Find the latest high power diode laser technical white papers and product information to help you with your purchasing decisions.
High-Power Visible Spectrum Diode Lasers for Display and Medical Applications Beam Sources with Tailored Beam Quality and Spectral Characteristics - Photonics West 2014In this paper we report on the further progress of fiber coupled high power diode lasers in the visible spectral range with regard to beam quality and spectral characteristics. Improved beam shaping concepts allow coupling of red and blue diode lasers into smaller fibers. For medical applications beam sources with narrow wavelength distribution in the blue spectral region were developed. Modules up to 100W in a 400μm NA0.22 fiber were realized. Progress in manufacturing technologies allows for coupling of more than 25W into a 200μm NA0.22 fiber in the blue wavelength range.
Scalable and Modular Diode Laser Architecture for Fiber Coupling that Combines High-Power, High-Brightness and Low Weight - Photonics West 2014We have developed a scalable and modular diode laser architecture that combines high-power, high-brightness, and low weight that fulfills these requirements for a multitude of applications. At the heart of the concept is a specially tailored diode laser bar with an epitaxial and lateral structure designed such that only standard fast- and slow-axis collimator lenses are required to couple the beam into a 200μm core fiber with a numerical aperture (NA) of 0.22. To fulfill the requirements of scalability and modularity, a reduced size heat sink populated with multiple tailored bars is used. This enables a compact and lightweight design with minimum beam path length. The design concept is capable of providing single wavelength, high-power laser diode modules, with optional volume holographic gratings for wavelength stabilization. Modules with output power levels of more than one kW at a power-to-weight ratio of less than 1 kg/kW are achievable. In this paper, two laser modules based on this concept are presented. The optical output power is above 500W at a module weight less than 500g and 300W at 300g. Both modules are coupled into a 200μm, 0.22NA fiber.
Feedback-Induced Catastrophic Optical Mirror Damage (COMD) on 976nm Broad Area Single Emitters with Different AR Reflectivity - Photonics West 2014We have carried out a comprehensive study on 976nm single emitters with different AR coatings (1%, 3%, 4%, and 5%), which have been exposed to optical feedback to investigate damages caused by back-reflected light and how to prevent them. By observing the near-field pattern while varying the probe current, we got information about the influence on filamentation and on peak-power densities with and without external optical feedback. For constant feedback strength, filamentation became more pronounced and more dynamic with increasing current. We observed bistable and chaotic "jumping" of high-intensity filaments. For usual operation currents and external feedback strengths of ≥4%, single emitters with low AR coating show COMDs; their positions correlate with excessive peaking in the near-field pattern. Finally we found that an increasing AR reflectivity depletes the influence of feedback light on the near-field pattern as well as on the emission spectra and lowers the risk of COMD.
Narrow Line Diode Laser Stacks for DPAL Pumping - Photonics West 2014Diode pumped alkali metal vapor lasers (DPALs) offer the promise of scalability to very high average power levels while maintaining excellent beam quality, making them an attractive candidate for future defense applications. A variety of gain media are used and each requires a different pump wavelength: near 852nm for cesium, 780nm for rubidium, 766nm for potassium, and 670nm for lithium atoms. The biggest challenge in pumping these materials efficiently is the narrow gain media absorption band of approximately 0.01nm.
Evidence of Photodarkening Mitigation in Yb-Doped Fiber Lasers by Low Power 405 nm Radiation - Photonics West 2014We investigate the impact of a 405 nm radiation on photodarkening generation in Yb-doped fiber laser. Simultaneous photodarkening and photobleaching effects induced by 976 and 405 nm radiations, respectively, were investigated in a 1070 nm laser and compared with the loss induced in an irradiated active fiber. We observed a significant photobleaching effect due to 405 nm radiation but not a complete recovery. A strong absorption of the 405 nm radiation by the excited ions was also observed and could be the limiting factor for the bleaching performance. We also observed for the first time, to the best of our knowledge, ground-state absorption induced photodarkening in pristine fiber irradiated at 405 nm. This effect could generate additional residual losses in the laser system.
