Guided mode resonance was numerically demonstrated in the tapered silicon nitride nanorod arrays on glass substrate. Finite difference time domain technique was employed to investigate the detailed light-matter interaction dynamics and the generation of resonance at femtoseconds. Enhanced electromagnetic (EM) field intensity with enhancement factor of 200∼250 could be achieved. This highly concentrated electromagnetic field could be extended to the nanorod array tips and substrate for higher order resonance modes, which allows future application of this transverse propagating field in optical signal amplification, like fluorescence or Raman enhancement.

Resonant optical rod antennas are made from aluminum using electron-beam lithography and are optically characterized by linear dark-field microscopy and nonlinear multi-photon luminescence spectroscopy. It is demonstrated that by exciting close to the interband transition of aluminum at about 1.5 eV different radiative decay channels can be addressed. Over a period of weeks, a slight spectral red-shift and a decrease in the scattering intensity are observed due to the formation of a native oxide layer at the metal-air interface. To investigate the concurrent influence of shape transformation and dielectric environment on the spectral response function we carry out numerical calculations using finite difference time domain (FDTD) methods. It is found that the induced energy shift is mainly determined by the change of the dielectric constant in the nanovicinity resulting in an overall red-shift as seen in the experiment. These findings allow for a better understanding of designing and modeling plasmonic aluminum nanostructures for e.g. UV sensing where the shift in peak resonance and linewidth are key observables.

Thermal emission plays a critical role in a wide variety of applications, including adjusting radiative losses in photovoltaics and selective solar absorbers, as well as enhancing the emission of high energy photons for thermophotovoltaics and photon-enhanced thermionic emission. In this work, we consider the benefit to thermal emission associated with replacing conventional mirrors with meta-mirrors following Generalized Snell’s Law. By reflecting light at a different angle than incident, they can couple internally guided thermal radiation modes to the escape cone, ideally starting from any internally-guided angle. We illustrate the concept with two meta-mirror structures: a graded index material and a xylophone structure. Even without optimization, angle-averaged selective thermal emission is significantly enhanced compared to the planar case at selected wavelengths. Furthermore, the central wavelength and bandwidth of the enhancement can be matched with the requirements of each application.

We have demonstrated some facile ways to fabricate the large area polymer surfaces with varying roughness followed by studying their anti-reflective properties. One of the approaches is based on electrospun nanofibers deposited on a substrate in an uneven non-woven matrix. This electrospun fabric was used as a master template to fabricate the negative replica of the fibers by soft lithography generating the roughness in polydimethylsiloxane (PDMS) surfaces. The second approach is based on biomimicking of flower petals. Petals are used as a master template to transfer surface features with hierarchical roughness over PDMS surface using replica moulding. As fabricated polymer surfaces with varied roughness have then tested for their anti-reflective properties using UV-VIS spectroscopy over a wide range of wavelengths and angles of incidence of light. These measurements show near zero reflection of patterned PDMS surfaces as compared to planar PDMS. This omnidirectional broadband anti-reflection behaviour of polymer surfaces can be used in wide variety of engineering applications including in solar cells.

We report on our recent progress in the study of single Dibenzoterrylene (DBT) molecules as single photon sources and nanoscale probes. We consider DBT molecules embedded in thin anthracene films, a system that allows stable single photon emission both at room and at cryogenic temperatures. We investigate the most important optical properties of the DBT:anthracene system as a whole. We then perform a full statistical study of the coupling between single DBT molecules by measuring the lifetimes of DBT both in the coupled and in the uncoupled case. The experimental results are framed into a simple universal scaling model, where the magnitude of coupling depends solely on universal parameters and on the distance d between the single emitter and the graphene monolayer. We apply this model to infer d and provide a proof of principle for a position ruler at the nanoscale [1].

We report here on the chemical methodologies that are being settled in our labs for the insertion in diamond of foreign atoms and consequent creation of fluorescent defects. The inclusion of Si, Cr, Ge, able to produce color centers, is directly obtained during the process of diamond synthesis by means of a CVD technique. The deposition of the diamond films takes place on substrates of different nature, treated following procedures specifically settled to control the insertion of the different species. The photoluminescence emission from a series of diamond samples grown on different substrates (Si, Ge and Ti) has been investigated and is discussed with reference to the morphological/structural features of the diamond phase and to the experimental procedures adopted for substrate preparation.

We have numerically investigated the unique effects of the core-shell nanoparticles on the integrated micro disk resonator. By attaching the core-shell nanoparticle to the disk resonator with gold core and polymer shell, the coupling between the disk resonator and the core-shell nanoparticle results in shift of the resonance wavelength of the disk resonator, depending on the core size/shell thickness of the nanoparticle. An ‘invisibility’ phenomenon found from the coupled core-shell nanoparticle and integrated disk resonator system is emphasized: at certain core size/shell thickness ratio, compared to the original resonance wavelength without core-shell nanoparticle, there is almost no resonance wavelength shift observed. The dependence of the position and number of core-shell nanoparticles is also discussed. Future studies on this coupled photonic systems will stimulate wide variety of applications.