Comparitive Study of Coaxial Bragg Resonators
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Comparitive Study of Coaxial Bragg Resonators Yu Zhang & Shi-Chang Zhang & Hui-Bo Zhang & Qi Xin & Yan-Yan Kong & Bin Chai
Received: 28 June 2010 / Accepted: 20 July 2010 / Published online: 1 August 2010 # Springer Science+Business Media, LLC 2010
Abstract A coaxial Bragg resonator can be performed in four kinds of structures: it is constructed by inserting a regular waveguide between two selective Bragg reflectors (being called the upstream reflector and downstream reflector, respectively), or it consists of only two Bragg reflectors without regular waveguide section between them, where connection of these two reflectors is smooth with phase difference Δ=0 or is step-changed with corrugation phase difference Δ = +π or −π, respectively. The present paper is devoted to a comparative study for the response of reflectivity and quality factor on frequency in these four kinds of coaxial Bragg resonators, including the influences of the location and corrugation-phase difference of the step-changed connection of the two reflectors. Results show that a coaxial Bragg resonator possesses most attractive properties when the corrugation-phase difference is Δ = +π at the point of connection and the upstream reflector is longer than the downstream reflector. Keywords Coaxial Bragg resonator . Coaxial Bragg reflector . Reflectivity . Q-factor
1 Introduction Since Bragg structures were widely employed in microwave electronics, integrated and nonlinear optics [1–5], important applications have been opened in high-power free electron radiation sources such as the cyclotron autoresonance maser and free-electron laser oscillators due to excellent mode selectivity and frequency selectivity [6–33]. Generally, a Bragg structure can be realized by corrugating rectangular or sinusoidal ripples on the surface of metallic waveguide. Physically speaking, selectivity of mode or frequency in a Bragg structure is based on the effect of the ripple-corrugation boundary, which results in the so-called stop-band or pass-band transmission for selective mode and frequency. Y. Zhang : S.-C. Zhang (*) : H.-B. Zhang : Q. Xin : Y.-Y. Kong : B. Chai Institute of Photoelectronics, School of Information Science and Technology, Southwest Jiaotong University, Campus Mail Box 50, Chengdu, Sichuan 610031, People’s Republic of China e-mail: [email protected]
J Infrared Milli Terahz Waves (2010) 31:1126–1135
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Early investigation was mainly concentrated on the planar or cylindrical Bragg structures [1–13]. As insertion of a corrugated inner rod into a cylindrical Bragg structure provides extra possibility to control the stop-band or pass-band, now growing attention is paid to the coaxial Bragg structures [14–25]. A traditional Bragg resonator is performed by two Bragg reflectors separated by a regular waveguide section, where the first reflector is refereed to as the upstream reflector and the second one as the downstream reflector. If the regular waveguide section between the two reflectors is absent, the Bragg resonator is simplified to consi
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