JP2018010118A - Optical deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical deflector requiring low applied voltage, including small number of signal lines and allowing downsizing.SOLUTION: Optical waveguides 13 are grouped into plural output ports 15 consecutively provided in one vertical row arrangement direction. The optical waveguide 13 of each group is provided with a common first electrode 16 for each optical waveguide 13 constituting the group, and electrode parts 17 connected to each other by electrodes of each optical waveguide. The electrode part 17 is longer or shorter in a lengthwise direction of the optical waveguide 13 in the order of the one row arrangement of the output port 15 for each electrode member provided in each optical waveguide 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical deflecting device.

(What is a light deflector?)
In fields such as optical communication and three-dimensional distance measurement, research and development of an optical phased array (for example, Patent Document 1) (hereinafter referred to as “optical deflecting device”) that can sweep light at high speed without mechanical scanning is progressing. It has been.
An optical deflecting device is a device that generates a combined light beam based on a plurality of output lights, and includes a plurality of output ports, and controls a phase distribution of each output light beam output from each output port to thereby obtain a desired light beam. A combined light beam having a deflection direction and convergence / divergence can be obtained.

(Main performance index of optical deflector)
The main performance indicators of the optical deflection apparatus are the number of recognizable synthesized light beams (number of resolution points) and the scanning speed of the synthesized light beam. Here, the number Nr of resolution points is a value obtained by dividing the maximum deflection angle θ _max (the maximum deflection angle at which light can be deflected by the optical deflector) by the minimum spread angle Ψ _min (the minimum value of the spread angle of the combined light beam). Is defined as

The deflection of the light beam of the optical deflector follows the diffraction theory of multiple apertures (similar to the diffraction principle of a linear array antenna). For this reason, when the arrangement interval of each output port is small and the phase difference between the output lights of the adjacent output ports is large, a combined light beam having a large deflection angle is generated.
In the optical deflecting device, when the phase distribution of output light and the arrangement interval of output ports are determined, the minimum light spread angle Ψ _min is determined by the number of output ports. It is possible to increase the number of resolution points Nr of the deflecting device.

  On the other hand, the scanning speed of the optical deflector is determined by the control speed of the phase distribution of each output light. The phase distribution of the output light from the optical deflecting device is controlled by changing the refractive index of the optical path in the phase shifter connected to each output port based on an optical signal or an electrical signal. Accordingly, in order to control the phase of the output light from the optical deflecting device at high speed, a material whose refractive index changes rapidly by an external signal is required. Therefore, in addition to a liquid crystal element that has been put into practical use (for example, Patent Document 2). The use of electro-optic (EO) materials (for example, Patent Document 3), organic EO polymers (for example, Non-Patent Document 1), etc. is promising.

In particular, the organic EO polymer using the electric field response of the π electron distribution has an operation speed that theoretically exceeds GHz, and in recent years, a material having a large amount of refractive index change has been proposed. Is also expected.
An optical deflector that operates at high speed using an organic EO material or an EO polymer can be miniaturized and integrated by adopting an optical waveguide type device configuration. The applicable range of such an optical deflector is as follows. It becomes very wide.

(Operating principle of the optical deflector)
Next, the operation principle of the optical deflection apparatus will be described. FIG. 6 shows an example of an optical deflecting device 101 of an 8-channel optical waveguide type using an organic EO material. In general, an optical waveguide type optical deflecting device 101 includes an input port 103, a (beam) splitter 104, an optical waveguide 105, a phase shifter 106, an output port 107, an electrode formed on a substrate 102, respectively. 108.

The optical deflecting device 101 is shown in FIG. 6A as being assumed that the phase of the output light from each output port 107 is the same in the state where voltage application described below is not performed. The optical path adjusting parts and voltage correction may be introduced as appropriate.
The input port 103 is an optical element that converts spatial light into propagation light in the optical waveguide. A ball lens or a cylindrical lens is disposed on the end surface of the optical waveguide 105 that guides the input light, or on the side surface of the optical waveguide 105. A prism coupler and a grating coupler are arranged or formed.

  The splitter 104 is an element that distributes the propagating light to the optical waveguide 105. In addition to the multi-stage connection of 1 × 2 MMI (Multi Mode Interference) couplers shown in FIG. 6, a single use of 1 × 8 MMI coupler, Y branch Consists of multi-stage coupler connection, star coupler, etc. In other words, the 1 × N MMI coupler is an optical element that can distribute one input light to N (integer) optical waveguides 105. Specifically, here, eight optical waveguides 105, phase shifters 106, output ports 107, and electrodes 108 are provided (eight of the above-mentioned propagation lights by the splitter 104). This is an example of the optical deflection apparatus 101 that branches into

The optical waveguide 105 has a width W, a thickness T, a length La (shown in FIG. 6A), and a refractive index nc. The optical deflection apparatus 101 is an element in which eight optical waveguides 105 are arranged in the plate width direction of the substrate 102, and at least a part of the optical waveguide 105 is made of an organic EO material surrounded by one or more electrodes 108. Composed.
A region of the optical waveguide 105 that is affected by the electric field generated by the electrode 108 is referred to as a phase shifter 106, and the phase of the propagating light is controlled by a refractive index change Δn (E) caused by the applied electric field E.
However, instead of the organic EO material, a thermo-optic (TO) material may be used instead. In this case, the organic EO material is generated along with conduction of current by the electrode 108 instead of the applied electric field E in the above description. The change of the refractive index nc of the optical waveguide with respect to the propagating light is controlled by Joule heat.

