Fabrication of optical waveguide taper couplers utilizing SiO(2)

Stable, low-loss optical waveguides and micromirrors fabricated in acrylate polymers

Acrylate-based optical waveguides have been fabricated with optical loss of 0.5 dB/cm at 1300 nm by means of a new material system that ensures stable optical and mechanical properties over a wide temperature range. No increase in loss was measured after 500 h at temperatures up to 150 degrees C, and there was no significant increase in loss during short (<5 min) temperature excursions to 300 degrees C for bonding. Single-mode waveguides were fabricated with refractive indices for core and clad of 1.505 and 1.500, respectively, so that the mode field is very similar to that of single-mode silica fiber. Guides were fabricated on both planar and structured substrates of Si and GaAs as well as on substrates coated with metals and dielectrics. Fabrication involved spin coating and UV exposure to cross-link the polymer, but the substrate temperature did not exceed 180 degrees C. With this method guides could be fabricated on a range of substrates up to 125 cm in diameter, including those with multilayer metallization for multichip modules, providing optical interconnect capability. Microprism reflecting surfaces were fabricated in the waveguides to couple light out normal to the substrate. All the processing was compatible with normal semiconductor fabrication.

High efficiency light coupling from antiresonant reflecting optical waveguide to integrated photodetector using an antireflecting layer

The dispersion characteristics and radiation loss characteristics of ARROW (antiresonant reflecting optical waveguide), a novel single-mode slab waveguide, are analyzed in detail. The mechanism by which the waveguide produces a large amount of light radiation from the waveguide core to the semiconductor substrate is explained and some approximate formulas of propagation characteristics are obtained, which are useful for the design of ARROW. Two novel integrated structures of ARROW and photodetector are proposed to realize high coupling efficiency from waveguide to photodetector, small device size, and easy fabrication process. In these structures, an antireflecting (AR) layer is introduced to greatly enhance coupling efficiency. Their performance is discussed compared with the conventional waveguide structure. It is shown theoretically and experimentally that a high coupling efficiency (>90%) is achievable with short detector length in the ARROW structures.

Lightwave coupler utilizing a tapered buffer layer

We discuss the performance of a lightwave coupler utilizing a tapered buffer layer. The coupler with a ridge waveguide is fabricated on a glass substrate and high coupling efficiencies of 75% and 50% are measured for the operations of coupling from the waveguide to a light beam and from the laser beam into the waveguide, respectively. Further, experimental results of the rigid connection between the optical fiber and the waveguide are demonstrated. We also describe how the coupler differs from the conventional tapered guiding-layer coupler.

Coupling of guided light through a periodic multilayer

The structure of a coupler using a periodic multilayer between two waveguides is studied from the aspect of fabrication technology. The coupling is expected to be by Bragg instead of conventional evanescent waves. Because of the successful use of the peculiar nature of the Bragg waves, there is a chance of relaxing the fabrication tolerance. As a result, it is possible to make the coupler with standard design considerations and techniques that are not available for the fabrication of conventional evanescent wave couplers.