Linear dichroism transition and polarization-sensitive photodetector of quasi-one-dimensional palladium bromide

Perpendicular optical reversal of the linear dichroism transition has promising applications in polarization-sensitive optoelectronic devices. We perform a systematical study on the in-plane optical anisotropy of quasi-one-dimensional PdBr_(2) by using combined measurements of the angle-resolved polarized Raman spectroscopy(ARPRS) and anisotropic optical absorption spectrum. The analyses of ARPRS data validate the anisotropic Raman properties of the PdBr_(2) flake.And anisotropic optical absorption spectrum of PdBr_(2) nanoflake demonstrates distinct optical linear dichroism reversal. Photodetector constructed by PdBr_(2) nanowire exhibits high responsivity of 747 A·W^(-1) and specific detectivity of 5.8×10^(12) Jones. And the photodetector demonstrates prominent polarization-sensitive photoresponsivity under 405-nm light irradiation with large photocurrent anisotropy ratio of 1.56, which is superior to those of most of previously reported quasi-one-dimensional counterparts. Our study offers fundamental insights into the strong optical anisotropy exhibited by PdBr_(2), establishing it as a promising candidate for miniaturization and integration trends of polarization-related applications.

BLIND PARAFAC SIGNAL DETECTION FOR UNIFORM CIRCULAR ARRAY WITH POLARIZATION SENSITIVE ANTENNAS

The received signal of the polarization sensitive array is proved to have trilinear model characteristics. The blind parallel factor（PARAFAC） signal detection algorithm for the polarization sensitive array is proposed. The trilinear alternating least square （TALS） algorithm is used to abtain the source matrix, and then the matrix is judged. Simulation results show that the bit error rate （BER） of the detection algorithm is close to that of the non-blind decorrelating method and the algorithm works well under the array error condition. BER difference between the non-blind method and this algorithm is less than 2 dB under a high SNR. The algorithm is blind and robust. The channel fading, the direction of arrive（DOA） imformation and the polarization information are needless in the algorithm.

Blind Joint DOA and Polarization Estimation for Polarization Sensitive Coprime Planar Arrays via a Fast-Convergence Quadrilinear Decomposition Approach

The problem of joint direction of arrival(DOA)and polarization estimation for polarization sensitive coprime planar arrays(PS-CPAs)is investigated,and a fast-convergence quadrilinear decomposition approach is proposed.Specifically,we first decompose the PS-CPA into two sparse polarization sensitive uniform planar subarrays and employ propagator method(PM)to construct the initial steering matrices separately.Then we arrange the received signals into two quadrilinear models so that the potential DOA and polarization estimates can be attained via quadrilinear alternating least square(QALS).Subsequently,we distinguish the true DOA estimates from the approximate intersecting estimations of the two subarrays in view of the coprime feature.Finally,the polarization estimates paired with DOA can be obtained.In contrast to the conventional QALS algorithm,the proposed approach can remarkably reduce the computational complexity without degrading the estimation performance.Simulations demonstrate the superiority of the proposed fast-convergence approach for PS-CPAs.

Water–soluble and polarity–sensitive near–infrared fluorescent probe for long–time specific cancer cell membranes imaging and C. Elegans label

A novel D–π –A structure and near–infrared fluorescent probe(DCITT) with high polarity sensitivity and membrane targeting was reported. The fluorescent spectra of DCITT were polarity dependent and Stokes shift was greater than 300 nm. Due to its high fluorescence quantum yield, low cytotoxicity and photostability, DCITT could be used as a labeling probe in multicellular organisms. In particular, DCITT effectively distinguished tumor cells from normal cells because it could specifically light up the cancer cells membrane based on strong red fluorescence for a long time. On this basis, a polar–sensitive cell membrane probe is developed to differentiate tumor cells from normal cells, which provides an idea and method for the early diagnosis of tumor at cellular level.

MoTe_(2)/Ta_(2)NiSe_(5)/MoTe_(2)范德华双异质结实现超快、宽带和偏振敏感光电探测器

高效光电探测器在监控、热成像、光通信和环境监测等领域具有广泛、迫切的应用需求.优化光电探测器参数如微型化、高量子效率、超快响应速度等,仍然是一项艰巨的任务.我们提出了一种由顶部/底部MoTe_(2)和中间Ta_(2)NiSe_(5)层组成的双范德华异质结.利用双异质结界面增强光收集效率和产生两个对立的内置电场,使得器件具有400到1550 nm的宽光谱响应,并表现出优异的性能,包括82.9%的外量子效率和3.5/4.2μs的快速响应速度.此外,利用二维Ta_(2)NiSe_(5)纳米片的面内各向异性,我们实现了在635和1550 nm波长下的极化灵敏度,分别为16.3和8.1.这项研究为开发高性能和多功能光电探测器提供了平台,为先进光电器件的设计和应用提供了新的方向.

DOA and polarization estimation via signal reconstruction with linear polarization-sensitive arrays

This paper addresses the problem of direction-of-arrival （DOA） and polarization estima- tion with polarization sensitive arrays （PSA）, which has been a hot topic in the area of array signal processing during the past two or three decades. The sparse Bayesian learning （SBL） technique is introduced to exploit the sparsity of the incident signals in space to solve this problem and a new method is proposed by reconstructing the signals from the array outputs first and then exploit- ing the reconstructed signals to realize parameter estimation. Only 1-D searching and numerical calculations are contained in the proposed method, which makes the proposed method computa- tionally much efficient. Based on a linear array consisting of identically structured sensors, the proposed method can be used with slight modifications in PSA with different polarization structures. It also performs well in the presence of coherent signals or signals with different degrees of polarization. Simulation results are given to demonstrate the parameter estimation precision of the proposed method.

