Scanning probe optical microscope using a solid immersion lens

摘要

A scanning probe microscope uses a high refractive index solid immersion lens (SIL) probe to provide optical images with a resolution better than the diffraction limit in air. The SIL probe has a spherical upper surface and a conical (or pyramidal) lower surface with a sharp tip. The SIL reduces the focused spot size because the spherical surface increases the angle of the marginal rays and the high refractive index material shortens the wavelength. The focused spot generates an evanescent wave having an amplitude that decays exponentially with distance from the SIL. The sharp tip on the lower surface reduces the tip-sample contact area and the tip-sample separation so that sample is within the near-field of the SIL probe. The sample perturbs the evanescent wave and a photodetector monitors characteristics of the light. A cantilever carries the SIL probe and a cantilever deflection sensor permits precise control of tip-sample forces and separation. The cantilever deflection sensor operates in a force feedback loop to maintain the tip-sample gap within the near-field as the SIL probe scans over the sample in a raster pattern to generate optical data.