JP2011181786A - Surface emitting laser element, surface emitting laser array, optical scanner, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface emitting laser element that has a stable polarization direction while controlling oscillation in high-order lateral mode. <P>SOLUTION: The surface emitting laser element has a p-side electrode 113, provided surrounding a projection region, on an emitting surface where laser light is projected. In the projection region, a mode filter 115 which is an optically transparent dielectric film provided surrounding a center part of the projection region is formed to an optical thickness of λ/4. Then a part of relatively high reflectivity of the center part of the projection region is different in length with respect to two mutually orthogonal directions (X-axial direction and Y-axial direction) in the emitting surface, and a current injection region of the p-side electrode 113 which is in contact with a contact layer 109 has shape anisotropy. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface emitting laser element, a surface emitting laser array, an optical scanning apparatus, and an image forming apparatus. More specifically, the present invention relates to a surface emitting laser element that emits laser light in a direction perpendicular to a substrate, a surface emitting laser array, The present invention relates to an optical scanning device having a surface emitting laser element or a surface emitting laser array, and an image forming apparatus including the optical scanning device.

  A vertical cavity surface emitting laser (Vertical Cavity Surface Emitting Laser) emits light in a direction perpendicular to a substrate, and is an edge emitting semiconductor laser device that emits light in a direction parallel to the substrate. In recent years, it has been attracting attention because of its low price, low power consumption, small size, suitable for two-dimensional devices, and high performance.

  As an application field of the surface emitting laser element, an optical writing light source (oscillation wavelength: 780 nm band) in a printer, a writing light source (oscillation wavelength: 780 nm band, 850 nm band) in an optical disk apparatus, and a LAN (Local Area) using an optical fiber are used. And a light source (oscillation wavelength: 780 nm band, 850 nm band, 1.3 μm band, 1.5 μm band) of an optical transmission system such as Network). Furthermore, it is also expected as a light source for light transmission between boards, within a board, between chips of an integrated circuit (LSI: Large Scale Integrated circuit), and within a chip of an integrated circuit.

  In these application fields, it is desired that light emitted from the surface emitting laser element (hereinafter also referred to as “emitted light”) has a single transverse mode and high output. In particular, there are many applications in which the fundamental transverse mode oscillation is high and the output is high. For this purpose, it is necessary to suppress high-order transverse mode oscillation, and various attempts have been made.

  For example, Patent Document 1 discloses a semiconductor substrate in which a lower multilayer reflector, an active layer region, and an upper multilayer reflector that constitutes a resonator together with the lower multilayer reflector are sequentially stacked, and the upper multilayer reflector. An upper electrode provided in an upper layer and provided with an opening for forming an emission region of the laser beam generated in the active layer region, and provided between the upper electrode and the lower multilayer reflector, A current confinement portion formed by insulating the peripheral portion of the resonator, and based on the reflectance of the resonator in the region corresponding to the upper electrode, the optical loss of the resonator and the laser light in the higher-order transverse mode of the laser light There is disclosed a surface emitting semiconductor laser in which the opening diameter of the upper electrode and the opening diameter of the current confinement portion are determined so that the difference from the optical loss of the resonator in the fundamental transverse mode becomes large. This surface-emitting type semiconductor laser gives a loss to a high-order transverse mode with a high light intensity at least in a region away from the center of the emission region, and a weak fundamental transverse mode in a region where the light intensity is strong at the center of the emission region and away from the center. Is selectively oscillated. Specifically, the electrode opening diameter is 0.5 μm larger than the current confinement portion.

  In addition, it has an upper electrode provided around the emission area on the emission surface from which the laser beam is emitted, and is transparent so that the reflectance is different between the central part and the peripheral part in the emission area. A filter provided with a mode selection filter using a dielectric film has been proposed (see, for example, Patent Documents 2 to 4). Specifically, in the emission area, the central part has a higher reflectance than the peripheral part, and the basic transverse mode operation is facilitated to increase the fundamental mode output, or the peripheral part has a higher reflectance than the central part. Some have made the next horizontal mode easier to operate.

  Various attempts have been made to control the polarization direction of the emitted light (see, for example, Patent Document 5 and Patent Document 6).

  Furthermore, it has been studied to achieve both higher-order transverse mode oscillation control and polarization direction control (see, for example, Patent Document 7 and Patent Document 8).

  However, in the surface-emitting type semiconductor laser disclosed in Patent Document 1, since the optimum size ranges for the opening diameter of the upper electrode and the opening diameter of the current confinement portion are both narrow, mass production is difficult and practical. There wasn't. In particular, in the array element, it is difficult to make the light emission characteristics of the plurality of light emitting portions uniform. Furthermore, since the periphery of the emission region is shielded from light by a metal member, the loss with respect to the fundamental transverse mode with light intensity is large although it is weak, which is disadvantageous for high output.

  On the other hand, in the surface emitting semiconductor lasers disclosed in Patent Documents 2 to 4, since the filter is transparent, the loss with respect to the fundamental transverse mode in the peripheral part of the emission region is small. However, it has been difficult to stably obtain a high output with the surface emitting semiconductor laser.

  Further, in the laser device disclosed in Patent Document 5 and the surface emitting semiconductor laser disclosed in Patent Document 6, it is difficult to achieve both higher-order transverse mode oscillation control and polarization direction control. was there.

  Further, in the surface emitting semiconductor laser disclosed in Patent Document 7, there is a risk that the lifetime is reduced due to an increase in electric resistance and an increase in current density.

  Furthermore, the surface-emitting type semiconductor laser device disclosed in Patent Document 8 has a disadvantage in that mass production is difficult because crystal growth is required a plurality of times during manufacture.

  The present invention has been made under such circumstances, and a first object thereof is to provide a surface-emitting laser element and a surface-emitting laser array in which the polarization direction is stable while controlling oscillation of a high-order transverse mode. There is to do.

  A second object of the present invention is to provide an optical scanning device capable of performing stable optical scanning.

  A third object of the present invention is to provide an image forming apparatus capable of forming a high quality image.

  According to a first aspect of the present invention, there is provided a resonator structure including an active layer, a semiconductor multilayer reflector provided across the resonator structure, and an emission surface on which light is emitted. A surface-emitting laser element that includes an electrode that surrounds the region and at least a part of which is in contact with the contact layer, and is provided in the emission region, and is transparent so that the reflectance of the peripheral portion differs from the reflectance of the central portion A portion having a different reflectance at the central portion is different in length in two directions perpendicular to each other in the emission surface, and a current injection region in contact with the contact layer in the electrode is: A surface-emitting laser element having shape anisotropy.

  According to this, the polarization direction can be stabilized while controlling the oscillation of the high-order transverse mode.

  From a second viewpoint, the present invention is a surface emitting laser array in which the surface emitting laser elements of the present invention are integrated.

