JP2002056569A - Optical pickup and information recording / reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of optical characteristics by mounting an entire optical system on a movable part and aligning an optical axis of a semiconductor laser element having the shortest wavelength with an optical axis center of an objective lens. Provided is a pickup and an information recording / reproducing device equipped with the same. SOLUTION: A movable section 6 on which at least a plurality of semiconductor laser elements 2 for irradiating a laser beam onto an optical recording medium 12, an objective lens 1 for condensing the laser beam, a base section 7 supporting the movable section 6, The movable unit 6 is swung so that the movable unit 6 swings in the focus direction and the tracking direction of the optical recording medium 12.
And a supporting part 8 connected to the base 7. The optical axis of the semiconductor laser element having the shortest wavelength of the plurality of semiconductor laser elements 2 is aligned with the optical axis center of the objective lens 1. As a result, when the position of the objective lens changes, it is possible to prevent an optical shift from occurring in the optical system and to reduce the influence of lens aberration and the like on the short-wavelength semiconductor laser device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an information recording / reproducing apparatus for information processing / communication and the like, and an optical pickup used therein. In particular, the present invention relates to an optical pickup in which the entire optical system from light emission to light reception is integratedly mounted on a movable part.

[0002]

2. Description of the Related Art Digital versatile discs (D
With the advent of VD), the density of optical disks has been increased, and currently, an optical disk having a large capacity of 8.5 GB has been realized. A general DVD playback device is DVD
Not only that, compact discs (CDs) need to be played back, and in addition, write-once CDs have begun to spread rapidly in recent years.
In some cases, reproduction and recording of (CD-R) are required. A 650 nm band red laser is used as the reproduction light for reproducing the DVD, and an 780 nm band infrared laser is used as the reproduction light for reproducing the CD or CD-R. Therefore, the current DVD reproducing device is equipped with two semiconductor laser chips, a red semiconductor laser chip that generates red laser light and an infrared semiconductor laser chip that generates infrared laser light.

An optical pickup is used to read and write information on an optical recording medium such as a DVD or a CD. FIG. 13 shows a configuration diagram of a side surface of the optical pickup. The movable part 106 having the objective lens 101 and the coil 105 is provided with four support wires 108 with respect to the base 107.
And are swingably supported. The semiconductor laser chip, the integrated element 102 of the light receiving element, the collimator lens 104, and the mirror 103 are fixed to the optical base 109. In FIG. 13, two of the four support wires are used.
The book is not shown because it is hidden behind the two support wires shown. Since the optical recording medium 112 undergoes surface deflection during rotation, the light flux L condensed by the objective lens 101
It is necessary to keep the position of the information recording surface of the optical recording medium 112 within one depth of field. Further, since the optical recording medium 112 is decentered during rotation, it is necessary that the light beam L1 condensed by the objective lens 101 accurately follow the information recording sequence on the optical recording medium 112. It is required to have a focus adjustment function and a focus error detection function, and a tracking position adjustment function and a tracking error detection function.

[0004] In the optical pickup, the focus of the optical recording medium 112 is adjusted by moving the objective lens 101 in the focus direction, which is the direction of the output optical axis, with respect to the runout of the optical recording medium 112. Further, with respect to the eccentricity of the optical recording medium 112, the objective lens 101 is made to follow the information recording sequence by moving the objective lens 101 in a tracking direction which is a direction crossing the information recording sequence on the optical recording medium. With this configuration, the information recording signal is written or read.

[0005] In recent years, with the demand for miniaturization of information devices such as personal computers, it is necessary to advance the miniaturization and thinning of the DVD reproducing apparatus. Is indispensable. As a method for reducing the size and thickness of an optical pickup, simplification of an optical system can be cited. As one of the methods, integration of a red semiconductor laser chip and an infrared semiconductor laser chip can be considered. The current DVD reproducing apparatus is composed of two optical system components for a red semiconductor laser chip and an infrared semiconductor laser chip. Since optical components can be shared, the size and thickness of the optical pickup can be reduced.

For integration of a red semiconductor laser chip and an infrared semiconductor laser chip, a monolithic semiconductor laser element array integrated on one substrate is disclosed in
1-118651 (first conventional example) and 60th Autumn Lecture on Applied Physics 3a-ZC-10 (second conventional example). Japanese Patent Application Laid-Open No. H11-144307 (third conventional example) discloses an optical pickup that shares two optical components by integrating two red and infrared semiconductor laser chips in a hybrid manner.
And JP-A-11-149652 (fourth conventional example)
Has been reported to.

[0007]

However, the above-mentioned conventional optical pickup has the following problems. A monolithic semiconductor laser element array integrated on one substrate according to a first conventional example is a red laser and an infrared laser as current block (constriction) layers for efficiently injecting current into an active layer. In both cases, GaAs having an energy gap equal to or smaller than the energy gap (band gap) of each active layer is used. Thus, a complex refractive index waveguide structure is adopted in which the generated light is effectively confined in the stripe region by absorbing the laser light emitted from each active layer.
However, a semiconductor laser device using a complex refractive index waveguide structure has a self-excited oscillation characteristic and a high-temperature high-output characteristic required for an information recording / reproducing device because generated light is absorbed by a current blocking layer made of GaAs. It is extremely difficult.

Further, the semiconductor laser device array according to the second conventional example has a so-called gain-guided structure in which no current blocking layer is provided, so that light absorption by the current blocking layer does not occur. However, since the semiconductor laser device having this gain waveguide structure does not have a refractive index waveguide structure that effectively confines generated light, in order to reduce noise required for an information recording / reproducing apparatus, for example, a large oscillation spectrum is required. A means for suppressing coherence by changing the mode is required.

