| 摘要 |
PURPOSE:To obtain a coupler having excellent reliability, reproducibility and yield by widely and thickly forming the coupler in the layer direction of the waveguide layer of a coupler part, thereby widening the effective process range of working depth and working position and widening the degree of freedom of processes and facilitating control of branching ratios and coupling efficiency. CONSTITUTION:The working front end of a slit 2 is confined to the neighborhood of the center of a field distribution 11b in a layer direction (i.e., to the active layer 7b part where the center of the field distribution 11b exists) and is subjected to wave front division in a lamination direction. The thickness of the waveguide layer 7b of the coupler part 3 is increased in such a manner, by which the working depth of the slit 2 is widened in its effective range and the field distribution 11b in the coupler part 3 is made broader than the field distribution 11a before the entry to the coupler part 3 and, therefore, the control of the branching ratio is facilitated. Fine processing techniques, such as etching by a convergent ion beam and etching by a reactive ion beam are utilizable in formation of the slit 2. |
