Sensor based on angular interrogation of Surface Plasmon Resonance by using an elliptical reflector structure

We report a method to make simplification and improve stability of Surface Plasmon Resonance (SPR) sensor by using an elliptical reflector in angular interrogation. The sensitive plate is K7 glass coated with about 50nm gold film. The centers of sensitive plate and the detector are set on each of the two focus of the elliptical reflector respectively. According to the geometrical optics, the detector on one focus can receive the light reflected by the elliptical reflector from another focus when incident angle of input light changes continuously. In addition, we use an opto-coupler switch to adjust the starting point of the rotary stage. The angular interrogation method has been used to study the performance of the sensor in terms of intrinsic sensitivity that includes the width and shifts of the SPR curve for a given refractive index of sensing layer. SPR curves can be observed through the rotation of angular movement of stepper motor, then the resonance angle of gold film is calculated. The preliminary experimental results confirmed that structure can be used as a steady sensor that could detect refractive index changes by precise measurement of the resonance angle and develop this sensor as a practicable high-stability biosensing device.