JP2825873B2 - Optical waveguide - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for recording / reproducing a signal on / from an optical information recording medium and an optical waveguide applicable to an optical head for an optical printer. .

[Conventional technology]

As an optical head (optical pickup) used for recording / reproducing a signal on / from an optical information recording medium such as an optical disk, for example, a combination of optical components as shown in FIG. 6 is well known.

In the optical head having the configuration shown in FIG. 6, a light beam emitted from a semiconductor laser 21 as a light source is converted into a parallel light beam by a collimator lens 22, and after passing through a polarizing prism (polarizing beam splitter) 23, it becomes 1/4. The light is converted into circularly polarized light by the wave plate 24 and is condensed by the objective lens 25 as a light spot having a diameter of about 1 μm on the recording surface of the optical information recording medium 26. Then, the reflected light from the optical information recording medium 26 is again converted into a parallel light flux by the objective lens 25, and is returned to linearly polarized light through the quarter-wave plate 24.
Since the 90 ° polarization plane is changed, the light is reflected in a substantially right angle direction by the polarizing prism 23 and is condensed on the photodetector 29 through the converging lens 27 and the cylindrical lens 28 to detect a recording signal, a focus error signal, and the like. Done.

However, since the optical head shown in FIG. 6 is configured by combining a large number of optical components, there are disadvantages in that the number of components is large, and the optical head is large and heavy.
There is a drawback that the production cost increases because the number of optical components is large. In addition, since a large number of optical components are combined and assembled, there is a problem that it takes time to adjust the assembly and optical axis alignment.

In order to solve this problem, an optical head for recording / reproducing an optical disk signal using an optical waveguide has been proposed. For example, a diffraction grating for optical coupling was formed on a flat optical waveguide. A configuration is known (see Japanese Patent Application Laid-Open No. 61-236037).

[Problems to be solved by the invention]

However, in this type of optical head, since a diffraction grating is used to extract light to the outside or to introduce reflected light from an optical disk into an optical waveguide, for example, the guided light is diffracted to both sides of the diffraction grating. Therefore, there are problems such as low light utilization efficiency with respect to irradiation to the optical disk, and difficulty in manufacturing a diffraction grating for coupling.

The present invention has been made in view of the above circumstances, and has an object to provide a novel optical waveguide that can be applied as a condensing optical system such as an optical head and can easily realize miniaturization of the optical head and the like. I do.

[Means for solving the problem]

In order to achieve the above object, an optical waveguide according to the present invention comprises:
A substrate having a flat surface for forming a waveguide layer, having a lower refractive index than the waveguide layer and being transparent to the guided light, and being formed on the flat surface of the substrate, and radiating the guided light to the substrate side at the tip thereof; A waveguide layer provided with a tapered waveguide layer, and a reflection surface formed on an end face of the substrate and reflecting radiation emitted to the substrate side by the tapered waveguide layer. Features.

[Action]

In the optical waveguide according to the present invention, the guided light propagated in the waveguide layer is emitted to the substrate side by the tapered waveguide layer. Then, the radiated light emitted to the substrate side is reflected by the reflection surface formed on the end face of the substrate, propagates in the substrate in the opposite direction, reaches the other end face of the substrate, and is emitted out of the substrate.

Therefore, according to the present invention, the length of the optical waveguide can be significantly reduced with respect to the optical path length, and the size of the optical head can be easily reduced.

〔Example〕

Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 is a view showing an embodiment in which an optical waveguide according to the present invention is applied to an optical head, and FIG. 1 (a) is a plan view of the optical head viewed from the waveguide layer side. FIG.
FIG. 3 is a side view of the optical head when viewed from the side.

