Browsing by Subject "Photonics"

Now showing 1 - 20 of 42

Open Access
2D material liquid crystals for optoelectronics and photonics
(Royal Society of Chemistry, 2017) Hogan, Ben T.; Kovalska, Evgeniya; Craciun, Monica F.; Baldycheva, Anna
The merging of the materials science paradigms of liquid crystals and 2D materials promises superb new opportunities for the advancement of the fields of optoelectronics and photonics. In this review, we summarise the development of 2D material liquid crystals by two different methods: dispersion of 2D materials in a liquid crystalline host and the liquid crystal phase arising from dispersions of 2D material flakes in organic solvents. The properties of liquid crystal phases that make them attractive for optoelectronics and photonics applications are discussed. The processing of 2D materials to allow for the development of 2D material liquid crystals is also considered. An emphasis is placed on the applications of such materials; from the development of films, fibers and membranes to display applications, optoelectronic devices and quality control of synthetic processes. © 2017 The Royal Society of Chemistry.
Open Access
Active Nanophotonics
(IEEE, 2020) Alu, A.; Demir, Hilmi Volkan; Jagadish, c
Being able to manipulate and control light flows at small scales holds the promise to open groundbreaking opportunities for a variety of technologies. Consider, for instance, the challenges currently faced in the world of computing: as data rates and processing demands increase worldwide at an exponential rate, we are facing unsustainable increases in energy consumption associated with data centers and streaming providers. To address these challenges, optical computing and communications offer an interesting alternative to electronic-based systems. Using light for these purposes, however, is hindered by the fact that photons are not easily squeezed to volumes beyond the diffraction limit, i.e., below the wavelength scale, which would be required both to enable lowenergy computation at sufficiently high speeds and to match the degree of integration density available in electronic systems. Today, the field of optoelectronics, which combines highdensity electronic devices to process the data and low-energy data transport enabled by light, is growing at a very fast pace.
Open Access
Anisotropic stimulated emission from aligned CdSe/CdS dot-in-rods
(IEEE, 2014-10) Gao, Y.; Ta, V. D.; Zhao, X.; Wang, Y.; Chen, R.; Zhao, Y.; Dang, C.; Sun, X.; Sun, H.; Demir, Hilmi Volkan
Anisotropic optical properties of CdSe/CdS dot-in-rods loaded in a capillary tube are demonstrated, suggesting nanorods' alignment with a microfluidic approach. Polarized emissions from photoluminescence and whispering gallery mode lasing show promising applications for lighting and displays. © 2014 IEEE.
Open Access
Arrays of suspended plasmonic nanodiscs
(IEEE, 2013) Uran, Can; Demir, Hilmi Volkan
We demonstrate lateral arrays of suspended metal nanodiscs, erected in parallel, partially encased in a dielectric-wrap using in-template synthesis with their polarization-dependent properties controlled as a function of disc-gap/-width tailoring their scattering/absorption spectra. © 2013 IEEE.
Open Access
Asymmetric light propagation in chirped photonic crystal waveguides
(Optical Society of American (OSA), 2012) Kurt H.; Yilmaz, D.; Akosman, A.E.; Özbay, Ekmel
We report numerical and experimental investigations of asymmetric light propagation in a newly designed photonic structure that is formed by creating a chirped photonic crystal (PC) waveguide. The use of a non-symmetric distribution of unit cells of PC ensures the obtaining of asymmetric light propagation. Properly designing the spatial modulation of a PC waveguide inherently modifies the band structure. That in turn induces asymmetry for the light's followed path. The investigation of the transmission characteristics of this structure reveals optical diode like transmission behavior. The amount of power collected at the output of the waveguide centerline is different for the forward and backward propagation directions in the designed configuration. The advantageous properties of the proposed approach are the linear optic concept, compact configuration and compatibility with the integrated photonics. These features are expected to hold great potential for implementing practical optical rectifier-type devices. © 2012 Optical Society of America.
