JPH0658468B2 - Optical coupler - Google Patents

Description

DETAILED DESCRIPTION [Outline] An optical coupler having no polarization dependence, in which incident light Po incident on a coupler film is separated into a P wave and an S wave, and each polarized light is converted into a λ / 4 wavelength plate. After being converted into circularly polarized light by using it, it is divided by a coupler film.

[Industrial application field]

The present invention relates to an optical coupler, and more particularly to an optical coupler having no polarization dependence which is configured not to depend on the polarization state of incident light.

In optical communication devices, optical devices, etc., optical multiplexers / demultiplexers,
Optical devices such as optical branching / combining devices are widely used. When light is incident on the coupler film for optical branching in such an optical device, the splitting ratio changes depending on the polarization state of the incident light, so the incident light is split once and each is converted into circular polarization. There is a demand for the emergence of an optical coupler that splits and splits without polarization dependency.

[Conventional technology]

Conventional optical couplers have adopted a method of reducing the polarization dependence by forming a multilayer film that divides incident light.

FIG. 2 is a curve diagram showing the polarization dependence of the conventional coupler film.

In the figure, the vertical axis (Y axis) represents the transmittance (%), and the horizontal axis (X axis).
If the wavelength is taken on the (axis), the P-wave and S-wave have a difference in polarization dependence as shown in the figure.

[Problems to be solved by the invention]

The conventional coupler with little polarization dependence has a problem that the polarization dependence cannot be removed by the multilayer film that is formed,
If the coupler film that splits the incident light is a metal film,
There was each problem of absorption loss.

[Means for solving problems]

The present invention provides an optical coupler that solves the above problems. That is, the incident light Po composed of a combination of the P wave and the S wave incident from the single mode fiber is separated into a P wave and an S wave, and the P wave and the S wave are converted into circular polarized waves by a λ / 4 wavelength plate. The wave and the S wave are made incident on the coupler film to be split into 50% / 50%.

[Action]

The optical coupler has a structure in which different polarized lights contained in incident light are once separated by a polarization separation film, converted into circular polarized lights by a λ / 4 wavelength plate, and then divided into equal parts by a coupler film. It was done.

[Embodiment] FIG. 1 is a configuration diagram for explaining an embodiment of the present invention.

In the figure, incident light Po composed of a combination of P-waves and S-waves having different polarization dependences is separated into P-waves and S-waves by a polarization separation film 1. That is, the polarization separation film 1 made of a multilayer film transmits P waves,
The S wave is reflected, and the reflected S wave is reflected by the total reflection film 2 and the P wave transmitted through the polarization separation film 1,
The S wave reflected by the total reflection film 2 is converted into a circularly polarized wave by the λ / 4 wave plate 3. Of the P wave and the S wave converted into the circularly polarized wave, the P wave is reflected by the total reflection film 4 and is divided into 50% / 50% in the coupler film 4 made of a dielectric multilayer film. , And each of them is divided into Po / 2 and emitted.

〔The invention's effect〕

As is clear from the above description, according to the present invention, it is possible to provide an optical coupler that does not depend on the polarization state of incident light, and it is extremely effective when applied to various optical devices.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of the present invention, and FIG. 2 is a curve diagram showing polarization dependence by a conventional coupler film. In the figure, 1 is a polarization separation film, 2 and 4 are total reflection films, and 3 is λ /
A four-wave plate and a coupler film, respectively.

Claims (1)

[Claims] 1. An incident P from a single mode fiber.
Of incident light Po composed of a combination of S and S waves
The wave is separated by a light separating film (1), the reflected S wave is reflected by a total reflection film (2), and the reflected S wave and the transmitted P wave are λ / 4 wave plate (3). After the circularly polarized wave is converted into a circularly polarized wave by, the P wave converted into the circularly polarized wave is reflected by the total reflection film (4), and the P wave and the S wave are incident on the coupler film (5) and split. An optical coupler that is characterized.