JPH07174925A - Waveguide type light reflecting and condensing optical system and waveguide type optical signal detecting element using the same as well as optical pickup - Google Patents

Abstract

PURPOSE:To make an element compact by utilizing the face that the critical angle can be made small when boundary surface is formed by air layer at the max. CONSTITUTION:This waveguide type light reflecting and condensing optical system 20 consisting of waveguide type light reflecting and condensing devices having reflection surfaces formed by the boundary surfaces of waveguide layers and air layers is provided with the first waveguide type light reflecting and condensing devices 17a, 17b which take in approximately half the guided light and reflect and condense this light outward the waveguides, the second waveguide type light reflecting and condensing devices 18a, 18b which have the reflection surfaces arranged in a relation where the incident angle on the outermost side of the reflected luminous fluxes thereof is larger than the critical angle at the boundary surfaces, and reflect these luminous fluxes toward the rear of the first waveguide type light reflecting and condensing devices 17a, 17b, and the third waveguide type light reflecting and condensing devices 19a, 19b which have the reflection surfaces arranged in a relation where the incident angle on the outermost side of the reflected luminous fluxes thereof is larger than the critical angle at the boundary surfaces, and reflect these luminous fluxes toward the rear part positions of the first waveguide type light reflecting and condensing devices 17a, 17b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type optical reflection and focusing optical system using a slab type optical waveguide applicable to an optical disk drive and the like, a waveguide type optical signal detecting element and an optical pickup using the same. .

[0002]

2. Description of the Related Art In recent years, various studies have been made in various fields to reduce the size and cost of optical discs by integrating optical pickups for optical disc devices on a single substrate with a waveguide. One of them is the slab type optical waveguide (slab opt
As a structure for deflecting guided light propagating in an optical waveguide by reflection, a waveguide type optical reflection deflector is known in which a cross section (boundary surface) perpendicular to the substrate is formed in the waveguide and the light is reflected at this cross section. (For example, the document “Applied
Physics Letters, Vol. 27, No. 4,15 August
Pp.251-253 in "1975""Novel metal-clad optical"
components and method of isolating high-index subs
trates forming integrated optical circuits ”). That is, when there is a difference in the refractive index of the medium, the refractive index of the medium guided when the guided light is guided toward the boundary surface of the medium is When it is higher than the rate, the so-called
The guided light can be reflected by total internal reflection.

In addition to such a property, by giving a curvature to the boundary surface, guided light propagating in the slab type optical waveguide can be condensed or diverged by reflection. Such a waveguide-type light reflection concentrator is guided using a total reflection condition by giving a desired difference in refractive index to two media A and B having different refractive indices that sandwich the boundary surface forming the reflection surface. It is designed to reflect wave light, and its boundary surface has a curvature so that it also exerts a condensing effect. At this time, the boundary surface is formed perpendicular to the slab type optical waveguide plane (substrate).

Under these conditions, when the two media A and B sandwiching the boundary surface are both waveguide media, the media A and B are used.
Under the current circumstances, it is difficult to increase the refractive index difference between the two. For example, the refractive index of the core layer of the waveguide n _core = 1.8 (assuming silicon nitride), the refractive index of the cladding layer of the waveguide n.
_{When clad} = 1.5 (assuming silicon oxynitride), the critical angle θ at the interface is θ = 56.4 °, and it is necessary to increase the number of reflections in order to downsize the optical system.

However, when the two media A and B sandwiching the boundary surface are the waveguide medium and the air layer, the critical angle θ at the boundary surface can be made smaller than the above case. For example, when the refractive index n _{core of the} waveguide medium is 1.8 (assuming silicon nitride), θ = 33.7 °, and the refractive index n _{clad of the} waveguide medium is 1.5 (silicon oxynitride is Assuming), θ = 41.8 °.

[0006]

According to the results of such examination, it is clear that the guided light can be reflected and reflected more greatly when the boundary surface is formed by the waveguide medium and the air layer. However, there is no example of a proposal to make the waveguide type light reflection / focusing optical system compact by using such characteristics ("compacting" here means the focal length and NA (numerical aperture) of the optical system. ) Means that the area occupied by the optical system is small even if the value is equal). The characteristics expected of the slab type optical waveguide device are thinness, small size, light weight and cost reduction, but there is room for improvement in order to achieve size reduction, weight reduction and cost reduction.