  According to this, the polarization direction can be stabilized while controlling the oscillation of the high-order transverse mode.

  From a third aspect, the present invention is an optical scanning device that scans a surface to be scanned with light, the light source having the surface-emitting laser element of the present invention; a deflector that deflects the light from the light source; A scanning optical system that condenses the light deflected by the deflector onto the surface to be scanned.

  According to this, since the light source has the surface emitting laser element of the present invention, stable optical scanning can be performed.

  According to a fourth aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned with light, a light source having the surface emitting laser array of the present invention; a deflector that deflects light from the light source; A scanning optical system that condenses the light deflected by the deflector onto the surface to be scanned.

  According to this, since the light source has the surface emitting laser array of the present invention, stable optical scanning can be performed.

  According to a fifth aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device according to the invention for scanning the at least one image carrier with light modulated in accordance with image information. And an image forming apparatus.

  According to this, since the optical scanning device of the present invention is provided, as a result, a high-quality image can be formed.

It is a figure for demonstrating schematic structure of the laser printer which concerns on one Embodiment of this invention. It is the schematic which shows the optical scanning device in FIG. It is a figure for demonstrating the surface emitting laser element contained in a light source. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. FIG. 6A and FIG. 6B are diagrams for explaining an inclined substrate, respectively. It is a figure for demonstrating the lamination | stacking state of the several semiconductor layer in a surface emitting laser element. FIGS. 8A and 8B are views (No. 1) for describing a method of manufacturing a surface emitting laser element, respectively. FIGS. 9A and 9B are views (No. 2) for describing the method for manufacturing the surface emitting laser element, respectively. It is a figure for demonstrating an etching mask. It is the figure which expanded a part of FIG. 12A and 12B are views (No. 3) for describing the method for manufacturing the surface emitting laser element, respectively. It is a figure for demonstrating the resist pattern at the time of vapor-depositing the electrode material of p side. FIGS. 14A and 14B are views (No. 4) for describing the method for manufacturing the surface emitting laser element, respectively. It is a figure for demonstrating the part which the p side electrode and the contact layer are contacting. It is FIG. (5) for demonstrating the manufacturing method of a surface emitting laser element. It is a figure for demonstrating the influence of the mode filter which has on the relationship between the area of an electric current passage area | region, and a fundamental transverse mode output. It is FIG. (1) for demonstrating the conventional surface emitting laser element A. FIG. It is FIG. (2) for demonstrating the conventional surface emitting laser element A. FIG. It is FIG. (1) for demonstrating the conventional surface emitting laser element B. FIG. It is FIG. (2) for demonstrating the conventional surface emitting laser element B. FIG. It is FIG. (1) for demonstrating the conventional surface emitting laser element C. FIG. It is FIG. (2) for demonstrating the conventional surface emitting laser element C. FIG. It is a figure for demonstrating the modification 1 of a low reflectance area | region and a high reflectance area | region. It is a figure for demonstrating the part which the p side electrode and contact layer in FIG. 24 have contact | connected. It is a figure for demonstrating the modification 2 of a low reflectance area | region and a high reflectance area | region. It is a figure for demonstrating the modification 3 of a low reflectance area | region and a high reflectance area | region. It is a figure for demonstrating the modification 4 of a low reflectance area | region and a high reflectance area | region. It is a figure for demonstrating the modification 1 of a surface emitting laser element. It is AA sectional drawing of FIG. It is a figure for demonstrating the part which the p side electrode and contact layer in the modification 1 of a surface emitting laser element are contacting. It is a figure for demonstrating the modification 2 of a surface emitting laser element. It is AA sectional drawing of FIG. It is a figure for demonstrating the modification 3 of a surface emitting laser element. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is a figure for demonstrating the modification 1 of the low reflectance area | region and the high reflectance area | region in the modification 3 of a surface emitting laser element. It is a figure for demonstrating the modification 2 of the low reflectance area | region and the high reflectance area | region in the modification 3 of a surface emitting laser element. It is a figure for demonstrating the modification 4 of a surface emitting laser element. It is AA sectional drawing of FIG. It is a figure for demonstrating the part which the p side electrode and contact layer in the modification 4 of a surface emitting laser element are contacting. It is a figure for demonstrating a surface emitting laser array. It is AA sectional drawing of FIG. It is a figure for demonstrating schematic structure of a color printer.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a laser printer 1000 according to an embodiment.

  The laser printer 1000 includes an optical scanning device 1010, a photosensitive drum 1030, a charging charger 1031, a developing roller 1032, a transfer charger 1033, a charge eliminating unit 1034, a cleaning unit 1035, a toner cartridge 1036, a paper feeding roller 1037, a paper feeding tray 1038, A registration roller pair 1039, a fixing roller 1041, a paper discharge roller 1042, a paper discharge tray 1043, a communication control device 1050, a printer control device 1060 that comprehensively controls the above-described units, and the like are provided. These are housed in predetermined positions in the printer housing 1044.

  The communication control device 1050 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The photosensitive drum 1030 is a cylindrical member, and a photosensitive layer is formed on the surface thereof. That is, the surface of the photoconductor drum 1030 is a scanned surface. The photosensitive drum 1030 rotates in the direction of the arrow in FIG.

  The charging charger 1031, the developing roller 1032, the transfer charger 1033, the charge removal unit 1034, and the cleaning unit 1035 are each disposed near the surface of the photosensitive drum 1030. Then, along the rotation direction of the photosensitive drum 1030, the charging charger 1031 → the developing roller 1032 → the transfer charger 1033 → the discharging unit 1034 → the cleaning unit 1035 are arranged in this order.

  The charging charger 1031 uniformly charges the surface of the photosensitive drum 1030.

  The optical scanning device 1010 scans the surface of the photosensitive drum 1030 charged by the charging charger 1031 with a light beam modulated based on image information from the host device, and corresponds to the image information on the surface of the photosensitive drum 1030. A latent image is formed. The latent image formed here moves in the direction of the developing roller 1032 as the photosensitive drum 1030 rotates. The configuration of the optical scanning device 1010 will be described later.

  The toner cartridge 1036 stores toner, and the toner is supplied to the developing roller 1032.

  The developing roller 1032 causes the toner supplied from the toner cartridge 1036 to adhere to the latent image formed on the surface of the photosensitive drum 1030 to visualize the image information. Here, the latent image to which the toner is attached (hereinafter also referred to as “toner image” for the sake of convenience) moves in the direction of the transfer charger 1033 as the photosensitive drum 1030 rotates.

  Recording paper 1040 is stored in the paper feed tray 1038. A paper feed roller 1037 is disposed in the vicinity of the paper feed tray 1038, and the paper feed roller 1037 takes out the recording paper 1040 one by one from the paper feed tray 1038 and conveys it to the registration roller pair 1039. The registration roller pair 1039 temporarily holds the recording paper 1040 taken out by the paper supply roller 1037, and in the gap between the photosensitive drum 1030 and the transfer charger 1033 according to the rotation of the photosensitive drum 1030. Send it out.

