A full-field heterodyne surface plasmon resonance dynamic bio-imaging system

Two-dimensional (2D) phase imaging system based on phase-shift interferometry (PSI) techniques can achieve a very high accuracy, but it has a degraded dynamic characteristic due to the inherent limitation of the PSI. Hence, the phase imaging system is incapable of obtaining real-time information pertaining to phase variations. To develop a label-free, high sensitivity, and dynamic bio-imaging system, a surface plasmon resonance (SPR) biosensing is combined with full-field heterodyne interferometry to develop a common-path full-field heterodyne SPR dynamic phase imager. The phase imager provides some advantages for biosensing such as label-free sensing, high sensitivity, high throughput, long-term stability, and dynamic capability. We build a 16×16 pixel photodiode array with a frame rate of up to 10 kHz as the 2D detector as opposed to a CCD camera with 30 Hz and employ an electro-optic modulator to generate a heterodyne light source. The multi-channel and real-time demodulation is calculated by utilizing a home-made digital signal processing-based lock-in amplifier. The SPR phase imager can detect refractive index changes better than 10^-6 by testing the difference between nitrogen and argon gases, and will be used to analyze the biomolecular interaction on sensing surface with high throughput screening.