Gallium Phosphide Nanowires in a Free-Standing, Flexible, and Semitransparent Membrane for Large-Scale Infrared-to-Visible Light Conversion

Abstract

Engineering of nonlinear optical response in nanostructures is one of the key topics in nanophotonics, as it allows for broad frequency conversion at the nanoscale. Nevertheless, the application of the developed designs is limited by either high cost of their manufacturing or low conversion efficiencies. This paper reports on the efficient second-harmonic generation in a free-standing GaP nanowire array encapsulated in a polymer membrane. Light coupling with optical resonances and field confinement in the nanowires together with high nonlinearity of GaP material yield a strong second-harmonic signal and efficient near-infrared (800−1200 nm) to visible upconversion. The fabricated nanowire-based membranes demonstrate high flexibility and semitransparency for the incident infrared radiation, allowing utilizing them for infrared imaging, which can be easily integrated into different optical schemes without disturbing the visualized beam.

Visible‐to‐Ultraviolet Light Conversion: Materials and Applications

“…Considering these symmetry constraints, SHG is best produced from structures without inversion symmetry combined with a high degree of organization and orientation, such as an array structure of endogenous structural proteins, semiconductor nanowires, and metal–organic frameworks. [ 12 ] Efficient visible‐to‐UV SHG is mostly observed in anisotropic crystals with transparent windows in the UV regime.…”

“…SHG processes have recently been reported in arrays of semiconductor nanowires (e.g., GaP, ZnO, and GaAs) or oriented metal–organic frameworks. The alignment in these nano/microstructured materials can lead to strong incident localization for frequency‐doubling in broad spectral range at the nanoscale [12a] . Color‐tunable light emission was obtained with NIR‐to‐visible SHG with a conversion efficiency of up to 10 −4 in free‐standing GaP nanowires.…”

Tailoring Morphology and Vertical Yield of Self-Catalyzed GaP Nanowires on Template-Free Si Substrates

“…Gallium phosphide (GaP) is of great interest for the fabrication of nonlinear photonic components owing to the large values of the nonlinear susceptibility (χ (2) ~ 70 pm/V at a wavelength around 1 µm [ 26 ]) in combination with the broad optical transparency range (0.5–11 μm [ 27 ]). Since the resonant electromagnetic properties of NWs strongly depend on their morphology, the controllable synthesis of GaP NWs is very essential for nanoscale optical devices [ 28 ]. Despite the indirect bandgap nature of GaP, recent works demonstrated quasi-direct bandgap in the GaP wurtzite phase stabilized in Au-catalyzed NWs [ 24 , 29 , 30 ] grown by the MOVPE approach allowing band structure engineering via crystal phase control [ 30 , 31 ].…”

Anomalously Strong Second‐Harmonic Generation in GaAs Nanowires via Crystal‐Structure Engineering

“…It offers an efficient and convenient approach for the realization of next‐generation frequency references and combs, [ 2–4 ] as well as for infrared‐to‐visible light conversion that can be used in tunable nanoscale light sources [ 10,11 ] and for infra‐red light visualization. [ 12 ]…”

“…Due to a large surface‐to‐volume ratio, utilizing nanostructures, for example, nanowires (NWs), for such applications not only is important for efficient miniaturization but also allows one to tailor and enhance the nonlinear response. [ 10–30 ] Considering that a dielectric NW represents a naturally formed cavity, strong localization of the fundamental light and highly directional SHG can be achieved due to Mie resonances caused by interference of the cavity modes, [ 10 ] and also by integrating the dielectric NWs into plasmonic structures. [ 27,31–34 ] An additional degree of freedom in the engineering of the SHG response is provided by the ability to grow NWs with different lattice structures and, therefore, to explore nonlinearity of crystallographic polytypes that cannot be fabricated in bulk under conventional growth conditions.…”