Comparison of focusing of short pulses in the Debye approximation

We have examined different types of pulses and features of their frequency spectra. Calculations have shown that a significant distinction between the pulses only takes place at a very short pulse duration (shorter than the oscillation period). In this case, the Gaussian pulse becomes nonphysical and one needs to use other types of pulses, for example, the Poisson pulse. We performed comparative modeling of focusing of short pulses by an aplanatic lens for different polarization states and vortex singularity orders in the Debye approximation. We have shown that the polarization state and the presence of vortex phase singularity essentially affect the distribution in the focal area for a subcycle Poisson pulse.

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Generation of Multiple Vector Optical Bottle Beams

Photonics ◽

10.3390/photonics8060218 ◽

2021 ◽

Vol 8 (6) ◽

pp. 218

Author(s):

Svetlana N. Khonina ◽

Alexey P. Porfirev ◽

Sergey G. Volotovskiy ◽

Andrey V. Ustinov ◽

Sergey A. Fomchenkov ◽

...

Keyword(s):

Intensity Distribution ◽

Polarization State ◽

Spatial Dynamics ◽

Surface Structures ◽

Optical Traps ◽

Spatial Transformation ◽

Optical Elements ◽

Periodic Surface ◽

Matter Interaction ◽

Different Types

We propose binary diffractive optical elements, combining several axicons of different types (axis-symmetrical and spiral), for the generation of a 3D intensity distribution in the form of multiple vector optical ‘bottle’ beams, which can be tailored by a change in the polarization state of the illumination radiation. The spatial dynamics of the obtained intensity distribution with different polarization states (circular and cylindrical of various orders) were investigated in paraxial mode numerically and experimentally. The designed binary axicons were manufactured using the e-beam lithography technique. The proposed combinations of optical elements can be used for the generation of vector optical traps in the field of laser trapping and manipulation, as well as for performing the spatial transformation of the polarization state of laser radiation, which is crucial in the field of laser-matter interaction for the generation of special morphologies of laser-induced periodic surface structures.

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High-power excilamps with short-pulse duration

10.1117/12.407308 ◽

2000 ◽

Cited By ~ 1

Author(s):

Victor F. Tarasenko

Keyword(s):

Pulse Duration ◽

High Power ◽

Short Pulse ◽

Short Pulse Duration

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Unidirectional propagation of the Bloch surface wave excited by the spinning magnetic dipole in two-dimensional photonic crystal slab

Scientific Reports ◽

10.1038/s41598-021-98056-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Li-Ming Zhao ◽

Yun-Song Zhou

Keyword(s):

Photonic Crystal ◽

Surface Wave ◽

Magnetic Dipole ◽

Incident Light ◽

Polarization State ◽

Oscillation Period ◽

Unit Cell ◽

Average Spin ◽

Component Wave ◽

Bloch Surface Wave

AbstractThe photonic spin Hall effect (PSHE) can be realized in a photonic crystal (PC) slab, that is, the unidirectional Bloch surface wave can propagate along the surface of the PC slab under the excitation of elliptical polarized magnetic dipole. It is further proved that PSHE is caused by the interference of the component surface waves excited by the different components of the incident light, which is the so called component wave interference (CWI) theory. In addition, we also find that the spin of the surface wave oscillates periodically in space, and the oscillation period is a unit cell. In a unit cell, the average spin keeps the spin orbit locked. The results show that the spin separation can also be modulated by the position and the polarization state of the magnetic dipole.

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Synchronization and Bursting Activity in the Model for Two Predator-Prey Systems Coupled By Predator Migration

Математическая биология и биоинформатика ◽

10.17537/2019.14.588 ◽

2019 ◽

Vol 14 (2) ◽

pp. 588-611

Author(s):

M.P. Kulakov ◽

E.V. Kurilova ◽

E.Ya. Frisman

Keyword(s):

Phase Synchronization ◽

Oscillation Period ◽

Logistic Growth ◽

Predator Prey ◽

Different Types ◽

The Difference ◽

Minimum Numbers ◽

Fast Oscillations ◽

Bursting Activity ◽

Type Ii Functional Response

The papers is devoted to a model for two non-identical predator-prey communities coupled by migration and characterized by logistic growth of prey and Holling type II functional response. The coupling is a predator migration at constant weak rate. The non-identity is the difference in the prey growth rates or predator mortalities in each patch. We studied the equilibrium states of model and scenarios of loss of their stability and emerge of complex periodic solutions. It was shown that in some domains of the parameter space there is a bursting activity which are that the dynamics of two communities contain segments of slowly resting dynamic (as part of a fast-slow cycle or canard) and regular bursts of spikes. In the resting part, the dynamics of the second community, as a rule, follow the slow changes in the first community, i.e. the dynamics in different patches are synchronous. But in the fast part there is only phase synchronization between the fast-slow cycle in first patch and bursts in second. We classified the scenarios of transition between different types of bursting activity by location spiking manifold and canard. These types differ not so much in size, shape or numbers of spikes as in the order of bursts emerge relative a slow-fast cycle. In a typical case the start of burst (divergent fast oscillations) coincides with the minimum numbers or quasi-extinction of prey in the first patch. After a rapid increase in the prey number in the first patch, diverging fluctuations give way to damped in the second patch. Such dynamics correspond to the rhombus-wave shape of spikes cluster. Another case is interesting, when the burst of spikes is formed after the full recovery of prey and with a certain predator number in the first patch. In this case, the spikes cluster takes the shape of a triangle-wave or a truncated rhombus-wave. It was shown that transitions between these types of bursts are accompanied by a change in the oscillation period and the degree of synchronization. Triangular-wave bursters correspond to complete synchronization of the predator dynamics in the resting part and rhomboid-wave correspond to antiphase synchronization. In the fast part with many spikes, communities are completely asynchronous to each other.

