An improved optical method for surface plasmon resonance experiments

In this paper an inexpensive optical device is described, which is capable of measuring the optical reflectance at different angles, while keeping the laser spot stationary at one point of the surface. This is accomplished by applying cylindrical optics. Its use is demonstrated in a surface plasmon resonance (SPR) sensor. A coil-operated vibrating mirror is used to obtain an angle scan of about 4 degrees. The angle of minimum reflectance can be detected with an accuracy of approximately 2 × 10−3 degrees. Despite the use of simple optical components, disturbance of laser beam parallelism is no more than 0.02 degrees. Displacement of the laser spot at the surface during the angle scan is kept within 0.2 mm. The device eliminates disturbances due to surface irregularities in measurements.