Phase-matched second-harmonic generation in a ferroelectric liquid crystal waveguide

Ferroelectric nematic liquid crystals exhibit unique non-linear optical properties, with the potential to become transformative materials for photonic applications. A promising direction relies on the fabrication of tailored polar orientational patterns via photoalignment, thus shaping the non-linear optical susceptibility through thin slabs of the ferroelectric fluid. Here, we explore the fabrication of 2D periodic SHG active arrays in ferroelectric nematic fluids, for diffe...

A binary mixture of ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The FLCs possess two important functionalities: a chromophore with a high hyperpolarizability $\beta$ and photoreactive groups. The smectic liquid crystal is aligned in layers parallel to the glass plates in a sandwich geometry. This alignment offers several advantages, such as that moderate electric fields are sufficient to achieve a high degree of polar order. The arrang...

Materials that exhibit high nonlinear optical (NLO) susceptibilities are considered as promising candidates for a wide range of photonic and electronic applications. Here we argue that the ferroelectric nematic (NF) materials have sufficient potentialities to become materials for the next-generation of NLO devices. We have carried out a study of the efficiency of optical second-harmonic generation in a prototype NF material, finding a nonlinear susceptibility of 5.6 pmV-1 in ...

A novel mechanism of efficient second harmonic generation in domain wall series is reported. By employing angle modulation, obvious intensity peaks of second harmonic appear at specific incident angles utilizing the continuous laser source of 200mW, and the single-pass conversion efficiency comes up to 5%/W only through dozens of domain walls. It can be shown that the phenomenon is caused by coherent superposition of Cherenkov second harmonics (CSH) generated by different dom...

A comparative experimental investigation of the dependence of second harmonic generation (SHG) on applied external voltage between the standard nematic liquid crystalline material and an analogue ferromagnetic nematic liquid crystalline material was performed by using a fundamental optical beam at 800 nm wavelength. For a ferromagnetic material, the dependence of SHG on an applied magnetic field was also examined. Three different polarization combinations of the fundamental a...

Second harmonic generation is a powerful tool directly connected to the symmetry of materials. Phase transitions, lattice rotations or electromagnetic coupling in multiferroic compounds can be revealed by using second harmonic generation.[1-4] Here we show that the sense of the spontaneous electric polarization Ps in trigonal ferroelectrics can lead to a pronounced spatial dependence of the second harmonic generation. By using a two-dimensional nonlinear photonic structure we...

The recently discovered ferroelectric nematic liquids incorporate to the functional combination of fluidity, processability and anisotropic optical properties of nematic liquids, an astonishing range of physical properties derived from the phase polarity. Among them, the remarkably large values of second order optical susceptibility encourage to exploit these new materials for non-linear photonic applications. Here we show that photopatterning of the alignment layer can be us...

Second harmonic generation (SHG) extensively employs periodically poled nonlinear crystals through forward quasi-phase-matching to achieve efficient frequency conversion. As poling periods approach sub-micrometers, backward quasi-phase-matching has also been demonstrated, albeit by utilizing pulsed laser drives. The realization of symmetric second harmonic generation, characterized by counterpropagating pumps, however, has remained elusive despite theoretical predictions. The...

We present a liquid-crystal laser device based on the chiral ferroelectric nematic phase (NF*). The laser medium is obtained by mixing a ferroelectric nematic material with a chiral agent and a small proportion of a fluorescent dye. Notably, in the NF* phase very low electric fields perpendicular to the helical axis are able to reorient the molecules, giving rise to a periodic structure whose director profile is not single harmonic but contains the contribution of various Fou...

We report on the second harmonic generation performance of a ferroelectric nematic fluid consisting of the prototype ferroelectric nematic liquid crystal, RM734 mixed with the classical chromophore Dispersed-Orange 3 at 5 %wt. The mixture exhibits an interesting mesomorphic behavior with a wide temperature range of the ferroelectric mesophase, high nematic order parameter and ease of alignment in cells. In the study, two fundamental wavelengths (1064 nm and 1574 nm) have been...