High-Resolution Spectral Mapping of a Lensed High Power Laser Bar - Photonics West 2014Alkali gas lasers based on rubidium vapor have an extremely narrow absorption band (<0.01 nm at STP) at 780 nm. Diode-pumped alkali lasers (DPALs) require high-power diode arrays having emission spectra which are closely matched to this absorption peak. There are several methods which can be used for narrowing and stabilizing the output spectrum of a diode laser bar including external locking via a volumetric holographic grating (VHG). While this approach offers several advantages over internal stabilization techniques, the effect of pointing error arising from bar smile can be detrimental to the locked performance of the lensed array. In order to investigate the effect of smile on wavelength locking, a system capable of mapping the emission spectrum of the lensed diode laser bar was developed. The approach utilizes an imaging system and spatial filter to couple light from individual emitters of the lensed array into a commercial optical spectrum analyzer. This approach offers a larger dynamic range than traditional spectral mapping techniques, with a resolved signal to noise ratio in excess of 60 dB. Results from the characterization of a VHG-locked 780 nm laser bar array will be presented.
Diode Lasers used in Plastic Welding and Selective Laser Soldering Applications and ProductsAside from conventional welding methods, laser welding of plastics has established itself as a proven bonding method. The component-conserving and clean process offers numerous advantages and enables welding of sensitive assemblies in automotive, electronic, medical, human care, food packaging and consumer electronics markets. Diode lasers are established since years within plastic welding applications. Also, soft soldering using laser radiation is becoming more and more significant in the field of direct diode laser applications. Fast power controllability combined with a contactless temperature measurement to minimize thermal damage make the diode laser an ideal tool for this application. These advantages come in to full effect when soldering of increasingly small parts in temperature sensitive environments is necessary.
Narrow-Line, Tunable, High-Power, Diode Laser Pump for DPAL Applications - SPIE Defense, Security + SensingWe report on a high-power diode laser pump source for diode-pumped alkali lasers (DPAL), specifically rubidium alkali vapor lasers at 780nm, delivering up to 100W/bar with FWHM spectral line width of 0.06nm (~30GHz). This pump is based on a micro-channel water-cooled stack with collimation in both-axes. Wavelength-locking of the output spectrum allows absorption in one of the very narrow resonance lines of the atomic rubidium alkali vapor. To achieve these results, research was conducted to deliver the highest performance on all key components of the product from the diode laser bar which produces the optical power at 780nm to the external Bragg gratings which narrow the spectrum line width. We highlight the advancements in the epitaxy, device design, beam collimation, grating selection, alignment, tunability and thermal control that enable realization of this novel pump-source for DPALs.
Characterization of Laser Diodes Under Short-Pulsed Conditions with High Pulse Energies - Photonics West 2013New applications require diode lasers to be driven at ultra short pulses in the sub-micro second range. The goal is to minimize both cost and size of the diode laser module by reducing the amount of laser bars to the minimum required number while maintaining a lifetime that is desired for the application. Products demanded by the market range from QCW stacks to fiber coupled modules. Damage thresholds, slow axis divergence of the diode laser, and emitter size are investigated under various pulse conditions for different chip materials. A design study for fiber coupled modules with high pulse energies based on the test results will be shown for various wavelengths.
High-Power Fiber-Coupled 100W Visible Spectrum Diode Lasers for Display Applications - Photonics West 2013Diode lasers in the blue and red spectral range are the most promising light sources for upcoming high-brightness digital projectors in cinemas and large venue displays. They combine improved efficiency, longer lifetime and a greatly improved color space compared to traditional xenon light sources. In this paper we report on high-power visible diode laser sources to serve the demands of this emerging market. A unique electro-optical platform enables scalable fiber coupled sources at 638nm with an output power of up to 100W from a 400µm NA 0.22 fiber. For the blue diode laser source we demonstrate scalable sources based on single emitters ranging from 5 W to 100 W from a 400µm NA 0.22 fiber.
Multi-kW High-Brightness Fiber-Coupled Diode Lasers - Photonics West 2013The ongoing improvement in the brightness of diode lasers makes more and more industrial applications accessible to diode lasers. For many applications in materials processing multi-kW output power with a beam quality of better than 30 mm x mrad is needed. Previously we have reported on a modular diode laser platform with an output power of up to 785W out of a 200µm NA 0.22 fiber at a single wavelength of 976nm. We have now extended that platform to different wavelengths in the range from 900nm to 1100nm. Combining of different wavelengths enables scalable multi-kW high-brightness diode laser units. In this paper we report on a diode laser unit with 3.5kW output power and a beam quality of 25 mm x mrad.
