Archives 2021

News On Metasurface

In this days, the journal of optical material express published a new paper entitled as “Non-Hermitian metasurfaces for the best of plasmonics and dielectrics”

Abstract: Materials and their geometry make up the tools for designing nanophotonic devices. In the past, the real part of the refractive index of materials has remained the focus for designing novel devices. The absorption, or imaginary index, was tolerated as an undesirable effect. However, a clever distribution of imaginary index of materials offers an additional degree of freedom for designing nanophotonic devices. Non-Hermitian optics provides a unique opportunity to take advantage of absorption losses in materials to enable unconventional physical effects. Typically occurring near energy degeneracies called exceptional points, these effects include enhanced sensitivity, unidirectional invisibility, and non-trivial topology. In this work, we leverage plasmonic absorption losses (or imaginary index) as a design parameter for non-Hermitian, passive parity-time symmetric metasurfaces. We show that coupled plasmonic photonic resonator pairs, possessing a large asymmetry in absorptive losses but balanced radiative losses, exhibit an optical phase transition at an exceptional point and directional scattering. These systems enable new pathways for metasurface design using phase, symmetry, and topology as powerful tools.

News On Bio-Sensors

In this days, the journal of sensors publishes a new paper entitled as “Pain and stress detection using wearable sensors and devices—A review“

Pain is a subjective feeling; it is a sensation that every human being must have experienced all their life. Yet, its mechanism and the way to immune to it is still a question to be answered. This review presents the mechanism and correlation of pain and stress, their assessment and detection approach with medical devices and wearable sensors. Various physiological signals (ie, heart activity, brain activity, muscle activity, electrodermal activity, respiratory, blood volume pulse, skin temperature) and behavioral signals are organized for wearables sensors detection. By reviewing the wearable sensors used in the healthcare domain, we hope to find a way for wearable healthcare-monitoring system to be applied on pain and stress detection. Since pain leads to multiple consequences or symptoms such as muscle tension and depression that are stress related, there is a chance to find a new approach for chronic pain detection using daily life sensors or devices. Then by integrating modern computing techniques, there is a chance to handle pain and stress management issue.

Congratulations for Our new paper in Journal of Scientific Reports

Trace of evanescent wave polarization by atomic vapor spectroscopy

M. Mosleh¹, M. Ranjbaran², S. M. Hamidi^1,*

Various efforts have been made to determine the polarization state of evanescent waves in different structures. The present study shows the reliability of magneto-optical spectroscopy of D1 and D2 lines of rubidium metal and polarization-dependent transitions to investigate and trace the changes in the polarization state of evanescent fields during total internal reflection over different angles. For this purpose, we design and fabricate atomic- evanescent Rb vapor cells and examine the effect of polarization changes of evanescent waves, depending on the propagation direction of evanescent waves in anisotropic rubidium vapor media under different external magnetic field configurations theoretically and experimentally. The results confirm the dependency of allowed  transitions on the magneto optical configuration as a tool to determine changes in the polarization of evanescent waves in more complicated wave states in anisotropic media.

News On Quantum Networks

Bringing quantum networks to life

Control over the interaction between photons with atoms promises quantum systems to serve as transmitters, receivers, and memory elements for information in a future quantum network.

How can information encoded in atoms or molecules be exchanged with single photons without corruption or loss? That is the key problem with which laser physicist Professor Gerhard Rempe, a director of the Max Planck Institute for Quantum Optics (MPQ; Garching, Germany), and his research group are concerned. In their efforts to solve it, they have designed optical resonators made up of pairs of mirrors placed in diametrically opposite positions in an ultrahigh-vacuum chamber (see Fig. 1). The volume enclosed by such an optical cavity is much less than a cubic millimeter, but the reflectivity of the mirrors is extremely high. Once inside a resonator, a photon will be reflected on the order of 100,000X before it is transmitted through one of the mirrors.

In their experiments, the researchers prepared a single atom, which has been cooled to a temperature of much less than 1 mK and place it in a resonator or at the center of two crossed resonators positioned orthogonally to each other (see Fig. 2). If a photon were to interact with the atom only once, the interaction would be very weak. However, because each photon makes the round trip between the cavity’s mirrors many times, the interaction is correspondingly amplified.

