Large Dynamic Range SPR Measurements Using a ZnSe Prism

A large dynamic index measurement range （n =1 to n = 1.7） using surface plasmon resonance （SPR） shifts was demonstrated with a ZnSe prism at 632.8nm, limited by the available high index liquid hosts. In contrast to borosilicate based SPR measurements, where angular limitations restrict solvent use to water and require considerable care dealing with Fresnel reflections, the ZnSe approach allows SPR spectroscopies to be applied to a varied range of solvents. An uncertainty in angular resolution between 1.5° and 6°, depending on the solvent and SPR angle, was estimated. The refractive index change for a given glucose concentration in water was measured to be n = （0.114 ± 0.007）/%[C6H12O6]. Given the transmission properties of ZnSe, the processes can be readily extended into the mid infrared.