Frequency Doubling Research Articles

Parametric resonance brain model

The paper introduces a parametric resonance model for characterizing some features of the brain’s electrical activity. This activity is assumed to be a fundamental aspect of brain functionality underpinning functions from basic sensory processing to complex cognitive operations such as memory, reasoning, and emotion. A pivotal element of the proposed parametric model is neuron synchronization which is crucial for generating detectable brain waves. The analysis of the frequency content of brain waves, categorized as delta (0÷4 Hz), theta (4÷7 Hz), alpha (8÷12 Hz), beta (13÷30 Hz), and gamma (30÷100 Hz) reveals, notably, that the mean frequency of each of these brain wave classes is, in sequence, approximately the double of that of the previous one. Based on this observation, the proposed parametric resonance model suggests a cascade of amplification effects. Following the proposed model, in the transition from wakefulness to sleep, the brain wave bands are energized at double frequency by higher frequency neighboring bands; on the contrary, in the sleep to awake transition, brain waves are energized at a half frequency by their lower frequency neighbor waves. Finally, the trend of increasing amplitude values from higher to lower frequencies lends empirical support to the parametric resonant brain model validity.

Rolling bearing fault diagnosis method based on SSA-IWT-EMD

Aiming at the problem of insufficient wavelet threshold noise reduction and unclear extraction of characteristic frequency of EMD decomposition, a rolling bearing fault diagnosis method based on SSA-IWT-EMD is proposed. Two adjustment factors are introduced to propose an improved threshold function (IWT), which overcomes the shortcomings of traditional soft and hard thresholds, and the sparrow search optimization algorithm (SSA) is used to globally optimize its parameters to achieve rolling bearing signal noise reduction. A comprehensive index P is proposed to select and reconstruct the components generated by empirical mode decomposition (EMD) to highlight the fault characteristic information of the signal. Envelope spectrum analysis is used to realize bearing fault diagnosis. Simulation and measurement results verify the effectiveness of the proposed method; at the same time, compared with the method of selecting components with a single index and the literature method, it is shown that the comprehensive index P and the proposed method have stronger noise reduction and feature extraction capabilities, and the envelope spectrum amplitude and frequency doubling components are more obvious, which can better realize the fault diagnosis of rolling bearings.

Evaluation of Accessory Infraorbital Foramen with Cone Beam Computed Tomography

Objective: to assess the incidence, number and position of accessory infraorbital foramina (AIOF) according to cone beam computed tomography (CBCT).Material and methods. CBCT data from 156 patients who received dental care at a private medical center in Minsk (The Republic of Belarus) in 2018–2023 were analyzed.Results. In 29 (18.6%) patients, 38 AIOF were found. Unilateral doubling of the infraorbital foramen was more common than bilateral (21 patients compared to 8). In 1 case, the presence of two AIOF simultaneously on one side was noted. They were located medial and superior relative to the main infraorbital foramen at a distance 3.73–14.5 mm from it. In 2 of 13 patients with simultaneously visualized upper and lower jaws, an accessory mental foramen was found on the AIOF side. AIOF were more often identified on the left side (p<0.05); no gender differences in their occurrence were detected.Conclusion. The obtained results demonstrate a high frequency of infraorbital foramen doubling. To increase the effectiveness of surgical manipulations in the middle third of the face and prevent iatrogenic neurological complications, it is recommended to conduct a preoperative CBCT to clarify the localization of the main and accessory infraorbital foramina.

Retinal Function in Young Adults Following Topical Application of Levodopa to the Eye.

