Reliable high-efficiency high-brightness laser diode bars at 940 nm

High-quality InGaAs/AlGaAs laser diode bars emitting at 940 nm have been fabricated by low-pressure metal-organic chemical vapor deposition (LP-MOCVD). Two hundred and ten Watts maximum continuous-wave output power and a maximum power conversion efficiency of 60% at an output power of 72 W have been demonstrated for a single 1-cm-wide laser bar. These bars exhibit a very good beam quality of 5.7°×27.2° (full-width at half-maximum). Reliability test have been carried out for over 2000 h at 58 W at room temperature. Under these conditions, the extrapolated lifetime is 100,000 h, which suggests that AlGaAs-based lasers of proper designs could have similar long-term reliability as their Al-free counterpart.     

Blue‐green light generation using high brilliance edge emitting diode lasers

A review about second harmonic generation using edge emitting diode lasers and nonlinear crystals to obtain laser radiation in the blue‐green spectral range is presented. Therefore, pump laser radiation with high brightness and narrow bandwidth is necessary. Thus, this review gives an overview of the advances made with distributed feedback and Bragg reflector lasers, tapered lasers and amplifiers as well as external cavity diode lasers and master oscillator power amplifier schemes to achieve high brilliance emission. Since periodically poled materials have enabled high second harmonic conversion efficiencies with low and moderate pump powers, the review is focused on frequency doubling using those materials. The most commonly used materials, their properties and limitations are discussed briefly. Single pass and resonant SHG setups with waveguide and bulk nonlinear crystals are discussed and an emphasis on building compact and integrated devices is made.     

High-power Tm-doped fiber distributed-feedback laser at 1943 nm

We report on high-power operation of a fiber distributed-feedback (DFB) laser fabricated from Tm-doped photosensitive alumino-silicate fiber and in-band pumped by an Er/Yb fiber laser at 1565 nm. The fiber DFB laser yielded up to 875 mW of single-ended output at 1943 nm on two orthogonally polarized modes for 3.5 W of absorbed pump power. Further scaling of the DFB laser output power was achieved with the aid of a simple Tm-doped fiber amplifier stage spliced directly to the DFB fiber without the need of an optical isolator. The maximum output power from the DFB laser and fiber amplifier was >3 W for a combined absorbed pump power of 8.1 W. The influence of thermal loading, owing to quantum defect heating in the Tm-doped core, on the output power and longitudinal mode behavior is discussed, and the prospects for further improvement in performance are considered.     

Nd:LuYAG混晶1123 nm被动调Q激光器

文章报道了一个二极管激光抽运的1123 nm被动调Q激光器. 激光晶体为混晶Nd:LuYAG, 饱和吸收体选为Cr⁴⁺:YAG晶体. 在连续运转情况下, 最高输出功率为2.77 W, 对应的光-光转换效率为29.53%. 调Q运转时, 在9.38 W吸收抽运功率下, 最高输出功率为0.94 W. 脉冲宽度整体在105 ns左右. 在最高吸收抽运功率下, 1123 nm激光的输出重复频率为9.40 kHz, 对应的单脉冲能量可达100 μJ, 高于目前报道的单晶Nd:YAG 1123 nm单脉冲能量, 证明其在能量存储方面较单晶Nd:YAG更具优势. 另外, 据我们所知, 这是关于混晶Nd:LuYAG 1123 nm输出的首次报道.     

Room temperature CW lasing operation of monolithically grown 1.55 μm vertical external cavity surface emitting laser

We report room temperature (20 °C) continuous-wave operation of 1.55 μm vertical-external-cavity surface-emitting lasers. The optically pumped monolithic InP-based structure, grown by metal–organic chemical vapor deposition, includes a InP/InGaAsP Bragg reflector, and an active region with strain compensated quantum wells. Output power up to 4 mW is obtained at 0 °C. The thermal impedance of the structure is deduced from the experimental data.     