Open Access
Broadband one way propagation via dielectric waveguides with unequal effective index
(IEEE, 2014) Öner, B. B.; Üstün, K.; Kurt, H.; Okyay, Ali Kemal; Turhan-Sayan, G.
We present an efficient approach for broad band one way propagation of light by parallel and unequal dielectric waveguides leading different effective phase shifts. Three dimensional numerical simulations show that 30% operating bandwidth is achieved.
Open Access
Buried waveguides written deep inside silicon
(OSA, 2017) Turnalı, Ahmet; Tokel, Onur; Kesim, Denizhan Koray; Makey, Ghaith; Elahi, Parviz; İlday, Fatih Ömer
Summary form only given. Silicon waveguides are widely used as optical interconnects and they are particularly important for Si-photonics. Si-based devices, along with other optical elements, are entirely fabricated on the top surface of Si wafers. However, further integration of photonic and electronic devices in the same chip requires a new approach. One alternative is to utilize the bulk of the wafer for fabricating photonic elements. Recently, we reported a direct-laser-writing method that exploits nonlinear interactions and can generate subsurface modifications inside silicon without damaging the surface. Using this method, we fabricated several functional optical elements including gratings, lenses, and holograms. In this work, we demonstrate optical waveguides entirely embedded in Si.
Open Access
Compact left-handed metamaterial based on double-layer planar metal strip arrays
(Optical Society of America, 2006) Guven, K.; Çalışkan, Deniz; Özbay, Ekmel
The existence of a left-handed transmission peak of a metamaterial consisting of double-layer planar metal strip arrays at 15 GHz is demonstrated. This design is very suitable to submicron scales required at communication wavelengths. © 2006 Optical Society of America.
Open Access
Design of all-silicon photonic and plasmonic perfect absorbers and their applications
(2016-06) Gök, Abdullah
Majority of the optoelectronic devices works either in infrared regime or in visible spectrum. Among these, perfect absorbers attracted great attention due to their high applicability in solar cells and high performance photodetectors as well as special applications such as surface enhanced sensing. However, high material costs and elaborate nano-fabrication procedures to build perfect absorbers are prohibitive issues that researchers or processors have to deal with. In this work, all-Silicon (Si) practical low-cost photonic and plasmonic perfect absorbers are investigated by theoretical modeling and the designed devices are fabricated by utilizing standard CMOS technology. In order to model the optical response of Si, the effect of charge carrier mobility on the dielectric is analyzed. We showed that high performance devices that can perform better than the state of the art are possible without requiring high cost materials and elaborate fabrication techniques. Photonic perfect absorbers that have promising band properties in infrared are designed and fabricated. Experimental results support theoretical predictions. We used computational approach to investigate the effect of temperature.
Open Access
Electrically controlled resistive switching assisted active ultra-broadband optical tunability in the infrared
(IEEE, 2013) Battal, Enes; Özcan, Ayşe; Okyay, Ali Kemal
We present an electrically tunable optical device with ultra-broadband tunability operating in 2-10 μm spectrum. We also, for the first time, optically observe resistive switching behavior in reflection measurements under electrical bias. © 2013 IEEE.
Open Access
Electro-optic modulation of InAs quantum dot waveguides
(Technische Universiteit Eindhoven, 2008) Akça, İmran. B.; Dâna, Aykutlu; Aydınlı, Atilla; Rossetti, M.; Li, L.; Fiore, A.; Dağlı, N.
The linear electro-optic properties in waveguides containing self-organized In As quantum dots were studied experimentally. Fabry-Perot measurements at 1515 nm on InAs/GaAs quantum dot structures yield a significantly enhanced linear electro-optic efficiency compared to bulk GaAs.
