Watts-level, short all-fiber laser at 1.5 microm with a large core and diffraction-limited output via intracavity spatial-mode filtering

We report over 2 W of single spatial-mode output power at 1.5 microm from an 8-cm-long, large-core phosphate fiber laser. The fiber has a numerical aperture of approximately equal to 0.17 and a 25-microm-wide core, heavily doped with 1% Er(+3) and 8% Yb(+3). The laser utilizes a scalable evanescent-field-based pumping scheme and can be pumped by as many as eight individual multimode pigtailed diode laser sources at a wavelength of 975 nm. Nearly diffraction-limited laser output with a beam quality factor M2 approximately equal to 1.1 is achieved by use of a simple intracavity all-fiber spatial-mode filter. Both spectrally broadband and narrowband operation of the laser are demonstrated.     

Compact TEM<Subscript>00</Subscript> grazing-incidence Nd:GdVO<Subscript>4</Subscript> laser using a folded cavity

A compact diode-side-pumped Nd:GdVO₄ laser system using a folded cavity and grazing-incidence configuration is presented. The highest multimode output power obtained was 21.8 W at 36 W of effective diode pump power. Highest optical-to-optical conversion efficiency of 61.5% was achieved at 33 W of effective diode pump power with 20.3 W of multimode output power. For single-mode TEM₀₀ operation, an intracavity telescope was adopted for mode matching in the horizontal direction. Because of the folded cavity and the intracavity telescope, this laser head was the most compact to our knowledge of the TEM₀₀ grazing-incidence laser geometry. At last, an output power of 15 W was produced at 36 W of effective diode pump power. The stable Q-switching operation was also obtained. PACS 42.55.-f; 42.55.Xi; 42.60.Gd     

Polychromatic light interferometer for high-accuracy positioning

Superposition of different-wavelength, multimode- and single-mode laser diode beams is investigated to locate the fringe of zero interference order in a Twyman-Green interferometer. The possibility of central fringe detection using three multimode laser diodes or one single-mode together with a pair of multimode laser diodes is shown. If a single-mode laser diode is applied, a simultaneous fringe-counting technique for displacement measurement is available. The influence of the angle between wavefronts entering the interferometer is analyzed. A repeatability of about 5 nm is shown for surface position determination when using three-beam source.     

High-average-power Nd:YAG planar waveguide laser that is face pumped by 10 laser diode bars

A planar waveguide Nd:YAG laser is pumped with 430 W of power from 10 laser diode bars to produce a multimode output power of 150 W at an optical efficiency of 35%. Use of a hybrid resonator of the positive-branch confocal unstable type for the lateral axis and of one of the near-case I waveguide type for the transverse axis increased the laser brightness by a factor of ~26 with only 12% less power than in the multimode case.     

利用半导体激光器环产生27 GHz的平坦宽带混沌激光

关键词： 激光器 混沌 宽带 环形结构     

Enhancement of the wavelength selectivity of a volume hologram by use of multimode optical fiber referencing

Wavelength multiplexing of a volume hologram was combined with multimode fiber referencing. A photorefractive volume hologram was recorded and probed by reference light diffracted from a multimode optical fiber. A tunable laser diode was used as a light source that was launched into the multimode fiber. As the wavelength of the source laser shifted, the speckle patterns from the multimode fiber changed. The wavelength selectivity of the volume hologram was enhanced by the combined effect of wavelength change and speckle change.     