Joint frequency,2-D DOA,and polarization estimation using parallel factor analysis

This paper proposes a new algorithm for joint frequency, two-dimensional （2-D） directions-of-arrival （DOA）, and polarization estimation using parallel factor （PARAFAC） analysis model and cumulant. The proposed algorithm designs a new array configuration, and extends the PARAFAC analysis model from the common data-domain and subspace-domain to the cumulant one, and forms three-way arrays by using the three cumulant matrices obtained from the properly chosen dipole outputs, and analyzes the uniqueness of low-rank decomposition of the three-way arrays, and then jointly estimates the source parameters via the low-rank decomposition of the constructed PARAFAC model. In comparison with the conventional methods, the proposed method alleviates the aperture loss, and avoids pairing parameter. Finally, the simulation results are presented to validate the performance of the proposed method.

Ultra-short plasmonic polarization beam splitter-rotator using a bent directional coupler

We propose and analyze a silicon hybrid plasmonic polarization splitter-rotator with an ultra-short footprint using an asymmetric bent directional coupler on a silicon-on-insulator platform.Benefitting from the large birefringence induced by the bent structure and plasmonic effect,the cross-polarization coupling length is only 5.21μm.The transverse magnetic to transverse electric polarization conversion efficiency is over 99.9%,with an extinction ratio of 20.6 dB(32.5 dB)for the transverse magnetic(transverse electric)mode at 1.55μm.Furthermore,the polarization conversion efficiency is higher than 90%while maintaining cross talk below-19 dB within the bandwidth of 80 nm.

Altered birefringence of peripapillary retinal nerve fiber layer in multiple sclerosis measured by polarization sensitive optical coherence tomography

Background:The retina has been used to study the pathophysiology of multiple sclerosis(MS).Peripapillary retinal nerve fiber layer(pRNFL)thinning has been suggested as an ocular biomarker of neurodegeneration in MS.The goal of this project was to determine the birefringence of the pRNFL by measuring the fiber birefringence using polarization sensitive optical coherence tomography(PS-OCT).Methods:Sixty-six MS patients without history of optic neuritis(age:39.9±11.0 yrs.old,53 females and 13 males)and 66 age-and gender-matched normal controls(age:40.7±11.4 yrs.old)were recruited.Custom built PS-OCT was used to measure phase retardation per unit depth(PR/UD,proportional to the birefringence)and pRNFL thickness in each quadrant of the pRNFL.In addition,clinical manifestation was used to correlate with the pRNFL birefringence.Results:The pRNFL was thinner in the temporal and inferior quadrants in MS patients compared with normal controls(P<0.05).The PR/UD of the pRNFL was significantly decreased in MS patients(P<0.05)in all quadrants except for the nasal quadrant.In both groups,the PR/UD from all four quadrants was not related to the averaged pRNFL thickness(P>0.05).In MS patients,the PR/UD was not related to the expanded disability status scale(EDSS)nor disease duration(r ranged from−0.17 to 0.02,P>0.05).Conclusion:This is the first study using PS-OCT to study the pRNFL birefringence in MS patients.Decreased birefringence of the pRNFL may indicate microtubule abnormality,and could be a potential biomarker for detecting early neurodegeneration in MS.

Integrated transmitter devices on InP exploiting electro-absorption modulation

InP technology is the principal enabler for implementing fully monolithic photonic integrated circuits(PIC),uniquely including transmitter elements.In this article we present an overview of recent achievements on ultra-high speed electro-absorption modulated lasers(EML)which represent a simple transmitter PIC comprising a singlemode laser diode and an electro-absorption modulator.Using a so-called identicallayer approach single-wavelength modulation rates up to 100 Gb/s have been accomplished.By additionally integrating an optical amplifier section modulated optical output power of>10 dBm has been achieved.Multi-level amplitude modulation was successfully demonstrated.Extended EML chips designed for wavelength-division and space-division multiplexing,respectively,will be presented.For dual-polarization transmission a novel EML related transmitter as well as a corresponding receiver PIC have been introduced.The latter devices were made on a generic PIC platform that is available for open-access foundry service.

Cramér-Rao bound for multiple parameters estimation using a polarization sensitive array

In this paper, new Cramér-Rao lower bounds （CRB） of the estimates of frequencies, two-dimensional arrival angles and polarization parameters of multiple incident signals are derived for a polarization sensitive array. The incident sources have distinct carrier-frequencies, in contrast to the modeling of all sources to be at the same known carrier-frequency, which has been investigated in the existing research literature on the Cramér-Rao bounds （CRB） for polarization sensitive direction finding. The derived CRBs are compact closed-form expressions and applicable to an arbitrary array geometry. Numerical examples and analysis of some special cases provide insights into the fact that the estimation accuracy of all parameters is enhanced with the increasing signal-to-noise ratio （SNR） and number of snapshots. In addition, they are hardly influenced by the sampling frequency and independent of the initial phase of incident sources. These insights offer guidelines to the system engineer on how to improve parameters＇ estimation accuracy.

PCARSMeasurementofNucleiosidesVibrationalStructure

The polarization sensitive CARS (coherent anti stokes Raman spectroscopy) method is used for the direct spectroscopic investigating of the vibration of double bonds in nucleiosides. The nonresonant background in CARS has been effectively suppressed and the vibration mode of these double bonds can be clearly resolved. The spectral features are discussed in terms of the characteristic group frequency and analogies with spectra of molecules with related structures. These spectral feature may be of use for studying biomolecules of unknown composition.