Research On Tunable Interference Characteristics In Ring Resonators

Ring resonators have been the building blocks due to its dr amatic intracavity intensity buildup, wavelength selection, compact size, flexible and versatile functionalities. The ring resonator based devices have been applied in varieties of communities such as optical communications, optical networks, biochemistry sensing and so on. Nevertheless, the static single ring resonator cannot generate the tunable high order resonance characteristics required by varieties of applications such as tunable Fano resonances, reconfigurable multiple channel filtering characteristics, large product of delay-bandwidth and so on. To improve the performance of the static single ring resonator, the tunable interference characteristics between resonance modes in ring resonator configurations are studied. The main contents in this thesis are listed as follows:The research advances on the coherent interference characteristics in ring resonator configurations are reviewed. Since the coherent interference characteristics in ring resonator configurations depends on the coupled schemes between ring resonators, the most widely used three coupled schemes such as series-coupled, parallel-coupled, and resonator coupled interferometers schemes are introduced. Also, the high order resonance characteristics resulting from the interference characteristics using these schemes such as Fano resonances, high order channel dropping filtering characteristics, interferometric rotation sensing characteristics and so on are reviewed. From the view of these applications, the advantages and the shortcomings of the interference characteristics are given.The two most widely used theory model such as the transfer matrix theory and the coupling theory of modes in time are reviewed. The conditions for which the two theories are respectively suitable and unsuitable are given. To improve the shortcomings of the two theories, a theory model relating interference to delay is modeled in order to explain the origin of the light pulse delay in coupled ring resonators and directly calculate the explicit expressions of the gr oup delay.The tunable Fano resonances in dispersion-tuned ring resonator coupled Mach-Zehnder interferometers(RCMZIs) is studied. The theoretical and experimental results reveal that the slope and the asymmetry parameter q of the Fano resonance are determined by the dispersion(group delay) of of the ring resonator structure. Furthermore, the slope and the asymmetry parameter q experience a sign reversal when the dispersion of the the second-order series-coupled ring resonator structure is tuned from abnormal dispersion(fast light) to normal dispersion(slow light). These theoretical and experimental results indicate that the reversible Fano resonance which holds significant implications for some attractive device applications such as highly sensitive bio chemical sensors, ultrafast optical switches and routers can be realized by the dispersion tuning scheme in the RCMZI.A reconfigurable dual-mode resonator based dual-channel dropping filtering characteristics in a self coupled resonator Sagnac interferometer are investigated. The theoretical and experimental results reveal that, the dual dropping channels are generated within a free spectral range(FSR) via the interference between the electromagnetically induced transparency(EIT)-like and electromagnetically induced absorption(EIA)-like resonances despite only one resonator used in the filter. Depending on the phase tuning, the reconfiguration of the dual channels enabling the truly on/off switching mechanism is achieved, and the three output modes are provided. The compact, reliable, flexible, versatile, and extendable filter has profound implications for wavelength division multiplexing(WDM) applications in optical interconnection networks.Two schemes are provided to improve the performance of the re sonator based interferometric fiber optic gyroscope(R-IFOG). In the first scheme, a dynamically tuned add-drop resonator based IFOG is theoretically proposed. Taking the impact of the linewidth of incident light on the Sagnac effect into account, the effect of rotation on the propagation of a partially coherent light field is studied in this dynamically tuned structure. It is demonstrated that the sensitivity-linewidth product will be enhanced by two orders of magnitude in comparison to that of the corresponding static resonator based IFOG. Furthermore, the optical gyroscope based on the dynamically tuned add-drop resonator can acquire ultrahigh and uniform sensitivity by extremely short fiber length without a high-performance laser source of narrow linewidth and a complex laser frequency stabilization system. In the second scheme, the modulation period and amplitude of the typical square wave phase bias modulation(SWPBM) applicable to R-IFOGs is proposed. The theoretical research results reveal that the sensitivity of the R-IFOG with the SWPBM to slow rotation rate is boosted in comparison to that without phase bias. Furthermore, the ultrahigh sensitivity can be attained by the R-IFOG with the SWPBM of extremely short fiber length. Therefore, the SWPBM of the proposed modulation period and amplitude enables highly sensitive and compact integrated closed-loop R-IFOGs.The preceding research will improve the performance of the static single ring resonator, making the ring resonator based devices such as optical sensors, ultrafast optical switch, routers, high order add/drop filters, multiplexers, interleavers, and optical gyroscopes more flexible, more feasible, and more promising.