JPH01122042A - Waveguide type optical head - Google Patents

Abstract

PURPOSE:To efficiently produce an optical head with less read error by emitting emission light beams from a focusing grating coupler to a substrate side, and next, making the light beams incident vertically on an optical disk. CONSTITUTION:A photodetector 5 is attached to the end surface of a light waveguide 8, and the light beams from a semiconductor laser 1 are coupled to the light waveguide 8, and the waveguided light beams are led to the focusing grating coupler FGC 9, and the waveguided light beams are diffracted into the substrate 7 by the FGC 9, and are emitted from the end surface of the substrate, and in addition, images a focus on the surface of the optical disk 6. The reflected light beams from the optical disk 6 surface return to the FGC 9, and return again to the waveguide 8, and the light beams are divided into two parts by a grating lens 11, and the each divided light beams are supplied the photodetector 5, and information is read. Then, only the emission light from the substrate end surface, cut diagonally and ground, among the emission light beams from the FGC 9 are reflected by a reflecting mirror 12 formed on the surface of a case 13, and come incident vertically on the optical disk 6 surface.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to an optical recording medium that can read information from an optical recording medium.
This relates to a companion waveguide type optical head that uses all optical waveguides.

[Conventional technology]

Is the optical head a tiny spot created by laser beam VC? make use of,
It is capable of high-density optical recording or magneto-optical recording and high-speed reading of information on optical recording media. For example, read-only discs have been put into practical use as video discs and digital audio discs. Well done,
Optical disk systems and magneto-optical systems that allow additional writing are also in the development stage.

This type of optical head that can read information from an optical storage medium is known to use optical components such as lenses, prisms, and beam slits. FIG. 4 is a schematic diagram showing an example of a conventional optical head. In this FIG. 4, 1 is a semiconductor laser, 2 is a collimator lens that can convert the emitted light from this semiconductor laser 1 into parallel light, 3 is a beam splitter, and 4 is a light beam from this beam splitter 3. A condensing lens that can condense light onto the optical recording medium 6, and 5 a photodetector.

In the Yuko head configured in this way, the semiconductor laser 1
The emitted light is collimated by the collimator lens 2, passed through the beam sinter 3, and roughly formed as a spot on the optical recording medium 6 by the condenser lens 4. By passing the reflected light from this spot through the condensing lens 4 and the beam 1 ritter 5 and detecting it with the photodetector 5.

iI'U Read the information on the optical recording system 6.

However, in this unconventional optical system, it is necessary to accurately adjust the position of each optical component, and the adjustment requires a long time. Furthermore, there are limits to the reduction in size of the optical head as a whole, as well as the reduction in size of the optical components.

In order to solve all of the problems of the optical head shown in FIG.
Publication No. 4).

FIG. 5 is a front view showing an example of a conventional waveguide type optical head. In FIG. 5, 8 is a thin film optical waveguide formed on the substrate 7, 10.11 is a beam splitter and a waveguide lens formed on the leading waveguide 8 and is a 7'C thin film, and 9 is a leading waveguide. A condensing type grating coupler that emits light upward from the tip metal optical waveguide surface with four waves and condenses the emitted light, 1 and 5 are semiconductor lasers and photodetectors respectively provided on the end face of the optical waveguide. It is.

With this configuration and 7t%, the light is 4?8! The light from the semiconductor laser 1 is incident from the end face of the path 8, its traveling direction is changed by the beam splitter 10, and the light is emitted by the condensing grating coupler 9, so that the light is applied to the varnish hole H on the optical recording medium (not shown) of the optical disk 6. Form. The reflected light from this spot is then guided into the optical waveguide again using a condensing grating, travels straight through the beam splitter, is focused by the waveguide lens 11, and is guided to the photodetector. =9, I can read the information sound on the light record @ plot.

[Problems that the invention aims to solve]

Conventional waveguide optical heads have the following manufacturing and characteristic problems. That is, the manufacturing problem relates to condensing grating type Kagura (hereinafter referred to as FGC). The shape pattern of an FGC is generally a hyperbola, and the hyperbola is formed in a material with a refractive index different from that of the optical waveguide, and the average value of the spacing between each hyperbola, that is, the lattice spacing A of the grating, is (1) It is given by Eq. Here, A is - When FGCi is formed using a convergent material, A=a/(N-008ψ) (1) ψ: Output angle of guided light with respect to the leading wavefront N: Effective refractive index of optical waveguide λ: Air The wavelength of the light inside is 2 jm or less, and therefore the hyperbolic line width is half of A, that is, 1 μm or less, making it difficult to efficiently form pFGc. For example, using a SiO□-based N=1.5 glass waveguide, -30. In the case of a general optical head where A is α7μm, A is 1.1βm, which is half of A, or 05μm.
The hyperbola in May must be fully formed.