For example, as one of the examples proposed by the present applicants, there is a waveguide type light reflection / focusing optical system or a waveguide type optical signal detecting element as shown in FIG. This is because a prism coupler 2 is mounted on a substrate 1 with a slab type optical waveguide, which is formed by stacking optical waveguide layers (core layer, clad layer) via a buffer layer, and reflects light from an optical disc (not shown). Waveguide excitation is performed in the slab type optical waveguide through the prism coupler 2, and a boundary surface (a surface vertical to the substrate 1) having a curvature between the waveguide layer 3 and the air layer 4 is formed symmetrically with the optical axis. The pair of concave mirrors 5a and 5b are divided into two parts to reflect and condense the light, and further, the pair of flat mirrors 6a and 6b arranged outside the substrate 1 reflect the light toward the rear to focus the focus position at the end of the substrate 1. A pair of photodetectors 7a to 7 provided in the vicinity with optical axis symmetry
It is configured such that the wave is guided to the d side. 10 is also similar, in which the concave mirror 5b and the plane mirror 6a are formed back to back using the same air layer 4, and the photodetectors 7a to 7d are arranged close to one side. is there.

Therefore, in the case of such a proposed example, useless space is generated, and the total length of the substrate 1, and hence the element, is long. In particular, considering that it is advantageous to lengthen the optical length of the condensing optical system in order to have a function of detecting the defocus amount at the optical disk position and to increase the detection sensitivity thereof, FIG. 9 and FIG. In the case of the above configuration, the total length of the element becomes long.

As a result, in addition to the above proposed example, as shown in, for example, Japanese Patent Application Laid-Open No. 2-176606, a photodetector is provided outside the converging point of a slab type optical waveguide with a waveguide type optical reflection concentrator. In addition, or in constructing a waveguide type optical signal detector or optical pickup in which a photodetector is internally provided in a slab type optical waveguide as shown in JP-A-2-7238. However, it will limit the size and weight.

[0010]

According to a first aspect of the present invention, a boundary surface between a waveguide layer forming a slab type optical waveguide and an air layer is formed substantially perpendicular to the plane of the slab type optical waveguide. In a waveguide type light reflection / collection optical system formed by a waveguide type light reflection / condenser having a reflection surface, by taking in approximately half of this guided light including the optical axis of the guided light with respect to the slab type optical waveguide. A first waveguide type light reflection concentrator for reflecting and concentrating toward the outside of the waveguide, and the first waveguide type light reflection concentrator formed in the vicinity of the first waveguide type light reflection concentrator. A reflection surface is arranged so that the outermost incident angle of the reflected light flux from the reflection condenser is larger than the critical angle at the boundary surface, and is directed toward the rear of the first waveguide type light reflection condenser. Second waveguide type optical reflection condensing unit for reflecting and reflecting The first guide having a reflecting surface formed in the vicinity of the first waveguide type optical reflection concentrator so that the incident angle of the reflected light beam from the second waveguide type light reflecting concentrator is larger than the critical angle at the boundary surface. A third waveguide type light reflection concentrator for reflecting back toward the rear position of the waveguide type light reflection concentrator is provided.

According to a second aspect of the present invention, there is provided a waveguide coupler which couples and excites external light to the slab type optical waveguide.
The waveguide-type light reflection / focusing optical system described above and a photodetector arranged near the focal point of the waveguide-type light reflection / focusing optical system are provided for the slab-type optical waveguide to provide the waveguide-type light. A signal detecting element was constructed.

According to the third aspect of the invention, in addition to the configuration of the second aspect of the invention, an incident direction regulating opening is provided at the guided light incident position with respect to the photodetector.

According to a fourth aspect of the invention, in addition to the structure of the third aspect, a light shielding member is provided on the outermost surface of the slab type optical waveguide corresponding to the position of the photodetector.

According to a fifth aspect of the present invention, a light source, a condensing optical system for converging and irradiating the light emitted from the light source onto the optical information recording medium, and a signal based on the return light from the optical information recording medium With a slab type optical waveguide, which mounts the waveguide type light reflection / focusing optical system according to claim 1 and a photodetector arranged in the vicinity of the focal point of the waveguide type light reflection / focusing optical system. A substrate, an incident surface that is mounted on the substrate with the slab type optical waveguide and receives the light emitted from the light source, a bottom surface that reflects the captured light, and the reflected light is emitted toward the condensing optical system. In addition, an optical pickup is constituted by a prism coupler having an emission surface for coupling a part of the return light to the slab type optical waveguide via the bottom surface.

