Development of a 60 w pulsed fiber laser amplifier for materials processing

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2014
Aydın, Yiğit Ozan
Fiber lasers have the advantage of high beam quality, high efficiency, small size, air cooling and therefore much interest in the development of high power fiber laser systems have arisen recently in the world. Almost all commercially developed fiber lasers with nanosecond pulse duration, that are being used for material processing, are Q-switched systems. Vital parameters in the material processing such as repetition rate, pulse energy and pulse duration are correlated with each other and they cannot be adjusted independently in the Q-switch mechanism. In this study, ytterbium doped all-fiber laser amplifier with 60 W average power and more than 20 kW peak power at 1 μm wavelength was developed, and its potential for processing of different material types is investigated. This master-oscillator power-amplifier (MOPA) architectured system is composed of pulses, produced by an electronically pumped diode, and amplified by a series of fiber amplifiers. In contrast with Q-switch lasers, MOPA architecture allows us to adjust pulse duration, repetition rate and power independently. Beam quality is nearly diffraction limited, and the typical M2 value is1.5. The system is an all-fiber one where the maximum pulse energy achieved at 100 kHz repetition rate is 0.6 mJ and minimum pulse duration is ~30 ns at this energy level. Due to multi-stage architecture and special precautions, the system works without a high amplified spontaneous emission (ASE) level and shows an optical efficiency of 76%. After development of the laser amplifier, and certification of its materials processing capability, an industrial prototype was configured by taking the cost-efficiency into account . The laser components were placed into a compact case which has a simple design for thermal cooling. The developed industrial laser amplifier prototype has several unique properties with respect to other equivalent MOPA design fiber lasers. In material processing, high stability and high beam quality lead to high consistency. Reduced diameters of active and passive fiber cores and specially optimized fiber splices, which are used in the system architecture, result with higher beam quality thus the focusing is superior to many contemporary commercial lasers. As the intensity (areal power density) is the physical quantity that drives the nature of interaction of laser output with materials, the developed system offers long operation life-time due to its capability of operation at lower power levels than its contemporaries. In order to demonstrate the efficiency and the ability of processing various different kinds of materials with the developed laser amplifier system, a multitude of processing applications such as micro drilling, solar cell edge isolation, deep engraving and color marking were tested on metal, semiconductor and insulator surfaces and the results are discussing in relationship with various system operation parameters.
Citation Formats
Y. O. Aydın, “Development of a 60 w pulsed fiber laser amplifier for materials processing,” M.S. - Master of Science, Middle East Technical University, 2014.