Category Archives: Uncategorized

Our Paper on “Super-resolution far-field sub-wavelength imaging”was accepted for publication in Optical Society of America.

Abstract

Losing the information contained in evanescent waves scattered from an object limits the best achievable resolution in far-field optical imaging systems to about half of the wavelength. This limitation is known as the diffraction limit. In this paper, we propose a new holography-based far-field imaging technique to go beyond the diffraction limit and achieve super-resolution images. In the proposed method, after the recording process, multiple reconstruction processes with appropriate reconstruction waves are performed to extract information about sub-wavelength features of a target object encoded in the evanescent waves scattered from it. It is analytically proved that in the proposed method, by increasing the number of reconstruction steps, the resolution increases. The performance of the method is numerically validated. In numerical analysis, by performing two reconstruction steps, a resolution of 1/14 of the working wavelength is achieved. This resolution can be further improved by increasing the number of reconstruction steps.

link:

https://opg.optica.org/josab/abstract.cfm?uri=josab-38-3-670

Our Paper on “enhance the efficiency of solar cells”was accepted for publication in Optical Society of America.

Abstract
With the advances in the field of plasmonics, techniques for trapping and localizing light have become more feasible at the nanoscale. Several works have shown that plasmonics-based photovoltaic devices have yielded an improved absorption capability, enabling the design of thin-layered photovoltaic absorbers. In this review, we shed light on recent advances that employ plasmonics and nano-sized structures and thin-film technologies intended to increase solar cell efficiency. In this work, we provide an overview of the challenges associated with developing high-efficiency solar cells. Despite significant efforts by numerous groups to improve the efficiency of solar cells, practical realization of these concepts has yet to materialize. The conclusions made here hope to encourage researchers to re-examine the factors and challenges that could have created barriers to full realization of all concepts proposed over the past 15 years. In fact, because of the immense impact of improving the efficiency of solar cells on the environment and economy, it is hoped that this review encourages new technology paradigms that can be translated into commercially viable products.

link:

https://opg.optica.org/josab/abstract.cfm?uri=josab-38-2-638

Our paper on “Optical Tunable Metasurfaces” was accepted for publication in Optics Express!

Abstract:
Tunable metasurfaces enable us to dynamically control light at subwavelength scales. Here, using phase change materials and transparent graphene heaters, a new structure is proposed to develop tunable metasurfaces which support first-order Mie-type resonance in the near-IR regime. In the proposed structure, by adjusting the bias voltages applied to transparent graphene heaters, the crystallization levels of the phase change materials are controlled, which in turn modifies the response of the metasurface. The proposed metasurface is able to modulate the phase of the reflected wave in the range of 0° to −270° at the telecommunication wavelength of λ = 1.55 µm. A comprehensive Joule heating analysis is performed to investigate the thermal characterizations of the proposed structure. The results of this analysis show that there is a suitable thermal isolation between adjacent unit cells, making individual control on unit cells possible. The potential ability of the proposed metasurface as a beam steering device is also demonstrated. By using the proposed unit cells, a beam-steering device is designed and numerically studied. This study shows that the device can reflect a light normally incident on it in the range of ±65° with reasonably low sidelobe levels. The proposed structure can be used in developing low-cost integrated LiDARs.

 

Link:

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-28-23-33876&id=441947