JP2007294744A - Surface emitting laser array, optical scanner, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-emitting optical laser array which disposes a plurality of surface emitting optical laser elements at a high density without increasing the thermal interference. <P>SOLUTION: Each VCSEL is partly connected to other regions (outer regions) than the VCSEL through an epitaxial part orthogonally to the laminating direction (X-axial direction). Compared with the conventional mesa-shaped VCSEL array enclosed fully with trenches, the radiation is great in the direction orthogonal to the lamination to reduce the temperature rise of each VCSEL. One VCSEL is enclosed with a plurality of trenches 106 to raise the proportion of its portion connected to the outer region through the epitaxial part, compared with that enclosed with a simple trench. It is separated from adjacent VCSELs through one trench, this enabling a high density layout, and suppressing the thermal interference low with the adjacent VCSELs, the same as the mesa-shaped array. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface emitting laser array, an optical scanning device, and an image forming apparatus. More specifically, the present invention relates to a surface emitting laser array in which a plurality of surface emitting laser elements are two-dimensionally integrated, and the surface emitting laser. The present invention relates to an optical scanning device having an array and an image forming apparatus including the optical scanning device.

  In electrophotographic image recording, an image forming method using laser light is widely used as an image forming means for obtaining high-definition image quality. In the case of electrophotography, a method of forming a latent image by rotating a drum (sub-scanning) while scanning laser light (main scanning) using a polygon mirror in the axial direction of a photosensitive drum is used. It is. In such an electrophotographic field, higher definition of images and higher speed of output are required. In order to increase the definition of an image, when the resolution of the image is doubled, twice the time is required for both main scanning and sub-scanning. Therefore, four times the time is required for image output. Therefore, in order to achieve high definition of images, it is necessary to simultaneously achieve high speed image output.

  As a method for realizing high-speed image output, it is conceivable to increase the output of the laser, increase the number of beams, increase the sensitivity of the photosensitive member, and the like. In particular, in a high-speed output machine, it is common to use a multi-beam writing light source. Compared to the case of using one laser beam, when n laser beams are used at the same time, the latent image forming area is n times, and the time required for image formation is 1 / n.

  An element having a plurality of light emitting sources on one chip is disclosed in Patent Document 1 and Patent Document 2. Each element disclosed in Patent Document 1 and Patent Document 2 has a configuration in which a plurality of edge-emitting semiconductor lasers are arranged one-dimensionally. In these cases, the power consumption increases as the number of beams increases, and a new cooling system is required. Therefore, the cost is limited to about 4 beams or 8 beams.

  Further, if the number of beams is extremely increased, the one-dimensional arrangement results in an increase in the amount of beam deviation with respect to the optical axis of the optical element of the optical system, and the optical characteristics of the beam deteriorate.

  On the other hand, a surface emitting laser (vertical cavity surface emitting laser, VCSEL) is a semiconductor laser that emits light in a direction perpendicular to a substrate, and is easily two-dimensionally integrated. Further, the power consumption is about an order of magnitude smaller than that of the edge-emitting semiconductor laser, which is advantageous for integrating more light sources in two dimensions.

  Patent Document 3 discloses a light emitting element array in which a plurality of light emitting elements are two-dimensionally arranged. An image forming apparatus having a surface emitting laser array is disclosed in Patent Document 4. Further, Patent Document 5 discloses an optical scanning device including a surface emitting laser having a plurality of light sources. Non-patent document 1 discloses an application of a VCSEL array to a laser printer. The VCSEL array disclosed in Non-Patent Document 1 (see FIG. 23) has 32 VCSELs arranged in a two-dimensional array of 8 × 4, and each VCSEL has a mesa shape by etching its entire periphery. This is an oxidized constriction type VCSEL. The wiring passes between the VCSELs and is connected to bonding pads (not shown) outside the area (around the array).

  In the VCSEL array disclosed in Non-Patent Document 1, a plurality of VCSELs are arranged at equal intervals d in the sub-scanning direction (drum rotation direction) and arranged at equal intervals X in the main scanning direction (drum longitudinal direction). In addition, the VCSELs are arranged so that the positional relationship between the VCSELs in the sub-scanning direction when the vertical line is dropped from the center of each VCSEL in the sub-scanning direction is an equal interval C (= d / n). Thereby, writing at a high density of 2400 dpi (dot / inch) is realized.

  Further, Patent Document 6 discloses a surface emitting laser having a plurality of laser structures. In this surface emitting laser, a plurality of cylindrical cavities are formed for one laser structure, and an oxide layer is oxidized therefrom to form an oxidized region so as to surround the laser aperture. The adjacent laser structure portions are adjacent to each other in a state where a plurality of semiconductor layers (so-called epi portions) by epitaxial growth are connected.

  A VCSEL array is disclosed in Patent Document 7. In this VCSEL array, one semi-circular groove is formed for one VCSEL, and an oxidized region is formed so as to surround the aperture by oxidizing the AlAs layer therefrom. Note that there are two grooves and an unetched epi portion between adjacent VCSELs.

