This PDF file contains the front matter associated with SPIE Proceedings Volume 9346, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.

High power diode laser arrays need special micro-optic beamshaping to optimize for collimation and spot focusing. A known and established solution makes use of cylindrical micro- optics for fast axis collimation and subsequent individual twisting of each emitter beamlet by a micro-optic cylindrical telescope array in order to achieve a symmetric beam parameter product. A crucial factor for the overall performance is the achievable transmission to collimation and the fiber coupling efficiency. We present an optical analysis of vignetting effects on the transmission in the beam twisting setup and show an optimization which can be achieved by advanced micro-optic production technologies.

Fiber laser manufacturers demand high-brightness laser diode pumps delivering optical pump energy in both a compact fiber core and narrow angular content. A pump delivery fiber of a 105 μm core and 0.22 numerical aperture (NA) is typically used, where the fiber NA is under-filled to ease the launch of laser diode emission into the fiber and make the fiber tolerant to bending. At SCD, we have developed multi-emitter fiber-coupled pump modules that deliver 50 W output from a 105 μm, 0.15 NA fiber at 915, 950 and 976 nm wavelengths enabling low-NA power delivery to a customer’s fiber laser network. In this work, we address the challenges of coupling and propagating high optical powers from laser diode sources in weakly guiding step-index multimode fibers. We present simulations of light propagation inside the low-NA multimode fiber for different launch conditions and fiber bend diameters using a ray-racing tool and demonstrate how these affect the injection of light into cladding-bounded modes. The mode filling at launch and source NA directly limit the bend radius at which the fiber can be coiled. Experimentally, we measure the fiber bend loss using our 50 W fiber-coupled module and establish a critical bend diameter in agreement with our simulation results. We also employ thermal imaging to investigate fiber heating caused by macro-bends and angled cleaving. The low mode filling of the 0.15 NA fiber by our brightness-enhanced laser diodes allows it to be coiled with diameters down to 70 mm at full operating power despite the low NA and further eliminates the need for mode-stripping at fiber combiners and splices downstream from our pump modules.

High power diode lasers have increased application in many fields. In this work, a sophisticated high power and high performance conduction cooled diode laser stack has been developed for long pulse duration and high duty cycle using gold-tin (AuSn) bonding technology. The transient thermal behavior and optical simulation of the laser diode stack module are investigated to optimize the laser device structure. CTE-matched submount and AuSn hard solder are used for bonding the laser diode bar to achieve higher reliability and longer lifetime. Guided by the numerical simulation and analytical results, conduction cooled diode laser stack with high power, long pulse duration and high duty cycle is fabricated and characterized. Compared with the conventional indium bonding technology, the new design is a promising approach to obtain improved performance with high reliability and long lifetime.

Due to their high electrical-optical conversion efficiency, compact size and long lifetime, high power diode lasers have found increased applications in many fields. As the improvement of device technology, high power diode laser bars with output power of tens or hundreds watts have been commercially available. With the increase of high current and output power, the reliability and lifetime of high power diode laser bars becomes a challenge, especially under harsh working conditions and hard-pulse operations. The bonding technology is still one of the bottlenecks of the advancement of high power diode laser bars. Currently, materials used in bonding high power diode laser bars are commonly indium and goldtin solders. Experimental and field application results indicates that the lifetime and reliability of high power diode laser bars bonded by gold-tin solder is much better than that bonded by indium solder which is prone to thermal fatigue, electro-migration and oxidization. In this paper, we review the bonding technologies for high power diode laser bars and present the advances in bonding technology for single bars, horizontal bar arrays and vertical bar stacks. We will also present the challenges and issues in bonding technology for high power diode laser bars and discuss some approaches and strategies in addressing the challenges and issues.

