JP6491615B2 - Optical deflector - Google Patents

Description

  The present invention relates to an optical deflector that bends a light beam by an electric signal.

  As devices that change the traveling direction of a light beam such as laser light at high speed, so-called optical deflectors, devices that rotate a mirror by electromagnetic induction, such as galvanometer mirrors and polygon mirrors, have been often used. However, since these optical deflectors move a mirror with a finite mass, the operation speed is limited by inertia. Compared to this, an optical deflector (EO optical deflector) using the electro-optic effect (EO effect) has no movable part, and thus can be remarkably increased in speed.

  The EO effect is a phenomenon in which the refractive index of a substance changes when an electric field is applied to the substance, and this substance is sometimes called an electro-optic material. The EO optical deflector is often limited by the speed of the drive power supply for applying the electric field, but in principle, a response of several hundred MHz or more can be expected.

Conventionally, an EO optical deflector in which an electro-optic material is molded on a prism is known. When an electric field is applied to this prism, the refractive index changes as a whole, so that the angle of refraction of incident light changes, and incident light can be deflected. However, the refractive index change due to the EO effect is as small as about 10 ⁻³ and the deflection angle is also difficult.

  In recent years, a space charge type EO optical deflector that injects electrons into an electrooptic material and uses the space charge formed in the electrooptic material has been developed (see, for example, Patent Document 1). According to Gauss's law, since the gradient of the electric field distribution is proportional to the charge density, it can be seen that the distribution of the electric field occurs when space charge exists. For this reason, a refractive index distribution is generated by the EO effect, and the direction of the light beam can be changed by the refractive index distribution. In the space charge type EO optical deflector, by increasing the optical path length in the electro-optic material, the deflection angle can be increased and the entire width can be deflected by 10 degrees or more.

Japanese Patent No. 4751389

  In the EO optical deflector described above, by increasing the length of the electro-optic material, the effect of refractive index modulation is accumulated, and the deflection angle can be increased. However, when the length of the electro-optic material is increased, the deflection angle increases, but the deflected light cannot be contained in the end face emitted from the electro-optic material, hits a different surface from the end face, and is not emitted to the outside. was there. That is, the deflection angle is limited by the thickness of the electro-optic material in the light deflection direction.

  An object of the present invention is to provide an optical deflector that can increase the deflection angle without increasing the length and thickness of the electro-optic material.

In order to achieve the above object, according to one embodiment of the present invention, an embodiment includes an electro-optic material made of a single crystal having inversion symmetry, and a first surface formed on a first surface of the electro-optic material. A first electrode pair formed of an anode and a first cathode formed on a second surface opposite to the first surface and facing the first anode; and A second cathode formed on a surface and spaced from the first anode; and formed on the second surface and at a position facing the second cathode; And a second electrode pair formed with a second anode spaced apart from the first cathode, and when light is incident from a third surface orthogonal to the first surface, Transmitting between the first electrode pair and then passing through the second electrode pair toward the fourth surface facing the third surface Axis is set by said first electrode pair and the second electrode pair, by injecting carriers to form a space charge inside the electrooptic material, the electro-optical material by said first electrode pair The deflection origin of the light passing through is moved in a direction perpendicular to the optical axis, and the deflection angle of the transmitted light is changed based on the moved deflection origin by the second electrode pair .

  As described above, according to the present invention, the deflection angle of the deflection region sandwiched between the second electrode pairs is reversed with respect to the deflection angle of the deflection region sandwiched between the first electrode pairs. The deflection angle can be increased.

It is a figure which shows the structure of a space charge type EO optical deflector. It is a figure which shows the mode of the deflection | deviation in a space charge type EO optical deflector. It is a figure which shows the structure of the space charge type EO optical deflector concerning one Embodiment of this invention. It is a figure which shows the modification of the space charge type EO optical deflector concerning one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Operation principle of space charge type EO optical deflector)
FIG. 1 shows a configuration of a space charge type EO optical deflector. The EO optical deflector includes basic unit elements in which electrodes 102 and 103 are formed on the upper and lower surfaces of the electro-optic material substrate 101 in accordance with the outer shape of the substrate. A driving power source is connected to the electrodes 102 and 103, and an electric field is applied in the vertical direction of the electro-optic material substrate 101, that is, perpendicular to the optical axis of the incident light beam 104. When the EO effect is first order, that is, when it is a Pockels effect, the refractive index change Δn is expressed as follows: the original refractive index is n ₀ , the primary electro-optic coefficient is r, and the electric field is E.

