JP5721051B2 - Surface emitting laser element, surface emitting laser array, optical scanning device, and image forming apparatus - Google Patents

Description

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

  A vertical cavity surface emitting laser (VCSEL) is a semiconductor laser that emits light in a direction perpendicular to a substrate surface, and (1) resonates without being cleaved during manufacturing. It has the following features: (2) easy two-dimensional integration, (3) inspection at the wafer level, and easy device inspection. Therefore, the surface emitting laser element is considered to be used as a light source in optical communication such as optical interconnection, a light source of an optical pickup device, and a light source of an image forming apparatus.

  In such applications, the surface emitting laser element includes (a) a large active layer gain, (b) a low laser oscillation threshold, (c) high output, and (d) reliability. It is required to have high properties.

  By the way, since the surface emitting laser element has a small volume of the active layer, the light output is smaller than that of the edge emitting semiconductor laser.

  Therefore, as one method for increasing the light output of the surface emitting laser element, it has been considered to reduce the temperature rise in the light emitting region.

  In general, in a semiconductor laser as well as a surface emitting laser element, the degree of diffusion of heat generated by current injection greatly affects the laser output, optical spectrum, mode, and laser lifetime.

  In particular, the surface emitting laser element has a structure in which the active layer is sandwiched between semiconductor multilayer mirrors (DBR) having a high thermal resistance, and therefore the temperature rise of the active layer is large. When the active layer reaches a high temperature, the light output of the surface emitting laser element is saturated at a low point. This phenomenon occurs regardless of the wavelength of the oscillation light.

  For example, Patent Document 1 discloses a layer made of a material having an oxidation rate slower than that of an AlAs layer as an antioxidant layer for an AlAs layer in an oxidation process in which a partial region of a specific semiconductor layer is oxidized and converted into an oxide layer. A surface-emitting semiconductor laser element is disclosed that is interposed between an AlAs layer and an oxide layer on the active layer side of a semiconductor multilayer mirror.

  Patent Document 2 discloses a light emitting device in which a high thermal conductivity layer is provided between at least one of the light emitting layer and the lower reflector and between the light emitting layer and the upper reflector.

  However, in the surface emitting semiconductor laser element disclosed in Patent Document 1, it is difficult to sufficiently dissipate the heat of the active layer.

  Further, in the light emitting device disclosed in Patent Document 2, when an AlAs layer is used for the high thermal conductivity layer, oxidation proceeds from an exposed portion of the AlAs layer when an oxide constriction structure is formed. There is a possibility that the light emitting device is destroyed due to the increase in the resistance of the reflector or the expansion of the volume due to the oxidation of the AlAs layer.

  The present invention has been made under such circumstances, and a first object of the present invention is to provide a surface emitting laser element excellent in heat dissipation and corrosion resistance without incurring an increase in cost.

  A second object of the present invention is to provide a surface emitting laser array excellent in heat dissipation and corrosion resistance without incurring an increase in cost.

  A third object of the present invention is to provide an optical scanning device capable of performing stable optical scanning without incurring an increase in cost.

  A fourth object of the present invention is to provide an image forming apparatus capable of forming a high-quality image without increasing the cost.

According to a first aspect of the present invention, a resonator structure including an active layer, and a plurality of semiconductors including an upper semiconductor multilayer reflector and a lower semiconductor multilayer reflector provided with the resonator structure interposed therebetween In the surface-emitting laser device in which the layers are stacked on the substrate, the lower semiconductor multilayer film reflector includes a first lower semiconductor multilayer film reflector formed on the substrate side and a first lower semiconductor multilayer film reflector formed on the resonator structure side. and a second lower semiconductor multilayer reflection mirror, wherein the first lower semiconductor multilayer reflector of the low refractive index _{layer, Al x Ga 1-x as} (0 <x ≦ 1) comprises a semiconductor layer, the second lower At least a part of the low refractive index layer of the semiconductor multilayer mirror has an optical thickness larger than “oscillation wavelength / 4” and a thermal resistivity of the high refractive index layer of the first lower semiconductor multilayer mirror. _{Al y Ga 1-y as (} 0 having a value between the low refractive index layer a surface emitting laser element which comprises a y <x) semiconductor layer.

  According to this, heat dissipation and corrosion resistance can be improved without increasing the cost.

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

  According to this, heat dissipation and corrosion resistance can be improved without increasing the cost.

  According to a third aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned with light, a light source having the surface emitting laser element of the present invention, an optical deflector that deflects light from the light source, and And a scanning optical system for condensing the light deflected by the optical deflector onto the surface to be scanned.

  According to this, since the light source has the surface emitting laser element of the present invention, stable optical scanning can be performed without increasing the cost.

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

  According to this, since the light source has the surface emitting laser array of the present invention, stable optical scanning can be performed without increasing the cost.

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

  According to this, since the optical scanning device of the present invention is provided, as a result, a high-quality image can be formed without increasing the cost.

