Ivan Oladyshkin

Thermal mechanism of laser induced THz generation from a metal surface

We propose a new theoretical model of terahertz (THz) generation from a metal surface irradiated by femtosecond laser pulses. The mechanism is based on the inducing of the low-frequency polarization by the inhomogeneous temperature distribution of the electron gas near the surface. We present analytical and numerical results for the characteristic experimental parameters of a laser pulse. The experimentally observed duration of the THz signal (~1 ps) is interpreted as a time of the thermal energy relaxation after the optical radiation action. The total THz energy as a function of the initial laser pulse characteristics and metal parameters is obtained. The most important experimental features are discussed and interpreted on the basis of the thermal mechanism.

Laser-driven parametric instability and generation of entangled photon-plasmon states in graphene and topological insulators

We show that a strong infrared laser beam obliquely incident on graphene can experience a parametric instability with respect to decay into lower-frequency (idler) photons and THz surface plasmons. The instability is due to a strong in-plane second-order nonlinear response of graphene which originates from its spatial dispersion. The parametric decay leads to efficient generation of THz plasmons and gives rise to quantum entanglement of idler photons and surface plasmon states. A similar process can be supported by surface states of topological insulators such as Bi

Terahertz radiation from bismuth surface induced by femtosecond laser pulses

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Laser-driven parametric generation of coherent THz radiation in graphene and topological insulators (Conference Presentation)

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Millisecond measurements without equipment: time of collision of a ping-pong ball with a table

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Mechanisms of optical-to-THz conversion on metal and semimetal surfaces

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Optical-to-THz conversion and scattering in metals

We report on the first experimental observation of terahertz (THz) wave generation from bismuth mono- and polycrystalline samples irradiated by femtosecond laser pulses. Dependencies of the THz signal on the crystal orientation, optical pulse energy, incidence angle, and polarization are presented and discussed together with features of the sample surfaces. The optical-to-THz conversion efficiency was up to two orders of magnitude higher than for metal at a moderate fluence of ∼1u2009u2009mJ/cm2. We also found nonlinear effects not previously observed using other metal and semiconductor materials: (a)xa0asymmetry of THz response with respect to a half-turn of a sample around its normal, (b)xa0THz polarization control by orientation of the sample surface, and

Air density measurement with a falling A4 sheet

Massless Dirac electrons in graphene and on the surface of 3D topological insulators such as Bi2Se3 demonstrate strong nonlinear optical response and support tightly confined surface plasmon modes. Although both systems constitute an isotropic medium for low-energy in-plane electron excitations, their second-order nonlinear susceptibility becomes non-zero when its spatial dispersion is taken into account. In this case the anisotropy is induced by in-plane wave vectors of obliquely incident or in-plane propagating electromagnetic waves. In this work we develop a rigorous quantum theory of the second-order nonlinear response and apply it to the parametric amplification of mid-infrared and Thz radiation. We show that a strong near-infrared or mid-infrared laser beam obliquely incident on graphene can experience a parametric instability with respect to decay into lower-frequency (idler) photons and THz surface plasmons. The parametric gain leads to efficient generation of THz plasmons. Furthermore, the parametric decay process gives rise to quantum entanglement of idler photon and surface plasmon states. This enables diagnostics and control of surface plasmons by detecting idler photons. A similar parametric process can be implemented in topological insulator thin films.

GENERATION OF TERAHERTZ RADIATION BY INTERACTION OF INTENSE FEMTOSECOND LASER PULSES WITH A METAL SURFACE

We describe a simple experiment giving the opportunity to estimate the time of collision of a freely falling ping-pong ball and a table. The method is based on the ball deformation measurement and uses just elementary geometry and kinematics.

Thermal mechanism of laser-induced THz generation from metal particles

The paper is devoted to the very recent experimental and theoretical results on the laser-induced THz generation from metals and semimetals. Despite the relatively low efficiency, study of the optical-to-THz conversion on metal surface are still relevant, mostly because of possible applications in structural diagnostics and due to the fundamental interest in transformation mechanisms. Here we consider a thermal model of THz response and present some new experimental results on the anisotropic THz generation from the surface of mono- and polycrystalline bismuth samples.The paper is devoted to the very recent experimental and theoretical results on the laser-induced THz generation from metals and semimetals. Despite the relatively low efficiency, study of the optical-to-THz conversion on metal surface are still relevant, mostly because of possible applications in structural diagnostics and due to the fundamental interest in transformation mechanisms. Here we consider a thermal model of THz response and present some new experimental results on the anisotropic THz generation from the surface of mono- and polycrystalline bismuth samples.