JP 11-340570 A JP 11-354888 A JP 2002-314191 A JP 2005-274755 A JP 2005-234510 A Japanese Patent No. 3162333 EP0905835A1 Nobuaki Ueki, 4 others, "Application of VCSEL array to laser printer", IEICE Electronics Society Conference, CS-3-4, 2004

  Since the VCSEL array disclosed in Non-Patent Document 1 has a so-called mesa shape in which the entire periphery of each VCSEL is etched, heat generated in the active layer during the operation of each VCSEL is mainly dissipated below the active layer, Insufficient lateral heat dissipation. Moreover, since the number of VCSELs is as large as 32 and these are densely integrated, the problem of thermal interference with the surrounding VCSELs is serious, and the output varies depending on the number of lighting, and the deterioration of the VCSELs is suppressed. However, there was a disadvantage that it had to be used at a low output. In the case of a surface-emitting laser element, a high problem is a serious problem, especially since high output is a big problem.

  In the surface emitting laser disclosed in Patent Document 6, the laser structure part and the peripheral part are connected to the epi part, and the heat radiation in the lateral direction is larger than that of the VCSEL array disclosed in Non-Patent Document 1. The heat dissipation effect is high. However, there is no groove due to etching between adjacent laser structure portions, and the adjacent epitaxial structure is adjacent to each other, and the degree of thermal interference with the adjacent laser structure portion becomes high.

  In addition, the VCSEL array disclosed in Patent Document 7 has a small amount of epi portion that connects the VCSEL portion and a portion other than the VCSEL, and thus the heat radiation in the lateral direction is small. In addition, the VCSEL array disclosed in Patent Document 7 has a small degree of thermal interference with adjacent VCSELs, but two grooves and an unetched epi portion remain between adjacent VCSELs. It is not suitable for narrowing the VCSEL interval, and it is difficult to arrange a plurality of VCSELs at high density.

  The present invention has been made under such circumstances. A first object of the present invention is to provide a surface emitting laser array capable of arranging a plurality of surface emitting laser elements at high density without increasing thermal interference. It is to provide.

  A second object of the present invention is to provide an optical scanning device capable of scanning a surface to be scanned at high density and high speed.

  A third object of the present invention is to provide an image forming apparatus capable of forming a high-definition image at high speed.

  According to a first aspect of the present invention, a stack in which a plurality of semiconductor layers including an oxidizable layer are stacked on a substrate is surrounded by an electrically insulating region in which the oxidizable layer is partially oxidized. In a surface-emitting laser array in which a plurality of element regions having conductive regions are two-dimensionally formed and a plurality of surface-emitting laser elements are integrated, each element region in the plurality of element regions is surrounded by the element region. A direction toward the substrate is a depth direction, and at least two concave portions in which the oxidizable layer appears on the inner side surface are provided, and each concave portion is provided between two element regions adjacent to each other in the plurality of element regions. Each of the surface emitting laser arrays is provided.

  According to this, since the element region and the region other than the element region are connected via a plurality of semiconductor layers (epi portions), heat radiation in a direction (lateral direction) orthogonal to the stacking direction is increased, and each element The temperature rise in the region can be reduced. Further, since at least two recesses for forming one conductive region surrounded by the electrically insulating region are provided, one recess is provided as in the VCSEL array disclosed in Patent Document 7. Compared with the case where it exists, the ratio of the epi part connected with area | regions other than an element area | region can be made high. That is, heat dissipation can be improved. Furthermore, since the adjacent element regions are separated by only one concave portion, a plurality of element regions can be arranged with high density, and thermal interference with adjacent element regions can be suppressed. Therefore, a plurality of surface emitting laser elements can be arranged at high density without increasing thermal interference.

  According to a second aspect of the present invention, in an optical scanning device that scans a surface to be scanned with a plurality of light beams, the surface emitting laser array according to the present invention that emits the plurality of light beams is provided. This is an optical scanning device.

  According to this, since the surface emitting laser array of the present invention is provided, it is possible to scan the surface to be scanned at high density and high speed.

  According to a third aspect of the present invention, there is provided at least one scanning object; and at least one optical scanning device according to the present invention that scans a plurality of light beams including image information on the at least one scanning object. And a transfer device that transfers the image formed on the at least one scanning object to the transfer object.

  According to this, since at least one optical scanning device of the present invention is provided, a high-definition image can be formed at high speed.

<< First Embodiment >>
A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic configuration of a surface emitting laser array 100 according to the first embodiment of the present invention.

  The surface emitting laser array 100 is a surface emitting laser array in which 16 surface emitting laser elements (VCSEL) are two-dimensionally arranged as an example. Here, the 16 VCSELs are arranged in a matrix of 4 × 4 in a row direction in the Z-axis direction and a column direction in the Y-axis direction. Around the 16 VCSELs, 16 bonding pads 105 are provided corresponding to each VCSEL. Each VCSEL has an upper electrode (p-side individual electrode) 103 and a bonding pad 105 connected via a wiring 104. The central opening region of each upper electrode 103 is the light emitting portion 102.

