| 摘要 |
PURPOSE:To allow good-quality light transmission without causing wavelength chirping by admitting only the surely modulated laser beam to an optical fiber coupled to an output port even if a sepn. layer has about the thickness sufficient for executing directional coupling type optical modulation. CONSTITUTION:This modulator has an n type InGaAsP waveguide layer 2 which is a 1st waveguide, an n type InP sepn. layer 3, an n type InGaAsP waveguide layer 4 which is a 2nd waveguide, an electrode 6 of the directional coupling type optical modulator part MD which passes the current to change the refractive index in the one waveguide layer and an electrode 6' of an optical absorber part AD which passes a bias current in order to consume energy as a photocurrent when the laser beam is made incident on the light absorbing layer 4'. Only the surely modulated layer beam is, therefore, made incident to the optical fiber coupled to the output port Po even if the sepn. layer 3 between the waveguide layer which is the 1st waveguide 2 and the waveguide layer 4 which is the 2nd waveguide has about the thickness sufficient to execute the directional coupling type optical modulation. The good-quality light transmission without causing the wavelength chirping is executed in this way. |
