JPH10186419A - Optical deflection element and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a prism type optical deflection element which can be improved in the symmetricalness of the deflection angle of light beam and the uniformity of light beam diameter while maintaining a high speed characteristic and low-driving voltage characteristic, by geometrically symmetrically arranging electrodes with respect to the central axis of the beam. SOLUTION: The surface of a single crystal substrate, which constitutes a conductive or semiconductive lower electrode, is provided with an optical waveguide of a ferroelectric thin film. The upper electrode 13 of the conductive thin film or the semiconductive thin film is installed on this optical waveguide. The upper electrode 13 is divided to the two upper electrodes 13a, 13b respectively having prism-shaped patterns. At least one set of prism-shaped refractive index changing regions arranged geometrically symmetrically with respect to the central axis of the incident light beam 1 are generated in the optical waveguide by impressing voltage between the upper electrode 13 and the lower electrode, by which the light beam is deflected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention comprises an optical waveguide and a light source for directing a laser beam into the optical waveguide.
The present invention relates to an optical deflecting element provided with an electrode for deflecting a light beam in an optical waveguide by an electro-optic effect. Further, the present invention provides an optical deflection device having applications to general optoelectronics including an image forming apparatus such as a laser printer, a digital copying machine, a facsimile, and a pickup for an optical disc, an optical switch for an optical communication or an optical computer, and the like. About.

[0002]

2. Description of the Related Art As a laser beam optical scanning device used in a laser beam printer, a digital copier, a facsimile, etc., a rotating polygon mirror called a polygon mirror for deflecting a beam from a gas laser or a semiconductor laser,
A lens composed of an fθ lens that condenses the laser beam reflected by the rotating polygon mirror on an image forming surface such as a photoconductor in a linear motion at a constant speed is typically used. The light deflecting device using such a polygon mirror has problems in durability because the polygon mirror is rotated at a high speed by a motor, generates noise, and also has a problem in that the light scanning speed is limited by the number of rotations of the motor.

On the other hand, as a solid-state laser beam light deflector, there is a light deflector using an acousto-optic effect.
In particular, optical waveguide devices are expected. This optical waveguide device is being studied for application to a printer or the like as a laser beam light scanning device for solving the drawbacks of a laser beam light scanning device using a polygon mirror. This optical waveguide type optical deflection element has an optical waveguide made of LiNbO ₃ , ZnO, or the like, and means for coupling (incident) a laser light beam into the optical waveguide. It is equipped with a comb-shaped electrode for exciting surface acoustic waves to be deflected by the optical effect, and a means for outputting the deflected light beam from the optical waveguide. A thin film lens or the like is added to the element. However, the optical deflection element utilizing the acousto-optic effect generally has a problem of an upper limit of the laser deflection speed due to the deflection speed limit, and there is a limit in application to an image forming apparatus such as a laser printer, a digital copying machine, and a facsimile. .

On the other hand, "A. Yariv, Optical El.," Which uses an oxide ferroelectric material having an electro-optic effect having a higher modulation speed than the acousto-optic effect.
electronics, 4th ed. (New Y
ork, Rinehartand Winston,
1991) pp. 336-339. And the like are known. As such an element, there is a bulk element using a ceramic or a single crystal. However, since the size is large and the driving voltage is considerably high, a practical deflection angle cannot be obtained.

Further, a prism-type domain inversion light deflection element or a prism-type electrode light deflection element having a cascade-type prism using a LiNbO ₃ single crystal wafer on which a Ti diffusion type optical waveguide or a proton exchange type optical waveguide is manufactured has been proposed. Q. Chen, et al., J. Light
two Tech. vol. 12 (199
4) 1401. (Hereinafter referred to as Document (1)) and Japanese Patent Application Laid-Open No. 1-248141.

However, since the electrode spacing of about 0.5 mm, which is the thickness of the LiNbO ₃ single crystal wafer, is still required, the driving voltage is still high.
However, a deflection angle of only about 0.5 ° is obtained even with the driving voltage described above, and there is a problem that a practical deflection angle cannot be obtained. In addition, since a prism arrangement long in the beam axis direction with respect to the diameter of the incident laser beam is required, the aperture of the deflecting portion becomes small, and there is a problem that the resolution is small.

[0007]

On the other hand, the present inventor has an optical waveguide provided on a conductive substrate, and a light source for inputting a light beam into the optical waveguide. Invented a prism type optical deflecting element using a thin film optical waveguide provided with an electrode for deflecting a beam by an electro-optic effect, and filed a Japanese Patent Application No. 176939/1995 (hereinafter referred to as Reference (2)).
To solve the above-mentioned problem of the drive voltage.

[0008] Regarding the enlargement of the opening of the deflecting portion or the improvement of the resolution, see Ninomiya, IEICE (C), 56-C.
(1973) 345 ", reference (2), or JP-A-62-47627 discloses a prism type optical deflection element in which prisms are arranged in an array type. However, when such an array-type prism-type optical deflector is used, first, since the prism shape is not symmetric with respect to the incident laser beam, the characteristic of the deflection angle of the light beam with respect to the applied voltage is asymmetric. Second, there is a problem that the light beam diameter changes greatly depending on the deflection angle.

The first problem is that the absolute value of the deflection angle differs from the absolute value of the positive and negative applied voltages. In a prism type optical deflection element having such a problem, for example, the deflection angle when applying +10 V is different from the deflection angle when applying −10 V, or the deflection angle when applying the former is a fixed deflection angle. Has a certain beam quality, but when the latter is applied, the deflection itself is not observed,
And other phenomena. Such a prism light deflecting element is not suitable because it requires a complicated driving operation when used in applications such as a laser printer and a digital copying machine, which are the object of the present invention.

The second problem is that, for example, a beam diameter at a deflection angle of 0 ° and a beam diameter at 20 ° exhibit an extremely different phenomenon. Even if it is difficult at present to completely suppress the change in the beam shape due to such a deflection angle, the ratio of the beam diameter at the deflection angle of 0 ° to the beam diameter at the deflection angle of 20 ° is three times or more. In such a prism-type light deflecting element, for example, in a laser printer, the thickness of a line forming the character changes extremely depending on the position of the character, and the printing quality is degraded.