Here, the optical waveguide according to the present invention includes a glass substrate 9 having a plane for forming a waveguide layer, having a lower refractive index than the waveguide layer, and being transparent to the guided light, and A waveguide layer 3 having a tapered waveguide layer (tapered coupler) 10 for emitting guided light toward the glass substrate 9 at the end thereof; and a tapered coupler formed on an end face of the glass substrate 9. 10, a reflection surface 5 for reflecting the radiation light radiated toward the substrate side is provided. In the configuration shown in FIG. 1, a semiconductor laser is further provided on the optical waveguide for use as an optical head. 1. Optical elements such as a photodetector 2, a collimating lens 4, a mirror 6, a beam splitter 7, a waveguide lens 8a, and a grating lens 13a are integrated and integrated. In the illustrated example,
The focusing objective lens is provided outside the substrate.

Hereinafter, the operation of the optical head having the configuration shown in FIG. 1 will be described.

In FIG. 1, a semiconductor laser 1 as a light source is end-coupled to an optical waveguide, and a light beam emitted from the semiconductor laser 1 to a waveguide layer 3 is collimated by a collimating lens 4 and then collimated by a beam splitter 7. The light is bent by 90 °, becomes focused light by the waveguide lens 8a, and propagates through the waveguide layer 3. The light propagated through the waveguide layer 3 is radiated from the waveguide layer 3 to the glass substrate 9 by the taper coupler 10. This radiated light is reflected by the reflection surface of the reflection plate 5 provided on the end face of the substrate, propagates through the substrate 9, and reaches the end face of the substrate on the other side. Here, as shown by a broken line in the drawing, when the substrate end surface on the emission side is substantially perpendicular to the light propagation direction,
The light beam is emitted from the end face, is focused by the objective lens 11 ', and is condensed on the optical disk 12' to form a light spot. When the light emitting side end face of the substrate 9 has a tapered shape inclined at a predetermined inclination angle (for example, 45 °) with respect to the light beam propagation direction as shown by a solid line in the figure, Is reflected at the end face of the substrate,
The light is emitted from the lower surface side of the substrate 9. The emitted light is converged by the objective lens 11 arranged in the emission direction, and is condensed on the optical disk 12 to form a light spot.

The light reflected by the optical disk 12 (or 12 ′) passes through the objective lens 11 (or 11 ′) and the end face of the substrate, propagates through the substrate again, is reflected again by the reflector 5, and is guided by the taper coupler 10. The light is incident on the layer 3. Then, the reflected light from the disk incident on the waveguide layer 3 is converted into a waveguide lens.
After being converted into parallel light by 8a and passing through the beam splitter 7, the mirror 6 is bent in a substantially 90 ° direction by a mirror 6 and split into two by a beam splitting grating lens 13a.
The light is received by the photodetector 2 and converted into an electric signal.

By the way, in the optical head having the configuration shown in FIG. 1, when the reflection plate 5 is not provided on the end face of the substrate 9, as shown in FIG. 2, the light beam is emitted out of the substrate as shown by a broken line in the drawing. The light is condensed on the recording surface of the optical disk 12 "via the objective lens 11". In this case, a space corresponding to the optical path length L 'outside the substrate is not provided between the optical waveguide and the objective lens 11 ". However, there is a problem that the size of the optical head cannot be reduced for the length of the optical waveguide, whereas in the present invention, the reflector 5 is provided on the end face of the substrate 9 of the optical waveguide. Since the light flux is propagated in the substrate 9, the length corresponding to the length L ′ can be compensated by the substrate length L, so that the entire length of the optical head can be shortened and the size can be easily reduced. Can be.

In addition, as shown in FIGS. 1 and 2, the light emitting side view of the substrate 9 is formed in a tapered shape so that light propagated in the substrate is emitted from the lower surface side of the substrate 9. In
The optical disk 12 can be set in parallel with the optical waveguide,
It has the advantages that the degree of freedom in design can be improved and the thickness of the optical disk drive device and the like can be easily reduced.

Next, FIG. 3 shows another embodiment in which the optical waveguide according to the present invention is used as an optical head for an optical disk, and the same reference numerals as in FIG. 1 denote the same components. In the optical head having the configuration shown in FIG. 3, a grating lens 13b for beam splitting is provided together with the waveguide lens 8, and reflected light from the optical disk split by the grating length 13b is provided on both sides of the substrate and the waveguide layer 3. The light is received by the detected photodetector 2. The side structure is substantially the same as that shown in FIG.

