JP4109514B2 - Optical waveguide device for polarization control - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical waveguide device for polarization control suitable for use in configuring a polarization controller in an optical communication system, for example.
[0002]
[Prior art]
Conventionally, the polarization state of an optical signal propagating through a transmission line such as an optical fiber having birefringence is returned to the original state by a polarization controller. The polarization controller is an element that can freely move the polarization state from an arbitrary point to an arbitrary point, and can be configured using, for example, an optical waveguide device 600 as shown in FIG. It has become.
[0003]
Here, the optical waveguide device 600 includes an x-cut lithium niobate (LiNbO)._Three) An optical waveguide 601 is formed on a substrate made of a crystal, that is, a so-called LN crystal so as to be y-propagating, and further, three electrode pairs forming a pair across the both sides along the light propagation direction in the optical waveguide 601 611 to 613 and two pairs of comb electrode pairs 621 and 622 are provided in tandem and alternately.
[0004]
By connecting an electric signal supply source (not shown) to the optical waveguide device 600 as shown in FIG. 15 and controlling electric signals (voltage signals) supplied to the electrodes 610 to 650, for example, as shown in FIG. The state of polarization can be freely controlled from any point on the Poincare sphere 700 to any point.
Note that the Poincare sphere 700 shown in FIG. 16 can indicate all polarization states at positions on the sphere. For example, point A on the S1 axis is the TE mode, point B is the TM mode, point C on the S2 axis is 45 ° linearly polarized light, and each point on the equator E indicates linearly polarized light. Further, the north pole NP on the S3 axis is clockwise circularly polarized light, the south pole SP is counterclockwise circularly polarized light, and elliptical polarized light is shown on the equator E and other than the poles.
[0005]
First, the operation of the electrodes 611 to 613 will be described below with reference to FIGS. As described above, each of the electrode pairs 611 to 613 forms a pair so as to sandwich both sides of the optical waveguide 601 in the light propagation direction, like the electrode pair 610 of FIG. Here, for example, by supplying an electric signal to the electrode pair 610, the polarization state can be changed as shown in FIGS. 18 (a) to 18 (c).
[0006]
That is, since the refractive index change differs between the polarization components TE and TM due to the voltage signal applied to the electrode pair 610, a phase difference occurs between the polarization components, and the polarization state changes. . For example, when the polarization as shown in FIG. 18A is input and the phase is shifted by a quarter wavelength between the TE component and the TM component, elliptical polarization as shown in FIG. Thus, when it is deviated by ½ wavelength, it becomes linearly polarized light as shown in FIG. 18C, and when it is deviated by one wavelength, it returns to the original polarization state (see FIG. 18A).
[0007]
Therefore, the electrode pair 610 (611 to 613) described above functions as a phase shifter electrode for shifting the phase of the polarization component of light propagating through the optical waveguide 601 between the TE component and the TM component.
When the above-described change in the polarization state is shown on the Poincare sphere 700, it becomes a trajectory that rotates around the S1 axis, such as T1 in FIG. In other words, the electrode pairs 611 to 613 of the optical waveguide device 600 can be rotated around the S1 axis of the Poincare sphere 700 with respect to the polarization state of the light propagating through the optical waveguide 601 by the applied electric signal. .
[0008]
Next, the operation of the electrode pairs 621 and 622 will be described below with reference to FIGS. As shown in the electrode pair 620 in FIG. 20, the electrode pairs 621 and 622 are configured so that the pair of comb-shaped electrode pairs 620-1 and 620-2 meshes with each other between the tooth portions 620 a-1 and 620 a-2. Although formed, for example, by supplying an electric signal to the electrode pair 620, it functions as a mode converter only for a certain wavelength determined by a comb-shaped cycle (or interval).
[0009]
Specifically, with respect to light having the above-mentioned wavelength propagating through the optical waveguide 601, by supplying an electric signal to the electrode pair 620, the polarization state is changed as shown in FIGS. 21 (a) to 21 (c). Can be changed. That is, for example, when a polarization as shown in FIG. 21A is input, the polarization state is sequentially changed to the states of FIG. 21B and FIG. 21 (a)]. When this is shown on the Poincare sphere 700, a locus T2 as shown in FIG. 22 is obtained. That is, the polarization state rotates around the S3 axis.
[0010]
When the change in the polarization state described above is shown on the Poincare sphere 700, it becomes a locus on the equator E rotating around the S3 axis as shown by T2 in FIG. In other words, the electrode pair 621 and 622 of the optical waveguide device 600 can be rotated around the S3 axis of the Poincare sphere 600 with respect to the polarization state of the light propagating through the optical waveguide 601 by the applied electric signal. It is.
[0011]
As described above, the electrode pairs 611 to 613, 621, and 622 are alternately attached (namely, as shown in FIG. 15, reference numerals 611, 621, 612, 622, and 613 from the incident side of light propagating through the optical waveguide 601). (In the order of the electrodes), any polarization state can be changed to any polarization state. Accordingly, for example, when the incident light is TE light, the polarization state cannot be changed in the first electrode pair 611, but the polarization state can be controlled in the subsequent electrode pairs 612 and 613.
[0012]
In addition to the one shown in FIG. 15 described above, the prior art related to the optical waveguide device for configuring the polarization controller is configured by connecting ellipticity conversion elements 32 and 34 on both sides of the phase shifter element 33. There is a polarization controller that can follow the polarization state infinitely (see, for example, FIG. 5 of Japanese Patent Laid-Open No. 63-118709 (hereinafter referred to as Patent Document 1)).
Further, in the waveguide polarization controller described in FIG. 6 of Japanese Patent Laid-Open No. 05-313109 (hereinafter referred to as Patent Document 2), an optical waveguide having a light propagation action, and an optical path length of the optical waveguide are set. An optical waveguide type polarization beam splitter, which comprises an optical phase shifter to be controlled and a stress applying film for controlling birefringence of the optical waveguide, and outputs linearly polarized waves having polarization planes orthogonal to each other from two output optical waveguides; The optical waveguide type polarization beam splitter has two optical waveguides coupled to the two output optical waveguides, and converts the linearly polarized wave propagating through one of the optical waveguides into another orthogonal linearly polarized wave. A wave mode converter, an optical phase shifter that is provided in at least one of the two optical waveguides to control the optical path length of the optical waveguide, and a tunable cap that couples the light of the two optical waveguides with an arbitrary coupling ratio Includes the door, thereby reducing the laser trimming operation step or the like for the polarization-independent of each individual circuit of the optical waveguide.
