JP2009277781A - Surface light emission type laser array element, optical scanning apparatus, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light emission type laser array element which has a heat dissipation layer and is structured to be prevented from deteriorating. <P>SOLUTION: The surface light emission type laser array element is constituted by arraying a plurality of surface light emission type semiconductor lasers each having a lower reflector, an active layer, a selectively oxidized layer, and an upper reflector formed on a surface of a semiconductor substrate, and also having mesa structure composed of the active layer, selectively oxidized layer, and upper mirror. The semiconductor substrate has a surface inclined from a (100) plane to a (111) A plane as its surface, a plurality of predetermined high-refractive-index semiconductor films among high-refractive-index semiconductor films constituting the lower reflector and made of high-refractive-index materials have a film thickness of ≥λ/(4×n), and a protection film is formed of nitride to cover a part of the surface light emission type laser array element where a cross section of the lower reflector is exposed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface emitting laser array element, an optical scanning device, and an image forming apparatus that are excellent in environmental durability.

  A surface emitting semiconductor laser (VCSEL) is a semiconductor laser that emits light in a direction perpendicular to a substrate to be formed, and is lower in cost and higher performance than an edge emitting semiconductor laser. Are used for applications such as a light source for optical communication, a light source for an optical pickup, and a light source for an image forming apparatus such as a laser printer.

  As the characteristics of the surface emitting semiconductor laser used for such applications, there is a demand for an active layer having a large gain, a low threshold and a high output, excellent reliability, and a controlled polarization direction.

  Usually, the surface emitting semiconductor laser is formed by laminating a semiconductor film on a GaAs substrate. Specifically, a lower reflective mirror (DBR) made of a semiconductor multilayer film formed by alternately laminating films made of AlGaAs and AlAs on a GaAs substrate, a lower clad layer made of AlGaAs, GaAs By stacking a quantum well active layer made of AlGaAs, an upper cladding layer made of AlGaAs, an upper reflector (DBR) made of a semiconductor multilayer film formed by alternately laminating films made of AlGaAs and AlAs, and further laminating a contact layer It is configured. The semiconductor layer thus formed is etched in the vertical direction with respect to the substrate surface until the surface of the lower reflecting mirror is exposed, thereby forming a mesa structure, and insulating the sidewalls and the like of the formed mesa structure. By applying a current between the electrode formed on the substrate and the electrode connected to the contact layer formed on the upper reflecting mirror, laser light is emitted from the light emitting surface opened on the upper surface of the mesa structure. It is the structure which radiate | emits.

  Such a surface emitting semiconductor laser arrayed two-dimensionally is called a surface emitting laser array element (surface emitting semiconductor laser array). Among the surface emitting semiconductor lasers having such a mesa structure, there is a so-called selective oxidation type VCSEL in which high performance is achieved by forming a current confinement layer between an upper cladding layer and an upper reflecting mirror. This selective oxidation type VCSEL is formed by forming an AlAs film or an AlGaAs film having a high Al composition as a selective oxidation layer on the upper clad layer when the above-mentioned semiconductor layers are stacked, and a mesa structure is formed. Later, a portion of this selective oxidation layer is oxidized to have a current confinement structure. By adopting such a structure, it is possible to improve characteristics such as threshold current and power consumption in the surface emitting semiconductor laser.

  Patent Documents 1 and 2 disclose a structure in which a heat dissipation layer is formed on the active layer side in the lower reflecting mirror (DBR) in order to prevent the characteristics of the surface-emitting type semiconductor laser from being increased due to high output or heat. Yes. Specifically, the lower reflecting mirror is formed by alternately laminating semiconductor films made of materials having different refractive indexes. Of these, the active layer is formed of a film made of a high refractive index material containing a large amount of Al. On the side close to, by forming several layers having an optical film thickness of 3λ / 4 thicker than λ / 4, the heat generated from the active layer is efficiently radiated.

Patent Document 3 discloses a method of dividing a chip after forming a groove reaching a substrate in a chip dividing line, exposing a lower DBR end face, and covering a passivation film.
US Pat. No. 6,720,585 Japanese Patent Laid-Open No. 2005-354061 JP 2006-302919 A

  However, the surface emitting semiconductor lasers described in Patent Documents 1 and 2 are easily affected by characteristics due to moisture and the like. Specifically, in a layer containing a large amount of Al, the influence of oxidation or the like is large. As described in 1 and 2, this is particularly noticeable when the optical film thickness of the Al-rich layer is as thick as 3λ / 4.

