Master Tezleri

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Antiproliferative and anticancerogenic effects of 5-ASA and its novel synthesized oligomer
(Izmir Institute of Technology, 2017-07) Atahanova, Hurshida; Şanlı Mohamed, Gülşah
In the world, colorectal cancer (CRC) is third common malignant diseases and fourth leading cause of cancer-related death. More recently, epidemiological studies have suggested that regular intake of 5-aminosalicylic acid (5-ASA), the drug used in treatment of inflammatory bowel disease (IBD), reduces the risk of CRC developing in patients with ulcerative colitis. Several action mechanisms of 5-ASA are proposed which are independent from its weak cyclooxygenase (COX) inhibitory property, found overexpressed in many cancer types. Lately, polymeric prodrugs developed which contain bioactive unit and have prolonged activity by sustained release, consequently reduced toxicity. However, large molecular weight and long chain can be challenging in penetrating into the cell membrane. Thus, oligomers with shorter chain of monomer units and lower molecular weight can be preferred choice. In the present study we evaluated antiprolifertaive and anticancerogenic effect of novel synthesized 5-ASA based oligomer compared to its active monomer, 5-ASA in Caco-2, DLD-1, HeLa and CCD-18Co cells. According to MTT, apoptotic rate, cell cycle phase distribution and scratch assay analysis the oligomer showed higher activity compared to its monomer, 5- ASA at lower doses. The oligomer induced cell death and cell cycle arrest in colorectal cancer cells and in HeLa cells. However, no significant induced cell death and cell cycle arrest observed in normal human colon cells, CCD-18Co when exposed to 5-ASA and the oligomer. Overall results indicate that the oligomer can be promising candidate for prodrugs in treatment and prevention of colorectal cancer.
Chemometric studies for classification of olive oils and detection of adulteration
(Izmir Institute of Technology, 2008) Gürdeniz, Gözde; Özen, Banu
The aim of this study is to classify extra-virgin olive oils according to variety, geographical origin and harvest year and also to detect and quantify olive oil adulteration. In order to classify extra virgin olive oils, principal component analysis was applied on both fatty acid composition and middle infrared spectra. Spectral data was manipulated with a wavelet function prior to principal component analysis. Results revealed more successful classification of oils according geographical origin and variety using fatty acid composition than spectral data. However, each method has quite good ability to differentiate olive oil samples with respect to harvest year.Middle infrared spectra of all olive oil samples were related with fatty acid profile and free fatty acidity using partial least square analysis. Orthogonal signal correction and wavelet compression were applied before partial least square analysis.Correlation coefficient and relative error of prediction for oleic acid (highest amount fatty acid) were determined as 0.93 and 1.38, respectively. Also, partial least square regression resulted in 0.85 as R2 value and 0.085 as standard error of prediction value for free fatty acidity quantification.In adulteration part, spectral data manipulated with principal component and partial least square analysis, to distinguish adulterated and pure olive oil samples, and to quantify level of adulteration, respectively. The detection limit of monovarietal adulteration varied between 5 and 10% and R2 value of partial least square was determined as higher than 0.95. Hazelnut, corn-sunflower binary mixture, cottonseed and rapeseed oils can be detected in olive oil at levels higher than 10%, 5%, 5% and 5%, respectively.
