近红外低损耗AgI/Ag空芯光纤的制作EI北大核心CSCD

内面镀有碘化银和银(AgI/Ag)的空芯光纤在中红外波段已有较成熟的制备工艺并得到广泛应用。由于AgI膜厚和表面粗糙度的控制存在较大难度,近红外低损耗的AgI/Ag空芯光纤尚未见报道。通过一系列工艺改进,包括以酒精作为碘的溶剂,在低温中对银膜进行碘化,并采用真空泵提高并稳定碘溶液流速,制备了碘化银膜厚为70nm的AgI/Ag空芯光纤。实现了AgI/Ag空芯光纤在近红外区域的低损耗传输。采用发光波长为1.064μ闾m的二极管抽运固体激光器系统测得长度为1m、内径为0.7mm的AgI/Ag空芯光纤损耗约为1.15dB/m。进一步研究了碘溶液浓度、温度等参数对碘化银膜镀膜工艺的影响,并评价了多种内径AgI/Ag空芯光纤在近红外波段的传输特性和弯曲损耗特性。     

内窥镜的红外激光传输用柔性空芯光纤的研制

通过理论计算确立了多功能介质-金属结构空芯光纤的结构参量,优化了液相镀膜法的有关条件,明确了具体制作参量。制作了以聚碳酸酯毛细管为基管的,高柔韧性的,可同时低损耗传输红外目标波长激光和可见导航光红外的空芯光纤。对光纤传输性能进行了测试。在2.94μm波长的Er∶YAG和0.63μm波长的红色半导体激光器的直线损耗分别为0.4 dB/m和3 dB/m。组装在医疗内窥镜中的柔性空芯光纤,在先端以0.9 cm半径135°角弯曲时,对Er∶YAG激光仍有近70%的传输效率;绿色导航光在内窥镜中的的损耗值为11 dB,绿色指示点在内窥镜的视窗中清晰可见。结果表明此种光纤在内窥镜的激光传输方面有重要的应用价值。     

介质/金属结构太赫兹空芯光纤的传输特性

理论分析了金属、介质/金属结构空芯光纤在THz波段的模式结构和传输特性.金属空芯光纤支持TE11模式,介质/金属空芯光纤的介质膜厚在取最优值时支持HE11模式.对于波长为200μm的太赫兹波,内径为1 mm的两种空芯光纤,TE11和HE11模式的损耗分别为8.4 dB/m和2 dB/m.为优化介质/金属结构宅芯光纤的传输性能,分析了金属和介质材料的光学常数对衰减系数的影响.基于几种已发表的金属在太赫兹波段的光学常数,计算结果表明铝是最好的选择;初步测量结果显示,在各种树脂材料中聚乙烯在THz波段吸收较小,并且其折射率接近介质膜的最优值1.41,为太赫兹波空芯光纤中介质膜材料的理想选择.     

介质镀膜空芯光纤在THz频段的传输特性

 理论分析了介质镀膜空芯光纤在THz频段的传输特性，得出了该光纤的特征方程及模式分布。利用射线光学原理计算了介质膜材料为聚酰亚胺、介质膜厚度为0.05 mm的光纤的衰减常数随介质膜内直径的变化情况。得出其主模在THz频段的衰减常数小于1 dB/m，该值远小于相同内径的金属圆波导在这一频段的衰减常数。模拟计算了介质膜厚度为0.05 mm、内径为1 mm，金属膜内径为1.05 mm的介质镀膜空芯光纤在0~1 THz的S参数，模拟结果显示该光纤在THz频段有很宽的通带，且在通带内衰减常数小于0.5 dB/m，可用于THz频段电磁波远距离传输。     

吸收介质膜/金属空芯光纤的太赫兹波传输特性

介质/金属结构空芯光纤是一种有发展前景的太赫兹波传输媒质.介质膜在有效增加内面反射率从而降低传输损耗的同时,其材料吸收会引起附加损耗.讨论了介质材料吸收对太赫兹空芯光纤结构参数的影响.计算结果表明,相比于无吸收的理想介质,吸收介质的最优膜厚变小.最优折射率变大.综合考虑了光纤内直径、介质膜折射率和传输波长等因素,分析了介质膜的材料吸收容限.分析结果表明,吸收容限随光纤内直径减小或传输波长增大而减小.当光纤内直径很小或传输波长很大时,吸收容限可能不存在.分析结果对介质/金属太赫兹空芯光纤的设计和材料选择具有重要参考价值.     

中红外色散平坦硫系光子晶体光纤设计及性能研究

本文以自制Ge20Sb15Se65硫系玻璃为基质材料,设计一种正八边形结构色散平坦型中红外硫系光子晶体光纤,并采用多极法对其中红外色散和传输特性进行数值研究.结果表明:控制该光纤占空比(d/Λ)在0.323—0.367之间,其色散及传输特性在3—5μm范围内可调.当孔间距Λ=3.4μm,孔直径d=1.1μm时,光纤在4.1—4.9μm波段的色散值在0.8—0.8 ps·nm 1·km 1波动,且具备单模低损耗传输(Loss0.049dB/m),小模场面积(Aeff8.46μm2)特性,适合于中红外非线性应用领域.     

