JP2009048021A - Light deflection element and light deflection module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light deflection element which permit high-speed light beam deflection, is compact and can provide a large deflection angle. <P>SOLUTION: The deflection element has a light input part 111, a light distribution part 112, an optical waveguide array 113, a light output part 114, a control electrode 120 and the like on a substrate 110, distributes light inputted to the light input part to respective optical waveguides of the optical waveguide array by means of the light distribution part and imparts a retardation to light guided through the optical waveguide array 113 between waveguides with the control electrode 120 and so on to emit the light from the light output part. Therein, the optical waveguide array 113 is an array arrangement of at least two optical waveguides using high-refractive index difference optical waveguides, at least core 116 or the like is formed of material having an electrooptical effect, further, the respective waveguides have phase modulation structures having curved optical waveguide parts 118 with a curvature, and such phase modulation that the control electrode imparts to a guided light retardations different between the optical waveguides due to the electrooptical effect is performed for the phase modulation structures in the optical waveguide array. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an optical deflection element and an optical deflection module.
The light deflection element / light deflection module of the present invention can be used as, for example, a deflection means for optical scanning in a laser printer, an image forming apparatus, or the like.

As an element that deflects a light beam at high speed using the electro-optic effect, “light with the same phase wavefront” is made incident on the input portions of a plurality of optical waveguides arranged close to each other and parallel to each other. A device that realizes light beam deflection by giving a phase difference to guided light for each optical waveguide by control is known (Patent Document 1).
The element described in Patent Document 1 can deflect light beams at high speed, but a plurality of optical waveguides arranged in close proximity to each other are linear, and give a phase difference to light guided through each optical waveguide. The “length of the field effect region for each optical waveguide” is made different from each other. For example, when trying to realize “a deflection angle of 40 degrees or more” necessary for optical scanning in an image forming apparatus such as a digital copying apparatus. In addition, the length of each waveguide becomes long, and it is inevitable that the element itself becomes large.

Japanese Patent No. 3224585

  The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to realize a compact optical deflection element that can perform high-speed light beam deflection by utilizing the electro-optic effect, can realize a large deflection angle, and is compact. . Another object of the present invention is to realize an optical deflection module using the optical deflection element.

  The light deflecting element according to the present invention has “a light input section, a light distribution section, an optical waveguide array, a light output section, and a control electrode on a substrate, and the light input to the light input section is a light distribution section. An optical deflecting element that distributes to each optical waveguide of the optical waveguide array by the control electrode and causes the light guided through the optical waveguide array to be phase-differed between the optical waveguides and emitted from the light output unit by the control electrode ” It has the following features (claim 1).

That is, the “optical waveguide array” is an array arrangement of two or more optical waveguides by a high refractive index difference optical waveguide formed of different materials for the core and the clad, and at least the core is formed of a material having an electro-optic effect. Is done. The optical waveguide array has a phase modulation structure in which each optical waveguide has a “curved optical waveguide portion having a curvature”.
The “control electrode” performs phase modulation on the phase modulation structure in the optical waveguide array by applying “different phase difference between the optical waveguides” to the guided light by the electro-optic effect.
The “high refractive index difference optical waveguide” is an optical waveguide having a large refractive index difference between a core and a clad formed of different materials, and is known as a “HIC optical waveguide (High Index Contrast optical waveguide)”. In the high refractive index difference optical waveguide used in the optical deflecting element of the present invention, at least the core of the core and the clad is formed of “a material having an electro-optic effect”. The phase modulation by the control electrode is performed by changing the refractive index of the core portion in the high refractive index difference waveguide by the electro-optic effect.

The “bent optical waveguide portion” is a structural portion in which the optical waveguide is folded two-dimensionally or three-dimensionally by a bent portion that bends smoothly with a finite curvature.
The high refractive index difference optical waveguide has the property of strongly confining the guided light in the core, and has a large effect of confining the guided light in the core, so it is possible to “reduce the cross-sectional area of the core”. The arrangement interval between the optical waveguides in the light output portion can be reduced. In addition, since the guided light is strongly confined in the core, even when the optical waveguide is “smoothly bent with a large curvature”, loss at the bent portion can be substantially prevented.

  That is, in the optical deflecting element of the present invention, each optical waveguide constituting the optical waveguide array is a high refractive index difference optical waveguide. Therefore, by thinning the core and folding it two-dimensionally or three-dimensionally A long optical waveguide can be arranged in a “small region”, and the optical waveguide array can be made compact despite the long optical waveguide.

  Since the length of each optical waveguide arranged in the array can be increased in this way, a large deflection angle can be realized, and high-speed light beam deflection can be achieved by using the electro-optic effect for phase modulation.

The phase modulation control by the control electrode can continuously deflect the deflection angle from 0 degree to the maximum deflection angle: θ _max , and the optical deflection element is used for, for example, “for optical scanning of a digital copying apparatus”. it can. In addition, the optical deflection element can be used as an optical switching element by performing phase modulation with binary or multivalued on / off.

In the optical deflection element according to claim 1, "the cross-sectional area of the core of each optical waveguide in the optical waveguide array: S" is a condition with respect to the waveguide light wavelength: λ (wavelength for propagation in vacuum):
S ≦ (1.5λ) ² (1)
It is preferable to satisfy the condition (Claim 2).
In the high refractive index difference optical waveguide satisfying the condition (1), the “confining action in the core” of the guided light is favorably performed.

The optical deflection element according to claim 1 or 2 is configured such that the control electrode individually applies an electric field to each bent optical waveguide portion with respect to the plurality of bent optical waveguide portions constituting the phase modulation structure of the optical waveguide array. (Claim 3).
It is preferable that the light input portion in the optical deflection element according to any one of claims 1 to 3 has an “optical coupling structure” (claim 4). By providing the optical input unit with an optical coupling structure, the input light can be efficiently coupled to the optical distribution unit.

It is preferable that the output end of the light output portion of the optical deflection element according to any one of claims 1 to 4 has a “mode conversion optical waveguide structure” (claim 5). In this way, output light can be extracted with “higher efficiency” from the output end of the light output unit.
It is preferable that the optical waveguide in the light output portion of the optical deflection element according to any one of claims 1 to 5 has a “phase adjustment structure” (claim 6).

  The “light distribution part” in the optical deflection element according to any one of claims 1 to 6 can be a one-input multi-output optical waveguide slab (claim 7), and any one of claims 1 to 7. The light distribution unit in the optical deflection element according to claim 1 may have a “multistage branch structure”.

The optical deflection module according to the present invention is an optical module using the optical deflection element according to any one of the first to eighth aspects as a part of the module (inventions 9 to 13).
An optical deflection module according to claim 9 has “another optical element” on the light input part side and / or the light output part side of the optical deflection element according to any one of claims 1 to 8. To do. As another optical element, for example, a “semiconductor laser having a light output end” as a light source provided on the light input side, or a lens for output light provided on the light output side and output from the light deflection element Examples thereof include a refractive optical system such as a planar lens, a microlens, and a microlens array that act, a reflecting surface that bends the optical path of output light, and the like.

When a “semiconductor laser having a light output end” is provided as a light source on the light input side, the light input end in the light input portion of the light deflection element and the light output end of the semiconductor laser are preferably arranged close to each other.
In this case, the semiconductor laser having the optical output end can be integrated and provided on the substrate of the optical deflection element.

An optical deflection module according to claim 10 deflects the optical deflection element according to any one of claims 1 to 8 and output light from the optical deflection element in a “direction intersecting a deflection plane by the optical deflection element”. It has a deflection means. The “deflection plane by the light deflection element” is a virtual plane in which the light beam deflected by the light deflection element sweeps with deflection. The optical deflection module according to claim 10 can also be configured to have “other optical elements” similar to the above on the optical input portion side and / or the optical output portion side of the optical deflection element. ).
Examples of the deflecting means include “a mechanically oscillating element” in the direction intersecting the deflection plane itself, “an oscillating mirror” that can be oscillated by driving, an acoustooptic element, and the like.

  An optical deflection module according to a twelfth aspect is an optical deflection module in which a plurality of optical deflection elements according to any one of the first to eighth aspects are integrally arrayed. The optical deflection module according to claim 12 may be configured such that the input sides of a plurality of optical deflection elements arranged in an array are “coupled by a coupling optical waveguide”.

  A light source such as a semiconductor laser having an output end on the light input unit side and / or the light output unit side, a planar lens, or the like for one or more of the plurality of light deflection elements in the light deflection module according to claim 11 or 12 A refracting optical system, a reflecting surface, and the like can be provided. Further, the deflecting unit can be provided in common for each light deflecting element or for a plurality of light deflecting elements arranged in an array.