Rempe and his team have used this configuration as the basis for the construction of novel light sources that generate a stream of single-photon bits, and even quantum mechanically entangled photons, on demand.¹ In addition, the setup can be used to transfer quantum information encoded in a single photon to the atom in a controlled manner.² Furthermore, the group has shown that the presence or absence of a single photon can be nondestructively measured without altering the information encoded in the particle. That’s roughly analogous to checking whether there is a letter in the post office box without reading the content of that letter. However, it’s much more difficult to verify the arrival of a quantum letter without reading the quantum content.³ Experiments such as these are being performed in several of the group’s laboratories.

Rempe is one of the initiators in the field of cavity quantum electrodynamics. In 1987, he was the first person to demonstrate the repeated absorption and re-emission of a single microwave photon by a single atom. He went on to study how optical photons behaved when introduced into cavities formed by highly reflective mirrors. With this work, he became one of the pioneers of cavity quantum electrodynamics in the optical frequency range.

Congratulations for Our new paper in Journal of magnetism and magnetic materials

One-dimensional optomagnonic microcavities for selective excitation of perpendicular standing spin waves

V.A.Ozerov, D.A.Sylgacheva, M.A.Kozhaev, T. Mikhailova, V.N.Berzhansky, Mehri Hamidi, A.K. Zvezdin, V.I. Belotelov

Here we propose a method of the excitation of perpendicular standing spin waves (PSSWs) of different orders in an optomagnonic microcavity by ultrashort laser pulses. The microcavity is formed by a magnetic dielectric film surrounded by dielectric non-magnetic Bragg mirrors. Optical cavity modes in the magnetic layer provide concentration and strongly non-uniform distribution of the optical power over the layer thickness and therefore induce the effective field of the inverse Faraday effect also spatially non-uniform. It results in excitation of PSSWs. PSSWs whose wavevector is closest to the wavevector characterizing distribution of the inverse Faraday effect field are excited most efficiently. Consequently, a key advantage of this approach is a selectivity of the PSSW excitation which allows to launch PSSWs of required orders only. All-optical operation of the optomagnonic cavities opens new possibilities for their applications for quantum technologies.

Congratulations for our new paper in International Journal of Optics and Photonics

Flat and Flexible 2D Plasmonic Crystal for Color Production

Neda Roostaei, S. M. Hamidi

Abstract— Recently, color production by using plasmonic structures has widely been studied. In this research, a flat and flexible two-dimensional Kapton-copper plasmonic crystal with very low thickness has been fabricated in a new and optimal way. Color production is performed using our proposed plasmonic structure and different colors are achieved by changing the incidence angle of light. Also, the plasmonic resonance response of the fabricated structure has been recorded at the incidence angle of 58 degrees. Advantages of our proposed structure are low cost, easy fabrication, and very small dimensions, and thus this research can be useful due to the increasing needs for the integration and miniaturizing of optical devices in modern nanophotonic systems.

News On Plasmonics

The journal of Nano Letters published a paper entitled as “Magnesium Nanoparticle Plasmonics”

Nanoparticles of some metals (Cu/Ag/Au) sustain oscillations of their electron cloud called localized surface plasmon resonances (LSPRs). These resonances can occur at optical frequencies and be driven by light, generating enhanced electric fields and spectacular photon scattering. However, current plasmonic metals are rare, expensive, and have a limited resonant frequency range. Recently, much attention has been focused on earth-abundant Al, but Al nanoparticles cannot resonate in the IR. The earth-abundant Mg nanoparticles reported here surmount this limitation. A colloidal synthesis forms hexagonal nanoplates, reflecting Mg’s simple hexagonal lattice. The NPs form a thin self-limiting oxide layer that renders them stable suspended in 2-propanol solution for months and dry in air for at least two week. They sustain LSPRs observable in the far-field by optical scattering spectroscopy. Electron energy loss spectroscopy experiments and simulations reveal multiple size-dependent resonances with energies across the UV, visible, and IR. The symmetry of the modes and their interaction with the underlying substrate are studied using numerical methods. Colloidally synthesized Mg thus offers a route to inexpensive, stable nanoparticles with novel shapes and resonances spanning the entire UV-vis-NIR spectrum, making them a flexible addition to the nanoplasmonics toolbox.

