JPH0821754B2 - Optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A. Industrial fields of use B. Outline of invention C. Background art [Figs. 3 and 4] D. Problems to be solved by the invention E. Means for solving problems F. Action G. Embodiments [FIGS. 1 and 2] H. Effects of the Invention (A. Fields of Industrial Application) The present invention relates to an optical device, in particular, light from a light-emitting element is reflected to the outside by a prism and returned from the outside. The present invention relates to an optical device in which a prism is guided to a light receiving element.

(B. Summary of the Invention) The present invention particularly relates to an optical device in which light from a light-emitting element is reflected to the outside by a prism and return light from the outside is guided to a light-receiving element by a prism. In order to achieve higher accuracy, smaller size, and lower cost, the prism and the mount of the light emitting element are integrally formed by a transparent crystal substrate.

(C. Background Art) [FIGS. 3 and 4] An optical head used for signal reading in a compact display, a laser disc player, etc. is conventionally composed of three beams (one main beam and one main beam by a diffraction grating). A type in which two sub-beams are formed, tracking is performed by the three-beam method, and then focusing is performed by the astigmatism method using a cylindrical lens has been widely used.

However, such a conventional optical head is composed of a large number of parts such as a light emitting element (laser diode), a diffraction grating, a beam splitter, an objective lens, a cylindrical lens, and a light receiving element, and the cost of all the parts used increases. In addition, since the above optical components must be assembled so as to have a predetermined positional relationship and adjusted with extremely high precision, the cost required for assembling and adjusting the optical components also becomes very high. The large number of constituent optical components of the optical head inevitably constrains the miniaturization of the optical head, which in turn impedes the miniaturization of compact and video displayers.

Therefore, the applicant company has developed an optical head using an optical device as shown in FIGS. 3 and 4, and has made various proposals relating to the same, in Japanese Patent Application Nos. 61-38576 and 61-1.
26318 and Japanese Patent Application No. 61-38575.

In the drawing, a is an optical device, and laser diode b
Is fixed to the Si substrate c by tin solder or the like, and the photodetectors d, e, f, and g are formed on the Si substrate c, and the prism h having a trapezoidal cross section made of glass is adhered to the photodetector d,
It is fixed on e and f.

In the prism h, an inclined surface i facing the laser diode b and a part of the surface j facing the Si substrate c other than the vicinity of the photodetector f are semitransparent reflecting surfaces, The inner surface k facing the surface j is an inner reflecting surface.

As shown in FIG. 4, each of the photodetectors d and e has three photodetectors d1 to d3 and e1 to e3 arranged in a fixed direction, and these photodetectors d1 to d3, e1 to e3 are operational amplifiers l
Connected to ~ n.

The photodetector f has four photodetectors and is used for trunking detection. Further, the photodetector g is used as a monitor for controlling the automatic output of the laser diode b.

In such an optical device, a part of the laser beam o emitted from the laser diode b is reflected by the inclined surface i,
After passing through an objective lens of a cap (not shown) for enclosing an optical device, the optical recording medium such as a compact disc is irradiated with the light and reflected there. The reflected laser beam passes through the objective lens and returns to the inclined surface i of the prism h, and the inclined surface i
A part of the beam returning to the position (1) passes through the inclined surface i and enters the surface j. However, in the surface j, the vicinity of the photodetector d is a semitransparent reflecting surface, so that part of the beam o passes through the surface j and is incident on the photodetector d, and the remaining beam o is at the surface j. Is reflected.

The beam o reflected by the surface j is reflected by the surface k and re-enters the surface j. Then, part of the beam o incident on the surface j is incident on the photodetector e, and the rest is incident on the photodetector f reflected by the surface j and the surface k.

In this optical device a, the optical recording medium is the beam o.
The size and the like of the prism h are set so that the conjugate point of this convergence point is located on the surface k when it is located at the convergence point. Therefore, as shown in FIG. 4, the spot P of the beam o on the detectors d and e is the beam o on the optical recording medium.
When the optical recording medium is located at the converging point of, the optical recording medium is displaced from the converging point of the beam o, and when one is large, the other is small.

As a result, signals corresponding to the focus error amount are obtained from the operational amplifiers l, m, and n. Therefore, if the signal obtained from the operational amplifier n is used as the focus error signal to drive the focus servo system, focusing can be performed.

Thus, by using such an optical device, it is possible to provide an optical head which is very small in size, has a small number of parts, and is relatively easy to assemble. Therefore, the optical device having the structure shown in FIG. 3 can be expected to contribute to the cost reduction and downsizing of compact disc players and the like.

(D. Problem to be Solved by the Invention) By the way, the above-mentioned prism h must be processed by polishing glass in the present technology, and it is difficult to reduce the size and cost of the prism. Further miniaturization of the device a is restricted by the prism h, and the ratio of the manufacturing cost of the prism h to the total manufacturing cost of the optical device a is increased, so that the optical device a is further miniaturized and reduced in price. Is blocked. And the prism h
It is difficult to sufficiently increase the positioning accuracy among the photodetectors d, e, f and the laser diode b.

