JPS5913224A - Polarizing element - Google Patents

Abstract

PURPOSE:To reduce the distance between separated projected light beams, to improve operation efficiency, and to perform high-speed operation by providing a polarizing separation film at part of one surface of a transparent flat plate which has parallel planes and a light reflecting film at part of the other surface. CONSTITUTION:The polarizing separation film 32 made of a dielectric multilayered film is formed at part of one surface of the parallelplane glass plate 31 with about 1mm. thickness, and the reflecting film 33 (thin metallic film or dielectric multilayered film) is formed at part of the other surface. Incident light in a direction X3 is separated by the polarizing element into a horizontal polarized wave Y3 and a vertical polarized wave Y4. In this case, the distance (dl) between the emitted light beams Y3 and Y4 is as shown by an equation, where (i) is the angle of incidence of the light in the direction X3, (t) is the thickness of the plate 31, and (n) is a refractive index. Consequently, the distance between the emitted light beams separated by the polarizing element is reduced, a Faraday rotating element is reduced in size, and high-speed operation is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to optical circuit elements, and particularly to polarizing elements □ used in optical switches, optical circulators, and the like.

(b) Background of the Technology In optical circuits currently in practical use, an optical switch consisting of polarizing elements 1 and 2 and a Faraday rotation element 3 as shown in FIG. 1 is used.

Optical circulators based on a combination of these U are also used.

In FIG. 1, light incident on the polarizing element 1 from the direction of Xi is separated by a polarization separation film 11 into horizontally polarized light and vertically polarized light.

That is, generally, horizontally polarized waves contained in incident light are transmitted through the polarization separation film, whereas vertically polarized waves are transmitted by the polarized light component III!
l! ! This is because it is reflected by

In FIG. 1, the horizontally polarized wave passes through the polarization separation film 11,
After being reflected by the reflective surface 12 of the polarizing element 1 , it enters the Faraday rotation element 3 , and the -power and vertically polarized waves are reflected by the polarization separation film 11 and enter the Faraday rotation element 3 .

When the polarization plane of any of the separated lights is not rotated by the Faraday rotation element 3, it passes through the Faraday polarization rotation element 3 as it is and enters the polarization element 2. In this case, the horizontally polarized wave that has entered the polarization separation film 21 of the polarization element 2 is transmitted through it and exits in the direction of vl, and the vertically polarized wave is reflected by the reflection surface 22 of the polarization element 2 and is reflected by the polarization separation film 21. The light enters 21, but is reflected again and exits in the direction of Ml.

In the above, when the light separated by the polarizing element 1 has its plane of polarization rotated by 90 degrees by the Faraday rotator 3, the horizontally polarized wave incident on the Faraday rotator 3 becomes vertically polarized wave, and this The vertically polarized wave reflected by the polarization separating film 21 and emitted in the direction of v2, and similarly incident on the Faraday rotator 3, becomes a horizontally polarized wave, which is reflected by the reflective surface 22 of the polarizer 2. The light passes through the polarization separation film 21 and is emitted in the Y2' (71) force direction.

In this way, the direction of light emitted from the polarizing element 2 can be switched by separating the incident light by the polarizing element 1 and controlling the rotation of the polarization plane of the separated lights by the Faraday rotation element 3.

Furthermore, the same thing can be done for the light that enters the polarizing element l from the x2 direction, and thereby it is also possible to selectively extract two lights that have different incident directions.

(C) Prior art and problems Conventionally, the distance Md (see Figure 1) between the optical paths of horizontally polarized waves and vertically polarized waves separated by the polarizing element l is 105 m 1
iii l & azuta.

This is based on the geometrical -1 method of the polarizing element 1, that is, the distance between the surface of the polarization separation film 11 and the reflecting surface 12. It is extremely difficult to reduce the distance to less than one length, and achieving this has the drawback of increasing manufacturing costs.

That is, a polarizing element with a conventional structure consists of a part A and a part B shown in FIG. 2, which are manufactured separately.
It was manufactured by providing a polarization separation film 11 on the part B and then bonding it to the part B. Moreover, in these, surfaces 4 and 5 are precisely kept parallel, surfaces 6 and 7 are assembled so as to be exactly on the same plane, and surfaces 6, 7, 8, and 9 are precisely It is necessary that the polarizing element be subjected to surface polishing, and with such a structure, the smaller the polarizing element becomes, the more difficult it becomes to handle and maintain accuracy.

