Maskless femtosecond laser two-photon polymerization micromachining technology is capable of inducing triggered two-photon polymerization (2PP) to fabricate three-dimensional additive templates with structural linewidths capable of exceeding the optical diffraction limit. With the help of polymer templates, disordered structural unit nanoparticles are spontaneously assembled into ordered structures through element-to-element interactions driven by free-energy minimization. In this paper, quadrilateral and hexagonal patterned tiling polymer templates were successfully fabricated by designing and tuning the processing parameters. The nanoparticle of appropriate size arrangement corresponding to the template pattern is expected to be successful in obtaining it by directed self-assembly. At the same time, the near-field and far-field optical properties of the template area under different assembly schemes were simulated and analyzed by CST Studio Suite based on finite element analysis.
We demonstrate the creation of hybrid metal-dielectric nanostructures (NPs) using femtosecond-laser exposure of copper-silicon and gold-silicon films. The formation of arrays of nanoparticles takes place in the process of irradiation of a bilayer film along a circular trajectory. The internal structure of the obtained NPs was studied by means of transmission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The resulting hybrid structures represent a mixture of gold and silicon, and both considered systems demonstrate broadband photoluminescence in the range of 450 - 900 nm with a quantum efficiency of up to 1.1%.
In this work, we investigate silicon nanocavities to increase brightness and control directivity pattern in the near-IR wavelength range. Designed nanocavities consist of the silicon nanocylinder with Mie magnetic dipole resonance. Theoretically we predict that the Purcell factor can be enhanced by up to three orders of magnitude and consider directivity patterns. We use electron lithography and laser annealing methods to fabricate nanostructures. Experimentally, photoluminescence spectra are measured and demonstrated. We believe that results of this work can find its application in optical telecommunication systems.
At the present time, hybrid nanostructures attract significant attention among researchers because such materials allow combining advantages of different materials. For instance, the ability of metal nanoparticles to localize electromagnetic energy can be combined with low losses in the visible range of high-index nanoparticles. In this work, we demonstrate the method of creation of hybrid Au/TiO2 spherical nanoparticles using nanosecond pulsed laser ablation in deionized water. A titanium foil with a sprayed gold film of various thicknesses was used as an initial sample. The effect of the thickness of the gold film on the morphology of the obtained hybrid structures was demonstrated via SEM, and the elemental composition of the created nanoparticles was studied using EDX. The size distribution of the obtained nanoparticles was studied using DLS. We believe the obtained results create the basis for the development of affordable and efficient photocatalysts operating in the visible wavelength range.
Accurate thermal monitoring is essential tool for photothermal therapy or for application light-responsive drug delivery platforms, because overheating of living cells is related with unwanted side effects in surrounding tissues. In this work, we investigated a multifunctional polymer capsule embedded with nitrogen vacancies (NV) centers as nanothermometers and gold (Au) nanoparticles (NPs) as heating agents to perform of laser-induced release of bioactive compounds from the carriers with a simultaneous temperature measurements inside living cells.
In this work, we numerically investigate a dielectric nanocavity composed of gallium phosphide nanocylinders. Our results demonstrate that proposed structures allow to increase the emission rate into zero phonon line of NV-center by a factor of 10. We compare properties of cavities made of crystalline silicon and gallium phosphide. Obtained parameters of the nanocavity are suitable for nanodiamonds with NV or SiV color centers and adopted for the existing lithography methods. We believe the proposed system is perspective for creation of a quantum nanophotonic chip for application in quantum telecommunication and quantum computing.
In this work we propose a simple one-step method for creation of hybrid Au/Si micro- and nanostructures with strong nonlinear response. We demonstrate that such structures depending on laser structuring parameters can produce strong enhancement of second harmonic signal compared to the initial Au/Si films or/and broadband white-light photoluminescence in the visible optical range. To explain this dependence, the studies of the fabricated structures were carried out by the Raman spectroscopy demonstrating strong correlation between phase composition of the structures and their nonlinear properties. We believe that proposed structures can be used as efficient nonlinear souses for different applications in bioimaging and nanospectroscopy.
