Dual Laser Beam Processing of Semiconducting Thin Films by Excited State Absorption

We present a unique dual laser beam processing approach based on excited state absorption by structuring 200 nm thin zinc oxide films sputtered on fused silica substrates. The combination of two pulsed nanosecond-laser beams with different photon energies—one below and one above the zinc oxide band gap energy—allows for a precise, efficient, and homogeneous ablation of the films without substrate damage. Based on structuring experiments in dependence on laser wavelength, pulse fluence, and pulse delay of both laser beams, a detailed concept of energy transfer and excitation processes during irradiation was developed. It provides a comprehensive understanding of the thermal and electronic processes during ablation. To quantify the efficiency improvements of the dual-beam process compared to single-beam ablation, a simple efficiency model was developed.

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Characterization of dissimilar aluminum-copper material joining by controlled dual laser beam

10.21203/rs.3.rs-980159/v1 ◽

2021 ◽

Author(s):

Joon Ho Cha ◽

Hae Woon Choi

Keyword(s):

Laser Beam ◽

Power Distribution ◽

Near Infrared ◽

Weld Zone ◽

Tensile Tests ◽

Bead Width ◽

Single Beam ◽

The Core ◽

Beam Laser ◽

Dual Laser

Abstract Laser technology has many advantages in welding for the manufacture of EV battery packs. Aluminum (Al) and copper (Cu) are welded using a dual laser beam, suggesting the optimum power distribution for the core and ring beams. Due to the very high reflectance of Cu and Al exposed to near-infrared lasers, the material absorbs a very small amount of energy. Compared to single beam laser welding, dual beam welding has significantly improved surface quality by controlling surface solidification. The study focused on the quality of weld surface beads, weld properties and tensile strength by varying the output ratio of the core beam to the ring beam. Optimal conditions of Al6061 were a 700 W core beam, a 500 W ring beam and 200 mm/s of weld speed. For the C1020P, the optimum conditions were a center beam of 2500 W, a ring beam of 3000 W and a welding speed of 200 mm/s. In laser lap welding of Al-Al and Al-Cu, the bead width and the interfacial bead width of the joint increased as the output increased. The penetration depth did not change significantly, but small pores were formed at the interface of the junction. Tensile tests were performed to demonstrate the reliability of the weld zone, and computer simulations provided analysis of the heat distribution for optimal heat input conditions.

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Zigzag Multirod Laser Beam Merging Approach for Brighter TEM00-Mode Solar Laser Emission from a Megawatt Solar Furnace

Energies ◽

10.3390/en14175437 ◽

2021 ◽

Vol 14 (17) ◽

pp. 5437

Author(s):

Hugo Costa ◽

Joana Almeida ◽

Dawei Liang ◽

Miguel Catela ◽

Dário Garcia ◽

...

Keyword(s):

Laser Beam ◽

Laser Power ◽

Power Level ◽

Fused Silica ◽

Solar Furnace ◽

Laser Beams ◽

Output Power Level ◽

Mode Laser ◽

Tem00 Mode ◽

Pump Cavity

An alternative multirod solar laser end-side-pumping concept, based on the megawatt solar furnace in France, is proposed to significantly improve the TEM00-mode solar laser output power level and its beam brightness through a novel zigzag beam merging technique. A solar flux homogenizer was used to deliver nearly the same pump power to multiple core-doped Nd:YAG laser rods within a water-cooled pump cavity through a fused silica window. Compared to the previous multibeam solar laser station concepts for the same solar furnace, the present approach can allow the production of high-power TEM00-mode solar laser beams with high beam brightness. An average of 1.06 W TEM00-mode laser power was numerically extracted from each of 1657 rods, resulting in a total of 1.8 kW. More importantly, by mounting 399 rods at a 30° angle of inclination and employing the beam merging technique, a maximum of 5.2 kW total TEM00-mode laser power was numerically extracted from 37 laser beams, averaging 141 W from each merged beam. The highest solar laser beam brightness figure of merit achieved was 148 W, corresponding to an improvement of 23 times in relation to the previous experimental record.

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Polymer Materials Design for Optical Limiting

MRS Proceedings ◽

10.1557/proc-479-89 ◽

1997 ◽

Vol 479 ◽

Cited By ~ 10

Author(s):

B. H. Cumpston ◽

K. Mansour ◽

A. A. Heikal ◽

J. W. Perry

Keyword(s):

Excited State ◽

Excited State Absorption ◽

Polymeric Materials ◽

Optical Limiting ◽

Polymer Materials ◽

Homogeneous Distribution ◽

Saturable Absorption ◽

Nanosecond Laser ◽

Reverse Saturable Absorption ◽

Discrete Elements

AbstractPhthalocyanines (PC's) containing heavy metal central atoms have recently been recognized as leading candidates for reverse saturable absorption and optical limiting (OL) applications in the visible spectrum. Strong triplet excited state absorption brought about by a large intersystem crossing rate is responsible for the excellent limiting performance of these molecules. Moreover, devices which maximize the excited state population along the light path will demonstrate maximum limiting efficiency. A non-homogeneous distribution of indium tetra(tert-butyl) phthalocyanine chloride (InC1PC) has been shown to be very effective in attenuating 532 nm nanosecond laser pulses. This was accomplished by approximating a hyperbolic distribution of chromophores using discrete elements of fixed dye concentration. Greater OL should be achieved by fabricating materials containing a continuous concentration gradient of chromophore. This paper focuses on issues concerning the preparation of solid polymeric materials that contain such a chromophore gradient. This design is achieved by diffusing chromophore-containing solutions into partially polymerized poly(methyl methacrylate) (PMMA).

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