Nanoscale Heat Transport in Self-Organized Ge Clusters on Si(001)

2012 ◽  
Vol 1456 ◽  
Author(s):  
Tim Frigge ◽  
Annika Kalus ◽  
Friedrich Klasing ◽  
Martin Kammler ◽  
Anja Hanisch-Blicharski ◽  
...  
Keyword(s):  
Laser Pulses ◽  
Transient Temperature ◽  
Equivalent Thickness ◽  
Time Resolved ◽  
Pump Probe ◽  
Nanoscale Heat Transport ◽  
Self Organized ◽  
Transmission Electron ◽  
Fs Laser ◽  
Cooling Behavior

ABSTRACTUltrafast time resolved transmission electron diffraction (TED) in a reflection geometry was used to study the cooling behavior of self-organized, well defined nanoscale germanium hut and dome clusters on Si(001). The clusters were heated in a pump-probe scheme by fs-laser pulses. The resulting transient temperature rise was then determined from the drop in diffraction intensity caused by the Debye-Waller effect. From a cooling time of τ =177 ps we estimated a strongly reduced heat transfer compared with homogeneous films of equivalent thickness.

scholarly journals Dual-shot dynamics and ultimate frequency of all-optical magnetic recording on GdFeCo

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Sicong Wang ◽  
Chen Wei ◽  
Yuanhua Feng ◽  
Hongkun Cao ◽  
Wenzhe Li ◽  
...  
Keyword(s):  
Magnetization Reversal ◽  
Energy Efficient ◽  
High Speed ◽  
Data Transfer ◽  
Laser Pulses ◽  
Time Resolved ◽  
All Optical ◽  
Fs Laser ◽  
High Speed Data ◽  
Natural Way

AbstractAlthough photonics presents the fastest and most energy-efficient method of data transfer, magnetism still offers the cheapest and most natural way to store data. The ultrafast and energy-efficient optical control of magnetism is presently a missing technological link that prevents us from reaching the next evolution in information processing. The discovery of all-optical magnetization reversal in GdFeCo with the help of 100 fs laser pulses has further aroused intense interest in this compelling problem. Although the applicability of this approach to high-speed data processing depends vitally on the maximum repetition rate of the switching, the latter remains virtually unknown. Here we experimentally unveil the ultimate frequency of repetitive all-optical magnetization reversal through time-resolved studies of the dual-shot magnetization dynamics in Gd27Fe63.87Co9.13. Varying the intensities of the shots and the shot-to-shot separation, we reveal the conditions for ultrafast writing and the fastest possible restoration of magnetic bits. It is shown that although magnetic writing launched by the first shot is completed after 100 ps, a reliable rewriting of the bit by the second shot requires separating the shots by at least 300 ps. Using two shots partially overlapping in space and minimally separated by 300 ps, we demonstrate an approach for GHz magnetic writing that can be scaled down to sizes below the diffraction limit.

scholarly journals Understanding the Seeding Pulse-Induced Optical Amplification in N 2 + Pumped by 800 NM Femtosecond Laser Pulses

Photonics ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 99
Author(s):  
Zhengquan Fan ◽  
Xiang Zhang ◽  
Qi Lu ◽  
Yu Luo ◽  
Qingqing Liang ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Optical Gain ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Time Resolved ◽  
Optical Amplification ◽  
Pump Probe ◽  
Amplification Process ◽  
Energy Amplification

Nitrogen ions pumped by intense femtosecond laser pulses present an optical gain at 391.4 nm, evident by energy amplification of an injected resonant seeding pulse. We report a time-resolved measurement of the amplification process with seeding pulses having varying intensities. It is found that the amplification factor depends on the intensity of the seeding pulse and the effective temporal window for the optical gain becomes longer by applying more intense seeding pulses. These two features are in sharp contrast with classic pump-probe experiments, pinpointing the crucial role of macroscopic coherence and its dynamics during the lasing process. We further measure the temporal profile of the amplified emission for seeding pulse injected at different time delays. A complicated temporal behavior is observed, which highlights the nature of the superfluorescence.