Here, the principle of light beam deflection will be described with reference to FIG. 1 using a “light deflection element known in the art” as an example, and the improvements made by the present invention will also be described.
In FIG. 1, reference numeral 1 denotes a conventionally known “light deflection element”. The optical deflection element 1 has a configuration in which a plurality of optical waveguides are formed on a substrate and “electrodes for applying an electric field to each optical waveguide” are formed.

In the example shown in FIG. 1, four optical waveguides are formed in close proximity to each other, and reference numerals 2A, 2B, 2C, and 2D indicate “cores” of these four optical waveguides.
The four optical waveguides are formed in a straight line with “all the same length”, the cores 2A to 2D are formed of “the same material having an electro-optic effect”, and have the same refractive index.

  On the other hand, the electrodes indicated by reference numerals 3A, 3B, 3C, and 3D are strip-shaped and are formed so as to cover “parts in the length direction” of the core portions 2A, 2B, 2C, and 2D of the corresponding optical waveguides. . The lengths of the electrodes 3A to 3D are different from each other, and the length (distance at which the electric field acts on the core portion) decreases from the electrodes 3A to 3D by “equal difference due to LP difference”. The counter electrode for the electrodes 3A to 3D is formed as one surface in common with the electrodes 3A to 3D on the opposite side to the electrodes 3A to 3D through the optical waveguide array.

  From the light input section on the left side of FIG. 1, “lights whose phases are aligned in the traveling direction” are simultaneously incident on the cores 2 </ b> A to 2 </ b> D of the optical waveguide through a light distribution section (not shown). At this time, when "the electric field by the electrodes 3A to 3D is not applied to the optical waveguide", the guided light propagates through each optical waveguide at "the same speed" and is emitted as a spherical wave having the same phase from the right light output portion in the figure. However, the wave front portions having the same phase strengthen each other and propagate as “a plane wave toward the right side of the figure”.

  Next, when an electric field is applied to the optical waveguide by the electrodes 3 </ b> A to 3 </ b> D, the “refractive index of the core portion where the electric field is applied” increases due to the electro-optic effect of the core. Assuming that the refractive index of the medium through which light propagates is n, the propagation speed of light in the medium: V is “V = C / n” with respect to the speed of light in vacuum: C. The light propagation speed is slow in the “part where the refractive index increases due to the action of the electric field” in the cores 2A to 2D of the optical waveguide.

  In the cores 2 </ b> A to 2 </ b> D, the “magnifying electric field magnitudes” are equal to each other, and the refractive index change due to the electro-optic effect: dn is also equal to each other. Propagation speed of guided light in the core portion where the rate is changed: V ′ is equal to “V ′ = C / (n + dn)”. However, the longer the distance that the electric field acts, the longer the “time to propagate this distance”. become longer.

  The “distance for applying an electric field” to the core decreases in the order of the electrodes 3A to 3D. Accordingly, when the light incident on the core portions 2A to 2D in the same phase is subjected to an electric field on the “core portion corresponding to the length of the electrode” by the electrodes 3A to 3D, from the core 2D side to the core 2A side. The “time to guide the core” gradually increases toward the core, and the wave fronts having the same phase are separated in the length direction of the core.

  For example, when the wavefront of the light guided through the core 2A reaches the light output unit, the light having the same phase as the wavefront has already been emitted from the light output unit in the cores 2B to 2D. The “distance from the light output portion” of the in-phase wavefront in “increases in an equal manner” in the order of the cores 2A to 2D.

  For this reason, the spherical waves emitted from the cores 2A to 2D are “in-phase wavefront portions are intensified”, and as shown in the drawing, a plane wave (“deflected light beam”) deflected at a deflection angle θ is obtained. .

In the structure of the optical deflection element in FIG. 1, the refractive index change amount at the phase modulation portion (the portion to which the electric field is applied): dn, the difference in the length of the region on which the electric field acts: LP, The deflection angle of the deflected light beam: θ
θ∝dn · LP / d (A)
Thus, it is proportional to “dn · LP / d”.
As apparent from the equation (A), as a method of increasing the deflection angle: θ, the refractive index change amount: dn and / or the length difference of the phase modulation portion: LP is increased, or the output optical waveguide There is a method of reducing the core center interval d.

  First, considering the case of increasing the LP, when the number of optical waveguides formed in the optical deflection element is m, the length of the electrode on which the electric field should be applied is “shortest” and “longest”. Therefore, the longest electrode is longer than the shortest electrode by “LP (m−1)”. As described above, the plurality of optical waveguides formed in the optical deflecting element must have the same length. Therefore, when the LP is increased, each of the optical waveguides increases as “LP · (m−1)” increases. The length also increases, and the optical deflection element eventually becomes larger.

  Next, in the method of increasing the refractive index change: dn, there is a restriction on the electro-optic constant of a material having an electro-optic effect. For example, in an optical crystal having an electro-optic effect such as lithium niobate, “the maximum refractive index change due to the electro-optic effect is generally about 0.001”. Although materials that give a larger refractive index change are known, they are difficult to obtain and the cost of the materials themselves increases.

In the case of the method of reducing the distance between adjacent waveguides in the optical output portion: d, it is difficult to bring the optical waveguides closer to each other than the width of the core. Talk "occurs. In the conventional “optical waveguide using the electro-optic effect”, it was not possible to “set the distance between adjacent optical waveguides to about 10 μm or less” in order to suppress the occurrence of crosstalk.
The optical deflecting element of the present invention realizes downsizing of the element and a large deflection angle with the above-described configuration. In order to achieve this problem, a “high refractive index difference optical waveguide” is used as the optical waveguide. As will be described later, the high refractive index difference waveguide has a large “effect of confining light (guided light) in the core”, and the guided light is difficult to leak out of the core. Due to such a property, the “core diameter can be made much smaller than the conventional one”, and “the distance between the optical waveguides: d” can be made much smaller than the conventional one at the light output portion.

  Also, even if the core of the optical waveguide is thinned and “the optical waveguide is folded two-dimensionally or three-dimensionally”, if the bent portion for folding is “smooth bend with finite curvature”, As long as the curvature of the bent portion does not become extremely large, it is possible to substantially prevent “leakage of guided light” from the bent portion.

  Therefore, by folding the optical waveguide two-dimensionally or three-dimensionally to form a “bent optical waveguide portion”, the “optical waveguide length necessary for realizing a large deflection angle” can be secured in this bent optical waveguide portion. Since a long optical waveguide can be disposed in a “small region”, the optical waveguide array can be configured compactly even though the optical waveguide is long, a large deflection angle can be realized, and the optical deflection element can be miniaturized.

Here, the high refractive index difference optical waveguide and its characteristics will be described.
FIG. 2 illustrates the state of the “cross section perpendicular to the optical waveguide” in the high refractive index difference optical waveguide. In FIG. 2, reference numeral 101 denotes a substrate, reference numeral 102 denotes a core, and reference numeral 103 denotes a clad. The right diagram in FIG. 2 shows the refractive index distribution in the “A1-A2 cross section” in the left diagram. The core 102 has a refractive index: n ₁ , and the cladding 103 has a refractive index: n ₂ . In this example, the substrate 101 and cladding 103 are the same material, therefore, the substrate 101 may refractive index: is _{n 2.}

The core 102 is surrounded by the clad 103. The magnitude relationship between the refractive indexes of the core 102 and the clad 103 is “n ₁ > n ₂ ”, and a material that increases the difference between these refractive indexes is selected. When the difference in refractive index between the core and the clad increases, the “guided light confinement” in the core becomes stronger, and a “curved optical waveguide portion” that does not substantially leak guided light can be formed.

  The clad 103 is not necessarily “necessary to cover the core 102 with the same material”. A plurality of “materials having a refractive index lower than that of the core” may be used, and air may be used as the cladding. FIG. 2 shows a “rectangular core cross section” from the viewpoint of ease of manufacture, but the cross sectional shape may be circular or polygonal.

  When the “high refractive index difference optical waveguide” is used, the guided light is confined very strongly inside the core, so that the cross-sectional area of the optical waveguide can be reduced, and the “interval between optical waveguides” can be reduced. In addition, there is almost no “loss due to waveguide light leakage at the bent portion (hereinafter referred to as“ bending loss ”)” even in a bent portion with a small radius of curvature of the order of μm, and flexible optical waveguide wiring is possible. A compact optical waveguide circuit can be configured.

The “high refractive index difference optical waveguide” is an optical waveguide in which a core and a clad are formed by combining materials having an extremely large refractive index difference.
As described above, relative refractive index difference: Δ, which is a “parameter representing the refractive index difference between the core and the clad”, is defined by the following equation with respect to the refractive index of the core: n ₁ and the refractive index of the clad: n ₂ .