  FIG. 2 shows a state where each bonding pad 105, each wiring 104, and each upper electrode 103 are removed from the surface emitting laser array 100 of FIG. Grooves (concave portions) 106 are provided on the ± Z side and ± Y side of each element region. That is, four grooves 106 are provided around each element region, and one groove 106 exists between two element regions adjacent to each other in the Z-axis direction and the Y-axis direction.

  An enlarged view of a portion of the surface emitting laser array 100 is shown in FIG. FIG. 4 is a sectional view taken along line AA in FIG. 4 is an enlarged view of a part of FIG.

  Each VCSEL is a 780 nm band VCSEL, and as shown in FIG. 4, on the n-GaAs substrate 111, a lower reflecting mirror 112, a spacer layer 113, an active layer 114, a spacer layer 115, an upper reflecting mirror 117, and Semiconductor layers such as the p contact layer 118 are sequentially stacked. Hereinafter, a structure in which a plurality of these semiconductor layers are stacked is also referred to as a “stacked body” for convenience.

The lower reflecting mirror 112 includes a pair of a low refractive index layer 112a made of n-Al _0.9 Ga _0.1 As and a high refractive index layer 112b made of n-Al _0.3 Ga _0.7 As. I have 5 pairs. Each layer is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ. Note that a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition between the low refractive index layer 112a and the high refractive index layer 112b in order to reduce electrical resistance. Is provided.

The spacer layer 113 is a layer made of Al _0.6 Ga _0.4 As.

The active layer 114 includes a quantum well layer 114a made of Al _0.12 Ga _0.88 As and a barrier layer 114b made of Al _0.3 Ga _0.7 As.

The spacer layer 115 is a layer made of Al _0.6 Ga _0.4 As.

  A portion composed of the spacer layer 113, the active layer 114, and the spacer layer 115 is called a resonator structure, and is set to have a one-wavelength optical thickness.

The upper reflecting mirror 117 includes 24 pairs of a low refractive index layer 117a made of p-Al _0.9 Ga _0.1 As and a high refractive index layer 117b made of p-Al _0.3 Ga _0.7 As. Have. Each refractive index layer is set to have an optical thickness of λ / 4. A composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition in order to reduce electric resistance between the low refractive index layer 117a and the high refractive index layer 117b. Is provided.

  A selective oxidation layer 116 made of AlAs is provided at a position away from the resonator structure in the upper reflecting mirror 117 by λ / 4.

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

(1) The laminate is formed by crystal growth using metal organic chemical vapor deposition (MOCVD) or molecular beam crystal growth (MBE).

(2) Grooves 106 having a depth of, for example, 4.5 μm are formed in four directions (± Z side and ± Y side) of the region to be an element region by dry etching (see FIG. 6). The bottom of the etching is provided at least beyond the selective oxidation layer 116. That is, the selectively oxidized layer 116 appears on the inner side surface of the trench 106. The bottom surface of the etching may reach the lower reflecting mirror 112. A groove is also formed around the laminate.

(3) The selective oxidation layer 116 whose side surface is exposed by the groove forming step by etching is heat-treated in water vapor to oxidize the periphery to an Al _x O _y insulator layer, and the device driving current path is oxidized at the center. A current confinement structure is formed that limits only to the unfinished AlAs region. Normally, the element region has a mesa shape that is surrounded by a groove around the entire periphery, but in this embodiment, an electrical insulating region (selective oxidation constriction region) is formed by oxidation from four grooves to electrically insulate. The structure has a conductive region (current injection portion) surrounded by the region (see FIG. 7).

(4) In order to electrically isolate the element regions from each other, proton ions are implanted into the region between the element regions and the element regions (between the broken line indicating the element region in FIG. 8 and the broken line outside thereof) (see FIG. 8). 8).

(5) Except for the region where the upper electrode 103 is formed on each element region and the light emitting portion 102, for example, a SiO ₂ protective layer 120 having a thickness of 150 nm is provided, and each groove 106 is filled with polyimide 119 and planarized. (See FIG. 9).

(6) The upper electrode 103 is formed in each element region except for the light emitting portion 102 on the p contact layer 118, and each bonding pad 105 is formed around the laminated body. Then, each wiring 104 connecting each upper electrode 103 and the corresponding bonding pad 105 is formed. In this case, as shown in FIG. 10, each wiring 104 is formed so that a part thereof passes over the groove 106 in which at least one polyimide 119 is embedded.

(7) The lower electrode (n-side common electrode) 110 is formed on the back surface of the multilayer body (the surface on the −X side).

