Intensity Of Echo Signal Research Articles

Enhancing Ultrasonic Echo Response of AlN Thin Film Transducer Deposited by RF Magnetron Sputtering.

Accurate measurement of the pretightening stress for bolts has great significance for improving the assembly quality and safety, especially in severe environments. In this study, AlN thin film transducers were deposited on GH4169 nickel base alloy bolts using the RF magnetron sputtering, enabling a systematic investigation into the correlation between structures and the intensity of ultrasonic echo signals. Employing the finite element method resulted in consistency with the experimental data, enabling further exploration of the enhancement mechanism. With the increasing thickness of both the piezoelectric layer and the electrode layer, the intensity of the ultrasonic echo signals saw a great enhancement. The maximum-intensity observed increase is 14.7 times greater than that of the thinnest layers. Specifically, the thicker piezoelectric layer improves its mechanical displacement, while the increased thickness of the electrode layer contributes to better densification. An electrode diameter of nearly 4 mm is optimal for an AlN thin film transducer of M8 bolts. For pretightening the stress measurement, the sample with a strong and stable echo signal shows a low measurement error of pretightening below ±2.50%.

Research on Laser Dual-Mode Fusion Detection Method of Ship Wake Bubbles

Addressing the issues of weak echo signals and strong background interference in the laser detection of ships’ wakes, an analysis of the laser backscatter detection characteristics of ships’ wakes has been conducted. Based on the Monte Carlo method, a simulation model for the dual-mode fusion detection of ship wake bubbles using laser technology was constructed under different target characteristics. A dual-mode fusion detection system for ships’ wakes was designed, and an indoor experimental platform for the dual-mode fusion detection of ship wake bubbles using laser technology was established. To address problems such as a wide range of echo signal intensity changes, severe signal fluctuations, low resolution, poor image contrast, and blurred target edge information, an algorithm based on multi-timescale hierarchical fusion signal processing and temporal difference accumulation image processing was proposed. Verification experiments for ship wake detection were conducted, which revealed that the dual-mode fusion detection method for ship wake bubbles using laser technology can effectively enhance the detection signal-to-background ratio and counter the maneuvering evasion of underwater weapons by ships. It achieved high sensitivity, large dynamic range, high resolution, and a wide field of view detection and real-time signal processing of ship wake bubble targets of different magnitudes against a strong reverberation background. The effectiveness of the dual-mode fusion detection mode was validated, providing theoretical support for the overall system design and parameter settings.

Wide-bandwidth immersion ultrasound transducer made of Mn:PIMNT single crystal/epoxy 1–3 composite

The sensitivity and bandwidth of immersion ultrasound transducer directly determine the echo signal intensity and axial resolution of the immersion ultrasonic testing (IUT) equipment. The active piezoelectric material, which is the core part of the transducer, usually operates in a thickness-stretching vibrational mode. Hence, it is necessary for piezoelectric materials to possess high piezoelectric performance. In this work, a relaxor-based ferroelectric Mn:PIMNT single crystal with excellent electromechanical performance (d33=1220 pC/N, g33=37.87×10−3 Vm/N, and k33=90%) was used to fabricate a crystal/epoxy 1–3 composite transducer. The crystal-based transducer has a center frequency of 3 MHz. The −6 dB bandwidth is 111.4%, and the insertion loss is −25.2 dB, which are much better than PZT-5 H 1–3 composite transducer (74.5% and −32.9 dB). Additionally, the imaging test reveals that the 1–3 composite transducer made of Mn:PIMNT single crystal exhibits better axial resolution, which shows a good application prospect in the field of ultrasonic nondestructive testing.

Study of off-axis incident rotational speed measurement based on coherent synthetic vortex beams