  Here, the phase change amount φ generated when propagating light of wavelength λ passes through the optical waveguide 105 is Ls (shown in FIG. 6) of the length of the phase shifter 106 and EO generated by application of the voltage V to the phase shifter 106. When the electric field of the polymer is E and the refractive index n (E) of the light of the EO polymer at the electric field E is “n (E) = nc + Δn (E)”, approximately “2π {nc · (La−Ls) + n (E) · Ls} / λ ″. Accordingly, the phase difference Δφ of the output light generated at the output port 107 with respect to the presence / absence of voltage application at the phase shifter 106 can be controlled by “Δφ = (2π · Δn (E) · Ls) / λ”. it can.

For example, when an EO polymer having a refractive index n and an electro-optic (EO) coefficient r is used as the phase shifter 106, the refractive index change amount is given by “0.5n ³ · r · E (V)”. Therefore, in order to obtain the phase difference Δφ, the electric field E applied to the phase shifter 106 formed of the EO polymer is
E = (Δφ / 2π) (λ / (n ³ · r · Ls)) (4)
Apply a voltage so that

Since the derivation of the applied voltage V from the applied electric field E depends on the device structure of the optical deflection apparatus 101, it is necessary to obtain the electrostatic field distribution in detail by numerical analysis or the like. However, for example, when the phase shifter 106 has a structure in which a thin-film EO polymer having a thickness T is sandwiched between two thin-film electrodes, the formula for calculating the applied voltage V is simplified to “V = (Δφ / 2π) (T / (N ³ · r · Ls)) ”.
Similarly to the input port 103, the output port 107 is an optical element capable of coupling spatial light and propagating light (in this example, the edge portion where the optical waveguide 105 is exposed to the outside becomes the output port 107), and the output port One-dimensional light deflection control can be performed by one-dimensionally arranging 107 in the plate width direction of the substrate 102 at an equal pitch P (shown in FIG. 6A).

When the phase difference of the output light emitted from the adjacent output port 107 is ± Δφ, and the phase of the light from the output port 107 at one end to the output port 107 at the other end is monotonously increased. That is, when the secondary wavefront of the output light forms a wavefront inclined with respect to the output end of the optical deflecting device 101, the deflection angle θ of the combined light beam (shown in FIG. 6) is “sin ⁻¹ {(Δφ / 2π ) (Λ / P)} ”.
Based on the above operation principle, it is possible to control the deflection angle of the combined light beam by applying a voltage to the phase shifter 106 of the optical deflection apparatus 101.

On the other hand, when the intensity of the output light is uniform, the divergence angle ψ is approximately “λ / (7P + W)” (when there are eight output ports 107 as shown in FIG. 6). Here, “7P + W” is the aperture diameter of the optical deflector 101, and is given by “(Ne−1) P + W” with respect to the number of output ports 107 (number of elements) Ne (8 in this example). In order to increase the number of resolution points Nr, that is, “Nr = θ _max / Ψ _min ”, it is essential to increase the number of elements Ne.

  The pitch P of the output ports has been described as being equal to the interval between the optical waveguides 105. However, when a taper structure or the like is introduced in the path to the output port 107 and the pitch of the output port 107 is converted to P ′, The opening diameter of the deflecting device 101 is “7P ′ + W”, and the spread angle Ψ is generally given by “λ / (7P ′ + W)”.

  FIG. 7 shows the state of the output light and the combined light beam output from the light deflection apparatus 101. That is, numbers (channel numbers) are assigned to each output port 107 in order from the first, such as No. 1, No. 2,... N, and output from No. 1, No. 2,. The phase of the output light beam (reference numeral 111) is provided with a phase difference of Δφ in order of φ, φ + Δφ, φ + 2Δφ,. Due to this phase difference, the output light 111 output from each output port 107 becomes a spherical wave as indicated by reference numeral 112, and in the example of FIG. 6C (enlarged plan view of the reference numeral 121 in FIG. 6B). The combined light beam (reference numeral 113) is deflected to the right, and its wavefront is as indicated by reference numeral 114.

US Pat. No. 5,093,740 Japanese Patent No. 2579426 Japanese Patent No. 5285120 Japanese Patent No. 5613712 JP 2012-155045 A

Akira Otomo, “Development of electro-optic light modulator using organic dye molecules”, KARC FRONT, vol.26, Spring 2013, pp.3-7 P. F. McManamon, “A Review of Phased Array Steering for Narrow-Band Electro optical Systems”, Proc. Of the IEEE, Vol. 97, No. 6, June 2009

  As described above, in the optical deflecting device 101, the number of resolution points Nr can be increased by arranging a large number of output ports 107 at a narrow interval. For this reason, the number of output ports is generally large in the optical deflecting device 101 (in the above example, the number of output ports is shown and described for convenience of eight, but there are actually much more). Problems associated with such an increase in the number of output ports 107 include increasing the applied voltage V, increasing the number of signal lines connected to the phase shifter 106, and obtaining a desired phase distribution. The required size of the electrode 108 is increased.

  These problems will be specifically described with reference to FIGS. In FIG. 8 and FIG. 9, the members and the like having the same reference numerals as those in FIG. 6 and FIG. 8 and 9, the splitter 104 is not shown, unlike FIG. Further, in the examples of FIGS. 8 and 9, the output light 111 (not shown in FIGS. 8 and 9) output from each output port is provided with a phase difference of Δφ as shown in the figure. Yes. 8 and 9 illustrate the phase of the output light, and therefore, for convenience, the output light 113 is illustrated away from the output port 107. However, in reality, the output light 113 is directly from the output port 107. Needless to say, it is emitted.

