JP2001155366A - Optical head and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diminish chromatic aberration when the wavelength of a light source fluctuates by change in temperature for example and to make an optical path vertical against an optical recording medium. SOLUTION: The optical head 101 is constituted by forming a semiconductor laser 1 and a photodetector 7 on a substrate 2 through a buffer layer 47, forming an opening in the lower part of a laser beam emitting and receiving surfaces, filling a first glass layer 3 in the opening, forming a diffraction grating 4 on the lower face of the first glass layer 3, laminating a second glass layer 5 beneath the first glass layer 3, and forming a condensing lens 6 with a diameter of 1 mm or less by a grating lens on the lower face of the second glass layer 5. As a result, attenuation of a laser beam is small, eliminating a problem of chromatic aberration when the wavelength from the light source fluctuates by change in temperature for example. A noise problem due to return light is also eliminated. There are no longer problems due to tilting of the optical path against the optical disk and due to SCOOP structure. The whole optical head can be reduced in size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head and a method of manufacturing an optical head, and more particularly, to a method of reducing chromatic aberration when the wavelength of a light source changes due to a temperature change or the like, and obliquely setting an optical path to an optical disk. The present invention relates to an optical head and an optical head improved so as not to cause a problem caused by the above-mentioned problem and a problem of the SCOOP structure.

[0002]

2. Description of the Related Art Optical heads (optical pickups) described in, for example, JP-A-64-46242 and JP-A-64-43822 are known. JP-A-64-
No. 46242 discloses an optical head in which a surface emitting laser and a photodetector are formed on the same substrate, a glass plate is laminated on the substrate, and a grating condensing lens (hologram lens) is provided on the surface of the glass plate. It is formed. An optical head described in JP-A-64-43822 is an optical head having the configuration described in JP-A-64-46242 as an optical head body, and the optical head body is attached to a flying slider. It is.

[0003] Other related prior arts include "Optical disc technology; Radio Technology Co., supervised by Morio Onoe", "Optical discs; Ohmsha; Edited by the Institute of Electronics, Information and Communication Engineers", "Optoelectronics;Maruzen; Junichi Shimada", and Emission laser; Ohmsha;
Co-authored by Kenichi Iga and Fumio Koyama ".

[0004]

SUMMARY OF THE INVENTION The above-mentioned JP-A-64-46 is disclosed.
In the optical head described in Japanese Patent Publication No. 242, a grating condenser lens is used, but in the case of the grating condenser lens, chromatic aberration is large when the wavelength of the light source changes due to a temperature change or the like. The publication states that no wavelength change occurs when a surface emitting laser is used.
Vol. 0 No. 1 (1991) p. 8 Iga "Surface emitting semiconductor laser" As described in FIG. 12, the wavelength changes depending on the temperature, which also has an effect, but there is a problem that this is not considered. is there. Furthermore, in the optical head described in the publication, the optical path to the optical disk is oblique to separate the optical path of the laser beam from the surface emitting laser to the optical disk and the optical path of the return light from the optical disk to the photodetector. However, if the optical path is oblique, there is a problem that aberrations and an asymmetric intensity distribution are easily generated, and the spot size becomes large. In consideration of the problem caused by the oblique optical path, the application of the SCOOP structure is
Although proposed in the same publication, the SCOOP structure has a drawback that it cannot detect a tracking signal or a magneto-optical signal because only a difference in reflectance of a medium can be detected.

Therefore, a first object of the present invention is to reduce the chromatic aberration when the wavelength of a light source changes due to a temperature change and the like, and to solve the above-mentioned problems and the SCOOP structure caused by making the optical path oblique to the optical disk. An object of the present invention is to provide an optical head improved so as not to cause the above problem. A second object of the present invention is to provide a method for manufacturing an optical head using a surface emitting laser.

