JPH0519309A - Surface acoustic wave optical deflecting element - Google Patents

Abstract

PURPOSE:To reduce light guide loss by realizing a small-sized surface acoustic wave optical deflecting element. CONSTITUTION:The light of a semiconductor laser 3 which is joined closely to an end surface of a light guide layer 1 is collimated by a light guide lens 4 and after Bragg diffraction with a surface acoustic wave 6 by a surface acoustic wave exciting electrode 5, the light is reflected by an end surface reflecting mirror, passed through the light guide lens 4 again, and converged and projected on the light guide end surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave light deflection element used in an optical information processing apparatus such as an optical disk or a laser beam printer, and a coupling method therefor.

[0002]

2. Description of the Related Art In recent years, in order to reduce the information processing time of an optical information processing apparatus such as an optical disk, it has been proposed to use a small-sized and high-speed optical deflection element such as a surface acoustic wave optical deflection element. For example, Applied Optics 29,2
(1990) pp. 247-250 (Appl. Opt.
29, 2 (1990) pp247-250),
As shown in FIG. 7, the semiconductor laser 3 is brought close to the end face of the optical waveguide 1, the light coupled to the optical waveguide 1 is collimated by the geodesic optical waveguide lens 4, and a high frequency voltage is applied to the surface acoustic wave excitation electrode 5. Then, the excited surface acoustic wave 6 is Bragg-diffracted at an angle corresponding to the frequency and emitted from the end face of the optical waveguide as it is.
This is collimated by a cylindrical lens and focused on an optical recording medium through a bulk optical system to read recorded information. At this time, in order to follow the light spot focused on the vibration of the recording track of the optical recording medium, the frequency of the surface acoustic wave is changed according to the track error signal to move the light spot. The surface acoustic wave optical deflection element has characteristics that it has a quick response and is strong against vibration compared to a mechanical optical deflection element such as a galvanometer mirror that has been conventionally used for optical disks and the like because it has no moving parts with mass. In the optical disc, it contributes to the improvement of the access time. The surface acoustic wave is an ultrasonic wave localized at a depth of about the sound wave wavelength on the surface of the medium, and can also efficiently interact with the guided light confined in the optical waveguide layer on the surface. The power consumption is about 0.1W. On the other hand, in the light deflection by the bulk-type acousto-optic crystal, energy is not concentrated in both sound waves and light, so that power of 1 W or more is required to obtain high diffraction efficiency.

For the optical waveguide and the surface acoustic wave excitation, the Ti diffused LiNbO ₃ optical waveguide is used in the above conventional example. Other surface acoustic wave light deflection elements include ZnO.
There are examples using / SiO ₂ / Si, As ₂ O ₃ / SiO ₂ / Si (surface acoustic wave excitation section ZnO) and the like.

As a method of optical coupling to the optical waveguide, there are methods such as prism coupling and grating coupling in addition to the end face coupling as in the above-mentioned conventional example. Since these couple the collimated light by an external bulk lens, an optical waveguide lens is unnecessary. Further, both can be optically coupled with high efficiency of about 80%. However, the optimum incident angle varies depending on the wavelength, and its allowable range is narrow. Therefore, when a semiconductor laser is used as a light source, the influence of wavelength variation due to temperature change and the crystal of lithium niobate, etc. The incidence efficiency fluctuates greatly due to the influence of the change in the refractive index. These effects are relatively small in the end face coupling, and a semiconductor laser and a collimator lens are integrated. However, the coupling efficiency reported so far is about 15%, which is not very good. In addition to the method of directly fixing the semiconductor laser close to the end face of the optical waveguide as in the above-mentioned conventional example, there is also a method of condensing the light from the semiconductor laser on the end face of the optical waveguide by a bulk lens and coupling. Is 8
A good coupling efficiency of about 0% is obtained.

As the optical waveguide lens, there are a mode index lens and a grating lens in addition to the above-mentioned geodesic lens, but the geodesic lens is generally the one with the highest performance and the short focal length can be expected. The geodesic lens is characterized by the fact that the optical path is not affected by the wavelength in principle because it processes the indentation on the optical waveguide and causes the lens action by the difference in the geometrical length of the optical path of the light traveling on the surface. There is. This is convenient for semiconductor lasers. However, the processing is performed by cutting or the like, and the productivity is poor.

