Optical module

1. An optical module comprising:

an optical semiconductor device in which a semiconductor laser and an optical modulator are integrated, the optical semiconductor device including an anode electrode of the semiconductor laser and an anode electrode of the optical modulator, the optical semiconductor device including a cathode electrode common to the semiconductor laser and the optical modulator;

a bypass capacitor including a lower electrode and an upper electrode, the bypass capacitor being connected in parallel to the semiconductor laser;

a dielectric substrate having an upper surface and a lower surface, the optical semiconductor device and the bypass capacitor being surface-mounted on the upper surface, the dielectric substrate having a conductor pattern on the upper surface, the cathode electrode and the lower electrode being bonded to the conductor pattern; and

a conductor block supporting the lower surface of the dielectric substrate,

the lower electrode of the bypass capacitor having an overlap area overlapping with the upper surface of the dielectric substrate, the lower electrode of the bypass capacitor having an overhang area overhanging from the upper surface of the dielectric substrate.

2. The optical module according to claim 1 , wherein

the conductor pattern includes a bonding portion bonded to the cathode electrode, the conductor pattern including an extension portion extending from the bonding portion toward the bypass capacitor and at least partially overlapping with the lower electrode, and

the extension portion has a section outside the lower electrode, the section being smaller in area than the overhang area of the lower electrode.

3. The optical module according to claim 2 , wherein the extension portion includes a pad bonded to the overlap area and a line connecting the bonding portion and the pad.

4. The optical module according to claim 2 , further comprising a spacer between the overlap area of the lower electrode and the extension portion of the conductor pattern, the spacer electrically connecting the overlap area and the extension portion.

5. The optical module according to claim 4 , wherein the spacer includes an insulating substrate and a conductor penetrating the insulating substrate.

6. The optical module according to claim 4 , wherein the spacer includes an insulating substrate having a recess on a side surface and a castellation electrode in the recess.

7. The optical module according to claim 6 , wherein the castellation electrode is bonded to the extension portion of the conductor pattern with gold-tin solder.

8. The optical module according to claim 1 , wherein the entire lower surface of the dielectric substrate is opposed and fixed to the conductor block.

9. The optical module according to claim 1 , wherein

the dielectric substrate has a first portion fixed to the conductor block, and

the dielectric substrate has a second portion overhanging from the conductor block.

10. The optical module according to claim 9 , wherein the first portion and the second portion, of the dielectric substrate, are adjacent to each other only in one direction.

11. The optical module according to claim 9 , wherein the first portion and the second portion, of the dielectric substrate, are adjacent to each other in at least two intersecting directions.

12. The optical module according to claim 9 , wherein

the conductor block has a first area and a second area on an upper surface, the second area being lower than the first area,

the first portion of the dielectric substrate is fixed to the first area, and

the second portion of the dielectric substrate is spaced from and opposed to the second area.

13. The optical module according to claim 12 , wherein the overhang area of the lower electrode is not opposed to the first area and is spaced from and opposed to the second area.

14. The optical module according to claim 9 , wherein the second portion of the dielectric substrate is not opposed to the conductor block.

15. The optical module according to claim 14 , wherein the overhang area of the lower electrode is not opposed to the conductor block.

16. An optical module comprising:

an optical semiconductor device in which a semiconductor laser and an optical modulator are integrated, the optical semiconductor device including an anode electrode of the semiconductor laser and an anode electrode of the optical modulator, the optical semiconductor device including a cathode electrode common to the semiconductor laser and the optical modulator;

a bypass capacitor including a lower electrode and an upper electrode, the bypass capacitor being connected in parallel to the semiconductor laser;

a dielectric substrate having an upper surface and a lower surface, the optical semiconductor device and the bypass capacitor being surface-mounted on the upper surface, the dielectric substrate having a conductor pattern on the upper surface, the cathode electrode and the lower electrode being bonded to the conductor pattern;

a spacer between the bypass capacitor and the conductor pattern, the spacer electrically connecting the bypass capacitor and the conductor pattern; and

a conductor block supporting the lower surface of the dielectric substrate,

the conductor pattern including a bonding portion bonded to the cathode electrode, the conductor pattern including a pad bonded to the lower electrode,

the lower electrode being larger in area than the pad.

17. The optical module according to claim 16 , wherein the spacer includes an insulating substrate and a conductor penetrating the insulating substrate.

18. The optical module according to claim 16 , wherein the spacer includes an insulating substrate having a recess on a side surface and a castellation electrode in the recess.

19. The optical module according to claim 18 , wherein the castellation electrode is bonded to the conductor pattern with gold-tin solder.