JPH03208006A - Polarized light controller - Google Patents

Abstract

PURPOSE:To take out the polarized light whose polarized light state is known by converting an incident light to linearly, elliptically and circularly polarized light by two phase compensators, and also, adjusting arbitrarily an angle of polarization by a polarized light rotating device. CONSTITUTION:An incident light 11 having an arbitrary polarized light is converted to a polarized light having a polarized light main axis azimuth on the X axis or on the Y axis by the control of a phase compensator 1. Subsequently, this controlled incident light 11 is converted to an arbitrary polarized light whose polarized light main axis azimuth is on the X axis or on the Y axis by a phase compensator 2. Accordingly, the incident light is converted to an arbitrary polarized light of a linearly polarized light, an elliptically polarized light and a circularly polarized light by the phase compensators 1,2. Thereafter, by rotating the polarized light by a polarized light rotating device 3, the polarized light whose polarized light main exis azimuth is varied continuously can be taken out. In such a way, an arbitrary polarized light whose polarized light state is known can be taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a polarization control device that converts incident light whose polarization state is unknown to arbitrary polarization light whose polarization state is known.

[Conventional Technology] Next, the structure of a polarization device according to the prior art will be explained with reference to FIG.

In Fig. 2, l and 2 are phase compensators, 4 is a beam splitter,
1 is the incident light, 12 is the output light, 13 is the monitor light, 2l is the beam splitter, 22 is the Wollaston prism, 23
and 24 are photodetectors, 25 is a control section, 26 is a quarter wavelength plate, 27 is a Wollaston prism, 28 and 29 are photodetectors, and 30 is a control section.

After the incident light beam passes through the phase compensator 2, it is separated by the beam splitter 4 into output light 12 and monitor light 13.

For the phase compensator 2, birefringence that occurs when voltage is applied to an electro-optic crystal, birefringence that occurs when stress is applied to glass, etc. can be used.

The monitor light 13 is separated into monitor lights 14 and 15.

The monitor light 14 is separated into orthogonal polarization components by the Wollaston prism 22, and the power difference between the orthogonal polarization components is detected by the photodetectors 23 and 24 and the control unit 25, and the phase compensator 1
control.

The monitor light 15 passes through the ↓/4 wavelength plate 26, is separated into two orthogonal polarization components by the Wollaston prism 27, and is divided into two orthogonal polarization components by the photodetectors 28 and 29 and the control section 30, which converts the power difference between the orthogonal polarization components to a certain extent. The signal is detected and the phase compensator 2 is controlled.

The principal axes of the two phase compensators 1 and 2 are arranged at an angle of 45 degrees to each other.

The principal axes of the two Wollaston prisms 22 and 27 are also arranged at an angle of 45 degrees to each other, and the Wollaston prism 22
The principal axis direction of is arranged to coincide with the principal axis direction of the quarter-wave plate 26.

The outputs of the photodetectors 23 and 24 are input to the control section 25, and the difference between the outputs is made to be rOJ.

That is, the phase compensator 1 is controlled so that a certain difference between the orthogonal polarizations of the monitor light l4 becomes "0".

Thereby, the direction of the principal axis of polarization of the incident light 1l can be made to match the direction of the principal axis of the Wollaston prism 27.

The outputs of the photodetectors 28 and 29 enter a control section 30, which controls the phase compensator 2 so that the output difference becomes rOJ.

Thereby, the incident light 11 is controlled to be linearly polarized light.

[Problems to be Solved by the Invention] In the prior art shown in FIG. 2, control is limited to setting the output difference between the orthogonal polarization components of each monitor light to "0" due to the configuration of the detection system. The polarization state of the output light is limited to linear polarization.

Another problem is that even if other configurations are used in the detection system, the two phase compensators are limited to controlling the phase difference for the orthogonal polarization components of the incident polarization, so the state of polarization cannot be changed continuously. There is.

This invention employs two phase compensators and one polarization rotator as a system for controlling the polarization state, and a system for detecting the polarization state so as not to overlap with the principal axes of the two phase compensators. By employing an analyzer whose transmission axis direction is arranged and a photodetector that receives the light transmitted by the analyzer, the polarization state can be set to any polarization among linear polarization, elliptical polarization, and circular polarization. Another object of the present invention is to provide a polarization control device that can arbitrarily adjust the azimuth angle of the principal axis of polarization and can continuously change the polarization state.

[Means for solving tLD] In order to achieve this objective, in this invention, the incident light 11
and a second phase compensator that provides a phase difference in a direction 45" different from the first phase compensation D1 for the incident light 11 that has passed through the first phase compensator 1. a phase compensator 2, a polarization rotator 3 that rotates the polarization plane of the incident light 1 that has passed through the second phase compensator 2, and a polarization rotator 3 that rotates the polarization plane of the incident light 11 that has passed through the second phase compensator 2; Beam splitter 4 that separates into 13, ↓ phase compensator 1 and 2
The polarization control state by the first phase compensator 1, the second phase compensator 2, and the polarization rotator 3 is converted into a light amount. analyzer 5 and monitor light 1 that has passed through the analyzer 5
3, and a control section 7 that receives the output of the photodetector 6 and controls the first phase compensator 1, the second phase compensator 2, and the polarization rotator 3.