Thin Nd:YAG slab laser pumped by lens duct coupled diode laser stacks

High power continuous wave operation of a diode face-pumped thin Nd:YAG slab laser is reported. A novel pumping geometry for a thin Nd:YAG slab using cylindrical lens duct coupled diode laser stacks is demonstrated. In a close-coupled resonator, a maximum laser output power of 260 W in multimode operation is obtained. This corresponds to a slope efficiency of 34% and an optical-to-optical efficiency of 27%, respectively. In high-brightness operation, a polarized laser output of 70 W has been obtained with a beam quality factor close to 4 in both directions. The polarization contrast ratio is >100. PACS 42.55.Xi; 42.60.Pk; 42.60.By     

Phase-Drift-Suppression in Heterodyne Detection Using Coherent Light Source

The validity of the phase-drift-suppression method (PDSM) using coherent light sources of a single-mode laser diode (LD) or multimode Nd:YAG laser has been experimentally shown. PDSM can enhance the stability of an output signal in heterodyne detection using higher order harmonics. In the Michelson interferometer, the fundamental and second harmonics in heterodyne beat signals were detected by two lock-in amplifiers, and the computed signal intensity (CSI) was obtained in the computer as an output signal. Relations between the stability of CSI and modulation indexes in sinusoidal phase modulations were measured. The CSI stability was enhanced about twice by PDSM using a single-mode laser diode, and from 4 times to 9 times using a multimode laser.     

Multi-wavelength mode-locked Er/Yb Co-doped fiber laser with square nano-second pulse output

We report a multi-wavelength mode-locked Er/Yb codoped fiber laser with square nano-second pulse output, which is constructed with a “figure-of-eight” cavity structure. A section of polarization-maintaining Er/Yb co-doped double clad fiber was used as the gain medium and pumped by a fiber pigtailed multimode laser diode working at 975 nm via a multimode fiber combiner. Several megahertz repetition rate output pulses with peak power up to 9.2 W and pulse duration around several nanoseconds were obtained.     

High-Resolution Reflectometry by Optical Multidigitized Coherence

We propose and confirm a novel technique of optical frequency domain reflectometry based on multidigitized coherence using a multimode laser. The proposed system can easily provide the potential for high resolution on the order of 10 μm without scanning frequencies as in frequency domain reflectometers of either continuous or stepwise sweep. The theoretical approach agrees well with the experimental results demonstrated using a commercially available multimode laser diode.     

Grating-Stabilized External Cavity Diode Lasers for Raman Spectroscopy—A Review

Abstract: Conventional Raman techniques require a continuous-wave laser with stabilized wavelength, narrow line width, and sufficient output power. Due to their miniature size and low cost, diode lasers are good choice as light sources for Raman spectroscopy, especially when compact and portable instruments are needed. However, a solitary multimode diode laser has certain drawbacks that limit its use for Raman application. To circumvent these drawbacks, an external cavity can be coupled to the active gain medium of the diode to enhance the laser performance. A grating-based external cavity allows the laser to operate in a single longitudinal mode with greatly reduced line width and stabilized wavelength. This article examines the fundamentals of semiconductor lasers to show the necessity of operating diode lasers in an external cavity for Raman applications. Two feedback grating-based external cavity diode laser (ECDL) designs, viz. Littrow and Littman-Metcalf configurations, are explained. Historic and recent progress in the development of ECDL devices is reported. An updated summary of ECDL-equipped Raman systems applied to fields such as in vivo biomedical studies and in situ process/quality control is provided. Topics on mode-hop-free continuous scanning, wavelength stabilization, and dealing with ambient conditions are discussed.     

200W级高亮度半导体激光器光纤耦合模块

光纤激光器系统需要高可靠性、高亮度、高功率光纤耦合输出二极管激光器模块作为泵浦源。基于mini-bar二极管激光器芯片,采用光束精密准直技术、自由空间合束技术来获得高亮度、高功率光纤耦合输出,针对光纤芯径为200μm、数值孔径为0.22的多模光纤,开展了线偏振二极管激光光纤耦合实验,实验结果表明:光纤稳定输出功率达280 W,对应亮度为5.87 MW/(cm2·sr),电-光效率为45.0%。采用偏振合束技术,光纤预期输出功率可达500 W,对应亮度超过10 MW/(cm2·sr)。该方法可应用于研制数百瓦级高亮度二极管激光光纤耦合输出激光器模块。     

Diode end-pumped high-efficiency Nd:YAG laser

A close-coupled scheme has been developed to end-pump the Nd:YAG rod using diode lasers tuned to 808 nm. By using a single diode laser, an optical-to-optical conversion efficiency of about 40% has been demonstrated in the multimode operation at 1064 nm.     

