Endoscopes are medical inspection devices allowing doctors to examine internal organs without the need for large incisions. Made of optical fibers and an imaging lens at the tip, one of their most critical parameters is the size of the imaging optical system, limiting the agility and accessibility for clinical applications. Metalens-based fiber-optic endoscopes offer a promising alternative to conventional devices to reduce the size while maintaining the image quality. However, the accurate modelling and analysis required to design these devices can be challenging as they combine nanoscopic elements in a macroscopic optical system. In this work, we present a new multiscale metalens design solution for fiber-optic endoscopes, utilizing full-wave electromagnetic simulations and ray-tracing techniques. The metalens consists of subwavelength scatterers (meta-atoms) characterized individually using Rigorous Coupling Wave Analysis (RCWA). By controlling their distribution in size according to a target phase profile optimized in ray-tracing optics software, one can manipulate the phase, amplitude and polarization of the transmitted light. Smaller scale metalens (~100λ),can be directly simulated and their near-/far-field results can be obtained with the Finite Difference Time Domain (FDTD) method. For larger metalens (≫ 100 λ) stitching the near field or summing up the farfield from individual metaatoms to obtain the overall response of the metalens is more efficient than the direct simulationFinally, we can perform ray-tracing simulations to characterize the full system in a macro-scale environment, utilizing the response of the metalens.
We present the tomographic study of the refractive index distribution in polymer bridges between two optical fibers. Detailed refractive index maps are needed in order to improve the technological process for manufacturing those bridges and to achieve a lower return loss. At first, the technological process of the fabrication of bridges through photopolymerization is presented. The interferometric measurements of reference fibers used to produce those bridges and two series of microbridges are performed experimentally in the visible (VIS; 632.8 nm) and infrared (IR; 1550 nm) wavelength regions. The relation between the VIS and IR results is determined, which allows performing tomographic measurements in more accurate conditions in the VIS spectrum. The experimentally obtained refractive index distributions in the microbridges are used for modeling the insertion and return losses, which are compared with the real loss obtained for the produced microbridges. This knowledge will be used for better understanding the manufacturing process and its further optimization.
In this paper we present the tomographic studies of refractive index distribution in polymer bridges between two optical fibers. Detailed refractive index maps are needed in order to improve the technological process of manufacturing of those bridges and to achieve lower return losses. At first the technological process of bridges fabrication through photopolymerization is presented. The interferometric measurements of reference fibers used to produce those bridges and two series of microbridges are performed in visible (632.8 nm) and infrared (1550 nm) experimental systems. The relations between vis and IR results are determined, which allows for performing tomographic measurements in more accurate conditions secured in visible spectrum. The experimentally obtained refractive index distributions in microbridges are used for modeling the insertion and return losses, which are compared with the real losses obtained for the produced microbridges. This knowledge will be used for better understanding of the manufacturing process and its further optimization.
In this paper we present a simple method of manufacturing micrometer-sized polymer elements at the extremity of both
single mode and multimode optical fibers and its possible modifications in order to provide requested functionalities. We
show that the knowledge about 3D distribution of refractive index and birefringence in these elements is required and
that interferometric and elastooptics tomography are the methods which provide these data. Exemplary polymer
microtips manufactured from the polymeric material with different concentration of heptafluorobutyric acid are
investigated in tomographic systems and the obtained results are discussed in reference to the theoretically expected
refractive index distributions.
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