Ultrasensitive total internal reflection sensor with rotatory biased weak measurement
A modified weak measurement scheme, rotatory biased weak measurement, is proposed to significantly improve the sensitivity and resolution of the total internal reflection sensor. This method introduces an additional phase in the post-selected procedure and generates an extinction point in the spectrum distribution. The biased post-selection makes smaller coupling strength available, which leads to an enhancement of phase sensitivity and refractive index sensitivity. In rotatory biased weak measurement, an enhanced refractive index sensitivity of 13605 nm/RIU is achieved compared to 1644 nm/RIU in standard weak measurement. The performance of total internal reflection sensors with different sensitivity is analyzed, and it is shown the optimal refractive index resolution of sensors increases with sensitivity. An optimal refractive index resolution of 4 × 1 0 − 7 RIU on a total reflection structure is demonstrated, which is far beyond the state-of-the-art resolution of 3 × 1 0 − 6 RIU of total internal reflection sensors. The rabbit anti-mouse IgG and mouse IgG binding reaction experiments demonstrate that our system has a high response to the concentration of IgG in a wide range and the limit of detection is 15 ng/mL. This work provides a total internal reflection sensor with the advantages of simple structure, low cost, and high resolution at the same time.
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