JP5843178B2 - Surface emitting laser element, surface emitting laser array, optical scanning device, and image forming apparatus - Google Patents

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. 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.

  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, the surface emitting semiconductor lasers disclosed in Patent Documents 2 to 4 have the disadvantages that it is difficult to stably obtain a high output and that the lifetime is short.

  The inventors have conducted various experiments and the like, and the above-described inconvenience factors of the surface emitting semiconductor lasers disclosed in Patent Documents 2 to 4, the large electric resistance of the surface emitting semiconductor laser (hereinafter, It was found that the heat was generated by “element resistance”.

  The present invention has been made on the basis of the novel knowledge obtained by the inventors described above, and has the following configuration.

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. In the surface emitting laser element in which the emission region and the electrode are provided on the mesa structure, the emission region and the electrode are formed in the emission region and deviated from the center of the emission region. wherein the reflectance of the portion of the injection region further comprises a dielectric film that is lower than the reflectance of the central portion, when viewed from the injection direction, the front SL unit content includes two areas which sandwich the said central portion, The dielectric film has shape anisotropy in two directions orthogonal to each other, and the shape of the mesa structure viewed from the emission direction includes a maximum width and a minimum width, and the electrode and the contact layer are The shape of the outside of the contacting part in the maximum width direction Is a surface-emitting laser element characterized by greater than a width of the minimum width direction of the outer shape.
According to a second 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. In the surface emitting laser element in which the emission region and the electrode are provided on the mesa structure, the emission region and the electrode are formed in the emission region and deviated from the center of the emission region. wherein the reflectance of the portion of the injection region further comprises a dielectric film that is lower than the reflectance of the central portion, when viewed from the injection direction, the front SL unit content includes two areas which sandwich the said central portion, The dielectric film has shape anisotropy in two directions orthogonal to each other, and the shape of the mesa structure viewed from the emission direction includes a plurality of sides and is a portion where the electrode and the contact layer are in contact with each other. The outer shape is the same as the plurality of sides and the plurality of sides. A surface emitting laser element which comprises a parallel sides.
According to a third 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. In the surface emitting laser element in which the emission region and the electrode are provided on the mesa structure, the emission region and the electrode are formed in the emission region and deviated from the center of the emission region. wherein the reflectance of the portion of the injection region further comprises a dielectric film that is lower than the reflectance of the central portion, when viewed from the injection direction, the front SL unit content includes two areas which sandwich the said central portion, In the surface emitting laser device, a part of a portion where the electrode and the contact layer are in contact exists between the two regions.

According to this, it is possible to reduce the element resistance without increasing the width of the mesa while performing the single transverse mode operation with high output.

From the fourth 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, since it is possible to integrate without increasing the pitch between the elements (light emitting portion spacing), it is possible to integrate the surface emitting laser elements with a low element resistance and capable of single transverse mode operation with high output at high density. Can do.