  A voltage having a polarity opposite to that of the toner is applied to the transfer charger 1033 in order to electrically attract the toner on the surface of the photosensitive drum 1030 to the recording paper 1040. With this voltage, the toner image on the surface of the photosensitive drum 1030 is transferred to the recording paper 1040. The recording sheet 1040 transferred here is sent to the fixing roller 1041.

  In the fixing roller 1041, heat and pressure are applied to the recording paper 1040, whereby the toner is fixed on the recording paper 1040. The recording paper 1040 fixed here is sent to the paper discharge tray 1043 via the paper discharge roller 1042 and is sequentially stacked on the paper discharge tray 1043.

  The neutralization unit 1034 neutralizes the surface of the photosensitive drum 1030.

  The cleaning unit 1035 removes the toner remaining on the surface of the photosensitive drum 1030 (residual toner). The surface of the photosensitive drum 1030 from which the residual toner has been removed returns to the position facing the charging charger 1031 again.

  Next, the configuration of the optical scanning device 1010 will be described.

  As shown in FIG. 2 as an example, the optical scanning device 1010 includes a deflector-side scanning lens 11a, an image plane-side scanning lens 11b, a polygon mirror 13, a light source 14, a coupling lens 15, an aperture plate 16, and a cylindrical lens 17. , A reflection mirror 18, a scanning control device (not shown), and the like. These are assembled at predetermined positions of the optical housing 30.

  In the following, for convenience, the direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and the direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

  The coupling lens 15 converts the light beam output from the light source 14 into substantially parallel light.

  The aperture plate 16 has an aperture and defines the beam diameter of the light beam through the coupling lens 15.

  The cylindrical lens 17 forms an image of the light flux that has passed through the opening of the aperture plate 16 in the vicinity of the deflection reflection surface of the polygon mirror 13 via the reflection mirror 18 in the sub-scanning corresponding direction.

  The optical system arranged on the optical path between the light source 14 and the polygon mirror 13 is also called a pre-deflector optical system. In the present embodiment, the pre-deflector optical system includes a coupling lens 15, an aperture plate 16, a cylindrical lens 17, and a reflection mirror 18.

  As an example, the polygon mirror 13 has a hexahedral mirror having an inscribed circle radius of 18 mm, and each mirror serves as a deflecting reflection surface. The polygon mirror 13 deflects the light flux from the reflection mirror 18 while rotating at a constant speed around an axis parallel to the sub-scanning corresponding direction.

  The deflector-side scanning lens 11 a is disposed on the optical path of the light beam deflected by the polygon mirror 13.

  The image plane side scanning lens 11b is disposed on the optical path of the light beam via the deflector side scanning lens 11a. Then, the light beam that has passed through the image plane side scanning lens 11b is irradiated onto the surface of the photosensitive drum 1030, and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 1030 as the polygon mirror 13 rotates. That is, the photoconductor drum 1030 is scanned. The moving direction of the light spot at this time is the “main scanning direction”. The rotation direction of the photosensitive drum 1030 is the “sub-scanning direction”.

  The optical system arranged on the optical path between the polygon mirror 13 and the photosensitive drum 1030 is also called a scanning optical system. In the present embodiment, the scanning optical system includes a deflector side scanning lens 11a and an image plane side scanning lens 11b. Note that at least one folding mirror is disposed on at least one of the optical path between the deflector side scanning lens 11a and the image plane side scanning lens 11b and the optical path between the image plane side scanning lens 11b and the photosensitive drum 1030. May be.

  As an example, the light source 14 includes a surface emitting laser element 100 as shown in FIGS. In this specification, the laser oscillation direction is defined as the Z-axis direction, and two directions perpendicular to each other in a plane perpendicular to the Z-axis direction are described as the X-axis direction and the Y-axis direction. 4 is a cross-sectional view taken along the line AA in FIG. 3, and FIG. 5 is a cross-sectional view taken along the line BB in FIG.

  The surface emitting laser element 100 is a surface emitting laser having an oscillation wavelength band of 780 nm, and includes a substrate 101, a lower semiconductor DBR 103, a lower spacer layer 104, an active layer 105, an upper spacer layer 106, an upper semiconductor DBR 107, a contact layer 109, p side. An electrode 113, an n-side electrode 114, a mode filter 115, and the like are included.

  As an example, as shown in FIG. 6A, the substrate 101 has a normal direction of the mirror-polished surface (main surface) of the surface with respect to the crystal orientation [1 0 0] direction, the crystal orientation [1 1 1 ] An n-GaAs single crystal semiconductor substrate inclined by 15 degrees (θ = 15 degrees) in the A direction. That is, the substrate 101 is a so-called inclined substrate. Here, as an example, as shown in FIG. 6B, the crystal orientation [0 −1 1] direction is arranged in the + X direction, and the crystal orientation [0 1 −1] direction is arranged in the −X direction. .

The lower semiconductor DBR 103 is stacked on the + Z side of the substrate 101 via a buffer layer (not shown), and includes a low refractive index layer made of n-AlAs and a high refractive index layer made of n-Al _0.3 Ga _0.7 As. Of 40.5 pairs. Between each refractive index layer, in order to reduce electric resistance, a composition gradient layer having a thickness of 20 nm (not shown in FIGS. 4 and 5) in which the composition is gradually changed from one composition to the other composition. 7) is provided. Each refractive index layer includes 1/2 of the adjacent composition gradient layer, and is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ. When the optical thickness is λ / 4, the actual thickness D of the layer is D = λ / 4n (where n is the refractive index of the medium of the layer).

The lower spacer layer 104 is stacked on the + Z side of the lower semiconductor DBR 103 and is a layer made of non-doped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P.

  The active layer 105 is stacked on the + Z side of the lower spacer layer 104 and is an active layer having a triple quantum well structure having three quantum well layers and four barrier layers. Each quantum well layer is made of GaInAsP, which has a composition that induces 0.7% compressive strain, and has a band gap wavelength of about 780 nm. Each barrier layer is made of GaInP, which is a composition that induces a tensile strain of 0.6%.

The upper spacer layer 106 is laminated on the active layer 105 on the + Z side, and is a layer made of non-doped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P.

  A portion composed of the lower spacer layer 104, the active layer 105, and the upper spacer layer 106 is also called a resonator structure, and the thickness thereof is set to be an optical thickness of one wavelength. The active layer 105 is provided at the center of the resonator structure at a position corresponding to the antinode in the standing wave distribution of the electric field so that a high stimulated emission probability can be obtained.