It is. The optical path length S when the incident light beam 104 passes through the basic unit element is S ₀ as the original optical path length and L as the length of the electro-optic material substrate 101 in the light traveling direction.

It becomes. The light beam is deflected because the optical path length S depends on the position coordinate x. The deflection angle θ is

It becomes. In order to cause the deflection in the configuration of FIG. 1, carriers (electrons or holes) are injected into the electro-optic material by applying a voltage to the EO optical deflector. For simplicity, the charge due to the injected carriers is uniformly distributed, so that the charge density ρ is constant. If the charge density is ρ and the dielectric constant is ε, Gauss's law

Therefore, after all, the deflection angle θ is

It becomes. From this, it can be seen that the deflection angle is proportional to the length L, and therefore a large deflection angle can be obtained by using a long substrate.

  Of course, the larger the EO effect, the larger the deflection angle. As a material having a large EO effect, potassium tantalate niobate (KTN) described later can be suitably used. In the case of KTN, since the EO effect is not the first order but the second order Kerr effect, the refractive index change Δn is expressed by taking the second order electro-optic coefficient as s.

It becomes. In this case, if the charge density ρ is constant as in the above example,

And the deflection angle depends on the position. Here, d is the thickness of the electro-optic material substrate 101, which corresponds to the distance between the electrodes, and V is the applied voltage. Taking the position at the midpoint d / 2 between the electrodes, the deflection angle θ is

A simple shape can be obtained.

  When the EO effect is first order, the deflection angle is proportional to the charge density ρ according to the equation (1). Therefore, the deflection angle is controlled by changing the charge density according to the voltage. Since the charge density is changed, the moving speed of electrons becomes a factor that limits the control speed of the deflection angle. On the other hand, in the case of KTN in which the EO effect is second order, the deflection angle is proportional to the voltage V from the equation (2). In this case, even if the charge density does not change, that is, the electrons do not move in response to the voltage, the deflection angle can be directly controlled by the voltage. Therefore, it is possible to realize a high-speed optical deflector that responds in a time of 1 μs or less (frequency is 500 kHz or more) even if the estimation is delayed from the voltage application. For this reason, an electro-optic material having a secondary EO effect is suitable as a material constituting the optical deflector of the present embodiment. An electro-optic material having a second-order EO effect can be rephrased as an electro-optic material having inversion symmetry. The materials having inversion symmetry will be described later together.

(Limit of deflection angle due to longer substrate)
FIG. 2 shows a state of deflection in the space charge type EO optical deflector. A state in which a light beam passing through the inside of the space charge type EO optical deflector of FIG. 1 is observed from the side surface of the electro-optic material substrate 101 is shown. In the electro-optic material substrate 101, the light beam 106 is gradually deflected as shown in the figure by the refractive index distribution. Finally, when the light is emitted from the electro-optic material substrate 101 to the outside, the light beam is refracted at the light emission end surface according to Snell's law, and becomes a light beam 105 as shown in the figure. At this time, if the tangent of the light beam just before going outside is extrapolated, it intersects with the extrapolated straight line of the incident light beam 104 at the center of the electro-optic material substrate 101 as shown by the broken line in the figure. In other words, although the light beam 106 actually draws a curve as shown in the figure, for convenience, it may be considered that the light beam 106 goes straight inside the substrate 101, bends at the center, and goes straight again. Here, the point where the light beam is virtually bent is referred to as a deflection origin 107.

