Sharif Digital Repository

In this dissertation, the statistical analysis of ultrashort light pulse detectors, in presence of different noise sources, is presented. By investigating performance degradation of ultrashort light pulses detection based on linear conventional detectors, the necessity of all optical preprocessors prior to the low speed photodetectors is approved. By using these preprocessors, we achieve high discrimination between noise and ultrashort light pulses at the photodetector input, for simplicity in detection of light pulses by conventional low speed photodetectors. Among various types of preprocessors, in this dissertation, we focus on optical crystals with dominant imposed nonlinear second... 

High photonic responsivity and excellent quantum efficiency of high-Tc superconductors make them a promising candidate for photonic detectors. Interesting features of detectors which are based on Josephson Junctions such as high sensitivity in a wide range of frequencies, potentially have many advantages over other semiconductor-based photo-detectors. According to variety of applications of high-Tc superconductors, particularly YBCO, and significant progress in manufacturing of thin films and Josephson junctions, this thesis mainly focuses on investigation of light emission effects on high-Tc Josephson Junctions and its theory. In our work, at the beginning, the current-voltage... 

In this work, we have simulated graphene nanoribbon based photodetector and impact of changing the width, and Boron-Nitride doping and Stone-Wales defects on the optical properties of GNR has study. The energy band structure of GNR with nearest-neighbor approximation in a tight binding model calculated. To correspond with experiment and accuracy, we need to consider the impact of third nearest neighbors and edge bond relaxation. By Using the band structure, we calculated joint density of state and optical matrix elements and obtain inter band selection rule for A-GNR and Z-GNR. Then, using the Fermi’s golden rule, we investigate optical properties of GNR such as optical conductivity and... 

The purpose of this thesis is construction of a characterization system, for plasmonic nanoparticles. plasmonic nanoparticles are metallic particles in nanometer scale, which can confine the electromagnetic field, in their induced electric dipole, in a wide range of frequency. This optical property lead to many applications such as, medicine cancer therapy, controlled releasing of drugs, solar cells and interconnections in integrated photonic circuits.Since, optical properties are the most important properties of plasmonic nanoparticles, we need a system to characterize them optically. There are different ways of optical characterization, which need a common tools, including light sources,... 

Today, the internal connections of the CPUs with a few billion wired transistors in 14 copper layers on the silicon wafer are possible. Recently, power dissipation has slowed the growth rate of clock growth in CPUs, and nowadays sometimes more than 60% power is lost in connections. In this situation, the increase in efficiency has been achieved in accordance with Moore's law with multi-core chips. This theme has made the connections between the cores much more important than before. Usually the information in the network structure on chip (NOC) is transmitted on these connections. Therefore, all three aspects of delay, power dissipation and bit rate are important for communication channels.... 

Organic photodetectrors(OPD) are new generation of photodetectors that use of organic materials to convert optical signal to electrical current. Organic photodetectors in recent decade have witnessed significant improvements and many recent research allocated to this photodetectors. This OPD’s have important application so that the inorganic photodetectors have some problems in that application , for example: wide area imagination , biomedical sensors , flexible application and . . . .This work focus on the design and simulation of a panchromatic photodetector that use of new material and have high bandwidth and low dark current. One of application of this OPD is to use in optical... 

Optical Tweezers (OT) are non-invasive micro-manipulation tools based on a tightly focused Gaussian laser beam for applying and measuring pico-Newton range optical forces. They are also utilized for trapping and moving particles and biological specimens. The force exerted by OT is mainly determined by detecting the position of the trapped object inside the harmonic potential well of OT. Conventionally,a Quadrant Photo-Diode (QPD) positioned at the Back Focal Plane (BFP) of the condenser lens provides the position of the bead with MHz temporal and nanometer spatial resolution. As a disadvantage of this detection scheme, it is impossible to obtain simultaneously the maximal lateral and axial... 

Graphene based photodetectors which are modified with quantum dots, are the new generation of detectors. In these supplies an integration of graphene’s unique characteristics like high conductivity and mobility and the high light absorption of quantum dots, are used.In this research graphene by chemical vapor deposition in centimetric large scales, tungsten disulfide quantum dots, boron nitride and graphene quantum dots and 2D tungsten disulfide have been synthesized. In the next step each of them were characterized to modify the quality of used layers in heterostructure.Based on the characteristic tests, quantum dots aspect ratios were 1 to 5 nanometers. Also tungsten disulfide was obtained... 

The Large Hadron Collidor (LHC) will increase its luminosity to more than 10e35 cm-2 s-1. The large amount of data rates will provide enough datasets needed to probe rare Higgs processes, study the scattering of longitudinally polarized W bosons and physics beyond the standard model(BSM). In the upgraded version of the LHC, called High Luminosity LHC (HL-LHC), the number of simultaneous interactions per bunch crossing, aka pile-up, increases to 140-200. The large number of pile increases the possibility of confusion in distinguishing vertexes of interest due to the contamination from non-interesting vertexes. One of the methods to mitigate the pile-up, complementary to the precision tracking... 

Enhancing the detection range, sensitivity and stability of phototdetectors due to their vast applications are in great importance. In recent years, Lead sulfide quantum dots, in order to their absorption over a wide range of wavelengths including Near-infrared (NIR), multiple exciton generation effect and solution processability are promising materials.However, long organic surface ligands which are necessary in synthesis process can suppress the carrie transport and the common method to overcome this weakness, is ligand exchange process. In this way, using short organic ligands because of their low electron mobility and methylammonium lead iodide ligands in order to their instability,... 

Intelligent transportation systems (ITS), refers to systems in which various types of data receiving and processing operations of traffic and transportation, as well as management and control, are used by automated and intelligent tools and by using modern electronic and control platforms along with the relevant planning. In intelligent transportation systems, new communication, electronic and optical technologies along with computer technologies, mechanical equipment, etc. are used for data retrieval and data mining that the required data is usually received and collected automatically and instantaneous, integrated and simultaneous access to the data set of the transportation network makes... 

A novel optoelectronic property of two-dimensional (2D) materials suggests they can be used for high-performance photodetector design. There has been a lot of attention paid to MoS2 and Despite its higher optical absorbance, MoSe2 has received little attention. A chemical vapor deposition system was used to prepare atomically thin MoSe2 films. Our research developed a method of preparing hexagon-shaped MoSe2 photodetector on Si/SiO2 substrates in atmospheric pressure with sawtooth edges, leading to large-scale MoSe2 layers with the size of ∼ 70µm . The Raman characterization of the grown flakes indicated that they possessed high quality few layers of MoSe2 and the distance between the two...