The upper semiconductor DBR 107 is laminated on the + Z side of the upper spacer layer 106, and has a low refractive index layer made of p-Al _0.9 Ga _0.1 As and a high refractive index made of p-Al _0.3 Ga _0.7 As. It has 24 pairs of layers. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer in which the composition is gradually changed from one composition to the other composition (not shown in FIGS. 4 and 5; see FIG. 7) Is provided. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer.

  In one of the low refractive index layers in the upper semiconductor DBR 107, a selectively oxidized layer 108 made of p-AlAs is inserted with a thickness of 30 nm. The insertion position of the selectively oxidized layer 108 is a position corresponding to the third node from the active layer 105 in the standing wave distribution of the electric field.

  The contact layer 109 is stacked on the + Z side of the upper semiconductor DBR 107 and is a layer made of p-GaAs.

  The mode filter 115 is provided on the + Z side of the contact layer 109 and in a portion deviated from the central portion in the emission region, and a transparent dielectric film that makes the reflectance of the portion lower than the reflectance of the central portion. Consists of.

  Next, a method for manufacturing the surface emitting laser element 100 will be briefly described. Note that a structure in which a plurality of semiconductor layers are stacked over the substrate 101 as described above is also referred to as a “stacked body” for convenience in the following.

(1) The laminate is formed by crystal growth by metal organic vapor phase epitaxy (MOCVD) or molecular beam epitaxy (MBE) (see FIG. 8A).

Here, in the case of the MOCVD method, trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as the Group III material, and phosphine (PH ₃ ), Arsine (AsH ₃ ) is used. Further, carbon tetrabromide (CBr ₄ ) and dimethyl zinc (DMZn) are used as the raw material for the p-type dopant, and hydrogen selenide (H ₂ Se) is used as the raw material for the n-type dopant.

(2) A square resist pattern having one side L1 (here, 25 μm) is formed on the surface of the laminate.

(3) A substantially square columnar mesa structure (hereinafter abbreviated as “mesa” for convenience) is formed by ECR etching using Cl ₂ gas, using the resist pattern as a photomask. Here, the bottom surface of the etching is located in the lower spacer layer 104.

(4) The photomask is removed (see FIG. 8B).

(5) The laminated body is heat-treated in water vapor. As a result, Al (aluminum) in the selectively oxidized layer 108 is selectively oxidized from the outer peripheral portion of the mesa, and an unoxidized region 108b surrounded by the Al oxide layer 108a remains in the central portion of the mesa. (See FIG. 9A). In other words, a so-called oxidized constriction structure is formed that restricts the drive current path of the light emitting part only to the central part of the mesa. The non-oxidized region 108b is a current passing region. In this manner, a substantially square current passing region having a width of about 4 μm to 6 μm, for example, is formed.

(6) A protective layer 111 made of SiN is formed by vapor phase chemical deposition (CVD) (see FIG. 9B). Here, the optical thickness of the protective layer 111 is set to λ / 4. Specifically, since the refractive index n of SiN is 1.86 and the oscillation wavelength λ is 780 nm, the actual film thickness (= λ / 4n) is set to about 105 nm.

(7) An etching mask (referred to as a mask M) for opening a window for the p-side electrode contact is formed on the upper part of the mesa serving as a laser light emission surface. Here, as shown in FIG. 10 and FIG. 11 in which only the mesa in FIG. 10 is taken out and enlarged as an example, it is desirable to sandwich the periphery of the mesa, the side surface of the mesa, the periphery of the top surface of the mesa, and the central portion of the top surface of the mesa. A mask M is formed so that two small regions (first small region and second small region) facing each other in the direction parallel to the polarization direction P (here, the X-axis direction) are not etched. In FIG. 11, L2 is 20 μm, L3 is 13 μm, L4 is 5 μm, and L5 is 2 μm.

(8) The protective layer 111 is etched with BHF to open a window for the p-side electrode contact.

(9) The mask M is removed (see FIGS. 12A and 12B). The protective layer 111 remaining in the first small region becomes the mode filter 115A, and the protective layer 111 remaining in the second small region becomes the mode filter 115B. That is, the mode filter 115 includes a mode filter 115A and a mode filter 115B. The region sandwiched between the mode filter 115A and the mode filter 115B has shape anisotropy.

(10) A resist pattern M is formed in a region serving as a light emitting portion on the top of the mesa, and a p-side electrode material is deposited. Here, as shown in FIG. 13, the resist pattern M includes a circular pattern having a diameter L3 covering two mode filters, and a rectangle having a length L5 in the X-axis direction and a length L2 in the Y-axis direction. This resist pattern has a shape overlapping with the pattern.

  As the electrode material on the p side, a multilayer film made of Cr / AuZn / Au or a multilayer film made of Ti / Pt / Au is used.

(11) The electrode material deposited in the injection region is lifted off to form the p-side electrode 113 (see FIG. 14A). A region surrounded by the p-side electrode 113 is an emission region. Note that FIG. 14B shows an enlarged view of only the mesa in FIG.

  In this embodiment, the mode filter 115A is formed as a transparent dielectric film made of SiN having an optical thickness of λ / 4 on two small regions (first small region and second small region) in the emission region. A mode filter 115B is present. As a result, the reflectance of the two small regions (the first small region and the second small region) is lower than the reflectance at the center of the emission region. That is, in this embodiment, a low reflectance region (peripheral portion) and a high reflectance region (center portion) exist in the emission region.

  The high reflectance region has a different length in the X-axis direction and in the Y-axis direction on the exit surface (here, the XY plane). That is, the high reflectance region has shape anisotropy.

  Further, a region where the p-side electrode 113 and the contact layer 109 are in contact (hereinafter also referred to as “current injection region”) is composed of two regions as shown in FIG. Opposite the X axis direction across the center of the injection region. The current injection region has a length L11 in the Y-axis direction and a length (L12 + L13) in the X-axis direction within the emission surface (here, the XY plane). That is, the current injection region has shape anisotropy.

(12) After polishing the back side of the substrate 101 to a predetermined thickness (for example, about 100 μm), an n-side electrode 114 is formed (see FIG. 16). Here, the n-side electrode 114 is a multilayer film made of AuGe / Ni / Au.

(13) Ohmic conduction is established between the p-side electrode 113 and the n-side electrode 114 by annealing. Thereby, the mesa becomes a light emitting part.

(14) Cut for each chip.

  Then, the surface emitting laser element 100 is obtained through various post-processes.

  With respect to the surface emitting laser device 100 manufactured in this way, the optical output (basic transverse mode output) and the area of the current passing region where the suppression ratio SMSR (Side Mode Suppression Ratio) of the higher order transverse mode to the fundamental transverse mode is 20 dB. Sought a relationship with. The result is shown in FIG. 17 together with a comparative example without a mode filter. Note that the SMSR is desirably about 20 dB or more in a copying machine or the like.

