Guoyi's RepositoryAn integrated laser lithography control system developed by the Nanomaterials Research Lab, NUS
Author: Chen Guoyi, Sun Yudong, Wu Mingsong, Lan Ziying
Principal Investigators: Sharon Xiaodai Lim, Sow Chorng Haur
DOI: 10.5281/zenodo.13119830
This open-sourced project is sponsored by the NUS Department of Physics.
The Nanomaterials Laboratory uses Micos SMC Basic linear translation stages, which consist of X and Y axis pairs. These stages provide a translation step resolution of 0.5 µm and a maximum velocity of 1000 µm/s. They are positioned below the objective lens of an optical microscope (where the optical path is conventionally considered the Z-axis), enabling precise micrometer movement of the camera relative to the samples.
The stages are controlled by a microcontroller box that accepts a fixed set of serial commands from a user’s computer via an RS232 cable. Therefore, laptop users need an RS232 to USB adapter and relevant drivers (for Windows systems) to connect with the stages.
To simplify stage integration in programming, we developed a Python script that provides an interface for easier stage control. More details are provided in Section 2.
In our experiments, we often use a laser beam to cut a rectangular raster on our samples, focused through a modified microscope. With the XY linear translation stages moving the sample relative to the stationary laser beam, we can cut any pattern in the XY plane. To prevent the laser beam from entering the microscope between cuts, it was initially blocked manually with pulleys at the user's work area.
To automate this cutting process, we developed a shutter using a small 5V servo motor (SG90 9g). Typically, an integrated control (IC) board (such as Arduino) and a motor driver are required to power and control servo motors. To avoid purchasing costly circuit boards for a single motor setup, we devised an alternative approach:
In our laboratory, ND filters are essential for attenuating laser light to achieve specific power levels. We currently use Thorlabs’s AR Coated Mounted Round Variable ND Filters (NDC-50C-2M-A). These filters are coated to provide optical densities (OD) directly proportional to the rotation angle, orthogonal to the incident light path.
However, the rotation is manually operated, requiring the user to adjust the wheel by hand while checking the laser power with a meter. By machining a custom acrylic axle for the wheel, we can integrate our ND filters with a 360° OA servo motor. This allows users to perform precise and programmable rotations, thus enabling automated power adjustments.
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