JPH05303762A - Optical head device - Google Patents

Abstract

PURPOSE:To facilitate its manufacture and to increase the NA of a laser beam by providing a laser element on the low step part of a semiconductor substrate, a reflection mirror on the slope and a photodetector on the high step part and specifying the height of the laser element and the angle of the slope. CONSTITUTION:A laser beam outgoing from the light emitting part 18 of the laser element 5 mounted on the low step part of the semiconductor substrate 1 is reflected by the reflection mirror 7 on the slope 1b surface opposing to the light emitting part 18. Although the reflected beam is reflected by the end surface 5a of the element 5 and outgoes from a laser device, at this time, a member 19 having higher reflectance than the light emitting part 18 is applied on the part of the end surface 5a of the element 5 except the light emitting part 18. Then they are arranged so that the angle Q of the slope 1b provided on the step part of the substrate l to the substrate surface and the height h2 of the element from the low step part are satisfied by h2>=h+h1-(x+y)tan(2theta-theta') where 90 deg.<2theta-theta'<180 deg., x<=h1/tantheta', T>=h1+h. Thus, the manufacture is facilitated by reducing the step and the NA of the outgoing beam is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device, and more particularly to an optical head device used for recording / reproducing optical information on / from an optical information recording medium using a laser beam. ..

[0002]

2. Description of the Related Art Conventionally, various optical head devices have been proposed in which a laser diode and a photodetector are integrally formed on a silicon substrate to miniaturize an optical system. An example of such an optical head device is disclosed in Japanese Patent Laid-Open No. 64-46243. FIG. 3 is a diagram showing a configuration of an example of the optical head device disclosed in this publication. The semiconductor substrate 1 and the cover member 2 are the upper surface 1 a of the semiconductor substrate 1.
And the lower surface 2a of the cover member 2 are arranged so as to face each other with a space therebetween. A step is formed on the upper surface 1a of the semiconductor substrate 1, and the first and second photodetectors 3 and 4 are provided in the high step portion, and the semiconductor laser element 5 and the monitor photodetector 6 are provided in the lower step portion. It is arranged. Further, the inclined surface 1 facing the laser emission surface of the semiconductor laser element 5 is formed in the stepped portion.
b is provided.

The upper surface 1a of the semiconductor substrate 1 is accurately processed by, for example, an etching process. Upper surface 1a
A total reflection grating portion 7 is provided on the surface of the inclined surface 1b provided in the stepped portion, and totally reflects the laser light oscillated from the semiconductor laser element 5 toward the cover member 2. A hologram 8 having a function of a beam splitter is formed on the upper surface 2b of the cover member 2.

In this example, the laser beam L ₁ emitted from the semiconductor laser element 5 is split into three laser beams L ₂ by the total reflection grating portion 7 and reflected upward. These three laser beams L
_The light beams 2 enter the lower surface 2 a of the cover member 2, pass through the cover member 2, and then enter the beam splitter 8 provided on the upper surface of the cover member 2. The three reflected laser beams L ₃ reflected by the information recording medium (not shown) are
After passing through the beam splitter 8 again, the light passes through the cover member 2 and enters the first photodetector 3. A part of this laser beam L ₃ is reflected by the first photodetector 3 and further reflected by the lower surface 2 a of the cover member 2 and reaches the second photodetector 4.

FIG. 4 is a diagram showing the configuration of another example of the optical head disclosed in the above-mentioned Japanese Patent Laid-Open No. 64-46243. In this example, instead of providing a step on the semiconductor substrate 1, the prism 9 is arranged so as to face the laser emitting surface of the semiconductor laser element 5.

