High-precision grayscale lithography
OPTICAL PRODUCT
Figure 4: Grayscale design( top) and print of a Moiré lens( bottom). These diffractive lenses can be used to adjust the focus length.
spectrum and extending into the near-infrared and ultraviolet ranges, as well as photopolymers with different refractive indices and Abbe numbers. Both Two-Photon Polymerization and Two-Photon Grayscale Lithography support a wide range of such resins, enabling fabrication of micro-optical components precisely matched to diverse application requirements. Two-Photon Grayscale Lithography utilizes liquid negative-tone resins, thus overcoming the height limitations imposed by Beer’ s law in one-photon grayscale lithography, where film thicknesses of positive resists typically restrict structure heights to around 60 µ m. In contrast, 2GL enables fabrication of 2.5D microstructures with heights up to 1 mm and with high aspect ratios as exemplified by a 3D-printed microlens array in figure 2. Furthermore, the photoresists used in one-photon grayscale lithography are often highly sensitive to environmental factors, such as humidity and temperature, which can significantly affect process stability. Two-Photon Grayscale Lithography, however, offers robust processing conditions during preparation, printing, and development. In most cases, neither spin-coating nor pre- or post-processing steps are required. Thanks to its robust process and the low proximity effect, 2GL does not require additional proximity correction
tools, which helps reduce process complexity and simplifies data preparation workflows.
MARKETS AND APPLICATIONS REFRACTIVE 2.5D MICRO-OPTICS Two-Photon Grayscale Lithography expands design possibilities beyond classical optical geometries while maintaining submicron resolution. Applications include beam shaping, collimation, light homogenization, illumination, and imaging. The 2GL technology enables fabrication of almost any 2.5D shape, including spherical, aspherical, sharpedged and freeform refractive optics. Both regular microlens arrays and random lens arrangements can be printed with fill factors up to 100 % and high aspect ratios are also possible.
DIFFRACTIVE OPTICAL ELEMENTS Diffractive optical elements( DOEs) are nanostructured surfaces that manipulate light based on the principle of diffraction( figure 3). By encoding spatial phase profiles into subwavelength or micron-scale surface reliefs, they can shape light to produce precise far-field intensity distributions, such as spot arrays, gratings and complex intensity or phase images. DOEs are used in applications that require precise beam shaping, such as holographic projection, laser beam homogenization, beam splitting in
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