scholarly journals Micromachining of Invar Foils with GHz, MHz and kHz Femtosecond Burst Modes

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 733 ◽  
Author(s):  
Simas Butkus ◽  
Vytautas Jukna ◽  
Domas Paipulas ◽  
Martynas Barkauskas ◽  
Valdas Sirutkaitis
Keyword(s):  
Repetition Rate ◽  
Laser System ◽  
Single Shot ◽  
Burst Mode ◽  
Average Laser Power ◽  
Order Of Magnitude ◽  
Multiple Pulses ◽  
Constant Duration ◽  
Percussion Drilling

In this work, a burst mode laser is used for micromachining of 20 µm–250 µm thick Invar (Fe64/Ni36) foils. Holes were drilled by firing multiple pulses transversely onto the sample without moving the beam (percussion drilling). The utilized laser system generates a burst of a controllable number of pulses (at 1030 nm) with tunable pulse-to-pulse time spacing ranging from 200 ps to 16 ns. The sub-pulses within the burst have equal amplitudes and a constant duration of 300 fs that do not change regardless of the spacing in time between them. In such a way, the laser generates GHz to MHz repetition rate pulse bursts with a burst repetition rate ranging from 100 kHz to a single shot. Drilling of the material is compared with the non-burst mode of kHz repetition rate. In addition, we analyze the drilling speed and the resulting dependence of the quality of the holes on the number of pulses per burst as well as the average laser power to find the optimal micromachining parameters for percussion drilling. We demonstrate that the micromachining throughput can be of an order of magnitude higher when using the burst mode as compared to the best results of the conventional kHz case; however, excess thermal damage was also evident in some cases.

scholarly journals Selective etching of 10 MHz repetition rate fs-laser inscribed tracks in YAG

2021 ◽  
Vol 255 ◽  
pp. 10003
Author(s):  
Kore Hasse ◽  
Detlef Kip ◽  
Christian Kränkel
Keyword(s):  
Aspect Ratio ◽  
Repetition Rate ◽  
Laser System ◽  
Selective Etching ◽  
Etching Process ◽  
Acid Mixture ◽  
Laser Structuring ◽  
Order Of Magnitude ◽  
Fs Laser

We investigated fs-laser structuring of YAG crystals at high writing velocities up to 100 mm/s using a commercial 10 MHz fs-laser system supplied by Coherent Inc. and selective etching of these structures for fabrication of ultrahigh aspect ratio microchannels. Usage of a diluted acid mixture of 22% H3PO4 and 24% H2SO4 accelerated the etching process significantly to an etching parameter D of 11.2 μm2/s, which is three times higher than previously reported. Additionally, the selectivity of the etching process was increased by an order of magnitude.

scholarly journals DFB diode seeded low repetition rate fiber laser system operating in burst mode

2017 ◽  
Vol 88 ◽  
pp. 99-103 ◽  
Author(s):  
M. Šajn ◽  
J. Petelin ◽  
V. Agrež ◽  
M. Vidmar ◽  
R. Petkovšek
Keyword(s):  
Fiber Laser ◽  
Repetition Rate ◽  
Laser System ◽  
Burst Mode ◽  
System Operating

Micro Cutting of Biliary Stent with Nanosecond Fiber Laser System

2014 ◽  
Vol 939 ◽  
pp. 209-213 ◽  
Author(s):  
Ping Tun Teng ◽  
Fuh Yu Chang ◽  
Yu Ting Chang ◽  
Po Chin Liang ◽  
Kai Wen Huang
Keyword(s):  
Fiber Laser ◽  
Repetition Rate ◽  
Laser Power ◽  
Laser System ◽  
Cutting Speed ◽  
Cutting Parameters ◽  
Biliary Stent ◽  
High Quality ◽  
Cutting System

A biliary stent cutting system based on nanosecond fiber laser was designed in this study. In order to achieve the stent cutting, the main modules and the critical technologies were analyzed. Then with the cutting system, the kerf width size was studied for different cutting parameters including laser power, repetition rate, cutting speed and assisting gas pressure. Finally, a high quality of fabricated nitinol biliary stent was achieved.

scholarly journals High-quality percussion drilling with ultrashort laser pulses

2021 ◽  
Vol 127 (9) ◽  
Author(s):  
A. Feuer ◽  
R. Weber ◽  
R. Feuer ◽  
D. Brinkmeier ◽  
T. Graf
Keyword(s):  
Stainless Steel ◽  
Laser Fluence ◽  
Ablation Threshold ◽  
Laser Pulses ◽  
Ultrashort Laser Pulses ◽  
High Quality ◽  
Edge Quality ◽  
Ultrashort Laser ◽  
Percussion Drilling

AbstractThe influence of the laser fluence on the quality of percussion-drilled holes was investigated both experimentally and by an analytical model. The study reveals that the edge quality of the drilled microholes depends on the laser fluence reaching the rear exit of the hole and changes with the number of pulses applied after breakthrough. The minimum fluence that must reach the hole’s exit in order to obtain high-quality microholes in stainless steel was experimentally found to be 2.8 times the ablation threshold.

