JPH07162100A - Semiconductor laser device and its drive method - Google Patents

Abstract

PURPOSE:To make it possible to move the position to emit laser beams of a semiconductor laser, to fix the emitting position even when a laser beam moves, and to form the laser beam in symmetry with respect to its peak. CONSTITUTION:In a semiconductor laser device where at least three stripe electrodes 9A-9D which can be controlled independently and extend in the resonator direction are arranged side by side in a direction orthogonal to the resonator direction, width and gap of the stripe electrodes 9A-9D are made smaller than a carrier diffusion length, and current is injected simultaneously from at least three stripe electrodes so as to complementarily change the amount of current injected from stripe electrodes on both sides of the three stripe electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device used as a light source in a laser beam printer, an optical disk device or the like, and more particularly, to controlling the injection current to move the beam position of the laser beam on the emission surface. The present invention relates to a semiconductor laser device capable of manufacturing. The present invention also relates to a tracking mechanism of an optical disk device using a semiconductor laser device capable of moving the beam position of laser light, and an image recording device such as a laser beam printer.

[0002]

2. Description of the Related Art For example, in a laser beam printer, a laser beam emitted from a semiconductor laser is deflected by being reflected by a rotating polygon mirror to scan the surface of a photoconductor in the main scanning direction. Further, in the optical disk device, a movable optical system driven by a servo motor is used in order to match the irradiation position of the laser beam with the recording track.

However, the rotary polygon mirror and the movable optical system have a complicated structure and a large size, and since the laser beam is mechanically scanned, there is a problem that the high speed operation is limited.

In order to solve this problem, a technique of directly scanning a laser beam emitted from a semiconductor laser on the emission surface of the semiconductor laser has been proposed (for example, DR Scifres et al .: "Beam scan").
ning with twin-stripe inj
section lasers ", Appl. Phys.
Lett. 33 (8), 15 October, 197
8, pp. 702-704, JP-A-3-57633, JP-A-63-23383, etc.).

For example, in the above-mentioned Japanese Patent Laid-Open No. 63-23383, an optical waveguide having a forbidden band width wider than the active layer of the semiconductor laser is provided on one cavity end face side of the semiconductor laser having two injection electrodes. A light beam deflection type semiconductor laser is proposed in which a region is formed and one or a plurality of stripe-shaped current inflow regions are formed in the optical waveguide region in the same direction as the optical resonator direction.

In the semiconductor laser section, two injection electrodes flow currents independently of each other, and the phase of light is modulated by the gradient of the injection carrier concentration.
The wavefront of light in the active layer is bent, and the outgoing beam is deflected.
Further, the deflected beam is introduced into the optical waveguide portion, carriers are injected by a plurality of injection electrodes provided in the optical waveguide, and the phase is modulated in the optical waveguide.
By appropriately selecting the injection current value here, the beam position on the emitting surface when emitted from the optical waveguide can be moved.

However, the above-mentioned Japanese Patent Laid-Open No. 63-2338.
In the structure described in Japanese Patent Publication No. 3, the active layer and the optical waveguide layer having different forbidden band widths must be formed on the same substrate, and there is a problem that it is very difficult to form such a semiconductor layer. Further, in order to largely move the emission position of the laser beam, the optical waveguide region must be formed long.
However, when the optical waveguide region is lengthened in this way, there is a problem that optical loss due to spread of light in the optical waveguide region and optical loss due to optical absorption by free carriers in the optical waveguide region increase. Further, since the emission angle is different depending on the emission position, there is a problem that the amount of light incident on the collimator lens provided for collimating the laser beam emitted from the semiconductor laser changes depending on the emission position. In addition, since the phase is modulated in the optical waveguide region, the spot shape of the laser beam on the emission surface is also distorted in the deflection direction when the laser beam is deflected and becomes asymmetric, which changes depending on the emission position. .

The above Appl. Phys. Let
t. 33 (8), 15 October, 1978, p.
p. In 702-704 and Japanese Patent Laid-Open No. 3-57633, when the carrier density in the active layer is asymmetric with respect to the cavity direction, the refractive index distribution in the active layer caused by the injected carriers is also asymmetric, and the emitted laser is emitted. It is disclosed that the beam is deflected. This is 2
When carrier is injected from the striped electrodes of the book,
This is because the carrier density distribution in the active layer becomes asymmetric.

However, such asymmetric carrier density distribution causes a problem that the cross section, that is, the profile of the laser beam is distorted. In particular, when the distance between the electrodes becomes longer than the diffusion length, the carrier density distribution becomes bimodal and the asymmetry becomes stronger, and the asymmetry strongly depends on the distance between the adjacent strip electrodes.
Therefore, the distortion of the cross section of the laser beam becomes more remarkable. Further, since the scanning is performed by deflecting the laser beam, the laser beam is obliquely incident on the irradiation surface at the left and right ends of the deflection, and the shape of the beam spot on the irradiation surface is distorted. I will end up.