Long-wavelength GaInAsSb/AlGaAsSb DFB lasers emitting near 2.6 μm

We have successfully fabricated and characterized room temperature continuous wave (cw) GaInAsSb/AlGaAsSb distributed feedback lasers emitting in the wavelength region between 2.499 and 2.573 μm. To the best of our knowledge, this is the longest emission wavelength realized with a GaSb-based DFB laser diode. The laser structure used for DFB processing was grown by solid source molecular beam epitaxy. A DFB concept requiring no subsequent overgrowth step was used by defining first-order Cr-Bragg gratings laterally patterned to a ridge waveguide. Threshold currents smaller than 60 mA and room temperature cw output powers up to 6.5 mW were obtained. The laser diodes show single mode emission with side mode suppression ratios (SMSR) of up to 32 dB.     

60-W continuous wave laser diode arrays emitting at a wavelength of 808 nm

Samples of cw laser diode arrays (LDAs) with an output power higher than 60 W emitting in the spectral range of 808 nm are developed and fabricated. Main output parameters, including light–current, current–voltage characteristics, and emission spectra of a lot of 5 LDAs are measured.     

Efficient diode-pumped intracavity frequency-doubled CW Nd : YLF laser emitting in the red

We demonstrate an efficient continuous-wave diode-pumped Nd : YLF laser emitting in the red (660.5 and 657 nm) by intracavity frequency doubling with a LBO crystal. We obtained more than 1 W of average power (in two output beams) for 12 W of pump power with a TEM₀₀ mode. This power is to our knowledge the highest obtained with a frequency-doubled Nd : YLF laser emitting in the red. Comparison between “a-cut” and “c-cut” crystals has been carried out in terms of performance and wavelength emission.     

940nm波长高功率线阵二极管激光器封装研究

 对940nm波长高功率线阵二极管激光器的封装结构进行了重新设计，并在此基础上开展了芯片的封装实验。封装出的线阵二极管激光器，在连续工作时输出激光功率达40W，在准连续工作时（占空比0.5%），输出峰值功率可达100W。     

940nm波长高功率线阵二极管激光器封装研究

对940nm波长高功率线阵二极管激光器的封装结构进行了重新设计,并在此基础上开展了芯片的封装实验。封装出的线阵二极管激光器,在连续工作时输出激光功率达40W,在准连续工作时（占空比0.5%）,输出峰值功率可达100W。     

Quasi-CW diode pumped Nd:KGW laser at low temperature

We have studied the laser performance of Nd: KGW and Nd: YAG rods by monitoring the 1.06 μm laser emission at 78.5 K and 300 K. Our observations indicate that the laser efficiency from Nd: KGW is much higher than from Nd: YAG at these two temperatures. The laser threshold in Nd: KGW is lower at 78.5 K than at 300 K but it is always lower than that in Nd:YAG.     

Comment on: “Impact of modulated multiple optical feedback time delays on laser diode chaos synchronization” [Opt. Commun. 282 (2009) 3568]

Synchronization between laser diodes subject to multiple incoherent, delayed, optical feedback has been recently investigated [Shahverdiev, Shore, Opt. Commun. 282 (2009) 3568] through numerical simulations. Here, I explain that the model that was proposed and used is not suitable when the lasers are subject to multiple feedbacks of this kind.     

980 nm半导体激光器n型波导结构优化

为了提高980 nm半导体激光器的输出功率并获得较小的远场发散角,在非对称波导结构的基础上设计了n型波导结构,即在n型波导中引入高折射率的内波导层。采用理论计算和SimLastip软件模拟对常规非对称波导结构和内波导结构进行了研究。利用分子束外延系统生长980 nm内波导结构的外延材料, 并制作了激光器。对于条宽为100 m、腔长为1000 m的器件,阈值电流为97 mA,斜率效率为1.01 W/A;当注入电流为500 mA时,远场发散角为29(垂直向) 8(水平向),与模拟结果相符。理论计算和实验结果表明：较之于常规非对称波导结构,内波导结构可有效降低光场限制因子,提高输出功率,减小远场发散角。     

High-efficiency Nd:GdVO4 laser at 1341 nm under 880 nm diode laser pumping into the emitting level

Highly efficient 1341 nm continuous-wave laser under 880 nm diode laser pumping in Nd:GdVO₄ crystal is reported. Comparative results obtained by the traditional pumping at 808 nm were presented, showing that the slope efficiency and the threshold with respect to the absorbed pump power under 880 nm pumping was 34.9% higher and 12.6% lower than those of 808 nm pumping. A high slope efficiency of 49.1% was achieved under 880 nm pumping, with an optical-to-optical conversion efficiency of 41.7%.     