_{^{Δ = (n 1 2 -n 2}} 2) / 2n 1 2 formula (B)
The relative refractive index difference: Δ can be used as “a guideline representing the performance of the optical waveguide”, and the larger this value: Δ, the more strongly the guided light is “confined in the core”.
In a “conventional optical waveguide such as an optical fiber made of quartz or an optical waveguide formed by lithium diffusion in lithium niobate”, the relative refractive index difference: Δ is 1% or less, but the high refractive index difference light In the waveguide, the relative refractive index difference: Δ can be 10% or more.

  For example, when the refractive index of the core is 2.2 and the refractive index of the cladding is 1.45, the relative refractive index difference: Δ is 28%, which is an extremely large value as compared with a normal optical waveguide. As a material having such a refractive index configuration, a “lithium niobate single crystal material having an electro-optic effect” can be used for the core, and a “glass structural material such as quartz” can be used for the cladding.

  FIG. 3 shows a simulation result in which the relationship between the core size (horizontal axis: μm unit) of the high refractive index difference optical waveguide and the equivalent refractive index (vertical axis) is obtained. The simulation was performed using the “three-dimensional light beam propagation method”. This is a simulation result in which the refractive index of the core is 2.2, the refractive index of the cladding is 1.45, the cross-sectional shape of the core is a square shape (Core width = Core height), and the wavelength of the guided light is 850 nm.

  As the core width (horizontal axis) increases, the equivalent refractive index of “0th-order mode, which is propagating light having an electric field peak in the center” increases. The “next mode” begins to exist. The “width in which only the 0th-order mode exists” can be used as a single mode propagation region, and the “single mode region” may be used to form a wavefront in which interference between different modes does not occur.

The maximum value of the waveguide width giving the single mode region is the maximum core width of the high refractive index difference optical waveguide used in the optical deflection element of the present invention. In this simulation, the maximum core width is calculated to be 440 nm, and from this, an extremely thin optical waveguide called “submicron-wide core cross section” can be used.
In the “conventional optical waveguide having a relative refractive index difference: Δ of about 1%”, the core width for providing a single mode needs to be about several μm to 10 μm. In contrast, it can be seen that the submicron core width of the high refractive index difference optical waveguide is extremely small. In the optical deflection element of the present invention, by using the high refractive index difference optical waveguide, “the distance between adjacent optical waveguides can be further narrowed compared with the case of using the conventional optical waveguide”.

  FIG. 4 shows a simulation result regarding the above-mentioned “bending loss” with respect to the high refractive index difference optical waveguide. In this simulation, calculation was performed using the “three-dimensional time domain difference (FDTD) method”. For an optical waveguide having a “square core cross section” having a core refractive index of 2.2, a cladding refractive index of 1.45, and a side length of 0.4 μm (w = h = 400 nm in the figure). On the other hand, calculation was performed assuming that light having a wavelength of 850 nm is guided. In FIG. 4, the horizontal axis represents “curvature radius” and the vertical axis represents “loss”.

  A TM mode ("TMmode" in the figure) having an electric field perpendicular to the substrate surface is also applied to a "TE mode (" TEmode "in the figure)" having an electric field parallel to the substrate surface (surface on which the clad is formed). ")", When the radius of curvature is 3 μm or more, the “bending loss” is 0.1 dB or less. Therefore, by using a high refractive index difference optical waveguide, the “curvature radius of the bent portion of the bent optical waveguide portion” can be reduced to several μm without substantially generating a bending loss.

  In the conventional optical waveguide, the “curvature radius with negligible bending loss” is on the order of several millimeters to several centimeters. Therefore, the optical deflection element of the present invention has a “radius of curvature less than 1/1000” with respect to the conventional optical waveguide. A bent optical waveguide portion can be formed. That is, in the optical deflection element of the present invention, the “long optical waveguide” necessary for realizing a large deflection angle is a “bent optical waveguide portion” in which the optical waveguide is folded two-dimensionally or three-dimensionally. Therefore, an extremely compact optical waveguide array can be realized.

The high refractive index difference optical waveguide also has a feature that “the cross-sectional area of the waveguide providing a single mode is extremely small”.
FIG. 5 shows the result of a simulation for determining the relationship between the relative refractive index difference: Δ (horizontal axis) and the “value obtained by normalizing the width of the core having a square cross-sectional shape with the wavelength (vertical axis)”. When the core width normalized by the wavelength (vertical axis) is less than or equal to the wavelength, the “core width normalized by wavelength” varies greatly logarithmically with respect to the relative refractive index difference: Δ (horizontal axis). . That is, the high refractive index difference optical waveguide can be configured as “an optical waveguide having a core having a width comparable to that of a light wavelength in vacuum: λ”.

As shown in FIG. 5, the core cross-sectional area: S of the high refractive index difference optical waveguide is preferably “(1.5λ) ² or less” with respect to the wavelength: λ when converted into a square shape, Preferably, it is (1.0λ) ² or less. When (1.0λ) is ² or less, the relative refractive index difference: Δ is 8% or more.

  Thus, by using a high refractive index difference optical waveguide for the optical deflecting element, the core cross-sectional area of the optical waveguide can be reduced, so that adjacent cores can be brought close to an interval of about the wavelength, and the bent optical waveguide portion It is also possible to reduce the “curvature radius of the bent portion” to the order of μm, so that the optical waveguide array can be made compact by free optical waveguide wiring.

The high refractive index difference optical waveguide in the optical deflection element of the present invention is formed of “a material having at least a core having an electro-optic effect” as described above.
As a material having an electro-optic effect, the above-mentioned “lithium niobate” can be cited as a representative example, but other “materials having a large non-linear optical coefficient” can also be used. In addition to optical crystals, semiconductors and organic materials Etc. can be used. Typical nonlinear optical materials include optical crystals such as lithium niobate and titanium niobate, KTP, KTN, KDP, ADP, and SBN, semiconductors such as GaAs, InAs, InSb, GaSb, and ZnO, or PZT, PZLT, and the like. Ceramic molecules, azo dyes, stilbenzene dyes, organic molecules such as dust, organic crystals, and the like can be used. These are examples, and the material is not limited.

  As described above, according to the present invention, a compact optical deflection element having a large deflection angle can be realized. An optical deflection module capable of “deflecting the light beam with a large deflection angle” can be realized using the optical deflection element. The optical deflecting element / optical deflecting module of the present invention is capable of deflecting light beams at a high speed when used in laser printers, image generating apparatuses, and the like. High performance such as fine drawing becomes possible. Further, the degree of freedom of phase change of the guided light can be increased, and an image forming apparatus and optical modeling that can easily perform image control at high speed are possible.

Hereinafter, embodiments will be described.
FIG. 6 schematically shows a basic form of implementation of the optical deflection element.
On the substrate 110, an optical input unit 111, an optical distribution unit 112, an optical waveguide array 113, and an optical output unit 114 are formed. “Linear portions” other than the light distribution portion 112 indicate the core of the optical waveguide. The cross-sectional shape of the waveguide is, for example, as shown in FIG. The light input to the light input unit 111 is distributed to each waveguide of the optical waveguide array 113 by the light distribution unit 112.

  The optical waveguide array 113 is a high refractive index difference optical waveguide (hereinafter also simply referred to as “optical waveguide”) formed of a material having a different core and clad, and at least the core is formed of a material having an electro-optic effect. . In the figure, “four optical waveguides (having cores 116, 117, 118, and 119)” are shown, but “the number of optical waveguides arranged in an array” can be appropriately set according to the performance of the optical deflection element. In the example shown in the figure, the input light is distributed and guided to four cores 116 to 119 by the light distribution unit 112. The clad surrounds the four cores in common.

  Each of the optical waveguides constituting the optical waveguide array is given a reference symbol representing the curved optical waveguide portion 115 having a curvature (“one curved optical waveguide portion” for the sake of avoiding the complexity of the drawing). The same is true), and a “phase modulation structure” is set in a region including these bent optical waveguide portions.

  The “total waveguide length” of the optical waveguides constituting the optical waveguide array 113 is the same for all the optical waveguides, but the length for applying phase modulation (the length for applying an electric field for changing the refractive index due to the electro-optic effect). ) Differs for each optical waveguide. The configuration of the control electrode is adjusted as a method of changing the “optical waveguide length of the portion to which phase modulation is applied” for each optical waveguide.

  The control electrode is formed so as to “pinch the optical waveguide array 113” in a direction orthogonal to the drawing, and an electrode (referred to as a “lower electrode”) formed on the substrate surface constitutes the optical waveguide array 113. This is a single-layer metal film shared by all optical waveguides. The “upper electrode” sandwiching the optical waveguide array 113 together with the lower electrode is divided into four electrode portions 121, 122, 123, 124 as shown in the figure.

