JPH02173613A - Polarizing device - Google Patents

Abstract

PURPOSE:To obtain a low-loss, efficient polarizing device by disposing a 1/2- wavelength plate between a polarized light separating plate and a 2nd lens and on the path of only ordinary or abnormal light passing between them, thereby projecting linear polarized light regardless of the polarized state of incident light. CONSTITUTION:Light which is emitted by a single-mode fiber 1 is collimated by a 1st lens 11 into parallel luminous flux, which is made incident on the polarized light separating plate 12 and separated into the ordinary light E0 and abnormal light Ex. Both the light beams have their planes of polarization deviating by 90 deg., but the ordinary light E0 is made incident on a 2nd lens 13 as it is and the abnormal light Ex is made incident on the 2nd lens 13 through the 1/2-wavelength plate 14; and the abnormal light Ex passing through the 1/2-wavelength plate 14 has the plane of polarization rotated by 90 deg., so the plane of polarization is coincident with the plane of polarization of the extraordinary light E0. Consequently, light which is converted after passing through the 2nd lens 13 becomes linear polarized light and the polarization angle of a constant polarization fiber 2 is made coincident with that of the linear polarized light to obtain the polarizing device which has extremely small loss.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a polarizing device, and more specifically to a polarizing device that aims to reduce loss of light amount within the polarizing device.

(Prior art) There have been various configurations of polarizers (polarizers) for obtaining linearly polarized light whose vibration plane is limited to one plane. There are some that use refraction. This utilizes the property that when light enters a birefringent material such as rutile, it splits into two linearly polarized lights with different refraction directions, and blocks one of the two separated lights. Alternatively, the structure is such that linearly polarized light can be obtained by emitting two light beams with their paths sufficiently separated.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional polarizing device, among the light incident on the polarizing device, only light having a polarization plane parallel to the axis of the polarizing device passes through, and other light cannot pass through, resulting in a loss.

The purpose of using a polarizer is to convert light with different planes of polarization, such as elliptically polarized light, into light with a single plane of polarization, so the above-mentioned loss always occurs. Moreover, there are various problems such as the amount of loss varies depending on the polarization state of the incident light.

This invention was made in view of the above-mentioned background, and its purpose is to produce linearly polarized light that is emitted regardless of the polarization state of the incident light, thereby achieving low loss and high efficiency. An object of the present invention is to provide a polarizing device.

(Means for Solving the Problems) In order to achieve the above object, the polarizer according to the present invention includes a first lens that converts light into a parallel light beam along the forward direction of the light, and a first lens that converts the parallel light beam into an ordinary light beam. A polarization separation plate that separates the light into extraordinary light, and a second lens that converges the light that has passed through the polarization separation plate and inputs it into the polarization constant fiber are arranged, and the polarization separation plate and the second lens are arranged. 1/2 on the path of only one of the ordinary light and the extraordinary light passing between the two lenses.
A wave plate was installed.

(Function) The light incident on the present polarizing device passes through the first lens and the polarization separation plate, and is emitted as two parallel beams with polarization planes shifted by 90 degrees.

Of the two lights, one enters the second lens as is, but the other light passes through the 1/2 wavelength plate and enters the second lens.
will be incident on the lens.

Then, when passing through the 1/2 wavelength plate, the plane of polarization of the light is rotated by 90 degrees and coincides with the plane of polarization of one of the lights.

Therefore, the light emitted from the polarizer becomes linearly polarized light, and since the linearly polarized light is formed by combining two lights separated by the polarization separation plate, the polarizer has extremely low loss.

(Embodiments) Hereinafter, preferred embodiments of the polarizing device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an embodiment of a polarizing device according to the present invention.

As shown in the figure, this embodiment is an example in which the fiber is installed between two fibers. Specifically, a single mode fiber 1 and a polarization constant fiber 2 are arranged approximately on the same line,
A polarizing device 10 of the present invention is inserted between both fibers 1 and 2. This polarizing device 10 basically includes a first lens 11, a polarization separation plate 12, and a second lens 13.
are arranged coaxially along the forward direction of light.

The polarization splitting plate 12 is formed of a uniaxial birefringent plate such as a rectangular rutile single crystal plate, and its optical axis X is inclined at 30 degrees with respect to the boundary surface.

Furthermore, in the present invention, a 1/2 wavelength plate 14 is disposed between the polarization splitting plate 12 and the second lens 13. At this time, the 1/2 wavelength plate 14 is positioned only on one path (on the extraordinary light EX in this embodiment) of the ordinary light EO and the extraordinary light Ex emitted from the polarization separation plate 12.

Further, this 1/2 wavelength plate 14 is also formed from a rutile single crystal plate, and is disposed so that its optical axis y is located in a direction perpendicular to the path of light.

Next, the operation of the above embodiment will be explained. First, light having a wavelength of λ-1°55 C is emitted from the single mode fiber 1. Then, the first lens 11 converts the parallel light beam into a parallel light beam, which enters the polarization separation plate 12. On the way of its passage, it meets the ordinary light Eo, which has a plane of polarization perpendicular to the optical axis, at the boundary surface of the polarization separation plate 12. Extraordinary light Ex with a plane of polarization
(the planes of polarization of both lights are 90 degrees apart), the ordinary light Eo travels straight along the optical axis, and the extraordinary light Ex travels straight along the optical axis at θ-9°8.
It refracts at 5 degrees and moves along the direction of separation. Furthermore, in this embodiment, since the thickness of the polarization splitting plate 12 was set to 10 mm,
After exiting the polarization separation plate 12, the extraordinary light EX travels parallel to the ordinary light Eo with a deviation of 1.74 m+s.

Next, of the two emitted lights, the ordinary light Eo is incident on the second lens 13 as it is, but the extraordinary light Ex is incident on the second lens 13 via the 1/2 wavelength plate 14. become. Therefore, the extraordinary light Ex passing through the 1/2 wavelength plate 14 becomes ordinary light E because the plane of polarization is rotated by 90 degrees during the passage.

coincides with the plane of polarization.

As a result, the light converged after passing through the second lens 13 becomes linearly polarized light, and by matching that polarization angle with that of the constant polarization fiber 2, the polarization plane of the light incident on the polarizer 10 becomes 90 degrees. The rotated component can also be made to enter the polarization constant fiber 2.

In the above embodiments, a single mode optical fiber was used as the input fiber, but the present invention is not limited to this, and various types of fibers can be used.

Furthermore, the location where the polarization device is attached is not limited to inside the fiber.

Further, although a rutile single crystal plate was used as the polarization splitting plate and the 1/2 wavelength plate in the above embodiment, the present invention is not limited to this, and various other axial birefringent plates such as calcite may be used. Can be used.

Furthermore, the position where the 1/2 wavelength plate is provided may be on the ordinary light path instead of the above-mentioned extraordinary light path.

(Effects of the Invention) As described above, in the polarizing device according to the present invention, the emitted light can be linearly polarized light regardless of the polarization state of the incident light.

Furthermore, since the linearly polarized light is formed by combining two lights separated by a polarization separation plate, loss within the polarizer can be kept extremely low.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a preferred embodiment of a polarizing device according to the present invention. 1...Single mode fiber

Claims (1)

[Claims] A first lens that converts the light into a parallel beam along the forward direction of the light, a polarization splitter that separates the parallel beam into ordinary light and extraordinary light, and a polarization splitter that converges the light that has passed through the polarization splitter to determine the A second lens input to the polarization fiber is arranged between the polarization splitting plate and the second lens, and on the path of only one of ordinary light and extraordinary light passing between them. A polarizing device characterized in that a 1/2 wavelength plate is disposed in the polarizing device.