[0015]

According to the invention of claim 1, a waveguide-type optical reflection concentrator has a reflection surface which is formed substantially perpendicularly to the optical waveguide plane by the boundary surface between the waveguide layer and the air layer. Taking advantage of the feature that the critical angle can be made small and the optical path of the guided light can be largely changed, the first to third waveguide type light reflection concentrators having such a configuration are folded back by inward reflection. Since the slab type optical waveguide is formed in such a positional relationship as to form a light optical path, the inside of the slab type optical waveguide can be effectively utilized under the condition that the guided light can be efficiently condensed while suppressing the light quantity loss at the time of reflection. Therefore, there is no wasted space, and the structure of the waveguide type light reflection and collection optical system device can be made compact.

According to the second aspect of the invention, since a waveguide coupler and a photodetector are added to such a waveguide type optical reflection and focusing optical system to form a waveguide type optical signal detecting element. It is possible to achieve compactness of the waveguide type optical signal detection element device. As a result, when the waveguide type optical signal detecting element device is manufactured on the same wafer at the same time, the number of manufacturing elements per wafer increases,
The manufacturing cost of the device can be reduced.

In this case, since the optical path of the condensed and guided light is set so as to form the folded condensed optical path toward the inside, the guided light directed to the photodetector intersects within the waveguide, and the reflection surface. Since the photodetectors are close to each other, the probability that scattered light enters the photodetectors becomes high. In this respect, in the invention according to claim 3, since the incident direction regulating aperture is provided at the guided light incident position of each photodetector, the incidence of scattered light can be reduced, and the detection signal of the photodetector can be reduced. The S / N ratio can be improved.

Further, in the invention according to claim 4,
Since the light shielding member is also provided on the outermost surface of the slab type optical waveguide corresponding to the position of the photodetector, it is possible to prevent the scattered light from entering the photodetector from the outside of the waveguide, and the S /
The N ratio can be further improved.

According to a fifth aspect of the present invention, a substrate with a slab type optical waveguide on which such a waveguide type light reflection / focusing optical system and a photodetector are mounted and a prism coupler are combined with a light source or the like to form an integrated type. Since it constitutes an optical pickup,
The optical pickup can be made compact without impairing the detection sensitivity.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. First, as shown in FIG. 2, the waveguide substrate 11
A slab type optical waveguide 15 in which a core layer (waveguide layer) 13 and a clad layer 14 are sequentially laminated on a buffer layer 12
Is provided. On such a slab type optical waveguide 15, a prism coupler (waveguide coupler) 16 for guiding and exciting external light to the core layer 13 is mounted, for example, via an adhesive layer. A pair of concave mirrors (first waveguide) that captures and collects the left and right halves of the guided light including the optical axis φ of the guided light guided through the core layer 13 via the prism coupler 16 (first waveguide). Type light reflection concentrator) 17a, 1
7b is formed symmetrically about the optical axis. These concave mirrors 17a and 17b reflect and condense each guided light toward the outside obliquely rearward of the waveguide substrate 11, and a pair of plane mirrors (second waveguide type light) on the guided light path. Reflective concentrators 18a and 18b are formed symmetrically with respect to the optical axis. These plane mirrors 18a and 18b reflect the guided light toward the inside of the rear end of the waveguide substrate 11, respectively.
A pair of plane mirrors (third waveguide type light-reflecting concentrator) 19a, 19b are formed on the guided optical path symmetrically with respect to the optical axis. These plane mirrors 19a and 19b reflect back the respective guided lights in a state of intersecting toward the rear positions of the concave mirrors 17b and 17a, and as a whole, the return converging light path from the outer side to the inner side is sequentially formed. A waveguide-type light reflection / focusing optical system 20 is formed. More specifically, the concave mirrors 17a and 17b are formed so as not to have spherical aberration so as to exhibit a condensing function by, for example, a parabolic surface, and the flat mirrors 18a and 18b are arranged along the optical axis φ (ridgeline of the device). The plane mirror 19 is formed in parallel.
a and 19b are formed so as to be orthogonal to the optical axis φ. A pair of photodetectors 21a to 21d is provided near the focal point position (the rear position immediately after the concave mirrors 17a and 17b) passing through the last plane mirrors 19a and 19b. A waveguide type optical signal detection element 22 is constituted by the prism coupler 16, the waveguide type optical reflection and focusing optical system 20, and the photodetectors 21a to 21d.