Levodopa has been investigated as a therapeutic solution for ocular disorders involving dysregulation of the dopaminergic system, especially in the context of myopia. However, given the critical role dopamine plays in normal vision, this phase I trial examined whether levodopa/carbidopa eye drops induce any regional changes in retinal structure and function. Twenty-nine healthy male subjects 18 to 30 years of age were randomly assigned to receive either a low (1.4/0.34 µmoles/day, n = 14) or high (2.7/0.68 µmoles/day, n = 15) dose of levodopa/carbidopa eye drops in 1 eye for 28 consecutive days. A placebo solution was applied to all fellow eyes. Measures included visual acuity, regional frequency doubling perimetry, regional multifocal electroretinogram (mfERG) and optical coherence tomography (retinal thickness). Outcome measures were undertaken at baseline, end-of-treatment (4 weeks), and at a follow-up (4 months post-treatment). For low dose treated eyes, regional analysis showed a small, statistically significant change in mfERG recordings (increase in ring 5 amplitude in low dose treated eyes, P < 0.05) and the retinal thickness map (localized retinal thinning in low dose treated eyes, P < 0.05). These changes were not clinically significant. No significant changes were observed in high dose treated eyes. Pharmacokinetic analysis (rabbits) demonstrated that levodopa was not detectable within blood and peaked within the eye at 15 to 30 minutes (and eliminated within 4 hours). No clinically significant effects of levodopa/carbidopa eye drops were found with regard to normal retinal structure and function following short-term use. This study further demonstrates the safety of topical levodopa, which may support its use in the treatment of ocular disorders in which the dopamine system is dysregulated.

Design and Implementation of a Ka-Band Frequency Source Based on DS+DDS Hybrid Method

Abstract This article proposes a design scheme for a broadband agile frequency conversion Ka-band frequency source, which adopts a mixed frequency synthesis method of DS+DDS. This method combines the advantages of DDS such as fast frequency switching speed, small frequency step, and wide DS frequency bandwidth, and uses segmented filtering to effectively suppress the disadvantage of DDS spurious error. DS adopts an up conversion and double frequency doubling scheme to broaden the frequency band, with simple design and low cost. The deterioration of phase noise is offset by selecting a low phase noise PLL. Actual measurement shows that the output bandwidth of the frequency source is 8GHz, with spurious suppression ≤ −61dBc, frequency switching time ≤ 140ns, output power ≥ 15dBm, step frequency of 1MHz, and phase noise ≤ −100dBc/Hz@1kHz, meet the design requirements.

Fractional Talbot Lithography for Predesigned Large-Area Liquid-Crystal Alignment

To address the increasing demands for cost-effective, large-area, and precisely patterned alignment of liquid crystals, a fractional Talbot lithography alignment technique was proposed. A light intensity distribution with a double spatial frequency of a photomask could be achieved based on the fractional Talbot effect, which not only enhanced the resolution of lithography but also slashed system costs with remarkable efficiency. To verify the feasibility of the alignment method, we prepared a one-dimensional polymer grating as an alignment layer. A uniform alignment over a large area was achieved thanks to the perfect periodicity and groove depth of several hundred nanometers. The anchoring energy of the alignment layer was 1.82 × 10−4 J/m2, measured using the twist balance method, which surpassed that of conventional rubbing alignment. Furthermore, to demonstrate its ability for non-uniform alignment, we prepared polymer concentric rings as an alignment layer, resulting in a liquid-crystal q-plate with q = 1 and α0 = π/2. This device, with a wide tuning range (phase retardation of ~6π @ 633 nm for 0 to 5 V), was used to generate special optical fields. The results demonstrate that this approach allows for the uniform large-area orientation of liquid-crystal molecules with superior anchoring energy and customizable patterned alignment, which has extensive application value in liquid-crystal displays, generating special optical fields and intricate liquid-crystal topological defects over a large area.

Growth, optical and thermal properties of YbxSm1-xCa4O(BO3)3 crystals

YbxSm1-xCOB (x = 0.1, 0.2) crystals were grown by the Bridgman method for the first time. The purpose of this paper is to evaluate the application prospect of Yb:SmCOB crystal in quasi-parametric chirped pulse amplification (QPCPA) and frequency-doubling laser. The phase structure, thermal properties and optical properties of Yb:SmCOB were studied, and the density of states of SmCOB crystal was calculated by first-principles. The effective segregation coefficient Keff of Yb0.1Sm0.9COB and Yb0.2Sm0.8COB crystals are 0.89 and 0.88, respectively. The thermal diffusivity and thermal conductivity of Yb:SmCOB decrease with increasing temperature. The specific heat increases with the increase of temperature and eventually tends to be constant. The specific heat of Yb:SmCOB crystal is greater than 0.70 J/(g·K) at room temperature. The transmittance of Yb:SmCOB crystal reaches 87 % in the range of 500 ∼ 900 nm. With the increase of Yb3+ doping concentration, the UV absorption cut-off edge is red shifted. The frequency doubling emission peak of Yb:SmCOB crystal at 490 nm was measured by 980 nm laser. Yb:SmCOB has the characteristics of high transmittance and high specific heat, and has application potential in laser frequency doubling and QPCPA.