scholarly journals Effects of Field Processing of Sorghum Grain on Popping Traits

Agronomy ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 839
Author(s):  
Mitchell Kent ◽  
William Rooney
Keyword(s):  
Impact Force ◽  
Grain Sorghum ◽  
Expansion Ratio ◽  
Direct Impact ◽  
Order Of Magnitude ◽  
Rubber Belt ◽  
Sorghum Grain ◽  
Harvest Moisture ◽  
Quality Measurements

Interest in the use of popped sorghum in food products has resulted in a niche market for sorghum hybrids with high popping quality but little work has been done to assess the relative effects of field processing methods of grain on popping quality. This study evaluated the relative effects of harvest moisture and threshing methods on the popping quality of sorghum grain. A grain sorghum hybrid with good popping quality was produced during two different years in Texas wherein it was harvested at two moisture levels (low and high) and grain was removed from panicles using five different threshing methods (hand, rubber belt, metal brushes and two metal concave bar systems). Years, harvest moisture content and threshing method influenced all three popping quality measurements (popping efficacy, expansion ratio and flake size), but threshing method had an order of magnitude larger effect than either moisture level or year. While many of the interactions were significant, they did not influence the general trends observed. As such, the threshing methods with less direct impact force on the grain (hand and rubber belt) had higher popping quality than those samples threshed with greater impact force on the grain (metal-based systems). The popping quality differences between threshing system are likely due to a reduction in kernel integrity caused by the impacts to the kernel that occurred while threshing the grain. The results herein indicate that field processing of the grain, notably threshing method has significant impacts on the popping quality and should be taken into consideration when grain sorghum is harvested for popping purposes.

scholarly journals 1178 J, 527 nm near diffraction limited laser based on a complete closed-loop adaptive optics controlled off-axis multi-pass amplification laser system

2021 ◽  
Vol 9 ◽  
Author(s):  
Deen Wang ◽  
Xin Zhang ◽  
Wanjun Dai ◽  
Ying Yang ◽  
Xuewei Deng ◽  
...  
Keyword(s):  
Laser Beam ◽  
Adaptive Optics ◽  
Closed Loop ◽  
Focal Spot ◽  
Beam Quality ◽  
Laser System ◽  
Diffraction Limit ◽  
Kdp Crystal ◽  
Main Amplifier

Abstract A 1178 J near diffraction limited 527 nm laser is realized in a complete closed-loop adaptive optics (AO) controlled off-axis multi-pass amplification laser system. Generated from a fiber laser and amplified by the pre-amplifier and the main amplifier, a 1053 nm laser beam with the energy of 1900 J is obtained and converted into a 527 nm laser beam by a KDP crystal with 62% conversion efficiency, 1178 J and beam quality of 7.93 times the diffraction limit (DL). By using a complete closed-loop AO configuration, the static and dynamic wavefront distortions of the laser system are measured and compensated. After correction, the diameter of the circle enclosing 80% energy is improved remarkably from 7.93DL to 1.29DL. The focal spot is highly concentrated and the 1178 J, 527 nm near diffraction limited laser is achieved.

Low repetition rate, narrow-linewidth, all-fiber 1064 nm laser system

2021 ◽  
pp. 103930
Author(s):  
Yaoyao Qi ◽  
Yu Zhang ◽  
Song Yang ◽  
Xiaowei Huo ◽  
Zhenxu Bai ◽  
...  
Keyword(s):  
Repetition Rate ◽  
Laser System ◽  
Narrow Linewidth

Microbial Quality of Ground Beef after Simulated Freezer Failure

1981 ◽  
Vol 44 (1) ◽  
pp. 62-65 ◽  
Author(s):  
FATIMA S. ALI ◽  
FRANCES O. VANDUYNE
Keyword(s):  
Clostridium Perfringens ◽  
Microbial Quality ◽  
Ground Meat ◽  
Frozen Foods ◽  
Mean Values ◽  
Power Failure ◽  
Order Of Magnitude ◽  
Plate Counts ◽  
Coagulase Positive Staphylococci

Six lots of ground meat, obtained at intervals from a local supermarket, were frozen, and later held with other frozen foods in the freezer compartment of a refrigerator-freezer where power failure was simulated by unplugging the unit. Mean values for the counts (log10) of the beef as purchased were as follows: aerobic and psychrotrophic plate counts 6.35 and 6.66, respectively; presumptive coliforms 4.48; coagulase-positive staphylococci 4.67; and presumptive Clostridium perfringens 1.43. Presumptive salmonellae were detected in three of the six lots. Counts of the same order of magnitude as above were obtained after 7 days in the freezers, complete defrost of the meat and 6 h thereafter. Between 6 and 24 h, aerobic and psychrotrophic plate counts and numbers of coliforms and coagulase-positive staphylococci increased approximately 10-fold. Forty-eight hours after complete defrost, further increases in counts occurred. The appearance and aroma of the meat were acceptable 24 h after defrost; after 48 h, it would have been discarded because of browning, slime and off-odors.

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