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Düşük dereceli dönel simetriye sahip iki-boyutlu fotonik kristal yapılarının sağladığı optik fenomenler ve nanofotonik alanındaki uygulamaları/ Utku Görkem Yasa.

By: Yasa, Utku Görkem.
Material type: materialTypeLabelBookPublisher: Ankara : TOBB ETÜ Fen Bilimleri Enstitüsü, 2018Description: xv, 76 pages : charts and colored illustrations ; 29 cm.Content type: text Media type: unmediated Carrier type: volumeContained works: TOBB Ekonomi ve Teknoloji Üniversitesi Fen Bilimleri Enstitüsü.Subject(s): Dissertations, Academic | Tezler, Akademik | Fotonik kristaller | Dönel simetri | Düşük dönel simetri | Polarizasyon ayırıcılar | Sıfır kırıcılık indisi | Anizotropi | Dalga Kılavuzları | Mach-Zehnder interferometreleri | Optik sensörler | Mod dönüştürücüler | Photonic crystals | Rotational symmetry | Low rotational symmetry | Polarization beam splitters | Zero-refractive-index, Anisotropy | Waveguides, Mach- Zehnder interferometers | Optical sensors, Mode convertersOnline resources: Ulusal Tez Merkezi Dissertation note: Tez (Yüksek Lisans)--TOBB ETÜ Fen Bilimleri Enstitüsü Mart 2018 Summary: Most of the two-dimensional photonic crystals that are studied in the literature are based on the high rotational symmetric unit cells consisting of circular dielectric rods or circular air-holes. Inclusion of additional dielectric elements or modifying the shapes of existing circular elements gives rise to a reduction on the rotational symmetry order of two-dimensional photonic crystals unit cells. Low rotational symmetric unit cells involve structural variety and pave the way for extraordinary optical properties. In this thesis, novel optical phenomena and photonic device designs, which are achieved by utilizing various dispersion properties of low rotational symmetric unit cells, were presented. The proposed concepts were investigated in both frequency and time domains by exploiting plane wave expansion and finite-difference timedomain methods, respectively. One of the studies is about the polarization beam splitters that use polarizationsensitive self-collimation phenomenon of photonic crystals consisting of C2 symmetric air holes. The proposed polarization beam splitters were investigated with vii different unit cell configurations. In addition, presented devices are novel and have high polarization extinction ratios. The device, which has maximum polarization extinction ratios of 26 dB (TE) and 22 dB (TM) at = 1550 nm. Operational bandwidth of the device was measured to be 59 nm. Another study is about the numerical and experimental analyses of anisotropic zerorefractive- index materials that were achieved by performing a rotational symmetry reduction on the unit cells of photonic crystals exhibiting Dirac-like cone dispersion. Accidental degeneracy of two Bloch modes in the Brillouin zone center of C2 symmetric photonic crystals gives rise to the semi-Dirac cone dispersion. The proposed photonic crystals expose impedance-matched zero-refractive-index feature ( eff 0, eff 0) for one propagation direction and impedance-unmatched zerorefractive- index behavior ( eff 0, eff effective medium approach was utilized to verify proposed material s properties. The advantages of photonic crystals exhibiting semi-Dirac cone dispersion over periodic structures showing Dirac-like cone dispersion were stated in both frequency and time domains for photonic applications. By using anisotropic behavior of the proposed photonic crystals, photonic designs such as beam deflectors, beam splitters, and focusing lenses were proposed. In the last study, controlling the guided modes of waveguides, which consist of C1 symmetric unit cells, were investigated depending on the unit cell rotation. By controlling the geometrical properties of C1 symmetric unit cells lying along the airdefect, adjustable phase properties of guided electromagnetic waves were achieved. Using this property, Mach-Zehnder interferometers based photonic applications such as wavelength-selective transmission, gas sensing, and mode converters were investigated in frequency and time domains.
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Item type Current location Collection Call number Copy number Status Date due Barcode
Thesis Thesis Merkez Kütüphane
Tez Koleksiyonu / Thesis Collection
Tezler TEZ TOBB MUH ELE YL’18 YAS (Browse shelf) 1 Ödünç Verilemez-Tez / Not For Loan-Thesis TZ00850

Tez (Yüksek Lisans)--TOBB ETÜ Fen Bilimleri Enstitüsü Mart 2018

Most of the two-dimensional photonic crystals that are studied in the literature are
based on the high rotational symmetric unit cells consisting of circular dielectric rods
or circular air-holes. Inclusion of additional dielectric elements or modifying the
shapes of existing circular elements gives rise to a reduction on the rotational
symmetry order of two-dimensional photonic crystals unit cells. Low rotational
symmetric unit cells involve structural variety and pave the way for extraordinary
optical properties.
In this thesis, novel optical phenomena and photonic device designs, which are
achieved by utilizing various dispersion properties of low rotational symmetric unit
cells, were presented. The proposed concepts were investigated in both frequency
and time domains by exploiting plane wave expansion and finite-difference timedomain
methods, respectively.
One of the studies is about the polarization beam splitters that use polarizationsensitive
self-collimation phenomenon of photonic crystals consisting of C2
symmetric air holes. The proposed polarization beam splitters were investigated with
vii
different unit cell configurations. In addition, presented devices are novel and have
high polarization extinction ratios. The device, which
has maximum polarization extinction ratios of 26 dB (TE) and 22 dB (TM) at =
1550 nm. Operational bandwidth of the device was measured to be 59 nm.
Another study is about the numerical and experimental analyses of anisotropic zerorefractive-
index materials that were achieved by performing a rotational symmetry
reduction on the unit cells of photonic crystals exhibiting Dirac-like cone dispersion.
Accidental degeneracy of two Bloch modes in the Brillouin zone center of C2
symmetric photonic crystals gives rise to the semi-Dirac cone dispersion. The
proposed photonic crystals expose impedance-matched zero-refractive-index feature
( eff 0, eff 0) for one propagation direction and impedance-unmatched zerorefractive-
index behavior ( eff 0, eff
effective medium approach was utilized to verify proposed material s properties. The
advantages of photonic crystals exhibiting semi-Dirac cone dispersion over periodic
structures showing Dirac-like cone dispersion were stated in both frequency and time
domains for photonic applications. By using anisotropic behavior of the proposed
photonic crystals, photonic designs such as beam deflectors, beam splitters, and
focusing lenses were proposed.
In the last study, controlling the guided modes of waveguides, which consist of C1
symmetric unit cells, were investigated depending on the unit cell rotation. By
controlling the geometrical properties of C1 symmetric unit cells lying along the airdefect,
adjustable phase properties of guided electromagnetic waves were achieved.
Using this property, Mach-Zehnder interferometers based photonic applications such
as wavelength-selective transmission, gas sensing, and mode converters were
investigated in frequency and time domains.

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