A comparative study on the photocatalytic activity of dye-sensitized and non-sensitized graphene oxide-TİO2 composites under simulated and direct sunlight
(01. Izmir Institute of Technology, 2019-12) İlhan, Hatice; Demir, Mustafa; Varlıklı, Canan; Demir, Mustafa Muammer; 01. Izmir Institute of Technology
Amine modified graphene oxide (mGO) and TiO2 composite was synthesized by low temperature hydrothermal method. Characterization of the synthesized material was carried out by using X-ray diffraction, X-ray photoelectron spectroscopy, and BET analysis techniques. The films of mGO:TiO2 and formerly synthesized TiO2, N-TiO2, GO-TiO2 and GO:N-TiO2 were fabricated by doctor blade method and employed as photocatalysts for the photodegradation of Rhodamine-B (RhB) dye under simulated (Xe lamb) and direct sun-light. P25 was also used as reference photocatalyst for all of the synthesized ones. Photodegradation of RhB was monitored by UV-Vis spectroscopy. Among all the catalysts, GO:N-TiO2, the composite of GO and N-doped TiO2, presented the best photocatalytic activity and although the activity of mGO:TiO2 was better than the activities of P25 and TiO2, it presented lower degradation rate constant even than that of the N-TiO2. It is proposed that increased abundance of C-C bonds and decreased number of oxygenated functional groups on mGO:TiO2, in addition to the morphological difference between GO (sheet like) and mGO (dot like) has great influence on their photocatalytic activities. Among the GO containing photocatalysts including mGO:TiO2, specific surface area (SSA) and number of RhB molecules per film volume were the lowest and particle size was the highest for mGO:TiO2. Although the number of RhB molecules per film volume was higher in mGO:TiO2 than that of the N-TiO2, it is thought that approximately 2 folds higher SSA of N-TiO2 allowed better photocatalytic performance. Additionally, the films were sensitized with PTE dye to obtain effective catalysts in visible region and reusability of the films were also tested. Degradation rate constants of all fabricated films have increased under both of the irradiation media and no significant change in rate constants were detected after the reusability tests.
Design and fabrication of a wearable, flexible pulse oximeter
(01. Izmir Institute of Technology, 2020-12) Aydın, Ahmed; Tekin, Hüseyin Cumhur; 01. Izmir Institute of Technology
Oxygen is vital for the healthy functioning of tissues and organs. For this reason, it is indispensable to monitor the oxygen saturation of the human body during daily activities in order to improve the quality of life, in the detection and tracking of respiratory diseases. Pulse Oximeter is an electro-optic device that non-invasively measures peripheral oxygen saturation and provides information about how well oxygen diffuses the tissues. Conventional devices are not suitable for daily use due to their bulky structure and designs that restrict movement. With this thesis, the design and production of a flexible reflectance type Pulse Oximeter device that is conformally adapt to measurement suite, can be used all day long and is intended for continuous measurement has been realized.
Design of the kiosk for more effective utilization in hospital queues
(Izmir Institute of Technology, 2019-10) Bilen, Eren; Başoğlu, Ahmet Nuri
Nowadays, various queuing systems are applied in many medical institutions. These systems aim to perform consumer operations in a specific order and to prevent long waiting times. This study focusses explicitly on the queuing system that is present in the Blood Collection Unit of İzmir Tepecik Training and Research Hospital. It was stated that the touch screen kiosk called Phlerobo used in this system could not be used effectively and therefore service failures occurred. It is aimed to examine and redesign the kiosk interface and body design in order to use this system more efficiently. This study started with literature studies that will direct the new model to comprehend the importance of the system. Then, experimental methods such as field observation and interview studies were carried out. As a result of the recommendations developed to solve the problems of the current system, design suggestions were made, and these designs were visualized. Then the designs were tested to determine the appropriate design. For this purpose, the designs were presented to the user via survey and a special web application. Interface and body design were developed by determining the appropriate design with the data obtained from the tests. Thus, the redesigned kiosk was predicted to be used more effectively. It was determined that the design of the data obtained will be used more efficiently than the previous one.
