JPS61113024A - Waveguide type polarizing element - Google Patents

Abstract

PURPOSE:To obtain a waveguide type polarizing element which has low loss and high reliability by irradiating the core part of a single-mode optical waveguide with a light beam in a direction different from the light propagation direction of the single-mode optical waveguide. CONSTITUTION:A projection beam from an eximer laser 3 is converted by a lens system 5 into a light beam 4 which is flat in a sectional shape of about 5X500mum on the center axis of a core to illuminate the optical axis of the core 2. The energy of the irradiated partial light beam 4 is absorbed to generate heat. Parts at both sides along the optical axis which are not irradiated with the light beam 4 generate no heat. Consequently, only the part which is irradiated with the light beam and generates heat increase in refractive index by the thermooptic effect of a quartz glass optical fiber 1, and consequently the part irradiated with the light beam and parts at both sides of the irradiated part and different in the propagation constant of light propagating in the core of the optical fiber 1, thereby varying the polarization state of the propagation light.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a single mode optical waveguide type polarizing element that has low loss and high reliability.

(Prior Art and its Problems) In optical heterodyne communication systems and optical fiber sensor systems that use a single mode optical fiber output, it is important to fully control the polarization state of the optical fiber output. As a method to control this polarization state, L
One way to control the polarization state of light is to propagate the output light from an optical fiber through an iNb0a crystal and apply a voltage to the LiNbO3 crystal to control its refractive index. Such a polarization control method is described, for example, by Kito et al. [IEE Journal on Quantum Electronics JQE-17, No. 16.
From pages 991 to 994 of the June 1981 issue, “
Volatility, Control on Output, and Single-Mode Optical Fibers
It is published under the title. However, the polarizing element with this unconventional configuration has a large connection loss between the optical fiber and the LiNb0a crystal, making it difficult to reduce the loss, and also has low reliability because the optical fiber and the LiNb0a crystal are connected. There were some drawbacks.

(Objective of the Invention) An object of the present invention is to eliminate all of the above-mentioned drawbacks and to provide a waveguide type polarizing element with low loss and high reliability.

(Structure of the Invention) According to the present invention, a single mode optical waveguide having a core;
Waveguide-type polarized light comprising a light-emitting element and gold, and characterized in that the light beam emitted from the light-emitting element is irradiated onto the core portion of the single-mode optical waveguide from a direction different from the light propagation direction of the single-mode optical waveguide. An element is obtained.

(Operation/Principle of the Invention) The present invention solves the conventional problems by adopting the above-described configuration. In other words, when a light beam is irradiated onto the core portion on the optical axis of a single mode optical waveguide from a direction different from the light propagation direction, the portion irradiated with the light beam absorbs the energy of the light beam and generates heat. . In particular, if the portion irradiated by the light beam has a large light absorption coefficient at the wavelength of the light beam, heat will be generated more effectively. On the other hand, the portions that are not irradiated with the light beam, that is, the portions on both sides of the irradiated portion along the optical axis, do not generate heat. As a result, due to the thermo-optic effect, the refractive index of the part of the core that is irradiated with the light beam changes, which causes the propagation constant in the single mode optical waveguide to be different from the part of the core that is irradiated with the light beam. ,
The polarization state of the light propagating all through the single-mode optical waveguide can change depending on the non-illuminated parts on its sides.

Therefore, as mentioned above, it is possible to use the thermo-optic effect to change the total output of the light beam irradiated to the core part of the single mode optical waveguide, and change the amount of heat generated in the irradiated part. By changing the refractive index, the polarization state of light propagating in a single mode optical waveguide can be controlled.

Since the present invention uses a light beam to change the polarization state as described above, it does not require any connection between the optical fiber and the polarizing element as in the conventional technology. is obtained.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

1 and 2 are a plan view and a front view, respectively, showing an embodiment of the present invention, and in FIG. A core 2 having a core diameter of 10 μm is formed on the top, and an excimer laser 3 equipped with a lens system 5 is provided on the side surface of the silica glass optical fiber 1 . The excimer laser 3 equipped with this lens system 5 has a wavelength of 0.3 μm.
It emits a light beam 4, and is provided at a position such that the light beam 4 travels across the optical axis of the core 2 of the silica glass optical fiber 1.

Now, with this configuration, the beam emitted from the excimer laser 3 is converted into a flat light beam 4 with a cross-sectional shape of about 5 μm x 500 μm on the central axis of the core 2 using the full lens system 5, as shown in FIG. And as shown in FIG. 2, the light is irradiated onto the optical axis of the core 2.

At this time, the beam width of the light beam 4 at the outer diameter portion of the silica glass optical fiber 1 is approximately 5.2 μm, which does not widen at all. The irradiated portion absorbs all the energy of the light beam 4 and generates all heat. Also, the parts on both sides along the optical axis that were not irradiated with the light beam 4, that is, the second
In the figure, the parts above and below the dotted line through which the light beam 4 passes are:
No heat is generated. Therefore, due to the thermo-optic effect of the silica glass optical fiber 1, the refractive index of only the part that is irradiated with the light beam and generates heat increases, and as a result, the optical fiber 1 is The propagation constant of the light propagating inside the core is different, and the polarization state of the propagating light can be changed. For example, if the configuration described above is irradiated with a light beam 4 with an output of about 00 (mJ), the refractive index will change by about 1 × 10, and the phase difference of the propagating light will change by about π (r a d). It can be changed. The insertion loss at this time was as low as 0.1 dB or less. Further, with the above configuration, by further changing the output of the light beam and changing the refractive index, the polarization state of the propagating light can be arbitrarily controlled.

In this example, a silica glass optical fiber was used as the single mode optical waveguide, but the invention is not limited to this, and any single mode optical waveguide made of a material that generates heat with a light beam can be used. . Furthermore, a polarization maintaining optical fiber or the like may be made of gold as a single mode optical waveguide. In addition, in this example,
Although an excimer laser is used, the present invention is not limited to this, and any light emitting element may be used as long as it has a wavelength band that is absorbed by a single mode optical waveguide.

(Effects of the Invention) According to the above-mentioned feature 9, according to the present invention, since a light beam is used to change the polarization state, it is possible to obtain a highly reliable waveguide type polarizing element with low loss and reliability.

[Brief explanation of the drawing]

1 and 2 are a plan view and a front view showing one embodiment of the present invention. In the figure, 1 is a silica glass optical fiber, 2 is a core, 3 is an excimer laser, 4 is a light beam, and 5 is a lens system.

Claims (3)

[Claims] (1) It has a single mode optical waveguide having a core and a light emitting element, and the light beam emitted from the light emitting element is transmitted to the single mode optical waveguide from a direction different from the light propagation direction of the single mode optical waveguide. A waveguide-type polarizing element characterized by irradiating light onto the core portion of. (2) The waveguide type polarizing element according to claim (1), wherein the single mode optical waveguide is formed of a material having a large absorption coefficient for light emitted from the light emitting element. (3) The waveguide type polarizing element according to claim (1), wherein the irradiated light beam has a flat cross-sectional shape.