Side Band Research Articles

CURTAINs for your sliding window: Constructing unobserved regions by transforming adjacent intervals.

We propose a new model independent technique for constructing background data templates for use in searches for new physics processes at the LHC. This method, called Curtains, uses invertible neural networks to parameterise the distribution of side band data as a function of the resonant observable. The network learns a transformation to map any data point from its value of the resonant observable to another chosen value. Using Curtains, a template for the background data in the signal window is constructed by mapping the data from the side-bands into the signal region. We perform anomaly detection using the Curtains background template to enhance the sensitivity to new physics in a bump hunt. We demonstrate its performance in a sliding window search across a wide range of mass values. Using the LHC Olympics dataset, we demonstrate that Curtains matches the performance of other leading approaches which aim to improve the sensitivity of bump hunts, can be trained on a much smaller range of the invariant mass, and is fully data driven.

Quantum Emitters with Narrow Band and High Debye-Waller Factor in Aluminum Nitride Written by Femtosecond Laser.

Solid-state quantum emitters (QEs) are central components for photonic-based quantum information processing. Recently, bright QEs in III-nitride semiconductors, such as aluminum nitride (AlN), have attracted increasing interest because of the mature commercial application of the nitrides. However, the reported QEs in AlN suffer from broad phonon side bands (PSBs) and low Debye-Waller factors. Meanwhile, there is also a need for more reliable fabrication methods of AlN QEs for integrated quantum photonics. Here, we demonstrate that laser-induced QEs in AlN exhibit robust emission with a strong zero phonon line, narrow line width, and weak PSB. The creation yield of a single QE could be more than 50%. More importantly, they have a high Debye-Waller factor (>65%) at room temperature, which is the highest result among reported AlN QEs. Our results illustrate the potential of laser writing to create high-quality QEs for quantum technologies and provide further insight into laser writing defects in relevant materials.

Compound super-oscillation lens for reflective confocal imaging

The super-oscillation lens (SOL) can achieve super-resolution focusing but have to trade-off with weaker hotspots and higher sidebands. We propose a single compound SOL to achieve reflective confocal imaging in principle without additional lenses. The designed SOL consists of an outer lens and an inner lens which play the role of focusing lens and collective lens respectively. As a result, focusing and collecting functions can be simultaneously realized. The improved system can achieve excellent imaging performance with an ultra-high resolution (<0.314λ/NA, NA stands for numerical aperture), and almost negligible side lobe ratio and no side bands, which proved superior to conventional laser scanning confocal microscopy and single SOL. This technology can be attractive for a variety of applications in super-resolution imaging and biomedical sciences.

Experimental and theoretical investigations on the modulation capabilities of a sample of vertical cavity surface emitting laser diodes for atomic vapour applications

This paper discusses various frequency modulation and intensity modulation capabilities within a sample of direct laser current modulated identical vertical cavity surface emitting laser diodes. The presented analysis is based on measurements of the spectral amplitudes as a function of the applied modulation power at a constant modulation frequency of 3.517 GHz. Their evaluation by Bessel function fits produces the three modulation parameters: frequency modulation index, intensity modulation index (via the alpha parameter) and the side band asymmetry of the first order side bands. The variation of the laser diode’s modulation capability is discussed. It is found that the individual laser diodes show a significant variations in their modulation capabilities. Thus an experimental preselection of the laser diode is required to find laser diodes which are suitable as a light source for atomic vapour applications, with special emphasis on a coherent population trapping-based scalar magnetometers.

Incremental use of FFT as a solution for low BT-product reverberation time measurements