Dimension dependent optoelectronic properties of cesium lead halide perovskites
(Izmir Institute of Technology, 2019-06) Özcan, Mehmet; Şahin, Hasan; Balcı, Sinan
All-inorganic cesium lead halide perovskites (ILHPs), are gaining wide variety of role as strong contenders due to their extraordinary photovoltaic features in optoelectronic research with tunable band-gap, large absorption cross-section, long carrier lifetime, and high carrier mobility. Most of the initial studies focused on bulk-like perovskite materials, while the rapidly growing colloidal perovskite nanocrystals impress additional interest because of their unique properties. In this thesis, colloidal lead halide perovskite nanocrystals’ optoelectronic properties are investigated and associated with their size and dimensionality. The photoluminescence characteristics of colloidal lead halide perovskite nanocrystals can be tuned by reducing their dimensionality. Thin layer fabrication of CsPbBr3 films which consist of 2D lead halide perovskite nanoplatelets, is achived by a novel coating approach via electrospraying from precursor solution. Electrospraying method represents not only a new and fast perovskite film fabrication but also dimensional tunability by changing the amount of oleylamine which is intercalating agent. Moreover, thicknessdependence of the structural, electronic and vibrational properties of orthorhombic CsPbI3, which is one of the most stable phase at room temperature, is investigated by means of state-of-the-art first-principles calculations. It is also investigated that the electronic band gap increases with decrease in perovskite thickness due to quantum size effect. Lastly, it is investigated that water induced transition to form large bundles of CsPbBr3 nanowires show a a redshifted photoluminescence. Water molecule causes the detachment of ligands from the perovskite surface which leads to form bundles. In summary, this thesis provides an understanding of dimension dependent optoelectronic properties of lead halide perovskite.
Emission characteristics of a solution processed, single layer white organic light emitting diode
(01. Izmir Institute of Technology, 2020-12) Bozkuş, Volkan; Varlıklı, Canan; Gültekin, Burak; 01. Izmir Institute of Technology
White organic light emitting diodes (WOLEDs) are getting more attention day by day because of their some superior properties like viewing angle, refresh rate, flexibility, easy production process and consequently relatively cost-effective natures. Within the scope of this thesis, WOLED has been prepared and characterized by using the single emitter layer prepared by solution process method. In the emission layer, the host material is used for both obtaining the blue region of the visible spectrum and for efficient energy transfer to the green and orange-red guest material. Poly(N-vinylcarbazole) (PVK): 2-(4-Biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) or 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl] phenylene (OXD-7) matrices are used as host for orange-red emitting material of N,N'-bis(2-ethylhexyl)perylene-3,4,9,10-dicarboxylic diimide (PDI) and green emitting material of perylene-3,4,9,10-tetracarboxy tetrabutylester (PTE). Electron and hole mobility, L-V-J characteristics and morphologies of two different host matrix of PVK:PBD and PVK:OXD-7 were examined. As a result of these evaluations, the appropriate host was determined as PVK:PBD. Host:PTE and Host:PDI emission characteristics were examined and exciplex, electroplex formations were detected. After, Host:PTE:PDI configuration were discussed and high white light properties of optimized WOLED are displayed CIE 1931 coordinates (x, y) of (0.34, 0.36), correlated colour temperature of 4916 K and CRI of 96. Finally, lethal time 70 of the latest devices was examined.
Experiment station to observe the solar charge station behaviour for a year period
(Izmir Institute of Technology, 2003) Tatar, Farah; Atagündüz, Gürbüz
The main purpose of this project is to set-up an experiment station, which will investigate the behavior of a portable "Solar Charge Station" that charges electric or hybrid vehicles, which work at the city centers.The solar charge station is constructed on Classrooms Building in Engineering Faculty of Izmir Institute of Technology. Sixteen monocrystalline silicon photovoltaic modules having the dimensions of 1.293mx 0.329mx 0.034m and 55W power rating are used as the photovoltaic generator of the solar charge station. Modules are mounted as if they create an .Omega Shape. which gives its name to the station (Omega Type Solar Charge Station). Vertical and tilted reflectors are used to enhance the electricity generation. Generated electricity is used to charge a lead acid battery, which is protected by five solar charge regulators in order to prevent discharging and overcharging. 50 W halogen lamps working with direct current are chosen as the loads. The system is analyzed both theoretically and experimentally. Theoretical results have shown that Omega Type Solar Charge Station generates more or less steady electricity, approximately 240 MJ through a year period. The reflectors operate better in winter than in summer, theoretically. According to the stations shape, it uses less space on rooftops. Experiments have shown that efficiency of the charge station during summer is considerably high. The efficiencies calculated by using direct solar radiation on inclined surface is 31.65315%, for the experiment on 21.08.2003, 27.90379% for the experiment carried out without reflectors on 11.09.2003 and 35.70939% for the experiment carried out with optimum inclination angles for September, on 12.09.2003.Omega shape of the station and the reflectors increase the efficiency more or less 3% in Omega shape of the station and the reflectors increase the efficiency more or less 3% in cost of the station if the energy gain is considered.
