JPH08152534A - Prism coupler and optical pickup device - Google Patents

Abstract

PURPOSE: To provide a prism coupler which has high coupling efficiency and can have its wavelength variation in the coupling efficiency suppressed within a permissible range and a small-sized optical pickup device which uses the prism coupler. CONSTITUTION: In the prism coupler which inputs and outputs light to and from a light guide 18 consisting of a substrate 11 and at least one layer of dielectric layers 13 and 14 formed on the substrate, the prism 15 is equipped with a convex lens 16 on its light incidence surface. The convex lens 16 converts incident light at least on the surface of the light guide 18 into nearly parallel light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prism coupler for inputting light into an optical waveguide composed of a substrate and at least one dielectric layer formed on the substrate, and recording using the prism coupler. The present invention relates to an optical pickup device that records / reproduces information on / from a carrier.

[0002]

2. Description of the Related Art In recent years, optical waveguides have been applied to optical devices such as optical integrated circuits and optical pickup devices. The coupler inputs light into the optical waveguide and is one of the important elements in an optical device using the optical waveguide. There are grating couplers and prism couplers in the coupler, but when the prism coupler is used, the input efficiency of the incident light to the optical waveguide (hereinafter referred to as coupling efficiency)
Is big. As an optical pickup device using a prism coupler, the one shown in FIG. 12 is known (JP-A-4-28953).

This optical pickup device will be described below with reference to FIG. The buffer layer 32 is formed on the substrate 31.
An optical waveguide layer 33 is formed via the optical waveguide layer 33, and a photodetector 34 is connected to the optical waveguide layer 33. The optical waveguide layer 33 has a first gap layer 35 having a refractive index lower than that of the optical waveguide layer 33, and an opening 37 formed on the first gap layer 35. A second gap layer 36 having a refractive index is laminated. An adhesive layer 38 having a refractive index higher than that of the optical waveguide layer 33 is formed in the opening 37 of the second gap layer 36. A prism 39 made of a dielectric material having a refractive index higher than that of the optical waveguide layer 33 is adhered and fixed on the adhesive layer 38.

The light emitted from the semiconductor laser 40 is collimated by the collimator lens 41, and then the prism 3
Guided to 9. A part of the light is reflected by the bottom surface of the prism 39, and the other light is guided to the inside of the optical waveguide layer 33 and then emitted to the prism 39 again. In this way, the light that has entered the prism 39 again exits from the prism 39, is condensed by the objective lens 42, is irradiated onto the surface of the optical disc 43, and information is recorded / reproduced.

The reflected light from the optical disk 43 enters the prism 39 through the objective lens 42. Then, a part of the light is reflected by the bottom surface of the prism 39, but the remaining light is guided to the optical waveguide layer 33 through the adhesive layer 38 and the first gap layer 35. The guided light is transmitted through the second gap layer 36.
Therefore, the light propagates through the optical waveguide layer 33 without being emitted to the prism 39, is condensed on the photodetector 34 side, and a signal is detected.

By the way, the coupling efficiency of the prism coupler is determined by the beam spot diameter of the incident light and the radiation coefficient determined by the refractive index of the prism and the structure of the optical waveguide. In the prism coupler used in the optical pickup device shown in FIG. 12, the beam spot diameter of the incident light is determined from the beam diameter before being condensed on the optical disc 43. Need to be adjusted. Normally, the maximum coupling efficiency is obtained when the reciprocal of the radiation coefficient (hereinafter referred to as the coupling length) is substantially equal to the beam spot diameter of the incident light, but in the case of FIG. Then, the beam spot diameter of the incident light becomes as large as 1 mm or more. Therefore, in order to improve the coupling efficiency, it is necessary to set the coupling length long. That is, the radiation coefficient of the prism coupler must be set small.

