Search

Laser-induced cleaning by the elimination of liquid contaminant droplets from the surface of a solid substrate is an attractive application of laser technology. We report the laser-induced ejection of an organic carbonate liquid droplet from an aluminum surface using three different infrared (IR) laser pulse durations (5.7 ns, 35 ns, and 90 µs). Single-shot cleaning of a large area sample through a non-contact process was achieved by irradiation with a nanosecond-pulsed laser. The dynamic behavior of liquid desorption was observed with a high-speed CCD camera. The threshold laser fluences for liquid desorption by laser irradiations were determined for each of the lasers. The laser pulse duration increased with increasing threshold laser fluence. [ABSTRACT FROM AUTHOR]

The laser-induced cleaning of a liquid droplet from the surface of a solid substrate is an attractive application of laser technology. We report the laser-induced ejection of an organic carbonate liquid droplet from an aluminum surface using a one Joule per pulse class nanosecond-pulsed laser. The dynamic behavior of the liquid desorption was observed with a high-speed CCD camera. The use of high-power laser equipment makes it possible to perform single-pass cleaning of large areas on a solid surface with a non-contact process. [ABSTRACT FROM AUTHOR]

We report damage in trenches produced by laser irradiation of a carbon fiber reinforced plastic (CFRP) plate. Laser cutting of CFRP was performed by multi-pass irradiation with a continuouswave fiber IR laser (multi-mode laser, average power: 3.3 kW). The damaged sidewall of the trench in the samples was analyzed by microscopic X-ray computed tomography. Low-speed laser scanning with a galvanometer scanner significantly damaged the sidewall surface and created a wide heat-affected zone. As the thickness of the damaged area was correlated with the scanning speed of the laser beam, the damaged region length was analyzed using the heat penetration depth equation. [ABSTRACT FROM AUTHOR]

Fabrication of micropit array structures on silica glass by fast beam-scanning LIBWE was employed for laser marking of glass materials. Microstructures were fabricated by LIBWE employing a DPSS laser (λ = 355 nm, τ ~ 15 ns) and toluene saturated with pyrene. When the beam scanning speed is low, microtrenches with 30 μm width are formed. On the other hand, micropit array structures can be fabricated under fast beam scanning conditions. Each micropit in an array structure obtained by single scan was fabricated by single laser pulse irradiation. Micropits with maximum depths of up to 0.35 μm could be fabricated by single laser pulse irradiation. For fabricating micropit array structures, the pulse repetition rate becomes an important parameter, since cavitation limits the etching at high pulse repetition rates. The effect of cavitation on etching was investigated by the measurement of transient pressure signals observed upon single and double pulse irradiation. Fabricated micropit array structures can be utilized for fast laser marking of glass materials. [ABSTRACT FROM AUTHOR]

We report deep-trench microstructures fabricated on carbon-fiber-reinforced thermoplastic (CFRTP; a CFRP containing thermoplastic resin). Well-defined laser cutting free of debris around the trench was achieved for various types of CFRTP plates by single-mode laser irradiation with a fast beam galvanometer scanner using a multiple-scan-pass method. The microfabrication of a CFRTP containing pitch-type carbon fibers and a polycarbonate resin, performed by 600-scan-pass irradiation with a cw kilowatt single-mode IR fiber laser (average power: 1 kW), yielded a trench microstructure with a depth of 18.2 mm and an opening width of 0.32 mm. The laser-induced damage in the samples was analyzed by microscopic X-ray computed tomography. Laser cutting by high-speed beam scanning resulted in a clean top and excellent sidewall quality, along with a negligible heataffected zone. [ABSTRACT FROM AUTHOR]

We report here laser cutting of carbon fiber reinforced plastic (CFRP) with an IR fiber laser (average power: 2 - 3 kW). The CFRP samples contain thermoplastic resin (CFRTP; carbon fiber reinforced thermo-plastic) or thermosetting resin as binding plastic. Well-defined laser cutting free of debris around the groove was performed for various type of CFRP plates by the laser irradiation with a fast beam galvanometer scanner on a multiple-scan-pass method. The laser-induced damage in the samples was observed and analyzed by microscopic X-ray Computed Tomography. Laser cutting with a high speed beam scanning exhibits a clean top and excellent sidewall quality along with a negligible heat-affected zone. [ABSTRACT FROM AUTHOR]

