Nonlinear laser absorption over a dielectric embedded with nanorods

An analytical formalism of laser absorption in a nanorod embedded dielectric surface has been developed. Nanorods lie in the plane of the dielectric, in the form of a planar array. A laser, impinged on them with an electric field perpendicular to the lengths of the nanorods, imparts oscillatory velocity to nanorod electrons. As the free electrons of a nanorod are displaced, a space charge field is developed in the nanorod that exerts restoration force on the electrons and their drift velocity shows a resonance at ${\rm \omega} = {\rm \omega} _{\rm p}/\sqrt 2 $, where ωp denotes the plasma frequency of free electrons inside the nanorod. It is inhibited by collisions and nanorod expansion. At the resonance, the electrons are efficiently heated by the laser and laser energy is strongly absorbed, resulting in significant reduction in laser transmissivity. The transmissivity decreases with laser intensity.

Coherently coupled solitons in photorefractive media due to pyroelectric effect

The existence of bright–bright, dark–dark and gray–gray coherently coupled soliton pairs is predicted in unbiased photorefractive pyroelectric materials, provided that the two mutually-coherent incident optical beams have the same wavelength and same polarization. The external electric field is replaced by a finite temperature change and hence the space charge field is formed due to pyroelectric effect only. We study the effect of the mutual phase difference and the beam intensity ratio on the soliton profiles. In addition, we find that the magnitude and sign of the temperature change can influence the formation and characteristics of these soliton pairs.

Excitation of terahertz radiation generation by obliquely incident beating lasers on a hot magnetized plasma with step density profile

A scheme of resonant terahertz (THz) radiation generation by non-linear beating of two lasers in hot magnetized plasma with step density profile is investigated. Beating lasers of frequency difference ω1 − ω2 ≈ ωp(~1 THz) is incident obliquely on plasma surface and exerts non-linear ponderomotive force on plasma electrons. The plasma electrons start oscillating in the plane of incidence and give rise to space charge field to maintain plasma neutrality. In turn, both ponderomotive force and space charge field excites a non-linear surface current, responsible for THz radiation generation on the reflection side. The coupling between plasma wave and electromagnetic wave present (inside the plasma as well as on reflection side) becomes stronger in the presence of the transverse DC magnetic field. THz radiation amplitude is optimized at an angle of incidence θ ~ 50–70°.