However, the method of Ulrich (JO
URNAL OF THE OPTICAL SOCI
ETY OF AMERICA vol. 60,197
According to the calculation result of the wavelength dependence of the coupling efficiency based on 0, 1337 to 1350), the wavelength variation of the coupling efficiency becomes large when the radiation coefficient is small. Therefore, in this prism coupler, even if the radiation coefficient is reduced to increase the coupling efficiency, there is a problem that the coupling efficiency is lowered due to the wavelength variation of the incident light.

In order to solve the above problem, the present applicant has previously proposed an optical pickup device capable of changing the beam spot diameter of the incident light on the optical waveguide device (Japanese Patent Application No. 5-317220, Japanese Patent Application No. 5-317220). Date: December 17, 2005
Date, title of invention: Optical pickup device). FIG. 13 is a structural diagram showing the optical pickup device. The operation will be described below.

The light emitted from the light source (semiconductor laser) 1 passes through the hologram 2 and the collimator lens 3 and is changed in direction by the compound mirror 4 composed of a half mirror and a total reflection mirror. Is focused on. The light reflected by the magneto-optical disk 6 enters the composite mirror 4 through the objective lens 5 and is split into two, that is, servo error signal detection light and magneto-optical signal detection light. The servo error signal detection light is condensed from the composite mirror 4 by the collimator lens 3, enters the hologram 2, is diffracted, is guided to the photodiode 7, and the signal is detected. On the other hand, the magneto-optical signal detection light is reflected on the inner surface of the half mirror having a wedge-shaped cross section, emitted from the combining mirror 4 at an angle of θ with the servo error signal detection light, and condensed by the collimator lens 3 to form the hologram 2. The prism 23 on the optical waveguide element 22 which is not passed through and is arranged in the same package as the light source 1.
Be led to. FIG. 14 is an enlarged view showing a prism coupler constituted by the prism 23. As shown in the figure, the light enters the prism 23 and then enters the optical waveguide 24.

In the above example, the light condensed by the collimator lens 3 is incident on the optical waveguide element 22 incorporated in the same package as the light source 1. Therefore, by changing the position of the package, the optical waveguide element 22 is guided to the optical waveguide element 22. The beam spot diameter of the incident light can be changed arbitrarily. Therefore, the structure of the optical waveguide is determined so that the wavelength variation of the coupling efficiency of the light in the prism coupler falls within the allowable range, and the radiation coefficient is determined. The beam spot diameter should be set.

[0011]

In the pickup shown in FIGS. 13 and 14, the light incident on the optical waveguide 24 is not parallel light. Therefore, the return light from the magneto-optical disk 6 becomes focused light with a large numerical aperture when entering the optical waveguide element 22, and this light enters the prism coupler as it is. Therefore, the incident light is, as shown in FIG.
It has a phase component that advances in different directions depending on the position of incidence on the prism 23. On the other hand, the prism coupler can input the incident light to the optical waveguide 24 when the light propagation direction component of the phase of the incident light on the surface of the optical waveguide 24 and the phase constant of the optical waveguide 24 substantially match. Therefore,
When the incident light has various phase components on the surface of the optical waveguide 24 as in the above example, only a part of the incident light can enter the optical waveguide 24, so that it is impossible to obtain high coupling efficiency. It was

In view of the above points, the present invention provides a prism coupler which has a high coupling efficiency and can suppress the wavelength fluctuation of the coupling efficiency within an allowable range, and a small optical pickup device using the prism coupler. To aim.

[0013]

In the prism coupler and the optical pickup device of the present invention, the prism forming the prism coupler is provided with means for making incident light at least on the surface of the optical waveguide substantially parallel light. .

[0014]

The prism coupler can input incident light to the optical waveguide when the phase component of the incident light on the surface of the optical waveguide in the light propagation direction and the phase constant of the optical waveguide substantially match. In the present invention, a convex lens or a concave lens is provided on the light incident surface of the prism to convert the incident light into substantially parallel light at least on the surface of the optical waveguide. The light has the same phase on the waveguide surface. Therefore, if the light propagation direction component of the phase of the parallel light is set to be substantially equal to the phase constant of the optical waveguide, almost all the incident light can be input to the optical waveguide. That is, the coupling efficiency can be increased.