  Of these electrode portions 121, 122, 123, and 124, the electrode portion 121 is arranged so that an electric field can be applied to “four bent optical waveguide portions” of the optical waveguide having the core 116. The electrode 123 is arranged so that an electric field can be applied to the “three bent optical waveguide portions” of the optical waveguide having 117, and the electrode 123 acts on the “two bent optical waveguide portions” of the optical waveguide having the core 118. The electrode 124 is arranged so that an electric field can be applied to “one bent optical waveguide portion” of the optical waveguide having the core 119.

  Thus, the “region where the electric field acts on the optical waveguide” is set for each optical waveguide in the region where the bent optical waveguide portion is formed. Assuming that the length of one bent optical waveguide portion 115 is the aforementioned “parameter representing the difference in length of the phase modulation portion: LP”, the electrode portions 121, 122, The field action lengths by 123 and 124 are reduced by LP, such as 4LP, 3LP, 2LP, and LP.

  When an electric field is applied to the “corresponding bent optical waveguide part core” by these electrode parts 121 to 124, the refractive index of the core part to which the electric field is applied (as described above, at least the core of the optical waveguide is electrically It is made of a material having an optical effect.) "Changes slightly. Due to this change, a phase difference is generated in the wavefronts of the light propagating through the respective optical waveguides, and the wavefronts of the light emitted from the respective optical waveguides are shifted to deflect the light beam as the output light.

In the optical output array 114, the optical waveguide array outputs light by making the optical waveguide interval close to the distance d. The output light proceeds in the direction: a when the phase difference due to the action of the electric field is not generated. When the electric field is applied by applying a voltage, the output light is “deflection angle with respect to the direction: a: "Inclined by θ" direction: go to b.
The deflection angle: θ is determined according to “dn · LP / d” as described above.

Here, a “specific numerical example” for the embodiment shown in FIG. 6 is given and compared with the conventional example.
In the conventional optical deflecting element 1 shown in FIG. 1, the interval d between adjacent optical waveguides is “must be about the core width as the gap between the cores” in order to prevent interference between the optical waveguides. Met. The core width of the conventional optical waveguide is 10 μm, whereas the core width of the high refractive index difference optical waveguide is 0.5 μm. Therefore, in the optical waveguide array used for the optical deflection element of the present invention, the interval between the optical waveguides is The optical waveguide can be wired by reducing it to “twentieth of the conventional one”. Thus, by narrowing the distance d between the optical waveguides in the light output portion, a large deflection angle can be obtained as is apparent from the equation (A).

Based on the equation (A), the optical waveguide array used in the above embodiment and the conventional optical waveguide array are numerically compared with respect to the deflection angle. When the refractive index change amount of the core due to the action of the electric field is dn = 0.001 and the length difference of the phase modulation portion is LP = 1000 μm, the distance between the conventional optical waveguide arrays (the distance between the centers of adjacent cores): d = 20 μm, the deflection angle: θ is calculated as 2.8 degrees.
In the optical deflector of the embodiment of FIG. 6, the refractive index change amount: dn = 0.001, the phase modulation portion length difference: LP = 1000 μm, and the interval between adjacent optical waveguides (between the centers of adjacent cores) Distance): When d is 1 μm, 45 degrees is calculated as the deflection angle: θ. That is, by using the optical deflecting element of the present invention, a “much larger deflection angle than the conventional one” can be realized.

  Difference in length of phase modulation portion between adjacent optical waveguides: Even when LP is reduced to 500 μm, the deflection angle of the optical deflection element of the present invention is 27 degrees. Deflection angle: a deflection angle substantially corresponding to 60 degrees ”.

  When lithium niobate is used as a material having an electro-optic effect, the amount of change in the refractive index is 0.0001 to 0.001, and as an example, if dn = 0.005, then Lp = 1000 μm, The deflection angle of the emitted light is 27 degrees, and the above performance can be maintained by “adjusting the length of the optical waveguide”.

As described above, the light deflection element of the present invention can reduce the “distance between adjacent optical waveguides: d” in the light output portion, and thus can realize a large deflection angle.
In order to reduce the size of the optical deflection element, it is necessary to make the optical waveguide wiring of the phase modulation structure portion compact. However, the high refractive index difference waveguide used in the optical waveguide array of the optical deflection element of the present invention is substantially Without causing bending loss, the radius of curvature at the bent portion for folding can be made extremely small, such as about 10 μm, and the folded optical waveguide portions are spaced apart by about 1 μm as “intervals that do not interfere with each other”. When the optical waveguide is folded in two dimensions, an optical waveguide having a length of 1000 μm (1 mm) can be accommodated in a size of “several tens of μm square”.

  Assuming that the number of optical waveguides constituting the optical waveguide array is N and the difference in the length of the phase modulation portion of the adjacent optical waveguide in the phase modulation structure is LP, the difference between the maximum and minimum lengths of the phase modulation portion However, in the optical deflection element of the present invention, a long waveguide can be accommodated in a small size by folding the optical waveguide to form a “bent waveguide portion”.

  For example, when a length of a bent optical waveguide portion: LP = 1000 μm is wound around a 50 μm square with a radius of curvature of 10 μm (four corners having a radius of 10 μm), 10 optical waveguides are “500 μm”. By arranging the optical waveguide wiring appropriately, ten optical waveguides with a length of 10 × 1000 μm = 10 mm can be accommodated in the area area of “several 100 μm square”. Even if these components are taken into consideration, the entire optical waveguide array can be formed within 1 mm square.

If such a configuration is to be realized by using a conventionally known “normal optical waveguide”, the size of the optical waveguide array becomes “cm ² order”.
In other words, the optical deflection element of the present invention can reduce the size of the portion constituting the optical waveguide array to “1/100 or less that of a conventional optical waveguide array” in terms of area. Advantages and device stability can be realized at the same time. In FIG. 6, the bent waveguide portion 115 is “circular” for simplicity of illustration, but the optical waveguide wiring pattern of the bent waveguide portion satisfies the condition that “substantial bending loss does not occur”. Can be set arbitrarily.

Another embodiment will be described with reference to FIG.
In this embodiment, lithium niobate which is an optical crystal is used as the “material having an electro-optic effect”. The material substrate used to “form the core of the optical waveguide array” is a “z-cut substrate whose optical crystal axis faces the z direction (direction perpendicular to the drawing)”, and the cores 200A, 200B, 200C, and 200D are the z-cut. It is formed by patterning the substrate.

  7A shows a plan view, and FIG. 7B shows a side view. An optical input unit 202 and an optical distribution unit 203 are formed on the substrate 201, and the optical distribution unit 203 is connected to the optical waveguide array 204. The optical waveguides other than the light distribution unit 203 are formed of high refractive index difference optical waveguides having lithium niobate as a core and quartz glass as a cladding.

  The optical waveguide array is formed by four optical waveguides (the cores of these optical waveguides are denoted by reference numerals 200A, 200B, 200C, and 200D), and each optical waveguide is bent and phase-modulated by the optical waveguide portion 205. ing. That is, each optical waveguide has four bent optical waveguide portions 205, and the arrangement of a total of 16 bent optical waveguide portions forms a “phase modulation structure”.

In the example of FIG. 7, the optical waveguide array is composed of four optical waveguides. However, this is an example, and the number of optical waveguides is not limited. The number of optical waveguides constituting the optical waveguide array may be two or more, and the number of optical waveguides can be adjusted according to the characteristics required for the optical deflection element.
In the example of FIG. 7, the length of the optical waveguide in one bent optical waveguide portion 205 is set to “difference of“ length to give phase modulation ”between adjacent optical waveguides: LP.

The bent waveguide portion 205 has a “shape folded into a quadrangular shape”.
When a bent optical waveguide portion having a bending radius of about 10 μm for folding is used, a “length: several mm optical waveguide” can be folded and arranged within a size: several tens of μm square. In this way, the “optical waveguide having a size of mm on the order of a straight line” can be miniaturized to the order of μm.

The light guided through the optical waveguide array passes through the light output unit 206 and is output as output light from the output end 207. Since each optical waveguide is a high refractive index difference optical waveguide, the interval between adjacent optical waveguides at the output end 207 (the distance between the centers of adjacent cores) can be reduced to about 1 μm. In order to prevent the optical output unit 206 from becoming large while realizing the close arrangement of the optical waveguides at the output end 207, it is necessary to prevent each optical waveguide located in the optical output unit 206 from extending in the horizontal direction in the drawing. However, since the optical waveguide can be bent and wired with a curvature radius of about 10 μm, it can be arranged so that the size of the light output portion 206 does not greatly increase the overall size.
Control electrodes 208 and 209 are formed for the phase modulation structure, and electrical control is possible.

