News on Atomic Optics

In this days, Physical Review Journal published a paper entitled as “An Atomic-Array Optical Clock with Single-Atom Readout”

Currently, the most accurate and stable clocks use optical interrogation of either a single ion or an ensemble of neutral atoms confined in an optical lattice. Here, we demonstrate a new optical clock system based on an array of individually trapped neutral atoms with single-atom readout, merging many of the benefits of ion and lattice clocks as well as creating a bridge to recently developed techniques in quantum simulation and computing with neutral atoms. We evaluate single-site-resolved frequency shifts and shortterm stability via self-comparison. Atom-by-atom feedback control enables direct experimental estimation of laser noise contributions. Results agree well with an ab initio Monte Carlo simulation that incorporates finite temperature, projective readout, laser noise, and feedback dynamics. Our approach, based on a tweezer array, also suppresses interaction shifts while retaining a short dead time, all in a comparatively simple experimental setup suited for transportable operation. These results establish the foundations for a third optical clock platform and provide a novel starting point for entanglement-enhanced metrology, quantum clock networks, and applications in quantum computing and communication with individual neutral atoms that require optical-clock-state control.




News on magnetoelectric sensors

In this days, Materials journal publishes a new paper entitled as “Magnetic Proximity Sensor Based on Magnetoelectric Composites Colis”

Magnetic sensors are mandatory in a broad range of applications nowadays, being the increasing interest on such sensors mainly driven by the growing demand of materials required by Industry 4.0 and the Internet of Things concept. Optimized power consumption, reliability flexibility, versatility, lightweight and low-temperature fabrication are some of the technological requirements in which the scientific community is focusing efforts. Aiming to positively respond to those challenges, this work reports magnetic proximity sensors based on magnetoelectric (ME) polyvinylidene fluoride (PVDF)/Metglas composites and an excitation-printed coil. The proposed magnetic proximity sensor shows a maximum resonant ME coefficient (α) of 50.2 V/(Cm Oe) , an Ac linear response (R^2=0.997) and a maximum voltage output of 362 mV, which suggests suitability for proximity-sensing applications in the areas of aerospace, automotive, positioning, machine safety, recreation and advertising panels, among others.




Congratulations for our new paper in ACS OMEGA

Plasmophore Enhancement in Fibroblast Green Fluorescent Protein-Positive Cells Excited by Smoke

Foozieh Sohrabi, Tannaz Asadishad, Mohammad Hossein Ghazimoradi, Tayebeh Mahinroosta, Sajede Saeidifard, Seyedeh Mehri Hamidiand Shirin Farivar

Considering the large consumption of nicotine and its sedative/stimulant effect on different organs of the body, the detection of low concentration of this material and its subsequent effect on live animals plays a significant role. Optical detection techniques such as plasmonics are the pioneers in highly sensitive detection techniques. However, for investigating the nicotine/smoke effect on live cells, not only the interaction between cell nicotine should be optimized but also the plasmonic interface should show a high sensitivity to the reception of nicotine by the cell receptors. In this study, the sensitivity of the plasmonic detection system was greatly increased using the coupling of plasmon and fluorophore. This coupling could enhance the main plasmonic signal several orders of magnitude besides improving Δ and Ψ ellipsometry parameters. Benefiting from the green fluorescence proteins, the phase shift and the amplitude ratio between the reflections under s- and p-polarized light enhance considerably which verifies the coupling of the dipole of the fluorescence emitter and the plasmons of the metal nanostructure. For 1 s increase of the maintenance time, we encountered a considerable increase in the Δ values that were 0.15° for Te = 1 s and 0.24° for Te = 3 s. Benefiting from extracted ellipsometry parameters, this study could open new avenues toward studying the effect of various types of drugs and stimulants on biological samples using a novel plasmophore platform.




News on plasmonics

In this days, Nano Letters journal publishes a new paper entitled as ” Plasmon-based biofilm inhibition on surgical implants”

The insertion of an implant in the body of a patient raises the risk of a posterior infection and formation of a biofilm, which can have critical consequences on the patient health and be associated to a high sanitary cost. While antibacterial agents can be used to prevent the infection, such a strategy is time-limited and causes bacteria resistance. As an alternative to biochemical approaches, we propose here to use light-induced local hyperthermia with plasmonic nanoparticles. This strategy is implemented on surgical meshes, extensively used in the context of hernia repairing, one of the most common general surgeries. Surgical meshes were homogeneously coated with gold nanorods designed to efficiently convert near-infrared light into heat. The modified mesh was exposed to a biofilm of Staphylococcus aureus (S. aureus) bacteria before being treated with a train of light pulses. We systematically study how the illumination parameters, namely fluence, peak intensity and pulse length, influence
the elimination of attached bacteria. Additionally, fluorescence confocal microscopy provides us some insight on the mechanism involved in the degradation of the biofilm. This proof-of-principle study opens a new set of
opportunities for the development of novel disinfection approaches combining light and nanotechnology.




News on photo-acoustic imaging

Nature Methods Journal published a paper entitled as “Contrast agents for molecular photoacoustic imaging”

Photoacoustic imaging (PAI) is an emerging tool that bridges the traditional depth limits of ballistic optical imaging and the resolution limits of diffuse optical imaging. Using the acoustic waves generated in response to the absorption of pulsed laser light, it provides noninvasive images of absorbed optical energy density at depths of several centimeters with a resolution of ~100 μm. This versatile and scalable imaging modality has now shown potential for molecular imaging, which enables visualization of biological processes with systemically introduced contrast agents. Understanding the relative merits of the vast range of contrast agents available, from small-molecule dyes to gold and carbon nanostructures to liposome encapsulations, is a considerable challenge. Here we critically review the physical, chemical and biochemical characteristics of the existing photoacoustic contrast agents, highlighting key applications and present challenges for molecular PAI.