[0006]

According to a first aspect of the present invention, a substrate, a buffer layer formed on the substrate, a laser light emitting surface of a semiconductor laser and a light receiving surface of a photodetector are arranged in the same direction. A semiconductor laser and a photodetector formed on the buffer layer, an opening formed in the substrate below the laser light emitting surface and the light receiving surface, and a first transparent layer filled in the opening. A diffraction grating formed on the lower surface of the first transparent layer, a second transparent layer laminated below the first transparent layer, and a grating lens or a refractive index formed on the lower surface of the second transparent layer. A laser beam emitted from the semiconductor laser passes through the substrate, the first transparent layer, the diffraction grating, and the second transparent layer, and is directly below the condensing lens. Focused towards An optical spot is formed on the optical recording medium remote from the optical lens, and the reflected light reflected by the optical recording medium passes through the condenser lens and the second transparent layer, and is received by the photodetector by the diffraction grating. An optical head is provided that is diffracted toward a surface, passes through the first transparent layer, and is received by the photodetector. In the optical head of the present invention according to the first aspect, since the semiconductor laser is formed via the buffer layer and the opening is formed below the laser light emitting surface of the substrate, the attenuation of the laser light is reduced. Also, a diffraction grating is provided between the semiconductor laser and the condenser lens,
After the light emitted from the condenser lens and reflected by the optical recording medium again enters the same condenser lens, the light is directed to the light receiving surface of the photodetector capable of detecting a tracking signal, a magneto-optical signal, and the like. For this reason, the problem caused by making the optical path oblique to the optical disk and the problem of the SCOOP structure do not occur.

According to a second aspect of the present invention, a semiconductor laser and a photodetector are formed on the same substrate via a buffer layer with the laser light emitting surface of the semiconductor laser and the light receiving surface of the photodetector facing in the same direction. An opening is formed in the substrate below the laser light emitting surface and the light receiving surface by etching, and a first transparent layer filling the opening is laminated under the substrate by plasma CVD, sputtering, or the like. A diffraction grating is formed on the lower surface of the layer by a photomask exposure process, a second transparent layer is laminated below the first transparent layer by plasma CVD, sputtering, or the like, and a lower surface of the second transparent layer is formed by a photomask exposure process. An optical head manufacturing method comprising forming a grating lens or forming a gradient index lens or a convex lens by an ion exchange process. Subjected to.

Further, there is provided a method of manufacturing an optical head, wherein a surface emitting laser and a photodiode are simultaneously manufactured by the following processes (a) to (f). (A) A first reflection mirror layer in which an n-type AlGaAs buffer layer is grown on an n-type GaAs substrate, an n + -type GaAs layer is grown thereon, and n-type AlAs and GaAlAs are alternately stacked thereon. To form (B) The first reflection mirror layer is removed by etching only at the portion where the photodiode is to be formed, and an n-type AlGaAs layer is grown on the removed portion. (C) First reflective mirror layer and n-type AlGaAs
An n-type AlGaAs clad layer is formed on the layer, a p-type GaAlAs / GaAs quantum well layer is grown thereon to form an active layer, and a p-type GaAlAs clad layer is formed thereon. Then, a second reflection mirror layer in which n-type AlAs and GaAlAs are alternately stacked thereon is grown thereon. (D) The second reflection mirror layer is removed by etching only at the portion where the photodiode is to be formed, and the p-type G
An aAs layer is formed. (E) A p + type GaAs layer is formed on the second reflection mirror layer and the p type GaAs layer, and A
A u electrode is formed. (F) forming a groove for separating the surface emitting laser from the photodiode;

In the method for manufacturing an optical head according to the second aspect of the present invention, the optical head according to the present invention can be integrally manufactured using a semiconductor process such as a photomask exposure process. Further, a surface emitting laser and a photodiode can be manufactured at the same time.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 is a sectional view showing the structure of an optical head 101 according to a first embodiment of the present invention. The optical head 101 has a surface emitting laser 1
And the photodiodes 7, 7 are arranged such that the laser light emitting surface of the semiconductor laser 1 and the light receiving surface of the photodiodes 7, 7 are n-
Toward the GaAs substrate 2, AlGaAs is placed on the n-GaAs substrate 2.
s formed through the buffer layer 47, an opening is formed in the lower substrate on the laser light emitting surface and the light receiving surface, and the opening is filled with the first glass layer 3; A diffraction grating 4 is formed, a second glass layer 5 is laminated below the first glass layer 3, and a condensing lens 6 having a diameter of 1 mm or less by a grating lens is formed on the lower surface of the second glass layer 5. is there.

A laser beam (shown by a broken line in the figure) emitted from the surface emitting laser 1 passes through the buffer layer 47, the first glass layer 3, the diffraction grating 4 and the second glass layer 5, and passes through the focusing lens 6 The light is condensed directly below, and the recording surface of the optical recording medium R separated from the condenser lens 6 has a diameter of 0.4 μm.
A light spot of 2 μm is formed. The distance between the condenser lens 6 and the recording surface of the optical recording medium R is 1 mm or less.

