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Optimization Of Broad Area Gaas Diode Lasers For High Powers And High Efficiencies In The Temperature Range 200 220 K
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Book Synopsis Optimization of Broad-area GaAs Diode Lasers for High Powers and High Efficiencies in the Temperature Range 200-220 K by : Frevert Carlo
Download or read book Optimization of Broad-area GaAs Diode Lasers for High Powers and High Efficiencies in the Temperature Range 200-220 K written by Frevert Carlo and published by . This book was released on 2019-07-11 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work focuses on the development of AlGaAs-based diode laser (DL) bars optimized for reaching highest powers and efficiencies at low operation temperatures. Specifically, the quasi continuous wave (QCW) pumping of cryogenically cooled Yb: YAG solid-state lasers is targeted, setting requirements on the wavelength (940 nm), the pulse conditions (pulse length 1.2 ms) and frequency (10 Hz) as well as the lowest DL operating temperature THS 200 K, consistent with economic cooling. High fill-factor bars for QCW operation are to reach high optical performance with optical output powers of P 1.5 kW and power conversion efficiencies of ŋE 60% at these power levels. Understanding the efficiency-limiting factors and the behavior at lower temperatures is necessary to design these devices. Optimizations are performed iteratively in three stages. First, vertical epitaxial designs are studied theoretically, adjusted to the targeted operation temperatures and specific laser parameters are extracted. Secondly, resulting vertical designs are processed into low power single emitters and their electro-optical behavior at low currents is experimentally assessed over a wide range of temperatures. The obtained laser parameters characteristic to the vertical design are then used to extrapolate the laser's performance up to the high targeted currents. Finally, vertical designs promising to reach the targeted values for power and efficiency are processed into high power single emitters and bars which are measured up to the highest currents. Eventually, laser bars are fabricated reaching output powers of 2 kW and efficiencies of 61% at 1.5 kW at an operation temperature of 203 K.
Book Synopsis Epitaxial Design Optimizations for Increased Efficiency in GaAs-Based High Power Diode Lasers by : Thorben Kaul
Download or read book Epitaxial Design Optimizations for Increased Efficiency in GaAs-Based High Power Diode Lasers written by Thorben Kaul and published by Cuvillier Verlag. This book was released on 2021-04-09 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work presents progress in the root-cause analysis of power saturation mechanisms in continuous wave (CW) driven GaAs-based high-power broad area diode lasers operated at 935 nm. Target is to increase efficiency at high optical CW powers by epitaxial design. The novel extreme triple asymmetric (ETAS) design was developed and patented within this work to equip diode lasers that use an extremely thin p-waveguide with a high modal gain. An iterative variation of diode lasers employing ETAS designs was used to experimentally clarify the impact of modal gain on the temperature dependence of internal differential quantum efficiency (IDQE) and optical loss. High modal gain leads to increased free carrier absorption from the active region. However, less power saturation is observed, which must then be attributed to an improved temperature sensitivity of the IDQE. The effect of longitudinal spatial hole burning (LSHB) leads to above average non-linear carrier loss at the back facet of the device. At high CW currents the junction temperature rises. Therefore, not only the asymmetry of the carrier profile increases but also the average carrier density in order to compensate for the decreased material gain and increased threshold gain. This carrier non-pinning effect above threshold is found in this work to enhance the impact of LSHB already at low currents, leading to rapid degradation of IDQE with temperature. This finding puts LSHB into a new context for CW-driven devices as it emphasizes the importance of low carrier densities at threshold. The carrier density was effectively reduced by applying the novel ETAS design. This enabled diode lasers to be realized that show minimized degradation of IDQE with temperature and therefore improved performance in CW operation.