[0013]
[Problems to be solved by the invention]
However, in the technique described in FIG. 15 and Patent Document 1 described above, the mode converter using the comb-shaped electrode is effective only for a certain wavelength determined by the period of the comb-shaped electrode. Cannot perform polarization control. In the technique described in Patent Document 2, light in an arbitrary polarization state can be converted into a constant linear polarization, but cannot be converted into an arbitrary polarization state.
[0014]
In order to apply to wavelength division multiplexing communication systems that have been actively developed in recent years, it is possible to perform polarization control to change a certain polarization state to an arbitrary polarization state in light of a wide wavelength band, In other words, it is desirable to develop a device capable of performing polarization control with improved wavelength dependency.
The present invention was devised in view of such problems, and an object of the present invention is to provide an optical waveguide device for polarization control which can improve the wavelength dependency and can constitute a polarization controller having infinite follow-up property. .
[0015]
[Means for Solving the Problems]
  For this reason, the optical waveguide device for polarization control of the present invention is based on an optical waveguide formed on a substrate having an electro-optic effect and an electric signal provided along the light propagation direction of the optical waveguide. The polarization state point represented on the Poincare sphere is provided with an electrode that can rotate about the first axis of the Poincare sphere, and the optical waveguide downstream of the light propagation direction with respect to the electrode.On the roadA wave plate is arranged by shifting the angle of the crystal axis by a predetermined angle with respect to the crystal axis of the substrate, and a polarization state point rotated about the first axis is a second orthogonal to the first axis. Configured to rotate around an axisA plurality of pairs of electrodes and wave plates are arranged in tandem so that the electrodes and wave plates are alternately arranged along the light propagation direction, and the light propagation of the optical waveguide is arranged at the most downstream in the light propagation direction. A polarization state point provided along the direction and represented on the Poincare sphere based on the supplied electrical signal is provided with a most downstream electrode that can rotate around the first axis of the Poincare sphere, and in the tandem arrangement. Among the two adjacent electrode / wave plate pairs, the wave plate forming one electrode / wave plate pair was prepared by shifting the angle of the crystal axis by about 22.5 degrees with respect to the crystal axis of the substrate. The wave plate constituting the other electrode / wave plate pair is composed of a quarter wave plate with the angle of the crystal axis shifted from the crystal axis of the substrate by about 45 degrees. IsIt is characterized byThe
[0019]
  Further, in this case, among the electrodes that form the electrode / wave plate pair including the 1/2 wave plate, the electrode / wave plate is the odd-numbered 1/2 wave plate from the most downstream in the light propagation direction. The pair of electrodes is configured as a second axis rotating electrode for rotating a polarization state point represented on the Poincare sphere about a second axis orthogonal to the first axis, The electrode forming the electrode / wave plate pair with the even-numbered half-wave plate from the most downstream in the light propagation direction rotates around the first axis about the polarization state point represented on the Poincare sphere. Among the electrodes that constitute the electrode / wave plate pair including the ¼ wavelength plate, the odd-numbered ¼ from the most downstream in the light propagation direction. The electrode that forms the electrode / wave plate pair with the wave plate is The polarization state point represented on the anchor sphere is configured as a third axis rotation electrode for rotating about the third axis orthogonal to the first axis, and from the most downstream in the light propagation direction. The first axis rotation for rotating the polarization state point represented on the Poincare sphere about the first axis by the electrode forming the electrode / wave plate pair with the even-numbered quarter wave plate It may be configured as an electrode forYes.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[A1] Description of the first embodiment
FIG. 1 is a schematic top view showing a polarization controlling optical waveguide device 100 according to the first embodiment of the present invention. The polarization controlling optical waveguide device 100 according to the first embodiment includes a wave plate inserted behind electrodes similar to those used as the phase shifter electrodes 611 to 613 (see FIG. 15). A function of rotating the polarization state about S2 orthogonal to the axis is provided, and further, these electrodes and wave plates are combined to provide infinite follow-up described later.
[0021]
Here, the polarization controlling optical waveguide device 100 according to the first embodiment is x-cut having an electro-optic effect (cut parallel to the x axis of the crystal axis) as shown in FIG. An optical waveguide 101 is formed on a substrate made of an LN crystal so as to be y-propagating (so that light propagates in parallel to the y-axis of the crystal axis), and a pair is formed so as to sandwich both sides of the optical waveguide 101. Five electrode pairs (hereinafter simply referred to as electrodes) 111 to 115 are arranged in tandem, and half-wave plates 121 to 124 are interposed between the electrode pairs 111 to 115.
[0022]
In other words, the electrode 111 and the wave plate 121, the electrode 112 and the wave plate 122, the electrode 113 and the wave plate 123, and the electrode 114 and the wave plate 124 constitute an electrode / wave plate pair 131 to 134, respectively. By arranging the electrode 115 together with the electrode / wave plate pairs 131 to 134 in tandem, the electrodes 111 to 115 and the wave plates 121 to 124 are arranged alternately along the light propagation direction.
[0023]
Further, the electrode 115 is the most downstream electrode provided along the light propagation direction of the optical waveguide 101 at the most downstream side in the light propagation direction, and is a bias represented on the Poincare sphere 700 based on the supplied electric signal. The wave state point can rotate around the S1 axis as the first axis of the Poincare sphere 700 (see FIG. 4).
Next, for the convenience of explanation, the movement of the polarization state point due to the provision of the half-wave plates 121 to 124 on the downstream side of the electrodes 111 to 114 in the light propagation direction, as in the electrode / wave plate pairs 131 to 134. Therefore, the electrode / wave plate pair 130 including the electrode 110 and the wave plate 120 shown in FIG.
[0024]
The electrode 110 in the electrode / wavelength plate pair 130 has the S1 axis (the TE point A and the TM point B as the first axis of the Poincare sphere) for the polarization state point represented on the Poincare sphere by the supplied electrical signal. It can rotate around a passing axis. Specifically, the electrode 110 changes the phase of TM and TE, which are polarization components of light propagating through the optical waveguide 101, according to the applied voltage, and functions as a phase shifter. It has become.
[0025]
The half-wave plate 120 is provided on the optical waveguide 101 on the downstream side in the light propagation direction with respect to the electrode 110. The half-wave plate 120 is, for example, shown in FIGS. As shown in b), the angle of the crystal axis is shifted by 22.5 ° with respect to the crystal axis of the LN substrate.
