JPS61212826A - Polarization compensating element - Google Patents

Abstract

PURPOSE:To provide a titled element which is small in size and can be driven with a low voltage and to make easy the production thereof by providing two electrode pairs on the opposite side faces of a (Pb, La) (Zr, Ti)O3 member in such a manner that the voltage impressing directions incline at 45 deg. with each other. CONSTITUTION:The 1st and 2nd electrode pairs 2, 3 of which the voltage impressing directions incline at 45 deg. with each other are provided on the side faces, in parallel with the light propagating direction, of a light transmittable ceramic member 1 consisting essentially of (Pb, La) (Zr, Ti)O3 and having a rhombic section. Light in a polarized state is made incident from a fiber 7 through a lens system 6 on the member 1. The voltage is impressed between the electrode pairs 2 and 2' to double diffract the light. The voltage is impressed to the electrode pairs 3, 3' with 45 deg. inclination with the polarized state. The polarized state of the propagation light is therefore made to the desired linearly polarized light, elliptically polarized light, circularly polarized light, etc. always in the specified direction. The element which is small in size, can be driven with the low voltage and can be easily produced is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a polarization compensation element that converts arbitrary polarized incident light into a desired polarization state.

(Prior art and its problems) In recent years, in optical communication systems, particularly in long-distance, high-capacity optical communications, research and development of original heterodyne communication using a single mode fiber as an original fiber transmission system has become active.

In original heterodyne communication, it is necessary that the polarization states of the output light of the local oscillation (local oscillation light) and the output light after long-distance transmission of the single mode fiber match. but,
In a single-mode fiber, the birefringence inside the fiber changes depending on temperature, pressure, etc., so the polarization state at the fiber output end changes in a complicated manner and does not always match the polarization state of the local light, which may affect reception sensitivity. There was a problem that caused a significant decline.

For this reason, in optical heterodyne communication, it is necessary to insert a polarization compensator to always obtain a desired polarization state at the output end of a single mode fiber or at the local oscillation light source side.

On the other hand, even in waveguide optical devices such as switches and optical modulators, which have been actively researched and developed recently because they can be made smaller, more integrated, have higher performance, and higher reliability, the polarization state of the guided light Because the effects of their functions are different, a polarization compensator is required when connecting a single mode fiber between waveguide optical elements. , for example, by Kando et al., published in the magazine “I-EeeeeΦ
I EBE Journal of Quantum Electronics
n Electronics) J vol. 17, 1981.

It is reported on pages 991-994. This is a configuration in which two phase modulators using two bulk sheets of lithium niobate (LiNbO3) are combined and tilted at 45 degrees to each other.
3 to change the phase difference of the propagating light and change the polarization state of the emitted light. However, this polarization compensation element has a thickness of 0.5 mm.

Since the length is 40 mm and the pressure at half wavelength is 66 (V),
It has the disadvantages of high driving voltage and large size. This polarization compensation element aligns the phase modulators at 45° with respect to each other.
It has the disadvantage that it is difficult to manufacture because it needs to be placed at an angle.

(Object of the Invention) An object of the present invention is to eliminate these drawbacks and to provide a polarizing sleeve compensator which is small in size, can be driven at a low voltage, and can be easily manufactured.

(Structure of the invention) The structure of the polarization compensation element of the invention is (Pb, La) (Zr
, Tr)Os as a main component and has a prismatic shaft whose pillar axis is in the propagation direction of light, and a side surface of this member that is parallel to the pillar axis and faces each other, the direction of voltage application is 45
It is characterized by comprising a pair of first and second electrodes arranged in series so as to be tilted.

(Operation and principle of the invention) The primary and secondary electro-optic effects of the (Pb, La) (Zr, Tr) O3 member used in the present invention are very large, and for example, the change in the refractive index of the material with respect to the applied voltage is Conventional Li
It is more than an order of magnitude thicker than NbO5 material. This (Pb, La) (Zr, Ti) O! +By injecting propagating light into the material and applying a driving voltage, large birefringence is produced, which changes the phase difference of the propagating light, making it easier to change the polarization state of the emitted light than before. can be done. Therefore, it is possible to lower the driving voltage. Since the 1 (Pb, La) (Zr, '["1) O3 material is polycrystalline, it differs from the conventional LiNbO3 material in that the direction of the voltage is different, and the magnitude of the electro-optic effect may be different. Therefore, there is no need for a device that tilts two phase modulators at 45 degrees to each other, as in conventional polarization compensation elements.
With the (Z'r, Ti)O'3 member, it is sufficient to provide the electrode pairs in an M1 series in the upward direction where the voltage directions are inclined at 45 degrees with respect to each other, and manufacturing becomes very easy. In this way, a polarization compensating element that can change the polarization state with a low driving voltage, has small dimensions, and is easy to fabricate can be obtained.

(Example) The present invention will be described in detail below with reference to the drawings.
1 and 2 are a perspective view and a plane view of a member 1 showing a two-nosed embodiment of the present invention. In the figures, 1 is ('pb.

Translucent ceramic part side containing L'a')"(Z'r,"T i)'03 as a main component, 2", 2',
3. ``3'' is an electrode pair, 4.5 is 1 node end gear, ``6''
, 6' are lens systems, and 7 and 7' are single mode fibers. This (Pb, La) (Zr.

The Ti)O3 member 1 has a rhombic cross-sectional shape, and the first electrodes 2, 2' and the second electrode are connected in series so that the side surfaces parallel to the light propagation direction are inclined at 45 degrees to each other in the direction in which a voltage is applied. A pair 3.3' is provided. Lead terminals 4 are connected to these first and second electrode pairs 2.2' and 3.3', respectively.
4' and 5,5' are connected. This (Pb,
L'a)(Zr',Ti)O3 Lens systems 6°6' are arranged on the entrance/exit end face side perpendicular to the light propagation direction of the O3 member 1, and 'the lens systems 6°6' of (Pb, L
a) (Zr,'l''1)O3 A single mode fiber 7,7' is connected to the side facing away from the component 1, respectively.

In this jfu formation, (P'b, La) (Zr', 'l'1
) O3 member 1 has a − side of 180 μm and a corner between the two sides.
It has a 5° rhombic cross-sectional shape and a length of 10 mm.

Further, the composition of this member 1 is PbZrC, which has a relatively large electro-optic effect as follows: /PbTi01=65/35.
La = 8 atoms, and the first and second electrode pairs 2.2' and 3. '3' is made of aluminum. The lens systems 6 and 6' include a focusing type Rondo L/
7 lenses are used so that the propagating light has a minimum beam diameter at the center of the (Pb, La) (Zr, Ti) O3 member 1. The single mode fiber 7°7' has an outer diameter of 125 μm and a core diameter of 9 μm.

In this flexible configuration, light of any polarization state is emitted. Here, between the lead terminals 4 and 4' 1-, that is, the first electrode pair 2,
When a voltage is applied between 2', (Ph, La) (Z
r, 'T, '1) The Os member 1 causes birefringence due to the first-order electro-optic effect, and changes the phase difference between two mutually orthogonal polarization modes of the propagating light. Due to this, the polarization state of the propagating light changes and becomes linearly polarized light.

It becomes either elliptically polarized light or bicircularly polarized light.

In addition, since the voltage application direction of the second electrode pair 3.3' is inclined by 145 degrees with respect to the polarization direction of the previously obtained polarization state, the necessary voltage can be applied between the lead terminals 5.5'. Alternatively, the polarization state of the propagating light can always be set to a desired polarization state in a fixed direction, such as linear polarization, elliptically polarized light, or 9-circularly polarized light. The propagating light having such a polarization state is coupled to the single mode fiber 7' via the lens thread 6'.

With this configuration, when changing the polarization state of propagating light from linearly polarized light to the next linearly polarized light in which this linearly polarized light and the Hayabusa 1 wavefront are orthogonal, the phase difference between the two orthogonal polarization modes is π (rad). It needs to change. This π(rad
) As a result of measuring the half-wave voltage to be changed, it was found to be a low voltage of about 5 [V]. Also, when c7') (P b ,
L a ) (Z r , T i ) 03 member 1
The maximum beam diameter within was approximately 63 μm, which was sufficiently small compared to the thickness, and its diffraction loss was negligible, and the insertion loss was approximately 0.5 [dll].

In addition, in this configuration, the polarization state of the propagating light obtained by the polarization compensation element is detected, and the necessary driving voltage is applied between the first and second electrode pairs 2, 2' and 3, 3' using the detected signal. By providing a feedback control system, automatic control of the polarization state of propagating light becomes possible.

In this example, (Pb, La) (Zr, 'I'i
) The cross-sectional shape of the O3 member 1 is rhombic, but the first and second electrode pairs 2.2' and 3.3' are arranged in series so that the directions in which voltage is applied are inclined at 45 degrees to each other. For example, it may be a hexagon, a hexagon, etc. −
Further, in this embodiment, a -order electro-optic effect is used, but a second-order electro-optic effect may be used, and the composition at that time is not limited.

For example, PbZrO3 has a relatively large secondary electro-optic effect.
/PbTi03=65/35. A composition such as La=9 atomq6 may be used.

(P b , L a ) (Z r
, T + ) 03 Member composition PbZrO3/Pb
Tit3=65/35. La=8atom% is not limited to this, for example, PbZrO3/PbTi03=6
2/38. La=7atom%, PbZr01/P
bTiO3=40/60. La = 12 atoms and further metamorphosis with other elements (Pb (La, Li)) (Zr
,'['1)Os,PLZT-(Pb,La)(Zn,
Nb)O3 or the like may also be used.

Furthermore, (Pb, La) (Zr, Ti
) The light input end face and the output end face of the O3 member were made flat, but in order to make the propagating light enter and exit more efficiently, the light input end face and the output end face were formed with curved surfaces to have a lens effect. Also good. In this case, the lens system 6,
There is an advantage that 6' is not necessary. Here (pb.

If an anti-reflection coating is applied to the light input/output end face of the La)(Zr, Ti)O3 member or the end face of a single mode fiber, the end face reflection loss can be eliminated.

In addition, the lens system 6.
6', but the propagating light is (Pb, La) (Zr.

The lens system 6,6' may be arranged to form a parallel beam within the Ti)O3 member 1.

Note that although aluminum is used as the material for the electrode, it is not limited thereto; for example, transparent electrodes such as ITO, chromium, nickel, etc. may be used.

(Effect of the invention) As described above, according to the present invention, (Pb, La
) (Zr, Ti) O3 is the main component, so it is small and can be driven at low voltage, and the groove can be constructed from a single (Pb, La) (Zr, Ti) O3 member, making it easy to manufacture. It is possible to obtain a simple nine-sleeved compensation.

[Brief explanation of the drawing]

FIGS. 1 and 2 are a perspective view of an embodiment of the present invention and a sectional view of a part 1. FIG. In the figure, 1......(
Pb, La) (Zr, Ti) O3 member, 2,2'$mi and 3,3'...First and second electrode pair, 4°4' and 5.5'... ...Lead terminal, 6.6'
. . . Lens system, 7.7' . . . Single mode fiber. 10th muscle Z diagram

Claims (1)

[Claims] A prismatic translucent ceramic member whose main components are (Pb, La) (Zr, Ti) O_3 and whose column axis is in the propagation direction of light, and a voltage applied to the mutually opposing side surfaces parallel to the column axis of this member. The first
and a second electrode pair.