  The wavefront 114 of the combined light beam 113 formed by the light deflection apparatus 101 as shown in FIG. 7 can be realized as follows. That is, assuming that the channel number of the output port 107 is number 1,..., Number 8 in order from the top to the bottom of FIG. 8A in the parallel direction, the output light 111 (from FIG. This can be realized if the phase of (a) (not shown) gradually changes and monotonically decreases with Δφ (in the example of FIG. 7, it is monotonically increased, but here an example of monotonic decrease is shown).

However, in order to obtain a large light deflection angle, a large Δφ is necessary, and there is a problem of increasing the voltage applied to the optical deflection apparatus 101. That is, electrodes 1081 to 1088 are provided corresponding to the output ports 107 of No. 1,..., Respectively, and voltage sources V _{1 to} V ₈ for applying voltages of the electrodes 1081 to 1088 are provided (each (The GND connected to the electrode is not shown). Here, in order to obtain a large Δφ, the output voltage is sequentially increased in the order of the voltage sources V _{1 to} V ₈ , and the voltage source V ₈ is significantly increased, or the voltage sources V _{8 to} V ₁ order by successively higher voltage is the output voltage, so that the voltage source V ₁ corresponding high voltage.

Therefore, an electrode structure shown in FIG. 8B has been proposed (see, for example, Patent Document 4). As is clear from the above description, since the phase difference of the output light 111 at the output port 107 is “Δφ∝Δn (E) · Ls”, the amount of change in the refractive index of light due to voltage application to the optical deflecting device 101. Δn (E) depends on the length Ls of the phase shifter 106. As a result, the voltage applied to the voltage source V ₈ in FIG. 8 (b), the voltage is applied _(power source maximum voltage in the example in FIG. 8 (a)) the voltage source V ₈ in FIG. 8 (a) 1 / It can be reduced to about 8.

However, the number of signal lines 110 in FIG. 8B is the same as that in the example of FIG. 8A, and the problem of an increase in the number of signal lines 110 with respect to an increase in the number of resolution points Nr is not solved.
Therefore, as shown in FIG. 9A, an optical deflection device 101 in which all the electrodes 1081 to 1088 are connected to the same signal line 110 has also been proposed (see Patent Document 5). Here, the electrodes 1081 to 1088 are all connected to each other.

However, in this case as well, as in FIG. 8B, the length of the electrode 108 is “Ne · Ls” (in the example of FIG. 9A, the number of elements Ne = 8). Since the size of the device 101 becomes larger in proportion to the number of output ports, there arises a problem that the optical deflection device 101 cannot be reduced in size.
On the other hand, a control means called modulo 2π control shown in FIG. 9B has been proposed as means for suppressing the increase in the applied voltage regardless of the electrode structure (for example, see Non-Patent Document 2 above). ).

That is, since the wavefront 114 of the combined light beam 113 is formed as an equiphase surface of the output light 111 (not shown in FIG. 9B), it is an integral multiple of the length λ along the light traveling direction in space. Even if output lights having different optical path lengths are included, a light wavefront is formed.
Therefore, in the configuration of FIG. 9B in which the remainder obtained by dividing the phase distribution of FIG. 8A by 2π is given as the phase distribution of the output port, the combined light beam 114 is directed in the same direction as in FIG. Can be formed.

In such a means, the applied voltage is lower than the voltage V _2π that gives the phase difference 2π at the output port 107, so that the applied voltage can be prevented from being increased.
However, even in this case, there is a problem that an increase in the number of signal lines 110 is unavoidable.
It is an object of the present invention to provide an optical deflecting device that requires only a low applied voltage, has a small number of signal lines, and can downsize the device.

  The optical deflecting device of the present invention includes a splitter that divides input light into a plurality of parts, and guides each light divided into a plurality of parts by the splitter, and the output side edges are aligned in a line to form an output port. A plurality of optical waveguides, wherein each of the optical waveguides is grouped for each of the plurality of outlet side edges that continuously appear in the row direction, and the electrodes are A common electrode for each of the optical waveguides constituting each group and a separate electrode when the group is different, and a first electrode group comprising a plurality of first electrodes that can be individually set with an applied voltage; and A second electrode comprising a plurality of electrode portions formed of electrode members for each optical waveguide and connected to each other, wherein the second electrode is arranged in the order of the row in each group. Before being provided in The length in the length direction of the optical waveguide of the electrode portion is gradually increased, the length of the first electrode portion of each group in the row is the shortest, and the length of the last electrode portion of each group is reduced. It is characterized by the longest length.

According to the present invention, by dividing the electrodes of each optical waveguide into the first electrode and the second electrode, the applied voltage to each optical waveguide can be distributed not only to the first electrode and the second electrode, Since the voltage V _2π that gives the phase difference 2π can be appropriately added or subtracted based on the physical law that is the same even if the phase of light is added or subtracted by 2π, the maximum value can be suppressed.
Also, the number of signal lines required is only the number corresponding to the number of groups (number of groups x 2) corresponding to the first electrode, and only two corresponding to the second electrode are required. Since it can, it can be suppressed.
In addition, since the first optical waveguide of each group is the shortest and the length of the last optical waveguide of each group is the longest in a single row, the fluctuation cycle of the optical waveguide length matches the grouping. I'm doing it. Therefore, the maximum electrode length in each optical waveguide (corresponding to each optical waveguide, “the length of the first electrode + the length of the electrode portion”) is also “the length of the first electrode + the length of the first electrode”. Since the length of the electrode portion of the two electrodes can be suppressed to the “maximum length of the electrode portion”, the optical deflection apparatus can be reduced in size.

  According to the present invention, it is possible to provide an optical deflecting device that requires a low applied voltage, has a small number of signal lines, and that can downsize the device.