However, even if the oscillation spectrum is made multimode, the emitted light and the return light tend to interfere with each other because the half width of each spectrum is narrow, and the relative noise intensity (RIN) desired for the information recording / reproducing apparatus is reduced. -130dB
/ Hz or less. for that reason,
In the case of the semiconductor laser device array having the gain waveguide structure according to the second conventional example, RIN is performed using a ４λ plate (λ is the wavelength of laser light emitted from the semiconductor laser device) or the like.
Therefore, means for reducing the number of components is required, and it becomes difficult to reduce the number of components constituting the optical pickup. In order to solve these problems, it is indispensable that the semiconductor laser element array has self-pulsation characteristics.

In addition, the gain-guided semiconductor laser device array has a current confinement function, but does not have a light confinement function utilizing a refractive index distribution in a horizontal direction with respect to the main surface of the active layer. For this reason, when reproducing DVD or CD, 10
In a low output operation state of mW or less, the single transverse mode characteristic can be maintained at room temperature, but at a high temperature, the carrier is in a high injection state and the higher order mode can easily obtain a gain. It is difficult to obtain. Further, in the high-power operation state of the semiconductor laser element array, since there is no optical confinement mechanism, it is more difficult to stabilize the transverse mode characteristics.

Further, in the monolithic two-wavelength laser element array, since the optical system components are shared, it is preferable that the position of the active layer of each laser element, that is, the height from the substrate surface, be made identical. However, even though it is monolithic, there is a problem that the active layers in each laser element have different compositions, so that the growth steps must be performed separately, and the heights of the active layers vary.

The optical pickups according to the third and fourth conventional examples use an element in which a red semiconductor laser chip and an infrared semiconductor laser chip are integrated on a substrate including a light receiving element. .

However, even if the red semiconductor laser chip and the infrared semiconductor laser chip are integrated in a hybrid manner, there is a problem that it is difficult to control the position of the active layer and the interval between the light emitting points of each semiconductor laser chip. Was.

Further, in each of the conventional optical pickups, as shown in FIG. 13, an integrated element 102 of a semiconductor laser chip and a light receiving element, a collimating lens 104, a mirror 1
While the object 03 is fixed, only the objective lens 101 moves, and follows the surface deflection of the optical recording medium 112 and the information recording sequence. At this time, a change in the position of the objective lens 101 causes the optical system of the optical pickup to be in an optically deviated state, so that there is a problem that the optical characteristics deteriorate due to the occurrence of lens aberration and the like.

An object of the present invention is to solve the above-mentioned conventional problems by mounting an entire optical system from light emission to light reception on a movable part and using an objective lens with an optical axis of a semiconductor laser element having the shortest wavelength. It is an object of the present invention to provide an optical pickup capable of preventing deterioration of optical characteristics by adjusting the optical axis to the center of the optical axis, and an information recording / reproducing apparatus equipped with the optical pickup.

[0016]

In order to achieve the above object, an optical pickup according to the present invention comprises a plurality of semiconductor laser elements for irradiating an optical recording medium with laser light, and a laser light emitted from the semiconductor laser element. A movable portion on which at least an objective lens for converging light is mounted, a base portion supporting the movable portion, and the movable portion and the base portion so that the movable portion swings in a focus direction and a tracking direction of the optical recording medium. And at least two of the plurality of semiconductor laser elements have oscillation wavelengths different from each other, and the optical axis of the semiconductor laser element having the shortest wavelength is set at the optical axis center of the objective lens. It is characterized by the following.

According to the optical pickup as described above, since the optical system for emitting and receiving laser light is formed integrally with the movable part, the optical pickup for the case where the position of the objective lens changes is obtained.
It is possible to prevent an optical shift from occurring in the optical system. Further, since the optical axis of the semiconductor laser element having the shortest wavelength is aligned with the optical axis center of the objective lens, the influence of lens aberration and the like on the short-wavelength semiconductor laser element can be reduced, and the optical characteristics of the optical pickup deteriorate. Can be prevented. Furthermore, even if the objective lens follows the optical recording medium, the optical system moves as a unit, so that even if the position of the objective lens changes, the optical axis of the semiconductor laser element having the shortest wavelength is adjusted. The relationship coinciding with the optical axis center of the lens is maintained. For this reason, it is possible to prevent the optical characteristics from deteriorating without performing a special adjustment accompanying a change in the position of the objective lens.

In the optical pickup, the plurality of semiconductor laser elements are preferably elements included in a semiconductor laser element array having a plurality of oscillation wavelengths. According to the optical pickup as described above, it is possible to reduce the optical path interval of a plurality of laser beams emitted from the semiconductor laser element array, and to reduce the influence of lens aberration or the like on the plurality of laser beams.

Further, in the optical pickup, the semiconductor laser element array is formed on a first substrate formed on a substrate.
A first laser element having a first active layer made of a semiconductor and a second laser element formed on the substrate at a distance from the first laser element and having a larger energy gap than the first active layer. A second laser element having a second active layer made of a semiconductor, wherein a height of the first active layer from the substrate surface is substantially the same as a height of the second active layer from the substrate surface. Is preferred. According to the optical pickup as described above, it is possible to prevent variations in the height of the light emitting points of the laser beams having different wavelengths, to facilitate the optical adjustment of the optical pickup, and to suppress the lens aberration, thereby stabilizing the optical characteristics. it can.

