Phase-shift Control In Multi-beam Laser Interference Lithography

With the increasing demands from industries for fabrication of new micro and nano materials, devices and systems, laser interference nanolithography technology has been developed. In laser interference nanolithography applications, large area or high density nano-surface structures are often required. Therefore, the precise phase shift should be controlled to ensure the accuracy of interference patterns.This dissertation presents the method of phase-shift control in a multi-beam laser interference nanolithography system using a phase-shift positioning system to achieve phase shift control. In the two-beam or multi-beam laser interference nanolithography system, two or more coherent laser beams combine and interfere, by controlling the phase-shift of the phase-shift positioning system to change the optical path length to achieve the phase-shift of interference patterns and positions.Phase-shift can be introduced by an optical wedge, LCD and fiber element in laser interference. In this work, the phase-shift positioning system consists of voltage sources, displacement drives and mirrors. By applying different voltages to displacement drives, making the mirror or mirrors move forward and backward to change the optical path lengths and achieve phase-shifts of interference patterns and positions. The phase positioning system can precisely control the phase shift and reduce its drifts by the detection of fringe patterns and feedback control (such as phase locking).