The light reflected by the recording surface of the optical recording medium R (indicated by a two-dot chain line in FIG.
The light passes through the glass layer 5, is diffracted by the diffraction grating 4 toward the light receiving surfaces of the photodiodes 7, 7, passes through the first glass layer 3, and is received by the photodiodes 7, 7.

The reason why the buffer layer is formed below the laser light emitting surface and the light receiving surface and the opening is formed in the substrate 2 is that absorption is large at the laser oscillation wavelength (α = 104 (cm−1)).
The GaAs substrate is removed, and the absorption is small (α = 20 (cm−
1)) This is for supporting the laser with the AlGaAs buffer layer. Even if AlGaAs is used, the electrical conductivity is not different from that of GaAs, so that the electrical resistance can be reduced by increasing the thickness of the buffer layer without increasing the light absorption loss. Also,
The reason why the aperture of the condenser lens 6 is 1 mm or less is to suppress the chromatic aberration when the wavelength of the light source changes due to a temperature change or the like to at least λ / 4 or less at the maximum value. That is, the spherical aberration W of the hologram is W (h) = Ah4 (1), where h is the height of the incident light beam from the optical axis on the hologram (Optical Engineering Handbook; Terutsu Kose et al .; Asakura Shoten; p180). Here, the distance Ro from the hologram to the object point, the distance Rr to the reference light source at the time of recording, the distance Rc to the reference light source at the time of reproduction, the distance Ri to the reproduction image point, the wavelength λ at the time of recording, and the wavelength λ 'at the time of reproduction are given. For example, A = {(λ ′ / λ) (1 / Rr3-1 / Ro3) −1 / Rc3 + 1 / Ri3} (2) On the other hand, the imaging relationship is 1 / Ri = 1 / Rc + (λ ′ / λ) (1 / Ro−1 / Rr) (3) Therefore, if Rr → −∞ and Rc → −∞, W (h) = (１ ／ Ro3) ｛(λ ′ / λ) 3- (λ ′ / λ)｝ h4 (4). If the wavelength variation Δλ and the numerical aperture NA are λ ′ / λ = (λ + △ λ) / λ (5) (NA) = h / Ro (6), W (h, NA) = ｛(NA) 3 Δλ / (4λ)｝ h (7) That is, when the numerical aperture NA is constant, the wavelength variation Δ
It can be seen that the maximum spherical aberration W caused by λ is proportional to the height h of the incident light from the optical axis on the hologram.
For example, NA = 0.55, λ = 0.78 μm, △ λ = 3
For nm, W (h = 2.0 mm) = 0.41λ W (h = 1.0 mm) = 0.21λ W (h = 0.5 mm) = 0.10λ. Thus, when the diameter 2h of the condenser lens 6 is set to 1 mm or less, the aberration is reduced to λ /
It can be suppressed to 10 or less. The same applies to a condensing lens using a convex lens. For example, when a lens having one spherical surface is considered, the spherical aberration W is given by: W (h) = − ｛3n /, where the refractive index of the object space is 1, the refractive index of the image space is n, and the focal length is f. (8 (n-1) 2f3)｝ h4 (8). Assuming that the numerical aperture NA is NA = nh / f (9), W (h) =-{3 (NA) 3 / (8 (n-1) 2n2)} h (10). Thus, the numerical aperture NA is kept constant, and the aperture 2h
Is small, the aberration can be reduced. This is not limited to spherical aberration, and the same applies to other aberrations.

Now, the provision of the diffraction grating 4 branches the reflected light and makes the optical path to the optical recording medium R vertical, so that the problem caused by the oblique optical path does not occur. If the diffraction efficiency obtained by combining the ± 1st-order diffracted lights by the diffraction grating 4 is 50%, 25% of the reflected light returns to the surface-emitting laser 1, but mode hopping due to the return light hardly occurs in the surface-emitting laser 1. , Little impact. The total amount of light received by the photodiodes 7, 7 can be a maximum value of 25%.

