JP2014135371A - Surface emitting laser, surface emitting laser array and optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface emitting laser which can inhibit disconnection and reduction in life.SOLUTION: A surface emitting laser comprises: light emitting parts each including 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, a dielectric layer 110, an interlayer insulation film 111, a p-side electrode 113, an n-side electrode 114, a disconnection prevention member 115 and the like. The disconnection prevention member 115 is provided on a mesa bottom, for smoothing a region running from a mesa sidewall to a mesa bottom face. In this case, shortage of coverage of a wiring material and induction of crystal defects inside the mesa can be inhibited. As a result, disconnection and reduction in life can be inhibited.

Description

  The present invention relates to a surface emitting laser, a surface emitting laser array, and an optical scanning device. More specifically, the present invention relates to a surface emitting laser that emits light in a direction orthogonal to a substrate surface, and a surface emitting laser array in which the surface emitting laser is integrated. And an optical scanning device having the surface emitting laser or the surface emitting laser array.

  A surface emitting laser (VCSEL) is a semiconductor laser that emits light in a direction perpendicular to the surface of a substrate, compared to an edge-emitting semiconductor laser that emits light in a direction parallel to the surface of the substrate. , (1) low price, (2) low power consumption, (3) small size and high performance, and (4) easy two-dimensional integration.

  The surface emitting laser has a so-called mesa structure, and various effects of the step on the p-side electrode for injecting current into the active layer are considered (for example, see Patent Documents 1 to 9).

  However, in the conventional surface emitting laser, there is a risk of disconnection due to insufficient coverage (coverability) of the wiring member on the side wall of the mesa, and there is a possibility that the lifetime may be reduced due to an increase in crystal defects due to internal stress.

  The present invention provides a surface emitting laser having a mesa structure light emitting portion in which a lower reflecting mirror, a resonator structure including an active layer, and an upper reflecting mirror are stacked on a substrate. The surface emitting laser is characterized in that a disconnection preventing member is provided which is in contact with and smoothes a region where the side wall is shifted to the bottom surface.

  According to the surface emitting laser of the present invention, it is possible to suppress disconnection and lifetime reduction.

1 is a diagram for describing a schematic configuration of a color printer according to an embodiment of the present invention. FIG. FIG. 2 is a diagram (part 1) for describing the optical scanning device in FIG. 1; FIG. 3 is a second diagram for explaining the optical scanning device in FIG. 1; FIG. 3 is a third diagram for explaining the optical scanning device in FIG. 1; FIG. 4 is a diagram (part 4) for explaining the optical scanning device in FIG. 1; It is a figure for demonstrating a surface emitting laser array. It is a figure for demonstrating the arrangement state of the several light emission part in a surface emitting laser array. It is a figure for demonstrating the structure of a light emission part. FIGS. 9A and 9B are views (No. 1) for describing a method for manufacturing a surface emitting laser array, respectively. FIGS. 10A and 10B are views (No. 2) for describing the method for manufacturing the surface emitting laser array, respectively. FIGS. 11A and 11B are views (No. 3) for describing the method for manufacturing the surface emitting laser array, respectively. It is a figure for demonstrating the relationship between the height from the mesa bottom face of a disconnection prevention member, and the lifetime of a light emission part. FIGS. 13A and 13B are views (No. 4) for describing the method of manufacturing the surface emitting laser array, respectively. It is FIG. (5) for demonstrating the manufacturing method of a surface emitting laser array. FIGS. 15A and 15B are diagrams for explaining a first modification of the surface emitting laser array. FIGS. 16A and 16B are diagrams for explaining a second modification of the surface emitting laser array. It is a figure for demonstrating a dummy mesa. It is a figure for demonstrating the case where it connects to a bonding pad from the mesa upper surface of a light emission part via a dummy mesa. It is a figure for demonstrating the modification 3 of a surface emitting laser array. It is a figure for demonstrating the modification of a disconnection prevention member.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a color printer 2000 according to an embodiment.

