Electrically tunable plasmonic metasurface as a matrix of nanoantennas.

We report the fabrication and characterization of a plasmonic metasurface comprising electrically-contacted sub-wavelength gold dipole nanoantennas, conformally coated by a thin hafnia film, an indium tin oxide layer and a backside mirror, forming metal-oxide-semiconductor (MOS) capacitors, for use as an electrically-tunable reflectarray or metasurface. By voltage biasing the nanoantennas through metallic connectors and leveraging the carrier refraction effect in the MOS capacitors, our measurements demonstrate phase control in reflection over a range of about 30°, with a constant magnitude of reflection coefficient of 0.5, and the absence of secondary lobes.

Inverse design of optical pulse shapes for time-varying photonics.

Recent advancements in materials and metamaterials with strong, time-varying, nonlinear optical responses have spurred a surge of interest in time-varying photonics. This opens the door to novel optical phenomena including reciprocity breaking, frequency translation, and amplification that can be further optimized by improving the light-matter interaction. Although there has been recent interest in applying topology-based inverse design to this problem, we propose a novel approach in this article.

Tunable plasmonics on epsilon-near-zero materials: the case for a quantum carrier model.

The carrier density profile in metal-oxide-semiconductor (MOS) capacitors is computed under gating using two classical models - conventional drift-diffusion (CDD) and density-gradient (DG) - and a self-consistent Schrödinger-Poisson (SP) quantum model. Once calibrated the DG model approximates well the SP model while being computationally more efficient. The carrier profiles are used in optical mode computations to determine the gated optical response of surface plasmons supported by waveguides incorporating MOS structures.

Hyperpolarizability of Plasmonic Meta-Atoms in Metasurfaces.

Plasmonic metasurfaces are promising as enablers of nanoscale nonlinear optics and flat nonlinear optical components. Nonlinear optical responses of such metasurfaces are determined by the nonlinear optical properties of individual plasmonic meta-atoms. Unfortunately, no simple methods exist to determine the nonlinear optical properties (hyperpolarizabilities) of the meta-atoms hindering the design of nonlinear metasurfaces.

On the performance of optical phased array technology for beam steering: effect of pixel limitations.

Optical phased arrays are of strong interest for beam steering in telecom and LIDAR applications. A phased array ideally requires that the field produced by each element in the array (a pixel) is fully controllable in phase and amplitude (ideally constant). This is needed to realize a phase gradient along a direction in the array, and thus beam steering in that direction.

Mechanism of laser induced filamentation in dielectrics.

Femtosecond laser filamentation in transparent media has a wide range of applications, from three dimensional manufacturing to biological technologies to supercontinuum generation. While there has been extensive investigations over the last two decades, there remain aspects that are not understood, owing to the complexity of the interaction. We revisit intense femtosecond laser interaction with dielectric materials at 800nm under tight focusing via high resolution three dimensional simulations, where the complete set of Maxwell's equations is solved.

Elimination of imaging artifacts in second harmonic generation microscopy using interferometry.

Conventional second harmonic generation (SHG) microscopy might not clearly reveal the structure of complex samples if the interference between all scatterers in the focal volume results in artefactual patterns. We report here the use of interferometric second harmonic generation (I-SHG) microscopy to efficiently remove these artifacts from SHG images. Interfaces between two regions of opposite polarity are considered because they are known to produce imaging artifacts in muscle for instance.

Plasmonic colours predicted by deep learning.

Picosecond laser pulses have been used as a surface colouring technique for noble metals, where the colours result from plasmonic resonances in the metallic nanoparticles created and redeposited on the surface by ablation and deposition processes. This technology provides two datasets which we use to train artificial neural networks, data from the experiment itself (laser parameters vs. colours) and data from the corresponding numerical simulations (geometric parameters vs.

Investigating the Optical Properties of a Laser Induced 3D Self-Assembled Carbon-Metal Hybrid Structure.

Carbon-based and carbon-metal hybrid materials hold great potential for applications in optics and electronics. Here, a novel material made of carbon and gold-silver nanoparticles is discussed, fabricated using a laser-induced self-assembly process. This self-assembled metamaterial manifests itself in the form of cuboids with lateral dimensions on the order of several micrometers and a height of tens to hundreds of nanometers.

Effect of refractive index mismatch on forward-to-backward ratios in SHG imaging.

Nonlinear optical imaging in the epi-direction is used to image subresolution features. We find that a refractive index mismatch between the object to be imaged and the background medium can change the far-field intensity image. As an example, we study second harmonic generation (SHG) microscopy where the forward-to-backward (F/B) ratio is used to quantify subresolution features.

Genomic structural differences between cattle and River Buffalo identified through comparative genomic and transcriptomic analysis.

Water buffalo ( L.) is an important livestock species worldwide. Like many other livestock species, water buffalo lacks high quality and continuous reference genome assembly, required for fine-scale comparative genomics studies.

Gouy phase shift measurement using interferometric second-harmonic generation.

We report on a simple way to directly measure the Gouy phase shift of a strongly focused laser beam. This is accomplished by using a recent technique, namely, interferometric second-harmonic generation. We expect that this method will be of interest in a wide range of research fields, from high-harmonic and attosecond pulse generation to femtochemistry and nonlinear microscopy.

