JP4537934B2 - Optical polarization element and optical switch using the same - Google Patents

Description

  The present invention relates to an optical deflection element having an electro-optic effect suitable for configuring an optical module used for optical communication and the like, and an optical switch using the same.

  Currently, in the field of optical communication networks, in order to cope with the processing of communication data that is rapidly increasing, it is expected that the performance of optical modules produced by combining various optical elements and optical waveguides will be improved.

  Among optical modules, an optical switch module (for example, refer to Patent Document 1) in which an optical deflection element having an electro-optic effect and an optical waveguide substrate are combined is applied with a voltage to the optical deflection element. Since the propagation direction of the propagating optical signal can be changed, it is possible to perform the switching process at a high speed without changing the communication data to be processed into the electric signal.

  FIGS. 3A and 3B are explanatory views showing a principal plane (upper part) and a principal-part cut side surface (lower part) of a light polarizing element according to the prior art. FIG. 3A shows two channels, FIG. 3B shows four channels, and FIG. 8 channels are shown respectively.

The optical deflection element is obtained by epitaxially growing a crystal film having an electro-optic effect such as a PLZT film on a single crystal substrate 1 such as an Nb-doped SrTiO ₃ substrate to form a slab waveguide 2. The prism electrode 3 is formed at a required location. Note that the slab waveguide 2 has a three-layer structure of PLZT films 2A, 2B, and 2C as shown in the figure. When the refractive indexes thereof are 2A and 2C are n ₂ and 2B is n ₁ , ₂ <n ₁ .

  In this optical polarization element, the direction of the optical signal propagating through the slab waveguide 2 can be changed by applying a voltage to the prism electrode 3, and the shape and arrangement of the prism electrode 3 constitute the slab waveguide 2. The electro-optic constant, the necessary deflection angle, the size of the optical signal, the number of channels, and the pitch between channels are designed as parameters.

  By the way, the size of the prism electrode 3 is determined by the width of the optical signal, that is, the collimated light, and the necessary deflection angle, and the size increases as the deflection angle increases.

In this state, when the number of channels of the optical switch is increased, the required deflection angle is increased and the electrode size is also increased. Therefore, the size of the optical deflection element must be increased. This not only makes manufacturing difficult, but also causes a significant increase in manufacturing costs.
JP 2002-318398 A

  In the present invention, by adopting a simple means for flexibly determining the size of the prism electrode and the pitch between channels in the optical deflection element in accordance with the required deflection angle, the optical deflection element, The optical switch is miniaturized to support multi-channel.

  In the optical deflection element according to the present invention and the optical switch using the optical deflection element, the optical deflection element includes an optical waveguide made of a material having an electro-optic effect formed on a single crystal substrate, and light of the optical waveguide. A prism electrode is provided near both ends of the traveling direction and deflects light passing through the channel, and the size of the prism electrode corresponds to a channel located at the center of the channels arranged in a direction intersecting the light traveling direction. The size of each prism electrode is sequentially increased from the prism electrode to the prism electrode corresponding to the channel located at the end portion, and the channel located at the center portion of the channel arranged in the direction intersecting the light traveling direction is located at the end portion. In addition, the optical switch is characterized in that the pitch between channels is increased gradually until the optical deflection element is connected to the optical waveguide. It is characterized by being obtained formed in a direction near both ends.

  By adopting the above means, even if the number of optical switches is increased, the optical switch can be downsized as compared with the optical switch manufactured by the conventional technology, and thus the manufacturing cost can be kept low. it can.

  FIG. 1 is a plan view of an essential part showing an embodiment of an optical deflecting element according to the present invention. In the figure, 12 is a slab waveguide, and 13A to 13H are virtual channels in the slab waveguide 12 ( 14A to 14H respectively indicate prism electrodes corresponding to the channels, and a, b, c, and d indicate pitches between the channels. In this embodiment, the deflection angle of the optical signal is large. That is, it can be seen that the channel pitch is a> b> c> d according to the size of the prism electrode.

  In the illustrated optical deflection element, when the prism electrode 14A corresponding to the channel 13A or the prism electrode 14H corresponding to the channel 13H deflects the optical signal to the maximum extent, it will deflect at the largest angle in the optical deflection element, Therefore, the size needs to be the largest, and when the prism electrode 14D corresponding to the channel 13D or the prism electrode 14E corresponding to the channel 13E deflects the optical signal to the maximum extent, other prisms in the optical deflecting element are used. It will be deflected at the smallest angle compared to the maximum deflection of the optical signal due to the electrodes, and therefore the size is the smallest.