  In the comparative example, as the area of the current passage region is increased, the fundamental transverse mode output is significantly reduced. This is because a high-order transverse mode having a light output peak at the periphery of the emission region is likely to oscillate.

On the other hand, in the surface emitting laser element 100, the fundamental mode output is larger than that of the comparative example, and a fundamental transverse mode output of 2.5 mW or more is obtained even when the current passage area is 30 μm ^{2 in} particular.

  By the way, if the area of the current passing region is small, the current density during operation is high, the element resistance is high, and the thermal characteristics are deteriorated. There are also many inconveniences such as short life. In a copying machine or the like, the basic transverse mode output is preferably 1 mW or more.

  As is apparent from FIG. 17, in the comparative example, the area range of the current passing region that satisfies the condition that the fundamental transverse mode output is 1 mW or more is narrow. In this case, it is extremely difficult to make the area of the current passage region with good reproducibility and uniformity, and the yield during manufacturing is poor.

  On the other hand, in the surface emitting laser element 100, the area range of the current passing region that satisfies the above conditions is wide. Therefore, it is possible to increase the area of the current passage region while maintaining a high fundamental transverse mode output. As a result, it is possible to obtain a surface emitting laser element having a low element resistance, excellent thermal characteristics, a long lifetime, and a high production yield.

  In general, the light output of the fundamental transverse mode is the largest near the center of the emission region, and tends to decrease as it goes to the periphery. On the other hand, the higher-order transverse mode becomes larger at least in the periphery of the emission region, although it depends on the mode. Usually, in the primary transverse mode that starts to oscillate next to the fundamental transverse mode and has the greatest influence on the output of the fundamental transverse mode, the periphery tends to become strongest as it approaches the center. In the surface emitting laser element 100, the reflectance of the peripheral part of the emission region is lower than the reflectance of the central part, so that the reflectance of the high-order transverse mode is reduced without reducing the reflectance of the fundamental transverse mode. Therefore, it is possible to suppress high-order transverse mode oscillation.

  18 and 19 show a surface emitting laser element (referred to as surface emitting laser element A) having a conventional standard device structure in which a mode filter is not provided.

  20 and 21 show a surface-emitting laser element (referred to as a surface-emitting laser element B) in which the aperture diameter of the electrode is narrower than that of the surface-emitting laser element A (see Patent Document 1). In the surface emitting laser element B, higher-order transverse mode oscillation is suppressed as compared with the surface emitting laser element A. Further, in the surface emitting laser element B, compared with the surface emitting laser element A, the contact area between the p-side electrode 113 and the contact layer 109 is large, and the element resistance is low. However, since the peripheral region of the emission surface is completely shielded from light by the metal (p-side electrode), the output becomes small.

  22 and 23 show a conventional surface emitting laser element (referred to as surface emitting laser element C) provided with an annular mode filter made of a dielectric film (see Patent Documents 2 to 4). In this surface emitting laser element C, the mode filter is a transparent dielectric film, so that the fundamental transverse mode output is higher than that of the surface emitting laser element B.

  Next, the polarization suppression ratio PMSR (Polarization Mode Suppression Ratio) was examined. The polarization suppression ratio PMSR is the ratio of the light intensity in the desired polarization direction to the light intensity in the direction orthogonal thereto, and may be 10 dB or more in a copying machine or the like, but preferably 20 dB or more.

  When an inclined substrate is used, the polarization direction is stabilized and the polarization suppression ratio PMSR is increased. In a surface-emitting laser element (referred to as surface-emitting laser element D) having a structure similar to that of the surface-emitting laser element 100 and having no mode filter, mainly the effect of the tilted substrate, but also the effect of distortion in the active layer or the like is added, As a result, it becomes easy to polarize in the tilt axis direction (here, the X axis direction, see FIG. 6A). In this case, the polarization suppression ratio PMSR was 20 to 30 dB.

  On the other hand, the surface emitting laser element C has a polarization direction different from that of the surface emitting laser element D by 90 degrees, and is polarized in a direction perpendicular to the tilt axis of the substrate (here, the Y axis direction). In the surface emitting laser element C, the polarization suppression ratio PMSR was 10 to 20 dB.

  On the other hand, the surface emitting laser element 100 was polarized in the tilt axis direction of the substrate similarly to the surface emitting laser element D, and the polarization suppression ratio PMSR was 20 to 30 dB. That is, the surface-emitting laser element 100 has an improved polarization suppression ratio PMSR compared to the surface-emitting laser element C.

  In the surface-emitting laser element 100, a part of the mode filter is missing from the surface-emitting laser element C, so that the fundamental mode output is almost the same as that of the surface-emitting laser element C although it is slightly lower than that of the surface-emitting laser element C. It was.

  Thus, the surface emitting laser element 100 has a high fundamental transverse mode output, a low element resistance, and a high polarization suppression ratio PMSR.

  By the way, as a factor that the surface emitting laser element 100 is superior in polarization stability to the surface emitting laser element C, the surface emitting laser element 100 has two directions orthogonal to each other (here, the X axis direction and the Y axis direction). It is considered that anisotropy occurs in the light confinement action.

  In the surface emitting laser element 100, there is an effect of confining light whose polarization direction coincides with the tilt axis direction of the substrate (here, the X axis direction) in the central portion having a relatively high reflectance in the emission region. . Therefore, the oscillation threshold value of the light whose polarization direction matches the tilt axis direction of the substrate is lower than that of the light whose polarization direction matches the direction perpendicular to the tilt axis of the substrate. As a result, it is considered that the polarization suppression ratio PMSR is improved with respect to the surface emitting laser element C.

  In this way, by dividing the mode filter into a plurality of parts and giving shape anisotropy to the relatively highly reflective region in the center, anisotropy can be generated in the lateral confinement action. . As a result, the polarization component having a strong confinement effect oscillates more easily than the polarization component having a weak confinement effect, and the polarization direction can be controlled to a direction having a strong confinement effect.

  In addition, since the current injection region in contact with the contact layer in the p-side electrode has shape anisotropy, anisotropy occurred in the current flow, and the polarization direction could be further stabilized. .

  As described above, according to the surface emitting laser element 100 according to the present embodiment, the lower semiconductor DBR 103, the lower spacer layer 104, the active layer 105, the upper spacer layer 106, the upper semiconductor DBR 107, and the contact layer 109 are formed on the substrate 101. Are stacked. A p-side electrode 113 is provided on the emission surface from which the laser beam is emitted so as to surround the emission region. In the emission region, a mode filter 115, which is an optically transparent dielectric film provided so as to surround the center of the emission region, is formed with an optical thickness of λ / 4.

  And the part where the reflectance of the center part of an injection | emission area | region is comparatively high differs in length regarding two directions (here X-axis direction and Y-axis direction) mutually orthogonal | vertical within an emission surface. Further, the current injection region in contact with the contact layer 109 in the p-side electrode 113 has shape anisotropy.

