Fabrication of subwavelength scale optical nanostructures
Haq, Mohammad Tahdiul.
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Sub-wavelength scale optical nanostructures can be engineered for specific applications in multiple disciplines. This thesis describes the fabrication of three such optical nanostructures and the process development and optimization performed to improve the nanofabrication capabilities of our research group. Along with our collaborators we have fabricated a subwavelength-scale solid immersion lens. The fabrication process of cylinders of precise dimensions in resist is discussed as well as the measurements and characterization of the final fabricated device. The second device is a1-D antireflective rectangular grating in silicon with 800nm period, which is fabricated, simulated and characterized. The lithography process is calibrated for gratings with 250-600nm line widths and the etching process is optimized to obtain depths precise to within + or - 10nm. The final device is a mid-infrared polarizing beam splitter. The fabrication of this device is not yet complete, but the correct grating structure in silicon is fabricated and some process improvements for gold deposition have been realized.