We theoretically investigate the series-coupled fiber double-ring resonator is not exactly the same perimeter, that is, when the double-ring resonator cannot be completely in resonance state, the output characteristics and dispersion characteristics of spectrum and its manifestations. In this paper, we introduce light exhibits different spectral output characteristics through double-ring resonator, when the two rings’ length ratios are δ=1,1.1,1.5, 2. Among them, δ=2 is particularly representative. When the second resonator has the same parameters, the group refractive index of the double-ring resonator whose length ratio is 2 higher than the single ring resonator two or three orders, these results indicate that we could improve the sensitivity of the double-ring resonator because sensitivity is directly related to the group refractive.
In the present paper, we first demonstrate NaLuF<sub>4</sub>: Yb<sup>3+</sup>: Tm<sup>3+</sup>/Ho<sup>3+</sup> rare earth nanocrystals in microstructure hollow fiber. An analysis of the intense blue upconversion emission at 450 and 475 nm in Tm<sup>3+</sup>/Yb<sup>3+</sup> codoped NaLuF<sub>4</sub> under excitation power 0.65W available from solid laser emitting at 980nm, has been undertaken. Fluorescence intensity ratio (FIR) variation of temperature-sensitive blue upconversion emission at 450and 475 nm in this material was recorded in the temperature range from 300 to 345 K. The maximum sensitivity derived from the FIR technique of the blue upconversion emission is approximately 0.005 K−1. The results imply that Tm<sup>3+</sup>/Yb<sup>3+</sup> codoped NaLuF<sub>4</sub> is a potential candidate for the optical temperature sensor.
We compare the temperature sensitivity between the nested fiber ring resonator (NFRR) and the nested fiber ring resonator coupled Mach-Zehnder interferometer (NFRRCMZI). Theoretical results indicate that the temperature sensitivity of the NFRR is almost twelve times higher than that of NFRRCMZI with same parameters, hence complex MZI system can be removed and the whole sensing system will be more compatible without sacrificing the sensitivity. Taking feedback waveguide part as the sensing element in NFRR structure, the limitation of optical quality factor on sensitivity will be broken and arbitrary sensitivity can be acquired by easily setting different feedback waveguide length.
We theoretically analyze the electromagnetically induced transparency (EIT)-like spectrum in the Eye-like resonator configuration. The EIT-like spectrum results from the interference between the inner ring and the outer ring. In this paper, we obtain a tunable group delay and bandwidth of the transparency window through changing the coupling coefficients and the attenuation factors of the inner and the outer ring. The tunable group delay and the bandwidth will have potential application in optical switching or tunable delay lines and tunable bandwidth filter.
The filtering characteristic of double-waveguide parallel-coupled microring resonators is theoretically investigated in this paper. Transfer matrix of the structure consisting of arbitrary number of rings is deduced. Number of very narrow symmetrical transparent channels within each stop-band can increase to any integer by extending rings of the structure, and any one or more channels can be continuously tuned and switched on/off selectively by adjusting the additional phase shift between adjacent rings. The structure is compact, reliable, flexible and tunable, and has potential vital applications for optical switches in dense wave division multiplexing (DWDM) systems.
We theoretically investigate an all-fiber interleaver consisting of a two-stage cascaded Mach-Zehnder interferometer (MZI). The simulation results of the all-fiber interleaver presented symmetrical and asymmetrical output spectra and a uniform flat-top spectral response by changing the coupling coefficient of the couplers. In addition, the interleaver proposed can realize arbitrary passband width ratio between the two output ports by adjusting the coupling coefficient of the couplers involved. A near box-shaped spectral response can be generated through setting suitable parameters, at the same time, the passband and stopband of optical interleaver are improved significantly. This interleaver proposed should be useful to realize the deployment of flat-top all-fiber asymmetric interleaver in dense wavelength division multiplexing (DWDM) networks of high spectral efficiency.
We theoretically and experimentally study an add-drop ring resonator to achieve tunable Fano resonance. In this system, the Fano resonance results from the interference of two beams from add and through port. The line shapes of the Fano resonances are tunable through controlling the phase bias of the two beams from add and through port. At the same time, add-drop ring resonator structure enabling the truly on/off switching mechanism is realized when the phase bias is 0 or π. The experimental results well agree with the theoretical calculation.
The interaction between plasmonic resonances, sharp modes, and light in nanoscale plasmonic systems often leads to Fano interference effects. This occurs because the plasmonic excitations are usually spectrally broad and the characteristic narrow asymmetric Fano line-shape results upon interaction with spectrally sharper modes. We investigate a plasmonic waveguide system using the finite-difference time-domain (FDTD) method, which consists of a metal-insulator-metal waveguide coupled with a rectangle and a ring cavity. Numerical simulations results show that the sharp and asymmetric Fano-line shapes can be created in the waveguide. Fano resonance strongly depends on the structural parameters. This has important applications in highly sensitive and multiparameter sensing in the complicated environments.
We theoretically investigate the series-coupled double micro-ring resonator as tunable optical delay line.
Tunable optical delay line can be achieved by tunable self-coupling coefficient and attenuation factor of
micro-ring waveguide. Through choosing suitable parameters of structure, the series-coupled double
micro-ring resonator can obtain flat delay line that mitigates the deleterious effects of group delay
We demonstrate the electromagnetically induced transparency like spectrum in the nested fiber ring resonator with the transfer matrix theory; the system consists of two rings and two waveguides which are connected by four couplers. The simulation results show that the tunable group delay can be realized by changing the coupling coefficients. At transmission window, the transmittance can achieve approximately 97.2% with the 0.05ns group delay. Through tuning the coupling coefficients, the group delay can vary from 0.05ns to -21.23ns and the bandwidth of the transparency window can vary from 37MHz to 15MHz.The ability for realizing such transparency resonance and for controlling the group delay or the bandwidth of such resonance is important for applications such as optical switching, as well as tunable bandwidth filter applications.
We experimentally demonstrate that the spectral resolution of Fourier transform interferometer could be greatly
enhanced by utilizing the dispersive property of semiconductor GaAs in the near infrared region and it is inversely
proportional to the maximum group delay time that can be achieved in the system. The spectral resolution could be
increased 6 times approximately by using GaAs contrast with conventional FT interferometer under the same conditions.