  The color printer 2000 is a tandem multi-color printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow), and includes an optical scanning device 2010, four photosensitive drums (2030a, 2030b, 2030c, 2030d), four cleaning units (2031a, 2031b, 2031c, 2031d), four charging devices (2032a, 2032b, 2032c, 2032d), four developing rollers (2033a, 2033b, 2033c, 2033d), transfer A belt 2040, a transfer roller 2042, a fixing device 2050, a paper feed roller 2054, a paper discharge roller 2058, a paper feed tray 2060, a paper discharge tray 2070, a communication control device 2080, and a printer control device 209 that comprehensively controls the above-described units. And and the like.

  The communication control device 2080 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The printer control device 2090 includes a CPU, a program described in a code decodable by the CPU, a ROM storing various data used when executing the program, a RAM that is a working memory, an amplification circuit And an A / D conversion circuit for converting analog data into digital data. Then, the printer control device 2090 notifies the optical scanning device 2010 of multi-color image information from the host device received via the communication control device 2080.

  The photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, and the cleaning unit 2031a are used as a set, and constitute an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image.

  The photosensitive drum 2030b, the charging device 2032b, the developing roller 2033b, and the cleaning unit 2031b are used as a set, and constitute an image forming station (hereinafter also referred to as “C station” for convenience) that forms a cyan image.

  The photosensitive drum 2030c, the charging device 2032c, the developing roller 2033c, and the cleaning unit 2031c are used as a set, and constitute an image forming station (hereinafter also referred to as “M station” for convenience) that forms a magenta image.

  The photosensitive drum 2030d, the charging device 2032d, the developing roller 2033d, and the cleaning unit 2031d are used as a set, and constitute an image forming station (hereinafter also referred to as “Y station” for convenience) that forms a yellow image.

  Each photosensitive drum has a photosensitive layer formed on the surface thereof. That is, the surface of each photoconductive drum is a surface to be scanned. Each photosensitive drum is rotated in the direction of the arrow in the plane of FIG. 1 by a rotation mechanism (not shown).

  Each charging device uniformly charges the surface of the corresponding photosensitive drum.

  The optical scanning device 2010 is charged correspondingly with a light beam modulated for each color based on multicolor image information (black image information, cyan image information, magenta image information, yellow image information) from the printer control device 2090. The surface of the photosensitive drum is scanned. Thereby, a latent image corresponding to the image information is formed on the surface of each photosensitive drum. The latent image formed here moves in the direction of the corresponding developing device as the photosensitive drum rotates. The configuration of the optical scanning device will be described later.

  As each developing roller rotates, toner from a corresponding toner cartridge (not shown) is thinly and uniformly applied to the surface thereof. Then, when the toner on the surface of each developing roller comes into contact with the surface of the corresponding photosensitive drum, the toner moves only to a portion irradiated with light on the surface and adheres to the surface. In other words, each developing roller causes toner to adhere to the latent image formed on the surface of the corresponding photosensitive drum so as to be visualized. Here, the toner-attached image (toner image) moves in the direction of the transfer belt 2040 as the photosensitive drum rotates.

  The yellow, magenta, cyan, and black toner images are sequentially transferred onto the transfer belt 2040 at a predetermined timing, and are superimposed to form a color image.

  Recording paper is stored in the paper feed tray 2060. A paper feed roller 2054 is disposed in the vicinity of the paper feed tray 2060. The paper feed roller 2054 takes out the recording paper one by one from the paper feed tray 2060. The recording paper is sent out toward the gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. As a result, the color image on the transfer belt 2040 is transferred to the recording paper. The recording paper on which the color image is transferred is sent to the fixing device 2050.

  In the fixing device 2050, heat and pressure are applied to the recording paper, thereby fixing the toner on the recording paper. The recording paper on which the toner is fixed is sent to the paper discharge tray 2070 via the paper discharge roller 2058 and is sequentially stacked on the paper discharge tray 2070.

  Each cleaning unit removes toner (residual toner) remaining on the surface of the corresponding photosensitive drum. The surface of the photosensitive drum from which the residual toner has been removed returns to the position facing the corresponding charging device again.

