Pattern formation of second harmonic conical waves in a nonlinear medium with extended defect structure

Abstract

We experimentally demonstrate the propagation of the conical second harmonic fields generated from a nonlinear crystal with extended defects to investigate their pattern formation. The generated second harmonic waves are found to be the interference of multiple Bessel-like beams that originate from distinct longitudinal layers inside the crystal. To reconstruct the experimental results, we model the individual Bessel-like beam to be the superposition of an ensemble of identical decentered Gaussian waves with random phases. We present that the randomness of the phases leads the Bessel-like beams to show wave profiles with different extent of localization. Moreover, we use the coherent superposition of the developed wave functions with a phase factor to manifest the interference of multiple Bessel-like beams. The relative phases among the Bessel-like beams are shown to be closely related to the near and far-field patterns. With the experimental observations and the theoretical model, the relative phases are decided to successfully reconstruct the propagation characteristics of the multiple Bessel-like beams.

Scattering-assisted second harmonic generation of structured fundamental wave

“…Moreover, the nonlinear signals also can be used to enclose the structure property of the nonlinear crystal directly. Thus it is a way to probe the structure of NPCs using optical methods [20][21][22]. Nevertheless, the limitations of such special structured NPCs are the complex fabrication and fixed properties.…”

Multiple shape light sources generated in LiNbO3nonlinear photonic crystals with Sierpinski fractal superlattices

“…Nonlinear photonic crystal (NPC) is a kind of processed ferroelectric crystal, in which partial domains are reversed by applying high voltage electric field. Over the past few decades, much attention has been focused on several aspects of NPCs; for example, the type of ferroelectric crystals, the structure of domain distribution and their optical properties [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Traditionally, researchers select LiTaO 3 (LT), LiNbO 3 (LN), KTP or strontium barium niobate (SBN), etc, as the crystal raw materials.…”