  The light beam 106 shown in FIG. 2 is emitted without hitting the substrate. However, when the deflection angle becomes large, the light beam 106 does not hit the upper surface of the electro-optic material substrate 101 before reaching the emission end face. When the length of the electro-optic material substrate 101 in the optical axis direction is L, the thickness is d, and the deflection angle inside the substrate 101, that is, the internal deflection angle 108 at the deflection origin 107 is θ, the deflection origin 107 is Because it is in the center,

Gives the limit of deflection angle. In other words, it seems that the deflection angle becomes larger as L becomes larger according to the equation (2), but actually, if L is too large, the limit of the deflection angle is suppressed according to the equation (3). Naturally, when L is small, a sufficiently large deflection angle cannot be obtained by the equation (2).

  In order to raise the limit by the equation (3), there is a method of increasing the thickness d in addition to the adjustment of L. However, when d is increased, the deflection angle decreases unless the applied voltage is increased according to the equation (2). Further, when d is increased, unless the voltage is increased, the charge density ρ is also reduced, and the deflection angle is reduced by a synergistic effect.

  As another countermeasure, there is a method of changing the incident position of the incident light beam 104 on the incident end face. In FIG. 2, the incident light beam 104 is incident on an intermediate point in the vertical direction of the incident end face. This incident position is shifted to the vicinity of the surface of the electrode 103 under the electro-optic material substrate 101. As a result, the same state as when d is nearly doubled is realized, so the limit of the deflection angle approaches twice that of the expression (3).

  On the other hand, in the configuration of FIG. 2 that is incident on an intermediate point between the upper and lower substrate surfaces, deflection in the direction opposite to that in FIG. 2 is possible by reversing the polarity of the voltage. If a power supply capable of bipolar output is used as the drive power supply, the full width of the deflection angle is twice that of the expression (3). On the other hand, if the incident position is shifted near the lower electrode surface, the upward polarization angle in the figure is almost doubled, but even if the voltage is reversed, the downward deflection in the figure becomes almost impossible. . For this reason, simply shifting the incident position does not increase the deflection angle, and is not a fundamental solution.

(Increase in deflection angle by using two electrode pairs)
FIG. 3 shows a configuration of a space charge type EO optical deflector according to an embodiment of the present invention. Therefore, in the present embodiment, the above-described problems are solved by forming two electrode pairs. The EO optical deflector includes a basic unit element in which two electrode pairs, that is, electrodes 202 and 203 and electrodes 212 and 213 are formed on the upper and lower surfaces of the electro-optic material substrate 201. The first anode 202 formed on the first surface closer to the light incident side and the second surface facing the first surface are formed at a position facing the first anode. The first cathode 203 is used as a first electrode pair. A second cathode 212 formed on the first surface closer to the light emission side and spaced from the first anode; and a second cathode 212 formed on the second surface. A second anode 213 formed at a position facing each other and spaced from the first cathode is used as a second electrode pair. The first electrode pair and the second electrode pair are characterized in that the electric field application direction is opposite and the deflection direction is opposite. Hereinafter, the operation principle will be described.

  When light is incident from a third surface orthogonal to the first surface, the light passes through the first electrode pair and then passes through the second electrode pair so as to face the third surface. The optical axis is set so that light is emitted from the fourth surface. In FIG. 3, an incident light beam 204 incident from the third surface on the left side of the electro-optic material substrate 201 is deflected upward by the first electrode pair. In this state, when the light beam goes straight through the electro-optic material substrate 201, it reaches the position of the upper surface of the electro-optic material substrate 201. However, when the incident light beam passes between the first electrode pair, it enters between the second electrode pair. In contrast to the first electrode pair, the second electrode pair is deflected downward. The light beam transmitted through the electro-optic material substrate 201 has a gradually reduced polarization angle that has been directed to the upper right direction. Further, the deflection is advanced by the second electrode pair, and the deflection is directed downward to the right. After the deflection angle is sufficiently increased, the light beam 205 is emitted from the fourth surface on the right side of the electro-optic material substrate 201.

