SURFACE EMITTING LASER, SURFACE EMITTING LASER ARRAY, AND IMAGE FORMING APPARATUS INCLUDING SURFACE EMITTING LASER

• US 20090135872A1
• Filed: 11/17/2008
• Published: 05/28/2009
• Est. Priority Date: 11/22/2007
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Uchida, Takeshi, Takeuchi, Tetsuya
• Granted Patent: US 7,839,913 B2
• Time in Patent Office: Days
• US Class Current: 372/44.10
• CPC Class Codes: G03G 15/04072 by laser
• CPC Class Codes: G03G 15/326 by application of light, e.g. using a LED array
• CPC Class Codes: G03G 2215/0404 Laser
• CPC Class Codes: H01S 2301/166 Single transverse or lateral mode
• CPC Class Codes: H01S 2301/173 The laser chip comprising special buffer layers, e.g. dislocation prevention or reduction
• CPC Class Codes: H01S 5/024 Arrangements for thermal management
• CPC Class Codes: H01S 5/02461 Structure or details of the laser chip to manipulate the heat flow, e.g. passive layers in the chip with a low heat conductivity
• CPC Class Codes: H01S 5/18313 by oxidizing at least one of the DBR layers
• CPC Class Codes: H01S 5/18358 containing spacer layers to adjust the phase of the light wave in the cavity
• CPC Class Codes: H01S 5/423 having a vertical cavity

Abstract

A surface emitting laser that oscillates at a wavelength λ includes an upper reflector, a lower reflector, an active layer, and a spacer layer. The spacer layer is a laminated structure that includes a first semiconductor sublayer having a composition of Al_xGa—_−xAs (1≧x≧0) and a second semiconductor sublayer having a composition of Al_yGa—_−yAs (1>y>0 and x>y).

Claims

1. A surface emitting laser that oscillates at a wavelength λ

, comprising;

an upper reflector;

a lower reflector;

an active layer disposed between the upper reflector and the lower reflector; and

a spacer layer disposed between the upper reflector or the lower reflector and the active layer,

wherein the spacer layer is a laminated structure that includes a first semiconductor sublayer having a composition of Al_xGa_1-xAs (1≧

x>

0) and a second semiconductor sublayer having a composition of Al_yGa_1-yAs (1>

y>

0 and x>

y).

2. The surface emitting laser according to claim 1, wherein the first semiconductor sublayer has a composition of Al_xGa_1-xAs (1≧

x≧

0.90).

3. The surface emitting laser according to claim 1, wherein the first semiconductor sublayer has a composition of AlAs.

4. The surface emitting laser according to claim 1, wherein each of the first semiconductor sublayer and the second semiconductor sublayer has an optical thickness of an integral multiple of λ

/2.

5. The surface emitting laser according to claim 1, wherein the first semiconductor sublayer has a same optical thickness as that of the second semiconductor sublayer.

6. The surface emitting laser according to claim 1, wherein the first semiconductor sublayer is disposed closer to the active layer than the second semiconductor sublayer is, and the first semiconductor sublayer has a larger optical thickness than the second semiconductor sublayer.

7. The surface emitting laser according to claim 1, wherein the active layer is formed of GaInP, and the wavelength λ

ranges from 630 to 690 nm.

8. The surface emitting laser according to claim 7, wherein the second semiconductor sublayer has a composition of Al_yGa_1-yAs (1>

y≧

0.50).

9. The surface emitting laser according to claim 7, wherein the second semiconductor sublayer has a composition of Al_yGa_1-yAs (0.60≧

y≧

0.50).

10. The surface emitting laser according to claim 1, wherein the spacer layer includes an uppermost AlGaAs sublayer, with an Al/(Al+Ga) atomic ratio being 0.95 or less.

11. The surface emitting laser according to claim 1, wherein a cavity length defined by the upper reflector and the lower reflector is at least 2 μ

m.

12. The surface emitting laser according to claim 3, wherein the first semiconductor sublayer has a thickness of 1 μ

m or less.

13. The surface emitting laser according to claim 1, wherein the upper reflector and the lower reflector are multilayer reflectors.

14. A surface emitting laser according to claim 1, wherein the surface emitting laser is included in a plurality of surface emitting lasers as part of a surface emitting laser array, and wherein the plurality of surface emitting lasers are one- or two-dimensionally disposed on a substrate.

15. An image forming apparatus, comprising:

a photo conductor;

a charging unit configured to electrify the photo conductor to produce an electrified photo conductor;

a light-beam irradiation unit configured to irradiate the electrified photo conductor with light to form an electrostatic image; and

a developing unit configured to develop the electrostatic image,

wherein the light-beam irradiation unit includes a surface emitting laser as a light source, in which the surface emitting laser includes;

an upper reflector;

a lower reflector;

an active layer disposed between the upper reflector and the lower reflector; and

a spacer layer disposed between the upper reflector or the lower reflector and the active layer,

wherein the spacer layer is a laminated structure that includes a first semiconductor sublayer having a composition of Al_xGa_1-xAs (1≧

x>

0) and a second semiconductor sublayer having a composition of Al_yGa_1-yAs (1>

y>

0 and x>

y).

16. A surface emitting laser that oscillates at a wavelength λ

, comprising;

an upper reflector;

a lower reflector;

an active layer disposed between the upper reflector and the lower reflector; and

a spacer layer disposed between the upper reflector or the lower reflector and the active layer,

wherein the spacer layer is a laminated structure that includes a first semiconductor sublayer and a second semiconductor sublayer, the second semiconductor sublayer having a lower thermal conductivity than the first semiconductor sublayer.

17. A surface emitting laser according to claim 16, wherein each of the first semiconductor sublayer and the second semiconductor sublayer has an optical thickness of an integral multiple of λ

/2.

18. An image forming apparatus, comprising:

a photo conductor;

a charging unit configured to electrify the photo conductor to produce an electrified photo conductor;

a light-beam irradiation unit configured to irradiate the electrified photo conductor with light to form an electrostatic image; and

a developing unit configured to develop the electrostatic image,

wherein the light-beam irradiation unit includes a surface emitting laser array as a light source, in which the surface emitting laser array includes a plurality of surface emitting lasers, and in which each surface emitting laser includes;

an upper reflector;

a lower reflector;

an active layer disposed between the upper reflector and the lower reflector; and

a spacer layer disposed between the upper reflector or the lower reflector and the active layer,

wherein the spacer layer is a laminated structure that includes a first semiconductor sublayer having a composition of Al_xGa_1-xAs (1≧

x>

0) and a second semiconductor sublayer having a composition of Al_yGa_1-yAs (1>

y>

0 and x>

y)