Prevalence of glaucoma in Canada: results from the 2016–2019 Canadian Health Measures Survey

ObjectiveTo estimate the prevalence of glaucoma in Canada based on self-reports and test data, including Frequency Doubling Technology Perimetry (FDT), optic nerve vertical cup-to-disc ratio (CDR), intraocular pressure (IOP), and use of glaucoma medications. DesignCross-sectional survey. Participants2,600–4,100 participants aged 40–79 in the Canadian Health Measures Survey 2016–2019 with available information from self-report, CDR, FDT, and IOP. MethodsGlaucoma was defined by self-reports, CDR ≥ 0.7 only, or failed FDT only. Incorporating results of CDR, FDT, IOP, and use of glaucoma medications, participants were further classified as definite glaucoma (failed FDT and CDR ≥ 0.7) or glaucoma suspects (CDR ≥ 0.7 only, failed FDT only, or IOP > 21 mmHg only, or “normal” values of FDT, CDR, and IOP but used glaucoma medications). Survey weights were used in analyses. ResultsThe glaucoma prevalence was 2.5% (95% confidence interval [CI] 1.7%–3.3%) utilizing self-reports, 3.0% (95% CI 2.1%–3.9%) by CDR ≥ 0.7 only and 10.3% (7.8%–12.8%) with failed FDT only. Merging test data, the prevalence of definite glaucoma was 0.7% (95% CI 0.3%–1.1%) and the prevalence of suspected glaucoma was 16.3% (95% CI 13.2%–19.4%). Among the patients suspected of having glaucoma, 44.4% had ocular hypertension (OHT, mean IOP 22.8 mmHg) and 6.8% used glaucoma medications. IOP ≥28 mmHg was found in 2.4% of OHT individuals, and none used glaucoma medications.37.5% of Canadians with definite glaucoma were unaware they had glaucoma. ConclusionsGlaucoma prevalence in Canadians aged 40–79 varied between 0.7% and 10.3% depending on definition used. 16.3% of Canadians were labeled “glaucoma suspects”. Nearly 40% of Canadians with definite glaucoma were unaware of having glaucoma.

Design and simulation of a Ka-band frequency doubling gyroklystron amplifier

The design methodology of a Ka-band frequency doubling two cavity gyroklystron has been discussed in this paper. In this study, the amplifier’s design and simulation are accomplished by employing nonlinear analysis and validated using particle-in-cell simulation techniques. The output cavity functions in the TE02 mode at two times the input signal frequency at the second harmonic of the cyclotron frequency, while the input cavity is powered by a 17.5 GHz source and functions in the TE01 mode at the first harmonic of the cyclotron resonance. The device’s performance has been examined both in the presence and in the absence of a beam. A number of factors were taken into account in order to optimize the interaction structure dimension to reach the device’s targeted performance. By adjusting the structural features and electron beam parameters, the device’s RF output power is assessed in an effort to increase efficiency. Simulation results estimate that the device displays a gain of 21.5 dB, an efficiency of 21.6%, a power of 227 kW, and a −3 dB bandwidth of ∼0.3%.