The reason why such a compact device configuration is possible will be described. First, the reflecting surface 23 forming each of the mirrors 17a to 19b is formed as a surface vertical to the plane of the waveguide substrate 11 as shown in FIG. Also,
The reflecting surface 23 of each of the mirrors 17a to 19b is formed by a boundary surface between two media, but in this embodiment, it is formed as a boundary surface between the core layer 13 and the air layer 24. As a result, for example, when the core layer 13 is formed of silicon oxynitride (SiON), its refractive index is in the vicinity of 1.5, and taking n = 1.5 as an example, the reflection surface 23 The critical angle θ is θ = sin ~ ¹ (1 / 1.5) ≒ 4
It is as small as 1.8 °. That is, as described above, the critical angle θ at the reflecting surface 23 can be reduced by 15 ° or more as compared with the case where the waveguide media are used. Then, by combining the plane mirrors 18a to 19b having no power with the light reflected by the concave mirrors 17a and 17b exhibiting the light condensing action, the light path is sequentially folded back inward while maintaining the light condensing characteristic. We are aiming for miniaturization. First, since the light reflected by the concave mirrors 17a and 17b is directed to the outside of the device, the plane mirrors 18a and 18b are used to return the light to the inside. In this case, since the critical angle θ can be made small, the incident angle with respect to the plane mirrors 18a and 18b can be set to 45 ° or less.
The a and 18b can be arranged so as to be parallel to the optical axis φ. The reflected light from the plane mirrors 18a and 18b can be placed close to the concave mirrors 17a and 17b within a range that is not guided to the concave mirrors 17a and 17b again.

Here, of the light reflected on the plane mirrors 18a and 18b, if the optical axis light incident angle is θ ₂₀ and the peripheral light (outermost) incident angle is θ ₂₁ , it is a condensed light, so θ ₂₀ > Θ ₂₁ holds. Therefore, regarding the relationship between the concave mirrors 17a and 17b and the plane mirrors 18a and 18b, the ambient light incident angle θ
₂₁ plane mirror 18a, relative to the critical angle theta in 18b, if a positional relationship that satisfies theta _21> theta the relationship, is always filled even theta _20> theta, a concave mirror 17
Light reflected by a and 17b are all plane mirrors 18a and 18b.
It will be totally reflected at b. That is, the loss of light quantity at the time of reflection is suppressed, and the guided light is efficiently guided by the plane mirror 19.
The light can be guided to the a and 19b sides.

On the other hand, of the light reflected by the plane mirrors 19a and 19b, if the optical axis light incident angle is θ ₃₀ and the ambient light (outermost) incident angle is θ ₃₁ , conversely, θ ₃₀ <θ ₃₁ is established. To do. Therefore, the concave mirrors 18a, 18b and the plane mirrors 19a, 1
Regarding the relationship with 9b, the optical axis light incident angle θ ₃₀ is θ ₃₀ > θ with respect to the critical angle θ in the plane mirrors 19a and 19b.
If the positional relationship is such that the following relationship is satisfied, then θ ₃₁ > θ
Is always satisfied, the light reflected by the concave mirrors 18a and 18b is totally reflected by the plane mirrors 19a and 19b. That is, the loss of light quantity at the time of reflection is suppressed, and the guided light can be efficiently guided to the photodetectors 20a to 20d side.

According to this embodiment, the air layer 24
In the case of the vertical reflecting surface 23 using the boundary surface as a boundary surface, the critical angle θ can be made small and the amount of deflection of the optical path can be made large, and the plurality of mirrors 17a to 19b are arranged to satisfy the total reflection condition. Since the guided light is sequentially folded back inside the device, the concave mirrors 17a, 1
It will be able to focus in the dead space behind 7b,
By effectively utilizing the entire surface of the waveguide, the device can be made compact.