Vortex beam (VB) is a structured light beam with a helical wavefront and carrying orbital angular momentum (OAM). Compared with Gaussian beam, the VB possesses the rotational Doppler effect (RDE), which is anticipated to compensate for the shortcoming of traditional detection methods in the spin motion of the target object. However, in practical applications, the rotational speed measurement technology based on the VB is facing some challenges, such as weak echo signal intensity due to low vortex beam light power and OAM spectrum expansion caused by off-axis incidence of the vortex beam. These above-mentioned problems directly limit the accuracy and application range of rotational speed measurement. To expand the application range of detection scheme based on the VB, we study the measurement scheme of the target rotational speed based on the combined vortex beam (CVB), which is on the basis of the experimental device for rotational speed measurement with CVB generated by fibre laser arrays. Firstly, the OAM spectra of the off-axis incidence situation are simulated. According to the simulation results, we derive a general model of the peak distribution of echo signals under the off-axis incidence, and propose a rotational speed measurement scheme based on the frequency interval between adjacent spectral peaks. Secondly, we carry out the target rotational speed measurement experiment in off-axis incidence case, and the difference in frequency between two adjacent spectral peaks is obtained from the spectrum map of the echo signal to measure the rotational speed of the target object. The results show that the target rotational speed can be accurately measured regardless of the lateral displacement and angular deflection in the case of off-axis incidence, which confirms the validity of the universal model for rotational speed measurement. The rotational speed measurement scheme proposed in this study takes into consideration the off-axis incidence prevalent in practical application, thereby improving the applicability in the target object rotational speed measurement, and providing technical reference for remote sensing detection application based on the VB.

Near-infrared lunar laser ranging: Research on pointing error of Lunokhod 2 corner reflector based on effective echo signal broadening

The effective echo intensity of lunar laser ranging (LLR) has always been a concern, which not only reflects the detection ability of the LLR system but also affects the ranging uncertainty of LLR. The initial pointing of the corner-cube reflector (CCR) has a certain relationship with the echo intensity and ranging uncertainty of LLR. In our previous work, we analyzed the pointing error of the CCR array by studying the change in echo signal intensity. This paper will continue to research the initial pointing error of the CCR array from the perspective of ranging uncertainty. In this paper, based on the ranging system of the TianQin laser ranging station, the ranging uncertainty is obtained by analyzing the data, and finally, the pointing error of the CCR array is researched by summarizing the variation law of the ranging uncertainty. Firstly, the delay model introduced by the pointing error of the corner reflector is established, and the theoretical uncertainty introduced by the pointing error of the corner reflector is calculated. Secondly, the ranging uncertainty is analyzed through the experiment of LLR. Finally, the pointing error of the CCR array is calculated by inversion of ranging uncertainty. Theoretical analysis and experimental measurement results show that there is a pointing error in the L2 (Lunokhod 2) corner reflector, and its pointing error is about 5° ∼ 10°. This study is of great guiding significance for analyzing and studying the ranging uncertainty of LLR and arranging the next generation of LLR reflectors.

Drug delivery by sonosensitive liposome and microbubble with acoustic-lens attached ultrasound: an in vivo feasibility study in a murine melanoma model

Conventional chemotherapy methods have adverse off-target effects and low therapeutic efficiencies of drug release in target tumors. In this study, we proposed a combination therapy of doxorubicin (DOX)-loaded ultrasound (US)-sensitive liposomal nanocarriers (IMP301), microbubbles (MBs) under focused US exposure using convex acoustic lens-attached US (LENS) to tumor treatment. The therapeutic effects of each treatment in a murine melanoma model were evaluated using contrast-enhanced US (CEUS) and micro-computed tomography (micro-CT) imaging, bioluminescence and confocal microscopy imaging, and liquid chromatography–mass spectroscopy (LC/MS) analysis. Tumor-bearing mice were randomly assigned to one of the following groups: (1) G1: IMP301 only (n = 9); (2) G2: IMP301 + LENS (n = 9); (3) G3: IMP301 + MB + LENS (n = 9); (4) G4: DOXIL only (n = 9); and (5) G5: IMP301 without DOXIL group as a control group (n = 4). Ten days after tumor injection, tumor-bearing mice were treated according to each treatment strategy on 10th, 12th, and 14th days from the day of tumor injection. The CEUS images of the tumors in the murine melanoma model clearly showed increased echo signal intensity from MBs as resonant US scattering. The relative tumor volume of the G2 and G3 groups on the micro-CT imaging showed inhibited tumor growth than the reference baseline of the G5 group. DOX signals on bioluminescence and confocal microscopy imaging were mainly located at the tumor sites. LC/MS showed prominently higher intratumoral DOX concentration in the G3 group than in other treated groups. Therefore, this study effectively demonstrates the feasibility of the synergistic combination of IMP301, MBs, and LENS-application for tumor-targeted treatment. Thus, this study can enable efficient tumor-targeted treatment by combining therapy such as IMP301 + MBs + LENS-application.