  Further, as described in Patent Document 3, it is difficult to sufficiently prevent the influence of oxidation or the like by simply covering the passivation film.

  The present invention has been made to solve such a problem, and in a surface-emitting laser array element in which a plurality of surface-emitting semiconductor lasers are arrayed, by preventing characteristics from being deteriorated due to the influence of oxidation or the like. The present invention provides a surface emitting laser array element, an optical scanning device, and an image forming apparatus that have a high heat radiation effect and high reliability.

  The present invention provides a lower reflector formed by alternately laminating semiconductor films having different refractive indexes on a surface of a semiconductor substrate, an active layer made of a semiconductor material on the lower reflector, Formed by alternately laminating a selective oxidation layer in which a current confinement structure is formed by oxidizing a partial region of a semiconductor material on the active layer and a semiconductor film having a different refractive index on the selective oxidation layer. A mesa structure is formed in at least the active layer, the selective oxidation layer, and the upper reflector on the semiconductor substrate, a lower electrode is formed on the semiconductor substrate, and a mesa structure is formed on the upper reflector. A surface-emitting type semiconductor laser that emits a laser beam perpendicular to the semiconductor substrate surface by connecting an upper electrode and passing a current between the upper electrode and the lower electrode In the surface-emitting type laser array element arrayed on the same substrate, the semiconductor substrate has a surface inclined from the (100) plane toward the (111) A plane, and the surface emitting Of the high refractive index semiconductor film made of the high refractive index material constituting the lower reflector, where λ is the oscillation wavelength of the type semiconductor laser and n is the refractive index of the high refractive index material at the oscillation wavelength, The film thickness of the predetermined plurality of high refractive index semiconductor films is λ / (4 × n) or more, and is nitrided so as to cover a portion where the cross section of the lower reflecting mirror in the surface-emitting laser array element is exposed A protective film made of a material is formed.

  Further, the present invention is characterized in that the semiconductor substrate has a surface inclined by 2 to 20 degrees in the (111) A plane direction from the (100) plane.

  Further, the present invention is characterized in that the nitride is SiN.

  Further, the present invention is characterized in that the nitride is formed by CVD.

  In the present invention, the high refractive index semiconductor film having the predetermined plurality of optical film thicknesses of λ / (4 × n) or more is provided on the active layer side in the lower reflecting mirror. It is characterized by.

  In the present invention, the film thickness of the high refractive index semiconductor film having an optical film thickness of λ / (4 × n) or more is (m × λ) / (4 × n) (m is An integer of 2 or more).

  The present invention is characterized in that a film thickness of the high refractive index semiconductor film having an optical film thickness of λ / (4 × n) or more is 600 [nm] or less.

  Further, the present invention is characterized in that the thickness of the protective film in the direction perpendicular to the cross section of the lower reflecting mirror is 100 [nm] or more.

  The present invention also provides an optical scanning device that scans a surface to be scanned with a light beam, the light source unit having the surface-emitting laser array element described above, and a deflecting unit that deflects the light beam from the light source unit; And a scanning optical system for condensing the light beam deflected by the polarizing means on the surface to be scanned.

  According to another aspect of the invention, there is provided at least one image carrier and at least one optical scanning device described above that scans a light beam including image information with respect to the at least one image carrier. And

  According to the present invention, by using a tilted substrate tilted in a specific direction, a protective film made of nitride is formed on the cross section of the laminated film in the surface emitting laser array element, thereby progressing oxidation of the semiconductor film. Accordingly, it is possible to provide a surface emitting laser array element, an optical scanning device, and an image forming apparatus that have a high heat dissipation effect and high reliability.

  Next, the best mode for carrying out the present invention will be described below.

[First Embodiment]
The first embodiment according to the present invention relates to a structure and manufacturing method of a surface-emitting laser array element in which surface-emitting semiconductor lasers (VCSEL) are two-dimensionally arranged. This surface-emitting semiconductor laser has an oscillation wavelength of about 780 [nm] and has a current confinement structure.