Layered heterogeneous structures integrated device for multiplication, division arithmetic unit and multiple-physical sensing

A layered heterogeneous structure (LHS), consisting of silver, liquid crystal, and nonlinear dielectric layers, is proposed to realize functions of computing and sensing. By leveraging the optical Tamm state, the intrinsic absorption principle of liquid crystal, and nonlinear effects, the design of an integrated device capable of passive multiplication and division operations, along with high-performance multi-physical quantity sensing functionalities, is achieved. The given LHS exhibits Janus properties, with different physical functions manifested depending on the direction of electromagnetic wave (EW) propagation. During forward propagation of EWs, the LHS displays high and sharp absorptivity peaks at 774.8 and 1517.6 nm. The relationship between the two peaks approximates a frequency multiplication factor of 1.960, enabling signal multiplication. Furthermore, the two absorptivity peaks at different wavelengths facilitate the sensing of serum creatinine solution concentration and external pressure, with sensitivity (S), quality factors (Q), and figure of merit (FOM) of 266.76 μmol L−1/nm and 213.33 GPa/nm, as well as 248.76 and 348.22, 84.1 L (μmol)−1 and 49.06 GPa−1, respectively. During backward propagation of EWs, absorptivity peaks with distinct resolutions are observed at 1423 and 2809 nm, with a multiple relationship between them of 1.974, enabling frequency doubling for signal division. Additionally, the absorptivity curve facilitates temperature sensing over a wide range from 257 to 347 K. Owing to the unique temperature S of liquid crystal, different sensitivities and resolutions are observed at 257 to 297 K and 307 to 347 K, with S of 1.015 and 0.686 K/nm, and corresponding Q and FOM of 21.57 and 12.576, 0.076 K−1 and 0.003 04 K−1, respectively.

Predicting the potential global distribution of Ixodes pacificus under climate change.

In order to predict the global potential distribution range of Ixodes pacificus (I. pacificus) under different climate scenario models in the future, analyze the major climate factors affecting its distribution, and provide references for the transformation of passive vector surveillance into active vector surveillance, the maximum entropy model (MaxEnt) was used in this study to estimate the global potential distribution range of I. pacificus under historical climate scenarios and different future climate scenarios. The global distribution data of I. pacificus were screened by ENMtools and ArcGIS 10.8 software, and a total of 563 distribution data of I. pacificus were obtained. Maxent 3.4.1 and R 4.0.3 were used to screen climate variables according to the contribution rate of environmental variables, knife cutting method and correlation analysis of variables. R 4.0.3 was used to calculate model regulation frequency doubling and feature combination to adjust MaxEnt parameters. The model results showed that the training omission rate was in good agreement with the theoretical omission rate, and the area under ROC curve (AUC) value of the model was 0.978. Among the included environmental variables, the Tmin2 (minimum temperature in February) and Prec1 (precipitation in January) contributed the most to the model, providing more effective information for the distribution of I. pacificus. MaxEnt model revealed that the distribution range of I. pacificus was dynamically changing. The main potential suitable areas are distributed in North America, South America, Europe, Oceania and Asia. Under the future climate scenario model, the potential suitable areas show a downward trend, but the countries and regions ieeeeeeenvolved in the suitable areas do not change much. Therefore, the invasion risk of the potential suitable area of I. pacificus should be paid attention to.

Investigation into NSAW excitation and modulation utilizing the grating mask technique

Narrowband surface acoustic wave (NSAW) method is a promising ultrasonic detection technique, with its laser-induced excitation technology offering the advantages of non-contact and flexible regulation. This paper proposes an NSAW excitation and modulation system based on the grating mask method to detect the nonlinear characteristics of the spectra caused by the variation in material surface properties. According to Doyer’s sharp line excitation theory, a strip line source array excitation model formed by superposition principle is established, and the effects of duty ratios of the masks on NSAW spectra amplitude characteristics are interpreted. An NSAW excitation and B-scan experimental system that can realize line source spacing changes is developed, and the effects of cylindrical lens height and masks with different duty ratios on NSAW spectra modulation are studied. The experimental results show that the amplitude ratios (the ratio of the double frequency amplitude to the second harmonic amplitude) are consistent with the results of the Doyer superimposed strip line source array excitation model in which the excitation light source energy is evenly distributed. The second-order nonlinear coefficients extracted from the experimental spectra can effectively characterize the surface properties of 6061 aluminum alloy at different annealing temperatures.

