Strontium Barium Niobate as a Multifunctional Two‐Dimensional Nonlinear “Photonic Glass”

Abstract

The ability of Strontium Barium Niobate crystal as a two‐dimensional nonlinear optical multiple‐wavelength‐and‐direction converter is demonstrated, showing how harmonic generation can be obtained in an extremely large spectral range. The whole visible spectral region can be continuously generated without any angle or temperature tuning by using different nonlinear schemes involving SHG and THG in different configurations. The dominant frequency conversion mechanisms acting in each case are experimentally determined. The system can act as a nonlinear prism since the SHG conical radiation from 430 to 680 nm can be dispersed into an external angle range of 36°. Conical nonlinear processes are also demonstrated under intracavity conditions from a diode pumped Nd3+:SBN laser crystal. Different harmonic generated rings appear simultaneously inside the cavity, while the crystal is lasing at 1063 nm. The system constitutes the first experimental example of a two‐dimensional generalized nonlinear photonic glass on a tunable solid state laser and can be useful for novel optical multifunctional devices such as nonlinear prism self‐frequency converted solid state lasers.

Ultrabroadband generation of multiple concurrent nonlinear coherent interactions in random quadratic media

“…Note that for the type-0 process, QPM-SHG in SBN has been reported by involving domain sizes which only represent $2% of the total distribution. 2 Furthermore, on this basis, a triply coincident QPM configuration for the three symmetry allowed parametric (polarization) processes can be predicted in the 800-1300 nm spectral range, its maximum being centered around 1 lm. As a representative example, the required coherent lengths to obtain triple QPM-SHG for a fundamental wavelength of 1.06 lm have been marked with solid dots in Fig.…”

“…In this letter, we have focused our attention on as-grown congruent Strontium Barium Niobate (SBN) crystal due to its large nonlinear coefficients and to the presence of a random distribution of ferroelectric domains. 2,4 Up to three different coincidental quadratic nonlinear parametric interactions, with different input/output polarization states, are experimentally demonstrated to occur in a broad spectral range covering the whole visible spectrum. These three SHG processes are simultaneously obtained at room temperature and involve a single fundamental beam and first order quasi-phase matching (QPM) collinear interactions.…”

“…However, their simplicity, compared to other nonlinear tunable devices based on more sophisticated superstructures of inverted domains, makes them attractive sources for the development of advanced multi-photon devices. [1][2][3][4][5][6][7] Substantially less explored is the capability of these systems to manipulate and control the polarization state of the generated nonlinear beams in a broad frequency range. The simultaneous presence of two or more different phase matching processes, involving different polarization states, is of interest in many applications.…”

“…SBN belongs to the 4 mm symmetry group. Accordingly, for a fundamental beam propagating perpendicular to the ferroelectric z-axis, the non-zero components of the quadratic nonlinear susceptibility tensor, v (2) , allows up to three different concurrent SH interactions with the same frequency, but with different input/output polarization states. The three simultaneous nonlinear interactions are eee (type 0), ooe (type I), and oeo/eoo (type II), e and o being the extraordinary and ordinary polarization, respectively.…”

“…An estimation of the conversion efficiency for the green spectral region gave a value in the order of 0.001% for the eee process. 2 The efficiency values for the ooe and oeo processes are expected to be 0.6 and 0.2 times lower than eee, respectively, according to the relative value of the involved nonlinear coefficients.…”