Fabrication of mesa structures on superconducting Bi2Sr2CaCu2O8+& single crystals
(Izmir Institute of Technology, 2005) Kurter, Cihan; Özyüzer, Lütfi
There have been tremendous efforts to understand the relatively much more sophisticated mechanism of superconductivity in high temperature superconductors (HTSC). In order to investigate the inherent features and tunneling characteristics just only peculiar to HTSC, micron-sized mesa structures were fabricated on the surfaces of both pristine optimally doped and HgBr2 intercalated Bi2Sr2CaCu2O8+& (Bi-2212) single crystals using photolithography and Argon ion beam etching techniques. The surface topography and heights of the mesas were examined with atomic force microscopy.Hysteretic I-V curves with multiple branches and temperature dependence of tunneling characteristics were investigated by means of a novel technique, point contact tunneling (PCT) and experiments were carried out in a large range of temperatures from 4.2 K to 300 K. The results of SIN single junctions and SIS break junctions obtained by tunneling measurements using PCT technique on bulk crystals were compared withtunneling measurements using PCT technique on bulk crystals were compared with intrinsic Josephson junction quasiparticle spectra generally showing sharp peaks at the gap voltages and no dip/hump structures; which are reconciled with overheating in the mesa. The IJJ measurements performed with HgBr2 intercalated Bi-2212 samples showed far more enhanced characteristics indicating less heating. The zero bias conductance versus temperature plots were examined to scrutinize the existence of pseudogap in electronic excitation spectra of investigated samples. Besides, the normalized gap voltages were plotted against normalized temperature to show the deviation from BCS fit, which displays the novelty of HTSC.
Flexible transparent conducting electrodes based on silver nanowire, graphene, and two-dimensional transition metal dichalgogenide
(01. Izmir Institute of Technology, 2020-12) Tertemiz, Necip Ayhan; Balcı, Sinan; 01. Izmir Institute of Technology
In recent years, transparent conductive electrodes have attracted great interests owing to their critical applications in various optoelectronic devices, such as light emitting diodes, solar cells, liquid crystal displays, optical modulators, and touch screens. In this thesis, graphene-silver nanowires-transition metal dichalcogenide based hybrid transparent and conductive electrodes have been fabricated. In order to reach this goal; (1) single layer graphene on copper foil has been synthesized in large area in a CVD furnace, (2) ultrathin and very long silver nanowires have been synthesized by using wet chemistry methods, (3) MoS2 and WS2 single layer flakes and multilayer thin films have been synthesized in a CVD furnace, (4) electrodes of graphene, silver nanowires, and transition metal dichalcogenides have been fabricated on rigid and flexible substrates.
Graphene-like materials for electronic applications
(01. Izmir Institute of Technology, 2020-12) Başkurt, Mehmet; Şahin, Hasan; Balcı, Sinan; 01. Izmir Institute of Technology
Two-dimensional (2D) materials have gained vast interest in nanotechnology since these materials exhibit extraordinary properties due to electron confinement. Starting with graphene, many other 2D materials with characteristics of metals, semiconductors, insulators, and their magnetic analogues have been studied over the years. Insulators show importance as dielectric layers. Low dimensional metallic materials are used in electrical conduction. Ultra-thin semiconductors have variety of potential applications due to their characteristic band gap. Magnetic analogues of low dimensional materials are used in spintronics, offering high frequency, controllable switching. In addition, defects in these materials alter their physical properties and the concept can be adopted in order to use in different practices. Therefore it is important to study array of such materials and consider the alteration in their lattice theoretically and experimentally. In this thesis, first-principles calculations are used to predict insulating calcium halide single-layers are predicted, determine the effects of strain and V dopant in recently synthesized magnetic semiconducting VI3 single-layers, propose synthesis of magnetic, semiconducting manganese fluorides from manganese dichalcogenides, investigate the affects of defects and simulate scanning tunneling microscopy images in order to compare with experimental results, and finally to determine rather the detection of volatile organic compounds (VOC) such as methanol and ethanol by graphene-based sensors is feasible or not. Experiments are carried out to construct and further investigate the mechanism of VOC detection and working, highly sensitive alcohol sensors.