Evaluating the effects of material reflectivity and atmospheric attenuation on photonic radar performance in free space optical channels

Abstract The automotive industry is on the verge of embracing autonomous vehicles in the near future. In the pursuit of developing self-driving cars, photonic radars have emerged as a reliable sensor technology. These radars operate based on free space optical channels, but they are vulnerable to various atmospheric challenges. In this research, the objective is to examine the effect of material reflectivity on target recognition by utilizing photonic radar under various atmospheric conditions within free space optical channels. We explore four distinct scenarios representing targets with reflectivity ranging from 90 % to 20 %. The findings of this study indicate a decrease in received signal strength as reflectivity decreases across all analysed atmospheric conditions. The key findings include successful detection of stationary targets at a 1000-m range, the impact of target reflectivity on echo signal intensity and resolution, and the system’s effective performance in detecting targets even in dense fog conditions of up to 50 dB/km and are further validated through theoretical analysis.

Free-space remote detection of a spinning object using the combined vortex beam.

The rotational Doppler effect (RDE) associated with orbital angular momentum (OAM) has been used for remote sensing of a spinning object. However, one of the challenges of long-range detection stems from the low echo signal power. In this paper, we propose a new detection scheme that uses the combined vortex beam (CVB) generated by coherent beam combining (CBC) technology as the probe beam to enhance the echo signal power. Furthermore, we establish a rotational speed remote sensing model based on RDE, the emitted power and emission diameter of the probe beam are investigated in detail. The results show that, compared with the superposition vortex beam (SVB) generated by a single laser beam, the CVB detection scheme can significantly enhance the echo signal intensity and detection distance. The measuring range and accuracy of rotational speed are also studied in detail. And finally, we present the first experimental demonstration of the RDE arising directly from the interaction of the CVB with a rotating rough surface. The scheme proposed in our paper offers a good reference for practical application of the remote detection based on RDE.

Analysis of the Impact of Changes in Echo Signal Parameters on the Uncertainty of Distance Measurements in p-ToF Laser Rangefinders.

The article presents results of research on the influence of changes in parameters of the digitally recorded echo signals on the uncertainty of pulsed Time-of-Flight (p-ToF) laser distance measurements. The main objective of the study was to evaluate the distance calculation method developed by the authors. This method is based on the acquisition of the full-waveform of the echo pulse signal and approximation of its shape by the second-degree polynomial (we called it SDPA for short). To determine the pulse transit time and measure the distance, the position of the vertex of this parabola is sought. This position represents the maximum intensity of the incoming echo signal and is related to the round-trip propagation time of the laser pulse. In the presented work, measurement uncertainty was evaluated using simulation tests for various parameters of the echo pulse. All obtained results were used to formulate the general relationship between the measurement uncertainty of the SDPA algorithm and the parameters of the received echo signals. This formula extends the base knowledge in the domain of laser p-ToF distance measurements. It can be used to estimate the measurement uncertainty of a FW LiDAR at an early design stage. This greatly improves capabilities of analysis of expected performance of the device. It can also be implemented directly into the rangefinder’s measurement algorithm to estimate the measurement uncertainty based on the emission of a single pulse rather than a series of pulses.

Ultrasound and magnetic resonance imaging of cyclic arginine glycine aspartic acid-gadopentetic acid-polylactic acid in human breast cancer by targeting αvβ3 in xenograft-bearing nude mice

ABSTRACT Effective early detection shows the potential to reduce breast cancer mortality. This study aimed to establish a targeted contrast agent for Magnetic Resonance Imaging (MRI)/ultrasound dual-modality molecular radiography for breast cancer. The cyclic arginine-glycine-aspartate-gadopentetic acid-polylactic acid (cRGD and Gd-DTPA) coated by multi-functional blank poly (lactic-co-glycolic acid) (PLGA) nanoparticles) was successfully constructed by chemical synthesis method with high stability. The safety of cRGD-Gd-DTPA-PLGA was demonstrated in vitro and in vivo, and their affinity to breast cancer cells was revealed. Moreover, MRI/ultrasound dual-modality molecular radiography in vitro showed that as the concentration of contrast agent increased, the echo enhancement and signal intensity of MRI imaging were also elevated. The mouse models of human breast cancer also indicated significant target enhancements of cRGD-Gd-DTPA-PLGA magnetic nanoparticles in the mouse tumor. Thus, cRGD-Gd-DTPA-PLGA magnetic nanoparticles were suggested as qualified MRI/ultrasound dual-modality molecular radiography contrast agent. We further explored the targeting mechanism of cRGD-Gd-DTPA-PLGA in breast cancer. The results showed that αvβ3 was highly expressed in breast cancer tissues, and cRGD-Gd-DTPA-PLGA used for MRI/ultrasound dual-modality molecular radiography by targeting αvβ3. Additionally, we found that the signal-to-noise ratio of MRI was positively correlated with microvessel density (MVD). The cRGD-Gd-DTPA-PLGA dynamicly and quantitatively monitored breast cancer by monitoring the state of neovascularization. In conclusion, in the present study, we successfully constructed the cRGD-Gd-DTPA-PLGA magnetic nanoparticles for MRI/ultrasound dual-modality molecular radiography. The cRGD-Gd-DTPA-PLGA showed potential in early detection and diagnosis of metastasis, and dynamic evaluation of the efficacy of molecular targeted therapy of integrin αvβ3.

