JP5177358B2 - Surface emitting laser array, optical scanning device, image forming apparatus, optical transmission module, and optical transmission system - Google Patents

Description

  The present invention relates to a surface emitting laser array, an optical scanning device, an image forming apparatus, an optical transmission module, and an optical transmission system. More specifically, the present invention relates to a surface emitting laser array having a plurality of light emitting units, and light having the surface emitting laser array. The present invention relates to a scanning device, an image forming apparatus including the optical scanning device, an optical transmission module including the surface emitting laser array, and an optical transmission system including the optical transmission module.

  The surface emitting laser has a pair of distributed Bragg reflectors provided on a semiconductor substrate, and an active layer and a resonator spacer layer provided therebetween. Then, current is injected into the active layer by the electrodes provided in each distributed Bragg reflector, and laser oscillation is generated perpendicular to the semiconductor substrate.

Further, the surface emitting laser has a current confinement structure formed by oxidizing a semiconductor layer containing Al (aluminum) in order to reduce the threshold current and control the transverse mode, and oxidizes the semiconductor layer containing Al. In addition, the light emitting portion is generally processed into a mesa shape. The mesa-shaped structure is protected by an insulating film such as SiO ₂ .

  The surface emitting laser has the characteristics that (1) the threshold current is low, (2) a circular emission beam shape is obtained, and (3) the laser output can be extracted in a direction perpendicular to the semiconductor substrate. In particular, since a laser output can be taken out in a direction perpendicular to the semiconductor substrate, it is easy to integrate a plurality of light emitting units on one semiconductor substrate with high positional accuracy. Therefore, a surface emitting laser array having a plurality of light emitting portions has been attracting attention as a writing light source or a parallel light interconnection light source in an electrophotographic system.

By the way, since the light emitting part has a mesa shape, it is thermally insulated from the surrounding semiconductor layer, and the thermal resistance of the insulating film such as SiO ₂ is much larger than the thermal resistance of the semiconductor. Low heat dissipation. Specifically, for example, the thermal conductivity of semiconductor GaAs is 54 [W / mK], whereas the thermal conductivity of SiO 2 is 1.4 [W / mK]. Therefore, in the surface emitting laser array, there is a possibility that a plurality of light emitting units may cause thermal interference with each other. In general, the laser output characteristics of the light emitting part are very sensitive to temperature, and the upper limit of the laser output is limited by thermal saturation. Therefore, it is very important to improve the heat dissipation of the heat generated in the light emitting part in order to obtain a high laser output.

  For example, Patent Document 1 discloses a surface emitting semiconductor laser in which a resonator is formed on a semiconductor substrate and emits light in a direction perpendicular to the semiconductor substrate. This surface-emitting type semiconductor laser includes a columnar portion that constitutes at least a part of the resonator, and an insulating layer that covers a side surface of the columnar portion, and the insulating layer includes a filler.

  Patent Document 2 discloses a surface emitting semiconductor laser array in which a plurality of surface emitting semiconductor lasers that emit laser light in a direction perpendicular to the substrate are arranged on the same substrate. In this surface emitting semiconductor laser array, a bank-like heat pipe is provided on the substrate surface between adjacent surface emitting semiconductor lasers.

  Patent Document 3 discloses a semiconductor element having a projecting structure processed into a projecting shape, in which a heat dissipation uneven structure is formed on a part or all of the side wall of the projecting structure. ing.

  Patent Document 4 discloses an active layer on a semiconductor substrate, a resonator spacer layer provided adjacent to both sides of the active layer, and a pair of distributed Bragg reflectors opposed to each other with the resonator spacer layer interposed therebetween. In a surface emitting laser array having a plurality of mesa structures formed by processing a part of the laminated structure into a convex shape and an electrode for current injection on the mesa structure, the laminated structure at the periphery of the array is removed. In addition, surface emission in which a heat radiation electrode is provided between the regions on the regions between the plurality of mesa structures and on the region from which the stacked structure around the periphery of the array is removed. A laser array is disclosed.

JP 2002-344081 A JP-A-11-261162 JP 2002-198613 A JP 2007-73585 A

  However, when the arrangement of the plurality of light emitting units in the surface emitting laser array is further increased, the surface emitting laser array disclosed in Patent Documents 1 to 4 sufficiently dissipates heat generated in the light emitting units. It is difficult.

  The present invention has been made under such circumstances, and a first object of the present invention is to provide a surface emitting laser array in which a plurality of light emitting units can output high power laser light.

  A second object of the present invention is to provide an optical scanning device that can perform high-density optical scanning.

