Electro-optic Detection Research Articles

A fast alignment method for shipbore SINS with the aid of electro-optical detection system

Aiming at the challenge of the extensive initial alignment time required for small ship strapdown inertial navigation system (SINS) under swaying base on the sea, an alignment method aided by electro-optical detection system (EODS) is proposed. By employing the EODS to track a target on the shore with a known position, the relative distance and orientation to the ship are obtained as auxiliary information. A direct relation between the SINS misalignment angle and the error in target position estimation has been established. This method theoretically ensures a high observability degree for yaw misalignment. Simulation and semi-physical simulation indicate that the proposed method does not rely on an accurate initial attitude and is capable of rapid correction of a 5∘ yaw error. The use of two or more sets of EODSs and targets can further eliminate the necessity for precise positioning information. In semi-physical simulation, the yaw angle converges within 100 s, with the alignment accuracy reaching the upper limit determined by inertial measurement unit (IMU) precision. This method has potential engineering utility for scenarios such as rapid initialization of SINS on unmanned surface vehicles (USVs) in nearshore mooring conditions.

Diagnostic models for differentiating fatty liver disease of alcohol and non-alcoholic genesis

Introduction. Fatty liver disease is the largest contributor to the burden of chronic liver disease worldwide. Current approaches do not allow sufficient differentiation between alcoholic and non-alcoholic etiology of the process.Aim. Create diagnostic panels including electrical and viscoelastic parameters of erythrocytes to differentiate fatty liver disease of alcoholic and non-alcoholic genesis.Materials and methods. The study included 38 men (47.5 ± 2.9 years) with NAFLD; 31 men with alcoholic fatty liver disease (AFLD) (45.1 ± 3.1 years) according to ultrasound of the abdominal organs, the degree of fibrosis did not exceed F1 (FibroScan® 502). Electrical and viscoelastic parameters of erythrocytes were studied by dielectrophoresis using an electro-optical cell detection system. To determine the parameters of erythrocytes – biomarkers for distinguishing between AFLD and NAFLD, a system of machine learning methods – Random Forest was used.Results. Electrical, viscoelastic parameters of erythrocytes, which are biomarkers for distinguishing between AFLD and NAFLD, were established: cell membrane capacity (p = 1.21E-11), the degree of change in the deformation amplitude at a frequency of 5 x 105 Hz (p = 2.38E-08), cell polarizability at a frequency of 106 Hz (p = 9.38E-08), the speed of erythrocyte movement to the electrodes (p = 4.32E-06), the magnitude of the dipole moment (p = 1.66E-05), relative polarizability (p = 2.35E-05), the index of erythrocyte destruction at a frequency of 5 x 105 Hz (p = 0.016), the position of the crossover frequency (p = 2.13E- 06). The diagnostic model, including five parameters – the position of the crossover frequency, cell polarizability at a frequency of 106 Hz, cell electrical conductivity, membrane capacity, the degree of change in the deformation amplitude at a frequency of 5 x 105 Hz, provided the highest diagnostic accuracy with an AUC of 0.975, a sensitivity of 96.3%, and a specificity of 91.8% in differentiating between AFLD and NAFLD.Conclusion. Thus, systematic exposure to alcohol modifies the structure of erythrocyte membranes, leading to a decrease in the surface charge, the barrier function of membranes, reducing the resistance of cells, their ability to deform, which determines the key role of the identified electrical, viscoelastic parameters of erythrocytes in differentiating between AFLD and NAFLD.

χ (2)-induced artifact overwhelming the third-order signal in 2D Raman-THz spectroscopy of non-centrosymmetric materials.

Through comprehensive data analysis, we demonstrate that a χ(2)-induced artifact, arising from imperfect balancing in the conventional electro-optic sampling detection scheme, contributes significantly to the measured signal in 2D Raman-THz spectroscopy of non-centrosymmetric materials. The artifact is a product of two 1D responses, overwhelming the desired 2D response. We confirm that by analyzing the 2D Raman-THz response of an x-cut beta barium borate crystal. We furthermore show that this artifact can be effectively suppressed by implementing a special detection scheme. We successfully isolate the desired third-order 2D Raman-THz response, revealing a distinct cross-peak feature, whose frequency position suggests the coupling between two crystal phonons.

