JPH07201065A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a thin and inexpensive optical recording/reproducing device. CONSTITUTION:A beam outgoing from a laser diode 1a is connected to a #7059 glass heaped layer 5b by a coupler 2a. The waver guided light of the #7059 glass heaped layer 5b is emitted from a coupler 2b and converged on an optical disk 4 by a lens 3. A reflected light of the optical disk 4 advances inversely on the same optical path and is diffracted by a beam splitter 2d then emitted to a photodiode 1b from a coupler 2c. From an output current of the photodiode 1b, a focus error signal is detected by a double knife edge method and a track error signal is detected by a push-pull method.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a compact disc,
A focus error detection mechanism and a track error detection mechanism for recording and reproducing an optical disk such as a phase change optical disk,
The present invention relates to an optical recording / reproducing device having an information signal detecting mechanism.

[0002]

2. Description of the Related Art As an example of a conventional optical recording / reproducing apparatus,
There is an optical head described in the ISO / ODS'93 conference record (pages 18 and 19). FIG. 4 shows a cross-sectional view of this optical head, and FIG. 5 shows the structure of the optical module that is the key device.

A conventional optical head is an optical module 10
Holder 105 for all optical systems such as 0 and lens 101
The optical disc 106 is reproduced by driving the holder 105 in the focus direction and the track direction of the optical disc 106. The emitted light from the laser diode 107 is reflected by the mirror 108, the mirror 103, and the mirror 104, and the optical disc 1 is reflected by the lens 101.
It is focused on 06. The light reflected by the optical disk 106 travels in the same optical path in the opposite direction, and the hologram optical element 10
The light is diffracted by 2 and received by the photodiode 109.

Laser diode 10 in one package
The optical module 100 of the conventional example in which 7 and the photodiode 109 are hermetically sealed has been downsized and its reliability has been secured. In addition, the optical head of the conventional example includes the mirror 10
The light was turned back by the mirror 3 and the mirror 104 to achieve a thin structure.

The optical head of the conventional example was significantly thinner than the previous optical heads, but was still thicker than the hard disk head. However, to make the lens 101 thinner is to make the lens 1
01 is deteriorated, which is difficult and the mirror 103
Therefore, it is required to reduce the thickness of the optical system including the mirror 104 and the hologram optical element 102.

The use of the optical waveguide is very effective as a means for reducing the thickness of the optical system. As an example of an optical recording / reproducing device equipped with an optical waveguide, an optical memory symposium '
There is an optical integrated disk pickup described in 92 papers (pages 109 and 110). FIG. 6 shows an optical integrated disc pickup.

The light emitted from the laser diode 110 is coupled to the movable head portion 112 by the optical fiber 111 and guided through the optical waveguide portion 112a. This guided light is transmitted through the condensing grating coupler 112b to the optical disc 114.
Is focused on. Reflected light from the optical disc 114 travels in the same optical path in the opposite direction, is diffracted by the grating beam splitter 112c, and is received by the photodiode 112d.

The optical waveguide portion 112a is a photodiode.
SiO is formed on the Si substrate 113a on which 112d is formed.₂Bag
Fiber layer 113b and # 7059 glass waveguide layer 113c and S
iO₂ It is produced by sequentially depositing the cover layer 113d.
Made Further, the condensing grating coupler 112
b and the grating beam splitter 112c
It was formed by depositing a SiN film on the waveguide 112a. Well
Also, the photodiode 112d may be loaded with an Al film.
Stray light is blocked by and.

The optical integrated disk pickup is an example of an optical recording / reproducing apparatus which is made as thin as possible by using an optical waveguide. However, if the laser diode 110 is used to actually construct an optical integrated disk pickup, a temperature controller and an isolator are indispensable. This is because the oscillation wavelength of the laser diode 110 becomes unstable when the temperature changes or the light reflected by the optical disc 114 returns, and the condensing grating coupler 112b is sensitive to the wavelength of the light. This is because it is not possible to collect light of wavelengths other than the above. In fact, in the experiment of the operation of the optical integrated disk pickup, it was confirmed by using a Ti: Al ₂ O ₃ laser having a stable oscillation wavelength instead of the laser diode 110.

[0010]

Since the optical integrated disk pickup uses the condensing grating coupler 112b instead of the lens 101, it is necessary to keep the wavelength of the light source constant. This is because of the optical recording / reproducing apparatus. It causes the price to rise. Further, the optical integrated disc pickup uses the Si substrate 113a, which is expensive enough to form the photodiode 112d, also as the substrate of the optical waveguide portion 112a without photoelectric conversion, but this is also the price of the optical recording / reproducing apparatus. Cause rise.