In the above-mentioned optical pickup, the second laser device may be configured such that a height of the first active layer from the substrate surface is substantially the same as a height of the second active layer from the substrate surface. It is preferable to have a height adjusting buffer layer made of a third semiconductor of the first conductivity type. According to the optical pickup as described above, since the height of the first active layer and the second active layer from the substrate surface can be substantially matched by having the height adjusting buffer layer, lasers having different wavelengths can be used. Variations in the height of light emitting points can be prevented, optical adjustment of the optical pickup can be facilitated, lens aberrations can be suppressed, optical characteristics can be stabilized, and the crystallinity of the second active layer can be improved. The reliability of the laser device can be improved.

Further, in the optical pickup, it is preferable that a light receiving element for receiving return light from the optical recording medium is further mounted on the movable portion. According to the optical pickup as described above, the semiconductor laser element and the light receiving element are displaced integrally, so that the semiconductor laser element and the light receiving element can be integrated.

In the optical pickup, the plurality of semiconductor laser elements and the light receiving element are integrally formed with a substrate interposed therebetween, and the substrate reflects laser light emitted from the semiconductor laser element. Preferably, an inclined surface is formed. According to the optical pickup as described above, the semiconductor laser element and the light receiving element can be integrated on one semiconductor substrate, so that the movable part can be reduced in size and thickness.

In the optical pickup, the plurality of semiconductor laser elements are preferably elements included in a semiconductor laser element array having a plurality of oscillation wavelengths. According to the optical pickup as described above, a semiconductor laser element array having a plurality of oscillation wavelengths can be integrated and arranged at one place on a semiconductor substrate, and a plurality of separate semiconductor laser elements are arranged on the semiconductor substrate. Adjustment of the semiconductor laser element is easier than in the case.

Further, in the optical pickup, it is preferable that each of the support components is composed of a plurality of potential independent metal members, and at least one of the plurality of metal members is a power supply line for a semiconductor laser device. According to the optical pickup as described above, the wiring for driving the semiconductor laser element array to be mounted and the many electrode terminals necessary for the obtained signal output are also used as the supporting components, so that the wiring and the mounting of the flexible substrate are required. It can be unnecessary.

Further, in the optical pickup, a light receiving element for receiving return light from the optical recording medium is further mounted on the movable portion, and at least one of the plurality of metal members is supplied to the light receiving element. Preferably, it becomes an electric wire. Also in the above-described optical pickup, it is possible to eliminate the need for attaching a wiring or a flexible substrate.

Next, an information recording / reproducing apparatus according to the present invention is characterized in that the above-mentioned optical pickups are mounted. According to the information recording / reproducing apparatus as described above, since the optical pickup of the present invention is used, reproduction or recording can be performed on a plurality of optical recording media having different optimum wavelengths while preventing deterioration of optical characteristics. Thus, an information recording / reproducing apparatus with stable signal characteristics can be realized, and it is advantageous for miniaturization and thinning.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the drawings. The drawings used in the following description are only schematically shown to the extent that the present invention can be understood, and the present invention is not limited to only the examples shown in the drawings.

(Embodiment 1) FIG. 1 shows a configuration diagram of an optical pickup according to Embodiment 1 of the present invention, and is partially shown in a cross-sectional state for easy understanding of the configuration. In the pickup shown in this figure, an objective lens 1, an integrated element 2 of a semiconductor laser element array and a light receiving element, a mirror 3, a hologram optical element 4, a coil 5, and the like are mounted on a movable part 6. The movable part 6 is formed by using 20 support parts 8.
Is fixed to the base 7. The movable part 6 can swing in the focus direction and the tracking direction of the optical recording medium 12 by bending the support component 8.

Incidentally, 18 of the 20 supporting parts 8 are not shown because they are hidden behind the two shown. Although not shown, the end of the support component 8 is connected to a control circuit or the like by a flexible substrate or the like. Further, the light beam L1 represents both the laser light emitted from the semiconductor laser element array of the integrated element 2 and the return light from the optical recording medium.

The semiconductor laser device array of the integrated device 2 has a plurality of oscillation wavelengths, and the optical axis of the semiconductor laser device having the shortest wavelength is aligned with the optical axis center of the objective lens 1.

FIG. 3 shows a main part when the optical pickup shown in FIG. 1 is viewed from the direction of arrow A. Movable part 6
In addition, when the resin of the base 7 is molded, the support component 8 is embedded integrally with them. Further, the support component 8 is arranged symmetrically with respect to an II line passing through the center of the objective lens 1.

FIG. 4 is a sectional view taken along line II-II of FIG. A braking hole 13 is provided in the base 7 so as to surround the base end of the support component 8, and the inside thereof is filled with a viscoelastic gel-like braking member 14 to suppress occurrence of resonance. As the gel braking member 14, a UV-curable silicone-based gel material was used.

The support component 8 is made of a metal material. Stable control is possible by using phosphor bronze, beryllium copper, titanium copper, or the like, which is harder and more elastic than copper, and is less likely to rust.

The support components 8 are independent of each other in terms of potential, and also serve as wiring for supplying power to and exchanging signals with the semiconductor laser element array and the light receiving element. FIG. 5 shows a cross-sectional view taken along the line III-III of FIG.
It can be seen that it is embedded and fixed in the base 7.

Further, as shown in FIG. 1, the coil 5 is attached to the movable portion 6, and the magnet 11 is attached to the yoke 10 attached to the optical base 9.
The coil 5 and the magnet 11 can form a magnetic circuit. Due to the magnetic force generated by this magnetic circuit,
The support component 8 can be curved, and the swing of the movable part 6 integrated with the support component 8 can be controlled in both the focus direction and the tracking direction.

FIG. 2 is a configuration diagram of an optical pickup according to another embodiment. The arrangement of each part in the movable part 6 is different from that of the embodiment shown in FIG. However, the configuration in which the objective lens 1, the semiconductor laser element array and the light receiving element integrated element 2, the mirror 3, the hologram optical element 4, and the coil 5 are mounted on the movable section 6 is the same as the configuration shown in FIG. The basic operation is the same as the configuration shown in FIG.

