The purpose of this work is to offer a low cost and noninvasive set up aimed at measuring droplet dimensions in real time. The system is composed of an acrylic microfluidic device coupled to a perpendicularly positioned optical fiber, a laser diode light source and a photodetector. This optofluidic system is capable of producing droplets with sizes varying from 250 up to 400 μm, by changing the inlets flow rates. FEM modeling was introduced in order to understand the transmittance pattern observed while the droplets crossed the optical path.

In this work, we investigated a platform for real-time emulsion droplet detection and size measurement in optofluidic platforms. An 8.2 µm core diameter input optical fiber and a multi-mode Gradient Refractive Index (GRIN) output fiber were integrated into an acrylic microfluidic channel platform consisting of three layers. Water-in-oil emulsions were investigated, since relevant applications have emerged in the recent past for these types of emulsions, such as drug encapsulation as well as droplet-based Polymerase Chain Reaction (PCR) amplification of DNA, among others. The main contribution of this work is in understanding the main physical phenomena (i.e., total internal reflection, refraction, and interference) behind the complex transmittance pattern obtained for these droplets. For this purpose, a frequency domain electromagnetic wave propagation modelling of the structure using the Finite Element Method (FEM) was used along with experimental measurements.

In this review we present recent advances regarding pedestal waveguides using different cores based on GeO2Bi2O3, GeO2-PbO, Ta2O5 and SiOxNy materials for optical amplifiers and nonlinear optics applications. The pedestal platform, based on Si technology, is interesting for materials that are hardly etched by conventional techniques as is the case of heavy metal oxide cores. The present results review recent technological advances to fabricate pedestal waveguides with and without Cr mask. The fabrication mechanism that does not use Cr mask and avoids micromasking effect is shown. The advantages of this process are discussed as well as its appropriateness to produce pedestal waveguides for optical amplification at 1.53 mu m and nonlinear optics applications. Comparison with pedestal waveguides prepared with Cr mask is also included to highlight the advantages that the new technique performed in the absence of Cr mask may provide, regarding propagation losses at the infrared region. Results of pedestal waveguides performance improvement, due to the scattering of large silicon nanostructures is also reviewed opening new possibilities for more efficient pedestal waveguides for optical amplification.

Mosquito-borne diseases are among the most significant challenges facing societies around the world. In Brazil, current official epidemiological reports show increasing numbers of cases of mosquito-borne diseases, such as chikungunya, dengue, yellow fever and Zika, which are spreading to new areas of the country. Therefore, it can be stated that current methods used for the management of mosquito vectors in Brazil, established since 2002, have been ineffective. Thus, there is a necessity for readjustment or updating of the Aedes aegypti control programmes that are being applied in Brazil. As recommended by the World Health Organization (WHO), the best way to combat these pathogen vectors is an integrated approach where several convenient and compatible control techniques are combined to efficiently reduce or potentially eliminate a targeted insect vector population. In this manuscript, we updated a review published in 2015 by the same authors about Aedes control programmes in Brazil showing their basic concept and the principal components of Aedes integrated control programmes. Strategies such as public education, community engagement and responsibility; mechanical elimination of mosquito breeding habitats; the use of larvicides and adulticides; massive collection of eggs and adults using traps; and the reduction in the vector population through the promotion of sterility of mosquitoes by ionizing radiation, use of symbiont bacteria such as Wolbachia, or genetic modification, are discussed. The Brazilian experience to test and evaluate some of these technologies is described and compared with strategies to prevent and manage mosquito populations in other countries. It is concluded that there are new control methods that can be integrated on an area-wide basis to suppress mosquito populations successfully. Nevertheless, epidemiological studies are also needed to evaluate their impact on disease transmission, in addition to the proof-of-concept that they suppress mosquito populations.

Secure quantum key distribution (QKD) is limited by the Earth's horizon, weather, and turbulence in the atmosphere. We will outline the analysis, design, and early stages of our mobile small unmanned aircraft system (sUAS) free-space optical quantum communication system. This reconfigurable, quantum-secure communication platform can potentially open up a novel communication layer that can avoid local weather interruptions as well as provide a substantial reduction in turbulence-related loss by transmitting above ground level. We review the design and testing of a custom cage-system mode analyzer to be implemented as the receiving optics module on a sUAS. The tests of our design, within predicted operational parameters, suggests that this is a feasible option for a mode analyzer on a light-weight mobile platform.

We propose a novel platform for detecting as well as measuring the size of individual droplets in microfluidic channels using microstrip transmission lines. The most outstanding feature of our platform is that, as opposed to previous related works, its design allows for the droplet to flow in a microfluidic channel fabricated between the top strip and the ground plane of a microstrip transmission line. This provides enhanced interaction of the electromagnetic field with the detected droplets. The proposed design allows us to measure droplet size directly from the phase of the microwave signal, without the need for a resonator. The platform is based on low temperature co-fired ceramic (LTCC), which makes it more compatible with Radiofrequency (RF) and microwave technology than platforms used in previous works. With this platform, we are able to measure droplets as small as 150 µm in radius. It is worth pointing out that our device could also be used for detection, counting and measurement of other microscopic objects.