When the profile of the laser beam or the shape of the beam spot on the irradiation surface is distorted, the recording density or recording quality when recording information or an image using a laser beam in an optical disc device or an image recording device is deteriorated. There is a problem of deterioration.

[0011]

Therefore, an object of the present invention is to move the emitting position of the laser beam of the semiconductor laser without providing an optical waveguide region separately from the semiconductor laser region, and to emit the laser beam by moving the laser beam. An object of the present invention is to provide a semiconductor laser device in which the direction is constant and the shape of the laser beam is symmetric about its peak.

[0012]

The present invention comprises at least 3
In a semiconductor laser device in which two stripe-shaped electrodes extending in the cavity direction, which are independently controllable, are arranged side by side in a direction perpendicular to the cavity direction, the width and interval of the stripe-shaped electrodes are made smaller than the diffusion length of carriers. It is characterized by

The present invention is also the method for driving a semiconductor laser device as described above, wherein current is simultaneously injected from the at least three stripe-shaped electrodes and is injected from the stripe-shaped electrodes on both sides of the three stripe-shaped electrodes. It is characterized in that the amount of current is changed complementarily.

[0014]

The operation of the present invention will be described in detail with reference to FIGS. 1 and 2.

FIG. 1A is a schematic sectional view of a semiconductor laser device having one stripe-shaped electrode, and FIG.
It is explanatory drawing which shows the carrier density distribution of the semiconductor laser device shown to the same figure (a).

Perpendicular to the emission direction of the laser beam,
In a so-called gain-guided laser that does not have a light confinement structure in the lateral direction along the active layer, laser oscillation occurs at the position where the light is most gained, that is, the position where the carrier density is highest in the active layer. . In the gain-guided laser, as shown in FIG. 1A, a first clad layer 52, an active layer 53, a second clad layer 54, and a contact layer 55 are sequentially laminated on a substrate 51. Contact layer 55
Striped electrodes 56 are formed on the upper surface of the substrate 5
The electrode 57 is also formed on the entire back surface of No. 1.

In the structure of the semiconductor laser having one stripe-shaped electrode 56 as shown in FIG. 1A, carriers injected from the stripe-shaped electrode 56 are usually in the contact layer 55 and the first cladding layer 54. It spreads and further diffuses laterally in the active layer 53, and its diffusion length is estimated to be approximately 2 to 3 μm. Therefore, the carrier density distribution in the active layer 53 has a shape as shown in FIG. 1B, and the gain is almost proportional to the carrier density. Therefore, the gain distribution is similar to this carrier density.

Therefore, in the present invention, as shown in FIG. 2A, three or more stripe-shaped electrodes 56A, 56B, whose width and adjacent distance are about the diffusion length of carriers or shorter than the diffusion length of carriers, 56C is formed. The carrier density distributions when carriers are individually injected from the respective electrodes 56A, 56B, and 56C are the thin lines indicated by A, B, and C in FIG. 2B, but if carriers are injected simultaneously from the respective electrodes, , Because these electrodes are closer than the diffusion length of the carriers, they are superposed on each other as shown in FIG.
As shown by the thick line in (b), the carrier density distribution has a single peak, a single gain region is formed, and one laser beam is emitted.

As described above, the shape of the carrier density distribution can be changed by bringing the electrodes closer than the diffusion length of carriers and controlling the injection amount of carriers from each electrode independently.

Therefore, the peak position of the carrier density distribution can be continuously moved from one electrode to the other electrode by changing the amount of carriers injected into the two electrodes in a complementary manner. Since the emitting position of the laser beam coincides with the peak position of the carrier density distribution, the emitting position of the laser beam can be continuously moved. That is, it becomes possible to control the emission position of the laser beam with an accuracy equal to or less than the electrode interval.

Further, when the position of the laser beam is moved only by two electrodes, if the distance between the adjacent electrodes is longer than the diffusion length of carriers, a region where carriers cannot be injected occurs between the electrodes and the laser beam is generated. The beam cannot be moved continuously. Therefore, the distance between adjacent electrodes is limited to about the diffusion length of carriers, and the distance that the laser beam can move is also limited to about several μm.

Therefore, a large number of striped electrodes having a width and a distance adjacent to each other are equal to or shorter than the diffusion length of carriers or shorter than that, and a plurality of electrodes adjacent to each other are selected to inject the carriers. As a result, the gain region can be formed at a desired position in a wide range where the striped electrodes are formed, and the laser beam can be emitted. Furthermore, by injecting carriers from several electrodes and emitting a laser beam from a specific position, by continuously changing the injection amount of carriers to adjacent electrodes, the laser beam emitted from the semiconductor laser The emission position can be continuously moved over a wide range in the lateral direction along the active layer.