Since the beam spot diameter of the incident light can be changed by moving the position of the prism coupler back and forth, after the structure of the optical waveguide is determined so that the wavelength fluctuation of the coupling efficiency falls within the allowable range. The beam spot diameter can be determined so that the optimum coupling efficiency can be obtained. Therefore, it is possible to achieve both suppression of wavelength fluctuation of the coupling efficiency and high efficiency of the coupling efficiency.

When the above-mentioned prism coupler is used in the optical pickup device, incident light can be input into the optical waveguide with high efficiency, so that the amount of signal light detected by the photodetector can be increased and the signal quality can be improved.

[0017]

【Example】

(First Embodiment) FIG. 1 is a side view showing a first embodiment. The surface of the Si substrate 11 is thermally oxidized to form a transparent quartz glass layer 12. A first dielectric layer 13 having a refractive index higher than that of the transparent quartz glass layer 12 is formed, and the first dielectric layer 13 is further formed thereon.
The second dielectric layer 14 having a lower refractive index than that is formed, and these constitute the optical waveguide 18.
The prism 15 is fixed on the optical waveguide 18 with its side surface in close contact with the surface of the optical waveguide 18. Prism 1
A convex lens 16 is adhered to the light incident surface of 5. The light incident on the prism 15 is converted into substantially parallel light by the convex lens 16 and then introduced into the optical waveguide 18.

In this prism coupler, as shown in FIG. 1, after the incident light is focused in front of the prism 15,
The light enters the convex lens 16 on the surface of the prism 15. Figure 2
It is an enlarged view of the light-incidence surface of a prism. A method of determining the focal length of the convex lens 16 will be described below with reference to FIG.

The light incident on the convex lens 16 has its numerical aperture (NA) changed and is transmitted through the prism 15. As shown in FIG. 2, the beam diameter at the position where the NA is converted is w ₁ , the distance from the focus position to the NA conversion position is f ₁ , and the optical path length from the conversion position to the incident position on the waveguide is g ₁ , When the incident beam diameter at the bottom of the prism is x ₁ , the total power incident on the coupler is P, NA
If the value of is NA ₁ , the pupil radius of the lens is a ₁ , and the wavelength of the incident light is λ, then the intensity distribution I ₁ of the incident light is

[0020]

[Equation 1]

NA ₁ = a ₁ / g ₁ (3) t ₁ = 2a ₁ / w ₁ (4) ba = 2πr (NA ₁ ) / λ (5) However, the function J represents a Bessel function. Further, assuming that the value of NA ₁ is sin γ, the focal length F _{1 of the} lens and the beam diameter w ₁ at the conversion position are expressed by the following equation (6),
It is related in (7).

1 / F ₁ = 1 / f ₁ + 1 / g ₁ (6) f ₁ = w ₁ / 2tan γ (7) From these formulas (6) and (7), F ₁ = 1 / (2tan γ / w ₁ +1) / G ₁ ) (8) is obtained. That is, the focal length F _{1 of the} lens is determined by determining the optical path length g ₁ .

As for the pupil radius a _{1 of the} lens, the maximum value I _{m of} I ₁ is obtained by substituting the expression (8) into the expressions (1) to (5).
As _{a x, I 1 (x 1} /2) / I m a x = 1 / e 2 may be determined so as to satisfy the (e is the base of natural logarithm) (9).

From the beam diameter w ₁ at the conversion position, g
_If the length of ₁ is taken long enough, at the bottom of the prism 15,
Almost parallel light will be incident. In particular, if the g ₁ is designed to be infinity, Equation _{(8), F 1 = w 1 / 2tanγ} (8 ') , and the beam diameter at the value sinγ conversion position of the NA of the incident light The focal length F _{1 of the} lens can be determined from w ₁ .

