JPS6390887A - Optical apparatus - Google Patents

Abstract

PURPOSE:To provide a high precision and small size as well as simplified and inexpensive manufacture to an optical device adapted for reflecting the light from a light emitting element to the exterior by means of a prism and guiding the light returning from the exterior to a photo detector by means of the prism by integrally forming the prism, photo detector and light emitting element using a crystal as the material. CONSTITUTION:A groove 4 having a 'V'-shaped cross section is formed in the intermediate part of the surface of a transparent crystal substrate 1, and one side of the groove 4 of the crystal substrate 1 is made into a prism 7 having one or a plurality of photo detectors 9-11 formed on the surface or the side thereof. Also, the surface 14 of the other side of the rear groove 4 is made lower than the height of the surface 2 of the one side, and on the surface 14, a light emitting element 15 for emitting a light directing to the prism 7 is integrally formed. For instance, in the intermediate part of the surface 2 of a crystal substrate 1 made of n-type A GaAs, a groove 4 having a 'V'-shaped cross section is formed by means of an anisotropical etching, and photo diodes 9-11 are formed in the rear side 3 of the prism 7 on the left of the groove 4. Further, as to a light emitting element forming section 13 on the right, the height of the surface 14 is made lower than that of the surface 2, and on the surface 14 a laser diode 15 is formed.

Description

Detailed description of the invention A. Industrial field of application B1 Overview of the invention C1 Background art [Figures 7 and 8] D1 Problems to be solved by the invention E9 Means for solving the problems F1 Effects G. Examples [Figures 1 to 6] H9 Effects of the invention (A. Field of industrial application) The present invention reflects light from an optical device, particularly a light emitting element, to the outside by a prism, and returns the light from the outside. The present invention relates to an optical device in which light is directed to a light receiving element f through a prism.

(B. Outline of light emission 111) The present invention reflects light from one light emitting element to the outside by a prism, and returns light from the outside to the light receiving element f.
In order to simplify manufacturing, increase rust resistance, reduce size, and reduce costs, optical devices designed to lead to This is what I did.

(C, Background Art) [Figures 7 and 8] In the past, optical heads used for signal reading in compact display players and laser disc player caps have three beams (one main beam and one main beam) using a diffraction grating. Many types were used in which two sub-beams were created, tracking was performed using a three-beam method, and focusing was performed using an astigmatism method using a cylindrical lens.

However, such conventional optical heads include light emitting elements (laser diodes), diffraction gratings, beam splitters,
It consists of a large number of parts, such as an objective lens, a cylindrical lens, and a light receiving element, which not only increases the price of the parts used as a whole, but also requires that each of the above optical parts be assembled in a predetermined positional relationship. Since adjustments must be made with extremely high precision, the cost of assembling and adjusting optical components has also become extremely high. Furthermore, the large number of optical parts constituting an optical head inevitably restricted the miniaturization of the optical head, which in turn hindered the miniaturization of compact display players and video display players.

Therefore, the applicant company has developed an optical head using an optical device as shown in FIGS. 126318, Japanese Patent Application No. 61-38575, etc.

In the drawing, a denotes an optical device, in which a laser diode b is fixed to a Si substrate C by tin soldering or the like, photodetectors d, e, f, and g are formed on the 3Si substrate C, and a prism h made of glass and having a trapezoidal cross section is formed. the photodetector d by glue,
It is fixed on e and f.

The prism h has an inclined surface i facing the laser diode b, and a portion of the prism j facing the Si substrate C other than the vicinity of the photodetector f, which is a semi-transparent reflective surface. The inner surface facing J is an internal reflective surface.

As shown in FIG. 8, the photodetectors d and e are three photodetectors d1 to d3 and el- arranged in a fixed direction, respectively.
e3, and these photodetecting parts dlNd3, e1 to e3
are connected to operational amplifiers R, ~n.

The photodetector f hits four photodetectors and is used for trunking detection. In addition, the photodetector g is a laser diode'
It is used as a monitor for automatic output control of b.

In such an optical device, a portion of the laser beam 0 emitted from the laser diode b is reflected by the inclined surface i, passes through an objective lens of an optical device enclosing cap (not shown), and is irradiated onto an optical recording medium such as a compact disk. and is reflected there. The reflected laser beam passes through the objective lens 'JtL, returns to the inclined surface i of the prism h, and returns to the inclined surface i. However, since the surface j near the photodetector d is a semi-transparent reflective surface, a part of the beam 0 passes through the surface j and enters the photodetector d, and the remaining beam 0 is reflected at the surface j. reflected.