We have made a comparative review of photovoltaic properties of laboratory-scale Cu(In,Ga)Se2 (CIGS) solar cells electrically-isolated from each other by two types of femtosecond laser scribes: "Type 1" with removing both transparent conductive oxide (TCO) and CIGS layers and "Type 2" with complete removal of only TCO. The shunt resistance drastically decreased in the case of the "Type 1" scribing, degrading the photovoltaic efficiency. The "Type 2" scribing did not accompany a sharp drop in the shunt resistance, keeping relatively-high efficiency. The difference in the efficiency between before and after the "Type 2" scribing was only 0.1, while a typical drop for the "Type 1" was 1.3. In order to investigate the laser irradiation effect on a buried p-n junction in the "Type 2" laser-scribed CIGS solar cells, an electron-beam-induced current (EBIC) analysis was also performed. As a result, EBIC signals were clearly observed along a sidewall of the laser-scribed trench, indicating that the p-n junction survived after our femtosecond laser scribing even at the sidewall of the laser-scribed trench. Femtosecond laser scribing is an effective tool for CIGS solar cells with keeping high efficiency. [ABSTRACT FROM AUTHOR]

Laser-induced dot transfer (LIDT) is one of promising additive manufacturing techniques because it can realize flexible patterning of micron and submicron-sized dots even at atmospheric room-temperature conditions. In the LIDT process, a laser pulse is tightly focused onto a source film, leading to a transient melting of the film followed by sub-spot transfer using one-to-one microdot deposition with laser-illuminated area. Recently, we have developed a novel double-pulse LIDT process using the first pulse for preheating the source film and the second pulse for dot transfer. To investigate the double-pulse effect on microdot transfer of oxides, temporal high-temperature distributions of a thick indium tin oxide source film during double-pulse irradiation have been simulated using a Finite Element Method (FEM) approach. As a result, preheating by the first pulse decreased a difference in film temperature along both the film thickness and in-plane directions. This is effective to avoid film fracture, leading to high-quality patterning of a wide variety of microdots. [ABSTRACT FROM AUTHOR]

We report on the laser cutting of carbon fiber reinforced thermo-plastic (CFRTP) with a cw IR fiber laser (average power: 1 kW). CFRTP is a composite material which contains carbon fibers and binding thermoplastic. A well-defined cutting of CFRTP which was free of debris around the groove was performed by the laser irradiation with a fast beam galvanometer scanning on a multiple-scan-pass method. The area of laser-induced damages in the samples was observed by microscopic X-ray Computed Tomography and micro- Raman spectroscopy. Laser cutting with a high speed beam scanning exhibits a clean top and an excellent sidewall quality along with a negligible heat affected zone. [ABSTRACT FROM AUTHOR]

Neutral fragments from a nanosecond KrF excimer laser-ablated carbon fiber reinforced plastic (CFRP, carbon fiber/epoxy resin composite) were investigated by laser-ionization time-of-flight (TOF) mass spectrometry in order to explore the laser ablation dynamics of CFRP. The neutrals were detected after the post-ionization by an ArF excimer laser pulse at variable delay times, td, relative to the ablation KrF excimer laser pulse. Depending on the ablation fluence, TOF mass spectra and laser-etched surface morphology drastically changed. At the laser fluence of 0.3 J.cm-2, the resins were preferentially ablated. The TOF mass spectra contained a main peak at 36 amu assigned to C3+ in early delay times, and then the main peak changed to 39 amu assigned to C3H3+. At 1.0 and 1.5 J.cm-2, both of carbon fibers and resins were ablated. The most prominent peak was C3+ independent of the delay time. The delay-time distribution of C3+ exhibited a single peak at 0.3 J.cm-2 and then changed to two peaks at 1.5 J.cm-2. The fits with shifted Maxwell-Boltzmann distribution gave good agreement, suggesting transient maximum CFRP temperature of 4700, 6400, and 7100 K at 0.3, 1.0 and 1.5 J.cm-2, respectively. [ABSTRACT FROM AUTHOR]

Flexible and rapid preparation of FeSi2 microdots and indium tin oxide (ITO) microstructure patterns was performed using laser-induced forward transfer with a nanosecond high-frequency diode-pumped solid-state laser/galvanometer-based point-scanning system. Different types of source materials, i.e., FeSi2 and ITO, were used to explore the materials dependence of transfer. FeSi2 spheres with a lateral diameter of 5.5 μm were successfully arrayed on a micrometer scale. Sub-spot transfer was achieved, and we refer to this as laser-induced dot transfer (LIDT). In the case of ITO, although the transferred shape is flower-like rather than spherical, site-controlled transfer was achieved. The LIDT technique is useful for integrating functional micro-patterns with sub-spot resolution under room-temperature atmospheric conditions. [ABSTRACT FROM AUTHOR]