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

  A fourth object of the present invention is to provide an optical transmission module capable of generating a high-quality optical signal.

  A fifth object of the present invention is to provide an optical transmission system capable of performing high-quality optical transmission.

According to a first aspect of the present invention, there is provided a surface emitting laser array having a plurality of mesa-shaped structures formed by etching a stacked body including a plurality of semiconductor layers stacked on a substrate. of structure, a first heat radiating member provided on the first etching of the periphery of the structure located at the center, among the plurality of structures, surrounding structures located around the second A second heat dissipating member provided in the etching part, a part of the first etching part is covered with a first heat insulating member, and a part of the second etching part is 2 is covered with a heat insulating member, and the first heat radiating member is in contact with a portion of the first etching portion that is not covered with the first heat insulating member, and the second heat radiating member is The second etching portion in the second etching portion A part of the semiconductor layer that is in contact with a portion that is not covered with the heat member, and a part that is in contact with the second heat insulating member, and that is in contact with the first and second heat dissipation members of the plurality of semiconductor layers. Is a surface emitting laser array having the same conductivity type as that of the substrate .

According to this, the reducing thermal interference in the light emitting portion of the multiple, it becomes possible in which a plurality of light-emitting portions are both outputs laser light of high power.

  According to a second aspect of the present invention, there is provided an optical scanning device for scanning a surface to be scanned with light, the light source unit having the surface emitting laser array of the present invention; and a deflector for deflecting the light from the light source unit. And a scanning optical system for condensing the light deflected by the polarizer on the surface to be scanned.

  According to this, since the surface emitting laser array of the present invention is provided, as a result, high-density optical scanning can be performed.

  According to a third aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device according to the invention that scans the at least one image carrier with light including image information. An image forming apparatus provided.

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

  According to a fourth aspect of the present invention, there is provided an optical transmission module that generates an optical signal in accordance with an input electric signal, the surface emitting laser array of the present invention; An optical transmission module comprising: a driving device that is driven according to an electrical signal.

  According to this, since the surface emitting laser array of the present invention is provided, as a result, it is possible to generate a high-quality optical signal.

  According to a fifth aspect of the present invention, an optical transmission module of the present invention; an optical transmission medium that transmits an optical signal generated by the optical transmission module; and an optical signal that passes through the optical transmission medium is converted into an electrical signal. An optical transmission system comprising: a converter for converting.

  According to this, since the optical transmission module of the present invention is provided, as a result, high-quality optical transmission can be performed.

<Surface emitting laser array>
Hereinafter, a surface emitting laser array 100 of 0.78 μm band will be described as an embodiment of the surface emitting laser array of the present invention.

  As an example, the surface-emitting laser array 100 includes 16 light emitting units arranged two-dimensionally as shown in FIG. 1A and FIG. 1B which is a cross-sectional view taken along the line AA in FIG. have. In the present specification, the laser oscillation direction in the surface emitting laser array 100 is described as a Z-axis direction, and two directions perpendicular to each other in a plane perpendicular to the Z-axis direction are described as an X-axis direction and a Y-axis direction.

  Each light emitting unit is formed on an n-GaAs substrate 101, an n-GaAs buffer layer 102, a lower reflecting mirror 103, a lower spacer layer 104, an active layer 105, an upper spacer layer 106, a selective oxidation layer 107, an upper reflecting mirror 108, Semiconductor layers such as a GaAs contact layer (not shown) are sequentially stacked. Hereinafter, a structure in which a plurality of these semiconductor layers are stacked is also referred to as a “semiconductor stacked body” for convenience.

The lower reflecting mirror 103 is a pair of a low refractive index layer made of n-Al _0.9 Ga _0.1 As and a high refractive index layer made of n-Al _0.3 Ga _0.7 As. Have. Then, between the low refractive index layer and the high refractive index layer, a composition gradient layer having a thickness of 20 nm (illustrated) in which the composition is gradually changed from one composition to the other composition in order to reduce electrical resistance. (Omitted) is provided. Each refractive index layer includes 1/2 of the composition gradient layer, and is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ.

The lower spacer layer 104 is a layer made of non-doped Al _0.3 Ga _0.7 As.

The active layer 105 is an AlGaAs / Al _0.3 Ga _0.7 As multiple quantum well active layer.

The upper spacer layer 106 is a layer made of non-doped Al _0.3 Ga _0.7 As.

  The 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 one wavelength optical thickness. The active layer 105 is provided at the center of the resonator structure at a position corresponding to the antinode of the standing wave distribution of the electric field so as to obtain a high stimulated emission probability.