Optical Limiting With Neutral Nickel Dithiolene Complexes

1999 ◽  
Vol 597 ◽  
Author(s):  
W. L. Tan ◽  
W. Ji ◽  
J. L. Zuo ◽  
J. F. Bai ◽  
X. Z. You ◽  
...  
Keyword(s):  
Benzene Solution ◽  
Excited State Absorption ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Optical Limiting ◽  
Linear Absorption ◽  
Time Resolved ◽  
Pump Probe ◽  
Limiting Behavior ◽  
Picosecond Pulses

AbstractWe report an investigation of optical-limiting behavior in two neutral nickel complexes with multi-sulfur 1,2 dithiolene ligands, [Ni(medt)2] I (medt = 5,6-dihydro-6-methyl-1,4-dithiin-2,3- dithiolate) and [Ni(phdt)2] 2 (phdt = 5,6-dihydro-5-phenyl-l,4-dithiin-2,3-dithiolate) in benzene solution. The fluence-dependent transmission of the complexes was observed with nanosecond and picosecond laser pulses at 532-nm wavelength. The limiting thresholds of the complexes were ˜0.3 J/cm2, when measured with the picosecond pulses. Both picosecond time-resolved pump-probe and Z-scan measurement revealed that the limiting effects should originate from excited-state absorption and refraction. The transparency window (400˜900 nm), observed in the linear absorption spectra of the complexes, indicated that their limiting response should cover a wider range than those of fullerenes and phthalocyanines.

scholarly journals Ultrafast and Distinct Spin Dynamics in Magnetic Alloys

SPIN ◽  
2015 ◽  
Vol 05 (03) ◽  
pp. 1550004 ◽  
Author(s):  
I. Radu ◽  
C. Stamm ◽  
A. Eschenlohr ◽  
F. Radu ◽  
R. Abrudan ◽  
...  
Keyword(s):  
Exchange Interaction ◽  
Data Storage ◽  
Magnetic Circular Dichroism ◽  
Dynamic Properties ◽  
Spin Dynamics ◽  
Magnetic Moments ◽  
Dynamical Behavior ◽  
Laser Pulses ◽  
Time Resolved ◽  
Fs Laser

Controlling magnetic order on ultrashort timescales is crucial for engineering the next-generation magnetic devices that combine ultrafast data processing with ultrahigh-density data storage. An appealing scenario in this context is the use of femtosecond (fs) laser pulses as an ultrafast, external stimulus to fully set the orientation and the magnetization magnitude of a spin ensemble. Achieving such control on ultrashort timescales, e.g., comparable to the excitation event itself, remains however a challenge due to the lack of understanding the dynamical behavior of the key parameters governing magnetism: The elemental magnetic moments and the exchange interaction. Here, we investigate the fs laser-induced spin dynamics in a variety of multi-component alloys and reveal a dissimilar dynamics of the constituent magnetic moments on ultrashort timescales. Moreover, we show that such distinct dynamics is a general phenomenon that can be exploited to engineer new magnetic media with tailor-made, optimized dynamic properties. Using phenomenological considerations, atomistic modeling and time-resolved X-ray magnetic circular dichroism (XMCD), we demonstrate demagnetization of the constituent sub-lattices on significantly different timescales that depend on their magnetic moments and the sign of the exchange interaction. These results can be used as a “recipe” for manipulation and control of magnetization dynamics in a large class of magnetic materials.

scholarly journals Laser-Inscribed Stress-Induced Birefringence of Sapphire

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1414 ◽  
Author(s):  
Hua Fan ◽  
Meguya Ryu ◽  
Reo Honda ◽  
Junko Morikawa ◽  
Zhen-Ze Li ◽  
...  
Keyword(s):  
Bessel Beam ◽  
Laser Pulses ◽  
Visible Spectral Range ◽  
Vortex Generation ◽  
Cross Sectional ◽  
Optical Elements ◽  
High Birefringence ◽  
Self Organized ◽  
Fs Laser ◽  
Spatially Varying

Birefringence of 3 × 10 - 3 is demonstrated inside cross-sectional regions of 100 μ m, inscribed by axially stretched Bessel-beam-like fs-laser pulses along the c-axis inside sapphire. A high birefringence and retardance of λ / 4 at mid-visible spectral range (green) can be achieved using stretched beams with axial extension of 30–40 μ m. Chosen conditions of laser-writing ensure that there are no formations of self-organized nano-gratings. This method can be adopted for creation of polarization optical elements and fabrication of spatially varying birefringent patterns for optical vortex generation.

scholarly journals Few Percent Efficient Polarization-Sensitive Conversion in Nonlinear Plasmonic Interactions Inside Oligomeric Gold Structures

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 59
Author(s):  
Nikolay Busleev ◽  
Sergey Kudryashov ◽  
Irina Saraeva ◽  
Pavel Danilov ◽  
Andrey Rudenko ◽  
...  
Keyword(s):  
Plasmon Resonance ◽  
Laser Pulses ◽  
Visible Range ◽  
Oligomeric Structure ◽  
Self Organized ◽  
Electromagnetic Interactions ◽  
Nanoscale Characterization ◽  
Fs Laser ◽  
The Individual ◽  
Anti Stokes

