| 摘要 |
PURPOSE:To reduce the absorption loss of a light by placing two prisms at a narrower interval than the wavelength of the light to be modulated, and forming the opposite surfaces and the reverse surfaces of each prism stepwise or in the shape of a saw tooth. CONSTITUTION:Prisms 11, 12 having saw tooth-shaped cross sections are combined. Each plane for forming a saw tooth cross section of the outside is parallel to each other and vertical to the surface for forming step difference, and the light is made incident in parallel roughly to its step difference. A reflection preventing film 21 is formed on each plane of the saw tooth part. Therefore, the light is made incident almost vertically on the plane for forming the saw tooth cross section, is made incident and emitted at an incident angle equal to a prism angle on the overlapped plane of the prisms 11, 12, and the total reflection type optical modulator of a thin type prism is realized. According to this constitution, when the number of saw teeth of the section is denoted as (m), the tickness of an inclined part of the prism is reduced to 1/m. |