That is, as shown in FIGS. 3A and 3B, the crystal of the half-wave plate 120 with respect to the crystal axis (x axis-z axis) of the LN substrate in the y-propagating optical waveguide 101 The axes (f-axis-s-axis) are shifted by 22.5 °. In other words, the z axis that is the crystal axis in the optical waveguide 101 and the f axis that is the crystal axis of the half-wave plate 120 are shifted by an angle of 22.5 °.
[0026]
In general, a half-wave plate is represented on the Poincare sphere 700 as shown in FIG. 4 when the crystal axis is shifted by 45 ° with respect to the crystal axis of the LN crystal constituting the substrate. The polarization state X only moves to the polarization state Y represented by a point B that is symmetric with respect to the plane formed by the S2 axis and the S3 axis. That is, as shown in FIG. 5, the locus R3 centered on the S1 axis indicated by the solid line only moves to the locus R3 ′ on the same axis (S1 axis) indicated by the dotted line.
[0027]
However, as in the first embodiment, the half-wave plate 120 is arranged with the crystal axis shifted by 22.5 ° with respect to the crystal axis of the LN crystal constituting the substrate, as shown in FIG. The polarization state X is a point Z symmetrical with respect to a plane formed by the S3 axis and the S4 axis that forms an angle of 45 ° between the S1 axis and the S2 axis and passes through the point F on the equator E. Moving.
[0028]
As a result, as shown in FIG. 6, the locus R3 centered on the S1 axis indicated by the solid line moves to the locus R4 centered on the S2 axis indicated by the dotted line. That is, by applying a voltage to the electrode 110 on the upstream side of the half-wave plate 120, the polarization state of the propagating light can be controlled to rotate by a desired angle about the S2 axis.
The electrodes 111 to 114 shown in FIG. 1 pass through a plurality of half-wave plates on the downstream side in the light propagation direction. As will be described later, the rotation axis of the polarization state point on the Poincare sphere 700 for these electrodes 111 to 114 changes depending on the number of half-wave plates that pass through.
[0029]
In addition, as in the polarization control optical waveguide device shown in FIG. 1 described above, among the electrode / wave plate pairs 131 to 134 arranged in tandem, the electrodes arranged in the odd-numbered stages from the most downstream in the light propagation direction The electrodes 114 and 112 forming the wave plate pair 134 and 132 are electrodes for S2 axis rotation, and the electrodes 113 and 111 forming the electrode / wave plate pair 133 and 131 arranged at the even-numbered stages from the most downstream in the light propagation direction are used. , S1 axis rotation electrode.
[0030]
That is, the electrode 114 of the electrode / wave plate pair 134 arranged in the first stage from the most downstream side and the electrode 112 of the electrode / wave plate pair 132 arranged in the third stage from the most downstream side described above are Poincare. The polarization state point represented on the sphere 700 is configured as an orthogonal axis rotating electrode / wave plate pair for rotating about the S2 axis which is an orthogonal axis orthogonal to the S1 axis.
[0031]
Furthermore, the electrode 113 of the electrode / wave plate pair 133 arranged in the second stage from the most downstream in the light propagation direction, and the electrode 111 of the electrode / wave plate pair 131 arranged in the fourth stage from the above-mentioned most downstream. The polarization state point represented on the Poincare sphere 700 is configured as a first axis rotating electrode / wave plate pair for rotating about the S1 axis.
As described above, when a voltage is applied to the electrode 115 as the most downstream electrode, the polarization state can be rotated around the S1 axis, and when a voltage is applied to the electrode 114, the light emitted from the wave plate 124 is reflected. The polarization state can be rotated around the S2 axis.
[0032]
Further, when a voltage is applied to the electrode 113, the polarization control point can be rotated around the S1 axis as the first axis. That is, the light that has passed through the electrode 113 passes through the two half-wave plates 123 and 124. The polarization control point located on the trajectory R3 in FIG. 6 based on the voltage applied to the electrode 113 is placed on the trajectory R4 shown by the dotted line in FIG. Then, the second half-wave plate 124 returns to the orbit (centered on the S1 axis) R3 shown by the solid line in FIG.
[0033]
Further, the light that has passed through the electrode 112 passes through the three half-wave plates 122 to 124. That is, the rotation axis trajectory of the polarization control point by applying a voltage to the electrode 112 also moves according to the case of the electrode 113 described above, and the S2 axis as the second axis becomes the rotation orbit axis. In other words, the electrode 112 functions as an electrode for rotating the second axis.
[0034]
Similarly, the light that has passed through the electrode 111 passes through the four half-wave plates 121-124. That is, the rotation axis trajectory of the polarization control point by applying a voltage to the electrode 111 has the S1 axis as the first axis as the rotation trajectory axis. In other words, the electrode 111 functions as an electrode for rotating the first axis.
From the above, by applying a voltage to each of the electrodes 111 to 115, the rotation axes of the polarization state controlled in the electrodes 111 to 114 and the most downstream electrode 115 forming the electrode / wave plate pairs 131 to 134 are respectively Alternating with S1, S2, S1, S2 and S1.
[0035]
Therefore, in the polarization controlling optical waveguide device 100 according to the first embodiment, the electrodes 111 to 115 having the same configuration as the phase shifter electrodes 611 to 613 shown in FIG. 15 and the wavelengths such as the wave plates 121 to 124 are used. By alternately arranging elements having less dependency in tandem, the dependency on the wavelength at which the polarization can be controlled is improved as compared with the conventional comb electrodes 621 and 622 shown in FIG. A polarization controller capable of controlling from a state to an arbitrary polarization state can be configured.
[0036]
By the way, when the polarization controlling optical waveguide device 100 as described above is applied as a polarization controller, so-called infinite followability is required. That is, even when the voltage applied to any of the electrodes 111 to 115 reaches the maximum voltage that can be applied, the polarization control is continued by controlling the voltage applied to the other electrodes. Need to be able to.
[0037]
In order to achieve this infinite follow-up, like the polarization control optical waveguide device 100 shown in FIG. 1, corresponding to the arrangement of the electrodes 111 to 115, the rotation axis of the polarization state is between two rotation axes orthogonal to each other. In the case of alternately controlling at least five electrodes may be arranged in tandem for the following reasons.