A Method of Range Walk Error Correction in SiPM LiDAR with Photon Threshold Detection

A silicon photomultiplier (SiPM) LiDAR with photon threshold detection can achieve high dynamic performance. However, the number fluctuations of echo signal photons lead to the range walk error (RWE) in SiPM LIDARs. This paper derives the RWE model of SiPM LiDAR by using the LiDAR equation and statistical property of SiPM’s response. Based on the LiDAR system parameters and the echo signal intensity, which is obtained through the SiPM’s photon-number-resolving capability, the RWE is calculated through the proposed model. After that, we carry out experiments to verify its effectiveness. The result shows that the method reduces the RWE in TOF measurements using photon threshold detection from 36.57 cm to the mean deviation of 1.95 cm, with the number of detected photons fluctuating from 1.3 to 46.5.

Photon counting correction method to improve the quality of reconstructed images in single photon compressive imaging systems.

Compressive sensing has been widely used in single photon imaging systems because of its advantages of high efficiency and low cost. However, when the received photon flux is large, some photons cannot be recorded by single photon detectors due to the dead time effect, which introduces nonlinear errors between the measurement results and actual values and further damages the imaging quality. In this paper, a photon counting correction method specific to paralyzable detectors is proposed to improve the quality of reconstructed images in single photon compressive imaging systems. To verify this method, a single photon compressive imaging system is built, which uses a digital micromirror device (DMD) to modulate the light and a PMT as the single photon detector. The Monte Carlo simulation is also implemented to double validate the performance of the proposed method and the results from the experiment. Peak signal-to-noise ratio (PSNR) is used as the imaging quality evaluation standard. The experimental and simulation results indicate that our method can overcome negative effect of the dead time and accurately recover the intensity and waveform shape of echo signal, which can significantly improve the quality of reconstructed images and has a better performance than traditional methods in the single photon compressive imaging system.

Relaxation processes and high-field coherent spin manipulation in color center ensembles in 6 H -SiC

Coherent spin manipulations of spin-$\frac{3}{2}$ color center ensembles in 6H-SiC crystal have been studied in high magnetic fields using methods of pulsed electron paramagnetic resonance, Rabi oscillations, and pulsed electron-electron double resonance under optical alignment conditions of the spin level populations. Rabi oscillation experiments show room temperature coherent control of these spin-$\frac{3}{2}$ color center ensembles in strong magnetic fields. A sharp decrease of the spin-lattice relaxation time ${T}_{1}$, \ensuremath{\sim}40 times, was observed in 6H-SiC at magnetic field of \ensuremath{\sim}3.5 T with increasing temperature from 100 to 300 K, while the spin-spin relaxation time ${T}_{2}$ is only shortened by \ensuremath{\sim}1.3 times. With an increase in the magnetic field, the times ${T}_{1}$ and ${T}_{2}$ were shown to decrease. The relaxation time ${T}_{1}$ in the case of magnetic field directed along the axis of the spin-$\frac{3}{2}$ center is \ensuremath{\sim}2 times longer than ${T}_{1}$ in magnetic field perpendicular to this axis. Relaxation times of the spin center in crystal grown with a reduced concentration of an isotope $^{29}\mathrm{Si}$ are significantly longer than crystal, with the natural content of isotopes. With a decrease in the $^{29}\mathrm{Si}$ content in our experiments by a factor of \ensuremath{\sim}5, the effective nuclear spin bath in SiC is reduced by a factor of \ensuremath{\sim}2. In a zero magnetic field resonance, transitions are allowed as magnetic dipole transitions with frequency ${\ensuremath{\omega}}_{0}$ which correspond to the zero-field splitting. In zero magnetic field and in fixed magnetic fields, the Rabi frequency was shown, using so-called ``Feynman-Vernon-Hellwarth transformation,'' to be ${\ensuremath{\omega}}_{R}=|\ensuremath{\gamma}|{B}_{1}$. In pulsed electron-electron double resonance experiments, a change in the intensity of the electron spin echo signal corresponding to one of the spin-allowed fine structure transitions is recorded depending on the sweep of the second frequency. The experiments show the possibility to coherently detect the optical spin alignment between ${M}_{S}=\ifmmode\pm\else\textpm\fi{}\frac{3}{2}$ via optically pumped silent ${M}_{S}=\ifmmode\pm\else\textpm\fi{}\frac{1}{2}$ sublevels of the spin-$\frac{3}{2}$ color centers, including a detection of Rabi oscillations.