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Q-switched all-fiber laser with short pulse duration based on tungsten diselenide

Laser Physics ◽

10.1088/1555-6611/aa9e38 ◽

2018 ◽

Vol 28 (5) ◽

pp. 055104 ◽

Cited By ~ 16

Author(s):

Wenyi Li ◽

Yuyi OuYang ◽

Guoli Ma ◽

Mengli Liu ◽

Wenjun Liu

Keyword(s):

Fiber Laser ◽

Pulse Duration ◽

Short Pulse ◽

Tungsten Diselenide ◽

Short Pulse Duration

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Q-Switch Nd:YAG Laser-Assisted Decontamination of Implant Surface

Dentistry Journal ◽

10.3390/dj7040099 ◽

2019 ◽

Vol 7 (4) ◽

pp. 99 ◽

Cited By ~ 2

Author(s):

Namour ◽

El Mobadder ◽

Magnin ◽

Peremans ◽

Verspecht ◽

...

Keyword(s):

Pulse Duration ◽

Nd:Yag Laser ◽

Yttrium Aluminum Garnet ◽

Short Pulse ◽

Sem Analysis ◽

P Value ◽

Implant Surface ◽

Contact Mode ◽

Short Pulse Duration ◽

Clean Contaminated

Peri-implantitis (PI) is an inflammatory disease of peri-implant tissues, it represents the most frequent complication of dental implants. Evidence revealed that microorganisms play the chief role in causing PI. The purpose of our study is to evaluate the cleaning of contaminated dental implant surfaces by means of the Q-switch Nd:YAG (Neodymium-doped Yttrium Aluminum Garnet) laser and an increase in temperature at lased implant surfaces during the cleaning process. Seventy-eight implants (titanium grade 4) were used (Euroteknika, Sallanches, France). Thirty-six sterile implants and forty-two contaminated implants were collected from failed clinical implants for different reasons, independent from the study. Thirty-six contaminated implants were partially irradiated by Q-switch Nd:YAG laser (1064 nm). Six other contaminated implants were used for temperature rise evaluation. All laser irradiations were calibrated by means of a powermetter in order to evaluate the effective delivered energy. The irradiation conditions delivered per pulse on the target were effectively: energy density per pulse of 0.597 J/cm2, pick powers density of 56 mW/cm2, 270 mW per pulse with a spot diameter of 2.4 mm, and with repetition rate of 10 Hz for pulse duration of 6 ns. Irradiation was performed during a total time of 2 s in a non-contact mode at a distance of 0.5 mm from implant surfaces. The parameters were chosen according to the results of a theoretical modeling calculation of the Nd:YAG laser fluency on implant surface. Evaluation of contaminants removal showed that the cleaning of the irradiated implant surfaces was statistically similar to those of sterile implants (p-value ≤ 0.05). SEM analysis confirmed that our parameters did not alter the lased surfaces. The increase in temperature generated at lased implant surfaces during cleaning was below 1 °C. According to our findings, Q-switch Nd:YAG laser with short pulse duration in nanoseconds is able to significantly clean contaminated implant surfaces. Irradiation parameters used in our study can be considered safe for periodontal tissue.

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Point source of UV-radiation with a frequency of 1 khz and short pulse duration

Russian Physics Journal ◽

10.1007/s11182-012-9742-4 ◽

2012 ◽

Vol 54 (11) ◽

pp. 1276-1279 ◽

Cited By ~ 1

Author(s):

E. Kh. Baksht ◽

V. F. Tarasenko ◽

Yu. V. Shut’ko ◽

M. V. Erofeev

Keyword(s):

Point Source ◽

Pulse Duration ◽

Uv Radiation ◽

Short Pulse ◽

Short Pulse Duration

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Forming Fine V-Grooves on a Tungsten Carbide Workpiece with a PCD Electrode by EDM

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.329.631 ◽

2007 ◽

Vol 329 ◽

pp. 631-636 ◽

Cited By ~ 2

Author(s):

Sadao Sano ◽

Kiyoshi Suzuki ◽

Wei Li Pan ◽

Manabu Iwai ◽

Yoshihiko Murakami ◽

...

Keyword(s):

Tungsten Carbide ◽

Pulse Duration ◽

Flat Surface ◽

Short Pulse ◽

Chemical Vapor ◽

Polycrystalline Diamond ◽

Chemical Vapor Deposition Diamond ◽

Electrically Conductive ◽

Short Pulse Duration ◽

Low Wear

Polycrystalline diamond (PCD) exhibits a thermal conductivity similar to that of the electrically conductive chemical vapor deposition diamond (EC-CVD diamond) found to function as zero-wear electrodes at short pulse duration. In this study, PCD was used as electrodes applied to EDM on tungsten carbide. Two kinds of PCD (CTB-010 and CTH-025) with a flat surface were used. The wear of the PCD electrodes was about 1.5% for very short pulse duration such as te=1μs, but it was zero wear at te=30μs, though the wear of a Cu-W electrode was 10% even on the machine recommended conditions for the low wear. EDM experiment using a V-shaped PCD electrode with an included angle of 45° was also carried out and the performance was compared with the case using a V-shaped Cu-W electrode. Under the conditions of a no load voltage of 60V, a set peak current of 2A, and a medium pulse duration of te=15μs, there was no wear on PCD electrodes when observed under the SEM, whereas a 50μm-deep wear on the Cu-W electrodes even under the machine recommended condition for the low wear was observed.

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