Conical third-harmonic generation in a hexagonally poled LiTaO3 crystal

Abstract

We experimentally observed conical third harmonic generation (THG) in a two-dimensional periodically poled LiTaO3 nonlinear photonic crystal. The conical THG was attributed to cascaded quasi-phase matching (QPM) processes assisted by scattering fundamental waves in the nonlinear photonic crystal. The characteristics of the generated conical beam, such as the emit angle and beam size, varied with the fundamental wavelength because it changed the scattering-assisted QPM configuration. Our experimental results demonstrated that scattering light can be effectively involved in a cascade nonlinear optical process through QPM, which provides a possible way to produce short-wavelength conical beams to meet the demands of practical applications.

Second-harmonic interference imaging of ferroelectric domains through a scanning microscope

“…The second-order nonlinear coefficients of the inverted domains have different signs; thus, the periodical nonlinear coefficients enable quasi-phasematching techniques for efficient frequency conversion in both one-and two-dimensional structures [1][2][3][4][5]. In addition, this class of materials provides more possibilities for the discovery of novel phenomena, such as conical second-harmonic generation (SHG) [6,7], nonlinear Airy beams [8], Cerenkov secondharmonic generation [9][10][11], the nonlinear Talbot effect [12,13], and superfocusing [14]. During the development of new materials, thin films of periodically inverted domains have been fabricated [15][16][17][18][19] that retain the ability of quasi-phasematching of bulk structures; furthermore, as potential building blocks for integrated devices, thin films would have advantages in many applications, such as miniaturization, ease of tuning [16], and tight mode confinement [17,18].…”

Cascaded Third-Harmonic Generation in Optically Induced 3D Nonlinear Photonic Crystals

“…where k 1 , k 2 , and k 3 are wave vectors of the fundamental, second-, and third-harmonic waves, respectively, and G 1 and G 2 are RLVs provided by the nonlinear photonic crystal. The cascading processes have been widely studied in electric-field-poled ferroelectric crystals [24][25][26][27][28][29][30], but they have not yet been reported on for optically poled crystals. The main reason is that the efficiency of the intermediate process, namely, second-harmonic generation, is usually too low to cascade the second process in optically poled ferroelectric crystals.…”

Propagation and Transformation of Vortexes in Linear and Nonlinear Radio-Photon Systems

“…In [12], it was experimentally established that in a multilayer nonlinear medium with periodically alternating layers of LiTaO 3 with oppositely directed optical axes to ensure spatial phase matching during the generation of the sum harmonic, topological charges are summed. In [13] a two-dimensional periodically poled LiTaO 3 nonlinear photonic crystal is used to generate conical third harmonic; phase matching is achieved by crystal poling. Moreover, it was shown [14] that the filamentation of femtosecond pulses (used to ensure phase matching condition) allows the formation of a vortex mode due to the third-harmonic generation (THG) process in Ti: sapphire chirped pulse amplifier.…”