The limitations in performance of band-pass filters to accurately process rapid decaying signals in lower frequency bands is an obstacle for some measurements within building acoustics. For instance, it would be beneficial to be able to accurately measure reverberation times down to the 20 Hz one-third octave band for impact sound in timber buildings. Here, it is tested whether calculations with FFT with small incremental steps may be a way to achieve discrete frequency time signals with faster performance than traditional band-pass filters. The tests show that incremental FFT gives accurate estimations of the reverberation time corresponding down to 0.1 s at 20 Hz with a spectral resolution of 2 Hz. Using the one-third octave limits it is possible to form approximate one-third octave band results. It is seen that accurate estimations of reverberation time are achievable for BT⩾0.5 (T=0.1 seconds for the 20 Hz one-third octave band) and possibly even lower, if the dynamic range in the interrupted noise signal is sufficient. The higher one-third octave results show to work as well. A disadvantage with the method is that during short reverberation times (0.1 s) there is a severe spectral leakage to the side bands. Also, the method requires higher dynamic range decay signals compared to band-pass filtered signals. If a one-third octave resolution is requested, a dynamic range of 50 dB or greater is preferable. With a coarse resolution of e.g., 10 Hz and having no averaging into one-third octave bands, it is possible to measure short reverberation times (0.1 s) with signals having close to the same dynamic range used in classical band-pass filtered reverberation time measurements.

Theoretical Study on Weibel instability in the existence of large amplitude Langmuir wave inside a Plasma

This paper investigates how an electrostatic Langmuir wave having large amplitude affects the Weibel instability (WI) in the existence of ions and an electron beam. Two Langmuir side band waves are produced by coupling of EM perturbation to the Langmuir wave. The Langmuir wave (LW) increases the growth rate beyond its linear value. Here, we noticed that the growth rate Γ(sec−1) scales linearly with the electron beam velocity vbe and 1/2 power of the electron beam density nbe. As we increase the density of ions inside the plasma, the growth rate stabilizes. Additionally, we find that the growth rate is very sensitive to the plasma frequency of ions. Therefore, our work finds an application in space, galactic cosmic rays and supernovas. Also, our work covers a range of application from the development of fusion power to understand the various astrophysical phenomena.

Echo modulations under homonuclear decoupling

A simple Hahn echo in a single-spin system with a static Hamiltonian can lead to echo modulations if the static Hamiltonian contains a component along the direction of the echo pulse. These modulations manifest as side bands in the Fourier transform of the echo decay. Experimentally, echo modulations that can be explained by such a model have been observed under homonuclear decoupling in solids where pulse imperfections can lead to residual effective fields in the interaction frame that have arbitrary orientations in space. We show analytically that such echo modulations are significantly reduced in intensity using double-echo sequences in agreement with experimental observations. Using pulse shapes for homonuclear decoupling that mimic and amplify the pulse distortions expected from pulse transients, we show that these effective fields can be one explanation for the observed reduction in echo modulations going from a single to a double Hahn-echo sequence.

Circularly Polarized Light Probes Excited-State Delocalization in Rectangular Ladder-type Pentaphenyl Helices.

Ladder-type pentaphenyl chromophores have a rigid, planar π-system and show bright fluorescence featuring pronounced vibrational structure. Such moieties are ideal for studying interchromophoric interactions and delocalization of electronic excitations. We report the synthesis of helical polymers with a rigid square structure based on spiro-linked ladder-type pentaphenyl units. The variation of circular dichroism with increasing chain length provides direct evidence for delocalization of electronic excitations over at least 10 monomeric units. The change in the degree of circular polarization of the fluorescence across the vibronic side bands shows that vibrational motion can localize the excitation dynamically to almost one single unit through breakdown of the Born-Oppenheimer approximation. The dynamic conversion between delocalized and localized excited states provides a new paradigm for interpreting circular dichroism in helical polymers such as proteins and polynucleic acids.

Circularly Polarized Light Probes Excited‐State Delocalization in Rectangular Ladder‐type Pentaphenyl Helices

AbstractLadder‐type pentaphenyl chromophores have a rigid, planar π‐system and show bright fluorescence featuring pronounced vibrational structure. Such moieties are ideal for studying interchromophoric interactions and delocalization of electronic excitations. We report the synthesis of helical polymers with a rigid square structure based on spiro‐linked ladder‐type pentaphenyl units. The variation of circular dichroism with increasing chain length provides direct evidence for delocalization of electronic excitations over at least 10 monomeric units. The change in the degree of circular polarization of the fluorescence across the vibronic side bands shows that vibrational motion can localize the excitation dynamically to almost one single unit through breakdown of the Born‐Oppenheimer approximation. The dynamic conversion between delocalized and localized excited states provides a new paradigm for interpreting circular dichroism in helical polymers such as proteins and polynucleic acids.