  In the present embodiment, the second electrode pair is responsible for the main part of deflection, and the first electrode pair is positioned to assist the second electrode pair. In the configuration of FIG. 3, the deflection origin moves above the electro-optic material substrate 201 even though the incident position of the incident light beam 204 on the incident end face is an intermediate point. Accordingly, in the equation (3) indicating the limitation on the deflection angle, an effect equivalent to increasing d to nearly twice can be obtained, so that the internal deflection angle is also improved to nearly twice.

  The method of shifting the incident position on the incident end face of the incident light described above does not increase the total deflection angle because the angle of deflection in the opposite direction due to the voltage of the opposite polarity is reduced on the one hand while increasing the polarization angle in one direction. In this embodiment, if attention is paid only to the second electrode pair, this is equivalent to shifting the incident position. By using the first electrode pair, the direction of shifting the incident position can be dynamically controlled. Can also be considered. For this reason, not only the polarization angle on one side but also the deflection angles in both the upper and lower directions can be increased simultaneously.

  The feature of this embodiment is that the deflection direction is reversed by the first electrode pair and the second electrode pair, and there are several methods for realizing it. First, the polarity of the voltage applied by the first and second electrode pairs is reversed. Second, when there are both positive and negative carriers that form space charges in the electro-optic material substrate 201, for example, when both electrons and holes can be carriers, space charges are generated by electrons between the first electrode pair. And a space charge may be formed by holes between the second electrode pair. Even if the voltages applied by the first and second electrode pairs are in the same direction, the deflection direction can be reversed. In order to change the carrier, there is a method of changing the electrode material, and selection of the electrode material will be described later. In addition, when it is difficult to cause electrons and holes to coexist on one substrate, the substrate material may be changed between the first electrode pair region and the second electrode pair region.

  A deflection region sandwiched between the first electrode pairs is referred to as a first deflector, and a deflection region sandwiched between the second electrode pairs is referred to as a second deflector. The deflection angle of the second deflector is set to a value exceeding twice the deflection angle of the first deflector. In the second deflector, the first deflection angle generated by the first deflector is canceled out, and a second deflection angle equal to or larger than the first deflection angle is given in the opposite direction, whereby the above-described conventional deflector is provided. A deflection angle exceeding the deflection angle of the EO optical deflector can be obtained.

  In order to make the second deflection angle more than twice the first deflection angle, as shown in the equation (2), the voltage V is made more than twice, the charge density ρ is made more than twice, the electrode It is conceivable that the length L is more than doubled. Regarding the dielectric constant ε, in the electro-optic material having inversion symmetry, since the second-order electro-optic coefficient s has a property proportional to the square of the dielectric constant ε, the deflection angle is proportional to ε. Therefore, in order to make the deflection function more than twice, the dielectric constant should be made more than twice. The dielectric constant ε of the electro-optic material having inversion symmetry can be largely changed by changing the temperature. However, it is somewhat difficult to create a temperature difference that doubles the dielectric constant in the same substrate. Also, the control of the charge density ρ has the same difficulty. In order to apply different voltages, it is inconvenient to prepare two systems of driving power supplies. From the above, it is considered that the easiest means is to make the electrode length L, that is, the length along the optical axis, more than twice the second electrode pair with respect to the first electrode pair.

  FIG. 4 shows a modification of the space charge type EO optical deflector according to the embodiment of the present invention. In order to obtain a sufficient deflection angle, it is necessary to increase the electrode length to a certain value or more, and accordingly, it is necessary to increase the length of the electro-optic material substrate to a certain value or more. At this time, as shown in FIG. 3, in addition to increasing the length of the electro-optic material substrate itself, a high-reflectance mirror is installed on the surface of the electro-optic material substrate and internally reflected to increase the optical path length. There is a way to do it.

  FIG. 4 shows this state, and is a view of the deflector of FIG. 3 observed from above. A state in which a light beam passing through the space charge type EO optical deflector is observed from the upper surface of the electro-optic material substrate 201 is shown. In FIG. 4, an incident light beam 204 is incident on the electro-optic material substrate 201 obliquely from the upper left. The incident light is refracted on the surface and travels inside the electro-optic material substrate 201. When the incident light reaches the surface opposite to the incident surface, it is reflected by the high reflection film 221 formed on the surface, and again the electro-optic material. It proceeds inside the substrate 201. When the reflected light reaches the light incident surface again, it is reflected again by the high reflection film 222 also formed here. In FIG. 4, the highly reflective films 221 and 222 allow the light to pass through the electro-optic material substrate 201 five times. As a result, the optical path length is about five times that of the EO optical deflector shown in FIG. The light beam is emitted to the outside as an outgoing light beam 205 from a gap where the highly reflective film 221 is not formed.

