Hybrid metal–dielectric nanophotonics

Miniaturized silicon-based nanostructures are highly desirable for on-chip communication and sensing due to their precise fabrication methods. However, silicon’s low photoluminescence quantum yield limits its use in light-emitting devices. Here, we propose a way to increase the broadband photoluminescence quantum yield of a silicon-based emitter by using plasmonic cavity modes in a metasurface. The cavity resonances’ spectral positions are optimized for efficient multiphoton absorption in the near-infrared and broadband photoluminescence enhancement in the visible range. The experimental characterization of nanocavity modes under different excitation conditions reveals a strong correlation between numerically estimated Purcell factor (F p (t o t a l) ∼ 10^3) and spectrally resolved photoluminescence lifetime measurements. The results demonstrate that plasmonic cavity modes boost silicon’s quantum efficiency to 0.35% using multiphoton excitation within a record-low silicon volume (∼10^5 nm^3). Our research enables precise tuning of plasmonic cavity resonances, facilitating the control of indirect bandgap semiconductor emission for nanoscale silicon-based light sources and sensors.

Hybrid metal–semiconductor nanostructures unifying plasmonic and high-refractive-index materials in a single resonant system demonstrate a wide set of unique optical properties. Such systems are a perspective for a broad palette of applications, but the link between their inner structure and optical properties is a very sensitive issue, which is still not revealed. Here, we describe the influence of internal microstructure of a hybrid gold–silicon nanoparticle (the gold nanoparticle with embedded silicon nanograins) on the up-conversion white-light photoluminescence. The evolution in the internal microstructure of the system during thermal treatment up to 500 °C is tracked in situ through the HAADF and EDS STEM techniques. The studies show the redistribution of the materials inside the hybrid nanoparticle and the reduction of the silicon nanograin numbers under heating without an external modification of the nanoparticle shape. We have established numerically that the dependence of the enhancement factor spectral width on the S / V ratio of the nanoparticle plasmonic component is close to the linear behavior. The shrinkage of the photoluminescence spectrum (up to 42%) of the hybrid nanoparticle reconfigured by laser exposure and thermal treatment is shown experimentally, which supports our numerical conclusions. The results shed light on the connection of optical properties of complex hybrid systems with their complex internal composition, providing a powerful tool to control their optical properties through microstructure rearrangement. They also open the way to the development of reconfigurable silicon-based up-conversion light nanosources for integrated optical devices and biophotonics.

Electric field is a powerful instrument in nanoscale engineering, providing wide functionalities for control in various optical and solid-state nanodevices. The development of a single optically resonant nanostructure operating with a charge-induced electrical field is challenging, but it could be extremely useful for novel nanophotonic horizons. Here, we show a resonant metal-semiconductor nanostructure with a static electric field created at the interface between its components by charge carriers generated via femtosecond laser irradiation. We study this field experimentally, probing it by second-harmonic generation signal, which, in our system, is time-dependent and has a non-quadratic signal/excitation power dependence. The developed numerical models reveal the influence of the optically induced static electric field on the second harmonic generation signal. We also show how metal work function and silicon surface defect density for different charge carrier concentrations affect the formation of this field. We estimate the value of optically-generated static electric field in this nanoantenna to achieve ≈10^8 V/m. These findings pave the way for the creation of nanoantenna-based optical memory, programmable logic and neuromorphic devices.

To keep up with the growing needs for data storage, new-generation nanophotonic devices are being actively developed, as they have a high potential to meet all the essential industrial requirements. In addition to the high stability and capacity of such systems, it is highly desirable to provide them with additional security features that would protect data from unauthorized reading. However, this usually leads to inevitable and critical complications of existing recording techniques. This work presents a novel and facile technology for hidden data storage, based on femtosecond laser processing of bi-layer gold-silicon films at low energy densities. It is shown that the recorded data can be successfully extracted using photoluminescence signal mapping, while remaining completely invisible in an optical microscope. Furthemore, the use of the investigated procedure for the optical random key generation is also demonstrated. The proposed technology stands out for its simplicity and reliability and, thus, has the potential to be an excellent choice for industrial use in the upcoming era of secure optical communication.

The control of fluorescent properties of single-photon sources in solid-state host systems via optically resonant nanostructures is a key issue in quantum nanophotonics. Here we propose a design of a resonant metal-dielectric nanoantenna for the Purcell factor and radiation pattern control of a quantum emitter placed in the gap between metal and dielectric components of the nanostructure. We demonstrate that large Purcell factor, considerable field enhancement in the gap as well as high directivity can be achieved. The developed nanosystem can be utilized for different solid-state host systems from nanocrystals to 2D materials.

Plasmonic nanosponges are a powerful platform for various nanophotonic applications owing to extremely high local field enhancement in metallic nanopores. The filling of the nanopores with high-refractive index semiconductors (e.g. Si, Ge, GaP, etc.) opens up opportunities for the enhancement of nonlinear effects in these materials. However, this task remains challenging due to the lack of knowledge on the integration process of metal and high-index semiconductor components in such nanoobjects. Here, we investigate metal-dielectric nanoparticles fabricated from bilayer Si/Au films by the laser printing technique via a combination of theoretical and experimental methods. We reveal that these hybrid nanoparticles represent the Au sponge-like nanostructure filled with Si nanocrystallites. We also demonstrate that the Au net provides strong near-field enhancement in the Si grains increasing the white light photoluminescence in the hybrid nanostructures compared to uniform Si nanoparticles. These results pave the way for engineering the internal structure of the sponge-like hybrid nanoparticles possessing white light luminescence and control of their optical properties on demand.