Book Synopsis Broad-Area Laser Bars for 1 kW-Emission by : Matthias M. Karow
Download or read book Broad-Area Laser Bars for 1 kW-Emission written by Matthias M. Karow and published by Cuvillier Verlag. This book was released on 2022-06-27 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: ndustrial laser systems for material processing applications rely on the availability of highly efficient, high-brightness diode lasers. GaAs-based broad-area laser bars play a vital role in such applications as pump sources for high-beam-quality solid-state lasers and, increasingly, as direct processing tools. This work studies 940 nm-laser bars emitting 1 kW optical power at room temperature, identifying those physical mechanisms that are currently limiting electrical-to-optical conversion efficiency as well as lateral beam quality. In the process, several diagnostic studies on bars with varied lateral-longitudinal design were carried out. The effects of technological measures for performance optimization were analyzed, yielding a new benchmark in efficiency and lateral divergence. The studies into altered resonator lengths of 4 and 6 mm as well as fill factors between 69 and 87 % successfully reduce both the voltage dropping across the device and power saturation at high currents, enabling 66 % efficiency at the operation point. Concrete measures how to reach efficiencies ≥70 % are presented thereafter, showing that doubling the efficiency value of the first 1 kW-demonstration in 2007 – amounting to 35 % – is in near reach. Investigation of the beam quality bases on a herein proposed and realized concept, in which the far field is resolved for each individual bar emitter. In this way, it is possible to determine how far-field profiles vary along the bar width and how much these variations affect the overall bar far-field. Further, such effects specific to bar structures can be separated into non-thermal and thermal influences. The effect of mechanical chip deformation (bar smile) as well as neighboring-emitter interaction has been investigated for the first time in active kW-class devices, yielding a lateral divergence as low as 8.8° at the operation point.
Book Synopsis High-Power Diode Lasers by : Roland Diehl
Download or read book High-Power Diode Lasers written by Roland Diehl and published by Springer Science & Business Media. This book was released on 2003-07-01 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starting from the basics of semiconductor lasers with emphasis on the generation of high optical output power the reader is introduced in a tutorial way to all key technologies required to fabricate high-power diode-laser sources. Various applications are exemplified.
Book Synopsis Optimized Performance GaAs-Based Diode Lasers: Reliable 800-nm 125W Bars and 83.5% Efficient 975-nm Single Emitters by :
Download or read book Optimized Performance GaAs-Based Diode Lasers: Reliable 800-nm 125W Bars and 83.5% Efficient 975-nm Single Emitters written by and published by . This book was released on 2005 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: GaAs-based high power diode bars produce wavelengths in the range of 780 to 980 nm and are widely used for pumping a broad range of rare earth doped solid-state lasers. As the markets for these laser systems mature, diode lasers that operate at higher power levels, greater overall efficiency, and higher reliability are in high demand. In this paper we report efficiencies of up to 83.5% in the 9xx-nm band, continuous wave power levels over 360-Watts in the 8xx-nm band, and reliable operation at 125-Watts.
Book Synopsis Design, simulation and analysis of laterally-longitudinally non-uniform edge-emitting GaAs-based diode lasers (Band 73) by : Jan-Philipp Koester
Download or read book Design, simulation and analysis of laterally-longitudinally non-uniform edge-emitting GaAs-based diode lasers (Band 73) written by Jan-Philipp Koester and published by Cuvillier Verlag. This book was released on 2023-09-19 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: Edge-emitting quantum-well diode lasers based on GaAs combine a high conversion efficiency, a wide range of emission wavelengths covering a span from 630 nm to 1180 nm, and the ability to achieve high output powers. The often used longitudinal-invariant Fabry-Pérot-type resonators are easy to design but often lead to functionality or performance limitations. In this work, the application of laterally-longitudinally non-uniform resonator configurations is explored as a way to reduce unwanted and performance-limiting effects. The investigations are carried out on existing and entirely newly developed laser designs using dedicated simulation tools. These include a sophisticated time-dependent laser simulator based on a traveling-wave model of the optical fields in the lateral-longitudinal plane and a Maxwell solver based on the eigenmode expansion method for the simulation of passive waveguides. Whenever possible, the simulation results are compared with experimental data. Based on this approach, three fundamentally different laser types are investigated: • Dual-wavelength lasers emitting two slightly detuned wavelengths around 784 nm out of a single aperture • Ridge-waveguide lasers with tapered waveguide and contact layouts that emit light of a wavelength of around 970 nm • Broad-area lasers with slightly tapered contact layouts emitting at 910 nm The results of this thesis underline the potential of lateral-longitudinal non-uniform laser designs to increase selected aspects of device performance, including beam quality, spectral stability, and output power.