Identification of single-layer crystalline structures through their electronic and optical properties
(01. Izmir Institute of Technology, 2021-07) Sözen, Yiğit; Şahin, Hasan; Balcı, Sinan; 01. Izmir Institute of Technology
A large number of two-dimensional (2D) van der Waals type materials have become a focus of interest in many scientific fields, ever since the thinnest carbon compound, graphene, takes to the stage with its exceptional electronic properties. The outstanding electronic behavior resulting from quantum size effects requires an investigation of the electronic and optical features of materials at the atomic scale. The understanding of such properties of matter within the framework of the theoretical approaches is the first step to shed light on the discovery of electronic and optoelectronic devices including brand new features. This thesis discusses the identification of electronic and optical properties of several types of atomically thin crystals, consisting of 2D and lead-free perovskite structures, by means of density functional theory (DFT). In the first study, primarily, the strong interaction mechanism between Ge atom and single-layer GaAs was studied starting from single atom adsorption to detached germanene layer formation. Following that dynamically stable metallic structures of Janus and alloy type GaGeAs crystals are discovered by performing one-sided and alternated decoration of GaAs single-layer with Ge atoms, respectively. %The Raman spectroscopy is found to be applicable for phase detection as the theoretically calculated Raman spectra of each polytype exhibit distinctive signals. In the second study, bulk and dynamically stable ultra-thin structures of lead-free CsMnCl$_3$ are discussed. According to total energy and electronic band structure calculations, bulk, bilayer, and single-layer structures of CsMnCl$_3$ are robust antiferromagnetic insulators. In third and fourth chapters are devoted to the identification of different stacking types of GaP/GaSe heterobilayers, and two different hexagonal phases of single-layer Germanium Oxide by means of electronic and optical characterization tools, respectively. In these studies, for the purpose of providing an accurate solution for the prediction of absorption, reflectance, and transmission spectra of materials, excitonic effects are considered by employing Bethe-Salpeter formalism following the $G_0W_0$ approximation. Wide range of atomically thin crystal structures studied within the framework of this thesis are verified to be promising candidates for the development of future nano-sized electronic and optoelectronic device applications thanks to their attractive electronic and optical properties arising from strong quantum confinement effects.
Investigation of photodetectors using graphene field effect transistors incombination with functional dyematerials
(Izmir Institute of Technology, 2020-07) Yakar, Ozan; Balcı, Sinan; Şahin, Hasan
A J-aggregate dye is a type of water-soluble, functional dye, which has a sharp and narrow absorption peak after it self-assembles into a brick-wall structure at high concentrations. The absorption peak of the J-aggregates is sharp, narrow and shifted to longer wavelengths compared to their monomer form and it is in the visible or near infrared spectrum. Due to its very sharp and narrow absorption, it has been used in silver halide photography, non-linear optics, lasing and sensing applications. On the other hand, graphene is one atom layer thick, honeycomb lattice of carbon atoms. In the pure, freestanding form, the bands of its electronic structure touch at one point, making it a gapless semimetal. Due to this characteristic, it is possible to manipulate its optical and electronic properties by changing the Fermi energy of graphene. Therefore, graphene found applications in many fields such as light emitting diodes, photodetectors, Hall sensors, optical modulators and flexible optoelectronics. The functional dye materials have not been combined with graphene photodetectors even though they are highly sensitive to light, less toxic than their competitors and stable at room temperature. In this thesis, using a J-aggregate dye, which has a sharp absorption peak around 585 nm wavelength, a graphene phototransistor has been demonstrated. By changing the charge concentration on graphene, using the charge carriers that arise from the excitation of J-aggregate dye, reversible modulation of graphene Dirac point has been demonstrated. In addition, a novel thin film formation technique has been developed in this study. Porous polyethylene membrane has been used to create thin films of water-soluble materials, such as J-aggregates, on hydrophobic surfaces.
