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2,669 results on '"Adibi, Ali"'

103. A Dual-Stage Photonic Integrated Circuit Spectrometer

Author

Evans, Christopher C., primary, Dorsey, Kyle J., additional, Subotic, Sasha, additional, Cwik, Michal, additional, Young, Brandon D., additional, Eftekhar, Ali A., additional, Hosseinnia, Amir H., additional, Adibi, Ali, additional, and Hensley, Joel M., additional

Published
2022
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140. Proceedings of SPIE: Wavelength-resolved Purcell enhancement of PbS/CdS quantum dots measured on a chip-based platform

Author

Elsinger, Lukas, Gourgues, R.B.M., Esmaeil Zadeh, I.Z., Maes, Jorick, Guardiani, A., Bulgarini, G., Pereira, S.F., Dorenbos, S.N., Zwiller, Val, Adibi, Ali, Lin, Shawn-Yu, and Scherer, Axel

Subjects
Silicon nitride, Condensed Matter::Materials Science, Physics::Instrumentation and Detectors, Colloidal quantum dots, Physics::Optics, Photonic integration, Plasmonic antennas, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Superconducting nanowire single-photon detectors
Abstract

Future quantum optical networks will require an integrated solution to multiplex suitable sources and detectors on a low-loss platform. Here we combined superconducting single-photon detectors with colloidal PbS/CdS quantum dots (QDs) and low-loss silicon nitride passive photonic components to show their combined operation at cryogenic temperatures. Using a planar concave grating spectrometer, we performed wavelength-resolved measurements of the photoluminescence decay of QDs, which were deterministically placed in the gap of plasmonic antennas, in order to improve their emission rate. We observed a Purcell enhancement matching the antenna simulations, with a concurrent increase of the count rate on the superconducting detectors.

Published
2020

142. Optimal sparse solution for fluorescent diffuse optical tomography: theory and phantom experimental results

Author

Mohajerani, Pouyan, Eftekhar, Ali A., Huang, Jiandong, and Adibi, Ali

Subjects
Optical tomography -- Methods, Image processing -- Methods, Diagnostic imaging -- Methods, Astronomy, Physics
Abstract

We present a method to accurately localize small fluorescent objects within the tissue using fluorescent diffuse optical tomography (FDOT). The proposed method exploits the localized or sparse nature of the fluorophores in the tissue as a priori information to considerably improve the accuracy of the reconstruction of fluorophore distribution. This is accomplished by minimizing a cost function that includes the [L.sub.1] norm of the fluorophore distribution vector. Experimental results for a milk-based phantom using a fiber-based cw FDOT system demonstrate the capability of this method in accurately localizing small fluorescent objects deep in the phantom. OCIS codes: 170.3010, 170.0170, 170.3880, 170.7050.

Published
2007

143. Light confinement in low-index particles with all-dielectric anisotropic metamaterial shell (Conference Presentation)

Author

Adibi, Ali, Lin, Shawn-Yu, Scherer, Axel, Jahani, Saman, Bahng, Joong Hwan, Montjoy, Douglas, Yao, Timothy A., Kotov, Nicholas A., Marandi, Alireza, Adibi, Ali, Lin, Shawn-Yu, Scherer, Axel, Jahani, Saman, Bahng, Joong Hwan, Montjoy, Douglas, Yao, Timothy A., Kotov, Nicholas A., and Marandi, Alireza

Abstract

We propose and demonstrate low-refractive-index particles with all-dielectric metamaterial shell which lead to formation of high intensity photonic nanojets. We show that the extra degree of freedom because of the anisotropy of the shell gives rise to an increase in the photonic jet intensity inside the metamaterial shell without a need to increase the size of the particle. The anisotropy of the shell can also control the spectral and spatial location of the Mie-type multipolar resonances to achieve the desired scattering. In experiments, the metamaterial shell is composed of strong nonlinear materials leading to enhanced nonlinear wavelength conversion at nanoscale.

