Second harmonic generation with full Poincaré beams

Abstract

We report a concise yet efficient experiment to extend the study of full Poincaré beams to incorporate the nonlinear optical effect. The main feature of our scheme is the employment of Type-II phase-matching KTP crystal to implement the second harmonic generation with structured vector light from invisible to visible region. Of particular interest is the revelation and visualization of the hidden topological structures transferred from the input polarization state to the output observable intensity patterns. The experimental results are in good agreement with the numerical simulations. Our present work provides us with the insight into the interaction of full Poincaré beams with media in the nonlinear regime.

Vectorial nonlinear optics: Type-II second-harmonic generation driven by spin-orbit-coupled fields

“…The results here provide a unified description of type-II SHG compatible with both the scalar and the vector cases. The theory can be used, on the one hand, to explain the spatial structures of SHG beams observed in past work [36][37][38][39][40][41][42][43][44]55]. On the other hand, it contributes to our fundamental understanding of nonlinear optics mediated by photonic SOC and lays a foundation for future studies, such as on the frequency conversion of SOC states and the generation of vector modes via type-II SHGs.…”

Vectorial light-matter interaction -- exploring spatially structured complex light fields

“…Studying the effect of polarization structures in the fundamental beam on SHG was also shown to reveal varying spatial modes, while wiping out the polarization structure from the fundamental beam. 133 Many recent publications investigate the conversion of vector vortex beams, from fundamental infrared to visible harmonic frequencies. The challenge here is to maintain the inhomogeneous polarization structure of the fundamental mode.…”

“…The challenge here is to maintain the inhomogeneous polarization structure of the fundamental mode. This can be achieved in two complementary approaches: either by using two cascading type I crystals, [134][135][136] each addressing one polarization component of the beam at a time, or interferometrically, by separating the polarization components and performing independent SHG. The latter has been demonstrated in a Mach-Zehnder configuration 137 but is more commonly performed in Sagnac interferometers.…”

Nonlinear optical vortex coronagraph

“…In the same year, Wu et al provided a theoretical toolkit to analyze the type-II SHG, which was applicable to the scalar and the vector cases [28]. Zhang et al conducted the SHG with the full Poincare beams and observed the hidden topological structures transferred from the input polarization state to the output observable intensity patterns [29]. They further realized frequency conversion from vector fields to vector fields based on the vectorial nonlinear optical process [30].…”