Patent ID: 8660161

Claim:
An apparatus comprising: a semiconductor optical-output device formed on a substrate, wherein the optical-output device includes: a first electrically conductive mirror structure; a second electrically conductive mirror structure; a third electrically conductive mirror structure; a first active region optically and electrically located in a first optical cavity between the first mirror structure and the second mirror structure; a second active region optically and electrically located in a second optical cavity between the second mirror structure and the third mirror structure; a first electrical terminal electrically connected to the first mirror structure; a second electrical terminal electrically connected to the second mirror structure; a third electrical terminal electrically connected to the third mirror structure, wherein electrical current between the first electrical terminal and the second electrical terminal passes through the first active region, and electrical current between the third electrical terminal and the second electrical terminal passes through the second active region; a current source operatively coupled to apply a first constant-current value of forward-bias current to the first active region and to apply a second constant-current value of forward-bias current to the second active region; and a signal source operatively coupled to add a modulation-current signal to the forward-bias current applied to the first active region and to subtract the modulation-current signal from the forward-bias current applied to the second active region.