This research report describes a development of the theory for the design of divergent beam-based handheld SPR sensor, experimentalverification of the validity of the developed theory and testing of optical platform of the handheld SPR device. For a given range of samplerefractive indices, our analytical method allows quantitative calculations of optimum beam illumination and detection parameters for equilateral and right angle prisms of different materials. Besides finding the importance of the position of the beam incident on the prism for the sensor optimization, the proposed analytical method shows that the light detector must be inclined with respect to the prism exit surface in order to prevent elongation of the detected light pattern. The mathematical relation between the resonance angle and the size of the light detector is presented. The validity of the optimal divergent beam illumination and detection has been experimentally verified by sensing simultaneously air - water and air - ethanol. The experimental results are in good agreement with the analytical conditions even for a largerange of refractive index measurements. The errors in the RI measurements are found to be smaller than 1 , with the sensing of air gives the smallest error, while ethanol is the highest. The increase in error stems from the lower accuracy in depth detection of the broadened SPR dip. It is also found that the divergent beam-based SPR sensor has sensitivity almost the same as that of the conventional SPR sensor based on an angular interrogation technique. Finally, it can be concluded that the efficiency of the photon energy transfer does not only depend on the polarization state of the electric field of the illuminating beam, but is also determined by the incident position of the beam on the prism entrance side and the inclination angle of a light detector.