  First, a semiconductor substrate used in the present embodiment will be described with reference to FIG. The semiconductor substrate used in this embodiment is an n-GaAs substrate. FIG. 1A shows a top view of the n-GaAs substrate 10 which is not inclined, and FIG. 1B shows a cross-sectional view taken along a broken line A1-A2 in FIG. As shown in FIGS. 1 (a) and 1 (b), the surface of the n-GaAs substrate 10 whose principal surface is an untilted (100) plane is a (100) plane.

  FIG. 1C is a cross section of the n-GaAs substrate 11 inclined from the (100) plane by the angle α in the (011) direction. The angle α is generally 2 to 20 °, but in this embodiment, an inclined substrate inclined by 15 ° from the (100) plane in the (011) direction is used. As described above, by using the inclined substrate, a gain difference is generated in the active layer between the inclined direction and the direction orthogonal thereto, and the polarization direction can be controlled to a constant direction.

  Next, a method for manufacturing the surface-emitting type laser array element in the present embodiment will be described with reference to FIGS.

First, as shown in FIG. 2A, a high refractive index film made of n-Al _0.3 Ga _0.7 As and n-Al _0.9 Ga _{0.1 is formed} on an n-GaAs substrate 11. A lower reflector 12 in which 40.5 pairs of low refractive index films made of As are alternately formed, a lower spacer layer 13 made of Al _0.6 Ga _0.4 As, and an Al _0.12 Ga _0.88 As film A quantum well active layer 14 composed of a quantum well layer made of AlGaAs and a barrier layer made of an AlGaAs film, an upper spacer layer 15 made of Al _0.6 Ga _0.4 As, a selective oxide layer 16 made of AlGa, A high refractive index film made of p-Al _0.3 Ga _0.7 As and a low refractive index film made of p-Al _0.9 Ga _0.1 As each have an optical film thickness of λ / 4. The upper reflector 1 is formed by alternately stacking 24 pairs with such a film thickness. When is obtained by laminating a contact layer 18 for connecting the upper electrode to be described later. Note that λ is an oscillation wavelength of the surface emitting semiconductor laser in the present embodiment.

  Here, about 37 pairs of the lower reflecting mirror 12 from the top of the n-GaAs substrate 11 are alternately arranged so that the optical film thickness of each of the low refractive index film and the high refractive index film is λ / 4. After that, the low refractive index film was alternately laminated so that the optical film thickness of the low refractive index film was λ / 4 and the optical film thickness of the high refractive index film was 3λ / 4. Of structure. Thus, by increasing the film thickness of the high refractive index film to 3λ / 4, it is possible to efficiently dissipate heat generated from the quantum well active layer 14, and this layer is particularly referred to as a heat dissipation layer. The optical film thickness is a film thickness that takes into account the refractive index of the material. When the optical film thickness is λ / 4, the material having a refractive index n at the wavelength λ is n. It means a film thickness of λ / (4 × n).

  Each layer made of the above semiconductor material is formed by MOCVD or MBE, and resistance is reduced in each of the high refractive index film and the low refractive index film formed on the lower reflecting mirror 12 and the upper reflecting mirror 17. Therefore, the structure has a composition gradient.

  Next, as shown in FIG. 2B, a mesa structure 31 is formed by a photolithography process and an etching process. At this time, the element isolation region 32 is also formed. Specifically, after applying a photoresist on the contact layer 18 shown in FIG. 2A, a resist pattern having a shape similar to the planar shape of the mesa structure formed by performing pre-baking, exposure, and development. After forming (not shown), dry etching is performed by RIE (Reactive Ion Etching) to remove the semiconductor layer in the region where the resist pattern is not formed, and the mesa structure 31 and the element isolation region 32 are formed. To do. The dry etching by RIE is performed until the surface of the lower spacer layer 13 is exposed.

  Next, as shown in FIG. 2C, a partial region of the selective oxidation layer 16 in which the mesa structure 31 is formed is oxidized. Specifically, the selective oxidation layer 16 contains a large amount of Al and has a characteristic of being easily oxidized as compared with other semiconductor layers. For this reason, by performing heat treatment in water vapor, oxidation proceeds from the cross section of the selective oxidation layer 16 exposed on the side surface of the mesa structure 31. That is, the oxidation proceeds from the periphery as a side toward the center, and an oxidized region (oxidized region) 34 in the peripheral portion and a non-oxidized region (current confinement region) 35 in the central portion are formed. . An insulator that becomes AlxOy is formed in the oxidized region 34, and a current confinement structure is formed in which current concentrates in the current confinement region 35 when a current is passed through the element.