The upper reflecting mirror 108 has 24 pairs of a low refractive index layer made of p-Al _0.9 Ga _0.1 As and a high refractive index layer made of p-Al _0.3 Ga _0.7 As. ing. Then, between the low refractive index layer and the high refractive index layer, a composition gradient layer having a thickness of 20 nm (illustrated) in which the composition is gradually changed from one composition to the other composition in order to reduce electrical resistance. (Omitted) is provided. Each refractive index layer is set to have an optical thickness of λ / 4, including 1/2 of the composition gradient layer.

  A selective oxidation layer 107 made of p-AlAs is provided at a position away from the resonator structure in the upper reflecting mirror 108 by λ / 4.

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

(1) The semiconductor stacked body is formed by crystal growth using metal organic chemical vapor deposition (MOCVD) or molecular beam crystal growth (MBE) (see FIG. 2A).

Here, trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as the Group III material, and arsine (AsH ₃ ) gas is used as the Group V material. Further, carbon tetrabromide (CBr ₄ ) is used as a p-type dopant material, and hydrogen selenide (H ₂ Se) is used as an n-type dopant material.

(2) A photomask including a photomask 109 corresponding to the light emitting portion is patterned by photolithography on the surface of the stacked body which is the surface (surface opposite to the substrate 1) in the semiconductor stacked body (see FIG. 2B). ). Here, as an example, the shape of the photomask 109 corresponding to each light emitting portion is a square shape having a side of 20 μm, and the gap between two adjacent photomasks 109 is 20 μm.

(3) A mesa shape is formed by a dry etching method using a photomask as an etching mask (see FIG. 2C). Hereinafter, for convenience, a mesa-shaped portion (structure) is abbreviated as “mesa”. Here, the etching is performed until the bottom surface of the etching reaches the lower reflecting mirror 103.

(4) The photomask is removed (see FIG. 3A).

(5) The semiconductor stacked body is heat-treated in water vapor to selectively oxidize the selectively oxidized layer 108 in the mesa. Then, an unoxidized region in the selective oxidation layer 108 remains in the central portion of the mesa. As a result, a so-called current confinement structure is formed in which the drive current path of the light emitting unit is limited to only the central part of the mesa (see FIG. 3B). The non-oxidized region (current passing region) has a square shape with a side length of 3 μm.

(6) A metal film 110 as a heat dissipation member is formed on the bottom surface of the etching by a lift-off method (see FIG. 3C). In other words, the entire surface of the metal film 110 on the −Z side is in contact with the lower reflecting mirror 103 of the semiconductor stacked body. Here, a gold thin film having a thickness of 0.5 μm is used as the metal film 110. Further, as shown in FIG. 4 as an example, the metal film 110 is formed not only between the mesas in the plurality of mesas but also in a region surrounding the plurality of mesas.

(7) An insulating film 111 made of SiO ₂ is formed as a passivation film by using a chemical vapor deposition method (CVD method) (see FIG. 5A).

(8) Flatten with polyimide 112 (see FIG. 5B).

(9) Open a window for the P-side electrode contact in the upper part of the mesa (see FIG. 5C). Here, after masking with a photoresist, the opening at the top of the mesa is exposed to remove the photoresist at that portion, and then the polyimide 112 and the insulating film 111 are etched and opened with BHF.

(10) A square resist pattern having a side of 10 μm is formed in a region to be a light emitting portion on the upper part of 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 of the light emitting part is lifted off to form the p-side electrode 113 (see FIG. 6A).

(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. 6B). 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, each mesa becomes a light emission part, respectively.

(14) The semiconductor laminate is cut for each chip.

  As described above, according to the surface-emitting laser array 100 according to the present embodiment, the metal film 110 whose one surface is in contact with the lower reflecting mirror 103 of the semiconductor laminate is formed between the light-emitting portions in the plurality of light-emitting portions. And a region surrounding the plurality of light emitting portions. As a result, the heat generated in each light emitting part is quickly radiated to the peripheral part of the surface emitting laser array 100 via the metal film 110, and the thermal interference between the light emitting parts can be reduced as compared with the conventional case. Therefore, any of the plurality of light emitting units can output high-power laser light.