It is a top view of the optical deflection device which is one embodiment of the present invention. FIG. 2 is an enlarged longitudinal sectional view of an optical waveguide and a first electrode (second electrode) of an optical deflecting device that is an embodiment of the present invention, and a diagram showing a connection of a voltage source to the electrode. It is a top view of the optical deflection apparatus which is one example of the present invention. It is a table | surface which shows the prescribed value of each part of the optical deflection apparatus which is one Example of this invention. It is explanatory drawing which shows the verification result of the optical deflection | deviation apparatus which is one Example of this invention. It is explanatory drawing which shows an example of the optical deflection | deviation apparatus of an 8-channel optical waveguide type using an organic electro-optic material. (A) is a perspective view, (b) is a plan view, and (c) is an enlarged plan view of a part of (b). It is explanatory drawing which shows the mode of the output light by a light deflection apparatus and a synthetic | combination light beam in the example of FIG. It is explanatory drawing explaining the subject of this invention, (a) and (b) are top views which show the example of the optical deflection apparatus of a respectively different structure. It is explanatory drawing explaining the subject of this invention, (a) and (b) are top views which show the example of the optical deflection apparatus of a respectively different structure.

Hereinafter, an embodiment of the present invention will be described.
In the following description, symbols and the like common to the above-mentioned [Background Art] and [Problems to be Solved by the Invention] are the same as those described above, and thus detailed description may be omitted (the above-mentioned description may be omitted). See description).

(Outline of configuration of optical deflector)
The optical deflecting device 1 of this embodiment shown in FIG. 1 includes an input port 11, a (beam) splitter 12, an optical waveguide 13, a phase shifter 14, an output port 15, a first electrode 16, and a second electrode. 21, the substrate 18, the signal line 19, and the same number of voltage sources V ₁ , V ₂ ,..., V _g and V _s as the optical waveguide group g. The first electrode 16 and the second electrode 21 are illustrated as being connected to the voltage sources V ₁ , V ₂ ,..., V _g , and V _s only through the single signal line 19. However, this is an illustration for the sake of convenience, and the actual connection state will be described later. Further, the output light b described later is directly output from the output port 15 as described later, but since the channel number and the phase of the output light are displayed in FIG. 1, the output light b is output from the output port 15 for convenience. (The same applies to FIG. 3 in the embodiment described later).

Each optical waveguide 13 is preferably formed of an electro-optic (EO) material. However, a thermo-optic (TO) material may be used as the material of each optical waveguide 13.
Hereinafter, a detailed configuration of each part of the optical deflection apparatus 1 will be described.

(Substrate 18)
The substrate 18 can be configured using various materials. For example, as the material of the substrate 18, soda glass, SiO ₂ , quartz, methyl acrylate, silicon, LiNbO ₃ , LiTaO ₃ , alumina, GaAlAs, InP, or the like can be used.
On one surface of the substrate 18, the input port 11, splitter 12, optical waveguide 13, phase shifter 14, output port 15, first electrode group 22, second electrode 21, and signal line 19 Part is formed.

(About input port 11)
The input port 11 is an optical element that converts input light into propagating light in the optical waveguide 13, and a ball lens or a cylindrical lens is disposed on the end surface of the optical waveguide 13 that guides the input light, or a prism is provided on the side surface of the optical waveguide. A coupler and a grating coupler are arranged or formed.

(About splitter 12)
As shown in FIG. 1, the optical deflection apparatus 1 includes a splitter 12 that divides input light into a plurality of parts. The splitter 12 is an element that distributes the propagating light input from the input port 11 to the optical waveguide 13. In addition to the multistage connection of 1 × 2 MMI (Multi Mode Interference) couplers shown in FIG. A multi-stage connection of 8MMI couplers, a multi-stage connection of Y branch couplers, and the like can be used. That is, the 1 × N MMI coupler is an optical element that can distribute one input light to N (integer) optical waveguides 13. In the specific example of FIG. 1, the splitter 12 shows the 1 × 2 MMI coupler in only four stages for convenience, and the others are omitted. However, in reality, there are more stages depending on the number N of optical waveguides. (The number of steps varies depending on whether a 1 × 2 MMI coupler, a 1 × 8 MMI coupler, or a Y branch coupler is used). Nc is the maximum number of optical waveguides sharing the voltage sources V1 to Vg, and is set to satisfy “(g−1) · Nc <N ≦ g · Nc”. In the embodiment, the propagating light is branched into N, and each of them is distributed to N optical waveguides 13.

(About the optical waveguide 13, the phase shifter 14, the first electrode 16, and the second electrode 21)
As shown in FIG. 1, the light deflection apparatus 1 guides each light divided into a plurality of pieces (g · Nc in this example) by the splitter 12, and the edge on the exit side of the light is aligned in one row (in FIG. A plurality (g · Nc in this example) of optical ports 13 forming a plurality (g · Nc in this example) of output ports 15 are arranged in a line from the bottom to the bottom.
The optical waveguide 13 has a width of W, a thickness of T, a length of La, and a refractive index of nc. The optical deflection device 1 is an element in which g · Nc optical waveguides 13 are arranged in the plate width direction of the substrate 18 (vertical direction in FIG. 1).
A region of the optical waveguide 13 that is affected by the electric field created by the first electrode 16 and the second electrode 21 is referred to as a phase shifter 14, and the phase of the propagating light is changed by a refractive index change Δn (E) caused by the applied electric field E. To control.