In this embodiment as described above, an integrated element 2 including a semiconductor laser element array and a light receiving element, and optical elements such as a mirror 3 are fixed to the objective lens 1. That is, since the optical system for emitting and receiving laser light is formed integrally with the movable part 6, the objective lens 1
When the position changes, it is possible to prevent occurrence of optical shift in the optical system. For this reason, when following the surface deflection of the optical recording medium 12 or the information recording sequence, it is possible to prevent the optical characteristics from deteriorating due to the occurrence of aberration or the like.

Further, in the present embodiment, the optical axis of the semiconductor laser element having the shortest wavelength among the semiconductor laser elements constituting the semiconductor laser element array of the integrated element 2 as described above is centered on the optical axis of the objective lens 1. I'm matching. As a result, laser light from a short-wavelength semiconductor laser device that is easily affected by lens aberration and the like passes near the optical axis of the objective lens 1 with a small degree of lens aberration. For this reason,
The influence of lens aberration and the like on the short-wavelength semiconductor laser device can be reduced, and deterioration of the optical characteristics of the optical pickup can be prevented.

This effect becomes more effective when the optical system is combined with the configuration in which the optical system is formed integrally with the movable portion 6 as described above. In other words, even if the objective lens 1 performs an operation of following the optical recording medium 12, the optical system moves together, so that even if the position of the objective lens 1 changes, the light of the semiconductor laser element having the shortest wavelength can be obtained. The relationship that the axis coincides with the center of the optical axis of the objective lens 1 remains unchanged. Therefore, even if the position of the objective lens 1 changes, the objective lens 1
The effect of preventing the deterioration of the optical characteristics can be obtained without performing any special adjustment accompanying the change in the position.

Although the present embodiment has been described with reference to the example of the semiconductor laser element array, the same effect can be obtained even when a plurality of semiconductor laser elements formed separately are used instead of an array.

The same effect can be obtained by soldering, UV resin bonding, bonding with molten glass, or the like to the end of the support component 8 not embedded in the housing.

It is preferable that the movable part 6, the base part 7, and the support part 8 are simultaneously resin-molded with a mold. This makes it possible to obtain a structure in which both the support component length and the stress are uniform.

(Embodiment 2) Embodiment 2 is an embodiment relating to a semiconductor laser device, and can be used for the optical pickup according to Embodiment 1.

FIG. 6 shows a sectional configuration of a semiconductor laser element array according to the second embodiment of the present invention. As shown in FIG. 6, an infrared semiconductor laser device 1 separated from each other by a separation groove 16 is provided on a substrate 15 made of n-type GaAs.
7A and the red semiconductor laser element 18A are formed monolithically.

The infrared semiconductor laser element 17A is
The layers shown below are sequentially formed on the top. A buffer layer 19 made of n-type GaAs on the substrate 15 and improving the crystallinity of each semiconductor layer grown on the substrate 15
Are formed.

On the buffer layer 19, an n-type Al _x Ga
_{A first} n-type cladding layer 20 is formed of _1-x As (0 <x ≦ 1) and confines carriers (electrons) and recombination light of carriers in a first active layer described later.

On the first n-type cladding layer 20, AlG having a composition having an oscillation wavelength of 750 nm to 850 nm is formed.
A first active layer 21 made of aAs is formed. First
On the active layer 21, p-type Al _X1 Ga _1-x1 As (0 <x
1 ≦ 1), and a first p-type cladding layer 22 for confining carriers (holes) and recombination light of carriers is formed in the first active layer 21.

The first p-type cladding layer 22 is made of p-type Al _x2 Ga _1-x2 As (0 ≦ x2 ≦ 1) and serves as an etching stopper when an opening of the first current block layer described later is formed. A second p-type cladding layer 23 is formed.

On the second p-type cladding layer 23, an energy gap (band gap) larger than the energy of light emitted from the first active layer 21 is provided.
An n-type Al _y1 Ga _{1 -y 1} As (0 <y 1 ≦ ₁ ) having an opening 24 a for forming a stripe-shaped current channel in 1 (the opening 24 a extends in the vertical direction in the drawing).
The first current blocking layer 24 of 1) is formed.

On the first current block layer 24, a p-type A
Opening 24 made of l _x3 Ga _1-x3 As (0 <x3 ≦ 1)
a third p-type cladding layer 2 formed to fill a
5 are formed.

On the third p-type cladding layer 25, a first p-type contact layer 26 made of p-type GaAs and in ohmic contact with a first p-side electrode (not shown) formed on the upper surface thereof is formed. Have been.

The red semiconductor laser element 18 A is provided on the buffer layer 19 with the infrared semiconductor laser element 17 A and the separation groove 16.
Each layer shown below is formed sequentially. On the buffer layer 19, the crystallinity of each semiconductor layer grown on the substrate 15 is improved, and the heights of the first active layer 21 and a second active layer, which will be described later, from the surface of the substrate 15 match. N-type G of the first conductivity type whose film thickness is adjusted
A height adjusting buffer layer 27 made of aAs is formed.

The n-type (Al _z Ga _{1 -z} ) _0.5 In _0.5 P (0 <z ≦ 1) is formed on the height adjusting buffer layer 27, and carriers (electrons) are added to a second active layer described later. In addition, a second n-type clad layer 28 for confining recombination light of carriers is formed.

On the second n-type cladding layer 28, AlG having a composition having an oscillation wavelength of 635 nm to 680 nm is formed.
A second active layer 29 having a multiple quantum well structure made of aInP is formed.