  Next, as shown in FIG. 3A, a groove 33 is formed in the element isolation portion 32 by a photolithography process and an etching process. Specifically, after a photoresist is applied to the surface on which the semiconductor layer shown in FIG. 2C is applied, a resist having the same shape as the groove 33 to be formed is obtained by performing pre-baking, exposure, and development. After forming the pattern (not shown), the trench 33 is formed by removing the semiconductor layer in the region where the resist pattern is not formed by performing dry etching by RIE or the like. Note that dry etching by the RIE method or the like is performed until the surface of the n-GaAs substrate 11 is exposed. By this dry etching, the cross section of the lower reflecting mirror 12 is also exposed, and thus the cross section of the heat dissipation layer described later is also exposed.

  Next, light etching is performed. This light etching is performed in order to improve the adhesion with the passivation film. By performing the light etching, it is possible to prevent film peeling and film floating during the manufacturing process. This light etching is so-called wet etching, and is performed for 10 to 20 [seconds] using BHF (buffered hydrofluoric acid: hydrofluoric acid concentration 10 [%]) as a light etching solution.

  FIGS. 4B and 4C show the state around the heat dissipation layer in the lower reflecting mirror 12 after the light etching. 4A is an enlarged view of the central portion of FIG. 3A, and enlarged views of a region P surrounded by a broken line are FIGS. 4B and 4C. 4B is a cross section when the orientation flat (OF) is in the left direction on the paper surface, and FIG. 4C is a cross section when the orientation flat (OF) is in the downward direction on the paper surface.

  As shown in FIGS. 4B and 4C, the lower reflecting mirror 12 has optical films of a high refractive index film 25 and a low refractive index film 26 on the side close to the n-GaAs substrate 11. It is formed by alternately laminating layers having a thickness of λ / 4. However, in several pairs near the upper spacer layer 13 on the side close to the quantum well active layer 14, the high refractive index film 27 is formed. Are formed by alternately laminating layers having such a film thickness that the optical film thickness of the low refractive index film 26 is λ / 4. The high refractive index film 27 is formed of a material having a high thermal conductivity with a large film thickness, and has a function of releasing heat generated in the quantum well active layer 14, and therefore is called a heat dissipation layer. In the present embodiment, as shown in FIGS. 4B and 4C, three high refractive index films 27 serving as a heat dissipation layer having an optical film thickness of 3λ / 4 are formed.

  The high refractive index films 25 and 27 contain more Al than the low refractive index film 26 in order to increase the refractive index. For this reason, the etching rate in the high refractive index films 25 and 27 by BHF is fast, and a specific surface is exposed in the high refractive index films 25 and 27 as shown in FIGS. It becomes a shape.

  Next, as shown in FIG. 3B, a protective film 22 is formed on the light etching by BHF, and an opening is formed in the upper surface portion of the mesa structure 31. Specifically, the protective film 22 is a SiN film formed by a P-CVD (plasma CVD) method, and has a thickness of 150 to 200 [nm]. In this way, by forming a SiN film of 150 to 200 [nm] as the protective film 22 by the P-CVD method, 1000 hours in a high temperature and high humidity test (temperature 85 [° C.], humidity 85 [%]). After the lapse of time, deterioration of the high refractive index film 27 which is a heat dissipation layer was not confirmed. A nitride film such as SiN has a high barrier property, and in particular, a SiN film has a high barrier property. In addition, a good step coverage can be obtained for a film formed by a CVD method such as P-CVD. In this embodiment, the SiN film is formed by the P-CVD method. Further, it has been confirmed that a good step coverage can be obtained if the film thickness T of the high refractive index film 27 serving as a heat dissipation layer is 600 [nm] or less. 22 confirms that it is difficult to prevent deterioration from the heat dissipation layer after light etching. Further, when the SiN film is used as the protective film 22, in consideration of the influence of pinholes and other coverage, at least 100 [nm] or more is necessary.

