Semiconductor laser diode and optical communication system

• US 6,680,965 B2
• Filed: 01/25/2002
• Issued: 01/20/2004
• Est. Priority Date: 01/26/2001
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kinoshita, Junichi
• Primary Examiner(s): DAVIE, JAMES W
• Application Number:
  US10/057,310
• Publication Number:
  US 20020114369A1
• Time in Patent Office: 725 Days
• Field of Search: 372/96
• US Class Current: 372/96
• CPC Class Codes: H01S 5/026 Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers stabilisation of output H01S5/06
• CPC Class Codes: H01S 5/04254 characterised by the shape
• CPC Class Codes: H01S 5/1032 Coupling to elements comprising an optical axis that is not aligned with the optical axis of the active region
• CPC Class Codes: H01S 5/1071 Ring-lasers
• CPC Class Codes: H01S 5/18308 having a special structure for lateral current or light confinement
• CPC Class Codes: H01S 5/18313 by oxidizing at least one of the DBR layers
• CPC Class Codes: H01S 5/18333 only above the active layer
• CPC Class Codes: H01S 5/18344 characterized by the mesa, e.g. dimensions or shape of the mesa
• CPC Class Codes: H01S 5/2027 Reflecting region or layer, parallel to the active layer, e.g. to modify propagation of the mode in the laser or to influence transverse modes
• CPC Class Codes: H01S 5/2063 obtained by particle bombardment

Abstract

A surface emitting laser that provides an improved temperature characteristic, an improved optical output, and easy forming process. An optical communication system using this surface emitting laser is also provided. A surface emitting laser comprising: a substrate; a vertical cavity of layers formed on said substrate for propagating and resonating light along an axis vertical to a surface of said substrate, said light emitted from an active layer by current injection; and a reflective film disposed concentrically with the vertical axis around the outer periphery of said vertical cavity for reflecting the light from said active layer in a horizontal direction parallel to the surface of said substrate, the light emitted from said active layer forming a laser beam due to resonation, which laser beam is then emitted in a vertical direction. An optical communication system using the surface emitting laser.

Claims

1. A surface emitting laser comprising:

a substrate;

a vertical cavity of layers formed on said substrate for propagating and resonating light along an axis vertical to a surface of said substrate, said light emitted from an active layer by current injection; and

a reflective film disposed concentrically with the vertical axis around the outer periphery of said vertical cavity for reflecting the light from said active layer in a horizontal direction parallel to the surface of said substrate,

the light emitted from said active layer forming a laser beam due to resonation, which laser beam is then emitted in a vertical direction.

2. The surface emitting laser according to claim 1, wherein the light from said active layer are reflected by said reflective film to thereby resonate also in the horizontal direction.

3. The surface emitting laser according to claim 1, wherein said vertical cavity has a second-order or more optical periodicity along the vertical axis, and said light take the form of a radiation mode that propagates within said vertical cavity.

4. The surface emitting laser according to claim 3, wherein said vertical cavity further has a discontinuity in a phase of said periodicity.

5. The surface emitting laser according to claim 3, wherein said periodicity is asymmetrical along the vertical axis.

6. The surface emitting laser according to claim 1 further comprising:

a phase modulator provided between said vertical cavity and said reflective film for controlling the phase of the light.

7. The surface emitting laser according to claim 1, wherein said vertical cavity comprises said active layer.

8. The surface emitting laser according to claim 1, wherein said active layer is provided between said vertical cavity and said reflective film.

9. An optical communication system comprising:

a surface emitting laser comprising;

a substrate;

a vertical cavity of layers formed on said substrate for propagating and resonating along an axis vertical to a surface of said substrate, said light emitted from an active layer by current injection; and

a reflective film disposed concentrically with the vertical axis around the outer periphery of said vertical cavity for reflecting the light from said active layer in a horizontal direction parallel to the surface of said substrate, the light emitted from said active layer forming a laser beam due to resonation and being emitted in a vertical direction;

an optical fiber for transmitting the laser beam from said surface emitting laser therethrough; and

a photodetector for receiving the laser beam from said optical fiber and for converting the laser beam to an electrical current.