On the second active layer 29, a p-type (Al _x4 G
a _1-x4 ) _0.5 In _0.5 P (0 <x4 ≦ 1), and a fourth p-type cladding layer 30 for confining carriers (holes) and recombination light of carriers is formed in the second active layer 29. .

The fourth p-type cladding layer 30 is made of p-type (Al _x5 Ga _{1 -x5} ) _0.5 In _0.5 P (0 ≦ x5 ≦ 1) and has an opening of a second current block layer to be described later. A fifth p-type cladding layer 31 serving as an etching stopper at the time of formation is formed.

The fifth p-type cladding layer 31 has an energy gap larger than the energy of the light emitted from the second active layer 29, and forms a stripe-shaped current channel in the second active layer 29. First current blocking layer 2
N-type (Al _y2 Ga _1-y2 ) _0.5 In _0.5 P (0 <y2 ≦
A second current block layer 32 of 1) is formed.

On the second current block layer 32, a sixth layer made of p-type (Al _x6 Ga _1-x6 ) _0.5 In _0.5 P (0 <x6 ≦ 1) is formed to fill the opening 32a. P
A mold cladding layer 33 is formed.

On the sixth p-type cladding layer 33, a second p-type contact layer 3 made of p-type GaAs and in ohmic contact with a second p-side electrode (not shown) formed on the upper surface.
4 are formed.

Light emitting point S1 of infrared semiconductor laser element 17A
D1 between the light emitting point S2 of the red semiconductor laser element 18A and the light emitting point S1
Can be controlled with the accuracy of photolithography in the semiconductor diffusion process, so that the distance and distance can be made very high in accuracy and short as compared with those in which a laser chip is assembled in a hybrid manner.

Here, the separation groove 16 is in a state where the upper surface of the buffer layer 19 is exposed, but may be in a state where the substrate 15 is exposed. Further, the buffer layer 27 for height adjustment of the red semiconductor laser element 18A may also serve as the buffer layer 19.

Here, in the infrared semiconductor laser device 17A according to the present embodiment, the effective refractive index n1 in the direction perpendicular to the substrate surface in the region included in the opening 24a of the first current blocking layer 24, and the opening Difference Δn from the effective refractive index n2 perpendicular to the substrate surface in the region excluding 24a
Is a refractive index waveguide type laser element in which structural parameters such as the thickness of each semiconductor layer and the composition of Al are set so that is about 2 × 10 ⁻³ to about 1 × 10 ⁻² .

Similarly, also in the red semiconductor laser device 18A according to the present embodiment, the effective refractive index n1 in the direction perpendicular to the substrate surface in the region included in the opening 32a of the second current block layer 32, and the opening The difference Δ from the effective refractive index n2 perpendicular to the substrate surface in the region excluding 32a
A refractive index guided laser device in which structural parameters such as the thickness of each semiconductor layer and the composition of Al are set so that n is about 2 × 10 ⁻³ to about 1 × 10 ⁻² .

An example of structural parameters for giving the infrared semiconductor laser device 17A and the red semiconductor laser device 18A self-sustained pulsation characteristics required for noise reduction will be described below with reference to the drawings.

FIG. 8 shows the thickness of the first p-type cladding layer 22 and the Al composition x3 of the third p-type cladding layer 25 in the infrared semiconductor laser device 17A according to the present embodiment, and the effective refractive index difference Δn. Are obtained by calculation. Here, other structural parameters are set as follows. That is, the thickness of the first n-type cladding layer 20 is set to about 1.5 μm, and the Al composition x is set to 0.5.
The thickness of the first active layer 21 is about 0.06 μm. The Al composition x1 of the first p-type cladding layer 22 is set to 0.5. The thickness of the second p-type cladding layer 23 is about 0.01 μm.
m, and the Al composition x2 is 0.2. The thickness of the first current block layer 24 is set to about 1 μm, and the Al composition y1 is set to 0.65. The thickness of the third p-type cladding layer 25 is about 2.2 μm.

As can be seen from FIG. 8, the smaller the thickness dp of the first p-type cladding layer 22 and the smaller the Al composition X3 of the third p-type cladding layer 25, the smaller the effective refractive index difference Δ
n increases. In order to obtain stable self-sustained pulsation characteristics, it is necessary to satisfy an effective refractive index difference Δn = 2 × 10 ^{−3 to} 5 × 10 ⁻³ . For example, when the thickness dp of the first p-type cladding layer 22 is 0.20 μm, the Al composition X3 of the third p-type cladding layer 25 may be about 0.61 to 0.74. You can see that.

The effective refractive index difference Δn = 2 shown in FIG.
The combination of structural parameters for realizing × 10 ^-3 ~5 × 10 ^-3 is only an example, changing the other structural parameters (Al composition and the film thickness of each semiconductor layer), the appropriate combination is changed Needless to say.

Similarly, also in the red semiconductor laser element 18A, the self-excited oscillation characteristics can be improved by appropriately selecting structural parameters for realizing the effective refractive index difference Δn = 2 × 10 ^{−3 to} 5 × 10 ^−3. Can be realized. For example,
The Al composition z of the second n-type cladding layer 28 is set to 0.7,
The oscillation wavelength of the second active layer 29 is 635 nm to 680 nm. The Al composition x4 of the fourth p-type cladding layer 30 is set to 0.1.
7 and a film thickness of about 0.1 μm to 0.3 μm. Fifth
The Al composition x5 of the p-type cladding layer 31 of 0.0 to 0.1
And the film thickness is about 0.009 μm. The Al composition y2 of the second current block layer 32 is set to 0.5, and the Al composition x6 of the sixth p-type cladding layer 33 is set to 0.6 to 0.75.
Thereby, an effective refractive index difference Δn = 2 × 10 ^{−3 to} 5 × 10 ⁻³ in the red semiconductor laser element 18A can be realized.