For example, in Patent Document 4, since an insulating film having a large thermal resistance is interposed between the heat radiation electrode and the semiconductor layer, if the arrangement of the plurality of light emitting portions in the surface emitting laser array is further increased, the efficiency of heat radiation is increased. It is expected to decline. Specifically, the thermal conductivity of GaAs, which is often used as a semiconductor substrate of a surface emitting laser array, is 54 [W / mK], whereas the thermal conductivity of gold, which is widely used as an electrode material, is 315 [ W / mK], and a good heat dissipation effect by the electrode is expected. However, the thermal conductivity of, for example, SiO ₂ widely used for insulating films is as low as 1.4 [W / mK], which is only about 1/40 that of GaAs. A large thermal resistance is generated between the heat radiation electrodes. On the other hand, in this embodiment, since it is set as the structure which provides the heat radiating member which contacted the semiconductor layer directly, heat dissipation efficiency can be improved significantly conventionally. Therefore, it is possible to effectively reduce the thermal interference between the light emitting units and the temperature rise of the light emitting unit array, and a high output can be obtained.

  In particular, in a surface emitting laser array with a high degree of integration, the width between the light emitting portions becomes small, so that the area of the heat dissipation member between the light emitting portions cannot be made very large. In order to increase the efficiency of heat dissipation under such restrictions, the entire surface of one side of the heat dissipation member may be in direct contact with the semiconductor. Of course, it is necessary to consider that the heat dissipation member does not cross the PN junction so that the characteristics of the surface emitting laser array are not impaired by the heat dissipation member in contact with the semiconductor.

  In the above-described embodiment, the case where etching is performed until the bottom surface of the etching reaches the lower reflecting mirror 103 when forming the mesa shape has been described, but the present invention is not limited to this. For example, the bottom surface of the etching may be in the lower spacer layer 104.

In the above-described embodiment, the case where the entire surface of the metal film on the −Z side is in contact with the lower reflecting mirror 103 of the semiconductor stacked body has been described. For example, as illustrated in FIGS. In the vicinity of the light emitting portion at the outer peripheral portion, instead of the metal film 110, almost half of the −Z side surface (110A ₁ ) is in contact with the lower reflecting mirror 103, and the rest of the −Z side surface (110A ₂ ) is A metal film 110 </ b> A in contact with the insulating film 111 may be formed. Here, 110 A ₂ is closer to the light emitting part at the outer peripheral part in the two-dimensional array. FIG. 8 shows the semiconductor stacked body before being planarized with the polyimide 115.

  In this case, in the method for manufacturing the surface-emitting laser array 100, instead of the steps (6) and (7), the insulating film is formed before the metal film is formed as shown in FIG. As shown in FIG. 9B, the step of forming the film 111, the step of removing the insulating film 111 where the metal film is in contact with the lower reflecting mirror 103, and the step of FIG. A step of forming a metal film on the bottom surface of the etching and a step of forming an insulating film 111 on the metal film (not shown) are performed.

  In particular, in a surface emitting laser array with a high degree of integration, since the area occupied by the light emitting portion increases, the length of the heat radiating member extending to the peripheral portion also increases. As a result, heat is gradually emitted from the heat radiating member during the period from the center of the array to the periphery of the array, which may increase the temperature of the entire array. In addition, a non-uniform temperature distribution occurs in the array in which the temperature at the center of the array is high and the temperature at the periphery is low, resulting in variations in the light output characteristics of the plurality of light emitting units. On the other hand, the metal film 110 is provided at the center in the two-dimensional array, and the metal film 110A is provided around the light emitting portion at the outer peripheral part in the two-dimensional array, so that the heat radiating member having the main function of heat absorption and exhaust heat. Reduces the thermal resistance to the semiconductor layer by making direct contact with the semiconductor layer, and the heat-dissipating member whose main function is heat transfer is to use a part of the insulating film to prevent direct contact with the semiconductor layer. Can be raised. Accordingly, it is possible to efficiently dissipate the heat of the central part in the two-dimensional array to the peripheral part without causing thermal interference with the light emitting part at the outer peripheral part in the two-dimensional array.

In the above embodiment, as shown in FIGS. 10 and 11 as an example, in the area surrounding the plurality of light emitting portions, in place of the metal film 110, a part of the surface on the -Z side (110B ₁₎ is A metal film 110 </ _b > B that is in contact with the lower reflecting mirror 103 of the semiconductor stacked body and in which the remaining (110B ₂ ) of the −Z side surface is in contact with the substrate 101 may be formed. Here, closer to the light emitting portion of the outer peripheral portion of the two-dimensional array is 110B _1. FIG. 11 shows the semiconductor stacked body before being flattened with the polyimide 115. A part of the side surface of the metal film 110 </ b> B comes into contact with the n-GaAs buffer layer 102.