通信用低损耗蜘蛛网结构包层空芯塑料布喇格光纤

提出并分析了利用蜘蛛网结构包层空芯布喇格光纤在0.65 μm~1.55 μm和200 μm ~500 μm波长范围得到低损耗传输的可能性.采用渐近转移矩阵公式所做的分析结果表明：这种光纤的传输损耗远低于构成光纤所用塑料的吸收损耗.在0.65 μm ~1.54 μm的可见至近红外波段,这种光纤结构可把构成光纤所用塑料的吸收损耗抑制为1/237 000,甚至可抑制为1/1 300 000；在200 μm ~500 μm的太赫兹波段,这种光纤结构可把构成光纤所用塑料的吸收损耗抑制为1/8 962,甚至可抑制为1/83 390.因此用便宜的塑料,可以在可见至太赫兹波段用这种光纤构成较长距离、较高带宽的光纤通信系统,并实现波分复用（WDM）.     

长波红外量子级联激光器的高效率光纤合束

长波红外量子级联激光器（QCL）具有波长设计灵活、体积小、寿命长等优点。目前单横模QCL较低的输出功率（1～3 W）是限制其应用的主要因素。光纤功率合束技术是提升输出功率的有效手段。然而由于长波红外波段缺少低传输损耗的玻璃光纤,使得高效率长波红外光纤功率合束的实现难度很大。本文研究了基于低损耗单模空芯光纤的长波红外激光功率合束技术。针对基横模长波红外QCL有源区尺寸大、发散角大的特点,设计了大数值孔径扩展光源双非球面准直镜,有效提高了单模光纤耦合效率。设计制备了无端面损耗的长波红外单模光纤束,光纤传输效率高达91.2%,实现了7.6～7.8μm波段QCL的高效率合束。当4个长波红外QCL的输出总功率为2.27 W时,采用所设计的光纤耦合光学系统及制备的4×1单模空芯光纤合束器获得了1.5 W的连续输出,总合束效率为66%。此外,测量得到单根单模长波红外光纤耦合输出光的光束质量因子M2为1.2,光强分布和光束质量因子均优于QCL的直接输出激光,说明空芯单模光纤具有一定的非高斯光束模式净化作用。合束光束的传输质量因子为2.6,依然具有较好的光束质量。本文所研究的光纤合束方式对QCL的输出波...     

新型全固态准晶体结构大模场光纤特性研究

大模场单模光纤在高功率激光器、高功率光传输和高灵敏度传感器等领域具有重要意义.设计了一种新型超低损耗大模场单模光纤,包层空气孔由掺氟硅玻璃棒代替,掺氟硅玻璃棒排列呈六重准晶体结构.基于有限元法对光纤的传输特性进行了数值模拟.研究了光纤结构参量变化对模式特性和有效模场面积的影响.结果表明:波长在1064 nm处,有效模场面积高达5197μm2,基模的限制性损耗低于10-5dB/km,解决了大模场与低损耗之间的冲突;在1064—2000 nm波段内,基模与二阶模的限制性损耗相差7个量级,实现单模传输;半径为10 cm时,弯曲损耗小于0.01 dB/m,具有良好的低弯曲损耗特性.此光纤能够提高光纤热损伤阈值,减少接续损耗,全固态结构有效避免了空气孔塌陷,简化制备工艺,对高功率激光传输、光纤激光器和光纤放大器的发展具有重要意义.     

空芯光波导在光谱气敏检测中的应用

空芯光波导(HWG)用于光谱气体检测中,既可以实现光路的传输,又可以充当气体样品池实现长光程高灵敏度测量,具有体积小,响应时间快、成本低、光路稳定灵活等优点。介绍了基于镀银/碘化银的空芯光波导(Ag/AgI-HWG)、光子带隙空芯光波导(PBG-HWG)和基片集成空芯光波导(iHWG)等类型的空芯光波导,并总结了近年来空芯光波导在光谱气敏检测中的研究及进展,梳理了其应用方式及应用领域。研究表明,空芯光波导替代传统的气体池与傅里叶变换红外光谱(FTIR)、激光吸收光谱和拉曼光谱等不同的光谱技术结合已取得一系列成果,且已经应用于环境监测、呼气诊断和工业过程检测和控制等领域。其中,基于中红外激光吸收光谱的空芯光波导传感器组成相对简单,成本较低,与各类光波导的兼容性和环境适应性较强,发展前景较好。总之,随着激光技术、光波导技术和光谱技术的发展,基于空芯光波导的光谱气体检测正在迅速发展,并逐步由实验室走向现场应用。     

Optical properties of AgI/Ag infrared hollow fiber in the visible wavelength region

We report on AgI/Ag infrared hollow fiber with low-loss in visible region. Improved methods of silver plating and iodination were proposed to fabricate the hollow fiber. The surface roughness of the silver layer and the silver iodide layer was reduced by the pretreatment with an SnCl2 solution and low iodination temperature. Losses for the Er:YAG and green laser light were 0.4 and 7dB/m. The loss property of green laser beam was low to deliver a pilot beam for the invisible infrared laser light. Owing to the smooth and uniform AgI film, the loss spectrum of the hollow fiber showed clear interference peaks in the visible region. An empirical formula for AgI material dispersion was derived, which is of special importance for the design of high-performance AgI/Ag hollow fiber.     