A SAR Target Image Simulation Method With DNN Embedded to Calculate Electromagnetic Reflection

Electromagnetic (EM) scattering calculation is a very important part of most synthetic aperture radar (SAR) target image simulation methods. It affects the intensity of the radar echo signal to a great extent, thus affecting the quality of the final simulation image. EM reflection models are usually approximate formulas derived under certain assumptions. The errors between these models and the actual situation can cause significant differences between simulated images and real images. To solve this problem, we propose a novel modified SAR target image simulation framework, in which the deep neural network (DNN) is embedded to calculate the EM reflection, so that the DNN can directly learn and fit the EM reflection models from real SAR images. First, the intensity calculation of radar signal in a single reflection is separated from the cumulative calculation of multiple radar reflection signals intensity in each pixel. Thus, the approximate calculation formulas of EM reflection can be replaced with the DNN models. Next, the DNN model is trained with the backpropagation algorithm to learn the actual EM reflection model from real SAR images. Finally, the fitted EM reflection models and an image post-processing model are applied to simulate images of the target under different imaging angles. In the simulation framework, the functions of the neural network models are limited to calculating the reflection coefficient and adding sidelobe and speckle noise. The imaging model is still the original simulation method based on ray tracing, which ensures the correctness and generalization of the simulation method. Experiments show that the proposed simulation method can significantly improve the quality of the simulation image. When the image is normalized to [0, 1], the minimum mean square error between the simulated SAR images and the real images of the Sandia laboratory implementation of cylinders target can reach 0.003. The visualization results of the DNN models show that the fitted reflection coefficient calculation curve and the convolution kernel used for image post-processing are consistent with the laws in the theoretical model. In addition, when the proposed method is used to simulate complex targets, the similarity of simulation images can also be significantly improved.

Focal nodular marrow hyperplasia: Imaging features of 53 cases.

To describe the characteristic imaging features of focal nodular marrow hyperplasia (FNMH). Retrospective review of all patients with a diagnosis of FNMH between January 2007 and September 2019. The study included 53 patients, 7 males and 46 females with a mean age of 58 years (range 12-95 years). All had MRI with conventional spin echo sequences showing a poorly defined round/oval lesion with mild T1W iso/hyperintensity compared to skeletal muscle, low T2W turbo spin echo (TSE) signal intensity (SI) compared to marrow fat and variable SI on STIR, but never associated with reactive marrow oedema. All 53 patients had follow-up MRI, with all lesions remaining stable or partially resolving. In-phase (IP) and out-of-phase (OP) chemical shift imaging (CSI) was obtained in 31 of these, with 28 (90.3%) showing >20% SI drop on the OP sequence, while 3 (9.7%) demonstrated <20% SI drop. CT was available in 26 cases, 17 (65.4%) showing mild medullary sclerosis. Single-photon emission computed tomography CT (SPECT-CT) was available in four cases and Flourodeoxyglucose positron emission tomography CT (FDG PET-CT) in 2, all showing increased uptake. Focal uptake was also seen in three of eight patients who had undergone whole body bone scintigraphy. Only one lesion was biopsied, confirming FNMH. The imaging appearances of FNMH have been described on various modalities, particularly MRI with emphasis on the role of IP and OP CSI typically demonstrating >20% SI reduction. FNMH should be recognised and treated as a 'do not touch' lesion which does not require biopsy or prolonged follow-up. We describe and clarify the imaging characteristics of FNMH on MRI, including CSI, CT and various nuclear medicine modalities. An imaging algorithm is suggested for allowing a non-invasive diagnosis.