It is an object of the present invention to provide a thin and inexpensive optical recording / reproducing apparatus.

[0012]

In order to solve the above-mentioned problems, an optical recording / reproducing apparatus of the present invention comprises a module in which a semiconductor light emitting element and a semiconductor light receiving element are hermetically sealed, and an output from the semiconductor light emitting element. A lens for converging the emitted light on the recording medium, which is provided between the module and the lens, guides the emitted light to the lens, and deflects the reflected light from the recording medium to the outside of the optical axis of the emitted light. In an optical recording / reproducing device including a light guide element for guiding the deflected light to the semiconductor light receiving element, the light guide element is a flat optical waveguide, and the emitted light and the reflected light are provided in the optical waveguide. The configuration is characterized in that a coupler for coupling the deflected light is provided, and the module and the lens are mounted on the same surface of the light guide element.

[0013]

Since the module in which the semiconductor light emitting element and the semiconductor light receiving element are hermetically sealed is mounted on the same surface as the lens of the light guide element, the optical recording / reproducing apparatus of the present invention has the same thickness as the light guide element. No more than the sum of the lens thicknesses. Further, since the optical recording / reproducing apparatus of the present invention uses the coupler and the lens together and does not give the light-collecting action to the coupler, even if the wavelength of the light source changes, the light is condensed on the optical disc. Wavefront aberration does not occur in the emitted light.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the optical recording / reproducing apparatus of the present invention will be described with reference to FIG. Here, FIG. 7A is a perspective view of this embodiment, FIG. 7B is a sectional view of this embodiment, and FIG. 7C is a plan view of this embodiment as seen from the optical waveguide 2 side. is there. In this embodiment, a laser diode 1a and a photodiode 1b are used.
Is composed of a module 1 hermetically sealed, an optical waveguide 2, and a lens 3.

The optical waveguide 2 has # 70 on the SiO ₂ substrate 5a.
After the 59 glass is deposited by sputtering, the couplers 2a, 2b, 2c and the beam splitter 2d are formed on the # 7059 glass deposition layer 5b by etching.

The light emitted from the laser diode 1a is coupled to the # 7059 glass deposition layer 5b by the coupler 2a. The guided light of the # 7059 glass deposition layer 5b is emitted from the coupler 2b and focused on the optical disc 4 by the lens 3. The light reflected by the optical disk 4 follows the same optical path in the opposite direction, is diffracted by the beam splitter 2d of the optical waveguide 2, and is emitted from the coupler 2c to the photodiode 1b.

A plan view of the module 1 is shown in FIG. The photodiode 1b has a light receiving portion 1 divided by a dividing line 1d.
c and a light receiving portion 1e, and a light receiving portion 1f and a light receiving portion 1h divided by a dividing line 1g. The two emitted lights from the coupler 2c are condensed on the dividing line 1d and the dividing line 1g, respectively. The currents output from the light receiving portions 1c, 1e, 1f, 1h are respectively output currents Ic, Ie, If, I.
If h, the focus error signal is detected from (Ic-Ie)-(If-Ih) by the double knife edge method, and the track error signal is (Ic +) by the push-pull method.
Ie)-(If + Ih). The information signal is detected from (Ic + Ie) + (If + Ih).

In this embodiment, the Si substrate is used only for the photodiode 1b which must be the Si substrate, and the inexpensive S
The cost is reduced by using the iO ₂ substrate for the optical waveguide.

A second embodiment of the optical recording / reproducing apparatus of the present invention will be described with reference to FIG. The present embodiment is an apparatus in which the optical waveguide 2 of the first embodiment is replaced with an optical waveguide 6 whose sectional view is shown in FIG. FIG. 3A is a sectional view showing the entire optical waveguide 6,
3B is an enlarged sectional view showing the coupler 6c of the optical waveguide 6, FIG. 3C is an enlarged sectional view showing the coupler 6a of the optical waveguide 6, and FIG. 3D is an optical waveguide. It is sectional drawing which expanded and showed the coupler 6b of No. 6.

Since an amorphous semiconductor such as As ₂ S ₃ has a property that its refractive index changes when exposed to light, a sinusoidal refractive index change inclined with respect to the surface can be realized by two-beam interference exposure. Therefore, the coupler using the amorphous semiconductor has a maximum coupling efficiency of 10 by designing the inclination angle of the refractive index change so as to satisfy the Bragg diffraction condition.
It can be 0%. If the coupling efficiency is high, the light emission intensity of the light source can be lowered, so that the power consumption and life of the light source can be improved. In addition, the coupler using Bragg diffraction is
Since the coupling angle does not change even if the wavelength of light changes, when used in an optical recording / reproducing apparatus, no wavefront aberration occurs in the focused spot.