Practical considerations for the amplification of electro-optically detected THz signals

Advances in THz methods and applications require the detection of weak THz pulsed signals. One solution to this problem is to amplify weak signals using optically biased electro-optical (EO) techniques. Several different EO amplification schemes are compared. The simplest of these involves using a non-polarizing beam splitter followed by two quarter-wave plates set to small positive and negative angles, respectively. The signals are then passed through polarizers perpendicular to the polarization of the 800 nm EO detector crystal gating beam. As long as sufficient intensity is present in the gate pulse for linear photodiode detection, amplification of up to 10 times with dynamic ranges for single sweep scans of >104 is obtained.

Electrical and Viscoelastic Parameters of Erythrocytes as a Part of Diagnostic Models for Differentiating Fatty Liver Disease of Mixed Genesis from Non-Alcoholic and Alcohol-Related Fatty Liver Disease

Aim:creation of diagnostic models including electrical, viscoelastic parameters of erythrocytes to distinguish fatty liver disease of mixed etiology (metabolic + alcoholic) from non-alcoholic and alcoholic fatty liver disease.Materials and methods.We examined 46 men with non-alcoholic fatty liver disease (NAFLD), 43 men with alcoholic fatty liver disease (AFLD), as well as 54 men with fatty liver disease (FLD) of mixed genesis (metabolic + alcohol-related); average age of the patients included in the study made 48.4 ± 9.6 years. The diagnosis was established on the basis of liver ultrasound findings and FLI liver steatosis index with a fibrosis grade of F1 or less (FibroScan®502, Echosens, France). The electrical and viscoelastic parameters of erythrocytes were investigated by the diagnostic technique of dielectrophoresis using an electrooptical cell detection system.Results.The most significant parameters for differentiating fatty liver disease of mixed genesis (metabolic + alcoholic) from NAFLD using the Volcano plot have turned out to be cell polarizability at a frequency of 106Hz (p= 6.49 ×10-5), erythrocyte cell membrane capacity (p= 0.00077), relative polarizability (p= 0.001), the levels of which were higher in patients with NAFLD. On the contrary, the index of red blood cells destruction at 105Hz was higher in FLD of the mixed genesis (p= 0.047) and the crossover frequency was shifted to the high frequency range more than in NAFLD (p= 0.0005). The discriminant analysis has additionally revealed the significance of the degree of erythrocyte deformation at 5 ×105Hz in distinguishing between mixed-genesis FLD and NAFLD. In differentiating FLD of mixed genesis from NAFLD, a diagnostic model incorporating the above red blood cells parameters has provided an AUC of 0.829 (confidential interval: 0.742–0.916), sensitivity of 80.9 %, and specificity of 83.3 %. Two indicators of red blood cells have been established that statistically significantly distinguish the mixed-genesis FLD from the AFLD (Volcano plot); these are the index of red blood cells destruction at a frequency of 5 ×105Hz, which was higher with AFLD (p= 0.0007), and the capacity of cell membranes, the value of which prevailed in mixed-genesis FLD (p= 0.011). When distinguishing the mixed-genesis FLD from the AFLD, the combined model with the inclusion of three parameters of red blood cells, namely the index of red blood cells destruction at a frequency of 5 ×105Hz, the capacity of erythrocyte membranes, and polarizability at a frequency of 106Hz, has shown the highest levels of diagnostic accuracy, namely AUC = 0.751 (confidential interval: 0.611–0.908) with a sensitivity of 79.5 %, specificity of 74.7 %.Conclusion.The electrical and viscoelastic parameters of erythrocytes studied using the diagnostic technique of dielectrophoresis should be considered as promising biomarkers for the diagnosis of diffuse liver disease.