Recently femtosecond laser has been proved to shift the resonance in the far-field and enhance the field distribution in the near field by modifying the shape of nanoparticles. Here we estimate the photoluminesence properties of hybrid oligomers integrated with nanodiamonds by examining the near-field distribution and calculating the Purcell factor in 3D orientations.
The resonant high-index nanostructures open opportunities for control many optical effects via optically-induced electric and magnetic Mie resonances, mostly localized inside the structures. Especial interest such nanostructures represent for quantum emitters placed inside, that makes possible enhancement of quantum source emission through resonant coupling to localized modes. We have proposed the concept of active dielectric nanoantennas based on nanodiamonds with embedded NV-centers. The study of theoretically dependence of optical properties of this system on the spectral position of the resonant modes has demonstrated that that at some sizes of the diamond spherical particles and certain position of the dipole in the sphere the Purcell factor can achieve the value of 30. We have demonstrated experimentally that the photoluminescence properties of the NV-centers can be controlled via scattering resonances and observed a decrease of the NV-centers lifetime in the studied diamond particles, as compared to nonresonant nanodiamonds. These results are in a good agreement with our theoretical calculations for the average Purcell factor for multiple NV-centers within a nanoparticle. The simplicity of the proposed concept compared to existing photonic cavity systems and applicability for a wide range of color centers in diamond make active diamond nanoantenna an effective tool for creating controllable emitting elements in the visible range for future nanophotonic devices.
We demonstrate that a hybrid c-Si/Au nanocavity can serve as a multifunctional sensing platform for nanoscale (about 100 nm) thermometry with high accuracy (>0.4 K) and fast response (<0.1 second), controlled local optical heating up to 1200 K and also provide Raman scattering enhancement (>10^4 fold). The system has been tested in the experiment on thermally induced unfolding of BSA molecules, plased inside the hybrid nanocavity. Moreover, numerical modeling reveal, that two possible operation modes of the system: with and without considerable optical heating at the nanometer scale, while other functionalities (nanothermometry, RS enhancement, and tracing the events) are preserved. These regimes make the hybrid nanocavity more versatile sensing system than fully plasmonic counterparts. The simplicity and multifunctionality of the hybrid nanocavity make it a promising platform for photochemistry and photophysics applications.
Two series of MgxZn1-xO/ZnO multiple quantum wells with 18 at.% and 27 at.% of magnesium content in barrier layers and well width Lw from 1 nm to 20 have been grown by pulsed laser deposition method. The stimulated emission is observed in photoluminescence spectra excited by pulsed laser (λexc=248 nm). The pump density threshold of stimulated emission nonmonotonously depends on the well width that is associated with an increase of the internal quantum efficiency of two-dimensional structures caused by a reduction of radiative lifetime of excitons at decreasing of the well width as it has been shown by the time-resolved photoluminescence spectra analysis. The minimum value of a lifetime τr=355 ps was obtained for the Mg0.27Zn0.73O/ZnO MQW with the well width Lw=2.6 nm.
The Mg0.27Zn0.73O/ZnO multiple quantum wells with different well width Lw have been grown by pulsed laser
deposition method. The interface roughness of quantum wells was inherited from the bottom one and did not exceed 1
nm. The quantum confinement effect has been observed. The exciton binding energy of the two-dimensional
Mg0.27Zn0.73O/ZnO structures was two times higher in comparison with the bulk ZnO. A sharp increase of exciton peak
intensity in the photoluminescence spectra at well width reduction was observed. The optical excited stimulated
emission in quantum wells Mg 0.27Zn0.73O/ZnO with an excitation threshold ~210 kW/cm2 has been demonstrated.
The formation of laser-induced structures on the multicrystalline silicon surface has been investigated. Optimum
performances of the surface structurization have been explored. A cardinal decrease in reflectance from modified
surface has been discovered in a wide spectral range in comparison with the samples of chemically texturized
monocrystalline silicon. The influence of subsequent chemical etching on the reflection spectra of the texturized
samples surface has been analyzed.
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