Sub-wavelength modulation of χ(2) optical nonlinearity in organic thin films

Abstract

Modulating the second-order nonlinear optical susceptibility (χ(2)) of materials at the nanoscale represents an ongoing technological challenge for a variety of integrated frequency conversion and nonlinear nanophotonic applications. Here we exploit the large hyperpolarizability of intermolecular charge transfer states, naturally aligned at an organic semiconductor donor–acceptor (DA) interface, as a means to control the magnitude and sign of χ(2) at the nanoscale. Focusing initially on a single pentacene-C60 DA interface, we confirm that the charge transfer transition is strongly aligned orthogonal to the heterojunction and find that it is responsible for a large interfacial nonlinearity probed via second harmonic generation that is sufficient to achieve d33>10 pm V−1, when incorporated in a non-centrosymmetric DA multilayer stack. Using grating-shadowed oblique-angle deposition to laterally structure the DA interface distribution in such multilayers subsequently enables the demonstration of a χ(2) grating with 280 nm periodicity, which is the shortest reported to date.

Aggregation‐induced emission materials for nonlinear optics

“…[ 123 ] Noted that the β converges toward zero for the centrosymmetric material systems whereby it demands the asymmetry or noncentrosymmetric space groups for second‐order NLOs. [ 124–126 ]…”

“…[123] Noted that the β converges toward zero for the centrosymmetric material systems whereby it demands the asymmetry or noncentrosymmetric space groups for second-order NLOs. [124][125][126] SHG is the most developed and vital second-order NLO process in which the output frequency is twofold of the incident photon field. [127] Some of AIE molecules have been deemed to have the potential for second-order NLO and forecasted the SHG activity.…”

Synthesis and Nonlinear Studies on Selected Organic Compounds in Nanostructured Thin Films

“…Acentric supramolecular architecture, as essential requirement for preservation of NLO properties, is a challenge to be achieved from chromophores and polyelectrolytes in LbL film technique. The conventional LbL technique should be adjusted in order to ensure the density and stability of the optic active molecules in the obtained film, with particular attention to be paid to the orientation of chromophore [72].…”

Laser shaping and optical power limiting of pulsed Laguerre-Gaussian laser beams of high-order radial modes in fullerene C60

“…[3][4][5][6][7][8][9] The propagation of light in a nonlinear optical medium is affected by both nonlinear refraction and nonlinear absorption processes. [10,11] Nonlinear optical processes for realization of the optical power limiting (OPL) effect [12,13] involve nonlinear scattering, [14] photorefraction, [15] self-focusing, selfdefocusing, two-photon absorption (TPA), [16][17][18][19][20] reverse saturable absorption (RSA) [21][22][23][24][25][26] and so on. Among them, RSA has attracted considerable attention from experimentalists and theorists and has been widely studied.…”