In this work, the behavior of refractive index sensors based on optical micro-ring resonators is studied in detail. Using a result of waveguide perturbation theory in combination with numerical simulations, the optimum design parameters of the system, maximizing the sensitivity of the sensor, are determined. It is found that, when optimally designed, the sensor can detect relative refractive index changes of the order of Δn/n≈3×10⁻⁴, assuming that the experimental setup can detect relative wavelength shifts of the order of Δλ/λ≈3×10⁻⁵. The behavior of the system as bio-sensor has also been examined. It is found that, when optimally designed, the system can detect refractive index changes of the order of Δn≈10⁻³ for a layer thickness of t=10 nm, and changes in the layer thickness of the order of λt≈0.24 nm, for a refractive index change of Δn=0.05.

Hyperthermia acts as a powerful adjuvant to radiation therapy and chemotherapy. Recent advances show that gold nanoparticles (Au-NPs) can mediate highly localized thermal effects upon interaction with laser radiation. The purpose of the present study was to investigate via in silico simulations the mechanisms of Au-NPs and microwave-induced hyperthermia, in correlation to predictions of tumor control (biological endpoints: tumor shrinkage and cell death) after hyperthermia treatment. We also study in detail the dependence of the size, shape and structure of the gold nanoparticles on their absorption efficiency, and provide general guidelines on how one could modify the absorption spectrum of the nanoparticles in order to meet the needs of specific applications. We calculated the hyperthermia effect using two types of Au-NPs and two types of spherical tumors (prostate and melanoma) with a radius of 3 mm. The plasmon peak for the 30 nm Si-core Au-coated NPs and the 20 nm Au-NPs was found at 590 nm and 540 nm, respectively. Considering the plasmon peaks and the distribution of NPs in the tumor tissue, the induced thermal profile was estimated for different intervals of time. Predictions of hyperthermic cell death were performed by adopting a three-state mathematical model, where “three-state” includes (i) alive, (ii) vulnerable, and (iii) dead states of the cell, and it was coupled with a tumor growth model. Our proposed methodology and preliminary results could be considered as a proof-of-principle for the significance of simulating accurately the hyperthermia-based tumor control involving the immune system. We also propose a method for the optimization of treatment by overcoming thermoresistance by biological means and specifically through the targeting of the heat shock protein 90 (HSP90), which plays a critical role in the thermotolerance of cells and tissues.

We present an investigation of amplified spontaneous emission (ASE) and laser action of two polymers, emitting in the blue, with alternating conjugated and flexible aliphatic segments of different lengths, in tetrahydrofuran (THF) solutions and in solid poly(methyl methacrylate) (PMMA) matrices. Laser action and ASE occur simultaneously, permitting their main differences such as coherence and tunability to be distinguished and the detrimental effect of ASE on laser action to be investigated. The polymer with the longer aliphatic segment is the more efficient material in both laser and ASE. The neat films of these polymers showed no spectral narrowing; this is attributed to the presence of aggregates. An investigation of the role of aggregates on spontaneous emission and mainly on ASE was realized in solutions by increasing the aggregate concentration through a technique based on a combination of good and poor solvent. It is proved that in these solutions both aggregates and isolated chains exist. Aggregates are responsible for the spontaneous emission while the isolated chains for the ASE.

We investigate the phenomenon of quantum interference in spontaneous emission for a three-level V-type quantum emitter placed between two bismuth-chalcogenide (Bi${}_2$Te${}_3$, Bi${}_2$Se${}_3$) microspheres. In particular, we find that the degree of quantum interference can become as high as 0.994, a value which is attributed to the strong dependence of the spontaneous emission rate on the orientation of an atomic dipole relative to the surfaces of the microspheres, at the excitation frequencies of phonon-polariton states of the bismuth-chalcogenide microspheres (anisotropic Purcell effect). As a consequence of the high degree of quantum interference, we observe the occurrence of strong population trapping in the quantum emitter. To the best of our knowledge, the reported values of the degree of quantum interference are record values and are obtained for a relatively simple geometrical setup such as that of a microparticle dimer.