Reliable QCW Diode Laser Arrays for Operation with High Duty Cycles - Photonics West 2013We present performance and reliability data of two novel high-brightness QCW arrays with a custom, compact and robust design for an operation with high duty cycles. Both designs are based on single diodes consisting of a 1cm laser bar that is AuSn soldered between two CuW submounts. The available optical output power is shown to be strongly depending on the wavelength and fill factor of the laser bars as well as on the duty cycle. One of the new array designs can be operated above 1.1 kW at 45°C without additional cooling with 15HZ and 15% duty cycle.
Overview on New Diode Lasers for Defense Applications - SPIE Europe Security & Defence 2012Diode lasers have a broad wavelength range, from the visible to beyond 2.2μm. This allows for various applications in the defense sector, ranging from classic pumping of DPSSL in range finders or target designators, up to pumping directed energy weapons in the 50+ kW range. Also direct diode applications for illumination above 1.55μm, or direct IR countermeasures are of interest.
Advancements in High-Power Diode Laser Stacks for Defense Applications - DEPS/Advanced High Power Lasers 2012This paper reports on the latest advancements in high-power diode laser stacks, which deliver the most compact footprint, power scalability and highest power/bar of any diode laser package. Electro-optical (EO) data on water-cooled (micro-channel) stacks with wavelengths ranging from 7xx nm to 9xx nm and power levels of up to 5.8kW, delivered @ 200W/bar, CW mode, and power-conversion efficiency of 60%, with both-axis collimation will be presented. Also, presented is E-O data on a compact,conductively cooled, hard-soldered, stack package based on conventional CuW and AlN materials, delivering average power/bar 15W operating up to 25% duty cycle, 10ms pulses @ 45C. Results from a 300W, 200mm core/0.22NA fiber coupled package that meets the critical kg/kW metric for directed energy systems will be detailed. These devices can be used as pump-sources for diode-pumped alkali lasers (DPALs), for more traditional DPSS lasers which are power/brightness scaled for directed energy weapons applications, as conductively-cooled arrays for illuminators and as diode pump sources for high brightness fiber lasers.
Enhanced Fiber Coupled Laser Power and Brightness for Defense Applications through Tailored Diode and Thermal Design - SPIE Defense, Security + Sensing 2012Advances in both diode laser design and packaging technology, particularly thermal management, are needed to enhance the brightness of fiber coupled diode lasers while maintaining the small size and light weight required for defense applications. The principles of design for high efficiency fiber coupling are briefly covered. Examples are provided of fielded and demonstrated 100 and 200 micron diameter fiber coupled packages ranging in output from a few hundred to kW-class units in fibers, to include sub-kg/kW capabilities.
Advancements in High-Power Diode Laser Stacks for Defense Applications - SPIE Defense, Security + Sensing 2012
This paper reports on the latest advancements in vertical high-power diode laser stacks using micro-channel coolers, which deliver the most compact footprint, power scalability and highest power/bar of any diode laser package. We present electro-optical (E-O) data on water-cooled stacks with wavelengths ranging from 7xx nm to 9xx nm and power levels of up to 5.8kW, delivered @ 200W/bar, CW mode, and a power-conversion efficiency of >60%, with both-axis collimation on a bar-to-bar pitch of 1.78mm. Also, presented is E-O data on a compact, conductively cooled, hardsoldered, stack package based on conventional CuW and AlN materials, with bar-to-bar pitch of 1.8mm, delivering average power/bar >15W operating up to 25% duty cycle, 10ms pulses @ 45C. The water-cooled stacks can be used as pump-sources for diode-pumped alkali lasers (DPALs) or for more traditional diode-pumped solid-state lasers (DPSSL) which are power/brightness scaled for directed energy weapons applications and the conductively-cooled stacks as illuminators.
