超宽带太赫兹调频连续波成像技术

太赫兹调频连续波成像技术具有高功率、小型化、低成本、三维成像等特点,在太赫兹无损检测领域受到了广泛关注。然而由于微波及太赫兹器件限制,太赫兹信号带宽难以做大,从而制约了成像的距离向分辨力。虽然高载频可实现较大宽带,但伴随的低穿透性和低功率会限制太赫兹调频连续波成像系统的应用场景。因此,聚焦于太赫兹波无损检测领域,提出一种时分频分复用的114～500 GHz超宽带太赫兹信号的产生方式,基于多频段共孔径准光设计,实现超带宽信号的共孔径,频率可扩展至1.1 THz。提出一种频段融合算法,实现了超宽带信号的有效融合,距离分辨力提升至460μm,通过人工设计的多层复合材料验证了系统及算法的有效性,并得到封装集成电路(IC)芯片的高分辨三维成像结果。     

微纳复合结构增强硅基太赫兹调制器性能

研究了由微米金字塔阵列和纳米级氧化铝(Al2O3)薄膜构成的微纳复合结构对硅基光控太赫兹调制器调制性能的增强效应和机制。实验表明,相对于半导体硅片,硅表面的微米金字塔阵列能够显著减少激光反射率,提高对激光的利用率,且能增加太赫兹波的调控面积。更重要的是,金字塔阵列上沉积的纳米级厚度Al2O3薄膜还能进一步降低激光反射率,并能明显提升太赫兹波的调制效果,在95.5 mW/mm2的激光功率密度下,其调制深度可达91.2%。该光控太赫兹调制器在低激光功率下拥有高调制深度,在太赫兹成像和通信领域都有巨大的应用潜力。     

硅基金字塔结构光控太赫兹调制器

提出一种硅基金字塔结构光控太赫兹波调制器。通过化学刻蚀方法在高阻硅基底形成微米级的金字塔结构,研究该结构与高阻硅片对激光的反射率及对太赫兹的调制情况。实验表明,金字塔结构可有效降低激光反射率,提升激光利用率,并且通过增加太赫兹波调制面积,达到显著增强太赫兹波的调制效果,其调制深度达到90%以上。该硅基金字塔结构光控调制器可在极低的激光功率下工作,具有宽带、大幅度调制的特点,在太赫兹成像领域具有重要应用价值。     

聚四氟乙烯材料的太赫兹特性

太赫兹(THz)辐射能够穿透很多对可见光不透明的非金属、非极性材料,而用X辐射对这些材料成像的对比度又相对低,因此,太赫兹成像在安全检测和生产质量控制等领域日益受到重视。对成像材料的太赫兹特性的实际测量是太赫兹成像技术的重要组成部分。利用CO_2激光抽运太赫兹激光对聚四氟乙烯材料的太赫兹吸收特性和透过光斑轮廓进行了实验研究,获得聚四氟乙烯在70.51μm,96.5μm,118.83μm,122.4μm,158.51μm,184.31μm和214.58μm波长的吸收系数。     

太赫兹成像技术用于皮肤烧伤检测的研究进展

随着太赫兹(0.1~10 THz)光谱技术的快速发展,太赫兹成像开始应用于生物医学等领域,尤其是应用于皮肤烧伤检测中,但如何将这一技术从实验室研究转向实际临床检测还面临着巨大挑战。太赫兹技术在皮肤烧伤程度评估领域已经得到了较为深入的研究,包括成像系统、离体实验和活体实验研究等,得到了较为清晰的太赫兹图像。首先概述了皮肤烧伤程度分类方法和现有诊断方法,然后介绍太赫兹成像应用于皮肤烧伤评估的研究进展,本文重点从成像系统、检测结果和烧伤程度评估方法三个方面进一步说明了其研究进展和不足,最后提出了面向皮肤烧伤临床检测的太赫兹成像发展趋势和需要解决的问题。     

基于飞秒激光成丝的太赫兹成像

太赫兹成像作为太赫兹应用的关键技术之一,在安检、无损检测等方面有着广阔的前景。本文采用飞秒激光成丝产生太赫兹波,对掩膜板扫描成像,实现了约100 μm成像分辨率(峰值频率0.51 THz);研究了等离子体丝不同截断位置对太赫兹波产生的影响;通过特征提取,对比了不同时域、频域特征分析下的成像结果。结果显示:积分能量成像方法可以实现最优的成像效果。     