(d) Purpose of the Invention An object of the present invention is to provide a polarizing element having a novel structure that can be made smaller and lower in cost, unlike conventional polarizing elements.

(e) Structure of the Invention The present invention is characterized in that a polarized light separation film is provided on a part of one side of a transparent flat plate having parallel planes, and a dead reflection film is provided on a part of the other side. , (') Embodiments of the Invention Below, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a schematic diagram showing an embodiment of a polarizing element according to the present invention.

In the figure, 31 has a thickness of about l+n, and 1. It is a glass plate with parallel planes. A polarization separation film 32 made of a dielectric multilayer film is formed on a part of one side of the glass plate 31, and a reflective film 33 (made of a metal thin film or a dielectric multilayer film) is formed on a part of the other side. do.

These films may be formed using thread vacuum deposition, sputtering, and photoetching techniques.

The light incident on the polarizing element obtained as described above from the direction The wave is emitted at Y4.

Further, the light incident from the x4 direction is separated according to the path indicated by the broken line, and the horizontally polarized wave is outputted to v4, and the vertically polarized wave is outputted to Y3.

In these cases, the distance 1 [dl] between the output lights v3 and v4 is
If the incident angle of light in the X3 direction to the polarizing element is i, the thickness of the glass plate 31 is t, and its refractive index is n, then dl=2
t-cosi-sini / (n"-5in'i
Since it is a reed, t = l ma, 1 = 45°, n =,
If it is 1.5, then dl' = 1.26 cranes.

According to the present invention, as long as the parallelism of both sides of the glass plate 310 is maintained, the thickness of the glass plate 310 can be even thinner, and the value of dl can be further reduced in proportion to this thickness.

FIG. 4 is a schematic diagram showing another embodiment of the present invention.

The polarizing element shown in the same figure has a glass plate 31 provided with a polarization separation film 32 and a reflection 111Ii33 in the same manner as in FIG.
1 and 42 are attached and assembled from both sides, and Figure 8 (8) is a perspective view before attachment.
B) is a sectional view after bonding.

In the case of the polarizing element of this structure, as is clear from FIG. 4(B), the light incident from x5 and x6 is incident almost perpendicularly to the respective surfaces 43 and 44 of the polarizing element. , the reflection loss at the incident surface 43 or 44 is reduced, and the incident and exit angles of light at the interface between the polarization M film 32 and the glass plate 31 are increased, improving the separation performance for two polarized waves. can do.

(g) Effects of the Invention According to the present invention, it is easy to reduce the distance between the emitted lights separated by the polarizing element, thereby making it possible to miniaturize the Faraday rotator and its operating efficiency (constant applied voltage). This has the effect of increasing the degree of rotation angle of the plane of polarization that is possible depending on the voltage, and enabling high-speed operation. Furthermore, since the structure and processing thereof are relatively simple, it is possible to provide a polarizing element that can be mass-produced at low cost.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining the outline of an optical switch using a polarizing element, Figure 2 is a diagram showing the structure of a conventional polarizing element, and Figures 3 and 4 are diagrams showing the structure of a polarizing element according to the present invention. FIG. In the figure, l and 2 are polarization elements, 3 is a Faraday rotation element, 4.5.6.7.8 and 9 are planes, and 11.21 and 32 are polarization components 1i111N! ji, 12 and 22
is a reflective surface, 3I is a glass plate, 33 is a reflective film, 4I and 42 are right angle prisms, 43 and 44 are incident surfaces, 45 is an exit surface, xl...×6 is the incident direction of light, v4...v
6 is the light emission direction, and d and dl are the distances between polarized waves. Figure 1 α2I211义5Figure 4 Figure 4 (A) 3 (B)

Claims (1)

[Claims] Polarized light component sum on a part of one side of a transparent flat plate with parallel planes
A polarizing element, characterized in that a light reflecting film is provided on a part of the other side.