New Insights on Water Buffalo Genomic Diversity and Post-Domestication Migration Routes From Medium Density SNP Chip Data.

The domestic water buffalo is native to the Asian continent but through historical migrations and recent importations, nowadays has a worldwide distribution. The two types of water buffalo, i.e.

Vectorial control of nonlinear emission via chiral butterfly nanoantennas: generation of pure high order nonlinear vortex beams.

We report on a chiral gap-nanostructure, which we term a "butterfly nanoantenna," that offers full vectorial control over nonlinear emission. The field enhancement in its gap occurs for only one circular polarization but for every incident linear polarization. As the polarization, phase and amplitude of the linear field in the gap are highly controlled, the linear field can drive nonlinear emitters within the gap, which behave as an idealized Huygens source.

Comparative sequence alignment reveals River Buffalo genomic structural differences compared with cattle.

This study sought to characterize differences in gene content, regulation and structure between taurine cattle and river buffalo (one subspecies of domestic water buffalo) using the extensively annotated UMD3.1 cattle reference genome as a basis for comparisons. We identified 127 deletion CNV regions in river buffalo representing 5 annotated cattle genes.

Genome assembly and transcriptome resource for river buffalo, Bubalus bubalis (2n = 50).

Water buffalo is a globally important species for agriculture and local economies. A de novo assembled, well-annotated reference sequence for the water buffalo is an important prerequisite for studying the biology of this species, and is necessary to manage genetic diversity and to use modern breeding and genomic selection techniques. However, no such genome assembly has been previously reported.

Design and validation of a 90K SNP genotyping assay for the water buffalo (Bubalus bubalis).

Background: The availability of the bovine genome sequence and SNP panels has improved various genomic analyses, from exploring genetic diversity to aiding genetic selection. However, few of the SNP on the bovine chips are polymorphic in buffalo, therefore a panel of single nucleotide DNA markers exclusive for buffalo was necessary for molecular genetic analyses and to develop genomic selection approaches for water buffalo. The creation of a 90K SNP panel for river buffalo and testing in a genome wide association study for milk production is described here.

Laser-induced plasmonic colours on metals.

Plasmonic resonances in metallic nanoparticles have been used since antiquity to colour glasses. The use of metal nanostructures for surface colourization has attracted considerable interest following recent developments in plasmonics. However, current top-down colourization methods are not ideally suited to large-scale industrial applications.

A novel polymorphism in the oxytocin receptor encoding gene (OXTR) affects milk fatty acid composition in Italian Mediterranean river buffalo.

The oxytocin receptor, also known as OXTR, is a protein which functions as receptor for the hormone and neurotransmitter oxytocin and the complex oxytocin-oxytocin receptor plays an important role in the uterus during calving. A characterisation of the river buffalo OXTR gene, amino acid sequences and phylogenetic analysis is presented. The DNA regions of the OXTR gene spanning exons 1, 2 and 3 of ten Mediterranean river buffalo DNA samples were analysed and 7 single nucleotide polymorphisms were found.

Elucidating the genetic basis of an oligogenic birth defect using whole genome sequence data in a non-model organism, Bubalus bubalis.

Recent strong selection for dairy traits in water buffalo has been associated with higher levels of inbreeding, leading to an increase in the prevalence of genetic diseases such as transverse hemimelia (TH), a congenital developmental abnormality characterized by absence of a variable distal portion of the hindlimbs. Limited genomic resources available for water buffalo required an original approach to identify genetic variants associated with the disease. The genomes of 4 bilateral and 7 unilateral affected cases and 14 controls were sequenced.

Effects of refractive index mismatch on SRS and CARS microscopy.

An inhomogeneous linear refractive index profile, such as that occurring in biological tissues, is shown to significantly alter stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS) microscopy images. Our finite-difference time-domain simulations show that near-field enhancement and microlensing can lead to an increase of an object's perceived molecular density by a factor of nine and changes in its perceived position by 0.4 μm up to 1.

The SNP g.1311T>C associated with the absence of β-casein in goat milk influences CSN2 promoter activity.

Quantitative individual differences in the amount of β-casein in goat milk are determined by at least nine alleles. In particular, two alleles (CSN2(0) and CSN2(01) ) are associated with an undetectable amount of this protein in milk. The CSN2(01) allele is characterized by a single nucleotide substitution at position 373 of the seventh exon (AJ011018:g.

The Impact of Collagen Fibril Polarity on Second Harmonic Generation Microscopy.

In this work, we report the implementation of interferometric second harmonic generation (SHG) microscopy with femtosecond pulses. As a proof of concept, we imaged the phase distribution of SHG signal from the complex collagen architecture of juvenile equine growth cartilage. The results are analyzed in respect to numerical simulations to extract the relative orientation of collagen fibrils within the tissue.

Analysis of forward and backward Second Harmonic Generation images to probe the nanoscale structure of collagen within bone and cartilage.

Collagen ultrastructure plays a central role in the function of a wide range of connective tissues. Studying collagen structure at the microscopic scale is therefore of considerable interest to understand the mechanisms of tissue pathologies. Here, we use second harmonic generation microscopy to characterize collagen structure within bone and articular cartilage in human knees.