A dynamic surface plasmon resonance imager based on interferometric phase measurements

A dynamic surface-plasmon-resonance (SPR) imaging sensor was developed to realize high-resolution high-throughput applications. The SPR device consisted of a half-cylinder prism, 47.5nm-thick gold thin film and a custom-designed flow cell to construct the Kretschmann configuration. A cylindrical lens pair in conjunction with the half-cylinder prism was used to simplify the optical alignment procedure and to ensure plane-wave propagation inside the prism. Phase-shifting interferometry was implemented by using a piezoelectric transducer (PZT) driven by a triangular voltage waveform. A CCD camera was employed to acquire the sequential interference patterns required for phase calculations. A reference signal obtained from a photodiode before the SPR device was used to compensate the system instability from the laser intensity, environmental disturbances, and mechanical vibrations from the PZT. Integrating-bucket data acquisition was realized with the synchronization between the photodiode and the CCD camera to preserve the dynamic capability of the SPR sensor. System evaluations were performed by salt-water mixture measurements and gold-spot array imaging. The achieved phase-measurement stability was 0.40 degrees and the system sensitivity was 5.14×10 ⁴ degree/RIU (refractive index unit). The corresponding system resolution was 7.8×10^-6 RIU. This SPR imager is anticipated to find applications in studying biomolecular interactions with high resolution, stability, throughput and dynamic capability.