As shown in FIG. 7B, a lower electrode 209 is formed below the lower cladding layer 210 of the high refractive index difference optical waveguide, an upper electrode 208 is formed on the upper cladding layer 211, and “z” is formed on the core 209. "Axial voltage (electric field)" can be applied.
The lower electrode 209 is a single metal film, but the upper electrode 208 is divided into four electrode portions 208A, 208B, 208C, and 208D as shown in FIG. In order not to cause light loss due to the electrode structure, it is necessary to provide a gap between the upper electrode and the lower electrode. However, since the size of the core of the optical waveguide is submicron, voltage application at intervals of several μm is sufficient. A large electric field EF can be applied even with a voltage.

  In order to give a phase difference between the guided light beams guided through the respective optical waveguides, the structure applies a difference in the voltage application region length to each optical waveguide. As shown in FIG. 7A, the cores 200A and 200B , 200C and 200D, the size of the electrode portions 200A to 200D is made different for each optical waveguide, and the electrode portion 208A is “four bent optical waveguide portions (FIG. 7A) with respect to the core 200A. Then, the four bent optical waveguide portions in the core 200A) are covered, and a voltage can be applied to these four bent optical waveguide portions.

  For the core 200B, the electrode portion 208 covers “three bent optical waveguide portions (the three bent optical waveguides on the left side of the core 200B in FIG. 7A)”, and these three bent optical waveguides. A voltage can be applied to the portion. For the core 200C, the control electrode 208 covers “two bent optical waveguide portions (the two bent optical waveguide portions on the left side of the core 200C in FIG. 7A)”, and these two bent optical waveguide portions are covered. A voltage can be applied to the waveguide.

  For the core 200D, the control electrode 208 covers “one bent optical waveguide portion (one bent optical waveguide portion on the left side of the core 200D in FIG. 7A)” and this one bent optical waveguide. A voltage can be applied to the waveguide portion. In this manner, by “giving a phase difference between guided light” in each optical waveguide, it is possible to output a light beam deflected from the output end 207.

  In the example shown in FIG. 7, the control electrodes are formed for all the optical waveguides of the optical waveguide array. However, “the electrodes are not formed” in that a phase difference is given to the guided light between the optical waveguides. An optical waveguide array (an optical waveguide that is not affected by an electric field) may be included in the optical waveguide array.

  The wiring and arrangement of the optical waveguide can be set more freely than the conventional optical waveguide depending on the difference in the electric field action length of the optical waveguide in the phase modulation structure: LP and the shape of the control electrode. It can be set flexibly according to the application.

  Further, by forming a “dummy optical waveguide” outside the optical waveguide array, it is possible to configure an optical waveguide array that suppresses variations in the optical waveguide during manufacture.

FIG. 8 schematically shows another embodiment.
As a “material having an electro-optic effect”, lithium niobate, which is an optical crystal, is used for the “core of the optical waveguide”. In this embodiment, the optical crystal axis of “lithium niobate” constituting the core is in the x-axis direction (upward in the drawing). An optical input unit 222 and an optical distribution unit 223 are formed on the substrate 221, and the optical distribution unit 223 is connected to the optical waveguide array 224. The optical waveguide array 224 includes four optical waveguides 224A, 224B, 224C, and 224D. These optical waveguides are “high refractive index difference optical waveguides”.

  The optical waveguides 224A to 224D are “folded so as to meander” as shown in the figure to form a bent optical waveguide portion, and form a phase modulation structure. The control electrode for applying an electric field to the phase modulation structure includes a first electrode 226 and a comb electrode EP6 connected to the first electrode 226, and a second electrode 227 and a comb electrode EP7 connected to the first electrode 226. By “crossing fingers”, a voltage can be applied to each bent optical waveguide portion. Each of the optical waveguides 224 </ b> A to 224 </ b> D reaches the output end 229 through the light output unit 228. The light guided through the optical waveguide array 224 is output from the output end 229.

Since the optical crystal axis of lithium niobate forming the core of each optical waveguide is parallel to the x-axis direction (vertical direction in the figure), the electric field needs to be applied in the x direction parallel to the surface of the substrate 221. For this purpose, as shown in FIG. 8, the comb electrodes EP6 and EP7 of the first and second electrodes constituting the control electrode are “bending the bent optical waveguide portion in a plane parallel to the substrate 221”. The first electrode 226 and the second electrode 227 apply different voltages to cause an electric field in the x direction to act on each optical waveguide.
As shown in FIG. 8, the “length of the optical waveguide” sandwiched by the intersecting portions of the comb-teeth electrodes gradually decreases from the optical waveguide 224A toward the optical waveguide 224D by the aforementioned length: LP.

  FIG. 9 is a diagram for explaining two methods of voltage application for applying an electric field to the optical waveguide in the embodiment shown in FIG. 8, and shows a cross-sectional state of the optical waveguide. FIG. 9A shows a method in which comb-shaped electrodes 901 and 902 are formed on the upper portion of the clad 904 to apply an electric field to the core 903, and FIG. 9B shows the comb-shaped electrodes 905 and 906 connected to the clad 904. A method is shown in which an electric field is applied to the core 903 by being formed so as to be inserted into the inside. Comb electrodes 901, 902, 905, and 906 in FIG. 9 are portions that sandwich the optical waveguide in FIG.

  In the voltage application method of FIG. 9A, the comb electrodes 901 and 902 can be formed relatively easily, but the “electric field effect” on the core 903 may become unstable. In the voltage application method of FIG. 9B, formation of the cores 905 and 906 is somewhat difficult as compared with FIG. 9A, but the action of the electric field on the core 903 is stable. These voltage application methods can be appropriately selected depending on the performance required for the optical deflection element.

  Since the waveguide width of the optical waveguide is submicron, even if the interdigital electrodes are separated until the influence of the electrodes on the guided light can be ignored, the distance between the electrodes is only a few μm, and low voltage driving is possible. In the embodiment shown in FIGS. 8 and 9, the electrode configuration for “applying an electric field in the x direction” is shown. Can do.

  The entire optical waveguide array including the phase modulation structure can be formed extremely compact by using a bent optical waveguide portion having a small radius of curvature of the bent portion as the phase modulation structure portion shown in FIG. For example, when the optical waveguide having a length of about 1 mm is folded in a meandering manner as shown in FIG. 8 and “bending radius of curvature: 5 μm to“ about 200 μm ””, the bending portion for folding. Are four places, and the width of the folded part (the vertical width in the figure) is 40 μm. When four optical waveguides folded in this way are arrayed at intervals of 10 μm as shown in the figure, the area occupied by the optical waveguides arranged is approximately 190 μm × 200 μm, and four 1 mm optical waveguides are placed in this region. An array can be formed. Waveguide length difference that gives a phase difference to the four waveguides: Even if the LP is arranged at 1 mm, the size of the optical deflection element is only about 1 mm square, which is almost the same as the structure in which the core is formed from the z-cut substrate in FIG. The size can be changed.

Furthermore, by “combining polarization reversal and comb electrodes”, further high-density wiring of the optical waveguide becomes possible.
FIG. 10 shows only one feature of the embodiment in this case. An optical waveguide (which constitutes one of the optical waveguide arrays) having a core portion denoted by reference numeral 231 is folded so as to meander at a bent portion having a curvature radius of about 5 μm to form a “curved optical waveguide portion”. The core 231 of this optical waveguide has its crystal axis direction reversed in polarity by the domain-inverted structure for each adjacent folded portion in the “polarization inversion region” shown in the folded portion. Yes.

  When a comb electrode EP2 connected to the first electrode 232 and a comb electrode EP3 connected to the second electrode 233 are crossed as shown in FIG. The electric field acting on the sandwiched core part is in the opposite direction at the folding parts adjacent to each other, but the polarization inversion structure can make the direction of the crystal axis and the electric field the same, so the amount of refractive index change due to the electric field is the same. Can be.

  As shown in FIG. 10, a “substrate having a domain-inverted structure (used for core formation)” applies a high voltage to a z-cut substrate having a thickness of several millimeters to form a “domain-inverted region having a width of several μm”. It can be formed and sliced at the zx plane. In the current technology, the size of the domain-inverted region that can be formed is limited to several mm square, but the high refractive index difference optical waveguide used in the optical deflecting element of the present invention has a cross-sectional width of submicron and a length: Since an optical waveguide of 1 mm or more can be accommodated in several tens of μm square, a substrate formed by the above process can be used.

FIG. 11 is a diagram for explaining a characteristic part of another embodiment of the optical deflection element.
In this embodiment, an “optical waveguide array” in which four optical waveguides are arranged in four rows from the top to the bottom of the figure is used, and each of the four optical waveguides has four “curved optical waveguide portions (representative). 1 is attached with a reference numeral 501). Therefore, the “phase modulation structure” in the optical waveguide array is configured by a square matrix of 4 × 4 “bent optical waveguide portions 501”.

