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Selected Topics in Quantum Electronics, IEEE Journal of

Issue 4 • Date July-Aug. 2000

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Displaying Results 1 - 16 of 16
  • The impact of LOC structures on 670-nm (Al)GaInP high-power lasers

    Page(s): 564 - 570
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (189 KB)  

    We investigate the potential of large optical cavity (LOC)-laser structures for AlGaInP high-power lasers. For that we study large series of broad area lasers with varying waveguide widths to obtain statistically relevant data. We study in detail I/sub th/, /spl alpha//sub i/, /spl eta//sub i/, and P/sub max/, and analyze above-threshold behavior including temperature stability and leakage current. We got as expected for LOC structures minimal /spl alpha//sub i//spl les/1 cm/sup -1/ resulting in /spl eta//sup d/=1.1 W/A for 64/spl times/2000 /spl mu/m/sup 2/ uncoated devices. We obtain total output powers /spl ges/3.2 W (qCW) and /spl ges/1.5 W (CW) at 20/spl deg/C. View full abstract»

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  • Low-divergence laser structures for cost-effective fiber coupling applications

    Page(s): 571 - 576
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (86 KB)  

    We report on the design of lasers using waveguide engineering to achieve low divergence emission with high butt-coupling efficiency to single-mode (SMF) and multimode fiber (MMF). A tolerant design principle is introduced for achieving low-divergence normal to the junction using a single epitaxial growth step. The design method is compatible with a wide range of material systems and is demonstrated using a 980-nm laser structure. The full-width half-maximum of the beam is reduced from more than 32/spl deg/ to 21/spl deg/. Direct butt-coupling losses are improved from -10 dB to near -3 dB for ridge waveguide to SMF coupling, while broad area devices coupled to MMF showed coupling efficiencies of >75%. View full abstract»

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  • Design consideration and performance of high-power and high-brightness InGaAs-InGaAsP-AlGaAs quantum-well diode lasers (/spl lambda/=0.98 /spl mu/m)

    Page(s): 577 - 584
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (181 KB)  

    We conduct a theoretical analysis of the design, fabrication, and performance measurement of high-power and high-brightness strained quantum-well lasers emitting at 0.98 /spl mu/m. The material system of interest consists of an Al-free InGaAs-InGaAsP active region and AlGaAs cladding layers. Some key parameters of the laser structure are theoretically analyzed, and their effects on the laser performance are discussed. The laser material is grown by metal-organic chemical vapor deposition and demonstrates high quality with low-threshold current density, high internal quantum efficiency, and extremely low internal loss. High-performance broad-area multimode and ridge-waveguide single-mode laser devices are fabricated. For 100-/spl mu/m-wide stripe lasers having a cavity length of 800 /spl mu/m, a high slope efficiency of 1.08 W-A, a low vertical beam divergence of 34/spl deg/, a high output power of over 4.45 W, and a very high characteristic temperature coefficient of 250 K were achieved. Lifetime tests performed at 1.2-1.3 W (12-13 mW//spl mu/m) demonstrates reliable performance. For 4-/spl mu/m-wide ridge waveguide single-mode laser devices, a maximum output power of 394 mW and fundamental mode power up to 200 mW with slope efficiency of 0.91 mW//spl mu/m are obtained. View full abstract»

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  • Dynamic model of tapered semiconductor lasers and amplifiers based on transmission-line laser modeling

    Page(s): 585 - 593
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (198 KB)  

    We have proposed a new dynamic model for both tapered laser oscillator and laser amplifier structures based on transmission-line laser modeling. The internal laser processes are represented in terms of microwave circuit theory, giving additional insight to the operation of the laser. The model is semianalytical to improve computational efficiency and is in time domain to allow inclusion of nonlinear effects. Simulation results agree with published results, proving the validity of the model. The dynamics of picosecond pulse amplification in tapered amplifier structures have been studied using the model, taking into account the effects of pulse energy and residual reflectivity. It has been found that residual reflectivity can give an almost undistorted amplified pulse, at the expense of pulse energy gain. View full abstract»

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  • Tapered-cavity surface-emitting distributed-Bragg-reflector semiconductor lasers: modeling and experiment

    Page(s): 594 - 600
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (247 KB)  

    We report on the design and fabrication of tapered cavity grating coupled surface-emitting distributed Bragg reflector (DBR) lasers in the 980-nm regime. A curved second-order grating is used at the end of a tapered gain section to provide feedback as well as collimated surface out-coupling. A detailed numerical analysis shows that operation up to approximately twice the threshold is possible without significant degradation of the far field. Near diffraction-limited collimated surface-emitting output with moderate power of about 150 mW is obtained under continuous operation. View full abstract»

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  • High-brightness semiconductor laser sources for materials processing: stacking, beam shaping, and bars

    Page(s): 601 - 614
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (469 KB)  