In the case where an SiO ₂ film was used as the protective film 22, all deterioration was confirmed within 75 hours on the surfaces shown in FIGS. 4B and 4C. Further, in the case where a SiO ₂ film is used as the protective film 22, the progress of deterioration is slower when the surface in the inclined direction shown in FIG. 4C is exposed, and is not in the inclined direction shown in FIG. 4B. The deterioration progressed faster when the surface was exposed. Specifically, the surface that is not in the inclined direction shown in FIG. 4B has been completely deteriorated within 24 hours from the exposed surface, but the surface in the inclined direction shown in FIG. From the exposed surface, deterioration started after 24 hours for the slow ones, and it took about 50 to 75 hours for all deterioration.

  This means that since the surface that is not in the inclined direction is equivalent to the surface of the substrate that is not the inclined substrate, it is assumed that deterioration can be suppressed by using the inclined substrate. That is, the inventor has found that the use of an inclined substrate is a factor for preventing deterioration. Therefore, by using the SiN film formed by the P-CVD method using this inclined substrate as the protective film 22, it is possible to further prevent deterioration.

  Next, as shown in FIG. 3C, an upper electrode 23 that contacts the contact layer 18 in the region where the opening of the mesa structure is formed is formed, and a lower electrode 24 is formed on the back surface of the n-GaAs substrate 11. To do. Specifically, a region where the upper electrode 23 is not formed is formed by applying a photoresist on a semiconductor layer having a mesa structure by a spin coater or the like and then performing pre-baking, exposure and development with an exposure apparatus. A resist pattern is formed thereon. Thereafter, a metal film to be the upper electrode 23 is formed by vacuum deposition or sputtering. Thereafter, the upper electrode 23 is formed by performing lift-off by performing ultrasonic cleaning in an organic solvent such as acetone. In the present embodiment, the upper electrode 23 serves as a p-side electrode and is formed of a laminated film made of Cr / AuZn / Au. Thereafter, the back surface of the n-GaAs substrate 11 is polished to 100 to 300 [μm], and then the lower electrode 24 is formed. The lower electrode 24 serves as an n-side electrode, and is formed by forming a laminated film made of AuGe / Ni / Au by vacuum deposition or sputtering. Thereby, an ohmic contact can be obtained. The n-GaAs substrate 11 on which a large number of surface-emitting semiconductor lasers are formed in this manner is separated for each chip by dicing or scribing to obtain a surface-emitting laser array element.

  The surface-emitting laser array element obtained by this embodiment has a heat dissipation layer provided for heat dissipation in the lower reflecting mirror 12, and even if light etching is performed in the manufacturing process, a predetermined inclined substrate is used. A surface-emitting laser array element composed of a surface-emitting type semiconductor laser that can obtain sufficient resistance to moisture and the like, has a high yield and reliability, and has a long lifetime. Obtainable.

[Second Embodiment]
The second embodiment according to the present invention is an image forming apparatus using the surface emitting laser array element according to the present invention as a light source. This embodiment will be described with reference to FIG.

  A laser printer as an image forming apparatus according to the present embodiment includes an optical scanning device 100, a photosensitive drum 101, a charging charger 102, a developing roller 103, a toner cartridge 104, a cleaning blade 105, a paper feed tray 106, and a paper feed roller 107. , A registration roller pair 108, a fixing roller 109, a paper discharge tray 110, a transfer charger 111, a paper discharge roller 112, a charge removal unit 114, and the like.

  Specifically, in the rotation direction of the photosensitive drum 101, the charging charger 102, the developing roller 103, the transfer charger 111, the static elimination unit 114, and the cleaning blade 105 are arranged in the vicinity of the photosensitive drum 101.

  A photosensitive layer is formed on the surface of the photosensitive drum 101. Here, the photosensitive drum 101 is configured to rotate clockwise as shown in the figure. The charging charger 102 has a function of uniformly charging the surface of the photosensitive drum 101.

  The optical scanning device 100 irradiates the surface of the photosensitive drum 101 charged by the charging charger 102 with light modulated based on image information from a host device such as a personal computer. By this light irradiation, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 101. The area where the latent image is formed on the surface of the photosensitive drum 101 moves in the direction in which the developing roller 103 is provided as the photosensitive drum 101 rotates. Details of the optical scanning device 100 will be described later.

