scholarly journals Tunable GaAs metasurfaces for ultrafast image processing

2021 ◽  
Vol 2015 (1) ◽  
pp. 012057
Author(s):  
Viacheslav Iushkov ◽  
Alexander Shorokhov ◽  
Andrey Fedyanin
Keyword(s):  
Image Processing ◽  
Optical Switching ◽  
Optical Pumping ◽  
Relaxation Times ◽  
Optical Computing ◽  
Fused Silica ◽  
Optical Pump ◽  
Pump Probe ◽  
Ultrafast Optical ◽  
Ultrafast Switching

Abstract The design and construction of optical semiconductor metasurfaces for various applications have become an important topic in the last decade. However, most metasurfaces are static; they are optimized for only one exact purpose and typically realize only one operation. In this work, we discuss the basic methods for creating dynamic metasurfaces giving special attention to ultrafast optical switching and provide numerical modeling of metasurfaces made of GaAs material realizing different amplitude-phase profiles under asymmetrical optical pumping. The metasurfaces are composed of semiconductor discs immersed in a fused silica medium. We demonstrate that based on Fourier transform and spatial filtering methods, these structures can be used for image processing and optical computing. Ultrafast switching is achieved by using an optical pump-probe scheme. The characteristic relaxation times between the pumped state and the relaxed state are on the order of several picoseconds.

scholarly journals Measurement of Ultrafast Carrier Dynamics in Epitaxial Graphene

2008 ◽  
Vol 1081 ◽  
Author(s):  
Jahan M. Dawlaty ◽  
Shriram Shivaraman ◽  
Mvs Chandrashekhar ◽  
Michael G. Spencer ◽  
Farhan Rana
Keyword(s):  
Relaxation Times ◽  
Epitaxial Graphene ◽  
Optical Pump ◽  
Carrier Relaxation ◽  
Pump Probe ◽  
Graphene Layers ◽  
Ultrafast Optical ◽  
Interband Scattering ◽  
Ultrafast Carrier ◽  
Probe Spectroscopy

ABSTRACTUsing ultrafast optical pump-probe spectroscopy, we have measured carrier relaxation times in epitaxial graphene layers grown on SiC wafers. We find two distinct time scales associated with the relaxation of nonequilibrium photogenerated carriers. An initial fast relaxation transient in the 70-120 fs range is followed by a slower relaxation process in the 0.4-1.7 ps range. The slower relaxation time is found to be inversely proportional to the degree of crystalline disorder in the graphene layers as measured by Raman spectroscopy. We relate the measured fast and slow time constants to carrier-carrier and carrier-phonon intraband and interband scattering processes in graphene.

INTERBAND TWO-PHOTON TRANSITION IN MOTT INSULATOR AS A NEW MECHANISM FOR ULTRAFAST OPTICAL NONLINEARITY

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3628-3632 ◽  
Author(s):  
M. Ashida ◽  
T. Ogasawara ◽  
N. Motoyama ◽  
H. Eisaki ◽  
S. Uchida ◽  
...  
Keyword(s):  
Excited State ◽  
Optical Switching ◽  
Near Infrared ◽  
Optical Nonlinearity ◽  
Infrared Region ◽  
Pump Probe ◽  
Two Photon ◽  
Ultrafast Optical ◽  
Order Of Magnitude ◽  
Probe Transmission

The dimensionality dependence of optical nonlinearity in cuprates was investigated by sub-picosecond pump-probe transmission measurements in the near-infrared region. It was found that cuprates with one-dimensional Cu-O networks show nonlinearity one order of magnitude larger than that of conventional band semiconductors and picosecond relaxation of the excited state. In contrast, a two-dimensional cuprate shows one order of magnitude smaller nonlinearity and slower decay of the excited state, as well as picosecond relaxation. The possibility for application of the present material to all-optical switching devices is also discussed.

scholarly journals Understanding Multiferroic Hexagonal Manganites by Static and Ultrafast Optical Spectroscopy

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Yu Ting Wang ◽  
Chih Wei Luo ◽  
Takayoshi Kobayashi
Keyword(s):  
Electronic Structure ◽  
Magnetic Ordering ◽  
Optical Pump ◽  
Pump Probe ◽  
Spin Lattice ◽  
Ultrafast Optical ◽  
Ultrafast Optical Spectroscopy ◽  
Hexagonal Manganites ◽  
Spin Charge Coupling ◽  
Probe Spectroscopy

Multiferroic hexagonal manganites ReMnO3studied by optics are reviewed. Their electronic structures were revealed by static linear and nonlinear spectra. Two transitions located at~1.7 eV and~2.3 eV have been observed and attributed to the interband transitions from the lower-lying Mn3+dxy/dx2-y2anddxz/dyzstates to the Mn3+d3z2-r2state, respectively. These so-called d-d transitions exhibit a blueshift as decreasing temperatures and an extra blueshift nearTN. This dramatic change indicates that the magnetic ordering seriously influences the electronic structure. On the other hand, the ultrafast optical pump-probe spectroscopy has provided the important information on spin-charge coupling and spin-lattice coupling. Because of the strongly correlation between electronic structure and magnetic ordering, the amplitude of the initial rising component inΔR/Rshows striking changes at the vicinity ofTN. Moreover, the coherent optical and acoustic phonons were observed on optical pump-probe spectroscopy. Both the amplitude and dephasing time of coherent phonons also exhibit significant changes atTN, which provide the evidence for spin-lattice interaction in these intriguing materials.

scholarly journals High-pressure thermal conductivity and compressional velocity of NaCl in B1 and B2 phase

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wen-Pin Hsieh
Keyword(s):  
Thermal Conductivity ◽  
High Pressure ◽  
Phonon Transport ◽  
Optical Pump ◽  
Pump Probe ◽  
Ultrafast Optical ◽  
Pressure Medium ◽  
Diamond Anvil ◽  
B2 Phase ◽  
Compressional Velocity

AbstractSodium chloride (NaCl) is an important, commonly used pressure medium and pressure calibrant in diamond-anvil cell (DAC) experiments. Its thermal conductivity at high pressure–temperature (P–T) conditions is a critical parameter to model heat conduction and temperature distribution within an NaCl-loaded DAC. Here we couple ultrafast optical pump-probe methods with the DAC to study thermal conductivity and compressional velocity of NaCl in B1 and B2 phase to 66 GPa at room temperature. Using an externally-heated DAC, we further show that thermal conductivity of NaCl-B1 phase follows a typical T−1 dependence. The high P–T thermal conductivity of NaCl enables us to confirm the validity of Leibfried-Schlömann equation, a commonly used model for the P–T dependence of thermal conductivity, over a large compression range (~ 35% volume compression in NaCl-B1 phase, followed by ~ 20% compression in the polymorphic B2 phase). The compressional velocities of NaCl-B1 and B2 phase both scale approximately linearly with density, indicating the applicability of Birch’s law to NaCl within the density range we study. Our findings offer critical insights into the dominant physical mechanism of phonon transport in NaCl, as well as important data that significantly enhance the accuracy of modeling the spatiotemporal evolution of temperature within an NaCl-loaded DAC.

Ultrafast Optical Pump−Probe Studies of the Cytochromeb6fComplex in Solution and Crystalline States

2007 ◽  
Vol 111 (51) ◽  
pp. 14405-14410 ◽  
Author(s):  
Naranbaatar Dashdorj ◽  
Eiki Yamashita ◽  
John Schaibley ◽  
William A. Cramer ◽  
Sergei Savikhin
Keyword(s):  
Optical Pump ◽  
Pump Probe ◽  
Ultrafast Optical
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