Next, the structure of the polarization control device according to the present invention will be explained with reference to FIG.

In FIG. 1, 1 and 2 are phase compensators, 3 is a polarization rotator, 4 is a beam splitter, 5 is an analyzer, 6 is a photodetector, and 7 is a control section.

[Function] Next, the arrangement of the phase compensators 1 and 2 and the analyzer 5 shown in FIG. 1 will be explained with reference to FIG. 3.

In FIG. 3, the birefringence axis direction of the phase compensator 1 is set to the X-axis direction, the birefringence axis direction of the phase compensator 2 is set at -45° with respect to the phase compensator 1, and the transmission axis direction of the analyzer 5 is set to the X-axis direction. This shows the case where the angle is α0 with respect to the X-axis direction.

However, the birefringence axis direction of the phase compensator 2 is
It may be +45'' with respect to the birefringence axis direction.

Furthermore, when the transmission axis direction α0 of the analyzer 5 overlaps with the birefringence axis direction of the phase compensator 1 or phase compensator 2, the amount of phase compensation of the phase compensator whose birefringence axis direction overlaps changes. However, since the amount of light transmitted through the analyzer 5 does not change even if the analyzer 5 is used, the transmission axis direction α° of the analyzer 5 and the birefringence axis direction of the phase compensator 2 need to be made so that they do not overlap.

At the rear of the phase compensators 1 and 2, a polarization rotator 3 such as a Faraday rotator that can freely rotate the azimuth of the principal axis of polarization depending on the magnitude of the magnetic field is placed, so that any incident polarization can be converted into any known polarization. can be converted continuously.

Next, the process of continuously converting arbitrary incident polarized light into known arbitrary polarized light will be explained with reference to FIGS. 4 and 5.

The P-Q-R displayed at the bottom of Fig. 4 is the fifth
You will be contacted via P-Q-R displayed at the top of the diagram.

Under the control of the phase compensator 1, the incident light 11 having arbitrary polarization is converted into polarized light having the principal axis of polarization azimuth on the X-axis or the Y-axis.

At this time, if the polarization principal axis azimuth of the incident light 11 is different from the X-axis or Y-axis, the polarization principal axis azimuth will be on the X-axis or Y-axis although the polarization shape is different from that of the incident light 1l. controlled on a phase compensator.

The incident light 11 whose principal axis of polarization azimuth is controlled to be on the X-axis or the Y-axis by the phase compensator 1 is converted into arbitrary polarized light whose principal axis of polarization azimuth is on the X-axis or the Y-axis by the phase compensator 2. Ru.

Therefore, by converting the polarized light into a specific polarized light having the polarization principal axis azimuth on the X-axis or Y-axis using the phase compensators 1 and 2, and then rotating the polarized light with the polarization rotator 3, the polarization principal axis azimuth can be changed continuously. It is possible to extract polarized light that changes.

In addition, by fixing the polarization rotation angle of the polarization rotator 3 at a specific angle and changing the shape of the polarization with the phase compensator 2,
It is also possible to extract polarized light whose polarization shape changes continuously.

Note that by continuously controlling the phase compensator 2 and the polarization rotator 3, it is also possible to control the polarization so that the shape of the polarization and the azimuth of the polarization principal axis change continuously.

[Example] Next, the operation of the phase compensator 2 and the polarization rotator 3 shown in FIG. 1 will be explained with reference to FIGS. 6 to 10, assuming that the transmission axis direction of the analyzer 5 is 25 degrees.

FIG. 6 shows an example in which the incident light 11 is arbitrary elliptically polarized light.

FIG. 7 shows the polarization state in which the azimuth of the polarization principal axis is controlled to overlap on the X-axis or the Y-axis when the phase difference of the incident light 1l is changed by the phase compensator 1, and FIG. Compensator 1
FIG. 3 is a diagram showing changes in the amount of monitor light 13 after passing through the analyzer 5 in the control process.

To superimpose the polarization principal axis azimuth of the incident light 11 on the X-axis or the Y-axis, first set the phase difference given by the phase compensator 2 to zero, the rotation angle given by the polarization rotator 3 to zero, and pass it through the analyzer 5. The optical detector 6 receives the amount of light from the monitor optical device 3, and the control unit 7 controls the phase compensator 1 so as to give a phase difference δMAX that maximizes the amount of light or a phase difference δMIN that minimizes the amount of light. do.

At this time, the polarization state of the incident light 11 becomes linearly polarized light as shown in FIG. 9 when the amount of light received by the photodetector 6 is the maximum, and becomes linearly polarized light as shown in FIG. 10 when the amount of light received by the photodetector 6 is the minimum.

