Surface emitting laser, photodetector and optical communication system using the same

• US 20070058982A1
• Filed: 09/13/2006
• Published: 03/15/2007
• Est. Priority Date: 09/13/2005
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Ueda, Tetsuzo, Onishi, Toshikazu, Ueda, Daisuke
• Granted Patent: US 7,873,090 B2
• Time in Patent Office: Days
• US Class Current: 398/152
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 31/035281 Shape of the body
• CPC Class Codes: H01L 31/105 the potential barrier being of the PIN type
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/04253 having specific optical properties, e.g. transparent electrodes
• CPC Class Codes: H01S 5/04256 characterised by the configuration
• CPC Class Codes: H01S 5/18311 using selective oxidation
• CPC Class Codes: H01S 5/18319 comprising a periodical structure in lateral directions
• CPC Class Codes: H01S 5/18344 characterized by the mesa, e.g. dimensions or shape of the mesa
• CPC Class Codes: H01S 5/18355 having a defined polarisation
• CPC Class Codes: H01S 5/18358 containing spacer layers to adjust the phase of the light wave in the cavity
• CPC Class Codes: H01S 5/18386 Details of the emission surface for influencing the near- or far-field, e.g. a grating on the surface
• CPC Class Codes: H01S 5/3432 the whole junction comprising only (AI)GaAs
• CPC Class Codes: H01S 5/423 having a vertical cavity
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A surface emitting laser includes a plurality of light-emitting portions for emitting laser light beams in different linearly polarized light directions. The light-emitting portions are formed on the substrate and located close to each other. The light-emitting portions include metal opening arrays through which light beams in different linearly polarized light directions respectively pass.

Claims

1. A surface emitting laser, comprising a plurality of light-emitting portions for emitting laser light in different linearly polarized light directions, the light-emitting portions being formed on a substrate and located close to each other.

2. The surface emitting laser of claim 1, wherein the light-emitting portions are formed within a region having a diameter of 100 μ

m.

3. The surface emitting laser of claim 1, wherein the light-emitting portions include respective metal opening arrays each including a metal layer and provided at a light-emitting surface of the light-emitting portion,

the metal layer includes a plurality of openings arranged at regular intervals in such a manner that the directions of the respective openings orthogonal to longitudinal directions thereof are oriented in a direction,

each of the openings has a shape having a width in the direction orthogonal to the longitudinal direction equal to or smaller than an oscillation wavelength of the laser light, and

the directions of the metal opening arrays orthogonal to the longitudinal directions differ from one another.

4. The surface emitting laser of claim 3, wherein each of the openings has a shape of one of an ellipse and a rectangular.

5. The surface emitting laser of claim 3, wherein the openings are arranged to form a square lattice, and

P satisfies a relationship:

0.9×

P≦

λ

×

(i²+j²)^1/2/(ε

₁ε

₂/(ε

₁+ε

₂))^1/2≦

1.1×

P

where P is a lattice pitch of the openings, ε

₁ is a dielectric constant of the metal layer, ε

₂ is a dielectric constant of a medium in contact with one of an upper surface and a lower surface of the metal layer, λ

is an oscillation wavelength of the laser light, and i and j are integers which are not negative.

6. The surface emitting laser of claim 3, wherein the openings are arranged to form a lattice in the metal layer, and

the direction of the lattice coincides with the longitudinal direction.

7. The surface emitting laser of claim 6, wherein each of the openings has a shape of one of an ellipse and a rectangular, and

the lattice is a hexagonal lattice.

8. The surface emitting laser of claim 3, wherein the openings are arranged to form a lattice in the metal layer, and

the direction of the lattice coincides with the direction orthogonal to the longitudinal direction.

9. The surface emitting laser of claim 8, wherein each of the openings has a shape of one of an ellipse and a rectangular, and

the lattice is a hexagonal lattice.

10. The surface emitting laser of claim 1, wherein the light-emitting portions include respective metal opening arrays each including a metal layer and provided at a light-emitting surface of the light-emitting portion,

the metal layer includes a plurality of openings arranged at regular intervals and each having a diameter equal to or smaller than an oscillation wavelength of the laser light,

the openings are arranged to form a rectangular lattice having two different lattice pitches, and

the lattice direction of the rectangular lattice differs among the metal opening arrays.

11. The surface emitting laser of claim 10, wherein one of the two lattice pitches satisfies a surface plasmon resonance condition with respect to the laser light.

12. The surface emitting laser of claim 10, wherein P satisfies a relationship:

0.9×

P≦

λ

×

(i²+j²)^1/2/(ε

₁ε

₂/(ε

₁+ε

₂))^1/2≦

1.1×

P

where P is one of the two lattice pitches, ε

₁ is a dielectric constant of the metal layer, ε

₂ is a dielectric constant of a medium in contact with one of an upper surface and a lower surface of the metal layer, λ

is an oscillation wavelength of the laser light, and i and j are integers which are not negative.

13. The surface emitting laser of claim 1, wherein the light-emitting portions include respective metal opening arrays each including a metal layer and provided at a light-emitting surface of the light-emitting portion,

the metal layer includes a plurality of openings arranged at regular intervals and each having the shape of a stripe having a width equal to or smaller than an oscillation wavelength of the laser light, and

the stripes extend in different directions among the metal opening arrays.

14. The surface emitting laser of claim 1, wherein the substrate has a semi-insulating property, and

the light-emitting portions are formed in respective regions which are electrically isolated from one another by a trench formed in the substrate.

15. The surface emitting laser of claim 14, wherein each of the light-emitting portions includes:

a stack of a plurality of semiconductor layers formed on the substrate; and

two electrodes for applying a voltage to the stack of semiconductor layers, and

the two electrodes are formed at one side of the substrate.