  Therefore, the polarization direction can be stabilized while controlling the oscillation of the high-order transverse mode.

  According to the optical scanning device 1010 according to the present embodiment, since the light source 14 includes the surface emitting laser element 100, stable optical scanning can be performed.

  Since the laser printer 1000 according to the present embodiment includes the optical scanning device 1010, a high-quality image can be formed.

  In the above-described embodiment, the polarization control action by the tilted substrate has been described as the action of trying to stabilize the polarization direction in the tilt axis direction (X-axis direction). However, the polarization direction is orthogonal to the tilt axis ( The action may be to stabilize in the Y-axis direction. In this case, a mode in which the desired polarization direction is a direction orthogonal to the tilt axis and the shape of the region having a relatively high reflectivity is the longitudinal direction is the tilt axis direction as shown in FIG. Divide the filter. At this time, the portion of the p-side electrode that is in contact with the contact layer is preferably divided into two parts so as to face each other in the Y-axis direction (see FIG. 25). The polarization control action by the inclined substrate can be controlled by changing the strain state including the strain of the active layer.

  Moreover, although the said embodiment demonstrated the case where the mode filter divided | segmented into 2 was provided symmetrically with respect to the axis | shaft parallel to a Y-axis passing through the center of an injection | emission area | region, it is not limited to this. It is only necessary to have mode filters on one side and the other side of the axis passing through the center of the emission region and parallel to the Y axis.

  Moreover, although the said embodiment demonstrated the case where the shape of each mode filter was a shape which divided a donut into two, it is not limited to this. For example, the shape of each mode filter may be an arbitrary shape such as a rectangular shape, a semicircular shape, and an elliptical shape (see FIG. 26).

  Moreover, although the said embodiment demonstrated the case where two mode filters were provided, it is not limited to this. For example, as shown in FIG. 27, one mode filter having an elliptical shape and having different widths in two directions orthogonal to each other may be provided. Further, as shown in FIG. 28, one mode filter having a shape in which a part of the annular shape is missing may be provided.

  In short, it is only necessary that the region having a relatively high reflectance in the central portion has shape anisotropy in a desired polarization direction and a direction perpendicular thereto.

  Moreover, although the said embodiment demonstrated the case where the two mode filters were the same material, it is not limited to this.

  In the above embodiment, the case where the normal direction of the main surface of the substrate is inclined 15 degrees toward the crystal orientation [1 1 1] A direction with respect to the crystal orientation [1 0 0] direction is described. However, the present invention is not limited to this. The normal direction of the main surface of the substrate may be inclined toward one direction of crystal orientation <1 1 1> with respect to one direction of crystal orientation <1 0 0>.

  In the above-described embodiment, the case where the protective layer and the mode filter are SiN has been described. However, the present invention is not limited to this. For example, any of SiNx, SiOx, TiOx, and SiON may be used. The same effect can be obtained by designing the film thickness according to the refractive index of each material.

  Moreover, although the said embodiment demonstrated the case where the optical thickness of the mode filter was (lambda) / 4, it is not limited to this. For example, the optical thickness of the mode filter may be 3λ / 4. In short, if the optical thickness of the mode filter is an odd multiple of λ / 4, an effect similar to that of the surface emitting laser element 100 can be obtained.

  Moreover, in the said embodiment, it may replace with the said surface emitting laser element 100, and may use the surface emitting laser element 100_1 shown by FIG.29 and FIG.30. 30 is a cross-sectional view taken along the line AA in FIG. In the surface-emitting laser element 100_1, the length in the Y-axis direction of the region having a relatively high reflectance at the center is shorter than that of the surface-emitting laser element 100. When viewed from the Z-axis direction, the shape of the p-side electrode is isotropic. However, as shown in FIG. 31, the current injection region in contact with the contact layer in the p-side electrode maintains the shape anisotropy and has the same polarization direction controllability as the surface emitting laser element 100. Yes. Further, the anisotropy of the light divergence angle is small because the shape anisotropy of the emission region is eliminated.

  Further, in the above embodiment, instead of the surface emitting laser element 100, as shown in FIG. 32 and FIG. 33 as an example, the optical thickness is further 2λ / 4 over the entire emission region of the surface emitting laser element 100. Alternatively, a surface emitting laser element 100_2 in which a dielectric film 116 made of SiN is stacked may be used. The actual film thickness (= 2λ / 4n) of the dielectric film 116 is set to about 210 nm because the refractive index n of SiN is 1.86 and the oscillation wavelength λ is 780 nm.

  At this time, the central portion of the emission region is covered with a dielectric film 116 made of SiN having an optical thickness of 2λ / 4. The mode filter includes a dielectric film 111 made of SiN having an optical thickness of λ / 4 and a dielectric film 116 made of SiN having an optical thickness of 2λ / 4. That is, the mode filter is composed of a dielectric film made of SiN having an optical thickness of 3λ / 4. In addition, the region excluding the mode filter in the peripheral portion of the emission region, that is, the portion where the p-side electrode is missing (two locations) is also covered with a protective layer (dielectric film) having an optical thickness of 2λ / 4. .

  In this case, since the entire emission region is covered with the dielectric film 116, oxidation and contamination of the emission region can be suppressed. Note that although the central portion of the emission region is covered with the dielectric film 116, the optical thickness is an even multiple of λ / 2. Optical characteristics equivalent to those obtained without the same were obtained.

  That is, if the optical thickness of the portion where the reflectance is to be lowered is an odd multiple of λ / 4 and the optical thickness of the other portion is an even multiple of λ / 4, the same as the surface emitting laser element 100 An effect is obtained.

  Further, in the above embodiment, instead of the surface emitting laser element 100, as shown in FIGS. 34 to 36 as an example, a high reflectance region composed of two transparent dielectric layers is provided at the center of the element. A surface-emitting laser element 100_3 that is provided and has a low-reflectance region formed of a single dielectric layer in a region off the center may be used. The thickness of each dielectric layer is set such that the optical thickness is an odd multiple of λ / 4. The peripheral portion of the upper surface of the mesa is also covered with two transparent dielectric layers.

Here, at the center portion, two kinds of dielectrics of SiO ₂ and SiN are laminated on the contact layer 109 in order from the lower layer. In this case, it is necessary to set the refractive index of the lower dielectric layer 117 to be smaller than the refractive index of the upper dielectric layer 111. Although depending on the film formation conditions, the refractive index of SiO ₂ that is the lower dielectric layer 117 is about 1.5 and the refractive index of SiN that is the upper dielectric layer 111 is about 1.86. is there.

  On the other hand, only SiN is laminated in a region deviated from the center periphery of the element.