High-Power Diode Laser Pumps for Alkali Lasers (DPALs) - Photonics West 2012We present performance data of recent high-power laser diodes emitting at typical pump wavelengths for alkali vapor lasers: 852nm for cesium, 780nm for rubidium, 766nm for potassium, and 670nm for lithium atoms. Due to different approaches in alkali laser systems, we report on usual pumps at these non-standard wavelengths with typical line widths of a few nm used for collisional and pressure broadened gas absorption lines as well as on wavelength stabilized laser diodes using volume Bragg gratings (VBGs) for systems with narrow gas absorption lines. The detailed characterization of laser diodes available at DILAS includes power, efficiency, spectral data, and life time results. While bars at 6xx and 7xx nm are limited in optical output power due to the strong in-built strain, especially the bars at 852nm with a small inbuilt strain have the biggest potential in terms of pump power. The power conversion efficiency in cw operation is as high as 60% at 100W. Higher power and operation at increased heat sink temperatures up to 50°C are possible depending on lifetime requirements.
KW-Class Line Sources for Direct Applications - Photonics West 2012A new series of high power diode laser line sources is reported on. The modules are designed for the industrial materials processing market and include both fiber coupled and direct beam configurations. Typical applications include welding, hardening and semiconductor processing. Fiber coupled diode laser modules are available at power levels ranging from 600W to 5kW at various wavelengths. Free space systems are available at even higher power levels. Two modules will be described in detail. The first module is a 600W line source with line dimensions of 10.5mm x 150um at a working distance of 160mm. The second module operates at 3kW output power and creates a homogenized line with dimensions of 9mm x 1.5mm at a working distance of 200mm.
Scalable High-Power and High-Brightness Fiber Coupled Diode Laser Devices - Photonics West 2012In this paper we present a detailed characterization of different diode laser sources based on the scalable modular concept. The optical output power is scaled from 180 W coupled into a 100 μm NA 0.22 fiber up to 1.7 kW coupled into a 400 μm NA 0.22 fiber. In addition we present a lightweight laser unit with an output power of more than 300 W for a 200 μm NA 0.22 fiber with a weight vs. power ratio of only 0.9 kg/kW.
An Overview of Diode Lasers for Defense Applications - SSDLTR 2011Diode lasers emitting from the visible red to 2.2 microns and beyond have broad utility in the defense space. Pumping applications range from fiber and solid state directed energy laser weapons including DPALs, eye safe lasers to include LIDAR, to infrared counter measures. Direct diode uses include illuminators from the near IR to the eye safe regime as well as countermeasures. Package types include micro-channel cooled stacks, conduction cooled arrays, high brightness fiber coupled units and next generation heat sinks. An overview of diode laser capabilities will be presented to include a rated 600+W conduction cooled 200 micron core, 0.22 NA fiber coupled package, a 2kW 400 micron core, 0.22NA fiber coupled unit, tapered lasers, diodes emitting beyond 2.1 microns, and next generation designs.
Fiber Coupled Diode Laser Beam Parameter Product Calculation and Rule for Optimized Design- Photonics West 2011It is desirable to calculate the 'diagonal' (fiber) BPP, using the BPPs of the fast and slow axes before detailed design and simulation processes. A commonly used expression derived in an earlier work has been found to consistently under-predict the fiber BPP (i.e. better beam quality is predicted than is actually achievable in practice). In this paper, using a simplified model, we provide the proof of the proper calculation of the diagonal component of the fiber BPP using BPPs of the fast and slow axes as input. Using the same simplified model we offer proof that the fiber BPP can be shown to have a minimum (optimal) value if certain rule between the conjugate variables of beam sizes and the numerical apertures along the two axes is obeyed. This optimization is easily calculated before detailed design and it offers valuable insights for the detailed design.
Macro-Channel Cooled, High Power, Fiber Coupled Diode Lasers Exceeding 1.2kW of Output Power- Photonics West 2011
We report on a new series of fiber coupled diode laser modules exceeding 1.2kW of single wavelength optical power from a 400um / 0.2NA fiber. The units are constructed from passively cooled laser bars as opposed to other comparably powered commercially available modules that use micro-channel heat-sinks. Micro-channel heat sinks require cooling water meeting demanding specifications and are therefore prone to failures due to contamination and increase the overall cost to operate and maintain the laser. Dilas' new series of high power fiber coupled diode lasers are designed to eliminate micro channel coolers and their associated failure mechanisms and cost. Low-smile soldering processes were developed to maximize the brightness available from each diode laser bar. The diode laser brightness is optimally conserved using Dilas' recently developed propriety laser bar stacking geometry and optics. A total of 24 bars are coupled into a single fiber core using a polarization multiplexing scheme. The modular design permits further power scaling through wavelength multiplexing. Other customer critical features such as industrial grade fibers, pilot beams, fiber interlocks and power monitoring are standard features on these modules. The optical design and the beam parameter calculations will be presented to explain the inherit design trade offs. Results for single and dual wavelength modules will be presented.
