Fabrication of Silver-Silicon Gratings for Surface Plasmon Excitation Using Nanosecond Laser Interference Lithography

We introduce a new two-step method to fabricate silver-silicon gratings that can excite surface plasmons efficiently. The grating structure was firstly created on a flat silicon substrate by single-pulse nanosecond laser interference lithography. Next, a silver layer of 50 nm was evaporated on the silicon substrate. With proper laser energy, a silver-silicon grating with a period of 1120 nm and depth of 18 nm was successfully fabricated. This grating can produce high-quality surface plasmon resonance (SPR) peaks at various incident angles. Moreover, a SPR sensor was experimentally demonstrated based on the silver-silicon grating, which had high sensitivity of 961.5 nm/RIU and figure of merit of 60. Our method is an efficient way to fabricate periodically nanostructured metals at high speed and low cost.