Abstract
We present a novel homodyne frequency-shifting interference pattern locking
system to enhance the exposure contrast of interference lithography and scanning beam
interference lithography (SBIL). The novel interference pattern locking system employs a
special homodyne redundant phase measurement interferometer (HRPMI) as the sensor and an
acousto-opto modulator (AOM) as the actuator. The HRPMI offers the highly accurate value
as well as the direction recognition of the interference pattern drift from four
quadrature interference signals. The AOM provides a very fine resolution with a high
speed for phase modulation. A compact and concise system with a short optical path can
be achieved with this new scheme and a small power laser head in tens of microwatts is
sufficient for exposure and phase locking, which results in a relatively low-cost system
compared with the heterodyne system. More importantly, the accuracy of the system is at
a high level as well as having robustness to environmental fluctuation. The experiment
results show that the short-time (4 s) accuracy of the system is ±0.0481 rad(3σ) at
present. Moreover, the phase of the interference pattern can also be set arbitrarily to
any value with a high accuracy in a relatively large range, which indicates that the
system can also be extended to the SBIL application.
© 2016 Chinese Laser Press
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