Sharif Digital Repository

Optical ¬memories are one of the most important elements in photonic integrated circuits (PCI). Usually these memories have been designed in type of inactive and were based on nonlinear optic effects such as saturation absorption and Kerr effect in Micro¬ ring resonator. Semiconductor Micro¬ ring laser is appropriate candidate for designing and constructing of optical memories. Bifurcation analysis indicates that semiconductor Micro ring laser coupled with waveguide in the presence of external optical feedback from end face of waveguide has two stable modes. Phase differences of clockwise and counter clockwise fields of these modes in the coupling point for one of them is zero (in phase... 

Examining composite quantum systems through quantum thermodynamics, we face the new concept of binding energy. In this thesis, we are going to present a general definition for binding energy in quantum systems which covers any kind of interactions. First of all, we examine the possibility of energy exchange in a quantum system using quantum thermodynamics. In this theory, energy exchanges of an open quantum system may be divided in to two portions: heat and work; due to an accepted definition, heat is the portion of energy that is supposed to change entropy, while work has no influence on that. In this research, we restrict our calculations to the systems which are thermally closed and... 

The coupling of optical and mechanical degrees of feedom via radiation pressure has been a subject of early research in the context of gravitational wave detection. Recent experimental advances have allowed studying the modifications of mechanical dynamics provided by radiation pressure. First, this thesis reviews the consequences of dynamic back-action in optical microcavities with mechanical degree of feedom, and presents a unified treatment of its two manifestations: the parametric instability (mechanical amplification or oscillation) and radiation pressure back-action cooling. Then, by considering the Fabry-Perot cavity with two movable mirrors, and using Multi-Reflection Method, we... 

Precise leak detection by acoustic signal analysis calls for robust similarity measures to estimate the time delay between recorded leakage signals and minimize the probability of false alarms, in the face of dispersive propagation, multiple reflections, and unknown correlated, uncorrelated and impulsive background noise. Providing evidence that higher order modes and multi-reflected signals behave like sets of correlated noise, this thesis uses a regression model to optimize residual complexity in the presence of both correlated and uncorrelated noise. This optimized residual complexity (ORC) is highly robust since it takes into account both the level and complexity of noise and signal,... 

Photonic lattices can provide an inexpensive and fine tools to investigate some common phenomena in condensed matter physics, quantum optics, relativistic mechanics,atomic and molecular physics. These phenomena contain Anderson localization,Bloch oscillation, Dynamic localization, coherent and squeezed states, Relativistic Dirac equation, Rabi oscillation, ... .In this thesis, it was investigated three worthy phenomena of them, which at first are introduced in condensed matter physics for electronic systems, in photonic lattices. These phenomena are as follow: Transverse localization of light wave, Bloch oscillation and dynamic localization of light. It was also simulate classically, the... 

In recent years, a strong interplay between quantum mechanics and the physics of waveguide arrays was established based on a formal analogy between atomic and photonic lattices. The study of light evolution in photonic lattices has provided deep insights into the physics of wave function dynamics and, hence, peculiar quantum mechanical features. Arrays of evanescently coupled waveguides is a very versatile model system for discrete physics. Anderson localization and Bloch oscillations are two examples of coherent quantum transport phenomena, which have been investigated in this thesis. In the first part of this thesis, we investigate numerically the effect of long-range interaction on the... 

Optomechanical systems have attracted considerable attention in the last decade. Such a raising prominence is mainly due to its capability in providing new insight into the quantum behavior of macroscopic objects and exploring the interface between quantum and classical mechanics. Alongside this fundamental quest, cavity optomechanics has many other benefits, ranging from very precise measurements on forces and positions to quantum information processing. In this thesis, we investigate quantum properties of such systems. Particularly, we study cooling of the mechanical resonator toward its ground state and the entanglement between this mechanical resonator and the cavity field. Cooling the... 

Optomechanical systems have attracted much attention over the last decades, especially as a macroscopic lab for observing quantum mechanical effects . In this thesis , optomechanical quantum memories are studied . In p articularl , we study cooling of the mechanical resonator down to its ground state, which is the necessary condition to obtain a good quantum memory and also explore the limitations of cooling and storing protocols . Quantum state of light can be stored in the mechanical mode of the system by optomchanically induced transparency effect (OMIT) . This effect is formally equivalent to electromagnetically induced transparency effect (EIT) which is seen in an ensemble of... 

A cavity optomechanical system is created when the resonance frequency of an optical cavity is influenced by the position of a mechanical oscillator. To observe quantum effects and quantum applications of these systems, cooling of mechanical mode(s) participating in these interactions is very important. At first, the dissertation focus on the trend that people were trying to study radiation pressure theoretically and experimentally and then present classical and the quantum picture of radiation pressure. Next, the diverse geometries are based on the optomechanical interaction are described concisely. Fabry-Perot cavity with one degree of freedom has considered and then the Stokes and The... 

Circuit model quantum computing, provides a powerful tool that allows humans to process information faster. Excessive noise and its impact on quantum systems which can lead to data loss are major obstacls in accessing quantum computers, since the systems proposed to make quantum computers are indeed open systems, noise can cause data loss. Therefore, the achievement of quantum computing, has been delayd. One of the most effective ways to neutralize this noise is to use a geometric phase to make evolutions. Holonomic quantum gates utilize the geometric phase to implement the noise resilience gate. In this thesis, we intend to use a composite optomechanical system, consisting of two optical... 

Polyvinylidene fluoride (PVDF) is remarkable since its mechanical properties, chemical stability and significant ferroelectricity. This Polymer has a simple chemical structure and can be found in five different crystal phases (α,β ,ɣ,δ and ε). Between these phases, beta shows a substantial pyro and piezoelectric activity since its great dipole moment. In this study PVDF/Poly(vinyl acetate)/Nanodiamond (ND) nanocomposite films were synthetized by solving in dimethylformamide adding ND particles to PVDF/PVAc blend in order to improve mechanical and piezoelectric properties. Scanning electron microscopy results showed that PVDF/PVAc are miscible and lead to a single crystal phase and dispersion... 

Continuous-variable quantum key distribution (CV-QKD) protocols, that share an unconditionally secure key between at least two legitimate parties, are based on the modulation of information on the continuous characteristics of light. CV-QKD is low-cost, has a high rate, and is compatible with conventional technology. However, one of the major drawbacks of CV-QKD is its poor performance at long distances. Such a limitation can be overcome with the assistance of noiseless linear amplifiers (NLAs). In this thesis, we aim to use Quantum scissor (QS), as a realistic NLA, to overcome this limitation. To this end, we suggested a three-photon QS that truncates all multiphoton number states with...