Tetsuya Mizumoto

Demonstration of Flat-Passband Multi/Demultiplexer Using Multi-Input Arrayed Waveguide Grating Combined With Cascaded Mach–Zehnder Interferometers

We demonstrate multi/demultiplexers with a very flat passband and small excess loss using a multi-input arrayed waveguide grating combined with a cascaded Mach-Zehnder interferometer structure. We also analyze the impact of coupling between input waveguides just before the input slab on chromatic dispersion and investigate a waveguide structure for reducing the chromatic dispersion. We fabricated flat-passband multi/ demultiplexers with 100-GHz channel spacing using 2.5%-Delta silica waveguides and experimentally investigated the dependence of their optical characteristics on design parameters to demonstrate the effectiveness of the proposed theoretical model. We obtained a very flat passband response having a 1-dB bandwidth of 0.645-0.658 nm and 20-dB bandwidth of 0.944-0.960 nm with a loss penalty due to the passband-flattening of 0.9-1.0 dB and chromatic dispersion of -22.1-17.5 ps/nm over 0.5 nm in the passband. The measured passband shape and chromatic dispersion generally agreed with the simulation results.

An effective method for coupling single-mode fiber to thin-film waveguide

An effective method for coupling optical signals from single-mode fibers to thin-film waveguides is proposed. The authors show that this method provides high coupling efficiency for connecting fibers of different core diameters to thin-film waveguides of different film thicknesses or refractive indexes. The authors summarize the theoretical treatment of the coupler. Examples of couplers designed for SiO/sub 2/-based materials as well as iron garnets are presented. Fabrication of the proposed coupler and its experimental results are described. >

A novel three-guide optical coupler using a taper-formed waveguide

A novel taper‐formed three‐guide coupler is presented. Its unique power coupling characteristics are experimentally demonstrated. By virtue of adopting the taper‐formed waveguide, the severe restrictions imposed on the device fabrication process are greatly relaxed. This makes the coupler advantageous to application in a variety of integrated optics, such as power splitters and combiners, and as constituent elements of devices like optical isolators.

Modeling of Multi-Input Arrayed Waveguide Grating and Its Application to Design of Flat-Passband Response Using Cascaded Mach–Zehnder Interferometers

We present a theoretical model of a multi-input arrayed waveguide grating (AWG) based on Fourier optics and apply the model to the design of a flattened passband response. This modeling makes it possible to systematically analyze spectral performance and to clarify the physical mechanisms of the multi-input AWG. The model suggested that the width of an input/output mode-field function and the number of waveguides in the array are important factors to flatten the response. We also developed a model for a novel AWG employing cascaded Mach-Zehnder interferometers connected to the AWG input ports and numerically analyzed its optical performance to achieve low-loss, low-crosstalk, and flat-passband response. We demonstrated the usability of this model through investigations of filter performance. We also compared the filter spectrum given by this model with that given by simulation using the beam propagation method

Analysis of the coupling characteristics of a tapered three-guide coupled system

Optical coupling characteristics of a three-guide coupled system are discussed. Application of a taper-formed waveguide in the system is proposed. A theoretical analysis of the tapered waveguide system is presented by applying a modified coupled-mode theory, with the tapered guide being approximated by successive stepped small guide segments. Based on numerical examinations, particular coupling characteristics of the tapered guide system are demonstrated. An application of the tapered three-guide coupled system in a type of optical isolator is proposed. The main working principles of the isolator are presented. >

Improved perturbation feedback method for the analysis of rectangular dielectric waveguides

A simple and accurate method for analyzing rectangular dielectric waveguides is proposed. By investigating some improved equivalent guide models, which can be defined by a successive perturbation feedback process, propagation constants of the original guides can be reasonably obtained with accuracy better than those obtained by applying current approximate approaches, especially when the modes exist at or around the weakly confined region. >

Design of wavelength-flattened coupler using a novel diagram

A novel diagram which describes the condition of 3 dB coupler is proposed. Using the proposed diagram, the design of a wavelength-flattened 3 dB directional coupler composed of a uniform coupled waveguide is investigated. Normalized waveguide parameters are introduced to characterize a five-layer planar waveguide. This enables us to generalize the discussion and to reduce the number of parameters required for characterizing a coupled waveguide. A broadband 3 dB coupler having 50/spl plusmn/5% coupling ratio over a wavelength range of 1.1-1.7 /spl mu/m is designed.

Analytical and experimental study of waveguide optical polarization splitter with Langmuir-Blodgett cladding layer

The waveguide-type optical polarization splitter, which utilizes birefringence of a Langmuir-Blodgett cladding layer, is studied theoretically and experimentally. By means of the beam propagation method based on Galerkins principle, characteristics of the polarization splitter are analyzed. Results of the numerical calculation predict excellent polarization splitting properties with a crosstalk of -30 dB and an insertion loss of less than 0.1 dB for both TE and TM polarization. Successful operation of the polarization splitter was demonstrated in an experimental device. >

Waveguide-type optical attenuator

This paper describes the performance characteristics of a waveguide-type optical attenuator effectual not only forEybutExmodes. Attenuation of more than 150 dB/mm for both modes is experimentally demonstrated.