Modified Bridgman assisted ZnTe crystal growth for THz device applications

Zinc Telluride (ZnTe) single crystals have enormous potential for generating and detecting broadband terahertz (THz) radiation, making them suitable for a wide range of applications in communication, defence security and biomedical applications. The quality and homogeneities of the crystal plays an important role in obtaining THz response. This paper elaborates on the steps involved in the crystal growth of ZnTe and the characterization technique utilized for the determination of quality of the grown crystal, identifications of defects and qualifications of THz signals. Single crystal was grown by the Bridgman technique in vacuum sealed carbon-coated quartz ampoule with excess tellurium (Zn:Te/3:7). To obtain maximum THz response, crystals were oriented along (110) direction using a Laue diffraction pattern and sliced accordingly. Three different crystals along the length (bottom-middle-top) of size ∼ 10 mm × 10 mm are taken for analysis. The crystallinity of ZnTe was confirmed with X-ray diffraction pattern and lattice parameters were obtained using Rietveld refinement. Raman analysis was carried out at three different regions of the grown crystal which revealed the presence of same high-intensity mode at 413 cm−1 in all the regions confirming the quality of the crystal. The EDS compositional analysis confirms the stoichiometry along the grown crystal length. Optical bandgap of 2.216 eV was measured by UV-Vis-NIR spectra and >55 % transmission was obtained across the grown crystal length. The size and distribution of Te inclusions were measured using IR microscopy. The crystals were subjected to terahertz investigation in the range of 0.1–4 THz using a time domain spectrometer. All the crystals exhibited negligible absorption coefficients in the 0.1–3.75 THz range, confirming the maximum transmission in the THz domain. The crystals also exhibit excellent electro-optic detection which is confirmed by signal-to-noise ratio in the measured range.

Noncollinear electro-optic detection of terahertz waves: Advantages and limitations

Electro-optic sampling of terahertz waves by noncollinearly propagating femtosecond laser pulses in electro-optic crystals can provide high efficiency and high spectral resolution of terahertz detection with various types of crystals and laser wavelengths, unlike the conventional collinear scheme. We develop an analytical theory of noncollinear electro-optic sampling detection technique that describes the modulation of the probe laser beam polarization as a result of nonlinear interaction between the optical and terahertz fields. The theory accounts for finite widths of the terahertz and probe beams. It is found that noncollinear scheme operates as a low-pass terahertz filter with the frequency cut-off determined by the width of the probe beam and the crossing angle of the terahertz and probe beams. We apply the theory to two practical situations: sampling of terahertz waves by fiber laser pulses (1.55 μm wavelength) in a GaAs crystal and sampling by Ti:sapphire laser pulses (800 nm wavelength) in a LiNbO3 crystal.

Small tracking error correction for moving targets of intelligent electro-optical detection systems

Small tracking error correction for moving targets of intelligent electro-optical detection systems

Thin-film lithium niobate electro-optic terahertz wave detector

The design, fabrication, and validation of a thin-film lithium niobate on insulator (LNOI) electro-optic (EO) time-domain terahertz (THz) wave detector is reported. LNOI offers unprecedented properties for the EO detection of freely propagating THz wave radiation pulses and transient electric fields because of the large EO coefficient of the material, engineering of the velocity matching of the THz wave and optical wave, and much reduced detector size. The proof-of-concept device is realized using thin-film lithium niobate optical waveguides forming a Mach–Zehnder interferometer with interferometer arms electrically poled in opposite directions. THz waves are coupled effectively to the fully dielectric device from free space without using antennas or plasmonics. The detection of THz waves with frequencies up to 800 GHz is successfully demonstrated. The detector allows for the detection of THz frequency electric fields up to 4.6 MV/m. The observed frequency response of the device agrees well with theoretical predictions.

Optimizing Controls to Track Moving Targets in an Intelligent Electro-Optical Detection System

Electro-optical detection systems face numerous challenges due to the complexity and difficulty of targeting controls for “low, slow and tiny” moving targets. In this paper, we present an optimal model of an advanced n-step adaptive Kalman filter and gyroscope short-term integration weighting fusion (nKF-Gyro) method with targeting control. A method is put forward to improve the model by adding a spherical coordinate system to design an adaptive Kalman filter to estimate target movements. The targeting error formation is analyzed in detail to reveal the relationship between tracking controller feedback and line-of-sight position correction. Based on the establishment of a targeting control coordinate system for tracking moving targets, a dual closed-loop composite optimization control model is proposed. The outer loop is used for estimating the motion parameters and predicting the future encounter point, while the inner loop is used for compensating the targeting error of various elements in the firing trajectory. Finally, the modeling method is substituted into the disturbance simulation verification, which can monitor and compensate for the targeting error of moving targets in real time. The results show that in the optimal model incorporating the nKF-Gyro method with targeting control, the error suppression was increased by up to 36.8% compared to that of traditional KF method and was 25% better than that of the traditional nKF method.