The beam 0 reflected by j is reflected by k and enters the surface j again. Then, a part of the beam 0 incident on j is incident on the photodetector e, and the remainder is
, and is reflected by k and enters the photodetector f.

In this optical device a, the size of the prism h is set so that when the optical recording medium is located at the convergence point of beam 0, it is located above the conjugate point of this convergence point. . Therefore, as shown in figure frJ8, the detectors d, e-
When the optical recording medium is located at the convergence point of beam 0, the spots P of beam 0 in When one gets bigger, the other gets smaller.

A signal corresponding to the focus error is obtained.

Therefore, focusing can be performed by driving the focus servo system using the signal obtained from the operational amplifier n as a focus error signal.

Therefore, by using such an optical device, it is possible to provide an optical head that is extremely small, has a small number of parts, and is relatively easy to assemble. Therefore, it is expected that the optical device having the structure shown in FIG. 7 will contribute to the reduction in cost and size of compact disc players and the like.

(Problem to be solved by the invention) By the way, with the current technology, the prism h has to be processed by polishing glass, making it difficult to reduce the size and cost of the prism. Further miniaturization of optical device a is restricted by prism h, and the manufacturing cost of prism h occupies a large proportion of the total manufacturing cost of optical device a, making it difficult to further reduce the size and price of optical device a. blocked.

Therefore, an object of the present invention is to improve the precision, reduce the size, simplify manufacturing, and reduce cost of an optical device.

(E. Means for Solving the Problems) In order to solve the above problems, the optical device of the present invention reflects the light from the light emitting element to the outside by a prism, and guides the returned light from the outside to the light receiving element by the prism. This optical device is characterized in that the prism, the light-receiving element and the light-emitting element formed on the front or back surface of the prism are integrally formed using a crystal material.

(F. Effect) According to the optical device of the present invention, since the prism is integrated with the light-emitting element and the light-receiving element, it can be manufactured by making full use of semiconductor device manufacturing technology. There is no need to make prisms as parts,
It can be manufactured in a small size with a high degree of strength, and mass production is also possible. The positions between the prism, light-emitting element, and light-receiving element can be precisely determined using phosphorography technology used in manufacturing T-conductor devices.
And no adjustment is required after assembly. Therefore,
Miniaturization of optical devices and optical pickup using the same,
High precision and low cost can be achieved.

(G. Embodiment) [FIGS. 1 to 6] The optical apparatus of the present invention will be explained in detail according to the illustrated embodiments below.

FIG. 1 is a sectional view showing a first embodiment of the optical device of the present invention. In the drawings, 1 is n-type AlxGa, -xAs
It is a crystal substrate consisting of, and its X is, for example, 0.3. The crystal of A I O, 3G a 0.7As is transparent to the laser beam of 780 nm wavelength used for the reading of Ai No. 1 of the Viteo Disc Brayer, etc., and can function well as a prism, so it is suitable for this book. This is the back side of the crystal substrate 1 of the optical device.

4 is a cross-sectional or V-shaped groove formed by anisotropic etching in the middle part of the surface 2 of the crystal substrate 1, 5 is one sloped surface of the groove 4, and 6 is the direction of the sloped surface 5. The slope angle α of the slope surface 5 is, for example, 60
It is about °. The V-shaped groove 4 having the inclined surface 5.6 can be formed by anisotropic etching using the difference in etching rate with respect to the crystal plane of the crystal substrate. The portion to the left of the V-shaped groove 4 in the crystal substrate 1 in FIG. 1 constitutes a prism 7.

A reflective film 8 is formed on the surface 2 of the prism 7 of the crystal substrate 1 to make that surface a completely internal reflective surface. On the back surface 3 of the prism 7 are formed photodiodes 9 and 10 for a focus servo and a photodiode 11 for a tracking servo. These phototiortes 9, 10, and 11 have GaAs on the back surface 3 of the crystal substrate 1.
Alternatively, the conductor layer 12 may be made of a compound such as AuAs. rJ, “-no
し j'l IJ IM Jlllf; L(:
l, -k is formed by selectively etching the semiconductor layer 12 of 3A-'.

The part to the right of the groove 4 of the crystal substrate 1 in FIG. is also lowered appropriately, and its surface 14
A laser diode 15 is formed thereon. The laser diode 15 can be formed by selective epitaxial growth of GaAs or AlGa, or by epitaxial growth on the entire surface and selective etching of the epitaxially grown layer.

