We present an improved optical sensor based on surface plasmon resonance and phase detection. The sensor incorporates a surface plasmon resonance (SPR) device and a total internal reflection (TIR) device. In addition, a quarter-wave-plate (QWP) is placed in front of and behind the sensor. This gives rise to the optimization of the response curve and then the sensitivity. Theoretical simulations have been developed and verified by experimental results. With this new design, we obtain a sensitivity-tunable optical sensor whose resolving ability of refractive index is 1×10-6 RI.
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