FIG. 3 shows a modification of the flat mirror 18a,
18b is arranged non-parallel to the optical axis φ. Also in this case, the inclinations of the plane mirrors 18a and 18b need to satisfy the above-described condition, that is, θ ₂₁ > θ, and the tilts of the plane mirrors 18a and 18b are closer to the optical axis φ in the reflected light. Things are concave mirrors 17a, 17
As much as possible inside the element (optical axis φ
It is better to place them closer to each other. Correspondingly, the positions of the plane mirrors 19a and 19b are set inside the element so that the light collection positions of the light reflected and condensed by the plane mirrors 19a and 19b are as close as possible to the rear part of the concave mirrors 17a and 17b. It is preferable to dispose them closer to the concave mirrors 17a and 17b.

FIG. 4 shows another modification, which is a plane mirror 19.
a and 19b are arranged in a state not orthogonal to the optical axis φ. Also in this case, the plane mirrors 19a and 19b
Is required to satisfy the above-mentioned condition, that is, θ ₃₀ > θ.

Further, in this embodiment including these modifications, the plane mirrors 18a to 19b are formed so as to form a continuous reflecting surface by the pattern of the continuous air layer 24, but these are formed separately. Alternatively (see, for example, FIG. 6 described later). The separated formation reduces the etching area, so that the time required for etching can be shortened and the contamination in the chamber can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIGS. Basically, the same configuration as that of the above-described embodiment is adopted, but in this embodiment, the configuration and operation of the photodetectors 21a to 21d as the waveguide type optical signal detection element 22 will be clarified. is there.

The photodetectors 21a to 21d are arranged in the vicinity of the focal position of the waveguide type light reflection / focusing optical system 20 as described above, but more specifically, they are juxtaposed rearward of the focal position and symmetrically with respect to the optical axis. To be done. Photodetectors 21a and 21b and photodetector 21
Since they are arranged symmetrically with respect to c and 21d with respect to the optical axis φ, a pair of photodetectors 21a and 21b will be described as an example in FIG. That is, the pair of photodetectors 21a and 21b
Are juxtaposed at symmetrical positions with respect to the optical axis of the guided light 25.

As a result, for example, when the external incident light guided through the prism coupler 16 is parallel light, the guided light 25 is detected by the photodetectors 21a and 2a as shown in FIG. 5 (a).
Since the light is focused at the central position between 1b, these photodetectors 2
The output signal difference between 1a and 21b becomes zero. On the other hand, when the external incident light is non-parallel light (divergent light), the waveguide type light reflection / condensing optical system 20 becomes a finite system, the focal length on the image side is extended, and the guided light 25 becomes as shown in FIG. As shown, a difference occurs in the output signals of these photodetectors 21a and 21b (in this case, photodetector 21b becomes larger). On the contrary, when the external incident light is non-parallel light (convergent light), the focal length is shortened and the guided light 25 becomes as shown in FIG. 5B, so that the output signals of these photodetectors 21a and 21b are output. (In this case, the photodetector 21a becomes larger and the sign is different from that of the difference signal in the case of FIG. 5C).

Therefore, for example, in the optical disc apparatus, the state shown in FIG. 5A is the focused state, the state shown in FIG. 5B is the defocused state where the optical disc is far, and the state shown in FIG.
It can be seen that the state shown in (c) can be utilized as an optical signal detection system, for example, by detecting the focus error signal of the optical disc by setting the optical disc to a near defocused state.

By the way, in the case of the configuration of the waveguide type light reflection and collection optical system 20 of the present embodiment, a plurality of mirrors 17a to 19b are provided.
Thus, since the reflected light paths that are sequentially turned inward are formed to achieve compactness, the light paths in the plane of the slab type optical waveguide 15 intersect in a complicated manner. At this time, since the mirror and the photodetector are close to each other, stray light generated on the reflecting surface may enter the photodetectors 21a to 21d. In this case, the stray light becomes a noise signal and becomes a factor that reduces the detection function (S / N ratio) of the photodetectors 21a to 21d. Therefore, in this embodiment, as shown in FIG. 6, the photodetectors 21a and 21b are
An incident direction regulation opening 26 is formed so as to surround only the pair and the pair of photodetectors 21c and 21d, and to allow only guided light from the corresponding plane mirrors 19a and 19b to be guided. The incident direction regulating opening 26 is also formed by a boundary surface with an air layer obtained by etching a part of the slab type optical waveguide 15 in a predetermined pattern similarly to the mirrors 17a to 19b. Such an incident direction control opening 2
By having 6 around the photodetectors 21a-21d,
Incident of stray light, which is a scattered light component, on the photodetectors 21a to 21d can be reduced as much as possible, and S of the photodetectors 21a to 21d can be reduced.
The / N ratio can be improved.

