Dynamic and Quantum Properties of Parity-Time Symmetric Microring Lasers
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Parity-time (PT) symmetry offers new opportunities to investigate non-Hermitian systems, such as lasers. In this thesis, the lasing properties at the exceptional point of PT-symmetric microring lasers with mixed index and gain gratings, externally coupled to a bus waveguide, have been studied. The dynamic study shows robust unidirectional lasing emission and the related frequency-resolved output radiation intensity is derived based upon the quantum theory with considering quantum excessive noise. In Chapter 1, we briefly introduce the basic concepts of PT symmetry; In Chapter 2, we present the configuration of a PT-symmetric microring laser and discuss its various lasing conditions and properties in the PT breaking phase and at the exceptional point. In Chapter 3, we analyze the dynamic properties of lasing at the exceptional point and proved its stability and robustness. In chapter 4, we successfully derive the optical spectrum in a quantum regime. The quantum noise inside the amplification and absorption is considered through a scattering input-output formalism. Specially, the spectrum at the exceptional point is investigated. The Lorentzian lineship and its relation compared to the classical theory are further discussed..