A 60 GHz low phase noise VCO with second harmonic tail extraction in 40-nm CMOS

This work presents a 60 GHz continuously adjustable mm-wave cross-coupled voltage − controlled oscillator (VCO) utilizing an innovative frequency doubling technique in 40 nm CMOS technology. The extraction of the second harmonic is performed through a transformer from the tail of the 30 GHz fundamental VCO. The primary side of the transformer serves a dual purpose, functioning both as a filter for the second harmonic and as a balun simultaneously. The circuit incorporates a MOS varactor along with a four-bit binary weighed capacitor bank to achieve coarse and fine frequency tuning respectively. Post Layout simulation results indicate that the VCO spans a broad tuning range of 12.3 GHz, covering frequencies from 52.7 to 64.98 GHz. Phase noise (PN) remains below −96.3 dBc/Hz at a 1 MHz frequency offset within all bands Power consumption, including the output stage, is 21.8 mW from a 1.1-Volt supply. The VCO provides more than −13 dBm output power in all frequency bands and occupies a chip area of 0.53 mm2.

A wavelength analyzer using laser self-mixing interferometry

In this paper, we propose a simple yet effective method to measure the operating wavelength of a laser using laser self-mixing interferometry (SMI). Analyzing the self-mixing interference signals acquired from external objects with known motion patterns allows us to deduce the laser's operating wavelength. To validate the accuracy of our method further, we constructed a laser self-mixing linear motion sensing system. This system captured the self-mixing interference signals generated as external targets moved at a uniform linear velocity under various laser wavelengths. By conducting FFT analysis, we obtained the signal frequency, which was then converted from laser Doppler frequency to optical frequency, ultimately determining the laser's wavelength. Our experiment specifically focused on analyzing the impact of frequency doubling on the results, discussing its causes and potential solutions. Numerical analysis indicates that the laser's working wavelength parameter is precisely measured from external targets moving at a uniform speed of 0.4 to 2.4 mm/s. Additionally, the experimental results show a absolute error of less than 1.230 nm and an relative error of less than 0.12 %. In conclusion, our experimental, simulation, and theoretical analysis results mutually validate each other, confirming the accuracy and practicality of the measurement method.

Heat extremes linearly shift with global warming, with frequency doubling per decade since 1979

Abstract Heat extremes have been increasing both in frequency and in intensity in most land regions of the world, and this increase has been attributed to human activities. In the last decade, many outstanding and record shattering heat extremes have occurred worldwide, triggering fears of a nonlinear behaviour or an “acceleration” in the development of heat conditions, considering the warming level when the event occurred. Here we show that the evolution of yearly temperature maxima, with return periods above 10 years, consistently shifts with global temperatures and does not significantly depart from this behaviour in recent years or decades when considered globally or at the scale of continents. This result is obtained by using a classical statistical event attribution technique, where the assumption that the distribution of block-maxima extremes linearly shifts with global warming is tested across years and world land regions. However, the pace of frequency change is large, with the probability of heat extremes exponentially rising and nearly doubling every decade since 1979, particularly when considering events with a return period of about 10 to 50 years in 2000. This makes the climate of a decade ago unrepresentative of today’s climate. Our results overall mean that we do not expect events like the recent outstanding extremes to undergo nonlinear changes, despite fast changes. They also show that assumptions underlying attribution techniques used in many recent studies are consistent with recent temperature trends.&amp;#xD;