As described above, by making the distance between adjacent striped electrodes shorter than the diffusion length of carriers, the carrier density distribution can be made unimodal and asymmetry can be suppressed.

Further, when the position of the laser beam is moved between the electrodes by two electrodes, the shape of the carrier density distribution is uniquely determined when the position of the laser beam and the optical output are determined, so that it is asymmetrical. It is not possible to correct the lost carrier density distribution. Therefore, if the carrier density distribution forming one gain region is always formed by injecting carriers from three or more electrodes and the position of the laser beam is moved, the degree of freedom increases as the number of electrodes increases, Even if the position of the laser beam and the optical output are determined, it is possible to change the shape of the carrier density distribution and correct it so that it becomes a symmetrical shape. Therefore, an arbitrary carrier density distribution can be formed by further increasing the number of electrodes for forming the carrier density distribution forming one gain region.

In general, in the gain-guided laser, the transverse mode is unstable and the far-field pattern is likely to be bimodal. According to 934 (1992), even in a semiconductor laser having a gain-guiding structure, by providing a recess in the center of the carrier density distribution in the active layer, it becomes a refractive index-guiding property, and a stable transverse mode and unimodal property It has been reported that far-field images can be obtained. This is because the effective refractive index in the recessed region increases because the refractive index changes depending on the carrier density. However, in this case, since the gain region is formed by the two electrodes, the range in which the carrier density distribution having the depression is provided is narrow to a part between the electrodes.

Therefore, carriers are injected from a plurality of electrodes, and at that time, the amount of carriers injected from the central electrode is reduced as compared with the amount of carriers injected from both ends to form a recess in the carrier density distribution. By continuously changing the injection amount of carriers to the adjacent electrodes as described above, it becomes possible to move the laser beam of the single-peaked far-field pattern in a stable transverse mode.

Further, in order to finely control the movement of the emitted laser beam, the electrodes are separated before and after the resonator direction. Then, on the emission side, the lateral spread of the carriers from the electrode is changed to change the lateral refractive index to confine the light and control the transverse mode of the emitted laser beam. On the other hand, on the side opposite to the emission side, the light output is controlled by changing the injection amount of carriers from the electrode. As a result, the light output can be changed independently of the lateral mode, so that the degree of freedom in controlling the lateral mode is increased.

[0028]

FIG. 3 is a perspective view of a semiconductor laser device showing a first embodiment of the present invention.

In FIG. 3, 1 is an n-type GaAs substrate and 2 is
Is n-type GaAs first buffer layer, 3 is n-type Al _0.2 Ga
_0.8 As Second buffer layer, 4 is n-type Al _0.4 Ga _0.6 A
s Third buffer layer, 5 n-type Al _0.6 Ga _0.4 As first cladding layer, 6 quantum well active layer, 7 p-type Al _0.6 G
a _0.4 As second clad layer, 8 p-type GaAs contact layer, 9A to 9H each independently provided stripe-shaped p-side electrode, 10 insulating film, 12A to 12H wiring, 13A to 13H bonding A pad, 14 is an n-side electrode, and 15 is a light emitting region.

In the semiconductor laser shown in FIG. 3, a current injected from a wire (not shown) flows from the bonding pads 13A to 13H to the striped p-side electrodes 9A to 9H through the wirings 12A to 12H. Further, by being injected into the quantum well active layer 6, laser oscillation occurs in the light emitting region 15. At this time, the position of the laser beam is moved by controlling the amount of current flowing through the stripe-shaped p-side electrodes 9A to 9H. Details of the operation of moving the position of the laser beam will be described later.

Next, a method of manufacturing the above semiconductor laser device will be described with reference to FIG.

First, as shown in FIG. 4A, a Se-doped GaAs substrate 1 having a thickness of 0.1 μm is formed by Se-doping.
m GaAs first buffer layer 2, Se-doped 0.1 μm thick Al _0.2 Ga _0.4 As second buffer layer 3,
Se-doped 0.1 μm thick Al _0.4 Ga _0.6 A
s Third buffer layer 4, Se-doped Al _0.6 Ga _0.4 As
1 μm thick first clad layer 5 composed of undoped Ga
Undoped Al is formed by forming three well layers of As having a thickness of 10 nm.
Quantum well active layer 6 and Mg dove separated by two barrier layers of _0.3 Ga _0.7 As and having a thickness of 5 nm and sandwiched by two optical waveguide layers of undoped Al _0.3 Ga _0.7 As and having a thickness of 0.1 μm. Thickness of Al _0.6 Ga _0.4 As 1
The second clad layer 7 having a thickness of μm and the semiconductor layer including a contact layer 8 having a thickness of 0.1 μm and made of Mg-doped GaAs are MO.
The layers are sequentially stacked by the CVD method.

