High conductivity buried layer in optical waveguide

DETAILED DESCRIPTION According to the present invention, an optical device is provided which has an active region for radiation propagation and injecting means for injecting charge carriers into the active region, characterised in that the injecting means incorporates a high conductivity buried layer between two wafer elements of a bonded wafer couplet and the device incorporates concentrating means between the buried layer and the active region for concentration of charge carriers in the active region.
The invention provides an advantage that the high conductivity layer provides an electrical path for biasing the device with reduced dissipation compared to prior art optical devices.
Moreover, the invention provides an advantage that the device modulates radiation more effectively than prior art devices because the concentrating means concentrates charge carriers in the active region where radiation propagates.
The device may incorporate a dielectric insulating layer for electrically isolating it within the wafer couplet.
This provides an advantage, for example when several devices are fabricated together on the couplet, that the device is isolated from the wafer elements.
The active region may incorporate dopant impurity to a concentration to a concentration of less than 10.
sup.
16 atoms cm.
sup.
-3.
This provides an advantage that the active region is capable of providing a propagation path for radiation where radiation attenuation is less than 1 dB cm.
sup.
-1.
The active region may provide radiation waveguiding means with refractive index modulatable by the injecting means.
This provides a convenient device configuration for modulating radiation propagating in the active region, especially when the active region comprises material having a centro-symmetrical crystal structure.
The concentrating means may comprise a first electrode located upon one side of the active region and the device includes a second electrode located upon the other side.
This provides an advantage of being a simple practical configuration for the device