  Next, the configuration of the optical scanning device 2010 will be described.

  2 to 5 as an example, the optical scanning device 2010 includes four light sources (2200a, 2200b, 2200c, 2200d), four coupling lenses (2201a, 2201b, 2201c, 2201d), four openings. Plate (2202a, 2202b, 2202c, 2202d), four cylindrical lenses (2204a, 2204b, 2204c, 2204d), optical deflector 2104, four scanning lenses (2105a, 2105b, 2105c, 2105d), six folding mirrors ( 2106a, 2106b, 2106c, 2106d, 2108b, 2108c), 4 synchronization detection mirrors (2205a, 2205b, 2205c, 2205d), 4 synchronization detection sensors (2206a, 2206b, 2206c, 2206d) And a like scan control device (not shown).

  Here, in the XYZ three-dimensional orthogonal coordinate system, the direction along the longitudinal direction (rotation axis direction) of each photosensitive drum is defined as the Y-axis direction, and the direction parallel to the rotation axis of the optical deflector 2104 is defined as the Z-axis direction. To do.

  In the following, for convenience, in each optical member, a direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and a direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

  The scanning control device controls four light sources (2200a, 2200b, 2200c, 2200d) and an optical deflector 2104.

  A light source 2200a, a coupling lens 2201a, an aperture plate 2202a, a cylindrical lens 2204a, a scanning lens 2105a, a folding mirror 2106a, a synchronization detection mirror 2205a, and a synchronization detection sensor 2206a are optical members for forming a latent image on the photosensitive drum 2030a. It is.

  The light source 2200b, the coupling lens 2201b, the aperture plate 2202b, the cylindrical lens 2204b, the scanning lens 2105b, the folding mirror 2106b, the folding mirror 2108b, the synchronization detection mirror 2205b, and the synchronization detection sensor 2206b form a latent image on the photosensitive drum 2030b. It is an optical member for.

  The light source 2200c, the coupling lens 2201c, the aperture plate 2202c, the cylindrical lens 2204c, the scanning lens 2105c, the folding mirror 2106c, the folding mirror 2108c, the synchronization detection mirror 2205c, and the synchronization detection sensor 2206c form a latent image on the photosensitive drum 2030c. It is an optical member for.

  A light source 2200d, a coupling lens 2201d, an aperture plate 2202d, a cylindrical lens 2204d, a scanning lens 2105d, a folding mirror 2106d, a synchronization detection mirror 2205d, and a synchronization detection sensor 2206d are optical members for forming a latent image on the photosensitive drum 2030d. It is.

  As shown in FIG. 6 as an example, each light source has a surface emitting laser array 100 in which 32 light emitting units are two-dimensionally arranged. Around the 32 light emitting units, 32 bonding pads corresponding to the respective light emitting units are provided. Here, in each light source, the laser oscillation direction is the z-axis direction, the main scanning corresponding direction is the y-axis direction, and the sub-scanning corresponding direction is the x-axis direction.

  As shown in FIG. 7, the 32 light emitting units have the same light emitting unit interval (“d1” in FIG. 7) when all the light emitting units are orthogonally projected onto a virtual line extending in the sub-scanning corresponding direction. Is arranged. In this specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions. Details of each light emitting unit will be described later.

  Each coupling lens is disposed on the optical path of the light beam emitted from the corresponding light source, and makes the light beam a substantially parallel light beam.

  Each aperture plate has an opening, and shapes the light beam via the corresponding coupling lens.

  Each cylindrical lens forms an image of the light beam that has passed through the opening of the corresponding aperture plate in the vicinity of the deflection reflection surface of the optical deflector 2104 in the Z-axis direction.

  The optical system disposed on the optical path between each light source and the optical deflector 2104 is also called a pre-deflector optical system.