Note that since the lattice constants of AlGaAs, GaAs, and A/lAs are substantially the same, a compound semiconductor layer such as GaAs or ARAs is formed on the front surface 14 or the back surface 3 of the transparent substrate 1 made of AuGaAs to form a photodiode or a laser diode. It is quite possible to form one.

Note that 16 is an active layer of the laser diode 15.

FIGS. 2(A) to 2(D) are cross-sectional views showing an example of the method for manufacturing the optical device in the order of steps, and the manufacturing method will be explained with reference to the drawings.

(A) Several layers of a compound semiconductor layer 12 made of GaAs or the like are formed on the back surface 3 of a wafer-shaped crystal substrate 1 by epitaxial growth, and then a reflective film 8 made of metal or the like is deposited on the surface 2 of the crystal substrate 1 by vapor deposition, etc. and then removed by photoetching. After selectively removing the reflection 11Q8 in this way, a resist film 1 is placed on the surface 2 of the crystal substrate 1.
7 is formed and patterned into a predetermined shape to form an etching window 18. Then, by anisotropically etching the surface of the crystal substrate 1 through the window portion 18, a V-shaped 4.5 mm is formed hitting the inclined surface 5.6.

(B) Next, resist IIQ is applied to the surface of the crystal substrate 1 again.
is formed, and the resist film 19 is patterned so as to mask the area other than the portion 13 which is to be the light-receiving element forming area. Then, in that state, etching is performed using RIE etc.
The height of the surface 14 of the light receiving element forming portion 13 is made lower than the height of the surface 2 of the prism 7. FIG. 2(B) shows the state after the etching is completed.

(C) Thereafter, photodiodes 9, 10, and 11 are formed by selectively etching the compound semiconductor layer 12 formed on 'AI]'Ii3 of the crystal substrate 1. Figure 2 (C) shows the state after the selective etching has been completed.
0 (D) Thereafter, as shown in FIG. 2(D), the surface 14-1 of the light emitting element forming portion 13 whose height has been lowered
A laser diode 15 is formed at -. The laser diode 15 can be formed by selective epitaxial growth of several compound semiconductor layers made of GaAs or the like, or by overall epitaxial growth and selective etching of the layer formed by the growth. After that, we did a tying process and attached each optical device! Separate into different parts.

In this way, the entire laser diode 15 can be manufactured as one semiconductor device by using the optical device 11 as shown in FIG. 1 and making full use of semiconductor device manufacturing technology. Therefore, the optical device can be made very compact, the processing precision can be made very high, and costs can be reduced through mass production. Furthermore, the prism 7, the photodiodes 9, 10, 11, and the laser diode 15 can be positioned with the high granularity of photolithography, and there is no need for positioning to be performed by assembly work. Therefore, it is possible to improve the characteristics of the optical device while reducing costs.

3 and 4 show modified examples of the optical device of the present invention, and the optical device shown in FIG. 3 monitors the output of the laser diode 15 on the back surface 3 of the crystal substrate 1. A monitor photodiode 20 is provided for controlling. The photo printer 20 is located on the side opposite to the prism of the light emitting element f-forming section 13.

Note that this photodiode 20 is a photodiode.The optical device shown in FIG. 3
The optical device shown in the figure differs only in that a monitoring photodiode is provided on the front side of the crystal substrate l.

FIG. 5 shows a second embodiment of the optical device of the present invention.

In this optical device, photodiodes 9 and 10 are arranged on the front surface 2 side of the prism 7, and a reflective film 8 is placed on the back surface 3 of the prism 7.
It is placed on the side. The servo photodiodes 9 and 10 are formed at the same time as the laser diode 15 and the monitor photodiode 21. Note that this optical device includes a tracking servo photodiode 11.
Needless to say, the photodiode 11 may be provided.

FIG. 6 is a sectional view showing a modification of the optical device shown in FIG. 5. This optical device has a compound semiconductor layer 22 made of n-AnGaAs for electrode extraction and light absorption.

