Enhanced Scattered Light Imaging of Nanoparticles by Controlling the Polarization Distribution with Photonic Crystals

Abstract

An optical microscopy with a high sensitivity and resolution is required for observing semiconductor wafers and biological cells for nanotechnology and biotechnology applications. However, it is difficult to observe samples that are small compared with the optical wavelength since the signal is swamped by background noise such as dark noise and electrical noise and other signals besides that from the sample. Furthermore, light scattered from the sample cannot be focused into a spot in the image plane due to interference of polarized light, resulting in a blurred image that has a low resolution. This study proposes a method for removing the background noise and for improving the image resolution of nanoparticles by controlling the polarization direction. This method can be used to perform optical microscopy with a high sensitivity and resolution. We verify the effectiveness of this method by performing simulations and experiments. Simulations predict that the peak intensity obtained using this method will be 3.4 times higher than that obtained using a conventional microscope and that the resolution of this technique will be 0.43 times smaller than that of conventional microscopy. Experiments show that this method with a photonic crystal utilized as a radial polarization converter is capable of detecting 23-nm-diameter PSLs on a silicon wafer.