Electro-optical modulator

摘要

A downsized, low-power electro-optical modulator that achieves reducing both of the additional resistance in the modulation portion and the optical loss each caused by electrodes at the same time is provided. The electro-optical modulator includes a rib waveguide formed by stacking a second semiconductor layer 9 having a different conductivity type from a first semiconductor layer 8 on the first semiconductor layer 8 via a dielectric film 11, and the semiconductor layers 8 and 9 are connectable to an external terminal via highly-doped portions 4 and 10, respectively. In a region in the vicinity of contact surfaces of the semiconductor layers 8 and 9 with the dielectric film 11, a free carrier is accumulated, removed, or inverted by an electrical signal from the external terminal, and whereby a concentration of the free carrier in an electric field region of an optical signal is modulated, so that a phase of the optical signal can be modulated. At least one of the semiconductor layers 8 and 9 is wider than the stacked portion. At least one of the highly-doped portions 4 and 10 is formed outside the stacked portion.

主权项

1. An electro-optical modulator comprising:
a first semiconductor layer; a second semiconductor layer; and a dielectric film, wherein
the first semiconductor layer and the second semiconductor layer are being doped so that a conductivity type of the first semiconductor layer is different from that of the second semiconductor layer,a portion of the first semiconductor layer is a first highly-doped portion with a high doping concentration compared with the other portion of the first semiconductor layer,a portion of the second semiconductor layer is a second highly-doped portion with a high doping concentration compared with the other portion of the second semiconductor layer,the first highly-doped portion and the second highly-doped portion each is connectable to an external terminal directly or via other member,a rib waveguide is formed by stacking the second semiconductor layer on an upper side of the first semiconductor layer via the dielectric film,in a region in the vicinity of contact surfaces of the first semiconductor layer and the second semiconductor layer with the dielectric film, a free carrier is accumulated, removed, or inverted by an electrical signal from the external terminal, and whereby a concentration of the free carrier in an electric field region of an optical signal is modulated, so that a phase of the optical signal can be modulated,at least one of the first semiconductor layer and the second semiconductor layer is wider than a stacked portion including the first semiconductor layer, the dielectric film, and the second semiconductor layer,at least one of the first highly-doped portion and the second highly-doped portion is formed outside the stacked portion,a portion of the first semiconductor layer on which the dielectric film and the second semiconductor layer are stacked has a concavo-convex shape,the dielectric film and the second semiconductor layer are stacked on the portion so as to be fitted in the concavo-convex shape,the concavo-convex shape of the first semiconductor layer is a shape having a curvature, andwith respect to a thickness W (nm) of a region of the second semiconductor layer in which a free carrier is accumulated, removed, or inverted, at least one of a maximum width of a convex portion in the concavo-convex shape of the first semiconductor layer and a maximum width of a buried portion of the second semiconductor layer buried in a concave portion of the first semiconductor layer is 2 W (nm) or less.