JPH04237029A - Optical scanning element - Google Patents

Abstract

PURPOSE:To provide the small-sized optical scanning element which does not require movable parts, such as rotating mechanisms, is simple in constitution and is high in productivity. CONSTITUTION:The optical scanning element 10 is constituted of a Ti diffused waveguide 14 which is produced by dispersing Ti, etc., into a substrate 12 consisting of LiNbO3, etc., having an electrooptical effect and plural electrodes 16a, 16b which consist of Al, etc., and are formed on both sides thereof. The spacing between the electrode 16a and the 16b is narrower nearer the front end 21 of the bent waveguide. A higher electric field is impressed to the waveguide 20 as the inter-spacing of the electrodes is narrower and, therefore, the decrease of the refractive index of the waveguide increases and the confinement of the light into the waveguide is weakened. The light is no longer confined in the waveguide and is radiated to the outside of the bent waveguide 20. Then, the radiation position of the light in the bent waveguide 20 is controlled by changing the magnitude of the voltage to be impressed to the electrodes 16a, 16b.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an optical scanning element that irradiates light onto a photoreceptor drum in an optical printer and performs scanning exposure, or performs optical scanning in a barcode reader, etc., and more specifically, an optical waveguide. The present invention relates to an optical scanning element that performs optical scanning.

[Prior Art] Conventionally, an exposure device for exposing a photoreceptor drum such as a laser printer has a semiconductor laser 101 and a collimator lens 102, as shown in FIG.
, a polygon mirror 104, an fθ lens 106, and a reflection mirror 108. A laser beam emitted from a semiconductor laser 101 is turned into parallel light by a collimator lens 102, and is irradiated onto a rotating polygon mirror 104. Since the laser beam reflected by the polygon mirror 104 is deflected at a constant angular velocity, the laser beam is converted by the fθ lens 106 so that it moves at a constant velocity, and the total reflection mirror 1
After being reflected at 08, the photoreceptor drum 110, which has been charged in advance, is scanned and exposed. Since the exposed portion of the photoreceptor drum 110 loses charge due to photoconductivity,
Toner charged to the same polarity as the photoreceptor drum 110 adheres without being repelled. After transferring this toner to paper, printing is completed by fixing it by heating or the like.

0003

[Problems to be Solved by the Invention] However, in laser printers, the scanning optical system using polygon mirrors and lenses is complicated, making it difficult to adjust the optical axis, and requiring high processing precision, resulting in low productivity. There is a problem in that miniaturization is difficult because a mirror rotation mechanism is required.

The present invention was made in order to solve the above-mentioned problems, and it applies an electric field having a distribution that gradually increases or changes in the direction of propagation of light to a curved waveguide having an electro-optic effect. The object of the present invention is to provide a compact optical scanning element that does not require a movable part such as a rotation mechanism, has a simple structure, and has high productivity by applying an electric current.

[0005]

[Means for Solving the Problems] In order to achieve this object, the optical scanning element of the present invention includes a substrate, a curved waveguide formed on the substrate or on the surface of the substrate and having an electro-optic effect, and a curved waveguide having an electro-optic effect. It consists of an electrode that applies an electric field to the wave path, and the electric field is distributed so that it gradually increases or changes in the direction of propagation of light. Further, it may include an electrode that applies an electric field around the curved waveguide. Furthermore, the portion of the end surface of the substrate from which light is emitted to the outside may be made convex or other non-planar.

[0006]

[Operation] In the optical scanning element of the present invention having the above configuration, light emitted from a light source such as a semiconductor laser and guided into the curved waveguide propagates in the curved waveguide from the base to the tip. When an electric field is applied to the curved waveguide,
Due to the electro-optic effect, the refractive index of the curved waveguide decreases, so that light is no longer confined within the waveguide and is radiated out of the waveguide. The electric field applied to a curved waveguide has a distribution that gradually increases in the direction of light propagation, and when a certain voltage is applied, the refractive index decreases at a lower rate at the tip than at the base. growing. That is, the applied voltage required to reduce the refractive index of the waveguide by the same amount may be lower as it approaches the tip of the curved waveguide. Therefore, by applying a low voltage near the tip of the curved waveguide, the refractive index of the waveguide is reduced, so that light can no longer be confined and light is emitted. On the other hand, unless a high voltage is applied near the base of the curved waveguide, the refractive index of the waveguide will not decrease and no light will be emitted. As a result, the position from which light is emitted can be controlled by the magnitude of the applied voltage. Furthermore, in a curved waveguide, if the light is emitted at a different position, the emitted direction is also different, so the direction of the light emitted can be controlled by an applied voltage, and optical scanning can be performed. Note that instead of changing the refractive index of the curved waveguide using an electric field, optical scanning can be similarly performed by changing the refractive index around the curved waveguide. In addition, by processing the end surface of the substrate from which light is emitted to the outside into a non-planar shape such as a convex shape,
Functions such as focusing the emitted light can be added.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will be described below with reference to the drawings.