10. A surface emitting laser comprising:

a substrate;

a first DBR formed on said substrate and taking the form of a cylinder having a central axis vertical to a surface of said substrate and exhibiting a high reflectivity to light having a wavelength of λ

;

a first conductive type cladding layer formed on an overall surface of said first DBR;

an active layer formed on an overall surface of said first conductive type cladding layer for emitting light having a wavelength of λ

by current injection;

a second conductive type cladding layer formed on an overall surface of said active layer;

a second DBR taking the form of a cylinder formed on said second conductive type cladding layer and smaller in radius than said first DBR, said second DBR having the same central axis as said second conductive type cladding layer, said second DBR exhibiting a high reflectivity to the light having a wavelength of λ

;

said first DBR, said first conductive type cladding layer, said active layer, said second conductive type cladding layer, and said second DBR composing a vertical cavity;

a burying layer of a second conductive type formed on said second conductive type cladding layer around the outer periphery of said second DBR, said burying layer exhibiting a lower refractive index than said second DBR;

a reflective film covering the outer peripheries of said first DBR, said first conductive type cladding layer, said active layer, said second conductive type cladding layer, and said burying layer, said reflective film exhibiting a high reflectivity to the light having a wavelength of λ

;

the light from said active layer are resonated in a horizontal direction due to reflection of the light by said reflective film and focused in the vicinity of said central axis, the focused light are also resonated in a vertical direction by said vertical cavity to thereby form a laser beam, which is then extractable in the vertical direction from said second DBR.

11. The surface emitting laser according to claim 10 further comprising:

a first electrode for injecting a current via said first conductive type cladding layer into said active layer; and

a second ring-like electrode formed on said burying layer for injecting a current into said active layer via said burying layer and said second conductive type cladding layer.

12. The surface emitting laser according to claim 10, wherein said substrate is made of GaAs, each of said first and second DBRs comprising alternate layers of AlGaAs and AlAs, each of said first and second cladding layers being made of AlGaAs, said active layer being made of GaAs, said burying layer being made of GaAlAs.

13. The surface emitting laser according to claim 10, wherein said reflective film is made of an insulator.

14. The surface emitting laser according to claim 11, wherein said second electrode comprises a plurality of ring-like subelectrodes disposed concentrically.

15. A surface emitting laser comprising:

a substrate;

a cylindrical vertical cavity waveguide formed on said substrate and having a central axis vertical to said substrate, said waveguide comprising a lamination of alternate layers of different refractive indexes for causing light having a wavelength of λ

to resonate in a vertical direction;

a cladding layer formed around the outer periphery of said vertical cavity waveguide on said substrate, said cladding layer exhibiting a smaller refractive index than an average refractive index of said vertical cavity waveguide;

a conductive area formed around the outer periphery of said cladding layer on said substrate, said conductive area comprising a first conductive type cladding layer, an active layer formed on said first conductive type cladding layer for emitting light having a wavelength of λ

by current injection, and a second conductive type cladding layer formed on said active layer;

a reflective film covering the outer periphery of said conductive area and exhibiting a high reflectivity to the light having a wavelength of λ

;

the light from said active layer are resonated in a horizontal direction and also in a vertical direction by said vertical cavity to thereby form a laser beam, which is then extractable in the vertical direction from said vertical cavity waveguide.

16. The surface emitting laser according to claim 15 further comprising:

a first electrode for injecting a current via said first conductive type cladding layer into said active layer; and

a second ring-like electrode formed on said conductive area for injecting a current into said active layer via said second conductive type cladding layer.

17. The surface emitting laser according to claim 15, wherein said substrate is made of GaAs, said vertical cavity waveguide comprising alternate layers of AlGaAs and AlAs, each of said first and second cladding layers is made of AlGaAs, and said burying layer is made of GaAlAs.

18. The surface emitting laser according to claim 15, wherein said reflective film is made of an insulator.

19. The surface emitting laser according to claim 15, wherein said vertical cavity waveguide comprises a phase shifter flush with said active layer for shifting by λ

/4 the phase of light having a wavelength of λ

from said active layer.

20. The surface emitting laser according to claim 16, wherein said second electrode comprises a plurality of ring-like subelectrodes disposed concentrically.