[0006]

When the surface acoustic wave optical deflection element is used in the pickup of an optical disk as in the above-mentioned conventional example, in order to secure the working distance and the focusing spot size of the focusing lens to the optical recording medium. The optical waveguide lens requires a certain collimated beam width. Here, the semiconductor laser usually has an elliptic far-field image having a short axis in the direction of the active layer, and is linearly polarized in that direction. Since the TE mode guided light has a larger interaction with the surface acoustic wave than the TM mode, the coupling to the optical waveguide layer is such that the minor axis direction of the elliptical beam is incident in the direction parallel to the waveguide layer. Need to let. Therefore, assuming that the divergence angle of the incident semiconductor laser light in the waveguide layer direction is 15 ° (1 / e ² ),
For example, LiNbO ₃ has an extraordinary refractive index of 2.175 (780
Therefore, in the waveguide, the spread angle is about 7 ° due to the law of refraction. Therefore, in order to secure the beam width of 4 mm, the focal length of the optical waveguide lens needs to be 30 mm or more.

Usually, a titanium-diffused LiNbO ₃ optical waveguide has a waveguide loss of 0.5 to 1 dB / cm. Therefore, if the element length is 40 mm for the above reason, the light intensity will be only due to the waveguide loss. There is a problem that it becomes 50 to 25%. Further, the size of such an element also affects an increase in access time in an information processing device such as an optical disc. In the optical disc, the pitch of the optical recording tracks is very small, 1.6 μm, so a highly accurate positioning mechanism is required. At present, it is 2 for fine adjustment and coarse adjustment.
A stepped actuator is used, and in the above conventional example, a surface acoustic wave light deflection element is used as the fine adjustment actuator. Coarse actuators are often
Since the fine adjustment actuator element as described above is moved, an increase in the size of the element imposes a burden on the rough adjustment access, leading to an increase in access time.

An object of the present invention is to realize a small surface acoustic wave optical deflector for the above problems and reduce the optical waveguide loss.

[0009]

The above object is to provide an optical waveguide substrate having a low refractive index, an optical waveguide layer having a refractive index higher than that of the substrate provided on the optical waveguide substrate, and the optical waveguide. An optical waveguide end face having an optical mirror-polished surface on the side surface of the substrate or a surface state equivalent thereto, a semiconductor laser in which the active layer end face is closely fixed to the end face of the emitted laser light in the optical waveguide end face, and the optical waveguide from the end face An optical waveguide lens for collimating the divergent light from the semiconductor laser coupled to the layer in the optical waveguide, and an electrode for generating a surface acoustic wave that Bragg-diffracts the collimated light at an angle according to its frequency. A surface acoustic wave light deflection element, wherein the light diffracted by the surface acoustic wave is reflected at least once by a reflection mirror provided in the optical waveguide, It enters the fine optical waveguide lens is accomplished by emitted is focused on the optical waveguide end surface by the optical waveguide lens.

That is, in order to solve the above problems,
A semiconductor laser is fixed to the end face of the optical waveguide by fixing the end face of the active layer in the near field, and the divergent light coupled to the optical waveguide is collimated by the optical waveguide lens. At this time, the focal length of the optical waveguide lens may be as short as practically possible. For example, it is difficult to design a focal length of 5 mm or less in terms of efficiency even with a geodesic lens that can easily achieve a relatively short focal length. With a focal length of 5 mm, the collimated beam width is 0.6 mm for a beam divergence of 7 °. For Bragg diffraction by surface acoustic waves, it is said that the light beam width may be λL / NΛ or more, where L is 3 mm, where light wavelength λ, electrode length L, equivalent refractive index N, and acoustic wave wavelength Λ. λ = 0.78 μm, N =
If 2.18, Λ = 14 μm, this is 0.08 mm
Since it is a degree, the above conditions are sufficiently satisfied.