Next, the coupling efficiency of the prism coupler of this example will be concretely calculated. Here, the optical waveguide 18 has a non-alkali glass layer 13 (for example, # 7059 glass manufactured by Corning Co., Ltd.) of 570 μm on a Si substrate 11 on which a SiO ₂ (quartz glass) layer 12 having a thickness of 2 μm is formed on the surface.
It is assumed that the SiO ₂ layer 14 (200 μm) is laminated, and a prism 15 (for example, glass material LaSF08) is attached to the surface of the optical waveguide 18 to form a prism coupler. Table 1 shows the refractive indexes of the above materials constituting the prism coupler.

[0026]

[Table 1]

When parallel light is incident on the optical waveguide 18, the optimum beam spot diameter on the surface of the optical waveguide 18 (defined by the longer diameter of the elliptical beam spot)
Is 40 μm.

The effective refractive index of this prism coupler [the value obtained by dividing the phase constant of the optical waveguide by the wave number k (= 2π / λ)] N _{T E} , N _{T M} is N _{T E =} 1.4817, N a _{T M} = 1.4806, the incident angle theta to the surface of the optical waveguide 18 of the prism coupler, and the refractive index of the prism 15 and the ^{_{n p, Θ = sin - 1}} {(n T E + n T M) / 2n _p } (10), the incident angle Θ is calculated to be 52.4 °.

It is assumed that divergent light with NA = 0.17 is incident on this prism coupler. At this time, the optical waveguide 18
Since the optimum beam spot diameter on the surface of the laser beam is 40 μm and the incident angle to the optical waveguide 18 is 52.4 °, the beam spot diameter w ₁ at the NA conversion position is
May be 40 cos 52.4 ° = 24.4 μm.
(8) w ₁ = 24.4 to formula, γ = sin ^{- 1} (0.1
7), g ₁ = infinity is substituted, the focal length F ₁ of the convex lens 16 is found to be 70.7 μm. That is, the prism 15
If the convex lens 16 having a focal length of 70.7 μm is provided in, the incident light can be converted into substantially parallel light.

The coupling efficiency η of the prism coupler is

[0031]

[Equation 2]

It is represented by the approximate expression FIG. 3 is a diagram showing the incident angle (θ _i ) dependency of the coupling efficiency. As is clear from this figure, the maximum value of the coupling efficiency has a small allowable range with respect to the change of the incident angle. Therefore, when the NA of the incident light is 0.17, the coupling efficiency is 13% with respect to the TE light incident.
It's nothing but. On the other hand, in this example, the beam diameter is set so that the intensity center is at a position 13 μm from the end of the optical waveguide 18.
When light of 4.4 μm is incident and the light incident angle is 52.4 °, a coupling efficiency of 85% with respect to TE light can be obtained. Further, a coupling efficiency of 81% can be obtained for TM light.

As described above, in this example, since the prism 15 is provided with the convex lens 16 for converting incident light into substantially parallel light, most of the incident light can be input to the optical waveguide 18. That is, the coupling efficiency can be increased. Also, by appropriately moving the position of the prism coupler, the beam spot diameter of the light incident on the prism coupler can be changed. Therefore, the optical waveguide 18 is designed so that the wavelength fluctuation of the coupling efficiency is suppressed within the allowable range. After that, the beam spot diameter can be changed so as to obtain the optimum coupling efficiency for the optical waveguide 18. That is, it is possible to realize both suppression of wavelength fluctuation of coupling efficiency and improvement of coupling efficiency.

The prism coupler of the present invention is not limited to the above-mentioned structure, and for example, as shown in FIG.
The structure may be such that the adhesive 17 is sandwiched and fixed on the second dielectric layer 14 of the optical waveguide.

In this example, the incident light is converted into substantially parallel light by the convex lens 16 adhered to the prism 15. However, it is formed inside the prism 15 such as a microlens or a grating formed on the prism 15 itself. You may perform it by the high refractive index layer etc. which were mentioned.