  As shown in FIG. 1, each optical waveguide 13 includes g first electrodes grouped for each of the Nc outlet side edges (output ports 15) that continuously appear in the row direction. 16 and one second electrode 21 are provided. First, each optical waveguide 13 (and its corresponding output port 15) is given a channel number as shown in FIG. That is, the channel numbers are in order from the smallest number, number 1, number 2,..., Number Nc, number Nc + 1, number Nc + 2,..., Number 2Nc, ..., (g−1), number Nc + 1, (g−1), Nc + 2,..., G · Nc (g · Nc = Ne). Then, Nc optical waveguides 13 that are adjacent to each other in the order of channel numbers are grouped into one group, and the optical waveguides 13 (and Nc output ports 15 and optical waveguides 13 are provided in each group). The corresponding output ports 15) are grouped. Similarly, in the case of N ≠ g · Nc, numbers up to N are assigned, but grouping is performed by creating g−1 groups composed of Nc optical waveguides in order from the smallest number, and the last group. Is composed of g · Nc−N optical waveguides.

  The electrodes are common for each of the optical waveguides 13 constituting each of the g groups and are separated when the groups are different, and a plurality (g in this example) of first electrodes that can individually control the applied voltage. The first electrode group 22 including the electrodes 16 and the second electrode 21 including a plurality of (g · Nc in this example) electrode portions 17 formed of electrode members for each optical waveguide 13 and connected to each other.

FIG. 2 shows a portion of the phase shifter 14 where the first electrode 16 and the second electrode 21 are formed.
As shown in FIG. 2, the first electrode 16 (the basic configuration of the electrode portion 17 of the second electrode 21 is the same) is a pair of control electrodes 16a (of the electrode portion 17) constituting the first electrode 16 (electrode portion 17). The control electrode 17a) and the lower electrode 16b (in the case of the electrode portion 17, the lower electrode 17b). The control electrode 16 a (control electrode 17 a) is formed on the upper surface of the optical waveguide 13, and the lower electrode 16 b (lower electrode 17 b) is formed on the lower surface of the optical waveguide 13.

  As shown in FIG. 1, the second electrodes 21 are arranged in the length direction of the optical waveguides 13 of the electrode portions 17 provided in the respective optical waveguides 13 in the order of the one row in each group. The length gradually increases, the length of the first electrode portion 17 of each group becomes the shortest and the length of the last electrode portion 17 of each group becomes the longest in the row of rows. Thereby, the fluctuation cycle of the length of the electrode part 17 is in agreement with the said grouping. That is, for example, the electrode portions 17 of channel numbers 1, Nc + 1, 2Nc + 1,..., (G−1) · Nc + 1 are the shortest, and the electrode portions 17 of channel numbers Nc, 2Nc, 3Nc,.

  The optical waveguide 13 has, for example, a configuration in which an EO polymer core 13a is sandwiched between polymer clads 13b and 13c from above and below. The optical waveguide 13 having such a configuration is sandwiched between the control electrode 16a (control electrode 17a) and the lower electrode 16b (lower electrode 17b). This laminated structure is laminated on the substrate 18. The phase shifter 14 has a laminated structure in which a clad 13c, a core 13a, and a clad 13b are laminated in order from the bottom.

In FIG. 2, the power source (voltage source) V is a generic name of the first power source V ₁ , V ₂ ,..., V _g , or the second power source V _s, and the polarity of the power source V may be any. The plus side (or minus side) is connected to the control electrode 16 a (control electrode 17 a) side via a signal line 19. The minus side (or plus side) of the power source V is connected to the lower electrode 16 b (lower electrode 17 b) via the signal line 19. Thus, when the power source V applies a voltage between the control electrode 16a (control electrode 17a) and the lower electrode 16b (lower electrode 17b), an electric field E as shown by an arrow in FIG. 2 is applied to the core 13a.

  For the control electrode 16a (control electrode 17a) and the lower electrode 16b (lower electrode 17b), a metal material such as gold, silver, copper, aluminum, chromium, titanium, or a transparent conductive material such as ITO or IZO is used. Can do. These electrodes can be formed on the substrate 18 by means of spin coating, vapor deposition, photopolymerization, RF sputtering, CVD or the like. The lower electrode 16b (lower electrode 17b) is formed on the substrate 18.

The clads 13b and 13c include at least one dielectric layer (polymer in the above example), but one or both of the clads 13b and 13c may not be provided.
The core 13a is made of a transparent material (organic electro-optic polymer in the above example) having a higher dielectric constant than the clads 13b and 13c. When the clad 13c is not provided, the core 13a has a higher dielectric constant than that of the substrate 18. The material which has this shall be used.

Examples of the material of the core 13a and the claddings 13b and 13c include LiNbO ₃ , LiTaO ₃ , GaAlAs, InP, NH ₄ H ₂ PO ₄ , KH ₂ PO ₄ , SiO ₂ , CaCO ₃ , Al ₂ O ₃ , TiO. ₂ , SrTiO ₃ , Bi ₁₂ SiO ₂₀ , Bi ₁₂ GeO ₂₀ , ZnO, Y ₃ Fe ₅ O ₁₂ , semiconductor materials such as GaAs, Si, dielectric materials, inorganic materials, and organic materials such as acrylic resins and epoxy resins Polymers such as polyimide, fluorinated polyimide, polycarbonate, polysulfone, polyacrylate, polymethacrylate, polyetherimide, and polyethersulfone can be used.

  For the polymer core 13a and the clads 13b and 13c, or any of them, a system in which a low molecular compound having an electro-optic (EO) effect is dispersed as described above can be used. For example, such materials include azo dyes and merocyanine dyes, among them DR1 and 2-methyl-6- (4-N, N-dimethylaminobenzylidene) -4H-pyran-4-ylidenepropanedinitrile, 4 -{[4- (dimethylamino) phenyl] imino} -2,5-cyclohexadien-1-one and the like are preferable.

  The formation of the lower electrode 16b (lower electrode 17b), the clad 13c, the core 13a, the clad 13b, and the control electrode 16a (control electrode 17a) may be performed by patterning. That is, the material is selectively formed only in a desired pattern by an ion exchange method or the like, or uniformly laminated using a method such as spin coating, and then other than the desired pattern is obtained using a method such as RIE. Means such as selective removal can be used.