[0006]

In the optical information recording / reproducing apparatus, it is necessary to increase the strength of the objective lens particularly when recording or erasing information. Therefore, it is necessary to increase the NA of the laser beam emitted from the semiconductor laser element to improve the light utilization efficiency. FIG. 5 is a partially enlarged view of the stepped portion of the semiconductor substrate 1 of the device shown in FIG. 3, but in the case of the device shown in FIG. 3, the NA of the laser beam emitted from the laser element 5 is increased, that is, the emitted light is increased. Is used in a wide angle range, the height of the stepped portion H = H ₁
It is necessary to increase + H ₂ .

FIG. 6 shows a recording / reproducing apparatus for optical information.
A single semiconductor laser that is commonly used as a light source
It is a figure which shows a structure. This semiconductor laser is a GaAs substrate
G formed by epitaxially growing an active layer on 11
What is called aAlAs-based double heterostructure laser
Is. As shown in FIG. 6, reference numeral 12 is Ga._1-xAl _x
As, which is called an active layer. Change Al composition ratio x
Therefore, the oscillation wavelength is selected in the range of 680 to 880 nm.
You can The wavelength of 780 nm is for CD and VD
It has been adopted, and is 83 for high-power lasers for optical disks.
0 nm or 780 nm is used. Active layer 12
Formed on the upper and lower surfaces of the_1-yAl_yAs is clad
It is called layer 13 and is a layer that activates carriers (electrons, holes) and light.
It serves to lock in 12. Of the lower clad layer 13
The GaAs provided on the lower surface is called the cap layer 14,
It is provided to reduce the electrode resistance. The code
Reference numerals 15 and 16 are electrodes, respectively.

The normal size of the laser chip having such a configuration is 0.25 × 0.3 × 0.12 mm, which is very small. A pn junction is formed in the active layer 12, the p electrode is positive,
By applying a voltage with the n-electrode being negative, the active layer 1
Electrons and holes are injected into 2, and laser oscillation occurs when the threshold current value is exceeded. The laser chip is usually mounted on the mount material 16 with the growth layer side facing down via the brazing material 17. A copper block, silicon, or the like is used for the mounting material 16, and a soft In brazing material or a hard brazing material is used for the brazing material 17.
Au-Sn brazing material is used. The reflector required to construct the laser cavity is made by utilizing the cleavage plane of the crystal.

As shown in FIG. 6, the height Z ₁ of the growth layer including the active layer 12 having the light emitting point of the laser chip is usually 10 μm.
Since this growth layer is formed by epitaxial growth, it can be formed with high accuracy of ± 1 μm or less. On the other hand, the height Z of the GaAs substrate 11
₂ is as large as 110 μm, and this accuracy is almost determined by the thickness accuracy of the GaAs substrate. This GaAs substrate 1
Since No. 1 is formed by polishing a GaAs wafer, the thickness accuracy is about ± 10 μm, which is very low compared with the accuracy of Z ₁ .

In the case of the conventional optical head device shown in FIG. 3 described above, since the step of the semiconductor substrate 1 is formed by the etching process, it can be processed accurately. It is desirable that the height H of the step portion formed by this etching be as low as possible in order to shorten the etching time and ensure its accuracy. However, as shown in FIG. 5, normally, in order to maximize the NA of the laser beam emitted from the semiconductor laser element 5, the height H of the step portion is about twice the height of the laser element 5, that is, about It is very large at 200 μm.

In order to reduce the height H of the step portion formed by etching and increase the NA of the laser beam, as shown in FIG. 7, the end face 5 including the laser emission point is formed.
The distance x between a and the inclined surface 1b of the semiconductor substrate 1 may be reduced. However, as described above, the Ga of the laser chip 5 is
Since the height Z ₂ of the As substrate 11 is as high as about 110 μm, the reflected beam reflected by the inclined surface 1b is blocked by the laser element 5 itself (hatched portion in FIG. 7).