Book Synopsis Analysis and mitigation of the factors limiting the efficiency of high power distributed feedback diode lasers by : Christoph Matthias Schultz
Download or read book Analysis and mitigation of the factors limiting the efficiency of high power distributed feedback diode lasers written by Christoph Matthias Schultz and published by Cuvillier Verlag. This book was released on 2013-10-08 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-power, high-efficiency, wavelength-stabilized broad area (BA) diode lasers are promising devices for industrial applications. They can be used, for example, for pumping narrow absorption bands in gain media of solid-state and fiber lasers as well as for power scaling by means of dense spectral beam combining. This thesis focuses on the analysis and mitigation of the factors limiting the efficiency of high-power distributed feedback (DFB) diode lasers. In particular, it will be shown how a power conversion efficiency in the 60 %-range can be achieved from 10 W-class 100 μm stripe DFB-BA lasers – values close to those of state-of-the-art Fabry-Pérot (FP) BA lasers. For the first time world-wide, newly developed DFB-BA lasers achieve 12 W continuous mode optical output power with 62 % peak power conversion efficiency and 58 % at 10 W, respectively. Wavelength stabilization is demonstrated from threshold to 15 A with a spectral width below 0.8 nm containing 95 % of the emitted power. The factors limiting the efficiency of DFB-BA lasers compared to state-of-the-art 10 W-class FP-BA lasers have been identified and as a result largely eliminated.
Book Synopsis Tailoring the Emission of Stripe-array Diode Lasers with External Cavities to Enable Nonlinear Frequency Conversion by : Andreas Jechow
Download or read book Tailoring the Emission of Stripe-array Diode Lasers with External Cavities to Enable Nonlinear Frequency Conversion written by Andreas Jechow and published by Universitätsverlag Potsdam. This book was released on 2009 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: A huge number of applications require coherent radiation in the visible spectral range. Since diode lasers are very compact and efficient light sources, there exists a great interest to cover these applications with diode laser emission. Despite modern band gap engineering not all wavelengths can be accessed with diode laser radiation. Especially in the visible spectral range between 480 nm and 630 nm no emission from diode lasers is available, yet. Nonlinear frequency conversion of near-infrared radiation is a common way to generate coherent emission in the visible spectral range. However, radiation with extraordinary spatial temporal and spectral quality is required to pump frequency conversion. Broad area (BA) diode lasers are reliable high power light sources in the near-infrared spectral range. They belong to the most efficient coherent light sources with electro-optical efficiencies of more than 70%. Standard BA lasers are not suitable as pump lasers for frequency conversion because of their poor beam quality and spectral properties. For this purpose, tapered lasers and diode lasers with Bragg gratings are utilized. However, these new diode laser structures demand for additional manufacturing and assembling steps that makes their processing challenging and expensive. An alternative to BA diode lasers is the stripe-array architecture. The emitting area of a stripe-array diode laser is comparable to a BA device and the manufacturing of these arrays requires only one additional process step. Such a stripe-array consists of several narrow striped emitters realized with close proximity. Due to the overlap of the fields of neighboring emitters or the presence of leaky waves, a strong coupling between the emitters exists. As a consequence, the emission of such an array is characterized by a so called supermode. However, for the free running stripe-array mode competition between several supermodes occurs because of the lack of wavelength stabilization. This leads to power fluctuations, spectral instabilities and poor beam quality. Thus, it was necessary to study the emission properties of those stripe-arrays to find new concepts to realize an external synchronization of the emitters. The aim was to achieve stable longitudinal and transversal single mode operation with high output powers giving a brightness sufficient for efficient nonlinear frequency conversion. For this purpose a comprehensive analysis of the stripe-array devices was done here. The physical effects that are the origin of the emission characteristics were investigated theoretically and experimentally. In this context numerical models could be verified and extended. A good agreement between simulation and experiment was observed. One way to stabilize a specific supermode of an array is to operate it in an external cavity. Based on mathematical simulations and experimental work, it was possible to design novel external cavities to select a specific supermode and stabilize all emitters of the array at the same wavelength. This resulted in stable emission with 1 W output power, a narrow bandwidth in the range of 2 MHz and a very good beam quality with M²<1.5. This is a new level of brightness and brilliance compared to other BA and stripe-array diode laser systems. The emission from this external cavity diode laser (ECDL) satisfied the requirements for nonlinear frequency conversion. Furthermore, a huge improvement to existing concepts was made. In the next step newly available periodically poled crystals were used for second harmonic generation (SHG) in single pass setups. With the stripe-array ECDL as pump source, more than 140 mW of coherent radiation at 488 nm could be generated with a very high opto-optical conversion efficiency. The generated blue light had very good transversal and longitudinal properties and could be used to generate biphotons by parametric down-conversion. This was feasible because of the improvement made with the infrared stripe-array diode lasers due to the development of new physical concepts.
Book Synopsis Electrical & Electronics Abstracts by :
Download or read book Electrical & Electronics Abstracts written by and published by . This book was released on 1997 with total page 1860 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis High Power Diode Lasers by : Friedrich Bachmann
Download or read book High Power Diode Lasers written by Friedrich Bachmann and published by Springer. This book was released on 2007-05-26 with total page 553 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book summarizes a five year research project, as well as subsequent results regarding high power diode laser systems and their application in materials processing. The text explores the entire chain of technology, from the semiconductor technology, through cooling mounting and assembly, beam shaping and system technology, to applications in the processing of such materials as metals and polymers. Includes theoretical models, a range of important parameters and practical tips.
Book Synopsis Realization of High Power Diode Lasers with Extremely Narrow Vertical Divergence by : Agnieszka Pietrzak
Download or read book Realization of High Power Diode Lasers with Extremely Narrow Vertical Divergence written by Agnieszka Pietrzak and published by Cuvillier Verlag. This book was released on 2012-04-18 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: The doctoral thesis deals with high power InGaAs/GaAsP/AlGaAs quantum well diode lasers grown on a GaAs substrate with emission wavelengths in the range of 1050 nm – 1150 nm. The objective of this thesis is the development of diode lasers with extremely narrow vertical laser beam divergence without any resulting decrease in the optical output power compared to current state of the art devices. The work is focused on the design of the internal laser structure (epitaxial structure), with the goal of optical mode expansion (thus reduction of the beam divergence), and the experimental investigation of the electro-optical properties of the processed laser devices. Diagnosis of the factors limiting the performance is also performed. The optical mode expansion is realized by increasing the thickness of the waveguide layers. Structures with a very thick optical cavity are named in this work as Super Large Optical Cavity structures (SLOC). The vertical optical mode is modeled by solving the one-dimensional waveguide equation, and the far-field profiles are obtained from the Fourier transform of the electrical field at the laser facet (near-field). Calculations are performed by using the software tool QIP. The electro-optical properties (such as vertical electrical carrier transport and power-voltagecurrent characteristics, without self-heating effect) are simulated using the WIAS-TeSCA software. Both software tools are described in this thesis. The lasers chips, grown by means of MOVPE and processed as broad area single emitters, are experimentally tested under three measurement conditions. First, uncoated and unmounted laser chips with various lengths are characterized under pulsed operation (1.5 μs, 5 kHz) in order to obtain the internal parameters of the laser structure. In the second part of the laser characterization, the facet-coated and mounted devices with large (4 - 8 mm long) Fabry-Perot resonators are tested under quasi-continuous wave operation (500 μs, 20 Hz). Finally, these devices are also tested under ‘zero-heat’ conditions (300 ns pulse duration, 1 kHz repetition rate). The ‘zero-heat’ test is performed in order to investigate the factors, other than overheating of the device, that limit the maximum output power. All measurements are performed at a heat-sink temperature of 25°C. The measurement techniques used to characterize the electro-optical properties of the laser and the laser beam properties are also described. More specifically, the influence of the material composition and the thickness of the waveguide layers on the vertical beam divergence angle (perpendicular to the epitaxial structure) and on the electro-optical properties of the laser is discussed. It is shown that, due to the large cross section of the investigated laser chips, catastrophic optical mirror damage (COMD) is strongly reduced and that one of the major factors limiting the maximum optical power of the discussed diode lasers is weak carrier confinement in the active region leading to enhanced carrier and optical losses due to carrier accumulation in the thick waveguide. The reason for the vertical carrier leakage is a low effective barrier between the quantum well and the GaAs waveguide. Moreover, it is shown that the carrier confinement in the active region can be strengthened in three ways. Firstly, the QW depth is increased for lasers emitting at longer wavelength (here ~ 1130 nm). Secondly, utilizing a higher number of QWs lowers the threshold carrier density per QW. In this case, the electron Fermi-level shifts towards lower energies for lower threshold currents and thus the effective barrier heights are increased. Thirdly, in lasers emitting especially at wavelengths shorter than 1130 nm (around 1064 nm, a wavelength commercially interesting) the quantum wells are shallower and thus the effective barrier is lower. It is shown that AlGaAs waveguides are required to improve the carrier confinement. The AlGaAs alloys provide higher conduction and lower valence band edge energies of the bulk material. Consequently, the potential barrier against carrier escape from the QW to the waveguide is increased. Considering the mode expansion in the SLOC structures, it is shown, in simulation and experimentally, that the multi-quantum well