序言——加强太赫兹科学技术基础和应用研究

太赫兹（Tera—Hertz,THz）波是指频率在0．1THz～10THz（波长在3mm～30μm）范同内的电磁波,该频段介于毫米波与远红外光之间,是一个人类尚未充分认知和利用的频段。同微波相比,亚太赫兹和太赫兹波具有高出1～4个数量级的带宽,同光波相比,太赫兹波具有更高的能量转换效率和炯雾穿透能力,因此太赫兹波作为通信和雷达的新手段,可以极大地提高通信系统的容量和雷达的分辨率,以及保密性和抗干扰抗截获性能等。太赫兹波具有比X射线更低的能级和对非金属材料的穿透性,可以广泛应用于医学成像、安检、材料检测与结构分析、特殊过程测量等领域。     

太赫兹成像检测算法研究

由于太赫兹波所处波段位置特殊性以及现阶段太赫兹成像系统性能的限制等,太赫兹波成像质量低,无法满足可视化效果,限制了其发展和应用。结合太赫兹图像模糊特征和灰度信息提出利用灰度特征对太赫兹图像进行图像分割来提高太赫兹图像质量,抑制太赫兹图像背景噪声,保留太赫兹图像目标重要信息,实现太赫兹成像目标检测。实验结果与其他太赫兹图像处理方法结果对比表明,基于灰度特征的图像处理算法可以提高图像清晰度和对比度,实现精确分割,为太赫兹成像在安全检查和医学成像等应用中实现快速检测和提取目标奠定基础。     

硅表面太赫兹抗反射亚波长结构设计

亚波长结构是特征尺寸小于工作波长的连续阵列浮雕结构,可看成是一层折射率均匀的介质层,仅存在零级的透射和反射衍射。基于等效介质理论和严格耦合波理论介绍了亚波长抗反射结构。为提高111μm波长太赫兹辐射(2.7THz)的透过率,在硅表面设计了亚波长抗反射结构。该结构的透射率和反射率由其浮雕结构的周期、高度和占空比确定。利用等效介质理论和严格耦合波理论对其结构参数进行了优化设计。当周期为27μm、高度为13μm、占空比为0.75时,得到了99.05%的太赫兹辐射透过率。     

反射式太赫兹返波振荡器成像系统及其应用

实现了基于返波管源的太赫兹波反射式成像系统.这是一种新型的无损探伤成像方式.从样品表面或者基底反射回来的太赫兹波被焦热电探测器收集,最后经过计算机处理成像.频率为0.7THz的成像系统被用来对一系列样品进行无损检测,如硬币、徽章、模型飞机以及预埋了人工缺陷的工业样品.结果表明,很多工业材料相对于太赫兹波都是透明的,尤其是一些在航空航天技术中具有广泛应用价值的吸收微波的材料.     

Assessment of Terahertz Imaging for Excised Breast Cancer Tumors with Image Morphing

This paper presents an image morphing algorithm for quantitative evaluation methodology of terahertz (THz) images of excised breast cancer tumors. Most current studies on the assessment of THz imaging rely on qualitative evaluation, and there is no established benchmark or procedure to quantify the THz imaging performance. The proposed morphing algorithm provides a tool to quantitatively align the THz image with the histopathology image. Freshly excised xenograft murine breast cancer tumors are imaged using the pulsed THz imaging and spectroscopy system in the reflection mode. Upon fixing the tumor tissue in formalin and embedding in paraffin, a formalin-fixed paraffin-embedded (FFPE) tissue block is produced. A thin slice of the block is prepared for the pathology image while another THz reflection image is produced directly from the block. We developed an algorithm of mesh morphing using homography mapping of the histopathology image to adjust the alignment, shape, and resolution to match the external contour of the tissue in the THz image. Unlike conventional image morphing algorithms that rely on internal features of the source and target images, only the external contour of the tissue is used to avoid bias. Unsupervised Bayesian learning algorithm is applied to THz images to classify the tissue regions of cancer, fat, and muscles present in xenograft breast tumors. The results demonstrate that the proposed mesh morphing algorithm can provide more effective and accurate evaluation of THz imaging compared with existing algorithms. The results also showed that while THz images of FFPE tissue are highly in agreement with pathology images, challenges remain in assessing THz imaging of fresh tissue.     