Next, the collimated beam is Bragg-diffracted by a surface acoustic wave excited by applying a high frequency voltage to the comb-shaped electrode loaded on the optical waveguide layer. In Bragg diffraction, a diffraction efficiency close to 100% is obtained, but on the other hand, it is necessary to adjust the incident angle θ on the surface acoustic wave so as to satisfy the Bragg condition given by 2Λsin θ = λ / N.
This can be adjusted by finely moving the semiconductor laser in a direction parallel to the optical waveguide layer. The diffracted light is made to enter the optical waveguide lens again at a slightly different incident angle by the reflection mirror provided in the waveguide. The reflection mirror is an end face mirror that is optically polished on the end face of the optical waveguide and is installed so that light is incident thereon at an incident angle of not less than the critical angle for total reflection. The end face mirror has no chromatic aberration and is efficient (80% or more). . The above critical angle is arc sin (1 /
N), which is approximately 27 ° in the case of LiNbO ₃ . If the incident angle is less than the critical angle, a metal reflection film or the like may be coated. The angle of incidence on the lens is changed as described above in order to prevent the reflected light from being diffracted again by the surface acoustic wave.

The light that has re-entered the optical waveguide lens is condensed at different positions on the end face of the semiconductor laser that is closely joined. An optical waveguide lens having a rotationally symmetrical shape such as a geodesic lens or a Luneburg lens is desirable to maintain the lens condensing performance even at different incident angles. Also, if the diameter of the light spot focused on the end face is made to be about the same as the thickness of the optical waveguide layer, the near-field pattern of the light emitted from the waveguide will be close to a circular shape, so that the subsequent optical system will be aligned with the optical axis. Rotational symmetry makes adjustment easy. This focal point moves on the end face as the frequency of the surface acoustic wave is changed.

Although the light-condensing position is slightly displaced from the exit end face due to the light deflection by the surface acoustic wave, since the deflection angle is small, the deviation is within the depth of focus of the light-converging point by the lens and causes almost no problem. For example, in the case of a LiNbO ₃ optical waveguide (n = 2.1745), the deflection angle by the surface acoustic wave is θ = 1 °, the focal length f of the second waveguide lens is f = 8 mm, NA is 0.4, and the wavelength is λ = If it is 0.78 μm, the deviation of the focal position from the end face is f−fcos θ =
1.2 μm, depth of focus λ / (NA) ² = 4.9 μm
Small compared to. When such emitted light is focused on the optical recording medium by a finite objective lens, the focusing point can be scanned on the medium. Further, as a head configuration of an optical disk, a configuration has recently been proposed in which only the objective lens and the focus actuator are moved on a coarse actuator. In this case, since an infinite objective lens is required, it is only necessary to collimate once with the bulk lens and then condense with the objective lens.

As another means for solving the above problems, a bulk lens system is used to focus and couple the semiconductor laser light to the end face of the optical waveguide. At this time, the polarization direction of the semiconductor laser is arranged in a direction perpendicular to the optical waveguide layer, and the semiconductor laser is arranged between the semiconductor laser and the bulk lens system, or between the bulk lens system and the end face of the optical waveguide. ,
Insert the λ / 2 plate. Normally, the divergence angle of the outgoing beam in the polarization direction of the semiconductor laser is smaller than the divergence angle in the direction orthogonal to the polarization direction. With such a structure, the divergence angle in the optical waveguide direction can be increased. You can Further, since the λ / 2 plate has a property of rotating the polarization direction of the linearly polarized light that is incident according to its rotation angle, by inserting this, the polarization direction is rotated in the optical waveguide layer direction, and the TE mode Can be coupled in.

The numerical aperture (NA) of the condenser lens is limited by the necessity of bringing the condensed light intensity distribution in the direction perpendicular to the optical waveguide layer closer to the intensity distribution of the guided mode of the optical waveguide. For example, assuming that the width at which the light intensity distribution of the guided mode is 1 / e ² is 3 μm, the width at which the light intensity distribution of the focused spot in the direction perpendicular to the optical waveguide layer is 1 / e ² is about 3 μm. It has been shown from the theory of mode coupling that the highest coupling efficiency is obtained. Therefore, by inserting the λ / 2 plate, the beam divergence angle of 15 ° (NA
0.13) should be focused to 3 μm, so a wavelength of 0.7
The emission side NA is 0.26 when the thickness is 8 μm. On the other hand, a beam divergence angle of 30 ° (NA 0.26) in the waveguide layer direction requires NA 0.52 on the exit side. That is, as the condenser lens, one having an incident side NA of 0.26 and an emitting side NA of 0.52 may be used. Similarly, if the λ / 2 plate is not used, the condenser lens will have the same NA on both the input and output sides.
Since it needs to be 0.26, the beam divergence angle in the waveguide layer direction due to the insertion of the condenser lens is not improved at all.