active region, due to its high average refractive index, contributes significantly to the guiding of the modes. The optical mode is stronger confined in active regions with a higher number of quantum wells as well as in structures based on AlGaAs waveguides which are characterized by a lower refractive index compared to GaAs material. The increased mode confinement leads to a reduced equivalent vertical spot-size and results in a wider divergence angle of the laser beam. Moreover, by increasing the thickness of the waveguide layers the active region acts more and more as a waveguide itself thus preventing a further narrowing of the vertical far-field. As a new finding, it is presented that the introduction of low-refractive index quantum barriers (LIQB), enclosing the high-refractive index quantum wells, lowers the average refractive index of the multi-quantum well active region and thus reduces the beam divergence (the invention is content of a German Patent Application DEA102009024945). Through systematic model-based experimental investigations of a series of laser diode structures, the vertical beam divergence was reduced from 19° to 8.6° at full width at half maximum (FWHM) and from 30° to 15°, at 95% power content. The achieved vertical farfield angle is smaller, by a factor of ~3, than state-of-the-art laser devices. The 8 mm long and 200 μm wide single emitters based on the investigated SLOC structures deliver more than 30 W peak-power in quasi-continuous wave mode. The large equivalent spot-size together with the facet passivation prevent COMD failure and the maximum measured power is limited due to the overheating of the device. Moreover, a 4 mm long and 200 μm wide single emitter tested under ‘zero-heat’ condition delivers 124 W power. The maximal measured power was limited by the current supply.
Book Synopsis Improvement of the beam quality of high-power broad area semiconductor diode lasers by means of an external resonator by : Ahmad Ibrahim Bawamia
Download or read book Improvement of the beam quality of high-power broad area semiconductor diode lasers by means of an external resonator written by Ahmad Ibrahim Bawamia and published by Cuvillier Verlag. This book was released on 2012-04-03 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: The operation of high-power broad area laser diodes in an external resonator is studied with respect to the improvement of their lateral beam quality. A simple setup with a broad area laser diode as gain medium, two lenses and an external mirror is considered. The concept relies on the ability of the active region of the laser diode to act as a spatial filter for higher order modes oscillating inside the resonator. The geometries of the external cavity laser that favor fundamental mode operation in the lateral direction are inferred with the help of a theoretical model based on the ABCDmatrix treatment of Gaussian beams in a passive stable resonator. Thermal lensing that arises in the broad area laser diode is included in the model. The simulation results show that, for a given strength of the thermal lens arising inside the broad area laser diode, there exists one geometry of the external resonator that produces single mode operation as well as a high overlap between the optical mode and the gain medium of the laser diode. A novel experimental procedure that quantifies the thermal lens arising in the broad area laser diode to be used inside the external resonator is developed. The thermal lens coefficient is determined for different injection currents and pulse widths. The reliability of the method is validated by the comparison of the obtained results with values of the thermal lens coefficient derived from independent measurements and from the simulation of the temperature distribution inside the laser diode. Furthermore, the latter simulation at different pulse widths enables to explain the observed saturation of the thermal lens coefficient as injection current and pulse width are increased. The external cavity laser comprising a test broad area laser diode that emits at a wavelength in the region of 1.06μm, two lenses, and an external mirror is implemented. Additionally, an adjustable intra-cavity slit that serves as a supplementary spatial filter is inserted in the setup. The evolution of the output power and of the beam quality of the device as a function of the length of the resonator and of the width of the slit is studied at injection currents of 1A (close to laser threshold) and 5A (high power operation). It is observed that at both injection currents, the beam quality of the emission is significantly improved when the length of the resonator and the width of the slit are adjusted to their optimal values. In the case of the experiments at an injection current of 1A, the optimal conditions for the operation of the external resonator correspond to the theoretical predictions, but, at an injection current of 5A, they have to be determined experimentally since the behavior of the laser cannot be explained by the model of the passive resonator anymore. The criterion used to assess the performance of the external cavity laser, as compared to a similar free running laser, is the maximum output power weighted by the M2 value. In that respect, at an injection current of 1A, the M2 value is improved from 9.0 to 3.5, with an output power of 0.35W. At the injection current of 5A, the M2 value is improved from 18.7 to 5.6, with a corresponding output power of 2.5W. The latter result compares with the best values reported in the literature for the operation of broad area laser diodes in an external resonator.
