| 摘要 |
PURPOSE:To make high-accuracy control of a phase shift magnitude, by forming a recess individually on a substrate in end ports of mutually different positions of an optical wave-guiding path for reference light of both interferometers and using a surface of the recess as a reflecting surface of the reference light. CONSTITUTION:Recesses 15, 25 are formed on a substrate 1 at the end parts of optical wave-guiding paths 13, 23 of asymmetrical X-branching optical wave- guiding paths 10, 20. Beams of light reflected respectively by the reflecting surfaces formed in the recesses 15, 25 become beams of reference light. These light path differences equal to the distance between a reflecting surface of the recess 15 and that of the recess 25 and a phase difference corresponding to this light path difference generates between 2 beams of reference light. The distance between recesses 15 and 25 depend upon the accuracy of a photomask for formation of recesses 15, 25 and it stays unchanged even if the position of the photomask deviates move or less from the substrate 1. Consequently, when the photomask is kept manufactured with high accuracy, the required light path difference can be obtained. |
