Nonlinear THz Conductivity Dynamics in P-Type CVD-Grown Graphene

Hwang, Harold Y.; Brandt, Nathaniel C.; Farhat, Hootan; Hsu, Allen; Kong, Jing; Nelson, Keith A.

doi:10.1021/jp407548a

Cited by 90 publications

(104 citation statements)

References 33 publications

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“…Hwang 21 reported THz pump, THz probe measurements that showed a strong pumpinduced conductivity decrease (transmission increase) in CVD graphene samples. The THz pump can only drive intraband excitation, and should heat the carrier distribution without producing a population inversion, so this showed that population inversion is not required to observe negative differential conductivity in these experiments.…”

Section: Introductionmentioning

confidence: 99%

Carrier heating and negative photoconductivity in graphene

Heyman

Stein

Kaminski

et al. 2015

Journal of Applied Physics

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We investigated negative photoconductivity in graphene using ultrafast terahertz techniques. Infrared transmission was used to determine the Fermi energy, carrier density and mobility of p-type CVD graphene samples. Time-resolved terahertz photoconductivity measurements using a tunable mid-infrared pump probed these samples at photon energies between 0.35eV -1.55eV, approximately one-half to three times the Fermi energy of the samples. Although interband optical transitions in graphene are blocked for pump photon energies less than twice the Fermi energy, we observe negative photoconductivity at all pump photon energies investigated, indicating that interband excitation is not required to observe this effect. Our results are consistent with a thermalized free carrier population that cools by electron-phonon scattering, but inconsistent with models of negative photoconductivity based on population inversion.

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Section: Introductionmentioning

confidence: 99%

Carrier heating and negative photoconductivity in graphene

Heyman

Stein

Kaminski

et al. 2015

Journal of Applied Physics

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“…The Fermi level of graphene was determined by linear THz spectroscopy, and independently confirmed by Raman spectroscopy [3], to be at ~ 300 meV with respect to the Dirac point. In the nonlinear THz time-domain spectroscopy (THz TDS) arrangement based on tilted pulse front -pumped LiNbO 3 [4,5] (see Fig. 1), we have measured the peak-field dependent broadband conductivity of graphene in the peak THz field range 7.5 -180 kV/cm and in the spectral range 0.4 -1.6 THz.…”

Section: Measurementmentioning

confidence: 99%

“…1), we have measured the peak-field dependent broadband conductivity of graphene in the peak THz field range 7.5 -180 kV/cm and in the spectral range 0.4 -1.6 THz. We control the peak field strength in the singlecycle THz pulses using crossed wire-grid polarizers, which leaves the temporal shape of the THz waveforms unaffected [4,5]. The THz pulses were detected by free-space electro-optic sampling in a 0.5 mm thick (110)-cut ZnTe crystal.…”

Section: Measurementmentioning

confidence: 99%

Inherent Resistivity of Graphene to Strong THz Fields

Turchinovich

Mics

Jensen

et al. 2014

19th International Conference on Ultrafast Phenomena

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“…Recent theoretical and experimental studies have demonstrated that a recorded photon absorption rate of up to 46% and a transmission modulation reaching 28% could be achieved by moderate fluences of THz pulses [18][19][20]. Furthermore, many of these results were obtained by using polycrystalline graphene fabricated by chemical vapor deposition (CVD),…”

Section: Introductionmentioning

confidence: 99%

Boosting the terahertz nonlinearity of graphene by orientation disorder

Baek¹,

Hamm²,

Ahn³

et al. 2017

2D Mater.

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Abstract. The conical band structure is the cornerstone of graphene's ultra-broadband optical conductivity. For practical use of graphene in nonlinear photonics, however, substantial increases of the light-matter interaction strength will be required while preserving the promising features of monolayers, as the interaction of light with a single atomic layer is limited due to the extremely short interaction length and low density of state, particularly for the long-wavelength region. Here, we report that this demand can be fulfilled by random stacking of high-quality large-area monolayer graphene up to a requested number of layers, which leads to the electronic interaction between layers being effectively switched off due to turbostratic disorder. The nonlinear characteristics of randomly stacked multilayer graphene (RSMG), which originates from a thermo-modulational feedback mechanism through ultrafast free-carrier heating and temperature-dependent carrier-phonon collisions, show clear improvements in the terahertz (THz) regime with increasing layer numbers, whereas as-grown multilayer graphene (AGMG) exhibits limited behaviors due to strong interlayer coupling. This controllable nonlinearity enhancement provides an ideal prerequisite for developing efficient graphene-based THz photonic devices.

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Nonlinear THz Conductivity Dynamics in P-Type CVD-Grown Graphene

Cited by 90 publications

References 33 publications

Carrier heating and negative photoconductivity in graphene

Carrier heating and negative photoconductivity in graphene

Inherent Resistivity of Graphene to Strong THz Fields

Boosting the terahertz nonlinearity of graphene by orientation disorder

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