FIG. 2 shows a diffraction grating 4 and a photodiode 7.
FIG. The diffraction grating 4 is a linear diffraction grating that is inclined at 45 ° on both sides with respect to a center line parallel to the recording track direction of the optical recording medium R and orthogonal to each other. The photodiodes 7 are provided at four locations so as to be able to receive ± 1st-order diffracted light from the diffraction grating 4. The four photodiodes 7a, 7b, 7c, 7d are further divided into two in the direction in which the diffraction grating 4 is divided.

FIG. 3 shows four photodiodes 7a,
The light distribution at the time of back focus, at the time of in-focus, and at the time of front focus at the time of reflected light respectively entering 7b, 7c, 7d is shown. FIG. 4 is an example of a signal detection circuit in the optical head 101. The out-of-focus signal AF is obtained by adding the outputs of the four photodiodes on the upper and outer sides in FIG. 4 by an adder 8a, and adding the outputs of the four photodiodes on the upper and lower sides in an adder 8b.
And the outputs of both adders 8a and 8b are subtracted by a subtractor 9a. Since the track shift signal TR is obtained from the uneven distribution of the reflected light from the optical recording medium R due to the track shift, the difference between the amounts of light incident on the left and right sides of the diffraction grating 4 in FIG. Accordingly, the outputs of the four photodiodes on the upper left side and the lower right side in FIG. 4 are added by the adder 8c, and the outputs of the four photodiodes on the upper right inside and the lower left side are added by the adder 8d. 8
The outputs of c and 8d are obtained by subtraction by a subtractor 9b. When the optical storage medium R is a write-once or read-only optical disk, the reproduction signal may be the sum of the outputs of all the photodiodes. Therefore, the outputs of the two adders 8c and 8d are obtained by adding them in the adder 9c.

FIG. 5 illustrates a method of manufacturing the optical head 101. (a) An n-AlGaAs buffer layer 47 is grown on the lower surface of the n-GaAs substrate 2 and the reinforcing glass substrate 11 is formed on the lower surface.
And an Al electrode 12 is deposited on the upper surface. (b) The Al electrode 12 and the n-GaAs substrate 2 are etched to form a laser beam emitting hole 2b. (c) The first glass layer 3 is deposited on the Al electrode 12 and the n-GaAs substrate 2 by a method such as plasma CVD or sputtering and smoothed by a method such as polishing or filled with an ultraviolet curable resin. , Curing, etc., to fill the etching holes.

(D) A diffraction grating 4 is formed on the upper surface of the first glass layer 3 by a photomask exposure process. That is,
A photoresist is applied to the upper surface of the first glass layer 3, dried, exposed to a diffraction grating pattern, developed, and a diffraction grating 4 is manufactured by ion beam processing or the like. (e) A second glass layer 5 having a different refractive index is laminated on the first glass layer 3 by a method such as plasma CVD or sputtering, and a grating lens 6 is manufactured by a photomask exposure process. (f) The reinforcing glass substrate 11 is removed, and the surface emitting laser 1 and the photodiodes 7, 7 are formed on the lower surface of the buffer layer 47. FIG. 6 shows an example of a buried type configuration of the surface emitting laser 1. n-
On the AlGaAs buffer layer 47, an n + -type GaAs layer 14 to which a large amount of n-type impurities is added to increase conductivity is grown. On this, a reflection mirror layer 15a in which n-type AlAs and GaAlAs are alternately stacked is formed. An n-type GaAlAs cladding layer 16 is grown thereon. Further, a p-type GaAlAs / GaAs quantum well layer 17 is formed to form an active layer. Sufficient characteristics can be obtained by forming the active layer only with GaAlAs, but by using a quantum well, a lower threshold current can be achieved. On the quantum well layer 17, a p-type G
A cladding layer 18 of aAlAs is grown. A reflection mirror layer 1 on which n-type AlAs and GaAlAs are alternately stacked.
5b is formed. A p-type GaAs layer 19 to which a large amount of p-type impurities is added to increase the conductivity is formed thereon. Finally, an Au electrode 20 is formed.