There is a single-beam lithography system as a technology for forming submicron hyperbolic AT shadows, but the workability is poor when the device is used all around.
Since it takes a long time to form an FGC consisting of about 1,000 hyperbolic groups, there is a problem that it is not suitable for mass production.

On the other hand, there are problems with the characteristics as described below. That is, the fcFGC formed as described above has an emission angle i90'
Therefore, in principle, it is not possible to make light incident perpendicularly to the optical disc. In other words, the range in which equation (1) holds true is the condition of 90 degrees, and when the emission angle is inclined with respect to the optical disk, the shape of the spot is deformed on the optical disk surface, and the information can be read accurately. There were many times when I was unable to do so.

[Friendly means of solving problems]

The above problem? Ninthly, the present invention's 4'IB1. The path-shaped optical head is designed so that the light emitted from the F'GC is emitted diagonally downward with respect to the harmful wave path surroundings, that is, toward the substrate side, by increasing the grid spacing A, and the light emitted from the FCC is Before the light enters the optical disc, a reflector is installed to bend the entire direction of travel of the light so that the light enters the optical disc perpendicularly.

[Effect]

By outputting the light emitted from the FCC to the board side, the FGC
The lattice spacing A is as shown in the following equation. For example, A fable λ/
(N -n0oo8q) (2) no: A glass waveguide with a substrate refractive index of SiO
°, λf117sm - In the case of a convergent optical head, A
is 508 μm, and it is sufficient to form a hyperbola of line @1.54 am. This a is larger than the conventional method of emitting the light emitted from the FCC to the air side, and the machine width is at a level that allows FGC to be formed in the photolithography process without using an electron beam lithography device. This makes it possible to form FGC efficiently.

The advantageous effect of this invention is that the entire circumference of the substrate is made of a material with a high refractive index n0.

On the other hand, the angle of the reflecting mirror with respect to the optical waveguide surface is #gold? -1-
By installing the optical disk so that it is T, the light can be incident perpendicularly to the optical disk. Figure 2 is a cross-sectional view of this waveguide type optical head.
FIG. 5 is a perspective view showing the optical waveguide surface of this four-wavelength optical head.

To explain the outline of this waveguide type optical head, an optical waveguide is provided on the substrate 7, and the information on the optical disk 6 can be read by guiding the wave from the semiconductor laser 1 to the optical waveguide and converting it into a laser beam. It is something. In FIG. 5, a photodetector 5 is attached to the end face of the semiconductor laser 1, and the light from the semiconductor laser 1 is coupled to a 4-wave path 8. Therefore, the four-wave light is diffracted into the substrate and emitted from the surface of the substrate,
The light is focused on the optical disk surface, and the reflected light from the optical disk surface returns to the FGC, returns to the waveguide again, and is cut into two parts by the grating lens 11, and is divided into nine beams. The information is read by condensing the light and entering the photodetector 5.

Here, as shown in Figure 2, the light emitted from F'GO is
The light emitted from the end face of the nine substrates cut and polished diagonally is formed on the surface of the case 15, is reflected by nine reflections @12, and enters the optical disk surface perpendicularly.

FIG. 6 shows the emission angle of the guided light, the angle of the substrate end face, and the angle of the reflecting mirror with respect to the leading waveguide surface.

Here, if the angle that the diffracted light from the center of the FGC makes with the light 4e and the road surface is -, then the angle α of the cutting and polishing surface of the substrate end face is 6 wt T −9. Due to this construction, the light emitted from the FGC is emitted perpendicularly from the surface of the substrate. The inclination angle # of the reflecting mirror with respect to the optical waveguide surface is -1τ10.

To do this, the first step is to first make the light incident perpendicularly to the optical disk, which is oriented parallel to the optical waveguide surface.

The shape of the 1'GC and the shape of the waveguide lens can be found in the literature (Shogo Ura, Toshiaki Suhara, Hiroshi Nishihara, Tsugube Koyama: Journal of the Institute of Electronics and Communication Engineers, Vol.
lJ68-C, No. 1111.1985. P805~8
11) An edge can be formed by the method described in K. - The reflecting mirror 7 of the present invention can be easily formed by vacuum deposition of metal such as aluminum or gold. The reflecting mirror may be formed by forming a metal film on a specially prepared reflecting mirror forming substrate and bonding this to the case 15, or by directly vapor depositing metal onto the case. .

The case 15 of the present invention can be made by cutting and polishing various metals or by forming a glass material.