This paper talks about high performance heat sinks and heat spreaders made by hybrid structures based on metaldiamond composites. Thermal conductivities can be tuned between 450 and 650 W/mK while maintaining customizable thermal expansion of 6-10 ppm/K (@30°C). Using different hybrid structures in combination with the metal-diamond core significant changes in thermal properties can be identified. Applications targeted are LED, disc laser and laser diode heatsinks with these high performance inserts without the need of CTE matched submounts.

Packaging is an important part of high power diode laser (HPLD) development and has become one of the key factors affecting the performance of high power diode lasers. In the package structure of HPLD, the interface layer of die bonding has significant effects on the thermal behavior of high power diode laser packages and most degradations and failures in high power diode laser packages are directly related to the interface layer. In this work, the effects of interface layer on the performance of high power diode laser array were studied numerically by modeling and experimentally. Firstly, numerical simulations using finite element method (FEM) were conducted to analyze the effects of voids in the interface layer on the temperature rise in active region of diode laser array. The correlation between junction temperature rise and voids was analyzed. According to the numerical simulation results, it was found that the local temperature rise of active region originated from the voids in the solder layer will lead to wavelength shift of some emitters. Secondly, the effects of solder interface layer on the spectrum properties of high power diode laser array were studied. It showed that the spectrum shape of diode laser array appeared “right shoulder” or “multi-peaks”, which were related to the voids in the solder interface layer. Finally, “void-free” techniques were developed to minimize the voids in the solder interface layer and achieve high power diode lasers with better optical-electrical performances.

A new high-power semiconductor laser diode module, emitting at 760 nm is introduced. This wavelength permits optimum treatment results for fair skin individuals, as demonstrated by the use of Alexandrite lasers in dermatology. Hair removal applications benefit from the industry-standard diode laser design utilizing highly efficient, portable and light-weight construction. We show the performance of a tap-water-cooled encapsulated laser diode stack with a window for use in dermatological hand-pieces. The stack design takes into account the pulse lengths required for selectivity in heating the hair follicle vs. the skin. Super-long pulse durations place the hair removal laser between industry-standard CW and QCW applications. The new 760 nm laser diode bars are 30% fill factor devices with 1.5 mm long resonator cavities. At CW operation, these units provide 40 W of optical power at 43 A with wall-plug-efficiency greater than 50%. The maximum output power before COMD is 90 W. Lifetime measurements starting at 40 W show an optical power loss of 20% after about 3000 h. The hair removal modules are available in 1x3, 1x8 and 2x8 bar configurations.

9xx nm CW mini-bar diode lasers and stacks with high brightness and reliability are desired for pumping fiber lasers and direct fiber coupling applications. For the traditional cm-bar with 1mm-2mm cavity, it can provide CW output power up to 80W-100W and high reliability, whereas the brightness is relatively low. In comparison, mini-bar based diode lasers with 4mm cavity offer a superior performance balance between power, brightness, and reliability. However, the long cavity and large footprint of mini-bar diode laser renders its sensitivity towards thermal stress formed in packaging process, which directly affects the performances of high bright mini-bar diode lasers. In this work, the thermal stress correlating with package structure and packaging process are compared and analyzed. Based on the experiment and analysis results, an optimized package structure of CW 60W 976 nm mini-bar diode lasers is designed and developed which relieves thermal stress.

Today’s piezo-based micromanipulator technology allows for highly precise manipulation of optical components. A crucial question for the quality of optical assemblies is the misalignment after curing. The challenge of statistical deviations in the curing process requires a sophisticated knowledge on the relevant process parameters. An approach to meet these requirements is the empirical analysis such as characterization of shrinkage. Gaining sophisticated knowledge about the statistical process of adhesive bonding advances the quality of related production steps like beam-shaping optics, mounting of turning mirrors for fiber coupling or building resonators evaluating power, mode characteristics and beam shape. Maximizing the precision of these single assembly steps fosters the scope of improving the overall efficiency of the entire laser system. At Fraunhofer IPT research activities on the identification of relevant parameters for improved adhesive bonding precision have been undertaken and are ongoing. The influence of the volumetric repeatability of different automatic and manual dispensing methods play an important role. Also, the evaluation of UV-light sources and the relating illumination properties have a significant influence on the bonding result. Furthermore, common UV-curing adhesives are being examined on their performance and reliability for both highest precision prototyping, as well as their application as robust bonding medium in automated optics assembly cells. This paper sums up the parameters of most influence. Overall goal of these activities is the development of a prediction model for optimized shrinkage compensation and thus improved assembly quality.

Airborne molecular contaminations (AMCs) have been recognized as a major problem in semiconductor fabrication. Enormous technical and financial efforts are made to remove or at least reduce these contaminations in production environments to increase yield and process stability. It can be shown that AMCs from various sources in laser devices have a negative impact on quality and lifetime of lasers and optical systems. Outgassing of organic compounds, especially condensable compounds were identified as the main source for deterioration of optics. These compounds can lead to hazing on surfaces of optics, degradation of coating, reducing the signal transmission or the laser signal itself and can enhance the probability of laser failure and damage. Sources of organic outgassing can be molding materials, resins, seals, circuit boards, cable insulation, coatings, paints and others. Critical compounds are siloxanes, aromatic amines and high boiling aromatic hydrocarbons like phthalates which are used as softeners in plastic materials. Nowadays all sensitive assembly steps are performed in controlled cleanroom environments to reduce risks of contamination. We will demonstrate a high efficient air filter concept to remove AMCs for production environments with special AMC filters and methods for the qualification and monitoring of these environments. Additionally, we show modern techniques and examples for the pre-qualification of materials. For assembled components, we provide sampling concepts for a routine measurement for process, component and product qualification. A careful selection of previously tested and certified materials and components is essential to guarantee the quality of lasers and optical devices.

The Advanced Topographic Laser Altimeter System (ATLAS) will be the only instrument on the Ice, Cloud, and Land Elevation Satellite -2 (ICESat-2). ICESat-2 is the 2nd-generation of the orbiting laser altimeter ICESat, which will continue polar ice topography measurements with improved precision laser-ranging techniques. In contrast to the original ICESat design, ICESat-2 will use a micro-pulse, multi-beam approach that provides dense cross-track sampling to help scientists determine a surface's slope with each pass of the satellite. The ATLAS laser will emit visible, green laser pulses at a wavelength of 532 nm and a rate of 10 kHz and will be split into 6 beams. A set of six identical, thermally tuned optical filter assemblies (OFA) will be used to remove background solar radiation from the collected signal while transmitting the laser light to the detectors. A seventh assembly will be used to monitor the laser center wavelength during the mission. In this paper, we present the design and optical performance measurements of the ATLAS OFA in air and in vacuum prior to their integration on the ATLAS instrument.

In this contribution, we present a novel approach to enable virtual commissioning for process developers in micro-optical assembly. Our approach aims at supporting micro-optics experts to effectively develop assisted or fully automated assembly solutions without detailed prior experience in programming while at the same time enabling them to easily implement their own libraries of expert schemes and algorithms for handling optical components. Virtual commissioning is enabled by a 3D simulation and visualization system in which the functionalities and properties of automated systems are modeled, simulated and controlled based on multi-agent systems. For process development, our approach supports event-, state- and time-based visual programming techniques for the agents and allows for their kinematic motion simulation in combination with looped-in simulation results for the optical components. First results have been achieved for simply switching the agents to command the real hardware setup after successful process implementation and validation in the virtual environment. We evaluated and adapted our system to meet the requirements set by industrial partners-- laser manufacturers as well as hardware suppliers of assembly platforms. The concept is applied to the automated assembly of optical components for optically pumped semiconductor lasers and positioning of optical components for beam-shaping

Laser range finders (LRF) and target designators (TD) for military applications usually have stringent environmental requirements for optimal performance. Current technology and system architectures need LRF and TD lasers to function in more than one color (near IR and eye safe wavelengths) for multiple ground and airborne applications. In addition, these kind of lasers need to be packaged inside a small space for portability. It is for these reasons that a folded crossed porro-polarization- out coupled resonators is usually the chosen geometry. This work will explore polarization techniques to design a laser resonator cavity that works perfectly for more than one color, sometimes without the need of actual birefringence components (i.e waveplates) to achieve the goal of a stable laser resonator.

In many applications for high-power diode lasers, the production of beam-shaping and homogenizing optical systems experience rising volumes and dynamical market demands. The automation of assembly processes on flexible and reconfigurable machines can contribute to a more responsive and scalable production. The paper presents a flexible mounting device designed for the challenging assembly of side-tab based optical systems. It provides design elements for precisely referencing and fixating two optical elements in a well-defined geometric relation. Side tabs are presented to the machine allowing the application of glue and a rotating mechanism allows the attachment to the optical elements. The device can be adjusted to fit different form factors and it can be used in high-volume assembly machines. The paper shows the utilization of the device for a collimation module consisting of a fast-axis and a slow-axis collimation lens. Results regarding the repeatability and process capability of bonding side tab assemblies as well as estimates from 3D simulation for overall performance indicators achieved such as cycle time and throughput will be discussed.

Because of its ease of growth and large electro-optic effect, lithium niobate is the preferred choice for Q-switching mobile lasers. Temperature-induced pyro-electric charges however may lead to premature lasing. We manufactured and characterized temperature-stable LN Q-switch. A thermo-chemical anneal was performed creating a conductive material layer 0.5mm thick with increased conductivity. While this increases optical insertion loss by a few percent, this is tolerable in high gain lasers. We present details of treatment, the surface charge creation and dissipation mechanism and the setup used to assess the cold-performance used to demonstrate improved charge dissipation when compared to untreated crystals.

Crystals are widely applied in laser systems and they play important roles as polarization manipulators. A simple uniaxial crystal plate with a certain thickness may serve as a linear/circular polarizer. A uni/biaxial crystal with a proper orientation may work as a polarization beam splitter/combiner. A biaxial crystal at conical refraction may be used to generate radially polarized light or help form a Bessel beam. To design a laser system including crystal component(s), or to optimize the performance of such a system, simulation techniques which models the light propagation through crystals is required. We present a full-vectorial and electromagnetic method that enables the modeling of crystal components with general laser fields, based on the angular spectrum of plane waves. Propagation of general field within anisotropic media and the reflection and transmission at a planar interface between isotropic/anisotropic and anisotropic/anisotropic media are discussed. We demonstrate examples on how crystals are used to manipulate the polarization state of laser beams.

We report on the development and testing of optical isolators for use in 2-micron fiber laser systems. A variety of potential Faraday rotator materials were characterised to identify the most suitable materials for use in the 1700-2100nm wavelength range. Isolators based on the three best performing materials were then developed and packaged as fiber-in, fiber-out and fiber-in, beam-out devices. The isolators were then tested in CW, pulsed and ultrafast laser systems. The three different designs produced different performance characteristics, but all designs demonstrated isolation >25dB and insertion losses of <1.2 dB.

Phase masks are important optical elements that have been utilized for several decades in a large variety of applications. Recently, we demonstrated a new type of phase masks fabricated by encoding phase profiles into volume Bragg gratings, allowing these holographic elements to be used as phase masks at any wavelength capable of satisfying the Bragg condition of the hologram. Here, we present a new method of true achromatization of this type of phase masks that removes the need for angle tuning and is implemented by combining this holographic phase masks approach with a pair of surface diffraction gratings.