According to a fifth 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 element according to the present invention, a deflector that deflects light from the light source, And 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 sixth 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, And 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 seventh aspect of the present invention, 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 the light source in FIG. It is AA sectional drawing of FIG. It is a figure for demonstrating the lamination | stacking state of the several semiconductor layer in the surface emitting laser element of FIG. FIGS. 6A and 6B are views (No. 1) for explaining a method of manufacturing the surface emitting laser element of FIG. FIGS. 7A and 7B are views (No. 2) for describing a method of manufacturing the surface emitting laser element of FIG. It is a figure for demonstrating an etching mask. It is the figure which took out and expanded the mesa upper surface part in FIG. FIGS. 10A and 10B are views (No. 3) for describing a method of manufacturing the surface emitting laser element of FIG. FIGS. 11A and 11B are views (No. 4) for describing a method of manufacturing the surface emitting laser element of FIG. FIG. 5 is a view (No. 5) for explaining a method of manufacturing the surface emitting laser element of FIG. 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 contact area | region of the p side electrode and contact layer in the conventional surface emitting laser element C. FIG. It is a figure for demonstrating the contact area | region of the p side electrode and contact layer in the surface emitting laser element of FIG. It is a figure for demonstrating the modification 1 of a mode filter. FIG. 23A and FIG. 23B are diagrams for explaining an inclined substrate. It is a figure for demonstrating the modification 2 of a mode filter. It is a figure for demonstrating the modification of a p side electrode. FIG. 6 is a diagram (No. 1) for describing a first modification of the surface emitting laser element of FIG. 3; FIG. 10 is a diagram (No. 2) for explaining the first modification of the surface emitting laser element of FIG. 3; FIG. 10 is a diagram for explaining a modification of the mode filter in the surface emitting laser element of the first modification. FIG. 10 is a diagram (No. 1) for describing a second modification of the surface emitting laser element of FIG. 3; FIG. 10 is a diagram (No. 2) for explaining the modified example 2 of the surface emitting laser element of FIG. 3; 12 is a diagram for explaining a modification of the mode filter in the surface emitting laser element of Modification 2. FIG. It is a figure for demonstrating a surface emitting laser array. It is AA sectional drawing of FIG. It is a figure for demonstrating the case where the external shape of an element is an octagon. It is a figure for demonstrating the array by which the element of FIG. 34 was arrange | positioned two-dimensionally 3x3. 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 in the vicinity of 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.

  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.

  The substrate 101 is an n-GaAs single crystal semiconductor substrate.

The lower semiconductor DBR 103 is stacked via a buffer layer (not shown) on the + Z side of the substrate 101, and includes a low refractive index layer made of n-AlGaAs 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 electrical resistance, a composition gradient layer having a thickness of 20 nm in which the composition is gradually changed from one composition to the other composition (not shown in FIG. 4, see FIG. 5). ) 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 (not shown in FIG. 4, see FIG. 5) in which the composition is gradually changed from one composition to the other composition is provided. ing. 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 selective oxidation layer 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 contact layer 109 is electrically connected to the p-side electrode 113.

  The mode filter 115 is a transparent dielectric film and is formed in the emission region on the + Z side of the contact layer 109. Here, as an example, the mode filter 115 has an annular shape surrounding the central portion of the emission region, and the reflectance is lower than the reflectance of the central portion.

  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 above laminate is formed by crystal growth by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) (see FIG. 6A).

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 ) is used as the group V material. 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 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. 6B).

(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. 7A). 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 passage region (current injection 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. 7B). 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 an example, as shown in FIG. 8 and FIG. 9 in which only the mesa in FIG. 8 is taken out and enlarged, an inner diameter L4 (here 5 μm) provided with the mode filter 115, an outer diameter L3 (here 13 μm) is provided. The mask M is fabricated so that the annular region, the periphery of the mesa, and the periphery of the upper surface of the mesa are not etched. The width of the mode filter is 4 μm. In addition, the outer shape of the region where the p-side electrode 113 and the contact layer 109 are in contact with each other has a square shape with a side length L2 (here, 20 μm). At this time, a rounded rectangle with R at the corner of the square may be used.

(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. 10A and 10B). Here, the protective layer 111 remaining in the emission region becomes the mode filter 115.

(10) A circular resist pattern having a diameter L3 (here, 13 μm) is formed in a region to be a light emitting portion on the mesa, and a p-side electrode material is deposited. 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. 11A). A region surrounded by the p-side electrode 113 is an emission region. Note that FIG. 11B shows an enlarged view of only the mesa in FIG. The shape of the injection region is a circle having a diameter L3 (here, 13 μm). In the present embodiment, the mode filter 115 exists as a transparent dielectric film made of SiN having an optical thickness of λ / 4 in the emission region. As a result, the reflectance of the region where the mode filter 115 exists in the emission region is lower than the reflectance of the central portion 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.

(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. 12). 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.

  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. 13 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.

  When 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. 13, 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 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, a surface emitting laser element having low element resistance, excellent thermal characteristics, long life, and high yield can be obtained.