Mode-partition noise interferometric conversion function

We derive expressions that describe the maximum and minimum envelopes of mode-partition noise converted into intensity noise through an unbalanced interferometer, using a simple model of a multimode laser diode, and experimentally confirm the expressions.     

大功率激光二极管与多模光纤耦合效率分析

提出了一种用于大功率激光二极管与多模光纤耦合的新颖的铲形整形系统，详细分析了铲形光纤端头不同的切割角度、切割深度以及耦合距离对激光二极管与铲形光纤耦合效率的影响。提出了一种计算该系统耦合效率的方法，同时给出了耦合效率的计算实例，得出了可以最大程度地提高铲形耦合头作用的优化参量。     

高功率高效率光纤耦合半导体激光模块研制

采用光束整形和空间合束的方法,研制出高功率、高效率多阵列光纤耦合半导体激光模块。将波长为976nm连续工作的5个标准半导体阵列,通过对快轴进行准直和快慢轴光束旋转的方式进行光束整形,准直后进行空间合束,经耦合透镜聚焦,耦合入芯径400μm、数值孔径0.22的光纤。测量结果显示:光纤的出光功率最大可达到327 W,光纤耦合效率大于93.6%。     

Investigation of stimulated Brillouin scattering for broadband KrF laser

Stimulated Brillouin scattering (SBS) numerical mode for broadband multimode KrF laser pump with optical breakdown has been built up in this paper. The basic premises of the model are that KrF spectrum is composed of an umber of lines and SBS arises from these lines with coupling to some extent. The broadband SBS threshold strongly depends on pump bandwidth. SBS and optical breakdown occur nearly simultaneously when broadband SBS and breakdown have the same threshold. The decrease of saturation reflectivity for broadband pump radiation is explained with this model. Experimental results agree well with the model.     

Influence of injection patterns on chaos synchronization performance between a multimode laser diode and a single-mode laser

In this paper, based on a system composed of a multimode emitted laser diode and a single-mode received laser, chaos synchronization performance has been investigated numerically under different optical injection patterns. The results show that, for single mode injection (SMI) which means the received laser is injected by a selective longitudinal mode of the multimode emitted laser whose wavelength corresponds to that of the single-mode received laser, the system synchronization performance is better than that with multi mode injection (MMI); depending on the optical spectrum of the received laser, the physical mechanism of chaos synchronization deterioration for MMI is given. Additionally, after taking into account the parameter mismatches, the chaos synchronization performance of the system with different injection pattern have also been discussed. For either SMI or MMI, the synchronization performance with negative parameter mismatches is better than that with positive parameter mismatches.     

一种基于集成光学声光作用的新型光谱分析仪特性分析

介绍了一种基于集成光学声光相互作用原理的集成光学光谱分析仪,与传统光栅光谱仪相比具有体积小,精度高的特点.在理论上分析了这种光谱仪的基本原理、色散本领和分辨本领.给出了实验测量装置原理图,并在试验中对He:Ne激光器和多模半导体激光器输出光谱进行了测量,得到了理想的结果.     

Grazing-incidence YVO4-Nd:YVO4 composite thin slab laser with low thermo-optic aberrations

We present a novel grazing-incidence composite thin slab laser (CTSL) with an almost aberration-free gain medium. The laser consists of a 260-microm thin Nd:YVO4 plate that is diffusion bonded to an undoped YVO4 slab. The Nd:YVO4 plate is cooled at just one side, suppressing temperature gradients that would induce wave-front distortions in the laser field. The pump light of a noncollimated diode bar is directly coupled into the undoped YVO4 slab and guided by total internal reflection to the attached Nd:YVO4 plate. Since any pump-beam-shaping optics can be omitted, the laser is simple and compact. We obtained transverse multimode optical output powers of 14 and 9.3 W with M2 < or = 1.3.