Phaseless Terahertz Coded-Aperture Imaging for Sparse Target Based on Phase Retrieval Algorithm.

Phaseless terahertz coded-aperture imaging (PL-TCAI) is a novel radar computational imaging method that utilizes the coded aperture and the incoherent detector array to achieve forward-looking and high-resolution imaging without relying on relative motion. In this paper, we propose a more reasonable and compact architecture for the PL-TCAI system and derive the imaging model of PL-TCAI based on the random frequency-hopping signal. Since most phase retrieval algorithms for PL-TCAI utilize only the intensity of echo signals to accurately reconstruct the target, excessive measurement samples are usually required. In order to reduce the number of measurement samples required for imaging, this paper proposes a sparse Wirtinger flow algorithm with optimal stepsize (SWFOS) by using the sparse prior of the target. The specific procedures of the SWFOS algorithm include the support recovery, initialization by truncated spectral method, iteration via gradient descent scheme, hard threshold operation, and stepsize optimization of iteration. Numerical simulations are performed, and the results show that the SWFOS algorithm not only has good performance for the PR problem, but can also sharply reduce the number of measurement samples required for imaging in the PL-TCAI system.

Sub-Kelvin (100 mK) time resolved electron paramagnetic resonance spectroscopy for studies of quantum dynamics of low-dimensional spin systems at low frequencies and magnetic fields.

This article presents a time-resolved electron paramagnetic resonance spectrometry setup designed to work at frequencies below 20 GHz and temperatures down to 50 mK. The setup consists of an on-chip microstrip resonator (Q < 100) placed in a dilution cryostat located within a superconducting 3D vector magnet. A housemade spin echo circuitry controlled by a microwave network analyzer, a pulse pattern generator, and an oscilloscope connects to the microstrip through a series of copper, stainless steel, and superconducting semirigid coaxial lines which are thermally anchored to the different cooling stages of the fridge by means of power attenuators, circulators, and a cryogenic amplifier. Spin echo experiments were performed at a 0.5-T magnetic field on a spin 1 2 paramagnetic coal marker sample mounted on a 15 GHz microstrip resonator at temperatures ranging from 100 to 800 mK. The results show an increase in echo signal intensity as temperature is decreased until saturation as theoretically expected in reaching 99% spin polarization at 100 mK. Our technique allows tuning of the spin system in the pure-state regime and minimizing dipolar fluctuations, which are the main contribution to decoherence in solid-state samples of single-molecule magnets (SMMs) - molecular spin systems that are currently being tested for applications in quantum computation. The achievement of full spin polarization at 100 mK will allow for coherent control over the time evolution of spin systems without the need for large magnetic fields (commonly used to polarize the dipolar bath at higher temperatures) and high frequencies.

Using Artificial Neural Network in Nuclear Spin Echo Experiments

The possibility of using an artificial neural network for discriminating nuclear spin echo signals recorded under conditions where the echo signal intensity is comparable to the noise amplitude is demonstrated. It is proposed to teach the neural network using data obtained by superposition of the model Gaussian signals onto experimentally measured noise signals.

Analysis and characterization of accumulated photon echo signals by noncolinear laser pulses based on rare earth ion-doped crystal

Photon echo technique based on rare earth ion-doped crystal has potential applications in optical signal processing. However, the coexistence of different types of photon echo lead to a great reduction of signal-to-noise ratio (SNR). Noncolinear scheme can be adopted to improve SNR by separating such echo signals in the space domain. In this paper, by using the noncolinear beam configuration, we present a detailed analysis and characterization of the accumulated photon echo signals based on rare earth ion-doped crystal. Accumulated photon echo signals occurred at different moment can be analytically predicted using Cayley–Klein parameters method, which is confirmed with the numerical results by solving the Maxwell–Bloch equations. The performance of the spatial-spectral grating has been evaluated, including the grating period, grating amplitude and grating shape. Finally, in the case of noncolinear configuration, the influence parameters related to echo signal intensity has also been discussed compared with the collinear geometry. The results presented here may be helpful to gain new insights on the typical parameters for optical signal processing by using photon echo technology.

Raman lidar with for geoecological monitoring

Application of CCD array photodetector technology is shown to provide record synchronously hundreds of spectral intervals, increase essentially the relative aperture and intensity of echo-signals in the input optical path as well as to reduce the mass – dimension parameters of hyperspectral Raman LIDAR as a whole for geoecological monitoring by aerial and underwater unmanned vehicles.