JP2009164389A - Semiconductor laser, recording / reproducing pickup device using the same, and semiconductor laser manufacturing method - Google Patents

Abstract

To provide a semiconductor laser having two laser elements on the same chip, an optical pickup device for recording / reproducing using the same, and a method for manufacturing the semiconductor laser.
A chip includes an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type contact layer stacked in this order on the n-type GaN substrate. A part of the p-type cladding layer and the p-type contact layer constitute stripe-shaped ridge portions 30a and 30b, and regions corresponding to the ridge portion in the active layer are respectively a recording laser emission end face 32a and a reproduction-use surface. A laser emitting end face 32b is formed, and recording and reproducing lasers 33a and 33b are emitted. For example, the radiation angle is changed by changing the width of the ridge portion and the thickness of the p-cladding layer on both sides of the ridge portion. Laser quantum noise is reduced by using a laser having a small emission angle during recording by an optical pickup device and using a laser having a large emission angle during reproduction.
[Selection] Figure 1

Description

  The present invention relates to a semiconductor laser used in an optical disk recording / reproducing pickup device, and in particular, two nitride semiconductor laser elements formed on the same substrate (chip) emit two lasers having different emission angles. In addition, the present invention relates to a semiconductor laser used as a reproducing and recording laser, a recording / reproducing pickup device using the same, and a method for manufacturing the semiconductor laser.

  Development of an information storage / reproduction apparatus using a combination of a BD (Blu-ray Disk) or HD-DVD (High Definition Digital Versatile Disk) capable of high-density recording and a blue-violet semiconductor laser in the 405 nm wavelength band is advancing.

  FIG. 9 is a diagram showing an outline of a configuration example of a pickup device using a GaN-based semiconductor laser that performs recording / reproduction of a high-density optical disc such as a BD or an HD-DVD in the prior art, and FIG. FIG. 9 and FIG. 9B are plan views. FIG. 9 shows only a configuration example of an optical system of a pickup device for recording / reproducing BD for simplification, but an optical system for recording / reproducing HD-DVD is added to the optical system for recording / reproducing BD. Often incorporated.

  A laser emitted from a GaN-based semiconductor laser (BD LD) 69 having an oscillation wavelength of about 405 nm is incident on a polarization beam spiriter (PBS) 60 through an attenuator 90 and branched into two, and one is condensed by a lens 66. Then, the light is incident on a monitor PD (photodetector) 68, the other is reflected by a rising mirror 56 by a collimator lens 58, and is irradiated to a minute portion of the disk 50 through a quarter wave plate (QWP) 54 and an objective lens 52 for recording or recording. Playback is performed. When reproduction is performed, the laser beam reflected from the minute portion of the disk 50 passes through the objective lens 52, the quarter-wave plate (QWP) 54, the rising mirror 56, and the collimator lens 58 to obtain a polarized beam spiriter (PBS) 60. And is split into two. One is condensed by a lens 66 and incident on a monitor PD (light receiver) 68, and the other is incident on an optoelectronic integrated circuit (OEIC) 64 through a hologram optical element (HOE) 62. Then, the reproduction processing is performed with reference to the detection signal of the monitor PD 68.

  Since the recording power performance increases as the power of the laser on the disk surface of the semiconductor laser increases, the optical coupling efficiency of the laser (usually received by the light source monitor receiver among the lasers from the laser light source). The optical system is designed with priority given to the ratio of light to be transmitted. Therefore, when reproducing, since the optical coupling efficiency is high, the original power of the laser by the semiconductor laser becomes very small (for example, 2 mW or less), the quantum noise level of the laser becomes high, and the optical pickup for recording / reproducing is received. The noise level required by the optical system cannot be satisfied. As a countermeasure, usually, the original power of the laser by the semiconductor laser is increased by reducing the optical coupling efficiency during reproduction by the attenuator 90, and as a result, the quantum noise level of the laser is decreased.

  FIG. 10 is a diagram illustrating an outline of a configuration example of countermeasures against reproduction noise in a pickup device in the prior art, FIG. 10A is a plan view illustrating a configuration of an example using a liquid crystal attenuator, and FIG. FIG. 10C is a plan view showing the configuration of an example using a noise canceller, and FIG. 10C is a plan view showing the configuration of an example using an ND filter.

  The optical coupling is switched by using the liquid crystal attenuator 91 as shown in FIG. 10A, changing the transmittance by turning on and off the liquid crystal, and moving the ND filter 9 in and out of the motor as shown in FIG. 10B. It is done by the method of doing. Further, as shown in FIG. 10C, using the detection signals of the monitor PD 68 and the optoelectronic integrated circuit (OEIC) 64, the laser noise canceller 93 performs a process of subtracting the laser noise itself so as to satisfy the required noise level. Sometimes. In some cases, the noise canceller 93 is not provided, and the monitor PD 68 is enhanced to detect laser noise, and is subtracted from the detection signal of the optoelectronic integrated circuit (OEIC) 64 to cancel the noise.

  The semiconductor laser array is a well-known technique. For example, in Patent Document 1 described later, an internal stripe type semiconductor laser array including a plurality of lasers that can be driven independently on the same substrate is disclosed. There is a description that the stripe widths of the lasers are different.

JP-A-6-96468 (paragraph 0026)

  In order to increase the recording speed, the optical system is usually designed with priority given to the optical coupling efficiency of the laser. When reproducing, the optical coupling efficiency is high. Becomes very small, the quantum noise level of the laser becomes high, and the noise level required for the optical pickup light receiving optical system for recording and reproduction cannot be satisfied. Considering the manufacturing yield including the life performance and output performance of the semiconductor laser, it may be difficult to manufacture at a practical level due to manufacturing variations of semiconductor lasers having these performances.

  If a configuration using an attenuator or a configuration for canceling noise by a noise canceller is employed to lower the quantum noise level of the laser, the number of parts increases, leading to problems such as an increase in cost and an increase in reliability risk. In addition, there is a problem that it is difficult to completely subtract the noise canceling configuration.

  As described above, the recording / reproducing optical pickup for BD and HD-DVD leads to an increase in the number of parts, an increase in cost, an increase in reliability risk, etc., which were not a problem with conventional DVDs and CDs. There's a problem.

  In Patent Document 1, there is a description that stripe widths of a plurality of lasers are different in an internal stripe semiconductor laser array including a plurality of lasers that can be driven independently on the same substrate. This is different from the configuration of the present invention described below.

  The present invention has been made to solve the above-described problems, and its purpose is to emit lasers having different emission angles from each of two nitride semiconductor laser elements formed on the same chip. It is an object of the present invention to provide a semiconductor laser used as a reproducing and recording laser, a recording / reproducing pickup device using the same, and a method of manufacturing the semiconductor laser.