The light coupled to the optical waveguide is collimated by the optical waveguide lens. At this time, the focal length of the optical waveguide lens needs to be long enough so that the collimated beam width becomes the beam width required by the objective lens for focusing on the optical recording medium or the like.

The collimated light is Bragg-diffracted in the angular direction corresponding to the frequency of the surface acoustic wave excited by applying a high frequency voltage to the surface acoustic wave excitation electrode. Therefore, the semiconductor laser is adjusted to a position in the waveguide layer direction so that the Bragg condition is satisfied in the surface acoustic wave. It is not particularly necessary to make the diffracted light incident on the optical waveguide lens again, and the diffracted light is emitted from the end face and collimated by the cylindrical lens.

[0018]

[Function] By providing a reflection mirror in the optical waveguide and collimating, the light diffracted by the surface acoustic wave is condensed again on the end face of the optical waveguide by the optical waveguide lens and emitted, thereby increasing the collimated beam width. It is not necessary, and the focal length of the optical waveguide lens can be shortened. Therefore, the light propagation length can be shortened and the device can be downsized. When the propagation length of the optical waveguide is shortened as described above, the optical waveguide loss can be reduced and the light utilization efficiency can be improved.
Further, by using one optical waveguide lens twice, it is possible to substitute the function of two lenses with one lens. Furthermore, by folding the optical path with a reflection mirror, the size of the device can be reduced to almost half of the actual function. Furthermore, when the light is emitted from the end face of the optical waveguide, the optical waveguide or the optical waveguide lens is designed so that the focused beam diameter is the same as the thickness of the optical waveguide layer. You can take it out. This means that the optical system after that may be symmetrical about the optical axis, so that not only the optical adjustment is facilitated but also the aberration performance is excellent. In this way, by changing the frequency of the high-frequency voltage applied to the comb-shaped electrodes, the diffraction angle is changed and the light is deflected.

Further, when the semiconductor laser light is coupled from the end face of the optical waveguide using the Balg lens and the λ / 2 plate, the semiconductor laser is installed so that the polarization direction is perpendicular to the optical waveguide. be able to. Conventionally, a semiconductor laser has a large beam divergence angle in a direction orthogonal to the polarization direction. Therefore, when collimating with a light guide lens, a required collimated beam diameter can be obtained with a short focal length. Therefore, since the light propagation length can be shortened, the optical waveguide loss can be reduced, and the device can be downsized.

Further, in general, a higher coupling efficiency can be obtained by condensing the light on the end face of the optical waveguide layer with a lens, and this is also useful for improving the light utilization efficiency. For example, Applied Optics, 19 (1
980) 1847 (Appl. Opt. 19 (1980) p.
1847), a coupling method of joining a semiconductor laser to an end face of an optical waveguide reports a coupling efficiency of 15%. On the other hand, when the semiconductor laser light is focused and coupled on the end face of the optical waveguide through the lens, if the electric field distributions are matched, only the loss due to the Fresnel reflection is required, so that the efficiency of about 80% can be obtained.

[0021]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing a basic configuration of a surface acoustic wave optical deflector according to the present invention, FIG. 2 is a top view of the basic configuration of the surface acoustic wave optical deflector, FIG. 3 is an explanatory view of diffraction by a surface acoustic wave, and FIG. FIG. 5 is a diagram showing a beam shaping effect by converging and emitting light on the end face of the waveguide, FIG. 5 is a diagram showing a basic configuration of a surface acoustic wave optical deflection element using a λ / 2 plate, and FIG. 6 is a diagram showing an angular distribution of semiconductor laser light intensity. FIG. 8 is a diagram showing a comparison with a conventional example of a surface acoustic wave optical deflection element using a λ / 2 plate, and FIG. 9 shows an example of calculation of a relationship between a collimated beam width and a focal length by an optical waveguide lens in a LiNbO ₃ optical waveguide. FIG. 10 is a diagram showing another embodiment of a surface acoustic wave light deflecting element using an end face reflection mirror, FIG. 11 is a diagram showing an embodiment in which the surface acoustic wave light deflecting element of the present invention is applied to an optical disk pickup, FIG. Is a side view of the above embodiment 3 is a diagram showing an embodiment of an optical disc pickup for parallel light by the collimator lens the light emitted from the optical waveguide.