  In this case, in the method of manufacturing the surface-emitting laser array 100, the step of etching and removing the lower reflecting mirror 103 and the n-GaAs buffer layer 102 where the metal film is in contact with the substrate 101 before the metal film is formed. Done.

  As a result, heat generated in the plurality of light emitting units is immediately radiated to the substrate 101 in the peripheral portion of the surface emitting laser array 100.

In the above embodiment, as shown in FIG. 12 and FIG. 13 as an example, instead of the metal film 110, the periphery (110C ₁ ) of the −Z side surface is in contact with the lower reflecting mirror 103 of the semiconductor stacked body. The metal film 110 </ _b > C in which the central portion (110 </ _b > C ₂ ) of the −Z side surface is in contact with the substrate 101 may be formed. FIG. 13 shows the semiconductor stacked body before being planarized with polyimide 115. In addition, a part of the side surface of the metal film 110 </ b> C is in contact with the n-GaAs buffer layer 102.

  In this case, in the method of manufacturing the surface-emitting laser array 100, the step of etching and removing the lower reflecting mirror 103 and the n-GaAs buffer layer 102 where the metal film is in contact with the substrate 101 before the metal film is formed. Done.

  Thereby, heat dissipation can be performed more effectively.

  Further, in this case, the first etching bottom surface when forming the mesa shape may be in the lower spacer layer 104. At this time, the metal film is in contact with the lower spacer layer 104, the lower reflecting mirror 103, the n-GaAs buffer layer 102, and the substrate 101. The conductivity types of the lower spacer layer 104, the lower reflecting mirror 103, and the n-GaAs buffer layer 102 are the same as those of the substrate 101.

  Further, in the above embodiment, the wirings are provided close to each other, and due to the electrical coupling between the wirings, a potential is induced in the other wiring due to the potential applied to one, which may cause electrical noise (electrical interference). If there is, the heat dissipating member may be grounded. In order to reduce electrical interference, it is necessary to reduce the (capacitance) coupling coefficient between wirings. In general, when a larger grounded capacitance (a self-capacitance between grounds) is provided between two wirings, the coupling coefficient is reduced, and electrical interference can be reduced. In this embodiment, a heat radiating member is provided between the light emitting portions, and wiring is provided on the heat radiating member with an insulating film interposed therebetween. Since the area of the wiring is larger than its cross-sectional area, the capacity between the heat dissipation member and the wiring is larger than the capacity generated between the wirings. Therefore, by grounding the heat dissipating member, a self-capacitance between the grounds satisfying the above requirements can be provided in the wiring. As a result, the electrical interference between the wirings can be reduced, and the effect of improving the characteristics particularly during high-speed modulation can be obtained.

  Moreover, although the said embodiment demonstrated the case where the oscillation wavelength of a surface emitting laser array was a 0.78 micrometer band, it is not limited to this. For example, the wavelength band may be 0.65 μm band, 0.85 μm band, 0.98 μm band, 1.3 μm band, 1.5 μm band, or the like. In this case, a 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 0.65 μm band, an InGaAs mixed crystal semiconductor material in the 0.98 μm band, and a GaInNAs (Sb) mixed crystal semiconductor material in the 1.3 μm band and 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.

  Moreover, although the said embodiment demonstrated the case where the number of the light emission parts contained in one chip | tip was 16, it is not limited to this.

  Moreover, although the said embodiment demonstrated the case where the shape of each mesa was square shape, it is not restricted to this, For example, arbitrary shapes, such as circular shape, elliptical shape, and a rectangular shape, may be sufficient.

<Image forming apparatus>
Next, an embodiment of the image forming apparatus of the present invention will be described. FIG. 14 shows a schematic configuration of a laser printer 1000 as an image forming apparatus according to an embodiment of the present invention.

  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 static elimination unit 1034, a cleaning blade 1035, a toner cartridge 1036, a paper supply roller 1037, a paper supply tray 1038, A registration roller pair 1039, a fixing roller 1041, a paper discharge roller 1042, a paper discharge tray 1043, and the like are provided.

  A photosensitive layer is formed on the surface of the photosensitive drum 1030. That is, the surface of the photoconductor drum 1030 is a scanned surface. Here, 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 blade 1035 are each arranged in the vicinity of the surface of the photosensitive drum 1030. Then, with respect to the rotation direction of the photosensitive drum 1030, the charging charger 1031 → the developing roller 1032 → the transfer charger 1033 → the charge eliminating unit 1034 → the cleaning blade 1035 are arranged in this order.