On the contact layer 8, a stripe width of 0.5 to 1 is formed on the photoresist by photolithography.
Eight striped windows having a width of 0 μm and a distance between stripes of 0.5 to 5 μm are formed. Next, after depositing p-side electrodes 9A to 9H on the entire upper surface with a thickness of 50 to 1000 nm,
By removing the photoresist, the p-side electrodes 9A to 9H on the photoresist are removed by lift-off,
As shown in FIG. 4B, the stripe width is 0.5 to 10 μm.
The p-side striped electrodes 9A to 9H having an interval m of 0.5 to 5 μm between the stripes are electrically separated from each other. Although the number of p-side striped electrodes is eight here, the number may be changed as necessary.

Then, a Si ₃ N ₄ film 10 having a thickness of 200 nm is deposited as an insulating film on the entire surface by sputtering, and is formed on the photoresist by photolithography in a direction parallel to the stripe direction of the p-side stripe electrodes 9A to 9H. Portions corresponding to windows having a length of 1 to 50 μm and a length in a direction perpendicular to the stripe direction of 0.5 to 10 μm are formed on the p-side striped electrodes 9A to 9H, respectively. In this case, the windows are arranged so as to be shifted in the stripe direction so that wirings formed later do not come into contact with or intersect with each other. Then, by removing this photoresist, as shown in FIG. 4C, the Si ₃ N ₄ film 10 is formed.
The windows 11A to 11H are formed in.

After that, a metal to be wiring and a bonding pad is vapor-deposited on the entire surface to a thickness of 100 to 1000 nm. After that, the pattern of the wiring and the bonding pad is formed by photoresist by photolithography, and the metal is etched by using this photoresist as a mask.
Wiring 12A-1 by removing the photoresist
2H and bonding pads 13A to 13H are formed.
After that, the GaAe substrate 1 side is polished to 100 μm, and then the n-side electrode 14 is vapor-deposited to form the semiconductor laser device shown in FIG.

The insulating film used here may be an electrically insulating material such as a SiO ₂ film or a Si ₃ N ₄ film that does not corrode GaAs. Further, as the metal material for the p-side electrode, any one of Au, AuZn, Cr, Ti, Pt, or a combination thereof can be used.

Further, the semiconductor laser device of the present invention can be constructed with a semiconductor composition other than that of the above-mentioned embodiment, for example, A
lGaInP mixed crystal system, GaInAsP mixed crystal system, AlIn
It is also possible to use a material system such as an AsP mixed crystal system, a ZnSSe mixed crystal system, a CdZnSSe mixed crystal system.

FIG. 5 is a plan view showing the shape of the striped electrodes of the semiconductor laser device described above. In FIG. 5, eight p-side stripe electrodes having a uniform width are formed on the contact layer 8 in the cavity direction (vertical direction in FIG. 5) from the lower end face from which the beam is emitted to the opposite end face. Has been done. Here, in the present embodiment, the width of each of the striped electrodes 9A to 9H and the adjacent distance are selected to be about the carrier diffusion length or shorter.

Next, a specific method of changing the current density distribution in the active layer 6 in order to move the laser beam position on the emitting surface of the semiconductor laser will be described with reference to FIGS. 6 and 7.
Will be described in detail. FIG. 6 shows a semiconductor laser in which a plurality of stripe-shaped electrodes extending in the light emission direction for injecting current into the active layer are formed, and the electrode width is 3 μm.
As described above, it is a diagram showing a current injection method when the beam position is moved by two electrodes when the distance is as wide as 2 μm or more. FIG. 6A is a cross-sectional view showing the arrangement of the striped electrodes, FIG. 6B is an explanatory diagram showing changes in the current density distribution, and FIG. 6C shows changes in the injection current of each striped electrode. FIG.

First, at time t = t ₀ , a current not less than the oscillation threshold current of the laser is injected from the electrode 9A,
The current density distribution in the active layer 6 is as shown by the thin line, the light distribution on the emitting end face of the semiconductor laser is a thick line, and the beam emitting position is the peak position a of the current density distribution.

Next, as shown in FIG. 6B, the electrode 9A
By injecting a current from the electrode 9B while reducing the current injection from the electrodes, the distribution of the current density injected from the electrodes 9A and 9B becomes a thin line. However, this thin line shows the distribution when the current is individually injected into each of the electrodes 9A and 9B. When currents are simultaneously injected into the electrodes 9A and 9B, the electrodes 9A and 9B are arranged closer than the diffusion length of carriers, so that the actual current density distribution in the active layer 6 is a superposition of these. . Therefore, the peak position of the current density distribution moves to the electrode 9B side, and at t = t ₁ , the beam emission position also moves from a to b on the electrode 9B side.