As a prism type light deflecting element capable of improving the symmetry of the deflection angle of the light beam and the change of the light beam diameter due to the deflection angle, an electrode having a gap shape which becomes X-shaped with respect to the incident laser beam is an electrode having a four-division structure. Japanese Patent Laid-Open No. 3-2
No. 56026. However, since this device uses a bulk optical waveguide, the dimensions of the optical waveguide portion are 1 mm in length, and the thickness of the optical waveguide in the gap portion where the X shape is formed is 1.1 mm. For this reason, 10 kV is required as an applied voltage to obtain a deflection angle of 6 °, and the electric field in the gap portion on the substrate surface approaches 100 kV / cm, so that there is a problem that dielectric breakdown easily occurs. The beam shape largely deviates, and the beam shape after deflection is not good.

A first object of the present invention is to improve the symmetry of the light beam deflection angle while maintaining high speed and low drive voltage characteristics in a prism type optical deflection element using a thin film optical waveguide. A second object of the present invention is to maintain uniformity of the light beam diameter within a certain range regardless of the deflection angle while maintaining high speed and low drive voltage characteristics in a prism type optical deflection element using a thin film optical waveguide. That is. A third object of the present invention is to provide a prism type optical deflecting element using a thin film optical waveguide, which satisfies the first and second objects, while changing the beam shape depending on the deflection angle and increasing the height of the substrate surface gap. An object of the present invention is to provide a prism type light deflecting element that can solve problems such as resistance to dielectric breakdown caused by an electric field. Another object of the present invention is to provide a laser printer in which laser beam quality is important, using the above-described prism type optical deflection element.
Application to digital copiers, facsimile machines, etc.

[0013]

An object of the present invention is to provide a lower electrode made of a conductive or semiconductive single crystal substrate and an epitaxial or unidirectional thin film formed on the surface of the single crystal substrate. An optical waveguide, a plurality of upper electrodes made of a conductive thin film or a semiconductive thin film provided on the thin film optical waveguide, and applying a predetermined voltage between the lower electrode and the upper electrode to apply a predetermined voltage to the single crystal substrate surface. And at least one set of non-parallel refractive index changing surfaces (the refractive index changes discontinuously due to an electric field) A voltage-applying means for deflecting the light beam from the thin-film optical waveguide into a plane substantially parallel to the surface of the single crystal substrate by generating a prism-shaped refractive index change region having a Was it It can be solved by the light deflecting element characterized.

The prism-shaped refractive index change region is, for example, provided between an upper electrode having a prism-shaped pattern having at least one pair of sides that are not parallel to each other and a lower electrode opposed to the optical waveguide with the optical waveguide interposed therebetween. The first method is to apply a voltage to form a refractive index change region having a prism shape different from the other region in the region of the optical waveguide corresponding to the pattern of the upper electrode, or By providing a plurality of polarization domain inversion regions having a prism shape having at least one pair of sides, and applying a voltage between the upper electrode and the lower electrode, the polarization domain inversion region and the other regions having different prism shapes in the other regions. It can be created by any of the second methods of forming a refractive index change region.

Further, the image forming apparatus of the present invention comprises: a photoreceptor; charging means for uniformly charging the photoreceptor; exposure means for irradiating the photoreceptor with light to form a latent image; And an image forming apparatus provided with a developing means, wherein the light deflecting element described above is used as the exposing means.

In the present invention, as a thin-film optical waveguide material, an ABO ₃ type perovskite oxide may be tetragonal,
As orthorhombic or pseudo-cubic, for example, BaTiO ₃ , P
_{bTiO 3, Pb 1-x La} x (Zr y Ti 1-y) 1- x / 4 O
₃ (PZT, PLT, PLZ depending on the values of x and y
T), Pb (Mg _1/3 Nb _2/3 ) O ₃ , KNbO ₃ , a ferroelectric material represented by a hexagonal system such as LiNbO ₃ , LiTaO _3, etc .; and a tungsten bronze type oxide, Sr _x Ba _{1. -x} Nb ₂ O _6, Pb etc. _{x Ba 1-x Nb 2 O} 6, also in this _{addition, Bi 4 Ti 3 O 12,} Pb 2 KNb 5 O 15, K
₃ Li ₂ Nb ₅ O ₁₅ , which is further selected from substituted derivatives and the like, and has strong secondary PL effects such as PLZT, PZT, and PLT having a secondary electro-optic effect in which the refractive index changes in proportion to the square of the electric field. Dielectrics are most desirable.

The upper electrode used in the present invention is P
Various metal electrodes such as t, Al, and Cr, and transparent oxide electrodes such as ITO and Al-doped ZnO having a smaller refractive index than the optical waveguide can be used. When a cladding layer having a smaller refractive index than that of the optical waveguide is provided between the optical waveguide and the upper electrode, any material can be used for the upper electrode. It is desirable to use a transparent oxide electrode such as

When a conductive or semiconductive single crystal substrate or a conductive or semiconductive epitaxial or oriented thin film provided between the substrate and the optical waveguide is used as the lower electrode substrate, a thin film optical waveguide is used. SrTiO ₃ , Al-doped ZnO, In ₂ O ₃ , RuO ₂ , BaPbO ₃ , SrRu doped with Nb or the like having a smaller refractive index
O ₃ , YBa ₂ Cu ₃ O _7-x , SrVO ₃ , LaNiO ₃ , L
a _0.5 Sr _0.5 CoO ₃ , ZnGa ₂ O ₄ , CdGa ₂ O ₄ ,
Oxides such as CdGa ₂ O ₄ , Mg ₂ TiO ₄ and MgTi ₂ O ₄ are desirable, but it is also effective to use metals such as Pd, Pt, Al, Au and Ag.

The conductive or semiconductive single crystal substrate or the conductive or semiconductive epitaxial or oriented thin film is desirably selected according to the crystal structure of the ferroelectric thin film. The resistivity of a conductive or semiconductive thin film or a single crystal substrate used as an upper electrode or a lower electrode is 10 ⁻⁶ Ω · cm to 10 Ω · cm.
A range of about ³ Ω · cm is effective, but it can be used as an upper electrode or a lower electrode if the resistivity is such that the voltage drop is negligible. In addition, depending on the deflection speed or the modulation speed, an upper electrode material or a lower electrode material having an appropriate carrier mobility can be selected.

The thin film optical waveguide according to the present invention can be formed by electron beam evaporation, flash evaporation, ion plating, Rf-
Magnetron sputtering, ion beam sputtering, laser ablation, MBE, CV
D, a vapor phase growth method selected from plasma CVD, MOCVD and the like, and a solid phase growth method of a thin film formed by a wet process such as a sol-gel method and a MOD method.