    A compact, reliable semiconductor laser source for materials processing, medical, and pumping applications is described. This industrial laser source relies on a combination of technologies that have matured in recent years. In particular, effective means of stacking and imaging monolithic semiconductor laser arrays (a.k.a., bars), together with advances in the design and manufacture of the bars, have enabled the production of robust sources at market-competitive costs. Semiconductor lasers are presently the only lasers known that combine an efficiency of about 50% with compact size and high reliability. Currently the maximum demonstrated output power of a 10-mm-wide semiconductor laser bar exceeds the 260 W level when assembled on an actively cooled heat sink. (The rated power is in the range of 50-100 W). Power levels in the kilowatt range can be reached by stacking such devices. The requirements on the stacking technique and the optic assembly to achieve high brightness are discussed. Optics for beam collimation in fast and slow axis are compared. An example for an optical setup to use in materials processing will be shown. Spot sizes as low as 0.4 mm/spl times/1.2 mm at a numerical aperture of 0.3 and output power of 1 kW are demonstrated. This results in a power density of more than 200 kW/cm/sup 2/. A setup for further increase in brightness by wavelength and polarization coupling will be outlined. For incoherent coupling of multiple beams into a single core optical fiber, a sophisticated beam shaping device is needed to homogenize the beam quality of stacked semiconductor lasers. Applications economics dictate that reliable operation is achievable at numerous wavelengths (both for wavelength-specific applications and for brightness scaling through geometric wavelength multiplexing) and at ever higher per bar power levels. New material systems and epitaxial structures continue to be evaluated in this pursuit. Here we include details of designs and performance- for devices operating at 808, 830, and 915 nm. These include characteristics of both single-emitter devices and bars. View full abstract»

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  • Failure statistics for diode laser array modules and replacement model in large-scale laser systems

    Page(s): 615 - 622
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (191 KB)  

    This paper presents a methodology for synthesizing diode-laser array module failure statistics from the failure statistics of constituent diode laser arrays. In addition, a model is elucidated for analyzing replacement strategies of systems containing large numbers of diode laser array modules. Simulations reveal the dependence of synthesized module failure statistics and replacement characteristics on module size and failure statistics of the constituent diode laser arrays. View full abstract»

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  • Repetition rate scaling up to 100 kHz of a small-scale (50 W) kinetically enhanced copper vapor laser

    Page(s): 623 - 628
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (80 KB)  

    We report on the pulse repetition frequency (PRF) scaling of a small-scale (25 mm bore and 0.61 m long) copper vapor laser (CVL). When operated as an elemental CVL, the laser had a stable output power of 15 W at 15 kHz PRF (9.6% efficiency). After the addition of small quantities of hydrogen and hydrogen chloride to the neon buffer gas, the maximum recorded stable output power increased to 41 W at 25 kHz PRF (1.4% efficiency). This represents a record stable specific output power of 0.14 W cm/sup -3/. Pulse repetition frequency scaling of the laser was demonstrated up to 100 kHz where the output power was 9.0 W. By operating the laser at elevated input powers, transient output powers of over 50 W were achieved between PRFs of 25-40 kHz. These results are the highest recorded specific output powers (0.17 W cm/sup -3/) for a CVL with this tube diameter. View full abstract»

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  • High-power/high-brightness diode-pumped 1.9-/spl mu/m thulium and resonantly pumped 2.1-/spl mu/m holmium lasers

    Page(s): 629 - 635
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    We report high power (>36 W) with beam propagation factor M/sup 2//spl sim/2 in a diode end-pumped Tm:LiYF/sub 4/ (Tm:YLF) laser generating output near the 1.91-/spl mu/m region. Using the 1.91-/spl mu/m emission and high brightness achieved with the Tm:YLF laser we resonantly end-pump the Holmium /sup 5/I/sub 7/ manifold in Ho:YAG and demonstrate /spl sim/19 W of continuous-wave (CW) output. The diode-to-Holmium optical to-optical conversion efficiency achieved is /spl sim/18%. Using a CW pumped and repetitively Q-switched configuration, the Tm:YLF pumped Ho:YAG laser achieves >16 W of output power with an M/sup 2//spl sim/1.48 at 15 kHz. A Q-switched frequency range of 9 to >50 kHz is also achieved. View full abstract»

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  • Thermal effects in high-power end-pumped lasers with elliptical-mode geometry

    Page(s): 636 - 642
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (147 KB)  

    We discuss in detail the effects of thermal lensing and thermally induced stress in end-pumped lasers with a strongly elliptical pump and laser mode and compare this situation with cylindrical rod geometries. View full abstract»

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  • Power scalable TEM/sub 00/ CW Nd:YAG laser with thermal lens compensation

    Page(s): 643 - 649
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (306 KB)  

    We present finite-element analysis and experimental results to validate our approach for building high-power single-mode Nd:YAG lasers. We show that the thermooptical and thermomechanical properties of a slab laser can be controlled. This is essential for the use of the proposed unstable resonator, We include demonstration of an efficient subscale laser operating at 20 W TEM/sub 00/. View full abstract»