As a polarization controller, in order to move an arbitrary polarization state to an arbitrary polarization state, it is sufficient to alternately arrange electrodes that rotate about two orthogonal axes on the Poincare sphere 700 in a three-stage tandem. . If the input light whose polarization is to be controlled is at the polarization state point represented by the point on the axis on the Poincare sphere 700 rotated by the first electrode, the polarization state is shifted. This is because they cannot.
[0038]
As described above, in order to construct a polarization controller having infinite follow-up in addition to the function of moving from a certain polarization state to an arbitrary polarization state, as an electrode to be arranged in tandem, In addition, it is necessary to add two additional electrodes.
That is, in the polarization controlling optical waveguide device 100 applied as a polarization controller, the polarization state is controlled by the voltage applied to the electrodes 111 to 115, but when a certain voltage is applied, the original polarization state is restored. Therefore, in order to further change the polarization state, a further voltage is applied. For this reason, when the number of pairs of electrodes that perform rotation control of the polarization state on one axis is small, the voltage to be applied depends on the performance of the power supply and the electrodes themselves, etc. In some cases, the applied voltage is exceeded (a limit is reached in the voltage to be applied).
[0039]
That is, as in the device 100 shown in FIG. 1, the voltage to be applied to any one of the electrodes 111 to 115 exceeds the maximum applied voltage of the device performance or the power supply performance to control the polarization. When the voltage cannot be increased, the voltage applied to the electrode can be lowered while controlling the polarization with the spare electrode.
[0040]
For example, in the case where the polarization controlling optical waveguide device 100 shown in FIG. 1 is applied as a polarization controller, when the voltage applied to the electrode 113 is the limit, the polarization is controlled by the electrodes 111, 112, 114, 115, The voltage applied to the electrode 113 may be lowered.
That is, even by controlling the polarization using the electrodes 111, 112, 114, and 115 other than the electrode 113, the rotation axes of the polarization state can be set to S1, S2, S2, and S1, respectively. Can be controlled. Even when the voltage to be applied to the electrodes other than the electrode 113 exceeds the maximum value, it is possible to substantially ensure the three-stage alternating arrangement of the electrodes rotated around the two orthogonal axes on the Poincare sphere 700. it can.
[0041]
In other words, in the polarization controlling optical waveguide device 100 of the present embodiment, when the five electrodes 111 to 115 are arranged in tandem with the wave plates 121 to 124 interposed therebetween, the polarization controller is configured as a polarization controller. While improving the dependence of the wavelength on which the polarization control can be performed, it is possible to have infinite follow-up performance.
With the above-described configuration, in the polarization controlling optical waveguide device 100 according to the first embodiment of the present invention, for example, independent power sources (voltage signal supply sources) are connected to the electrodes 111 to 115, and each power source is illustrated. When a polarization controller is configured by connecting a control circuit that is not connected, this control circuit can achieve a desired polarization state according to the input polarization state point as shown in FIG. The voltage signal to be supplied to each of the electrodes 111 to 115 is controlled.
[0042]
For example, when the polarization state point of the light incident on the optical waveguide 101 is M point in the Poincare sphere 700 shown in FIG. 7, a desired voltage is applied to each of the electrodes 111 to 115 based on control by the control circuit. By applying this, the polarization state point can be moved to the N point by following the bold arrow shown in FIG. That is, as indicated by a thick arrow in the figure, the axis MM on the Pokancare sphere 700 centered on the S1 axis and the axis NN on the Poincare sphere 700 centered on the S2 axis are traced from the point M. The polarization state point is moved to the N point.
[0043]
At this time, by supplying a voltage signal to each of the electrodes 111 to 114 and the most downstream electrode 115 constituting the electrode / wave plate pair 131 to 134, the electrode / wave plate pair 131 to 134 and the most downstream electrode 115 are controlled. The rotation axes in the polarization state alternate with S1, S2, S1, S2, and S1, respectively. In this way, the polarization state of the light incident on the optical waveguide 101 is controlled to be emitted in a desired polarization state while improving the wavelength dependency as compared with the case of FIG.
[0044]
In addition, when the voltage applied to any one of the electrodes 111 to 115, for example, the electrode 113 is the limit, the polarization is controlled by the electrodes 111, 112, 114, and 115, so that the rotation axis of the polarization state is set respectively. As S1, S2, S2, and S1, the polarization state of the light incident on the optical waveguide 101 is controlled to an arbitrary polarization state. Further, by reducing the voltage applied to the electrode 113, it is possible to return to a state where the voltage can be applied again for polarization control.
[0045]
As described above, according to the polarization controlling optical waveguide device 100 according to the first embodiment of the present invention, the electrode that can rotate the polarization state point about the S1 axis of the Poincare sphere 700 is provided, and the crystal of the substrate A half-wave plate is arranged by shifting the angle of the crystal axis by 22.5 ° with respect to the axis, and the polarization state point rotated around the S1 axis is rotated around the S2 axis orthogonal to the S1 axis. Therefore, if the polarization controller is configured using this polarization control optical waveguide device 100, the dependency of the polarization state control on the wavelength of incident light can be improved. There are advantages.
[0046]
Also, by setting the number of electrodes to be at least five, the voltage to be applied to any one of the five electrodes 111 to 115 exceeds the maximum applied voltage for device performance or power supply performance, Even when the voltage cannot be increased to control the voltage, the voltage applied to the electrode can be lowered while controlling the polarization with the remaining electrode, thus ensuring infinite follow-up. There is also an advantage that can be.
[0047]
[A2] Description of Modification of First Embodiment
In the polarization controlling optical waveguide device 100 according to the first embodiment described above, the half-wave plates 121 to 124 are used as the wave plates in the crystal axis direction (x axis-z axis) of the LN substrate not shown in the device 100. It is arranged with an angle of 22.5 °.
[0048]
FIG. 8 is a schematic top view showing a polarization controlling optical waveguide device 100A according to a modification of the first embodiment of the present invention. The device 100A shown in FIG. 8 is the same as that in the first embodiment described above. Compared with the device 100, the type of the wave plate interposed between the electrodes 111 to 115 and the arrangement state thereof are different.
Here, 125 to 128 are quarter-wave plates, and these quarter-wave plates 125 to 128 are respectively located at the same positions as the half-wave plates 121 to 124 in the first embodiment described above, and As shown in FIGS. 9A and 9B, the LN substrate is disposed with an angle of 45 ° with respect to the crystal axis direction (x axis-z axis) of the LN substrate.