  The optical deflector 2104 has a two-stage polygon mirror. Each polygon mirror has four deflecting reflecting surfaces. The first-stage (lower) polygon mirror deflects the light beam from the cylindrical lens 2204a and the light beam from the cylindrical lens 2204d. The second-stage (upper) polygon mirror deflects the light beam from the cylindrical lens 2204b and the cylindrical lens 2204c. Are arranged so as to be deflected respectively. Note that the first-stage polygon mirror and the second-stage polygon mirror rotate with a phase shift of approximately 45 ° from each other, and writing scanning is alternately performed in the first and second stages.

  The light beam from the cylindrical lens 2204a deflected by the optical deflector 2104 is irradiated onto the photosensitive drum 2030a via the scanning lens 2105a and the folding mirror 2106a, thereby forming a light spot.

  The light beam from the cylindrical lens 2204b deflected by the optical deflector 2104 is irradiated to the photosensitive drum 2030b via the scanning lens 2105b and the two folding mirrors (2106b and 2108b), and a light spot is formed. The

  The light beam from the cylindrical lens 2204c deflected by the optical deflector 2104 is applied to the photosensitive drum 2030c through the scanning lens 2105c and the two folding mirrors (2106c and 2108c), thereby forming a light spot. The

  The light beam from the cylindrical lens 2204d deflected by the optical deflector 2104 is irradiated onto the photosensitive drum 2030d through the scanning lens 2105d and the folding mirror 2106d, thereby forming a light spot.

  The light spot on each photosensitive drum moves in the longitudinal direction of the photosensitive drum as the optical deflector 2104 rotates. The moving direction of the light spot at this time is the “main scanning direction”, and the rotation direction of the photosensitive drum is the “sub-scanning direction”.

  An optical system disposed on the optical path between the optical deflector 2104 and each photosensitive drum is also called a scanning optical system.

  Each synchronization detection sensor receives light, which is deflected by the optical deflector 2104 and travels toward the corresponding photosensitive drum and is not used for writing, via the corresponding synchronization detection mirror. Each synchronization detection sensor outputs a signal corresponding to the amount of received light to the scanning control device. The scanning control device obtains the writing start timing to the corresponding photosensitive drum based on the output signal of each synchronization detection sensor.

  Here, each light emitting part of the surface emitting laser array 100 will be described.

  FIG. 8 is a cross-sectional view taken along a plane parallel to the z-axis, including the center of one light emitting unit and the center of a bonding pad corresponding to the light emitting unit.

  Each light emitting unit is a surface emitting laser having an oscillation wavelength 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, and a dielectric layer 110. , An interlayer insulating film 111, a p-side electrode 113, an n-side electrode 114, a disconnection preventing member 115, and the like. In other words, the surface emitting laser array 100 is obtained by integrating a plurality of surface emitting lasers.

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

The lower semiconductor DBR 103 is stacked on the surface of the substrate 101 on the + z side via a buffer layer (not shown), and includes a low refractive index layer made of n-Al _0.9 Ga _0.1 As, n-Al _0. 40.5 pairs of high refractive index layers made of ₃ Ga _0.7 As are provided. Between each refractive index layer, in order to reduce an 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 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 laminated on the + z side of the lower semiconductor DBR 103 and is a layer made of non-doped Al _0.6 Ga _0.4 As.

The active layer 105 is laminated on the + z side of the lower spacer layer 104 and is an active layer including a quantum well layer of Al _0.12 Ga _0.88 As and a barrier layer of Al _0.3 Ga _0.7 As.

The upper spacer layer 106 is stacked on the + z side of the active layer 105 and is a layer made of non-doped Al _0.6 Ga _0.4 As.

  The portion composed of the lower spacer layer 104, the active layer 105, and the upper spacer layer 106 is also referred to as a resonator structure, and includes a half of the adjacent composition gradient layer, and has an optical thickness of one wavelength. It is set so as to be an appropriate thickness. 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. A composition gradient layer is provided between the refractive index layers. 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. This selective oxidation layer is inserted in the second pair of low refractive index layers from the upper spacer layer 106.

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

  Note that a structure in which a plurality of semiconductor layers are stacked on the substrate 101 is also referred to as a “stacked body” for convenience in the following.

