The quasi two-dimensional geometry of the disk laser results in conceptional advantages over other geometries.
Fundamentally, the thin disk laser allows true power scaling by increasing the pump spot diameter on the disk
while keeping the power density constant. This scaling procedure keeps optical peak intensity, temperature,
stress profile, and optical path differences in the disk nearly unchanged. The required pump beam brightness -
a main cost driver of DPSSL systems - also remains constant.
We present these fundamental concepts and present results in the wide range of multi kW-class CW-sources,
high power Q-switched sources and ultrashort pulsed sources.
It is astonishing how long it can take from the first idea to the industrial success of a laser technology product. Three
laser technologies in which TRUMPF participated will be investigated from conception to realization. The first case
study focuses on the diffusion cooled coaxial CO2 laser geometry with diffraction limited resonators. The second case
study highlights some of the stages along the very successful route to implementation of the thin disk laser; from the
conception at the IFSW1 and the ITP2, both in Stuttgart, to the successful industrial installations in automotive
applications. Finally the development of high power diodes for diode pumped solid state lasers is also discussed.
KEYWORDS: Polarization, Resistance, Quantum wells, Indium, Temperature metrology, High power lasers, Data modeling, Thermal modeling, Diodes, Laser welding
As diode pumped solid state lasers gain more market share, the performance, stability and lifetime of the diode pump
source faces unprecedented scrutiny. Lifetimes of diode pumps in excess of 35,000 hrs are sought with no intervention
or maintenance from the end user. One lifetime and power limiting phenomena for arrays is that of solder creep typical
with traditional mounting using soft solders such as Indium. Harder solders such as Gold/Tin on Copper-Tungsten
submounts provide a more robust and stable mounting system for long term high power pump sources. Furthermore,
beam multiplexing of laser bars require tight wavelength and polarization purity which are affected by mounting induced
strain. In this investigation, high power 940 nm laser bars, operating in the 100 to 200 W power range, were mounted
using AuSn/CuW and In soldering schemes. The differences in thermal and strain characteristics are investigated
through the examination of the emitter wavelength, nearfield measurements, polarization and smile. The measurements
are correlated with finite element modeling to predict the 3-dimensional thermal distributions within the laser bars.
The materials processing industry has recently mandated the need for more efficient laser systems with higher beam quality and longer life. Current multiplexing techniques, state-of-the-art laser diodes and novel cooling designs are now emerging as possibilities to meet the ever demanding industry needs. This paper describes the design and initial results of a direct diode system that is aimed at delivering 1.5 kW of output power and a beam divergence of 40 mm mrad on a long life macro-channel cooler. The design entails multiplexing 2 wavelength combined beams and 2 polarization combined beams. Each of the four branches of the direct diode system utilizes a novel stacking and cooling design. The results from one of these branches, 1 wavelength and 1 polarization, are presented where the light is coupled into a fiber with a 400 μm core diameter and a NA of 0.22. Each branch consists of 60 diode laser mini-arrays, where each mini-array consists of four 100 μm wide emitters and a lateral fill factor of 50%. An output power of 500W at 10°C water temperature and 420 W at 25°C are demonstrated through the 400 μm fiber.
KEYWORDS: Carbon dioxide lasers, Semiconductor lasers, Laser cutting, High power lasers, Solid state lasers, Manufacturing, Resonators, Diode pumped solid state lasers, Laser applications, High power diode lasers
Four major types of laser sources are used for material processing. Excluding Excimer lasers, this paper focuses on advances in High Power CO2 lasers, Solid State Lasers and Diode Lasers. Because of their unrivaled cost to brightness relationship the fast axial flow CO2 laser remains unrivaled for flat-sheet laser cutting. Adding approximately a kW of output power ever four years, this laser type has been propelling the entire sheet metal fabrication industry for the last two decades. Very robust, diffusion cooled annular discharge CO2 lasers with 2kW output power have enabled robot mounted lasers for 3D applications. Solid State Lasers are chosen mainly because of the option of fiber delivery. Industrial applications still rely on lamp-pumped Nd:YAG lasers with guaranteed output powers of 4.5 kW at the workpiece. The introduction of the diode pumped Thin Disc Laser 4.5 kW laser enables new applications such as the Programmable Focus Optics. Pumping the Thin Disc Laser requires highly reliable High Power Diode Lasers. The necessary reliability can only be achieved in a modern, automated semiconductor manufacturing facility. For Diode Lasers, electro-optical efficiencies above 65% are as important as the passivation of the facets to avoid Burn-In power degradation.
In order to get an understanding of the turbulent air-fuel mixing behavior and the subsequent combustion process of technically applied spray flames, spontaneous Raman scattering investigations were carried out in the flame of a commercial oil burning furnace. In this furnace a spray of liquid n-heptane is turbulently mixed with air by a swirl generating mixing device. The present geometry of the burner head creates a nonsymmetrical flame so that it was necessary to observe the whole flame volume in order to achieve meaningful data of the mixing behavior. For this reason spontaneous Raman scattering in combination with spatially resolving OMA-detection was applied. Using a simple polarization technqiue in addition to signal averaging over several hundred laser shots, broadband emissions of reacting hydrocarbons are suppressed effectively. This experimental setup facilitates simultaneous 1D spatial resolution of all majority species densities (fuel, N2, O2, CO2, and H2O) along the axis of the focused laser beam. Scanning the whole flame volume by the laser beam then offers 3D information. Quantitative densities of all majority species and the mean temperature were gained using calibration objects. The investigations offer information of stable recurring structures inside the turbulent spray flame. New insights into the mixing and combustion behavior of technically applied combustion systems were gained which are very promising for designing new burner head geometries in order to achieve more effective NO- reduction.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.