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

  The optical scanning device 1010 irradiates the surface of the photosensitive drum 1030 charged by the charging charger 1031 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 1030 on the surface of the photosensitive drum 1030. 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 blade 1035 removes toner (residual toner) remaining on the surface of the photosensitive drum 1030. The removed residual toner is used again. The surface of the photosensitive drum 1030 from which the residual toner has been removed returns to the position of the charging charger 1031 again.

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

  As shown in FIG. 15, the optical scanning device 1010 includes a light source unit 10, a coupling lens 11, an aperture plate 12, a cylindrical lens 13, a polygon mirror 14, an fθ lens 15, a toroidal lens 16, two mirrors (17, 18), and a control device (not shown) for comprehensively controlling the above-described units.

  As shown in FIG. 16 as an example, the light source unit 10 includes a surface emitting laser array 10A in which 40 light emitting units are two-dimensionally arranged. The surface emitting laser array 10A includes a heat radiating member similar to the surface emitting laser array 100. Note that the M direction in FIG. 16 indicates the direction corresponding to the main scanning direction, and the S direction indicates the direction corresponding to the sub scanning direction.

  In the surface emitting laser array 10 </ b> A, a light emitting unit array composed of 10 light emitting units arranged in a line at equal intervals along a direction inclined by an angle θ with respect to the M direction (hereinafter referred to as “T direction” for convenience). , Four rows are arranged at equal intervals d1 in the S direction. Further, when 40 light emitting units are orthogonally projected onto a virtual line extending in the S direction, the light emitting unit intervals are equal intervals d2.

  Returning to FIG. 15, the coupling lens 11 shapes the light emitted from the light source unit 10 into substantially parallel light.

  The aperture plate 12 has an aperture and defines the beam diameter of light that passes through the coupling lens 11.

  The cylindrical lens 13 condenses the light that has passed through the opening of the aperture plate 12 in the vicinity of the deflection reflection surface of the polygon mirror 14 via the mirror 17.

  The polygon mirror 14 is formed of a regular hexagonal columnar member having a low height, and six deflection reflection surfaces are formed on the side surface. Then, it is rotated at a constant angular velocity in the direction of the arrow shown in FIG. 15 by a rotation mechanism (not shown). Therefore, the light emitted from the light source unit 10 and condensed near the deflection reflection surface of the polygon mirror 14 by the cylindrical lens 13 is deflected at a constant angular velocity by the rotation of the polygon mirror 14.

  The fθ lens 15 has an image height proportional to the incident angle of light from the polygon mirror 14, and moves the image plane of light deflected by the polygon mirror 14 at a constant angular velocity at a constant speed in the main scanning direction.

  The toroidal lens 16 forms an image of the light from the fθ lens 15 on the surface of the photosensitive drum 1030 via the mirror 18.

  In this case, in the surface-emitting laser array 10A, since the intervals between the light emitting portions when the respective light emitting portions are orthogonally projected onto a virtual line extending in the S-axis direction are equal intervals d2, as shown in FIG. By adjusting the above, it can be considered that the configuration is similar to the case where the light sources are arranged at equal intervals in the sub-scanning direction on the photosensitive drum 1030. For example, if the distance d1 is 26.5 μm, the distance d2 is 2.65 μm. If the magnification of the optical system is doubled, writing dots can be formed on the photosensitive drum 1030 at intervals of 5.3 μm in the sub-scanning direction. This corresponds to 4800 dpi (dots / inch). That is, high-density writing of 4800 dpi (dot / inch) can be performed. Of course, the density can be increased by increasing the number of light emitting portions in the T direction, making the array arrangement in which the distance d1 is narrowed and the distance d2 is further reduced, or by reducing the magnification of the optical system. Printing is possible. Note that the writing interval in the main scanning direction can be easily controlled by the lighting timing of the light source.

  In this case, the laser printer 1000 can perform printing without decreasing the printing speed even if the writing dot density increases. Further, when the writing dot density is the same, the printing speed can be further increased.

  As described above, according to the optical scanning device 1010 according to the present embodiment, the light source unit 10 has the surface emitting laser array 10 </ b> A including the heat radiating member similar to the surface emitting laser array 100. Accordingly, each of the light emitting units can output a high-power laser beam, and as a result, high-density optical scanning can be performed.

  Further, the laser printer 1000 according to the present embodiment includes the optical scanning device 1010 that can perform high-density optical scanning, and as a result, a high-quality image can be formed.

  In the above embodiment, the case of the laser printer 1000 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 1010 can form a high-quality image.

  For example, an image forming apparatus that includes the optical scanning device 1010 and 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.

  Further, even an image forming apparatus that forms a multi-color image can form a high-definition image by using an optical scanning device that supports color images.

