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12 results on '"Akca, Imran B."'

4. On-chip Mach-Zehnder interferometer for OCT systems

Author

Van Leeuwen, Ton G., Akca, Imran B., Angelou, Nikolaos, Weiss, Nicolas, Hoekman, Marcel, Leinse, Arne, Heideman, Rene G., Van Leeuwen, Ton G., Akca, Imran B., Angelou, Nikolaos, Weiss, Nicolas, Hoekman, Marcel, Leinse, Arne, and Heideman, Rene G.

Published
2018
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6. Numerical model of optical coherence tomographic vibrography imaging to estimate corneal biomechanical properties

Author

Kling, Sabine, Akca, Imran B., Chang, Ernest W., Scarcelli, G., Bekesi, Nandor, Yun, S.- H., Marcos, Susana, Kling, Sabine, Akca, Imran B., Chang, Ernest W., Scarcelli, G., Bekesi, Nandor, Yun, S.- H., and Marcos, Susana

Abstract

Most techniques measuring corneal biomechanics in vivo are biased by side factors. We demonstrate the ability of optical coherence tomographic (OCT) vibrography to determine corneal material parameters, while reducing current prevalent restrictions of other techniques (such as intraocular pressure (IOP) and thickness dependency). Modal analysis was performed in a finite-element (FE) model to study the oscillation response in isolated thin corneal flaps/eye globes and to analyse the dependency of the frequency response function on: corneal elasticity, viscoelasticity, geometry (thickness and curvature), IOP and density. The model was verified experimentally in flaps from three bovine corneas and in two enucleated porcine eyes using sound excitation (100¿110 dB) together with a phase-sensitive OCT to measure the frequency response function (range 50¿510 Hz). Simulations showed that corneal vibration in flaps is sensitive to both, geometrical and biomechanical parameters, whereas in whole globes it is primarily sensitive to corneal biomechanical parameters only. Calculations based on the natural frequency shift revealed that flaps of the posterior cornea were 0.8 times less stiff than flaps from the anterior cornea and cross-linked corneas were 1.6 times stiffer than virgin corneas. Sensitivity analysis showed that natural vibration frequencies of whole globes were nearly independent from corneal thickness and IOP within the physiological range. OCT vibrography is a promising non-invasive technique to measure corneal elasticity without biases from corneal thickness and IOP

Published
2014

12. Electro-optic and electro-absorption characterization of InAs quantum dot waveguides

Author

Imran Akca, Marco Rossetti, Aykutlu Dana, Lianhe Li, Atilla Aydinli, Nadir Dagli, Andrea Fiore, Akca, İmran B., Dana, Aykutlu, Aydınlı, Atilla, Photonics and Semiconductor Nanophysics, and Semiconductor Nanophotonics

Subjects
electron, Optics and Photonics, Coefficients, Light, Fabry-Perot measurements, Physics::Optics, 02 engineering and technology, Electron, 01 natural sciences, Indium, Arsenicals, chemistry.chemical_compound, 020210 optoelectronics & photonics, equipment design, 0202 electrical engineering, electronic engineering, information engineering, Semiconductor quantum dots, Scattering, Radiation, Absorption (electromagnetic radiation), instrumentation, electronics, article, quantum dot, Gallium alloys, Equipment Design, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Atomic and Molecular Physics, and Optics, Band, organoarsenic derivative, Quantum dot laser, radiation scattering, Optoelectronics, equipment, Molecular beam epitaxy, Electric fields, Electrons, indium, indium arsenide, chemistry, 010309 optics, Condensed Matter::Materials Science, Optics, Electric field, 0103 physical sciences, Quantum Dots, Electroabsorption modulators, Electrooptical devices, Well Structures, Indium alloys, business.industry, InAs quantum dot waveguides, Well structures, Equipment Failure Analysis, Semiconductor, Quantum dot, Indium arsenide, Electronics, business, Waveguides
Abstract

Optical properties of multilayer InAs quantum dot waveguides, grown by molecular beam epitaxy, have been studied under applied electric field. Fabry-Perot measurements at 1515 nm on InAs/GaAs quantum dot structures yield a significantly enhanced linear electro-optic efficiency compared to bulk GaAs. Electro-absorption measurements at 1300 nm showed increased absorption with applied field accompanied with red shift of the spectra. Spectral shifts of up to 21% under 18 Volt bias was observed at 1320 nm. (C) 2008 Optical Society of America.

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