Tzu-Fang Tseng

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.

Fiber-based swept-source terahertz radar

We demonstrate an all-terahertz swept-source imaging radar operated at room temperature by using terahertz fibers for radiation delivery and with a terahertz-fiber directional coupler acting as a Michelson interferometer. By taking advantage of the high water reflection contrast in the low terahertz regime and by electrically sweeping at a high speed a terahertz source combined with a fast rotating mirror, we obtained the living objects distance information with a high image frame rate. Our experiment showed that this fiber-based swept-source terahertz radar could be used in real time to locate concealed moving live objects with high stability.

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.

In vivo sub-femtoliter resolution photoacoustic microscopy with higher frame rates

Microscopy based on non-fluorescent absorption dye staining is widely used in various fields of biomedicine for 400 years. Unlike its fluorescent counterpart, non-fluorescent absorption microscopy lacks proper methodologies to realize its in vivo applications with a sub-femtoliter 3D resolution. Regardless of the most advanced high-resolution photoacoustic microscopy, sub-femtoliter spatial resolution is still unattainable, and the imaging speed is relatively slow. In this paper, based on the two-photon photoacoustic mechanism, we demonstrated a in vivo label free laser-scanning photoacoustic imaging modality featuring high frame rates and sub-femtoliter 3D resolution simultaneously, which stands as a perfect solution to 3D high resolution non-fluorescent absorption microscopy. Furthermore, we first demonstrated in vivo label-free two-photon acoustic microscopy on the observation of non-fluorescent melanin distribution within mouse skin.

High-depth-resolution 3-dimensional radar-imaging system based on a few-cycle W-band photonic millimeter-wave pulse generator

We demonstrate that a near-single-cycle photonic millimeter-wave short-pulse generator at W-band is capable to provide high spatial resolution three-dimensional (3-D) radar imaging. A preliminary study indicates that 3-D radar images with a state-of-the-art ranging resolution of around 1.2 cm at the W-band can be achieved.

Pilot clinical study to investigate the human whole blood spectrum characteristics in the sub-THz region.

We have conducted a pilot clinical study to not only investigate the sub-THz spectra of ex-vivo fresh human whole blood of 28 patients following 8-hours fasting guideline, but also to find out the critical blood ingredients of which the concentration dominantly affects those sub-THz spectra. A great difference between the sub-THz absorption properties of human blood among different people was observed, while the difference can be up to ~15% of the averaged absorption coefficient of the 28 samples. Our pilot clinical study indicates that triglycerides and the number of red blood cells were two dominant factors to have significant negative correlation to the sub-THz absorption coefficients.

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.

THz fiber-based swept-source imaging radar

We demonstrate an all-THz fiber-based swept-source imaging radar system. Our experiment shows that this radar can be used in real time to nondestructively detect and locate the concealed living objects with high stability and sensitivity.