The optical device shown in FIG.
The IF prevents the light from the servo photodiode 9 and 10 from directly entering the servo photodiode 9 and 10 as stray light (in other words, rather than entering the external optical recording medium and being reflected there to become return light). By limiting the reflection area to a specific area,
In other areas, it is preferable to absorb light in the opposite direction. Therefore, in this optical device shown in FIG. 6, the reflective film 8 is selectively formed on the back surface 3 of the prism 7, and the reflective film 8 is
A compound semiconductor layer 22 made of GaAs is formed in the portion where the i8 is not formed, and the semiconductor layer 22 is used for light absorption and electrode extraction. In addition, 2
3 is an n-type metal layer (Au) formed on the surface of the semiconductor layer 22.
Ge/Ni/A u ).

The following method can be considered as a method for manufacturing such an optical device.

This optical device uses GaAs for light absorption and electrode extraction as a substrate instead of transparent n-Al1GaAs, and n-AflGaAs is epitaxially grown on the substrate, and the transparent crystal layer formed thereby is anisotropically etched. By making full use of this, the V-shaped groove 4 and the low-height light emitting element forming surface are formed. Thereafter, a laser diode 15 and a monitoring photodiode 21 are simultaneously formed by epitaxial growth and selective etching of the grown layer produced thereby. In addition, photodiode 9 for servo
．． 10 is formed in the same manner. In addition, photodiode 9
, lO, laser diode 15, photodiode-1'
21 may be formed at the same time. Then, on the surface of the photodiode 9.10, the laser diode 115, the photodiode 21, a P type, for example, TiP
t Form a metal layer consisting of AU.

Thereafter, the GaAs substrate is lapped (17) from the back side so that only a thin n-GaAs layer 22 remains. 1; n-GaAs layer 22 and an n-type metal layer (Au
After forming the reflective film 8 (Ge/Ni/Au) 23, the metal layer 23 and the semiconductor layer 22 in the area where the reflective film 8 is to be formed are removed by photoetching,
Alternatively, n-Al1.
An optical device as shown in FIG. 6 using a GaAs layer as the crystal substrate 1 can be obtained.

Incidentally, reference numeral 25 denotes an aperture compound semiconductor layer, which was formed at the same time as photodiodes 9 and 10.

As described above, the present invention can be implemented in various ways,
Many variations are possible.

(H, Effect of the Invention) As described above, the optical device of the present invention has a cross-sectional or V-shaped groove formed in the middle part of the surface of a transparent crystal substrate,
A prism is formed in which a plurality of light-receiving elements f are formed on one side, the front surface, or the back surface of the groove of the crystal substrate, and The prism is also characterized in that the height is reduced, and a light emitting element that generates light directed toward the prism is integrally formed on the reduced height surface on the other side of the groove.

Therefore, according to the optical device of the present invention, since the prism is formed integrally with the light emitting element and the light receiving element using a transparent crystal material, it can be manufactured by making full use of semiconductor device manufacturing technology. There is no need to polish the prism to create a prism as a separate component, and the prism can be made compact with high precision, and mass production is possible. Further, the positions between the prism, the light emitting element, and the light receiving element can be determined with high precision by the phosphorography technique used for manufacturing four-conductor devices, and assembly and alignment are not required. Therefore, the optical device and the optical pickup using the same can be made smaller, more precise, and lower in cost.

[Brief explanation of the drawing]

1 is a cross-sectional view showing an optical device, and FIGS. 2 (A) to (D) are cross-sectional views showing the manufacturing method of the optical device shown in FIG. 1 in order of process. , FIGS. 3 and 4 are sectional views showing modifications of the optical device shown in the optical device diagram shown in FIG. 1, and FIGS. 7 and 8 are for explaining the background art. FIG. 7 is a sectional view, and FIG. 8 is a circuit diagram. Explanation of symbols 1... Crystal substrate, 2... Surface of crystal substrate, 3... Back surface of crystal substrate, 4... V-shaped groove, 7... Prism, 9-11...
- Light receiving element, 15... Light emitting element. 1 and 2 show one example of the optical device of the present invention 9 to 11.
1. A cross-sectional view showing the side of the first light-receiving element. FIG. 1. A dark side view showing the manufacturing method in order. FIG. 2. 9-11 Illumination surface showing the first modified example of the element element FIGS. Figure 5 Deformed θ remote diagram

Claims (1)

[Claims] (1) A groove with a V-shaped cross section is formed in the middle part of the surface of a transparent crystal substrate, and one or more light receiving elements are formed on the front or back surface of one side of the groove of the crystal substrate to form a prism. The surface on the other side of the groove of the crystal substrate is made lower in height than the surface on one side, and light directed toward the prism is generated on the lowered surface on the other side of the groove. An optical device characterized in that a light emitting element is integrally formed.