Ronger Zheng

Ocean University of China | OUC · Department of Physics

The pore structure of marine natural gas-hydrate-bearing sediments is a key factor related to the physical properties of reservoirs. However, the resolution of micro-computed tomography (micro-CT) images is unsuitable for the analysis of pore structures in fine-grained sediments. In this regard, super-resolution (SR) reconstruction technology is ex...

In acoustics-related interdisciplinary areas, the shock wave of laser-induced breakdown has garnered significant attention. However, research on the propagation of shock waves in non-spherical symmetry is insufficient in both theoretical and experimental aspects. This paper aims to thoroughly study the evolution of underwater shock wave directivity...

As a biogenic calcium carbonate, the seashell plays a crucial role in marine environmental studies. In these studies, it is essential to investigate the composition of the seashell. In this study, we used laser-induced breakdown spectroscopy (LIBS) to analyze the elemental composition of cultured scallop-shell (Patinopecten yessoensis), with a spec...

Element recognition of laser-induced breakdown spectroscopy (LIBS) can be achieved by analyzing the corresponding peaks of plasma emissions. However, it is still challenging to make quick judgments due to database disagreements, such as wavelength or line-ratio. This study presents a simple method to conduct element recognition based on comparing v...

The three-dimensional reconstruction technique has been widely applied across various fields, with imaging serving as a fundamental approach to achieve this reconstruction. In the present study, we employed micro-imaging to realize 3D reconstruction based on the “shape from focus” and the chromatic aberration effect. This approach eliminates the ne...

The element ratio of Mg/Ca is a primary proxy in studying the composition of seashells, and laser-induced breakdown spectroscopy (LIBS) is a practical technique for elemental analysis. In this work, we tried to apply LIBS to investigate the Mg/Ca ratio in cultured seashells of two scallop species ( Chlamys farreri and Patinopecten yessoensis). It w...

Signal fluctuation is an important issue in confocal measurements because minor intensity variation would cause a distinct deviation in the measurement result. In this work, it is proposed to use laser modulation and power monitoring to suppress the signal fluctuation in confocal measurements. The power monitoring is utilized to obtain the referenc...

Research on the transient variation processes of oceanic dissolved CO2 makes significant sense because of the complexity and dynamics of the marine environment. Yet, it is inherently challenging due to the limitation of the response performance of in situ sensors. Here, we report a novel system solution capable of providing high-performance detecti...

Improving the stability of underwater LIBS is a key point for its practical use in oceanic applications. The traditional normalization method of using the internal standard element is often limited in some practical cases due to the lack of a suitable element as a reference. In this study, we compared three external normalization strategies by usin...

The underwater Fraunhofer-type absorption signal from a plasma generated on an immersed Cu target was investigated using single-pulse laser-induced breakdown spectroscopy (LIBS). We found that clear underwater Fraunhofer-type absorption lines...

The formation of laser-induced plasma on a solid target depends strongly on the laser pulse parameters and the ambient conditions. In this work, the characteristics of laser-induced plasma generated in...

The pore structure of marine sediments varies with the distribution of gas-hydrate, hence affecting the gas-water permeability. CT image is a conventional approach to view the internal structure, while for hydrate-bearing sediment investigation, rather poor resolution of obtained image has limited the accuracy of the analysis. Recently, super-resol...

Laser-induced breakdown spectroscopy (LIBS) is a capable technique for elementary analysis, while LIBS quantitation is still under development. In quantitation, precise laser focusing plays an important role because it ensures the distance between the laser and samples. In the present work, we employed spectral intensity as a direct way to assist l...

Microscale processes and interactions in the ocean are pervasive. They play a fundamental role in global biogeochemical cycles and have a significant impact on benthic marine ecosystems. However, our understanding of microscale processes and interactions that appeared in the benthic environment is still very limited, particularly for the deep ocean...

The absorption and scattering of light by marine water and suspended particles lead to the distortion of color in underwater microscopic images. This paper presents an improved cycle generative adversarial network (CycleGAN) algorithm for effectively correcting the color of microscopic images of underwater targets. The structural similarity index (...

Over the past decades, Raman spectroscopy has been proven to be a powerful tool for in situ detection in the deep sea. However, two important issues are usually presented for solid detection of Raman in the sea: a) the implementation of accurate laser focusing using the manipulator of remotely operated vehicles is difficult); b) it is challenging t...