Book Synopsis 360W And] 70% Efficient GaAs-Based Diode Lasers by :
Download or read book 360W And] 70% Efficient GaAs-Based Diode Lasers written by and published by . This book was released on 2005 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: High power GaAs-based high power diode bars produce wavelengths in the range of 780 to 980 nm and are widely used for pumping a broad range of rare earth doped solid-state lasers. As the markets for these laser systems mature, diode lasers that operate at higher power levels, greater overall efficiency, and higher reliability are in high demand. In this paper we report efficiencies of over 70% in the 9xx-nm band, continuous wave power levels over 340 Watts in the 8xx-nm band, and reliability data at or above 100 Watts. We will also review the latest advances in performance and detail the basic physics and material science required to achieve these results.
Book Synopsis Investigation of monolithically integrated spectral stabilization in high-brightness broad area diode lasers by : Jonathan Decker
Download or read book Investigation of monolithically integrated spectral stabilization in high-brightness broad area diode lasers written by Jonathan Decker and published by Cuvillier Verlag. This book was released on 2018-06-06 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-power distributed feedback broad area (DFB-BA) lasers are key components for pumping narrow absorption bands in solid-state lasers and for brightness scaling in direct diode laser systems via dense spectral beam combining. Today, the market for these lasers is dominated by DFB-BA lasers with low-order Bragg gratings that are integrated via buried overgrowth techniques. A promising alternative are DFB-BA lasers with high order grat-ings that are directly etched into the p-side of the epitaxial layer structure, so that no interruption of the epitaxial growth process is required. Prior to this work, studies of such DFB-BA lasers were restricted to experimental proof-of-principal realizations. Further, adequate simulation tools were not available, as surface-etched gratings introduce a high refractive index contrast and can therefore not be calculated directly within the coupled mode theory (CMT). Hence, this work treats the development of efficient high-bright-ness DFB-BA lasers and laser arrays with surface-etched gratings at 975 nm. The development of these lasers encompasses three steps: First, a design study of high-brightness Fabry-Pérot laser diodes that are suitable for the integration of surface-etched gratings. Second, the implementation of an adequate numerical model for the simulation of high-order surface-etched DFB grat-ings. Therefore, a simulation based on CMT is extended by bi-directional eigenmode expansion and propagation modelling. And third, a comprehensive experimental study of spectrally stabilized high-brightness DFB-BA lasers. Optimized DFB-BA lasers (L = 6 mm, W = 30 µm) operate with 56% peak conversion efficiency and achieve 5.8 W output power with a slow-axis beam parameter product ≤ 1.8 mm×mrad, and a linewidth ≤ 1.0 nm.
Download or read book Physics Briefs written by and published by . This book was released on 1993 with total page 1288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis International Aerospace Abstracts by :
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1993 with total page 1070 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Broad Area Distributed Gain, Distributed Index Profile GaAlAs Semiconductor Laser Diodes by :
Download or read book Broad Area Distributed Gain, Distributed Index Profile GaAlAs Semiconductor Laser Diodes written by and published by . This book was released on 1991 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-power operation of a simple non-planar index-guided quantum well heterostructure periodic laser array structure is described, in which lateral lasing is prevented in a manner that still allows for uniform and continuous front facet light emission. The compositional disordering and compensation effects of MeV oxygen implantation have been applied to form stripe geometry graded barrier quantum well heterostructure lasers. A new broad area as well as narrow stripe window laser structure is described, in which a nonabsorbing window region is formed in the vicinity of the mirror facets by utilizing a selectively etched substrate and the advantageous properties of uniform MOCVD growth on nonplanar substrates. The growth and characterization of strained layer InGaAs-GaAs heterostructure lasers by MOCVD has been addressed. Ethyldimethylindium has been shown to be suitable as a precursor for the growth of indium compounds. The results of time-zero characterization of strained-layer InxGa(1-x)As-GaAs quantum well heterostructure laser diodes with 70-A-thick wells and indium mole fractions between 0.08 and 0.42 are reported. High power, in-phase locked operation of a wide aperture array is reported in which the lateral lasing and amplified spontaneous emission, characteristic of wide aperture arrays, are suppressed by a nonplanar active region. The antiguiding behavior of InGaAs-GaAs strained layer lasers has been exploited for form multiple-element oxide-defined-stripe phase-locked high power long wavelength (y> 0.95 um) strained layer quantum well heterostructure diode arrays operating in the in-phase fundamental array mode.
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