  That is, the present invention includes a first conductivity type layer (for example, an n-type cladding layer 22 in an embodiment described later), an active layer (for example, a multiple quantum well structure active layer 24 in an embodiment described later), and a second conductivity. A semiconductor layer formed by laminating a mold layer (for example, a p-type cladding layer 26 and a p-type contact layer 28 in an embodiment described later) in this order, and a partial region of the second conductivity type layer is etched. The other regions other than the partial region are formed as stripe-shaped ridge portions (for example, stripe-shaped ridge portions 30a and 30b in the embodiments described later), and lasers having the same wavelength band Are formed on the same substrate (for example, an n-type GaN substrate 20 in the embodiments described later), and the first nitride semiconductor laser device A laser emitted from the second nitride semiconductor laser element (for example, a reproducing laser in an embodiment described later) has a radiation angle of the laser emitted (for example, a recording laser 33a in the embodiment described later). This relates to a semiconductor laser (for example, a GaN monolithic two-beam laser chip 10 in an embodiment described later) configured to be smaller than the radiation angle of 33b).

  In addition, the present invention includes a semiconductor layer configured by laminating a first conductivity type layer, an active layer, and a second conductivity type layer in this order, and a partial region of the second conductivity type layer is etched to have a predetermined The first and second nitride semiconductor laser elements that emit a laser having the same wavelength band are formed on the same substrate. Recording with a semiconductor laser configured such that the radiation angle of the laser emitted by the first nitride semiconductor laser element is smaller than the radiation angle of the laser emitted by the second nitride semiconductor laser element The present invention relates to an optical pickup device for reproduction.

  The present invention also includes a first step of stacking a first conductivity type layer, an active layer, and a second conductivity type layer in this order to form first and second semiconductor layers, and the first semiconductor layer of the first semiconductor layer. Etching a partial region of the second conductivity type layer to a first predetermined thickness and forming a region other than the partial region as a striped first ridge portion; Etching a part of the second conductivity type layer of the semiconductor layer to a second predetermined thickness and forming a region other than the part as a stripe-shaped second ridge portion. A first nitride semiconductor laser element in which a thickness of the second conductivity type layer in the region excluding the first ridge portion is the first predetermined thickness; and the second ridge A second nitride in which the thickness of the second conductivity type layer in the region excluding the portion is the second predetermined thickness Conductor laser element is formed on the same substrate, the first and second nitride semiconductor laser device is related to a method of manufacturing a semiconductor laser emitting a laser of the same wavelength band.

  According to the semiconductor laser of the present invention, the first and second nitride semiconductor laser elements that emit laser of the same wavelength band are formed on the same substrate, and are emitted by the first nitride semiconductor laser element. Since the radiation angle of the laser is configured to be smaller than the radiation angle of the laser emitted by the second nitride semiconductor laser element, the first nitridation of the optical pickup device for recording / reproducing high density optical discs It is possible to provide a semiconductor laser that can be suitably used as a recording semiconductor laser element for recording and the second nitride semiconductor laser element as a reproducing laser source.

  According to the recording / reproducing optical pickup device of the present invention, since the first nitride semiconductor laser element is used for recording and the second nitride semiconductor laser element is used as a reproducing laser source, Without using an attenuator, noise canceller, or the like, the quantum noise level of the laser can be lowered, and an optical pickup device for recording and reproduction with high reliability can be provided without causing an increase in cost due to an increase in the number of components.

  According to the method for manufacturing a semiconductor laser of the present invention, it is possible to provide a method for manufacturing a semiconductor laser that can be suitably used for a recording / reproducing optical pickup device.

  In the semiconductor laser of the present invention, the predetermined thickness of the partial region of the second conductivity type layer of the first nitride semiconductor laser element is approximately 0.1 μm, and the second It is preferable that the nitride semiconductor laser element is formed to be thicker than the predetermined thickness of the partial region of the second conductivity type layer. According to this configuration, the skirt portion of the ridge portion of the first nitride semiconductor laser element is more from the active layer (the emission end face portion) than the skirt portion of the ridge portion of the second nitride semiconductor laser element. The emission angle of the laser beam emitted from the first nitride semiconductor laser element is smaller than the emission angle of the laser beam emitted from the second nitride semiconductor laser element. Thus, it is possible to design the recording laser and the reproducing laser, respectively.

  The width of the ridge portion of the first nitride semiconductor laser element is preferably larger than the width of the ridge portion of the second nitride semiconductor laser element. According to this configuration, the width of the ridge portion on the laser emission end face side of the first nitride semiconductor laser element is larger than the width of the ridge portion on the laser emission end face side of the second nitride semiconductor laser element. Since it is formed large, the radiation angle of the laser beam emitted from the first nitride semiconductor laser element can be made smaller than the radiation angle of the laser beam emitted from the second nitride semiconductor laser element.

  The first nitride semiconductor laser element may have a first window structure (for example, a window portion 34a in an embodiment described later) on the laser emission end face side of the active layer. According to this configuration, since the first window structure is formed on the laser emitting end face side of the active layer of the first nitride semiconductor laser element, the first nitride semiconductor laser element is emitted from the first nitride semiconductor laser element. The radiation angle of the laser beam can be reduced.

  Further, the second nitride semiconductor laser element has a second window structure (for example, a window portion 34d in an embodiment described later) on the laser emission end face side of the active layer. The length of the window is preferably shorter than the length of the first window. According to this configuration, the length of the window of the second window structure is shorter than the length of the first window, so that the laser beam emitted from the first nitride semiconductor laser element Can be made smaller than the radiation angle of the laser beam emitted from the second nitride semiconductor laser element.

  The first and second nitride semiconductor laser elements may be formed on the substrate by the same crystal growth process. According to this configuration, the first and second nitride semiconductor laser elements are formed on the substrate by the same single crystal growth process, and the first and second nitride semiconductor laser elements each have a stripe shape. Since the ridge portion is formed to have a different shape and structure, the time required for the crystal growth process is shortened, and the radiation angle of the laser beam emitted from the first nitride semiconductor laser element is set to the second ridge portion. The radiation angle of the laser beam emitted from the nitride semiconductor laser element can be made smaller.

  Each of the first and second nitride semiconductor laser elements is preferably formed on the substrate by different crystal growth processes. According to this configuration, each of the first and second nitride semiconductor laser elements is formed on the substrate by different crystal growth processes, and each stripe of the first and second nitride semiconductor laser elements is formed. Since the shape and structure of the ridge portion are different from each other, the radiation angle of the laser beam emitted from the first nitride semiconductor laser element is emitted from the second nitride semiconductor laser element. Can be made smaller than the radiation angle of the laser beam.

