| 摘要 |
PURPOSE:To obtain a pi shifted diffraction grating without a step, by forming the pi shifted diffraction grating on a thin film of a semiconductor substrate, and simultaneously etching a positive part and a negative part with the thin film as a mask. CONSTITUTION:An SiO2 film 12 is formed on an InP substrate 11. Then irregularities are provided at the period of the length of the resonator of a semiconductor laser. Negative type photoresist 13 is applied on the entire surface. Thereafter, positive type photoresist 14 is applied on the entire surface. The positive type photoresist 14 is made to remain only in recess parts by a photographic method. With the resist 14 as a mask, the resist 13 at the projecting parts is removed. After the resist 14 is removed, the resist 14 is applied again on the entire surface. Exposure is performed by a two-luminous-flux exposing method. Then development is performed. With the resist 14 as a mask, a first diffraction grating is transferred on the SiO2. The resist 13 is developed. With the resist 13 as a mask, the diffraction grating is transferred on the SiO2 12. Thus the SiO2 diffraction grating, which is shifted by pi, can be formed. In this way the pishifted diffraction grating without error can be formed. |
