JPS61182025A - Polarizer - Google Patents

Abstract

PURPOSE:To form a simple and small-sized device, to improve durability and to control a polarizing angle easily by forming plural electrodes on an optical waveguide, changing voltages impressed between the electrodes with time and changing the inclination of refractive index distribution formed in the optical waveguide in accordance with the voltages impressed upon the electrodes. CONSTITUTION:An optical fiber 14 is coupled with one end part of the optical waveguide 12 and a laser beam incident from the end surface of the optical fiber 14 is converged into parallel light by a light converging part 16, polarized by a polarizing part 18 and compensated at its focus by a light flux compensating part 20. The parts 18, 20 are constituted by arranging many electrodes on the optical waveguide 12 through an interface layer 22. The interface layer 22 is constituted of a transparent substance such as SiO2 having a refractive index smaller than that of the optical waveguide 12 with about several mum thickness. To obtain a sufficient polarizing angle, the polarizing part 18 is constituted of two polarizing parts 24, 26.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an optical deflector, and more particularly to a technique for deflecting light by utilizing an electro-optic effect in an optical waveguide formed using an electro-optic material.

2. Description of the Related Art Devices such as laser beam printers and bar code leagues use optical deflection devices for deflecting light. Polygon mirrors, hologram scanners, etc. are known as such optical deflection devices, but all of them are equipped with mechanically movable parts such as a rotation mechanism and its drive device, making the devices complicated and large. Moreover, sufficient durability was not necessarily obtained.

Means for Solving the Problems The present invention has been made against the background of the above circumstances.
The gist of this method is to provide a plurality of electrodes spaced apart from each other in a direction crossing the direction of light propagation on an optical waveguide that has an electro-optic effect, and to change the voltage applied between the electrodes over time. The light passing through the optical waveguide is deflected by changing the slope of the refractive index distribution formed within the optical waveguide by applying a voltage to the electrode.

Operation and Effects of the Invention With this method, when a voltage is applied between the electrodes on the optical waveguide formed using an electro-optic material, the portion located between them will have an inclination depending on the strength of the electric field. A refractive index distribution is formed, and the light passing through the part where the refractive index distribution is formed is deflected according to the slope of the refractive index distribution between the electrodes, and the temporal change of the voltage applied between the electrodes. At the same time, when the slope of the refractive index distribution is changed, the deflection angle is changed over time.

Therefore, mechanically movable parts such as a rotation mechanism and its drive device are not required, and the device becomes simple and compact, and its durability is improved. Moreover, since a desired deflection angle can be obtained by changing the voltage applied between the electrodes, the deflection angle can be easily controlled.

The refractive index distribution formed between the electrodes is the distribution of the refractive index within the optical waveguide in the direction in which the electrodes are arranged, and its slope refers to the rate of change in the refractive index in the direction in which the electrodes are arranged. say.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIGS. 1 and 2, a substrate 1 of about 0.5 mm made of an electro-optic material, for example, LiNb0:+ crystal is shown.
An optical waveguide 12 is provided on one side of 0. This optical waveguide 12 has a refractive index larger than that of other parts of the substrate 10 and has a property of confining light in the thickness direction, so that light is suitably guided.For example, Ti (titanium) It is formed into a relatively thin layer of about several micrometers by diffusing it. Note that the substrate 10 and the optical waveguide 12 differ only in refractive index, and the refractive index changes continuously, so their boundary is shown by a broken line.

An optical fiber (optical fiber) is provided at one end of the optical waveguide 12.
14 are connected to each other, and in the process of being guided through the optical waveguide 12, the laser beam incident from the end face of the optical fiber 14 is converged into parallel light at the light converging section 16 and deflected at the light deflecting section 18. , the focus is corrected in the luminous flux correction section 20.

That is, in the light converging section 16, a diffusing material such as Tf is diffused in such a manner that the diffusion concentration increases as it approaches the optical axis L0 in the plane direction of the substrate 10 and in a direction perpendicular to the optical axis L0 of the laser beam. As a result, the closer the optical waveguide 12 is to the optical axis L0, the higher the refractive index becomes, providing a convex lens function. The group of straight lines shown in the light converging section 16 in FIG. 1 is for expressing the refractive index distribution, and the linear density thereof indicates the height of the refractive index. Note that the light converging section 16 may be configured with a geodesic lens or the like having a concave portion provided on the surface of the optical waveguide 12.

The optical deflection section 18 and the luminous flux correction section 20 are each constructed by disposing a large number of electrodes on the optical waveguide 12 with a buffer layer 22 interposed therebetween. The buffer layer 22 is
A transparent material having a lower refractive index than the optical waveguide 12, for example 5
It is made of iOz and has a thickness of about several μm,
Although this is for preventing absorption of light by the electrode, it does not necessarily have to be provided.

Since the optical deflector 18 is composed of two optical deflectors 24 and 26 that are configured similarly to each other in order to obtain a sufficient deflection angle, the optical deflector 24 will be explained below.

As shown in FIG. 3, the optical deflector 24 has a pair of electrodes 24a and 24b that are close to each other at a predetermined distance D in the plane direction of the substrate 10 and in the direction perpendicular to the optical axis L0 of the laser beam 30.
It is constructed by arranging a large number of pairs at 1. The electrodes 242 and the electrodes 24b are connected to each other by wiring (not shown), and the deflection control device 2 of FIG.
8, voltages of the same potential are applied to each of them. Therefore, in the optical deflector 24, as shown in FIG. 4, the distribution of the electric field E in the direction perpendicular to the optical axis L0 is formed in a sawtooth shape corresponding to the positions of the many electrodes 24a and 24b. Generally, electro-optic materials have the property of changing their refractive index depending on the strength of an electric field (electro-optic effect). For example, when the substrate 10 is L i N b Ox, there are many electrodes 24a.

The change Δn in the refractive index of the portion located between 24b and 24b is calculated by the following formula (1
), the distribution of the refractive index in the direction perpendicular to the optical axis L0, that is, the refraction severity Δn = (1/2
)n, 3r, -E H+ H- (1) where n is the refractive index of the substrate 10 for extraordinary light, and r33 is the electro-optic constant in the thickness direction of the substrate 10.

The distribution of Δn is also formed in a sawtooth shape inclined in one direction, corresponding to the distribution of the electric field E.

Therefore, when the voltage applied between each electrode 24a and each electrode 24b from the deflection control device 28 is changed over time, for example, as shown in the upper part of FIG. 5, the deflection angle of the laser beam 30 is synchronously changed. θ is changed as shown in the lower part of FIG. For example, the distributions of the changes in refractive index Δn corresponding to the applied voltages shown at points a, b, C, and d in FIG. 5 are also shown in FIGS. 6, 7, 8, and 9, respectively. The laser beam 30 passing through the optical deflector 24 has deflection angles θa, θb,
It is deflected at θC1θd.

Note that since the same voltage as above is applied from the deflection control device 28 to each electrode constituting the optical deflector 26, the laser beam 30 that has passed through the optical deflectors 24 and 26 is directed to one optical deflector 24. is deflected at a deflection angle that is approximately twice the deflection angle θ.

Here, FIG. 10 schematically shows the operation of the optical deflector 24 using a Fresnel lens 32. When the applied voltage is large, for example at point a in FIG. 5, the laser beam 30a is As shown, this is equivalent to the case where the light is incident at a position away from the center of the Fresnel lens 32, and the deflection angle at this time is θa. When the applied voltage is small, for example at point b in FIG. 5, a laser beam 30b appears, or when the polarity of the applied voltage is reversed, for example at point C in FIG. 32, and the deflection angle becomes θb or θC (negative), respectively.

Next, the beam correction section 20 is for converging the laser beam 30 deflected by passing through the optical deflection section 18 to one point, and as shown in FIG. It is composed of a plurality of correction electrode groups 34 arranged in a direction perpendicular to the optical axis L0 via the layer 22. In the correction electrode group 34, like the electrodes of the optical deflector 24, a pair of electrodes 34a and 34b are arranged at a predetermined interval D2.
Although many pairs are arranged with a distance of
For example, the pair of electrodes 34a and 34b has an optical axis L
A voltage is applied which has opposite polarity with respect to 0 and becomes larger as the distance from the optical axis L0 increases. For this reason, the 12th
As shown in the figure, the distribution of the magnitude of the refractive index formed between the correction electrode group 34, that is, the distribution of the refractive index change Δn, tilts in opposite directions with respect to the position corresponding to the optical axis L0. It forms a sawtooth shape, and its inclination is toward the optical axis L0.
The further away you are from it, the larger it becomes. Such a distribution corresponds to a Fresnel lens with a convex lens function.

The focal length of the luminous flux correction unit 20 is changed according to the voltage applied from the deflection control device 28,
It is adjusted according to the deflection angle in the light deflection section 18. Since the spread of the laser beam 30 that has passed through the optical deflection section 1B depends on the deflection angle θ, the focal length becomes shorter as the deflection angle θ becomes larger. Here, the polarity inversion position of the voltage applied to the electrodes 34a and 34b does not need to be the optical axis L0, and may be changed depending on the deflection angle of the light. Note that the distance D2 between each pair of electrodes 34a and 34b may be made smaller as the distance from the optical axis L0 increases, so that the distribution of the refractive index change Δn is as shown in FIG. 13. This has the advantage that even if the applied voltage is constant, the focal length is shortened when the beam is incident on a position distant from the optical axis.

Therefore, in the device configured as above,
The laser beam 30 entered into the optical waveguide 12 from the optical fiber 14 is made into parallel light by the light converging section 16, and then deflected at a desired angle by the light deflecting section 18. The deflection in the optical deflection section 18 utilizes the electro-optic effect of the electro-optic material that constitutes the optical waveguide 12,
This is done by temporally changing the voltage applied to the optical deflector 24 or 26 to temporally change the slope of the refractive index distribution within the optical deflector 24 or 26.

The laser beam 30 deflected in this manner is converged by the beam correction unit 20 onto a point on an object (not shown) regardless of the deflection angle, and the laser beam spot is scanned at a desired deflection angle on the object. They are made to do so.

As described above, according to this embodiment, there is no need for mechanically movable parts such as a rotation mechanism for deflecting light and a driving device for the rotation mechanism for deflecting light, which are provided in conventional devices, making the device simple and compact, and also durable. This will improve your sexual performance. Moreover, by changing the voltage applied to the optical deflector 24 or 26 constituting the optical deflection section 18, a desired deflection angle can be obtained, and there is an advantage that the scanning position of the laser beam spot can be easily controlled.

Next, another embodiment of the present invention will be described. In the following description, parts common to those in the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

The light deflection unit 18 arranges a large number of electrodes 40 at regular intervals and sequentially applies different voltages to individual electrodes constituting a group among the large number of electrodes 40, thereby adjusting the distribution of refractive index change. It may be configured to have a sawtooth shape inclined in one direction. The lower part of FIG. 14 shows a large number of electrodes 40 configured in this way, and the upper part of FIG. 14 shows those electrodes 40.
The distribution of the refractive index change Δn formed corresponding to the applied voltage and the position of the electrode 40 is shown.

In addition, when applying different voltages sequentially to the individual electrodes constituting one group among the large number of electrodes 40 as described above, the first
As shown in FIGS. 5 and 16, a resistor 42 may be provided to connect one group of the many electrodes 40, and a voltage may be applied to electrodes located at both ends of the resistor 42. This has the advantage of simplifying the wiring on the substrate 10.

Although one embodiment of the present invention has been described above, the present invention is also applicable to other aspects.

For example, as shown in the upper part of FIG. 5, the applied voltage supplied to the optical deflection unit 18 described above was an alternating current whose polarity was reversed, but it was a direct current voltage that pulsated within a range where the polarity did not change. Good too. Furthermore, the arrangement and configuration of the electrodes constituting the light deflection section 18 and the voltage application method may be changed in various ways as long as the refractive index distribution is formed with an inclination in one direction and the inclination can be changed. .

Furthermore, in the optical deflection section 18, two optical deflectors 2 are provided.
4 and 26, the number of such optical deflectors may be one or three or more.

Moreover, the electrodes 24a and 24 of the optical deflection section 18 in the above-mentioned embodiment
b are arranged in a direction perpendicular to the optical axis L0,
It does not necessarily have to be a right angle. In short, if they are arranged in a direction intersecting the optical axis L0, a certain effect can be obtained.

Furthermore, although the optical waveguide 12 of the above-mentioned embodiment is formed by diffusing Ti onto one surface of the substrate 10 made of LiNbO3 crystal, it is possible to form the optical waveguide 12 by diffusing Ti onto one surface of the substrate 10 made of LiNbO3 crystal. SiO, which has no electro-optic effect, is deposited on a substrate with a
A thin film made of an electro-optical material such as V (vanadium), Nb (obium), etc. may be formed, and the metal material to be diffused may be
It may also be Cu (copper) or the like.

Further, although the optical fiber 14 is attached to the substrate 10 in the above embodiment, a semiconductor laser chip may be attached instead.

Note that the above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

1 and 2 are a plan view and a side view of an optical deflection device including an embodiment of the present invention. FIG. 3 is a diagram showing the main parts of FIGS. 1 and 2, and is a diagram illustrating the configuration of an optical deflector according to an embodiment of the present invention. FIG. 4 is a diagram showing an example of electric field distribution in the optical deflector of FIG. 3. FIG. 5 is a time chart showing changes in the applied voltage and changes in the deflection angle at the same time to explain the operation of the optical deflector shown in FIG. 6, 7, 8, and 9 are diagrams showing the distribution of refractive index changes in the optical deflector of FIG. 3 when the applied voltages are a to d in FIG. 5, respectively. . FIG. 10 is a diagram for explaining the operation of the optical deflector shown in FIG. 3. FIG. 11 is a diagram showing the configuration of the luminous flux correction section shown in FIGS. 1' and 2. FIG. 12 is a diagram showing an example of the distribution of refractive index changes in the luminous flux correction section of FIG. 11. FIG. 13 is a diagram corresponding to FIG. 12 in another example of the luminous flux correction section. FIG. 14 is a diagram showing another example of the optical deflector along with the applied voltage and the distribution of refractive index change. FIGS. 15 and 16 are a cross-sectional view and a perspective view of essential parts showing other examples of the deflector. 24.26: Optical deflector 24a, 24b, 40: Electrode Applicant: Brother Industries, Ltd. Figure 1 Figure 2 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 12
Figure 13 Figure 15 Procedural master's official document 1) Showa June - June 27 1, Indication of the case 1985 Patent application No. 022468 2, Name of the invention Light deflector 3, Person making the amendment Case and Relationship Patent Applicant Name (526) Brother Industries, Ltd. 6 Contents of Amendment (1) The following sentence is inserted on a new line between page 12, line 14 and line 15 of the specification. "Also, in order to control the deflection angle of the laser beam,
Instead of the light deflection section 18, a light deflection section 58 shown in the light deflection element 48 in FIGS. 17 and 18 may be used. The substrate of the optical deflection element 48 consists of a chip made of an electro-optic material, for example, LiNbOz crystal, and has a thickness of about 0.5 U, and an optical waveguide 52 is provided on its negative surface. This optical waveguide 52 has a larger refractive index than other parts of the substrate so that light is confined in a plane, so that it can be guided in a suitable manner.For example, Ti (titanium) It is formed into a relatively thin layer of about several micrometers by diffusing it. Note that the substrate and the optical waveguide 52 differ only in their refractive indexes, and the refractive indexes change continuously, so their boundaries are shown by broken lines.゛The semiconductor laser element 5 is in contact with one end of the optical waveguide 52.
The laser beam emitted from the end face of the semiconductor laser element 50 is converged into parallel light at the light converging section 56 and deflected at the light deflecting section 58 while being guided through the optical waveguide 52. At the same time, the focus is corrected in the luminous flux correcting section 60. That is, the light converging section 56 has its optical axis L0 in the plane direction of the substrate and in a direction perpendicular to the optical axis L0 of the laser beam.
By diffusing the light as it approaches the optical axis L0, the refractive index of the optical waveguide 52 increases as it approaches the optical axis L0, providing a convex lens function. The group of straight lines shown in the light collecting part 56 is for expressing the refractive index distribution, and the density of the straight lines indicates the height of the refractive index. Note that this light converging section 56
The optical waveguide may be constructed of a geodesic lens or the like having a concave portion provided on the surface of the optical waveguide. The optical deflection section 58 and the luminous flux correction section 60 are each constructed by disposing a large number of electrodes on the optical waveguide via a buffer layer 62. The buffer layer 62 is made of a transparent material having a refractive index lower than that of the optical waveguide 52, such as Sin, and has a thickness of approximately several μm, and is intended to prevent absorption of light by the electrodes described later. , does not necessarily have to be provided. The optical deflection unit 58 corresponds to an optical deflector that deflects a laser beam, and has a pair of electrodes 64.66 located on both sides of the optical axis L0, and a pair of electrodes 64.66 located obliquely to the optical axis L0 between the electrodes 64.66. It is composed of an electrode 68. By utilizing the electro-optic effect of the electro-optic material described above, for example, if the substrate is LiNbO5 (Y-cut crystal), the refractive index change Δ of the portion located between the electrodes 64 and 66
