| 摘要 |
PROBLEM TO BE SOLVED: To solve the problems where the increase in the parasitic capacitance and the trade-off of pileup are the problems in a low reflection window structure in a conventional electroabsorption optical modulating element, because the capacitance density of a p-n junction in the window structure is high, as compared with a pin junction as an optical absorption region, also field application to the optical absorption region becomes insufficient, when an electrode structure is moved away from the bonding part of the optical absorption region and the window structure and the discharge of photocarriers generated in the optical absorption region becomes difficult. SOLUTION: Between the optical absorption region and the low light reflecting window structure, an undoped waveguide structure comprising such a composition wavelength and film thickness structure that the composition wavelength of each multilayer, constituting the waveguide structure is sufficiently shorter than signal light and the average refractive index is at the same level as the optical absorption region, is provided. When the electrode structure is formed so as to cross the junction interface of the optical absorption region and the undoped waveguide, and not to be over the junction interface of the undoped waveguide and the window structure, both of the increase of the parasitic capacitance due to the pn junction of the window structure and the pileup are suppressed simultaneously. COPYRIGHT: (C)2008,JPO&INPIT |