As a laser used as a light source in carrying out the present invention, a gas laser such as He-Ne,
Examples include a compound semiconductor laser such as AlGaAs or a laser array thereof. Laser light generated by laser oscillation is introduced into the optical waveguide by a method selected from prism coupling, butt coupling (or end coupling), grating coupling, evanescent field coupling, and the like. Mode index lenses, Luneburg lenses, geodesic lenses, Fresnel lenses, grating lenses, etc. are suitable as thin film lenses. As the emission means, a prism coupler, a grating coupler, a focusing coupler, a SAW grating coupler, or the like is suitable.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle of the present invention will be described below in detail using mathematical expressions. In general, when an electric field is applied to a material having an electro-optic effect, the change in the refractive index due to the electric field in a crystal structure having no center of symmetry is as follows: Δn = n0−n = −aE−bE ² −. 1] Among these, the first-order term is called the Pockets effect and is generally expressed as follows: Δn = − ／ rn ³ E [2] The second-order term is called the Kerr effect and generally expressed as follows It is.

Δn = − ／ Rn ³ E ² [3] In the above equation, n is a refractive index, E is an electric field, and r and R are predetermined coefficients.

In practice, as the electric field is increased, the refractive index changes in such a manner that the secondary electro-optic effect, the Kerr effect, gradually overlaps with the primary electro-optic effect, the Pockets effect, as the electric field is increased. When such an electro-optic effect is used, a ferroelectric having a crystal structure without a center of symmetry and having a high coefficient is used.
iNbO3 and PLZT are typical. When a local electric field is applied to such a ferroelectric, the refractive index of that portion is reduced as described above, and by using this, the direction of the laser beam can be deflected or switched.

Here, the primary electro-optic effect, Poc
The principle of a prism type optical deflection element using a ferroelectric substance having the kels effect will be described. In FIG. 27, two prisms (3) having a length l and a height D are different in refractive index.
Suppose there is a medium consisting of (4). Light A incident here
(1) passes through the prism (3) having the refractive index na, and its transit time τa is given by τa = 1 / ca [4], where c is the speed of light at the prism (3). Assuming the speed of light, τa = 1 / ca = 1 / c · na [5] Similarly, the transit time τb of the light B passing through the prism (4) having the refractive index nb is τb = 1 / cb = 1 / c · nb [6] Therefore, the difference between the transit times of light A and light B is na = n + Δ
Assuming that n and nb = n (Δn is the difference between the refractive indices of na and nb), Δτ = 1 / c · (na−nb) = 1 / c · Δn [7] The difference in the position of the wavefront before exiting the prism due to the difference in the transit time is as follows: Δy = cb · Δτ = c / nb · l / c · Δn = lΔn / n [8] Is equivalent to the refraction of
Utilizing that the refraction angle θD is approximated to tan θD when it is sufficiently small, tan (θD) = − Δy / D = −lΔn / Dn [9] If the angles θo and nair are the refractive index of air (= 1), then nair · sin θo = sin θo = n · sin θD [10], and θo = sin ⁻¹ (n · sin θD). Here, in the range where θD is sufficiently small, sin θ
Since D is approximated to .theta.D, .theta.o = n..theta.D = -n.l.DELTA.n / Dn = -1.DELTA.n / D.

Here, assuming that the two prisms have opposite polarization axes and an electric field is applied in a direction parallel to the z-axis, a region related to the primary electro-optical effect, the Pockets effect, is dominant. Then, Δn = − ／ rn ³ E
Thus, na = no− ／ rno ³ E [11] nb = no + ／ rno ³ E [12], and Δn = −rno ³ E [13] From Δn = na−nb, the applied voltage is V, When the thickness of the prism is d, θo = −lΔn / D = 1 / D · rno ³ E = 1 / D · rno ³ (V / d) [14], and the laser beam is proportional to the electric field or voltage. Can be deflected.

Instead of two prisms, a triangular electrode is placed at the position of prism (3) in FIG.
Assuming that the voltage is applied in the direction parallel to the axis, na = no− ／ rno ³ E [15] nb = no [16], and Δn = − ／ rno ³ E [17] from Δn = na−nb Therefore, assuming that the applied voltage is V and the thickness of the medium is d, θo = −lΔn / D = l / D ・ 1 / 2rno ³ E = l / 2D · rno ³ (V / d) [18]

In a prism type optical deflection element using a ferroelectric material having a Kerr effect, which is a secondary electro-optic effect, the expression [18] becomes as follows from the expression [3]. θo = −lΔn / D = l / D · 1 / 2Rno ³ E ² = l / 2D · Rno ³ (V / d) ² [19]

FIG. 2 shows an optical deflection element using such an element.
8 and FIG. FIG. 28 is a top view and FIG.
Is a cross-sectional view as viewed from the side. In this optical deflecting element, for example, a single crystal LiNbO ₃ substrate (5) is used as a substrate, and a Ti diffusion type optical waveguide or a proton exchange type optical waveguide (6) is formed on the substrate. A prism-shaped domain-inverted portion (7) is formed. The light (1) is incident on the light deflecting element from the left end face in FIG. 28, passes through the optical waveguide (6) and the polarization domain inversion portion (7) formed thereon, is deflected by the change in the refractive index, and is deflected. Are emitted as polarized light (2). When this type of optical waveguide type prism type optical deflector is used, there is a problem that the characteristic of the deflection angle of the light beam with respect to the applied voltage is asymmetric, and a problem that the diameter of the light beam changes depending on the deflection angle.

FIGS. 1 and 2 show an optical deflecting element according to one embodiment of the present invention. FIG. 1 is a top view and FIG.
Is a cross-sectional view as viewed from the side. In the light deflecting element according to the present embodiment, a single crystal substrate (11) serving as a conductive or semiconductive lower electrode and a photoconductive layer of an epitaxial or unidirectional ferroelectric thin film provided on the surface of the single crystal substrate. A waveguide (12) and an upper electrode (13) of a conductive thin film or a semiconductive thin film are provided on the optical waveguide. FIG.
Unlike the example shown in FIG. 9, in the optical deflecting element according to the present embodiment, the upper electrode (13) has two upper electrodes (13a, 13a).
b). The upper electrode (13) and the lower electrode (1
By applying a voltage between them, at least one set of prism-shaped refractive index changing regions (1) arranged geometrically symmetrically with respect to the central axis of the incident light beam in the optical waveguide.
4) to deflect the light beam. Here, the central axis of the beam indicates the exact center of the beam having the width D in FIG. 1, that is, the position D / 2 from the end of the beam. Referring to FIG. 1, when the sides of electrodes 13a and 13b in the direction perpendicular to the beam overlap, they are geometrically symmetric with respect to the central axis of the beam.

