Low Contrast Dielectric Metasurface Optics

Abstract

Abstract:The miniaturization of current image sensors is largely limited by the volume of the optical elements. Using a sub-wavelength patterned quasi-periodic structure, also known as a metasurface, one can build planar optical elements based on the principle of diffraction.However, recent demonstrations of high quality metasurface optical elements are mostly based on high refractive index materials. Here, we present a design of low contrast metasurface-based optical elements. We validate our theory by fabricating and experimentally characterizing several silicon nitride based lenses and vortex beam generators. The fabricated lenses achieved beam spots of less than 1 µμm with numerical apertures as high as ~ 0.75. A transmission efficiency of 90% and focusing efficiency of 40% in the visible regime was observed. Our results pave the way towards building low loss metasurface-based optical elements at visible frequencies using low contrast materials, and extend the range of prospective material systems for metasurface optics. Main Text:Conventional transmissive macroscopic optical elements primarily depend on refraction to control the propagation of light. Refraction relies heavily upon the exact curvature of the

Broadband high-efficiency dielectric metasurfaces for the visible spectrum

“…Due to the scientific and technological importance of visible wavelengths, there has been increasing effort to realize DMs at these wavelengths. For example, silicon nitride DMs have been realized at a red wavelength (λ = 633 nm) (10), scattering properties of coupled TiO 2 resonators (11) have been examined, and TiO 2 binary diffraction gratings have been fabricated via top-down etching (12). However, no current DM implementation has been capable of providing arbitrary phase control of an optical wavefront while maintaining high efficiency across the entire visible spectrum (especially at blue and green wavelengths).…”

Genetically optimized all-dielectric metasurfaces

“…However, PB phase approach is inherently limited to circularly polarized light and is unsuitable for linear polarization or for polarization independent metasurfaces. The second design technique utilizes the physical dimensions of the elements comprising the metasurface in order to obtain the desired local phase retardation of the transmitted wave [12][13][14][15][16][17][18][19][20]. Square (rectangular) [16] and circular (elliptic) [17,18] dielectric nano antennas are frequently employed for designing and realizing such metasurfaces.…”

Robust design of microlenses arrays employing dielectric resonators metasurfaces

“…A limited collection of these works can be found in. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] In the case of flat lenses, metasurface have been usually designed by mapping the required phase distribution onto a function of the characteristic parameters of the basic scattering elements, e.g. sizes of the dielectric resonators, 1,5,7,10,11 orientation of the dielectric posts, 16 local period of plasmonic gratings.…”