The optical waveguide 6 has # 70 on the SiO ₂ substrate 7a.
After depositing 59 glass by sputtering and loading As ₂ S _{3 on} this # 7059 glass deposition layer 7b, As ₂ S ₃ loading layer 7c
Further, the couplers 6a, 6b, 6c and the beam splitter 6d are manufactured by two-beam interference exposure. Here, the thickness and the change in the refractive index of the As ₂ S ₃ loading layer 7c are designed so that the coupling efficiency of the couplers 6a, 6b, 6c is 100%.

[0022]

As described above, according to the present invention, it is possible to realize a thin and inexpensive optical recording / reproducing apparatus which does not cause wavefront aberration in the focused spot even if the wavelength of the light source changes.

[Brief description of drawings]

1A and 1B are diagrams showing an optical recording / reproducing apparatus according to a first embodiment of the present invention, in which FIG. 1A is a perspective view, FIG. 1B is a sectional view, and FIG.
Is a plan view.

FIG. 2 is a plan view showing a module 1 which constitutes the optical recording / reproducing apparatus of the first embodiment of the present invention.

3A and 3B are cross-sectional views showing an optical waveguide 6 constituting an optical recording / reproducing apparatus of a second embodiment of the present invention, FIG. 3A is an overall view, FIG. 3B is an enlarged view near a coupler 6c, and FIG. () Is an enlarged view near the coupler 6a, and (d) is an enlarged view near the coupler 6b.

FIG. 4 is a conventional example of an optical recording / reproducing apparatus. It is sectional drawing of an optical head.

FIG. 5 is a structural diagram of an optical module that constitutes an optical head of a conventional example.

FIG. 6 is a perspective view of an optical integrated disk pickup that is a conventional example of an optical recording / reproducing apparatus.

[Explanation of symbols]

1 Module 1a Laser diode 1b Photodiode 1c Light receiving part 1d Dividing line 1e Light receiving part 1f Light receiving part 1g Dividing line 1h Light receiving part 2 Optical waveguide 2a Coupler 2b Coupler 2c Coupler 2d Beam splitter 3 Lens 4 Optical disk 5a SiO ₂ Substrate 5b # 7059 Deposited layer 6 Optical waveguide 6a Coupler 6b Coupler 6c Coupler 6d Beam splitter 7a SiO ₂ substrate 7b # 7059 Glass deposited layer 7c As ₂ S ₃ Loading layer 100 Optical module 101 Lens 102 Hologram optical element 103 Mirror 104 Mirror 105 Holder 106 Laser disk 107 Optical disk 107 Diode 108 Mirror 109 Photodiode 110 Laser diode 111 Optical fiber 112 Movable head part 112a Optical waveguide part 112b Light grating coupler 112c grating beam splitter 112d photodiode 113a Si substrate 113b SiO ₂ buffer layer 113c # 7059 glass waveguide layer 113d SiO ₂ cover layer 114 optical disc

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[Procedure amendment]

[Submission date] September 22, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Amorphous semiconductors such as As ₂ S ₃ are
Since the refractive index changes when exposed to light, a sinusoidal refractive index change inclined with respect to the surface can be realized by two-beam interference exposure. Therefore, a coupler using an amorphous semiconductor has a maximum coupling efficiency of 1 by designing the inclination angle of the refractive index change so as to satisfy the Bragg diffraction condition.
It can be set to 00%. If the coupling efficiency is high, the light emission intensity of the light source can be lowered, so that the power consumption and life of the light source can be improved.

Claims (2)

[Claims] 1. A module in which a semiconductor light emitting element and a semiconductor light receiving element are hermetically sealed, a lens for converging light emitted from the semiconductor light emitting element onto a recording medium, and a module disposed between the module and the lens. An optical recording / reproducing apparatus including: a light guide element that guides the emitted light to the lens, deflects the reflected light from the recording medium to the outside of the optical axis of the emitted light, and guides the deflected light to the semiconductor light receiving element. In, the light guide element is a flat optical waveguide, the optical waveguide is provided with a coupler for coupling the emitted light, the reflected light and the deflected light, the module and the lens are the same surface of the light guide element. An optical recording / reproducing apparatus, which is mounted on. 2. The amorphous semiconductor having a refractive index change that couples a light wave so as to satisfy a condition of Bragg diffraction.
The optical recording / reproducing apparatus described.