FIG. 7 shows an example of a mesa structure of the surface emitting laser 1. After fabricating the same structure as in FIG. 6, only the laser portion is left in a cylindrical shape, and the other portions are removed by etching. The diameter of the cylindrical mesa is 2 μm to 3 μm,
The height is about 5 μm. Since the diameter of the mesa portion is small, the emission angle θ of the laser beam from the laser portion is 30 ° to 44 °.
゜ is a large value. Therefore, for example, when the focal length = 0.
When using a condenser lens 6 of 1 mm, NA = 0.55,
If the refractive index of the glass layer is 1.5, the distance from the surface emitting laser 1 to the condenser lens 6 can be extremely short, 220 μm to 320 μm, and the optical head 101 can be downsized. In addition, since the effect of binding the optical electric field and the injected current is enhanced by using the mesa type, the threshold current can be reduced.

FIG. 8 shows a configuration example of the photodiode 7. On the n-type AlGaAs buffer layer 47, an n + -type GaAs layer 14 with a large amount of n-type impurities is grown. A GaAs layer 21 not doped with impurities is grown thereon.
A p-type GaAs layer 22 is partially grown thereon. p
Masking a portion of the GaAs layer 22 of the
Form 3 Next, the mask is removed, and the Au electrode 20 is removed.
To form

Normally, the photodiode 7 is manufactured after the surface-emitting laser 1 is manufactured, but both can be manufactured simultaneously. FIG. 9 shows a manufacturing method for simultaneously manufacturing the surface emitting laser 1 and the photodiode 7. (A) On the n-type AlGaAs buffer layer 47, an n + -type GaAs layer 14 to which a large amount of n-type impurities is added to increase conductivity is grown. On top of that, n-type AlAs and GaAlAs
Are alternately stacked to form a reflection mirror layer 15a. (B) Only the portion where the photodiode 7 is to be formed is etched to remove the reflection mirror layer 15a. An n-type AlGaAs layer 25 is formed on the portion where the reflection mirror layer 15a is removed.
Grow. (C) Reflection mirror layer 15a and n-type AlGaAs layer 2
On top of this, an n-type AlGaAs cladding layer 16 is formed. A p-type GaAlAs / GaAs quantum well layer 17 is grown thereon to form an active layer. On top of that, p-type GaAl
An As clad layer 18 is formed. On top of that, n-type Al
Reflection mirror layer 15b in which As and GaAlAs are alternately laminated
Grow. Only the part where the photodiode 7 is formed,
The reflection mirror layer 15b is removed by etching. Then, at the portion where the reflection mirror layer 15b is removed, p-type G
An aAs layer 22 is formed. Further, on the reflection mirror layer 15b and the p-type GaAs layer 22, a p + -type GaAs layer 19 to which a large amount of p-type impurities is added to increase conductivity is formed. (D) An Au electrode 20 is formed on the p + type GaAs layer 19. Then, the surface emitting laser 1 and the photodiode 7 are separated by etching. As described above, if the surface emitting laser 1 and the photodiode 7 are manufactured at the same time, the manufacturing process can be greatly simplified, and the cost can be reduced.

Second Embodiment FIG. 10 is a sectional view showing the configuration of an optical head 102 according to a second embodiment of the present invention. This optical head 102 uses a convex lens instead of the condenser lens 6 in the optical head 101 of FIG. 1 being a grating lens.

Third Embodiment FIG. 11 is a sectional view showing the configuration of an optical head 103 according to a third embodiment of the present invention. The optical head 103 is obtained by attaching film-shaped polarizers 28 and 29 to the lower substrate 2a immediately below the photodiode 7 in the optical head 101 of FIG. The polarizers 28 and 29 have transmission polarization directions orthogonal to each other. When the transmission polarization axis directions of the polarizers 28 and 29 are respectively ± 45 ° with respect to the polarization direction of the reflected light, the detection sensitivity is highest (Ojima, Kakuda “Magneto-optical recording technology” Optics, Vol. No. 11 (1989)
599). FIG. 12 is an example of a signal detection circuit in the optical head 103. As for the defocus signal AF, the outputs of the four photodiodes on the upper and outer sides in FIG. 12 are added by an adder 8a, and the outputs of the four photodiodes on the upper and lower sides are added by an adder 8b. Double adder 8
a, 8b are subtracted by the subtractor 9a. The track shift signal TR is obtained by adding the outputs of the four photodiodes on the upper left side and the lower right side in FIG.
The outputs of the four photodiodes on the upper right side and the lower left side are added by an adder 8d, and the outputs of both adders 8c and 8d are subtracted by a subtractor 9b. When the optical storage medium R is a rewritable MO-type optical disk, the magneto-optical signal MO represents the difference between the sum of the outputs of the photodiodes included in the polarizer 28 and the sum of the outputs of the photodiodes included in the polarizer 28. What should I do? Therefore, the outputs of the four photodiodes on the upper left and lower left in FIG. 12 are added by the adder 8e,
The outputs of the four photodiodes on the upper right side and the lower right side are added by an adder 8f, and the outputs of both adders 8e and 8f are subtracted by a subtractor 9d.

Fourth Embodiment FIG. 13 is a sectional view showing the configuration of an optical head 104 according to a fourth embodiment of the present invention. The optical head 104 includes the optical heads 101, 102, and 10 of the first to third embodiments.
An AF actuator 35 is provided around 3 (however, FIG. 13 includes an optical head 101). The optical recording medium R is an optical disk. The optical disc is generally 1.2 mm thick on the information reading side of the recording surface 40.
Of the transparent protective layer 34 of FIG. For example, laser side NA =
When a finite condensing lens 6 of 0.3 is used, the distance from the surface emitting laser 1 to the condensing lens 6 is about 2 mm, and the size of the optical head 104 is 3 mm × 3 mm × 3 mm.
About.

Fifth Embodiment FIG. 14 is a sectional view showing the configuration of an optical head 105 according to a fifth embodiment of the present invention. The optical head 105 includes the optical heads 101, 102, and 10 of the first to third embodiments.
The slider bottom reinforcing layer 13 made of a ceramic material such as zirconium oxide is formed on the bottom surface of the slider 3, and the whole is processed into a flying slider shape. Since the flying slider is formed integrally with the optical head by a film forming process, there is no need to adjust the positioning of the optical head with respect to the slider bottom surface.

The flying height of the optical head 105 is
5, depending on the shape of the optical recording medium R and the linear velocity of the optical recording medium R. Since the flying height fluctuation amount is about 10% of the flying height in the steady tracking state, the flying height is 26 μm.
About 2.6 μm. Since the focal depth of the condenser lens 6 is approximated by λ / NA2, λ = 0.78 μm
If m, NA = 0.55, it is about 2.6 μm. At this time, since the flying fluctuation amount 2.6 μm is equal to or less than the depth of focus of the condenser lens 6, control of defocus correction becomes unnecessary.
That is, the floating fluctuation amount may be equal to or smaller than the focal depth of the condenser lens 6. However, the optical recording medium R does not have a transparent protective layer on the information reading side of the recording surface, or the transparent protective layer reduces the floating amount from the back focus of the condenser lens in a medium having a refractive index of 1.0 to reduce the floating amount. It should be less than the thickness multiplied by the refractive index. If the transparent protective layer is not provided or the transparent protective layer has a thickness of less than about 100 μm, the dust adheres to the surface, which hinders reading. When the control of the defocus correction is unnecessary, the detection part of the defocus signal AF in the circuits of FIGS. 4 and 12 is also unnecessary.

FIG. 15 shows a method of manufacturing the optical head 105. (a) is a state produced by the process described in (a) to (f) of FIG. (b) The grating lens 6 is masked, and a ceramic such as zirconium oxide is deposited on the periphery thereof by a method such as sputtering to form the slider bottom reinforcing layer 13. The deposited thickness is an amount obtained by subtracting the flying height and the thickness obtained by dividing the thickness of the optical disk protective layer by the protective layer refractive index from the back focus of the grating lens 6 (the distance from the lens surface to the focal point in the air). (c) The reinforcing glass substrate 11 is removed, and the surface emitting laser 1 and the photodiodes 7, 7 are formed on the lower surface of the substrate 2.

Sixth Embodiment FIG. 16 is a sectional view showing the configuration of an optical head 106 according to a sixth embodiment of the present invention. The optical head 106 has a slider bottom reinforcing layer 13 on the bottom surface of the optical head 105 of the fifth embodiment.
And a thin-film type magnetic coil 39 for applying a magnetic field. FIG. 17 is an explanatory diagram of the magnetic coil 39 and its magnetic field. The magnetic field H generated by the circular current I having the number of turns n and the radius a is
On the central axis z, H = na2I / 2√ (a2 + z2) 3. For example, n = 5, a = 50 μm, z = 1
When μm and I = 160 mA, a magnetic field of H = 100 Oe can be obtained.