Manufacturing and characterization of perovskite thin films using novel methods
(Izmir Institute of Technology, 2020-07) Bıyıklı, Ozan; Sarı, Emre; Tekin, Hüseyin Cumhur
Perovskite photovoltaics is a promising technology due to its low-cost fabrication and high efficiency. Since their first demonstration in 2009, efficiencies of perovskite solar cells (PSCs) increased unprecedently fast from 3.81% to 25.2% in 10 years. The most common method for the deposition of the absorber layer of the perovskite solar cells is the spin-coating method, which is not a scalable method, and this method is an obstacle to their commercialization. Efficiencies obtained with scalable methods are currently lower than that of the spin-coating method. In this thesis, among the scalable deposition methods, a novel ultrasonic spray-coating was used by adding antisolvent vapor to the system. The antisolvent quenching technique, that is commonly used to improve the crystalline quality of the film by spin-coating was successfully adapted for ultrasonic spray coating. The interaction between diethyl ether (DE) vapor, which is used as an antisolvent, and MAPb(I(3-x)Brx)3 precursor solution (where the solvent is DMF:DMSO, 4:1) was utilized to improve the crystalline quality of the perovskite film. As a result of this interaction, the intermediate phase was observed. The transition to the intermediate phase is supported by data from characterization methods such as optical microscopy, scanning electron microscopy (SEM), X-Ray diffraction (XRD), and current-voltage measurement. Furthermore, n-i-p devices with the FTO/c-TiO2/m-TiO2/MAPb(I(1-x)Brx)3/Spiro-OMeTAD architecture were produced with different antisolvent vapors and their efficiencies was compared. It was observed that devices using DE vapor reach higher efficiencies than devices without any antisolvent vapor.
Plasmonic enhancement of perovskite photoluminescence
(Izmir Institute of Technology, 2020-07) Tan, Metin; Sarı, Emre; Balcı, Sinan
Recently emerged perovskite materials show superior features like high efficiency, defect tolerance, facile synthesis, bandgap tunability and wide color gamut over their rivals in photonics applications. On the other hand, metals have interesting characteristics as they go smaller in size. Their absorption and scattering properties are completely different as nanoparticles. Their confined electron oscillations bring peculiar consequences. Due to change in these features, metallic nanoparticles can enhance or quench fields around them. Light-matter interactions determine how we see the world. Understanding quantum nature of light and matter and their interactions can benefit higher efficiencies and can open paths for novel technologies. In accordance with this purpose, this thesis study involves synthesis of cesium lead halide perovskite emitters and investigation of their interactions with silver nanoisland films. It was concluded that direct contact between perovskite layer and nanoislands results in a fluorescence quenching where intensity average lifetime decreases below 1 ns. Separating these layers with an alumina dielectric layer increased photoluminescence intensity after 15 nm and the highest intensity was observed at 18 nm thickness with 78% of PL enhancement. With different spacer thickness values, we achieved to see the change in photoluminescence intensity.