Therefore, the present invention simplifies the manufacturing of an optical device in which the light from the light emitting element is reflected to the outside by a prism and the return light from the outside is guided to the light receiving element by the prism. The purpose is to achieve

(E. Means for Solving Problems) In order to solve the above problems, the optical device of the present invention reflects light from a light emitting element to the outside by a prism and guides return light from the outside to a light receiving element by the prism. In such an optical device, the prism and the mount portion of the light emitting element are integrally formed of a transparent crystal substrate.

(F. Action) According to the optical device of the present invention, the prism and the mount portion of the light emitting element are integrated with each other by using the crystalline body as a material, so that these can be manufactured by making full use of the semiconductor device manufacturing technology, and the glass is polished. Therefore, it is not necessary to form a prism as an independent component, and the entire optical device can be made with high precision and small size, and mass production becomes possible. Moreover, it is possible to easily and highly accurately align the light emitting element and the prism by the pellet bonding technique which is frequently used in the semiconductor device manufacturing technology without the trouble of aligning the prism with the light emitting element. Further, since the main part such as the prism is formed of the crystal substrate, the light receiving element formed on the front surface or the back surface can be inevitably formed by utilizing the manufacturing technology of the semiconductor device, and the positional relationship between the prism and the light receiving element is also increased. It can be controlled with high precision.

(G. Embodiment) [FIGS. 1 and 2] Hereinafter, the optical device of the present invention will be described in detail with reference to illustrated embodiments.

FIG. 1 is a sectional view showing an embodiment of the optical device of the present invention. In the drawing, 1 is a crystal substrate made of GaP. GaP crystal (energy gap Eg = 2.261eV) is 78
It is transparent to laser light having a wavelength of about 0 nm, and therefore can sufficiently function as a prism material. The crystal substrate 1
A GaP crystal ingot is sliced on a (001) plane or a plane inclined by 5.3 ° in the <110> direction with respect to the (001) plane to form a wafer, and 2 is a front surface and 3 is a back surface.

Reference numeral 4 denotes a groove having a V-shaped cross section formed by anisotropic etching in the middle portion of the surface 2 of the crystal substrate 1.
The inclined surface 5 constituting the above is the (1) surface, and the inclined surface 6 on the opposite side is the (111) surface. A portion on the left side in FIG. 1 from the V-shaped groove 4 of the transparent substrate 1 forms a prism 7.

A reflective film 8 is formed on the surface 2 of the prism 7 of the transparent substrate 1 so that the surface becomes a perfect internal reflection surface. Then, on the back surface 3 of the prism 7, photodiodes 9 and 10 for focus servo and a photodiode 11 for tracking servo are formed. These photodiodes 9, 10, 11 epitaxially grow a semiconductor layer 12 of an n-type silicon single crystal on the back surface 3 of the transparent substrate 1, and the semiconductor layer 12 is formed.
It is formed by epitaxially growing a P-type silicon single crystal semiconductor layer 13 thereon and then selectively etching the two semiconductor layers 12 and 13.

The portion on the right side in FIG. 1 from the groove 4 of the transparent substrate 1 is a light emitting element mount portion 14, which is etched by RIE or the like so that the surface 15 has a height of the surface 2 of the prism 7.
Is appropriately lower than the height of the
A laser diode 17 is mounted via 16.
Reference numeral 18 denotes the active layer, to which the laser diode 17 is soldered so that the laser beam emitted from the active layer 18 is incident on the inclined surface 5 of the prism 7. The inclined surface 5 is the (1) surface as described above, and is 54.7 with respect to the (001) surface.
The front and back surfaces 2 of the crystal substrate 1,
3 is (001) plane or 5.3 in <110> direction with respect to (001) plane
Since it is a tilted surface, the tilt angle of the tilted surface 5 is 54.7 ° or 60
And is a preferable value as the inclination angle of the inclined surface 5 of the prism 7 (60 ° is more preferable).

FIGS. 2A to 2D are cross-sectional views showing an example of a method of manufacturing the optical device in the order of steps, and the manufacturing method will be described with reference to FIG.

(A) An n-type semiconductor layer 12 made of silicon is epitaxially grown on the back surface 3 of the transparent substrate 1 made of GaP, and a P-type semiconductor layer 13 is further epitaxially grown on the n-type semiconductor layer 12.

Since GaP has a lattice constant of 5.54Å, and GaP and Si have almost the same lattice constant, it is easy to epitaxially grow Si on GaP.