Next, FIG. 4 shows still another embodiment in which the optical waveguide according to the present invention is used as an optical head for an optical disk, and the same reference numerals as those in FIGS. 1 and 3 denote the same components. Parts. In the optical head having the structure shown in FIG. 4, the light source 1 and the photodetector 2 are arranged at positions opposite to those shown in FIG.

Next, FIG. 5 shows still another embodiment in which the optical waveguide according to the present invention is used as an optical head for an optical disk, and the same reference numerals as those in FIGS. 1, 3 and 4 are used. Are similar components. The optical head having the configuration shown in FIG. 5 is obtained by omitting the collimating lens 4a from the optical head having the configuration shown in FIG. 4, and is a more simplified configuration.

In the above-described embodiments, an example in which the optical waveguide according to the present invention is applied to an optical head for an optical disk has been described. However, the optical waveguide according to the present invention may be used in addition to a read head for an optical card, an electrophotographic It can be easily applied to a writing head for an optical printer of a system.

[Effects of the Invention] As described above, according to the present invention, a tapered waveguide layer is provided at the tip of a waveguide layer formed on a transparent substrate of an optical waveguide, and the tapered upper waveguide layer side By providing a radiation surface on the end face of the substrate, the guided light propagated in the waveguide layer is radiated to the substrate side by the tapered upper waveguide layer, reflected by the reflection surface and propagated in the substrate, The light reaches the other end surface of the substrate and is emitted out of the substrate. For this reason, in the optical waveguide according to the present invention, the length of the optical waveguide can be significantly reduced with respect to the optical path length from the light source to the outside of the substrate. Therefore, when the optical waveguide according to the present invention is applied to an optical head for recording / reproducing such as an optical disk, the total length of the optical head including the objective lens can be shortened, and the overall structure of the optical head can be reduced in size. Can be.

In the optical waveguide according to the present invention, since the light beam is reflected by the reflection surface and propagated in the substrate, the light emitting position of the light beam can be set to an arbitrary position by processing the end surface of the substrate at the other end into a tapered shape or the like. Therefore, when the present invention is applied to an optical head, the optical waveguide and the recording medium can be arranged in parallel, so that the degree of freedom in design can be increased and the size of the apparatus can be easily reduced.

Further, in the optical waveguide according to the present invention, an optical element other than the objective lens, a photoelectric element, and the like can be integrally formed and integrated on a substrate for forming a waveguide layer. And the like, and the structure itself is simplified by integration, so that an inexpensive optical head that can be easily assembled and adjusted can be provided.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment in which an optical waveguide according to the present invention is applied to an optical head for an optical disk, and FIG. 1 (a) is a schematic plan view of the optical head viewed from the waveguide layer side. FIG. 1B is a schematic side view of the optical head when viewed from the side. FIG. 2 is an explanatory view of the optical head, FIG. 3 to FIG. 5 are schematic plan views showing another embodiment in which the optical waveguide according to the present invention is applied to an optical head for an optical disk, and FIG. FIG. 1 is a schematic configuration diagram of an optical head showing an example of the related art. 1 ... light source, 2 ... photodetector, 3 ... waveguide layer, 4,4a ...
Collimating lens, 5 ... Reflector, 6 ... Mirror, 7 ...
… Beam splitter, 8a… Waveguide lens, 9… Glass substrate, 10… Tapered waveguide layer (taper coupler), 11
…… Objective lens, 12… Optical disc, 13a, 13b …… Grating lens for beam splitting.

Claims (1)

(57) [Claims] 1. A substrate having a plane for forming a waveguide layer, having a lower refractive index than the waveguide layer and being transparent to guided light, and a waveguide formed on the flat surface of the substrate and having a leading end at its tip. A waveguide layer provided with a tapered waveguide layer that emits light toward the substrate side, and a reflection surface formed on an end surface of the substrate and reflecting radiation emitted to the substrate side by the tapered waveguide layer. An optical waveguide, comprising: