8-nm narrowband photodetection in diamonds

Spectrally-selective photodetection plays a crucial role in various applications,including target imaging and environmental monitoring.Traditional deep-ultraviolet(DUV)narrowband photodetection systems consist of broadband photodetectors and filters,which complicates the architecture and constrains imaging quality.Here,we introduce an electronic-grade diamond single-crystal photodetector exhibiting an exceptionally narrow spectral response in the DUV range with a full width at half maximum of 8 nm.By examining diamond photodetectors with varying dislocation densities,we propose that mitigating the defect-induced trapping effect to achieve charge collection narrowing,assisted by free exciton radiative recombination,is an effective strategy for narrowband photodetection.The superior performance of this device is evidenced through the imaging of DUV light sources,showcasing its capability to differentiate between distinct light sources and monitor human-safe sterilization systems.Our findings underscore the promising potential applications of electronicgrade diamond in narrowband photodetection and offer a valuable technique for identifying electronic-grade diamond.

Esophageal early basaloid squamous carcinoma with unusual narrowband imaging magnified endoscopy findings

Basaloid squamous carcinoma(BSC)is a rare variant of esophageal cancer.There are very few reports of"early"BSC.Here we report a case of early BSC with unusual findings by narrowband imaging magnified endoscopy(NBI-ME).A 70-year-old man with a middle thoracic esophageal tumor was referred to our hospital.White-light endoscopy revealed a reddish depressed lesion 5 mm in diameter having a subepithelial tumor-like prominence with a gentle rising slope.NBI-ME revealed irregular loop-shaped microvessels coexistent with thick irregularly branched non-looped vessels.Iodine staining revealed a pale brown lesion.We performed endoscopic submucosal dissection for diagnostic treatment.Histologic examination showed the proliferation of basal cell-like hyperchromatic tumor cells in the lamina propria and with slight invasion into the submucosa at a depth of 320μm.The tumor cells formed solid nests and microcystic structures,containing an Alcian blue-positive mucoid matrix.The surface was covered with squamous epithelium without cellular atypia.Thin vessels were observed in the intra-epithelial papilla and thick vessels were observed around the solid nests beneath the epithelium.Based on these findings together,we diagnosed the lesion as BSC.In this case,the NBI-ME findings differed from those of typical squamous cell carcinoma in that both non-invasive cancer-like irregular loop-shaped microvessels coexisted with massively invasive cancerlike thick non-looped vessels.We speculate that the looped and non-looped vessels observed by NBI-ME histologically corresponded to thin vessels in the intraepithelial papilla and thick vessels around the tumor nests,respectively.These NBI-ME findings might be a feature of early esophageal BSC.

Multi-narrowband signals receiving method based on analog-to-information convertor and block sparsity

The analog-to-information convertor(AIC) is a successful practice of compressive sensing(CS) theory in the analog signal acquisition. This paper presents a multi-narrowband signals sampling and reconstruction model based on AIC and block sparsity. To overcome the practical problems, the block sparsity is divided into uniform block and non-uniform block situations, and the block restricted isometry property and sub-sampling limit in different situations are analyzed respectively in detail. Theoretical analysis proves that using the block sparsity in AIC can reduce the restricted isometric constant, increase the reconstruction probability and reduce the sub-sampling rate. Simulation results show that the proposed model can complete sub-sampling and reconstruction for multi-narrowband signals. This paper extends the application range of AIC from the finite information rate signal to the multi-narrowband signals by using the potential relevance of support sets. The proposed receiving model has low complexity and is easy to implement, which can promote the application of CS theory in the radar receiver to reduce the burden of analog-todigital convertor(ADC) and solve bandwidth limitations of ADC.

Improve the Nonparametric Image Segmentation with Narrowband Levelset and Fast Gauss Transformation

Nonparametric method based on the mutual information is an efficient technique for the image segmentation. In this method, the image is divided into the internal and external labeled regions, and the segmentation problem constrained by the total length of the region boundaries will be changed into the maximization of the mutual information between the region labels and the image pixel intensities. The maximization problem can be solved by deriving the associated gradient flows and the curve evolutions. One of the advantages for this method does not need to choose the segmentation parameter;another is not sensitive to the noise. By employing the narrowband levelset and Fast Gauss Transformation, the computation time is reduced clearly and the algorithm efficiency is greatly improved.

Motion compensation algorithm in narrowband imaging for mid-course targets

Imaging precession targets based on the narrowband radar to distinguish the real warhead from mid-course targets is a new technique in missile defense systems. Aiming at the typical mid-course flying scene, this paper describes the principle of the narrowband imaging method, and analyzes the influence on the narrowband imaging by the target translational motion. Then the precision qualification is deduced for both the distance compensation and the velocity compensation, and the conclusion that the velocity compensation is more appropriate for the motion compensation in the narrowband imaging is given. Furthermore, this paper proposes a motion compensation algorithm for the narrowband radar which reduces the interference of the signal phase chaos caused by the rebuilt real signal phase, thus realizing the precise translational motion compensation of the narrowband signal. Finally, the effectiveness of this method is proved by both theoretic analysis and experiment results.

Data-Aided Frequency Offset Estimation with Narrowband Interference

An algorithm for carrier frequency offset estimation with narrowband interference in burstmode transmissions is proposed.The algorithm is data-aided and has a feedforward structure that can be easily implemented digitally.The principle of the algorithm is based on a properly designed training sequence and an interpolation technique.Simulation results indicate that the estimation range is about ±20% of the symbol rate.The performance is satisfactory for a signal-to-noise ratio(SNR)as low as -13 dB and the mean square error(MSE)is approximately irrelevant to signal-to-interference ratio(SIR)values over -20 dB.

Narrowband perfect terahertz absorber based on polar-dielectrics metasurface

We theoretically propose a narrowband perfect absorber metasurface(PAMS) based on surface phonon polaritons in the terahertz range. The PAMS has unit cell consisting of a silver biarc on the top, a thin polar-dielectric in the middle and a silver layer at the bottom. The phonon polaritons are excited at the interface between the silver biarc and the polar dielectric, and enhance the absorption of the PAMS. The absorption peak is at 36.813 μm and the full width half maximum(FWHM) is nearly 36 nm, independent of the polarization and incidence angle. The electric fields are located at the split of the biarc silver layer and the quality factor Q is 1150. The FWHM decreases with the decreasing split width. When the thickness of the bottom layer is larger than 50 nm, the narrow band and high absorption are insensitive to the thickness of those layers. The designed absorber may have useful applications in terahertz spectra such as energy harvesting, thermal emitter, and sensing.

Therapeutic Comparison between Sun Irradiation vs. Narrowband UVB Phototherapy along with Concomitant Topical Tacalcitol for Vitiligo Vulgaris

In addition to therapeutic options such as steroid ointment, immunosuppressive drug and ultraviolet phototherapy, recent reports have demonstrated the clinical efficacy of topical vitamin D3 for vitiligo vulgaris. However, there seems to be little clinical effect of vitamin D3 without UV exposure. In the present study, we evaluated the clinical difference of sun irradiation vs. narrowband UVB in combination with tacalcitol assessing the change of lesion size and color tone by a spectrophotometer. Thirty-three vitiligo patients were composed of 19 treated with sun illumination and 14 treated with narrowband UVB in combination with topical use of tacalcitol. The mean % size reduction was higher in the group of sunbathing than narrowband UVB (29% vs. 23%). Delta L score, which represented the difference of whiteness between lesional and perilesional skin, was significantly improved after treatment in the group of sun irradiation instead of narrowband UVB (p = 0.0023). Therefore, we consider that sun illumination along with tacalcitol may be able to induce natural repigmentation and be an alternative therapeutic option for vitiligo vulgaris.

Narrowband time delay estimation based on correlation coefficient

The problems of time delay estimation of narrowband signals are presented.The disadvantages of the existing algorithms are analyzed,and a new narrowband time delay estimating algorithm based on correlation coefficient is proposed.The original time delay information is transfered into the delay between the autocorrelation and cross-correlation function,and the precise estimating result by wave-comparison is given.The algorithm proposed here is also compared with other algorithms and its advantages over other algorithms are proved.The theoretical analysis and simulation show the effectiveness of the proposed algorithm.

Aliasing-free high resolution imaging of fast rotating targets with narrowband radar

Narrowband radar has been successfully used for high resolution imaging of fast rotating targets by exploiting their micro-motion features.In some practical situations,however,the target image may suffer from aliasing due to the fixed pulse repetition interval(PRI)of traditional radar scheme.In this work,the random PRI signal associated with compressed sensing(CS)theory was introduced for aliasing reduction to obtain high resolution images of fast rotating targets.To circumvent the large-scale dictionary and high computational complexity problem arising from direct application of CS theory,the low resolution image was firstly generated by applying a modified generalized Radon transform on the time-frequency domain,and then the dictionary was scaled down by random undersampling as well as the atoms extraction according to those strong scattering areas of the low resolution image.The scale-down-dictionary CS(SDD-CS)processing scheme was detailed and simulation results show that the SDD-CS scheme for narrowband radar can achieve preferable images with no aliasing as well as acceptable computational cost.

Improved HHT and its application in narrowband radar imaging for precession cone-shaped targets

Imaging the spatial precession cone-shaped targets with narrowband radar is a new technical approach in mid-course recognition problem. However, most existing time-frequency methods still have some inevitable deficiencies for extracting microDoppler information in practical applications, which leads to blurring of the image. A new narrowband radar imaging algorithm for the precession cone-shaped targets is proposed. The instantaneous frequency of each scattering point is gained by using the improved Hilbert-Huang transform, then the positions of scattering points in the parameter domain are reconstructed. Numerical simulation and experiment results confirm the effectiveness and high precision of the proposed algorithm.

New Technique for Estimating and Suppressing Narrowband Interference in DSSS Systems

A generalized approach for narrowband interference(NBI)suppression in direct sequence spread spectrum(DSSS)communication systems using adaptive infinite impulse response(IIR)filter is presented.The excision filter coefficients depend on both the jammer power and its instantaneous frequency.The dependency of the filter construction on the jammer power is significant as it allows optimal tradeoff between interference removal and signal distortion by maximizing the receiver signal to noise ratio improvement(SNRI).Instead of traditional adaptive line enhancer(ALE)estimator,a preferable NBI estimator-Fourier interpolation estimator(FIE)is proposed.Closed-form expressions of the SNR improvement and theoretical bit error rate(BER)based on the assumption that the output of the correlator is Gaussian distributed are both derived.Performance results obtained by numerical simulation are also presented and compared with theoretical results.

A tunable dual-narrowband band-pass filter using plasma quantum well structure

A tunable dual-narrowband pass-band filter is designed. A one-dimensional photonic crystal(1D PC) is comprised of alternate dielectric layer and vacuum layer. Two quantum wells(QWs) as defects can be constructed by sandwiching two plasma slabs symmetrically in the 1D PC, and a dual-narrowband pass-band filter is formed. The conventional finitedifference time-domain(FDTD) method and piecewise linear current density recursive convolution(PLCDRC)–FDTD method are applied to the dielectric and plasma, respectively. The simulation results illustrate that the dual-narrowband frequencies can be tuned by changing the plasma frequency. The pass band interval and the half-power bandwidths(-3-dB band widths) are related to the space interval between two QWs.

Realization of double resonance for a bright frequencytunable source of narrowband entangled photons

In this paper,we report an interesting phenomenon when precisely adjust the tuning crystal for double-resonance of a type-II configured parametric amplifier cavity,which is later verified as a cavity-enhanced effect in optics alignment.The theoretical result indicates that an angle accuracy error within 0.09 is necessary to achieve a high contrast ratio of 100:1 for a cavity with a finesse of about 205,which is crucial but high-demanding to get a high-quality narrowband entanglement source.Meanwhile,we figure out a method to release such a high requirement and get high visibility in a moderate-accuracy alignment.

Generation of narrowband Lamb waves based on the Michelson interference technique

An optical method of generating narrowband Lamb waves is presented. It is carried out with a laser line array in a thermoelastic regime implemented by the Michelson interference technique, where the formed array element spacing can be flexibly and conveniently changed to achieve selective mode excitation. In order to simulate the displacement response generated by this array, its intensity distribution function is presented to build a theoretical analysis model and to derive the integral representation of the displacement response. The experimental device and measuring system are built to generate and detect the Lamb waves on a steel plate. Numerical calculation results of narrowband Lamb wave displacement signals based on the theoretical model show good agreement with experimental results.

New Kalman Filtering Algorithm for Narrowband Interference Suppression in Spread Spectrum Systems

A new Kalman filtering algorithm based on estimation of spread spectrum signal before suppression of narrowband interference (NBI) in spread spectrum systems, using the dependence of autoregressive (AR) interference, is presented compared with performance of the ACM nonlinear filtering algorithm, simulation results show that the proposed algorithm has preferable performance, there is about 5 dB SNR improvement in average.

Modulated Lapped Biorthogonal Transform for Non-orthogonal Narrowband Interference Excision in Spread Spectrum Communications

Traditional lapped transform domain excision techniques obtain good performance at the expense of increased processing delay. Extension of transform domain filtering techniques to the lapped biorthogonal transform domain can help solve the problem. By incorporating biorthogonality into the lapped transforms, more flexibility is obtained in the design of windows. Thus transform bases with better stopband attenuation can be generated by designing windows, but not by increasing the overlapping factor. In this paper, a new modulated lapped biorthogonal transform (MLBT) with optimized windows is introduced for efficient compression of multi-tone interfering signal energy. The bit error rate (BER) performance of the receiver employing the proposed MLBT excision technique is analyzed and compared with that of the lapped transform domain excision-based receivers. Simulation results demonstrate the improved performance and increased robustness of the proposed technique.

Narrowband blue emitter based on fused nitrogen/carbonyl combination with external quantum efficiency approaching 30%

Multi-resonance thermally activated delayed fluorescence(MR-TADF)emitters can enable narrowband emission with high color purity and electroluminescence efficiency.Nitrogen/carbonyl(N/C=O)system is receiving increasing attention while the nitrogen/boron(N/B)system has been widely studied.Donor decoration is an effective approach for N/B type MR-TADF system but always leads to broadening and red-shifting of the emission band in N/C=O MR-TADF system.We attribute these unfavorable phenomena to the formation of intramolecular charge transfer between the MR-core and peripheral donors.To address this issue,we have developed a new strategy by decorating DMQAO(a fused N/C=O MR-core)with a triazine acceptor and a neutral terphenyl group to construct MTDMQAO and MBDMQAO,respectively.The introduction of the triazine acceptor not only realizes efficient narrowband emission in MTDMQAO,but also accelerates the reverse intersystem crossing process through enhanced spin-orbital coupling.As a result,MTDMQAO exhibits a significantly higher external quantum efficiency of 29.4%compared to the referent emitters,validating the rationality of our derivation strategy.This study highlights the potential of the N/C=O system for MR-TADF emitters and provides important insights for understanding the difference between N/B and N/C=O systems.