News on Spintronic

In this days, Applied Physics Letters journal publishes a new paper entitled as “Terahertz excitation of spin dynamics in ferromagnetic thin films incorporated in metallic spintronic-THz-emitter”

Abstract: An experimental approach to trigger ultrafast spin dynamics at frequencies of the terahertz (THz) regime is explored by directly incorporating ferromagnetic Ni80Fe20 films to a Fe/Au spintronic-THz-emitter. It is found that Ni80Fe20 magnetization is directly coupled to the terahertz magnetic fields, in which the magnetic responses of Ni80Fe20 are phase-locked with terahertz pulses. High efficiency of metallic spintronic-terahertz emitters in driving terahertz-induced magnetization dynamics is observed; the maximum precession amplitude of the out-of-plane component of the Ni80Fe20 magnetization reaches over 10% of its saturation magnetization. Analytical integrations of THz magnetic field pulses reproduce the experimental results, confirming that the underlying mechanism of the observed spin dynamics is the Zeeman coupling between the terahertz magnetic field and magnetization in the Ni80Fe20 film. Our results open up possibilities for the studies of terahertz spin dynamics by integrating highly efficient low-cost metallic spintronic-THz-emitters into magnetic thin film elements.




News on dielectric metasurfaces

In this days, Optics Express journal published a paper entitled as “Dielectric metasurfaces based on a rectangular lattice of a-Si:H nanodisks for color pixels with high saturation and stability”

Abstract: Silicon dielectric metasurfaces based on a square lattice of nanoparticles have been extensively utilized to create transmissive structural colors. Yet it is a huge challenge to obtain stable yellow color with high saturation due to the relatively large absorption of silicon in the short wavelength regime and the applied square lattice. In this study, we propose a new design strategy of independently altering the mutually perpendicular periods of a hydrogenated amorphous silicon nanodisk array-enabled metasurface to meticulously modulate the transmission spectra for the realization of high-saturation and stable cyan, magenta and yellow (CMY) color pixels. By introducing rectangular lattice, the yellow pixel can provide a narrowband transmission spectrum with a highly suppressed dip at 455 nm. The high suppression in transmission contributes to give rise to high-saturation yellow color. The attained narrowband spectrum that enables low spectral cross-talk is attributed to the overlap between magnetic dipole resonance excited by individual nanodisks and lattice resonance arising from the dipole coupling between the nanodisks. Compared with the square lattice, the proposed pixels exhibit fairly stable output color responses for a large period range. Meanwhile, the proposed CMY pixels are capable of both the relaxed angular tolerance and low dependence on the incident polarization states. It is anticipated that the proposed color pixels pave the way for extensive applications in compact color displays.




News on metasurfaces

In this days, OSA Continuum journal publishes a paper entitled as “Adjustable large-area dielectric metasurfaces for near-normal oblique incident excitation”

Abstract: We present large-area (25 cm2) dielectric metasurfaces based on silicon photonic crystal slabs. Adjustment of the slab thickness allows to systematically shift the metasurface resonances over several hundreds of nanometers. We compute the three-dimensional field energy density near the surface and determine optimum slab thicknesses for selected near-infrared excitation wavelengths applied in biophotonics. We explain this behaviour via the coupling of external radiation with symmetryprotected bound states in the continuum. These results enable metasurface-enhanced spectroscopy on large areas and underline the benefit of slight oblique incidence excitation conditions.




News on magnetoplasmonics

In these days, ACS Applied materials & interfaces journal publishes a paper entitled as “Magnetic Layer-by-Layer Assembly: From
Linear Plasmonic Polymers to Oligomers”

One-dimensional (1D) nanostructures with controllable aspect ratios are essential for a wide range of applications. An approach for magnetic superparticle (SP) assembly over large areas (55 mm × 25 mm) is introduced via co-assistance of electrostatic and magnetic fields, so-called magnetic layer-by-layer (MLBL) assembly, on an arbitrary hydrophilic substrate within minutes. The SP structures (diameter (d.) = 120-350 nm) of Fe3O4 or Ag@Fe3O4 composites composed of hundreds of magnetite nanocrystals (d. 10–20 nm) are used as colloidal monomers to fabricate arrays of high-aspect-ratio (up to 102) linear nanochains, viz. colloidal polymers, where thermal disturbances were minimized. The arrays of colloidal polymers exhibit strong optical polarization effects owing to their geometrical anisotropy, which can be used as a simple optical filter.




Our new paper in Journal of the Optical Society of America B

Double-stadium Si-MZI racetrack micro-ring resonator circuits – way to generate optical digital patterns

M. GHASEMI, S.M. HAMIDI, A. DEHZANGI, AND P.K. CHOUDHURY

Silicon (Si)
photonic components, namely grating couplers and three-port splitters and
couplers, were designed and combined to form double-stadium Si-Mach-Zehnder interferometer
(MZI) racetrack micro-ring resonator circuits for efficient control over resonance
in certain wavelength range and free-spectral range (FSR). It was found that variable
micro-ring resonator arms and the values of free-space distance (between the
arms) as 200 nm and 5 μm can yield two and six OFF-phase zones, respectively,
within the wavelength range of 1.5−1.6 μm. Furthermore, it was observed that
the smaller arms downsize the FSR, whereas the larger arms upsize its value
within the transmission spectrum. The usefulness of these structures can be
conceptualized in the area of optical digital pattern code generation because
suitably controlling the MZI arm lengths would create certain optical digital
patterns in the frequency domain of operation. Apart from these, the usefulness
of racetrack optical delay lines remains in optical sensing or biomedical
sensing as well.