Ultrasensitive Optical Refractive Index Detection of NaCl and Alcohol Solutions Based on Weak Value Amplification
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Ultrasensitive Optical Refractive Index Detection of NaCl and Alcohol Solutions Based on Weak Value Amplification Liping Xu 1,2 & Lan Luo 3 & Hao Wu 2,4 & Zhengchun Luo 1 & Tianying Chang 1 Hong-Liang Cui 1,2
&
Peng Wu 2 & Chunlei Du 2 &
Received: 13 May 2019 / Accepted: 10 September 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract An ultrasensitive surface plasmon resonance (SPR) refractive index detection scheme based on weak value amplification is presented. Extremely low refractive index change (9.8 × 10−7 RIU) of sodium chloride solution was readily measurable, with a resolution of 1.3 × 10−7 RIU, a nearly three orders of magnitude increase in sensitivity over conventional SPR index-sensors via intensity interrogation. Preliminary measurement of refractive index change of alcohol solution demonstrated a minimum of 4.0 × 10−6 RIU with a resolution of 3.7 × 10−7 RIU, better than those obtained through wavelength-modulated heterodyne interferometry (with a resolution of 1.5 × 10−6 RIU). The system is highly stable, having a simple and compact configuration, lending to easy and repeatable operation in standard ambient environment. Keywords Ultrasensitive index change detection . Weak value amplification . Surface Plasmon resonance
Introduction Surface plasmon resonance (SPR), since first introduced for chemand bio-sensing in 1983 [1], has become a widely accepted approach for high-sensitivity bio-sensors [2]. SPR’s popularity is attestedbyitsubiquitousapplicationsindiversefieldssuchasmedical diagnostics, food quality control and safety analysis, and environmental monitoring [2]. These sensors work by monitoring the excitation of SPR and its dependence on the incident angle [3], wavelength [4], intensity [5], and phase [6, 7] of the probing light. It seems to be a consensus that the phase-interrogated SPR biosensors are the most sensitive in terms of resolution among the demodulation scenarios mentioned above [7]. * Tianying Chang [email protected] * Peng Wu [email protected] 1
College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130012, Jilin, China
2
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Science, Chongqing 400714, China
3
College of Physical Science and Technology, Sichuan University, Chengdu 610064, China
4
Department of Physics, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
SPR sensors invariably detect changes of the optical index of refraction in unit of RIU, and their quality is judged mainly based on two technical parameters, the minimum detectable change of the index, and the resolution of detection. Giorgini et al. [8] reported a resolution 6 × 10−8 RIU of sodium chloride solution with a minimum detectable change of 1 × 10−4 RIU. Although phase-interrogated SPR bio-sensors have better resolutions, they also have more complex optical configuration and their minimum detectable refractive index changes are too high, insufficient in dealing with extremely low concentration s
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