Photonic Integrated Frequency Shifter Based on Double Side Band Modulation: Performance Analysis

In this research, we present an analysis of a photonic integrated frequency shifter as a stage for a THz dual comb generator. We studied the performance of the PIC by simulating it with standard building blocks, and aimed toward an improvement of the output signal quality. We revised two approaches of the PIC by simulating two modes of generating a double side band modulation suppressed carrier (DSB-SC) with a Mach Zehnder modulator structure (MZM). One approach was using a single Electro-Optic Phase Modulator (EOPM) on an MZM structure (SE-MZM), and the other one was using Double EOPM (DE-MZM). We found a cleaner spectrum with the DE-MZM, since this structure is usually applied to reduce the chirp effect in optical communication systems. We obtained 23 dB of side mode suppression ratio SMSR with one filter, and 44 dB of SMSR with a two-stage filter. In the case of DE-MZM, we obtained a clean tone on intermediate frequency (IF) free of spurious sidebands and comb in IF frequency with 10 dB more power compared to SE-MZM.

Continuous Variable Entanglement in an Optical Parametric Oscillator Based on a Nondegenerate Four Wave Mixing Process in Hot Alkali Atoms.

We present the measurement of entanglement between twin beams generated with a doubly resonant optical parameter oscillator (OPO) based on four-wave mixing in hot ^{85}Rb vapor above threshold. This is the first measurement of entanglement in an OPO with a χ^{(3)} media above threshold. We reconstruct the covariance matrix for several configurations and based on a full picture of the four side band mode state, we study entanglement between all possible bipartitions. We show a robust generation of entanglement with stronger generation for a specific pair of modes. For this system, we show that atomic density is a determinant factor for the generation and loss of quantum correlations. The generation of entangled fields with an atomic OPO operating close to atomic resonance of alkali atoms enables a natural integration into quantum networks.

Sonotriboluminescence of aqueous suspensions of ZnS and Tb(acac)3·H2O crystals

Intense sonotriboluminescence was found under sonication on aqueous suspensions of ZnS and Tb(acac)3·H2O crystals. These materials with intense triboluminescence are basic for many other luminescent applications, but their sonotriboluminescence in aqueous suspensions was still not studied. A broad band with a maximum at 470 nm and a side band at around 540 nm were observed in the sonotriboluminescence spectrum of zinc sulfide suspension. An intense emission of the Tb3+ ion was recorded with maxima at 488, 544, and 585 nm for a suspension of terbium acetylacetonate. These sonotriboluminescence spectra coincide with the photoluminescence spectra of crystals. The sonication on aqueous suspensions leads to fragmentation and increases the active surface, the defects in the crystals involved into the luminescence excitation. It is shown that emission intensity during sonotriboluminescence of Tb(acac)3·H2O suspensions is 400 times higher than that during sonoluminescence of terbium salts aqueous solutions. A possible mechanism for the excitation of sonotriboluminescence of zinc sulfide and terbium acetylacetonate aqueous suspensions is discussed. Obviously, the excitation of emitters under sonication of aqueous suspensions occurs during recombination of charges in crystals electrified upon their high-speed collisions. The sonotriboluminescence can be useful for developing a spectroscopic method qualitatively monitor suspensions.

Incoherent Rayleigh Scattering Noise Depression for Single Laser Stable Radio Frequency Transmission

The stable radio frequency (RF) transmission scheme involving single wavelength has received increasing attention due to the feature of accurate phase information extraction. However in single laser system, the single side band (SSB) phase noise of output signal will be deteriorated by Rayleigh scattering during long-distance optical transmission. In this work, we propose an incoherent Rayleigh scattering noise depression method in the passive phase compensation stable RF transmission scheme with single laser. The carrier of scattering light is suppressed with narrow-band optical filter based on the Stimulated Brillouin scattering (SBS) effect, so that the noise generated by the beat of scattering itself will be significantly reduced. As a result, a 5-GHz RF signal stability transmission over 50-km single mode fiber is demonstrated experimentally. The SSB phase noise at 10 KHz offset is 10.9 dB lower than the scenarios without incoherent Rayleigh scattering noise depression. Meanwhile, the phase jitter mean square error is 1.12 ps during <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 10^{4}$ </tex-math></inline-formula> seconds.