Lidar is a reliable tool for active remote sensing detection of atmospheric aerosols. A multi-wavelength aerosol lidar (MWAL) with 355 nm, 532 and 1064 nm as detection light sources has been developed and deployed for operational observations at Haidian District Meteorological Service of Beijing. The structure design, specifications, observation ca...

Laser-induced breakdown spectroscopy (LIBS) is a practical technique for in-situ detection, but self-absorption effect has been a big issue for quantitative applications of this technique. In presented work, a method was developed to correct self-absorption to improve the quantitation of underwater LIBS. We proposed “relative self-absorption coeffi...

Laser-induced breakdown spectroscopy is a promising technique in ocean applications due to the great capability of in-situ detection. However, the LIBS detection is not satisfying in water, and a typical performance is that emission lines usually overlap with the high spectral background. So, it is necessary to correct the baseline (i.e. spectral b...

Hydrostatic pressure is a key factor that influences laser-induced bubble dynamics in water. In this work, we investigated laser-induced bubble dynamics at high hydrostatic pressures up to 53.2 MPa, by using a high-pressure chamber combined with the shadowgraph imaging technique. It was shown that at the atmosphere pressure, the bubble evolution ag...

The detection capability of long-pulse laser-induced breakdown spectroscopy (LIBS) for the simultaneous analysis of submerged solids and bulk water has been investigated with a Cu target immersed in a CaCl2 solution. It is shown that a short pulse leads to the formation of Fraunhofer-type absorption lines at shorter delays and severe self-reversal...

As a powerful in situ detection technique, Raman spectroscopy is becoming a popular underwater investigation method, especially in deep-sea research. In this paper, an easy-to-operate underwater Raman system with a compact design and competitive sensitivity is introduced. All the components, including the optical module and the electronic module, w...

The detection of dissolved gases in seawater plays an important role in oceanic observations and exploration. As a potential technique for oceanic applications, Raman spectroscopy has been successfully applied in hydrothermal vents and cold seep fluids, but it has not yet been used in common seawater due to the technique’s lower sensitivity. In thi...

Temporal-resolved measurement plays an important role in laser-induced breakdown spectroscopy (LIBS), and intensified CCD camera (ICCD) is widely applied in this field. In this work, we proposed a simple way instead of ICCD to achieve temporal-resolved detection using a dual light-collection worked with 2 CMOS cameras or 2 fiber spectrometers. In t...

Continuous observation of aquatic pCO2 at the ocean surface, with a sensitive response time and high spatiotemporal resolution, is essential for research into the carbon biogeochemical cycle. In this work, a portable tunable diode laser absorption spectroscopy (TDLAS) system for dissolved CO2 detection in surface seawater, coupled with a home-made...

The effects of pulse duration on spectral emission of H and O obtained by laser-induced breakdown spectroscopy (LIBS) in bulk water have been investigated. We found distinct atomic lines of H and O by irradiating with a laser pulse of 100 ns duration or longer. The time-resolved emission spectra show that higher emission intensity and longer plasma...

Laser-induced breakdown spectroscopy (LIBS) signals in water always suffer strong pulse-to-pulse fluctuations that result in poor stability of the spectrum. In this work, a spectrum normalization method based on acoustic signals measured by a hydrophone immersed in water was developed and compared with laser energy normalization. The characteristic...

Laser-induced breakdown spectroscopy (LIBS) has been successfully applied for in-situ detection in the sea, and the water pressure is found as the main influence for LIBS signal compared with the temperature or the salinity. In this work, we brought in the self-absorption to evaluate the pressure effect on LIBS detection. By using fast imaging and...

Long ns pulses have been proven to be effective in enhancing the LIBS signals of submerged solids. However, the enhancement effect on the liquid detection has yet to be further...

Laser-induced breakdown spectroscopy (LIBS) has been successfully developed into the oceanic chemical sensor for deep-sea exploration. However, the LIBS signals will be affected by marine environmental factors, and this effect...

In recent years, the investigation and exploitation of hydrothermal region and polymetallic mineral areas has become a hot topic. The emergence of underwater vehicle platforms has made it possible for new chemical sensors to be applied in marine in-situ detection. Laser-induced breakdown spectroscopy (LIBS), with its advantages of rapid real-time a...