A third embodiment of the present invention will be described with reference to FIG. In this embodiment, in addition to the structure of the embodiment shown in FIG. 6, a light shielding layer (light shielding member) is provided on the outermost surface of the slab type optical waveguide 15 corresponding to the positions of the photodetectors 21 (21a to 21d).
27 is formed. In the present embodiment as well as the above-mentioned embodiment, the photodetector 21 is internally formed on the waveguide substrate 11 and is configured to be coupled to the core layer 13, and is electrically connected through the lead wire pattern 28 communicating to the outside. It can be taken out as a target signal.

According to this embodiment, stray light in the plane of the slab type optical waveguide 15 with respect to the photodetector 21 can be regulated by the incident direction regulating aperture 26, and in addition, from the direction perpendicular to the plane of the slab type optical waveguide 15. The noise light that tries to enter the photodetector 21 can be cut by the light shielding layer 27. Eventually, the plane mirror 19 for the photodetector 21
Light other than the original detection light guided from a and 19b can be cut as much as possible, and noise components and offsets in the light detection signal can be suppressed, and the S / N ratio can be further improved.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the optical pickup 30 is constructed by using the slab type optical waveguide substrate 29 as shown in each of the above-mentioned embodiments. As described above, the substrate 29 with the slab type optical waveguide includes the waveguide type light reflection and collection optical system 20 and the photodetector 21 in the slab type optical waveguide 15.
a to 21d are incorporated, and the prism coupler 16 is also mounted on the surface thereof. The prism coupler 16 is formed in a trapezoidal cross section, has an entrance surface 16a, a bottom surface 16b, and an exit surface 16c.
6b is adhered to the surface of the slab type optical waveguide 15 via an adhesive layer or the like. A semiconductor laser (light source) 31 and a collimator lens 32 are arranged so as to face the entrance surface 16 a of the prism coupler 16. In addition, the exit surface 16
c is opposed to the optical disc (optical information recording medium) 33, and an objective lens 34 that constitutes a condensing optical system is provided between the emission surface 16c and the optical disc 33.
A quarter wave plate 35 is interposed on the side of the emitting surface 16c.

In such a structure, the semiconductor laser 3
The light (linearly polarized light) emitted from the beam splitter 1 is converted into parallel light by the collimator lens 32, and then the prism coupler 16
Is incident on the incident surface 16a of the light source, travels to the bottom surface 16b and the adhesive layer, and is reflected by the boundary surface between the adhesive layer and the surface of the slab type optical waveguide 15. This reflected light again passes through the adhesive layer and the bottom surface 16b in order, and is emitted to the outside of the prism coupler 16 from the emission surface 16c. The emitted light is converted into circularly polarized light by passing through the quarter-wave plate 35, and then is condensed and irradiated onto the recording surface of the optical disc 33 by the objective lens 34. The return light reflected from the optical disc 33 has the polarization direction of circularly polarized light reversed when reflected, passes through the objective lens 34 again, and passes through the quarter-wave plate 35. This quarter wave plate 3
By passing through 5, the return light is converted into linearly polarized light having a polarization direction orthogonal to the forward path and enters the prism coupler 16 again from the exit surface 16c. Return light that has entered the prism coupler 16 from the exit surface 16c is
b, the core layer 13 in the slab type optical waveguide 15 through the adhesive layer
Be combined with. After that, the light is guided in the core layer 13 and symmetrically about the optical axis φ by the concave mirrors 17a and 17b.
The light is reflected as a condensed light flux while being split, and is further reflected by the plane mirrors 18a, 18b, 19a, 19b and condensed on the photodetectors 21a, 21b, 21c, 21d side.