Since n is as shown in the above equation (11), the distribution of the magnitude of the refractive index in the direction perpendicular to the optical axis L0, that is, the distribution of the refractive index change Δn, also changes corresponding to the distribution of the electric field E, for example, , when a positive voltage is applied to the electrode 68 and a ground voltage is applied to the electrodes 64 and 66, the A-A and B-BSC of the optical deflection section 58 are applied.
The distributions of the electric field E and the refractive index change Δn on the -C line are as shown in FIGS. 19, 20, and 21, respectively. Therefore, the laser beam traveling parallel to the optical axis L0 experiences different refractive indexes at different parts of the light beam, and is bent toward the side with a higher refractive index. Therefore, when the voltages applied from the optical deflection element 48 between the electrode 68 and the electrodes 64 and 66 are changed over time in a sinusoidal manner, the deflection angle θ of the laser beam becomes sinusoidal in synchronization with the voltage. Can be changed synchronously. The electric field E in FIGS. 19 to 21 is shown with the downward direction in FIG. 17 being positive, and the electrode 64 is viewed from the right hand and the electrode 66 is viewed from the left hand. Next, the light flux correction section 60 includes a large number of three-dimensional optical waveguides 7.
2 radially, and a series of correction electrodes 74. Although seven three-dimensional optical waveguides 72 are shown in the figure for ease of understanding, in reality, a very large number of three-dimensional optical waveguides 72 are provided. The optical waveguide 72 is configured such that the refractive index becomes higher toward the center due to the diffusion of Ti, etc., and the laser beam 70 propagating through the optical waveguide 72 is periodically converged as shown in FIG. 22. The correction electrode 74 is disposed on the optical waveguide 72 as shown in FIG. 23, and is connected to the correction electrode 74a on the optical waveguides 72a and 72c adjacent to the optical waveguide 72b through which the laser beam 70 propagates. By applying a correction voltage between 74C, the electrode 7 of the optical waveguide 74b
The refractive index of the portion located between 4a and 74c is changed. For this reason, focus correction is performed by changing the state shown in FIG. 24(a) to the state shown in FIG. 24(b), for example. A signal for such focus correction is supplied in relation to the deflection angle from a light flux correction control circuit (not shown). Note that, as shown in FIG. 25, the optical deflection element 48
A toroidal lens 76 is provided as necessary to correct the vertical focus of the laser beam 70 output from the laser beam 70 . As described above, in the optical deflection element 48 shown in FIG. 17, the deflection action in the optical deflection section 58 utilizes the electro-optic effect of the electro-optic material constituting the optical waveguide 52, and the optical deflection element 48 of FIG. This is done by temporally changing the voltage applied between the electrodes 64 and 66 and 68 to temporally change the refractive index distribution of the optical waveguide 52 between the electrodes 64 and 66. Therefore, there is no need for mechanically movable parts such as a rotating mechanism for deflecting light and its drive device, which are provided in conventional devices, which eliminates device noise and improves reliability and durability. It is. ” (2) “Also...” on page 14, lines 3 to 5.
・It's good. ” to be deleted. (3) "This is a perspective view of the main parts" on page 15, line 9.
Insert the following text after. 17 and 18 are a front view and a side view of an optical deflection element including an optical deflector according to another embodiment of the present invention. 19, FIG. 20, and FIG. 21 are diagrams showing the electric field distribution and the distribution of the refractive index change amount on the AA line, the BB line, and the CC line of FIG. 17, respectively. Figure 22 is the first
FIG. 8 is a diagram showing a laser beam propagation state of the luminous flux correction section in FIG. 7; FIG. 23 is a diagram illustrating an electrode selection method during luminous flux correction. FIG. 24 is a diagram illustrating the correction action of the luminous flux correction section, in which (a) shows a state in which no voltage is applied;
弽) indicates the voltage application state. FIG. 25 is a diagram showing an example of a correction lens provided on the output side of the optical deflection element shown in FIG. 17. (4) r24a, 24b, 40 on page 15, line 11:
Electrode" r24a, 24b, 40, 64.66.68:
Corrected to "electrode". (5) Figures 17, 18, 19, and 2 of the attached sheet
Add Figure 0, Figure 21, Figure 22, Figure 23, Figure 24, and Figure 25. Above Figure 17 Figure 18

Claims (1)

[Claims] A plurality of electrodes are provided on an optical waveguide having an electro-optic effect, spaced apart from each other in a direction intersecting the direction of propagation of light,
By temporally changing the voltage applied between the electrodes and changing the slope of the refractive index distribution formed within the optical waveguide by the voltage applied to the electrodes, light passing through the optical waveguide can be controlled. An optical deflector characterized in that it deflects.