  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 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 is strongest and tends to become weaker as it approaches the center. In this embodiment, the reflectance of the region set in the periphery of the emission region is lower than the reflectance of the center portion, so that the reflection in the higher-order transverse mode is performed without reducing the reflectance with respect to the fundamental transverse mode. As a result, the higher-order transverse mode oscillation can be suppressed.

  14 and 15 show a surface emitting laser element A having a conventional standard device structure in which no mode filter is provided.

  16 and 17 show a surface-emitting laser element B in which the opening diameter of the electrode is narrower than that of the surface-emitting laser element A (see Patent Document 1). In this surface emitting laser element B, higher-order transverse modes are 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 area of the exit surface is completely shielded with metal, the output becomes small.

  18 and 19 show a conventional surface emitting laser element C provided with a mode filter 115 made of a dielectric film (see Patent Documents 2 to 4). In this surface-emitting laser element C, the mode filter 115 is a transparent dielectric film, so that the fundamental transverse mode output is higher than that of the surface-emitting laser element B. However, as shown in FIG. 20, the contact region between the p-side electrode 113 and the contact layer 109 is annular (width 3.5 μm), the contact area is small, and the element resistance is high.

  On the other hand, in the surface-emitting laser element 100, as shown in FIG. 21, the outer shape of the outside of the contact region between the p-side electrode 113 and the contact layer 109 is not an annular shape but includes a corner (square in FIG. 21). Therefore, the contact area between the p-side electrode 113 and the contact layer 109 is larger than that of the surface emitting laser element C. Thereby, the element resistance can be lowered while the single transverse mode operation is performed at a high output. The width of the mesa in the surface emitting laser element 100 in FIG. 21 is the same as the width (diameter) of the mesa in the surface emitting laser element C in FIG.

By the way, in the surface emitting laser element C, if a sufficient contact area between the p-side electrode 113 and the contact layer 109 is to be secured, the width of the mesa becomes large, and in the case of an array, there is a disadvantage that it cannot be integrated at a narrow pitch. . In addition, since the oxidation distance during the selective oxidation treatment becomes long, the controllability of the shape and size of the current passage region is deteriorated, and the yield is disadvantageously lowered.

  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.

The outer shape of the portion of the p-side electrode 113 that is in contact with the contact layer 109 has a corner. In this case, the contact area between the p-side electrode 113 and the contact layer 109 can be made larger than before without increasing the width of the mesa. Therefore, the element resistance can be lowered while the single transverse mode operation is performed at a high output. And it can be made longer life than before.

  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 embodiment, the case where the outer shape of the region where the p-side electrode 113 and the contact layer 109 are in contact with each other has a square shape has been described. However, the present invention is not limited to this. For example, the outer shape of the region where the p-side electrode 113 and the contact layer 109 are in contact may be rectangular. Further, it may be a quadrilateral or more polygon (for example, an octagon). At this time, the polygon which the circle | round | yen which is the external shape of the area | region where the conventional p side electrode and a contact layer contact may be inscribed. In this case, the contact area between the p-side electrode and the contact layer can be made larger than before without increasing the size of the mesa.

Further, in the above embodiment, the protective layer 111 has been described for the case of SiN, not limited to this, for _example, SiN _x, SiO x, may be any of TiO _x and SiON. The same effect can be obtained by designing the film thickness according to the refractive index of each material.

  In the above-described embodiment, the mode filter 115 is described as an annular shape surrounding the central portion of the emission region, but the present invention is not limited to this.

  For example, as shown in FIG. 22, even if the mode filter 115 is formed in two small regions that are opposed to each other with respect to the X-axis direction with the central portion interposed therebetween and that are provided at a portion deviating from the central portion of the emission region. good.

  In this case, as shown in FIG. 23A as an example, 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. [1 1 1] An n-GaAs single crystal semiconductor substrate inclined at 15 degrees (θ = 15 degrees) in the A direction may be used. That is, the substrate 101 may be a so-called inclined substrate. At this time, as shown in FIG. 23B as an example, the crystal orientation [0 −1 1] direction may be + X direction and the crystal orientation [0 1 −1] direction may be −X direction. good.

