18 research outputs found
Negative refraction and plano-concave lens focusing in one-dimensional photonic crystals
Negative refraction is demonstrated in one-dimensional (1D) dielectric
photonic crystals (PCs) at microwave frequencies. Focusing by plano-concave
lens made of 1D PC due to negative refraction is also demonstrated. The
frequency-dependent negative refractive indices, calculated from the
experimental data matches very well with those determined from band structure
calculations. The easy fabrication of one-dimensional photonic crystals may
open the door for new applications.Comment: 3 pages and 5 figure
Focusing by Plano-Concave lens using Negative Refraction
We demonstrate focusing of a plane microwave by a plano-concave lens
fabricated from a photonic crystal (PhC) having negative refractive index and
left-handed electromagnetic properties. An inverse experiment, in which a plane
wave is produced from a source placed at the focal point of the lens is also
reported. A frequency dependent negative refractive index, is obtained for the
lens from the experimental data which matches well with that determined from
band structure calculations
A new mechanism for negative refraction and focusing using selective diffraction from surface corrugation
Refraction at a smooth interface is accompanied by momentum transfer normal
to the interface. We show that corrugating an initially smooth, totally
reflecting, non-metallic interface provides a momentum kick parallel to the
surface, which can be used to refract light negatively or positively. This new
mechanism of negative refraction is demonstrated by visible light and microwave
experiments on grisms (grating-prisms). Single-beam
all-angle-negative-refraction is achieved by incorporating a surface grating on
a flat multilayered material. This negative refraction mechanism is used to
create a new optical device, a grating lens. A plano-concave grating lens is
demonstrated to focus plane microwaves to a point image. These results show
that customized surface engineering can be used to achieve negative refraction
even though the bulk material has positive refractive index. The surface
periodicity provides a tunable parameter to control beam propagation leading to
novel optical and microwave devices.Comment: 6 pages, 7 figures in RevTex forma
Negative Refraction and Left-handed electromagnetism in Microwave Photonic Crystals
We demonstrate negative refraction of microwaves in metallic photonic
crystals. The spectral response of the photonic crystal, which manifests both
positive and negative refraction, is in complete agreement with band-structure
calculations and numerical simulations. The negative refraction observed
corresponds to left-handed electromagnetism and arises due to the dispersion
characteristics of waves in a periodic medium. This mechanism for negative
refraction is different from that in metamaterials.Comment: 13 pages, 4 figure
Metamaterial superlenses operating at visible wavelength for imaging applications
© 2018 The Authors. Published by Nature. This is an open access article available under a Creative Commons licence.
The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1038/s41598-018-33572-yIn this paper, a novel design for a metamaterial lens (superlens) based on a Photonic Crystal (PC) operating at visible wavelengths is reported. The proposed superlens consist of a gallium phosphide (GaP) dielectric slab waveguide with a hexagonal array of silver rods embedded within the GaP dielectric. In-house 2DFDTD numerical method is used to design and optimize the proposed superlens. Several superlenses are designed and integrated within a same dielectric platform, promoting the proof-of-concept (POC) of possible construction of an array of superlenses (or sub-lenses to create an M-Lens) for light field imaging applications. It is shown that the concavity of the superlens and positioning of each sub-lens within the array strongly affects the performances of the image in terms of resolution. Defects and various geometrical shapes are introduced to construct and optimize the proposed superlenses and increase the quality of the image resolution. It is shown that the orientation of the active region (ellipse) along x and y axis has tremendous influence on the quality of image resolution. In order to investigate the performance characteristics of the superlenses, transmitted power is calculated using 2D FDTD for image projections at various distances (in x and y plane). It is also shown, how the proposed superlens structures could be fabricated using standard micro fabrication techniques such as electron beam lithography, inductively coupled Reactive ion etching, and glancing angle evaporation methods. To the best of our knowledge, these are the first reported POC of superlenses, integrated in a monolithic platform suitable for high imaging resolution that can be used for light field imaging applications at visible wavelength. The proposed superlenses (integrated in a single platform M-Lens) will have tremendous impact on imaging applications
Gonadal ER\u3b1/\u3b2, AR and TRPV1 gene expression: modulation by pain and morphine treatment in male and female rats.
The results of several studies strongly indicate a bidirectional relationship among gonadal hormones and pain. While gonadal hormones play a key role in pain modulation, they have been found to be affected by pain therapies in different experimental and clinical conditions. However, the effects of pain and pain therapy on the gonads are still not clear. In this study, we determined the long-lasting (72 h) effects of inflammatory pain (formalin test) and/or morphine on estrogen receptor (ER), androgen receptor (AR) and TRPV1 gene expression in the rat testis and ovary. The animals were divided into groups: animals receiving no treatment, animals exposed only to the experimental procedure (control group), animals receiving no pain but morphine (sham/morphine), animals receiving pain and morphine (formalin/morphine), and animals receiving only formalin (formalin/saline). Testosterone (T) and estradiol (E) were determined in the plasma at the end of the testing. In the sham/morphine rats, there were increases of ER\u3b1, ER\u3b2, AR and TRPV1 mRNA expression in the ovary; in the testis, ER\u3b1 and ER\u3b2 mRNA expression were reduced while AR and TRPV1 expression were unaffected by treatment. T and E plasma levels were increased in morphine-treated female rats, while T levels were greatly reduced in morphine-treated and formalin-treated males. In conclusion, both testicular and ovarian ER (ER\u3b1 and ER\u3b2) and ovarian AR and TRPV1 gene expression appear to be affected by morphine treatment, suggesting long-lasting interactions among opioids and gonads