Yuan-Fu Tsai

High-sensitivity in vivo THz transmission imaging of early human breast cancer in a subcutaneous xenograft mouse model.

We performed in vivo THz transmission imaging study on a subcutaneous xenograft mouse model for early human breast cancer detection. With a THz-fiber-scanning transmission imaging system, we continuously monitored the growth of human breast cancer in mice. Our in vivo study not only indicates that THz transmission imaging can distinguish cancer from the surrounding fatty tissue, but also with a high sensitivity. Our in vivo study on the subcutaneous xenograft mouse model will encourage broad and further investigations for future early cancer screening by using THz imaging system.

Demonstration of extensive mesenteric venous thrombosis and intestinal infarction with multidetector row CT: value of curved planar reformations

We describe a case of extensive mesenteric venous thrombosis with small bowel infarction. Multidetector row computed tomography with curved planar reformation clearly demonstrated the full extents of the mesenteric venous thrombus and the infarcted bowel loops. The length of infarcted segment could be estimated from the curved planar reformatted image and correlated well with operative findings. To our knowledge, this is the first presentation and measurement of infarcted bowel loops on curved planar reformation.

Terahertz polarization-sensitive rectangular pipe waveguides

We propose square and rectangular pipe waveguides for low-loss THz waveguiding and polarization control. Different from common circular-symmetric THz fibers and waveguides, the proposed rectangular pipe waveguides successfully remove the transmission degeneracy of two orthogonal polarizations and possess polarization sensitivity to the guided THz waves. By measuring the attenuation spectra, we find that the polarization sensitivity depends on the structure of the pipe waveguides. With butt coupling method, it is easy to combine circular pipe waveguides and the rectangular ones.

Terahertz pipe-waveguide-based directional couplers

We experimentally demonstrate a terahertz (THz) leaky mode directional coupler for future THz applications. The proposed directional coupler comprises two square pipe waveguides. The coupling efficiency is investigated for different frequencies, polarizations, and core sizes. Rectangular pipe-waveguide-based directional couplers and the issue of insertion loss are also discussed. It is found that the THz directional coupler works most efficiently in the minimal-attenuation wavelength regime.

Investigation on Strong Coupling Behaviors of THz Subwavelength Directional Couplers

To achieve strong coupling, conventional fiber-based directional couplers often require complicated fabrication. Here, by placing two identical THz subwavelength fibers parallel to each other and by simply tuning the separation in between, we investigate the strong coupling characteristics of the directional fiber coupler, which has not been experimentally explored before in the THz region. This strong coupling directional coupler is able to provide superior performance with an extremely short coupling length (30 times of wavelength) and a record low insertion loss (<; 0.3 dB). These performances are much improved when compared with the previously reported THz fiber/waveguide-based directional couplers.

Near-field sub-THz transmission-type image system for vessel imaging in-vivo.

A THz near-field transmission imaging system was successfully demonstrated to image the vessels inside the ears of nude mice in vivo. Wave-guided illumination and near-field scanning detection with a sub-wavelength aperture were applied. An operating frequency of 340 GHz was chosen to achieve a higher penetration depth in tissues with a reasonable signal-to-noise ratio. The near-field pattern of the power transmittance through the vessel was also numerically simulated and showed good correspondence to the measured results. The capability of the system for long-term monitoring in vivo was also demonstrated.

Strong-coupling behavior of THz sub-wavelength directional couplers

We investigated the strongly-coupled mode characteristic of THz sub-wavelength directional couplers. It provides superior performance to transfer power to the coupled arm with only 0.2dB insertion loss, or with a record-short 38 λ coupling length.