As shown in FIG. 8, if the laser element 5 is turned upside down and the GaAs substrate 11 side is fixed to the semiconductor substrate 1, the laser beam will not be blocked by the laser element 5 itself. The etching height H of the stepped portion of the substrate 1 must be increased. Further, since the dimensional accuracy of the height Z ₂ of the GaAs substrate 11 of the laser chip is lower than the dimensional accuracy of Z ₁ , the height accuracy of the light emitting point 18 cannot be obtained and the first and second photodetectors 3, There is a problem that the size of the light spot in 4 changes.

In a device using a prism as shown in FIG. 4, the NA can be easily increased by changing the size of the prism, but the size of the height Z ₂ of the GaAs substrate 11 of the laser chip is also the same. The accuracy is poor and the mounting accuracy of the prism 9 mounted on the semiconductor substrate 1 is also poor. Further, since the semiconductor substrate 1 and the prism 9 are separate parts, there is a problem that the number of manufacturing processes increases.

According to the present invention, the height of the step portion formed by etching on the semiconductor substrate is kept low, the accuracy of the light emitting point of the semiconductor laser element is kept high, and the NA of the laser beam emitted from the semiconductor laser can be made large. It is an object of the present invention to provide an optical head that can be used.

[0015]

In order to solve the above problems, an optical head according to the present invention includes a semiconductor substrate having a stepped portion on its surface and an inclined surface at the stepped portion, and a semiconductor substrate of this semiconductor substrate. A semiconductor laser device is provided in the low step portion with the emission side end face facing the inclined surface, a reflection mirror provided on the surface of the inclined surface, and a photodetector provided in the high step portion of the semiconductor substrate. Optical head device

X: distance between the laser light emitting end face of the semiconductor laser device and the reflection mirror θ: angle of inclined surface with respect to the semiconductor substrate surface θ ′: spread angle of laser light h: x′tan θ tan θ ′ / (tan θ -tan θ ′) h ₁ : height of emission point of semiconductor laser device h ₂ : height of semiconductor laser device x ′: x + h ₁ / tan θ (where θ> θ ′) y: (h + h ₁ ) / tan θ T : At the height of the step,

H ₂ ≧ h + h ₁ − (x + y) tan (2θ−θ ′) However, 90 ° <2θ−θ ′ <180 ° x ≦ h ₁ / tan θ ′ T ≧ h ₁ + h The semiconductor laser device is arranged, and the angle of the inclined surface with respect to the surface of the semiconductor substrate is determined. In the optical head of the present invention, in order to increase the NA of the laser beam emitted from the semiconductor laser element, the distance between the semiconductor laser element and the inclined surface provided on the stepped portion of the semiconductor substrate is set within the above range. At the same time, the angle of incidence on this inclined surface is set smaller than that of the conventional device so that the laser beam reflected by the inclined surface is not blocked by the semiconductor laser element itself, and the reflected laser beam reflected by this inclined surface becomes a semiconductor. The angle is set so that the laser beam is reflected by the end face of the laser element.

[0016]

1 is a diagram showing the overall structure of an optical head of the present invention, and FIG. 2 is an enlarged view showing the stepped portions of a semiconductor laser element and a semiconductor substrate of the optical head shown in FIG.
The same components as those of the conventional apparatus shown in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 1, the laser beam emitted from the semiconductor laser element 5 is reflected by a reflection mirror 7 provided on the inclined surface 1b of the step portion of the semiconductor substrate 1, and the reflected beam is further reflected by the semiconductor laser element. The end surface 5a including the laser emission point 18 of No. 5 is reflected toward the cover member 2. The laser beam transmitted through the cover member 2 and reflected from the information recording medium (not shown) enters the first and second photodetectors 3 and 4 similarly to the conventional device described above. Information recording / reproduction is performed.

As shown enlarged in FIG. 2, the semiconductor substrate 1
The laser beam emitted from the light emitting portion 18 of the semiconductor laser element 5 mounted on the lower step of the is reflected by the reflection mirror 7 formed on the surface of the inclined surface 1b formed facing the light emitting portion 18, The reflected laser beam is further reflected by the end surface 5a of the semiconductor laser element 5 and emitted from the semiconductor laser device. At this time, the light emitting portion 18 is formed on all parts of the end surface 5a of the semiconductor laser element 5 except the light emitting portion 18.
The member 19 having higher reflectance is coated.

