2ND-HARMONIC GENERATION IN THE INTERIOR OF AN ISOTROPIC MEDIUM WITH QUADRATIC NONLINEARITY BY A FOCUSED INHOMOGENEOUSLY POLARIZED PUMP BEAM

Citation
Sn. Volkov et al., 2ND-HARMONIC GENERATION IN THE INTERIOR OF AN ISOTROPIC MEDIUM WITH QUADRATIC NONLINEARITY BY A FOCUSED INHOMOGENEOUSLY POLARIZED PUMP BEAM, Journal of experimental and theoretical physics, 86(4), 1998, pp. 687-695
Citations number
22
Categorie Soggetti
Physics
ISSN journal
10637761
Volume
86
Issue
4
Year of publication
1998
Pages
687 - 695
Database
ISI
SICI code
1063-7761(1998)86:4<687:2GITIO>2.0.ZU;2-W
Abstract
This paper presents a theoretical study of second-harmonic generation (SHG) by a focused pump beam in the interior of an isotropic medium, e xperimentally observed earlier. It shows that the spatial dispersion o f the quadratic optical response of the substance can be responsible f or this nonlinear process even when a macroscopic inversion center is present in the medium. It is established that this effect, which is im possible in the plane-wave approximation, also does not occur when a G aussian pump beam with uniform distribution of the polarization state of the wave field over the cross section is used, but that the presenc e in the pump beam of higher transverse modes with polarization differ ent from the fundamental mode can cause an SHG signal to appear. The c onditions for a wave to appear at the doubled frequency are found, ana lytical dependences for its electric field and total power on the prop agation coordinate, the degree of focusing, and the other parameters o f the problem are obtained, and the requirements on the optimum experi mental geometry are formulated. The dependence of the signal-beam powe r on the wavevector detuning is studied,and it is shown that interfere nce effects can cause the wave at the second harmonic to disappear whe n a normal dispersion law is obeyed in the region between the fundamen tal and doubled frequencies. (C) 1998 American Institute of Physics.