Thus, one of the requirements of the present invention is to arrange the electrodes geometrically symmetric with respect to the central axis of the beam. Thus, it is possible to provide a prism type optical deflection element capable of improving the symmetry of the optical beam deflection angle and the uniformity of the optical beam diameter while maintaining the high speed and the low drive voltage characteristics. This is because this enables an equivalent change in the refractive index to be caused even when an electric field is applied in either the positive or negative direction to cause deflection.
In order to cause deflection by the refractive index changing region (14), it is necessary that at least one refractive index changing surface in that region be a refractive index changing surface in a direction other than perpendicular or parallel to the traveling direction of the beam. This refractive index changing surface corresponds to the hypotenuse of the right-angled triangle of the electrodes 13a and 13b in FIG. Since these requirements should be satisfied, the electrodes 13a and 13b each have at least one pair of sides (that is, the hypotenuses of two right triangles) that are not parallel to each other as shown in FIG. .

As a method of generating at least one set of prism-shaped refractive index change regions geometrically symmetrically arranged with respect to the central axis of the incident beam, for example, as shown in FIG. 1 and FIG. By applying a voltage between an upper electrode (13) having a prism-shaped pattern having at least one pair of sides that are not parallel and a lower electrode (11), a region of the optical waveguide corresponding to the pattern of the upper electrode is applied. Another method is to generate a refractive index change region (14) having a prism shape different from the other regions. As another method of generating at least one set of prism-shaped refractive index changing regions geometrically symmetrically arranged with respect to the central axis of the incident beam, for example, as shown in FIG. 3 and FIG. A prism-shaped domain-inverted region (7) having at least one pair of planes that are not parallel to each other is previously formed in the optical waveguide, and an upper electrode (13) and a lower electrode (11) having shapes different from those of the domain-inverted region. By applying a voltage between them, there is a method of generating a refractive index changing region (14) having a different prism shape in the polarization domain inversion region (7) and the other region.

Example 1 A first specific example (hereinafter, referred to as Example 1) of an optical deflecting element according to an embodiment of the present invention will be described with reference to FIGS. First, if the resistivity is 5
Nb-doped SrT of about mΩ · cm to 500 mΩ · cm
On the lower electrode substrate of iO ₃ (100) single crystal conductive (1
1) An epitaxial PLZT (12/40/60) thin film optical waveguide (12) is grown. Thickness dw = 600n
The PLZT layer having m and r = 120 × 10 ⁻¹² m / V is formed by solid phase epitaxial growth using a sol-gel method. First, anhydrous lead acetate Pb (CH ₃ COO) ₂ , lanthanum isopropoxide La (OiC ₃ H ₇ ) ₃ , zirconium isopropoxide Zr (OiC
₃ H ₇ ) ₄ and titanium isopropoxide Ti (O-
as starting material the _{i-C 3 H 7) 4} , 2- methoxy ethanol to dissolve performs reflux for 18 hours after performing the distillation for 6 hours, and finally 0.6M of PLZT in Pb concentration (1
2/40/60).

Further, the precursor solution is spin-coated on a substrate. All of the above operations are performed in an N ₂ atmosphere. Next, the temperature is raised at 10 ° C./sec in a humidified O ₂ atmosphere, kept at 350 ° C., kept at 650 ° C., and finally, the electric furnace is turned off to cool. As a result, a first-layer PZT thin film having a thickness of about 100 nm was grown by solid phase epitaxial growth. By repeating this further five times, an epitaxial PLZT thin film having a total film thickness of 600 nm can be obtained. The crystallographic relationship is PLZT (100) // Nb-S
rTiO ₃ (100), in-plane orientation PLZT [001] /
/ Nb-SrTiO ₃ [001] is obtained.

After the poling of the PLZT thin film optical waveguide (12), an IT having a resistivity of about 1 mΩ · cm and a film thickness of about 100 nm is formed on the PLZT thin film optical waveguide (12).
Bottom 2mm, height 10m by O transparent conductive oxide thin film
Two upper electrodes (13) are created which are triangular in m and arranged geometrically symmetric with respect to the central axis of the incident beam. The light source is a laser diode (16) having a wavelength of 780 nm and an output of 20 mW, and is collimated into a laser beam width of 2 mm by a lens (17), and then introduced into a PLZT thin film optical waveguide by a grating (15). Since the PLZT thin film optical waveguide has a higher refractive index than the ITO transparent conductive oxide thin film and the Nb-doped SrTiO ₃ (100) single crystal substrate, the laser beam (1) is
It is confined in a ZT thin film optical waveguide. The incident laser beam (1) is deflected by applying a voltage between the ITO thin film triangular electrode (13) and the Nb-doped SrTiO ₃ single crystal electrode (11). After the deflection, the deflected laser beam (2) is emitted from the end face, and can be applied to, for example, exposing a photosensitive member through an optical system such as an F / θ lens.

The device of Example 1 has a value of n in the formula [18].
= 2.50, r = 120 × 10 ⁻¹² m / V, l = 10 m
m, D = 2 mm, and d = 600 nm, and the deflection angle θ was 4.9 ° at an applied voltage of 12 V, and a sufficient deflection angle was obtained with an extremely low voltage as compared with the prior art. The voltage applied to the electrode (13a) is changed from 12V to 0V.
After sweeping to V, it was observed that the electrode (13b) could be deflected over an angle of 10.8 ° by sweeping the applied voltage from 0 to 12V. FIG. 6 shows the change in the light beam diameter with the deflection angle.
In the above, even if a light beam having a beam diameter of 2.0 mm is deflected by the optical deflecting element according to the first embodiment to a deflection angle of 6 °, the beam diameter is only 2.9 mm. In other words, the dependence of the beam diameter on the deflection angle is sufficiently small,
A practical deflection angle can be realized within a practical applied voltage range.

[Comparative Example 1] Comparative Example 1 will be described with reference to FIG. Note that FIG. 5 according to the first embodiment is also appropriately referred to. The thickness dw = 600 nm, r = 120 on an Nb-doped SrTiO ₃ (100) single-crystal conductive substrate in the same manner as in Example 1.
× 10 ⁻¹² m / V epitaxial PLZT (12 /
40/60) Growing the thin film optical waveguide (12). After the poling of the PLZT thin film optical waveguide (12), a resistivity of about 1 is formed on the PLZT thin film optical waveguide (12).
One triangular electrode (13) having a base of 2 m and a height of 10 mm made of an ITO transparent conductive oxide thin film having a thickness of about 100 nm is formed. The light source is collimated to a laser beam width of 2 mm using a laser diode (16) having a wavelength of 780 nm and an output of 20 mW, and then introduced into the PLZT thin film optical waveguide by a grating (15).
The laser beam (1) incident on the PLZT thin film optical waveguide is deflected by applying a voltage between the ITO thin film triangular electrode (13) and the Nb-doped SrTiO ₃ single crystal electrode. After the deflection, the deflected laser beam (2) is emitted from the end face.

