118 research outputs found
Nonlinear dynamics induced by parallel and orthogonal optical injection in 1550 nm Vertical-Cavity Surface-Emitting Lasers (VCSELs)
We report a first experimental study of the nonlinear dynamics appearing in a 1550 nm single-mode VCSEL subject to parallel and to orthogonal optical injection. For the first time to our knowledge we report experimentally measured stability maps identifying the boundaries between regions of different nonlinear dynamics for both cases of polarized injection. A rich variety of nonlinear behaviours, including periodic (limit cycle, period doubling) and chaotic dynamics have been experimentally observed. ©2010 Optical Society of America
Chiral metamaterial and high-contrast grating based polarization selective devices
Ankara : The Department of Electrical and Electronics Engineering and the Graduate School of Engineering and Science of Bilkent Univ., 2013.Thesis (Master's) -- Bilkent University, 2013.Includes bibliographical references leaves 159-173.The utilization of purposely designed artificial media with engineered electromagnetic
responses enables the obtaining of intriguing features that are either
impossible or difficult to realize using readily available natural materials. Here,
we focus on two classes of artificial media: metamaterials and high-contrast gratings.
Metamaterials and high-contrast gratings are designed within the subwavelength
periodicity range and therefore, they are non-diffractive. We exploit the
magnetoelectric coupling effect in chiral metamaterials to design several structures.
Firstly, we design a linear to circular polarization convertor that operates
for x-polarized normally incident plane waves. Then, we combine the chirality
feature and the electromagnetic tunneling phenomenon to design a polarization
insensitive 90◦ polarization rotator that exhibits unity transmission and crosspolarization
conversion efficiencies. Subsequently, we combine this polarization
rotator with a symmetric metallic grating with a subwavelength slit for the purpose
of enabling the one-way excitation of spoof surface plasmons and achieving
a reversible diodelike beaming regime. Then, we exploit the asymmetric transmission
property of chiral metamaterials and show that a polarization angle dependent
polarization rotation and a strongly asymmetric diodelike transmission
is realizable. Afterwards, a brief waveguide theory is provided and eventually,
the dispersion relations for a periodic dielectric waveguide geometry are derived.
Then, using these relations and considering the finiteness of the waveguide length,
we show the theoretical description of high-contrast gratings. Finally, we theoretically
and experimentally show that the achievement of a broadband quarter-wave
plate regime is possible by using carefully designed high-contrast gratings.Mutlu, MehmetM.S
High-extinction-ratio TE/TM selective Bragg grating filters on silicon-on-insulator
We report on the design and fabrication of TE and TM polarization selective Bragg grating filters in the form of sinusoidal perturbations on the waveguide sidewall and etched holes on the top of the waveguide, respectively. Combining the two geometries on a silicon-on-insulator waveguide resulted in Bragg grating filters with high extinction ratios of approximately 60 dB
High-extinction-ratio TE/TM selective Bragg grating filters on silicon-on-insulator
We report on the design and fabrication of TE and TM polarization selective Bragg grating filters in the form of sinusoidal perturbations on the waveguide sidewall and etched holes on the top of the waveguide, respectively. Combining the two geometries on a silicon-on-insulator waveguide resulted in Bragg grating filters with high extinction ratios of approximately 60 dB
A compact all-silicon temperature insensitive filter for WDM and bio-sensing applications
We propose a compact, temperature-insensitive, and all-silicon Mach-Zehnder interferometer filter that uses the polarization-rotating asymmetrical directional couplers. Temperature sensitivity of the filter is <8 pm/K for a wavelength range of 30 nm. The device achieves a reduced footprint by making use of different polarizations, which is made possible by the asymmetric directional couplers that act both as a splitter/combiner and as a polarization rotator. Simulation of the device shows that it can also be useful for gas sensing and bio-sensing applications with three times larger response to cladding changes while keeping a thermally robust behavior
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