Investigation of the thickness of Ag, AgI films in the capillary for hollow waveguides

A metallic (Ag)–dielectric (AgI) hollow glass waveguide is a promising and flexible fiber for the delivery of high-power CO₂ laser radiation. The thickness of metallic (Ag) films and dielectric (AgI) films is a critical factor which greatly influences the attenuation of the waveguides. In this paper, metallic (Ag)–dielectric (AgI) films were successfully prepared in the capillary whose inner diameter is 0.53 mm, and firstly investigated with theoretical analysis and measured by means of AES and SEM. There is good agreement between theoretical thickness and experimental results, which confirms the validity of the theoretical analysis, which makes the estimate of the thickness of both the metallic and dielectric films possible with high accuracy prior to the preparation of hollow glass waveguides. The attenuation spectra of Ag/AgI hollow waveguides shows the loss increases with the thickness of Ag, AgI films and indicates that the Ag/AgI hollow waveguide is suitable for the transmission of IR radiation.     

Low loss smart hollow waveguides with new polymer coating material

A new kind of cyclic olefin polymer COP-E48R has been selected as the dielectric material for a silver hollow glass tube. Owing to its lower extinction coefficient at the wavelength of 10.6 μm, transmission losses for the CO₂ laser light has been reduced significantly in the COP-E48R-coated silver (COP-E48R/Ag) hollow glass waveguide. By properly selecting the film thickness of COP, Er:YAG and CO₂ laser light are shown to be transmitted with low loss simultaneously or independently. Delivery properties of red and green pilot beams were also evaluated.     

Coupling external cavity mid-IR quantum cascade lasers with low loss hollow metallic/dielectric waveguides

We report on the optical coupling between hollow core waveguides and external cavity mid-IR quantum cascade lasers (QCLs). Waveguides with 1000???m bore size and lengths ranging from 2 to 14?cm, with metallic (Ag)/dielectric (AgI or polystyrene) circular cross-section internal coatings, have been employed. Our results show that the QCL mode is perfectly matched to the hybrid HE₁₁ waveguide mode, demonstrating that the internal dielectric coating thickness is effective to suppress the higher losses TE-like modes. Optical losses down to 0.44?dB/m at 5.27???m were measured in Ag/polystyrene-coated waveguide with an almost unitary coupling efficiency.     

Multiwavelength laser light transmission of hollow optical fiber from the visible to the mid-infrared

We report on low-loss multiwavelength laser delivery of hollow optical fiber in a wide wavelength region, from the visible to the infrared. Improved methods of liquid-phase coating were used to fabricate the hollow fiber with inner films of a silver and a cyclic olefin polymer (COP) layer. The surface roughness of the silver layer was reduced dramatically by pretreatment on the inner glass surface with an SnCl2 solution. The COP layer roughness was also decreased by using an ambient atmosphere of tetrahydrofuran (THF) solvent during the COP layer formation. Owing to the smooth surfaces, hollow fiber with optimum COP film thickness for CO2 laser light simultaneously yields low losses for a Er:YAG laser and a red pilot beam. The power durability of CO2 and Er:YAG lasers, as well as the loss properties for the pilot beam, is demonstrated.     

Loss reduction of dielectric-coated metallic hollow waveguides for CO2 laser light transmission

A condition for reducing transmission loss of a dielectric-coated metallic hollow waveguide is shown theoretically when the inner metallic surface is not perfect. It is also shown that the transmission loss for CO₂ laser light is 10.6 μm wavelength is able to be estimated from an attenuation spectrum of a short waveguide. By fabricating a ZnSe coated Ag hollow waveguide of short length, we have shown that it has a lower loss than a Ge coated waveguide for CO₂ laser light.     

Flexible hollow waveguides for delivery of excimer-laser light

A hollow waveguide consisting of a glass tube with a thin aluminum film on the inner surface is proposed for delivery of excimer-laser light. The waveguide, fabricated by a chemical-vapor-deposition method, shows low losses for KrF excimer laser light: the straight loss of a 1-mm-bore waveguide was 0.4 dB:m.     

Extremely low-loss hollow core waveguide for VUV light

A new type of an extremely low-loss optical waveguide is proposed. In the vacuum-ultra-violet (VUV) region (wavelength less than 300 nm) most solid-state materials have a refractive index less than unity due to plasma vibration of electrons. The energy of VUV light is confined within the hollow core due to the smaller n_r than unity of the cladding material of the hollow core waveguide. Typical expected loss for 50 nm-wavelength VUV light of a 0.1 mm hollow-core waveguide is on the order of 0.05 dB/km.     

Fabrication and Characterization of Novel 3-D Hollow Waveguide for Widely Tunable Devices

We propose a novel 3-dimensional hollow waveguide with a variable air core for widely tunable devices. We observed a wavelength shift of 1.8 nm in a hollow waveguide resonator with a displacement of 6 μm in an air core.