  The control electrode for applying an electric field to the phase modulation structure is composed of an upper electrode and a lower electrode, and the “lower electrode” (not shown) is the above “4 × 4 pieces of the phase modulation structure part of the optical waveguide array”. It is made common to the entire “square array of bent optical waveguide portions”, and in FIG. 11, it is arranged so as to cover the entire phase modulation structure from the back side of the figure.

  On the other hand, the upper electrode is divided into 4 × 4 16 electrode portions (represented by reference numeral 502), and these electrode portions 502 (each connected to an independent voltage application section). .) Is provided for each of the “4 × 4 bent optical waveguide portions” constituting the phase modulation structure as shown in FIG. 11, and a voltage can be applied independently to each of the bent optical waveguide portions. It is like that.

  As shown in the figure, between the 16 electrode portions 502 and the lower electrode, voltages: V11, V12, V13, V14, V21, V22, V23, V24, V31, V32, V33, V34, V41, V42, V43, V44. Can be applied to the 16 bent optical waveguide portions 502 independently. In this way, “various phase changes” can be given to the wavefronts of the light guided through each of the four optical waveguides, and not only the deflection function for deflecting the output light beam but also the output light is condensed. Or diffracting.

  A modification of the embodiment of FIG. 11 is shown in FIG. In the example of this figure, the optical waveguide arrays 502A to 502D by four optical waveguides are divided into two sets of optical waveguides (a set of optical waveguides 502A and 502B and a set of optical waveguides 502C and 502D). The bent optical waveguide portions of the waveguide (represented by reference numeral 503 as a representative) are arranged so as to alternately enter in the horizontal direction of the figure. The lower electrode is made common to all the bent optical waveguide portions 503, and individual electrode portions in the upper electrode by electrode portions (indicated by reference numeral 504 as one representative) divided for each bent optical waveguide portion. As shown in the figure, voltage application units for applying a voltage to the reference numeral 504 are arranged in the longitudinal direction of the optical waveguide array (the horizontal direction in the figure), and the above voltages: V11, V12, V13, V14, V21, V22, V23, V24. , V31, V32, V33, V34, V41, V42, V43, and V44 can be applied between the lower electrode. In this way, the length of the electrical wiring between each electrode portion 504 and the corresponding voltage application unit can be made substantially the same.

  11 and 12, the direction of the electric field applied to the bent optical waveguide portion is the z direction (direction orthogonal to the drawings). However, as in the examples shown in FIGS. In the case of applying an electric field, an electric field can be individually applied to each bent optical waveguide portion. Two examples of such cases are shown in FIG.

In FIGS. 13A and 13B, reference numerals LG1 and LG2 each exemplify one of the optical waveguides constituting the optical waveguide array. In this optical waveguide, four bent optical waveguide portions formed by folding the optical waveguide so as to meander are arranged in the horizontal direction of the drawing.
FIG. 13A shows a case of “wirings connecting bent optical waveguide portions 5031 to 5034 having the same shape”, and FIG. 13B shows an “excessive combination of bent optical waveguide portions 5035 to 5038 having a symmetrical structure. An optical waveguide structure that can eliminate the wiring portion is shown. The voltage is applied by combining comb electrodes as shown in the figure (represented by symbols EP + and EP− for one representative combination). In both cases (a) and (b), since the “length of the optical waveguide portion on which the electric field acts” is the same, the same performance can be obtained, and voltage application to each bent optical waveguide portion is performed independently. Thus, various wavefronts can be formed in the output light.

  Since the high refractive index difference optical waveguide constituting the optical waveguide array used in the optical deflection element of the present invention has a very small cross-sectional area of the core, if such an optical waveguide is also used in the optical input section, highly efficient optical input Is difficult. When light is input from an optical waveguide such as an optical fiber, the "method of increasing the cross-sectional area of the core of the optical input unit at the input end and gradually decreasing it in the waveguide direction" can be used. When it is necessary to input a laser beam or the like propagating through the optical waveguide of the optical input section with high efficiency, it is difficult to input with high efficiency only by the above method.

FIG. 14 is an explanatory diagram illustrating an “embodiment in which an optical coupling structure is provided in an optical input unit” for realizing highly efficient optical input.
A portion denoted by reference numeral 601 is a “portion from the light distribution portion to the light output portion of the light deflection element”, and has the configuration as in each of the embodiments described above. The light input portion of the light deflection element has a light coupling structure 603. The light applied to the optical coupling structure 603 is guided in the optical coupling structure 603 and converted in its traveling direction by reflection, and is coupled to the input section 602 of the optical waveguide having a small cross-sectional area.

  As shown in FIG. 14, by gradually reducing the “cross-sectional area size” of the optical waveguides constituting the optical coupling structure 603 in the waveguide direction, input light can be coupled to the input unit 602 with high efficiency.

  A specific structure is shown in FIG. FIG. 15A shows a structure in which the grating structure GL is formed on the upper clad 151 and the core 150 in the optical waveguide formed on the substrate BS. The traveling direction of the input light is changed by the grating structure GL. Enter 150. Reference numeral 152 denotes a lower cladding. FIG. 15B is a diagram in which an optical coupling structure is configured by the prism coupler PC. The light input to the prism coupler PC is changed in traveling direction by the prism coupler PC and is optically coupled to the core 150 of the optical waveguide with high efficiency.

  In the high refractive index difference optical waveguide used in the optical deflection element of the present invention, the refractive index of the core is large in order to realize a “large refractive index difference with the cladding”. For this reason, when “light is output from the cross section of the optical waveguide” at the light output portion, reflection is likely to occur at the end face of the core due to the difference in refractive index between the core and the outside, and it is difficult to extract light with high efficiency. In addition, if the refractive index difference between the core and the outside is large, the radiation angle in the direction of the substrate thickness is also large, and the handling of the output light beam tends to be difficult.

FIG. 16 is a diagram showing an embodiment capable of coping with such a problem, and only the characteristic part is illustrated as an explanatory diagram.
In FIG. 16, reference numerals 701 and 701A indicate the cores of the optical waveguide, and reference numeral 702 indicates the cladding.
In order to suppress reflection at the output end face of the core 701, it is sufficient to reduce the difference in refractive index from the outside by reducing the “equivalent refractive index of the optical waveguide”. “Adjusting the equivalent refractive index by adjusting the material” However, it is necessary to construct a sub-micron-width optical waveguide using several different materials.

In the embodiment of FIG. 16, “the mode conversion structure is formed in the core”.
The embodiment of FIG. 16A is an example in which the width of the core 701 in the light output unit is “a structure that narrows in a tapered shape”. With this structure, the “light confinement effect” of the core 701 gradually decreases toward the end of the light output portion, the equivalent refractive index of the optical waveguide gradually decreases, and reflection at the output end face of the core is suppressed. Good output light can be output.

  In the embodiment of FIG. 16 (b), the shape of the light output portion of the core 701A is set as a “tapered waveguide”, and the core width is gradually narrowed toward the output end portion. This is a structure formed as a “core having a certain width”. Also with this structure, it is possible to efficiently extract output light while suppressing reflection by the output end face. Although not shown in FIG. 16, the clad 702 can also realize a light output with higher efficiency by “using a material or structure that eliminates the difference from the refractive index of the outside world”.

FIG. 17 is an explanatory view showing another embodiment of the optical deflection element.
The form and arrangement form of the “curved optical waveguide portion” in the optical waveguide array, and the form of the control electrode are the same as in the embodiment of FIG. 7, and therefore, the same reference numerals as those in FIG. The description according to FIG. 7 is used.

  In order to “closest” each optical waveguide in the optical waveguide array 204 at the end of the light output unit while narrowing the distance between each other in the light output unit, it is necessary to bend the optical waveguide smoothly and largely at the light output unit. There is. On the other hand, the plurality of optical waveguides constituting the optical waveguide array must all have “the same waveguide length”. For example, in the case of the form shown in FIG. 6, since the lengths of the optical waveguides 116 to 119 in the light output unit 114 are different, it is necessary to adjust the difference in length between the “other portions in each optical waveguide”. is there.

  In the embodiment of FIG. 17, in order to “equalize the waveguide length” between the optical waveguides, the wiring shapes of the optical waveguides 812 and 813 among the four optical waveguides 811 to 814 are “ By “turning back” to the phase adjustment units 801 and 802, the waveguide lengths of the optical waveguides 812 and 813 are made equal to the waveguide lengths of the optical waveguides 811 and 814. In this way, it is possible to prevent a phase shift from occurring in each guided light guided through the optical waveguides 811 to 814.

  The arrangement positions of the phase adjustment units 801 and 802 are not limited to the positions shown in the drawing, and may be arranged in the middle of each optical waveguide in the optical waveguide array. Further, by forming electrodes 805 and 806 for applying an electric field to each of the phase adjusters 801 and 802 (the counter electrode is a lower electrode), the phase shift may be adjusted by the electro-optic effect.