Next, a reflective film 8 made of metal or the like is formed on the surface 2 of the crystal substrate 1.
Are formed by vapor deposition or the like, and are selectively removed by photoetching. After selectively removing the reflective film 8 in this manner, a resist film 19 is formed on the surface 2 of the crystal substrate 1,
This is exposed through a mask having a predetermined pattern,
It develops and forms the window part 20 for etching. Then, the surface portion of the crystal substrate 1 is anisotropically etched through the window portion 20 to form the V-shaped groove 4 having the inclined surfaces 5 and 6. FIG. 1 (A) shows a state after the groove 4 is formed.

(B) Next, a resist film 21 is formed on the crystal substrate 1 again, and a portion 14 of the resist film 21 to be a light-receiving element mounting portion is formed.
Other portions are masked, and in that state, etching is performed by RIE or the like, so that the height of the surface 15 of the light receiving element mounting portion 14 is made lower than the height of the surface 2 of the prism 7. FIG. 2B shows a state after the etching is completed.

(C) After that, the photodiodes 9, 10 and 11 are formed by selective etching of the semiconductor layers 12 and 13 formed on the back surface 2 of the crystal substrate 1. FIG. 2C shows the state after the selective etching is completed.

(D) Thereafter, as shown in FIG. 2 (D), the laser diode 17 is mounted via solder 16 on the surface 15 of the light emitting element mounting portion 14 whose height is lowered. Then, dicing is performed to separate the optical devices from each other.

As described above, according to the optical device as shown in FIG. 1, the prism 7 and the light emitting element mounting portion 14 are formed in a pair, so that the prism 7 and the light emitting element mounting portion 14 can be manufactured by a semiconductor device manufacturing technique. It can be manufactured in small size with precision. Moreover, since it is possible to manufacture a large amount at the same time, it is possible to reduce the manufacturing cost. Moreover, since the prism 7 and the light emitting element mounting portion 15 are integrated, the prism 7 and the laser diode 17 can be positioned with extremely high precision determined by the pellet bonding technique frequently used in the manufacture of semiconductor devices. There is no fear that it will take time to perform the work and adjustment.

Since the servo photodiodes 9 to 11 can be formed by a semiconductor layer epitaxially grown on the GaP 1, the positional relationship between the prism 7, the light emitting element mount portion 14 and the photodiodes 9 to 11 can be determined by the photolithography technique. Positioning can be performed with high accuracy, and no work such as assembly or adjustment after assembly is required.

In the above embodiment, the reflection film 8 was formed on the surface 2 of the prism 7, and the photodiodes 9 to 11 were formed on the back surface 3. However, the photodiodes 9 to 11 may be provided on the front surface 2 side of the prism 7 and the reflection film 8 may be formed on the back surface 3.

(H. Effect of the Invention) As described above, in the optical device of the present invention, a groove having a V-shaped cross section is formed in the middle portion of the surface of the transparent crystal substrate, and one of the grooves of the crystal substrate is formed. Side is formed with one or more light receiving elements on the front surface or the back surface to form a prism, and the surface of the other side of the groove of the crystal substrate is made lower in height than the surface of one side. And a light emitting element that emits light toward the prism is mounted on the light emitting element mounting portion.

Therefore, according to the optical device of the present invention, since the prism and the mount portion of the light emitting element are integrated, they can be manufactured by making full use of the semiconductor device manufacturing technology, and therefore it is not necessary to polish the glass to form the prism. The entire optical device can be made highly precise and small, and mass production becomes possible. Moreover, it is possible to easily and accurately align the light emitting element and the prism by the pellet bonding technique which is frequently used in the semiconductor device manufacturing technology without the trouble of aligning the prism with the light emitting element. Further, since the main part such as the prism is formed by the crystal substrate, the light receiving element formed on the front surface or the back surface can be inevitably formed by utilizing the semiconductor device manufacturing technology. The relationship can be controlled with high precision.

[Brief description of drawings]

FIGS. 1 and 2 are for explaining one embodiment of the optical device of the present invention. FIG. 1 is a sectional view of the embodiment, and FIGS. 2A to 2D are examples of a manufacturing method. 3A to 3D are sectional views showing the order of steps, FIGS. 3 and 4 are for explaining background art, FIG. 3 is a sectional view, and FIG. 4 is a circuit diagram. DESCRIPTION OF SYMBOLS 1 ... Crystal substrate, 2 ... Prism side surface, 3 ... Crystal substrate back surface, 4 ... V-shaped groove, 7 ... Prism, 9-11 ... Light receiving element, 14 ... Light emitting element mount, 17 …… Light emitting element.

Claims (1)

[Claims] 1. A groove having a V-shaped cross section is formed in an intermediate portion of the surface of a transparent crystal substrate, and one side of the groove of the crystal substrate has one or a plurality of light receiving elements formed on the front surface or the back surface. To form a prism, the surface of the other side of the groove of the crystal substrate is made lower in height than the surface of one side to form a light emitting element mounting portion, and the prism is formed on the light emitting element mounting portion. An optical device characterized in that a light emitting element that emits light toward it is mounted.