As shown in FIG. 6, the red semiconductor laser device 18A according to the present embodiment is such that each semiconductor of the red semiconductor laser device 18A is disposed between the buffer layer 19 and the second n-type cladding layer 28. In addition to improving the quality of the crystal, the infrared semiconductor laser device 17A from the surface of the substrate 15
The height of the first active layer 21 and the second height from the surface of the substrate 15.
A height adjusting buffer 27 for adjusting the height of the active layer 29 to be substantially the same is provided.

For example, when relatively high output operation is to be performed on the infrared semiconductor laser element 17A and the red semiconductor laser element 18A, the thickness of the first n-type cladding layer 20 should be 2.0 μm or more. On the other hand, the thickness of the second n-type cladding layer 28 may be 1.5 μm or more.
Therefore, in this case, the thickness of the height adjusting buffer layer 27 may be about 0.5 μm.

For relatively low output operation, the thickness of the first n-type cladding layer 20 is 1.5 μm.
The above is necessary, and the thickness of the second n-type cladding layer 28 needs to be 1.1 μm or more. Therefore, in this case,
The thickness of the height adjustment buffer layer 27 may be about 0.4 μm.

As described above, the surface of the substrate 15 is adjusted by adjusting the thickness of the buffer layer 27 for height adjustment in both the semiconductor laser element array for high-output operation and the semiconductor laser element array for low-output operation. The height of the first active layer 21 and the height of the second active layer 29 as a reference can be made equal, and variation in the height of the light emitting point can be prevented.

As described above, according to the present embodiment, a self-pulsation type semiconductor laser device array can be realized, and a high-output operation can be performed. Further, as described above, the red semiconductor laser element 18A on the short wavelength side of the two-wavelength laser element array has the first active layer 21 and the second active layer 29.
Is provided with a height adjusting buffer layer 27 for suppressing a variation in height from the substrate surface. That is, since the heights of the light emitting points of the respective semiconductor elements are standardized in advance, when the semiconductor laser element array according to the present embodiment is incorporated in an information recording / reproducing apparatus, it is easy to adjust the alignment with the optical system components. Becomes

The distance D1 between the light emitting point S1 of the infrared semiconductor laser element 17A and the light emitting point S2 of the red semiconductor laser element 18A can be controlled with the accuracy of photolithography in the semiconductor diffusion process. It is possible to achieve extremely high precision and a short distance as compared with.

The height of the light emitting point S1 of the infrared semiconductor laser element 17A and the light emitting point S1 of the red semiconductor laser element 18A
Assuming that the difference from the height of 2 is D2, the distance D3 between S1 and S2 is expressed by the following equation (1).

Equation (1) D3 = (D1 ² + D2 ² ) ^1/2 However, since the height adjusting buffer layer 27 is provided,
Since D2 ≒ 0 and D3 ≒ D1, D3 can be made the shortest distance with very high accuracy, and lens aberration can be suppressed. Therefore, as in the first embodiment, of the semiconductor laser elements constituting the semiconductor laser element array, the semiconductor laser element having the shortest wavelength (the red semiconductor element 18 in the example of FIG. 8).
When A) is aligned with the center of the optical axis of the objective lens 1, the deviation from the optical axis of the semiconductor laser element having the shortest wavelength can be minimized, so that the influence of lens aberration and the like on the short-wavelength semiconductor laser element is reduced. Therefore, the effect that the optical characteristics of the optical pickup can be prevented from deteriorating is further enhanced.

When a high-power laser beam required for a writable optical disk is required, the effective refractive index difference Δn is set to 4 × 10 ⁻³ to 1 × 10 ⁻² , so that the horizontal Since the mode is further stabilized, a high-output semiconductor laser element array can be realized.

(Embodiment 3) FIG. 7 shows a cross-sectional configuration of a semiconductor laser device array according to Embodiment 3 of the present invention. As shown in FIG. 7, an infrared semiconductor laser device 17B and a red semiconductor laser device 18B separated by a separation groove 16 are monolithically formed on a substrate 15 made of n-type GaAs.

The infrared semiconductor laser element 17B is
Each layer shown below is formed sequentially. On the substrate 15, a buffer layer 19 made of n-type GaAs is formed. On the buffer layer 19, an n-type Al _x
A _first n-type cladding layer 20 made of Ga _1-x As (0 <x ≦ 1) is formed.

On the first n-type cladding layer 20, AlGa having a composition having an oscillation wavelength of 750 nm to 850 nm is provided.
A first active layer 21 made of As is formed.

On the first active layer 21, p-type Al _x1 Ga
_{A first} p-type cladding layer 22 made of _1-x1 As (0 <x1 ≦ 1) is formed, and p-type _{Alx2Ga1 -x2As} is formed thereon.
A second p-type cladding layer 23 (0 ≦ x2 ≦ 1) is formed.

On the second p-type cladding layer 23, a third p-type made of p-type Al _x3 Ga _1-x3 As (0 <x3 ≦ 1) and having a ridge shape extending in the vertical direction in the drawing. A cladding layer 35 is formed. On the second p-type cladding layer 23, further formed on the second p-type cladding layer 23 in a region beside the third p-type cladding layer 35,
N-type Al _y1 Ga _{1 -y1} As (0 <) having an energy gap larger than the energy of light emitted from the active layer 21
A first current blocking layer 36 of y1 ≦ 1) is formed.

On the third p-type cladding layer 35 and the first current blocking layer 36, the third p-type GaAs formed on the entire surface including the third p-type cladding layer 35 is formed on the upper surface thereof. A first p-type contact layer 37 in ohmic contact with a 1p-side electrode (not shown) is formed.