Quantitative phase analysis in lensless digital inline holographic microscopy
(01. Izmir Institute of Technology, 2021-07) Demir, Ali Aslan; Tekin, Hüseyin Cumhur; Varlıklı, Canan; 01. Izmir Institute of Technology
Computational imaging modalities replace the bulky, complex, and expensive optical components of traditional imaging procedures with numerical reconstruction steps. Digital holographic microscopy is one of the most prominent ones with the possibility of obtaining quantitative phase information by measuring the phase shift change caused by the refractive index of objects. In the lensless digital holographic microscopy system, a pinhole and a light-emitting diode are sufficient to create a holographic pattern on the camera sensor. Here, the optimization of a digital lensless inline holographic microscopy setup was performed to obtain optimal phase value. Also, to retrieve the lost phase information during the recording step, the numerical solution was performed with the single and multi-shot phase retrieval methods. Then, human breast adenocarcinoma (MDA-MB-231) and human myeloid leukemia (U937) cells were analyzed to obtain phase shift, perimeter, and circularity values. These parameters were used to obtain a quantitative differentiation model to replace the traditional labeling or visual confirmation steps with a direct analysis manner. The analysis of respective cells with the classification, object detection, and conditional generative adversarial models can be used directly with pre-trained weights to lessen the computational workloads. With this study, the quantitative analysis with lensless holographic microscopy setup was shown to be a label-free differentiation mechanism to separate cancer cells from monocytes cells which could be used for the early diagnosis of cancer. Also, the proposed method has the potential to be used to identify other cells with links to the diagnosis of different diseases.
Strongly t-noncosingular modules
(Izmir Institute of Technology, 2010) Günyüz, Ozan; Büyükaşık, Engin
This thesis is mainly concerned with the T-noncosingularity issue of a module. Derya Keskin Tutuncu and Rachid Tribak introduced the T-noncosingular modules and gave some properties of these modules. A moduleM is said to be T-noncosingular relative to N if, for every nonzero homomorphism f from M to N, the image of f is not small in N. Inspired by this study, we define a new kind of module, as a particular case of T-noncosingular modules, and call it strongly T-noncosingular modules. We define M to be strongly T-noncosingular relative to N if, for every nonzero homomorphism f from M to N, the image of f is not contained in the radical of N. Obviously, if a module is strongly T-noncosingular, then it is also T-noncosingular, but the converse is, in general, not true. In an attempt to identify the situation when a T-noncosingular module is strongly T-noncosingular, we give necessary and sufficient conditions in terms of the specific ring structures as well as well-known module types.
Three-photon electromagnetically induced transparency in Rydberg atoms
(Izmir Institute of Technology, 2019-07) Oyun, Yağız; Sevinçli, Sevilay; Çakır, Özgür
Electromagnetically Induced Transparency (EIT) is a quantum coherence phe- nomenon, in which an atomic medium is rendered transperent via destructive interference of excitation pathways. EIT was first observed in a three-level lambda scheme where a modified optical response is achieved by the interference of light field induced atomic state coherences at the resonance of transition. An EIT system also produces important optical effects including giant Kerr non-linearity and slow light. Rydberg-EIT media have been used to study optical properties of atomic media, non-linear optical effects and to gain better understanding on interacting many-body systems due to the controllable in- teractions of Rydberg atoms. Recently EIT in a four-level ladder scheme was realized experimentally in a dressed-state manner with Cs atomic vapor, in which a strong dress- ing field allows for a transparency window to be opened for probe field. Rydberg EIT has potential applications in terahertz regime, electrometry, metrology and quantum in- formation science, but extensive studies on four-level Rydberg EIT schemes are scarce. In this thesis; three-photon EIT in a cold atomic ensemble that has a ladder type excita- tion scheme, in which the highest energy state is a Rydberg state is investigated. Atom- light interactions of a four-level ladder system is developed for non-interacting case, then extended to many-body case. Starting with the steady-state solutions without atomic in- teractions, Rydberg EIT system is analyzed using mean-field and rate equation methods, though due to inadequate computing power and lack of time we could not finalize the rate equation method. To understand effects of Rydberg-Rydberg interactions on these systems in detail, two-body case is investigated with mean-field method. Afterwards, to achieve more realistic results, a self-consistent mean-field method for larger systems is developed. It is observed that as the van der Waals interaction energy increases, Rydberg blockade becomes more prominent. Therefore induced transparency weakens, broadens and shifts away from the resonance as expected. This means that, controllable interac- tions in a Rydberg EIT medium enables to control and modify the optical response of the atomic medium.

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