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All-Optical Signal Processing Using Compact Photonic Devices

Pour Mohammad Qoli Vafa, Ali | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52505 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Khavasi, Amin
  7. Abstract:
  8. Digital computers, comprising universal logic gates, are tremendously versatile. This versatility associated with the increasing integrability of digital electronics due to Moore’s law has left nearly no room for analog computers in the last few decades. However, in the case of some specific problems such as modeling complex and nonlinear systems or pro-cessing large amounts of data, computation time and power is still a serious restriction of digital computing. Optical phenomena are fast enough and offer novel approaches to overcome the mentioned restrictions about the system speed and power consumption. Therefore, optical structures make possible to perform ultra-fast spatial analog computing such as image processing with nearly zero power consumption.Recently the concept of “Computational Metamaterials” has been introduced that uses the potential of metamaterials and metasurfaces to perform basic mathematical operations on optical signals. This offers high-throughput real-time all-optical computation with low power consumption using remarkably compact, thinner than the wavelength in some cases, and potentially integrable structures that may be employed as hardware accelerators for existing electronic computers. Different techniques to design such spatial analog optical computers have been categorized into two fundamental approaches: (I) metasurface (MS) approach and (II) Green’s function (GF) approach. In this research, we have exclusively focused on the GF approach, which uses the nonlocal (angular-dependent) response of optical structures to impart the transfer function of interest directly in the wave vector domain. After a brief review on optical mathematical operations based on this approach, we have introduced an optical high pass filter based on total internal reflection of light at the interface of two dielectric mediums for both TE and TM polarizations. Rigorous anal-ysis based on plane wave expansion has been carried out and the results have been veri-fied by full-wave numerical simulation. Next, the application of the designed filter for edge detection of input field profiles has been investigated. In the following, a sub-block has been added to the optical operator through which the hyperbolic dispersion of an ani-sotropic crystal beside the geometry of structure has been used to enhance the spatial band width of the optical operator. This has been implemented by a periodic multilayer structure of dielectric and metal layers. Eventually a perfectly isotropic two dimensional high pass filter has been introduced for both TE and TM polarizations using a periodic multilayer structure of dielectric layers. Also using an optimization algorithm, the thick-nesses of layers have been tuned to represent a better approximation of an ideal high pass filter. Next, the application of the designed filter for 2D edge detection of input field pro-file has been investigated
  9. Keywords:
  10. Edges Detection ; Analog Optical Computing ; Optical High Pass Filter ; Hyperbolic Disperssion ; Periodic Multilayer Structure

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