Watt-level red-emitting diode lasers and modules for display applications

Red-emitting lasers for display applications require high output powers and a high visibility. We demonstrate diode lasers and modules in the red spectral range based on AlGaInP with optical output powers up to 1 W and a nearly diffraction limited beam. These high-luminance light sources based on tapered lasers are well suited for laser TVs and projectors for virtual reality simulators based on the flying spot technology. Additionally, we developed diode lasers with internal distributed Bragg reflector (DBR) surface gratings. These DBR tapered lasers and master-oscillator power-amplifiers based on DBR ridge-waveguide lasers and tapered amplifiers feature high power, single mode emission with coherence lengths up to several meters, which are suitable for the next-generation 3D displays based on holography.     

Miniaturized highly brilliant diode laser modules for future display applications

We demonstrate diode laser modules with high spectral radiance larger than 1 GW/cm²/sr/nm in the visible spectral range. These highly brilliant laser light sources enable the development of next-generation 3D displays. About 1W output power from small-sized modules was achieved at 635 nm by direct diode laser emission and at 530 nm using single pass second harmonic generation (SHG) of a highly brilliant near-infrared laser diode.     

High-power and highly efficient Tm3+-doped silica fiber lasers pumped with diode lasers operating at 1150 nm

An output power of 1.74 W at 2.03 microm was generated at a slope efficiency of 51% when a double-clad Tm(3+)-doped silica fiber laser was pumped with high-power 1150 nm diode lasers. Pump excited state absorption from the upper laser level populates higher energy levels allowing cross relaxation to repopulate the upper laser level at a quantum efficiency greater than unity and to limit losses relating to additional pump excited state absorption. The output power was scaled to 4.77 W when both ends of the fiber were pumped.     

Phase perturbation investigation of laser diode for the laser diode to single-mode fiber coupling system

A novel phase-perturbation method as well as an experimental system were established to study the deviation of the laser diode (LD) far-field intensity distribution from the ideal Gaussian. An analytical expression of the LD far-field intensity distribution and a numerical method based on the Monte Carlo calculation were developed to fit the measured results. The loss of the LD to the single-mode fiber (SMF) coupling system caused by this kind of deviation of the LD far-field intensity distribution was quantitatively analyzed.     

A graded-index fiber taper design for laser diode to single-mode fiber coupling

A tapered graded-index fiber (GIF) structure is, for the first time, proposed for the efficient fiber-laser coupling. A simple analytical approach based on the ABCD law is utilized to optimally design the parameters of the hemispherically-ended GIF taper. A wide-angle beam propagation method is then employed to compute the fiber mode fields transmitted through the fiber taper in order to evaluate the coupling efficiency. By taking one commercially available GIF as an example, the effectiveness of the new design reported here is verified with a demonstration of high coupling efficiency of nearly 90%.     

Wavelength stabilized 980 nm uncooled pump laser modules for erbium-doped fiber amplifiers

We review the development of wavelength stabilized 980 nm pump laser modules without active temperature stabilization for applications in erbium-doped fiber amplifiers. Operation over a wide temperature range with an output power exceeding 400 mW at an ambient temperature of 70°C is demonstrated. The overall reliability of uncooled modules is estimated to be well below 500 FIT at all operating conditions. Such devices are made possible by continuous development and steady improvement of the pump laser chip, the optimization of the fiber Bragg grating stabilization scheme, careful design of the module package, and extended reliability analysis on the basis of stress tests as well as field data.     

Power scaling of laser diode pumped Pr3+:LiYF4 cw lasers: efficient laser operation at 522.6 nm, 545.9 nm, 607.2 nm, and 639.5 nm

We report efficient cw laser operation of laser diode pumped Pr(3+)-doped LiYF4 crystals in the visible spectral region. Using two InGaN laser diodes emitting at λ(P)=443.9?nm with maximum output power of 1?W each and a 2.9-mm-long crystal with a doping concentration of 0.5%, output powers of 938?mW, 418?mW, 384?mW, and 773?mW were achieved for the laser wavelengths 639.5?nm, 607.2?nm, 545.9?nm, and 522.6?nm, respectively. The maximum absorbed pump powers were approximately 1.5?W, resulting in slope efficiencies of 63.6%, 32.0%, 52.1%, and 61.5%, as well as electro-optical efficiencies of 9.4%, 4.2%, 3.8%, and 7.7%, respectively. Within these experiments, laser diode-pumped laser action at 545.9?nm was demonstrated for what is believed to be the first time.     

A novel technique for laser diode to single mode fiber coupling

An optical fiber coupler based on the semi-linear passive phase conjugate mirror is analyzed. The threshold coupling strength is determined from theoretical considerations. An estimate of 50% for the overall coupling efficiency is made, assuming there is good mode matching between the light incident on the fiber and the propagating mode. The coupler exhibits a high degree of alignment insensitivity allowing for simple manufacture.     

