We report on the utilization of Si in plasmonics research, specifically targeting deep ultraviolet (DUV) applications. By incorporating periodic submicron gratings on a Si surface, we demonstrate a photoconductive Si detector with significantly enhanced responsivity to DUV light, which is achieved via surface plasmon resonance (SPR). Notably, even without a metal, the detector exhibits improved responsivity only under TM-polarized light, supporting the interpretation that Si excites SPR. Our demonstration not only validates the effectiveness of Si plasmonics for enhancing photodetector performance but also introduces innovative techniques with potential applications in various research fields. Published by the American Physical Society 2025

Optical fields enhanced by surface plasmon polaritons (SPPs) on metal-dielectric interfaces are useful for increasing several light-matter interactions, and application to nonlinear optics (NLO) is one of the most important uses of this type of structure. Most previous studies on this subject took advantage of the nonlinear susceptibilities of metal surfaces. However, the limited NLO light-matter interaction lengths prevented the transfer of the technologies to practical use. In the present paper, we tried to overcome this problem by growing NLO polymer thin films on metal surfaces. The NLO responses of the system were characterized by second-harmonic generation (SHG) spectroscopy. Our experimental results suggested that SPP-enhanced optical fields induced not only surface nonlinearities in Ag but also bulk nonlinearities in NLO polymer. There was an optimal polymer thickness for the SHG conversions, and a greater thickness did not always result in higher conversion. The maximum conversion efficiency was approximately 40 times higher than that of the nonpolymer-coated bare Ag surface. The growth and propagation of the SHG waves were addressed with a numerical approach combining the transfer matrix method and Green's function analysis. The SHG conversion efficiencies were determined by three factors, the SPP-field enhancement factor, the nonlinear light-matter interaction length, and the degree of interference between the forward- and backward-propagating SHG waves. The latter two factors predominantly determined the optimal SHG conversion efficiencies. The proposed strategy of hybridizing NLO polymers brings us closer to practical uses for nonlinear plasmonics.

We developed a high spatially-resolved ion-imaging system using focused electron beam excitation. In this system, we designed a nanometric thin sensor substrate to improve spatial resolution. The principle of pH measurement is similar to that of a light-addressable potentiometric sensor (LAPS), however, here the focused electron beam is used as an excitation carrier instead of light. A Nernstian-like pH response with a pH sensitivity of 53.83 mV/pH and linearity of 96.15% was obtained. The spatial resolution of the imaging system was evaluated by applying a photoresist to the sensing surface of the ion-sensor substrate. A spatial resolution of 216 nm was obtained. We achieved a substantially higher spatial resolution than that reported in the LAPS systems.