Next, when the amount of light received by the photodetector 6 is maximum, in other words, when the polarization state is linear polarization as shown in FIG. do.

In addition, in the minimum case, by setting the phase difference given by the phase compensator 1 to (δMIN+π/2), the polarization principal axis azimuth overlaps the X-axis or the Y-axis in a clockwise direction as shown in Figure 7. elliptically polarized light is obtained.

However, assuming that the phase difference given when the output of the photodetector 6 is maximum is (δMAX + π/2) and the phase difference given when it is minimum is (δMIN-π/2), the polarization principal axis azimuth is on the X axis or Y It may also be counterclockwise elliptically polarized light that overlaps on the axis.

A phase compensator 2 is applied to the incident light 11 controlled as shown in FIG.
gives a phase difference in the direction of +45° or −45° with respect to the X-axis, and when the amount of light detected by the photodetector 6 becomes maximum, the polarization state of the incident light 11 becomes linearly polarized light in the X-axis direction.

Note that the incident light 11 may be linearly polarized in the Y-axis direction by controlling the phase compensator 2 so that the amount of light detected by the photodetector 6 is minimized.

Furthermore, from the state controlled to linearly polarized light in the X-axis direction, -4
When the phase compensation amount of the phase compensator 2 arranged in the 5° direction is decreased, the state changes from linearly polarized light to right-handed elliptically polarized light, and right-handed circularly polarized light is obtained.

As the amount of phase compensation is increased, the state changes from linearly polarized light to left-handed elliptically polarized light, and left-handed circularly polarized light is continuously obtained.

In addition, the phase compensator 2 adjusts the polarization principal axis azimuth on the X axis or on the Y axis.
By rotating the polarization principal axis azimuth of the polarized light controlled on the axis using the polarization rotator 3, it is possible to continuously obtain polarized light that differs only in the polarization principal axis azimuth.

Note that the phase compensators 1 and 2 can use the photoelastic effect of the fiber, and the polarization rotator 3 can use an element that uses the Faraday effect of the fiber. Also, beam splitter 4
The same operation can be achieved by using a fiber coupler for the analyzer 5 and a fiber polarizer for the analyzer 5.

[Effects of the Invention] According to the present invention, arbitrary incident polarized light can be converted into linearly polarized light, elliptically polarized light, and circularly polarized light with a constant polarization principal axis azimuth angle by a phase compensator, and the phase compensator Since the azimuth of the principal axis of polarization can be adjusted arbitrarily using a polarization rotator placed at the rear of the device, it is possible to extract any polarized light whose polarization state is known, and it is also possible to extract continuously changing polarized light.

[Brief explanation of drawings]

Figure w1 is a configuration diagram of a polarization control device according to the present invention, Figure 2 is a configuration diagram of a polarization control device according to the prior art, and Figure 3 is a configuration diagram of a polarization control device according to the prior art.
Figures 4 and 5 are illustrations of the arrangement of the phase compensators 1 and 2 and analyzer 5, Figures 4 and 5 are illustrations of the process of continuously converting arbitrary incident light 11 into known arbitrary polarized light, and Figure 6 10 are explanatory views of the operation of the phase compensator 1.2 and the polarization rotator 3 in FIG. 1 when the transmission axis direction of the analyzer 5 is set at 25 degrees. 1... Phase compensator, 2... Phase compensator, 3... Polarization rotator, 4... Beam splitter, 5...・Analyzer, 6...Photodetector, 7...Control unit, 11...Incoming light, 12...Output light, 13...・・Monitor light, l4・15・・・・Monitor light, 21・・・・
Beam splitter, 22...Wollaston prism, 23, 24...Photodetector, 25...
...Control unit, 26...1/4 wavelength plate, 27...
...Wollaston prism, 28, 29...photodetector, 30...control unit.

Claims (1)

[Claims] A first phase compensator (1) that provides a phase difference to the incident light (11), and a first phase compensator (1) that provides a phase difference to the incident light (11) that has passed through the first phase compensator (1). A second phase compensator (2) that provides a phase difference in a direction 45° different from that of the first phase compensator (1), and a polarization plane of the incident light (11) that has passed through the second phase compensator (2). a beam splitter (4) that separates the incident light (11) that has passed through the polarization rotator (3) into an output light (12) and a monitor light (13); The transmission axes of the phase compensator (1) and the second phase compensator (2) are arranged at an angle with respect to their principal axes such that their transmission axes do not overlap. (2)
and an analyzer (5) that converts the polarization control state by the polarization rotator (3) into light intensity, a photodetector (6) that detects the monitor light (13) that has passed through the analyzer (5), and a photodetector. The output of (6) is input, and the first phase compensator (
1), second phase compensator (2) and polarization rotator (3)
A polarization control device comprising: a control section (7) for controlling the polarization control device.