阵列半导体激光器的光束参数测量与光纤耦合

采用ISO推荐的方法测量了发光面为 1μm× 15 0 μm的阵列半导体激光器的光束半径、远场发散角、束腰位置、瑞利长度 ,并根据测量结果计算了光束传输因子 (M2 因子 )。以此为基础 ,研究了半导体激光器光束的快轴准直以及光纤耦合技术 ,采用微柱面透镜准直后 ,阵列半导体激光器快轴方向发散角可减小到 0 .48°。设计了光纤耦合光学系统 ,与 10 0 μm光纤耦合时的耦合效率为 71.0 % ,与 2 0 0 μm光纤耦合时的效率为 83.4%。     

Diode-pumped 1028 nm Ytterbium-doped fiber laser with near 90% slope efficiency

Highly efficient laser action from an Ytterbium-doped fiber (YDF) is demonstrated using a fiber Bragg grating (FBG) in conjunction with a 4% Fresnel reflection at room temperature. The YDF used is drawn from Yb₂O₃-doped preform, fabricated through deposition of porous layer of composition SiO₂-GeO₂ by the MCVD process in conjunction with a solution doping technique. The fabricated YDF has a core composition of 0.2 wt % of Yb₂O₃, 1.8 wt % of Al₂O₃ and 23 wt % of GeO₂ with a pump absorption of 9.0 dB/m. The fiber laser operates at wavelength of 1028 nm with a slope efficiency of 88% with respect to the launched 976 nm pump power using the YDF length of 7 m.     

Laser diode integrated with a low radiation loss thickness-tapered beam expander for highly efficient fiber coupling

The optimal structure of a laser diode monolithically integrated with a thickness-tapered beam expander waveguide is demonstrated by analyzing the relationship between fiber coupling efficiencies and radiation losses. It is also found that mode conversion loss is lowered in a ridge waveguide structure than in a buried hetero structure under equivalent fiber coupling. A fabricated ridge waveguide device based on this design shows threshold current as low as 16 mA and narrow beam divergences of 13° and 12°.     

半导体激光器线阵的棱镜组光束整形器和光纤耦合输出

针对半导体激光器线阵输出光束快慢轴方向光参数积不对称问题,提出并制作了基于直角棱镜片的光束整形器,其具有结构简单紧凑,制作安装容易的特点。通过数值仿真和实验对光束整形器进行了分析,研究表明整形器实现了半导体激光器线阵输出光束的对称化,并且光束经过透镜聚焦后对数值孔径为0.46,直径为200μm的光纤进行耦合,效率为53%。     

非对称波导结构提高980 nm激光二极管电光效率的机理研究

采用高电流注入条件下的载流子扩散方程和复折射率波导模型情况下的亥姆霍兹方程,对980nm高功率激光二极管外延材料的非对称和对称波导结构的光吸收损耗进行了理论计算。采用低压金属有机化学气相外延技术制备了两种波导结构的外延材料,并制作了激光器件,进行了光电特性测试和对比分析。理论计算和实验结果表明:与对称波导结构相比,非对称波导结构外延材料并未减小光吸收损耗,而是减小了串联电阻,因而降低了器件的焦耳热损耗,从而提高器件的电光效率。     

非对称波导结构提高980 nm激光二极管电光效率的机理研究

采用高电流注入条件下的载流子扩散方程和复折射率波导模型情况下的亥姆霍兹方程,对980 nm高功率激光二极管外延材料的非对称和对称波导结构的光吸收损耗进行了理论计算。采用低压金属有机化学气相外延技术制备了两种波导结构的外延材料,并制作了激光器件,进行了光电特性测试和对比分析。理论计算和实验结果表明：与对称波导结构相比,非对称波导结构外延材料并未减小光吸收损耗,而是减小了串联电阻,因而降低了器件的焦耳热损耗,从而提高器件的电光效率。     

An efficient shooting method for fiber amplifiers and lasers

A simple shooting method is proposed for the design of distributed multi-pumped Raman fiber amplifiers (RFAs) and Yb-doped double-clad fiber lasers (DCFLs). Using the proposed method a distributed RFA with 10 pump sources and 1700 mW total input pump power is simulated and high-power Yb-doped DCFL rate equations are solved numerically. The numerical simulation results show that the proposed method has good convergence in the condition of increasing numbers and power of input pump sources.     

Efficient 1061 and 1329 nm laser emission of Nd:CNGG lasers under 885 nm diode pumping into the emitting level

We report an efficiency Nd:CNGG laser operating at 1061 and 1329 nm, respectively, direct pumped by a diode laser at 885 nm for the first time to our knowledge. The maximum outputs of 4.5 and 2.9 W, at 1061 and 1329 nm, respectively, are obtained in a 6-mm-thick 0.5 at % Nd:CNGG crystal with 13.5 W of absorbed pump power at 885 nm, leading to a high slope efficiency with respect to the absorbed pump power of 32.2 and 22.1%. Under traditional pumping at 808 nm, the maximum outputs of 3.9 and 2.7 W, at 1061 and 1329 nm, respectively, are obtained with 15.4 W of absorbed pump power, corresponding to the slope efficiency with respect to the absorbed pump power of 25.2 and 17.9%.     

Simple ABCD matrix method for evaluating optical coupling system of laser diode to single-mode fiber with a lensed-tip

In this paper, we present a simple technique to determine the coupling efficiency between a laser diode and a lensed-tip based on the ABCD transformation matrix method. We have compared our analysis technique to that of previous work and have found that the presented method is reliable in predicting the coupling efficiency of lensed-tip and has the advantage of simplicity of coupling efficiency calculation even by a pocket calculator. The results can be useful for designing coupling optics.     

A beam shaping design for coupling high power diode laser stack to fiber with capability of spectral narrowing and stabilizing

We applied a VHG-FAC lens in our design in this work to collimate the fast axis and lock the output spectrally. We used a beam shaping technique to improve the beam symmetry and power density of a high power diode laser stack with a stripe mirror plate, a V-Stack mirror and polarization beam combining elements. By this technique, the beam of a high power diode laser stack is effectively coupled into a standard 365 μmcore diameter and a NA = 0.22 fiber. By this technique, compactness, higher efficiency, narrower spectral line width and lower production cost of the diodes are possible.