  The toner cartridge 104 stores toner, and this toner is supplied to the developing roller 103. The developing roller 103 causes the toner supplied from the toner cartridge 104 to adhere to the latent image formed on the surface of the photoconductive drum 101 to visualize the image information on the surface of the photoconductive drum 101. Thereafter, as the photosensitive drum 101 rotates, the area where the toner is attached to the latent image on the surface of the photosensitive drum 101 moves in the direction in which the transfer charger 111 is provided.

  Recording paper 113 is stored in the paper feed tray 106. A paper feed roller 107 is disposed in the vicinity of the paper feed tray 106, and the paper feed roller 107 takes out the recording paper 113 one by one from the paper feed tray 106 and conveys it to the registration roller pair 108. The registration roller pair 108 is disposed in the vicinity of the transfer charger 111, temporarily holds the recording sheet 113 taken out by the paper feeding roller 107, and exposes the recording sheet 113 in accordance with the rotation of the photosensitive drum 101. It is sent out toward the gap between the body drum 101 and the transfer charger 111.

  The transfer charger 111 is charged with a reverse polarity to the toner on the surface of the photoconductor 101 in order to electrically attract the toner on the surface of the photoconductor drum 101 to the recording paper 113. The toner on the surface of the photosensitive drum 101 is transferred to the recording paper 113 by this charge, that is, an image formed by the toner is transferred to the recording paper 113. Thereafter, the recording sheet 113 is sent to the fixing roller 109.

  In the fixing roller 109, heat and pressure are applied to the recording paper 113, whereby the toner is fixed on the recording paper 113. Here, the recording paper 113 on which the image is fixed is sent to the paper discharge tray 110 via the paper discharge roller 112, and is sequentially stacked on the paper discharge tray 110.

  The neutralization unit 114 neutralizes the surface of the photosensitive drum 101. The cleaning blade 105 removes toner remaining on the surface of the photosensitive drum 101 (residual toner). The removed residual toner is configured to be reusable. The surface of the photosensitive drum 101 from which the residual toner has been removed moves again in the direction in which the charging charger 102 is provided.

  Next, the optical scanning device 100 will be described with reference to FIG.

  The optical scanning device 100 includes a light source unit 121, a coupling lens 122, an aperture plate 123, an anamorphic lens 124, a polygon mirror 125, a deflector side scanning lens 126, an image plane side scanning lens 127, a processing device 140, and the like. I have. In FIG. 6, the left-right direction of the paper surface is the main scanning direction, and the direction perpendicular to the paper surface is the sub-scanning direction.

  The light source unit 121 includes a surface emitting semiconductor laser array in which a plurality of surface emitting semiconductor lasers in the first embodiment are formed.

  The coupling lens 122 is for making the light beam emitted from the light source unit 121 substantially parallel light.

  The aperture plate 123 has an aperture and is for defining the beam diameter of the light beam from the coupling lens 122.

  The anamorphic 124 converts the light beam that has passed through the opening of the aperture plate 123 into parallel light in the main scanning direction and converges near the surface of the polygon mirror 125 in the sub-scanning direction. The light flux from the anamorphic lens 124 is reflected by the rotating polygon mirror 125, is imaged by the deflector side scanning lens 126 and the image plane side scanning lens 127, and is collected as a light spot on the surface of the photosensitive drum 101. To be lighted.

  As described above, the polygon mirror 125 is rotated at a constant speed by a motor (not shown), and with this rotation, the light beam is deflected at a constant angular velocity, and light on the surface of the photosensitive drum 101 is reflected. The spot moves at a constant speed in the main scanning direction.

  The processing device 140 generates image data based on image information from a host device such as a personal computer, and outputs a semiconductor laser drive signal to the light source unit 121 according to the image data.

