Abstract

Low-loss coupling of a fiber to an InGaAsP/lnP waveguide requires that the small, elliptic spot of the former be matched to the large, circular spot of the latter. For this purpose lensed fibers, e.g., are in use, but they have the drawback of tight alignment tolerances. Integrated waveguide tapers circumvent this problem.^1-5 This paper presents novel waveguide fiber ports that use thickness tapering. Based on a previously reported mode-converter design,⁶ such components have been realized by using a new fabrication technology. The major virtues of this component are mode expansion by vertical, i.e., thickness, tapering (no resolution limits as imposed by lithography of a horizontal wedge); a simple epilayer sequence that avoids MQW structures or other sophisticated epitaxial techniques; singlemode waveguiding throughout; and adaptation of a taper profile to modal-field evolution.

© 1993 Optical Society of America