| 摘要 |
PURPOSE:To couple the light beam with external optical parts such as optical fiber, etc., with good coupling efficiency without using a condenser lens by providing a film having the Fresnel zone structure for condensing the light on the far field on the surface of mirror from which the laser beam is emitted. CONSTITUTION:When a forward voltage is applied to the upper and lower electrodes, the light emitted from an active layer 1 reaches oscillation after repeating reflection between the mirrors 6 and 9 and the light is emitted as a laser beam 12 to the external side from the end surface after passing through a multilayered dielectric film of the mirror 6. The laser beam emitted here is not the diverging light which is emitted from the prior art but has the minimum beam diameter on the far field because it is condensed effectively on the far field by a refraction ring of the Fresnel zone film 13. Here, since the focus distance can be changed freely depending on the pattern of Fresnel zone film 13, location on the far field of minimum beam and a value of minimum beam (w) can be set freely. Thereby, the laser beam condensed on the far field can be obtained and a condenser lens for improving coupling efficiency with optical fiber is no longer necessary. |