[0049]
In other words, the electrode 111 and the wave plate 125, the electrode 112 and the wave plate 126, the electrode 113 and the wave plate 127, and the electrode 114 and the wave plate 128 form the electrode / wave plate pairs 141 to 144, respectively.
At this time, the quarter wavelength plates 125 to 128 are provided on the optical waveguide 101 on the downstream side in the light propagation direction with respect to the electrodes 111 to 114, respectively. 9 (a) and 9 (b), the angle of the crystal axis is shifted by 45 ° with respect to the crystal axis of the LN substrate. In other words, the quarter-wave plates 125 to 128 are, as shown in FIGS. 9A and 9B, the crystal axes (x-axis-z-axis) of the polarization plane in the optical waveguide 101 for y propagation. In contrast, the crystal axes (f-axis-s-axis) are shifted by 45 °.
[0050]
Further, the movement of the polarization state point by providing the quarter wavelength plates 125 to 128 on the downstream side in the light propagation direction of the electrodes 111 to 114 as in the electrode / wave plate pairs 141 to 144 is described above. In the following description, it is assumed that a quarter-wave plate 120A is arranged in place of the half-wave plate 120 in FIG.
[0051]
That is, the polarization state of the light that has passed through the electrode 110 and the wave plate 120A as described above is based on the voltage applied to the electrode 110, as shown in FIGS. 10 and 11, based on the applied voltage. The sphere 700 rotates about the S3 axis.
Specifically, as shown in FIG. 10, the quarter-wave plate arranged by shifting the angle of the crystal axis by 45 ° with respect to the crystal axis of the LN substrate represents a point A on the equator E in the Poincare sphere 700. It is possible to move to a point B on the trajectory passing through the S2 axis and the S3 axis.
[0052]
Note that the electrodes 111 to 114 shown in FIG. 8 also pass through a plurality of quarter-wave plates on the downstream side in the light propagation direction. The rotation axes of the polarization state points on the Poincare sphere 700 for these electrodes 111 to 114 also vary depending on the number of quarter-wave plates that pass through, as in the case of the first embodiment described above. .
[0053]
Here, as in the case of the first embodiment described above, among the electrode / wavelength plate pairs 141 to 144 arranged in tandem as in the polarization controlling optical waveguide device 100A shown in FIG. The electrodes 114 and 112 forming the electrode / wave plate pairs 144 and 142 arranged at odd-numbered stages from the most downstream are used as electrodes for S3-axis rotation. In addition, the electrodes 113 and 111 forming the electrode / wave plate pairs 137 and 135 arranged in the even-numbered stages from the most downstream side together with the most downstream electrode 115 in the light propagation direction are used as the S1-axis rotation electrodes.
[0054]
Specifically, when a voltage is applied to the electrode 115 as the most downstream electrode, the polarization state can be rotated around the S1 axis, and when a voltage is applied to the electrode 114, the light emitted from the wave plate 124 The polarization state can be rotated around the S3 axis.
Further, when a voltage is applied to the electrode 113, the polarization control point can be rotated around the S1 axis as the first axis. That is, the light that has passed through the electrode 113 passes through the two quarter-wave plates 127 and 128. The polarization control point located on the trajectory R3 in FIG. 11 based on the voltage applied to the electrode 113 is placed on the trajectory R5 shown by the dotted line in FIG. 11 by the first quarter wave plate 127. Then, the second quarter wavelength plate 128 returns to the orbit (centered on the S1 axis) R3 shown by the solid line in FIG.
[0055]
The light that has passed through the electrode 112 passes through the three quarter-wave plates 122-124. That is, the rotation axis trajectory of the polarization control point by applying a voltage to the electrode 112 also moves according to the case of the electrode 113 described above, and the S3 axis as the third axis becomes the rotation orbit axis. In other words, the electrode 112 functions as an electrode for rotating the third axis.
[0056]
Similarly, the light that has passed through the electrode 111 passes through the four half-wave plates 121-124. That is, the rotation axis trajectory of the polarization control point by applying a voltage to the electrode 111 has the S1 axis as the first axis as the rotation trajectory axis. In other words, the electrode 111 functions as an electrode for rotating the first axis.
From the above, by applying a voltage to each of the electrodes 111 to 115, the rotation axes of the polarization state controlled in the electrodes 111 to 114 and the most downstream electrode 115 forming the electrode / wave plate pairs 141 to 144 are respectively Alternating with S1, S3, S1, S3 and S1.
[0057]
With such a configuration, also in the polarization controlling optical waveguide device 100A according to the modification of the first embodiment of the present invention, the polarization of the light incident on the optical waveguide 101 is shifted as in the case of the first embodiment. The wave state is emitted while being controlled to a desired polarization state while improving the wavelength dependency as compared with the case of FIG.
Therefore, in the polarization controlling optical waveguide device 100A according to the modification of the first embodiment of the present invention, an electrode capable of rotating the polarization state point about the S1 axis of the Poincare sphere 700 is provided, and the crystal of the substrate A quarter-wave plate is disposed with the crystal axis angle shifted by 45 ° with respect to the axis, and the polarization state point rotated about the S1 axis is rotated about the S3 axis orthogonal to the S1 axis. Therefore, the same advantages as those of the first embodiment can be obtained.
[0058]
[B] Description of the second embodiment
In the polarization control optical waveguide device 100 shown in FIG. 1 described above, the same type of half-wave plates 121 to 124 are disposed as the wave plates. Also in the polarization controlling optical waveguide device 100A shown in FIG. 8, the same kind of quarter wave plates 125 to 128 are disposed as the wave plates.
[0059]
FIG. 12 is a schematic top view showing a polarization controlling optical waveguide device 200 according to the second embodiment of the present invention. The device 200 shown in FIG. 12 is the device shown in FIG. 1 or FIG. Compared with 100 and 100A, the number of wave plates arranged as a wave plate interposed between the electrodes 211 to 214 is different from the number of electrodes and the number of wave plates arranged in tandem.
[0060]
Here, also in the polarization controlling optical waveguide device 200 shown in FIG. 12, the optical waveguide 201 is formed on the substrate made of the x-cut LN crystal having the electro-optic effect so as to be y-propagated. Four pairs of electrodes (hereinafter simply referred to as electrodes) 211 to 214 that are paired so as to sandwich both sides of the optical waveguide 201 are arranged in tandem.
