Lateral patterning of nonlinear frequency conversion with transversely varying quasi-phase-matching gratings

Abstract

We demonstrate control of the nonlinear conversion across a beam profile by using periodically poled lithium niobate with a laterally nonuniform quasi-phase-matching grating. As a representative experiment, generation of a flat-top second-harmonic beam is demonstrated.

Spatial switching of quadratic solitons in engineered quasi-phase-matched structures

“…This opens a whole range of new possibilities, which have become experimentally feasible with the progress in the use of periodically poled lithium niobate (PPLN). For example, pulse compression in frequency-conversion schemes in longitudinally chirped quasi-phasematched gratings has been observed, 3 and transverse quasi-phase-matched gratings have been made both for shaping of second-harmonic beams 4 and to extend the spectral coverage of optical parametric oscillators. 5 Engineered QPM patterns also hold great promise for use in soliton systems.…”

Comparison of two wavelength conversion schemes by exploiting cascaded harmonic and difference frequency generation in PPLN

“…Under the assumptions of plane wave approximation, slowly varying amplitudes, and negligible intrapulse group velocity dispersion (GVD) and higher order material dispersion because the GVD length for the PPLN waveguide is several times larger than the waveguide length, the SHG process in a uniform QPM waveguide is expressed as a transfer function relationship in frequency domain [13]:…”

Hexagonally Poled Lithium Niobate: A Two-Dimensional Nonlinear Photonic Crystal

“…Last, we note that NPCs are a specific example of more general nonlinear holograms which would convert a beam profile at one wavelength to an arbitrary profile at a second wavelength [10]. This would be a generalization of the concepts of Imeshev et al who converted a Gaussian profile beam at the fundamental to a square top second harmonic using transversely patterned periodically poled lithium niobate [11].…”