The dielectric layer 110 is stacked on the + z side of the contact layer 109. As a material of the dielectric layer 110, silicon nitride (SiN), silicon oxide (SiO ₂ ), silicon oxynitride (SiON), or the like can be used.

As a material of the interlayer insulating film 111, silicon nitride (SiN), silicon oxide (SiO ₂ ), silicon oxynitride (SiON), or the like can be used.

  The disconnection preventing member 115 is preferably a substance that is liquid when applied and can be cured after application from the viewpoint of workability. For example, as the disconnection preventing member 115, an organic resin such as so-called SOG (Spin On Glass) or polyimide can be used.

  SOG can be cured by heating. The organic resin includes a room temperature polymerization type, a heat polymerization type, and a photopolymerization type, and PBO (polybenzoxazole) which is a photopolymerization type photosensitive polyimide is preferable from the viewpoint of workability. SOG and polyimide are chemically stable materials, and function as highly reliable disconnection preventing members without deterioration over time.

  Next, a method for manufacturing the surface emitting laser array 100 will be described.

(1) The laminate is formed by crystal growth by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) (see FIG. 9A).

Here, trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as Group III materials, and phosphine (PH ₃ ) and arsine (AsH ₃ ) are used as Group V materials. ing. 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 dielectric layer 110 is formed on the surface of the stacked body by a plasma CVD method (see FIG. 9B).

(3) A resist mask including a pattern of a mesa region and a bonding pad region is formed on the surface of the dielectric layer 110.

(4) The dielectric layer 110 is removed by wet etching using the resist mask.

(5) Using the resist mask, the semiconductor layer is etched by an inductively coupled (ICP) dry etching method. Note that the shape of the mesa side wall and the taper angle θ can be adjusted according to the etching conditions. Here, as an example, the contact layer 109 is almost linear from the etching bottom. The bottom surface of the etching is positioned in the lower spacer layer 104. The etching depth at this time is L.

(6) The resist mask is removed (see FIG. 10A).

(7) Heat treatment in water vapor. Here, Al in the selective oxidation layer 108 is selectively oxidized from the outer periphery of the mesa. Then, an unoxidized region 108b surrounded by the Al oxide layer 108a is left in the center of the mesa (see FIG. 10B). As a result, an oxidized constriction structure that restricts the drive current path of the light-emitting portion to only the central portion of the mesa is created. The non-oxidized region 108b is a current passage region (current injection region).

(8) An interlayer insulating film 111 is formed on the entire surface by plasma CVD (see FIG. 11A).

(9) After applying the disconnection preventing member 115 to the bottom of the mesa by using a spin method or a dip method, the disconnection preventing member 115 is cured (see FIG. 11B). Here, PBO (polybenzoxazole) is used as the disconnection preventing member 115.

  At this time, the disconnection preventing member 115 is applied by adjusting the viscosity of the disconnection preventing member 115 so that the height from the bottom surface of the mesa is not L / 2 or less rather than the entire surface of the mesa side wall. Etch back after curing. When the disconnection preventing member 115 is formed up to a height of L / 2 or more from the bottom of the mesa, stress due to shrinkage during curing acts on the inside of the mesa, inducing crystal defects inside the mesa, and reliability. Or the life may be affected (see FIG. 12). Here, the height of the disconnection prevention member 115 is further set to be equal to or lower than the surface of the upper spacer layer 106 on the + z side, that is, the height of the resonator structure.

  The disconnection preventing member 115 is in contact with a part of the mesa side wall and smoothes a region that transitions from the mesa side wall to the mesa bottom surface. The disconnection preventing member 115 has a curved surface, and the height decreases as the distance from the mesa side wall increases.

(10) An etching mask for opening a so-called window is formed on the upper part of the mesa serving as a laser beam emission surface.

(11) The interlayer insulating film 111 and the dielectric layer 110 are etched with BHF.

(12) The etching mask is removed (see FIG. 13A).

(13) A resist pattern including a peripheral region on the upper surface of the mesa, a bonding pad region, and a wiring region connecting the two regions is formed.

(14) Evaporate the electrode material on the p side. 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. The film thickness of the multilayer film is 700 nm to 900 nm.

