Measurement of Ultrafast Carrier Dynamics in Epitaxial Graphene

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.

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Ultrafast Optical-Pump Terahertz-Probe Spectroscopy of the Carrier Relaxation and Recombination Dynamics in Epitaxial Graphene

Nano Letters ◽

10.1021/nl8019399 ◽

2008 ◽

Vol 8 (12) ◽

pp. 4248-4251 ◽

Cited By ~ 455

Author(s):

Paul A. George ◽

Jared Strait ◽

Jahan Dawlaty ◽

Shriram Shivaraman ◽

Mvs Chandrashekhar ◽

...

Keyword(s):

Epitaxial Graphene ◽

Optical Pump ◽

Carrier Relaxation ◽

Ultrafast Optical ◽

Probe Spectroscopy ◽

Recombination Dynamics

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Understanding Multiferroic Hexagonal Manganites by Static and Ultrafast Optical Spectroscopy

Advances in Condensed Matter Physics ◽

10.1155/2013/104806 ◽

2013 ◽

Vol 2013 ◽

pp. 1-13 ◽

Cited By ~ 7

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.

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Ultrafast carrier relaxation in Zn1-xCdxSe/ZnSySe1-ymultiple quantum wells studied by femtosecond pump-probe spectroscopy

Semiconductor Science and Technology ◽

10.1088/0268-1242/10/9/008 ◽

1995 ◽

Vol 10 (9) ◽

pp. 1253-1256 ◽

Cited By ~ 8

Author(s):

T Tokizaki ◽

H Sakai ◽

A Nakamura ◽

Y Manabe ◽

S Hayashi ◽

...

Keyword(s):

Quantum Wells ◽

Carrier Relaxation ◽

Pump Probe ◽

Ultrafast Carrier ◽

Probe Spectroscopy

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Tunable GaAs metasurfaces for ultrafast image processing

Journal of Physics Conference Series ◽

10.1088/1742-6596/2015/1/012057 ◽

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.

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Temperature evolution of quasiparticle dispersion and dynamics in semimetallic 1T−TiTe2 via high-resolution angle-resolved photoemission spectroscopy and ultrafast optical pump-probe spectroscopy

Physical Review B ◽

10.1103/physrevb.103.115108 ◽

2021 ◽

Vol 103 (11) ◽

Author(s):

Shuang-Xing Zhu ◽

Chen Zhang ◽

Qi-Yi Wu ◽

Xiao-Fang Tang ◽

Hao Liu ◽

...

Keyword(s):

High Resolution ◽

Temperature Evolution ◽

Photoemission Spectroscopy ◽

Optical Pump ◽

Pump Probe ◽

Angle Resolved Photoemission Spectroscopy ◽

Ultrafast Optical ◽

Probe Spectroscopy

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Radiation spectrum of hot excitons in Si nanocrystals

Lithuanian Journal of Physics ◽

10.3952/physics.v55i4.3226 ◽

2016 ◽

Vol 55 (4) ◽

Author(s):

Anton V. Gert ◽

Irina N. Yassievich

Keyword(s):

Energy Distribution ◽

Silicon Nanocrystals ◽

Energy Exchange ◽

Relaxation Times ◽

Exciton State ◽

Time Interval ◽

Pump Probe ◽

Si Nanocrystals ◽

Wide Energy ◽

Probe Spectroscopy

The self-trapped exciton state (STE) is very important for the dynamics of hot excitons in photoexcited silicon nanocrystals embedded in a SiO2 matrix. This fact has been recently confirmed by the experimental data obtained by the femtosecond pump– probe spectroscopy technique in Amsterdam University. In this work we have studied the energy exchange between the exciton localized in the STE state and the hot exciton in the core of silicon nanocrystals and have shown that it determines the dynamics of the energy distribution of the hot excitons. Using the Monte-Carlo we have simulated the energy distribution of excitons in the time interval 10–100 ps after excitation. Thus the model of formation of the distribution of hot excitons in silicon nanocrystals is developed and the fast formation of the wide energy distribution is demonstrated. The form of the photoluminescence spectrum almost directly corresponds to the energy distribution of excitons in a silicon nanocrystal at a given moment. In the result we have found the relaxation times of hot excitons equal to 100 ps and the inner quantum efficiency of the ultrafast photoluminescence of about 0.1%. These values are close to the experimentally observed ones.

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