(Second Embodiment) FIG. 5 is a side view showing a second embodiment. The same parts as those in FIG. 1 are denoted by the same symbols. The surface of the Si substrate 11 is thermally oxidized to form a transparent quartz glass layer 12. A first dielectric layer 13 having a refractive index higher than that of the transparent quartz glass layer 12 is formed, and a refractive index lower than that of the first dielectric layer 13 is formed on the first dielectric layer 13. An existing second dielectric layer 14 is formed, and these constitute an optical waveguide. A prism 15 is fixed on the optical waveguide with its side surface closely contacting the surface of the optical waveguide. The prism 15 has a concave lens 19 on its light incident surface. The concave lens 19 is formed by, for example, changing a part of the prism 15 to a high refractive index by a conventional ion exchange method. The light incident on the prism 15 is converted into substantially parallel light by the concave lens 19 and introduced into the optical waveguide 18.

In this example, the incident light enters the concave lens 19 on the surface of the prism 15 before being focused. FIG. 6 is an enlarged view of the light incident surface of the prism coupler. Figure 6 below
A method of determining the focal length of the concave lens 19 will be described with reference to. The NA of the light incident on the concave lens 19 is converted and the light is transmitted through the prism 15. The beam diameter at the position where the NA is converted is w ₂ , the distance from the focus position to the NA conversion position is f ₂ , the optical path length from the conversion position to the incident position on the waveguide is g ₂ , and the bottom surface of the prism 15 is Incident beam diameter x ₂
, The total power incident on the prism coupler is P ₂ , the NA value is NA ₁ , the lens pupil radius is a ₂ ,
When the incident wavelength is λ, the intensity distribution I ₂ of the incident light is

[0038]

(Equation 3)

NA ₂ = a ₂ / g ₂ (14) t ₂ = 2a ₂ / w ₂ (15) ba ′ = 2πr (NA ₂ ) / λ (16) Further, when the opening angle of the incident light is γ, the focal length F _{2 of the} lens and the beam diameter w ₂ at the conversion position are related by the following equations (17) and (18).

1 / F ₂ = 1 / f ₂ −1 / g ₂ (17) f ₂ = w ₂ / 2tan γ (18) From these formulas (17) and (18), F ₂ = 1 / (2tan γ / w ₂ The relationship of −1 / g ₂ ) (19) is obtained. That is, when the optical path length g ₂ is determined, the focal length F _{2 of the} lens is determined.

Further, the pupil radius a _{2 of the} lens is calculated by the equation (12).
Or on of substituting equation (19) into equation (16), the maximum value of I ₂ as _{I 2 m a x, I 2} (x 2/2) / I 2 m a x = 1 / e 2 (e Is the base of the natural logarithm) (20).

Here, g is obtained from the beam diameter w ₂ at the conversion position.
_If the length of ₂ is taken long enough, at the bottom of the prism 15,
Almost parallel light will be incident. In particular, when designing g _{2 to} be infinite, the focal length F _{2 of the} lens can be determined from the NA value sin γ and the beam diameter w ₂ at the conversion position.

Next, the coupling efficiency of the prism coupler of this example will be concretely calculated. Here, the optical waveguide 18 has a non-alkali glass layer 13 (for example, # 7059 glass manufactured by Corning Co., Ltd.) of 570 μm on a Si substrate 11 on which a SiO ₂ (quartz glass) layer 12 having a thickness of 2 μm is formed on the surface.
A SiO ₂ layer 14 (200 μm) is laminated, and a prism 15 having a concave lens 19 (for example, glass material LaSF08) is attached to the surface of the optical waveguide 18 to form a prism coupler. To do.
The refractive index of each component is the same as in Table 1 above. At this time, the coupling efficiency of this prism coupler is
Calculation can be performed by the same method as in the first embodiment. Light having a beam diameter of 24.4 μm is made incident so that the position of 13 μm from the end of the prism 15 on the surface of the optical waveguide 18 becomes the intensity center and the light incident angle is 52. In the case of 0.4 °, a coupling efficiency of 85% with respect to TE light is obtained. Further, a coupling efficiency of 81% can be obtained for TM light.

