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We report on the latest developments of various Terawatt class laser technologies for the generation of intense Terahertz pulses. We will present our advances in high energy Ti:Sapphire lasers optimized for broadband THz generation: flexible architecture, superior quality for both temporal and spatial beam profile, embedded intelligence for ease of use. We then turn to compact diode-pumped TW ultrafast laser as excellent sources for generating high energy THz radiation. Optical rectification in LiNbO3 with 15mJ ultrashort pulse already allowed to demonstrate 150μJ THz with as high as 0.36% conversion efficiency. We conclude by presenting a laser delivering 250mJ at 50Hz repetition rate and 480fs pulse duration, holding the potential to generate 1mJ-level Terahertz ultrashort in an equivalent setup.
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THz liquid photonics is a new research frontier in laser-matter interaction community. We have successfully demonstrated THz wave generation from ionized liquids, including from liquid water, liquid nitrogen, and liquid gallium. Preferable to general targets, a flowing liquid line provides a fresh area for each excitation pulse, so the chaos and debris caused by the previous pulse will not influence the next one. This makes it possible of using a kHz repetition rate laser for excitation. THz wave generation from ionized liquids presents photoionization processes that are different from those in gases.
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太赫兹(THz)光谱技术在生物医学领域具有巨大潜力。但生物样品组成复杂、含水量高,导致生物标志物的THz吸收峰信噪比差、难识别,目前未能真正进入临床应用。为此,我们从样本前处理、数据分析、仪器系统三个角度展开,分析研究生物医学检测中THz信噪比改善的相关工作,希望为后续THz技术在生物医学领域中的应用提供方向。
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太赫兹光谱技术对不同结构和组成的生物分子表现出特有的信号响应,这些特征指纹光谱在生物化学及药物的分子识别、定性定量分析以及生物医学无损无标记检测等方面具有重要的应用。太赫兹光谱探测与量子化学理论计算相结合,能有效揭示太赫兹光谱所包含的分子振动特点,加深理解有关分子结构和分子间相互作用信息。
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基于半导体多量子阱结构的电泵浦太赫兹(THz)量子级联激光器(QCL)具有大功率输出、高光束质量、宽频率覆盖等特点。在1-5 THz频率范围内,THz QCL是最高效的电泵浦THz辐射源之一,在成像、光谱检测、通信等方面具有重要应用。本报告将介绍简要我们在高性能THz QCL方面的研究成果,并进一步重点介绍THz QCL在生物医学成像方面的应用实例。
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Gliomas are invasive brain tumors with high rates of recurrence and mortality. One of the main directions of diagnostics and treatment of malignant tumors is investigation of the reasons of formation and the routes of the generation of cancer molecular markers for the elaboration of new methods of early diagnostics and therapy. Glioma molecular markers are found in brain tissues and body fluids and can be divided into: circulating tumor cells, extracellular vesicles, circulating tumor nucleic acids, proteins and metabolites. The determination of molecular markers in body fluids (plasma, serum, urine, saliva, CSF) has great potential for early diagnosis of gliomas and non-invasive/minimally invasive control of treatment. Glioma molecular markers have unique THz resonances, which prove the feasibility of using THz spectroscopy to diagnosis of gliomas. It has been recently shown that one of specific markers for glioma differential diagnostics are enantiomers of 2-hydroxyglutarate (L-2HG and D-2HG) in brain tissues and blood. The paper presents the results of a study of the most probable glioma molecular markers by the terahertz time-domain spectroscopy.
The work was supported by the RFBR and National Natural Science Foundation of China, research project № 19-52-55004.
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Scattering-type scanning near-field optical microscopy (s-SNOM) has emerged as a powerful tool for nanoscale imaging of surfaces. In conjunction with broadband input radiation, this approach offers the possibility for both imaging and spectroscopy on a deep sub-wavelength scale, with a resolution limited by the size of a sharp metal tip rather than by the radiation wavelength. However, in order to exploit these capabilities for quantitative measurements, it is crucial to develop an understanding of how the shape and size of the structures under study affects the measured signal. This concern is of particular significance in the long-wavelength infrared and terahertz regions of the spectrum, where spectroscopic features due to mobile charge carriers are typically very broad, so that a detailed fitting procedure to, e.g., the Drude model, is generally required to extract material parameters. Here, we present a broadband THz s-SNOM examination of subwavelength metallic structures of various sizes and shapes, deposited on an insulating substrate. Naively, one would expect that, for metallic objects that are much smaller than the wavelength (e.g., ?/200) but much larger than the tip radius (e.g., 50R), the scattered signal should be approximately independent of the object’s dimensions. Yet, we find surprising contrast features in our 2D images which are inconsistent with this expectation, including marked differences associated with whether or not the structures are electrically connected to extended (wavelength scale or larger) metal structures. These results will be critical in informing any quantitative analysis of sub-wavelength metallic components using s-SNOM techniques.
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超表面,作为一种二维的超材料,可实现对电磁波偏振、振幅、相位、极化方式等特性的有效调控。本次报告主要报道利用几何超表面结构实现对线偏振太赫兹波的偏振调控,如多通道偏振旋转操控。在此基础上,讨论电磁波在亚波长局域内的偏振调制,发展在广义偏振分布波束中植入图像信息,形成基于偏振调控产生的亚波长高分辨成像。进一步,报道太赫兹超构表面透镜与成像
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In recent years, the rapidly increasing demands for higher data-rate communications and super resolution imaging have pushed the wireless system carrier frequencies toward higher spectrum regions, i.e. the sub-millimeter and terahertz (THz) bands. Despite the huge potentials, THz wireless technologies are hindered by the severe propagation losses associated with atmospheric absorption and the lack of high-power transmitting sources and cost-effective sensitive receivers.
High-temperature superconducting (HTS) Josephson junction features low noise within a wide frequency range up to THz. Additionally, HTS material have considerably higher superconducting critical temperatures. Currently, miniature single-stage cryocoolers with base temperatures of around 40 K are commercially available, which means that more cost-effective and portable HTS-device-based systems are potentially feasible for wireless communications and sensing applications.
In this report, research progress of HTS Josephson THz mixers in CSIRO/UTS will be presented, including system modelling theory, device fabrication, module and system development and demonstrations.
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里德堡原子具有对电磁场响应灵敏,测量可溯源等优势,基于里德堡原子的微波、太赫兹测量已形成新的研究热点。本报告介绍山西大学基于缀饰里德堡原子微波超外差接收机实现微波电场的场强、频率及相位测量,场强测量灵敏度优于此前国际最好结果3个量级,研究在遥感、天文、通信等领域具有重要意义。