  Next, the surface emitting laser array element 200 in the present embodiment provided in the light source unit 121 will be described with reference to FIG. As shown in this figure, the positional relationship of each surface emitting semiconductor laser in the sub-scanning direction when the perpendicular is dropped from the center of each surface emitting semiconductor laser in the direction corresponding to the sub-scanning direction is equal (interval) Therefore, the light source is arranged on the photosensitive drum 101 at equal intervals in the sub-scanning direction by adjusting the lighting timing. For example, the size of the surface emitting semiconductor laser is φ20 [μm], the pitch in the direction corresponding to the main scanning direction is 40 [μm], and the pitch in the direction corresponding to the sub-scanning direction is 40 [μm]. In this case, the interval C is 10 [μm], and if the magnification of the scanning optical system is 1, 2400 [dpi] is realized. In this embodiment, by shifting the position of the surface emitting semiconductor laser arrayed in the main scanning direction in this way, the interval C in the sub-scanning direction can be narrowed, and high-density and high-quality printing is possible. It becomes.

  Further, by increasing the number of surface emitting semiconductor lasers in the direction corresponding to the main scanning direction, or by narrowing the pitch in the direction corresponding to the sub-scanning direction, that is, by reducing the interval C, the dot pitch can be increased. This makes it possible to perform higher quality printing. Note that the writing interval in the main scanning direction can be easily controlled by controlling the lighting timing of the surface emitting semiconductor laser as the light source.

  In the optical scanning device according to the present embodiment and the image forming apparatus using the same, the surface emitting laser array element according to the first embodiment that can be manufactured at low cost is used as the light source. Therefore, it is possible to obtain an optical scanning device and an image forming apparatus that are low in cost and high in quality at high speed.

  In the present embodiment, as shown in FIG. 7, the surface emitting laser array element 200 constituted by 16 (4 × 4) surface emitting semiconductor lasers has been described. However, by changing the arrangement or the like, A surface emitting laser element formed by a larger number of surface emitting semiconductor lasers can be obtained.

  Next, an image forming apparatus for forming a color image will be described with reference to FIG.

  This image forming apparatus is a color laser printer, which is a dandem color machine having a plurality of photosensitive drums for color images.

  This color laser printer 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, and a charging unit. C2, developing unit C4, cleaning unit C5, transfer charging unit C6, magenta (M) photosensitive drum M1, charging unit M2, developing unit M4, cleaning unit M5, transfer charging unit M6, yellow (Y) photosensitive drum Y1, charger Y2, developing unit Y4, cleaning unit Y5, transfer charging unit Y6, optical scanning device 100, transfer belt 201, fixing unit 202, and the like.

  In this color laser printer, the optical scanning device 100 includes a semiconductor laser for black, a semiconductor laser for cyan, a semiconductor laser for magenta, and a semiconductor laser for yellow. Each semiconductor laser is included in the present invention. It is comprised by the surface emitting semiconductor laser which concerns. The light beam from the black semiconductor laser is irradiated to the black photosensitive drum K1, the light beam from the cyan semiconductor laser is irradiated to the cyan photosensitive drum C1, and the light beam from the magenta semiconductor laser is magenta. The light beam from the yellow semiconductor laser is irradiated to the yellow photosensitive drum Y1, and the light beam from the yellow semiconductor laser is irradiated to the yellow photosensitive drum Y1.

  Each of the photosensitive drums K1, C1, M1, and Y1 rotates in the direction of the arrow, and in the order of the rotation direction, each of the chargers K2, C2, M2, and Y2, the developing devices K4, C4, M4, and Y4, for transfer. Charging means K6, C6, M6, Y6 and cleaning means K5, C5, M5, Y5 are arranged. Each of the chargers K2, C2, M2, and Y2 uniformly charges the surface of the corresponding photosensitive drum K1, C1, M1, and Y1. The charged surface of the photosensitive drums K1, C1, M1, and Y1 is irradiated with a light beam from the optical scanning device 100, and an electrostatic latent image is formed on the surface of the photosensitive drums K1, C1, M1, and Y1. It has become. Thereafter, toner images are formed on the surfaces of the photosensitive drums K1, C1, M1, and Y1 by the developing units K4, C4, M4, and Y4, and the transfer charging units K6, C6, M6, and Y6 corresponding to the toner images are formed. Thus, the toner images of the respective colors are transferred to the recording paper, and the image is fixed on the recording paper by the fixing unit 202. The cleaning means K5, C5, M5, and Y5 remove residual toner remaining on the surfaces of the corresponding photosensitive drums K1, C1, M1, and Y1.