The first electrode 16 is a common electrode for each adjacent Nc channel (each group). The length of the first electrode 16 in the waveguide direction is Lb.
The electrode portion 17 of the second electrode 21 has a difference in length between adjacent channels of Ls, a minimum length of Ls, and the length increases by Ls as the channel number increases from the length Ls. “Nc−1” times), and the cycle of returning to Ls again is repeated g times. When the total number of optical waveguides is smaller than g · Nc, the g-th repetition is finished by reducing the number of times by g · Nc−N times than Nc−1 times. The electrode portion 17 from being applied from the second power source _{V s} is the signal voltage _{V s.} For simplicity, it is illustrated and described as “Lb = Ls”.

(Determination of phase difference of output light beam)
First, assuming that the maximum number of the optical waveguides 13 constituting each group of the optical deflecting device 1 is Nc (an integer of 3 or more), from one end of the row of the above-described ones (the upper end of FIG. 1 of the optical deflecting device 1). The optical waveguide 13 corresponding to the i-th output port 15 will be described as an example. Here, the optical waveguide 13 is connected to the first power sources V ₁ , V ₂ ,..., V _g through the first electrode 16 given the number k defined as the smallest integer greater than or equal to “i / Nc”. Shall be. For each optical waveguide 13, the phase change amount of the output light determined by the action of the second electrode 21 and the deflection angle θ of the combined light beam composed of each output light emitted from each output port 15 In the meantime, Δφ _s having the relationship of the following equation (1) is considered. Further, for each optical waveguide 13, a phase change amount due to the action of the k-th first electrode 16 for two or more k and Δφ _k defined by the following equation (2) is considered. For each optical waveguide 13, the phase difference between the output light beams from the i-th and (i−1) -th output ports 15 is determined by the relationship of the following expression (3) using the expressions (1) and (2). It is determined that the light deflection apparatus 1 is configured.
Psinθ = (λ · Δφ _s ) / 2π (1)
Δφ _k = mod [(Nc−1) · Δφ _s + Δφ _k−1 , 2π] (2)
Δφ _i = −mod (i, Nc) · Δφ _s −Δφ _k (3)
(Where P is the pitch of the adjacent output ports, λ is the wavelength of the combined light beam, and Δφ _{k = 1} = 0 (Δφ _k = 0 when _k = 1).)

(The first power supply _{V 1, V 2, ...,} V g, for the second power supply _{V s)}
As shown in FIG. 1, one first power source V ₁ , V ₂ ,..., V _g is prepared for each of the groups corresponding to the g first electrodes 16. The first power sources (voltage sources) V ₁ , V ₂ ,..., V _g are respectively supplied to the first electrode 16 V _2d · Δφ _{k = 0} / 2π, V _d · Δφ _{k = 1} / 2π,. A bias voltage of _{k = g} / 2π is applied.
As shown in FIG. 1, a second power supply (voltage source) V _s applies a common voltage to the second electrode 21 (the set of electrodes 17). That is, one electrode portion 17 is arranged for each optical waveguide 13, and each electrode portion 17 is connected to each other to form a second electrode 21, and the second electrode 21 is connected to a specific second power source V _s . Connected. The voltage of the second power supply V _s is set to V _2π · Δφ _s / 2π.

(Operational effect of the light deflector 1)
Next, the function and effect of the optical deflection apparatus 1 having the above configuration will be described.
The first power sources V ₁ , V ₂ ,..., V _g and the second power source V _s of the optical deflector 1 are turned on, and input light is input from the input port 11. Then, the input light is branched into a bundle of N = g · Nc light beams by the splitter 12, and each light beam is propagated through N optical waveguides 13. In each optical waveguide 13, the refractive index of the optical waveguide medium changes due to the electric field generated by the first electrode 16 and the electrode unit 17 provided in the phase shifter 14, and the action causes a change in the phase of the propagation light. .

Here, the initial phase of the propagating light (the phase when not affected by the electric field) is φ. Voltage applied to the electrode portions 17 (second electrodes 21) of the second power source _{V s} is equal _{V s.} However, as described above, in each group, the length of each electrode portion 17 is increased by Ls in the order of the channel numbers. Therefore, even if the applied voltage is equal to V _s in each electrode portion 17, the phase of the propagation light due to the electric field generated in each electrode portion 17 decreases by Δφ _{s in} order of channel numbers 1, 2,..., Nc (Δφ _s , 2Δφ _s , 3Δφ _s , ...). The relative phase relationship within this group is the same for channel numbers Nc + 1 and above.

Further, the voltage applied by the first electrode 16, such voltage _{V 1,} V 2, ..., a phase delay of the propagating light due to _{V g.}

  As described above, in each optical waveguide 13, a phase change of propagating light is caused by an electric field generated in each of the first electrode 16 and the electrode portion 17.

Thus, the channel number, No. 1, No. 2,..., Nc No., Nc + 1 No., Nc + 2 No ...., 2Nc No.,..., (G−1) · Nc + 1 No., (g−1) · Nc + No. , The phase of propagating light in the optical waveguide 13 changes by Δφ _{s in} the order of g · Nc, but in a group next to a group including a channel that exceeds or falls below _2π , V _2π is subtracted from the bias voltage or In order to correct the addition, mod [Δφ _s , 2π] is obtained. Therefore, in the example of FIG. 1, the propagation light propagates through the optical waveguide 13 from the left direction to the right direction, but the combined light beam b of the output light beam output from each output port 15 is the upper right in the example of FIG. Deflect in the direction. In FIG. 1, symbol C is the wavefront of the combined light beam b.