The device of the present comparative example has a value of n in the formula [18].
= 2.50, r = 120 × 10 ⁻¹² m / V, l = 10
mm, D = 2 mm, d = 600 nm, and the deflection angle θ is 4.9 ° at an applied voltage of 12 V.
By sweeping the voltage applied to the electrode (13) from -12V to 12V, deflection is possible over an angle of 10.8 °. However, the change in the light beam diameter with the deflection angle is shown in FIG.
From 1.1 mm (deflection angle −5 °) to 2.9
mm (deflection angle + 5 °), and the maximum light beam diameter is three times less than the minimum light beam diameter of 1.1 mm. For this reason, the dependence between the deflection angle and the diameter of the light beam is too large to be practical.

Comparative Example 2 Comparative Example 2 will be described with reference to FIG. Note that FIG. 5 according to the first embodiment is also appropriately referred to. Nb
An epitaxial PLZT (12/40/60) thin-film optical waveguide (12) having a thickness of dw = 600 nm and r = 120 × 10 ⁻¹² m / V is grown on a doped SrTiO ₃ (100) single-crystal conductive substrate. After poling the PLZT thin-film optical waveguide (12), the PLZT thin-film optical waveguide (12) has a resistivity of about 1 mΩ · cm and a film thickness of about 1 μm.
A set of opposing triangular electrodes (13a) and (13b) having a base of 2 mm and a height of 10 mm made of a 00 mm ITO transparent conductive oxide thin film is prepared. Light source is 780n wavelength
After collimating the laser beam width to 2 mm using a laser diode (16) having an output power of 20 mW and PL
It is introduced into the ZT thin film optical waveguide by the grating (15). The laser beam (1) incident on the PLZT thin film optical waveguide is made of an ITO thin film triangular electrode (13) and Nb.
It is deflected by applying a voltage between the doped SrTiO ₃ single crystal electrodes. After the deflection, the deflected laser beam (2) is emitted from the end face.

The device of the present comparative example has n in the formula [18].
= 2.50, r = 120 × 10 ⁻¹² m / V, l = 10 m
m, D = 2 mm, and d = 600 nm. The electrode (13a) can be deflected by sweeping the applied voltage from 12V to 0V and then sweeping the electrode (13b) from 0V to 12V. Become. However, the electrodes (13
The deflection angle when 12V is applied to a) is 4.9 °,
On the other hand, the deflection angle in the case of applying 12 V to the electrode (13b) is 5.9 °, and the deflection angle characteristics of the light beam do not have symmetry with respect to the positive and negative applied voltages.

[Embodiment 2] A specific second embodiment (hereinafter referred to as embodiment 2) of the optical deflecting element according to the embodiment of the present invention will be described with reference to FIGS. Note that FIG. 5 according to the first embodiment is also appropriately referred to. A lower electrode (11) of a (0001) Al-doped ZnO conductive thin film having a resistivity of about 1 mΩ · cm is epitaxially grown on an insulating sapphire (0001) single crystal substrate (5) by Rf magnetron sputtering. 000
1) After epitaxial growth of the LiNbO ₃ thin film optical waveguide (12), poling was performed. This LiNbO
( ₃ ) Two prism-shaped polarization domain inversion portions (7) having a triangle shape with a base of 1 mm and a height of 10 mm and geometrically symmetrically arranged with respect to the central axis of the incident beam were formed on the thin film optical waveguide (12). After that, the LiNbO ₃ thin film optical waveguide has a thickness of about 100 nm and a resistivity of about 1 mΩ · c.
m ITO transparent conductive oxide thin film upper electrode (13a,
13b) is prepared. As a result, depending on the shape of the polarization domain inversion portion (7), a region in which the refractive index has changed is generated as in the first embodiment.

The region where the refractive index has changed is geometrically symmetric with respect to the central axis of the beam in the top view, and has at least one pair of sides that are not parallel to each other. The light source used was a laser diode (16) having a wavelength of 780 nm and an output of 20 mW.
After collimating to a thickness of 0.1 mm, the light is introduced into a LiNbO ₃ thin film optical waveguide through a grating (15). LiNbO
_{3 The} thin film optical waveguide is made of ITO transparent conductive oxide thin film and A
The laser beam is confined in the LiNbO ₃ thin film optical waveguide because it has a higher refractive index than the l-doped ZnO conductive thin film. The applied laser beam (1) is deflected by applying a voltage between the ITO electrode and the Al-doped ZnO electrode, thereby generating different refractive indices in the prism-shaped domain-inverted portion (7) and other portions. . After the deflection, the deflected laser beam (2) is emitted from the end face.

The device of the present embodiment is obtained by using n in the formula [14].
= 2.18, r = 30 × 10 ⁻¹² m / V, l = 10 m
m, D = 1 mm, d = 400 nm, and the deflection angle is 7.1 at an applied voltage of 16 V as shown in FIG.
°, and the deflection angle has symmetry with respect to positive and negative applied voltages. After the applied voltage is swept from 16 V to 0 V by the upper electrode (13a) at the prism-shaped domain-inverted portion (7a), the applied voltage is applied to the prism-shaped domain-inverted portion (7b) by the upper electrode (13b). By sweeping from 0 V to 16 V, the light beam diameter becomes 1.0 mm to 2.2 mm as shown in FIG.
, But within a sufficiently practical range. Therefore, the optical deflecting element according to the present embodiment has good symmetry over the deflection angle of 14.2 °, and the dependence of the beam diameter on the deflection angle is sufficiently small and practical.

[Comparative Example 3] Comparative Example 3 will be described with reference to FIG. Note that FIG. 5 according to the first embodiment is also appropriately referred to. After the lower electrode of the (0001) Al-doped ZnO conductive thin film and the (0001) LiNbO ₃ thin film optical waveguide (12) were epitaxially grown on an insulating sapphire (0001) single crystal substrate, poling was performed. After forming one triangular prism-shaped domain-inverted portion (7) having a base of 1 mm and a height of 10 mm on the LiNbO ₃ thin film optical waveguide (12), a thickness of about 100 nm is formed on the LiNbO ₃ thin film optical waveguide. Now the resistivity is about 1mΩ
cm of ITO transparent conductive oxide thin film upper electrode (13)
Is prepared. The light source was collimated to a width of 1 mm using a laser diode array (16) having a wavelength of 780 nm and an output of 20 mW, and then the laser beam (1) introduced into the LiNbO ₃ thin film optical waveguide through the grating (15) was used as an ITO electrode. By applying a voltage between the electrodes and between the Al-doped ZnO electrodes, different refractive indices are generated and deflected at the domain-inverted portion of the prism shape and at other portions. After the deflection, the deflected laser beam is emitted (2) from the single end face.