In FIG. 1, an optical waveguide substrate 2 having a low refractive index
The diverging light from the semiconductor laser 3 formed above and closely bonded to the end face of the optical waveguide layer 1 having a refractive index higher than that of the substrate 2 is collimated by the optical waveguide lens 4, and then the surface acoustic wave is generated. Bragg diffraction is performed by the surface acoustic wave 6 excited from the excitation electrode 5. The Bragg diffracted light is reflected on the end face of the waveguide and is incident on the optical waveguide lens 4 again. At this time, if the angle of incidence on the end face is larger than the total reflection angle given by arc sin (1 / N) where N is the equivalent refractive index of the optical waveguide, it is simply an optically polished end face and If it is too small, metal deposition is performed to form an end face mirror. The light incident on the optical waveguide lens 4 is condensed and emitted on the semiconductor laser junction end face. Although a geodesic lens is used as the optical waveguide lens 4 in the present embodiment, it is also possible to use a mode index lens or a grating lens.
However, it is preferable that the lens has rotational symmetry as much as possible and that the lens performance has little dependence on the incident angle. In that respect, geodesic lenses and Reneburg lenses are suitable. FIG. 2 is a top view of the above embodiment.

The diffraction angle 2θ due to the surface acoustic wave of wavelength Λ is
It is given by 2arcsin (λ / 2NΛ) ≈λ / NΛ in the optical waveguide, and in the case of a LiNbO ₃ optical waveguide, λ = 0.7
If it is 8 μm, N = 2.18, and Λ = 14 μm, it is about 1.5 °. For this reason, the state of diffraction cannot be clearly shown in FIG. 1 and FIG.
The schematic diagram is shown in FIG. It is possible to generate a surface acoustic wave 6 by applying a high frequency voltage across the surface acoustic wave excitation electrode 5 and diffract the guided light incident on the surface acoustic wave 6 with an efficiency close to 100%. As the optical waveguide, there are acousto-optic effect or electro-optic effect, LiNbO ₃ , Zn
It is necessary to use a material such as O or As ₂ O ₃ . Further, the surface acoustic wave excitation electrode 5 needs to be loaded in contact with a material having a piezoelectric effect, such as LiNbO ₃ or ZnO.

FIG. 4 is a diagram for explaining how a near-field image having a substantially circular shape is obtained on the end surface of the optical waveguide 1 when light is emitted after being condensed by the optical waveguide lens. The lateral light intensity distribution of the converging pattern on the end face of the optical waveguide is determined by the aberration performance of the optical waveguide lens and the numerical aperture, and is a distribution that is almost Gaussian. The depth direction is determined by the structure of the optical waveguide and has a slightly asymmetric light intensity distribution. However, by designing the optical waveguide lens and the optical waveguide so that the half-value widths of these distributions are approximately equal, it is possible to obtain divergent light having a substantially circular near-field image.

FIG. 5 shows a basic structure of a surface acoustic wave light deflection element using a λ / 2 plate. Here, the laser light emitted from the semiconductor laser 3 is focused on the end face of the optical waveguide 1 through the λ / 2 plate 7 and the distributed index lens 8 as the end face focusing lens, and is coupled. Λ / 2 plate 7
Has the function of rotating the polarization direction of linearly polarized light which is incident with the plane of polarization forming an angle of θ with respect to the crystal principal axis direction by 2θ. Therefore, when the main axis direction is inclined by 45 ° with respect to the waveguide surface, linearly polarized light in the TM direction in the optical waveguide can be rotated in the TE direction for coupling. FIG. 6 shows an example of the intensity distribution with respect to the angle in the direction parallel to the polarization direction of the semiconductor laser and in the direction perpendicular thereto. Since the beam divergence angle in the polarization direction is small, if the λ / 2 plate 7 is used, the direction in which the beam divergence angle is large can be coupled to the optical waveguide layer. Further, the end face condensing lens in FIG. 5 does not need to be the distributed index lens 8, but the distributed index lens currently on the market is extremely small, and thus the size of the entire element can be reduced by using this. be able to. Figure 7
In the conventional example shown in (1), the polarization direction of the semiconductor laser 3 is aligned with the waveguide direction in order to enhance the diffraction effect of the surface acoustic wave 6, so that the beam divergence angle in that direction is small and the optical waveguide having a long focal length. The lens 4 is used.

FIG. 8 shows a comparison of the top views of the respective elements of the embodiment shown in FIG. 5 and the conventional example shown in FIG.
Since the focal length of the optical waveguide lens 4 is shortened, the size of the optical waveguide is smaller than the conventional one. Figure 9 is Li
NbO ₃ is a diagram showing by calculating the relationship between the collimated beam width and the focal length by the optical waveguide lens in the optical waveguide. θ = 7 ° is the case where the major axis direction of the elliptical far-field pattern of the light emitted from the semiconductor laser is incident on the optical waveguide layer. Since the increase of NA by the condenser lens is not included here, the focal length can be further shortened by considering the effect.

FIG. 10 is a view showing another embodiment of the surface acoustic wave light deflection element using the end face reflection mirror. Optical waveguide layer 1
By forming the substrate 2 on which the above is formed into a polygonal shape as shown and making the obtained side end surface into an optical mirror-polished surface or a surface state equivalent thereto, the coupled principal ray of the semiconductor laser 3 becomes After being collimated by the waveguide lens, it is guided again to the center of the waveguide lens by using the two-faced waveguide reflection mirror, so that the required specifications such as aberration to the lens are alleviated.

FIG. 11 is a diagram showing an embodiment in which the surface acoustic wave light deflection element according to the present invention is applied to an optical disk pickup. The light that has been reflected by the polished surface of the end face of the optical waveguide, passes through the optical waveguide lens 4, is condensed on another end face of the optical waveguide, and is emitted from the surface acoustic wave optical deflection element passes through the beam splitter 9 and the objective lens 10, It is focused on the optical disk 11. Then, the recorded signal is read, reflected, passed through the beam splitter 9, and the photodetector 12 detects the signal. Here, the objective lens 10 is driven in the optical axis direction by a focusing actuator such as a voice coil,
It follows the rotational shake of the optical disk 11. A surface acoustic wave light deflection element is used for the tracking actuator. For the control signal detection, for example, the tracking error signal is 3
For the spot method and the focus error signal, a differential detection method of the light intensity distribution at the front focus may be used. The tracking error signal converts a voltage into a frequency to drive the surface acoustic wave, and the focus error signal is fed back to the focus actuator. FIG. 12 is a side view of the optical disc pickup. In FIG. 11, the distance between the optical elements is widened to make the structure easy to understand, but it is actually possible to reduce the size to the extent shown in FIG.

FIG. 13 is a diagram showing an embodiment of an optical system in which the divergent light emitted from the optical waveguide of the surface acoustic wave optical deflector is collimated by the collimator lens 13 and then condensed on the optical disk 11 in the above embodiment. is there. Objective lens 10,
This optical system corresponds to a configuration in which only the focus actuator and the raising mirror 14 are moved on the coarse adjustment actuator.

[0030]

As described above, the surface acoustic wave optical deflector according to the present invention is provided with an optical waveguide substrate having a low refractive index and an optical waveguide having a refractive index higher than that of the substrate provided on the optical waveguide substrate. A layer, an optical waveguide end face having an optical mirror polished surface on the side face of the optical waveguide substrate or a surface state equivalent thereto, and a semiconductor laser in which the end face of the active layer is fixed in proximity to the end face of the emitted laser light on the end face of the optical waveguide. , An optical waveguide lens for collimating the divergent light from the semiconductor laser coupled from the end face to the optical waveguide layer in the optical waveguide, and a surface elastic for Bragg-diffracting the collimated light at an angle according to its frequency. A surface acoustic wave light deflection element comprising an electrode for wave generation, wherein light diffracted by the surface acoustic wave is reduced by a reflection mirror provided in the optical waveguide. Both are reflected once, enter the optical waveguide lens again, and are condensed on the end face of the optical waveguide by the optical waveguide lens and emitted, so that the optical waveguide lens is used twice by the reflection mirror used in the optical waveguide. Since the surface acoustic wave light deflection element integrated with the semiconductor laser is configured, the focal length of the optical waveguide lens can be shortened and the element can be downsized. Therefore,
The light propagation length is also shortened, and the light utilization efficiency can be improved.

