Xi-Cheng Zhang

Xi-Cheng Zhang
ITMO University | SPbNRU ITMO · Department of Photonics and Optical Information Technology

About

144
Publications
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Publications

Publications (144)
Article
Broadband terahertz (THz) wave emission from flowing liquid targets has been demonstrated under short optical pulse excitation. Observations have been reported by using liquid THz sources, including optimal angle of incidence, preference of subpicosecond pulse excitation, and strong sideway emission. Compared with solid targets, the fluidity of liq...
Article
The terahertz Kerr effect (TKE) spectroscopy provides time-resolved measurement of low-frequency molecular motions of liquids. Here, the intense broadband terahertz (THz) pulses resonantly excite multiple molecular modes in pure ethanol and ethanol-water mixtures. For pure ethanol, the obtained unipolar TKE response contains the molecular relaxatio...
Article
Full-text available
In contrast to imaging using position-resolving cameras, single-pixel imaging uses a bucket detector along with spatially structured illumination to compressively recover images. This emerging imaging technique is a promising candidate for a broad range of applications due to the high signal-to-noise ratio (SNR) and sensitivity, and applicability i...
Article
Full-text available
Laser-driven nonlinear phenomena can both reveal the structural features of materials and become the basis for the development of various translated technologies, including highly intense terahertz sources. Here we realize a modified single-color double-pulse excitation scheme for enhancing the terahertz wave generation in flat liquid jets, and we...
Conference Paper
We propose and demonstrate a single-pixel temporal imaging system with high resolution, efficiency and sensitivity. A terahertz pulse with pulse energy as low as 5 fJ is compressively imaged with a resolution down to 16 fs.
Article
Developing efficient and robust terahertz (THz) sources is of incessant interest in the THz community for their wide applications. With successive effort in past decades, numerous groups have achieved THz wave generation from solids, gases, and plasmas. However, liquid, especially liquid water has never been demonstrated as a THz source. One main r...
Article
A laser plasma wake field in a single-color femtosecond laser filament determines the acceleration of ionized electrons, which affects the intensity and bandwidth of the emitted terahertz wave and is important for understanding the fundamental nonlinear process of THz generation. Since the THz wave generated by a laser wake field is extremely small...
Article
Full-text available
We proposed a simple and cost-effective method to manipulate the temporal and spectral properties of pulsed terahertz waves. A deep modulation of a pulse spectrum was both numerically and experimentally verified using Fresnel apertures with a radius ranging from several to several tens of the central wavelength of the broadband terahertz radiation....
Article
Full-text available
At present, the terahertz time-domain spectroscopic information of each component in multi-composition compounds detection is comprehensively combined. The lower resolution level of mixed spectra has posed many difficulties in signal analysis due to the overlapping characteristic information in the mixed ones. In this paper, to compare the performa...
Preprint
Full-text available
Temporal imaging, the temporal analog of spatial imaging, has been studied for decades to efficiently measure the fast-varying temporal structure of electromagnetic waves using techniques such as time lenses and temporal ghost imaging. Unfortunately, these techniques can be applied only to selected frequency bands with a limited temporal resolution...
Article
We experimentally show the spectrally averaged nonlinear refractive index and absorption coefficient for liquid water, water vapor, α -pinene, and Si using a full-phase analysis in the terahertz regime through a standard time-domain spectrometer. Our results confirm that the nonlinear index of refraction of the liquid samples in this regime exceeds...
Article
Full-text available
The fundamental properties of water molecules, such as their molecular polarizability, have not yet been clarified. The hydrogen bond network is generally considered to play an important role in the thermodynamic properties of water. The terahertz (THz) Kerr effect technique, as a novel tool, is expected to be useful in exploring the low-frequency...
Article
Full-text available
A convenient and practical scheme for spatially characterizing terahertz (THz) signals has been invented by scientists in the US. The approach could prove useful for applications such as beam profiling, biomedical sensing, flaw detection and security screening. Jiapeng Zhao and coworkers from the University of Rochester make use of the electrooptic...