Suppression of Four Wave Mixing Effects Under Different Spectrally Efficient Modulation Techniques in Hybrid DWDM-OTDM Systems

Next generation optical networks require high spectral efficiency to meet the demand of high bandwidth for ultra-long haul communication. Spectrally efficient modulations using hybrid DWDM-OTDM systems can be used to achieve this. However, fiber nonlinearities such as four-wave mixing (FWM) will increase simultaneously and this will degrade the performance of WDM optical system. This paper explores the FWM reduction in 32 channels, 40 Gb/s hybrid DWDM-OTDM network using RZ-OOK, 16-QAM and PDM-QPSK modulation format at 200 GHz and 100 GHz channel spacing. Optical received power, BER, Q- factor, eye diagram and FWM side band power are analyzed at -15dBm to +15dBm channel power. All these modulations have shown a significant reduction in FWM. In addition, the 16-QAM gives highest reduction in FWM along with least BER of 7.9×10−158 and maximum Q-value of 27.74.

A rapid, simple, and reliable assay to authenticate Peruvian kiwicha (A. caudatus) for food applications

Amaranth has acquired great economic impact as functional food, with species originating from Mexico dominating global trade. In contrast, the Peruvian A. caudatus (kiwicha) has been vastly neglected, although it is endowed with very promising nutritive traits. Morphological plasticity and taxonomic ambiguities render authentication of Amaranth difficult, such that the identity of commercial samples is often unclear. To safeguard the authenticity of kiwicha and, thus, consumer safety, we characterised a germplasm collection of 84 Amaranth accessions on both, the morphological and the genetic level. We show that kiwicha can be delineated phenotypically from other species by its late flowering, taller posture, and lower grain yields. Instead, flower and seed color, often used as proxy for identity, do not qualify as taxonomic markers. Using the plastidic barcoding marker psbA-trnH igs we were able to identify a specific Single Nucleotide Polymorphism (SNP) that separated kiwicha from all other species of Amaranth. This allowed us to develop a sequencing-free authentication assay using an Amplified Refractory Mutation System (ARMS) strategy. As a result kiwicha in commercial samples can be authenticated by a single duplex-PCR yielding a diagnostic side band reporting A. caudatus against all other species of Amaranthus. This fingerprinting assay will help to develop the nutritive potential of kiwicha and to safeguard seed material for A. caudatus against adulteration by the far more prevalent species from Mexico.

Accurate extraction of the +1 term spectrum with spurious spectrum elimination in off-axis digital holography.

In off-axis digital holography, spatial filtering is a key problem limiting the quality of reconstructed image, especially in the case of spurious spectrum generated by coherent noise in the hologram spectrum. In this paper, a new spatial filtering method with spurious spectrum elimination is proposed. Side band centering judgment is firstly implemented to locate the center point of the +1 term in the hologram spectrum. Then by roughly recognizing the region of +1 term spectrum, most of the -1 term, 0 term and the spurious spectral components are eliminated. Finally, Butterworth filtering is performed to extract the +1 term spectrum as enough as possible without introducing the spurious spectrum. Simulated hologram of E-shaped specimen with the spurious spectrum is generated to evaluate the performance of the proposed method. Experimental data of USAF 1951 resolution target, ovarian slice and microlens array are adopted to verify the effectiveness of the proposed method. Simulation and experimental results demonstrated that the proposed method is able to accurately extract the +1 term spectrum with spurious spectrum elimination and achieve a relatively good balance between the structural detail characterization and noise suppression.