  The present embodiment can be applied even to an EO optical deflector having such a structure. In FIG. 4, the electrode 202 is formed in a parallelogram shape closer to the light incident side. Similarly, the electrode 212 is formed in a parallelogram shape closer to the light emission side. Note that the electrodes 203 and 213 are not shown because they appear to overlap the electrodes 202 and 212. Even in such a configuration, the effect of increasing the deflection angle of the present embodiment can be obtained by making the width of the electrode 212 more than twice the width of the electrode 202.

(Electro-optic material)
Many electro-optic materials do not have inversion symmetry and develop a Pockels effect. On the other hand, some electro-optic materials have inversion symmetry, do not exhibit the Pockels effect, and the Kerr effect is dominant. Therefore, it is important to use a material having inversion symmetry as the electro-optic material constituting the electro-optic material substrate 201 of the present embodiment.

  In general, when an electric field is applied from the outside to a dielectric, polarization proportional to the electric field is generated, but when the electric field is removed, the polarization returns to zero. However, there are substances that retain finite polarization even when the electric field is removed. Polarization that exists even without an external electric field is called spontaneous polarization. There exists a substance capable of reversing the direction of this spontaneous polarization by an external electric field, which is called a ferroelectric.

  A single crystal having inversion symmetry refers to a crystal that has the same arrangement as the original arrangement of atoms when the arrangement of atoms is inverted in the x, y, z coordinate system around a certain origin. When a crystal having spontaneous polarization is inverted on the coordinate axis, the direction of spontaneous polarization is inverted, so that such a crystal cannot be said to have inversion symmetry. Therefore, since the ferroelectric has spontaneous polarization, it does not have inversion symmetry.

  On the other hand, there are substances that have spontaneous polarization but cannot be inverted by an external electric field. Such a material does not have inversion symmetry, but is not a ferroelectric material. Therefore, not all materials that do not have inversion symmetry are ferroelectric materials. Further, it cannot be a ferroelectric and has inversion symmetry.

As an electro-optic material having inversion symmetry, there is a single crystal material having a perovskite crystal structure. The perovskite single crystal material becomes a cubic phase having inversion symmetry in the use state if the use temperature is appropriately selected. In the cubic phase, the Pockels effect is not expressed and the Kerr effect is dominant. For example, even the most well-known barium titanate (BaTiO ₃ , hereinafter referred to as BT) has a cubic temperature as long as it exceeds the phase transition temperature around 120 ° C. It becomes a crystal phase and exhibits the Kerr effect.

In addition, a single crystal material mainly composed of potassium tantalate niobate (KTa _1-x Nb _x O ₃ , 0 <x <1, hereinafter referred to as KTN) has more preferable characteristics. BT has a predetermined phase transition temperature, whereas KTN can select a phase transition temperature depending on the composition ratio of tantalum and niobium. Thereby, the phase transition temperature can be set near room temperature. KTN has a cubic phase at a temperature higher than the phase transition temperature, has inversion symmetry, and has a large Kerr effect. Even in the same cubic phase, the Kerr effect becomes overwhelmingly closer to the phase transition temperature. For this reason, setting the phase transition temperature around room temperature is very important for easily realizing a large Kerr effect.

Further, as a single crystal material related to KTN, the main component of the crystal is composed of periodic group Ia group and Va group, group Ia is potassium, and group Va includes at least one of niobium and tantalum. Materials can be used. Moreover, 1 or multiple types of periodic table group Ia except potassium as an additional impurity, for example, lithium, or IIa group can also be included. For example, a cubic phase KLTN (K _1-y Li _y Ta _1-x Nb _x O ₃ , 0 <x <1, 0 <y <1) crystal may be used.

In addition, PbTi _1-x Zr _x O ₃ (PZT) and PLZT to which La is added are also perovskite crystals, and can have inversion symmetry by selecting the composition and use temperature. These can be used not only as a single crystal but also as a polycrystalline sintered body.

(Electrode material)
When a high voltage is applied to the electro-optic material, charges are injected from the electrodes, and space charges can be generated in the crystal. As described above, since the space charge causes an inclination of the electric field in the voltage application direction, the refractive index is also inclined. Therefore, in order to make the electro-optic material function as the space charge type EO optical deflector of the present embodiment, in order to obtain a desired refractive index distribution, when a voltage is applied to the electro-optic material substrate 201, the electro-optic material substrate It is preferable that a high-density space charge is formed inside the 201.

  The amount of space charge depends on the carrier injection efficiency. When the carriers contributing to electrical conduction in the electro-optic crystal are electrons, as the work function of the electrode material decreases, the electrode and the substrate approach an ohmic junction, and the carrier injection efficiency increases. Conversely, as the work function of the electrode material increases, the Schottky junction approaches between the electrode and the substrate, and the carrier injection efficiency decreases. Therefore, in order to function as a space charge type EO optical deflector, the electrode is preferably a material that forms an ohmic junction with the electro-optic material. Specifically, the work function of the electrode material is preferably less than 5.0 eV. For example, Ti (3.84) or the like can be used as an electrode material having a work function of less than 5.0 eV. The parentheses indicate work functions, and the unit is eV. Since the Ti single-layer electrode is oxidized and becomes high resistance, generally, an electrode in which Ti / Pt / Au is sequentially laminated is used to join the Ti layer and the electro-optic crystal. Furthermore, transparent electrodes such as ITO (Indium Tin Oxide) and ZnO can also be used.

  On the other hand, when the carriers contributing to electrical conduction in the electro-optic crystal are holes, the work function of the electrode material is preferably 5.0 eV or more in order to inject holes efficiently. For example, as an electrode material having a work function of 5.0 eV or more, Co (5.0), Ge (5.0), Au (5.1), Pd (5.12), Ni (5.15), Ir (5.27), Pt (5.65), Se (5.9) can be used.

  As shown in FIG. 3, electrodes 202, 203, 212, and 213 are formed on the upper and lower surfaces of an electro-optic material substrate 201 obtained by processing the electro-optic material into a plate shape. The electro-optical material substrate 201 is cut out of a KTN single crystal and formed into a shape of 40.2 mm × 1.2 mm × (thickness T =) 1.2 mm. The six surfaces of the electro-optic material substrate 201 are parallel to the (100) plane of the crystal and are subjected to optical polishing. Since this KTN single crystal had a phase transition temperature of 35 ° C., it was used at 37 ° C., which is slightly higher than this. At this temperature, the relative dielectric constant was 22,000. The four electrodes are formed by vapor-depositing titanium (Ti) on two 40.2 mm × 3.2 mm surfaces of the electro-optic material substrate 201. On the Ti electrode film, platinum and gold were successively formed and protected. The electrodes 202 and 203 were 10 mm in length in the optical axis direction. The electrodes 212 and 213 have a length in the optical axis direction of 30 mm.

  The collimated laser light is incident as incident light beam 204 while the temperature of the optical deflector is controlled at 37 ° C. The polarization of light is a straight line, and the direction of the oscillating electric field is the vertical direction in FIG. The deflection angle when a voltage was applied was about 7 degrees at the maximum when 320 V was applied between the electrodes 202 and 203 and −320 V was applied between the electrodes 212 and 213. When it was applied more than that, the light beam was not emitted normally. When all the polarities of the above voltages were reversed, it was -7 degrees, and a total of 14 degrees could be deflected.

  On the other hand, as shown in FIG. 2, electrodes 102 and 103 matched to the outer shape of the substrate were placed on the electro-optic material substrate 101 having a shape of 40.2 mm × 1.2 mm × (thickness T =) 1.2 mm. In this case, it was possible to deflect only up to 3.4 degrees. From this, the effect of this embodiment was confirmed.

