神马福利影片

Generalized ellipsometry can uncover the optical properties of anisotropic materials, in which the light–matter interaction alters the polarization state. In the terahertz frequency range, generalized ellipsometry has been infrequently realized due to the challenge of rapidly controlling and measuring THz polarization. Here, we report the development and calibration of a high-efficiency terahertz time-domain generalized ellipsometer based on two dual-channel photoconductive antennas. The fiber-coupled multi-pixel devices act as source and detector and achieve a high data throughput with four independent terahertz pulses in a single optical delay scan, without the need for any bulky or slow polarization elements such as polarizers. Following a one-off system calibration, an accurate optical characterization of a uniaxially birefringent Al₂O₃ crystal serves to validate the method. Our technique benefits from efficient data throughput, full polarization-resolved capability, and reduced system complexity, paving the way to in situ and real-time monitoring applications.

Terahertz (THz) sensing has gained significant attention as a non-ionizing modality capable of probing the superficial layers of biological tissue with high sensitivity to water content, structural changes, and biochemical composition. Its strong interaction with water makes it uniquely suited for investigating dermatological applications such as hydration assessment, wound and burn monitoring, and the detection and characterization of skin cancers. However, the shallow penetration depth of THz light, combined with the sensitivity of measurements to probe-skin coupling, contact pressure, and motion artifacts, poses persistent challenges for in vivo use. Overcoming these limitations requires carefully engineered hardware, robust measurement protocols, and advanced computational techniques tailored to biological variability. This article reviews the evolution of THz instrumentation for in vivo skin sensing, spanning early laboratory systems to emerging compact, handheld, robotic, and computationally enhanced platforms. Key developments in probe miniaturization, ergonomic design, and automated control of probe orientation and pressure are described, as these advances directly influence measurement reproducibility and clinical usability. We highlight recent progress in single-pixel imaging, which offers video-rate capabilities, the emergence of waveguide-integrated metamaterial sensors that push spatial resolution far below the diffraction limit, and THz ellipsometry that gives complementary contrast. In addition, we discuss the growing role of data-driven processing, compressed-sensing algorithms, and biophysical modeling in extracting clinically relevant parameters from THz measurements. Although promising, many of the emerging systems remain untested in in vivo dermatological scenarios, and challenges including motion artifacts, calibration stability, and inter-subject variability must be addressed. Continued interdisciplinary work between engineers, physicists, and clinicians is essential for transitioning THz systems toward practical, patient-compliant diagnostic tools.

Real-time, non-invasive imaging techniques are essential for advancing biomedical diagnostics and material analysis, yet existing terahertz (THz) systems often suffer from limited speed, bulky designs, and poor adaptability to in situ environments. Addressing these challenges, we present a fully fibre-coupled THz attenuated total internal reflection single-pixel imaging system, offering a compact, flexible, and robust platform for non-destructive spectroscopy and in vivo imaging. This all-fibre architecture enables seamless integration for in situ biomedical applications, including measurements directly on patients. Central to our design is a THz spatial light modulator based on an unpassivated silicon wafer, facilitating high-speed modulation and enabling video-rate imaging with a spatial resolution down to 360 渭m. Despite being in the reflection geometry and using fibre-coupled light, our system achieves an imaging throughput exceeding 30,000 pixels per second for 64-by-64 images - over five-fold higher than the state of the art - representing a substantial improvement in real-time THz imaging capabilities.

In this work, we demonstrate significant modifications to our robotically controlled terahertz (THz) sensing system, the 鈥淧icoBot,鈥� enabling it to perform in vivo imaging of skin rather than limiting it to single-point measurements. By integrating a robotic arm equipped with force-sensitive feedback control, we maintain consistent contact pressure between the probe and the skin surface throughout imaging. In conjunction with this hardware advancement, we introduce an accompanying image analysis pipeline that reduces noise and enhances repeatability across scans. These improvements allow for reliable intra- and inter-subject comparisons, a critical step toward the clinical utility of THz imaging. Our ultimate aim is to use THz imaging to detect skin cancer margins: this paper highlights progress towards this goal and skin evaluation in general.