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Laser diodes with high power and brightness are critical for pumping kW-class fiber lasers and direct diode laser systems. We present performance data of current generation broad area chips and new chips as well as multi-emitter fiber-coupled modules. Improved lateral beam quality at high power allows new designs to reach 15W power with lateral beam parameter product (BPP) <4 mm-mrad. A fiber-coupled...
This paper gives an overview about Additive Manufacturing (AM) in general and Selective Laser Melting (SLM) in more detail. We discuss the economic potential of AM and show that it is directly correlated to the process efficiency of AM. We present different new machine concept in order to increase process efficiency. We present one new, diode laser based SLM machine concepts.
We present a fibre-coupled diode laser module with an optical output power of 23 W ex 35 μm (NA 0.22). The system is based on dense wavelength division multiplexing of two narrow stripe broad-area diode laser mini-bars in an external resonator. Ultra-steep dielectric edge filters are used. By measuring the optical output power, the spectrum and the degree of polarization with and without external...
A 1.56 μm distributed feedback laser monolithically integrated with three stages of multi-mode interference couplers and semiconductor optical amplifiers was fabricated. The output exhibited a clear coherent interference far field pattern.
Optical pulses in the nanosecond and picosecond ranges can be generated by gain switching, Q-switching and mode-locking of diode lasers, either as stand-alone devices or in MOPA systems combining master oscillators (MOs) and power amplifiers (PAs). A review of recent progress achieved at FBH is presented. With a gain switched ridge waveguide (RW) laser optical pulses with a width of 1 ns and more...
We present a measurement platform to characterise combining elements used for dense wavelength division multiplexing, such as dielectric edge filters or Volume Bragg Gratings (notch filters). This platform enables the characterisation of the spectral and angular selectivity, the homogeneity of reflectance or transmittance and temperature-induced spectral shift of the band edge. The determination of...
We present the improvement of the lateral beam quality due to frequency stabilisation in a Dense Wavelength Division Multiplexing setup using Volume Bragg Gratings. The spectral width of each frequency stabilised channel amounts to less than 300 pm and an overall multiplexing efficiency of 86 % has been measured. The near and far field intensity distributions consist of discrete modes and were observed...
High power degradation mechanisms in gallium arsenide and gallium nitride based diode laser devices are compared. It will be demonstrated that in both material systems the same physical mechanism takes effect and causes a catastrophic optical damage. The differences in appearance of the degradation in the two systems are explained by intrinsic material properties.
Diode Lasers with output powers from 1 to 25 kW have become an industrial standard in many applications, from welding, brazing, cladding, repair welding, hardening to other surface treatment applications.
We present results of an extensive study on broad area lasers (BALs) with different antireflection (AR) coatings in the wavelength range from 780 nm to 1020 nm, which have been investigated under external optical feedback (EOF) to detect reversible and irreversible impacts caused by back-reflected laser radiation. The observation of the near-field (NF) distribution vs. injection current gave us information...
We present improvements of the lateral beam divergence and brightness of gain-guided mini-bars for emission at 976nm at highest brightness levels. The beam characteristics of devices in production are tailored for optimized fiber coupling to fiber diameter 200μm and numerical aperture 0.22, corresponding to a beam parameter product of 22 mm mrad. Cost-efficient coupling to this fiber requires a beam...
Dense wavelength beam combining (DWBC) of hundreds to thousands of few-power broad-area laser diode (BAL) emitters into a single high-power laser beam is a promising approach to establish direct diode lasers in classical multi-kW high-brightness laser applications, such as e.g. 2D-flatsheet metal cutting or remote laser welding. Compared to dissipative optically pumped solid-state lasers, direct diode...
High-power and high-reliability single emitter laser diodes with 8xx-9xx nm lasing wavelength based on Asymmetric Decoupled Confinement Heterostructure (ADCH) are demonstrated. Laser structure optimization in vertical layer design and stripe width enabled high power operation of 9xx nm LDs up to 15-17 W range with high reliability. Possibility of further improvement in high power operation is also...
High power terahertz quantum cascade lasers with symmetric, wafer bonded active regions are presented, which are ideally suited for object illumination for real-time terahertz imaging using a microbolometer camera.
Analytical and semi-analytical theory and numerical modelling of the major physical effects limiting the power conversion efficiency of semiconductor lasers at high injection currents are presented and overviewed. It is shown that the deterioration of output efficiency due to absorption by carriers in the Optical Confinement Layer is likely to be the main cause of efficiency degradation at high currents...
Polarization-related electric fields present one of the major challenges for conventional c-plane GaN-based hetero-structures. Nonpolar and semipolar orientations of GaN offer the potential for new device designs. In this presentation, we review the inherent features of these new crystal orientations for GaN for light emitters and discuss the major challenges and opportunities and some of the solutions...
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