At this time, as described with reference to FIG. 5, when the optical disk 33 is at the focal position of the objective lens 34, the operation shown in FIG.
It is at the center between the photodetectors 21a and 21b as shown in (a) (similarly to the photodetectors 21c and 21d side), and the difference between the detection signals is zero. However, when the optical disc 33 is farther than the focal position of the objective lens 34, the focal position of the waveguide-type light reflection / condensing optical system 20 becomes short, so that FIG.
As shown in (b), the light is focused at the front positions of the photodetectors 21a and 21b, and a difference occurs in the detection signals of the photodetectors 21a and 21b. On the contrary, when the optical disc 33 is closer to the focus position of the objective lens 34, the focus position of the waveguide-type light reflection / focusing optical system 20 becomes longer, so that FIG.
As shown in (c), the light is focused at the rear position of the photodetectors 21a and 21b, and a difference occurs in the detection signals of the photodetectors 21a and 21b. Therefore, the photodetectors 21a and 21b
(Or, the difference between the detection signals obtained from 21c and 21d) and the sign of the difference (so-called Foucault method) are used to detect the amount and direction of deviation of the optical disc 33 from the focus position of the objective lens 34. The focus error signal detection function is ensured.

Further, when the irradiation light on the optical disk 33 is in the on-track state, the photodetectors 21a and 21b.
Since the difference between the detection signals obtained by the pair and the pair of photodetectors 21c and 21d is zero (because it is equally divided into two),
The tracking error signal is detected by the photodetectors 21a, 21
Track deviation and its deviation direction can be detected by examining the difference between the detection signal obtained from the pair b and the detection signal obtained from the pair of photodetectors 21c and 21d and the positive / negative sign thereof (so-called push-pull method). become.

Further, the detection (reproduction) of the recording signal (that is, the RF signal) on the optical disk 33 is performed by all the photodetectors 21.
It suffices to take the sum of the detection signals at a to 21d. In this case, even if the optical disc 33 is a CD (compact disc) in which reflected light is scattered by the recording pits when there are recording pits, or a phase change type recording medium in which the intensity of the reflected light changes, the recording signal Can be detected.

[0040]

According to the first aspect of the invention, the reflecting surface is formed substantially perpendicular to the plane of the slab type optical waveguide by the interface between the waveguide layer forming the slab type optical waveguide and the air layer. In a waveguide type light reflection / condensation optical system formed by a waveguide type light reflection / concentrator having a waveguide, the waveguide is formed by taking in approximately half of the guided light including the optical axis of the guided light with respect to the slab type optical waveguide. A first waveguide type light reflection concentrator for reflecting and concentrating toward the outside, and the first waveguide type light reflection concentrator formed near the first waveguide type light reflection concentrator. Reflecting toward the rear of the first waveguide type optical reflection concentrator having a reflection surface arranged such that the outermost incident angle of the reflected light flux from the optical device is larger than the critical angle at the boundary surface. A second waveguide type light reflection concentrator to be provided, and in the vicinity of the second waveguide type light reflection concentrator. The first waveguide type light having a reflecting surface formed so that the incident angle of the reflected light flux from the second waveguide type optical reflection concentrator is larger than the critical angle at the boundary surface. Since a third waveguide type optical reflection concentrator for reflecting back toward the rear position of the reflection concentrator is provided,
With a waveguide-type optical reflection concentrator having a reflecting surface formed almost perpendicular to the optical waveguide plane by the boundary surface between the waveguide layer and the air layer, the critical angle can be made smaller and the optical path of the guided light can be greatly changed. The slab optical waveguide surface can be effectively used while keeping the light utilization efficiency of the guided light high while making maximum use of the features that can be achieved, and there is no wasted space, and the waveguide type light reflection and collection optical system is available. The device configuration can be made smaller and more compact.

According to the second aspect of the invention, since a waveguide coupler and a photodetector are added to such a waveguide type optical reflection and collection optical system to form a waveguide type optical signal detecting element, The waveguide type optical signal detecting element device can be made compact and compact. As a result, when the waveguide type optical signal detecting element device is produced on the same wafer at the same time, the number of producing elements per wafer is increased. Therefore, the manufacturing cost of the device can be reduced.

According to the third aspect of the invention, in addition to the configuration of the second aspect of the invention, since the incident direction regulating opening is provided at the guided light incident position with respect to the photodetector, the optical path for collecting and guiding the light is inward. The guided light directed to the photodetector, which is set so as to form a folded converging optical path, crosses in the waveguide,
Due to the proximity of the reflection surface and the photodetector, the probability that scattered light will enter the photodetector will increase, but this incident direction control aperture can reduce the incidence of scattered light. It is possible to improve the S / N ratio of the detection signal by the detector.

According to the invention described in claim 4, in addition to the structure described in claim 3, since the light shielding member is provided on the outermost surface of the slab type optical waveguide corresponding to the position of the photodetector, the light is emitted from such a portion. The scattered light can be prevented from entering the detector, and the S / N ratio of the detection signal can be further improved.

