| 摘要 |
PURPOSE:To obtain an echelette grating with a single blaze angle by forming a lattice groove in a film provided on a concaved substrate, by making the grate- shaped film a mask for the substrate and by treating the substrate by ion or electron etching. CONSTITUTION:The film 3 is provided on the concaved grating substrate 2 and is coated with the photoresist 4. An interference fringe that is an original form of a diffraction grating is printed on the substrate, which is developed to leave the grate-shaped film 3. The film 3 plays a role of the mask in the ion or electron etching process. The etching rate is minimum when the process is performed in the direction perpendicular or approximately parallel to the incident direction of ions, and it is maximum in a face that makes a certain angle with the incident beam. Accordingly when the ion beam I is applied to the surface of the substrate at a proper angle beta as shown in Figure, the etching is carried out quickly in the direction perpendicular to the surface of substrate, and is carried out slowly in the direction perpendicular to the grate face, then the etching progresses as shown by (A), (B) and (C) in Figure, the asymmetric groove is formed. An alpha is a blaze angle. |