Seventh Embodiment FIG. 18 shows an optical disk device 20 according to a seventh embodiment of the present invention.
1 is a perspective view of FIG. The optical disc device 201 includes an optical recording medium R having no transparent protective layer on the information reading side of the recording surface or a transparent protective layer having a thickness of less than 26 μm and the floating optical head 105 of the fifth embodiment or the floating optical head 105 of the fifth embodiment. The floating optical head 106 of the sixth embodiment, the support arm 46 supporting the optical head, and the tracking actuator 31 are built in a dustproof case 37, and a power supply and signal connection terminals 45 are provided. The optical disk device 201 has no thick transparent protective layer on the optical recording medium R, and does not include a defocus detection circuit or a defocus correction actuator. Therefore, the optical disc device 201 is extremely thin and lightweight, and can be a portable cartridge. In this case, as shown in FIG. 19, the optical disk writing / reading device 33 is detachably used. The optical disk writing / reading device 33 only needs to incorporate a drive mechanism for the optical recording medium R and a signal processing circuit, and does not require an optical head or a tracking actuator.

-Eighth Embodiment- FIG. 20 shows an optical disk device 20 according to an eighth embodiment of the present invention.
FIG. 2 is a perspective view of FIG. The optical disc device 202 includes an optical recording medium R having no transparent protective layer on the information reading side of the recording surface or a transparent protective layer having a thickness of less than 26 μm, and the floating optical head 105 of the fifth embodiment or the floating optical head 105 of the fifth embodiment. The floating type optical head 106 of the sixth embodiment and a support arm 46 supporting the optical head are built in a dustproof case 38, and a power supply and signal connection terminals 45 are provided. The tracking actuator 31 is provided in the optical disk writing / reading device 330 and can be connected to the support arm 46 of the optical disk device 202. Since the optical disk device 202 does not include the tracking actuator 31, it becomes smaller and less expensive.

[0032]

According to the optical head of the present invention, the attenuation of the laser beam is small, and the problem of chromatic aberration when the wavelength of the light source changes due to a temperature change or the like does not occur. Also,
The problem of noise due to the return light to the semiconductor laser does not occur. Further, there is no problem caused by making the optical path oblique to the optical disk and the problem of the SCOOP structure. According to the method of manufacturing an optical head of the present invention, using a semiconductor process such as a photomask exposure process,
The optical head of the present invention can be manufactured integrally. Further, a surface emitting laser and a photodiode can be manufactured at the same time.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating the relationship between a diffraction grating and a photodiode.

FIG. 3 is an explanatory diagram of a change in light distribution on a photodiode due to defocus.

FIG. 4 is a circuit diagram of a circuit for extracting a signal from the optical head of FIG. 1;

FIG. 5 is an explanatory diagram of a method of manufacturing the optical head of FIG.

FIG. 6 is a sectional structural view of a buried type surface emitting laser.

FIG. 7 is a cross-sectional structural view of a mesa-type surface emitting laser.

FIG. 8 is a sectional structural view of a photodiode.

FIG. 9 is an explanatory diagram of a method for simultaneously manufacturing a surface emitting laser and a photodiode.

FIG. 10 is a sectional view showing the configuration of an optical head according to a second embodiment of the present invention.

FIG. 11 is a sectional view showing the configuration of an optical head according to a third embodiment of the present invention.

FIG. 12 is a circuit diagram of a circuit for extracting a signal from the optical head of FIG. 11;

FIG. 13 is a sectional view showing a configuration of an optical head according to a fourth embodiment of the present invention.

FIG. 14 is a configuration sectional view of an optical head according to a fifth embodiment of the present invention.

15 is an explanatory diagram of the method for manufacturing the optical head of FIG.

FIG. 16 is a sectional view showing the configuration of an optical head according to a sixth embodiment of the present invention.

17 is an explanatory diagram of a magnetic coil and its magnetic field in the optical head of FIG.

FIG. 18 is a perspective view of an optical disc device according to a seventh embodiment of the present invention.

19 is an explanatory diagram of a use state of the optical disk device of FIG. 18;

FIG. 20 is a perspective view of an optical disc device according to an eighth embodiment of the present invention.

