跃折射率非线性光纤.采用飞秒脉冲抽运光纤,研究了光纤中超连续谱(supercontinuum,SC)的产生特性.在研究的Ge-As-S硫系玻璃中,具有化学计量配比的Ge0.25As0.1S0.65玻璃显示出最高的激光损伤阈值.以该玻璃作为纤芯材料、以与其相匹配的Ge0.26As0.08S0.66玻璃作为包层材料制备的光纤的数值孔径约为0.24,背景损耗<2 dB/m.采用4.8μm的飞秒激光抽运长度为10 cm的光纤,获得了覆盖2.5-7.5μm的SC.这些结果表明,Ge-As-S硫系玻璃光纤是一种有潜力的中红外高亮度宽带SC产生的非线性介质.     

Infrared Optical Fiber Sensors

Notably improved performance as well as extended application areas is expected in the technology of optical fiber sensors using infrared fibers that transmit radiation in a wavelength range beyond 2 μm. Measurement of infrared radiation is particularly important in thermometry and spectrometry. In these areas, the use of infrared fibers has been studied extensively not only as a transmission waveguide but also as a sensor chip. Of various infrared fibers, fluoride glass fibers exhibit the lowest transmission loss and hence are useful for remote sensing that requires light transmission over a long distance. The wide transmission range of chalcogenide glass fibers and halide crystalline fibers is valuable for thermometry in a low temperature range and for spectrometry of various molecules. Hollow waveguides are useful as a capillary flow cell that realizes fast-response spectrometry. The advantages and disadvantages of infrared fibers must be considered carefully in the development of fiber sensors. In this paper, the progress of infrared optical fiber sensors is reviewed with particular interest in thermometry and spectroscopy.     

Design of double-coated optical fibers to minimize long-term axial-strain-induced microbending losses

The design of double-coated optical fibers to minimize long-term axial-strain-induced microbending losses is investigated. The microbending loss is dominated by the compressive radial stress at the interface between the glass fiber and primary coating. To know the long-term axial-strain-induced microbending losses in double-coated optical fibers, the stresses in fibers are analyzed by the viscoelastic theory. To minimize these long-term microbending losses, the thickness and Young's modulus of the secondary coating should be decreased if the strength of coating is satisfied. Meanwhile, the Poisson's ratio of the primary coating should be increased, but the Young's modulus of the primary coating and relaxation time of the secondary coating should be decreased. Alternatively, the radius and relaxation time of the primary coating exist their optimum values. The long-term axial-strain-induced microbending losses in single-coated optical fibers are also discussed.     

Absorption and scattering in bismuth-doped optical fibers

The optical-loss spectra of bismuth-doped aluminosilicate glass core optical fibers have been investigated in the spectral range 200–1700 nm. Absorption (active and inactive) and scattering losses have been separated. The optical fibers under study were fabricated by methods of modified chemical vapor deposition and surface-plasma chemical vapor deposition.     

Ultraviolet radiation- and γ radiation-induced color centers in germanium-doped silica glass and fibers

Induced optical losses and paramagnetic Ge(n) centers were investigated in germanium-doped silica glass and optical fibers after γ and ultraviolet (UV) irradiation. It was found that both types of irradiation created similar effects. By means of selective UV irradiation, Ge (1 and 3) centers were identified in optical absorption spectra, presumably as induced bands centered at 4.4 eV and 6.2 eV, respectively. Moreover, photobleaching of Ge(1) centers took place under 266-nm wavelength excitation. In optical fibers no difference was observed between γ- and UV-induced loss spectra in the wavelength range from 480 nm to 1,900 nm. Partial reversibility of the photocoloration was observed. For comparison, the coloration effects were studied in glass prepared by means of modified chemical vapor deposition (MCVD) vapor-phase axial deposition (VAD), and plasma-activated chemical vapor deposition (PCVD) techniques.     

Linear and nonlinear optical properties of Ag-As-Se chalcogenide glasses for all-optical switching

We prepared Ag(x)(As0.4Se0.6)(100-x) chalcogenide glasses by a melt-quenching method and measured their linear and nonlinear optical properties to evaluate their potential applications to all-optical ultrafast switching devices. Their nonlinear refraction and absorption were measured by the Z-scan method at 1.05 microm. The addition of Ag to As2Se3 glass led to an increase in the nonlinear refractive index without introducing an increase in the nonlinear absorption coefficient. The glass with a Ag content of x = 20 at. % revealed high nonlinearity ranging from 2000 to 27,000 times that of fused silica, depending on the incident optical intensity.     

Optical signal processing using nonlinear fibers

Ultra-fast optical signal processing is a promising technology for future photonic networks. This paper describes possible applications of nonlinear fibers to optical signal processing. The third-order optical nonlinearities in a fiber are discussed by analyzing the interaction of co-propagating optical waves. The properties of a nonlinear fiber are then considered in terms of optimizing the dispersion for achieving phase matching and decreasing walk-off. A highly nonlinear fiber (HNLF) is a practical candidate for an ultra-high-speed signal processor. Using HNLF, the following experiments are successfully demonstated: ultra-broadband wavelength conversion/optical phase conjugation by four-wave mixing, 160 Gb/s optical 3R-regeneration, and optical switching up to 640 Gb/s using a parametric amplified fiber switch. Steps for further improvements are also discussed.     

Dispersion compensation in optical transmission systems using high negative dispersion chalcogenide/silica hybrid microstructured optical fiber

In this paper, a new hybrid microstructured optical fiber (H-MOF) based upon photonic bandgap (PBG) light guiding mechanism which can be used for dispersion compensation in optical transmission systems is designed and simulated. The H-MOF core is made up of silica glass and the holes in the cladding network are filled with As₂Se₃ chalcogenide glass. By selecting an appropriate geometrical parameters for the structure, the dispersion and confinement losses of the proposed H-MOF at 1.55 µm are calculated to be ?6700 ps/nm/km and 6?×?10^?4 dB/m, respectively. Relative dispersion slope (RDS) of the H-MOF at 1.55 µm is about 0.00347 nm^?1. The proposed H-MOF is suitable for use in wavelength division multiplexing and dispersion compensating systems in optical fiber transmission networks.     

掺Yb~(3+)双包层大模场面积微结构光纤光谱特性的研究

掺Yb3+双包层大模场面积微结构光纤(micro-structured fibers,MSF)是作为超大功率光纤激光器的理想介质。本文首先采用非化学气相熔炼法制备出掺Yb3+石英基玻璃材料,然后按照设计要求,通过排布拉制法制备了掺Yb3+双包层大模场面积微结构光纤。分别利用钛宝石飞秒激光器(波长调至为975 nm)和波长为980 nm LD激光器作为激励源,对掺Yb3+双包层大模场面积微结构光纤的荧光光谱进行分析,实验结果表明:该光纤在波长为1 050 nm处产生强的荧光,同时该光纤还能有效的抑制合作发光现象(coopera-tive luminescence)的产生。     

Photoinduced stable second-harmonic generation in chalcogenide glasses

We report on photoinduced second-harmonic generation (SHG) in chalcogenide glasses. Fundamental and second-harmonic waves from a nanosecond pulsed Nd:YAG laser were used to induce second-order nonlinearity in chalcogenide glasses. The magnitude of SHG in 20G?20A?60S glass was 10(4) larger than that of tellurite glass with a composition of 15Nb(2)O (5) 85TeO(2) (mol.%). Moreover, no apparent decay of photoinduced SHG in 20G?20A?60S glass was observed after optical poling at room temperature. We suggest that the large and stable value of chi((2)) is due to the induced defect structures and large chi((3)) of the chalcogenide glasses.