Surface patterning using speckle lithography for sers application
Laser speckles, a phenomenon caused when a laser reflects diffusely of a surface forming a granular pattern, is long considered as undesirable noise. In this project, the laser speckle effect is utilized to perform lithography to fabricate scattering substrates. Speckle lithography takes advantag...
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Format: | Final Year Project |
Language: | English |
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Nanyang Technological University
2024
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Online Access: | https://hdl.handle.net/10356/177758 |
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Institution: | Nanyang Technological University |
Language: | English |
Summary: | Laser speckles, a phenomenon caused when a laser reflects diffusely of a surface
forming a granular pattern, is long considered as undesirable noise. In this project, the
laser speckle effect is utilized to perform lithography to fabricate scattering substrates.
Speckle lithography takes advantage of the laser speckles to form the target pattern,
eliminating the use of an optical mask in conventional lithography. Initial simulations
in ANSYS Lumerical were carried out to understand the effect of surface roughness
in light localization. The simulations displayed a clear trend of increasing electric field
intensity with increasing surface roughness. Optimization of the experimental
parameters were then carried out by varying exposure time and power. Speckle
patterns of different sizes were created by varying the laser spot size at the diffuser.
The fabricated patterned surfaces are then used in Raman spectroscopy to test its
effectiveness as SERS substrate. The results of the Raman spectroscopy confirm the
findings from the simulations, where having higher surface roughness increases the
intensity of Raman signals. This project gives insight into the ability of speckle
lithography to fabricate scattering substrates over conventional lithography |
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