In recent years, laser-induced breakdown spectroscopy (LIBS) has gained significant attention as a means for simple elemental analyses. The suitability of LIBS for contactless analysis allows it to be a perfect candidate for underwater applications. While the majority of LIBS systems still rely upon sub-kHz pulsed lasers, this contribution introduc...

Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) has been demonstrated to enable efficient elemental analysis of bulk water. Its applications are based on the fundamental understanding of characteristics of the secondary plasma. However, due to the poor stability of the secondary breakdown, the inherent formation and evolution processes...

With the application of an orthogonal dual-pulse Laser-induced breakdown spectroscopy (DP-LIBS) excitation, when compared to single-pulse LIBS (SP-LIBS), significant emission intensity enhancements for a wide range of elements are obtained in seawater. The influence of time delay between two laser pulses on the underwater laser-induced plasma chara...

The knowledge on the laser-induced plasma emission in water at high pressures is essential for the application of laser-induced breakdown spectroscopy (LIBS) in the deep-sea. In this work, we investigate the spectral features of ionic, atomic and molecular emissions for the plasma in water at different pressures from 1 to 40 MPa. By comparing betwe...

Depth profiling investigation plays an important role in studying the dynamic processes of the ocean. In this paper, a newly developed hyphenated underwater system based on multi-optical spectrometry is introduced and used to measure seawater spectra at different depths with the aid of a remotely operated vehicle (ROV). The hyphenated system consis...

Laser-induced plasma in water always suffers from strong pulse-to-pulse fluctuations due to the multiple breakdown phenomenon, leading to a poor stability of underwater LIBS signals. The traditional normalization method by using the internal standard element is often limited in some practical cases due to the lack of a suitable element as a referen...

It has been proved that the detection of laser-induced breakdown spectroscopy (LIBS) could be improved by the flame. In this work, we applied flame enhanced LIBS for the detection of elements in water, while the flame was generated from the mixture of alcohol and aqueous solution. In the measurements, the flame is functioned as an assistance to enh...

Laser-induced breakdown spectroscopy (LIBS) has been successfully applied to ocean exploration, but the changes in marine environmental factors could have an important impact on the LIBS signals. The aim of the research is to investigate the ambient water temperature effects on laser-induced plasma in bulk water. Both the spectroscopic and fast ima...

The effects of salinity on underwater laser-induced breakdown spectroscopy (LIBS) were investigated with salinities ranging from 2‰ to 50‰. Both spectroscopic and fast imaging techniques were used to observe plasma emission. It was shown that as the salinity increased, emission intensities of the atomic lines increased, while intensities of the ion...

In recent years, Raman spectroscopy techniques have been successfully applied to the area of deep-sea exploration. However, there are still some problems impeding the further application of Raman systems. For example, the large size of an underwater Raman system makes it difficult to deploy on the underwater vehicle. Meanwhile, the sensitivity is o...

Underwater laser-induced breakdown spectroscopy (LIBS) and underwater laser Raman spectroscopy have been successfully applied in deep sea research. These two technologies have similar devices and complementary detecting targets. The combination of these two technologies is expected to be an improvement for deep-sea study. In this paper, a prototype...

Laser-induced breakdown spectroscopy (LIBS) has attracted extensive attention as a new technique for in-situ marine application. In this work, the influence of deep-sea high pressure environment on LIBS signals was investigated by using a compact LIBS-sea system developed by Ocean University of China for the in-situ chemical analysis of seawater. T...

Characteristics of the secondary breakdown of dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) in bulk water were investigated with different axial focusing arrangements and laser energies of the second laser pulse. Compared to the pre-focus or in-focus arrangement, post-focus arrangement could provide both stronger emissions and better re...

Laser-induced breakdown spectroscopy (LIBS) has been extensively applied due to the capabilities of real-time, multi- phase and multi-element analysis. With the advantages, portable LIBS is in rapid development with great potential of field measurements. In this work, a portable LIBS was developed by a 50 μJ level laser for excitation and an object...

The analytical characteristics of U isotopic analysis with laser-induced breakdown spectroscopy (LIBS) were investigated by analyzing a series of U3O8–Li2B4O7 fused glassy disks. The ²³⁵U isotopic contents in the samples ranged from natural abundance at ~0.72 atom-% to a highly enriched level at ~94 atom-%. Isotopic information of the sample was ex...