It is a figure for demonstrating schematic structure of the laser printer which concerns on one Embodiment of this invention. It is the schematic which shows the optical scanning device in FIG. It is a figure for demonstrating the surface emitting laser element contained in the light source in FIG. It is FIG. (1) for demonstrating the structure of the semiconductor layer in a surface emitting laser element. It is FIG. (2) for demonstrating the structure of the semiconductor layer in a surface emitting laser element. It is FIG. (1) for demonstrating the manufacturing method of a surface emitting laser element. It is FIG. (2) for demonstrating the manufacturing method of a surface emitting laser element. It is FIG. (3) for demonstrating the manufacturing method of a surface emitting laser element. It is FIG. (4) for demonstrating the manufacturing method of a surface emitting laser element. It is FIG. (5) for demonstrating the manufacturing method of a surface emitting laser element. It is FIG. (6) for demonstrating the manufacturing method of a surface emitting laser element. It is FIG. (7) for demonstrating the manufacturing method of a surface emitting laser element. It is a figure for demonstrating the relationship between the composition ratio of Al in AlGaAs, and a thermal resistivity. 4 is a diagram for explaining a configuration of a lower semiconductor DBR in the surface emitting laser element A. FIG. It is a figure for demonstrating the simulation result of the relationship between Al composition ratio and thermal resistance in AlGaAs. 4 is a diagram for explaining a configuration of a lower semiconductor DBR in the surface emitting laser element B. FIG. 4 is a diagram for explaining a region of interest for corrosion resistance in a surface emitting laser element B. FIG. It is a SEM image of a region of interest when the surface emitting laser element B is left in the atmosphere at room temperature for one week. It is a figure for demonstrating the position A in FIG. 20A and 20B are views (No. 1) for explaining the results of the durability test of the surface emitting laser element B, respectively. FIGS. 21A and 21B are views (No. 2) for explaining the results of the durability test of the surface emitting laser element B, respectively. 4 is a schematic diagram for explaining corrosion due to natural oxidation of the lower semiconductor DBR in the surface emitting laser element B. FIG. 4 is a diagram for explaining a region of interest for corrosion resistance in the surface emitting laser element 100. FIG. 6 is a diagram for explaining the results of a durability test of the surface emitting laser element 100. FIG. 4 is a schematic diagram for explaining corrosion due to natural oxidation of a second lower semiconductor DBR 103b in the surface emitting laser element 100. FIG. 6 is a diagram for explaining the results of a durability test of the surface emitting laser element A. FIG. 10 is a diagram for explaining a configuration of a lower semiconductor DBR in a surface emitting laser element according to Modification 1. FIG. FIG. 10 is a diagram for explaining a configuration of a lower semiconductor DBR in a surface emitting laser element according to Modification 2. FIG. 10 is a diagram for explaining a configuration of a lower semiconductor DBR in a surface emitting laser element according to Modification 3. FIG. 10 is a diagram for explaining corrosion due to natural oxidation of a second lower semiconductor DBR 103b in a surface emitting laser element according to Modification 3. It is a figure for demonstrating the thermal resistance (calculated value) of the surface emitting laser element A, the surface emitting laser element 100, and the surface emitting laser element of the modification 3. It is a figure for demonstrating the simulation result of the relationship between Al composition ratio and thermal resistance in AlGaAs with a three-layer structure. FIG. 10 is a diagram for explaining a configuration of a lower semiconductor DBR in a surface emitting laser element according to Modification Example 4. FIG. 10 is a diagram for explaining a configuration of a lower semiconductor DBR in a surface emitting laser element according to Modification Example 5. FIG. 10 is a diagram for explaining a configuration of a lower semiconductor DBR in a surface emitting laser element according to Modification 6; It is a figure for demonstrating the corrosion by the natural oxidation of 2nd lower semiconductor DBR103b in the surface emitting laser element of the modification 6. FIG. It is a figure for demonstrating a surface emitting laser array. It is AA sectional drawing of FIG. It is a figure for demonstrating schematic structure of a color printer.

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

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

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

  The printer control device 1060 includes a CPU, a ROM described in a program written in code readable by the CPU, various data used when executing the program, a RAM as a working memory, an analog data An AD conversion circuit for converting the signal into digital data. The printer control device 1060 controls each unit in response to a request from the host device, and sends image information from the host device to the optical scanning device 1010.

  The photosensitive drum 1030 is a cylindrical member, and a photosensitive layer is formed on the surface thereof. That is, the surface of the photoconductor drum 1030 is a scanned surface. The photosensitive drum 1030 is rotated in the direction of the arrow in FIG. 1 by a rotation mechanism (not shown).

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

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

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

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

  The developing roller 1032 causes the toner supplied from the toner cartridge 1036 to adhere to the latent image formed on the surface of the photosensitive drum 1030 to visualize the image information. Here, the toner-attached image (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 paper 1040 on which the toner image is transferred 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 on which the toner is fixed is sent to the paper discharge tray 1043 via the paper discharge roller 1042 and is sequentially stacked on the paper discharge tray 1043.

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

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

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

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

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

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

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

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

  The optical system arranged on the optical path between the light source 14 and the polygon mirror 13 is also called a pre-deflector optical system.

  The polygon mirror 13 is made of a regular hexagonal columnar member having a low height, and six deflecting reflection surfaces are formed on the side surface. The polygon mirror 13 deflects the light flux from the reflection mirror 18 while rotating at a constant speed around an axis parallel to the sub-scanning corresponding direction.

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

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

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

  The light source 14 includes a surface emitting laser element 100 as shown in FIG. 3 as an example. In this specification, the laser light oscillation direction is defined as a Z-axis direction, and two directions orthogonal to each other in a plane perpendicular to the Z-axis direction are described as an X-axis direction and a Y-axis direction. FIG. 3 is a view (longitudinal sectional view) showing a cut surface when the surface emitting laser element 100 is cut in parallel to the XZ plane.

  This surface emitting laser element 100 is a surface emitting laser element having an oscillation wavelength of 780 nm, and includes a substrate 101, a lower semiconductor DBR 103, a lower spacer layer 104, an active layer 105, an upper spacer layer 106, an upper semiconductor DBR 107, a contact layer 109, and the like. have.

  The substrate 101 is an n-GaAs substrate.

  The lower semiconductor DBR 103 includes a first lower semiconductor DBR 103a and a second lower semiconductor DBR 103b.