  When an inclined substrate is used, the polarization direction is stabilized and the polarization suppression ratio PMSR is increased. The polarization suppression ratio PMSR is a ratio between the light intensity in a desired polarization direction and the light intensity in a direction orthogonal thereto.

  For example, in a surface emitting laser element having a structure equivalent to that of the surface emitting laser element 100 and having no mode filter, mainly the effect of the tilted substrate is added, but the effect of distortion of the active layer and the like is added, resulting in the tilt direction of the substrate. It became easy to polarize in the direction orthogonal to (the X-axis direction in FIG. 23A). At this time, the polarization suppression ratio PMSR was 20 to 30 dB.

  Further, in the surface emitting laser 100 having an annular mode filter, it becomes easy to polarize in the substrate tilt direction (Y-axis direction in FIG. 23A). At this time, the polarization suppression ratio PMSR was reduced to 10 to 20 dB.

  When the mode filter 115 shown in FIG. 22 is formed, it becomes easy to polarize in the direction orthogonal to the tilt direction of the substrate (X-axis direction in FIG. 23A). At this time, the polarization suppression ratio PMSR was 20 to 30 dB. That is, the PMSR was improved as compared with a symmetric (non-anisotropic) shaped mode filter. In this case, although the dielectric film is missing in a part of the region surrounding the central portion of the emission region, the fundamental mode output is comparable to that of the surface emitting laser 100 in the above embodiment. As a result, a surface emitting laser with a high polarization suppression ratio PMSR in addition to a high fundamental transverse mode output and low element resistance can be obtained.

  Anisotropy in the light confinement effect in two directions orthogonal to each other as a factor that improves polarization stability by making the number of small regions where a transparent dielectric film having an optical thickness of λ / 4 is formed into plural It is possible that When the mode filter 115 shown in FIG. 22 is formed, the light whose polarization direction coincides with the direction orthogonal to the tilt direction of the substrate (X-axis direction in FIG. 23A) is the peripheral part of the emission region. Compared with the light, the confinement action at the center of the emission region having a high reflectance works, and the oscillation threshold value is lowered as compared with the light whose polarization direction coincides with the substrate tilt direction. As a result, it is considered that the polarization suppression ratio is improved.

  That is, by providing a plurality of mode filters and giving shape anisotropy to a region sandwiched between the mode filters, anisotropy can be generated in the lateral confinement action. As a result, the polarization component in the direction with strong confinement is more likely to oscillate than the polarization component in the direction with weak confinement, and the polarization direction can be matched with the direction with strong confinement.

  When the desired polarization direction is the substrate tilt direction (the Y-axis direction in FIG. 23A), the mode filter 115 is opposed to the Y-axis direction with the center portion interposed therebetween, and the center of the emission region. What is necessary is just to form in two small area | regions provided in the part remove | deviated from the part.

  By the way, the stable polarization direction without the mode filter can be changed by changing the strain state in the active layer or the like.

  In FIG. 22, the two small regions are provided so as to be symmetric with respect to an axis passing through the center of the emission region and parallel to the Y-axis direction. However, the present invention is not limited to this. There may be a first small area on one side of the axis passing through the center of the injection area and parallel to the Y axis, and a second small area on the other side.

  In addition, in FIG. 22, the case where the shape of each small region is a shape in which a donut is divided into two has been described, but the present invention is not limited to this. An arbitrary shape such as a rectangular shape (see FIG. 24), a semicircular shape, or an elliptical shape may be used.

  The dielectric films formed in the two small regions may be made of the same material or different materials.

  In addition, the mode filter 115 is provided in a portion deviated from the center of the emission region, and is formed in one small region having shape anisotropy in a desired polarization direction and a direction orthogonal thereto, like an elliptical shape. May be. At this time, shape anisotropy due to different widths may be used.

  By the way, when using an inclined substrate, the normal direction of the main surface of the substrate is inclined toward one direction of crystal orientation <1 1 1> with respect to one direction of crystal orientation <1 0 0>. It should be.