In this work, the non-linear refractive index (n2) of silicon oxynitride (SiOx Ny) is determined, obtaining a value for this material of n2 = 2.11×10-19 m2/W. The results demonstrate that this material has interesting properties for the development of non-linear optical devices. The paper presents in detail the waveguide fabrication process using the pedestal technique, which allows using different materials since it does not require etching to define the sidewalls of the waveguides. We show the results of the measurement of the n2 employing the non-linear optical phenomena of Self-Phase Modulation (SPM).

In this work, we investigate a pedestal tantalum oxide (Ta2O5) material platform for integrated nonlinear optics (NLO). In order to achieve low propagation losses with this material, pedestal waveguides with Ta2O5 cores were designed. The nonlinear refractive index n2 of this new platform was obtained by measuring the amount of spectral broadening due to self-phase modulation (SPM) of 23 fs optical pulses at 785 nm propagating through the waveguides. In this manner, a nonlinear index of (5.8 ± 2.0) × 10-19 m2W-1 was found for this material, which is in good agreement with values reported in related works where strip waveguides were used for a similar purpose. Furthermore, due to the pedestal configuration, propagation losses as low as 1.6 dB·cm-1 for narrow waveguides and 0.1 dB·cm-1 for large waveguides were obtained. Finite element method (FEM) mode analysis was performed to calculate the mode characteristics, as well as the effective areas of the waveguides. The high nonlinear and linear refractive indices, wide bandgap and low propagation losses make this platform ideal for applications extending from the visible into the mid-IR regions of the optical spectrum. Due the large gap, Ta2O5 should have low two photon absorption at the near-IR as well.

In this work, we present a numerical design of a pedestal waveguide as a suitable alternative for coupling between few-mode fibers and integrated devices. The proposed waveguide has a cylindrical core deposited over a pedestal base. Numerical simulations are performed to show that modes propagating in pedestal waveguides possess an electric field profile similar to the LP modes in few-mode fibers. The power coupling between these two devices can reach values up to than 96% (-0.18 dB). Besides this, the pedestal waveguide has low insertion loss (IL) and the return loss is around 8 dB. This approach is a suitable alternative in the study of multimode integrated devices in order to work alongside few-mode fibers.

In this work we review the recent advances and demonstrate possible future perspectives regarding pedestal waveguide fabrication technology. The optical waveguides produced using this technology represent a new platform to study novel optical materials that could not be explored differently as this fabrication process does not require etching of the core material itself. Thus, novel materials that are highly inert to chemical etchants, such as those composed of heavy metal elements, can be used with this new architecture that allows the fabrication of integrated optical devices. Lower propagation losses with pedestal waveguides when compared to rib waveguides are reviewed. The possibility to construct Mach-Zehnder interferometer structures using the pedestal waveguide technology is shown. The optical amplifiers with high gain are demonstrated using this pedestal process. Furthermore, using the pedestal architecture, it is presented the possibility to produce rare earth ions doped waveguides with gold nanoparticles, which demonstrated gain enhancement attributed to the efficient luminescence due to gold nanoparticles, thus opening possibilities for potential applications in integrated photonics. Finally, another research field that could benefit greatly in the near future from this new architecture is the integrated nonlinear optics as the pedestal waveguide fabrication technology opens up the possibility of using novel materials with high optical nonlinear susceptibilities.

This work reports the signal enhancement of Yb3+/Er3+ codoped PbO-GeO2 pedestal waveguides due to gold nanoparticles deposited over the core layer. The pedestal structure was obtained by conventional photolithography and plasma etching with a new procedure that does not use metallic hard-masks that normally introduce roughness, leading to light scattering. This new procedure brings advantages that benefit light guiding, reducing the propagation losses. Yb (3+)/Er3+ codoped PbO-GeO2 thin film was obtained by RF Magnetron Sputtering deposition and was used as core layer (410 nm height). In order to cover the core with gold nanoparticles the sputtering technique was used, followed by annealing at 400 degrees C during 1 h. The minimum propagation losses obtained were of 1.0 dB/cm at 1068 nm. Scanning Electron Microscopy (SEM) was employed for the waveguides structure inspection and transmission electronic microscopy (TEM) was used to verify the presence of gold nanoparticles on the waveguides. It was observed an enhancement of 180% for the relative gain that reached 7.8 dB/cm at 1530 nm, for an optical waveguide with 6 pm core width, under 980 nm excitation (pump power of 60 mW), attributed to the local field enhancement in the vicinity of the gold nanoparticles. The new fabrication process presented in this work opens possibilities for optical amplifiers with low propagation losses based on different metal dielectric composites, as well as other waveguide-based devices.

