2D Attogram Surface Plasmon Resonance Imaging
21st December 2014

Development of Detector Technologies

Camera detector technology will be developed using, for instance, CMOS integrated circuit technology. The reaction at the sample surface will modify the properties of the surface plasmons. These will monitored with differential surface plasmon resonance techniques (d-SPR) which require the laser to be modulated either in either wavelength, polarisation or intensity. The response of the sample at the modulation are then detected with the custom detectors to be developed within this project. The detectors enable one to perform phase sensitive detection over the sample array. Simple demonstrations of the pixellation have been shown using 10 x 10 arrays on a continuous gold surface. The project will develop much larger arrays moving into the megapixel range capable of sensitive phase sensitive measurements. The modulation frequency target is of order 1MHz, which places lower demands on the CMOS camera than two lifetime based techniques described below.

The e-CRDS and f-EI are lifetime measurements. e-CRDS monitors the decay lifetime of radiation in an optical cavity and f-EI monitors the lifetime of a fluorophore in a local fluid environment. Typically lifetimes are of order 50-500 ns for e-CRDS and accurate determination of the lifetime requires a high sampling rate with each pixel of the camera acting as a photodiode, making boxcar average on the signal. In addition, the light levels at the detector are low and this places a typical 10 nW light budget on the pixels. The fluorescence lifetimes are even shorter, 1-5 ns, and lifetime is characteristic of the local environment and will change with the binding event on the surface plasmon particle. The programme will develop time resolved array technology with excellent light efficiency.

The programme will compare the detection methods for lifetime and d-SPR and develop large scale detectors for the most promising techniques.