  The active layer of the first and second nitride semiconductor laser elements has a tapered shape, and the width of the active layer of the first nitride semiconductor laser element at the laser emission end surface is the second. The nitride semiconductor laser element is preferably formed to have a width larger than the width of the active layer at the laser emission end face. According to this configuration, the active layer of the first and second nitride semiconductor laser elements has a tapered shape, and the width of the active layer of the first nitride semiconductor laser element at the laser emission end face is Since the width of the active layer of the second nitride semiconductor laser element is larger than the width at the laser emission end face, the radiation angle of the laser beam emitted from the first nitride semiconductor laser element is The radiation angle of the laser beam emitted from the second nitride semiconductor laser element can be made smaller.

  The first and second nitride semiconductor laser elements may be GaN-based semiconductor laser elements. According to this configuration, since a GaN-based semiconductor laser element that emits a wavelength in the 405 nm band is used, the BD and HD-DVD that enable high-density recording can be used for the first and second nitride semiconductor laser elements. It can be suitably used for a recording / reproducing optical pickup to be used.

  In the recording / reproducing optical pickup device of the present invention, the predetermined thickness of the partial region of the second conductivity type layer of the first nitride semiconductor laser element is approximately 0.1 μm, and It is preferable that the second nitride semiconductor laser element is formed to be thicker than the predetermined thickness of the partial region of the second conductivity type layer. According to this configuration, the skirt portion of the ridge portion of the first nitride semiconductor laser element is more from the active layer (the emission end face portion) than the skirt portion of the ridge portion of the second nitride semiconductor laser element. The emission angle of the laser beam emitted from the first nitride semiconductor laser element is smaller than the emission angle of the laser beam emitted from the second nitride semiconductor laser element. Thus, it is possible to design the recording laser and the reproducing laser, respectively. Therefore, at the time of reproduction, the quantum noise level of the laser can be lowered without using an attenuator, a noise canceller or the like.

  The width of the ridge portion of the first nitride semiconductor laser element is preferably larger than the width of the ridge portion of the second nitride semiconductor laser element. According to this configuration, the width of the ridge portion on the laser emission end face side of the first nitride semiconductor laser element is larger than the width of the ridge portion on the laser emission end face side of the second nitride semiconductor laser element. Since it is formed large, the radiation angle of the laser beam emitted from the first nitride semiconductor laser element can be made smaller than the radiation angle of the laser beam emitted from the second nitride semiconductor laser element, Designs suitable for recording lasers and reproducing lasers can be made, respectively. Accordingly, the quantum noise level of the laser during reproduction can be lowered.

  The first nitride semiconductor laser element preferably has a first window structure on the laser emission end face side of the active layer. According to this configuration, since the first window structure is formed on the laser emitting end face side of the active layer of the first nitride semiconductor laser element, the first nitride semiconductor laser element is emitted from the first nitride semiconductor laser element. The radiation angle of the laser beam can be reduced, and the laser output can be increased.

  Further, the second nitride semiconductor laser element has a second window structure on the laser emission end face side of the active layer, and the length of the window of the second window structure is the length of the first window. It is preferable to have a structure formed shorter than the above. According to this configuration, the length of the window of the second window structure is shorter than the length of the first window, so that the laser beam emitted from the first nitride semiconductor laser element Can be made smaller than the radiation angle of the laser beam emitted from the second nitride semiconductor laser element, and it is possible to design the recording laser and the reproducing laser, respectively. Accordingly, the quantum noise level of the laser during reproduction can be lowered.

  The first and second nitride semiconductor laser elements may be formed on the substrate by the same crystal growth process. According to this configuration, the first and second nitride semiconductor laser elements are formed on the substrate by the same single crystal growth process, and the first and second nitride semiconductor laser elements each have a stripe shape. Since the ridge portion is formed to have a different shape and structure, the time required for the crystal growth process is shortened, and the radiation angle of the laser beam emitted from the first nitride semiconductor laser element is set to the second ridge portion. The radiation angle of the laser beam emitted from the nitride semiconductor laser element can be made smaller, and it is possible to design the recording laser and the reproduction laser, respectively. Accordingly, the quantum noise level of the laser during reproduction can be lowered.

  Each of the first and second nitride semiconductor laser elements is preferably formed on the substrate by different crystal growth processes. According to this configuration, each of the first and second nitride semiconductor laser elements is formed on the substrate by different crystal growth processes, and each stripe of the first and second nitride semiconductor laser elements is formed. Since the shape and structure of the ridge portion are different from each other, the radiation angle of the laser beam emitted from the first nitride semiconductor laser element is emitted from the second nitride semiconductor laser element. Therefore, it is possible to design the laser beam suitable for a recording laser and a reproducing laser, respectively. Accordingly, the quantum noise level of the laser during reproduction can be lowered.

  The active layer of the first and second nitride semiconductor laser elements has a tapered shape, and the width of the active layer of the first nitride semiconductor laser element at the laser emission end surface is the second. The nitride semiconductor laser element is preferably formed to have a width larger than the width of the active layer at the laser emission end face. According to this configuration, the active layer of the first and second nitride semiconductor laser elements has a tapered shape, and the width of the active layer of the first nitride semiconductor laser element at the laser emission end face is Since the width of the active layer of the second nitride semiconductor laser element is larger than the width at the laser emission end face, the radiation angle of the laser beam emitted from the first nitride semiconductor laser element is The radiation angle of the laser beam emitted from the second nitride semiconductor laser element can be made smaller, and it is possible to design suitable for a recording laser and a reproducing laser, respectively. Accordingly, the quantum noise level of the laser during reproduction can be lowered.

  The first and second nitride semiconductor laser elements may be GaN-based semiconductor laser elements. According to this configuration, since a GaN-based semiconductor laser element that emits a wavelength in the 405 nm band is used, the BD and HD-DVD that enable high-density recording can be used for the first and second nitride semiconductor laser elements. It can be suitably used for a recording / reproducing optical pickup to be used.

  In the semiconductor laser manufacturing method of the present invention, the above-described semiconductor laser is preferably formed. According to such a manufacturing method, the radiation angle of the laser beam emitted from the first nitride semiconductor laser element is smaller than the radiation angle of the laser beam emitted from the second nitride semiconductor laser element. Therefore, it is possible to manufacture a semiconductor laser that can be suitably used for an optical pickup for recording and reproduction and can reduce the quantum noise level of the laser during reproduction.

  The semiconductor laser according to the present invention is a nitride semiconductor laser composed of a III-V group compound semiconductor, and emits a 405 nm band laser. Here, the group III-V compound semiconductor means one containing at least one of the group 3B elements in the short period type periodic rate table and at least nitrogen (N) of the group 5B elements, A gallium nitride compound containing gallium (Ga) and nitrogen (N), such as GaN, AlGaN (aluminum nitride / gallium), AlGaInN (aluminum nitride / gallium / indium), etc. N-type impurities composed of Group IV and Group VI elements such as silicon (Si), germanium (Ge), oxygen (O), selenium (Se), or magnesium (Mg), zinc (Zn), carbon (C), etc. P-type impurities comprising Group II and Group IV elements.

