Surface plasmon resonance demodulation by optical ring-down cavity technology

The field of plasmonics has experience a renaissance in recent years by providing a large variety of new physical effects and applications. Surface plasmon polaritons, i.e. the collective electron oscillations at the interface of a metal/dielectric, may bridge the gap between electronic and photonic devices, provided a fast switching mechanism is identified. Here, we presents a cavity ring-down technique called SPR sensor for conducting demodulated applications. Theoretical derivation indicates the conditions in which the laser frequency and linewidth remain unchanged, the optical field strength that mainly depends on the cavity mirror reflectivity, and the PZT scanning speed. Simulated experiments show that higher ring-down cavity precision, smaller anti-cross linewidth, and less time for increases and ring-downs are observed when the reflection coefficient is large. As a photon leaves the ring-down cavity, the photon quantities decrease again. The relative light intensity in the ring-down cavity is large when the PZT scanning speed is small. The application of a demodulation system shows that the ring-down cavity technology can largely improve the sensitivity of SPR sensors. The demodulation speed can also reach the ms level. A demodulation system is important for biochemical reaction kinetics and remote monitoring applications.