optical resonance
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2022 ◽  
Author(s):  
Hu Lu ◽  
Lazaros Varvarezos ◽  
Piergiorgio Nicolosi ◽  
Alberto Andrighetto ◽  
Daniele Scarpa ◽  
...  

Abstract We report on measurements of resonant three-step, two-colour ionization of atomic molybdenum, using a hollow cathode lamp (HCL) with optogalvanic detection. Wavelength scans were made for two specific transitions involved in the ionization pathways under investigation, namely 4d5(6S)5s 7S3 - 4d5(6S)5p 7P4 and 4d5(6S)5p 7P4 - 4d5(6S)6d 7D5.So-called ‘slow’ and ‘fast’ optogalvanic signals were observed for each pathway. Results confirm the HCL as a cost effective spectroscopic investigation tool. In particular its use in the optogalvanic mode of operation allows one to precisely, easily and reliably tune the wavelength of one or more lasers to resonances of interest for experiments in the general domain of atomic vapour laser isotope selection (AVLIS). The measurements are closely related to the Selective Production of Exotic Species (SPES) project at the ISOL facility and were performed in the recently established laser laboratory in Legnaro National Laboratories of INFN.


2D Materials ◽  
2021 ◽  
Author(s):  
Joanna Sitnicka ◽  
Kyungwha Park ◽  
Paweł Skupiński ◽  
Krzysztof Grasza ◽  
Anna Reszka ◽  
...  

Abstract MnBi2Te4/(Bi2Te3)n materials system has recently generated strong interest as a natural platform for realization of the quantum anomalous Hall (QAH) state. The system is magnetically much better ordered than substitutionally doped materials, however, the detrimental effects of certain disorders are becoming increasingly acknowledged. Here, from compiling structural, compositional, and magnetic metrics of disorder in ferromagnetic MnBi2Te4/(Bi2Te3)n it is found that migration of Mn between MnBi2Te4 septuple layers (SLs) and otherwise non-magnetic Bi2Te3 quintuple layers (QLs) has systemic consequences - it induces ferromagnetic coupling of Mn-depleted SLs with Mn-doped QLs, seen in ferromagnetic resonance as an acoustic and optical resonance mode of the two coupled spin subsystems. Even for a large SL separation (n ≳ 4 QLs) the structure cannot be considered as a stack of uncoupled two-dimensional layers. Angle-resolved photoemission spectroscopy and density functional theory studies show that Mn disorder within an SL causes delocalization of electron wave functions and a change of the surface band structure as compared to the ideal MnBi2Te4/(Bi2Te3)n. These findings highlight the critical importance of inter- and intra-SL disorder towards achieving new QAH platforms as well as exploring novel axion physics in intrinsic topological magnets.


Author(s):  
Mohammadjavad Dowran ◽  
Timothy S. Woodworth ◽  
Ashok Kumar ◽  
Alberto Marino

Abstract Quantum states of light can enable sensing configurations with sensitivities beyond the shot-noise limit (SNL). In order to better take advantage of available quantum resources and obtain the maximum possible sensitivity, it is necessary to determine fundamental sensitivity limits for different possible configurations for a given sensing system. Here, due to their wide applicability, we focus on optical resonance sensors, which detect a change in a parameter of interest through a resonance shift. We compare their fundamental sensitivity limits set by the quantum Cramér-Rao bound (QCRB) based on the estimation of changes in transmission or phase of a probing bright two-mode squeezed state (bTMSS) of light. We show that the fundamental sensitivity results from an interplay between the QCRB and the transfer function of the system. As a result, for a resonance sensor with a Lorentzian lineshape a phase-based scheme outperforms a transmission-based one for most of the parameter space; however, this is not the case for lineshapes with steeper slopes, such as higher order Butterworth lineshapes. Furthermore, such an interplay results in conditions under which the phase-based scheme provides a higher sensitivity but a smaller degree of quantum enhancement than the transmission-based scheme. We also study the effect of losses external to the sensor on the degree of quantum enhancement and show that for certain conditions, probing with a classical state can provide a higher sensitivity than probing with a bTMSS. Finally, we discuss detection schemes, namely optimized intensity-difference and optimized homodyne detection, that can achieve the fundamental sensitivity limits even in the presence of external losses.


Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jian Zhang ◽  
Dandan Wang ◽  
Yunbin Ying ◽  
Hao Zhou ◽  
Xiaokai Liu ◽  
...  

Abstract Dynamic structural color based on tunable optical resonance plays a key role in applications including encryption visualization, camouflage and colorimetric sensing. However, the current design requires either complex growth processes of the high-quality tunable materials or complicated circuit designs. This work makes a humidity-swelling hydrogel layer for metal–insulator–metal (MIM) structure in the dynamic multi-color display. Here, polyvinyl alcohol (PVA) hydrogel structure is patterned through grayscale e-beam lithography and the controlled PVA thickness leads the programmable reflective resonance covering the entire visible range. By varying the ambient humidity between 9.8 and 90.1% RH, the reflective resonance of the structure is tailored across a wavelength range over 100 nm. Our materials platform of humidity-sensitive hydrogel resist presents a novel approach of the stepwise and reversible optical tunability for photonic devices.