For example, the semiconductor laser according to the present invention is a GaN-based monolithic two-beam semiconductor laser that emits a laser having the same wavelength in the 405 nm band, and has two resonators built in the same chip, and the radiation angles of the two lasers emitted. Are used as read-only laser sources and record-only laser sources in optical pickup devices for recording and playback for high-density optical discs such as BD and HD-DVD, and as noise countermeasures during low output (playback) A configuration that does not require external parts such as an attenuator and a noise canceller can be employed.
A GaN-based monolithic two-beam semiconductor laser has two resonators, and crystal growth of one laser resonator and crystal growth of the other laser resonator can be performed separately separately. The other laser resonator can be fabricated by the same crystal growth. Further, the radiation angles of the two laser emission can be changed by the difference in the window structure design of the laser resonator and the shape structure of the striped ridge portion.

  By using such a GaN-based monolithic two-beam semiconductor laser, external components such as an attenuator and noise canceller are not required as noise countermeasures at the time of low output (during reproduction), and high-density optical discs such as BD and HD-DVD Therefore, it is possible to realize an optical pickup device for recording and reproduction, and to obtain merits such as reduction in the number of parts of the optical pickup device, cost reduction, and improvement in reliability.

  In addition, by introducing the presence or absence of a window structure on the laser emission end face and the difference in the structure, a GaN-based monolithic 2 capable of emitting recording and reproducing two-beam lasers having different emission angles by one crystal growth. A beam semiconductor laser can be realized. This can be expected to reduce the manufacturing cost of the laser chip. Further, by introducing a design difference into the shape structure of the striped ridge portion, a GaN-based monolithic 2 capable of emitting recording and reproducing two-beam lasers having different emission angles by a single crystal growth. A beam semiconductor laser can be realized, and a reduction in manufacturing cost of the laser chip can be expected.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram for explaining the configuration of a GaN-based monolithic two-beam laser chip and recording / reproducing of an optical disc by a recording / reproducing pickup device using the same in an embodiment of the present invention. FIG. FIG. 1B is a front view illustrating the configuration of a GaN-based monolithic two-beam laser chip, FIG. 1C is a front view, and FIG. 1C is a diagram illustrating recording and reproduction of an optical disk using the two-beam laser chip. FIG.

  As shown in FIGS. 1A and 1B, a GaN-based monolithic two-beam laser chip 10 includes a first conductivity type layer, an active layer, and a second conductivity type layer stacked on an n-type GaN substrate 20 in this order. A semiconductor layer having a laser oscillation structure configured as described above, and having stripe-shaped ridge portions 30a and 30b above the second conductivity type layer, and a recording laser element for emitting a recording laser and a reproducing element A reproducing laser element that emits a laser is formed on the n-type GaN substrate 20.

  A recording laser element that emits a recording laser is constituted by the semiconductor layer having the ridge portion 30a, and a reproducing laser element that emits a reproducing laser is constituted by the semiconductor layer having the ridge portion 30b. The semiconductor layer includes an n-type cladding layer 22, a multiple quantum well structure active layer 24, a p-type cladding layer 26, and a p-type contact layer 28. The n-type cladding layer 22 corresponds to the first conductivity type layer. The p-type cladding layer 26 and the p-type contact layer 28 correspond to the second conductivity type layer. Hereinafter, the direction in which the above layers are stacked is referred to as a vertical direction, and the vertical direction and the direction perpendicular to the laser beam emission direction are referred to as a horizontal direction.

The thickness of the n-type GaN substrate 20 is, for example, 80 μm to 100 μm, the n-type cladding layer 22 is made of, for example, n-type AlGaN having a thickness of 1 μm, and the active layer 24 has a thickness of, for example, 30 nm. Having a multiple quantum well structure composed of a well layer and a barrier layer each formed of Ga _x In _1-x N (x ≧ 0) having different compositions, and the p-type cladding layer 26 has, for example, a thickness The p-type contact layer 28 is made of, for example, p-type GaN having a thickness of 0.1 μm.

  As shown in FIG. 1, a part of the p-type cladding layer 26 and the p-type contact layer 28 are formed in a striped ridge portion 30a having a rectangular shape with a thin thickness extending in one direction (resonator direction). , 30b. The stripe-shaped ridge portions 30a and 30b correspond to the resonators of the recording laser and the reproduction laser, respectively, and the regions corresponding to the ridge portions 30a and 30b in the active layer 24 are the recording laser emission end faces 32a. The reproducing laser emission end face 32b is used to emit a recording laser 33a and a reproducing laser 33b.

  A part of the p-contact layer 28 and the p-cladding layer 26 is etched to have a predetermined thickness, and other regions other than the part of the region are formed as striped ridge portions 30a and 30b. That is, other regions of the p contact layer 28 and the p clad layer 26 are left as they are as regions where the striped ridge portions 30a and 30b are formed, and a part of the p clad layer 26 having a predetermined thickness is left. The p-contact layer 28 and the p-cladding layer 26 are etched to form striped ridge portions 30a and 30b having a trapezoidal cross section and a convex shape. The ridge formed by the p-contact layer 28 and the p-cladding layer 26 is formed. The thickness of the p-cladding layer 26 on both sides of the portions 30a and 30b is a predetermined thickness that is thinner than the ridge portions 30a and 30b.

Of the regions of the p-contact layer 28 and the p-cladding layer 26 having the width W _1c , portions other than the region of the width (width of the ridge portion 30a) W _1r are etched and removed by the depth D ₁ , and p is formed on both sides of the ridge portion 30a. The cladding layer 26 is left with a thickness h ₁ (not shown), and the portion of the p contact layer 28 having the width W _2c and the region of the p cladding layer 26 other than the width (width of the ridge portion 30b) W _2r region. Is etched and removed by the depth D ₂ , and the p-cladding layer 26 is left with a thickness h ₂ (not shown) on both sides of the ridge portion 30b. When the ridges 30a and 30b have a trapezoidal cross section instead of an ideal cross section, the maximum side length is the width.

  A p-side electrode 29 is provided on the surface of the p-contact layer 28 of the ridge portions 30a and 30b, and is connected to a positive-side power source (not shown). An n-side electrode layer (formed on the back surface of the n-type GaN substrate 20) connected to a negative power source (not shown) is not shown.