[0061]
Further, a half-wave plate 221 is interposed between the electrodes 211 and 212, a quarter-wave plate 222 is interposed between the electrodes 212 and 213, and a half-wave plate 223 is interposed between the electrodes 213 and 214, respectively. Has been.
In other words, the electrode 211 and the half-wave plate 221, the electrode 212 and the quarter-wave plate 222, the electrode 213 and the half-wave plate 223 constitute electrode / wave plate pairs 231 to 233, respectively. By arranging the electrode 214 together with the pair of electrode / wave plate pairs 231 to 233 in tandem, the electrodes 211 to 214 and the wave plates 221 to 223 are arranged alternately along the light propagation direction.
[0062]
The electrode 214 is the most downstream electrode provided along the light propagation direction of the optical waveguide 101 at the most downstream side in the light propagation direction, and is a bias represented on the Poincare sphere 700 based on the supplied electric signal. The wave state point can rotate around the S1 axis as the first axis of the Poincare sphere 700 (see FIG. 13).
Further, the half-wave plates 221 and 223 are 22.5 with respect to the crystal axis direction (x-axis-z-axis) of the LN substrate, as in the case of FIG. 3A and FIG. The quarter wavelength plate 222 is arranged at an angle of °, and the crystal axis direction (x-axis-z-axis) of the LN substrate is the same as in the case of FIGS. 9 (a) and 9 (b). ) With an angle of 45 °.
[0063]
That is, one electrode / wave plate pair (see reference numeral 231 in this case) is formed from two adjacent electrode / wave plate pairs 231 to 233 (for example, electrode / wave plate pairs 231 and 232) in this tandem arrangement. The wave plate (see reference numeral 221) is composed of a half-wave plate provided by shifting the angle of the crystal axis from the crystal axis of the substrate by about 22.5 degrees, while the other electrode / wave plate pair ( A wave plate (see reference numeral 232) is a quarter wave plate provided by shifting the angle of the crystal axis by about 45 degrees with respect to the crystal axis of the substrate.
[0064]
Of the electrodes 213 and 211 forming the electrode / wave plate pair 233 and 231 including the half-wave plates 223 and 221, the odd-numbered (first) half-wave from the most downstream in the light propagation direction. The electrode 213 that forms the electrode / wave plate pair 233 with the plate 223 is a polarization state point represented on the Poincare sphere 700 shown in FIG. 13 with the S2 axis as the second axis orthogonal to the first axis as the center. It is configured as an electrode for S2 axis rotation for rotation.
[0065]
The electrode / wave plate pair 232 includes an odd-numbered (first) quarter wave plate 222 from the most downstream in the light propagation direction. The electrode 212 constituting the electrode / wave plate pair 232 is shown in FIG. The polarization state point represented on the Poincare sphere 700 shown in FIG. 14 is configured as an electrode for S3 axis rotation for rotating about the S3 axis as a third axis orthogonal to the S1 axis.
[0066]
Furthermore, an electrode 211 that forms an electrode / wave plate pair 231 with the even-numbered (second) half-wave plate 221 from the most downstream in the light propagation direction is a polarization represented on the Poincare sphere 700 shown in FIG. The state point is configured as an electrode for S1 axis rotation for rotating about the S1 axis as the first axis.
Specifically, based on the electrical signal applied to the electrode 213 forming the electrode / wave plate pair 233, the polarization state point of the light that has passed through the electrode 213 (for example, the polarization state on the orbit R3 shown in FIG. 13) The point moves to the polarization state point on the orbit R4 (centered on the S2 axis) indicated by the dotted line in FIG. 13 when passing through the latter half-wave plate 223. This is the same as the case of the electrode 114 in the device 100 shown in FIG.
[0067]
Furthermore, based on the electrical signal applied to the electrode 212 forming the electrode / wave plate pair 232, the polarization state point of the light passing through the electrode 212 (for example, the polarization state point on the orbit R3 shown in FIG. 13) is When the light passes through the quarter-wave plate 222, it moves to the polarization state point on the orbit R5 shown by the dotted line in FIG. 14, and when it passes through the half-wave plate 223, it is shown by the thick line in FIG. Move to the polarization state point on the trajectory R6 (rotating about the S3 axis).
[0068]
The light that has passed through the electrode 211 passes through the wave plates 221 to 223 in the order of the half-wave plate 221, the quarter-wave plate 222, and the half-wave plate 223. The polarization state point of the light that has passed through the electrode 211 (for example, the polarization control point on the trajectory R3 in FIG. 13) passes through the half-wave plate 221 so that the trajectory R4 illustrated by the dotted line in FIG. Move to the top point. This trajectory does not change even when it passes through the next quarter-wave plate 222, but returns to a point on the trajectory R3 (rotating about the S1 axis) again by passing through the last half-wave plate 223. .
[0069]
From the above, by applying a voltage to each of the electrodes 211 to 214, the rotation axis of the polarization state controlled in each of the electrode / wave plate pairs 231 to 234 and the most downstream electrode 214 is S1, S3, S2, respectively. S1.
With the above-described configuration, in the polarization controlling optical waveguide device 200 according to the second embodiment of the present invention, as in the case of the first embodiment described above, for example, an independent power source (voltage signal) is provided for each of the electrodes 211 to 214. By connecting a power source) and connecting a control circuit (not shown) to each power source, a polarization controller is configured so that a desired polarization state is obtained according to the input polarization state point. A voltage signal to be supplied to each of the electrodes 111 to 115 is controlled.
[0070]
At this time, by supplying a voltage signal to each of the electrodes 211 to 214, the rotation axes of the polarization state controlled in each of the electrodes 211 to 214 are alternated with S1, S3, S2, and S1, respectively. In this way, the polarization state of the light incident on the optical waveguide 101 is controlled to be emitted in a desired polarization state while improving the wavelength dependency as compared with the case of FIG.
[0071]
In the configuration in which the half-wave plates 223, 221 and the quarter-wave plates 222 are alternately arranged as in the second embodiment, if the number of tandem arrangements of the electrodes including the most downstream electrode 214 is at least 4, The same infinite followability as in the first embodiment can be ensured.
That is, when the voltage to be supplied to the electrode 212 (or the electrode 213) is the limit, the remaining three electrodes 211, 213, and 214 (or the electrodes 211, 212, and 214) are polarized so as to be in an arbitrary polarization state. Can be controlled. That is, the electrodes 211, 213, and 214 can rotate the polarization state about the S1, S2, and S1 axes, respectively, and the electrodes 211, 212, and 214 can be polarized about the S1, S3, and S1 axes, respectively. The state can be controlled.
[0072]
Even when the electrode 211 is at the limit, the polarization state can be rotated about the S3, S2, and S1 axes by the electrodes 212 to 214, respectively. Even when the electrode 214 is at the limit, the electrodes 211 to 213 can be rotated. Since the polarization state can be rotated about the S1, S2, and S3 axes, respectively, the polarization state can be moved to an arbitrary point.
[0073]
Therefore, in the polarization controlling optical waveguide device 200 according to the second embodiment of the present invention, the half-wave plate 221, the quarter-wave plate 222 and the half-wave plate 223 are provided, so that As in the case of the first embodiment, if a polarization controller is configured using this polarization control optical waveguide device 200, the advantage of improving the dependency of polarization state control on the wavelength of incident light can be improved. In addition, there is an advantage that a polarization controller with infinite follow-up can be configured with a smaller number of electrodes than in the case of the first embodiment.
[0074]
In the second embodiment described above, one quarter-wave plate 222 is arranged between the two half-wave plates 221 and 223. According to the present invention, this is the case. For example, a quarter wavelength plate is arranged at an angle of 45 ° with respect to the crystal axis of the substrate at a position where the two half wavelength plates 221 and 223 shown in FIG. Of course, it is also possible to arrange the half-wave plate at a position where the quarter-wave plate 222 is disposed at an angle of 22.5 ° with respect to the crystal axis of the substrate.
[0075]
[C] Other
In each of the above-described embodiments, the polarization control optical waveguide devices 100, 100A, and 200 in which five or four electrodes are arranged in tandem have been described in detail. However, according to the present invention, at least a single electrode and a wave plate are used. The device may be configured by combining with the above, and even in the device configured as described above, the wavelength dependency can be greatly improved as compared with the comb-shaped electrode as a mode converter as shown in FIG.
[0076]
Further, according to the present invention, various modifications other than the above-described embodiments can be implemented without departing from the spirit of the present invention.
For example, in the polarization controlling optical waveguide device 100, 100A shown in FIG. 1 or 8, a device is configured by arranging five or more electrodes in tandem, or in the polarization controlling optical waveguide device 200 shown in FIG. Four or more electrodes can be arranged in tandem.
[0077]
[D] Appendix
(Appendix 1) An optical waveguide formed on a substrate having an electro-optic effect;
A polarization state point provided along the light propagation direction of the optical waveguide and represented on the Poincare sphere based on the supplied electric signal is provided with an electrode that can rotate around the first axis of the Poincare sphere. With
A wave plate is disposed on the optical waveguide on the downstream side in the light propagation direction with respect to the electrode by shifting the angle of the crystal axis by a predetermined angle with respect to the crystal axis of the substrate, and the polarization rotated about the first axis is arranged. An optical waveguide device for polarization control, characterized in that the wave state point is rotated about a second axis orthogonal to the first axis.
[0078]
(Supplementary note 2) A plurality of pairs of electrodes and wave plates are arranged in tandem so that the electrodes and wave plates are alternately arranged along the light propagation direction,
The first axis of the Poincare sphere is set at the most downstream side in the light propagation direction along the light propagation direction of the optical waveguide, and the polarization state point represented on the Poincare sphere based on the supplied electric signal. The polarization-controlling optical waveguide device according to appendix 1, wherein the optical waveguide device is provided with a most downstream electrode that can rotate as a center.
[0079]
(Appendix 3) Among the electrode / wave plate pairs arranged in tandem,
The electrode constituting the electrode / wave plate pair arranged at odd-numbered stages from the most downstream in the light propagation direction is a polarization state point represented on the Poincare sphere with an orthogonal axis orthogonal to the first axis as a center. It is configured as an orthogonal axis rotation electrode for rotation,
A first axis rotation in which the electrodes forming the even-numbered stages from the most downstream in the light propagation direction rotate about the first axis with respect to the polarization state point represented on the Poincare sphere. That was configured as an electrode for
The optical waveguide device for polarization control according to appendix 2, which is characterized by
[0080]
(Supplementary note 4) The polarization controlling optical waveguide device according to Supplementary note 3, wherein the number of electrodes including the most downstream electrode is at least five.
(Supplementary note 5) Any one of Supplementary notes 1 to 3, wherein a half-wave plate is used as the wavelength plate, and the angle of the crystal axis is shifted by about 22.5 degrees with respect to the crystal axis of the substrate. An optical waveguide device for polarization control according to claim 1.
[0081]
(Supplementary note 6) Any one of Supplementary notes 1 to 3, wherein a quarter wave plate is used as the wave plate and the angle of the crystal axis is shifted by about 45 degrees with respect to the crystal axis of the substrate. An optical waveguide device for polarization control as described in the item.
(Supplementary note 7) Among the two electrode / wave plate pairs adjacent in the tandem arrangement, the wave plate forming one electrode / wave plate pair has an angle of the crystal axis of 22.5 degrees with respect to the crystal axis of the substrate. The wave plate constituting the other electrode / wave plate pair is formed by shifting the angle of the crystal axis by about 45 degrees with respect to the crystal axis of the substrate. An optical waveguide device for polarization control as set forth in appendix 2, characterized by comprising a quarter-wave plate.
[0082]
(Supplementary Note 8) Among the electrodes forming the electrode / wave plate pair including the half wave plate, the electrode / wave plate pair is formed by the odd half wave plate from the most downstream in the light propagation direction. The electrode is configured as a second axis rotating electrode for rotating a polarization state point represented on the Poincare sphere about a second axis orthogonal to the first axis;
The electrode forming the electrode / wave plate pair with the even-numbered half-wave plate from the most downstream in the light propagation direction rotates around the first axis about the polarization state point represented on the Poincare sphere. Configured as a first axis rotation electrode for
And among the electrodes forming the electrode / wave plate pair including the quarter wave plate,
The electrode forming the electrode / wave plate pair with the odd-numbered quarter wave plate from the most downstream in the light propagation direction has a polarization state point represented on the Poincare sphere orthogonal to the first axis. It is configured as a third axis rotating electrode for rotating about three axes,
The electrode forming the electrode / wave plate pair with the even-numbered quarter wave plate from the most downstream in the light propagation direction rotates around the first axis about the polarization state point represented on the Poincare sphere. Configured as an electrode for rotating the first axis for
The polarization-controlling optical waveguide device according to appendix 7, which is characterized by the following.