In recent years, cabled ocean observation technology has been increasingly used for deep sea in situ research. As sophisticated sensor or measurement system starts to be applied on a remotely operated vehicle (ROV), it presents the requirement to maintain a stable condition of measurement system cabin. In this paper, we introduce one kind of ROV-ba...

Laser-induced breakdown spectroscopy (LIBS) is a new technique for seashell elemental analysis, and now that application is in rapid development. In this work, LIBS was applied for scallop shell [Chlamys (Azumapecten) farreri] analysis using the element ratio Sr/Ca, and the analytical result was compared under objective lens (OL) focusing and singl...

The measurement of CO2 at air-sea interface is significant to marine scientific research. There are many commercial instruments can be used for CO2 measurements in marine environment, among which the instruments based on tunable diode laser absorption spectroscopy (TDLAS) play an important role due to the advantages of high sensitivity, good enviro...

Laser-induced breakdown spectroscopy (LIBS) has drawn more attention as a new technique for in situ detection of seawater, especially for hydrothermal areas. In order to evaluate the focusing geometry effect on laser-induced plasma in bulk water, four focusing arrangements were tried out with a single lens as well as with a double-lens combination....

By refering to the principle and structure of the Mueller matrix ellipsometry, a LIF ellipsometric setup with rotating waveplate was built up to investigate the polarization characterization of laser-induced fluorescence from the simulated oil spill samples under excitation of laser with different elliptical polarization states. The setup was calib...

Raman spectroscopy has great potential as a tool in a variety of hydrothermal science applications. However, its low sensitivity has limited its use in common sea areas. In this paper, we develop a near-concentric cavity-enhanced Raman spectroscopy system to directly detect bicarbonate in seawater for the first time. With the aid of this near-conce...

The exploitation and research of deep-sea hydrothermal vent has been an issue of great interest in ocean research in recent years. Laser-induced breakdown spectroscopy (LIBS) has great potential for ocean application due to the capabilities of stand-off, multiphase, and multielement analysis. In this work, a newly developed compact 4000 m rated LIB...

Laser-induced breakdown spectroscopy (LIBS) has been applied to classify French wines according to their production regions. The use of the surface-assisted (or surface-enhanced) sample preparation method enabled a sub-ppm limit of detection (LOD), which led to the detection and identification of at least 22 metal and nonmetal elements in a typical...

Laser induced fluorescence technique has been considered as one of the most effective means for the detection of marine oil spills, while its feasibility was limited by the fluorescence signal resulted from chlorophyll and CDOM in natural water. To eliminate those influence during the detection, a LIF polarization experimental setup with 532 nm cw-...

The influence of laser wavelength on the characteristics of laser-induced breakdown spectroscopy (LIBS) in bulk water was investigated by using 532- and 1064-nm lasers. We demonstrated that higher laser energy does not lead to higher LIBS signals because of the strong plasma shielding occurring at high laser energies, as shown by the spectroscopic...

Axial focusing arrangement effects on collinear dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) in a bulk solution were investigated by spectra and fast images. By properly defocusing the second laser pulse beyond the first laser formed bubble (LFB), brighter and larger plasmas could be produced due to higher breakdown efficiency and high...

Hydrothermal vent fluids, cold seep fluids, their associated chemosynthetic communities, and the biogeochemical anaerobic oxidation of methane (AOM) play very important roles in the biogeochemical sulfur and carbon cycles in the ocean. Based on our previous success developing and deploying a deep-sea sediment pore water Raman probe, we developed a...

For the exploration of gas hydrate resources by measuring the dissolved methane concentration in seawater, a continuous-wave cavity ringdown spectroscopy (CW-CRDS) experimental setup was constructed for trace methane detection. A current-modulation method, rather than a cavity-modulation method using an optical switch and a piezoelectric transducer...

The establishment of the seafloor cabled observatory network will help to learn how the ocean operates. This study reports the design of a shore-based terminal for the OUC-Raman (OUC: Ocean University of China) instrument node in an observatory network. Based on Raman spectrometry, it is used to detect radical ion in situ. The shore-based terminal...

The detection of dissolved gases in seawater plays an important role in ocean observation and exploration. As a potential technique for oceanic applications, Raman spectroscopy has already proved its advantages in the simultaneous detection of multiple species during previous deep-sea explorations. Due to the low sensitivity of conventional Raman m...