Design of flat lens-like graded index medium by photonic crystals: Exploring both low and high frequency regimes

Turduev, Mırbek; Giden, İbrahim Halil; Kurt, Hamza

doi:10.1016/j.optcom.2014.11.048

Cited by 25 publications

(18 citation statements)

References 41 publications

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“…The GRIN medium efficiently bends the light to follow curved trajectories because of the gradual change in refractive index along the radial or axial directions [28][29][30]. For this reason, the GRIN medium provides an opportunity to obtain curved light without curved interfaces for the optical phenomena such as focusing and/or collecting, and diverging and/or spreading [31]. In this regard, conceptual studies on optical cloaking by using GRIN optics have been reported recently in [32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Analytical, numerical, and experimental investigation of a Luneburg lens system for directional cloaking

et al. 2019

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In this study, the design of a directional cloaking based on the Luneburg lens system is proposed and its operating principle is experimentally verified. The cloaking concept is analytically investigated via geometrical optics and numerically realized with the help of the finite-difference time-domain method. In order to benefit from its unique focusing and/or collimating characteristics of light, the Luneburg lens is used. We show that by the proper combination of Luneburg lenses in an array form, incident light bypasses the region between junctions of the lenses, i.e., the "dark zone." Hence, direct interaction of an object with propagating light is prevented if one places the object to be cloaked inside that dark zone. This effect is used for hiding an object which is made of a perfectly electric conductor material. In order to design an implementable cloaking device, the Luneburg lens is discretized into a photonic crystal structure having gradually varying air cylindrical holes in a dielectric material by using Maxwell Garnett effective medium approximations. Experimental verifications of the designed cloaking structure are performed at microwave frequencies of around 8 GHz. The proposed structure is fabricated by three-dimensional printing of dielectric polylactide material and a brass metallic alloy is utilized in place of the perfectly electric conductor material in microwave experiments. Good agreement between numerical and experimental results is found.

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Section: Introductionmentioning

confidence: 99%

Analytical, numerical, and experimental investigation of a Luneburg lens system for directional cloaking

et al. 2019

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“…Moreover, study shows that the intensity of UV emission is higher for PS compared to Si, indicating that there is an improvement of the crystallinity of ZnO nanostructures due to free exciton emission [18]. In recent years, PS-based optical devices are widely used for photonic design, benefited from the easy preparation of PS by periodically altering etching time and etching current [19][20][21][22][23][24][25]. Among the photonic structures, porous silicon microcavity (PSM) attracts great interests of many scientists due to its interesting optical properties such as high reflectivity stop band with a sharp reflectance dip in the center of reflectance spectrum.…”

Section: Introductionmentioning

confidence: 99%

Application of porous silicon microcavity to enhance photoluminescence of ZnO/PS nanocomposites in UV light emission

Zhang

Jia

2017

Optik

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This paper presents ZnO nanostructures deposited on porous silicon (PS) and porous silicon microcavity (PSM) substrates by sol-gel method. The effects of annealing temperature and mass ration of zinc acetate to PVA on microstructure, and optical properties of ZnO/PS and ZnO/PSM nanocomposites were systematically investigated by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The XRD analysis confirmed that the ZnO/PS nanocomposite preferred strongly to (002) phase orientation. The PL spectra showed that there was a sharp and highly intense UV emission peak located at about 400 nm when annealing temperature was 800 o C for 30 min and the mass ratio of zinc acetate to PVA was 4:1. The detail cross-section FESEM images of ZnO/PSM showed that ZnO nanoparticles uniformly penetrated into all PS layers and adhered to them very well. Furthermore, ZnO/PSM nanocomposites showed relatively stronger UV emissions at around 400 nm compared to the PL spectra of ZnO/PS nanocomposites, that means one-dimension phonic crystal PSM can enhance the PL intensity of ZnO. Such a method may provide an interesting way to develop a new type of UV optoelectronic devices.

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“…due to altering the lattice spacing, the radii of rods (or holes) and the refractive index of a material. The GRIN PCs have numerous applications when forming mode-order converters [13,14], wavelength demultiplexers [15,16], couplers [17] and lenses [18].…”

Section: Introductionmentioning

confidence: 99%

Comprehensive analysis of two different graded-index photonic-crystal lenses

Gharaati¹,

Miri²

2017

Ukr. J. Phys. Opt.

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Abstract:We investigate two alternative approaches for implementing graded-index (GRIN) photonic-crystal (PC) structures that reveal a focusing effect. Gradient of the refractive index is achieved either using a symmetry-reduction approach (a structure of type I) or varying a filling fraction of PC elements (a structure of type II). We test the first structure for the frequencies located inside the first and second bands of the dispersion diagram. The focusing effect of the first structure characteristic for the frequencies located above the bandgap is stronger than that for the frequencies below the bandgap. It is demonstrated that variations of filling fractions of the elliptical air holes in the structure of type II produce a GRIN lens that manifests a pronounced focusing effect. We have also compared the focusing effects of the latter structure for the TE and TM polarizations. The both structures suggested in the present work can work in a broad enough band region.

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Design of flat lens-like graded index medium by photonic crystals: Exploring both low and high frequency regimes

Cited by 25 publications

References 41 publications

Analytical, numerical, and experimental investigation of a Luneburg lens system for directional cloaking

Analytical, numerical, and experimental investigation of a Luneburg lens system for directional cloaking

Application of porous silicon microcavity to enhance photoluminescence of ZnO/PS nanocomposites in UV light emission

Comprehensive analysis of two different graded-index photonic-crystal lenses

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