  As shown in FIG. 4, electrodes 202, 203, 212, and 213 are formed on the upper and lower surfaces of an electro-optic material substrate 201 obtained by processing the electro-optic material into a plate shape. The electro-optic material substrate 201 is cut out from a KTN single crystal and shaped into a shape of 8 mm (vertical direction) × 4 mm (horizontal direction) × (thickness T =) 1.2 mm. The six surfaces of the electro-optic material substrate 201 are parallel to the (100) plane of the crystal and are subjected to optical polishing. Since this KTN single crystal had a phase transition temperature of 35 ° C., it was used at 37 ° C., which is slightly higher than this. At this temperature, the relative dielectric constant was 22,000. The four electrodes are formed by vapor-depositing titanium (Ti) on two 8 mm × 4 mm surfaces of the substrate 101. On the Ti electrode film, platinum and gold were successively formed and protected. Further, as the highly reflective films 221 and 222, dielectric multilayer films were deposited so as to have desired shapes, respectively.

  The collimated laser light is incident as incident light beam 204 while the temperature of the optical deflector is controlled at 37 ° C. The polarization of light is a straight line, and the direction of the oscillating electric field is the direction perpendicular to the paper surface of FIG. The deflection angle when a voltage was applied was about 7 degrees at the maximum when 320 V was applied between the electrodes 202 and 203 and −320 V was applied between the electrodes 212 and 213. When it was applied more than that, the light beam was not emitted normally. When all the polarities of the above voltages were reversed, it was -7 degrees, and a total of 14 degrees could be deflected.

  On the other hand, as shown in FIG. 2, when the electrodes 102 and 103 matching the outer shape of the substrate are installed on the electro-optic material substrate 101 having a shape of 8 mm × 4 mm × (thickness T =) 1.2 mm, the maximum It could be deflected only up to 3.4 degrees. From this, the effect of this embodiment was confirmed.

101, 201 Electro-optic material substrate 102, 103, 202, 203, 212, 213 Electrode 104, 204 Incident light 105, 205 Emitted light 106 Light beam 107 Deflection origin 221, 222 High reflection film

Claims (7)

An electro-optic material made of a single crystal having inversion symmetry;
A first anode formed on the first surface of the electro-optic material and a second surface formed on a second surface opposite to the first surface and facing the first anode. A first electrode pair consisting of one cathode;
A second cathode formed on the first surface and spaced apart from the first anode, and formed on the second surface at a position facing the second cathode. And a second electrode pair consisting of a second anode spaced apart from the first cathode,
When light is incident from a third surface orthogonal to the first surface, the light passes through the first electrode pair and then passes through the second electrode pair. The optical axis is set toward the fourth surface facing the surface,
The first electrode pair and the second electrode pair inject carriers forming a space charge into the electro-optic material, and the light transmitted through the electro-optic material by the first electrode pair . An optical deflector that moves a deflection origin in a direction orthogonal to the optical axis and changes a deflection angle of the transmitted light based on the moved deflection origin by the second electrode pair .   2. The light according to claim 1, wherein a length of the second electrode pair along the optical axis is at least twice as long as the length of the first electrode pair along the optical axis. Deflector.   3. The optical deflector according to claim 1, wherein the first and second anodes and the first and second cathodes are made of a material that forms an ohmic junction with the electro-optic material. .   4. The optical deflector according to claim 1, wherein the electro-optic material is a perovskite single crystal material. The electro-optical material, potassium tantalate niobate _{(KTN: KTa 1-x Nb} x O 3, 0 <x <1) the optical deflector according to claim 4, characterized in that a.   The electro-optic material is characterized in that the main component of the crystal is composed of groups Ia and Va in the periodic table, group Ia is potassium, and group Va includes at least one of niobium and tantalum. The optical deflector according to claim 4.   The optical deflector according to claim 6, wherein the electro-optic material further includes one or more members of Group Ia or Group IIa of the periodic table excluding potassium as an additive impurity.

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