The vertical radiation angle (expansion angle) θ _V indicating the FFP (far field image) characteristics of the laser beams emitted from the recording laser emission end face 32a and the reproduction laser emission end face 32b, and the horizontal emission angle (expansion angle). ) Regarding θ _H , θ _V > θ _H and the shape of the laser beam has an elliptical shape that is long in the vertical direction. Since the optical pickup device uses light in the vicinity of the center of the elliptical beam, an elliptical shape that is long in the vertical direction. A laser beam having a shape is often not used, and the light utilization efficiency of the laser beam emitted from the semiconductor laser is lowered. In order to increase the light utilization efficiency, it is desirable to make the beam near circle by changing the vertical radiation angle θ _V or the horizontal radiation angle θ _H.

In the above description, the stripe-shaped ridge portion 30a which forms a rectangular body having a thin thickness has been described 30b, in the present invention, in order to change the horizontal beam divergence theta _H, ridges 30a, 30b For example, the width W _{1r of} the ridge portion 30a, the thickness h ₁ of the p-cladding layer 26 on both sides of the ridge portion 30a, the width W _{2r of} the ridge portion 30b, and both sides of the ridge portion 30b Changing the thickness h ₂ of the p-cladding layer 26, providing a window structure at at least one end in the longitudinal direction of the ridge portions 30a, 30b, and changing the width in the longitudinal direction of the ridge portions 30a, 30b to have a tapered shape. (These examinations will be described in detail later).

  By such a study, the laser beam is designed so that the radiation angle of the laser beam emitted from the recording laser emitting end face 32a of the recording laser element becomes small, and conversely, the radiation is emitted from the reproducing laser emitting end face 32b of the reproducing laser element. The laser beam is designed to have a large radiation angle. In the recording mode of the optical pickup device, the laser with the smaller emission angle (recording laser element) is used, giving priority to the optical coupling in the optical pickup device, maximizing the laser power on the surface of the optical disk, and maximizing the recording speed. In the reproduction mode, the laser with the larger emission angle (reproduction laser element) is used to reduce the optical coupling in the optical pickup device, and the quantum of the laser without using external components. Noise can be reduced, and low-noise signal reception is possible.

A typical example of the FFP characteristics of a laser beam used for BD recording / reproducing will be described. The vertical emission angle θ _V of the recording laser 33a is 21 degrees, and the horizontal emission angle θ _H is 8 degrees. The reproduction laser 33b has a vertical radiation angle θ _V of 24 degrees and a flat radiation angle θ _H of 10 degrees. In the case of these FFP characteristics, the ratio of the optical coupling efficiency (optical coupling efficiency of the reproduction laser beam / optical coupling efficiency of the recording laser beam) when the optical pickup device has a typical magnification of 11.3 times. When calculated, it becomes 0.747, and the optical coupling efficiency of the reproducing laser beam is about ¾ of the optical coupling efficiency of the recording laser beam, and the source of the laser light source when the laser power on the disk surface is constant. The power ratio (reproducing laser / recording laser) is 1.34, and the original power of the reproducing laser is 34% higher than the original power of the recording laser.

An example of the configuration of a laser element that satisfies the typical example of the above FFP characteristics is as follows. Regarding the recording laser element, the element length = 800 μm, the element width W _1c = 100 μm, the width W _1r of the ridge portion 30a = 2 μm, The thickness h ₁ of the p-cladding layer 26 on both sides of the ridge 30a is 0.1 μm, the height D ₁ of the ridge 30a is 0.4 μm, and the reproducing laser element has an element length of 400 μm and an element width. W _2c = 100 μm, width W _{2r of} the ridge portion 30a = 1 μm, thickness h ₂ of the p-cladding layer 26 on both sides of the ridge portion 30a = 0.07 μm, height D ₂ of the ridge portion 30a = 0.43 μm, etc. is there.

  As shown in FIG. 1C, the laser 44 emitted from the recording laser emission end face 32a of the GaN monolithic two-beam laser chip 10 uses an objective lens 46 to have recording / reproduction layers 42a, 42b,. For example, in the case of a phase change type optical disc, the recording layer is constituted only by the laser irradiated region by condensing and irradiating a minute region of 40 predetermined recording / reproducing layers 42a. The material to be dissolved once melts and re-solidifies, and a recording mark is formed in the minute region irradiated with the laser by the phase change from the crystal structure to the amorphous structure. When performing reproduction, the laser 44 emitted from the reproduction laser emission end face 32b uses a lens 46 to detect reflected light generated by condensing and irradiating a minute area of a predetermined recording / reproduction layer 42a.

  FIG. 2 is a front view seen from the laser emission end face for explaining a manufacturing process by two growth processes of the GaN-based monolithic two-beam laser chip in the embodiment of the present invention.

  As shown in FIG. 2A, an n-type cladding layer 22, an active layer 24, a p-type cladding layer 26, and a p-type contact layer 28 are stacked in this order on an n-type GaN substrate 20.

Next, as shown in FIG. 2B, the region of the width W _c1 forming one laser resonator is left as an island, and the other unnecessary region is etched away.

  Next, as shown in FIG. 2C, an n-type cladding layer 22, an active layer 24, a p-type cladding layer 26, and a p-type contact layer 28 are stacked in this order on the n-type GaN substrate 20.

Next, as shown in FIG. 2 (D), the region of the width W _c2 that forms the other laser resonator is left and other unnecessary portions are etched away. In this manner, the first semiconductor layer for forming one laser resonator and the second semiconductor layer for forming the other laser resonator are formed on the n-type GaN substrate 20.

  As described above, crystal growth for forming one laser resonator and crystal growth for forming the other laser resonator can be performed in separate processes. According to such a method, the composition and thickness of each of the n-type cladding layer 22, the active layer 24, the p-type cladding layer 26, and the p-type contact layer 28 constituting each of the first and second semiconductor layers are set. The first semiconductor layer and the second semiconductor layer can be different, and one and the other laser resonator can be designed and formed independently.

Next, as shown in FIG. 2 (E), p is etched by leaving the regions of the widths W _1r and W _2r of the striped ridges 30a and 30b of one and the other laser resonator to a depth D. The mold cladding layer 26 and a part of the p-type contact layer 28 are removed, and then the p-type contact layer 28 is formed.
In the step shown in FIG. _2E , the depths D ₁ and D ₂ leave the widths W _1r and W _2r separately for the striped ridge portions 30a and 30b of the one and the other laser resonators. Only by etching, ridge portions 30c and 30d can be formed as in FIG. 3D described later, and a laser diode having a laser beam radiation angle suitable for recording and reproduction can be formed. it can.

  The shape of the ridge portions 30a and 30b is not only a stripe shape having a rectangular shape with a thin thickness, but also a taper shape having a different width in the longitudinal direction in addition to a stripe shape having a rectangular shape with a thin thickness. It goes without saying that it can also be.