The first lower semiconductor DBR 103a is stacked on the + Z side surface of the substrate 101 through a buffer layer made of n-GaAs, and includes a low refractive index layer made of n-AlAs, and n-Al _0.3 Ga _0.7. There are 37 pairs of high refractive index layers made of As (see FIG. 4). Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) having a thickness of about 20 nm in which the composition is gradually changed from one composition to the other composition is provided. . Each refractive index layer includes 1/2 of the adjacent composition gradient layer, and is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ. The optical thickness and the actual thickness of the layer have the following relationship. When the optical thickness is λ / 4, the actual thickness D of the layer is D = λ / 4n (where n is the refractive index of the medium of the layer).

The second lower semiconductor DBR 103b is stacked on the surface of the first lower semiconductor DBR 103a on the + Z side, and includes a low refractive index layer made of n-Al _0.98 Ga _0.02 As, and n-Al _0.3 Ga _{0. 7} pairs of high refractive index layers made of ₇ As are provided. Between each refractive index layer, in order to reduce electrical resistance, a composition gradient layer (not shown) having a thickness of about 20 nm in which the composition is gradually changed from one composition to the other composition is provided. . The high refractive index layer is set so as to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer. Further, the low refractive index layer is set to have an optical thickness of 3λ / 4 including 1/2 of the adjacent composition gradient layer. That is, the low refractive index layer (n-Al _0.98 Ga _0.02 As) of the second lower semiconductor DBR 103b has an Al content relative to the low refractive index layer (n-AlAs) of the first lower semiconductor DBR 103a. And the optical thickness is 3 times.

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

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

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

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

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

  In one of the low refractive index layers in the upper semiconductor DBR 107, a selective oxidation layer 108 made of p-AlAs is inserted with a thickness of about 30 nm (see FIG. 5). The insertion position of the selectively oxidized layer 108 is a position corresponding to the third node from the active layer 105 in the electric field intensity distribution of the standing wave.

  The contact layer 109 is stacked on the + Z side of the upper semiconductor DBR 107 and is a layer made of p-GaAs. The contact layer 109 is electrically connected to the p-side electrode 113.

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

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

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

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

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

(4) The photomask is removed (see FIG. 7).

(5) The laminated body is heat-treated in water vapor. As a result, Al (aluminum) in the selectively oxidized layer 108 is selectively oxidized from the outer peripheral portion of the mesa, and an unoxidized region 108b surrounded by the Al oxide 108a remains in the central portion of the mesa. (See FIG. 8). In other words, a so-called oxidized constriction structure is formed that restricts the drive current path of the light emitting part only to the central part of the mesa. The non-oxidized region 108b is a current passage region (current injection region). In this way, for example, a substantially square current passing region having a width of about 4 μm is formed.

(6) A protective layer 111 made of SiN is formed by vapor phase chemical deposition (CVD) (see FIG. 9). The protective layer 111 is not necessarily applied to the end surface of the chip provided with the surface light emitting element.

(7) An etching mask for opening a window for the p-side electrode contact is formed on the upper part of the mesa serving as the laser light emission surface.

(8) The protective layer 111 is etched with BHF (buffered hydrofluoric acid) to open the window of the p-side electrode contact.

(9) The etching mask is removed (see FIG. 10).

(10) The portions other than the portion that becomes the p-side electrode are masked with a photoresist, and the p-side electrode material is deposited.

(11) Ultrasonic cleaning is performed in a solution in which a photoresist such as acetone is dissolved to form the p-side electrode 113 (see FIG. 11). A region surrounded by the p-side electrode 113 is an emission region. The p-side electrode is a multilayer film made of Cr / AuZn / Au or a multilayer film made of AuZn / Ti / Au.

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

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

(14) Separate for each chip. Here, after a chip separation groove reaching the substrate is formed between adjacent chips, the substrate is cleaved to form individual chips.

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

Thus, in the lower semiconductor DBR 103, the low refractive index layers included in three pairs close to the active layer 105 are layers made of n-Al _0.98 Ga _0.02 As, and the optical thickness thereof is It is 3λ / 4. That is, Al _0.98 Ga _0.02 As occupies 9λ / 4 and Al _0.3 Ga _0.7 As is 3λ / 4 within the range of the optical thickness of 3λ with respect to the −Z direction from the lower spacer layer. Accounted for.

FIG. 13 shows the relationship between the Al composition ratio x and the thermal resistivity in Al _x Ga _1-x As. The thermal resistivity increases as the composition ratio x increases, reaches a maximum near the composition ratio x, and decreases as the composition ratio x increases when the composition ratio x exceeds 0.5. When the composition ratio x is 1.0, the thermal resistivity is the smallest.

The thermal resistivity of Al _0.3 Ga _0.7 As is 8.5 [K · cm / W], and the thermal resistivity of Al _0.9 Ga _0.1 As is 3.9 [K · cm / W. The thermal resistivity of AlAs is 1.1 [K · cm / W].

Thus, AlAs has a thermal resistivity of 1/3 or less compared to Al _0.9 Ga _0.1 As, and is extremely effective for improving the heat dissipation of the element. However, AlGaAs mixed crystals have the property of being easily oxidized (corroded) as the Al composition ratio increases, and AlAs is most easily oxidized.

The thermal resistivity of Al _0.98 Ga _0.02 As is 1.7 [K · cm / W], and the thermal resistivity of Al _0.3 Ga _0.7 As is 8.5 [K · cm. / W]. That is, the thermal resistivity of Al _0.98 Ga _0.02 As is smaller than that of Al _0.3 Ga _0.7 As.

FIG. 14 shows a configuration of a lower semiconductor DBR in a conventional surface emitting laser element (referred to as “surface emitting laser element A”). Here, there are 40 pairs of a low refractive index layer made of n-AlAs and a high refractive index layer made of n-Al _0.3 Ga _0.7 As. That is, the lower semiconductor DBR having the same configuration as the first lower semiconductor DBR 103 a is stacked up to the vicinity of the active layer 105. In this case, AlAs occupies 6λ / 4 and Al _0.3 Ga _0.7 As occupies 6λ / 4 within an optical thickness of 3λ with respect to the −Z direction from the lower spacer layer.