  The method of forming the array arrangement in the first embodiment is to form a photomask along the array arrangement of the first embodiment, form an etching mask by a normal photolithography process, and perform etching. Can be formed. The width of each groove 106 is preferably at least about 5 μm. This is because if it is too narrow, it becomes difficult to control etching.

  As described above, according to the surface emitting laser array 100 according to the first embodiment, each VCSEL has a region other than the VCSEL (hereinafter referred to as an “external region” for convenience) and a partial stacking direction (X-axis). Heat dissipation in a direction perpendicular to the stacking direction compared to a conventional mesa-shaped VCSEL array, which is connected via an epi portion in the direction (lateral direction) perpendicular to the direction), and is completely surrounded by grooves. Increases, the temperature rise of each VCSEL can be reduced, and the lifetime can be extended. In addition, since one VCSEL is surrounded by a plurality of grooves, the ratio of being connected to the external region through the epi portion can be increased as compared with the case where the single VCSEL is surrounded by one groove. In addition, since the adjacent VCSELs are separated by a single groove, they can be arranged with high density (for example, at an interval of about 5 μm), and the thermal interference with the adjacent VCSELs is kept as low as the mesa array. be able to. That is, a plurality of VCSELs can be arranged with high density without increasing thermal interference.

Further, according to the surface emitting laser array 100 according to the first embodiment, since a part of each wiring 104 is formed on a thick insulator embedded with polyimide 119, thin SiO ₂ is interposed on the epitaxial portion. As compared with the case where the wiring is formed, the parasitic capacitance is reduced, which is advantageous for high-speed operation.

  In the first embodiment, the case where all the grooves 106 surrounding each VCSEL are filled with polyimide 119 has been described. However, the present invention is not limited to this. For example, as shown in FIG. The groove that does not pass does not need to be filled with polyimide 119. In short, it is sufficient that the polyimide 119 is embedded in at least the groove through which the wiring 104 passes. Thereby, since the stress due to the polyimide is reduced, the strain of the element region (particularly the active layer) can be reduced, and the life extension can be promoted.

  In the first embodiment, as shown in FIG. 12 as an example, each of the bonding pads 105 may be formed on polyimide (insulator) embedded in the groove. This further reduces the parasitic capacitance, which is more advantageous for high-speed operation.

  In the first embodiment, the case where the VCSEL is substantially square has been described. However, the present invention is not limited to this, and may be any shape such as a circle, an ellipse, and a rectangle. An example of a circular case is shown in FIG. Note that the size of the element region (width between the grooves) is preferably about 10 μm or more. If it is too small, heat may accumulate during operation and the characteristics may be degraded.

  Moreover, although the said 1st Embodiment demonstrated the case where the surface emitting laser array 100 had 16 VCSELs, it is not limited to this.

  In the first embodiment, the case where four grooves are provided around each element region has been described. However, the present invention is not limited to this, and at least two grooves are provided around each element region. It only has to be provided.

<< Second Embodiment >>
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. The surface-emitting laser array 200 according to the second embodiment of the present invention is different from the surface-emitting laser array 100 according to the first embodiment in that a material of a part of the plurality of semiconductor layers is used. Characterized by the changed points. Other configurations are the same as those in the first embodiment. Therefore, in the following description, differences from the first embodiment will be mainly described, and the same or equivalent components as those in the first embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted. Shall.

  FIG. 14 shows a cross-sectional view of a VCSEL included in the surface emitting laser array 200. 14 is an enlarged view of a part of FIG.

  Each VCSEL in the second embodiment is a 780 nm band VCSEL, and a spacer layer 213 is used instead of the spacer layer 113 of each VCSEL in the first embodiment, and an active layer 114 is used instead of the active layer 114. A layer 214 is used, and a spacer layer 215 is used instead of the spacer layer 115.

The spacer layer 213 is a layer made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P having a wide band gap.

The active layer 214 has a composition in which compressive strain remains and has a Ga _0.6 In _0.4 P barrier having a tensile strain of four layers lattice-matched with the three GaInPAs quantum well layers 214a having a band gap wavelength of 780 nm. Layer 214b.

The spacer layer 215 is a layer made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P having a wide band gap.

  A portion composed of the spacer layer 213, the active layer 214, and the spacer layer 215 is called a resonator structure, and is set to have a one-wavelength optical thickness.

  The surface emitting laser array 200 can be manufactured by the same process as that of the surface emitting laser element 100 according to the first embodiment.

  As described above, according to the surface emitting laser array 200 according to the second embodiment, each VCSEL is epitaxially formed in the external region and in a direction (lateral direction) partially orthogonal to the stacking direction (X-axis direction). Since they are connected via the unit, as in the first embodiment, the temperature rise of each VCSEL can be reduced and the life can be extended. Further, since the adjacent VCSELs are separated by one groove, a plurality of VCSELs can be arranged at high density without increasing thermal interference as in the first embodiment.

  Further, according to the surface emitting laser array 200 according to the second embodiment, each VCSEL uses an AlGaInP-based material for the spacer layer, and therefore, compared to each VCSEL in the first embodiment, The band gap difference between the active layer and the active layer can be made extremely large.