According to the fifth aspect of the present invention, a substrate with a slab type optical waveguide on which such a waveguide type light reflection / focusing optical system and a photodetector are mounted and a prism coupler are used as a light source, a focusing optical system, etc. Since the integrated optical pickup is configured in combination with the optical pickup, the optical pickup can be made compact and compact without impairing the detection sensitivity.

[Brief description of drawings]

FIG. 1 is a plan configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a waveguide structure.

FIG. 3 is a plan configuration diagram showing a modified example.

FIG. 4 is a plan configuration diagram showing another modification.

FIG. 5 is a plan configuration diagram for explaining a condensed state of a photodetector showing a second embodiment of the present invention.

FIG. 6 is a plan configuration diagram.

FIG. 7 is a sectional view showing a third embodiment of the present invention.

FIG. 8 is a schematic side view showing a fourth embodiment of the present invention.

FIG. 9 is a plan configuration diagram showing a conventional example.

FIG. 10 is a plan configuration diagram showing a conventional example.

[Explanation of symbols]

 13 Waveguide Layer 15 Slab Optical Waveguide 16 Waveguide Coupler, Prism Coupler 16a Incident Surface 16b Bottom Surface 16c Emission Surface 17a, 17b First Waveguide Type Light Reflecting Concentrator 18a, 18b Second Waveguide Type Light Reflector Concentrators 19a, 19b Third waveguide type light reflection / concentrator 20 Waveguide type light reflection / condensing optical system 21a to 21d Photodetector 22 Waveguide type optical signal detection element 23 Reflective surface 24 Air layer 26 Incident direction Restriction opening 27 Light-shielding member 29 Substrate with optical waveguide 30 Optical pickup 31 Light source 33 Optical information recording medium 34 Condensing optical system

Claims (5)

[Claims] 1. A waveguide type optical reflection concentrator having a reflection surface formed substantially perpendicular to the plane of the slab type optical waveguide by an interface between a waveguide layer forming the slab type optical waveguide and an air layer. In the waveguide type light reflection / condensation optical system formed by, approximately half of the guided light including the optical axis of the guided light with respect to the slab type optical waveguide is taken in and reflected and condensed toward the outside of the waveguide. 1 waveguide type light reflection concentrator, and the first
Is formed in the vicinity of the waveguide type optical reflection concentrator, and is arranged so that the outermost incident angle of the reflected light flux from the first waveguide type optical reflection concentrator is larger than the critical angle at the boundary surface. A second waveguide type optical reflection concentrator having a reflective surface and reflecting toward the rear of the first waveguide type optical reflection concentrator;
It is formed in the vicinity of the second waveguide type light reflection concentrator and is arranged so that the incident angle of the reflected light flux from the second waveguide type light reflection concentrator is larger than the critical angle at the boundary surface. And a third waveguide type optical reflection concentrator having a reflecting surface for reflecting back toward the rear position of the first waveguide type optical reflection concentrator. Type light reflection condensing optical system. 2. A waveguide coupler for coupling and exciting external light to a slab type optical waveguide, a waveguide type light reflection and focusing optical system according to claim 1, and a focus of the waveguide type light reflection and focusing optical system. A waveguide type optical signal detecting element, characterized in that a photodetector disposed near the position is provided for the slab type optical waveguide. 3. The waveguide type optical signal detecting element according to claim 2, wherein an incident direction regulating opening is provided at a guided light incident position with respect to the photodetector. 4. A waveguide type optical signal detecting element according to claim 3, wherein a light shielding member is provided on the outermost surface of the slab type optical waveguide corresponding to the position of the photodetector. 5. A light source, a condensing optical system for condensing and irradiating light emitted from the light source onto an optical information recording medium, and a signal for detecting a signal based on the return light from the optical information recording medium. A substrate with a slab type optical waveguide on which the waveguide type light reflection / focusing optical system according to Item 1 and a photodetector arranged near the focal point of the waveguide type light reflection / focusing optical system are mounted, and this slab type An incident surface that is mounted on a substrate with an optical waveguide and that captures the light emitted from the light source, a bottom surface that reflects the captured light, and a reflected light that is emitted toward the converging optical system An optical pickup comprising: a prism coupler having an exit surface for coupling the portion to the slab type optical waveguide through the bottom surface.