[Description of Signs] 101, 102, 103, 104, 105, 106
Optical head, 1 ‥‥ surface emitting laser, 2 ‥‥ n-GaAs substrate, 2a ‥‥ lower substrate, 3 ‥‥ first glass layer, 4 ‥‥ diffraction grating, 5 ‥‥ second glass layer, 6 ‥‥ collection Optical lens, 7,
7a, 7b, 7c, 7d {photodiode, 12}
‥ Al electrode, 8a, 8b, 8c, 8d, 8e, 8f, 9
c {adder, 9a, 9b, 9d} subtractor, 11
Glass substrate, 13 ‥‥ slider bottom reinforcement layer, 14 ‥‥ n +
Type GaAs layer, 15a, 15b reflection mirror layer, 16,
18 ° cladding layer, 17 ° quantum well layer, 19 ° p
+ Type GaAs layer, 20 ° Au electrode, 21 ° GaAs layer, 2
2 ‥‥ p-type GaAs layer, 23 ‥‥ SiO2 insulating layer, 25 ‥
{N-type AlGaAs layer, 28, 29} polarizer, 34}
Transparent protective layer, 36 ° convex lens, 39 ° magnetic coil,
201, 202 ‥‥ optical disk drive, 31 ‥‥ tracking actuator, 33,330 ‥‥ optical disk writer / reader, 45 ‥‥ connection terminal, 46 ‥‥ support arm,
R ‥‥ optical recording medium, 47 ... n-AlGaAs buffer layer

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Claims (3)

[Claims] 1. A substrate, a buffer layer formed on the substrate, a semiconductor laser formed on the buffer layer with the laser light emitting surface of the semiconductor laser and the light receiving surface of the photodetector facing in the same direction. A photodetector; an opening formed in the substrate below the laser light emitting surface and the light receiving surface; a first transparent layer filled in the opening; and a diffraction formed on the lower surface of the first transparent layer. A grating, a second transparent layer laminated below the first transparent layer, and a condenser lens formed by a grating lens, a gradient index lens, or a convex lens formed on the lower surface of the second transparent layer, Laser light emitted from the semiconductor laser passes through the substrate, the first transparent layer, the diffraction grating, and the second transparent layer, and is condensed downward by the condenser lens, and is separated from the condenser lens. Light spot on the recording medium The light reflected by the optical recording medium passes through the condenser lens and the second transparent layer, is diffracted by the diffraction grating toward the light receiving surface of the photodetector, and An optical head, which is transmitted through a transparent layer and received by the photodetector. 2. A semiconductor laser and a photodetector are formed on the same substrate via a buffer layer with a laser light emitting surface of the semiconductor laser and a light receiving surface of the photodetector facing in the same direction. An opening is formed below the light receiving surface by etching, and a first transparent layer filling the opening is laminated by plasma CVD, sputtering, or the like, and a diffraction grating is formed on the lower surface of the first transparent layer by a photomask exposure process. Then, a second transparent layer is laminated below the first transparent layer by plasma CVD, sputtering, or the like.
A method of manufacturing an optical head, wherein a grating lens is formed on a lower surface of a transparent layer by a photomask exposure process, or a gradient index lens or a convex lens is formed by an ion exchange process. 3. A method of manufacturing an optical head, comprising simultaneously manufacturing a surface emitting laser and a photodiode by the following processes (a) to (f): (a) n-type GaAs substrate on n-type GaAs substrate AlGaAs buffer layer is grown, an n + type GaAs layer is grown thereon, and a first reflection mirror layer in which n-type AlAs and GaAlAs are alternately stacked thereon is formed. (B) The first reflection mirror layer is removed by etching only at the portion where the photodiode is to be formed, and an n-type AlGaAs layer is grown on the removed portion. (C) An n-type AlGaAs cladding layer is formed on the first reflecting mirror layer and the n-type AlGaAs layer, and a p-type cladding layer is formed thereon.
A second reflective mirror layer in which a quantum well layer of GaAlAs / GaAs of the type is grown to be an active layer, a cladding layer of GaAlAs of the p type is formed thereon, and AlAs and GaAlAs of the n type are alternately stacked thereon. Grow. (D) The second reflection mirror layer is removed by etching only at a portion where a photodiode is to be formed, and a p-type GaAs layer is formed at the removed portion. (E) p is formed on the second reflecting mirror layer and the p-type GaAs layer.
A + type GaAs layer is formed, and an Au electrode is formed thereon. (F) forming a groove for separating the surface emitting laser from the photodiode;