As described above, in this example, since the prism 15 is provided with the concave lens 19 that converts the incident light into substantially parallel light, most of the incident light can be input to the optical waveguide 18. That is, the coupling efficiency can be increased. Also, by appropriately moving the position of the prism coupler, the beam spot diameter of the light incident on the prism coupler can be changed. Therefore, the optical waveguide 18 is designed so that the wavelength fluctuation of the coupling efficiency is suppressed within the allowable range. After that, the beam spot diameter can be changed so as to obtain the optimum coupling efficiency for the optical waveguide 18. That is, it is possible to realize both suppression of wavelength fluctuation of coupling efficiency and improvement of coupling efficiency.

Further, in this example, the conversion of the incident light into the substantially parallel light is performed by the concave lens 19 formed inside the prism 15, but it may be performed by a microlens or a grating formed on the surface of the prism 15.

(Third Embodiment) FIG. 7A is a structural view showing the optical pickup device of the present invention, and FIG. 8 is a plan view showing the structure of the optical waveguide device 8. In these figures, the same parts as those in FIGS. 13 and 14 are denoted by the same symbols. The light emitted from the light source 1 is a hologram 2,
The light passes through the collimator lens 3, is changed in direction by the compound mirror 4 including a half mirror and a total reflection mirror, and enters the compound mirror 4 through the objective lens 5. The light incident on the compound mirror 4 is split into two: servo error signal detection light and magneto-optical signal detection light. The servo error signal detection light is condensed from the composite mirror 4 by the collimator lens 3, enters the hologram 2, is diffracted, is guided to the photodiode 7, and the signal is detected. On the other hand, the magneto-optical signal detection light is reflected by the inner surface (total reflection mirror) of the half mirror having a wedge-shaped cross section, emitted from the composite mirror 4 at an angle of θ with the servo error signal detection light, and collected by the collimator lens 3. The light is guided through the optical waveguide element 8 without passing through the hologram 2. Then, as shown in the plan view of FIG.
The light guided to is incident on the optical waveguide 18 via the prism 15, then passes through the polarization separation element 20, and is detected by the photodiode 21.

FIG. 9 is a side view showing the structure of the composite mirror 4. The A surface is a half mirror and the B surface is a total reflection mirror. The A surface half mirror is configured to have a polarization characteristic, and the Kerr rotation angle is multiplied. The light incident on the surface A is reflected at a right angle there and is supplied to the magneto-optical disk 6 through the objective lens 5.
Is reflected by and is guided again to the A surface through the same optical path. The light is transmitted through the A side, totally reflected by the B side, and again A
The light is transmitted through the surface and emitted from the composite mirror 4.

The composite mirror 4 has a function of guiding a part of the return light onto the optical waveguide element 8 without passing through the hologram 2. Instead of the composite mirror 4, as shown in FIG. It is also possible to use the optical component 10 which has a property that the incident surface is partially transparent and the rear surface is substantially 100% reflective.

10 and 11 are enlarged views of the prism coupler portion of the optical waveguide device 8. 10 is a diagram when the prism coupler shown in FIG. 1 is used, and FIG. 11 is a diagram when the prism coupler shown in FIG. 5 is used. In FIGS. 10 and 11, the bottom surface of the optical waveguide device 8 is installed at an angle φ with respect to the bottom surface of the package so that the incident light enters the incidence surface of the prism 15 perpendicularly.
This angle φ is determined as follows. The refractive index of the prism 15 is n _p , the inclination between the incident light and the bottom of the package is θ _t ,
Let the effective refractive indices of TE light and TM light be N _{T E} and N _{T M.}
In this case, the base angle [psi prism ^{ψ = sin - 1 {(N} T E + N T M) / 2n p} is determined as (21), the angle phi of the bottom surface of the optical waveguide device 8, φ = ψ-θ _t (22).