Performance of modern high-power lasers can be strongly improved by control of irradiance distribution in laser optical systems: flat-top or super-Gaussian irradiance profiles are optimum for amplification in MOPA lasers and for reduction of thermal effects in crystals of solid-state ultra-short pulse lasers; variable profiles are also important in irradiating of photocathode of Free Electron lasers (FEL). This task can be easily solved with using beam shaping optics, for example, the field mapping refractive beam shapers like Shaper. The operational principle of these devices presumes transformation of laser beam intensity from Gaussian to flattop one with high flatness of output wavefront, saving of beam consistency, providing collimated output beam of low divergence, high transmittance, extended depth of field, negligible residual wave aberration, and achromatic design provides capability to work with ultra-short pulse lasers having broad spectrum. With using the same Shaper it is possible to realize various beam profiles like flattop, inverse Gauss or super Gauss by simple variation of input beam diameter. This paper will describe some design basics of refractive beam shapers of the field mapping type and optical layouts of their applying in optical systems of high-power lasers. Examples of real implementations and experimental results will be presented as well.

High-power and high-energy laser systems have firmly established their industrial presence with applications that span materials processing; high – precision and high – throughput manufacturing; semiconductors, and defense. Along with high average power CO₂ lasers operating at wavelengths of ~ 10 microns, solid state lasers and fiber lasers operating at ~ 1 micron wavelength are now increasingly being used, both in the high average power and high energy pulse regimes.

In recent years, polycrystalline diamond has become the material of choice when it comes to making optical components for multi-kilowatt CO₂ lasers at 10 micron, outperforming ZnSe due to its superior thermo-mechanical characteristics. For 1 micron laser systems, fused silica has to date been the most popular optical material owing to its outstanding optical properties. This paper characterizes high - power / high - energy performance of anti-reflection coated optical windows made of different grades of diamond (single crystal, polycrystalline) and of fused silica. Thermo-optical modeling results are also presented for water cooled mounted optical windows. Laser – induced damage threshold tests are performed and analyzed. It is concluded that diamond is a superior optical material for working with extremely high-power and high-energy laser beams at 1 micron wavelength.

Lasers used for diverse applications from industry to fundamental science tend to increasing output powers. Some applications require frequency conversion via nonlinear optical crystals, which suffer from the formation of temperature gradients at high power operation which causes thermal lensing or destruction of the crystal due to tensile stresses. To avoid these unwanted effects we joined a beta barium borate (BBO) crystal with sapphire disks serving as effective heat spreaders due to their high thermal conductivity (thermal conductivity κ = 42 W/Km). Therefore, smooth and flat crystal surfaces were joined by plasma-activated bonding. The joining relies on covalent bonds, which are formed via a condensation reaction of the surfaces which are first connected by Van der Waals forces. The cleaned surfaces are activated by plasma and brought into contact, pressed together and heat treated at a temperature of about 100°C. Special attention has been paid to the cleaning of the surfaces. Therefor the surfaces have been evaluated before and after treatment by means of atomic force microscopy. A stable connection has been formed successfully, which has been tested in a proof of principle experiment and demonstrated efficient second harmonic generation at up to 253 W of input power. Compared to a bare single BBO crystal it could be shown that the temperature within the crystal compound is significantly reduced. Such hybrid structures pave the way for frequency conversion at kilowatts of average power for future high power lasers.

Two years ago we reported about the development of solid state laser source for medical skin treatment with wavelength 310.6 nm and average power 200 mW. Here we describe the results of investigation of the advanced version of the laser, which is a more compact device with increased output power and flat top beam profile. Ti: Sapphire laser, the main module of our source, was modified and optimized such, that UV average power of the device was increased 1.7 times. Fiber optic homogenizer was replaced by articulated arm with diffraction diffuser, providing round spot with flat profile at the skin. We investigated and compare characteristics of Ti: Sapphire lasers with volume Bragg grating and with fused silica transmission grating, which was used first time for Ti: Sapphire laser spectral selection and tuning. Promising performance of last gratings is demonstrated.

We report on two low-loss 7:1 single-mode to multi-mode fiber coupler-designs generating more than 5 kW of output power. These all-glass fiber-optical devices have the objective to keep the brightness at its theoretical maximum and the heat load at its technical minimum. To the best of our knowledge, regarding all-fiber geometrical combined power generation, beam quality and heat stability, the presented results had never been reported before.

