a semiconductor electrooptic monolithic component comprising successively a first section capable of emitting light at a first wavelength and including a first active layer , a second section capable of absorbing light at the said first wavelength and including a second active layer , and a third section capable of detecting light at a second wavelength and including a third active layer . the component is characterized in that the second active layer is designed to ensure in the said second section an absorption higher than that which would be allowed by an active layer identical to the said first layer .