Impact of longitudinal fields on second harmonic generation in lithium niobate nanopillars

Abstract

An optimized focused ion beam process is used to fabricate micrometer-long LiNbO3 nanopillars with diameters varying between 150 and 325 nm. Polarimetric mappings of second harmonic generation from a wavelength of 850 nm demonstrate the ability to modify the polarization features of the nonlinear response through a fine adjustment of the pillar size. The effect is ascribed to the non-negligible contribution of the longitudinal fields associated with sub-wavelength light confinement in the LiNbO3 nanopillars. The results also highlight the importance of a fine control over the nanopillar size in order to effectively engineer their nonlinear response.

Tailorable second‐harmonic generation from an individual nanowire using spatially phase‐shaped beams

“…Tight focusing of radial polarization leads to a strong electric field component along the direction of beam propagation, usually referred to as the longitudinal component , which has been particularly favorable for several linear and nonlinear imaging modalities that rely on molecular orientation or symmetry as the source of contrast . Beyond imaging applications, it is also worth noting that the longitudinal fields produced by focusing radial polarization and other high‐order beams, such as linearly polarized Hermite‐Gaussian beams of order (1,0) (HG 10 ), can be used to optically trap microparticles , process subwavelength‐sized features in metals , induce mass transport in solid films , accelerate particles along the beam propagation axis , and influence nonlinear phenomena .…”

Underpotential‐Assisted Electrodeposition of Highly Crystalline and Smooth Thin Film of Bismuth

“…The polarization angles are relative to an arbitrary direction, while the maximum intensity was set to 0°. The intensities were fitted with good agreement with the Equation …”

“…Finally, CPL microscopy underlined an unexpected weak optical anisotropy all over the sample, which becomes strong in a couple of regions, whose size is of approximately a hundred microns and whose shape recalls a grain boundary. The optical anisotropy was evaluated by using a rotating circular stage and acquiring photos of the sample every 10°, then, the mean grey value in the identified areas was measured.…”

“…The intensities were fitted with good agreement with the Equation (1). [54] I ¼ asin 2 ðq þ fÞcos 2 ðq þ fÞ þ bcos 4 ðq þ fÞ (1) Where I is the light intensity, θ the relative rotation of the sample around the z axis, ϕ the phase and a and b the weight coefficients for the two polarization components.…”

Second-harmonic generation enabled by longitudinal electric-field components in photonic wire waveguides

“…Polarization rotators based on this principle have been implemented [13]. The impact of longitudinal * francois.leo@ulb.ac.be components on the second-order nonlinear polarization was studied in zinc-selenide crystals, lithium niobate, and gallium phosphide nanopillars [14][15][16] but, to the best of our knowledge, SH generation enabled by those components was not demonstrated for bound modes.…”