Second harmonic emission from an axially excited slab of a dielectric thin-film helicoidal bianisotropic medium

The electromagnetic properties of a thin-film helicoidal bianisotropic medium (TFHBM) are totally delineated by a reference crystallographic symmetry as well as a helicoidal rotation matrix. The response of a dielectric TFHBM slab to an axially exciting plane wave is investigated here, assuming that second-harmonic (SH) generation is possible inside the slab. The time-harmonic Maxwell postulates are used to formulate two 4×4 matrix differential equations. Analytical solution of these matrix differential equations is accomplished using an eigenvalue approach. The response of the TFHBM slab to axial planewave excitation is then set up as two boundary-value problems. The dependences of the linear and the SH responses on various structural -geometric as well as constitutive - parameters are graphically illustrated for a TFHBM slab with tetragonal 4̄2m reference crystallographic symmetry. The geometric parameters include the helicoidal pitch, the angle of rise above the transverse plane and the slab thickness. Both positive-uniaxial and negative-uniaxial reference symmetries are considered. The responses of the TFHBM slab to both left- and right-circularly polarized incident plane waves are studied. Zones of attenuative propagation inside the TFHBM are found and a zonal classification of the linear and the SH responses of the TFHBM slab is proposed. The intensities of the reflected/transmitted linear as well as the emitted SH plane waves are highly influenced by the handedness of the incident plane wave relative to the handedness of the TFHBM. The possible existence of an optimal set of structural parameters of the chosen TFHBM slab to maximize the total intensity of the emitted SH plane waves is examined. Nanostructural implications for fabricating HBMs as thin films are discussed. Optical rotatory characteristics of the reflected/transmitted linear and the emitted SH plane waves are presented.