Published
2020

144. Scalable fabrication of nano-architected materials using 3D interference lithography with metasurfaces at visible wavelengths (Conference Presentation)

Author

Adibi, Ali, Lin, Shawn-Yu, Scherer, Axel, Pearson, Phillippe, Kamali, Seyedeh Mahsa, Afshinmanesh, Farzaneh, Navrazhnykh, Luizetta, Ng, Ryan, Faraon, Andrei, Greer, Julia R., Adibi, Ali, Lin, Shawn-Yu, Scherer, Axel, Pearson, Phillippe, Kamali, Seyedeh Mahsa, Afshinmanesh, Farzaneh, Navrazhnykh, Luizetta, Ng, Ryan, Faraon, Andrei, and Greer, Julia R.

Abstract

Nano-architected materials have the potential to be adopted in several areas including photonic devices and structural materials. We present a 3D interference lithography technique with dielectric metasurfaces at visible wavelengths that allows patterning of thick epoxide films over areas on the order of 10 cm^2 with 100 nm resolution. By leveraging the ability of the metasurface to control the amplitude and phase of a wavefront, complex near-field 3D interference patterns can be designed. Pyrolysis of 3D patterned SU-8 produces a carbon-based material with sub-100 nm features and enhanced mechanical properties.

Published
2020

145. Preconditioned superprism-based photonic crystal demultiplexers: analysis and design

Author

Momeni, Babak and Adibi, Ali

Subjects
Photonics -- Research, Diffraction -- Analysis, Fiber optics -- Equipment and supplies, Fiber optics -- Design and construction, Astronomy, Physics
Abstract

We present the analysis and design of a new type of photonic crystal (PC) demultiplexers (i.e., preconditioned demultiplexer), in which the simultaneous existence of the superprism effect and the negative effective index for diffraction results in a compact structure by canceling the second-order spectral phase to avoid beam broadening inside the PC. This approach considerably relaxes the requirements for the large area of the structure and the small divergence of the input beam. As a result, the size of the preconditioned demultiplexers varies as [N.sup.2.5] (N being the number of wavelength channels) compared to the [N.sup.4] variation in the conventional superprism-based PC demultiplexers. We use a generalized effective index model to analyze, design, and optimize these demultiplexing structures. This approximate model can be used to extract all the basic properties of the PC device simply from the band structure and eliminates the need to go through tedious simulations especially for three-dimensional structures. Our results show that the preconditioned superprism-based PC demultiplexers have 2 orders of magnitude smaller size compared to the conventional ones.

Published
2006

146. Analysis of slitless holographic spectrometers implemented by spherical beam volume holograms

Author

Momtahan, Omid, Hsieh, Chao Ray, Adibi, Ali, and Brady, David J.

Subjects
Optical spectrometers -- Design and construction, Fourier transformations -- Analysis, Beam optics -- Research, Astronomy, Physics
Abstract

The analysis of a slitless volume holographic spectrometer is presented in detail. The spectrometer is based on a spherical beam volume hologram followed by a Fourier-transforming lens and a CCD. It is shown that the spectrometer is not sensitive to the incident angle of the input beam for the practical range of applications. A holographic spectrometer based on the conventional implementation is also analyzed, and the results are used to compare the performance of the proposed method with the conventional one. The experimental results are consistent with the theoretical study. It is also shown that the slitless volume holographic spectrometer lumps three elements (the entrance slit, the collimator, and the diffractive element) of the conventional spectrometer into one spherical beam volume hologram. Based on the unique features of the slitless volume holographic spectrometer, we believe it is a good candidate for portable spectroscopy for environmental and biological applications. OCIS codes: 090.7330, 300.6190, 070.2590.

Published
2006

147. Dynamic Hybrid Metasurfaces

Author

Abdollahramezani, Sajjad, primary, Hemmatyar, Omid, additional, Taghinejad, Mohammad, additional, Taghinejad, Hossein, additional, Kiarashinejad, Yashar, additional, Zandehshahvar, Mohammadreza, additional, Fan, Tianren, additional, Deshmukh, Sanchit, additional, Eftekhar, Ali A., additional, Cai, Wenshan, additional, Pop, Eric, additional, El-Sayed, Mostafa A., additional, and Adibi, Ali, additional

Published
2021
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