  It was 2942 [K / W] when the thermal resistance of the surface emitting laser element A was calculated by computer simulation.

  On the other hand, when the thermal resistance of the surface emitting laser element 100 was similarly calculated by computer simulation, it was 2857 [K / W].

  Thus, the surface emitting laser element 100 has a smaller thermal resistance than the surface emitting laser element A, and can suppress the temperature increase of the active layer 105 more than the surface emitting laser element A.

  In the surface emitting laser element 100, it is considered that the heat generated in the active layer 105 is diffused in the lateral direction (direction perpendicular to the Z axis) through the low refractive index layer of the second lower semiconductor DBR 103b.

  By the way, FIG. 15 shows the result of calculating the relationship between the Al composition ratio and the thermal resistance in the low refractive index layer of the second lower semiconductor DBR 103b by computer simulation. From FIG. 15, if the Al composition ratio in the low refractive index layer of the second lower semiconductor DBR 103 b is larger than 0.97, the overall thermal resistance of the surface emitting laser element can be made smaller than that of the surface emitting laser element A. I understand.

FIG. 16 shows the configuration of the lower semiconductor DBR in the surface emitting laser element (referred to as “surface emitting laser element B”) disclosed in Patent Document 2. In the surface emitting laser element B, the thickness of the AlAs layer near the active layer 105 is increased. That is, AlAs occupies 9λ / 4 and Al _0.3 Ga _0.7 As occupies 3λ / 4 within an optical thickness of 3λ with respect to the −Z direction from the lower spacer layer. AlAs has a thermal resistivity of 1/3 or less compared to Al _0.9 Ga _0.1 As. Therefore, the thermal resistance of the portion near the active layer 105 in the lower semiconductor DBR is smaller than that of the surface emitting laser element 100, and the temperature of the active layer 105 can be suppressed from increasing. The surface-emitting laser element B needs to ensure corrosion resistance because of the element having a thick AlAs layer. That is, it is necessary to take sufficient measures such as protecting the end face with an insulating film or the like or using a highly airtight package, which leads to an increase in cost.

  However, AlGaAs mixed crystals have the property of being easily oxidized (corroded) as the Al composition ratio increases, and AlAs is most easily oxidized.

  Therefore, as shown in FIG. 17 as an example, attention is paid to a lower semiconductor DBR exposed to the air by forming a chip isolation groove (hereinafter also referred to as “exposed lower semiconductor DBR” for convenience).

  FIG. 18 shows a scanning electron microscope (SEM) image of the exposed lower semiconductor DBR when the surface emitting laser element B is left in the atmosphere at room temperature for one week. At this time, corrosion was observed in the AlAs layer (see FIG. 19) having a thickness of 3λ / 4 near the active layer 105.

  The surface emitting laser element B was subjected to a durability test in an atmosphere at a temperature of 85 ° C. and a humidity of 85%. At this time, when 15 hours passed, the corrosion progressed from the periphery of the chip to about 200 μm. Then, after 300 hours, as shown in FIGS. 20A and 20B, the portion on the + Z side was peeled off from the AlAs layer having the thickness of −λ side of 3λ / 4 as shown in FIGS. A plan view at this time is shown in FIG. 21A, and an SEM image of the remaining lower semiconductor DBR is shown in FIG. No corrosion is observed in the λ / 4 AlAs layer. FIG. 21A is a top view of the surface on which the surface emitting laser elements are formed in an array as shown in FIG. That is, FIG. 12A shows that the layer on the + Z side has peeled off the entire surface formed in an array from the position A in FIG. 21B.

Thus, in the surface emitting laser element B, since the end surface of the lower semiconductor DBR is exposed to the air, the thicker the AlAs layer, the more the area that comes into contact with the air, and the more easily corroded (see FIG. 22). Therefore, in the surface emitting laser element B, corrosion due to natural oxidation of the AlAs layer proceeds with time. When this corrosion progresses, partial film peeling occurs due to the volume expansion of the AlAs layer due to oxidation, and the corrosion further progresses. As a result, the AlAs is oxidized and the Al ₂ O ₃ corroded portion of the insulator cannot conduct electricity, so that the lower semiconductor DBR may have a high resistance or the element itself may be destroyed. That is, the surface emitting laser element B has a short element life.

  Next, a durability test of the surface emitting laser element 100 was performed. Here, as an example, as shown in FIG. 23, a chip separation groove is used as a region of interest. FIG. 24 shows a region of interest before the test, after 20 hours, after 60 hours, and after 2500 hours. According to this, partial corrosion was observed after 20 hours (corrosion as shown in FIG. 18 occurred in the portion discolored in black), and the progress of corrosion almost stopped after 60 hours, and 2500 hours Even after the lapse of time, the corrosion is not so great. At this time, about 50 μm was corroded from the periphery of the chip.

In the surface emitting laser element 100, the thick layer near the active layer 105 is not an AlAs layer but an Al _0.98 Ga _0.02 As layer. Since Al _0.98 Ga _0.02 As contains Ga, it is less oxidized than AlAs, and the surface-emitting laser element 100 has higher corrosion resistance than the surface-emitting laser element B (see FIG. 25).

  Incidentally, the result of the durability test of the surface emitting laser element A is shown in FIG. According to this, it was hardly corroded even after 2500 hours. That is, in the surface emitting laser element A, it can be seen that the AlAs layer has a thickness of λ / 4 and is hardly corroded. On the other hand, in order to further improve the heat dissipation, it is desirable to increase the thickness of the AlAs layer, but it tends to corrode.

