Ultrathin corrugated metallic structures have been proved to support spoof surface plasmon polariton (SPP) modes on two-dimension (2D) planar microwave circuits. However, to provide stronger field confinement, larger width of strip is required to load deeper grooves, which is cumbersome in modern large-scale integrated circuits and chips. In this work, a new spoof SPP transmission line (TL) with zigzag grooves is proposed. This new structure can achieve stronger field confinement compared to conventional one with the same strip width. In other words, the proposed spoof SPP TL behaves equivalently to a conventional one with much larger size. Dispersion analysis theoretically indicates the negative correlation between the ability of field confinement and cutoff frequencies of spoof SPP TLs. Numerical simulations indicate that the cutoff frequency of the proposed TL is lower than the conventional one and can be easily modified with the fixed size. Furthermore, two samples of the new and conventional spoof SPP TLs are fabricated for experimental demonstration. Measured S-parameters and field distributions verify the ultra-strong ability of field confinement of the proposed spoof SPP TL. Hence, this novel spoof SPP structure with ultra-strong field confinement may find wide applications in microwave and terahertz engineering.

The mismatch between the AM1.5G spectrum and the photovoltaic (PV) cells absorption is one of the most limiting factors for PV performance. To overcome this constraint through the enhancement of solar energy harvesting, luminescent downshifting (LDS) layers are very promising to shape the incident sunlight and, thus, we report here the use of Tb3+- and Eu3+-doped organic-inorganic hybrid materials as LDS layers on Si PV cells. Electrical measurements on the PV cell, done before and after the deposition of the LDS layers, confirm the positive effect of the coatings on the cell''s performance in the UV spectral region. The maximum delivered power and the maximum absolute external quantum efficiency increased 14% and 27%, respectively. Moreover, a solar powered car race was organized in which the small vehicle containing the coated PV cells presented a relative increase of 9% in the velocity, when compared to that with the uncoated one.