(15) The resist pattern is dissolved and removed with an organic solvent (see FIG. 13B). Thereby, the p-side electrode 113 is formed. An area surrounded by the p-side electrode 113 on the upper surface of the mesa is an emission area.

(16) 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. 14). Here, the n-side electrode 114 is a multilayer film made of AuGe / Ni / Au.

(17) 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.

(18) Cut for each chip and mount each on a package.

  In the surface emitting laser array 100 manufactured in this way, a step of 3 μm to 5 μm exists between the mesa upper surface and the bonding pad. However, since the disconnection preventing member 115 is provided on the mesa bottom, No disconnection was observed in the light emitting part.

  As described above, according to the surface emitting laser array 100 according to the present embodiment, each light emitting unit includes the substrate 101, 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. A layer 109, a dielectric layer 110, an interlayer insulating film 111, a p-side electrode 113, an n-side electrode 114, a disconnection preventing member 115, and the like are included.

  The disconnection prevention member 115 is provided on the mesa bottom, and smoothes the region that transitions from the mesa side wall to the mesa bottom surface. In this case, lack of coverage of the wiring member can be suppressed.

  The disconnection preventing member 115 is formed not at the entire surface of the mesa side wall but at a height of L / 2 or less from the mesa bottom surface. In this case, it is possible to suppress a crystal defect from being induced inside the mesa due to shrinkage when the disconnection preventing member 115 is cured.

  Therefore, disconnection and life reduction can be suppressed. Therefore, the manufacturing yield of the surface emitting laser array 100 is improved, and the cost can be reduced.

  In the surface emitting laser array 100, the degree of integration of a plurality of light emitting units (surface emitting lasers) can be increased.

  Since each light source has the surface emitting laser array 100, the optical scanning device 2010 can perform stable optical scanning.

  Since the color printer 2000 includes the optical scanning device 2010, stable image formation can be performed as a result.

  By the way, in the surface emitting laser array 100, since the intervals between the light emitting portions when the respective light emitting portions are orthogonally projected onto the virtual line extending in the sub-scanning corresponding direction are equal intervals d2, the lighting timing is adjusted to adjust the light emitting portions on the photosensitive drum. Then, it can be considered that the configuration is the same as that in 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 2010 is doubled, high-density writing of 4800 dpi (dots / inch) can be performed. Of course, the number of light emitting portions in the direction corresponding to the main scanning is increased, the arrangement of the arrays in which the pitch d1 (see FIG. 7) in the direction corresponding to the sub scanning is narrowed to further reduce the interval d2, and the magnification of the optical system is decreased. For example, higher density can be achieved 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 color printer 2000 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 lifetime of the surface emitting laser array 100 is improved, the writing unit or the light source unit can be reused.

  In the above-described embodiment, the case where the mesa structure is formed in the step (5) of etching so as to be substantially linear from the contact layer 109 to the bottom surface of the etching is not limited to this.

  For example, the etching conditions may change during the process, and the taper angle of the mesa wall surface may change from θ1 to θ2 (> θ1) during the process as shown in FIG. In this case, in the region where the taper angle is θ2, conventionally, the wiring member is likely to be insufficiently covered. However, as shown in FIG. 15B, by providing the disconnection preventing member 115, the taper angle is θ2. It became possible to suppress the shortage of wiring member coverage in the region.

  Further, the etching conditions may change midway, and a notch may be formed at the bottom of the mesa as shown in FIG. In this case, the coverage of the wiring member has conventionally been liable to occur at the bottom of the mesa. However, as shown in FIG. 16B, by providing the disconnection preventing member 115, the coverage of the wiring member at the bottom of the mesa is insufficient. Can be suppressed.

  Further, in the above embodiment, as shown in FIG. 17 as an example, when a dummy mesa is formed around a plurality of light emitting units, the mesa bottom between the light emitting unit and the dummy mesa, and the dummy mesa and the bonding pad By providing the disconnection preventing member 115 at each mesa bottom, the wiring member from the mesa upper surface of the light emitting portion can be directed to the bonding pad via the dummy mesa without causing insufficient coverage of the wiring member ( (See FIG. 18).