Further, in the surface acoustic wave optical deflector for coupling the light from the semiconductor laser to the end face of the optical waveguide by using the λ / 2 plate or the condenser lens, the spread angle of the light coupled to the optical waveguide is set. The beam width required for focusing on the optical recording medium can be increased with a short focal length of the optical waveguide lens. Therefore, the light propagation length is shortened, and the light utilization efficiency can be improved.

[Brief description of drawings]

FIG. 1 is an embodiment diagram showing a basic configuration of a surface acoustic wave light deflection element according to the present invention.

FIG. 2 is a top view of a basic configuration of the surface acoustic wave light deflection element.

FIG. 3 is a diagram illustrating diffraction by surface acoustic waves.

FIG. 4 is a diagram showing a beam shaping effect by converging and emitting an end face of an optical waveguide.

FIG. 5 is an embodiment diagram showing a basic configuration of a surface acoustic wave light deflection element using a λ / 2 plate.

FIG. 6 is a diagram showing an angular distribution of semiconductor laser light intensity.

FIG. 7 is a diagram showing a conventional surface acoustic wave light deflection element.

FIG. 8 is a diagram showing a surface acoustic wave optical deflection element using a λ / 2 plate in comparison with a conventional example.

FIG. 9 is a diagram showing a calculation example of a relationship between a collimated beam width and a focal length by an optical waveguide lens in a LiNbO ₃ optical waveguide.

FIG. 10 is a diagram showing another embodiment of the surface acoustic wave light deflection element using the end face reflection mirror.

FIG. 11 is a diagram showing an embodiment in which the surface acoustic wave light deflection element of the present invention is applied to an optical disc pickup.

FIG. 12 is a side view of the optical disc pickup.

FIG. 13 is a diagram showing an embodiment of an optical disc pickup in which light emitted from an optical waveguide is collimated by a collimator lens.

[Explanation of symbols]

1 Optical waveguide layer 2 Optical waveguide substrate 3 Semiconductor laser 4 Optical waveguide lens 5 Surface acoustic wave excitation electrode 6 surface acoustic waves 7 λ / 2 plate 8 lens system

Claims (2)

[Claims] 1. An optical waveguide substrate having a low refractive index, an optical waveguide layer provided on the optical waveguide substrate and having a refractive index higher than that of the substrate, and an optical mirror-polished surface or a surface state equivalent thereto. An optical waveguide end face having, a semiconductor laser in which the active layer end face is closely fixed in the near field of the emitted laser light to the optical waveguide end face, and divergent light from the semiconductor laser coupled to the optical waveguide layer from the end face, A surface acoustic wave optical deflection element comprising an optical waveguide lens for collimating in an optical waveguide and an electrode for generating a surface acoustic wave for Bragg-diffracting collimated light at an angle according to the frequency, the surface acoustic wave The light diffracted by the wave is reflected at least once by the reflection mirror provided in the optical waveguide, enters the optical waveguide lens again, and is reflected by the optical waveguide lens. Surface acoustic wave deflection element for emitting focused on the light waveguide end face. 2. An optical waveguide substrate having a low refractive index, an optical waveguide layer having a refractive index higher than that of the substrate provided on the optical waveguide substrate, an optical mirror-polished surface on a side surface of the optical waveguide substrate, or An optical waveguide end face having a surface state equivalent to that, a semiconductor laser optically coupled from the optical waveguide end face to the optical waveguide layer via a lens system, and the lens system,
Surface acoustic wave optical deflection including an optical waveguide lens for collimating the coupled divergent light in the optical waveguide and an electrode for generating a surface acoustic wave that Bragg-diffracts the collimated light at an angle according to its frequency. A surface of a device in which a semiconductor laser is arranged such that the polarization direction is perpendicular to the optical waveguide layer, and a λ / 2 plate is inserted between the semiconductor laser and the lens system or between the lens system and the optical waveguide. Elastic wave light deflection element.