In this paper a commercial photothermal instrument is used to study the radiation effects on weakly absorptive optical thin film coatings induced by high repetitive laser pulses. Through in-situ measuring of the coatings’ absorption under irradiation of high repetitive laser pulses, the dynamic information of laser-material-interaction process is obtained, which is very useful for understanding and analyzing of laser damage mechanism of the coatings. In addition, absorption defects on the coatings are clearly determined through the photothermal imaging instrument.

Tremendous progress has been achieved in the last years in the field of ultrafast high-power sources. Among the different laser technologies driving this progress, thin-disk lasers (TDLs) have gained significant ground, both from amplifiers and modelocked oscillators. Modelocked TDLs are particularly attractive, as they allow for unprecedented high energy and average powers directly from an oscillator. The exponential progress in the performance of these sources drives growing needs for efficient means of beam delivery and pulse compression at high average power (< 100 W) and high peak power (> 10 MW). This remains a challenging regime for standard fiber solutions: microstructured large-mode-area silica photonic-crystal fibers (PCFs) are good candidates, but peak powers are limited to ≈4-6 MW by self-focusing. Hollow-core (HC) capillaries are adapted for higher peak powers, but exhibit high losses and are not suitable for compact beam delivery. In parallel to the progress achieved in the performance of ultrafast laser systems, recent progress in novel hollow-core PCF designs are currently emerging as an excellent solution for these challenges. In particular, Inhibited-coupling Kagome-type HC-PCFs are particularly promising: their intrinsic guiding properties allow for extremely high damage thresholds, low losses over wide transmission windows and ultra-low dispersion. In our most recent results, we achieve pulse compression in the hundred-watt average power regime using Kagome-type HC-PCFs. We launch 127-W, 18-μJ, 740-fs pulses from our modelocked TDL into an Ar-filled fiber (13 bar), reaching 93% transmission. The resulting spectral broadening allows us to compress the pulses to 88 fs at 112 W of average power, reaching 105 MW of peak power, at 88% compression efficiency. These results demonstrate the outstanding suitability of Kagome HC-PCFs for compression and beam delivery of state-of-the-art kilowatt-class ultrafast systems.

ISP SYSTEM has developed an electro-mechanical deformable mirror compatible with Ultra High Vacuum environment, suitable for ultra short pulsed lasers.

The design of the MD-AME deformable mirror is based on force application on numerous locations. μ-AME actuators are driven by stepper motors, and their patented special design allows controlling the force with a very high accuracy. Materials and assembly method have been adapted to UHV constraints and the performances were evaluated on a first application for a beam with a diameter of 250mm. A Strehl ratio above 0.9 was reached for this application. Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for standard MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses.

The deformable mirror design allows changing easily an actuator or even the membrane if needed, in order to improve the facility availability. They are designed for circular, square or elliptical aperture from 30mm up to 500mm or more, with incidence angle from 0° to 45°. They can be equipped with passive or active cooling for high power lasers with high repetition rate.

Laser diodes are efficient and compact devices operating in a wide range of wavelengths. Boosting power by beam combining while maintaining good beam quality has been a long-standing challenge. We discuss various approaches for beam combining with emphasis on solutions pursued at DirectPhotonics. Our design employs single emitter diodes as they exhibit highest brightness and excellent reliability. In a first step, after fast axis collimation, all single emitter diodes on one subunit are stacked side-by-side by a monolithic slow-axis-collimator thus scaling the power without enhancing the brightness. The emissions of all diodes on a subunit are locked by a common Volume Bragg grating (VBG), resulting in a bandwidth < 0.5nm and high wavelength stability. Second, two subunits with identical wavelength are polarization coupled forming one wavelength channel with doubled power and brightness. Third, up to five channels are serially spectrally combined using dichroic filters. The stabilized wavelengths enable dense spectral combining, i.e. narrow channel spacing. This module features over 500W output power within 20nm bandwidth and a beam parameter product better than 3.5mm*mrad x 5mm*mrad (FA x SA) allowing for a 100μm, 0.15NA delivery fiber [1]. The small bandwidth of a 500-W-module enables subsequent coarse spectral combining by thin film filters, thus further enhancing the brightness. This potential can only be fully utilized by automated manufacturing ensuring reproducibility and high yield. A precision robotic system handles and aligns the individual fast axis lenses. Similar technologies are deployed for aligning the VBGs and dichroic filters.