Article
Full-text available
By irradiating a water jet with double pulses, we demonstrate 4-fold higher THz wave generation than for a single pump pulse. The dependence of the enhanced THz signal on the temporal delay between two collinear pulses reveals the optimal time for launching signal pulse is near 2-4 ps, which corresponds to the time needed to create the complete pre...
Article
Full-text available
Terahertz radiation generation from liquid water has long been considered impossible due to strong absorption. A few very recent works reported terahertz generation from water, but the mechanism is not clear and the efficiency demands to be enhanced. We show experimentally that strong single-cycle terahertz radiation with field strength of 0.2MVcm−...
Article
Full-text available
Polar liquids are strong absorbers of electromagnetic waves in the terahertz range, therefore, historically such liquids have not been considered as good candidates for terahertz sources. However, flowing liquid medium has explicit advantages, such as a higher damage threshold compared to solid-state sources and more efficient ionization process co...
Preprint
Full-text available
Polar liquids are strong absorbers of electromagnetic waves in the terahertz range, therefore, historically such liquids have not been considered as good candidates for terahertz sources. However, flowing liquid medium has explicit advantages, such as a higher damage threshold compared to solid-state sources and more efficient ionization process co...
Preprint
Full-text available
Recently, there has been growing interest in terahertz (THz) wave generation from liquids under optical excitation. Here, we propose and demonstrate the use of liquid lines in place of liquid films as THz emitters to boost THz signals. The geometry of the emitter eliminates the total internal reflection at the flat liquid-air interface. In addition...
Article
With the increasing demands for remote spectroscopy in many fields ranging from homeland security to environmental monitoring, terahertz (THz) spectroscopy has drawn a significant amount of attention because of its capability to acquire chemical spectral signatures non-invasively. However, advanced THz remote sensing techniques are obstructed by qu...
Preprint
Full-text available
Recently, computational sampling methods have been implemented to spatially characterize terahertz (THz) fields. Previous methods usually rely on either specialized THz devices such as THz spatial light modulators, or complicated systems requiring assistance from photon-excited free-carriers with high-speed synchronization among multiple optical be...
Conference Paper
Full-text available
We measured n2 of liquid water in THz range by using the Z-scan method. The measured n2 is 3.5×10-10 cm2/W which is six orders higher than the values for VIS and NIR spectral ranges.
Article
Liquid water excited by intense two-color laser pulses radiates electromagnetic waves at terahertz frequencies. Compared with one-color excitation, two-orders of magnitude enhanced terahertz energy are observed by using asymmetric optical excitation with the same total excitation pulse energy and focusing geometry. Modulation of the terahertz field...
Article
The past two decades have seen an exponential growth of interest in one of the least explored region of the electromagnetic spectrum, the terahertz (THz) frequency band, ranging from to 0.1 to 10 THz. Once only the realm of astrophysicists studying the background radiation of the universe, THz waves have become little by little relevant in the most...
Article
Full-text available
Remote sensing is one of the major challenges for Terahertz (THz) radiation applications, due to the THz wave attenuation by the atmosphere water vapor during its propagation. THz-Radiation-Enhanced-Emission-of-Fluorescence (REEF) is a THz air-photonics technique that has the potential to bypass this issue, by having the sought-after THz spectral f...
Article
Full-text available
The present paper studies the generation mechanism of terahertz (THz) radiation from tightly focused femtosecond laser pulses in a gas medium. We measured the angular radiation pattern under different focusing conditions and observed that, with the deepening of focus, the angular radiation pattern changes and optical-to-THz conversion efficiency in...
Article
Background: The diagnosis of isolated visceral artery dissection (IVAD) has become more common with the increasing use of computed tomography angiography (CTA). We examined the presentation, treatment and outcomes of patients with IVAD treated at our institution. Methods: The records of 72 patients treated for IVAD between January 2010 and Augus...
Article
Full-text available
his paper describes research on the optics of functional materials, which can change their dielectric properties according to their function. Vanadium dioxide is a good example of such a material where the insulator-to-metal phase transition offers the possibility to control dielectric properties and to use them as a triggering element for photonic...
