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optical-phase-modulation
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Electromagnetically induced grating in the microwavedriven four-level atomic systems
, Article Applied Optics ; Volume 54, Issue 3 , 2015 , Pages 368-377 ; 1559128X (ISSN) ; Naseri, T ; Navadeh Toupchi, M ; Sharif University of Technology
Abstract
A new scheme to investigate an electromagnetically induced grating in an N-type configuration in the presence of a strong-standing coupling field, additional coherent fields, and microwave driven fields is presented. By considering the coherent population trapping (CPT) condition in a four-level microwave drivenN-type atomic system, a novel nonlinear optical storage is obtained via linear absorption vanishing and giant Kerr nonlinearity during light propagation. It is revealed that nonlinear properties in this atomic medium are maximum in the CPT condition, and these nonlinear properties could be affected and modulated by means of a microwave driven field. In this condition high-phase...
Statistical Characterization of Kerr Nonlinearity in Optical Fiber and Its Corresponding Applications
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
Optical fibers with the high amount of nonlinearity, or length such as highly nonlinear fibers (HNLF) and long optical transmission lines could not be simply modeled as linear systems; and, in fact, the propagation of signal through these types of mediums is governed by the nonlinear Schrödinger equation (NLSE). From the statistical point of view, the interaction between signal, noise, and Kerr nonlinearity along the fiber leads to an output random process that is not well studied in the literatures and the exploration in this area may play an important role in solving different practical problems. In order to investigate the aforementioned output random process, this thesis obtains the most...
Analysis of terahertz-induced optical phase modulation in a nonlinear dielectric slab
, Article Progress In Electromagnetics Research M ; Volume 13 , 2010 , Pages 41-51 ; 19378726 (ISSN) ; Izadi, S. A ; Shahabadi, M ; Sharif University of Technology
2010
Abstract
Frequency shift of the spectrum of an incident optical pulse by an intense THz pulse inducing cross-phase modulation (XPM) in a nonlinear dielectric slab is analyzed. The effect is predicted with a high degree of accuracy using the well-known transmission line matrix (TLM) technique. In this research, to model the THz-induced temporal and spatial variation of the dielectric permittivity of the nonlinear dielectric slab, the transmission lines of the TLM method are loaded with open shunt stubs. The parameters of the stubs are modified in accordance with the refractive index variation of the dielectric slab, here ZnTe, induced by the strong THz pulse. The obtained numerical results are...
Low-drift optoelectronic oscillator based on a phase modulator in a sagnac loop
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 65, Issue 7 , 2017 , Pages 2617-2624 ; 00189480 (ISSN) ; Banai, A ; Kartner, F. X ; Sharif University of Technology
Abstract
A low-drift optoelectronic oscillator (OEO) is developed and experimentally shown. In the proposed OEO, a fiber Sagnac interferometer, including an optical phase modulator (PM) and a nonreciprocal bias unit, functions as an intrinsically drift-free intensity modulator. The phase noise of the proposed OEO is modeled in phase space, which is verified by experiments. Phase noise and frequency stability of the photonically generated microwave signals are measured. The single-sideband phase noise of the generated microwave signal is -106.6 dBc/Hz at 10-kHz offset from the 10.833-GHz carrier, with 120-fs rms timing jitter integrated from 1 kHz to 10 MHz. Frequency drift measurements show ±0.85-ppm...
Tunable low-Jitter low-drift spurious-free transposed-frequency optoelectronic oscillator
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 65, Issue 7 , 2017 , Pages 2625-2635 ; 00189480 (ISSN) ; Banai, A ; Kartner, F. X ; Sharif University of Technology
Abstract
We propose and theoretically and experimentally demonstrate a novel tunable spurious-free single-loop optoelectronic oscillator (OEO) with low drift and low-phase noise. In the proposed transposed-frequency OEO (TF-OEO), a nonreciprocal bias unit and an optical phase modulator in a fiber Sagnac interferometer function jointly as an intrinsically drift-free intensity modulator, which improves the long-term drift. Besides, a transposed-frequency low-noise filtered amplifier is used which replaces the conventional radio frequency (RF) bandpass filter (BPF) and RF amplifier with an intermediate frequency (IF) BPF, an ultralow phase noise IF amplifier, and a tunable local oscillator, to attain...