Novel Bilayer Micropyramid Structure Photonic Nanojet for Enhancing a Focused Optical Field

Abstract

In this paper, synthetically using refraction, diffraction, and interference effects to achieve free manipulation of the focused optical field, we firstly present a photonic nanojet (PNJ) generated by a micropyramid, which is combined with multilayer thin films. The theory of total internal reflection (TIR) was creatively used to design the base angle of the micropyramid, and the size parameters and material properties of the microstructure were deduced via the expected optical field distribution. The as-designed bilayer micropyramid array was fabricated by using the single-point diamond turning (SPDT) technique, nanoimprint lithography (NIL), and proportional inductively coupled plasma (ICP) etching. After the investigation, the results of optical field measurement were highly consistent with those of the numerical simulation, and they were both within the theoretical calculation range. The bilayer micropyramid array PNJ enhanced the interference effect of incident and scattered fields; thus, the intensity of the focused light field reached 33.8-times that of the initial light, and the range of the focused light field was extended to 10.08λ. Moreover, the full width at half maximum (FWHM) of the focal spot achieved was 0.6λ, which was close to the diffraction limit.

Efficient Achromatic Broadband Focusing and Polarization Manipulation of a Novel Designed Multifunctional Metasurface Zone Plate

“…The high refractive index helps to reduce the aspect ratio of the structure. Si is not selected because the refractive index difference between upper and lower materials is too large, which will produce strong interference effect to interfere with broadband focusing [39]. The SiO 2 and SiN x used here have refractive index of 1.5 and 2.1, which can be prepared by plasma enhanced chemical vapor deposition (PECVD) [40].…”

Mesotronics: Some New, Unusual Optical Effects

“…Some physical concepts presented here and in [31,32,36,37,134,135] are very general and their application can be extended in many ways: for instance, to the terahertz, in which the absorption is at least of 3-4 orders higher than in optics, surface plasmons and acoustics, in which the dielectric structure is always anisotropic due to two sound waves (transverse and shear). Mesotronic methods are even applicable to explain some of the effects of the Great Pyramid [136,137], square microresonators [138][139][140], nanopattering [141], etc. Moreover, for example, the use of "waveguide mesotronics" concept [142], based on the mesoscale particle chain with periodical focusing modes through air gaps, makes it possible to double the propagation length [143,144] of plasmon waves [145].…”

Design of wide-spectrum antireflection microstructure with large angle

“…When the incident angle is 75°in the long-wave infrared band, the transmittance of the micro-pyramid array structure is all higher than 90%, which is obviously better than that of multilayer anti-reflection film at large angle. According to the analysis of equivalent medium theory, when the height of microstructure H=1 m, the spectral transmission resonance effect of sub-wavelength structure effectively reduces the reflection loss of light energy [12] . It can be seen that with the increase of incident angle, the fluctuation amplitude of reflectivity curve gradually increases.…”