The red semiconductor laser element 18 B is provided on the buffer layer 19 with the infrared semiconductor laser element 17 B and the separation groove 16.
Each layer shown below is formed sequentially. On the buffer layer 19, the crystallinity of each semiconductor layer grown on the substrate 15 is improved, and the height of the first active layer 21 and a second active layer, which will be described later, from the surface of the substrate 15 match. A height-adjusting buffer layer 27 made of n-type GaAs of the first conductivity type whose film thickness is adjusted is formed.

A second n-type cladding layer 28 of n-type (Al _z Ga _{1 -z} ) _0.5 In _0.5 P (0 <z ≦ 1) is formed on the height adjusting buffer layer 27. I have. The second n
The oscillation wavelength is 635 nm to 68
A second active layer 29 having a multiple quantum well structure made of AlGaInP having a composition of 0 nm is formed.

On the second active layer 29, a p-type (Al _{x 4} G
A fourth p-type cladding layer 30 made of a _1-x4 ) _0.5 In _0.5 P (0 <x4 ≦ 1) is formed, and a p-type (Al _x5 Ga _1-x5 ) _0.5 In _0.5 P layer is formed thereon. A fifth p-type cladding layer 31 composed of (0 ≦ x5 ≦ 1) is formed.

The fifth p-type cladding layer 31 is made of p-type (Al _x6 Ga _{1 -x6} ) _0.5 In _0.5 P (0 <x6 ≦ 1) and is substantially parallel to the third p-type cladding layer 35. A sixth p-type cladding layer 38 having a ridge shape extending in the vertical direction is formed. On the fifth p-type cladding layer 31, a light-emitting light from the second active layer 21 is formed in a region on the fifth p-type cladding layer 31 beside the sixth p-type cladding layer 38. N-type (Al _y2 Ga _1-y2 ) _0.5 In _0.5 P (0 <y2 ≦
A second current blocking layer 39 of 1) is formed.

On the sixth p-type cladding layer 38 and the second current blocking layer 39, p-type GaAs is formed on the entire surface including the sixth p-type cladding layer 38 and is formed on the upper surface thereof. A second p-type contact layer 40 in ohmic contact with a second p-side electrode (not shown) is formed.

Also in this embodiment, as shown in Embodiment 2, the effective refractive index difference Δn = 2 × 10 with respect to the infrared semiconductor laser element 17B and the red semiconductor laser element 18B.
By selecting structural parameters for realizing ^-3 to 5 × 10 ^-3 appropriately, it is possible to realize a self-pulsation characteristics. The effect of the height adjusting buffer layer 27 is the same as that of the second embodiment.

(Embodiment 4) FIG. 9 is a perspective view of an integrated element used for an optical pickup according to Embodiment 4 of the present invention. The integrated device shown in this figure is one in which a semiconductor laser device array and a light receiving device are integrally arranged, and is mounted on a movable portion (the movable portion 6 in the examples of FIGS. 1 and 2). Specifically, a semiconductor laser element array 41 is provided on a semiconductor substrate 44, and the semiconductor laser element array 4
An inclined surface 43 is formed at a position close to 1. The laser beam from the semiconductor laser element array 41 is reflected by the inclined surface 43 so that the optical axis thereof is perpendicular to the surface of the semiconductor substrate 44 as shown by the arrow a in the figure. In this embodiment, the inclined surface 43 is formed by etching a Si substrate. Further, on a semiconductor substrate 44 which is the same substrate, a plurality of divided light receiving elements 42 are arranged around the inclined surface 43.

FIG. 10 is a side view of an integrated device according to another example. Second semiconductor substrate 4 on semiconductor substrate 44
6, a semiconductor laser element array 41, and a prism 45 are provided. The prism 45 has an inclined surface 43, and as shown by an arrow b in the drawing, the laser beam from the semiconductor laser
4 is perpendicular to the surface. Further, a plurality of divided light receiving elements 42 are provided below the prism 45, and receive return light indicated by an arrow c.

According to this embodiment, since the semiconductor laser element array, the plurality of light receiving elements, and the inclined surface are integrated on the semiconductor substrate, that is, they are not separately arranged but are integrated via the same substrate. , The size of the optical pickup can be reduced, and the influence of aberration of the optical system can be suppressed.

In this embodiment, when the semiconductor laser element having the shortest wavelength among the semiconductor laser elements constituting the semiconductor laser element array is aligned with the center of the optical axis of the objective lens, the lens aberration with respect to the short-wavelength semiconductor laser element is obtained. As in the above embodiments, it is possible to reduce the influences of the optical pickup and to prevent the optical characteristics of the optical pickup from deteriorating.

(Embodiment 5) FIG. 11 is a perspective view of an information recording / reproducing apparatus according to Embodiment 5 of the present invention.
In the present embodiment, at least the optical pickup according to any of the above embodiments is used.

With this configuration, reproduction or recording can be performed on a plurality of optical recording media having different optimum wavelengths while preventing deterioration of optical characteristics, and an information recording / reproducing apparatus with stable signal characteristics can be realized. It can also be made smaller and thinner. FIG. 12 is a perspective view of a notebook computer using the information recording / reproducing apparatus according to the present embodiment.
According to the notebook personal computer as shown in the figure, since the information recording / reproducing apparatus according to the present embodiment is used, a plurality of optical recording media having different optimal wavelengths are prevented from deteriorating in optical characteristics. Playback or recording can be performed, and it is also useful for reducing the size and thickness of a notebook computer.