FIG. 18 is a view showing only another characteristic part of still another embodiment of the optical deflection element.
In this embodiment, the light distribution unit is configured as “one-input multiple-output optical waveguide slab”. The light input from the optical input unit 901 expands the wavefront while being guided through a one-input multiple-output optical waveguide slab 902 connected to the optical input unit 901, and is equally distributed to a plurality of optical waveguides 903. Connected to each core of the waveguide array.
By appropriately adjusting the shape of the optical waveguide slab 902, “loss in the optical distribution unit” can be reduced. In addition, by introducing a reverse taper structure in the connection between the “wavefront extension” of the optical waveguide slab and the equal distribution optical waveguide, it is possible to suppress light loss due to light leaking between the equal distribution optical waveguides. is there.

FIG. 19 is a diagram for explaining an embodiment in which equal distribution of input light is realized by a “branching structure”. By inputting the light input from the optical input unit (left side of the figure) to the optical distribution unit 1001 having a “multi-stage branching structure”, it can be equally distributed to “a plurality of optical waveguides”.
In ordinary optical waveguides, “distribution with low loss” tends to make the structure of the branching part large and it is difficult to reduce the size of the optical distribution part. However, when a multistage branching structure is formed of a high refractive index difference optical waveguide, it is “μm order”. A “branch circuit” can be configured.

  In FIG. 19, two branches are connected to form a multistage branch structure, thereby realizing four branches. If the loss at the branch portion is about 0.1 dB, even if 10 stages are connected, 1 dB can be equally distributed with a very low loss.

FIG. 20 shows a simulation result of “optical loss in the branched structure”.
As a simulation model, a “branching structure formed by a tapered portion and a bent optical waveguide” as shown in FIG. The core has a refractive index of 2.2, the cross-sectional shape is “0.4 μm × 0.4 μm square shape”, the bottom of the core is in contact with the lower clad with a refractive index of 1.45, and the other peripheral surface is refracted. A branched structure model was constructed by setting the radius of curvature of the optical waveguide surrounded by the upper side cladding with a ratio of 1.0 and branched at the tapered portion to 5 μm.
The result of calculating the optical loss for this branched structure model by a three-dimensional FDTD simulation is shown in FIG. The horizontal axis represents “taper length” and the vertical axis represents “optical loss”.

  That is, FIG. 20B shows “excess loss when the taper length is changed”. It can be seen that “excessive loss due to branching is 0.1 dB or less” when the taper length is in the range of 0.5 μm to 1.0 μm. The size of the branched portion is about 20 μm, and an extremely small branch circuit can be realized.

  If this branch circuit is stacked in two stages, four distributions can be made with a size of about 50 μm, and even if four stages are stacked, 16 branches can be made with a size of about 100 μm. Furthermore, the size of the optical deflection element can be reduced by optimizing the bent optical waveguide.

FIG. 21 is a diagram schematically showing an embodiment of an “optical deflection module”.
FIG. 21A is a plan view, and FIG. 21B is a side view.
An optical deflection element 1102 (the configuration is the same as that shown in FIG. 6 and the description relating to FIG. 6 is used for description) and a flat lens 1103 are provided on the support substrate 1101. The light output from the light deflection element 1102 is collected by the flat lens 1103. Here, the planar lens 1103 is shown as an example, but a configuration in which a cylindrical lens, a microlens, or the like is disposed on the support substrate 1101 may be used.

  As shown in FIG. 22, the lens 1103 can be arranged on the same substrate 2200 as the light deflection element 1102. FIG. 22A is a plan view and FIG. 22B is a side view. The lens 1103 can be formed of the same material as the light deflection element 1102 at once, or by applying an organic material or the like and patterning after forming the light deflection element 1102.

FIG. 23 is a diagram schematically showing another embodiment of the “light deflection module”.
This “optical deflection module” includes optical deflection elements 1201, 1202, and 1203 (the configuration of which is the same as that shown in FIG. 6 and the description relating to FIG. 6 is used for description) arranged in parallel on the same plane. The input portions 1204, 1205, and 1206 are optically coupled by a coupling optical waveguide 1207. As the optical deflection elements 1201, 1202, and 1203, the other forms described above can be arbitrarily used.

  With this structure, a plurality of light deflecting elements can be arranged, and light from the same light source can be deflected simultaneously or individually by a plurality of light deflector elements.

FIG. 24 is a diagram schematically showing another embodiment of the “optical deflection module”.
FIG. 24A is a plan view and FIG. 24B is a side view.
In the optical deflection module, a semiconductor laser 1302 (the configuration is the same as that shown in FIG. 6 and the description relating to FIG. 6 is used) and an optical deflection element 1303 are arranged on a support substrate 1301. It has a structure in which the output end and the light input portion of the light deflection element 1303 are arranged close to each other. As the light deflection element 1302, an appropriate element of the above-described embodiment can be used.

With such a structure, the semiconductor laser 1302 and the optical deflection element 1303 can be integrated, and a “small optical deflection module integrated with light sources” can be formed.
Although not shown in FIG. 24, in order to input the input light from the semiconductor laser 1302 with high efficiency, the “light waveguide width and refractive index adjusted structure” of the light input section or the semiconductor laser is radiated. Also, “an arrangement in which the output direction of the semiconductor laser 1302 and the output direction of the light deflecting element 1303 are shifted” so that the light that has not been input to the light input portion does not act as stray light on the output light from the light deflecting element. Good. A control electrode, a control electronic circuit, and the like of the semiconductor laser 1302 can be formed in advance on the support substrate 1301.

  The close arrangement of the semiconductor laser 1302 and the light deflecting element 1303 can be a three-dimensional arrangement as shown in FIG. 25A shows an example in which the semiconductor laser 1302 is disposed close to the upper portion of the optical deflection element 1303, and FIG. 25B shows an example in which the semiconductor laser 1302 is disposed close to the lower portion of the optical deflection element 1303. In either case, the light from the semiconductor laser 1302 is coupled to the light input portion of the light deflection element 1303 by optical coupling.

  The optical deflection module whose embodiment has been described with reference to FIG. 21, FIG. 22, FIG. 24, and FIG. 21 and 22, in the example of FIGS. 21 and 22, the other optical element is “a lens that is provided on the light output side and acts on the output light output from the light deflection element”. 24, 25, the other optical element is a semiconductor laser 1302 having a light output end as a “light source provided on the light input side”.

  The optical deflection module shown in FIG. 23 is an optical deflection module in which a plurality of optical deflection elements according to the present invention are integrally arrayed, and inputs of the plurality of optical deflection elements 1201, 1202, and 1203 that are arrayed. The sides are coupled by a coupling optical waveguide 1207.

  Hereinafter, an embodiment of an optical deflection module having deflection means for deflecting output light from the optical deflection element of the present invention in a direction crossing a deflection plane by the optical deflection element will be described.

  In the optical deflection module shown in FIG. 26, a mechanical drive element 1402 is formed on a support substrate 1401, and an optical deflection element 1403 is formed thereon. The mechanical drive element 1402 can swing in a direction (vertical direction in the figure) perpendicular to a deflection plane (a plane perpendicular to the drawing in the horizontal direction in the figure) of the output light from the light deflection element 1403. Oscillation driving can be performed, thereby enabling three-dimensional light beam deflection of the output light of the light deflection element.

  The optical deflection module shown in FIG. 27 is driven in an oscillating manner by an optical deflection element 1501 and a mechanical drive on a support substrate 1502, as shown in a plan view (a) and a side view (b). A mirror element 1503 is formed to enable three-dimensional light beam scanning.

  In the optical deflection module shown in FIG. 28, an optical deflection element 1601 of the present invention and an acousto-optic element 1603 (having a crystal part AO and an ultrasonic wave sight GN) are arranged on a support substrate 1602 and light. The output light from the deflecting element 1602 is deflected two-dimensionally by the acousto-optic element 1603. In the case of this embodiment, since a mechanical drive element is not used, durability can be improved.

  The optical deflection module whose embodiment is shown in FIGS. 26 to 28 is a high-speed optical beam deflection by the optical deflection element of the present invention that deflects the optical beam by the electro-optic effect, the mechanical drive element 1402, the mirror element 1503, the acoustic By combining with the deflection by the optical element 1603, the light beam can be deflected three-dimensionally. For example, a predetermined two-dimensional surface to be scanned can be optically scanned at high speed and with high definition.

  Also in the case of the optical deflection module shown in FIG. 26 to FIG. 28, another optical element on the optical input unit side and / or the optical output unit side of the optical deflection element, for example, a semiconductor laser as a light source, Needless to say, a lens or the like can be provided.