As described above, in order to set a phase difference in the propagation light by the phase shifter 14 in each optical waveguide 13, two types of electrodes, that is, the first electrode 16 and the electrode portion 17 are provided, and the action of the electric field generated at each of these electrodes is provided. Thus, the phase difference is formed. The voltage of the first, second,..., G-th group of the first electrode 16 is obtained by dividing the phase calculated using the equations (1) to (3) by _2π to obtain V _2π . The value multiplied. On top of that, in each group, the first, second, ..., Nc-th electrode portion 17 is applied voltage is equal V _s, the length of gradual electrode in this order becomes longer. Therefore, in each group, the phase of the propagation light by the electrode unit 17 in the phase shifter 14 of the first, second,..., Nc-th optical waveguide 13 changes by −mod [Δφ _s , 2π].

Therefore, in the order of the channel numbers, the phase of the output light beam from the output port 15 is φ−Δφ _s −Δφ ₁ , φ−2Δφ _s −Δφ ₁ ,..., Φ−Nc · Δφ _s −Δφ ₁ , φ−Δφ _s −Δφ ₂ , φ−2Δφ _s −Δφ ₂ ,..., φ−Nc · Δφ _s −Δφ _g .
Thus, by dividing the electrode into the first electrode 16 and the second electrode 21 (electrode part 17) by the phase shifter 14 of each optical waveguide 13, the voltage applied to each phase shifter 14 is the same as that of the first electrode 16. since it distributed to the second electrode 21 (electrode portion 17), the maximum value of the applied voltage can be suppressed to _{V g} (or _{V s).}

The number of necessary signal lines 19 is “g × 2” corresponding to the first electrode 16 and only “1 × 2” corresponding to the second electrode, so “2g + 2”. Can be suppressed.
In addition, the length of the maximum electrode in each optical waveguide 13 (the total length of the first electrode 16 and the electrode portion 17) can also be suppressed to “Lb + Nc · Ls” (Lb is the value in FIG. 1). As shown in the figure, the length of the first electrode 16) and the optical deflection device 1 can be reduced in size.
Also, the necessary voltage sources (different types of power supply voltages) can be suppressed to “g + 1”.

More generally, the phase “φ−j · Δφ _s −Δφ _k ” of the output light beam with respect to the output port 15 of the channel i is controlled in order to control the deflection angle of the combined light beam b output from the optical deflecting device 1. Is determined by the phase change amount Δφ _s of the propagating light determined by the signal voltage V _s and the phase change amount Δφ _k determined by the bias voltage (V ₁ , V ₂ ,..., V _g ). However, i, j, k are integers (i = 1, 2, 3,..., J = 1, 2, 3,..., K = 1, 2, 3,...), And the length of the electrode portion 17 is It is assumed that the relationship of “j = mod (i, Nc), k = i / Nc” is established between the number of pattern repetitions of change, that is, the number Nc of the electrode portions 17 in each group.

The phase change amount Δφ _s is calculated so as to satisfy “Psinθ = (λ · Δφ _s ) / 2π” (formula (1) above) in order to determine the slope of the phase distribution that gives the deflection angle θ of the output light beam. .
The phase change amount Δφ _k is responsible for phase matching between adjacent channels connected to different k-th first power supplies (V ₁ , V ₂ ,..., Or V _g ), and thus “Δφ _k = mod [ (Nc−1) · Δφ _s + Δφ _k−1 , 2π] ”(the above equation (2)) is sequentially calculated.

Accordingly, the signal voltage V _s and the bias voltages V ₁ , V ₂ ,..., Or V _g can be determined by the electric field given by the equation (4) described in the background art section.
According to the optical deflecting device 1, the maximum value of the applied voltage required for controlling the optical deflecting device 1 is suppressed to V _2π similar to the modulo 2π control, and at the same time, the number of signal lines 19 is reduced as described above. Thus, it is possible to reduce to “2 g (= 2Ne / Nc) +2”.
Such a reduction in applied voltage not only reduces the requirements regarding the withstand voltage performance of the circuit, but also has an effect of suppressing power consumption when the optical deflecting device 1 is viewed as a capacitive load.

Further, the longest electrode length required by the electrode structure of the optical deflecting device 1 is “Lb + Nc · Ls” as described above (Lb = Ls in the example of FIG. 1), as shown in FIG. 8B. Compared to the case of using the electrode structure, it can be shortened to about 1 / g.
Then, the phase difference Δφ of the output light beam between the adjacent output ports 15 can be appropriately set by the method of calculating the phase change amount Δφ _s .

  Furthermore, in order to control the phase of the output light beam at high speed, a material whose light refractive index changes rapidly by an external signal is required. In this respect, it is desirable to use an organic electro-optic material, in particular, an organic electro-optic polymer, as described above, as the material of the optical waveguide 13. This is because the organic electro-optic polymer using the electric field response of the π electron distribution theoretically has an operation speed of GHz order.

Next, an embodiment of the present invention will be described.
First, let us consider an embodiment as shown in FIGS. 3 and 4 in the optical deflecting device 1 described above. In FIGS. 3 and 4 and the description of the following embodiments, the same symbols and the like are used for the members and the like as described above, and the detailed description is omitted. FIG. 4 shows specific numerical values of each part of the optical deflecting device 1 of FIG.

The optical deflecting device 1 of the embodiment of FIGS. 3 and 4 is a verification using a 58-channel device. However, in FIG. 3 and FIG. 4, only 8 channels are shown for simplicity, and the 8-channel optical deflecting device is also shown below. This will be described as 1.
In such a configuration of the embodiment, in order to set the deflection angle of the combined light beam to 10 °, for example, it is necessary to set the phase distribution of the output light beam by setting the phase difference between adjacent channels to 2π / 5. .

At this time, the bias voltage V _s and the signal voltages V ₁ and V ₂ may be set as shown in the third and fourth stages of the table of FIG. The voltage becomes ± 130V.
This is a voltage 1/7 lower than the maximum applied voltage required to obtain the same characteristics in the optical deflecting device 101 of FIG.

Further, the number of signal lines of the optical deflection apparatus 1 of the embodiment is “3 × 2 = 6”, which is less than half the number of signal lines “8 × 2 = 16” of the optical deflection apparatus 101 of FIG. It is.
The electrode length 5Ls of the first electrode 16 and the electrode portion 17 (total of both electrodes) of the single optical waveguide 13 is about 60% of the electrode length 8Ls of the optical deflecting device 101 of FIG. Thus, the compact optical deflecting device 1 can be realized.

  FIG. 5 shows the result of numerical simulation performed as a verification experiment of this example. This simulation was carried out by a numerical calculation program using an FDTD (Finite-Different Time-Domain) method with a second-order temporal and spatial fourth-order accuracy. The specifications of the light deflection apparatus 1 handled in this simulation are as shown in the upper left table of FIG.

In the configuration of FIGS. 3 and 4, one first electrode 16 having a length Lb is arranged for four optical waveguides 13. In this verification experiment, the length “Lb” is set for three optical waveguides 13. One first electrode 16 of = Ls ″ is arranged. In this simulation, three types of driving conditions shown in the lower left table of FIG. 5 were used.
Further, when the target deflection angle θ is about 6 °, the signal voltage V _{s is set} to 130 V, the bias voltage is set to V ₁ = 0 V, and V ₂ = 390 V.

When the target deflection angle was about 10 °, the signal voltage V _s was 210 V, and the bias voltage was “V ₁ = V ₂ = 0V”.
When the target deflection angle was about 13 °, the signal voltage V _s was 260 V, and the bias voltage was “V ₁ = 0 V, V ₂ = −520 V”.
The simulation result is shown in the upper right graph of FIG. The deflection angle θ increases monotonously with respect to the signal voltage taken along the horizontal axis, and is expected to be 6.2 °, 10.4 °, and 13.4 ° with respect to the signal voltages of 130V, 210V, and 260V, respectively. The light deflection control operation was confirmed.

The maximum applied voltage in this verification experiment was 520 V, which was about half of the maximum applied voltage required for the optical deflector 101 in FIG.
The number of signal lines 19 of the optical deflection apparatus 1 used in this verification experiment is six corresponding to the three voltage sources, and the voltage source of the signal line 110 required for the optical deflection apparatus 101 of FIG. It was 40% or less of 16 of the number corresponding to.
The maximum electrode length in each optical waveguide 13 of the optical deflection apparatus 101 used in this verification experiment was 5 Ls, which was 62.5% of the maximum electrode length 8 Ls in the example of FIG.

1 optical deflecting device 12 splitter 13 optical waveguide 15 output port 16 first electrode 17 electrode 21 first electrode group second electrode 22 b combined light beam _{V 1, V 2, ...,} V g the first power supply V _S second power supply

Claims (5)

A splitter that splits the input light into multiple parts,
Each of the light divided into a plurality by the splitter, each having a plurality of optical waveguides that form an output port with the output side edges aligned in a row,
Each of the optical waveguides is grouped for each of the plurality of outlet side edges that appear continuously in the row direction, and electrodes are installed.
The electrode is
A first electrode group consisting of a plurality of first electrodes, each of which is common to the optical waveguides constituting each group and is a separate electrode when the group is different; and an applied voltage can be individually set;
A second electrode consisting of a plurality of electrode portions formed of electrode members for each optical waveguide and connected to each other;
The length of the second electrode in the length direction of the optical waveguide of the electrode portion provided in each optical waveguide in the sequence of the one row in each group is gradually increased. The length of the first electrode part of each group becomes the shortest and the length of the last electrode part of each group becomes the longest. A bias voltage is applied to the first electrode so that the applied voltage to each first electrode gradually increases in the direction in which the length of the optical waveguide in the length direction of the second electrode gradually increases. A first power source to be applied;
The optical deflection apparatus according to claim 1, further comprising a second power source that applies a voltage to the second electrode. The number of the optical waveguides constituting each of the groups is Nc (an integer of 3 or more), and the optical waveguide corresponding to the i-th output port counted from one end of the row is “i / When connected to the first power source through the first electrode given the number k defined as the smallest integer greater than Nc ″,
Between the phase change amount of the output light beam determined by the action of the second electrode and the deflection angle θ of the combined light beam composed of each output light beam emitted from each output port, the following ( 1) Δφ _s having the relationship of the equation:
Δφ _k which is a phase change amount due to the action of the k-th first electrode for two or more k, and is defined by the following equation (2):
3. The phase difference of the output light beam from the i-th and (i−1) -th output ports is determined by the relationship of the following expression (3) using: Optical deflection device.
Psinθ = (λ · Δφ _s ) / 2π (1)
Δφ _k = mod [(Nc−1) · Δφ _s + Δφ _k−1 , 2π] (2)
Δφ _i = −mod (i, Nc) · Δφ _s −Δφ _k (3)
Here, P is an interval between adjacent output ports, λ is the wavelength of the combined light beam, and Δφ _{k = 1} = 0 (Δφ _k = 0 when _k = 1).   The optical deflecting device according to any one of claims 1 to 3, wherein the optical waveguide is made of an organic electro-optic material.   The optical deflecting device according to claim 4, wherein the optical waveguide is made of an electro-optic polymer.

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