Jen-Tang Lu

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.

Bending loss of terahertz pipe waveguides

We present an experimental study on the bending loss of terahertz (THz) pipe waveguide. Bending loss of pipe waveguides is investigated for various frequencies, polarizations, core diameters, cladding thicknesses, and cladding materials. Our results indicate that the pipe waveguides with lower guiding loss suffer lower bending loss due to stronger mode confinement. The unexpected low bending loss in the investigated simple leaky waveguide structure promises variety of flexible applications.

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.

Efficient Structure Resonance Energy Transfer from Microwaves to Confined Acoustic Vibrations in Viruses.

Virus is known to resonate in the confined-acoustic dipolar mode with microwave of the same frequency. However this effect was not considered in previous virus-microwave interaction studies and microwave-based virus epidemic prevention. Here we show that this structure-resonant energy transfer effect from microwaves to virus can be efficient enough so that airborne virus was inactivated with reasonable microwave power density safe for the open public. We demonstrate this effect by measuring the residual viral infectivity of influenza A virus after illuminating microwaves with different frequencies and powers. We also established a theoretical model to estimate the microwaves power threshold for virus inactivation and good agreement with experiments was obtained. Such structure-resonant energy transfer induced inactivation is mainly through physically fracturing the virus structure, which was confirmed by real-time reverse transcription polymerase chain reaction. These results provide a pathway toward establishing a new epidemic prevention strategy in open public for airborne virus.

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.

Investigation on mode coupling and bending loss characteristics of terahertz air-core pipe waveguides

We demonstrate the magnificent flexibility of the terahertz air-core pipe waveguides. By measuring waveguide attenuation spectra, we found that the pipe waveguides can be easily butt coupled with high coupling efficiency and low bending loss.

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.