  When the thickness of the dielectric layer is set in this way, the central portion has the same configuration as that of a normal multilayer film reflecting mirror, and the reflectance is increased. In a region off the center, a single dielectric layer having an optical thickness of λ / 4 is provided on the semiconductor multilayer mirror. And since the refractive index of SiN is small with respect to the refractive index of a semiconductor layer, the reflectance of this area | region becomes low.

  Further, in the surface emitting laser element 100_3, the reflectance at the central portion is increased, so that the difference in reflectance between the central portion and the peripheral portion can be made larger than that in the surface emitting laser element 100.

  Also in this case, the effect of suppressing the high-order transverse mode is high, and the basic transverse mode output can be increased. Note that when the reflectance at the center portion is increased, oscillation tends to occur but the light extraction efficiency is reduced. Therefore, for example, the number of pairs of semiconductor DBRs may be reduced so that the reflectance of the central portion is the same as that of the surface emitting laser element 100.

  That is, the optical thickness of the dielectric film at the portion where the reflectance is to be lowered is an odd multiple of λ / 4, and the other portions are made of two kinds of dielectric materials having different refractive indexes, and the optical thicknesses of the respective dielectric thicknesses. If λ / 4 is an odd multiple of λ / 4, the same high-order transverse mode suppression effect can be obtained.

By the way, when viewed from the Z-axis direction, the emission angle of the laser beam becomes asymmetric when the center of the current passing region and the center of gravity of the mode filter are shifted. However, in the surface emitting laser element 100_3, SiO ₂ is formed. After that, since the mode filter pattern is formed at the same time when the etching mask for determining the mesa shape is formed, both are automatically aligned. Therefore, the center of the current passage region and the center of gravity of the mode filter can be easily made substantially coincident, and the radiation angle can be made symmetric.

  In this case, as shown in FIGS. 37 and 38, the emission region may be elliptical. Also in this case, since the entire emission surface is covered with the dielectric film, oxidation and contamination of the emission surface can be suppressed.

Note that the two-layer dielectric film in the region having a high reflectance at the center is not limited to SiO ₂ and SiN, and may be, for example, any one of SiNx, SiOx, TiOx, and SiON. The same effect can be obtained by designing the film thickness according to the refractive index of each material.

  Moreover, in the said embodiment, it may replace with the said surface emitting laser element 100, and may use the surface emitting laser element 100_4 shown by FIG.39 and FIG.40 as an example. In the surface emitting laser element 100_4, the length in the Y-axis direction of the region having a relatively high reflectance at the center is shorter than that of the surface emitting laser element 100_3. When viewed from the Z-axis direction, the shape of the p-side electrode is isotropic. However, as shown in FIG. 41, the current injection region in contact with the contact layer in the p-side electrode maintains the shape anisotropy and has the same polarization direction controllability as the surface emitting laser element 100_3. Yes. Further, the anisotropy of the light divergence angle is small because the shape anisotropy of the emission region is eliminated.

  In the above embodiment, the light source 14 may include a surface emitting laser array 100M shown in FIG. 42 as an example instead of the surface emitting laser element 100.

  In the surface emitting laser array 100M, a plurality (21 in this case) of light emitting units are arranged on the same substrate. Here, the X-axis direction in FIG. 42 is the main scanning corresponding direction, and the Y-axis direction is the sub-scanning corresponding direction. The plurality of light emitting units are arranged such that the intervals between adjacent light emitting units are equal to d2 when all the light emitting units are orthogonally projected onto a virtual line extending in the Y-axis direction. That is, the 21 light emitting units are two-dimensionally arranged. In this specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions. Further, the number of light emitting units is not limited to 21.

  Each light emitting section has the same structure as the surface emitting laser element 100 described above, as shown in FIG. 43 which is a cross-sectional view taken along the line AA of FIG. The surface emitting laser array 100M can be manufactured by the same method as the surface emitting laser element 100 described above. Thus, a plurality of laser beams can be obtained with a high single mode output with a uniform polarization direction between the light emitting units. Accordingly, it is possible to simultaneously form 21 minute light spots that are circular and have a high light density on the photosensitive drum 1030.

  Further, in the surface emitting laser array 100M, the intervals between the light emitting portions when the respective light emitting portions are orthogonally projected onto a virtual line extending in the sub-scanning corresponding direction are equal intervals d2, and therefore the photosensitive drum 1030 is adjusted by adjusting the lighting timing. In the above, it can be considered that the configuration is the same as the case where the light emitting units are arranged at equal intervals in the sub-scanning direction.

  For example, if the distance d2 is 2.65 μm and the magnification of the optical system of the optical scanning device 1010 is doubled, high-density writing of 4800 dpi (dots / inch) can be performed. Of course, higher density can be achieved by increasing the number of light emitting sections in the main scanning corresponding direction, or by arranging the array in which the pitch d1 in the sub scanning corresponding direction is narrowed to further reduce the interval d2, or by reducing the magnification of the optical system. And higher quality printing becomes possible. Note that the writing interval in the main scanning direction can be easily controlled by the lighting timing of the light emitting unit.

  In this case, the laser printer 1000 can perform printing without decreasing the printing speed even if the writing dot density increases. Further, when the writing dot density is the same, the printing speed can be further increased. Further, since the surface emitting laser element of the present invention has a high single mode output, it is possible to obtain a high printing speed and a high definition image quality.

  In this case, since the polarization directions of the light beams from the respective light emitting units are stably aligned, the laser printer 1000 can stably form a high-quality image.

  In the above embodiment, a surface emitting laser array in which light emitting units similar to the surface emitting laser element 100 are arranged one-dimensionally may be used instead of the surface emitting laser element 100.

  Moreover, although the said embodiment demonstrated the case where the oscillation wavelength of a light emission part was a 780 nm band, it is not limited to this. The oscillation wavelength of the light emitting unit may be changed according to the characteristics of the photoreceptor.

  Moreover, each said surface emitting laser element can be used also for uses other than an image forming apparatus. In that case, the oscillation wavelength may be a wavelength band such as a 650 nm band, an 850 nm band, a 980 nm band, a 1.3 μm band, and a 1.5 μm band depending on the application. In this case, a mixed crystal semiconductor material corresponding to the oscillation wavelength can be used as the semiconductor material constituting the active layer. For example, an AlGaInP mixed crystal semiconductor material can be used in the 650 nm band, an InGaAs mixed crystal semiconductor material can be used in the 980 nm band, and a GaInNAs (Sb) mixed crystal semiconductor material can be used in the 1.3 μm band and the 1.5 μm band.

  Further, by selecting the material and configuration of each reflecting mirror according to the oscillation wavelength, a light emitting unit corresponding to an arbitrary oscillation wavelength can be formed. For example, other than AlGaAs mixed crystal such as AlGaInP mixed crystal can be used. The low refractive index layer and the high refractive index layer are preferably a combination that is transparent with respect to the oscillation wavelength and can take a difference in refractive index as much as possible.

