Near-field optical microscopy using an integrating sphere

A scanning near-field optical microscope using an integrating sphere is demonstrated. The images from a usual near-field optical microscope often include contrasts caused by the sample structure because the reflection and transmission angles of signal waves depend on the size and shape of the sample. The observation angle dependency of signals can be avoided by using an integrating sphere. Background signals resulting from using the sphere can be reduced by using lock-in detection synchronously with modulation of tip–sample distance. The whole detection system is possibly useful for observing the distribution of the refractive index and/or the absorption coefficient.