31. An optical communication system, comprising:

a transmitter including the surface emitting laser of claim 1 and configured to output a polarization multiplexed optical signal in multiple channels composed of a plurality of laser light beams in different linearly polarized light directions emitted from respective light-emitting portions of the surface emitting laser; and

a receiver for detecting the polarization multiplexed optical signal in multiple channels with the polarization multiplexed optical signal being divided into portions corresponding to the respective channels.

33. The optical communication system of claim 31, wherein the receiver includes:

an analyzer rotatably provided and allowing only a light beam in a specific linearly polarized light direction to pass therethrough depending on an angle of rotation; and

a light-receiving portion for detecting the light beam which has passed through the analyzer.

34. The optical communication system of claim 33, wherein the analyzer includes a metal opening array including a metal film, and

a plurality of openings each having a width in a direction orthogonal to a longitudinal direction equal to or smaller than a wavelength of the polarization multiplexed optical signal are formed in the metal film in such a manner that the directions of the respective openings orthogonal to the longitudinal directions thereof are oriented in one direction.

35. The optical communication system of claim 31, further comprising an optical fiber for transmitting the polarization multiplexed optical signal to the receiver with the linearly polarized light directions of the polarization multiplexed optical signal preserved.

36. The optical communication system of claim 35, wherein a plurality of laser light beams emitted from the respective light-emitting portions are directly coupled to the optical fiber.

37. The optical communication system of claim 31, wherein the polarization multiplexed optical signal is transmitted to the receiver by space transmission.

38. The optical communication system of claim 37, further comprising a lens for focusing the polarization multiplexed optical signal output from the transmitter.

16. A photodetector, comprising:

a substrate; and

a plurality of light-receiving portions formed on the substrate and located close to each other,

wherein each of the light-receiving portions detects, as detected light, light in different linearly polarized light directions out of light incident on light-receiving surfaces of the respective light-receiving portions.

17. The photodetector of claim 16, wherein the light-receiving portions are formed within a region having a diameter of 100 μ

m.

18. The photodetector of claim 16, wherein the light-receiving portions include respective metal opening arrays each including a metal layer and provided at the light-receiving surface of the light-receiving portion,

the metal layer includes a plurality of openings arranged at regular intervals in such a manner that the directions of the respective openings orthogonal to longitudinal directions thereof are oriented in a direction,

each of the openings has a shape with a width in the direction orthogonal to the longitudinal direction equal to or smaller than an oscillation wavelength of the laser light, and

the directions of the metal opening arrays orthogonal to the longitudinal directions differ from one another.

19. The photodetector of claim 18, wherein each of the openings has a shape of one of an ellipse and a rectangular.

20. The photodetector of claim 18, wherein the openings are arranged to form a square lattice, and

P satisfies a relationship:

0.9×

P≦

λ

×

(i²+j²)^1/2/(ε

₁ε

₂/(ε

₁+ε

₂))^1/2≦

1.1×

P

where P is a lattice pitch of the openings, ε

₁ is a dielectric constant of the metal layer, ε

₂ is a dielectric constant of a medium in contact with one of an upper surface and a lower surface of the metal layer, λ

is an oscillation wavelength of the detected light, and i and j are integers which are not negative.

21. The photodetector of claim 18, wherein the openings are arranged to form a lattice in the metal layer, and

the direction of the lattice coincides with the longitudinal direction.

22. The photodetector of claim 21, wherein each of the openings has a shape of one of an ellipse and a rectangular, and

the lattice is a hexagonal lattice.

23. The photodetector of claim 18, wherein the openings are arranged to form a lattice in the metal layer, and

the direction of the lattice coincides with the direction orthogonal to the longitudinal direction.

24. The photodetector of claim 23, wherein each of the openings has a shape of one of an ellipse and a rectangular, and

the lattice is a hexagonal lattice.

25. The photodetector of claim 16, wherein the light-receiving portions include respective metal opening arrays each including a metal layer and provided at the light-receiving surface of the light-receiving portion,

the metal layer includes a plurality of openings arranged at regular intervals and each having a diameter equal to or smaller than an oscillation wavelength of the laser light,

the openings are arranged to form a rectangular lattice having two different lattice pitches, and

the lattice direction of the rectangular lattice differs among the metal opening arrays.

26. The photodetector of claim 25, wherein one of the two lattice pitches satisfies a surface plasmon resonance condition with respect to the detected light.

27. The photodetector of claim 25, wherein P satisfies a relationship:

0.9×

P≦

λ

×

(i²+j²)^1/2/(ε

₁ε

₂/(ε

₁+ε

₂))^1/2≦

1.1×

P

where P is one of the two lattice pitches, ε

₁ is a dielectric constant of the metal layer, ε

₂ is a dielectric constant of a medium in contact with one of an upper surface and a lower surface of the metal layer, λ

is an oscillation wavelength of the laser light, and i and j are integers which are not negative.

28. The photodetector of claim 16, wherein the light-receiving portions include respective metal opening arrays each including a metal layer and provided at the light-receiving surface of the light-receiving portion,

the metal layer includes a plurality of openings arranged at regular intervals and each having the shape of a stripe having a width equal to or smaller than an oscillation wavelength of the detected light, and

the stripes extend in different directions among the metal opening arrays.

29. The photodetector of claim 16, wherein the substrate has a semi-insulating property, and

the light-receiving portions are formed in respective regions which are electrically isolated from one another by a trench formed in the substrate.

30. The photodetector of claim 29, wherein each of the light-receiving portions is a photodiode formed on the substrate and including two electrodes, and the two electrodes are formed at one side of the substrate.

32. The optical communication system of claim 31, wherein the receiver includes the photodetector of claim 16.