  In FIG. 16, the material of the spacer layer / quantum well layer is an AlGaAs / AlGaAs system, and a wavelength of 780 nm band surface emitting laser (hereinafter referred to as “surface emitting laser A” for convenience), spacer layer / quantum well layer The material is an AlGaInP / GaInPAs system, a surface emitting laser with a wavelength of 780 nm band (hereinafter referred to as “surface emitting laser B” for convenience), and the spacer layer / quantum well layer material is an AlGaAs / GaAs system, and the wavelength is 850 nm. The band gap difference between the spacer layer and the quantum well layer, and the barrier layer and the quantum well layer in a typical material composition is shown for the band surface emitting laser (hereinafter referred to as “surface emitting laser C” for convenience). Yes. The surface emitting laser A corresponds to the VCSEL in the first embodiment, and the surface emitting laser B with x = 0.7 corresponds to the VCSEL in the second embodiment.

  According to this, it can be seen that the surface emitting laser B can take a larger band gap difference than the surface emitting laser C as well as the surface emitting laser A. Specifically, the band gap difference between the spacer layer and the quantum well layer in the surface emitting laser B is 767.3 meV, which is extremely larger than 465.9 meV of the surface emitting laser A. Similarly, the difference in band gap between the barrier layer and the quantum well layer is also superior to the surface emitting laser B, and better carrier confinement is possible.

  In each VCSEL in the second embodiment, since the quantum well layer has a compressive strain, the increase in gain increases due to band separation of heavy holes and light holes, resulting in a high gain. High output is possible. For this reason, the reflectance of the reflecting mirror on the light extraction side (here, the upper reflecting mirror 117) can be reduced, and a further increase in output can be achieved. Further, since the gain can be increased, it is possible to suppress a decrease in light output due to a temperature rise, and it is possible to narrow the interval between the VCSELs in the surface emitting laser array 200.

  In each VCSEL in the second embodiment, since the quantum well layer 214a and the barrier layer 214b are both made of a material not containing aluminum (Al), the incorporation of oxygen into the active layer 214 is reduced. Is done. As a result, formation of a non-radiative recombination center can be suppressed, and the life can be further extended.

  By the way, for example, when a surface emitting laser array is used for the writing optical unit, the writing optical unit is disposable when the life of the VCSEL is short. However, since the surface emitting laser array 200 has a long life as described above, the writing optical unit using the surface emitting laser array 200 can be reused. Therefore, promotion of resource protection and reduction of environmental load can be achieved. The same applies to other devices using the surface emitting laser array.

<< Third Embodiment >>
A third embodiment of the present invention will be described below with reference to FIGS. A surface-emitting laser element 300 according to the third embodiment of the present invention is characterized in that a plurality of VCSELs are arranged with two directions that are not orthogonal to each other as a row direction and a column direction.

  In the surface-emitting laser array 300 shown in FIG. 17, 32 VCSELs are arranged with the direction (α direction) inclined with respect to the Y-axis direction as the row direction and the Z-axis direction as the column direction. Here, a 4 × 8 (m × n) array is used. Note that m <n. When the surface-emitting laser array 300 is used in an optical scanning device, the Y-axis direction is a direction corresponding to the main scanning direction and the Z-axis direction is a direction corresponding to the sub-scanning direction. When the interval (equal interval) of the VCSELs arranged along the Z-axis direction is d, the interval (equal interval) C when the VCSELs arranged along the α direction are orthogonally projected onto the imaginary line extending in the Z-axis direction. Is d / n (see FIG. 18). Here, as an example, d = 24 μm and C = 3 μm. Further, when the VCSEL arranged along the α direction is orthogonally projected onto a virtual line extending in the Y-axis direction, the interval (equal interval) X is 30 μm, and the interval between the grooves is 16 μm.

  The surface emitting laser array 300 can be manufactured by the same process as that of the surface emitting laser element 100 according to the first embodiment.

  Also in this case, as shown in FIG. 19, each VCSEL is connected to the external region partially through the epi portion in a direction orthogonal to the stacking direction (X-axis direction), and completely surrounds the conventional periphery. Compared with a mesa-shaped VCSEL array surrounded by grooves, heat dissipation in the direction perpendicular to the stacking direction is increased, and the temperature rise of the VCSEL can be reduced, and the life can be extended. In addition, since one VCSEL is surrounded by a plurality of grooves, the ratio of being connected to the external region through the epi portion can be increased as compared with the case where the single VCSEL is surrounded by one groove. In addition, since the adjacent VCSELs are separated by a single groove, they can be arranged at high density, and thermal interference with the adjacent VCSELs can be kept low as in the mesa array. That is, a plurality of VCSELs can be arranged with high density without increasing thermal interference.