  Further, in this optical deflecting element, if the distance between the prism electrode corresponding to a certain channel and the prism electrode corresponding to the adjacent channel is maintained constant, the inter-channel pitch is determined depending on the size of the prism electrode. Therefore, the pitch between channels, which was unnecessarily wide in the conventional optical deflecting element, is naturally higher in the optical deflecting element shown in FIG. 1, so that the optical deflecting element, and thus the optical switch is small. Will be converted.

  FIG. 2 is a plan view of an essential part for explaining an embodiment of the optical switch using the optical deflection element described with reference to FIG. 1, in which 21 is an input side channel waveguide, and 22 is an input side two. A dimensional lens, 23 is an input side optical deflection element, 24 is a slab waveguide, 25 is an output side optical deflection element, 26 is an output side two-dimensional lens, and 27 is an output side channel waveguide.

  As apparent from FIG. 2, since this optical switch uses the optical deflection element described with reference to FIG. 1, the size of the prism electrode is selected according to the angle at which the optical signal is waved, that is, the deflection angle. In addition, the pitch between channels is determined spontaneously corresponding to the size of the prism electrode.

  The optical switch according to the present invention shown in FIG. 2 and the conventional optical switch, that is, the prism electrodes positioned at the left and right ends when viewed from the input side to the output side are sized to correspond to the largest deflection angle, In addition, when compared with the optical switch applied to the prism electrodes at all positions, the difference in size is obvious.

Next, a process for manufacturing the optical deflection element shown in FIG. 1 will be described.
(1)
A STO (SrTiO ₃ ) substrate doped with Nb is prepared as a single crystal substrate, and a slab waveguide is formed by forming a PLZT film on the STO substrate by applying a sol-gel method.

(2)
After the STO substrate on which the slab waveguide is formed is cut to a required size, the end face is optically polished to perform an antireflection treatment.

(3)
By applying the sputtering method, a W-Cu thin film having a thickness of 0.5 μm is formed on the PLZT film.

(4)
By applying a resist process in the lithography technique, a resist film having a prism electrode pattern is formed.

  Here, the size of the prism electrode pattern increases as the channel is closer to the left and right ends from the center channel of the light deflection element when seen in a plan view, and of course the pitch between channels according to the size. Also make it bigger.

(5)
By applying the wet etching method, the W-Cu thin film is etched using the resist film as a mask, prism electrodes corresponding to the respective channels are formed, and then the resist film is peeled off.

  The process described above is almost the same as the conventional technique and does not require any special technique. The point is that the size of the prism electrode is changed corresponding to the deflection angle of the optical signal, and the pitch between channels corresponding to the size of the prism electrode, that is, the prism electrode array constituting the channel, and If the space between the adjacent prism electrode rows constituting the adjacent channels is maintained at a required constant value, it is inevitably narrow at the center of the light deflection element corresponding to the size of the prism electrode, and left and right Since it becomes wider as it gets closer to both ends, the overall size is reduced.

  In order to fabricate an optical switch using this optical deflection element, a conventional technique, for example, a method disclosed in Patent Document 1, may be applied. For example, a slab waveguide of an STO substrate on which the optical deflection element is formed. What is necessary is just to produce a channel waveguide and a two-dimensional lens array in the position adjusted so that it might match the pitch between the channels of an optical deflection | deviation element at the longitudinal direction both ends on a path.

It is a principal part top view showing the optical deflection element which is an embodiment in the present invention. FIG. 2 is a plan view of a principal part showing an optical switch for explaining an embodiment of an optical switch using the optical deflection element explained with reference to FIG. 1. It is a principal part top view showing the conventional optical deflection | deviation element.

Explanation of symbols

12 Slab waveguides 13A to 13H channels 14A to 14H Prism electrodes corresponding to channels a to d Channel pitch

Claims (2)

An optical waveguide made of a material having an electro-optic effect formed on a single crystal substrate, and a prism electrode arranged near both ends of the optical traveling direction of the optical waveguide to deflect light passing through the channel,
The size of each prism electrode is gradually increased from the prism electrode corresponding to the channel located at the center of the channel aligned in the direction intersecting the light traveling direction to the prism electrode corresponding to the channel located at the end. And an interchannel pitch is sequentially increased from a channel located at the center of the channels arranged in a direction intersecting the light traveling direction to a channel located at the end. 2. An optical switch comprising the optical deflection element according to claim 1 formed near both ends of the optical waveguide in the light traveling direction.

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