  FIG. 3 is a front view seen from the laser emission end face, illustrating a manufacturing process by a single growth process of the GaN-based monolithic two-beam laser chip in the embodiment of the present invention.

  As shown in FIG. 3A, an n-type GaN substrate 20 is laminated with an n-type cladding layer 22, an active layer 24, a p-type cladding layer 26, and a p-type contact layer 28 in this order. Crystal growth to form the vessel is performed in a single process.

Next, as shown in FIG. 3B, the regions of the widths W _c1 and W _c2 forming one and the other laser resonators are left as islands, and other unnecessary portions are etched away. In this manner, the first semiconductor layer for forming one laser resonator and the second semiconductor layer for forming the other laser resonator are formed on the n-type GaN substrate 20.

Next, as shown in FIG. 3 (C), p is etched by leaving the regions of the widths W _1r and W _2r of the striped ridge portions 30a and 30b of one and the other laser resonator to a depth D. The mold cladding layer 26 and a part of the p-type contact layer 28 are removed, and then the p-type contact layer 28 is formed.

In the step shown in FIG. 3 (C), the depths D ₁ and D ₂ leave the widths W _1r and W _2r separately for the striped ridges 30a and 30b of one and the other laser resonator, respectively. As shown in FIG. 3D, ridges 30c and 30d can be formed by etching only, and a laser diode having a laser beam radiation angle suitable for recording and reproduction can be formed. .

  The shape of the ridge portions 30a and 30b is not only a stripe shape having a rectangular shape with a thin thickness, but also a taper shape having a different width in the longitudinal direction in addition to a stripe shape having a rectangular shape with a thin thickness. It goes without saying that it can also be.

  FIG. 4 is a diagram for explaining an example in which the structure of the stripe ridge portion is changed and the radiation angle is changed in the GaN-based monolithic two-beam laser chip in the embodiment of the present invention, and FIG. FIG. 4B and FIG. 4C are plan views for explaining the shape of the stripes. FIGS. 4B and 4C are diagrams illustrating an example of changing the width and height of the laser beam.

  As shown in FIG. 4A, the radiation angle of the laser beam can be changed by changing the shape of the ridge, that is, the width and height of the ridge.

As shown in FIG. 1B by one crystal growth process, as shown in FIG. 1B, W _1r <W _2r and D ₁ <D ₂ , that is, (the ridge portion 30c of the recording laser element) (Width) <(width of the ridge portion 30d of the reproducing laser element), the etching depth for forming the ridge portion 30c is decreased, and the etching depth for forming the ridge portion 30d is increased ( Etching depth for forming ridge portion 30c) <(etching depth for forming ridge portion 30d) and (thickness h ₁ of p-type cladding layer 26 on both sides of ridge portion 30c) <(ridge portion by the 30d thickness ₂ on both sides of the p-type cladding layer 26), and (radiation angle in the horizontal direction of the laser beam theta _H) <(horizontal beam divergence of the laser beam for reproduction theta _H) The one-time crystal growth process described above Scan by a different angle of radiation, recording, it is possible to realize a low-cost two-beam laser chip for emitting a two-beam laser for reproduction.

In general, the width of the ridge is about 1 μm to 2 μm. However, when the width of the ridge is reduced to, for example, more than 2 μm → the first half of 1 μm, the horizontal radiation angle θ _H of the laser beam is 1 Increased by 2 degrees. By controlling the thickness of the p-type cladding layer on both sides of the ridge portion (thickness left without being etched when the ridge portion is formed) h, for example, if this h is reduced from 0.1 μm to 0.05 μm The horizontal radiation angle θ _H of the laser beam is increased by about 5 degrees. When h = 0.1 μm, θ _H = 5 degrees, and when h = 0.05 μm, θ _H = 13 degrees. In general, the effect of changing θ _H by this change in h is greater than the effect of changing θ _H by changing the width of the ridge portion.

  As described above, the shape of the ridge portion is not limited to the stripe shape having a rectangular shape having a thin thickness, but the width in the longitudinal direction is changed in addition to the stripe shape having a rectangular shape having a thin thickness. It can also be a tapered shape.

  As shown in FIG. 4B, a concave portion is formed in the stripe shape by three linear portions as in the ridge portion 30e of the recording laser element, and three straight lines are formed in the stripe shape as in the ridge portion 30f of the reproducing laser element. As shown in FIG. 4C, the ridge portion of the reproducing laser element can be provided with a concave portion by a curved portion in a stripe shape like the ridge portion 30g of the recording laser element. A convex portion can be provided in the stripe shape by a curved portion as in 30 h.

As in the example shown in FIGS. 4B and 4C, the width of the ridge portions 30e and 30g of the recording laser element is increased at the laser emission end face, and the lasers of the ridge portions 30f and 30h of the reproducing laser element are increased. By reducing the width at the emission end face, (width at the laser emission end face of the ridge portion of the recording laser element)> (width at the laser emission end face of the ridge of the reproduction laser element), (horizontal of the recording laser beam) direction of radiation angle θ _H) <(may be a horizontal beam divergence theta _H) of the laser beam for reproduction, by a single crystal growth process described above, different radiation angle, for recording, reproducing A low-cost two-beam laser chip that emits the two-beam laser can be realized.

  5 and 6 are diagrams for explaining an example of changing the radiation angle by changing the structure of the stripe ridge portion in the GaN-based monolithic two-beam laser chip in the embodiment of the present invention. FIG. 6A is a front view for explaining the window structure, as viewed from the laser emission end face, and FIGS. 5B, 5C, 6B, and 6C are plan views. is there.

  As shown in FIGS. 5 and 6, the radiation angle of the laser beam can be changed depending on the region where the end face window structure is formed.

  The end face window structure is formed so that the band gap in the vicinity of the laser emission end face is larger than the band gap of the active layer so that the laser is not absorbed by the laser emission end face, and a larger output can be obtained. . The region where the window structure is formed is formed by implanting and diffusing impurities (for example, Zn) from the surface of the p-type cladding layer to the active layer by ion implantation, and in this diffusion process, the ordered structure of the active layer is converted into a disordered structure. Thus, the region (window portion) has a large band gap.

  Further, by providing a current non-injection region (a region where current is not injected and which is not transparent with respect to the laser oscillation wavelength) of several μm to several tens of μm in the vicinity of the laser emission end face, it is optical. Although not a window, this region can also be an end window structure (window) that changes the radiation angle of the laser beam.

  Further, the n-type cladding layer 22, the active layer 24, the p-type cladding layer 26, and the p-type contact layer 28 are changed by changing the crystal growth conditions in the vicinity of the laser emitting end face of the ridge portion (region of several μm to several tens of μm). Can be formed by selective growth, and this region can be an end face window structure (window portion).