  As described above, according to the surface emitting laser array 300 according to the third embodiment, since heat dissipation is excellent, even if a plurality of VCSELs are two-dimensionally integrated with high density, they can be used with high injection (current). Therefore, when used in an optical scanning device, it is advantageous for high-density writing and high-speed writing.

  By the way, in the VCSEL array disclosed in Non-Patent Document 1 (see FIG. 23), if d = 24 μm and X = 30 μm, C = 6 μm, and even if the VCSEL interval in the plane is the same, The surface emitting laser array 300 according to the embodiment has a higher density. This is because m <n.

  Note that the VCSEL size (here, the length between the grooves), the distance d, the distance X, and the width of the wiring are arbitrary. It is necessary to decide in consideration of the influence of thermal interference from the VCSEL. In any case, the VCSEL interval in the direction corresponding to the main scanning direction which does not affect the density increase in the direction corresponding to the sub-scanning direction is widened to d <X, and between adjacent VCSELs in the direction corresponding to the main scanning direction. It can be seen that it is advantageous for high-density writing if the wiring is arranged in the circuit. Furthermore, the influence of thermal interference between the VCSELs can be reduced by widening the VCSEL interval in the direction corresponding to the main scanning direction.

  In the third embodiment, the case where the surface emitting laser array 300 includes 32 VCSELs has been described. However, the present invention is not limited to this. Furthermore, it is not limited to a 4 × 8 (m × n) array. For example, a 4 × 10 (m × n) array may be used.

<Image forming apparatus>
Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 20 shows a schematic configuration of a laser printer 500 as an image forming apparatus according to an embodiment of the present invention.

  The laser printer 500 includes an optical scanning device 900, a photosensitive drum 901, a charging charger 902, a developing roller 903, a toner cartridge 904, a cleaning blade 905, a paper feeding tray 906, a paper feeding roller 907, a registration roller pair 908, and a transfer charger 911. , A static elimination unit 914, a fixing roller 909, a paper discharge roller 912, a paper discharge tray 910, and the like.

  The charging charger 902, the developing roller 903, the transfer charger 911, the charge removal unit 914, and the cleaning blade 905 are each disposed near the surface of the photosensitive drum 901. Then, with respect to the rotation direction of the photosensitive drum 901, the charging charger 902, the developing roller 903, the transfer charger 911, the static elimination unit 914, and the cleaning blade 905 are arranged in this order.

  A photosensitive layer is formed on the surface of the photosensitive drum 901. Here, the photosensitive drum 901 rotates clockwise (in the direction of the arrow) within the plane in FIG.

  The charging charger 902 uniformly charges the surface of the photosensitive drum 901.

  The optical scanning device 900 irradiates the surface of the photosensitive drum 901 charged by the charging charger 902 with light modulated based on image information from a host device (for example, a personal computer). As a result, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 901 on the surface of the photosensitive drum 901. The latent image formed here moves in the direction of the developing roller 903 as the photosensitive drum 901 rotates. The configuration of the optical scanning device 900 will be described later.

  The toner cartridge 904 stores toner, and the toner is supplied to the developing roller 903.

  The developing roller 903 causes the toner supplied from the toner cartridge 904 to adhere to the latent image formed on the surface of the photosensitive drum 901 to visualize the image information. Here, the latent image to which the toner is attached moves in the direction of the transfer charger 911 as the photosensitive drum 901 rotates.

  Recording paper 913 is stored in the paper feed tray 906. A paper feed roller 907 is disposed in the vicinity of the paper feed tray 906, and the paper feed roller 907 takes out the recording paper 913 one by one from the paper feed tray 906 and conveys it to the registration roller pair 908. The registration roller pair 908 is disposed in the vicinity of the transfer roller 911, temporarily holds the recording paper 913 taken out by the paper feed roller 907, and the recording paper 913 is synchronized with the rotation of the photosensitive drum 901. It is sent out toward the gap between 901 and the transfer charger 911.

  A voltage having a polarity opposite to that of the toner is applied to the transfer charger 911 in order to electrically attract the toner on the surface of the photosensitive drum 901 to the recording paper 913. With this voltage, the latent image on the surface of the photosensitive drum 901 is transferred to the recording paper 913. The recording sheet 913 transferred here is sent to the fixing roller 909.

  In the fixing roller 909, heat and pressure are applied to the recording paper 913, whereby the toner is fixed on the recording paper 913. The recording paper 913 fixed here is sent to the paper discharge tray 910 via the paper discharge roller 912 and sequentially stacked on the paper discharge tray 910.

  The neutralization unit 914 neutralizes the surface of the photosensitive drum 901.

  The cleaning blade 905 removes toner remaining on the surface of the photosensitive drum 901 (residual toner). The removed residual toner is used again. The surface of the photosensitive drum 901 from which the residual toner has been removed returns to the position of the charging charger 902 again.

<Optical scanning device>
Next, the configuration and operation of the optical scanning device 900 will be described with reference to FIG.