High-Power, High-Brightness, and Low-Weight Fiber Coupled Diode Laser Device- Photonics West 2011New solid-state laser devices, especially fiber laser systems, require increasingly higher optical output power provided by fiber-coupled diode laser pump modules. In particular for defense technology, robust but lightweight high-power diode laser sources with high brightness are needed. We present a detailed characterization of a diode laser source with 675 W of optical power coupled into a 200 µm, NA 0.22 fiber with a lightweight design due to a special housing optimized for low weight. Spectral quality is ensured over a wide range of temperature and current by means of volume holographic gratings. Nevertheless, an overall efficiency of more than 40 % has been achieved.
New Approach for High-Power Diode Laser Modules with Homogenized Intensity Distribution- Photonics West 2011In the last few years high-power diode laser modules with homogenized intensity distribution have found a growing number of applications, like annealing, hardening and surface illumination. The standard beam shaping concepts in such modules are using an optical waveguide or micro optical lens arrays for homogenization. In this paper we report on a new approach for homogenization of high-power diode laser modules by using linearly arranged fiber bundles to generate homogeneous lines. We present a detailed characterization of a modular diode laser system with 3 kW output power and homogenization by means of a fiber bundle. The dimension of the homogenized line is 200 mm x 2 mm.
Strategies for Polymer Welding with High-Power Diode Lasers - SIMETECH, July 2010Diode lasers have become an important tool for polymer welding in automotive industries, in medical and electronics manufacturing. High efficiency and well fitting beam quality make them a perfect tool for industrial applications. With adapted optics it is possible to fit the laser spot shape to the geometry of the work piece. Galvo scanners are the most flexible tool to apply local and precise dose of heat to the work piece. If this flexibility is not needed, the laser spot can be customized by optics to line, circular or arbitrary shaped geometries. For joining transparent parts either an absorbing layer or diode lasers with a wavelength of 1940nm can be used.
4kW, 1mm (0.20NA), CW, Single-Wavelength, 9xxnm, Fiber-Coupled, Turn-Key Diode-Laser System - SSDLTR 2010We report on an industrial grade, turn-key, fiber-coupled, diode-laser system operating in a single-wavelength (9xxnm +/-3nm) in CW mode at 4kW output power from a 1mm, 0.2NA fiber. The basic architecture of the system consists of a laser-head, beam focusing module, high-power fiber, power supply and chiller. The laser-head is powered by water-cooled stacks which collectively can emit up to 4800W of optical power (pre-fiber) at a wavelength of 9xx nm +/-3nm. The water-cooled diode laser stacks have proven field operation lifetimes in excess of 20,000 hours making the entire system an industrial grade product offering. We use incoherent beam combining techniques of spatial interleaving and polarization beam combining to achieve the beam quality need to couple into the 1mm, 0.20NA fiber. In addition, our beam focusing module further shapes the beam exiting the laser-head and focuses the raw optical power in a spot-size and NA needed for the 1mm fiber.
High-Power Diode Laser Modules from 410 nm - 2200 nm - Photonics West 2010In this work we report on high-power diode laser modules covering a wide spectral range from 410 nm to 2200 nm. Driven by improvements in the technology of diode laser bars with non-standard wavelengths, such systems are finding a growing number of applications.
Quasi-Simultaneous Laser Beam Welding of Polymers in Closed Loop - ANTEC 2009
Polymer welding with lasers is getting a state-of-the art tool in medical device manufacturing and automotive production. Most commonly used are contour welding and quasi-simultaneous welding. An advantage of contour welding is the availability of closed-loop pyrometercontrolled processing optics. On-axis sensors are used for measuring the part's temperature. The pyrometer controller allows the storage of process data for documentation and quality analysis. The new optics developed combine the benefit of contour welding with the speed and addressability of quasi-simultaneous welding. Possibilities and limits of quasi-simultaneous closed-loop welding will be discussed with examples of industrial applications.
