THz-radiation Spectrum Research Articles

Peculiarities of the reflective echelon in applications to the kinetic spectroscopy and information optics

In this paper we study specifics of an ultrashort pulse transformation with a device similar to the Michelson reflective echelon. The initial impulse transformation process is treated using the conception of pulse response of the optical system, in particular, of the dynamics of scattering of a δ(t — z/c) wave by the echelon. The advantage of this method is the possibility to calculate the response of any optical system to a signal of an arbitrary amplitude dependence on time by calculation of convolution of the function describing the signal with the pulse response, whether the pulse response exists. The urgency of the problem is due to the prospects of the echelon application to the solution of numerous modern problems of optics and optical informatics, such as modulation of the THz radiation spectrum, interferometry of ultrashort laser pulses and problems of absorption spectroscopy with high resolution in time.

Plasmonic absorption of THz radiation in graphene structure with a metal grating

The plasmonic absorption spectrum of THz radiation in the graphene with periodic metal grating is theoretically studied. It is shown that graphene exhibits strong plasmon absorption resonances at the frequencies of plasma oscillations in graphene for narrow-slit metal grating and a thin barrier layer.

Terahertz radiation from InAs with various surface orientations under magnetic field irradiated with femtosecond optical pulses at different wavelengths

We present the magnetic-field dependence of terahertz (THz)-radiation power from femtosecond-laser-irradiated InAs with various surface orientations. Under 800 nm optical excitation, the magnetic field that provides the maximum THz-radiation power is found to be affected by the surface orientation, and InAs (111) exhibits it at lower magnetic fields than that of the other surfaces. In contrast, under 1560 nm excitation, the dependence on the surface orientation almost disappeared, and saturation is observed at a much smaller magnetic field than that in the 800 nm excitation case. Additionally, from the results of magnetic-field dependence up to 14 T, the shift of the peak in the THz-radiation spectrum toward lower frequency is confirmed, depending on the magnetic field applied, which is possibly induced by the emergence of a magnetoplasma effect.

Intense THz-radiation from semiconductors under magnetic field irradiated with femtosecond laser pulses

The THz-radiation power from InAs reaches sub-mW level in a 1.7-T magnetic field irradiated with femtosecond laser pulses of 1.5-W average power. The THz-radiation power is related almost quadratically both to the magnetic field and to the excitation laser power. Furthermore, the THz-radiation spectrum is found to be controlled by the excitation pulsewidth, chirp direction of the excitation pulse, and the magnetic field.

Spectrum control of THz radiation from InAs in a magnetic field by duration and frequency chirp of the excitation pulses

The THz radiation spectrum from InAs in a magnetic field irradiated with femtosecond pulses can be controlled by varying the excitation pulse width and chirp direction of the excitation pulse. A longer excitation pulse width produces lower-frequency THz radiation. Also, positively chirped pulse excitation will generate higher power and higher frequency THz radiation.