Hereinafter, an example of a manufacturing method of a “high refractive index difference optical waveguide” that constitutes an optical waveguide array in an optical deflection element will be described by taking the case of the embodiment of FIG. 7 as an example.
First, a lithium niobate substrate and a pedestal substrate are prepared as electro-optic materials. As the base substrate, a substrate such as lithium niobate, glass, quartz, or silicon is used.
Referring to FIG. 7B, the lithium niobate substrate is a “portion that finally becomes the core layer 200” and a “z-cut substrate”. On the surface of this lithium niobate substrate, a quartz layer of a low refractive material that becomes the lower cladding layer 210 and a metal layer that becomes the lower electrode 209 are formed and laminated.

  The metal layer of the films formed in this way is bonded to the surface of the base substrate that becomes the substrate 201. For the bonding, methods such as bonding with an adhesive, heating bonding between wafers, low-temperature bonding using a plasma effect, and normal-temperature bonding can be used as appropriate. In an actual manufacturing example, bonding with an adhesive was used. The free plane of the bonded lithium niobate substrate (z-cut substrate) is “thinned to about the wavelength by polishing” to form a thin film layer. In addition to polishing, a method such as ion slicing can be used for forming the thin film layer.

  The thin film layer of lithium niobate formed in this way is patterned by electron beam lithography and dry etching to form the core shape of the optical waveguide and the parts such as the light input part and the light distribution part. Transfer to the thin film layer by etching. Next, the “high refractive index difference optical waveguide” is formed by embedding the pattern formed by etching with a low refractive index material (quartz or the like) to be the upper cladding layer 211. Processing into the electro-optic material is performed with a focused ion beam, and an optical deflection element can be manufactured by patterning the upper electrode 208 of the control electrode in the optical waveguide portion forming the phase modulation structure.

Finally, with reference to FIG. 29, a simulation related to the optical deflection element according to claim 5 will be described.
FIG. 29A is a diagram for explaining a simulation model in which the optical deflection element according to claim 5 is simplified. In the figure, symbol LG indicates the core of the optical waveguide. As shown in the figure, six cores LG are arranged in parallel at intervals of SP = 800 nm and surrounded by a common cladding CR to form an optical waveguide array. Each of the six cores LG has a “tapered portion that spreads toward the output end” in the light output portion (upper portion in the drawing). This taper portion is a “mode conversion optical waveguide structure” and has a function of suppressing wavefront disturbance. Tapered portion length: TL was 5 μm. Further, the symbol ΔL in the figure is “the difference in the length of the phase modulation portion between adjacent cores (previously“ LP ”)”.

  The simulation was performed using a two-dimensional FDTD (Finite Difference Time Domain) after two-dimensional approximation of the core LG by equivalent refractive index approximation. This simulation is a method of directly differentiating the electromagnetic field and simulating the behavior of the electromagnetic field. Since no approximation is used, a result with a small error can be expected in the simulation of an optical waveguide having a large refractive index difference.

  In the simulation, the wavelength of the guided light in vacuum is 650 nm, the guided mode is TM mode, the width of the core LG is 300 nm, the refractive index is 1.930829 (refractive index when no electric field is applied), the cladding CR The refractive index of air was 1.456700, and the refractive index of air was 1.0.

  Since the deflection angle depends on the optical path length difference, if the loss of the optical waveguide is sufficiently small, it can be handled as an actual device simulation. In the simulation, ΔL was set to a value smaller than the actual value: 20 μm, and the refractive index change: dn was changed in a range of ± 0.015 in order to obtain a desired light beam deflection angle with respect to ΔL.

  When the deflection angle is calculated from the center of the emitted light, as shown in FIG. 29B, when the optical path length difference (= ΔL × dn) shown on the horizontal axis is changed from −0.30 μm to 0.30 μm, It can be seen that the deflection angle (unit: degree) shown on the axis varies from 21 degrees to 18 degrees, and the light beam can be deflected nearly 40 degrees as a whole.

  If the range of ± 0.001 is used as the range of the actual refractive index change: Δn instead of the above refractive index change: ± 0.015, ΔL may be set to ΔL = 300 μm instead of 20 μm . The length of the core portion having such a length can be folded into a “curved optical waveguide portion” with a radius of curvature of about 50 μm as described above in a high refractive index difference optical waveguide, so that a large deflection angle can be obtained. An ultra-compact beam deflector can be configured.

It is a figure for demonstrating the prior art example of the optical deflection element using an optical waveguide array, and the principle of optical beam deflection. It is a figure for demonstrating a high refractive index difference optical waveguide. It is a figure for demonstrating the characteristic of a high refractive index difference optical waveguide. It is a figure for demonstrating the characteristic of a high refractive index difference optical waveguide. It is a figure for demonstrating the characteristic of a high refractive index difference optical waveguide. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating two forms of the electric field effect | action to a core in embodiment of FIG. It is a figure for demonstrating another example of the electric field effect | action to a core. It is a figure for demonstrating another example of the electric field effect | action to a core. It is a figure for demonstrating another example of the electric field effect | action to a core. It is a figure for demonstrating another example of the electric field effect | action to a core. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating one Embodiment of an optical deflection | deviation element. It is a figure for demonstrating one Embodiment of an optical deflection module. It is a figure for demonstrating one Embodiment of an optical deflection module. It is a figure for demonstrating one Embodiment of an optical deflection module. It is a figure for demonstrating one Embodiment of an optical deflection module. It is a figure for demonstrating one Embodiment of an optical deflection module. It is a figure for demonstrating one Embodiment of an optical deflection module. It is a figure for demonstrating one Embodiment of an optical deflection module. It is a figure for demonstrating one Embodiment of an optical deflection module. It is a figure for demonstrating the simulation with respect to invention of Claim 5, and its result.

Explanation of symbols

110 substrates
111 Optical input section
112 Light distributor
113 Optical waveguide array
114 Light output section
116, 117, 118, 119 Core of optical waveguide constituting optical waveguide array 115 Bent optical waveguide formed in optical waveguide 120, 121, 122, 123 Control electrode

Claims (13)

A light input section, a light distribution section, an optical waveguide array, a light output section, and a control electrode are provided on the substrate, and the light input to the light input section is input to the optical waveguide array by the light distribution section. In the optical deflection element that distributes to each of the optical waveguides and gives a phase difference between the optical waveguides to the light guided through the optical waveguide array by the control electrode and emits the light from the optical output unit.
The optical waveguide array is an array arrangement of two or more optical waveguides by a high refractive index difference optical waveguide formed of a material having a different core and clad, and at least the core is formed of a material having an electro-optic effect, and And each optical waveguide has a phase modulation structure having a curved optical waveguide portion having a curvature,
An optical deflecting element characterized in that the control electrode performs phase modulation on the phase modulation structure in the optical waveguide array by applying a phase difference different between the optical waveguides to the guided light by an electro-optic effect. The optical deflection element according to claim 1, wherein
The cross-sectional area of the core of each optical waveguide in the optical waveguide array: S is the propagation light wavelength: λ,
S ≦ (1.5λ) ²
An optical deflecting element satisfying the following condition: The optical deflection element according to claim 1 or 2,
An optical deflecting element, wherein a control electrode is configured to individually apply an electric field to each bent optical waveguide portion with respect to a plurality of bent optical waveguide portions constituting the phase modulation structure of the optical waveguide array. The optical deflection element according to any one of claims 1 to 3,
An optical deflection element, wherein the optical input section has an optical coupling structure. The optical deflection element according to any one of claims 1 to 4,
An optical deflection element having an output end of a light output portion having a mode conversion optical waveguide structure. In the optical deflection element given in any 1 of Claims 1-5,
An optical deflection element, wherein an optical waveguide of an optical output unit has a phase adjustment structure. In the optical deflection element given in any 1 of Claims 1-6,
An optical deflecting element, wherein the optical distribution unit is a single-input multiple-output optical waveguide slab. The optical deflection element according to any one of claims 1 to 7,
An optical deflecting element, wherein the optical distribution unit has a multistage branch structure.   An optical deflection module having another optical element on the light input part side and / or the light output part side of the light deflection element according to any one of claims 1 to 8.   9. A light comprising: the optical deflection element according to claim 1; and deflecting means for deflecting output light from the optical deflection element in a direction intersecting a deflection plane of the optical deflection element. Deflection module. The optical deflection module according to claim 10.
An optical deflection module having another optical element on the optical input unit side and / or optical output unit side of the optical deflection element.   An optical deflection module comprising a plurality of the optical deflection elements according to any one of claims 1 to 8 integrally arranged in an array. The optical deflection module according to claim 12, wherein
An optical deflection module, wherein input sides of a plurality of optical deflection elements arranged in an array are coupled by a coupling optical waveguide.

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