Highly efficient optical detection of surface-generated fluorescence

We present a theoretical study of a new highly efficient system for optical light collection, designed for ultrasensitive fluorescence detection of su rface-bound molecules. The main core of the system is a paraboloid glass se gment acting as a mirror for collecting the fluorescence. A special feature of the system is its ability to sample not only fluorescence that is emitt ed below the angle of total internal reflection (the critical angle) but al so particularly the Light above the critical angle. As shown. this is espec ially advantageous for collecting the fluorescence of surface-bound molecul es. A comparison is made with conventional high-aperture microscope objecti ves. Furthermore, it is shown that the system allows not only for highly ef ficient light collection but also for confocal imaging of the detection reg ion, which is of great importance for rejecting scattered light in potentia l applications such as the detection of only a few molecules. (C) 1999 Opti cal Society of America OCIS codes: 080.2740, 110.0180, 120.1880, 170.2520.