Harmonic Light Scattering to Study Supramolecular Assembly Processes

Characterization of complex dynamical processes such as supramolecular aggregation, (electro)chemical reactions or phase transitions, requires in-situ measurement techniques to provide insight into morphology changes, symmetry changes, concentration, or phase changes during the process. Currently available techniques are often not sensitive to all these aspects or too slow for in-situ studies. Instead, very fast and sensitive techniques are needed. Recently, we developed a method based on second-and third harmonic scattering that partially satisfies these requirements (1-3).Second-harmonic scattering is a nonlinear scattering process in which two incident photons of frequency ω are annihilated to create a new photon at the double frequency 2ω. It is a very sensitive tool to study dynamical processes since it is fast, sensitive to the symmetry of the scatterer and extremely sensitive to aggregation.For molecular scatterers, the intensity of the scattered second-harmonic light I2ω is given by:I2ω ∼ N<β2> Iω 2 With N the number scatterers, β the first hyperpolarizability, Iω the intensity of the incident light and < > refers to orientational averaging. Information about the point group symmetry of the scatterer can be inferred by analyzing the polarization components of the scattered light. For aggregated or correlated scatterers I2ω is given by: I2ω ∼ N'<(Mf(β))2> Iω 2 with N’ the number of scatterers, M the number of molecules in each aggregate, and f(β) a combination of molecular hyperpolarizability components. Also in this case, an analysis of the polarization components of the scattered light will yield information about the symmetry of the aggregated scatterers.Similar formula’s hold for third harmonic scattering where part of the incident light at frequency ω is scattered at the triple frequency 3ω . For molecular scatterers I3ω is given by I3 ω ∼ N<γ2> Iω 3 and for correlated scattersI3 ω ∼ N'<(Mf(γ))2> Iω 3 with γ the second hyperpolarizability.While both techniques may seem similar, there is an important difference: the symmetry selection rules are very different. Second-harmonic scattering is only allowed if the scatterer is non centrosymmetric, while third-harmonic scattering does not have any symmetry constraints. As such, both techniques are highly complementary. The combination of both, referred to as harmonic scattering, has been used as a very versatile method to study in-situ supramolecular aggregation of macrocycles and conjugated polymers with the ability to completely unravel the nucleation and aggregation dynamics.Now, we have extended this measurement platform to also include multi-photon fluorescence, linear light scattering, UV/Vis absorption and optical rotation. Hence, in total we can monitor 6 observables for any dynamical process in-situ. Several examples will be given on how this methodology can provide new insights in the mechanism and dynamics of supramolecular aggregation processes.References1) Moris, M. et al., Harmonic light scattering study reveals structured clusters upon the supramolecular aggregation of regioregular poly(3-alkylthiophene). COMMUNICATIONS CHEMISTRY, 2, Art.No. ARTN 130 (2019).2) Hattori, S., et al. Vortex-Induced Harmonic Light Scattering of Porphyrin J-Aggregates. JOURNAL OF PHYSICAL CHEMISTRY B, 125 (10), 2690-2695 (2021)3) Dok, A.R., et al. Nonlinear optical probes of nucleation and crystal growth: recent progress and future prospects. JOURNAL OF MATERIALS CHEMISTRY C, 9 (35), 11553-11568 (2021).

Comparison of Glaucoma Detection Performance of Binocular Perimetry Screening Program Using imo Perimetry With Frequency Doubling Technology.

We aimed to preliminarily compare the glaucoma detection accuracy of a head-mounted binocular visual perimeter "imo" screening program (ISP) with that of frequency doubling technology (FDT). This multicenter, diagnostic accuracy study based on prospectively collected data included 76 non-glaucoma (including pre-perimetric glaucoma) eyes and 92 glaucomatous eyes from patients visiting two hospitals. Patients underwent ISP and FDT (C-20-1 screening program) on the same day. Diagnostic efficacy was evaluated using receiver operating characteristic curves and areas under the curve (AUCs). In addition, we compared the ISP and FDT testing times. AUC values for ISP versus FDT were as follows: (1) mild-stage glaucoma (mean deviation [MD] > -6 dB), 0.82 (95% confidence interval [CI], 0.75-0.88) versus 0.76 (95% CI, 0.68-0.83); moderate-stage glaucoma (-6 dB ≥ MD ≥ -12 dB), 0.98 (95% CI, 0.95-1.00) versus 0.96 (95% CI, 0.93-1.00); and advanced-stage glaucoma (-12 dB > MD), 1.00 (95% CI, 1.00-1.00) versus 0.99 (95% CI, 0.98-1.00). In addition, mild-stage glaucoma was classified into two stages (MD > -3D) and (-3D ≥ MD > -6D). AUC values were 0.81 (95% CI, 0.73-0.88) versus 0.76 (95% CI, 0.68-0.84) for MD > -3D and 0.86 (95% CI, 0.77-0.94) versus 0.73 (95% CI, 0.61-0.86) for -3D ≥ MD > -6D. The testing time for the ISP was significantly shorter than that of FDT for all glaucoma stages (P < 0.001). The ISP demonstrates non-inferiority in detecting glaucoma and has a shorter testing time compared with FDT. These findings provide evidence for applied further studies on large-scale population-based glaucoma screening. Our study provides a non-inferior and quicker glaucoma screening than existing tools.

