Semiconductor optical modulator

• US 4,811,353 A
• Filed: 02/18/1987
• Issued: 03/07/1989
• Est. Priority Date: 02/21/1986
• Status: Expired due to Term

• Current Assignee: KDDI Corporation
• Original Assignee: Kokusai Densin Denwa Kabushiki Kaisha
• Inventors: Suzuki, Masatoshi, Noda, Yukio, Akiba, Shigeyuki, Kushiro, Yukitoshi
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Epps, Georgia Y.
• Application Number:
  US07/015,954
• Time in Patent Office: 748 Days
• Field of Search: 372/26, 372/44, 372/45, 372/46, 372/50, 372/96
• US Class Current: 372/45.01
• CPC Class Codes: G02F 1/025 in an optical waveguide structure G02F1/017, G02F1/2257 take precedence
• CPC Class Codes: H01S 5/0265 Intensity modulators intra-cavity modulators H01S5/0625
• CPC Class Codes: H01S 5/12 the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers comprising a photonic bandgap structure H01S5/11; surface-emitting lasers H01S5/18
• CPC Class Codes: H01S 5/16 Window-type lasers, i.e. with a region of non-absorbing material between the active region and the reflecting surface H01S5/14 takes precedence
• CPC Class Codes: H01S 5/164 with window regions comprising semiconductor material with a wider bandgap than the active layer
• CPC Class Codes: H01S 5/168 with window regions comprising current blocking layers

Abstract

A semiconductor optical modulator is disclosed which is capable of high-speed modulation without the necessity of increasing the modulating voltage. The present invention has its feature in that the carrier density of the clad layer adjoining the optical waveguide layer 3 is gradually raised toward the p-n junction or Schottky junction, thereby increasing the width of the depletion layer to decrease the junction capacitance.

Claims

1. In a semiconductor optical modulator having a substrate, a clad layer having a carrier density gradient and composed of at least one layer formed on the substrate, an optical waveguide layer on the clad layer for controlling light, semiconductor means for defining a p-n junction, said means being disposed on the optical waveguide layer, and the clad layer having a carrier density gradually decreasing as distance away from the optical waveguide toward the substrate increases.

2. In a semiconductor optical modulator according to claim 1, in which the carrier density of the clad layer continuously decreases progressively as said distance increases.

3. In a semiconductor optical modulator according to claim 1, in which the carrier density of the clad layer discretely decreases.

4. In a semiconductor optical optical modulator according to claim 1, in which the carrier density of the clad layer decreases from 10¹⁴ cm^-3 to 5×

10¹⁵ cm^-3.

5. In a semiconductor optical modulator according to claim 1, in which the thickness of the clad layer is about 1.4 μ

m.

6. In a semiconductor optical modulator according to claim 1, including a distributed feedback semiconductor laser formed therewith in a monolithic integration therewith, and the substrate and clad layer are common to the semiconductor optical modulator and the distributed feedback semiconductor laser.

7. In a semiconductor optical modulator having a substrate, a clad layer having a carrier density gradient and composed of at least one layer formed on the substrate, an optical waveguide layer on the clad layer for controlling light, means for defining a Schottky junction, said means being disposed on the optical waveguide layer, and the clad layer having a carrier density gradually decreasing as distance away from the optical waveguide toward the substrate increases.

8. In a semiconductor optical modulator according to claim 7, in the carrier density of the clad layer continuously decreases progressively as said distance increases.

9. In a semiconductor optical modulator according to claim 7, in which the carrier density of the clad layer discretely decreases.

10. In a semiconductor optical modulator according to claim 7, in which the carrier density of the clad layer decreases from 10¹⁴ cm^-3 to 5×

10¹⁵ cm^-3.

11. In a semiconductor optical modulator according to claim 7, in which the thickness of the clad layer is about 1.4 μ

m.

12. In a semiconductor optical modulator according to claim 7, including a distributed feedback semiconductor laser formed therewith in a monolithic integration therewith, and the substrate and clad layer are common to the semiconductor optical modulator and the distributed feedback semiconductor laser.