太赫兹辐射对小鼠脑神经发生及认知能力的影响

为探究太赫兹(THz)辐射对成年小鼠海马齿状回亚颗粒区(SGZ)神经发生及对老年小鼠认知能力的影响,用0.14 THz波照射实验小鼠头部,10 min/次,2次/d,连续21 d,对照组小鼠进行相同时间的麻醉。采用5-溴脱氧尿嘧啶核苷(BrdU)染色评价新生细胞存活、BrdU/神经元细胞核(NeuN)染色评价细胞分化、Morris水迷宫(MWM)实验分析认知能力变化。实验结果表明：与对照组相比,0.14 THz 10 min/次,2次/d,连续照射21 d后,可有效促进成年小鼠SGZ神经发生,成年小鼠SGZ新生细胞存活明显改善(P<0.05),新生细胞向神经元的分化无明显改变。老年小鼠逃避潜伏期,运动寻找轨迹无显著变化,THz辐射没有影响老年小鼠的空间认知能力。     

Cancer Cell Membrane‐Coated Nanoparticles for Personalized Therapy in Patient‐Derived Xenograft Models

Cell membrane coating nanotechnology, which endows nanoparticles with unique properties, displays excellent translational potential in cancer diagnosis and therapy. However, the preparation and evaluation of these cell membrane‐coated nanoparticles are based on cell lines and cell‐line‐based xenograft mouse models. The feasibility of cell membrane‐camouflaged nanomaterials is tested in a preclinical setting. Head and neck squamous cell carcinoma (HNSCC) patient‐derived tumor cell (PDTC) membranes are coated onto gelatin nanoparticles (GNPs) and the resulting PDTC@GNPs show efficient targeting to homotypic tumor cells and tissues in patient‐derived xenograft (PDX) models. When the donor‐derived cell membrane of PDTC@GNPs matched those of the host cells, significant targeting capability is observed. In contrast, mismatch between the donor and host results in weak targeting. Furthermore, it is demonstrated that autologous separation and administration of cellular membranes and anticancer cisplatin (Pt)‐loaded PDTC@GNPs, respectively, lead to almost complete tumor ablation in a subcutaneous model and effectively inhibit tumor recurrence in a postsurgery model. The work presented here reinforces the translation of these biomimetic nanoparticles for clinical applications and offers a simple, safe, and effective strategy for personalized cancer treatment.     

MUC1 Aptamer Targeted SERS Nanoprobes

Recently, surface‐enhanced Raman scattering (SERS) nanoprobes (NPs) have shown promise in the field of cancer imaging due to their unparalleled signal specificity and high sensitivity. This study reports the development of a DNA aptamer targeted SERS NP. Recently, aptamers are being investigated as a viable alternative to more traditional antibody targeting due to their low immunogenicity and low cost of production. A strategy is developed to functionalize SERS NPs with DNA aptamers, which target Mucin1 (MUC1) in human breast cancer (BC). Thorough in vitro characterization studies demonstrate excellent serum stability and specific binding of the targeted NPs to MUC1. In order to test their in vivo targeting capability, MUC1‐targeted SERS NPs are coinjected with nontargeted or blocked MUC1‐targeted SERS NPs in BC xenograft mouse models. A two‐tumor mouse model with differential expression of MUC1 (MDA‐MB‐468 and MDA‐MB‐453) is used to control for active versus passive targeting in the same animals. The results show that the targeted SERS NPs home to the tumors via active targeting of MUC1, with low levels of passive targeting. This strategy is expected to be an advantageous alternative to antibody‐based targeting and useful for targeted imaging of tumor extent, progression, and therapeutic response.     

Terahertz Imaging System for Medical Applications and Related High Efficiency Terahertz Devices

A terahertz (THz) imaging system and high efficient terahertz sources and detectors for medical applications were developed. A fiber laser based compact time domain terahertz tomography system was developed with a high depth resolution of less than 20 μm. Three-dimensional images of porcine skin were obtained including some physical properties such as applied skin creams. The discrimination between healthy human tissue and tumor tissue has been achieved using reflection spectra. To improve the THz imaging system, a ridge waveguide LiNbO₃ based nonlinear terahertz generator was studied to achieve high output power. A ridge waveguide with 5-7 μm width was designed for high efficiency emission from the LiNbO₃ crystal by the electro-optic Cherenkov effect. Terahertz electronic sources and detectors were also realized for future imaging systems. As electronic source devices, resonant tunneling diode (RTD) oscillators with a patch antenna were fabricated using an InGaAs/InAlAs/AlAs triple barrier structure. On the other side, Schottky barrier diode (SBD) detectors with a log-periodic antenna were fabricated by thin-film technology on a Si substrate. Both devices operate above 1 THz at room temperature. This electronic THz device set could provide a future high performance imaging system.     