Improved target detection method for space-based optoelectronic systems

The detection of faint and small targets by space-based surveillance systems is difficult owing to the long distances, low energies, high speeds, high false alarm rates, and low algorithmic efficiencies involved in the process. To improve space object detection and help prevent collisions with critical facilities such as satellites, this study proposes an improved method for the detection of faint and small space-based targets. The proposed method consists of two components: star atlas preprocessing and space-based target detection. The star atlas preprocessing step applies multi-exposure image pyramidal weighted fusion to the original image containing the faint and small space-based target. After obtaining the image pyramidal weighted fusion result atlas, the algorithm employs threshold segmentation to improve the overall image clarity, highlight image details, and provide additional information for target detection. The detection of targets partially relies on the local symmetry of the image. Accordingly, a diffusion function describing the local symmetry is established to precisely locate stars by measuring the symmetry factor in a small area surrounding each pixel in the star atlas. This effectively removes the background stars while retaining high-definition and high-contrast images. The efficacy of the algorithm is validated using simulated datasets consisting of space-based and real images. The results demonstrate that the proposed technique improves the applicability of the multistage hypothesis testing (MHT) method in the context of a complex space environment, thus improving the performance of the space-based electro-optical detection system to better catalogue, identify, and track space targets.

Investigations on Electro-Optical and Photoelectric Detection Performance of GaN-Based micro-LEDs by Removing p-AlGaN Electron-Blocking Layer

Investigations on Electro-Optical and Photoelectric Detection Performance of GaN-Based micro-LEDs by Removing p-AlGaN Electron-Blocking Layer

Application of Electro-Optic Sampling Detection Technology Based on BBO Crystals in Detecting Near-Infrared Few-Cycle Laser Pulses

Application of Electro-Optic Sampling Detection Technology Based on BBO Crystals in Detecting Near-Infrared Few-Cycle Laser Pulses

Optimization of Space Charge Electro-Optical Detection System in Power Electronic Insulation: Toward High Sensitivity

Optimization of Space Charge Electro-Optical Detection System in Power Electronic Insulation: Toward High Sensitivity

Femtosecond-resolution optical pulse interleaving time error detector

Pulse repetition rate multiplier (PRRM) is an essential component of microwave photonics systems, designed not only to alleviate photodiode saturation but also to provide more frequent pulses. However, the presence of interleaving time errors is known to compromise the advantages of PRRM. In this study, we present a high-sensitivity detection method for identifying these time errors using an electro-optic sampling-based timing detector (EOS-TD). We utilize two EOS-TDs: one for generating precise timing ruler signals and the other as a high-precision timing detector. In comparison to the conventional power ratio comparison method, our approach demonstrates sensitivity improvement by two orders of magnitude. This enhancement facilitates the measurement of femtosecond-level time errors. By enabling higher pulse rates while maintaining the ultralow jitter, this method can be useful for building higher-speed photonic systems.

Frequency response of terahertz electro-optic sampling detection technology with thin GaSe crystal

GaSe crystal has good applications in the broadband terahertz pulse generation and electro-optic sampling detection technology. In this paper, the frequency responses of GaSe crystal with different thicknesses in the electro-optic sampling (EOS) detection technology are investigated based on the numerical calculations. Then, the pulse distortions of terahertz induced by the EOS detection technology with thin GaSe crystal are investigated. It is found that the lower the central frequency of the terahertz pulse is, the less the distortion is. When the central frequency of terahertz pulse is higher than 4 THz, the pulse distortions, including the frequency shift and the bandwidth changing, are greatly obvious. Both induced by the EOS technology with different thickness of GaSe crystal are also given in detail. This work provides a good reference to evaluate the performance of EOS detection technology with thin GaSe crystal in the broadband terahertz science and technology.