  The optical scanning device 900 includes a light source unit 1, a coupling lens 2, an aperture 3, an anamorphic lens 4, a polygon mirror 5, a deflector-side scanning lens 6, an image plane-side scanning lens 7, a processing device 20, and the like. ing.

  The light source unit 1 includes the surface-emitting laser array 300 having a 4 × 10 (m × n) array, and can emit 40 light beams simultaneously. The surface emitting laser array 300 is arranged such that the Y-axis direction is a direction corresponding to the main scanning direction, and the Z-axis direction is a direction corresponding to the sub-scanning direction.

  The coupling lens 2 turns the plurality of light beams emitted from the light source unit 1 into weak divergent light.

  The anamorphic lens 4 passes through the coupling lens 2 and converges a plurality of light beams via the aperture 3 in the vicinity of the parallel mirror in the main scanning direction and in the vicinity of the polygon mirror 5 in the sub-scanning direction. Let it be a beam.

  The plurality of light beams from the anamorphic lens 4 are respectively deflected by the polygon mirror 5, and then imaged by the deflector side scanning lens 6 and the image plane side scanning lens 7, and the sub beam on the surface of the photosensitive drum 901. Light spots are collected at positions separated from each other by a predetermined distance in the scanning direction.

  The polygon mirror 5 is rotated at a constant speed by a polygon motor (not shown). Along with the rotation, the plurality of light beams are deflected at equal angular speeds, and each light on the photosensitive drum 901 is reflected. The spot moves at a constant speed in the main scanning direction.

  The processing device 20 generates image data based on image information from the host device, and outputs a drive signal for the surface emitting laser array 300 corresponding to the image data to the light source unit 1.

  In the surface emitting laser array 300, the positional relationship between the VCSELs in the sub-scanning direction when the vertical line is lowered from the center of each VCSEL in the sub-scanning direction becomes an equal interval C. Therefore, the photosensitive drum can be adjusted by adjusting the lighting timing. On 901, it can be considered that the configuration is the same as the case where the light sources are arranged at equal intervals in the sub-scanning direction. The interval written in the sub-scanning direction can be adjusted by adjusting the interval C in the surface emitting laser array 300 and the magnification of the optical system. For example, if the interval C = 2.4 μm and the magnification of the optical system is about 2.2 times, high-density writing of 4800 dpi (dots / inch) can be performed. Of course, the density can be increased by increasing the number of VCSELs in the main scanning direction, making the array arrangement to further reduce the interval C by narrowing the interval between adjacent VCSELs in the sub-scanning direction, or reducing the magnification of the optical system. And higher quality printing becomes possible. Note that the writing interval in the main scanning direction can be easily controlled by the lighting timing of the light source.

  Therefore, according to the optical scanning device 900 according to the present embodiment, since the light source unit 1 includes the surface emitting laser array 300, the photosensitive drum 901 can be scanned at high density and high speed.

  Further, since the laser printer 500 according to the present embodiment includes the optical scanning device 900, a high-definition image can be formed at high speed as a result.

  In the above embodiment, the case of the laser printer 500 as the image forming apparatus has been described. However, the present invention is not limited to this. In short, an image forming apparatus provided with the optical scanning device 900 can form a high-definition image at high speed.

  Even in an image forming apparatus that forms a color image, a high-definition image can be formed at a high speed by using an optical scanning device corresponding to the color image.

  As an example, as shown in FIG. 22, the image forming apparatus may be a tandem color machine corresponding to a color image and including a plurality of photosensitive drums. The tandem color machine shown in FIG. 22 includes a black (K) photosensitive drum K1, a charger K2, a developing device K4, a cleaning unit K5, a transfer charging unit K6, and a cyan (C) photosensitive drum. C1, charging unit C2, developing unit C4, cleaning unit C5, transfer charging unit C6, magenta (M) photosensitive drum M1, charging unit M2, developing unit M4, cleaning unit M5, and transfer charging unit M6, yellow (Y) photosensitive drum Y1, charger Y2, developing unit Y4, cleaning unit Y5, transfer charging unit Y6, optical scanning device 900, transfer belt 80, fixing unit 30, and the like. I have.

  In this case, in the optical scanning device 900, the plurality of VCSELs in the surface emitting laser array 300 are divided into black, cyan, magenta, and yellow. The light beam from each VCSEL for black is irradiated to the photosensitive drum K1, the light beam from each VCSEL for cyan is irradiated to the photosensitive drum C1, and the light beam from each VCSEL for magenta is irradiated to the photosensitive member. The drum M1 is irradiated with a light beam from each yellow VCSEL so that the photosensitive drum Y1 is irradiated. The optical scanning device 900 may include an individual surface emitting laser array 300 for each color. Further, an optical scanning device 900 may be provided for each color.