In this prism coupler, the prism 15
However, since the surface thereof is provided with means for making the incident light substantially parallel light, the incident light can be input to the optical waveguide element 8 with high efficiency without adding an optical component. For this reason,
The amount of signal light at the time of detecting a magneto-optical signal is increased, and the CN ratio (carrier to noise ratio) of the signal is improved. This will be specifically described below. Assuming that the coupling efficiency of the conventional prism coupler and the coupling efficiency of TE light of the prism coupler of this example are a and b (a <b), the signal light amount is proportional to the coupling efficiency, and the signal C
N ratio is _{20 (log 1 0 b-log} 1 0 a) [dB] improvement. Therefore, when the prism couplers shown in the concrete examples of the first and second embodiments are used, C
N ratio 20 than when using a conventional prism coupler _{(log 1 0 85-log 1} 0 13) = 16.3
[DB] is improved.

In this example, the prism coupler of the present invention is applied to the optical pickup device shown in FIG. 7, but the present invention is not limited to this and can be applied to optical pickup devices of various configurations.

[0052]

As described above, according to the present invention, since there is provided means for making the light incident on the prism coupler into substantially parallel light at least on the surface of the optical waveguide, the amount of light that can enter the optical waveguide is increased. You can That is, the coupling efficiency of the prism coupler can be increased.

Further, since the beam spot diameter of the incident light can be changed by moving the position of the prism coupler back and forth, both suppression of wavelength fluctuation of coupling efficiency and improvement of coupling efficiency can be realized. it can.

If this prism coupler is applied to an optical pickup device, the amount of light detected by the photodetector can be increased without adding optical parts, so that an optical pickup device that is compact and has an excellent CN ratio of the detection signal can be obtained. realizable.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment.

FIG. 2 is an enlarged view showing a light incident surface of a prism having a convex lens.

FIG. 3 is a diagram showing the dependence of coupling efficiency on a light incident angle.

FIG. 4 is a side view showing another configuration of the first embodiment.

FIG. 5 is a side view showing a second embodiment.

FIG. 6 is an enlarged view showing a light incident surface of a prism having a concave lens.

FIG. 7 is a configuration diagram showing a third embodiment.

FIG. 8 is a plan view of the optical waveguide device of FIG.

FIG. 9 is an enlarged view showing the structure of a composite mirror.

FIG. 10 is a side view showing an embodiment of a prism coupler.

FIG. 11 is a side view showing another example of the prism coupler.

FIG. 12 is a configuration diagram showing a conventional example of an optical pickup device.

FIG. 13 is a configuration diagram showing another conventional example of the optical pickup device.

FIG. 14 is an enlarged view showing a conventional prism coupler.

[Explanation of symbols]

 15 Prism 16 Convex lens 18 Optical waveguide 19 Concave lens

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Keio Yoshida 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Inventor Yukio Kurata 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Within the corporation

Claims (4)

[Claims] 1. A prism coupler comprising an optical waveguide composed of a substrate and at least one dielectric layer formed on the substrate, and a prism mounted on the optical waveguide. A prism coupler comprising means for converting at least light incident on the surface of the optical waveguide into substantially parallel light. 2. The prism coupler according to claim 1, wherein the prism has a convex lens on a light incident surface of the prism. 3. The prism coupler according to claim 1, wherein the prism has a concave lens on a light incident surface of the prism. 4. A prism coupler comprising a light source, an optical waveguide comprising a substrate and at least one dielectric layer formed on the substrate, and a prism mounted on the optical waveguide. An optical system that collects the light from the light source on a record carrier and guides at least a part of the return light from the record carrier to the prism coupler, and a signal based on the light guided through the optical waveguide. An optical pickup device comprising a photodetection element for detecting, wherein the prism constituting the prism coupler has means for converting at least incident light on the surface of the optical waveguide into substantially parallel light. Optical pickup device.