Welding and Soldering with High Power Diode Lasers - IIW 2009The wide range of available wavelengths, high brightness and increasing reliability are breaking new ground for diode lasers. Material processing with high power diode lasers in industrial manufacturing is getting more and more important. In automotive, medical device and also solar cell production they are important tools for automated production. Closed-loop temperature control by integrated on-axis pyrometer and fast beam deflection units are established tools for flexible processes documentation and quality control. Depending on the operating conditions, diode lasers have proven to run for several years in production nearly free of maintenance.
Wavelength Stabilized High-Power Diode Laser Modules - Photonics West 2009
High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser modules is an important means for more efficient pumping of solid-state lasers with a narrow absorption bandwidth.
High Power, High Brightness, Multi-Purpose, Laser-Head Module - AHPSL 2008
Basic concepts for high power and high brightness multi-purpose, laser-head module; modeling results, layout and design, characterization.
Power Beaming with Diode Lasers - SSDLTR 2008
Improvements in the electro optical efficiency and output power of diode lasers within the last few years have made the diode laser a viable source for power beaming. Combined with a growing market of photo voltaics, the key components for power beaming applications have evolved from scientific laboratory experiments into equipment ready for deployment into the field.
A Comprehensive Reliability Study of High-Power 808 nm Laser Diodes - Photonics West 2008
In the scope of the project TRUST, more than 20 aging tests have been performed on about 300 high-power laser diode bars with a variation of the mounting technology, current load, operation temperature, and operation mode. Our main goals were the improvement of the reliability and the determination of acceleration parameters for aging tests. We present selected results of long-time aging tests, acceleration factors, and thermal activation energies for high-power 808 nm laser diodes. Due to the increasing demand for higher output powers, we focus mainly on gold-tin mounted laser bars and show their great potential in comparison to the standard indium packaging technology.
Diode Laser Modules Based on New Developments in Tapered and Broad Area Diode Laser Bars - Photonics West 2008
In the last few years an increasing demand for high-brightness diode laser sources is observable, which is mainly driven by applications for fiber laser pumping and materials processing. A number of different approaches have been investigated in the past for the realization of such systems. In this paper we compare different concepts for highbrightness, high-power diode laser modules that are based on the new generation of tapered diode laser bars and new developments in broad area diode laser bars, respectively.
High Power Diode Lasers For Industrial Applications - ICALEO 2007
New wavelengths, high brightness and increasing reliability are breaking new ground for diode lasers. The higher brightness allows direct fiber coupling of several 100W in 200µm and 400µm fiber and therefore the pumping of fiber lasers. Besides pumping of solid state lasers high power diode lasers become more and more a competitive tool for many applications in material processing such as solar cell, etc.
11 kW Direct Diode Laser System with Homogenized 55 x 20 mm Top-Hat Intensity Distribution - Photonics West 2007
A diode laser system with 11 kW output power at a single wavelength of 940 nm aiming for customer specific large area treatment. This is the highest output power reported so far for a direct diode laser system. In addition, to the high output power the intensity distribution of the laser beam is homogenized in both axes leading to a 55 x 20 mm² Top-Hat intensity profile at a working distance of 400 mm. Homogeneity of the intensity distribution is better than 90%. The intensity in the focal plane is 1 kW/cm².
Novel High-Brightness Fiber Coupled Diode Laser Device - Photonics West 2007
High brightness becomes more and more important in diode laser applications for fiber laser pumping and materials processing. For OEM customers fiber coupled devices have great advantages over direct beam modules: the fiber exit is a standardized interface, beam guiding is easy with nearly unlimited flexibility. In addition, to the transport function the fiber serves as homogenizer: the beam profile of the laser radiation emitted from a fiber is symmetrical with highly repeatable beam quality and pointing stability.
High-Brightness High-Power kW-System with Tapered Diode Laser Bars - Photonics West 2005
We report on a diode laser system, which is based on tapered diode laser bars and provides a combination of high power and high beam quality comparable to high power lamp pumped solid-state-rod lasers. Until now diode laser systems with output powers in the kW-range are based on broad area diode lasers. However, the output of these kilowatt laser systems usually is characterized by a strongly asymmetric beam profile, which is a consequence of the asymmetric beam parameter product of broad area diode lasers with regard to the slow and the fast axis direction.