Open Access
Elimination of catastrophic optical mirror damage in high-power laser diodes using multi-section waveguides
(2022-08) Ebadi, Kaveh
One of the solid constraints of high-power laser diodes (LDs) has been catas-trophic optical mirror damage (COMD), restricting the operating power level and lifetime of commercial high-power laser diodes (LDs). The output facet of LD reaches a critical temperature leading to COMD, a permanent device fail-ure. Here, we fabricate multi-section LDs by tailoring the waveguide structure along the cavity that distances the output facet from the heat-generating lasing region. This method splits the LD waveguide into electrically isolated laser and window sections along the cavity. The laser section is operated at a high current to achieve high output power, and the window is biased at a low current with minor heat generation. This technique limits the thermal impact of the laser sec-tion on the facet, and the window section enables lossless transport of the laser to the output facet. First, we compared standard broad area laser diode with multi-section waveguide LDs up to the maximum achievable power. While tradi-tional single-section LDs show COMD failures, the multi-section waveguide LDs are COMD-free. Next, we implemented our method on narrow waveguide laser diodes and array lasers with different widths and confirmed the cooling effect on the fabricated LD facet. Therefore, our novel technique and results show that the multi-section waveguide method provides substantial reliability improvement for various LD types, such as broad-area, narrow waveguide, and array/bars.
Open Access
Enhancement and inhibition of photoluminescence in hydrogenated amorphous silicon nitride microcavities
(Optical Society of America, 1997-09-01) Serpenguzel, A.; Aydınlı, Atilla; Bek, A.
A Fabry-Perot microcavity is used for the enhancement and inhibition of photoluminescence in hydrogenated amorphous silicon nitride. The amplitude of the photoluminescence is enhanced 4 times, while its linewidth is reduced 8 times with respect to the bulk hydrogenated amorphous silicon nitride. The transmittance, reflectance, and absorptance spectra of the microcavity were also measured and calculated. The calculated spectra agree well with the experimental ones. (C) 1997 Optical Society of America
Open Access
Förster-type nonradiative energy transfer for assemblies of arrayed nanostructures: confinement dimension vs stacking dimension
(American Chemical Society, 2014-02-11) Hernandez-Martinez, P. L.; Govorov, A. O.; Demir, Hilmi Volkan
Forster-type nonradiative energy transfer (NRET) provides us with the ability to transfer excitation energy between proximal nanostructures with high efficiency under certain conditions. Nevertheless, the well-known Forster theory was developed for the case of a single donor (e.g., a molecule, a dye) together with single acceptor. There is no complete understanding for the cases when the donors and the acceptors are assembled in nanostructure arrays, though there are special cases previously studied. Thus, a comprehensive theory that models Forster-type NRET for assembled nanostructure arrays is required. Here, we report a theoretical framework of generalized theory for the Forster-type NRET with mixed dimensionality in arrays. These include combinations of arrayed nanostructures made of nanoparticles (NPs) and nanowires (NWs) assemblies in one-dimension (1D), two-dimension (2D), and three-dimension (3D) completing the framework for the transfer rates in all possible combinations of different confinement geometries and assembly architectures, we obtain a unified picture of NRET in assembled nanostructures arrays. We find that the generic NRET distance dependence is modified by arraying the nanostructures. For an acceptor NP the rate distance dependence changes from gamma alpha d(-6) to gamma alpha d(-5) when they are arranged in a ID stack, and to gamma alpha d(-4) when in a 2D array, and to gamma alpha d(-3) when in a 3D array. Likewise, an acceptor NW changes its distance dependence from gamma alpha d(-5) to gamma alpha d(-4) when they are arranged in a 1D array and to gamma alpha d(-3) when in a 2D array. These finding shows that the numbers of dimensions across which nanostructures are stacked is equally critical as the confinement dimension of the nanostructure in determining the NRET kinetics.
Open Access
High-quality InP/ZnS nanocrystals with high photometric performance and their application to white quantum dot light-emitting diodes
(IEEE, 2012) Yang, X.; Tan, S. T.; Demir, Hilmi Volkan; Sun, X. W.
Full visible range covering InP/ZnS core-shell nanocrystals with high photometric performance have been prepared. Making use of these nanocrystals, we demonstrate a white quantum dot LED with a high color rendering index of 91. © 2012 IEEE.