  Further, in the above embodiment, for the purpose of stabilizing the polarization direction while controlling the oscillation of the high-order transverse mode, as shown in FIG. 19 as an example, from the center of the emission region, as shown in FIG. An optically transparent dielectric film (116, 117) may be formed so that the reflectance of the detached portion is lower than the reflectance of the central portion of the emission region.

  Moreover, in the said embodiment, as FIG. 20 shows as an example, the disconnection prevention member 115 does not need to be in the center part of a mesa bottom face.

  Moreover, although the said embodiment demonstrated the case where a surface emitting laser array had 32 light emission parts, it is not limited to this.

  Moreover, although the case where each light source has the surface emitting laser array 100 has been described in the above embodiment, the present invention is not limited to this, and each light source is created in the same manner as the surface emitting laser array 100 and the light emitting unit has one surface emitting. You may have a laser element.

  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.

  Further, the surface emitting laser array 100 can be used for applications other than the 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 the above embodiment, the case of a color printer as the image forming apparatus has been described.

  In the above-described embodiment, the image forming apparatus that transfers the toner image to the recording paper has been described. However, the present invention is not limited to this. For example, the laser beam is directly applied to a medium (for example, paper) that develops color by laser light. May be an image forming apparatus that emits light.

  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.

  DESCRIPTION OF SYMBOLS 100 ... Surface emitting laser array, 101 ... Substrate, 103 ... Lower semiconductor DBR (lower reflector), 104 ... Lower spacer layer (part of resonator structure), 105 ... Active layer, 106 ... Upper spacer layer (resonator) Part of structure), 107: upper semiconductor DBR (upper reflecting mirror), 109: contact layer, 110: dielectric layer, 111: interlayer insulating film, 113: p-side electrode, 114: n-side electrode, 115: disconnection Preventing member, 2000 ... color printer, 2010 ... optical scanning device, 2030a to 2030d ... photosensitive drum, 2104 ... optical deflector, 2200a to 2200d ... light source.

Japanese Patent No. 4836258 JP 2006-086498 A JP 2003-249719 A Japanese Patent No. 4752201 JP 2006-294485 A JP 2006-202871 A JP 2006-351777 A JP 2008-112883 A JP 2010-161224 A

Claims (10)

In a surface emitting laser having a light emitting part of a mesa structure in which a lower reflecting mirror, a resonator structure including an active layer, and an upper reflecting mirror are stacked on a substrate,
A surface emitting laser comprising a disconnection preventing member that is in contact with a part of a side wall of the mesa structure and smoothes a region that transitions from the side wall to the bottom surface.   The surface emitting laser according to claim 1, wherein the disconnection preventing member has a height that decreases as the distance from the side wall increases.   The surface emitting laser according to claim 2, wherein a surface of the disconnection preventing member is a curved surface.   The surface light emission according to any one of claims 1 to 3, wherein a height of the disconnection preventing member from a bottom surface of the mesa structure is 1/2 times or less of a height of the mesa structure. laser.   The surface emitting laser according to claim 4, wherein a height of the disconnection preventing member from a bottom surface of the mesa structure is equal to or less than a height of the resonator structure.   The surface emitting laser according to any one of claims 1 to 5, wherein a material of the disconnection preventing member is SOG (Spin On Glass) or an organic resin.   The surface emitting laser according to claim 6, wherein the organic resin is polyimide.   The surface emitting laser according to claim 7, wherein the polyimide is PBO (polybenzoxazole).   A surface-emitting laser array in which the surface-emitting lasers according to any one of claims 1 to 8 are integrated. An optical scanning device that scans a surface to be scanned with light,
A light source comprising the surface emitting laser according to any one of claims 1 to 8, or the surface emitting laser array according to claim 9.
An optical deflector for deflecting light from the light source;
An optical scanning device comprising: a scanning optical system that condenses the light deflected by the optical deflector onto the surface to be scanned.

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