  In this embodiment, the photosensitive drum is described as the image carrier. However, the image carrier may be an image forming apparatus using a silver salt film. 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 similar to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by the same process as the printing process in the ordinary 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, an image forming apparatus using a color developing medium (positive photographic paper) that develops color by the heat energy of a beam spot as an image carrier may be used. In this case, a visible image can be directly formed on the image carrier by optical scanning.

  As mentioned above, although the form which concerns on implementation of this invention was demonstrated, the said content does not limit the content of invention.

Illustration of inclined substrate Manufacturing process diagram of surface-emitting type laser array element in the first embodiment (1) Manufacturing process diagram of surface-emitting type laser array element in the first embodiment (2) Sectional drawing of heat dissipation layer vicinity of surface emitting laser array element in 1st Embodiment Configuration of an image forming apparatus according to a second embodiment Configuration of an optical scanning device in an image forming apparatus according to a second embodiment Overview of surface-emitting laser array elements Configuration of an image forming apparatus capable of color printing according to a second embodiment

Explanation of symbols

11 n-GaAs substrate 12 lower reflector 13 lower spacer layer 14 quantum well active layer 15 upper spacer layer 16 selective oxide layer 17 upper reflector 18 contact layer 22 protective film 23 upper electrode 24 lower electrode 31 mesa structure 32 element isolation region 33 Groove 34 Oxidized region 35 Current confinement region

Claims (10)

A lower reflector formed by alternately laminating semiconductor films of different refractive indexes on the surface of a semiconductor substrate;
On the lower reflector, an active layer made of a semiconductor material;
On the active layer, a selective oxidation layer in which a current confinement structure is formed by oxidizing a partial region of a semiconductor material;
An upper reflecting mirror formed by alternately laminating semiconductor films having different refractive indexes on the selective oxide layer;
A mesa structure is formed in at least the active layer, the selective oxidation layer, and the upper reflecting mirror on the semiconductor substrate;
A lower electrode is connected to the semiconductor substrate, and an upper electrode is connected to the upper reflector, and a surface emits laser light perpendicular to the semiconductor substrate surface by passing a current between the upper electrode and the lower electrode. In a surface emitting laser array element in which a plurality of light emitting semiconductor lasers are arranged on the same substrate,
The semiconductor substrate has a surface inclined in the (111) A plane direction from the (100) plane,
A high-refractive-index semiconductor film made of a high-refractive-index material constituting the lower reflector, where λ is the oscillation wavelength of the surface-emitting semiconductor laser, and n is the refractive index of the high-refractive-index material at the oscillation wavelength Among these, the film thickness in the predetermined plurality of high refractive index semiconductor films is λ / (4 × n) or more,
A surface-emitting laser array element, wherein a protective film made of nitride is formed so as to cover a portion of the surface-emitting laser array element where a cross section of a lower reflecting mirror is exposed.   2. The surface-emitting laser array element according to claim 1, wherein the semiconductor substrate has a surface inclined by 2 to 20 degrees in a (111) A plane direction from a (100) plane.   The surface emitting laser array device according to claim 1, wherein the nitride is SiN.   4. The surface emitting laser array element according to claim 1, wherein the nitride is formed by CVD.   The high refractive index semiconductor film having the predetermined plurality of optical film thicknesses of λ / (4 × n) or more is provided on the active layer side in the lower reflecting mirror. 5. The surface emitting laser array element according to any one of 1 to 4.   The film thickness of the high refractive index semiconductor film having an optical film thickness of λ / (4 × n) or more is (m × λ) / (4 × n) (m is an integer of 2 or more). The surface-emitting type laser array element according to any one of claims 1 to 5,   7. The film thickness of the high refractive index semiconductor film having an optical film thickness of λ / (4 × n) or more is 600 [nm] or less. 7. Surface emitting laser array element.   10. The surface-emitting laser array element according to claim 1, wherein a thickness of the protective film in a direction perpendicular to a section of the lower reflecting mirror is 100 nm or more. An optical scanning device that scans a surface to be scanned with a light beam,
A light source unit comprising the surface-emitting laser array element according to claim 1;
Deflecting means for deflecting the light beam from the light source unit;
A scanning optical system for condensing the light beam deflected by the polarizing means on the surface to be scanned;
An optical scanning device comprising: At least one image carrier;
The optical scanning device according to claim 9, wherein the at least one image carrier is scanned with a light beam including image information;
An image forming apparatus comprising:

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