摘要
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M~2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的输出波长、偏振态均不敏感,且具有良好的可扩展性。实验结果表明,此方式可有效解决长波红外QCL单元器件输出功率偏低的问题。
Objective Quantum cascade laser(QCL) is a semiconductor laser based on sub-band electronic transition,which results in a broad emitting wavelength covering from 3 to 300 μm.QCL is an ideal light source in the fields of gas sensing,environmental monitoring,medical diagnosis,and photoelectric countermeasures.However,the relatively low output power(1-3 W) of the single transverse mode QCL is a major limitation for its applications.Laser beam combining technology is an effective way to enhance the output power.At present,the power beam combining of mid-infrared and long-wave infrared QCLs is heavily limited by the low-loss optical materials and component preparations.Beam combining with high efficiency and low loss is challenging,and few research results have been reported.Therefore,the fiber combining of long-wave infrared QCLs in the 7.6-7.8 μm wavelength band was studied in this paper.The laser power was combined with a 4-in-1 single-mode hollow-core fiber bundle.Methods In order to realize the high-efficiency single-mode fiber coupling of QCLs,the optical fiber coupling system was designed.The optical fiber system was composed of a QCL collimator and a fiber coupler.Due to the large QCL emitting area and large divergence angle,an aspheric collimator with a large numerical aperture was designed and fabricated.During the optical design and optimization,the QCL was assumed to be an extended light source.Using the optimized collimator,a fiber coupling efficiency of 88.9% was obtained.To combine the laser beams from individual QCL,a 4-in-1 fiber combiner was fabricated using AgI/Ag single-mode hollow-core fiber,which had a high damage threshold and low transmission loss.During the preparation,the outer protective layer of the fiber was stripped away,and the four fibers were tightly arranged in the sleeve and fixed.Finally,the fiber was protected by metal armor.The input terminals of the fiber combiner were four independent SMA905 fiber connectors,and a unified SMA905 connector was made at the output end.Results and
作者
张梦
王欣
杨苏辉
李宝
李卓
张金英
高彦泽
Zhang Meng;Wang Xin;Yang Suhui;Li Bao;Li Zhuo;Zhang Jinying;Gao Yanze(School of Optics and Photonics,Beijing Institute of Technology,Beijing 100081,China;Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology,Beijing Institute of Technology,Beijing 10008l,China;Key Laboratory of Information Photonics Technology,Ministry of Industry and Information Technology,Beijing Institute of Technology,Beijing 100081,China;The Eleventh Research Institute of China Electronic Science and Technology Group Corporation,Beijing 1oo015,China)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2024年第8期139-149,共11页
Acta Optica Sinica
关键词
长波红外
量子级联激光器
光纤合束
耦合效率
空芯光纤
long-wave infrared
quantum cascade laser
fiber combining
coupling efficiency
hollow-core fiber