Research on the identification method of key parts of ship target based on contour matching

A template matching method based on the contour fitting heading angle is proposed for the problem of identifying key parts of maritime ships. First, unmanned boats are used as hypothetical enemy targets to extract outer contours, build a matching template library, and establish relevant kinematic models. Based on the requirements of timeliness and relativism, the judgment conditions for fitting angles and heading angles are given. A traversal fitting framework is established based on the structural similarity index algorithm, and the target matching template is matched based on precise matching results. A motion space that combines position correlation, electro-optical detection distance, and target pitch decoupling is designed to obtain real heading angles. Finally, based on the relative position information of the template’s key parts, the key parts of the target are matched, and the normalized output matching image is obtained. The experiment shows that this method can achieve recognition instructions in real seaways where key parts of the target cannot be extracted due to the large amount of water mist, and it has advantages in timeliness, accuracy, and applicability compared with other algorithms. This method has strong robustness and provides a reference for the identification of key parts of various types of ship targets.

Improved Terahertz Time-Domain Spectroscopy via the Extended Kalman Filter

To implement terahertz time-domain spectroscopy (THz-TDS) systems that have short integration time and maintain performance, the extended Kalman filter (EKF) has been used. Performance of EKF with THz-TDS on vapor samples and solid samples is untested. Previous EKF methods were not adaptive for use on multiple THz-TDS systems. We provide an adaptive EKF method that can work on any THz setup, to improve maximum measurable absorption coefficient. Our adaptive EKF method responds to THz pulse properties. The adaptive EKF is exhaustively demonstrated for six different time-constant data sets spanning 1 ms to 300 ms for THz-TDS on vapor with electro-optic THz detection. The acquisition time saved is quantified and shown to significantly reduce acquisition time from 2.58 ms to 1 ms. This improvement of 2.58 times will have a significant effect to move spectral imaging from taking hours to taking minutes. Vapor absorption lines are maintained. We show the adaptive EKF maintain correct spectral information when compared to the high-resolution transmission molecular absorption (HITRAN) database. The adaptive EKF is also demonstrated for THz-TDS on vapor with photoconductive THz detection, thus demonstrating adaptability, and is applied for THz-TDS of a solid sample of polyethylene terephthalate glycol.

Prediction and Control of Small Deviation in the Time-Delay of the Image Tracker in an Intelligent Electro-Optical Detection System

A small deviation in the time-delay of the image tracker is essential for improving the tracking precision of an electro-optical system, and for future advances in actuator technology. The core goal of this manuscript is to address issues such as tracking the controller time-delay compensation and the precision of an electro-optical detection system using an advanced filter design, a fire control modeling, and an anti-occlusion target detection system. To address this problem, a small deviation in the time-delay prediction and control method of the image tracker is proposed based on the principle of linear motion transformation. The time-delay error formation is analyzed in detail to reveal the scientific mechanism between the tracking controller feedback and the line-of-sight position correction. An advanced N-step Kalman filtering controller model is established by combining a line-of-sight firing control judgment and a single-sample training anti-occlusion DSST target tracking strategy. Finally, an actuator platform with three degrees of freedom is used to test the optical mechatronics system. The results show that the distribution probability of the line-of-sight measuring error in a circle with a radius of 0.15 mrad is 72%. Compared with the traditional control method, the tracking precision of the optimal method is improved by 58.3%.

Dynamic absolute distance measurement with nanometer-precision and MHz acquisition rate using a frequency comb-based combined method

Distance metrology is crucial in supporting modern science and technology such as satellites interconnection, autonomous driving, motion control, and precision manufacturing. A combined method, which is a simultaneous distance measurement with multiple methods, was developed and widely utilized to increase the measurable range while maintaining high precision. However, the measurement speed has been limited to a few kHz due to the requirement for combining a precision measurement with a long-range measurement. In this work, we present a new dynamic distance measurement method based on electro-optic sampling timing detection (EOS-TD) that can preserve the non-ambiguity range (NAR) extension even at >1 MHz acquisition rate. By combining the EOS-TD-based pulse time-of-flight detection method with a microwave phase detection method, 300-mm NAR and 49-nm precision are made possible at 1-μs acquisition time. With longer averaging time, the best precision of 0.99 nm is achieved at 0.22-s acquisition time, corresponding to 169 dB maximum dynamic range. As a demonstration experiment, two mirrors that were ∼83 mm apart and each controlled by a piezo actuator with hundreds of nanometers of displacement variations had their distance between them precisely measured.