Illumination by Near-Critical-Angle Incidence for Imaging Fluorescence Correlation Spectroscopy with Electron-Multiplying Charge-Coupled Device Camera

摘要

We developed a novel illumination method for imaging fluorescence correlation spectroscopy (imaging FCS) with electron-multiplying charge-coupled device (EM-CCD) to regulate the depth of observation volume. In this method, a laser beam for excitation is incident to a glass-water boundary at an angle slightly smaller than critical angle. Transmitted light excites molecules only in the vicinity of the boundary. Through an FCS imaging experiment and a simulation based on a finite-difference time-domain (FDTD) method, we have confirmed that field intensity decays exponentially with distance and penetration depth varies with incident angle until 2nm, which is more than 10 times larger than that of a typical evanescent field.