The backscattering spectra of a 500 nm thick gold film, which was excited near the 525 nm transverse localized plasmon resonance of its constituent, self-organized, vertically-aligned nanorods by normally incident 515 nm, 300 fs laser pulses with linear, radial, azimuthal and circular polarizations, revealed a few-percent conversion into Stokes and anti-Stokes side-band peaks. The investigation of these spectral features based on the nanoscale characterization of the oligomeric structure and numerical simulations of its backscattering response indicated nonlinear Fano-like plasmonic interactions, particularly the partially degenerate four-wave mixing comprised by the visible-range transverse plasmon resonance of the individual nanorods and an IR-range collective mode of the oligomeric structure. Such oligomeric structures in plasmonic films may greatly enhance inner nonlinear electromagnetic interactions and inner near-IR hotspots, paving the way for their engineered IR tunability for broad applications in chemosensing and biosensing.

Microstructures induced by femtosecond laser pulses inside glasses

2009 ◽  
Vol 24 (6) ◽  
pp. 1983-1988 ◽  
Author(s):  
Dong Su ◽  
Nan Jiang ◽  
Jianrong Qiu ◽  
John C.H. Spence
Keyword(s):  
Structural Changes ◽  
Soda Lime ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Transmission Electron ◽  
Fs Laser ◽  
Soda Lime Silicate Glass ◽  
Spectroscopy Studies ◽  
Property Changes ◽  
Electron Energy Loss

In this article, the chemical and structural changes inside soda-lime glasses induced by femtosecond (fs) laser pulsing have been reported, based on transmission electron microscopy and electron energy loss spectroscopy studies. Under fs-laser interaction, Na-rich phases are formed, and Na nanoparticles are also precipitated around the Na-rich phases. These findings demonstrate how powerful and efficient the fs-laser pulsing and interaction can be in making novel microstructures in soda-lime silicate glass, and they bridge the gap between the macroscale property changes and nanometer-scale structures.

scholarly journals Laser Guiding of Three Phase Tesla Coil High Voltage Discharges

2020 ◽  
Vol 11 ◽  
pp. 54-59
Author(s):  
Samuel Kristiyana ◽  
Dilan Dwanurendra
Keyword(s):  
Laser Pulse ◽  
High Voltage ◽  
Laser Pulses ◽  
Voltage Source ◽  
Time Resolved ◽  
Laser Guiding ◽  
Three Phase ◽  
High Voltage Source ◽  
Fs Laser ◽  
Tesla Coil

Guiding and triggering of discharges from a three phase Tesla coil type 280 kHz AC high voltage source using filaments created by a femtosecond Terawatt laser pulse. Without the laser the discharges were maximum 30 cm long. With the laser straight, guided discharges up to 110 cm length were detected. The discharge length was limited by the voltage amplitude of the Tesla coil. A significant reduction of the breakdown voltage threshold due to the pre-ionization of the air gap by laser pulse filamentation was observed. The lifetime of filaments is measured by using time-resolved fluorescence spectrum, and the lifetime of filaments generated by dual fs laser pulses was doubled due to the re-ionization by the succeeding pulse

scholarly journals Nano-to-micro spatiotemporal imaging of magnetic skyrmion’s life cycle

2021 ◽  
Vol 7 (25) ◽  
pp. eabg1322
Author(s):  
Takahiro Shimojima ◽  
Asuka Nakamura ◽  
Xiuzhen Yu ◽  
Kosuke Karube ◽  
Yasujiro Taguchi ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Life Cycle ◽  
Transmission Electron Microscope ◽  
High Frequency ◽  
Pump Probe ◽  
Self Organized ◽  
Transmission Electron ◽  
Long Lifetime ◽  
Magnetic Skyrmions ◽  
Topological Charges

Magnetic skyrmions are self-organized topological spin textures that behave like particles. Because of their fast creation and typically long lifetime, experimental verification of skyrmion’s creation/annihilation processes has been challenging. Here, we successfully track skyrmion dynamics in defect-introduced Co9Zn9Mn2 by using pump-probe Lorentz transmission electron microscope. Following the nanosecond photothermal excitation, we resolve 160-nm skyrmion’s proliferation at <1 ns, contraction at 5 ns, drift from 10 ns to 4 μs, and coalescence at ~5 μs. These motions relay the multiscale arrangement and relaxation of skyrmion clusters in a repeatable cycle of 20 kHz. Such repeatable dynamics of skyrmions, arising from the weakened but still persistent topological protection around defects, enables us to visualize the whole life of the skyrmions and demonstrates the possible high-frequency manipulations of topological charges brought by skyrmions.

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