Patent ID: 8269297

Claim:
An apparatus, comprising: a waveguide having an input portion and first and second output portions, the input portion being configured to receive an optical signal, and the first and second output portions supplying first and second portions of the optical signal, respectively; a first photodiode configured to receive the first portion of the optical signal; a second photodiode configured to receive the second portion of the optical signal; first and second doped semiconductor layers, an interface between the first and second doped semiconductor layers constituting a first pn-junction, the first and second doped semiconductor layers being provided between the first photodiode and the first output portion of the waveguide; third and fourth doped semiconductor layers, an interface between the third and fourth doped semiconductor layers constituting a second pn-junction, the third and fourth doped semiconductor layers being provided between the second photodiode and the second output portion of the waveguide, wherein the first and second photodiodes are configured to be reversed biased and the first pn-junction is configured to be biased such that the first pn-junction is included in a first depletion region, and the second pn-junction is configured to be biased such that the second pn-junction is included in a second depletion region, wherein the first, second, third and fourth semiconductor layers include an aluminum containing quartenary semiconductor alloy and do not include a phosphorus containing quartenary semiconductor alloy.