Optical near-field probe integrated with self-aligned bow-tie antenna and electrostatic actuator for local field enhancement

Microelectromechanical systems (MEMS)-based near-field scanning optical microscopy (NSOM) probes with a bow-tie antenna structure consisting of two metal triangular electrodes separated by a narrow gap have been designed and fabricated. An electrostatic actuator is integrated on this bow-tie probe to decrease the gap width for enhancing the optical near-field intensity. A self-alignment process based on deep reactive ion etching and wet anisotropic etching is established to fabricate the symmetric bow-tie structure. The static and dynamic actuations of electrostatic actuators are examined. With the mechanical resonance of the antenna structure to lateral direction, NSOM imaging is performed in the visible range, and the subwavelength resolution beyond the diffraction limit of light is demonstrated.