[0096]

As described above, according to the present invention, since the optical system for emitting and receiving laser light is formed integrally with the movable part, the optical system in the optical system when the position of the objective lens changes. It is possible to prevent the occurrence of a deviation. Further, since the optical axis of the semiconductor laser element having the shortest wavelength is aligned with the optical axis center of the objective lens, the influence of lens aberration and the like on the short-wavelength semiconductor laser element can be reduced, and the optical characteristics of the optical pickup deteriorate. Can be prevented.
Furthermore, even if the objective lens follows the optical recording medium, the optical system moves together, so that even if the position of the objective lens changes, the optical axis of the semiconductor laser element having the shortest wavelength is adjusted. The relationship that coincides with the center of the optical axis of the lens is maintained. For this reason, it is possible to prevent the optical characteristics from deteriorating without performing special adjustment accompanying a change in the position of the objective lens.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a sectional configuration diagram of an optical pickup according to another example of Embodiment 1 of the present invention.

FIG. 3 is a top configuration diagram of the optical pickup shown in FIG. 1;

FIG. 4 is a sectional view taken along the line II-II of FIG. 3;

FIG. 5 is a sectional view taken along line III-III in FIG. 4;

FIG. 6 is a sectional configuration diagram of a semiconductor laser element array according to a second embodiment of the present invention;

FIG. 7 is a sectional configuration diagram of a semiconductor laser element array according to a third embodiment of the present invention;

FIG. 8 is a diagram showing a first p of an infrared semiconductor laser device in the semiconductor laser device array according to the second embodiment of the present invention;
Showing the relationship between the effective refractive index Δn and the film thickness of the p-type cladding layer and the Al composition of the third p-type cladding layer

FIG. 9 is a perspective view of an integrated device in which a semiconductor laser device array and a light receiving device according to a fourth embodiment of the present invention are integrated.

FIG. 10 is a side view of an integrated device in which a semiconductor laser device array and a light receiving device according to another example of Embodiment 4 of the present invention are integrated.

FIG. 11 is a perspective view of an information recording / reproducing device according to a fifth embodiment of the present invention.

FIG. 12 is a perspective view of a notebook computer equipped with an information recording / reproducing device according to Embodiment 5 of the present invention.

FIG. 13 is a sectional view showing an example of a conventional optical pickup.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Integrated element of semiconductor laser and light receiving element 3 Mirror 4 Hologram optical element 5 Coil 6 Movable part 7 Base 8 Supporting component 9 Optical base 10 Yoke 11 Magnet 12 Optical recording medium 13 Braking hole 14 Gel-like braking member 15 Substrate 16 Separation groove 17A, 17B Infrared semiconductor laser device 18A, 18B Red semiconductor laser device 19 Buffer layer 20 First n-type cladding layer 21 First active layer 22 First p-type cladding layer 23, 28 Second p Type cladding layer 24, 36 first current blocking layer 24a, 32a opening 25, 35 third p-type cladding layer 26, 37 first p-type contact layer 27 height adjusting buffer layer 29 second active layer 30 4 p-type cladding layer 31 fifth p-type cladding layer 32, 39 second current blocking layer 33, 38 sixth p-type cladding layer Head layer 34, 40 a second p-type contact layer 41 semiconductor laser device array 42 light-receiving element 43 inclined surface 44 semiconductor substrate 45 prism 46 second semiconductor substrate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaaki Yuri 1006 Kadoma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. F term (reference) 5D118 AA13 CC12 CG07 DC03 FB12 5D119 AA02 AA41 AA43 CA09 EC01 EC45 EC47 FA05 FA09 FA34

Claims (10)

[Claims] A movable section on which at least a plurality of semiconductor laser elements for irradiating a laser beam onto an optical recording medium, an objective lens for condensing laser light emitted from the semiconductor laser element, and the movable section are mounted. A supporting part that connects the movable part and the base so that the movable part swings in a focus direction and a tracking direction of the optical recording medium; and An optical pickup characterized in that at least two have different oscillation wavelengths, and the optical axis of the semiconductor laser element having the shortest wavelength is aligned with the optical axis center of the objective lens. 2. The optical pickup according to claim 1, wherein the plurality of semiconductor laser elements are elements included in a semiconductor laser element array having a plurality of oscillation wavelengths. 3. The semiconductor laser device array includes a first laser device having a first active layer made of a first semiconductor formed on a substrate, and an interval between the first laser device on the substrate. Formed of a second semiconductor having a larger energy gap than the first active layer.
And a second laser element having an active layer, wherein the height of the first active layer from the substrate surface is substantially the same as the height of the second active layer from the substrate surface. Optical pickup. 4. The second laser device, wherein the first conductive layer is formed such that a height of the first active layer from the substrate surface is substantially equal to a height of the second active layer from the substrate surface. The optical pickup according to claim 3, further comprising a height adjusting buffer layer made of a third semiconductor. 5. The optical pickup according to claim 1, wherein a light receiving element for receiving return light from the optical recording medium is further mounted on the movable portion. 6. The semiconductor laser device and the light receiving device are integrally formed with a substrate interposed therebetween, and the substrate has an inclined surface that reflects laser light emitted from the semiconductor laser device. The optical pickup according to claim 5. 7. The optical pickup according to claim 6, wherein the plurality of semiconductor laser elements are elements included in a semiconductor laser element array having a plurality of oscillation wavelengths. 8. The optical pickup according to claim 1, wherein each of the support components is composed of a plurality of metal members that are electrically independent from each other, and at least one of the plurality of metal members is a power supply line to the semiconductor laser element. 9. A light receiving element for receiving return light from the optical recording medium is further mounted on the movable portion, and at least one of the plurality of metal members serves as a power supply line for the light receiving element. An optical pickup according to claim 1. 10. An information recording / reproducing apparatus equipped with the optical pickup according to claim 1.