A glass molded material is particularly suitable for the optical head of the present invention because it has a light I content and is easy to manufacture.

The optical head constructed in this way is thin and lightweight, with a thickness of several millimeters, so we designed it to be mounted on an actuator that can vibrate in the focal direction (vertical direction) and in the direction orthogonal to the track. 9. It is possible to easily follow positional fluctuations of the optical disc.

Here, when the waveguide type optical head is turned on, the subsequent light emitted from the semiconductor laser enters the optical waveguide, forms a leading waveguide, passes through the optical waveguide lens, and enters the FGC.

The friendly light is diffracted by the FGCK and sinks into the substrate, and is emitted perpendicularly to the cut and polished surface from the end surface of the substrate that has been cut and polished at a predetermined angle.

The emitted light is reflected by a reflecting mirror, has its direction changed, and enters the optical disc perpendicularly. The light reflected by the information recording medium on the optical disk is reflected by one reflecting mirror, enters the FGC from the end face of the substrate, and enters the optical waveguide. The return destination that enters the optical waveguide is divided into two parts by the waveguide lens, and each part is focused and enters the photodetector (Lf).
, the information is read. The nine signals read are fed back to the vibration of the actuator and tracked as the incident light on the optical recorder comes into focus.

The substrate, thin film materials, and manufacturing method used in the present invention will be explained below. First, as the substrate material, semiconductors such as quartz, optical glass and Sl, and optical crystals such as LiNb (1, etc.) can be used.As the optical path, 5in2 thread glass, quartz, etc. can be used. A 4-layer film with a thickness of about 1 to 2 μm is used.If a material with a high refractive index such as 81 is used as the substrate, the 4-wave path area also has a refractive index between the 4-wavelength optical path and the substrate. Form a small thin film layer to reduce optical loss. For the waveguide lens and manufactured FGC, it is preferable to use a material with a relatively high refractive index such as TiO2, Ta, O, etc. from the viewpoint of efficiency. However, from the viewpoint of efficiency. , 5102 series glass thin films can also be used.

The waveguide lens and F'GC are formed by disposing a photoresist tm on the thin film for forming an optical element, exposing it to light through a photomask, and developing it to form a resist pattern for the optical element, and then removing the entire resist pattern. It is possible to form a mask by etching the thin film. The F'GC and waveguide lens were manufactured by Nishihara, Haruna,
Co-author Suhara: Hikarisu Kikaku P279, Ohmsha (1985
If you design it according to the method described in

〔Effect of the invention〕

As explained above, if the present invention is implemented, since the gap between the FCC patterns is large, optical elements can be formed in the photolithography process in semiconductor process technology, and optical heads can be efficiently produced. 'By using a reflecting mirror, the light emitted from the GC is incident perpendicularly to the optical disk surface, making it possible to produce an optical head with fewer reading errors.

[Brief explanation of the drawing]

1 is a perspective view showing a waveguide type optical head according to an embodiment of the present invention, FIG. 2 is a sectional view showing a cross section of the waveguide type optical head shown in FIG. 1, and FIG. FIG. 4 is a configuration diagram showing a conventional bulk type optical head, FIG. 5 is a schematic diagram showing a conventional waveguide type optical head, and FIG. 6 is a perspective view showing the optical waveguide surface of the waveguide type head. FIG. 3 is an explanatory diagram showing a cutting and polishing angle, an FGC emission angle, and a reflecting mirror installation angle of a substrate end face of a waveguide type optical head according to an embodiment of the invention. Explanation of symbols 1: Semiconductor laser, 58 photodetector, 6: Optical disk, 7: Substrate, 8: Optical waveguide, 9: Concentrating grating coupler, 11: Waveguide lens, 12
:Reflector, 13:Case

Claims (1)

[Claims] 1. In a waveguide-type optical head in which an optical waveguide is provided on a substrate and information on an optical recording medium can be read by laser light guided from a semiconductor laser to the optical waveguide, a semiconductor is provided on the end face of the optical waveguide. A laser and a photodetector are attached, and a thin film having a refractive index different from that of the optical waveguide layer is formed on the top surface of the optical waveguide in an unevenly spaced curved shape. A condensing grating coupler that has the function of converging the laser beam to one point, a reflecting mirror whose inclination angle is set so that the light emitted from the end face of the substrate is incident perpendicularly to the optical disk, and a reflection mirror that has the function of converging the laser beam to one point, A guide characterized in that a substrate is mounted on an actuator that has a grating lens that has a function of dividing light into two parts and focusing each part, and can vibrate in a direction perpendicular to the optical disk surface and in a direction perpendicular to the track. Wave-shaped optical head.