Conference Paper
Generation of terahertz (THz) radiation was observed in epitaxial VO 2 films grown on R- and C-cut sapphire substrates above and below the metal-insulator phase transition temperature. Polarization analysis of the emitted THz radiation reveals strong in-plane anisotropy of the conductive phase of VO 2 which is not observed for insulating phase, gen...
Article
Optics Letters announces the redesign of its journal article pages and new manuscript templates for authors.
Conference Paper
Exelis Geospatial Systems and its CEIS partners at the University of Rochester and Rochester Institute of Technology are developing an active THz imaging system for use in standoff detection, molecular spectroscopy and penetration imaging. The current activity is focused on developing a precision instrument for the detection of radiation centered o...
Article
Full-text available
The integration of ambient air plasmas as source and sensor in terahertz time-domain techniques allows spectral measurements covering the elusive terahertz gap (0.1-10 THz), further increasing the impact of those scientific tools in the study of the four states of matter. In this article we describe the experimental study of the terahertz emission...
Article
To evaluate our experience of the clinical management of spontaneous isolated superior mesenteric artery dissection (ISMAD). From January 2008 to July 2013, 18 patients with ISMAD were retrospectively analyzed, including 7 patients who received conservative therapy, 9 patients who received reconstruction with bare stents, and 2 patients who underwe...
Article
Optics Letters Editors strive to provide timely reviews and decisions for authors while bringing top quality papers to the optics community. The purpose of this editorial is to explain Optics Letters' acceptance criteria and editorial procedures. Our hope is that greater transparency concerning the decision-making process will increase understandin...
Article
Background: Spontaneous isolated superior mesenteric artery dissection (ISMAD) is exceedingly rare. The therapeutic options range from observation to medical treatment to surgery or endovascular repair. We present our experience of the clinical management of ISMADs. Methods: Sixteen patients with ISMAD from January 2008 to July 2012 were retrosp...
Article
Recently, air plasma, produced by focusing an intense laser beam to ionize atoms or molecules, has been demonstrated to be a promising source of broadband terahertz waves. However, simultaneous broadband and coherent detection of such broadband terahertz waves is still challenging. Electro-optical sampling and photoconductive antennas are the typic...
Article
Terahertz (THz) wave science and technology have been found countless applications in biomedical imaging, security screening, and non-destructive testing as they approach maturity. However, due to the challenge of high ambient moisture absorption, the development of remote open-air broadband THz spectroscopy technology is lagging behind the compell...
Article
This paper studies laser air-photonics used for remote sensing of short pulses of electromagnetic radiation at terahertz frequency. Through the laser ionization process, the air is capable of generating terahertz field strengths greater than 1 MV/cm, useful bandwidths over 100 terahertz, and highly directional emission patterns. Following ionizatio...
Article
Semiconductor nonlinearity in the range of terahertz (THz) frequency has been attracting considerable attention due to the recent development of high-power semiconductor-based nanodevices. However, the underlying physics concerning carrier dynamics in the presence of high-field THz transients is still obscure. This paper introduces an ultrafast, ti...
Conference Paper
Exelis Geospatial Systems and its CEIS partners at the University of Rochester and Rochester Institute of Technology are developing an active THz imaging focal plane for use in standoff detection, molecular spectroscopy and penetration imaging. This activity is focused on the detection of radiation centered on the atmospheric window at 215.5 GHz. T...
Article
Objective: The purpose of our study was to evaluate the technical feasibility, procedural complications, clinical follow-up, and computed tomography (CT) scan outcomes of hepatic artery pseudoaneurysms (HAPs) treated with stent graft. Methods: Between October 2004 and October 2009, we treated 8 patients with HAPs with stent graft. Results: Ste...
Conference Paper
We demonstrate in the experiment and simulations that interference between two contributions into the terahertz wave generation in a femtosecond filament, namely, the free electron photocurrent and the nonlinear polarization of neutrals, can be used for the femtosecond coherent control of the THz spectra.
