Abstract
Abstract To improve the efficiency of femtosecond laser direct writing, holographic femtosecond laser patterning using spatial light modulators has been widely used for the processing of micro/nanopatterns. However, the speckle noise of modulated optical fields severely limits the quality of fabricated patterns. We present a simple and effective method which involves interlacing a target pattern into a series of target subpatterns that consist of spaced spots to solve this problem. The separation of spots weakens the random interference between adjacent spots of optical fields, so the speckle noise reduces effectively, which improves the uniformity of the modulated optical fields and makes the fabricated patterns with high quality. With optimal interlacing numbers, complex micropattern arrays containing curved edges and sophisticated structures can be fabricated with superior quality and high efficiency. Binary holograms with improved optical characterization are realized by using the interlacing-pattern method, revealing the extensive potential of this method in micropattern processing and functional device fabrication with high quality and efficiency.
Highlights
As a unique processing technology, femtosecond laser direct writing (FLDW) has been widely used in drilling, cutting, surface/internal patterning, and microstructure/ nanostructure fabrication because of its flexibility, simplicity, and capability of processing various materials and three-dimensional (3D) structures [1,2,3,4,5,6,7]
We present a simple and effective method which involves interlacing a target pattern into a series of target subpatterns that consist of spaced spots to solve this problem
We proposed and validated a method to improve the fabrication quality of spatial light modulators (SLMs)-based holographic femtosecond laser patterning technology
Summary
As a unique processing technology, femtosecond laser direct writing (FLDW) has been widely used in drilling, cutting, surface/internal patterning, and microstructure/ nanostructure fabrication because of its flexibility, simplicity, and capability of processing various materials and three-dimensional (3D) structures [1,2,3,4,5,6,7]. Because its single-point processing which leads to low laser power utilization and long processing time, FLDW is unsuitable for fabricating large-scale structure arrays or patterns. To overcome this obstacle, various beam shaping devices, including diffractive optical elements [8], phase plates [9], microlens arrays [10], spatial light modulators (SLMs) [11,12,13], and digital micromirror devices [14], have been employed to increase the processing efficiency of FLDW by splitting a single laser beam into multiple parallel beam arrays [8, 10,11,12] or by shaping a Gaussian laser beam into a Bessel beam [15], vortex beam [9], or complex patterns [14, 16]. Conventional phase-retrieval algorithms, such as the optimal rotation angle algorithm [21], Gerchberg-Saxton (GS) algorithm, and its common derivative algorithms [22, 23], calculate the CGHs by constraining the intensity of the output optical field while
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