  Each photosensitive drum rotates in the direction of the arrow in FIG. 22, and a charging device, a developing device, a transfer charging device, and a cleaning device are arranged in the order of rotation. Each charger uniformly charges the surface of the corresponding photosensitive drum. The surface of the photosensitive drum charged by the charger is irradiated with a beam by the optical scanning device 900, and an electrostatic latent image is formed on the photosensitive drum. Then, a toner image is formed on the surface of the photosensitive drum by the corresponding developing device. Further, the toner image of each color is transferred onto the recording paper by the corresponding transfer charging means, and finally the image is fixed on the recording paper by the fixing means 30.

  In a tandem color machine, color misregistration of each color may occur due to machine accuracy or the like. However, since the optical scanning device 900 has a high-density surface emitting laser array 300, each color can be selected by selecting a VCSEL to be lit. The color misregistration correction accuracy can be improved.

  As described above, the surface emitting laser array of the present invention is suitable for arranging a plurality of surface emitting laser elements at high density without increasing thermal interference. The optical scanning device of the present invention is suitable for scanning the surface to be scanned at high density and high speed. The image forming apparatus of the present invention is suitable for forming a high-definition image at high speed.

It is a figure for demonstrating the surface emitting laser array which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the relationship between the element area | region and groove | channel in the surface emitting laser array of FIG. It is the figure which expanded a part of surface emitting laser array of FIG. It is AA sectional drawing in FIG. It is the figure which expanded a part of FIG. FIG. 3 is a view (No. 1) for describing a method of manufacturing the surface emitting laser array of FIG. 1; FIG. 8 is a diagram (No. 2) for explaining the method of manufacturing the surface emitting laser array of FIG. FIG. 4 is a diagram (No. 3) for explaining the method of manufacturing the surface emitting laser array of FIG. FIG. 4 is a view (No. 4) for explaining the method of manufacturing the surface emitting laser array in FIG. FIG. 6 is a view (No. 5) for explaining a method of manufacturing the surface emitting laser array of FIG. 1; It is a figure for demonstrating the modification 1 of the surface emitting laser array of FIG. It is a figure for demonstrating the modification 2 of the surface emitting laser array of FIG. It is a figure for demonstrating the modification 3 of the surface emitting laser array of FIG. It is a figure for demonstrating the surface emitting laser array which concerns on the 2nd Embodiment of this invention. It is the figure which expanded a part of FIG. It is a figure for demonstrating the characteristic of the surface emitting laser array of FIG. It is a figure for demonstrating the surface emitting laser array which concerns on the 3rd Embodiment of this invention. It is a figure for demonstrating arrangement | positioning of VCSEL in the surface emitting laser array of FIG. It is a figure for demonstrating the relationship between the element area | region and groove | channel in the surface emitting laser array of FIG. 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 schematic structure of a tandem color machine. It is a figure for demonstrating the conventional surface emitting laser array.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Surface emitting laser array, 103 ... Upper electrode, 104 ... Wiring, 105 ... Bonding pad, 106 ... Groove, 112 ... Lower reflecting mirror, 114 ... Active layer, 116 ... Selective oxidation layer, 117 ... Upper reflecting mirror, 119 DESCRIPTION OF SYMBOLS ... Polyimide, 214 ... Active layer, 300 ... Surface emitting laser array, 500 ... Laser printer, 900 ... Optical scanning device, 901 ... Photosensitive drum, 902 ... Charger, 903 ... Developing roller, 904 ... Toner cartridge, 909 ... Fixing Roller, 911, transfer charger, 913, recording paper, VCSEL, surface emitting laser element.

Claims (7)

Two element regions each having a conductive region surrounded by an electrically insulating region in which the oxidizable layer is partially oxidized are stacked in a stacked body in which a plurality of semiconductor layers including an oxidizable layer are stacked on a substrate. In a surface-emitting laser array in which a plurality of surface-emitting laser elements are integrated by forming in a dimension,
Around each element region in the plurality of element regions, a depth direction is a direction toward the substrate, and at least two recesses in which the oxidizable layer appears on the inner side surface are provided, A surface-emitting laser array, which is provided between two element regions adjacent to each other in a plurality of element regions. A plurality of bonding pads are provided corresponding to the plurality of element regions,
2. The surface emitting laser array according to claim 1, wherein each of the plurality of element regions is connected to a corresponding bonding pad by wiring passing over at least one recess.   3. The surface emitting laser array according to claim 2, wherein an insulator is embedded only in a concave portion through which the wiring passes.   4. The plurality of bonding pads are respectively provided on insulators embedded in recesses having a depth direction in a direction toward the substrate. 5. Surface emitting laser array. In an optical scanning device that scans a surface to be scanned with a plurality of light beams,
An optical scanning device comprising the surface-emitting laser array according to claim 1, which emits the plurality of light beams. At least one scan object;
6. The optical scanning device according to claim 5, wherein the at least one scanning object is scanned with a plurality of light beams including image information;
An image forming apparatus comprising: a transfer device that transfers an image formed on the at least one scanning object to the transfer object.   The image forming apparatus according to claim 6, wherein the image information is color image information.