Applying beam shaping optical components is important in various modern laser micromachining technologies like drilling holes, scribing, patterning. Typically micromachining systems contain such components like F-theta lenses, beam expanding and scanning optics like 2- and 3-axis galvo mirror scanners, therefore using of beam shapers require building of special optical systems combining all optical components. As the beam shaping optics it is suggested to apply field mapping refractive beam shapers like Shaper having some important features: low output divergence, high transmittance, extended depth of field, capability to work with TEM00 and multimode lasers, as result providing a freedom in building various optical systems. De-magnifying of flattop laser beam is realized with using imaging technique; the imaging optical system to be composed from F-theta lens of scanning head and additional collimating system to be used right after a Shaper. One of technical tasks in this approach is implementation of compact design of the collimating part, another task – simple switching between final spot sizes. As a solution it is suggested to apply a specially designed Beam Shaping Unit, which is based on a Shaper and combination of mirrors, locating between a laser and a scanning head; the functions of that combined system are: conversion from Gaussian to flattop laser beam irradiance profile, compact design, alignment features, easy adaptation to a laser and a scanning head used in particular equipment, stepwise switching between resulting spot sizes. There will be considered design features of refractive beam shapers and Beam Shaping Unit, examples of optical layouts to generate flattop laser spots, which sizes span from several tens of microns to millimetres. Examples of real implementations and results of material processing will be presented as well.

Component, e.g. Fabry-Perot interferometer, with internal multiple reflections plays an important role in laser technology. Its optical functionality is based on multiple reflections inside the component and the interference effect. In this paper, two electromagnetic concepts that allow the modeling of such components for general incident light are proposed. The first one is based on an iterative field tracing approach. With this approach multiple reflections through and inside the component are handled respectively. One typical example is the simulation of Newton’s rings effect or the modeling of an Etalon with thickness variation because of fabrication tolerances. The other one is based on the matrix method for stratified media, which is usually used to handle optical layer systems Fabry-Perot interferometer. We present the details, demonstrate various examples and also discuss sampling issues due to the internal multiple reflections.

We have developed highly compact RGB laser light modules to be used as light sources in multi-view autostereoscopic outdoor displays and projection devices. Each light module consists of an AlGaInP red laser diode, a GaInN blue laser diode, a GaInN green laser diode, as well as a common cylindrical microlens. The plano-convex microlens is a so-called “fast axis collimator”, which is widely used for collimating light beams emitted from high-power laser diode bars, and has been optimized for polychromatic RGB laser diodes. The three light beams emitted from the red, green, and blue laser diodes are collimated in only one transverse direction, the so-called “fast axis”, and in the orthogonal direction, the so-called “slow axis”, the beams pass the microlens uncollimated. In the far field of the integrated RGB light module this produces Gaussian beams with a large ellipticity which are required, e.g., for the application in autostereoscopic outdoor displays. For this application only very low optical output powers of a few milliwatts per laser diode are required and therefore we have developed tailored low-power laser diode chips with short cavity lengths of 250 μm for red and 300 μm for blue. Our RGB laser light module including the three laser diode chips, associated monitor photodiodes, the common microlens, as well as the hermetically sealed package has a total volume of only 0.45 cm³, which to our knowledge is the smallest RGB laser light source to date.

In this paper three dimensional characterization of the far field of diode laser beam is proposed. Both the divergence angle and intensity distribution can be extracted and analyzed from the measurement results with obliquity factor correction and power transmission correction. The instrument provides high resolution and fast measurement.