Development of ultra high sensitive terahertz imaging system

在我们的项目中，太赫兹波继续扩大其应用范围如下。由于缺乏对隐藏在邮件信封中的非法药物进行无损检查的技术，这类药物被自由地走私到国际边界。我们已经开发了一种太赫兹成像的基本技术，通过引入分量空间模式分析，可以检测和识别隐藏在信封中的药物^2。利用可调谐太赫兹波源测量的吸收光谱，从太赫兹多光谱透照图像中获得目标的空间分布和组成。我们进一步展示了使用二维电光太赫兹成像的化学成分空间模式分析，该成像可以捕获实时太赫兹图像^3。通过改变泵浦光束的光延迟，CCD相机记录了随时间变化的太赫兹图像。多光谱图像和光谱数据集在0.1 ~ 1.0 THz范围内测量；测定了其化学成分、空间分布和浓度差异。另一方面，为了检测大规模集成电路（LSI）中的电气故障，我们开发了激光太赫兹发射显微镜（LTEM），它记录了样品在激光脉冲激励下的太赫兹发射幅值图。当用激光束扫描芯片时，记录了IC芯片清晰的二维太赫兹发射图像。损伤芯片的tem图像显示出与正常芯片不同的模式。另外，通过调制IC芯片的输入信号，可以对信号线进行跟踪。这些结果表明，LTEM可以成为检测和监测集成电路质量的有用工具。作为演示，我们成功地获得了零偏置条件下MOSFET样品的太赫兹发射图像。

In our project, THz-waves continue to broaden their range of applications as following. The absence of non-destructive inspection techniques for illicit drugs hidden in mail envelopes has resulted in such drugs being freely smuggled across international borders. We have developed a basic technology for THz imaging which allows detection and identification of drugs concealed in envelopes by introducing the component spatial pattern analysis^2. The spatial distribution and the composition of the targets are obtained from THz multispectral transillumination images, using absorption spectra measured with a tunable THz wave source. We further demonstrated a component spatial pattern analysis of chemicals using 2-dimensional electro-optic THz imaging which can capture real-time THz images^3. By changing the optical delay of the pump beam, the CCD camera records time-dependent THz images. The multispectral images and the spectral data set were measured between 0.1 and 1.0 THz ; the chemical composition, the spatial distribution, and the difference in concentration were clearly determined. On the other hand, for inspecting electrical failures in large scale integration circuit (LSI), we developed the laser-THz emission microscope (LTEM), which records the map of THz emission amplitude in a sample upon excitation with fs laser pulses^4. Clear two-dimensional THz-emission images of the IC chip are recorded as the chip is scanned with laser beam. The LTEM images of damaged chips show different patterns from those of normal chips. Also, by modulating the input signal of the IC chip, the signal lines can be traced. These results suggest that the LTEM could become a useful tool for inspecting and monitoring IC quality. As a demonstration, we succeeded in obtaining the THz emission image of a MOSFET sample under zero bias condition.