News On Magnetophotonic

In this days, the journal of arXiv preprint arXiv:2110 publishes a new paper entitled as “Magnetophotonics for sensing and magnetometry towards industrial applications”

Magnetic nanostructures sustaining different kinds of optical modes have been used for magnetometry and label-free ultrasensitive refractive index probing, where the main challenge is the realization of compact devices able to transfer this technology from research laboratories to smart industry. This Perspective discusses the state-of-the-art and emerging trends in realizing innovative sensors containing new architectures and materials exploiting the unique ability to actively manipulate their optical properties using an externally applied magnetic field. In addition to the well-established use of propagating and localized plasmonic fields, in the so-called magnetoplasmonics, we identified a new potential of the all-dielectric platforms for sensing to overcome losses inherent to metallic components. In describing recent advances, emphasis is placed on several feasible industrial applications, trying to give our vision on the future of this promising field of research merging optics, magnetism, and nanotechnology.

News On Plasmonics

In this days, the journal of Biosensors and Bioelectronics publishes a new paper entitled as “Functionalized terahertz plasmonic metasensors: Femtomolar-level detection of SARS-CoV-2 spike proteins”

Effective and effcient management of human betacoronavirus severe acute respiratory syndrome (SARS)-CoV-2 virus infection i.e., COVID-19 pandemic, required sensitive and selective sensors with short sample-to-result durations for performing desired diagnostics. In this direction, one appropriate alternative approach to detect SARS-CoV-2 virus protein at low level i.e., femtomolar (fM) is exploring plasmonic metasensor technology for COVID-19 diagnostics, which offers exquisite opportunities in advanced healthcare programs, and modern clinical diagnostics. The intrinsic merits of plasmonic metasensors stem from their capability to squeeze electromagnetic felds, simultaneously in frequency, time, and space. However, the detection of low-molecular weight biomolecules at low densities is a typical drawback of conventional metasensors that has recently been addressed using toroidal metasurface technology. This research is focused on the fabrication of a miniaturized plasmonic immunosensor based on toroidal electrodynamics concept that can sustain robustly confned plasmonic modes with ultranarrow lineshapes in the terahertz (THz) frequencies. By exciting toroidal dipole mode using our quasi-infnite metasurface and a judiciously optimized protocol based on functionalized gold nanoparticles (AuNPs) conjugated with the specifc monoclonal antibody specifc to spike protein (S1) of SARS-CoV-2 virus onto the metasurface, the resonance shifts for diverse concentrations of the spike protein are monitored. Possessing molecular weight around ~76 kDa allowed to detect the presence of SARS-CoV-2 virus protein with signifcantly low as limit of detection (LoD) was achieved as ~4.2 fM. We envisage that outcomes of this research will pave the way toward the use of toroidal metasensors as practical technologies for rapid and precise screening of SARS-CoV-2 virus carriers, symptomatic or asymptomatic, and spike proteins in hospitals, clinics, laboratories, and site of infection.

News On Plasmonics

The Journal of Physical Chemistry C published a paper entitled as “Key Parameter Controlling the Sensitivity of Plasmonic Metal Nanoparticles: Aspect Ratio”

ABSTRACT: Currently the synthesis of plasmonic nanoparticles for sensing applications mostly focuses on their shape because it is believed that nanoparticles with sharp tips provide higher sensitivities than those without. Herein, by measuring and analyzing the sensitivities of more than 74 types of nanoparticles of various shapes, sizes, and compositions, we found that, contrary to this common belief, the correlation between shape and sensitivity is much weaker than that between aspect ratio and sensitivity. Among all the parameters investigated here, including size, shape, composition, aspect ratio, cross sectional area, and initial plasmonic resonance frequency, the aspect ratio (R) is the key parameter that controls the nanoparticle sensitivity (S) following an empirical equation, S = 46.87R + 109.37. Other parameters have much less influence on the nanoparticle sensitivity to refractive index changes. The stronger dependence of the sensitivity on aspect ratio than on shape encourages us to reassess the current focus of nanoparticle synthesis chemistry. In addition, the S-R linear relationship determined here can be used as a design rule for future synthesis and fabrication of highly sensitive nanomaterials for chemical, biological, biomedical, and environmental sensing.