  As an example, as shown in FIG. 24 and FIG. 25, the mode filter 115 is formed in two small regions that are opposed to each other with the central portion interposed therebetween and are provided in a portion that is off the central portion of the emission region, A part of the portion in contact with the contact layer 109 in the p-side electrode 113 may exist between the two small regions. In this case, the contact area between the p-side electrode 113 and the contact layer 109 is increased, and the element resistance can be further reduced. At this time, the p-side electrode may cover a part of the mode filter 115.

  Moreover, although the said embodiment demonstrated the case where the optical thickness of the mode filter 115 was (lambda) / 4, it is not limited to this. In short, the optical thickness of the mode filter 115 may be an odd multiple of λ / 4.

  In the above embodiment, instead of the surface emitting laser element 100, as shown in FIG. 26 and FIG. 27 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 100A in which a dielectric film 116 made of SiN is laminated 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 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.

  In this case, as shown in FIG. 28 as an example, the mode filter is formed in two small regions that are opposed to each other with the central portion of the emission region interposed therebetween and are provided at portions that are off the central portion of the emission region. May be. The substrate 101 may be an inclined substrate.

  In the above embodiment, instead of the surface emitting laser element 100, as shown in FIG. 29 and FIG. 30 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 100B that is provided and has a low-reflectance region made of a single dielectric layer in a region off the center may be used. The thickness of each dielectric layer is set to an odd multiple of λ / 4n (n is the refractive index of each dielectric layer with respect to the oscillation wavelength) with respect to the oscillation wavelength λ.

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 a λ / 4n thickness 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 100B, the reflectance at the central portion is improved, so that the difference in reflectance between the central portion and a region outside the central portion can be greatly increased.

  In this case, as shown in FIG. 31 as an example, the mode filter may be formed in two small regions that are opposed to each other with the central portion interposed therebetween and are provided in a portion that is off the central portion of the emission region. good. The substrate 101 may be an inclined substrate.

  In the above embodiment, the light source 14 may include a surface emitting laser array 100C shown in FIG. 32 as an example instead of the surface emitting laser element 100.

  In the surface emitting laser array 100C, a plurality (21 in this case) of light emitting units are arranged on the same substrate. Here, the X-axis direction in FIG. 32 is a main-scanning corresponding direction, and the Y-axis direction is a 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 portion has the same structure as the surface emitting laser element 100 described above, as shown in FIG. 33 which is a cross-sectional view taken along the line AA of FIG. The surface emitting laser array 100C can be manufactured by a method similar to that of 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.

  In the surface emitting laser array 100C, 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. Here, the external shape of each element (mesa) viewed from the top is a quadrangle, and the sides on the side of the physically adjacent elements are two-dimensionally arranged in a range parallel to each other, and are circular (elements). Compared with the case of forming, when the interval between the light emitting portions is made the same, the area of the mesa as viewed from above can be increased, and the electrode contact area can be increased as described above. When the contact area is the same, the pitch between the elements and the element pitch d1 (here, the same as the interval between the light emitting portions) can be reduced.

  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. According to the surface emitting laser array 100C, it is possible to narrow the interval between the light emitting portions, and it is possible to integrate the surface emitting laser elements having a small element resistance and capable of operating in a single transverse mode with a high output at a high density. . 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 reducing 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.

  Further, as shown in FIG. 34, elements having an octagonal outer shape may be two-dimensionally arranged. FIG. 35 is a diagram of a 3 × 3 array arrangement. They are two-dimensionally arranged so that the sides on the element side that are physically adjacent to each other are parallel to each other. Regarding the effect of expanding the contact area, the quadrangle is more effective, but it is more effective than the conventional element shape without corners.