As shown in FIGS. 5 and 6, the length of the window formed on the laser emission end face of the ridge portion 30a of the recording laser element (the length in the longitudinal direction of the ridge portion) is increased, and the reproducing laser element The length of the window portion formed on the laser emission end face of the ridge portion 30b is set to zero (that is, no window portion is formed) or smaller, and the length of the window portion formed on the laser emission end face of the ridge portion of the recording laser element is reduced. )> (Length of the window portion formed on the laser emission end face of the ridge portion of the reproduction laser element), the horizontal emission angle θ _H of the recording laser beam is reduced, and the reproduction laser beam by increasing the horizontal beam divergence theta _H, (recording laser beam horizontal beam divergence theta _H) of <can be a (horizontal radiation angle of the laser beam for reproduction theta _H), previously described Radiation angle by a single crystal growth process It is possible to realize a low-cost two-beam laser chip that emits a two-beam laser for recording and reproduction, which are different from each other.

  In the example shown in FIG. 5, windows are provided at both ends of the ridge portion 30a of the recording laser element, and windows are not provided at both ends of the ridge portion 30b of the reproducing laser element, and the example shown in FIG. In FIG. 5C, windows 34a and 36a having substantially the same length (the length in the longitudinal direction of the ridge 30a) are formed at both ends of the ridge 30a. In the example shown in FIG. The window portions 34b and 36b longer than the length of the window portion in the example shown in FIG. 5 are formed, and the length of the window portion 34b formed on the laser emission end surface 32a is longer than the window portion 36b.

  6A and 6B, the ridge portion 30a of the recording laser element and the ridge portion 30b of the reproducing laser element are provided with windows at both ends. Window portions 34d and 36d having substantially the same length are formed at both ends, and window portions 34c and 36c that are longer than the window portions 34d and 36d are formed at both ends of the ridge portion 30a of the recording laser element. The window 34c formed on the laser emission end face 32a is longer than the window 36c.

  In the example shown in FIG. 6C, the ridge portion 30b of the reproducing laser element is not provided with a window portion, and the crystal growth conditions in the vicinity of the laser emission end face 32a of the ridge portion 30a ′ (region of several μm to several tens of μm). In this example, the n-type cladding layer 22, the active layer 24, the p-type cladding layer 26, and the p-type contact layer 28 are formed by selective growth and this region is used as a window portion.

  FIG. 7 is a diagram illustrating a configuration example of a Bru-ray pickup device using a GaN-based monolithic two-beam laser chip according to an embodiment of the present invention. FIG. 7A is a side view, and FIG. B) is a plan view.

  The configuration shown in FIG. 7 does not use the attenuator 90 in the configuration shown in FIG. 9 and simplifies the configuration, and instead of the GaN-based laser 69, a GaN-based laser (BD based on a GaN-based monolithic two-beam laser chip) LD) 70, and as described above, the recording laser beam and the reproducing laser beam are selectively used.

  FIG. 8 is a diagram for explaining a configuration example of a Bru-ray pickup device using an optical integrated device mounted with a GaN-based monolithic two-beam laser chip in the embodiment of the present invention. FIG. FIG. 8B is a cross-sectional view showing the structure of the optical integrated device.

In the configuration shown in FIG. 8, the polarization beam spirit (PBS) 60 of the configuration shown in FIG.
A configuration is shown in which a hologram optical element 62, an optoelectronic integrated circuit 64, a lens 66, a monitor PD 68, and a GaN laser 70 are integrated to form a BD optical integrated element 72.

  A BD integrated optical element 72 that can be suitably used for BD recording / reproduction includes a prism system 74, a lens system 76, a half-wave plate (HWP) 77, a light receiving IC 78, and a two-beam laser chip 80. The lens system 76 and the half-wave plate (HWP) 77 perform the functions of the polarization beam spiriter (PBS) 60, the hologram optical element 62, and the lens 66 shown in FIG. 7, and the light receiving IC 78 is a photoelectron shown in FIG. The functions of the integrated circuit 64, the lens 66, and the monitor PD 68 are executed.

  As described above, by using the semiconductor laser according to the present invention, an external component such as an attenuator or a noise canceller is not required as a noise countermeasure at the time of low output (during reproduction). Therefore, it is possible to realize an optical pickup device for recording and reproduction. Therefore, merits can be obtained by reducing the number of parts of the optical pickup device, reducing the cost, and improving the reliability.

  In the above description, noise countermeasures have been described by taking BD, HD-DVD, etc. as an example. However, this noise countermeasure is similarly applied to other recording / reproducing medium systems that require similar noise countermeasures. Can be applied.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention is possible. For example, the composition and layer thickness of each layer constituting the semiconductor laser, the size of the window structure, the width and shape of the ridge portion, the thickness of the p contact layer on both sides of the ridge portion, etc. can be arbitrarily selected according to the purpose. Needless to say, a current confinement layer, an insulating layer, a protective layer, a buffer layer for crystal growth, and the like can be provided as necessary to improve the performance of the semiconductor laser. .

  As described above, according to the present invention, the quantum noise level can be lowered, the cost is not increased due to an increase in the number of parts, and the present invention can be suitably used for a highly reliable recording / reproducing optical pickup device. A semiconductor laser and a manufacturing method thereof can be provided.

It is a figure explaining the structure of a GaN-type monolithic 2 beam laser chip, and recording and reproduction | regeneration of an optical disk using the same in embodiment of this invention. It is the front view seen from the laser emission end surface explaining the manufacturing process by the two growth processes of a GaN-type monolithic 2 beam laser chip same as the above. It is the front view seen from the laser emission end surface explaining the manufacturing process by the single growth process of a GaN-type monolithic 2 beam laser chip same as the above. It is a figure explaining the example which changes the structure of a striped ridge part and changes a radiation angle in a GaN-type monolithic 2 beam laser chip same as the above. It is a figure explaining the example which changes the structure of a striped ridge part and changes a radiation angle in a GaN-type monolithic 2 beam laser chip same as the above. It is a figure explaining the example which changes the structure of a striped ridge part and changes a radiation angle in a GaN-type monolithic 2 beam laser chip same as the above. It is a figure explaining the structural example of the pick-up apparatus for BD using a GaN-type monolithic 2 beam laser chip same as the above. It is a figure explaining the structural example of the pickup apparatus for Bru-rays using the optical integrated element which mounted the GaN-type monolithic 2 beam laser chip same as the above. It is a figure which shows the outline of the structural example of the pick-up apparatus which performs the recording / reproduction | regeneration of high density optical disks, such as BD and HD-DVD in a prior art, in a prior art. It is a figure which shows the outline of the structural example of the reproduction noise countermeasure in a pickup apparatus same as the above.