2021 ◽  
pp. 2101374
Author(s):  
Mengmeng Yang ◽  
Jiahao Yan ◽  
Churong Ma ◽  
Wei Gao ◽  
Yuchen Zhou ◽  
...  

2021 ◽  
Author(s):  
N. S. Anad ◽  
Zakaria M Abd El-Fattah ◽  
M. Attallah ◽  
Hanaa M. Ahmed ◽  
Mohammed M. El-Okr ◽  
...  

Abstract Pristine and chromium-doped ZnO nanowires were prepared following the traditional co-precipitation method. X-ray diffraction data identified a pure wurtzite hexagonal crystal structure characteristic for ZnO, irrespective of the doping level. The particle size, as deduced form Williamson–Hall plots, was found to be 45-55 nm for all samples. Scanning electron microscopy revealed a clear nanowires morphology for the pure and doped samples, while elemental analysis ensured the successful Cr-doping. Distinct spectroscopic signatures of Cr-doping were revealed from a detailed deconvolution process applied to optical spectra of doped samples, where Cr 3+ optical transitions were unambiguously identified at ~420 and ~665 nm. Particularly relevant, is the spectral decomposition here performed for the superimposed absorption edge (~385 nm) and Cr 3+ optical resonance at ~420 nm, allowing to claim practically doping-independent optical band gap behavior in the present doping regime. This is further supported by identifying the characteristic ZnO near edge photoluminescence peak (~ 392 nm) which maintains fixed wavelength after Cr-doping. These findings contrast earlier studies on Cr-doped semiconductor nanoparticles and glass systems where the optical band gap has been largely underestimated. We attribute the inconsistence band gap values reported in literature for Cr-doped semiconductors to the proximity of Cr optical transitions to the semiconductor absorption edge.


Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Giovanni Finco ◽  
Mehri Ziaee Bideskan ◽  
Larissa Vertchenko ◽  
Leonid Y. Beliaev ◽  
Radu Malureanu ◽  
...  

Abstract Optical sensors typically provide compact, fast and precise means of performing quantitative measures for almost any kind of measurand that is usually probed electronically. High-contrast grating (HCG) resonators are known to manifest an extremely sharp and sensitive optical resonance and can constitute a highly suitable sensing platform. In this paper we present two advanced high-contrast grating designs improving the sensing performances of conventional implementations. These configurations, namely pedestal and half-buried HCGs, allow to enhance the shift of the photonic resonance while maintaining the spectral features of the standard configuration. First, the spectral feature of the HCGs was numerically optimized to express the sharpest possible resonance when the structure is immersed in serum. Second, the sensing properties of conventional and advanced HCG implementations were studied by modelling the biological entities to be sensed as a thin dielectric coating layer of increasing thickness. Pedestal HCGs were found to provide a ∼12% improvement in sensitivity and a six-fold improvement in resonance quality factor (Q-factor), while buried HCGs resulted in a ∼58% improvement in sensitivity at the expense of a slightly broader resonance. Such structures may serve as an improved sensitive biosensing platform for near-infrared spectroscopy.


2021 ◽  
pp. 100143
Author(s):  
Ningning Song ◽  
Bing Wei ◽  
Renxian Li ◽  
Shu Zhang ◽  
Bojian Wei ◽  
...  

2021 ◽  
pp. 13-23
Author(s):  
I. S. Golyak ◽  
A. N. Morozov ◽  
A. L. Nazolin ◽  
S. E. Tabalin ◽  
A. A. Esakov ◽  
...  

The gravitational waves predicted by the general theory of relativity and detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) have typical frequencies in the range of 30 ... 300 Hz. Current theories of gravity predict the existence of high-frequency gravitational waves with frequencies of 10 ... 100 MHz, including those of cosmological origin, induced by quantum fluctuations of the scalar field at the stage of cosmological inflation in the early Universe.Multi-beam optical resonators, in particular the Fabry-Perot interferometers, can be used to detect high-frequency gravitational waves. When using multi-beam optical resonators, it is possible to use the phenomenon of low-frequency optical resonance, which allows us to have a selective response to the gravitational wave effect. The gravitational-optical resonance in a multi-beam interferometer occurs if the condition is fulfilled that an integer number of half-waves of gravitational radiation is along the length of the resonator.The use of a multi-beam interferometer to detect high-frequency gravitational waves does not require the creation of a complex system for decoupling mirrors used for gravitational antennas operating in the low-frequency part of the spectrum. This is due to the fact that the frequency of mechanical vibrations of the interferometer mirrors is significantly less than the frequency of the gravitational wave.The paper considers possible optical schemes of a high-frequency gravitational antenna: based on the traditional Michelson interferometer, in the arms of which two Fabry-Perot interferometers are available, and on the basis of the Mach-Zehnder optical scheme, where Fabry-Perot interferometers can be made in the form of two perpendicular arms, with reflecting mirrors at the bend of the beam. The advantage of the second scheme is that three photo-detectors, one being main and two others being auxiliary, can be used, and there is a possibility to detect radiation transmitted by Fabry-Perot interferometers.To prove that detection of high-frequency gravitational waves is possible, a potential sensitivity of the high-frequency gravitational antenna has been estimated in the paper.


2021 ◽  
Vol 75 (8) ◽  
Author(s):  
Ali Dia ◽  
Marie Abboud ◽  
Pierre-Jean Nacher ◽  
Geneviève Tastevin

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