Providing a drive signal for optical modulator portions
A first transmission line comprises a first pair of electrodes receiving an electrical drive comprising first and second drive signals, which are loaded by a first series of p-n junctions applying optical phase modulation to respective optical waves propagating over a first section of the first and second optical waveguide arms of an MZI. A second transmission line comprises a second pair of electrodes configured to receive the electrical drive after an electrical signal delay. The second pair of electrodes are loaded by a second series of p-n junctions applying optical phase modulation to the respective optical waves propagating over a second section of the first and second optical waveguide arms after propagation over the first section. An electrode extension structure provides the electrical drive to the second pair of electrodes, and comprises an unloaded transmission line portion imposing the electrical signal delay based on an optical signal delay.
1 . An apparatus comprising:
an integrated circuit comprising
an optical waveguide structure forming a Mach-Zehnder interferometer that includes a first optical waveguide arm and a second optical waveguide arm,
a first electrical input port configured to receive a first drive signal,
a second electrical input port configured to receive a second drive signal,
a first transmission line comprising a first pair of electrodes on a first electrode layer configured to receive an electrical drive comprising the first drive signal and the second drive signal, where the first pair of electrodes are loaded by a first series of p-n junctions configured to apply optical phase modulation to respective optical waves propagating over a first section of the first and second optical waveguide arms, and
a second transmission line comprising a second pair of electrodes on the first electrode layer configured to receive the electrical drive after an electrical signal delay, where the second pair of electrodes are loaded by a second series of p-n junctions configured to apply optical phase modulation to the respective optical waves propagating over a second section of the first and second optical waveguide arms after propagation over the first section of the first and second optical waveguide arms;
an electrode extension structure configured to provide the electrical drive to the second pair of electrodes, where the electrode extension structure includes a transmission line portion that is in one or more layers above or below the first electrode layer; and
a radio-frequency (RF) shield disposed between at least a portion of the electrode extension structure and the first electrode layer, and configured to isolate at least a portion of the first transmission line from at least a portion of the second transmission line.
2 . The apparatus of claim 1 , further comprising
a first junction among three wires that include a first wire connected to the first electrical input port, a second wire connected to a first electrode of the first pair of electrodes, and a third wire connected to a first electrode of the electrode extension structure, and
a second junction among three wires that include a fourth wire connected to the second electrical input port, a fifth wire connected to a second electrode of the first pair of electrodes, and a third wire connected to a second electrode of the electrode extension structure.
3 . The apparatus of claim 1 , wherein the first series of p-n junctions and the second series of p-n junctions are of substantially equal lengths.
4 . The apparatus of claim 1 , wherein the transmission line portion is in a layer of the integrated circuit different from the first electrode layer.
5 . The apparatus of claim 1 , wherein the transmission line portion is in a layer of a device that is coupled to the integrated circuit by a controlled collapse chip connection.
6 . The apparatus of claim 1 , wherein the integrated circuit includes driver circuitry configured to provide the first and second drive signals.
7 . The apparatus of claim 6 , wherein the driver circuitry includes a first amplifier circuit that provides the first drive signal to the first pair of electrodes of the first transmission lines, and a second amplifier circuit that provides the second drive signal to the second pair of electrodes of the second transmission lines.
8 . The apparatus of claim 6 , wherein the circuitry comprises a differential electrical drive where the second drive signal has a negative amplitude relative to the first drive signal, and the optical phase modulation comprises a differential optical phase modulation between the first and second optical waveguide arms.
9 . The apparatus of claim 1 , wherein the integrated circuit is a first integrated circuit, and the first integrated circuit is coupled to a second integrated circuit that includes driver circuitry configured to provide the first and second drive signals.
10 . The apparatus of claim 9 , wherein the driver circuitry comprises signal splitting circuitry coupled to a differential signal output port of an electrical circuit.
11 . The apparatus of claim 9 , wherein the driver circuitry comprises transistor-level circuitry within an electrical circuit that includes two pairs of differential signal output ports.