Since the first blue lasers made from GaN-based semiconductors reached power levels making them suitable for industrial applications a few years ago, users where asking for more power. Quickly, output powers for fiber-coupled diode lasers increased from several hundred watts in early 2018 [1] to 1000 W in 2019 [2] and even 2000 W in 2020 [3]. But lifetime has always been an object of concern since the blue diode-laser moved out of the TO-can to enter the high power world. As part of the research project “FoulLas”, which started in 2019 and is funded by the German Federal Ministry for Economic Affairs and Energy (BMWi), Laserline took on the task of developing a cw fiber-coupled diode-laser exceeding 2 kW blue laser power for fouling removal of vessels and submarine structures. Caused by stronger restrictions on the use of biocide containing coatings for ship hulls, new strategies against marine fouling moved into the focus of development activities. A new approach is to lethally damage the microorganisms on the subsea surfaces by laser irradiation to be washed away by the streaming water. Apart from that, they can no longer contribute to the spread of species. This paper covers concepts and possibilities of power increase beyond 2 kW for fiber-coupled lasers based on blue diodelaser bars. Results of a laser with more than 2 kW output power are presented. In addition, new findings on degradation processes and lifetime tests are reported. To tie in with the application, insights into the maritime application of fouling removal are given.
The availability of high-power blue diode-lasers established a new class of laser sources for materials processing recently. With the significantly shorter wavelength compared to conventional laser sources for materials processing new applications are moving into the range of the feasible. There is a strong demand for welding applications with copper due to the change from internal combustion engines to electric drives, which even prompts laser manufacturers to find complex solutions to obtain a laser source in the wavelength range where copper shows higher absorption. With the appearance of high-power diode-laser bars in the blue wavelength range, proven optical concepts can be adapted for the setup of straightforward blue high-power diode-laser sources for materials processing. In context of the research project “BlauLas”, which is funded by the German Federal Ministry of Education and Research (BMBF) within the photonic initiative “EFFILAS” [1], Laserline, in cooperation with OSRAM, intends to realize a blue fiber-coupled cw diode-laser with a power exceeding 1 kW. Building on the results of the earlier presented 700 W fiber coupled laser source we present our new blue fiber coupled laser source with output powers surpassing 1 kW. A brief description of the optical concept and setup as well as an outlook on future strategies to increase output power and radiance of blue laser sources based on diode-laser bars are given. Additionally recently carried out application trials with this new powerful laser source are presented.
KEYWORDS: Semiconductor lasers, Copper, Laser systems engineering, Laser applications, High power lasers, Semiconductors, Materials processing, High power diode lasers, High power fiber coupled lasers, Fiber coupled lasers
A high-power blue laser source was long-awaited for processing materials with low absorption in the near infrared (NIR) spectral range like copper or gold. Due to the huge progress of GaN-based semiconductors, the performance of blue diode-lasers has made a major step forward recently. With the availability of unprecedented power levels at cw-operating blue diode-lasers emitting at 450 nm, it was possible to set up a high-power diode-laser in the blue spectral range to address these conventional laser applications and probably beyond that to establish completely new utilizations for lasers.
Within the scope of the research project “BlauLas”, funded within the German photonic initiative “EFFILAS” [8] by the German Federal Ministry of Education and Research (BMBF), Laserline in cooperation with OSRAM aims to realize a cw fiber-coupled diode-laser exceeding 1 kW blue laser power.
In this paper the conceptual design and experimental results of a 700 W blue fiber-coupled diode-laser are presented. Initially a close look had to be taken on the mounting techniques of the semiconductors to serve the requirements of the GaN laser diodes. Early samples were used for extensive long term tests to investigate degradation processes. With first functional laser-modules we set up fiber-coupled laser-systems for further testing. Besides adaption of well-known optical concepts a main task within the development of the laser system was the selection and examination of suitable materials and assembling in order to minimize degradation and reach adequate lifetimes. We realized R&D blue lasersystems with lifetimes above 5,000 h, which enable first application experiments on processing of various materials as well as experiments on conversion to white-light.
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