Conference Paper
Full-text available
Terahertz-Radiation Enhanced Emission of Fluorescence (THz-REEF) was studied in the counter-propagating configuration as a more accurate representation of stand-off THz sensing scenarios. Determination of the THz amplitude and phase using this technique was successfully demonstrated.
Article
Undesired reflection caused by impedance mismatch can lead to significant power loss and other unwanted effects. In the terahertz regime, anti-reflection method has evolved from simple quarter-wave antireflection coating to sophisticated metamaterial device and photonic structures. In this paper, we examined and compared the theories and techniques...
Conference Paper
We describe preliminary design, modeling and test results for the development of a monolithic, high pixel density, THz band focal plane array (FPA) fabricated in a commercial CMOS process. Each pixel unit cell contains multiple individual THz band antennae that are coupled to independent amplifiers. The amplified signals are summed either coherentl...
Article
By utilizing a terahertz (THz) pump/THz probe spectroscopy, the coherent plasma resonances in n-doped III-V semiconductors are clearly demonstrated through the modulations of reflection. The interaction between energetic electrons and the phonon field on the subpicosecond time scale is verified, and it is shown that this interaction applies for aco...
Article
Full-text available
Through the ionization process, the very air that we breath is capable of generating terahertz (THz) electromagnetic field strengths greater than 1 MV/cm, useful bandwidths of over 100 THz, and highly directional emission patterns. Following the ionization of air, the emitted air-plasma fluorescence or acoustics can serve as an omnidirectional, bro...
Article
Time-domain terahertz spectrometry is a promising technology for identifying substances covered by optically opaque dielectric materials. However, the performance of algorithms analyzing this data has been weak, especially with a low signal-to-noise ratio. We have developed a new approach for analyzing this data that is robust against the effects o...
Article
Full-text available
Terahertz (THz) wave generation and detection using gaseous medium as both the THz wave emitter and sensor, also termed “THz wave air photonics”, has attracted much scientific attention. We report the most recent progresses in THz generation and detection in laser-induced gas plasma. The overall emphasis of this paper is on THz wave detection with...
Article
Full-text available
The method allows retrieval of the absorbance of a sample without the need for a reference measurement. The method measures the dynamic variation of frequency resolution as the waveform is being acquired. In terahertz wave time-domain spectroscopy, the frequency resolution increases as the temporal window increases. Therefore, narrow absorption pea...
Article
The enhancement of laser-induced fluorescence by intense terahertz pulses was studied both theoretically and experimentally using selected gases. Semiclassical physical picture incorporating photoionization, electron heating, impact excitation, and dissociative recombination was used to explain the plasma dynamics under terahertz radiation in picos...
Article
In the last several decades, glow discharge detectors (GDD) have been utilized to detect microwave radiation. Recently, these detectors were used to study higher frequencies within the terahertz (THz) band of the electromagnetic spectrum. Commercial neon lamps can act as GDDs, and their performance at 0.2 THz was investigated. A THz continuous-wave...
Article
Full-text available
Ultrabroadband, intense terahertz (THz) waves can be generated and detected using gaseous media as both the THz wave emitter and sensor, with a bandwidth covering the entire “THz gap” and well beyond. We review our most recent experimental and theoretical progress in THz generation, detection, and manipulation in laser-induced gas plasma. In the ge...
Article
Pulsed THz wave spectroscopy using air as the THz wave emitter with the excitation of femtosecond laser provides intense (>100 kV/cm) and broadband THz waves (usable bandwidth from 0.3 to 11 THz). Using the air-biased-coherent-detection (ABCD) method, air can also coherently detect pulsed THz waves over a broadband spectrum. By utilizing these two...
Chapter
The development of techniques for inspection of explosives and other hazardous materials has become more and more attractive as concerns about public security have increased considerably in the past years 1–3. Among all explosive devices, landmine is the most demanding target to be detected. Landmines were widely used in all kinds of battlefields a...
Chapter
To develop technologies utilizing THz waves, one needs to first understand the interaction between THz waves and materials. In this chapter we will discuss the dynamics of THz wave interaction with different kinds of materials.