Further, when the current injection from the electrode 9A is decreased and the injection current amount from the electrode 9B is increased, the beam position passes through c and d at t = t ₁ , t ₂ and t ₃ , respectively. , E when only current is injected from the electrode 9B
Move to the position. Similarly, the beam position can be continuously moved by controlling the amount of current injected from the electrode 9C and a plurality of electrodes arranged in parallel with the electrode 9C.

As described above, by sequentially increasing the current of one of the two adjacent electrodes and sequentially increasing the current of the other electrode, the peak position of the current density distribution moves, and accordingly The beam position can be continuously moved.

By the way, the currents flowing through the two adjacent electrodes are different from each other except when the beam emission position is at the center of the two electrodes. When the values of the currents flowing through the two adjacent electrodes are different from each other, when the current density distribution is observed in detail, the current density distribution is asymmetric with respect to the peak position. For example, at t = t ₃ ,
The right slope of the current density distribution is steeper than the left slope. If the current density distribution becomes asymmetric, the emission conditions differ between the left and right sides of the laser beam, and the profile of the laser beam, which should be a perfect circle, is distorted into an ellipse or the like.
When the profile of the laser beam is distorted, problems such as a decrease in recording density and a decrease in recording quality occur when an image or information is recorded using this laser beam.

Therefore, in the embodiments described below, the distortion of the laser beam profile is reduced by using three electrodes to move the beam position.

In FIG. 7, the electrode width is 3 μm or less and the interval is 2
A method for injecting current when moving the beam position by three electrodes in the case where the width is as narrow as μm or less is shown. Figure 7 (a)
Is a cross-sectional view showing the arrangement of striped electrodes, FIG.
Is an explanatory view showing a change in current density distribution, and FIG. 6 (c) is an explanatory view showing a change in injection current of each stripe electrode.

As shown in FIG. 7B, at t = t ₀ , the beam position is set between the electrodes 9A and 9B.
From the state where the same current is injected from the electrodes 9A and 9B, the current injected from the electrode 9A is reduced while keeping the current injected from the electrode 9B constant from t = t ₁ to t ₄ , and at the same time, Increase the current injected from 9C.

As a result, the distribution of the current densities injected from the respective electrodes 9A, 9B, 9C in the active layer 6 becomes the shape shown by the thin line, the actual distribution of the current densities is the superposition of these, and the beam position is the electrode position. It moves from the side between 9A and 9B to the side between electrodes 9B and 9C.

Similarly, the beam position is moved by keeping the current injected from the central electrode of a plurality of electrodes arranged in parallel constant and increasing or decreasing the current injected from the adjacent electrodes on both sides complementarily. You can

Further, the moving distance of the beam position can be lengthened by increasing the number of electrodes regardless of the electrode width and the interval.

When a single beam is formed by simultaneously injecting current from a larger number of electrodes, it is possible to reduce the distortion of the beam profile by controlling the amount of current injected from each electrode.

That is, as described above, when only two electrodes are used, the current density distribution becomes asymmetric, but in the embodiment shown in FIG. Since there are current density distributions having lower peak values on both sides of the current density distribution having the maximum peak value at this time, the shape of the current density distribution approaches symmetry. Therefore, the emission conditions on the left and right sides of the laser beam are substantially equal, the distortion of the beam profile is reduced, and problems such as a decrease in recording density and a decrease in recording quality do not occur.

FIG. 8 is a plan view showing another shape of the striped electrode used in the semiconductor laser device of the present invention. In the embodiment shown in FIG. 8, a plurality of striped electrodes are further divided in the resonator direction (vertical direction in FIG. 8), and the emission surface side electrode groups 9A to 9H and the reflection surface side electrode groups 9I to 9P are formed. Has been formed. The reflection surface side electrode groups 9I to 9P are provided at positions displaced from the emission surface side electrode groups 9A to 9H by a half of the electrode center interval in the direction perpendicular to the resonator direction. That is, the center line of the emitting surface side electrode in the resonator direction is located at the center between two adjacent reflecting surface side electrodes, and the center line of the reflecting surface side electrode in the resonator direction is
It is located at the center of two adjacent electrodes on the emission surface side. Each electrode is electrically separated so that the current injected into each electrode can be controlled independently.

In the embodiment shown in FIG. 8, the electrodes of one electrode group and the electrodes of the other electrode group, which are adjacent to each other when viewed in the direction perpendicular to the resonator direction, are used in combination.
The distribution of carrier density in the active layer can be finely controlled.

Further, in the embodiment shown in FIG. 8, it is possible to suppress the spread of the lateral mode width when the emission point of the laser beam is moved, as described below.

FIG. 9 (a) is a plan view schematically showing the arrangement of the striped electrodes, FIG. 9 (b) is an explanatory view showing the change in the current density distribution, and FIG. 9 (c) is the implantation of each striped electrode. It is explanatory drawing which shows the change of an electric current. However, in FIG. 9A, only five stripe-shaped electrodes are shown in order to simplify the description.