  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. 36, 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. 36, 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 any one of a surface emitting laser similar to any of the surface emitting laser element 100, the surface emitting laser element 100A, and the surface emitting laser element 100B, or a surface emitting laser array similar to the surface emitting laser array 100C. Each color has a light source including the above. 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 100C, 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 of the present invention are suitable for reducing the element resistance while performing a single transverse mode operation at a high output. 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: 100A: Surface emitting laser element, 100B: Surface emitting laser element, 100C: Surface emitting laser array, 101: Substrate, 103: Lower semiconductor DBR (part of semiconductor multilayer reflector), 104: Lower spacer layer (resonant) 105 ... active layer, 106 ... upper spacer layer (part of resonator structure), 107 ... upper semiconductor DBR (part of 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 apparatus, 1030 ... photosensitive drum (image carrier), 2 00 ... 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

Claims (15)

A resonator structure including an active layer, a semiconductor multilayer reflector provided with the resonator structure interposed therebetween, and an electrode provided surrounding an emission region on an emission surface from which light is emitted In the surface emitting laser element in which the emission region and the electrode are provided on the mesa structure,
A dielectric film that is formed in the emission region and lowers the reflectance of the portion of the emission region that deviates from the central portion of the emission region, than the reflectance of the central portion;
When viewed from the injection direction, the front SL unit content includes two areas which sandwich the said central portion, the dielectric film has shape anisotropy in two orthogonal directions,
The shape of the mesa structure viewed from the injection direction includes the maximum width and the minimum width, and the width in the maximum width direction of the shape outside the portion where the electrode and the contact layer are in contact with each other is the outside A surface emitting laser element having a shape larger than a width in the minimum width direction. A resonator structure including an active layer, a semiconductor multilayer reflector provided with the resonator structure interposed therebetween, and an electrode provided surrounding an emission region on an emission surface from which light is emitted In the surface emitting laser element in which the emission region and the electrode are provided on the mesa structure,
A dielectric film that is formed in the emission region and lowers the reflectance of the portion of the emission region that deviates from the central portion of the emission region, than the reflectance of the central portion;
When viewed from the injection direction, the front SL unit content includes two areas which sandwich the said central portion, the dielectric film has shape anisotropy in two orthogonal directions,
The shape of the mesa structure viewed from the emission direction includes a plurality of sides, and the outer shape of the portion where the electrode and the contact layer are in contact is the same number as the plurality of sides and the side parallel to the plurality of sides. A surface-emitting laser element comprising:   The surface light emission according to claim 1 or 2, wherein the shape of the outer side of the portion where the electrode and the contact layer are in contact with each other and the shape of the mesa structure viewed from the emission direction are similar polygons. Laser element.   The surface emitting laser device according to claim 1, wherein the two regions are opposed to each other.   5. The surface emitting laser element according to claim 4, wherein a part of a portion where the electrode and the contact layer are in contact exists between the two regions. A resonator structure including an active layer, a semiconductor multilayer reflector provided with the resonator structure interposed therebetween, and an electrode provided surrounding an emission region on an emission surface from which light is emitted In the surface emitting laser element in which the emission region and the electrode are provided on the mesa structure,
A dielectric film that is formed in the emission region and lowers the reflectance of the portion of the emission region that deviates from the central portion of the emission region, than the reflectance of the central portion;
When viewed from the injection direction, the front SL unit content includes two areas which sandwich the said central portion,
A surface emitting laser element characterized in that a part of a portion where the electrode and the contact layer are in contact exists between the two regions.   The surface emitting laser element according to any one of claims 1 to 6, wherein the outer shape of a portion where the electrode and the contact layer are in contact includes four sides.   The surface emitting laser element according to any one of claims 1 to 7, wherein a shape inside a portion where the electrode and the contact layer are in contact includes a curve.   The surface-emitting laser element according to claim 1, wherein the dielectric film is formed in a portion deviating from a central portion of the emission region.   The surface-emitting laser element according to claim 1, wherein the dielectric film surrounds the central portion.   A surface-emitting laser array in which the surface-emitting laser elements according to any one of claims 1 to 10 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 any one of claims 1 to 10,
A deflector for deflecting light from the light source;
A scanning optical system that condenses 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 11;
A deflector for deflecting light from the light source;
A scanning optical system that condenses 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 12 or 13 that scans the at least one image carrier with light modulated according to image information. The image forming apparatus according to claim 14, wherein the image information is multicolor color image information.

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