External cavity quantum dot tunable laser through 1.55 μm

The optical performance of InAs/InGaAsP quantum dot (QD) lasers grown on (1 0 0) InP was studied for three different material structures. The most efficient QD laser structure, having a threshold current of 107 mA and an external differential quantum efficiency of 9.4% at room temperature, was used to form the active region of a grating-coupled external cavity tunable laser. A tuning range of 110 nm was demonstrated, which was mainly limited by the mirror and internal losses of the uncoated laser diode. Rapid state-filling of the QDs was also demonstrated by observing the evolution of the spectra with increasing injected current.     

Methane diode laser overtone spectroscopy at 840 nm

Overtone absorption lines of ¹²CH₄ have been examined by using a tunable diode laser (TDL) spectrometer in the region around (840 nm) where the combination overtone band ν₁+3ν₃ lies. The spectrometer sources are commercially available heterostructure GaAlAs TDLs operating in the “free-running” mode, which allowed the detection of the line positions within . The wavelength modulation spectroscopy (WMS) and the second harmonic detection technique permitted the measurements of minimum absorbances of the order of ?5×10^-6. This allowed to observe the weakest lines of the band with absorption cross-sections of the order of ?2×10^-25 cm²/molecule or /amagat. For some of them self-, air-, He- and H₂-broadening coefficients have been obtained at room temperature.     

Rapid shifted excitation Raman difference spectroscopy with a distributed feedback diode laser emitting at 785 nm

A distributed feedback (DFB) laser diode emitting at 785 nm was tested and applied as a light source for shifted excitation Raman difference spectroscopy (SERDS). Due to the physical properties of the laser diode, it was possible to shift the emission wavelength by 8 cm^-1 (0.5 nm) required for our SERDS measurements by simply changing the injection current. The internal grating ensured single mode operation at both wavelength with the frequency stability of ±0.06 cm^-1 (0.004 nm) required for high resolution Raman spectroscopic applications. The shifted spectra were used for calculating enhanced Raman spectra being obscured by a strong scattering background. A 16 dB (≈38 fold) improvement of the signal-to-background noise S̄/σ_B was demonstrated using blackboard chalk as a sample. The tunable DFB laser is a versatile excitation source for SERDS, which could be used in any dispersive Raman system to subtract fluorescence contributions and scattering background. PACS 82.80.Gk; 42.55.-f; 42.64.Fi     

243 nm稳频窄线宽半导体激光器

243 nm是氢原子1S-2S能级跃迁光谱波长. 本文利用Pound-Drever-Hall稳频技术将972 nm光栅反馈外腔半导体激光稳定在一个高精细度低膨胀系数的超稳法布里-珀罗腔上, 通过锥形放大器放大和腔内两次共振增强倍频得到243 nm激光, 最终实现用于探测氢原子1S-2S双光子跃迁的243 nm窄线宽激光.     

Diode-pumped Nd:LGS laser emitting at 888 nm

We present what is, to the best of our knowledge, the first diode-pumped Nd:La₃Ga₅SiO₁₄ (Nd:LGS) laser emitting at 888 nm, based on the ⁴ F _3/2-⁴ I _9/2 transition, generally used for a 904 nm emission. The use of a pump module with 16 passes through the crystal allowed the realization of a Nd:LGS thin-disk laser with 1.41 W of continuous wave (cw) output power at 888 nm. Moreover, intracavity second-harmonic generation (SHG) in cw mode has also been demonstrated with a power of 221 mW at 444 nm by using a BiB₃O₆ (BiBO) nonlinear crystal.     

二极管泵浦高能激光研究进展和展望

高能激光广泛应用于材料加工、科学研究、空间碎片清除、军事应用等领域。二极管泵浦高能激光具有结构紧凑,系统简单、全电驱无限弹仓的特点,近年来,各类二极管泵浦高能激光围绕着同时实现高功率、高效率、高光束质量这一总目标发展迅速。详细综述了国内外高平均功率块状固体激光、高功率可见光波段激光、高峰值功率激光、高功率光纤激光、碱金属蒸气激光等二极管泵浦高能激光的研究进展,并对其发展趋势进行了展望。