Stripe electrodes 9 are formed on the front and rear regions of the contact layer 8 in the cavity direction, and the end faces on the electrodes 9A, 9B and 9C side serve as the beam emission surface. The current density distribution injected from the electrodes 9A, 9B, 9C on the emission surface side is shown by a thick line, and the current density distribution injected from the electrodes 9I, 9J on the rear side is shown by a thin line.

First, at time t = t0, the electrodes 9A and 9I are
A laser oscillation is caused by injecting a current from. At this time, on the emission side, since the gain region is formed in the active layer below the electrode 9A, the beam is emitted from below the electrode 9A, and the lateral mode width at the emission surface is the active layer of the current injected from the electrode 9A. It depends on the width of the gain region due to the spread.

Next, the current from the electrode 9A is decreased and at the same time the current from the electrode 9B is increased. At this time, on the emission side, a gain region is formed between the lower part of the electrode 9A and the lower part of the electrode 9B. Therefore, the lateral mode width on the emission surface is determined by the spread of the current from the electrodes 9A and 9B in the active layer. Therefore, at t = t ₁ , by reducing the total amount of current injected from the electrodes 9A and 9B,
It is possible to reduce the spread of the current in the active layer on the emission surface side and prevent the width of the gain region from increasing. In this case, the amount of current from the electrode 9I is increased at the same time to compensate for the decrease in the amount of current from the electrodes 9A and 9B to keep the light output constant. Also, t = t ₂ ,
The beam position can be changed between the electrodes 9A and 9B by changing the ratio of the amount of current from the electrodes 9A and 9B as at t ₃ .

After that, the currents from the electrodes 9A and 9I are decreased and at the same time the current from the electrode 9B is increased,
At t = t4, by injecting current only from the electrodes 9B and 9I, a gain region is formed below the electrode 9B on the emission side, and the beam is emitted from below the electrode 9B.

Thus, the beam can be moved while controlling the spread of the beam. Then the electrode 9
By switching from I to the electrode 9J, the beam can be similarly moved from the lower part of the electrode 9B to the lower part of the electrode 9C. By arranging a large number of striped electrodes capable of moving such a beam, the beam can be moved over a wide range of the emission surface.

The semiconductor laser device of the present invention is, for example,
It is suitable for use as a light source for a tracking mechanism of an optical disk device. In the optical disc device, in order to record information on the optical disc and to optically reproduce the recorded information, it is necessary to irradiate the laser beam emitted from the optical head to a proper position of the track on the optical disc. For this reason, the optical disc apparatus is provided with a so-called tracking servo mechanism.

By using the semiconductor laser device according to the present invention, the laser beam emitted from the semiconductor laser is directly moved, so that the laser beam can be irradiated onto the target track without mechanically displacing the lens. it can.

FIG. 10 shows a tracking servo mechanism of an optical disk device using the semiconductor laser device described above. Further, FIG. 11 shows the relationship between the information track of the optical disc and the spot of the laser beam.

In FIGS. 10 and 11, 24 is an information track 24a stored in the form of an optically detectable marker.
, A semiconductor laser light source 20 for generating a laser beam incident on the optical disk 24, and 27 a non-recording area between the information track 24a and the information track 24a adjacent to the information track 24a along the beam optical path from the semiconductor laser device 20. 24b, a half mirror as a beam pointing device for directing a laser beam to a site extending over both
Reference numeral 22 is an objective lens for focusing the directed laser beam on the crossing portion of the information track and the non-recording area and receiving the reflected beam from the objective lens, 23 is a lens fixing cell holding the objective lens 22, and 21 is the reflected beam. A photodetector for converting into an electric signal, 28 is a laser driving device for controlling the current injected into the semiconductor laser device 20 based on the electric signal from the photodetector 21, and 29 is a feedback circuit. The semiconductor laser device 20 is arranged such that the moving direction of the emission position is a direction (indicated by an arrow X) that crosses the information track 24a.

In the above structure, the semiconductor laser device 20
The light emitted from the mirror is reflected by the half mirror 27, condensed on the optical disk 24 by the fixed lens 22, and the light reflected by the optical disk 24 is detected by the detector 21 to detect the deviation from the track. To do.

Next, the current injection into the semiconductor laser device 20 is controlled by the feedback circuit 29 to control the active layer 6
The distribution of the current density injected into the laser diode is changed to change the intensity distribution of the laser light emitted on the emission surface, whereby the position of the laser beam 25 emitted from the semiconductor laser device 20 is changed in the direction crossing the information track 24a. A tracking servo mechanism is constructed which moves and corrects the position of the spot 26 on the optical disk 24 from the shifted position shown by the broken line to the correct position shown by the solid line.

In this system, a gain region in which laser oscillation occurs is formed by direct modulation of the semiconductor laser device,
Since the spot position is corrected, the frequency band is several tens of MHz, and the data transfer rate can be increased.

