Interaction of few-cycle optical pulses in nonmetallic carbon nanotubes

Collision of two few-cycle optical pulses propagating in the medium of nonmetallic carbon nanotubes is described using joint solution of the Maxwell equations for the electromagnetic field and the Boltzmann equation for the electron subsystem.     

Extremely short two-dimensional optical pulses in an array of carbon nanotubes in the presence of a constant electric field

The interaction between the electromagnetic fields of extremely short two-dimensional optical pulses propagating in an array of zigzag-type carbon nanotubes and an external constant electric field is investigated. The evolution of the investigated system’s electromagnetic field is described by Maxwell’s equations.     

Extremely short electromagnetic pulses in an array of carbon nanotubes with a longitudinal field inhomogeneity

The propagation of bipolar electromagnetic pulses in an array of semiconductor carbon nanotubes has been investigated. The inhomogeneity of the pulse field along the axis of the nanotubes has been taken into account for the first time. The evolution of the electromagnetic field and charge density in the sample has been described by the set of Maxwell’s equations and the continuity equation. The possibility of stable propagation of bipolar electromagnetic pulses occurring in an array of nanotubes has been demonstrated by numerical simulation. It has been shown that the propagation of the electromagnetic pulses induces the redistribution of the electron density in the sample.     

The behavior of three-dimensional ultimately short optical pulses in a system of carbon nanotubes in the presence of an external magnetic field

The character of the behavior of three-dimensional ultimately short optical pulses propagating in a system of carbon nanotubes in the presence of an external magnetic field perpendicular to both the nanotubes’ axis and the direction of pulse propagation is investigated. Electromagnetic-field evolution is analyzed within the framework of the Maxwell’s equations, while the electronic system of the carbon nanotubes is investigated in the low-temperature approximation.     

Specific dynamics of faster-than-light (in the medium) extremely short optical pulses in an array of carbon nanotubes

Maxwell’s equations for an electromagnetic field propagating in an array of carbon nanotubes have been considered in the case when the velocity of the incident pulse is greater than the speed of light in the medium. The equation for the vector potential of the electromagnetic field has been derived and solved numerically. The dependence of the pulse on its velocity at the entrance to the array of carbon nanotubes has been revealed.     

Conductivity of carbon nanotubes in a longitudinal magnetic field

Multiwall carbon nanotubes exhibit oscillations of magnetoresistance with the period Φ₀=hc/2e [A. Bachtold, C. Strunk, J.-P. Salvetat, et al., Nature 397, 673 (1999)]. This effect is analogous to the Sharvin effect for a normal metal [D. Yu. Sharvin and Yu. V. Sharvin, Pis’ma Zh. Éksp. Teor. Fiz. 34, 285 (1981)]. It is shown that, along with the magnetoresistance peaks corresponding to the flux values that are multiples of Φ ₀, additional peaks with a period three times shorter can be observed in carbon nanotubes.     

Collision of extremely short optical pulses in semiconductor carbon nanotubes

The interaction of extremely short optical pulses in semiconductor carbon nanotubes is discussed. An equation is derived for the dynamics of the electromagnetic field in a system of semiconductor carbon nanotubes at low temperatures, whose solutions are analogs to the solitons of the sine-Gordon equation. The behavior of extremely short optical pulses in semiconductor carbon nanotubes on collision is analyzed.     

多壁碳纳米管阵列场发射研究

研究了Ar离子束轰击及温度对多壁碳纳米管阵列场发射性能的影响.经Ar离子轰击35min后，发现阵列顶端的Fe催化剂颗粒明显减少，弯曲的顶部被轰击掉，使碳纳米管的场发射电流明显减小而场发射像无明显改变.温度的增加引起碳纳米管的场发射电流也随之增加.还研 究了在透明阳极技术中涂在阳极的荧光粉对场发射电流的影响.对同一碳纳米管阵列样品，发现涂有荧光粉的透明阳极使测量到的场发射电流大幅度减小，只是未涂荧光粉阳极电流的 1/30左右.直接用二氧化锡导电膜作阳极时，测得样品的开启场强为1.0V/μm.沉积了荧光粉的二 关键词： 多壁碳纳米管 场发射     

Electronic transport spectroscopy of carbon nanotubes in a magnetic field

We report magnetic field spectroscopy measurements in carbon nanotube quantum dots exhibiting fourfold shell structure in the energy level spectrum. The magnetic field induces a large splitting between the two orbital states of each shell, demonstrating their opposite magnetic moment and determining transitions in the spin and orbital configuration of the quantum dot ground state. We use inelastic cotunneling spectroscopy to accurately resolve the spin and orbital contributions to the magnetic moment. A small coupling is found between orbitals with opposite magnetic moment leading to anticrossing behavior at zero field.     

Ultrashort pulse propagation in carbon nanotubes in a magnetic field

The problem of ultra-short optical pulse behavior in a system of carbon nanotubes with an applied magnetic field parallel to the nanotube axis was considered. The electromagnetic field was explored using the Maxwell equations. The electronic system of the carbon nanotubes was a quantum system and was mechanically investigated for the case of low temperatures. The distributional pattern of the ultra short pulses and their collision were established by means of numerical modeling.     