Growth, spectroscopic, thermal and laser frequency doubling properties of CTGAS crystal

A novel nonlinear optical crystal Ca3Ta(Ga0.7Al0.3)3Si2O14 (CTGAS) was successfully grown by the Czochralski method. The structural, spectroscopic and thermal properties have been systematically investigated, and the laser frequency doubling process has also been explored. Excellent thermal properties have been presented, such as moderate thermal conductivity, high specific heat, and low thermal expansion anisotropy. The electronic structure and optical properties have been investigated using the XPS technique and simultaneous assisted first-principles calculations. The optimal phase matching in type I (40.45°, 30.0°) and type II (64.73°, 0°) orientations were determined, frequency-doubling output was achieved in type I and type II, with laser energies of up to 10.04 mJ and 10.14 mJ obtained @ 532 nm, and optical-to-optical conversion efficiencies of 14.04 % and 17.21 %, respectively. The experimental findings demonstrate the great potential of CTGAS crystal as a frequency-doubling material.

Strongly coupled edge states in a graphene quantum Hall interferometer

Electronic interferometers using the chiral, one-dimensional (1D) edge channels of the quantum Hall effect (QHE) can demonstrate a wealth of fundamental phenomena. The recent observation of phase jumps in a Fabry-Pérot (FP) interferometer revealed anyonic quasiparticle exchange statistics in the fractional QHE. When multiple integer edge channels are involved, FP interferometers have exhibited anomalous Aharonov-Bohm (AB) interference frequency doubling, suggesting putative pairing of electrons into 2e\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\boldsymbol{2}}}{{\\boldsymbol{e}}}$$\\end{document} quasiparticles. Here, we use a highly tunable graphene-based QHE FP interferometer to observe the connection between interference phase jumps and AB frequency doubling, unveiling how strong repulsive interaction between edge channels leads to the apparent pairing phenomena. By tuning electron density in-situ from filling factor ν<2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\boldsymbol{\ u }}} \\, < \\, {{\\boldsymbol{2}}}$$\\end{document} to ν>7\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\boldsymbol{\ u }}} \\, > \\, {{\\boldsymbol{7}}}$$\\end{document}, we tune the interaction strength and observe periodic interference phase jumps leading to AB frequency doubling. Our observations demonstrate that the combination of repulsive interaction between the spin-split ν=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\boldsymbol{\ u }}}={{\\boldsymbol{2}}}$$\\end{document} edge channels and charge quantization is sufficient to explain the frequency doubling, through a near-perfect charge screening between the localized and extended edge channels. Our results show that interferometers are sensitive probes of microscopic interactions and enable future experiments studying correlated electrons in 1D channels using density-tunable graphene.

On the Possibility of Multiplying the Frequency of a Gigawatt Ultrashort Microwave Pulse

It has been shown that the frequency of an ultrashort microwave pulse of a lowest axisymmetric electric mode at the interaction with a counterpropagating relativistic tubular electron beam under the cyclotron resonance conditions can be doubled due to re-emission into a mode having resonance at the second harmonic of the gyrofrequency. The conversion of the 3-cm 1-ns gigawatt microwave pulse in a circular waveguide from the TM01 mode to the TM02 mode with the doubling of the frequency, reduction of the duration to 0.22 ns, and the achievement of the peak power above the initial value has been demonstrated in a numerical experiment. The possibility of forming an intense ultrashort frontal splash of oscillations with the doubled frequency has been shown for longer initial pulses with a subnanosecond front.