Combination of Bacterial‐Photothermal Therapy with an Anti‐PD‐1 Peptide Depot for Enhanced Immunity against Advanced Cancer

Photothermal therapy (PTT) is a promising cancer treatment, but it has so far proven successful only with relatively small subcutaneous tumors in animal models. Treating larger tumors (≈200 mm³) is challenging because most PTT materials do not efficiently reach the hypoxic, avascular center of tumors, and the immunosuppressive tumor microenvironment prevents T cells from fighting against residual tumor cells, thereby allowing recurrence and metastasis. Here, the widely used PTT material polydopamine is coated on the surface of the facultative anaerobe Salmonella VNP20009, which can penetrate deep into larger tumors. The coated bacteria are intravenously injected followed by near‐infrared laser irradiation at the tumor site, combined with a local inoculation of phospholipid‐based phase separation gel containing the anti‐programmed cell death‐1 peptide AUNP‐12. The gel releases AUNP‐12 sustainably during 42 days, maintaining the tumor microenvironment as immunopermissive. Using a mouse model of melanoma, this triple combination of biotherapy, PTT, and sustainable programmed cell death‐1 (PD‐1) blockade shows high efficiency on eliciting robust antitumor immune responses and eliminating relatively large tumors in 50% of animals within 80 days. Thus, the results shed new light on a previously unrecognized immunological facet of bacteria‐mediated therapy, and this innovative triple therapy may be a powerful cancer immunotherapy tool.     

偏振选择可调谐双带太赫兹吸收器

提出并研究了一种偏振选择可调谐双带太赫兹吸收器。吸收器由顶层方形劈裂石墨烯环、中间SiO₂介质层以及底层金反射层组成。基于时域有限差分法的仿真结果显示,该吸收器在不同偏振光入射下均可以实现双带高效率吸收。x偏振光时在7.86和12.63THz处的吸收率分别为97.9%和91.2%;y偏振光时在6.30和10.52THz处的吸收率分别为94.1%和93.2%。通过改变石墨烯费米能级,可以对两个偏振的双带吸收峰波长进行调谐。此外,研究了介质层厚度和石墨烯劈裂环的物理参数对共振吸收峰的影响。因为在两个偏振状态下都能产生双带高吸收,所以此吸收器在太赫兹偏振成像、太赫兹传感、选择性光谱检测和偏振复用等领域有重要的潜在应用价值。     

Enhanced Terahertz Imaging of Small Forced Delamination in Woven Glass Fibre-reinforced Composites with Wavelet De-noising

Terahertz (THz) reflection imaging is applied to characterize a woven glass fibre-reinforced composite laminate with a small region of forced delamination. The forced delamination is created by inserting a disk of 25- μ m-thick Upilex film, which is below the THz axial resolution, resulting in one featured echo with small amplitude in the reflected THz pulses. Low-amplitude components of the temporal signal due to ambient water vapor produce features of comparable amplitude with features associated with the THz pulse reflected off the interfaces of the delamination and suppress the contrast of THz C- and B-scans. Wavelet shrinkage de-noising is performed to remove water-vapor features, leading to enhanced THz C- and B-scans to locate the delamination in three dimensions with high contrast.     

A novel terahertz device with multi-function of polarization and switch based on phase transition of VO2

A terahertz (THz) polarizer and switch structure is proposed based on the phase transition of vanadium dioxide (VO2). When VO2 is in the insulation phase, the resonance frequencies of the proposed structure are 1.49 THz and 1.22 THz for the x- and y-polarization, respectively. It can perform as a THz polarizer with extinction ratios of 52.5 dB and 17 dB for the y- and x-polarization, respectively; When VO2 transforms into metallic phase, the resonance frequency for x-polarization wave shifts from 1.49 THz to 1.22 THz, while that remains still for the y-polarization component. It means that the structure can work as a polarization-dependent THz switch with a high extinction ratio of 32 dB.     

pH‐Activated Near‐Infrared Fluorescence Nanoprobe Imaging Tumors by Sensing the Acidic Microenvironment

Imaging tumors in their early stages is crucial to increase the surviving rate of cancer patients. Currently most fluorescence probes visualize the neoplasia by targeting the tumor‐associated receptor over‐expressed on the cancer cell membrane. However, the expression level of these receptors in vivo is hard to predict, which limits their clinical translation. Furthermore, the signal output of these receptor‐targeting probes usually stays at a high level, which leads to a strong background signal in normal tissue due to non‐specific binding. In contrast to receptors, characteristics of the tumor microenvironment – such as acidosis – are pervasive in almost all solid tumors and can be easily accessed. In this work, a novel biodegradable nanoprobe InNP1 that demonstrates pH‐activated near‐infrared (NIR) fluorescence in both human glioblastoma U87MG cancer cells in vitro and the subcutaneous U87MG tumor xenografts in vivo is developed. Bio‐distribution, in vivo optical imaging, and autoradiography studies demonstrate that the pH‐activated NIR fluorescence is the dominant factor responsible for the high tumor/normal tissue (T/N) ratio of InNP1 in vivo. Overall, the work provides a nanoprobe prototype to visualize the solid tumor in vivo with high sensitivity and minimal systemic toxicity by sensing the tumor acidic microenvironment.