Open Access
Highly flexible, full-color, top-emitting quantum dot light-emitting diode tapes
(IEEE, 2013) Yang X.; Mutlugün, Evren; Gao, Y.; Zhao, Y.; Tan, S.T.; Sun X.W.; Demir, Hilmi Volkan
We report flexible tapes of high-performance, top-emitting, quantum dot based, light-emitting diodes (QLEDs) with multicolor emission, actively working even when flexed. The resulting QLED tapes reach a high peak luminance level of 19,265 cd/m2. © 2013 IEEE.
Open Access
In-chip microstructures and photonic devices fabricated by nonlinear laser lithography deep inside silicon
(Nature Publishing Group, 2017) Tokel, O.; Turnalı, A.; Makey, G.; Elahi, P.; Çolakoǧlu, T.; Ergeçen E.; Yavuz, Ö.; Hübner R.; Borra, M. Z.; Pavlov, I.; Bek, A.; Turan, R.; Kesim, D. K.; Tozburun, S.; Ilday, S.; Ilday, F. Ö.
Silicon is an excellent material for microelectronics and integrated photonics 1-3, with untapped potential for mid-infrared optics 4 . Despite broad recognition of the importance of the third dimension 5,6, current lithography methods do not allow the fabrication of photonic devices and functional microelements directly inside silicon chips. Even relatively simple curved geometries cannot be realized with techniques like reactive ion etching. Embedded optical elements 7, electronic devices and better electronic-photonic integration are lacking 8 . Here, we demonstrate laser-based fabrication of complex 3D structures deep inside silicon using 1-μm-sized dots and rod-like structures of adjustable length as basic building blocks. The laser-modified Si has an optical index different to that in unmodified parts, enabling the creation of numerous photonic devices. Optionally, these parts can be chemically etched to produce desired 3D shapes. We exemplify a plethora of subsurface - that is, 'in-chip' - microstructures for microfluidic cooling of chips, vias, micro-electro-mechanical systems, photovoltaic applications and photonic devices that match or surpass corresponding state-of-the-art device performances.
Open Access
Large-area (> 50 cm × 50 cm), freestanding, flexible, optical membranes of Cd-free nanocrystal quantum dots
(IEEE, 2012) Mutlugün, Evren; Hernandez Martinez, Pedro L.; Eroğlu, Cüneyt; Coşkun, Yasemin; Erdem, Talha; Sharma, Vijay K.; Ünal, Emre; Panda, S. K.; Hickey, S. G.; Gaponik, N.; Eychmuller, A.; Demir, Hilmi Volkan
Colloidal semiconductor quantum dots (QDs) have been extensively explored for numerous applications ranging from optoelectronics to biotechnology. This strong demand for the colloidal QDs arises because of their favorable optical and electronic properties. From the application points of view, QDs typically need to be used in their solid form, as opposed to their as-synthesized dispersion form. For immobilization of QDs and homogeneity of their films, various polymers have been used to host QDs within solid media. However, the integration of QDs into a polymeric medium is commonly complex, which requires a high level of understanding to provide optical quality. © 2012 IEEE.
Open Access
Large-area semi-transparent light-sensitive nanocrystal skins
(IEEE, 2012) Akhavan, Shahab; Güzeltürk, Burak; Sharma, Vijay Kumar; Demir, Hilmi Volkan
Large area and semi-transparent highly light sensitive nanocrystal skin is demonstrated via spray-coating nanocrystals on top of polyelectrolyte-polymers based on photogenerated potential buildup where no external bias is applied. © 2012 IEEE.
Open Access
Low-cost, large-scale, ordered ZnO nanopillar arrays for light extraction efficiency enhancement in quantum dot light-emitting diodes
(IEEE, 2014) Yang, X.; Dev, K.; Wang, J.; Mutlugün, E.; Dang, C.; Zhao, Y.; Tan, S. T.; Sun, X. W.; Demir, Hilmi Volkan
We report a QLED with enhanced light outcoupling efficiency by applying a layer of periodic ZnO nanopillar arrays. The resulting QLED reaches the record external quantum efficiency (EQE) of 9.34% in green-emitting QLEDs with a similar device structure.