The device of this comparative example has a value of n in the formula [14].
= 2.18, r = 30 × 10 ⁻¹² m / V, l = 10 m
m, D = 1 mm and d = 400 nm. FIG. 13 shows that the applied voltage is changed from -16 V to 16 V by the upper electrode (13) at the prism-shaped domain-inverted portion (7).
Shows the change in deflection angle when sweeping to. On the plus side, a deflection angle of 7.1 ° was confirmed at 16 V, but on the minus side, it was difficult to observe deflection at around −10 V, and a voltage-deflection angle characteristic symmetric with respect to positive and negative applied voltages could not be obtained. Was. It is considered that the observation of the deflection became difficult at around −10 V because the diameter of the light beam became extremely small and the influence of the reflection in the refractive index change region of the prism shape. That is, as shown in FIG. 15, the diameter D of the incident light beam (1)
The reason is that the diameter D1 of the outgoing light beam (2) in one prism varies with the deflection direction according to the following equation [20], where α is the vertex angle of the prism and θ is the deflection angle.

D1 = (D0 / cos α) · sin (90−α−θ) [20] Further, as shown in FIG. 14, the change in the light beam diameter with the deflection angle is about ten times from 0.2 mm to 2.2 mm. Range. The dependence of the beam diameter on the deflection angle in this comparative example is too large and is not practical.

[Embodiment 3] A specific third embodiment (hereinafter, referred to as Embodiment 3) of the optical deflecting element according to the embodiment of the present invention will be described with reference to FIGS. An epitaxial PLZT (12/40/60) thin-film optical waveguide (12) was grown on an Nb-doped SrTiO ₃ (100) single crystal substrate (11). Thickness dw = 600 nm, r =
A 120 × 10 ⁻¹² m / V PLZT layer is produced in the same manner as in Example 1 by solid phase epitaxial growth using a sol-gel method. A prism electrode (13a) made of ITO transparent conductive oxide and two prism-shaped electrodes (13b) and (13c) arranged geometrically symmetrically with respect to the central axis of the incident beam are added to the PLZT thin-film optical waveguide. Formed. The light source is a laser diode having a wavelength of 780 nm and an output of 20 mW. The light is condensed on the end face of the PLZT thin-film optical waveguide by the lens (17) and then introduced into the PLZT thin-film optical waveguide. By using the electrode (13a) as a common electrode and applying the same voltage to (13a) and (13b) or (13a) and (13c), these three prism-shaped electrodes are separated by a gap of 10 μm. 2 geometrically symmetrically arranged with respect to the central axis of the upper incident beam
It functions as a prism-shaped electrode with a base of 2 mm and a height of 1.0 mm. The incident laser beam (1) is collimated to a laser beam width of 2 mm by the mode index lens (18), and then the ITO thin film electrode (13) and the Nb-doped SrTiO ₃ single crystal electrode (1)
It is deflected by applying a voltage during 1). After the deflection, the deflected laser beam (2) is emitted from the end face.

The device of the present embodiment has n in the formula [18].
= 2.50, r = 120 × 10 ⁻¹² m / V, l = 10 m
m, D = 2 mm and d = 600 nm, and the deflection angle was 5.4 ° at an applied voltage of 12 V. Also,
The voltage applied to the electrodes (13a) and (13b) is 12 V
After sweeping from 0 to 0 V, electrodes (13a) and (13
By sweeping the applied voltage to c) from 0 V to 12 V, it is possible to deflect over a deflection angle of 10.8 °, and the change in the light beam diameter with the deflection angle is 2.0 mm
From 2.9 mm, a practical deflection angle can be realized with a practical applied voltage. Further, the electric field in the gap between the prism electrodes in this embodiment is 12 kV / max.
cm, there is no possibility of dielectric breakdown. Also,
This is also effective for reducing the size of the light deflecting element as compared with the first and second embodiments.

[Embodiment 4] A specific fourth embodiment (hereinafter, referred to as embodiment 4) of an optical deflecting element according to an embodiment of the present invention will be described with reference to FIGS. On insulating sapphire (0001) single crystal substrate (5)
(0001) Al-doped Z having a resistivity of about 1 mΩ · cm
The lower electrode (11) of the nO conductive thin film was epitaxially grown, and the (0001) LiNbO ₃ thin film optical waveguide (12) was epitaxially grown, followed by poling. Polarized domain-inverted portions in the form of a two-row array of prisms arranged in a triangular shape with a base of 1 mm and a height of 10 mm and geometrically symmetrical with respect to the central axis of the incident beam to the LiNbO ₃ thin film optical waveguide (12). (7a, 7b)
Is formed, an ITO having a thickness of about 100 nm and a resistivity of about 1 mΩ · cm is formed on the LiNbO ₃ thin film optical waveguide.
An upper electrode (13) of a transparent conductive oxide thin film is produced.
The light source uses a dual beam laser diode (16) having a wavelength of 780 nm and an output of 20 mW, and a lens (1).
7) After collimating to a width of 1 mm by LiNbO
₃ Introduced into the thin film optical waveguide via the prism (19).
The applied laser beam (1) is deflected by applying a voltage between the ITO electrode and the Al-doped ZnO electrode so that different refractive indexes are generated in the domain-inverted portion of the prism shape and other portions. After the deflection, the deflected laser beam (2) is emitted from the end face.

The device according to the present embodiment has n in the formula [14].
= 2.18, r = 30 × 10 ⁻¹² m / V, l = 10 m
m, D = 1 mm and d = 400 nm, the deflection angle becomes 7.1 ° at an applied voltage of 16 V, and deflection becomes possible with good symmetry over the deflection angle of 14.2 °.

The voltage applied to the prism-shaped domain-inverted portion (7a) is set to 1 by the upper electrode (13a).
After sweeping from 6V to 0V, the applied voltage is swept from 0V to 16V by the upper electrode (13b) in the prism-shaped polarization domain inversion portion (7b), so that the light beam diameter varies from 1.0 mm to 2 depending on the deflection angle. .2 mm, but maintains the deflection angle dependence of the beam diameter small enough to be practical.