Further, the semiconductor laser device of the present invention is suitable for use as a light source of an image recording device using a laser beam such as a laser beam printer.

FIG. 12 shows an image recording apparatus using the semiconductor laser described above. Around the photosensitive drum 31,
A charger 32 that uniformly charges the surface of the photosensitive drum 31.
An exposure device 33 that irradiates the surface of the photosensitive drum 31 whose surface is uniformly charged with light to form an electrostatic latent image; and a developing device that develops the electrostatic latent image to generate a visible toner image. 34,
A transfer device 36 that transfers the toner image on the photosensitive drum 31 onto a recording medium 35 such as paper, a cleaning device 37 that removes the toner remaining on the photosensitive drum 31 after the transfer, and a static eliminator that erases the electrostatic latent image. 38 and the like are sequentially arranged.

The exposure device 33 described above uses the semiconductor laser device 33a capable of moving the emitting point, the collimator lens 33b for collimating the laser beam emitted from the semiconductor laser device 33a, and the collimated laser beam. A scanning mirror 33c for scanning in the main scanning direction on the photosensitive drum 31 and an imaging lens 33d for condensing the laser beam on the photosensitive drum 31 are provided.
The semiconductor laser device 33a is arranged so that the emission point of the laser beam moves in the circumferential direction of the photosensitive drum 31, that is, in the sub-scanning direction (indicated by arrow X).

In the laser beam printer shown in FIG. 12, basically, as shown in FIG. 13A, the spot of the laser beam on the photosensitive drum 31 is moved in the axial direction of the photosensitive drum 31 for main scanning. By scanning in the scanning direction and rotating the photosensitive drum, scanning in the sub scanning direction is performed.

Here, in the laser beam printer of this embodiment, as shown in FIG. 13B, a plurality of laser beam emission positions of the semiconductor laser device 33a are set in the sub-scanning direction during one main scanning. The image is recorded while moving it once. Sub-scanning by moving the emission point of the semiconductor laser device operates at an extremely high speed as compared with mechanical sub-scanning by a deflecting mirror, so that a large number of spots can be recorded within one main scanning period. As a result, consecutive spots in the main scanning direction are recorded at different positions in the sub scanning direction within one main scanning period. That is, two scanning lines can be formed by one main scan, and the same effect as in the case of using a two-beam semiconductor laser device can be obtained.

Although the image is formed at two different positions in the sub-scanning direction in FIG. 12, the image can be formed at three or more positions.

[0075]

According to the present invention, the following effects can be obtained.

(1) The emission position of the laser beam of the semiconductor laser can be moved without providing an optical waveguide region separately from the semiconductor laser region, the emission direction is constant by the movement of the laser beam, and the shape of the laser beam is It is possible to provide a semiconductor laser device in which is symmetrical about the peak.

(2) In the tracking servo mechanism of the optical disk device, the beam spot position on the optical disk can be moved by direct modulation of the semiconductor laser, so that high speed operation is possible. Further, a motor for moving a lens for performing tracking, which has been used conventionally, is not required, and the tracking servo mechanism can be reduced in size.

(3) In the image recording apparatus, while the laser beam is scanned by the mirror in the main scanning direction, the laser beam is moved and scanned in the sub-scanning direction to scan two or more lines in one main scanning. Since the recording can be performed in parallel by forming the, the recording speed can be increased. Further, since the position of the laser beam can be continuously moved, the interlaced scanning required by the multi-beam laser in which the emission position of the laser beam is fixed is unnecessary.

(4) In the recording apparatus, while the laser beam is scanned by the mirror in the main scanning direction,
By moving and scanning the laser beam in the sub-scanning direction and shifting the positions of the light spots in the sub-scanning direction and overlapping them, the shape of one dot can be modulated, and the gradation of the recorded image can be increased. Is possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a gain-guided laser having one stripe electrode and a diagram showing a carrier density distribution in an active layer.

FIG. 2 is a cross-sectional view of a gain-guided laser having a plurality of stripe electrodes and a diagram showing a carrier density distribution in an active layer.

FIG. 3 is a perspective view of a semiconductor laser device that is a first embodiment of the present invention.

FIG. 4 is a perspective view showing a manufacturing procedure of the semiconductor laser device according to the first embodiment of the present invention.

FIG. 5 is a top view showing the shape of the p-side stripe electrode of the semiconductor laser device which is the first embodiment of the present invention.

FIG. 6 is a diagram showing a method of injecting a current when moving a beam position by two electrodes of a semiconductor laser device.

FIG. 7 is a diagram showing a current injection method when moving a beam position by three electrodes of a semiconductor laser device.

FIG. 8 is a top view showing a shape of a p-side stripe electrode of a semiconductor laser device which is another embodiment of the present invention.