  For example, as shown in FIG. 18, a tandem color machine 1500 corresponding to a color image and including a plurality of photosensitive drums may be used. The tandem color machine 1500 includes a black (K) photosensitive drum K1, a charger K2, a developing unit K4, a cleaning unit K5, a transfer charging unit K6, a cyan (C) photosensitive drum C1, a charging unit. A developing unit C2, a developing unit C4, a cleaning unit C5, a transfer charging unit C6, a magenta (M) photosensitive drum M1, a charging unit M2, a developing unit M4, a cleaning unit M5, and a transfer charging unit M6; A yellow (Y) photosensitive drum Y1, a charger Y2, a developing unit Y4, a cleaning unit Y5, a transfer charging unit Y6, an optical scanning device 1010A, a transfer belt 80, a fixing unit 30 and the like are provided. .

  The optical scanning device 1010A includes a surface emitting laser array for black, a surface emitting laser array for cyan, a surface emitting laser array for magenta, and a surface emitting laser array for yellow. Each surface emitting laser array includes a heat radiating member similar to that of the surface emitting laser array 100. The light from the surface emitting laser array for black is irradiated to the photosensitive drum K1 through the scanning optical system for black, and the light from the surface emitting laser array for cyan passes through the scanning optical system for cyan. The light from the surface emitting laser array for magenta is irradiated to the photosensitive drum C1, and the light from the surface emitting laser array for yellow is irradiated to the photosensitive drum M1 through the magenta scanning optical system. The photosensitive drum Y1 is irradiated through the scanning optical system.

  Each photosensitive drum rotates in the direction of the arrow in FIG. 18, and a charger, a developer, a transfer charging unit, and a cleaning unit 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 light by the optical scanning device 1010A, 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 images of the respective colors are 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 mechanical accuracy or the like. However, the correction accuracy of color misregistration of each color can be improved by selecting a light emitting unit to be lit.

  In this tandem color machine 1500, instead of the optical scanning device 1010A, a black optical scanning device, a cyan optical scanning device, a magenta optical scanning device, and a yellow optical scanning device may be used. In short, each surface emitting laser array only needs to include a heat radiating member similar to that of the surface emitting laser array 100.

<Optical transmission system>
FIG. 19 shows a schematic configuration of an optical transmission system 2000 according to an embodiment of the present invention. In this optical transmission system 2000, an optical transmission module 2001 and an optical reception module 2005 are connected by an optical fiber cable 2004, and one-way optical communication from the optical transmission module 2001 to the optical reception module 2005 is possible.

  The optical transmission module 2001 includes a light source 2002 including a surface emitting laser array having a heat radiating member similar to the surface emitting laser array 100, and a laser beam output from the light source 2002 in accordance with an electric signal input from the outside. And a drive circuit 2003 that modulates the light intensity.

  The optical signal output from the light source 2002 is coupled to the optical fiber cable 2004, guided through the optical fiber cable 2004, and input to the optical receiving module 2005.

  The optical receiving module 2005 includes a light receiving element 2006 that converts an optical signal into an electric signal, and a receiving circuit 2007 that performs signal amplification, waveform shaping, and the like on the electric signal output from the light receiving element 2006.

  According to the optical transmission module 2001 according to the present embodiment, since the light source 2002 has a surface emitting laser array including a heat radiating member similar to the surface emitting laser array 100, there is less thermal interference between the light emitting units, A high-power laser beam can be output from each light emitting unit, and as a result, a high-quality optical signal can be generated.

  Also, according to the optical transmission system 2000 according to the present embodiment, since the optical transmission module 2001 capable of generating a high-quality optical signal is provided, the electrical interference is small and the code error rate is small. As a result, high quality optical transmission can be performed. Also, high-speed transmission is possible.

  In the present embodiment, a configuration example of unidirectional communication of a single channel is shown, but a configuration of bidirectional communication, a parallel transmission method, a wavelength division multiplex transmission method, or the like can also be adopted. In short, it is sufficient that the light source 2002 has a surface emitting laser array including a heat radiating member similar to the surface emitting laser array 100.

  Further, the optical transmission system 2000 can be applied not only between devices but also between boards, between chips, and in-chip interconnection.

  As described above, according to the surface emitting laser array of the present invention, each of the plurality of light emitting units is suitable for outputting high power laser light. Moreover, the optical scanning device of the present invention is suitable for performing high-density optical scanning. The image forming apparatus of the present invention is suitable for forming a high quality image. The optical transmission module of the present invention is suitable for generating a high-quality optical signal. The optical transmission system of the present invention is suitable for performing high-quality optical transmission.

