Optical modulation device

1. An optical modulation device comprising:

an optical modulator;

an insulating layer;

an RC circuit including a resistor and a capacitor connected in series;

a bonding wire connected between the optical modulator and the RC circuit;

a first metal layer provided on the insulating layer; and

a second metal layer that has a width larger than that of the first metal layer and is provided on the insulating layer,

the second metal layer being connected with a ground potential and being connected to the RC circuit via the first metal layer.

2. The optical modulation device as claimed in claim 1 , wherein the bonding wire has a length of 1.5 mm or less.

3. The optical modulation device as claimed in claim 1 , wherein the bonding wire is connected between the optical modulator and a region of an electrode on an upper face of the capacitor that is closer to the optical modulator than a center of the electrode.

4. The optical modulation device as claimed in claim 1 , wherein the first metal layer and the second metal layer are coupled to each other via a via hole penetrating the insulating layer.

5. The optical modulation device as claimed in claim 1 , wherein the optical modulator is integrated with a semiconductor laser.

6. The optical modulation device as claimed in claim 1 further comprising:

a transmission line that is composed of a distributed line and receives an input signal; and

a connecting element connected between the transmission line and the optical modulator, the connecting element being comprised by a bonding wire.

7. The optical modulation device as claimed in claim 1 wherein the first metal layer has a first region and a second region having a different width.

8. The optical modulation device as claimed in claim 7 wherein the first metal layer has a region of a taper shape connecting the first region and the second region.

9. The optical modulation device as claimed in claim 1 , wherein the first metal layer has a first region having a first width and a second region having a second width and adjacent to the resistor,

the first width being smaller than the second width.

10. The optical modulation device as claimed in claim 9 , wherein the first metal layer has a region of a taper shape connecting the first region and the second region.

11. The optical modulation device as claimed in claim 1 , wherein the first metal layer has a first region having a first width and a second region having a second width and adjacent to the capacitor,

the first width being smaller than the second width.

12. The optical modulation device as claimed in claim 11 , wherein the first metal layer has a region of a taper shape connecting the first region and the second region.

13. The optical modulation device as claimed in claim 1 , wherein the first metal layer is a distributed line.

14. The optical modulation device as claimed in claim 13 , wherein the distributed line is a coplanar line or a micro strip line.

15. The optical modulation device as claimed in claim 14 , wherein:

the coplanar line is structured with the first metal layer and the second metal layer on the insulating layer; and

the inductor component is determined by a length of the first metal layer and characteristic impedance determined by a distance between the first metal layer and the second metal layer or a width of the first metal layer.

16. The optical modulation device as claimed in claim 14 , wherein:

the micro strip line is structured with the first metal layer on an insulating layer and a metal layer that is provided under the insulating layer, and has a ground potential; and

the inductor component is determined by a length of the first metal layer and characteristic impedance determined by a thickness of the insulating layer or a width of the first metal layer.