Probing topological Floquet states in WSe2 using circular dichroism in time- and angle-resolved photoemission spectroscopy

Observing signatures of light-induced topological Floquet states in materials has been shown to be very challenging. Angle-resolved photoemission spectroscopy (ARPES) is well suited for the investigation of Floquet physics, as it allows to directly probe the dressed electronic states of driven solids. Depending on the system, scattering and decoherence can play an important role, hampering the emergence of Floquet states. Another challenge is to disentangle Floquet side bands from laser-assisted photoemission (LAPE), since both lead to similar signatures in ARPES spectra. Here, we investigate the emergence of Floquet state in the transition metal dichalcogenide 2H-WSe2, one of the most promising systems for observing Floquet physics. We discuss how the topological Floquet state manifests in characteristic features in the circular dichroism in photoelectron angular distributions (CDAD) that is determined by the transient band structure modifications and the associated texture of the orbital angular momentum. Combining highly accurate modeling of the photoemission matrix elements with an ab initio description of the light-matter interaction, we investigate regimes which can be realized in current state-of-the-art experimental setups. The predicted features are robust against scattering effects and are expected to be observed in forthcoming experiments.

Luminescence, spectroscopic properties and reddish-orange emission from Eu3+ ion doped tellurite and fluorotellurite glasses: A comparative study

In this study, the properties of tellurite (TeEu) glass and fluorotellurite (FTeEu) were compared with the addition of 2 mol% of europium. The chemical compositions of the samples were prepared by two formulars: 53TeO2-10ZnO-35BaO-2Eu2O3 (TeEu) and 53TeO2-10ZnF2-35BaO-2Eu2O3 (FTeEu) which were prepared by glass casting technique. The results showed that the molar volume and refractive index of the FTeEu sample were higher than TeEu, with values 29.0553 cm3/mol and 1.806, respectively. Measuring the UV–VIS–NIR absorption spectra with a proven measured in air atmosphere in the range of 200–2500 nm demonstrated an extension of intensity of absorption bands with ZnF2 contents increased. The spectroscopic studies consisted of two main themes: Judd-Ofelt and phonon side-band analyses. The results of the Phonon Side Band (PSB) spectral assays associated with the 7F0→5D2 transition of the Eu3+ ion showed that the phonon energy of the FTeEu sample was lower than TeEu, with value 667 cm−1. The relationship of the JO intensity parameter of the FTeEu sample is on the Ω2 > Ω4 > Ω6. The decay time and CIE coordinates, had calculated for prepared glass samples. In view of the results of our study, the FTeEu samples is a more suitable choice for reddish -orange laser materials, telecommunication applications and optical device applications.

Temporal Spinodal Decomposition of the Fe1+yTe1−xSex Crystals and its Impact on Superconducting Properties

Precipitated phases, formed by spinodal decomposition during long‐term storage in a desiccator in dry atmosphere, are found with the X‐ray diffraction (XRD) study of Fe1+y Te1−x Se x crystals. Their compositions are deduced from the position of satellite Bragg reflections in the XRD pattern. In particular, in the Fe1.19Te0.58Se0.42 crystal, traces of phases with significantly higher tellurium content, namely Fe1+y Te0.9Se0.1 and FeTe, are found. The detection and analysis of side bands in the diffraction pattern of an aged crystal indicate spinodal decay. It leads to the formation of a modulated structure in the entire volume of the sample and to strain in the crystal structure. In turn, this results in a significant improvement in the superconducting characteristics. Specifically, the resistive transition narrows to 2 K at the onset temperature 14.5 K, and the superconducting volume fraction increases up to about 100%.

Spectral Efficiency Improvement Techniques in OFDM and UFMC

Abstract: This article describes about to analyse the spectral efficiency of different modulation techniques in OFDM and UFMC. UFMC is a multi-carrier modulation technique in fifth generation network (5G). In this paper, we review the different modulation techniques in 5G technology and motivate the need of UFMC technique in 5G wireless communication. In 4G OFDM modulation technique, some drawbacks like side band leakages, high Peak to Average Power ratio (PAPR) and spectrum utilization degrades the performance of the system. Another multi carrier technique called Filter Bank Multi carrier (FBMC) which is better than OFDM, have some issues in practical aspects. So by considering the above parameters a move to another technique called Universal Filtered Multi Carrier (UFMC) is used because of good spectrum usage. This paper also explains about the UFMC system model. Based on the Simulation results in MATLAB, the spectrum utilization of UFMC system is much better than OFDM system. Keywords: UFMC, OFDM, 5G, IFFT, FFT, DAC, ADC and Spectrum efficiency.