FORCE IMAGING OF OPTICAL NEAR-FIELD USING NONCONTACT MODE ATOMIC-FORCE MICROSCOPY

We demonstrate a novel method to detect the van der Waals force gradie nt and the force gradient induced by the optical evanescent field on t he surface, simultaneously, with high resolution. We use the noncontac t mode atomic force microscopy (NC-AFM) with frequency modulation (FM) detection method, which can detect the force gradient with high sensi tivity in a vacuum. The force gradient due to the evanescent field can be enhanced by applying the bias voltage. The 100-nm-diameter polysty rene latex spheres are observed with spatial resolution better than 50 nm (lambda/14).