The Design And Fabrication Of Subwavelength High Contrast Gratings (HCGs)

The conventional focusing reflectors and lenses have an aspheric shape and bulky thickness. Itisn’t compatible with the standard micro fabrication processes. Zone plates and Fresnel lenses areplanar and compact components, zone plates cannot meet the needs of some applications where lowloss is required, because they absorb a significant part of input power. The concentric segments withcontinuous height variations in Fresnel lenses are difficult to fabricate at the micro scale, which hasbrought great inconvenience in the applications of the optics field. To solve the above problem, wefocus our research on a new structure of high contrast subwavelength gratings (HCGs) structure.These high contrast subwavelength gratings (HCGs) can replace conventional lenses due to theiradvantages of low loss, high reflectivity, simple structure as well as phase matching and strongfocuing ability. However, problems still remain during structural design, nano fabrication and datatest processes. Therefore, research work aiming at the above problems is conducted in the paper andthey are listed in the following.Firstly, subwavelength gratings is studied based on vector diffraction theory, By the aid ofsimulation software Rsoft, the structure of high contrast subwavelength grating is designed andoptimized based on rigorous coupled wave theory and finite difference time domain principle.Next, structure of new high contrast subwavelength gratings (HCGs) are designed, thefreestanding SOI high contrast subwavelength grating working in the infrared band isresearched.And the SOI high contrast subwavelength grating is fabricated with deep silicon etching;Besides, Research work is conducted in the fabrication process of thin GaN high contrastsubwavelength grating working in the visible band using nitride and silicon processing technologyand the behind thinning technology.Finally, new non-periodic high contrast subwavelength gratings (HCGs) are designed, which areequipped with strong focusing ability due to its phase-matching structure at the wavelength of1.55m. Through diffraction theory, the focus and reflection ability of non-periodic high contrastsubwavelength gratings (HCGs) is analyzed, and the non-periodic high contrast subwavelengthgratings with strong focing ability are obtained through calculation and fabrication.