[0083]
(Supplementary note 9) The optical waveguide device according to supplementary note 7, wherein the number of electrodes including the most downstream electrode is at least four.
[0084]
【The invention's effect】
As described above in detail, according to the optical waveguide device for polarization control of the present invention, an electrode that can rotate the polarization state point about the first axis of the Poincare sphere is provided, and the crystal axis of the substrate. The wave plate is arranged with the crystal axis angle shifted by a predetermined angle, and the polarization state point rotated about the first axis is rotated about the second axis orthogonal to the first axis. Therefore, if a polarization controller is configured using this polarization control optical waveguide device, there is an advantage that the dependency of polarization state control on the wavelength of incident light can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic top view showing an optical waveguide device for polarization control according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining the movement of a polarization state point by providing a half-wave plate on the downstream side in the light propagation direction of an electrode in the first embodiment of the present invention.
FIGS. 3A and 3B show that the half-wave plate in the first embodiment of the present invention is arranged with the crystal axis angle shifted by 22.5 ° with respect to the crystal axis of the substrate. FIG.
FIG. 4 is a diagram for explaining the movement of the polarization state in the first embodiment of the present invention.
FIG. 5 is a diagram for explaining the movement of the polarization state in the first embodiment of the present invention.
FIG. 6 is a diagram for explaining the movement of the polarization state in the first embodiment of the present invention.
FIG. 7 is a diagram for explaining the movement of the polarization state in the first embodiment of the present invention.
FIG. 8 is a schematic top view showing a polarization controlling optical waveguide device according to a modification of the first embodiment of the present invention.
FIGS. 9 (a) and 9 (b) show that a quarter-wave plate in a modification of the first embodiment of the present invention is arranged with the crystal axis angle shifted by 45 ° with respect to the crystal axis of the substrate. It is a figure explaining this.
FIG. 10 is a diagram for explaining the movement of the polarization state in a modification of the first embodiment of the present invention.
FIG. 11 is a diagram for explaining the movement of the polarization state in a modification of the first embodiment of the present invention.
FIG. 12 is a schematic top view showing an optical waveguide device for polarization control according to a second embodiment of the present invention.
FIG. 13 is a diagram for explaining the movement of the polarization state in the second embodiment of the present invention.
FIG. 14 is a diagram for explaining the movement of the polarization state in the second embodiment of the present invention.
FIG. 15 is a diagram showing an optical waveguide device.
FIG. 16 is a diagram for explaining the movement of the polarization state;
17 is a diagram for explaining an electrode pair of the optical waveguide device shown in FIG. 15. FIG.
18A to 18C are views for explaining the operation of the electrode pair of the optical waveguide device shown in FIG.
FIG. 19 is a diagram for explaining the operation of the electrode pair of the optical waveguide device shown in FIG. 15;
20 is a diagram for explaining a comb-shaped electrode of the optical waveguide device shown in FIG. 15;
21A to 21C are diagrams for explaining the operation of the comb-shaped electrode of the optical waveguide device shown in FIG.
22 is a view for explaining a comb-shaped electrode of the optical waveguide device shown in FIG. 15;
[Explanation of symbols]
100, 100A, 200 Polarization control optical waveguide device
101, 201 Optical waveguide
110-115, 211-214 Electrode pairs (electrodes)
120-124,221,223 half-wave plate
120A, 125-128, 222 1/4 wavelength plate
131-134, 141-144 electrode / wave plate pairs
600 Optical waveguide device
601 Optical waveguide
611-613 electrode pair
621,622 Comb electrode
700 Poincare sphere

Claims (2)

An optical waveguide formed on a substrate having an electro-optic effect;
A polarization state point provided along the light propagation direction of the optical waveguide and represented on the Poincare sphere based on the supplied electric signal is provided with an electrode that can rotate around the first axis of the Poincare sphere. With
The optical waveguide path of the optical propagation direction downstream side with respect to the electrode, by placing a wave plate by shifting a predetermined angle the angle of the crystal axis with respect to the crystal axis of the substrate, which is rotated about said first axis polarized The wave state point is configured to be rotated about a second axis orthogonal to the first axis ;
A plurality of sets of tandem electrodes and wave plate pairs are arranged so that the electrodes and wave plates are alternately arranged along the light propagation direction,
The first axis of the Poincare sphere is set at the most downstream side in the light propagation direction along the light propagation direction of the optical waveguide, and the polarization state point represented on the Poincare sphere based on the supplied electric signal. With the most downstream electrode that can rotate as the center,
Among the two electrode / wave plate pairs adjacent to each other in the tandem arrangement, the wave plate forming one electrode / wave plate pair is provided by shifting the angle of the crystal axis by about 22.5 degrees with respect to the crystal axis of the substrate. A quarter wave plate comprising the other electrode / wave plate pair, with the angle of the crystal axis shifted by about 45 degrees with respect to the crystal axis of the substrate. An optical waveguide device for polarization control characterized by comprising a wave plate . Among the electrodes forming the electrode / wave plate pair including the half-wave plate,
The electrode forming the electrode / wave plate pair with the odd-numbered half-wave plate from the most downstream in the light propagation direction has a polarization state point represented on the Poincare sphere perpendicular to the first axis. It is configured as a second axis rotating electrode for rotating about two axes, and
The electrode forming the electrode / wave plate pair with the even-numbered half-wave plate from the most downstream in the light propagation direction rotates around the first axis about the polarization state point represented on the Poincare sphere. Configured as a first axis rotation electrode for
And among the electrodes forming the electrode / wave plate pair including the quarter wave plate,
The electrode forming the electrode / wave plate pair with the odd-numbered quarter wave plate from the most downstream in the light propagation direction has a polarization state point represented on the Poincare sphere orthogonal to the first axis. It is configured as a third axis rotating electrode for rotating about three axes,
The electrode forming the electrode / wave plate pair with the even-numbered quarter wave plate from the most downstream in the light propagation direction rotates around the first axis about the polarization state point represented on the Poincare sphere. The polarization controlling optical waveguide device according to claim 1 , wherein the optical waveguide device is configured as an electrode for rotating the first axis.

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