Blue 450nm high power semiconductor continuous wave laser bars exceeding rollover output power of 80W

König, Harald; Lell, A.; Stojetz, Bernhard; Ali, Muhammad; Eichler, Christoph; Peter, M.; Löffler, Andreas; Strauß, Uwe; Baumann, Markus; Balck, Anne; Malchus, Joerg; Krause, Volker

doi:10.1117/12.2286875

Cited by 10 publications

(4 citation statements)

References 3 publications

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“…To meet this challenge arising during copper welding, high-power beam sources at even shorter wavelengths, especially frequency-doubled Yb:YAG lasers at λ = 515 nm (green wavelength region) [8,9] and diode lasers at λ = 450 nm (blue wavelength region) [10][11][12] have been developed, as higher absorptivity values at these shorter wavelengths were expected [6,10,13,14]. Initially, their industrial applicability was very limited due to their low laser power, and in the case of the diode lasers, their low beam quality.…”

Section: Introductionmentioning

confidence: 99%

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Kohl

Kaufmann

Schmidt

2022

Metals

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With its excellent automation capability and localized energy input enabling precise, reproducible welds, laser beam welding represents a preferred industrial joining technology. Electro-mobility drastically increases the need for defect-free and automatable copper joining technologies. However, copper welds that are produced with state-of-the-art infrared lasers often suffer from spattering and porosity. Recent publications show distinct improvements using novel beam sources at visible wavelengths, attributing them to increased absorptivity. Nevertheless, this cannot fully explain the steadier process behavior. This wavelength-dependent process stability has not yet been investigated sufficiently. Therefore, we have developed a predictive material-dependent criterion indicating process stability based on the example of copper heat-conduction spot welding. For this purpose, we combined energy balances with thermo-physical material properties, taking into account the wavelength and temperature dependence of the optical properties. This paper presents the key mechanism that we identified as decisive for process stability. The criterion revealed that X-points (unique, material-specific wavelengths) represent critical stability indicators. Our calculations agree very well with experimental results on copper, steel and aluminum using two different wavelengths and demonstrate the decisive, material-dependent wavelength impact on process stability. This knowledge will help guide manufacturers and users to choose and develop beam sources that are tailored to the material being processed.

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Section: Introductionmentioning

confidence: 99%

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Kohl

Kaufmann

Schmidt

2022

Metals

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“…Later in 90 s, the development of low threading dislocation GaN substrates further boosted the performance of nitride-based LDs [4][5][6][7]. To date, low-threshold (J th < 2 kA/cm 2 ) and state-of-art high-power (P > 10 Watt) edge-emitting lasers (EEL) have been demonstrated [8][9][10]. III-nitride vertical-cavity surface-emitting lasers (VCSELs) arrived even later.…”

Section: Introductionmentioning

confidence: 99%

Challenges and Advancement of Blue III-Nitride Vertical-Cavity Surface-Emitting Lasers

et al. 2021

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Since the first demonstration of (Al, In, Ga)N-based blue vertical-cavity surface-emitting lasers (VCSELs) in 2008, the maximum output power (Pmax) and threshold current density (Jth) has been improved significantly after a decade of technology advancements. This article reviewed the key challenges for the realization of VCSELs with III-nitride materials, such as inherent polarization effects, difficulties in distributed Bragg’s reflectors (DBR) fabrication for a resonant cavity, and the anti-guiding effect due to the deposited dielectrics current aperture. The significant tensile strain between AlN and GaN hampered the intuitive cavity design with two epitaxial DBRs from arsenide-based VCSELs. Therefore, many alternative cavity structures and processing technologies were developed; for example, lattice-matched AlInN/GaN DBR, nano-porous DBR, or double dielectric DBRs via various overgrowth or film transfer processing strategies. The anti-guiding effect was overcome by integrating a fully planar or slightly convex DBR as one of the reflectors. Special designs to limit the emission polarization in a circular aperture were also summarized. Growing VCSELs on low-symmetry non-polar and semipolar planes discriminates the optical gain along different crystal orientations. A deliberately designed high-contrast grating could differentiate the reflectivity between the transverse-electric field and transverse-magnetic field, which restricts the lasing mode to be the one with the higher reflectivity. In the future, the III-nitride based VCSEL shall keep advancing in total power, applicable spectral region, and ultra-low threshold pumping density with the novel device structure design and processing technologies.

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“…However, this situation has changed significantly with the improvement of coating and passivation technologies for the facets. [ 2 ] Therefore, damage signatures, [ 3–13 ] originally typical of front‐facet COD, are also observed in the bulk on such devices, especially after failure at high‐emission power levels, at the latest after preparative opening of the device in question. This form of COD is sometimes referred to as catastrophic optical bulk damage (COBD).…”

Section: Introductionmentioning

confidence: 99%

Catastrophic Optical Damage in Semiconductor Lasers: Physics and New Results on InGaN High‐Power Diode Lasers

Hempel

Dadgostar

Jiménez

et al. 2021

Physica Rapid Research Ltrs

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Among the limitations known from semiconductor lasers, catastrophic optical damage (COD) is perhaps the most spectacular power‐limiting mechanism. Here, absorption and temperature build up in a positive feedback loop that eventually leads to material destruction. Thus, this is truly an ultimate mechanism, and its continued suppression is a manifestation of progress in device design and manufacturing. After an overview of the current state of knowledge, new investigations of COD using artificially micrometer‐sized starting points created within the active zone in the cavity of 450 nm GaN semiconductor lasers are reported on. Defect growth mechanisms and characteristics are studied during 800 ns current pulses. The defect growth follows the highest light intensity. Secondary defect patterns are studied: complete destruction of the active zone and generation of a point defect cloud at least ≈10 μm into the remaining surrounding material. Extremely large angles (>90°) of damage growth are traced back to the material properties and the aging scenario. The results are compared with former experiments with GaAs‐based lasers.

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Blue 450nm high power semiconductor continuous wave laser bars exceeding rollover output power of 80W

Cited by 10 publications

References 3 publications

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Challenges and Advancement of Blue III-Nitride Vertical-Cavity Surface-Emitting Lasers

Catastrophic Optical Damage in Semiconductor Lasers: Physics and New Results on InGaN High‐Power Diode Lasers

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