[Embodiment 5] A specific fifth embodiment (hereinafter referred to as embodiment 5) of the optical deflecting element according to the embodiment of the present invention will be described with reference to FIGS. Example 1
To 4 use the Pockets effect, whereas in the present embodiment, PLZT exhibiting the Kerr effect
(8.5 / 65/35) was used. Resistivity is 5mΩ · c
Nb-doped SrTiO of about m to 500 mΩ · cm
₃ Thickness dw = (11) on (100) single crystal conductive substrate
An epitaxial PLZT (8.5 / 65/35) thin film optical waveguide (10) having a thickness of 500 nm and R = 3860 × 10 ⁻¹⁸ m ² / V ² is manufactured. The crystallographic relationship is PLZT (10
0) // Nb-SrTiO ₃ (100), in-plane orientation PL
This is a structure of ZT [001] // Nb—SrTiO ₃ [001].

On this PLZT thin-film optical waveguide (12), an IT having a resistivity of about 1 mΩ · cm and a thickness of about 100 nm
A prism electrode array having a shape similar to that of Example 3 made of an O transparent conductive oxide thin film and having a base of 1.0 mm and a height of 2.0 mm and being geometrically symmetrically arranged with respect to the center axis of an apparently upper incident beam ( 13) is produced. Light source is 780n wavelength
A laser is introduced into the PLZT thin-film optical waveguide by butt coupling using a laser diode having a power of 20 mW and a power of 20 mW. The incident laser beam (1) is converted into a laser beam width by a mode index lens (18).
After collimating to 4 mm, the prism electrode array (1
3) and Nb-doped SrTiO ₃ single crystal electrode (13)
It is deflected by applying an applied voltage during. After the deflection, the deflected laser beam (2) is emitted from the end face, and can be applied to, for example, exposing a photosensitive member through an optical system such as an F / θ lens.

The device according to the present embodiment has n in the formula [19].
= 2.50, R = 3860 × 10 ⁻¹⁸ m ² / V ² , l =
2 mm, D = 1 mm, d = 500 nm, and as shown in FIG. 22, a prism electrode array (13a)
After sweeping the applied voltage to (13b) from 1.2V to 0V, the prism electrode arrays (13a) and (1b)
By sweeping the applied voltage to 3c) from 0V to 1.2V, the angle 3 from -19.9 ° to 19.9 ° is obtained.
Deflection over 9.8 ° became possible. Further, the change in the light beam diameter with the deflection angle is 4.0 as shown in FIG.
mm to 6.1 mm, and a practical deflection angle can be realized with a practical applied voltage.

Comparative Example 4 In this comparative example, a prism having a base of 1.0 mm and a height of 2.0 mm, which is not apparently geometrically symmetric, was formed in the same manner as in Comparative Example 1 using an ITO transparent conductive oxide thin film. An electrode array is manufactured by arranging the electrodes in an array as in the fifth embodiment. As shown in FIG. 24, when the applied voltage was swept from -1.2 V to 1.2 V, the voltage was deflected from 19.9 ° to 0 ° from -1.2 V to 0 V, and again 0 ° from 0 V to 1.2 V. From 19.9 °, and no symmetrical voltage-deflection angle characteristics were obtained.

[Embodiment 6] A specific sixth embodiment (hereinafter, referred to as Embodiment 6) of an optical deflecting element according to an embodiment of the present invention will be described with reference to FIGS. G
Using the epitaxial PLZT (8.5 / 65/35) thin film grown on the (20) aAs semiconductor laser substrate, prism deflection elements as shown in these figures were produced.
This laser part (16) is made of AlGa by MOCVD.
It was fabricated by growing a multilayered structure of As and diffusing Si into a portion not serving as a laser cavity. Rf sputtering method using MgO buffer layer (21)
A b-doped SrTiO ₃ layer (11) and a PLZT thin film optical waveguide (12) were produced by epitaxial growth. The crystallographic relationship is PLZT (001) // MgO (100)
// AlGaAs (100), in-plane orientation PLZT [01
0] // MgO [001] // AlGaAs [001]
Structure. The laser light generated by the oscillation of the semiconductor laser formed a structure in which the optical waveguide of the laser section and the optical waveguide of the ferroelectric thin film optical modulator were integrated in series, and were introduced into the ferroelectric thin film optical waveguide by butt coupling.

On this PLZT thin film optical waveguide (12), a prism electrode array (13) similar to that of the fifth embodiment is formed. The light source oscillates a laser having a wavelength of 780 nm and an output of 10 mW, and introduces it into the PLZT thin-film optical waveguide by butt coupling. The incident laser beam (1) is collimated to a laser beam width of 4 mm by a mode index lens (18), and then the prism electrode array (13) and the Nb-doped SrTiO ₃ single crystal electrode (1) are used.
It is deflected by applying a voltage during 3). The element of this embodiment has the same characteristics as those of the fifth embodiment as shown in FIGS.

[0058]

According to the present invention, in a prism type optical deflection element using a thin film optical waveguide having an electro-optical effect,
Provided is a prism type optical deflection element that can simultaneously solve problems such as the symmetry of the optical beam deflection angle, the uniformity of the optical beam diameter, the beam shape, and the dielectric breakdown resistance while maintaining high speed and low drive voltage characteristics. Laser and
It can provide a laser beam deflecting element that can be used in printers, digital copiers, facsimile machines, and the like, and a light deflecting element that covers a wide range of optoelectronics including a pickup for an optical disc, an optical switch for an optical communication and an optical computer, and the like. .

That is, in the present invention, by applying a predetermined voltage between the lower electrode and the upper electrode, the center axis of the light beam incident on the thin-film optical waveguide substantially parallel to the surface of the single crystal substrate. It is possible to generate a prism-shaped refractive index change region having at least one set of non-parallel refractive index change surfaces that are geometrically symmetrical with respect to each other, so that the uniformity of the light beam diameter is changed to the deflection angle. Regardless, it is possible to maintain a constant and realize a deflection angle having a characteristic symmetrical with respect to positive and negative applied voltages. In the present invention, an optical waveguide layer such as a ferroelectric substance can be formed in a thin film state on a single crystal substrate or the like by epitaxial growth or the like. Problems such as destructibility can be solved.

[0060]

[Brief description of the drawings]

FIG. 1 is a top view of a first example of a light deflecting element according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a first example of the light deflecting element according to the embodiment of the present invention.

FIG. 3 is a top view of a second example of the light deflecting element according to the embodiment of the present invention.

FIG. 4 is a side sectional view of a second example of the optical deflecting element according to the embodiment of the present invention.

