انتشار امواج پلاسمون پلاريتون سطحي در ساختارهاي چند لايه نيم رسانا و فروالكتريك

چكيده انگليسي :

SPP Propagation in Semiconductor and Ferroelectric Multilayer Structures Naime Ghafarian n ghafarian@ec iut ac ir Date of Submission 4 18 2011 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Persian Amir Borji aborji@cc iut ac irAbstract Surface plasmon polaritons SPPs are electromagnetic waves coupled to free electron oscillations thatpropagate along the interface between a dielectric and a conductor with a negative real part of permittivity The most attractive feature of surface plasmons is their enhanced and spatially confined electromagneticfields at conductor dielectric interfaces Because of this SPPs have been exploited in many applicationssuch as chemo and bio sensors integrated photonic circuits and enhancement of weak optical processes However practical applications of SPPs are hindered by their short propagation length resulting from thepower dissipation in the metal Recently considerable efforts have been devoted to increase the propagationlength by introducing novel structures for SPP waveguides or compensating the loss by using activemediums such as dyes semiconductors multiple quantum wells MQWs quantum dots etc In this thesis a GaAs semiconductor layer is used as the gain medium which provides enough gain and is simple tofabricate Studies carried on active plasmonic waveguides so far have generally used simplistice models forthe gain medium Although these methods can be useful to obtain the general behavior of the activewaveguide they do not provide accurate results and can not account for some physical phenomena such asgain saturation due to increase in optical intensity In this thesis a more comprehensive model based onboth rate and quantum mechanical gain equations that covers the effects of frequency temperature field sintensity and bias value is used in order to analyze two proposed active semiconductor SPP waveguides One of these SPP waveguides is a semiconductor metal dielectric structure and the other one is ametal semiconductor metal structure Both waveguides are studied in an optical frequency range fordifferent dimensions by applying several different values of electrical pumps For SPP wave amplification saturation of the gain due to increase in the field intensity is theoretically analyzed and validated bysimulations It is also shown that when a sufficient proportion of the SPP field is distributed within theGaAs layer which ensures robust coupling between semiconductor gain medium and SPP wave there is aprofound impact on the propagation of the wave In the latter part of this thesis a double electrode SPPwaveguide incorporating a ferroelectric layer is proposed that can be used to control and increase thepropagation length of the supported SPP mode For ferroelectric SPP waveguide three cases based on thedirection of optical axis with respect to direction of propagation and electric bias field orientation areintroduced For each case the dispersion equation is obtained and it is shown that the best case forincreasing the propagation length of SPP wave is the case in which the optical axis is perpendicular to theelectric bias field and parallel to the propagation direction Keywords Surface plasmon polariton waveguide active semiconductor medium quantummechanical gain equations rate equations ferroelectric

غفاريان، نعيمه

انتشار امواج پلاسمون پلاريتون سطحي در ساختارهاي چند لايه نيم رسانا و فروالكتريك

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