SUMMARY The Lorentzian-shape filter response of a microring resonator filter is not suitable to the practical use in WDM systems, because of the lack of pass bandflatness, high cross talk, andthe large wing in the stop band . Therefore, the tailoring of filter response shape is requiredto improve the performance. In this paper, the authors designed and demonstrated the box-like filter response of microring resonator filter by using the supermodes of stacked double microring resonators. The thicknesses of microrings andthe separation between them were optimally designed to give the maximally flat response. A fine fabrication process was developed to achieve the deep and very smooth side wall. The shape factor, which is defined by the ratio of −1 dB bandwidth to −10 dB bandwidth, was successfully improvedby three factors from 0.17 of Lorentzian shape to 0.51.
The authors investigated the deposition conditions of the bias-sputtering technique to form some sophisticated thin-film geometries for photonic integrated circuits, and they successfully formed a dielectric film selectively on a vertical surface of a substrate. The deposition rate on the vertical surface increases with the increases of the bias RF power because of the resputtering effect from the bottom surface. When the etching rate by the bias RF power is balanced with the deposition rate on the horizontal surface, one can form a film selectively on the vertical surface. This technique can be applied to the AR coating of DFB lasers and the formation of a multilayer filter on the vertical surface of a waveguide.< >
A non-blocking wavelength channel switch (non-blocking tunable filter) using the thermo-optic (TO) effect of a double series coupled polymer microring resonator is demonstrated. This device can switch a wavelength channel without blocking other wavelength channels. An extinction ratio of more than 10 dB was realised.
Linearly polarized (LP) modes in few-mode fibers are not true eigenmodes but approximated modes constituting of linear combinations of true eigenmodes. Therefore, the vector field profile in a few-mode fiber must be expressed in terms of the true eigenmodes with complex amplitudes involving a phase difference corresponding to the propagation distance. Owing to this property of LP mode propagation, the propagation characteristics of few-mode fibers cannot be accurately analyzed using conventional LP modes. In this study, the crosstalk between LP 11 quasi-degenerate modes due to offset connection is accurately analyzed using matrix formalism expressing the linear combination of true eigenmodes. The difference in the analytical results between the LP modes and the eigenmodes revealed that the propagation of few-mode fibers should be analyzed using true eigenmodes.
We propose and analyze all-optical active microring logic gates for a microring processor that has various integrated all-optical signal processing functions. The active microring logic gate is composed of an InGaAsP/InP multiple quantum well and is operated on the basis of cross gain modulation (XGM) and cross phase modulation (XPM). The XGM and XPM are enhanced in the active microring resonator, leading to low-power consumption. We have analyzed and successfully demonstrated 10 Gbps wavelength conversion and NOT, NOR, OR and 5 Gbps AND gate operations by the transfer matrix method (TMM). The simulation results show that the proposed active microring can be operated with very low energy input signals as low as 1.0–20 fJ/pulse.
Multimode optical branching components are becoming essential in optical networks such as subscriber systems and local area networks. 1 There is a problem, however, that the branching characteristic strongly depends on the excited modal distribution, 2 and stable operation of multimode branching waveguides, therefore, has not been established.
Mode-evolutional serial branching mode multi/demultiplexer (SBMM) for homogeneous coupled multi-core fiber was demonstrated. This multi/multiplexer has some advantages such as the high fabrication tolerance and small wavelength and polarization dependences owing to the principle of adiabatic mode-evolutional phenomenon. The SBMM was fabricated using polymer materials. The selective four mode excitation with the low crosstalk of less than −10 dB and small wavelength dependence were realized within the CL-band.
We demonstrated all optical flip-flop and inverter using two adjacent lasing wavelengths by a semiconductor MQW microring laser. The lasing wavelength (1567.54nm) and both side adjacent lasing wavelengths (1565.84nm and 1569.24nm) were used as the injection light wavelength. These operations were realized in the same device with different control current.