  In the surface emitting laser element 100, in the durability test, partial corrosion is observed at the chip peripheral portion, but the corrosion stays at the chip peripheral portion and does not reach the light emitting portion. That is, the surface emitting laser element 100 can achieve both heat dissipation and corrosion resistance.

  The surface emitting laser element 100 is excellent in heat dissipation, so that the deterioration rate of the crystal is slow and the corrosion resistance (humidity resistance) of the element is excellent. ) Has been improved. As a result, the light source can be reused.

  As described above, according to the surface emitting laser element 100 according to the present embodiment, the lower semiconductor DBR 103, the resonator structure including the active layer 105, the upper semiconductor DBR 107 including the selective oxidation layer 108, and the like are provided on the substrate 101. Are stacked.

The lower semiconductor DBR 103 includes a first lower semiconductor DBR 103a and a second lower semiconductor DBR 103b, and the second lower semiconductor DBR 103b close to the resonator structure has a low refraction made of n-Al _0.98 Ga _0.02 As. Three pairs of a refractive index layer and a high refractive index layer made of n-Al _0.3 Ga _0.7 As are provided. In the second lower semiconductor DBR 103b, the high refractive index layer is set to have an optical thickness of λ / 4, including 1/2 of the adjacent composition gradient layer, and the low refractive index layer is adjacent. Including 1/2 of the composition gradient layer, the optical thickness is set to 3λ / 4.

The low refractive index layer of the second lower semiconductor DBR 103b is a heat between n-AlAs, which is the low refractive index layer of the first lower semiconductor DBR 103a, and n-Al _0.3 Ga _0.7 As, which is the high refractive index layer. Has resistivity. Since the low refractive index layer of the second lower semiconductor DBR 103b needs to be thick, the Al composition needs to be smaller than that of the low refractive index layer of the first lower semiconductor DBR. Therefore, the low refractive index layer of the second lower semiconductor DBR 103b is between n-AlAs, which is the low refractive index layer of the first lower semiconductor DBR 103a, and n-Al _0.3 Ga _0.7 As, which is the high refractive index layer. Having a thermal resistivity of

  In this case, both high heat dissipation and high corrosion resistance can be achieved. Therefore, a surface emitting laser element excellent in heat dissipation and corrosion resistance can be realized without increasing the cost.

  Further, each layer of the lower semiconductor DBR 103 has an optical thickness that is an odd multiple of λ / 4, and therefore can satisfy the phase condition of Bragg multiple reflection. Therefore, the second lower semiconductor DBR 103b can reduce the thermal resistance of the element while maintaining the reflectance as a reflecting mirror.

Also, using a AlGaInP mixed crystal _{(Al 0.1 Ga 0.9) 0.5 In} 0.5 P each spacer layer. In this case, the etching can be accurately stopped in the lower spacer layer 104 in the etching process when forming the mesa. Therefore, it is possible to prevent the end surface of the second lower semiconductor DBR 103b from being exposed to the side surface (side wall) of the mesa. That is, when the selective oxidation layer 108 is oxidized, the second lower semiconductor DBR 103b can be prevented from being oxidized simultaneously. Thereby, the manufacturing yield can be improved and the cost can be reduced.

  Each spacer layer need not be an AlGaInP mixed crystal. When the oscillation wavelength becomes longer, the Al composition ratio in AlGaAs that can be used for the spacer layer becomes smaller and the thermal resistance becomes smaller. Therefore, when the thermal resistivity of AlGaAs is smaller than that of the AlGaInP mixed crystal, the lower spacer layer 104 may be made of AlGaAs.

  According to the optical scanning device 1010 according to the present embodiment, the light source 14 includes the surface emitting laser element 100. Therefore, stable optical scanning can be performed without increasing the cost.

  In addition, the laser printer 1000 according to the present embodiment includes the optical scanning device 1010. As a result, it is possible to form a high-quality image without increasing the cost.

  Next, a modification of the surface emitting laser element 100 will be described. Each modification is characterized in that the configuration of the second lower semiconductor DBR 103b is different. In the following, differences from the surface-emitting laser element 100 will be mainly described, and the same or equivalent components as those of the surface-emitting laser element 100 described above will be denoted by the same reference numerals, and the description will be simplified or Shall be omitted.

<< Modification 1 >>
In the surface-emitting laser device of Variation 1 (referred to surface-emitting laser element 100 _1), as shown in FIG. 27, only the most + Z side of the lower refractive layers in the second lower semiconductor DBR103b is, its optical thickness 5λ / 4. Even in this case, heat dissipation and corrosion resistance can be improved. Since Al _0.98 Ga _0.02 As has a lower thermal resistivity than Al _0.3 Ga _0.7 As, 3λ / 4 is more than 3 pairs. Thermal resistance is reduced. Moreover, since Al _0.98 Ga _0.02 As is less oxidized than AlAs, it has better corrosion resistance than AlAs.

<< Modification 2 >>
In the surface-emitting laser device of Variation 2 (referred to surface-emitting laser element 100 _2), as shown in FIG. 28, the second lower semiconductor DBR103b is, the lower spacer layer 104 side, the optical thickness each lambda / 4 1 pair of a low refractive index layer made of n-AlGaAs and a high refractive index layer made of n-Al _0.3 Ga _0.7 As. Even in this case, heat dissipation and corrosion resistance can be improved.

<< Modification 3 >>
In the surface-emitting laser device of Variation 3 (referred to surface-emission laser device 100 _3), as shown in FIG. 29, the low refractive index layer of the second lower semiconductor DBR103b is optical thickness be 3 [lambda] / 4 It has a three-layer structure. In the three-layer structure, the first layer is a layer made of n-AlAs, the second layer is a layer made of Al _0.9 Ga _0.1 As, and the third layer is a layer made of n-AlAs. . The optical thickness of each layer in the three-layer structure is λ / 4.

