Improved polarization contrast method for surface plasmon resonance imaging sensors by inert background gold film extinction

• The imperfections of the conventional polarization contrast methods are discussed.
• A background extinction method using “gold microwell array” is proposed.
• An opposite-oriented SPR curve is exploited to achieve a high signal-to-noise ratio.
• High-contrast imaging of a SPRi sensor is achieved with an inert background.
• Extinction adjustment of polarization system in this method is easy to be realized.

To improve the performance of high-throughput surface plasmon resonance (SPR) imaging sensors, the imperfections of the conventional gold film polarization contrast method and the bare prism polarization contrast method are discussed, and a background extinction method is proposed. Thick gold film is coated as the background area, surrounding gold sensing spots, to form a “gold microwell array”. By blocking the light reflected from the background area with appropriate parameters, an opposite-oriented SPR curve is obtained, which can be exploited to achieve a high signal-to-noise ratio in trace amount detection. The contrast between the sensing spots and the background is effectively improved, and the background is inert to the change of solution. Influences of parameter errors on the SPR curve are also investigated, and results show that extinction adjustment in this method is easy to be realized. The practicability of the background extinction method is proved by an experiment using a home-built SPR imaging sensor.