There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Physical Review B

Over the past three decades a new spectroscopic technique with unique possibilities has emerged. Based on coherent and time-resolved detection of the electric field of ultrashort radiation bursts in the far-infrared, this technique has become known as terahertz time-domain spectroscopy (THz-TDS). In this review article the authors describe the technique in its various implementations for static and time-resolved spectroscopy, and illustrate the performance of the technique with recent examples from solid-state physics and physical chemistry as well as aqueous chemistry. Examples from other fields of research, where THz spectroscopic techniques have proven to be useful research tools, and the potential for industrial applications of THz spectroscopic and imaging techniques are discussed.

Terahertz spectroscopy and imaging – Modern techniques and applications

According to Edholm’s law, the demand for point-to-point bandwidth in wireless short-range communications has doubled every 18 months over the last 25 years It can be predicted that data rates of around 5–10 Gb/s will be required in ten years In order to achieve 10 Gb/s data rates, the carrier frequencies need to be increased beyond 100 GHz Over the past ten years, several groups have considered the prospects of using sub-terahertz (THz) and THz waves (100–2000 GHz) as a means to transmit data wirelessly Some of the reported advantages of THz communications links are inherently higher bandwidth compared to millimeter wave links, less susceptibility to scintillation effects than infrared wireless links, and the ability to use THz links for secure communications Our goal of this paper is to provide a comprehensive review of wireless sub-THz and THz communications

Review of terahertz and subterahertz wireless communications

Optically tunable photonic crystals used as devices for the THz range

Vibrational properties of superionic crystals with fluorite structure Ba 1−x R x F 2+x x (R = La, Nd) = were studied using infrared spectroscopy, Raman scattering and inelastic neutron scattering. Selected spectra were measured on heating as a function of temperature. Their main features are: (a) peaks due to translational symmetry breaking, (b) low-frequency modes assigned to localized vibrations of clusters of defects, (c) peaks connected to the presence of small regions with tysonite-like structure (RF3) at higher doping rates.

Vibrational spectroscopy of Ba 1−x R x F 2+x x (R = La, Nd) superionic conductors

This study deals with the ultrafast electron-hole plasma expansion of photo-excited carriers in GaAs. This work applies a novel experimental scheme for optical pump-terahertz probe (OPTP) measurements where the state of the photo-excited layer close to the sample surface is probed by means of an internal reflection of a picosecond terahertz (THz) pulse. This approach allows direct probing of the photo-excited layer from its back side. In conjunction with the possibility of phase-sensitive detection of THz pulses, the authors are able to observe the motion of the interface separating the excited and non-excited part of the sample.

Photon-assisted ultrafast plasma expansion in GaAs

RESEARCH ARTICLE Near-field terahertz imaging of ferroelectric domains in barium titanate

We use optical pump-terahertz probe spectroscopy for exploring photoinduced ionization and plasma formation in atmospheric gases. Multiphoton versus strong-field photoionization processes are investigated using variable intensity, polarization and wavelength of the femtosecond optical pump pulses.

Filip Kadlec

Papers

Optically tunable photonic crystals used as devices for the THz range

Vibrational spectroscopy of Ba 1−x R x F 2+x x (R = La, Nd) superionic conductors

Photon-assisted ultrafast plasma expansion in GaAs

RESEARCH ARTICLE Near-field terahertz imaging of ferroelectric domains in barium titanate

Photoionization Mechanisms of Atmospheric Gases Probed by Terahertz Pulses