Compared with the surface-emitting laser element B, the optical thickness of the low-refractive index layers in the three pairs close to the active layer is the same as that of 3λ / 4. while a single layer of n-AlAs in B, and the surface-emitting laser element 100 _3, 3-layer _{structure, n-Al} 0.9 _{Ga 0.1} as is sandwiched n-AlAs.

Since Al _0.9 Ga _0.1 As contains Ga, it is less likely to be oxidized than n-AlAs. Further, in the surface emitting laser element 100 _3, since the optical thickness of the AlAs layer is lambda / 4, a small area of the exposed portion in the AlAs layer, it is less likely to be corroded (see FIG. 30).

In addition, calculation of the thermal resistance of the surface emitting laser element 100 ₃ by computer simulation, a 2794 [K / W], was less than the surface-emitting laser element 100 (see FIG. 31).

  Incidentally, FIG. 32 shows the result of calculating the relationship between the Al composition ratio and the thermal resistance in the second layer having the three-layer structure by computer simulation. From FIG. 32, if the Al composition ratio in the second layer having the three-layer structure is larger than 0.54, the overall thermal resistance of the surface emitting laser element can be made smaller than that of the surface emitting laser element A.

<< Modification 4 >>
In the surface-emitting laser device of Variation 4 (referred to surface-emitting laser element 100 _4), as shown in FIG. 33, among the three pairs of the second lower semiconductor DBR103b, low refractive index layer of two pairs of -Z side The three-layer structure has an optical thickness of 3λ / 4, and the lowest refractive index layer on the most + Z side has a five-layer structure and an optical thickness of 5λ / 4.

The low refractive index layer having a three-layer structure is a layer in which the first layer is made of n-AlAs, the second layer is a layer made of Al _0.9 Ga _0.1 As, and the third layer is made of n-AlAs. It is a layer. The optical thickness of each layer in the three-layer structure is λ / 4.

The low refractive index layer having a five-layer structure includes a first layer made of n-AlAs, a second layer made of Al _0.9 Ga _0.1 As, and a third layer made of n-AlAs. The fourth layer is a layer made of Al _0.9 Ga _0.1 As, and the fifth layer is a layer made of n-AlAs. The optical thickness of each layer in the five-layer structure is λ / 4.

<< Modification 5 >>
In the surface-emitting laser device of Variation 5 (referred to the surface emitting laser element 100 _5), as shown in FIG. 34, the low refractive index layer of the second lower semiconductor DBR103b is optical thickness be 3 [lambda] / 4 It has a five-layer structure. In the five-layer structure, the first layer is a layer made of n-AlAs, the second layer is a layer made of Al _0.9 Ga _0.1 As, and the third layer is a layer made of n-AlAs. The fourth layer is a layer made of Al _0.9 Ga _0.1 As, and the fifth layer is a layer made of n-AlAs. The optical thickness of each layer in the five-layer structure is the same.

<< Modification 6 >>
In the surface-emitting laser device of Variation 6 (referred to surface-emission laser device 100 _6), as shown in FIG. 35, the low refractive index layer of the second lower semiconductor DBR103b is optical thickness be 3 [lambda] / 4 It has a five-layer structure. In the five-layer structure, the first layer is a layer made of n-AlAs, the second layer is a layer made of Al _0.7 Ga _0.3 As, and the third layer is Al _0.9 Ga _0.1. The layer is made of As, the fourth layer is a layer made of Al _0.7 Ga _0.3 As, and the fifth layer is a layer made of n-AlAs. The second and fourth layers are about 20 nm thick. The first layer and the fifth layer have an optical thickness of λ / 4. The combined optical thickness of the second layer and the third layer is λ / 4. The combined optical thickness of the second layer, the third layer, and the fourth layer is λ / 4.

Since Al _0.7 Ga _0.3 As has a smaller Al composition ratio than Al _0.9 Ga _0.3 As, it is less likely to be oxidized. Also, from the surface emitting laser element 100 _4, Al 0.9 _{Ga 0.1} consisting As the thickness of the layer is small, the exposed area becomes smaller, which is difficult to be more corrosion (see FIG. 36). Further, Al _0.7 Ga _0.3 As is much less likely to be oxidized than AlAs, so that film peeling due to volume expansion due to oxidation is suppressed, and corrosion does not easily proceed.

_{Incidentally, Al 0.9 Ga 0.1 As, Al} 0.7 Ga 0.3 As in the above three-layer structure and a five-layer structure is an example, but is not limited thereto. The film thickness is also an example, and the present invention is not limited to this. An appropriate composition ratio of Al and an appropriate film thickness can be set according to the required corrosion resistance.

  In the above embodiment, the light source 14 may include a surface emitting laser array 100M shown in FIG. 37 as an example instead of the surface emitting laser element 100.

  In the surface emitting laser array 100M, a plurality of (21 in this case) light emitting portions arranged in a two-dimensional manner are formed on the same substrate. Here, the X-axis direction in FIG. 37 is a main-scanning corresponding direction, and the Y-axis direction is a sub-scanning corresponding direction. The plurality of light emitting units are arranged such that the intervals between the light emitting units are equal to d2 when all the light emitting units are orthogonally projected onto a virtual line extending in the Y-axis direction. In the present specification, the interval between the light emitting units means the distance between the centers of the two light emitting units. Further, the number of light emitting units is not limited to 21.