FIG. 9 is a diagram showing a method of injecting current when moving a beam position by electrodes divided in a cavity direction of a semiconductor laser device.

FIG. 10 is a schematic view showing a tracking mechanism of an optical disc device using the semiconductor laser device of the present invention.

FIG. 11 is a schematic diagram for explaining the operation of the tracking mechanism shown in FIG.

FIG. 12 is a schematic view showing an image recording device using the semiconductor laser device of the present invention.

13 is an explanatory diagram showing a scanning mode of a laser beam in the image recording apparatus shown in FIG.

[Explanation of symbols]

1 ... GaAs substrate, 2 ... First buffer layer, 3 ... Second buffer layer, 4 ... Third buffer layer, 5 ... First clad layer, 6
... quantum well active layer, 7 ... second cladding layer, 8 ... contact layer, 9 ... p-side stripe electrode, 10 ... insulating film, II
… Windows, 12… Wiring, 13… Bonding pads, 14
... n-side electrode, 15 ... Light emitting region, 20 ... Semiconductor laser device, 21 ... Photodetector, 22 ... Lens fixed cell, 24 ... Optical disk, 25 ... Laser beam, 26 ... Spot, 2
7 ... Half mirror, 28 ... Laser drive device, 29 ... Feedback circuit, 31 ... Photosensitive drum, 32 ... Charger, 3
3 ... Exposure device, 34 ... Developing device, 35 ... Recording medium, 36 ...
Static eliminator, 37 ... Cleaning device, 38 ... Static eliminator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiromi Otoma, 2274 Hongo, Ebina City, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. (72) Inventor: Kaoru Yasukawa 2274, Hongo, Ebina City, Kanagawa Prefecture (72) ) Inventor Mario Fuse 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (10)

[Claims] 1. A semiconductor laser device in which at least three stripe-shaped electrodes extending in the cavity direction, which are controllable independently of each other, are arranged side by side in a direction perpendicular to the cavity direction. A semiconductor laser device characterized in that the diffusion length is smaller than the diffusion length. 2. The method for driving a semiconductor laser device according to claim 1, wherein the current is simultaneously injected from the at least three stripe electrodes, and the current is injected from the stripe electrodes on both sides of the three stripe electrodes. A method of driving a semiconductor laser device, characterized in that the amount of current applied is changed complementarily. 3. The method of driving a semiconductor laser device according to claim 2, wherein the amount of current injected from the striped electrode is continuously changed. 4. The method of driving a semiconductor laser device according to claim 2, wherein the amount of current injected from the striped electrode is changed stepwise. 5. The front electrode, wherein the striped electrode extends from a central portion of the resonator to a light emitting side end surface of the resonator, and a rear electrode, which extends from a central portion of the resonator to a rear end surface of the resonator. 2. The semiconductor laser device according to claim 1, wherein a plurality of the front electrodes and the rear electrodes are arranged side by side in a direction perpendicular to the cavity direction. 6. A center line of the front electrode in the resonator direction is located at a center between two adjacent rear electrodes,
6. The semiconductor laser device according to claim 5, wherein a center line of the rear electrode in the cavity direction is located at the center of two adjacent front electrodes. 7. The semiconductor laser device according to claim 5, wherein the width of the front electrode is equal to the width of the rear electrode. 8. An optical disc having information tracks stored in the form of optically detectable indicia, a laser light source for generating a laser beam incident on the optical disc, and a laser light source along a beam optical path. A beam directing device for directing the laser beam to a portion extending over both the information track and a non-recording area between adjacent tracks, and the directed laser beam for both the information track and the non-recording area. An objective lens which is focused on a straddling site and receives a reflected beam therefrom, a photodetector which receives the reflected beam and converts it into an electric signal, and the laser beam information based on the electric signal from the photodetector. In a tracking mechanism of an optical disk device for performing tracking by moving in a direction traversing a track, With using the semiconductor laser device according to claim 1 as a light source, the semiconductor laser device, an optical disk apparatus of the tracking mechanism moving direction of the emitting position is characterized by being arranged such that the direction crossing the information track. 9. A photosensitive drum, a charger for charging the photosensitive drum, an exposure device for exposing the charged photosensitive drum with a laser beam to form an electrostatic latent image, and an electrostatic device on the photosensitive drum. A developing device that develops a latent image to form a toner image and a transfer device that transfers the toner image onto a recording medium are provided, and main scanning is performed by moving a laser beam in the axial direction of the photosensitive drum. An image recording apparatus that performs sub-scanning by rotating the photosensitive drum, wherein the semiconductor laser device according to claim 1 is used as a light source of the exposure device, and the semiconductor laser device has An image recording apparatus, which is arranged so as to be in the scanning direction. 10. The image recording apparatus according to claim 9, wherein the semiconductor laser device moves the laser beam a plurality of times in the sub-scanning direction while performing one main scanning.