An optical scanning element 10 to which the present invention is suitably applied is, for example, as shown in FIG.
T fabricated by diffusing Ti, etc. onto a substrate 12 made of NbO3, etc.
It consists of an i-diffusion waveguide 14 and a plurality of electrodes 16a and 16b made of Al or the like formed on both sides thereof. The Ti diffusion waveguide 14 consists of a straight optical waveguide 18 and a curved waveguide 20. The curved waveguide 20 has a constant curvature. The distance between the electrodes 16a and 16b becomes narrower as it approaches the tip 21 of the curved waveguide. Further, a semiconductor laser 22 serving as a light source is attached to one end of the straight optical waveguide 18. Further, a light absorbing material 23 is provided at the tip of the curved waveguide 20.

A method of manufacturing such an optical scanning element 10 will be explained using FIG. 2. That is, as shown in FIG. 2(a),
A photoresist 24 is applied onto a substrate 12 made of LiNbO3 or the like by a spin coating method or the like. A mask 26 having a pattern of a predetermined waveguide shape is tightly attached thereon, and ultraviolet rays are irradiated for exposure. After exposure and development, the photoresist 24
As shown in Figure (b), the portion irradiated with ultraviolet rays remains. A Ti thin film 28 is formed thereon by well-known thin film forming means such as sputtering and vacuum evaporation. Thereafter, by removing the photoresist 24 with a solvent, the Ti thin film 28 can be processed into a predetermined waveguide shape as shown in FIG. 3(c). When this substrate 12 is heated to about 1000 °C and thermal diffusion is performed for several hours, the Ti thin film 28 is diffused into LiNbO3,
A Ti diffusion waveguide 14 is formed as shown in FIG. 2(d). Furthermore, as shown in FIG. 3(e), an Al thin film 30 that will become the electrode 16 is formed by a well-known thin film forming method such as sputtering or vacuum evaporation, and a photoresist 24 is applied thereon by a spin coating method or the like. Apply. A mask 32 having a pattern of a predetermined electrode shape is tightly attached thereon, and ultraviolet rays are irradiated for exposure. After exposure and development, only the portions of the photoresist 24 irradiated with ultraviolet rays remain as shown in FIG. 2(f). Here, the portions of the Al thin film 30 to which the photoresist 24 is not attached are etched using an etching solution such as acid or alkali or plasma etching, and then the remaining photoresist 24 is removed using a solvent or the like. figure(
The electrode 16 can be formed as in g).

The operation of the optical scanning element 10 of this embodiment will be explained using FIGS. 3 and 4.

The LiNbO3 used for the substrate 12 is a Y-cut plate whose optical axis is parallel to the substrate surface, and when a voltage is applied to the electrodes 16a and 16b as shown in FIG. 14. Here, if the applied voltage is E, the refractive index of LiNbO3 for ordinary and extraordinary light is no and ne, and the electro-optic constant is γ33,
TE in which the vibration direction of the electric field is a guided mode parallel to the substrate surface.
The refractive index ng of the waveguide 14 for the mode is LiNbO
When the optical axis (C axis) of 3 is perpendicular to the propagation direction of light, ng=
ne-(ne3γ33/2)E (1
), and the refractive index ng of the waveguide 14, that is, the curved waveguide 20, decreases in proportion to the electric field E. However, if the optical axis (C-axis) of LiNbO3 deviates from the direction perpendicular to the light propagation direction due to bending of the waveguide, the change in ng becomes small, but this can be compensated for by increasing the electric field E.

In FIG. 4A, laser light emitted from a semiconductor laser 22 serving as a light source is guided to a straight waveguide 18 and further propagates through a curved waveguide 20. In FIG. Here, a voltage is applied to the electrodes 16a and 16b, and the curved waveguide 2
By decreasing the refractive index of 0, the light 38 bends into the waveguide 20.
It is no longer confined inside the waveguide and is bent and radiated out of the waveguide 20. At this time, the electrodes 16a and 16b are formed so that the interval between them becomes gradually narrower in the light propagation direction, that is, in the direction of the tip of the curved waveguide 20.
If the voltage applied to a and 16b is constant, the narrower the electrode spacing, the higher the electric field applied to the waveguide 20, the greater the decrease in the refractive index of the waveguide, and the more light is confined within the waveguide. becomes weaker. Therefore, in the part 40 where the electrode spacing is narrow, simply applying a low voltage to the electrodes 16a and 16b reduces the refractive index of the curved waveguide 20, and the light 42 is no longer confined within the waveguide. radiates outward. On the other hand, if the applied voltage is constant, the electric field in the part 44 with a wide electrode spacing is smaller than that in the part 40 with a narrow electrode spacing. , 16b to greatly reduce the refractive index of the curved waveguide 20. In this way, since the electrodes 16a and 16b that apply an electric field to the curved waveguide 20 are formed so that the distance between them becomes narrow with respect to the propagation direction of light, the magnitude of the voltage applied to the electrodes 16a and 16b , the light emission position in the curved waveguide 20 can be controlled. As shown in FIG. 4(a), since the direction of light emission differs depending on the position where the light is emitted, the light is scanned by changing the voltage applied to the electrodes 16a and 16b and changing the light emission position. be able to. The emitted lights 38, 42, and 46 are focused onto the photoreceptor drum 50 by the lens 48 and exposed. For example, by applying a voltage having a waveform that changes as shown in FIG. 4(b) to the electrodes 16a and 16b, it is possible to scan from the bottom to the top in FIG. 4(a). Note that the light that is not emitted to the outside of the curved waveguide 20 is emitted from the curved waveguide 2.
The light is attenuated by a light absorbing material 23 using a metal cladding such as Al provided at the tip of the light beam.

Although one embodiment of the present invention has been described above in detail with reference to FIGS. 1 to 4, various other modifications can be made without departing from the spirit of the present invention. That is, the materials and shapes of the substrate, curved waveguide, and electrodes are not particularly limited. For example, the magnitude of the refractive index and the curvature of the curved waveguide 20 are not particularly limited, and further,
The curvature does not have to be constant. In addition, the substrate 12 and the electrode 1
A buffer layer made of SiO2 or the like may be provided between 6a and 16b. This can prevent the emitted light from being attenuated by the electrodes 16a and 16b. In addition, the electrode 16a
, 16b need not be constant. In addition, electrode 1
The waveform of the voltage applied to 6a and 16b is not particularly limited.

In addition, in the optical scanning element shown in FIG. 1, the closer the electrode 16a is to the base of the curved waveguide 20, that is, the connection between the curved waveguide 20 and the straight waveguide 18, the farther away it is from the curved waveguide 20. However, the shape of the electrodes is not particularly limited, and for example, as shown in FIG. may be formed. Further, the electrode spacing is not particularly limited, and as shown in FIG. 5(b), the electrodes 54a, 54
The interval b may be constant. At this time, the electrode 54a,
A material with relatively high resistance, such as NiCr or C, may be used for at least one electrode of the electrode 54b, so that a voltage distribution is generated. For example, in FIG. 5B, a material with relatively high resistance is used for the electrode 54a, and a voltage is applied to both ends of the electrode 54. As a result, a voltage distribution occurs in the electrode 54a, and the voltage becomes higher at a portion closer to the tip of the curved waveguide 20. Further, a voltage is also applied between the electrode 54a and the electrode 54b. Therefore, the voltage between the electrodes 54a and 54b becomes higher as it approaches the tip of the curved waveguide 20, and therefore the electric field applied to the curved waveguide 20 also increases as it approaches the tip. The operation of these optical scanning elements is shown in Figure 1.
This is exactly the same as the optical scanning element shown in .

Furthermore, the curved waveguide 20 does not need to be fabricated by Ti diffusion. That is, it is only necessary that one or both of the substrate and the curved waveguide be made of a material having an electro-optic effect, and LiTaO3 may be used for the substrate and LiNbO3 may be used for the curved waveguide. In addition, glass on the substrate,
Using sapphire etc., PLZT, ZnO in the curved waveguide
A thin film such as the above may also be used. The waveguide shape at this time is a ridge-type waveguide in which a ridge 64 is formed by cutting a part of the thin film 62 formed on the substrate 60, as shown in FIG. A ridge-type waveguide with an asymmetrical ridge shape may also be used. That is, by making the ridge shape asymmetric and making the outer side 66 thicker than the inner side 68, the radiation efficiency to the outside of the waveguide is improved. Furthermore, a three-dimensional waveguide 62 may be provided on the substrate 60 as shown in FIG. 6(c).

Furthermore, instead of applying an electric field to the curved waveguide 20 as shown in FIG.
A buffer layer 70 such as No. 2 is provided, and electrodes 72a, 7 are formed thereon.
2b is fabricated, and an electric field 76 is applied to the outside 74 of the curved waveguide 20.
may be applied. That is, it is sufficient that the interval between the electrodes 72a and 72b becomes narrower as the curve approaches the tip of the waveguide 20. At this time, the direction of the electric field is opposite to the direction shown in FIG. 3, and according to equation (1), the refractive index on the outside 74 of the curved waveguide 20 increases. Therefore, the light confinement in the curved waveguide 20 is weakened, and the light is radiated out of the waveguide.

Furthermore, the direction of the crystal axis of the crystal used for the substrate or waveguide is not limited, and for example, Y-cut LiN
Z-cut LiNbO3 may be used instead of bO3. In this case, S is placed on the Ti diffusion waveguide 14 as shown in FIG.
A buffer layer 70 such as iO2 is provided, and the Ti diffusion waveguide 14 is
Electrodes 74a, 74b, and 74c are formed on the top and both sides thereof. The electric field 76 at this time is generated in a direction perpendicular to the substrate surface. Due to this electric field, the refractive index ng of the waveguide for the TM mode in which the vibration direction of the magnetic field is parallel to the substrate surface is also
Since it is expressed by equation (1), as explained earlier, the electrode 74
Optical scanning can be performed by applying an electric field to a, 74b, and 74c. Also in this case, the electrodes 74a, 74b
, 74c should be narrower as the curve approaches the tip of the waveguide 20. Here, since the change in the refractive index ng of the waveguide does not depend on the change in the propagation direction of light due to the bending of the waveguide, the voltages applied to the electrodes 74a, 74b, and 74c can be easily controlled.

[0018] Furthermore, in order to fabricate a curved waveguide, Li
The material that diffuses into NbO3 is also not limited. Also,
There are no particular limitations on the refractive index distribution of the diffusion waveguide either. For example, as shown in FIG. 9(a), the refractive index distribution of the diffusion waveguide 80 may be formed such that the region with a high refractive index spreads outward. In this case, light confinement to the outside of the waveguide becomes weaker, making it easier to control radiation. Furthermore, the buffer layer 70
may be provided, and an electric field having opposite directions may be applied between the inside and outside of the diffusion waveguide 80 using the electrode 82. As a result, the refractive index on the inside of the diffusion waveguide 80 decreases and the refractive index on the outside increases, making it easier to emit light by applying an electric field. Furthermore, as shown in FIG. 2B, a region 86 having a lower concentration of diffused substances than the region 84 may be provided around, particularly outside, a region 84 which has a high concentration of diffused substances such as Ti and serves as a waveguide. Furthermore, as shown in FIG. 2(c), a material such as MgO that lowers the refractive index of the substrate 12 may be diffused into the inner side 87 and outer side 88 of the region 84 which is a waveguide and has a high concentration of diffused substances such as Ti. . This strengthens the confinement of light within the waveguide and prevents the light from being radiated outside when a weak electric field is applied, which is effective for the portion near the base of the curved waveguide 20. .

Furthermore, the curved waveguide 20 may be fabricated using well-known proton exchange instead of Ti diffusion. Since a large change in the surface refractive index can be realized by proton exchange, the radius of curvature of the curved waveguide 20 can be reduced overall, and the entire optical scanning element can be further miniaturized.

Furthermore, in the embodiment shown in FIG. 1, an electric field was applied to reduce the refractive index of the curved waveguide, but the direction of application of the electric field is not particularly limited. An electric field may be applied in a direction such that the rate increases. That is, the refractive index of the curved waveguide may be made small so that light is emitted when no electric field is applied, and when an electric field is applied, the refractive index increases and the light is confined. At this time, the electrodes may be formed such that the electrode spacing at the base of the curved waveguide is narrowed and the electrode spacing becomes wider as it approaches the tip. If a low voltage is applied to the part where the electrodes at the base are narrowly spaced, light will be confined. On the other hand, in the part of the tip where the electrode spacing is wide, light cannot be confined unless a high voltage is applied, so the light emission position can be controlled by the magnitude of the applied voltage.

Furthermore, the length, shape, etc. of the linear waveguide 18 in FIG. 1 are not limited. Further, the straight waveguide 18 is not necessarily required and may not be provided. At this time, the laser light may be made to directly enter the curved waveguide 20. Furthermore, the semiconductor laser 22, which is a light source, does not need to be directly coupled to the end face of the waveguide, but the laser light emitted from the semiconductor laser may be coupled to the straight waveguide 18 using an optical fiber as shown in FIG. 10(a). Good too. Alternatively, the laser beam emitted from the semiconductor laser 22 may be coupled to the linear waveguide 18 using an objective lens 92 as shown in FIG. 2(b).

Furthermore, the shape of the substrate 12 on which the curved waveguide 20 is formed is not particularly limited. For example, as shown in FIG. 11(a), the end surface 95 of the substrate 12 from which the radiation light is emitted may be processed into a convex shape. Thereby, light can be focused within a plane parallel to the substrate surface. The direction perpendicular to the substrate surface is focused using a cylindrical lens or the like. Also,
If the end surface 95 of the substrate 12 from which the radiation light is emitted is processed to have a convex shape also in the direction perpendicular to the substrate surface, the cylindrical lens becomes unnecessary. In addition, as shown in FIG.
The end surface 95 may be processed into a concave shape. By combining with the convex lens 97, the scanning range can be enlarged.

Furthermore, as shown in FIG. 12(a), a slab waveguide 98 may be formed in a region around the curved waveguide 20 through which the emitted light propagates. As a result, since the emitted light also propagates through the slab waveguide 98, it propagates without spreading in the direction perpendicular to the substrate surface. In addition, as shown in FIG. 6(b), the substrate 60
A slab waveguide 62 is formed on the top, and a SiO2
A similar effect can be obtained even if a dielectric material 99 such as the like is loaded. At this time, the dielectric 99 may be manufactured in the shape of a curved waveguide.

[0024]

[Effect of the invention] As is clear from the detailed description above,
According to the present invention, an optical scanning element is configured by applying an electric field having a distribution that gradually increases or changes in the propagation direction of light to a curved waveguide having an electro-optic effect, and a rotating mechanism etc. This eliminates the need for movable parts, which simplifies the configuration, increases productivity, and allows for downsizing.

[Brief explanation of the drawing]

FIG. 1 is a top view showing the configuration of an optical scanning element according to the present invention.

FIGS. 2(a) to 2(g) are explanatory diagrams showing a method for manufacturing an optical scanning element.

FIG. 3 is a cross-sectional view showing a method of applying an electric field.

FIG. 4(a) is a top view illustrating the operation of the optical scanning element;
(b) is an explanatory diagram showing the waveform of an applied electric field.

FIGS. 5(a) and 5(b) are top views showing the configuration of an optical scanning element.

FIGS. 6(a) to 6(c) are explanatory diagrams showing the shape of a waveguide.

FIG. 7 is a cross-sectional view showing a method of applying an electric field.

FIG. 8 is a cross-sectional view showing a method of applying an electric field.

FIGS. 9(a) to 9(c) are cross-sectional views showing the shape of a diffusion waveguide.

FIGS. 10(a) and 10(b) are explanatory diagrams showing a method of light incidence.

FIGS. 11(a) and 11(b) are explanatory diagrams showing the shape of a substrate of an optical scanning element.

FIGS. 12(a) and 12(b) are cross-sectional views illustrating the shape of a waveguide.

FIG. 13 is an explanatory diagram showing a conventional scanning device.

[Explanation of symbols]

12 Board 14 Diffusion waveguide 16a, 16b electrode 20 Curved waveguide 72a, 72b electrode 95　Board end surface

Claims (3)

[Claims] 1. A substrate, a curved waveguide having an electro-optic effect formed on the substrate or on the surface of the substrate,
an electrode for applying an electric field to the curved waveguide, and wherein the electric field applied to the curved waveguide has a distribution that increases or changes with respect to the propagation direction of light. 2. The optical scanning element according to claim 1, further comprising an electrode for applying an electric field around the curved waveguide. 3. The optical scanning element according to claim 1, wherein a portion of the end face of the substrate from which light is emitted to the outside is non-planar.