  In the above embodiment, the case where the optical scanning device 1010 is used in a printer has been described. However, the optical scanning device 1010 may be used in an image forming apparatus other than a printer, for example, a copier, a facsimile, or a multifunction machine in which these are integrated. it can.

  In the above embodiment, the laser printer 1000 is described as the image forming apparatus. However, the present invention is not limited to this.

  For example, an image forming apparatus that directly irradiates laser light onto a medium (for example, paper) that develops color with laser light may be used.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by a process equivalent to a printing process in a normal silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  As an example, as shown in FIG. 44, a color printer 2000 including a plurality of photosensitive drums may be used.

  The color printer 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow). The black “photosensitive drum K1, charging device K2, "Developing device K4, cleaning unit K5, and transfer device K6", cyan "photosensitive drum C1, charging device C2, developing device C4, cleaning unit C5, and transfer device C6", and magenta "photosensitive drum" M1, charging device M2, developing device M4, cleaning unit M5, and transfer device M6 ”,“ photosensitive drum Y1, charging device Y2, developing device Y4, cleaning unit Y5, and transfer device Y6 ”for yellow, and light A scanning device 2010, a transfer belt 2080, a fixing unit 2030, and the like are provided.

  Each photoconductor drum rotates in the direction of the arrow in FIG. 44, and a charging device, a developing device, a transfer device, and a cleaning unit are arranged around each photoconductor drum along the rotation direction. Each charging device uniformly charges the surface of the corresponding photosensitive drum. The surface of each photoconductive drum charged by the charging device is irradiated with light by the optical scanning device 2010, and a latent image is formed on each photoconductive drum. Then, a toner image is formed on the surface of each photosensitive drum by a corresponding developing device. Further, the toner image of each color is transferred onto the recording paper on the transfer belt 2080 by the corresponding transfer device, and finally the image is fixed on the recording paper by the fixing unit 2030.

  The optical scanning device 2010 includes a light source including any one of the surface-emitting laser element 100, a surface-emitting laser element similar to any of the surface-emitting laser elements 100_1 to 100_4, or a surface-emitting laser array similar to the surface-emitting laser array 100M. For each color. Therefore, the same effect as that of the optical scanning device 1010 can be obtained. In addition, since the color printer 2000 includes the optical scanning device 2010, the same effect as the laser printer 1000 can be obtained.

  By the way, in the color printer 2000, color misregistration may occur due to manufacturing error or position error of each component. Even in such a case, if each light source of the optical scanning device 2010 has a surface emitting laser array similar to the surface emitting laser array 100M, color misregistration is reduced by selecting a light emitting unit to be lit. can do.

  As described above, the surface-emitting laser element and the surface-emitting laser array according to the present invention are suitable for stabilizing the polarization direction while controlling the oscillation of the high-order transverse mode. Further, the optical scanning device of the present invention is suitable for performing stable optical scanning. The image forming apparatus of the present invention is suitable for forming a high quality image.

  DESCRIPTION OF SYMBOLS 11a ... Deflector side scanning lens (a part of scanning optical system), 11b ... Image surface side scanning lens (a part of scanning optical system), 13 ... Polygon mirror (deflector), 14 ... Light source, 100 ... Surface emitting laser Elements 100_1 to 100_4... Surface emitting laser element, 100M... Surface emitting laser array, 101... Substrate, 103. Lower semiconductor DBR (part of semiconductor multilayer reflector), 104. Part), 105 ... active layer, 106 ... upper spacer layer (part of the resonator structure), 107 ... upper semiconductor DBR (part of the semiconductor multilayer reflector), 109 ... contact layer, 113 ... p-side electrode ( Electrode), 115 ... mode filter (dielectric film), 1000 ... laser printer (image forming apparatus), 1010 ... optical scanning device, 1030 ... photosensitive drum (image carrier), 2000 ... color Printer (image forming apparatus), 2010 ... optical scanning device, K1, C1, M1, Y1 ... photosensitive drum (image bearing member).

JP 2002-208755 A JP 2001-156395 A US Pat. No. 5,940,422 JP 2006-210429 A Japanese Patent No. 3955925 JP 9-83066 A JP 2007-201398 A JP 2004-289033 A

Claims (14)

A resonator structure including an active layer, a semiconductor multilayer film reflector provided across the resonator structure, and an emission surface on which light is emitted are provided so as to surround an emission region, at least a part of which is provided. In a surface emitting laser device comprising an electrode in contact with a contact layer,
A transparent dielectric film provided in the emission region, and having a different reflectance at the periphery and a reflectance at the center;
The portions having different reflectivities in the central portion have different lengths in two directions orthogonal to each other in the exit surface,
The surface emitting laser device according to claim 1, wherein a current injection region in contact with the contact layer in the electrode has shape anisotropy.   2. The surface according to claim 1, wherein the peripheral portions having different reflectances include a plurality of small portions, and the plurality of small portions are opposed to each other with a central portion of the emission region interposed therebetween. Light emitting laser element.   The portion of the electrode that is in contact with the contact layer is composed of a plurality of small portions, divided into regions, and facing each other with a central portion of the emission region interposed therebetween. The surface emitting laser element described.   The portion having different reflectance at the peripheral portion has a transparent dielectric film having an optical thickness that is an odd multiple of "oscillation wavelength / 4". Surface emitting laser element.   5. The surface emitting laser element according to claim 4, wherein the dielectric film is any one of SiNx, SiOx, TiOx, and SiON.   6. The surface emitting laser element according to claim 4, wherein the central portion having a different reflectance has a transparent dielectric film having an optical thickness that is an even multiple of “oscillation wavelength / 4”. .   7. The surface emitting laser element according to claim 6, wherein the dielectric film of the portion having a different reflectance at the central portion is made of the same material as the dielectric film of the portion having a different reflectance at the peripheral portion.   7. The surface emitting laser device according to claim 6, wherein the dielectric film of the portion having a different reflectance at the center is formed by laminating two materials having different refractive indexes.   9. The surface emitting laser element according to claim 8, wherein the optical thicknesses of the two materials having different refractive indexes are each an odd multiple of “oscillation wavelength / 4”.   A surface-emitting laser array in which the surface-emitting laser elements according to claim 1 are integrated. An optical scanning device that scans a surface to be scanned with light,
A light source comprising the surface-emitting laser element according to claim 1;
A deflector for deflecting light from the light source;
A scanning optical system for condensing the light deflected by the deflector onto the surface to be scanned. An optical scanning device that scans a surface to be scanned with light,
A light source comprising the surface emitting laser array according to claim 10;
A deflector for deflecting light from the light source;
A scanning optical system for condensing the light deflected by the deflector onto the surface to be scanned. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to claim 11 or 12 that scans the at least one image carrier with light modulated according to image information.   The image forming apparatus according to claim 13, wherein the image information is multicolor color image information.

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