FIG. 5 is a schematic diagram of an optical deflection element system according to first and second examples of the optical deflection element according to the embodiment of the present invention.

FIG. 6 shows deflection angle-beam diameter characteristics of the first example of the optical deflection element according to the embodiment of the present invention.

FIG. 7 is a top view of an optical deflection element according to Comparative Example 1.

FIG. 8 shows a deflection angle-beam diameter characteristic of an optical deflection element according to Comparative Example 1.

FIG. 9 is a top view of an optical deflection element according to Comparative Example 2.

FIG. 10 shows a second example of the optical deflection element according to the embodiment of the present invention.
9 is an applied voltage-deflection angle characteristic of the example of FIG.

FIG. 11 shows a second example of the light deflection element according to the embodiment of the present invention.
13 is a deflection angle-beam diameter characteristic of the embodiment of FIG.

FIG. 12 is a top view of an optical deflection element according to Comparative Example 3.

FIG. 13 shows an applied voltage-deflection angle characteristic of the optical deflection element according to Comparative Example 3.

FIG. 14 shows a deflection angle-beam diameter characteristic of an optical deflection element according to Comparative Example 3.

FIG. 15 is a diagram for explaining a cause of deterioration of deflection angle-beam diameter characteristics of an optical deflecting element according to Comparative Example 3.

FIG. 16 shows a third example of the light deflection element according to the embodiment of the present invention.
It is a top view of the Example of FIG.

FIG. 17 shows a third example of the light deflection element according to the embodiment of the present invention.
FIG. 3 is a schematic view of a light deflection element system according to an embodiment of the present invention.

FIG. 18 shows a fourth example of the optical deflection element according to the embodiment of the present invention.
It is a top view of the Example of FIG.

FIG. 19 shows a fourth example of the optical deflection element according to the embodiment of the present invention.
FIG. 2 is a schematic view of a deflection element system according to the embodiment of FIG.

FIG. 20 illustrates a fifth example of the optical deflection element according to the embodiment of the present invention.
It is a top view of the Example of FIG.

FIG. 21 shows a fifth example of the optical deflection element according to the embodiment of the present invention.
FIG. 2 is a schematic view of a deflection element system according to the embodiment of FIG.

FIG. 22 illustrates a fifth example of the optical deflection element according to the embodiment of the present invention.
9 is an applied voltage-deflection angle characteristic of the example of FIG.

FIG. 23 shows a fifth example of the optical deflection element according to the embodiment of the present invention.
13 is a deflection angle-beam diameter characteristic of the embodiment of FIG.

FIG. 24 shows an applied voltage-deflection angle characteristic of the optical deflection element according to Comparative Example 4.

FIG. 25 shows a sixth embodiment of the light deflecting element according to the embodiment of the present invention.
It is a top view of the Example of FIG.

FIG. 26 shows a sixth embodiment of the optical deflection element according to the embodiment of the present invention.
It is sectional drawing from the side of Example of FIG.

FIG. 27 is a diagram for explaining the principle diagram of the prism type optical deflection element.

FIG. 28 is a top view of an optical waveguide prism light deflection element.

FIG. 29 is a cross-sectional view from the side of the optical waveguide prism light deflection element.

[Explanation of symbols]

 (1) Incident beam (2) Outgoing beam (3) Prism with refractive index na (4) Prism with refractive index nb (5) Insulating substrate (6) Proton exchange optical waveguide (7) Polarized domain inversion region (8) Upper electrode (9) Cladding layer (10) Lower electrode (11) Conductive electrode (12) Thin film optical waveguide (13) Upper electrode (14) Refractive index change region (15) Grating for incidence (16) Laser diode (17) ) Lens (18) Mode index lens (19) Incident prism (20) GaAs substrate (21) MgO buffer layer

Claims (10)

[Claims] 1. A lower electrode made of a conductive or semiconductive single crystal substrate, an epitaxial or unidirectional thin film optical waveguide formed on the surface of the single crystal substrate, and provided on the thin film optical waveguide. A plurality of upper electrodes made of a conductive thin film or a semi-conductive thin film, and applying a predetermined voltage between the lower electrode and the upper electrode, so that the thin film light guide is substantially parallel to the single crystal substrate surface. A plurality of prism-shaped refractive index changing regions arranged geometrically symmetrically with respect to a central axis of a light beam incident on the wave path, wherein the refractive index has at least one set of non-parallel refractive index changing surfaces. Voltage application means for deflecting the light beam from the thin-film optical waveguide in a plane substantially parallel to the surface of the single crystal substrate and emitting the light beam by generating a rate change region. element. 2. An optical deflecting element according to claim 1, wherein said thin film optical waveguide is a ferroelectric thin film having a secondary electro-optic effect in which a refractive index changes in proportion to the square of an electric field. Light deflecting element. 3. The light deflecting element according to claim 1, wherein the plurality of upper electrodes have a prism-shaped pattern having at least one pair of sides that are not parallel to each other, and the voltage applying unit is configured to be the predetermined voltage. Wherein the refractive index of a region of the thin-film optical waveguide corresponding to the pattern of each of the plurality of upper electrodes is changed by applying the following voltage. 4. The optical deflecting element according to claim 1, wherein the thin-film optical waveguide has a plurality of prism-shaped polarization domain inversion regions having at least one set of surfaces that are not parallel to each other, and wherein the voltage application is performed. Means for applying the predetermined voltage to generate a region having a different refractive index in the domain-inverted region and the other region. 5. The optical deflecting element according to claim 1, wherein the single crystal substrate is a dielectric single crystal substrate having a conductive or semiconductive epitaxial or oriented thin film on the surface. An optical deflecting element, comprising: 6. An optical deflecting element according to claim 1, wherein said single crystal substrate is an oxide having a smaller refractive index than said thin film optical waveguide. 7. An optical deflecting element according to claim 1, wherein said plurality of upper electrodes are oxides having a refractive index smaller than that of said thin-film optical waveguide. . 8. The light deflecting device according to claim 1, further comprising a light source for generating the light beam, wherein the light source oscillates a single laser beam, or
An optical deflecting element, which is a laser array formed on a single substrate that oscillates a plurality of laser beams. 9. An optical deflecting element according to claim 8, wherein said light source is formed on said single crystal substrate. 10. A photoreceptor, charging means for uniformly charging the photoreceptor, exposure means for irradiating the photoreceptor with light to form a latent image, and developing means for visualizing the latent image are provided. An image forming apparatus, wherein the exposure unit includes the light deflecting element according to any one of claims 1 to 9.