  Each light emitting section has the same structure as that of the surface emitting laser element 100 described above, as shown in FIG. The surface emitting laser array 100M can be manufactured by the same method as the surface emitting laser element 100 described above. Therefore, the surface emitting laser array 100M can achieve both high heat dissipation and high corrosion resistance. That is, it is possible to realize a surface emitting laser array excellent in heat dissipation and corrosion resistance.

  And since each light emission part is the structure where the heat dissipation characteristic was improved, the thermal interference between light emission parts is suppressed, and it can be set as the (dense) array where the several light emission parts were closer.

  Further, since the surface emitting laser array 100M is formed by a normal semiconductor process, the positional accuracy of the plurality of light emitting units is high. Furthermore, since the controllability at the time of mesa formation is improved, the cost can be reduced.

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

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

  In addition, since a large number of surface emitting laser elements 100 capable of operating at high output are integrated on the same substrate, simultaneous multi-beam writing is facilitated, and the writing speed is greatly improved. Even if the writing dot density increases, printing can be performed without reducing the printing speed. Further, when the writing dot density is the same, the printing speed can be further increased.

  Further, when the surface emitting laser array 100M is applied to an information communication device, data transmission by a large number of beams can be performed at the same time, so that the communication speed can be increased. Furthermore, the surface emitting laser array 100M operates with low power consumption because of its high output, and can suppress an increase in temperature particularly when incorporated in a device.

  Further, in the above embodiment, instead of the surface emitting laser element 100, a surface emitting laser array manufactured in the same manner as the surface emitting laser element 100 and in which the light emitting portions similar to the surface emitting laser element 100 are arranged one-dimensionally is used. It may be used.

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

  The surface-emitting laser element 100 and the surface-emitting laser array 100M can be used for applications other than the image forming apparatus. In that case, the oscillation wavelength may be a wavelength band such as a 650 nm band, an 850 nm band, a 980 nm band, a 1.3 μm band, and a 1.5 μm band depending on the application. In this case, a mixed crystal semiconductor material corresponding to the oscillation wavelength can be used as the semiconductor material constituting the active layer. For example, an AlGaInP mixed crystal semiconductor material can be used in the 650 nm band, an InGaAs mixed crystal semiconductor material can be used in the 980 nm band, and a GaInNAs (Sb) mixed crystal semiconductor material can be used in the 1.3 μm band and the 1.5 μm band.

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

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

  For example, the medium may be a printing plate known as CTP (Computer to Plate). That is, the optical scanning device 1010 is also suitable for an image forming apparatus that forms a printing plate by directly forming an image on a printing plate material by laser ablation.

  For example, the medium may be so-called rewritable paper. For example, a material described below is applied as a recording layer on a support such as paper or a resin film. Then, reversibility is imparted to color development by thermal energy control by laser light, and display / erasure is performed reversibly.

  There are a transparent cloudy type rewritable marking method and a color developing / erasing type rewritable marking method using a leuco dye, both of which can be applied.

  The transparent cloudy type is a polymer thin film in which fine particles of fatty acid are dispersed. When heated to 110 ° C. or higher, the resin expands due to melting of the fatty acid. Thereafter, when cooled, the fatty acid becomes supercooled and remains in a liquid state, and the expanded resin solidifies. Thereafter, the fatty acid solidifies and shrinks to become polycrystalline fine particles, and voids are formed between the resin and the fine particles. Light is scattered by this gap and appears white. Next, when heated to an erasing temperature range of 80 ° C. to 110 ° C., the fatty acid partially melts and the resin thermally expands to fill the voids. If it cools in this state, it will be in a transparent state and an image will be erased.

  The rewritable marking method using a leuco dye utilizes a reversible color development and decoloration reaction between a colorless leuco dye and a developer / decolorant having a long-chain alkyl group. When heated by laser light, the leuco dye and the developer / decolorant react to develop color, and when rapidly cooled, the colored state is maintained. Then, when it is slowly cooled after heating, phase separation occurs due to the self-aggregating action of the long-chain alkyl group of the developer / decolorant, and the leuco dye and developer / decolorizer are physically separated and decolored.

  In addition, when the medium is exposed to ultraviolet light, it develops in C (cyan) and is decolored by visible R (red) light, and when exposed to ultraviolet light, it develops in M (magenta). A photochromic compound that is decolored by G (green) light, a photochromic compound that develops color when exposed to ultraviolet light (Y) and is decolored by visible B (blue) light. So-called color rewritable paper provided on the body may be used.

  This is a method of expressing full color by controlling the color density of the three types of materials that develop color in Y, M, and C by the time and intensity of applying R, G, and B light once it is made black by applying ultraviolet light. However, if the strong light of R, G, and B is continuously applied, all three types can be decolored to become pure white.

  Such an apparatus that imparts reversibility to color development by light energy control can also be realized as an image forming apparatus including an optical scanning device similar to that of the above embodiment.

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

  As an example, as shown in FIG. 39, a color printer 2000 including a plurality of photosensitive drums may be used.

  The color printer 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow), and is a black station (photosensitive drum K1, charging device K2). , Developing device K4, cleaning unit K5, and transfer device K6), cyan station (photosensitive drum C1, charging device C2, developing device C4, cleaning unit C5, and transfer device C6), and magenta station ( The photosensitive drum M1, the charging device M2, the developing device M4, the cleaning unit M5, and the transfer device M6), and the yellow station (the photosensitive drum Y1, the charging device Y2, the developing device Y4, the cleaning unit Y5, and the transfer device Y6). ), Optical scanning device 2010, and transfer belt 2 80, and a fixing unit 2030.