FIG. 1A is a plan view of a surface emitting laser array according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG. FIGS. 2A to 2C are views (No. 1) for describing a method for manufacturing a surface emitting laser array, respectively. FIG. 3A to FIG. 3C are views (No. 2) for explaining the method of manufacturing the surface emitting laser array, respectively. FIG. 4 is a plan view of FIG. FIGS. 5A to 5C are views (No. 3) for describing the method of manufacturing the surface emitting laser array. FIGS. 6A and 6B are views (No. 4) for describing the method of manufacturing the surface emitting laser array, respectively. It is FIG. (1) for demonstrating the modification 1 of a surface emitting laser array. It is FIG. (2) for demonstrating the modification 1 of a surface emitting laser array. FIG. 9A to FIG. 9C are diagrams for explaining a manufacturing method of Modification 1 of the surface emitting laser array. It is FIG. (1) for demonstrating the modification 2 of a surface emitting laser array. It is FIG. (2) for demonstrating the modification 2 of a surface emitting laser array. It is FIG. (1) for demonstrating the modification 3 of a surface emitting laser array. It is FIG. (2) for demonstrating the modification 3 of a surface emitting laser array. 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 array contained in the light source unit in FIG. It is a figure for demonstrating a write dot. It is a figure for demonstrating schematic structure of a tandem color machine. It is a figure for demonstrating schematic structure of the optical transmission module and optical transmission system which concern on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Light source unit, 10A ... Surface emitting laser array, 14 ... Polygon mirror (deflector), 15 ... f (theta) lens (a part of scanning optical system), 16 ... Toroidal lens (a part of scanning optical system), 100 ... surface Light emitting laser array, 101 ... substrate, 110 ... metal film (heat radiating member), 110A ... metal film (heat radiating member), 110B ... metal film (heat radiating member), 110C ... metal film (heat radiating member), 1000 ... laser printer (image) Forming apparatus), 1010... Optical scanning apparatus, 1010A... Optical scanning apparatus, 1030... Photosensitive drum (image carrier), 1500 ... tandem color machine (image forming apparatus), 2000 ... optical transmission system, 2001. Optical transmission module), 2003 ... Drive circuit (drive device), 2004 ... Optical fiber cable (optical transmission medium), 2006 ... Light receiving element (converter) Some), 2007 ... part of the reception circuit (converter), K1, C1, M1, Y1 ... photosensitive drum (image bearing member).

Claims (8)

In a surface emitting laser array having a plurality of mesa-shaped structures formed by etching a stacked body composed of a plurality of semiconductor layers stacked on a substrate,
Among the plurality of structures, a first heat radiating member provided on the first etching of the periphery of the structure located at the center,
A second heat dissipating member provided in a second etching part around the structure located in the periphery of the plurality of structures , and
A part of the first etching part is covered with a first heat insulating member,
A part of the second etching part is covered with a second heat insulating member,
The first heat radiating member is in contact with a portion of the first etching portion that is not covered with the first heat insulating member,
A part of the second heat radiating member is not in contact with the second heat insulating member in the second etching part, and the remaining part is in contact with the second heat insulating member;
Of the plurality of semiconductor layers, a surface emitting laser array in which a conductivity type of a semiconductor layer in contact with the first and second heat dissipation members is the same as a conductivity type of the substrate . Wherein between two adjacent structures to each other in a plurality of structures, a surface emitting laser array according to claim 1, characterized in that it has a region in which all of the plurality of semiconductor layers are removed. The outer peripheral portion of a region in which a plurality of structures are formed, a surface-emitting laser array according to claim 1 or 2, characterized in that it has a region in which all of the plurality of semiconductor layers are removed. An optical scanning device that scans a surface to be scanned with light,
A light source unit having a surface-emitting laser array according to any one of claims 1 to 3;
A deflector for deflecting light from the light source unit;
A scanning optical system for condensing the light deflected by the polarizer on the surface to be scanned. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to claim 4 that scans the at least one image carrier with light including image information. The image forming apparatus according to claim 5 , wherein the image information is multicolor color image information. An optical transmission module that generates an optical signal according to an input electrical signal,
A surface-emitting laser array according to any one of claims 1 to 3 ;
An optical transmission module comprising: a driving device that drives the surface-emitting laser array in accordance with the input electric signal. An optical transmission module according to claim 7 ;
An optical transmission medium for transmitting an optical signal generated by the optical transmission module;
A converter for converting an optical signal through the optical transmission medium into an electric signal;

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