90 GW peak power few-cycle mid-infrared pulses from an optical parametric amplifier

We demonstrate a compact 20 Hz repetition-rate mid-IR OPCPA system operating at a central wavelength of 3900 nm with the tail-to-tail spectrum extending over 600 nm and delivering 8 mJ pulses that are compressed to 83 fs (<7 optical cycles). Because of the long optical period (～13 fs) and a high peak power, the system opens a range of unprecedented opportunities for tabletop ultrafast science and is particularly attractive as a driver for a highly efficient generation of ultrafast coherent x-ray continua for biomolecular and element specific imaging.     

Effect of an external magnetic field on Landau damping in carbon nanotubes

A quantum-mechanical formula for describing the dependence of the longitudinal permittivity of a nanotube on its characteristic parameters and the magnetic field strength was derived. The imaginary part of the permittivity was isolated, and the cases of a Boltzmann and degenerate electron gas were examined. For a degenerate electron gas, asymptotic expressions for absorption in the short- and long-wave ranges were obtained. It was demonstrated that the absorption coefficient for a longitudinal electromagnetic wave exhibits Aharonov-Bohm oscillations.     

Electromagnetic vortices in an array of carbon nanotubes

The dynamics of electromagnetic vortices in an array of carbon nanotubes is investigated. The electromagnetic field is described by Maxwell (two-dimensional wave) equations. Calculation modeling is performed. The resulting mass center velocity of the vortices is zero, and the intensity distribution its field changes periodically over time.     

Ultrashort optical pulses in carbon nanotubes and graphene with periodic impurities

The dispersion law for electrons has been derived by the Green’s function method using the Anderson periodic model, which has been proposed to describe the electron subsystem in carbon nanotubes and graphene with impurities. The combined dynamics of electrons and an electromagnetic field has been considered in the low-temperature limit, and the effective equation describing the propagation of ultrashort optical pulses has been obtained. The solutions to this equation as functions of the parameters of the problem have been presented.     

Single-pinhole diffraction of few-cycle isolated attosecond pulses with a two-color field

The spatio-temporal characterization of an isolated attosecond pulse is investigated theoretically in a two-color field.Our results show that a few-cycle isolated attosecond pulse with the center wavelength of 16 nm can be generated effectively by adding a weak controlling field. Using the split and delay units, the isolated attosecond pulse can be split to the two same ones, and then single-pinhole diffractive patterns of the two pulses with different delays can be achieved. The diffractive patterns depend severely on the periods of the attosecond pulses, which can be helpful to obtain temporal information of the coherent sources.     

Peierls相变与磁场中碳纳米管的场发射

应用紧束缚模型和WKB方法研究碳纳米管的out-of-plane型Peierls相变,及其对碳纳米管的场发射的影响.结果发现Peierls相变会在室温出现,并使碳纳米管费米面附近出现能隙,导致碳纳米管发生金属—半导体转变,从而抑制碳纳米管的场发射.磁场也会抑制Peierls形变,Peierls相变和磁场相互竞争影响碳纳米管的能带结构,从而影响碳纳米管的场发射. 关键词： 场发射 碳纳米管 Peierls相变     

On the quasi-soliton propagation of few-cycle optical pulses in isotropic dielectrics

A new combined approach for constructing approximate soliton-like solutions of nonlinear wave equations is proposed. The approach includes the method of analytic continuation of dispersion parameters to the complex plane and the averaged variational principle of the Ritz-Whitham type. Based on this approach, the solution of the nonlinear equation describing the propagation of an optical pulse in a transparent isotropic dielectric is found. The obtained solution involves both envelope solitons and breather-like pulses with duration down to one period of electromagnetic oscillations.     

Intense self-compressed, self-phase-stabilized few-cycle pulses at 2 microm from an optical filament

We report the compression of intense, carrier-envelope phase stable mid-IR pulses down to few-cycle duration using an optical filament. A filament in xenon gas is formed by using self-phase stabilized 330 microJ 55 fs pulses at 2 microm produced via difference-frequency generation in a Ti:sapphire-pumped optical parametric amplifier. The ultrabroadband 2 microm carrier-wavelength output is self-compressed below 3 optical cycles and has a 270 microJ pulse energy. The self-locked phase offset of the 2 microm difference-frequency field is preserved after filamentation. This is to our knowledge the first experimental realization of pulse compression in optical filaments at mid-IR wavelengths (lambda>0.8 microm).     

Ultimately short optical pulses in carbon nanotubes in dispersive nonmagnetic dielectric media

We consider Maxwell’s equations for an electromagnetic field propagating in carbon nanotubes placed in dispersive nonmagnetic dielectric media. An effective equation having the form of an analog of the classical sine-Gordon equation was obtained and analyzed numerically. The dependence of the pulse on the type of carbon nanotubes, initial pulse amplitude, and dispersion constants of the medium was revealed.     

Ultrashort optical pulses controlling electric fields in carbon nanotubes at low temperatures

Alternating electric field spreading in zigzag carbon nanotube system was studied in the case of low temperatures and applied external electric fields. The electron system of carbon nanotubes was considered macroscopically while the interaction with the phonon subsystem due to the ultrashort pulse of the electromagnetic field was omitted.