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  • A 1-kW CW thin disc laser

    Page(s): 650 - 657
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (218 KB)  

    The thin disc laser is presented as an optimal laser design for the operation of a quasi-three-level laser active medium in the high power regime with high optical efficiency. Numerical calculations of the laser output power show that operation with an output power up to 1 kW with an optical efficiency of 50% and more is possible at room temperature utilizing 16 absorption passes. Scaling of the output power can be realized by scaling the pumped area using one or more discs. The experimental investigations yield a maximum output power of 647 W at 51% optical efficiency for one crystal and of 1070 W with 48% optical efficiency for four crystals at a temperature of the cooling water of 15/spl deg/C. View full abstract»

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  • Ultrafast, ultrahigh-peak, and high-average power Ti:sapphire laser system and its applications

    Page(s): 658 - 675
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (481 KB)  

    We review progress in the generation of multiterawatt optical pulses in the 10-fs range. We describe a design, performance, and characterization of a Ti:sapphire laser system based on chirped-pulse amplification, which has produced a peak power in excess of 100 TW with sub-20-fs pulse durations and an average power of 19 W at a 10-Hz repetition rate. We also discuss extension of this system to the petawatt power level and potential applications in the relativistic, ultrahigh intensity regimes. View full abstract»

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  • Petawatt laser system and experiments

    Page(s): 676 - 688
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    We have developed a hybrid Ti:sapphire-Nd:glass laser system that produces more than 1.5 PW of peak power. The system has produced up to 680 J of energy on target at 1054 nm in a compressed 440/spl plusmn/20-fs pulse by use of 94-cm diffraction gratings. A focused irradiance of up to 6/spl times/10/sup 20/ W/cm/sup 2/ was achieved using an on-axis parabolic mirror and adaptive optic wavefront control. Experiments with the petawatt laser system focused the beam on solid targets and produced a strongly relativistic interaction. Energy content, spectra, and angular pattern of the photon, electron, and ion radiations were diagnosed in a number of ways, including several nuclear activation techniques. Approximately 40-50% of the laser energy was converted to broadly beamed hot electrons, with an associated bremsstrahlung beam. High luminosity ion beams were observed normal to the rear surface of various targets with energies up to /spl ges/55 MeV, representing /spl sim/7% of the laser energy. These and other results are presented. View full abstract»

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  • Surface texturing of aluminum alloy 2024-T3 via femto- and nanosecond pulse excimer laser irradiation

    Page(s): 689 - 695
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    Surface texturing effects of aluminum alloy 2024-T3 using femtosecond and nanosecond pulse laser irradiation were studied. The micrographs of the scanning electron microscopy (SEM) were characterized as a function of incident laser fluence. Results indicated that the surface features, ranging from nano to microdimension, can be developed through variation in laser fluence intensities. Two ablation regimes in the logarithmic fluence dependence of the ablated depth for the 500-fs-pulse irradiation were observed. The theoretical analysis for ablation processes is in good agreement with the experimental results. View full abstract»

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  • Manufacturing with novel high-power diode lasers

    Page(s): 696 - 705
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (615 KB)  

    Direct applications of high-power diode lasers (HPDLs) like hardening, heat conduction welding of metals, and joining of polymers have already been demonstrated also in the industrial environment. Relatively low intensities in the range of 10/sup 3/ W cm/sup -2/ are sufficient for these applications. While the commercial HPDL systems are built on the basis of diode laser bars with 40 W output power, in the meantime a record continuous-wave-output power of 267 W per bar has been demonstrated. The achievable higher output power per bar will lead to enhanced applicability of HPDLs and thus to a further steep increase of their industrial use. Improved packaging technology, multiplexing the emission of single bars and coherent coupling as well as promising new diode laser structures like Z-shaped broad area emitters, is discussed. In this paper, emphasis is laid on the potential applicability of commercial HPDLs for metal working with elevated intensities up to 10/sup 5/ W cm/sup -2/, like oxygen cutting and the worldwide first deep-penetration HPDL-weld up to a sheet thickness of 6 mm in stainless steel. These results have been predicted by proper theoretical modeling. Strong reduction of phase space dimension takes place in convective-diffusive-type free boundary problems typical for thermal processing. This property makes it possible to construct approximate finite-dimensional dynamical systems being solvable with controlled error. Numerical solutions of the full problem are used to investigate the quality of the approximate model. Observable quantities of the technical processes like signals from monitoring devices are part of the solution and solutions to the inverse problem are given. View full abstract»

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Aims & Scope

Papers published in the IEEE Journal of Selected Topics in Quantum Electronics fall within the broad field of science and technology of quantum electronics of a device, subsystem, or system-oriented nature.

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Meet Our Editors

Editor-in-Chief
John Cartledge
Queen's University