The angle of the inclined surface 1b provided at the stepped portion of the surface of the semiconductor substrate 1 with respect to the surface 1a of the semiconductor substrate 1 and the position of the semiconductor laser element 5 provided at the lower step are

X: distance between the laser light emitting end face of the semiconductor laser device and the reflection mirror θ: angle of the inclined surface with respect to the surface of the semiconductor substrate θ ′: spread angle of laser light h: x ′ tan θ tan θ ′ / (tan θ − Tan θ ′) h ₁ : height of emission point of semiconductor laser device h ₂ : height of semiconductor laser device x ′: x + h ₁ / tan θ (where θ> θ ′) y: (h + h ₁ ) / tan θ T : At the height of the step,

H ₂ ≧ h + h ₁ − (x + y) tan (2θ−θ ′) (1) However, 90 ° <2θ−θ ′ <180 ° x ≦ h ₁ / tan θ ′ T ≧ h ₁ + h is satisfied. It is arranged to.

By arranging the semiconductor laser element 5 and the inclined surface 1b so as to satisfy the above condition (1), it is possible to reduce the stepped portion provided on the semiconductor substrate 1 by etching and increase the NA of the laser beam. can do.

[0021]

As described above, in the optical head device according to the present invention, since the step on the surface of the semiconductor substrate is small, it can be easily manufactured, and the NA of the emitted light of the semiconductor laser element is increased. In addition, the accuracy of the light emitting point of the laser element can be kept high. That is,
It is possible to provide an inexpensive and high-performance optical head.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of an optical head device of the present invention.

FIG. 2 is a partially enlarged view of the optical head device shown in FIG.

FIG. 3 is a diagram showing a configuration of an example of a conventional optical head device.

FIG. 4 is a diagram showing the configuration of another example of the conventional optical head device.

5 is a partially enlarged view of the conventional device shown in FIG.

FIG. 6 is a diagram showing a configuration of a semiconductor laser chip.

FIG. 7 is a diagram showing the configuration of another example of the conventional optical head device.

FIG. 8 is a diagram showing the configuration of another example of the conventional optical head device.

[Explanation of symbols]

 1 semiconductor substrate 1b inclined surface 2 cover member 3, 4 photodetector 5 semiconductor laser element 7 reflection mirror-8 hologram element 11 GaAs substrate 12 active layer 13 clad layer 14 cap layer 15, 16 electrode 18 light emitting point 19 coating member

Claims (1)

[Claims] 1. A semiconductor substrate having a stepped portion on the surface thereof and an inclined surface provided on the stepped portion, and a semiconductor laser device having an emission side end face on the lower step portion of the semiconductor substrate facing the inclined surface. , An optical head device comprising a reflection mirror provided on the surface of the inclined surface and a photodetector provided on a high step of the semiconductor substrate, where: x: laser light emitting end face of a semiconductor laser device Distance from reflection mirror θ: Angle of inclined surface with respect to semiconductor substrate surface θ ′: Spread angle of laser light h: x′tan θ tan θ ′ / (tan θ− tan θ ′) h ₁ : Light emission point of semiconductor laser device Height h ₂ : Height of semiconductor laser element x ′: x + h ₁ / tan θ (where θ> θ ′) y: (h + h ₁ ) / tan θ ′ T: When the height of the step portion, [Formula 2] _{h 2 ≧ h + h 1 -} (x + y) tan (2θ-θ ') However, 90 ° <2θ-θ'<180 ° x h ₁ / tan θ 'so as to satisfy T ≧ h ₁ + h, the semiconductor laser element is arranged, the optical head device being characterized in that to determine the angle of the inclined surfaces with respect to the semiconductor substrate surface.