Explanation of symbols

10 ... GaN-based monolithic two-beam laser chip, 20 ... n-type GaN substrate,
22 ... n-type cladding layer, 24 ... active layer with multiple quantum well structure, 26 ... p-type cladding layer,
28 ... p-type contact layer, 29 ... p-side electrode layer,
30a to 30h: striped ridge portion, 32a: recording laser emission end face,
32b: Reproducing laser emission end face, 33a: Recording laser, 33b: Reproducing laser,
34a to 34e, 36a to 36d ... windows, 40 ... optical disc,
42a, 42b ... recording / reproducing layer, 44 ... laser, 46 ... objective lens, 50 ... disc,
52 ... Objective lens, 54 ... 1/4 wavelength plate (QWP), 56 ... Rising mirror,
58 ... Collimator lens, 60 ... Polarized beam spirit (PBS),
62 ... Hologram optical element (HOE), 64 ... Optoelectronic integrated circuit (OEIC),
66 ... Lens, 68 ... Monitor PD, 69, 70 ... GaN laser (BD LD),
72 ... BD integrated optical device, 74 ... prism system, 76 ... lens system,
77 ... 1/2 wavelength plate (HWP), 78 ... light receiving IC, 80 ... 2 beam laser chip,
90 ... Attenuator, 91 ... Liquid crystal attenuator, 92 ... ND filter,
93 ... Noise canceller

Claims (20)

  A semiconductor layer formed by laminating a first conductivity type layer, an active layer, and a second conductivity type layer in this order; a partial region of the second conductivity type layer is etched to a predetermined thickness; The first and second nitride semiconductor laser elements emitting the laser of the same wavelength band are formed on the same substrate, and other regions other than the region of the first portion are formed as a stripe-shaped ridge portion. A semiconductor laser configured such that an emission angle of a laser emitted by a semiconductor laser device is smaller than an emission angle of a laser emitted by the second nitride semiconductor laser device.   The predetermined thickness of the partial region of the second conductivity type layer of the first nitride semiconductor laser element is approximately 0.1 μm, and the second nitride semiconductor laser element of the second nitride semiconductor laser element The semiconductor laser according to claim 1, wherein the semiconductor laser is formed thicker than the predetermined thickness of the partial region of the second conductivity type layer.   3. The semiconductor laser according to claim 2, wherein a width of the ridge portion of the first nitride semiconductor laser element is formed larger than a width of the ridge portion of the second nitride semiconductor laser element.   The semiconductor laser according to claim 1, further comprising a first window structure on a laser emission end face side of the active layer of the first nitride semiconductor laser element.   The second nitride semiconductor laser element has a second window structure on the laser emission end face side of the active layer, and the window length of the second window structure is longer than the length of the first window. The semiconductor laser according to claim 4, which is formed short.   The semiconductor laser according to claim 1, wherein the first and second nitride semiconductor laser elements are formed on the substrate by the same crystal growth process.   2. The semiconductor laser according to claim 1, wherein each of the first and second nitride semiconductor laser elements is formed on the substrate by a different crystal growth process.   The active layers of the first and second nitride semiconductor laser elements have a tapered shape, and the width of the active layer of the first nitride semiconductor laser element at the laser emission end surface is the second nitride. The semiconductor laser according to claim 1, wherein the semiconductor laser is formed to be larger than a width at a laser emission end face of the active layer of the semiconductor laser device.   2. The semiconductor laser according to claim 1, wherein the first and second nitride semiconductor laser elements are GaN-based semiconductor laser elements.   A semiconductor layer formed by laminating a first conductivity type layer, an active layer, and a second conductivity type layer in this order; a partial region of the second conductivity type layer is etched to a predetermined thickness; The first and second nitride semiconductor laser elements emitting the laser of the same wavelength band are formed on the same substrate, and other regions other than the region of the first portion are formed as a stripe-shaped ridge portion. Recording / reproducing optical pickup device having a semiconductor laser configured such that a radiation angle of a laser emitted from a semiconductor laser device is smaller than a radiation angle of a laser emitted from the second nitride semiconductor laser device .   The predetermined thickness of the partial region of the second conductivity type layer of the first nitride semiconductor laser element is approximately 0.1 μm, and the second nitride semiconductor laser element of the second nitride semiconductor laser element 11. The optical pickup device for recording / reproducing according to claim 10, wherein the optical pickup device is formed thicker than the predetermined thickness of the partial region of the second conductivity type layer.   The recording / reproducing optical pickup according to claim 11, wherein a width of the ridge portion of the first nitride semiconductor laser element is formed larger than a width of the ridge portion of the second nitride semiconductor laser element. apparatus.   The recording / reproducing optical pickup device according to claim 10, further comprising a first window structure on a laser emission end face side of the active layer of the first nitride semiconductor laser element.   The second nitride semiconductor laser element has a second window structure on the laser emission end face side of the active layer, and the window length of the second window structure is longer than the length of the first window. 14. The optical pickup device for recording / reproducing according to claim 13, which is formed short.   The recording / reproducing optical pickup device according to claim 10, wherein the first and second nitride semiconductor laser elements are formed on the substrate by the same crystal growth process.   The recording / reproducing optical pickup device according to claim 10, wherein each of the first and second nitride semiconductor laser elements is formed on the substrate by different crystal growth processes.   The active layers of the first and second nitride semiconductor laser elements have a tapered shape, and the width of the active layer of the first nitride semiconductor laser element at the laser emission end surface is the second nitride. 11. The optical pickup device for recording / reproducing according to claim 10, wherein the active semiconductor layer is formed larger than the width of the active layer at the laser emission end face.   The recording / reproducing optical pickup device according to claim 10, wherein the first and second nitride semiconductor laser elements are GaN-based semiconductor laser elements. A first step of stacking a first conductivity type layer, an active layer, and a second conductivity type layer in this order to form first and second semiconductor layers;
A part of the second conductivity type layer of the first semiconductor layer is etched to a first predetermined thickness, and a region other than the part of the first semiconductor layer is used as a striped first ridge portion. Forming, and
A portion of the second conductivity type layer of the second semiconductor layer is etched to a second predetermined thickness, and a region other than the portion is used as a striped second ridge portion. Forming, and
A first nitride semiconductor laser element in which a thickness of the second conductivity type layer in the region excluding the first ridge portion is the first predetermined thickness; and the second ridge portion A second nitride semiconductor laser element having a thickness of the second conductivity type layer in the region excluding the second predetermined thickness is formed on the same substrate, and the first and second nitride layers A semiconductor laser manufacturing method in which a semiconductor laser device emits a laser having the same wavelength band.   The semiconductor laser manufacturing method according to claim 19, wherein the semiconductor laser according to claim 2 is formed.

Images