Slow light propagation through photonic crystal (PhC) slab devices has great potential to reduce the size and power consumption of silicon photonic optical circuits. Most commonly, slow light routing through photonic crystals is achieved by using W1 waveguide bends operating near their cutoff frequencies. Unfortunately, this leads to optical pulse distortion due the high group velocity dispersion (GVD) associated with these designs. In this letter, however, we study the coupling between slow light waveguides optimized for near-zero GVD and 60° PhC bends. Using numerical methods and the temporal coupled mode theory, we assess the performance of single bends coupled to input/output waveguides, and S-bends composed of two cascaded bends. In this latter, we observe that the bend-waveguide quality factor has great impact over transmission and dispersion. We propose a novel 60° PhC bend design for routing optical modes while maintained reduced dispersion. This is achieved over a -3 dB bandwidth of around 50 nm in devices with slowdown factor up to 40. We show that this 60° PhC bend has good stability under changes in S-bend length and fabrication induced disorder. These results can lead to great improvements in the design of monolithically integrated modulators, switches, (de)multiplexers, and filters based on photonic crystals, as well as on the routing of long optical buffers and delay lines.

In this work we present the details regarding the fabrication process of pedestal based optical waveguides, using different materials with large optical nonlinearities as core layer. With the pedestal fabrication process it is possible to use novel materials that are highly inert to chemical etchants or alloys composed of heavy metal elements, since this technique does not require etching of the core material itself. Lateral confinement of light is performed through the fabrication of pedestals by Reactive Ion Etching (RIE) on the lower cladding. The last step in the fabrication process is the deposition of the core layer and, for this reason, etching this layer is no longer necessary. The materials used as core layer are Aluminum Nitride and Titanium oxynitride films, due to the fact that these materials present a great potential for the fabrication of Nonlinear Optics integrated devices.

We use numerical simulations to show that, even under common perturbations such as waveguide bends, pedestal waveguides are suited for stable propagation of modes carrying orbital angular momentum (OAM) in integrated devices.

We propose a novel all-optical encryption technique that shuffles spectral slices of multiple wavelength-division multiplexing (WDM) channels. In particular, we investigate the application of this technique to two WDM 56-Gb/s quadrature phase-shift keying signals. Simulation results reveal that the encrypted signals could be propagated through transparent optical networks with diameters larger than 500 km and properly decrypted at the receiver. The technique enhances security because it forces eavesdroppers to discover the shuffled slices and to monitor multiple channels to recover data from just one of them.

In this work we review and summarize the recent developments regarding pedestal waveguide fabrication technology and demonstrate the applicability of this type of structure for Nonlinear Optics (NLO) integrated devices. Pedestals show great potential as a platform for exploring new optical materials. The fabrication process of this type of waveguide does not require etching of the core material itself, making it possible to explore materials that are highly inert to chemical etchants or alloys composed of heavy metal elements, which would not be usually suitable for this purpose otherwise. Lower propagation losses can be achieved with pedestal waveguide when compared to rib waveguides fabricated with different materials. Since the pedestal process allows the exploitation of novel materials, optical amplifiers with higher gain have been demonstrated using this procedure. We show that pedestals could also greatly benefit the field of nonlinear optics, where novel materials with high nonlinearities could be explored as well.

We demonstrate an all-optical quantum random number generator using a degenerate optical parametric oscillator in a silicon-nitride microresonator. We achieve a 2-MHz generation rate and verify the randomness using the NIST Statistical Test Suite.

We demonstrate quantum random number generation at 2 Mbps using binary phase state generation via degenerate optical parametric oscillation in a silicon-nitride microresonator. Such a system can potentially scale to rates > 1 Gbs.

Physical layer encryption (PLE) is a promising technology for increasing the security of communication networks. An important goal of PLE is to establish a mechanism that allows authorized users to understand cyphered messages. In this work, we show that this objective may be successfully accomplished by applying a double-lock strategy to the recently proposed optical spectral phase and delay encoding (SPDE) technique. The main feature of this strategy is that authorized users do not need to exchange a cryptographic key to achieve a safe communication. Computer simulation results suggest this double-lock approach may be effectively used by metropolitan area network end users deploying SPDE encrypted 100 Gb/s signals.

In this work we investigate the principles of an alternative method for defining sidewall in optical waveguides fabricated using planar technology. The efficiency of this method is demonstrated through simulations and experimental results regarding propagation losses of a solid core ARROW waveguide fabricated on silicon substrate. It is well known that waveguides fabricated using sidewalls etched via Reactive Ion Etching (RIE) can present high sidewall roughness, especially if metallic hard-masks are used. This is largely responsible for the undesirable losses observed in these waveguides. The basic strategy of the proposed method is to do the etching step, in the fabrication of the waveguides, before the deposition of the core, so as to have the lower cladding layer and part of the silicon substrate etched away. Only after this, is the core of the waveguide deposited. This results in a waveguide sustained by a silicon pedestal. With this process, losses as low as 0.45 dB cm-1 for multimode and 0.84 dB cm-1 for single mode waveguides are obtained. The numerical simulations demonstrate that roughness in sidewalls implicates in propagation losses which are at least five times larger that those in the bulk of the material, thus corroborating the idea behind the proposed method.