Terahertz emission from indium arsenide excited by femtosecond laser pulses was numerically simulated with the use of
particle method. It is shown that the largest terahertz emission is achieved when 800 nm femtosecond laser pulses are
used for excitation of InAs. We describe terahertz time-domain spectroscopy setup built that uses a relatively simple
terahertz emitter on the basis of indium arsenide plate.
The lateral photocurrent caused by anisotropic momentum distribution of photoelectrons in semiconductor excited by
linearly polarized femtosecond laser radiation is calculated analytically and numerically with the use of particle method.
We have considered three mechanisms of this effect: diffusive scattering of photoelectrons on the surface,
nonparabolicity of conduction band and dependence of electron momentum relaxation time on energy. It has been shown
that contributions of the lateral and normal photocurrent components to terahertz emission can be comparable.
The influence of magnetic field on terahertz pulse generation from InAs surface excited by femtosecond laser radiation is
considered. We propose an analytical model describing the non monotonic dependence of THz emission on magnetic field. It has been found that under magnetic field of about 2-3 T the efficiency of terahertz emission enhances in 5-6 times. Monte Carlo simulation performed gives nearly the same results.
Irradiating nitrogen doped 6<i>H</i>-SiC(000l) crystals with a focused beam of an N<sub>2</sub> pulse laser, we could form discrete
circularly placed nanohills on their surface. The necessary light intensities were close to the ablation threshold. The
evidence was obtained by atomic force microscopy and photoluminescence. The measurements demonstrated that in the
area acted upon, the surface morphology and the nitrogen concentration depended on the irradiation dose. Supplementary
data was obtained from the numerical modeling of the temporal depth dependence of the temperature in SiC in response
to an N<sub>2</sub> laser pulse. The appearance of the nanohills is accounted for by a temperature-gradient gathering of nitrogen
into the subsurface focal area and by a rapid surface vaporization. The former process leads, via the melting point
decrease, to a local area melting, and the latter, via the surface temperature decrease, to the capping of the melt with a
thin solid lid. The interplay between the pressures exerted by the light and the liquid ends in a lid-peripheral extrusion of
a portion of the liquid and formation of the nanohills. The whole process proceeds in a clearly distinguishable and
repeatable two-stage mode.