  Each photosensitive drum rotates in the direction of the arrow in FIG. 39, and a charging device, a developing device, a transfer device, and a cleaning unit are arranged around each photosensitive drum along the rotational direction. Each charging device uniformly charges the surface of the corresponding photosensitive drum. The surface of each photoconductive drum charged by the charging device is irradiated with light by the optical scanning device 2010, and a latent image is formed on each photoconductive drum. Then, a toner image is formed on the surface of each photosensitive drum by a corresponding developing device. Further, the toner image of each color is transferred onto the recording paper on the transfer belt 2080 by the corresponding transfer device, and finally the image is fixed on the recording paper by the fixing unit 2030.

  The optical scanning device 2010 has a light source for each color including either a surface emitting laser element or a surface emitting laser array manufactured in the same manner as the surface emitting laser element 100. Therefore, the same effect as that of the optical scanning device 1010 can be obtained. In addition, since the color printer 2000 includes the optical scanning device 2010, the same effect as the laser printer 1000 can be obtained.

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

  As described above, the surface emitting laser element according to the present invention is suitable for improving heat dissipation and corrosion resistance without incurring high costs. Further, the optical scanning device of the present invention is suitable for performing stable optical scanning without causing an increase in cost. The image forming apparatus of the present invention is suitable for forming a high-quality image without incurring an increase in cost.

  DESCRIPTION OF SYMBOLS 11a ... Deflector side scanning lens (a part of scanning optical system), 11b ... Image surface side scanning lens (a part of scanning optical system), 13 ... Polygon mirror (light deflector), 14 ... Light source, 100 ... Surface light emission Laser element, 100M... Surface emitting laser array, 101... Substrate, 103... Lower semiconductor DBR (lower semiconductor multilayer reflector), 103a... First lower semiconductor DBR (first lower semiconductor multilayer reflector), 103b. Lower semiconductor DBR (second lower semiconductor multilayer reflector), 104 ... lower spacer layer (spacer layer), 105 ... active layer, 106 ... upper spacer layer, 107 ... upper semiconductor DBR (upper semiconductor multilayer reflector), 1000 ... Laser printer, 1010 ... Optical scanning device, 1030 ... Photosensitive drum (image carrier), 2000 ... Color printer (image forming apparatus), 2010 ... Optical scanning device, K , C1, M1, Y1 ... photosensitive drum (image bearing member).

JP 2002-164621 A Japanese Patent Laid-Open No. 2005-354061

Claims (15)

Resonator structure including an active layer, and surface emitting laser in which a plurality of semiconductor layers including an upper semiconductor multilayer reflector and a lower semiconductor multilayer reflector provided between the resonator structures are stacked on a substrate In the element
The lower semiconductor multilayer reflection mirror includes a first lower semiconductor multilayer reflector formed on the substrate side and a second lower semiconductor multilayer reflector formed on the resonator structure side,
The low refractive index layer of the first lower semiconductor multilayer mirror includes an Al _x Ga _1-x As (0 <x ≦ 1) semiconductor layer,
At least a part of the low refractive index layer of the second lower semiconductor multilayer reflector has an optical thickness larger than “oscillation wavelength / 4” and a thermal resistivity higher than that of the first lower semiconductor multilayer reflector. A surface emitting laser element comprising an Al _y Ga _1-y As (0 ≦ y <x) semiconductor layer having a value between a refractive index layer and a low refractive index layer.   2. The optical thickness of the low refractive index layer of the second lower semiconductor multilayer mirror is larger than “oscillation wavelength / 4” and is an odd multiple of “oscillation wavelength / 4”. The surface emitting laser element according to 1. The resonator structure includes two spacer layers provided with the active layer interposed therebetween, at least one of which is made of either an AlGaInP mixed crystal or a GaInP mixed crystal,
3. The surface emitting laser element according to claim 1, wherein the low refractive index layer of the first lower semiconductor multilayer film reflecting mirror is made of AlAs.   4. The surface emitting laser element according to claim 1, wherein the semiconductor layer of the second lower semiconductor multilayer mirror has an Al composition ratio of less than 1 and greater than 0.97. 5. .   The low refractive index layer of the second lower semiconductor multilayer reflector is provided between the first semiconductor layer as the semiconductor layer and the first semiconductor layer, and the low refractive index layer of the first lower semiconductor multilayer reflector is low. The surface emitting laser element according to claim 1, further comprising two second semiconductor layers similar to the rate layer.   6. The surface emitting laser element according to claim 5, wherein the two second semiconductor layers have an optical thickness of “oscillation wavelength / 4” or less.   The low refractive index layer of the second lower semiconductor multilayer mirror includes a third semiconductor layer having a thermal resistivity between the first semiconductor layer and the second semiconductor layer. Item 7. The surface emitting laser element according to Item 5 or 6.   The surface emitting laser element according to claim 7, wherein the third semiconductor layer is provided between the first semiconductor layer and the second semiconductor layer.   9. The surface emitting laser element according to claim 7, wherein the third semiconductor layer has an optical thickness smaller than “oscillation wavelength / 4”.   The surface emitting laser element according to claim 7, wherein the third semiconductor layer has an Al composition ratio of less than 1 and greater than 0.54.   A surface-emitting laser array in which the surface-emitting laser elements according to any one of claims 1 to 10 are integrated. An optical scanning device that scans a surface to be scanned with light,
A light source comprising the surface-emitting laser element according to any one of claims 1 to 10,
An optical deflector for deflecting light from the light source;
A scanning optical system that condenses the light deflected by the optical deflector onto the surface to be scanned. An optical scanning device that scans a surface to be scanned with light,
A light source comprising the surface emitting laser array according to claim 11;
An optical deflector for deflecting light from the light source;
A scanning optical system that condenses the light deflected by the optical deflector onto the surface to be scanned. At least one image carrier;
14. An image forming apparatus comprising: the optical scanning device according to claim 12 or 13, wherein the at least one image carrier scans light modulated in accordance with image information. The image forming apparatus according to claim 14, wherein the image information is multicolor color image information.