KR19990041480A - Core deformation method of waveguide - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core deformation method of a planar waveguide (PLC), and to a method for enlarging the core of an input / output unit of a PLC in order to facilitate connection between a PLC and an optical fiber or another optical element. The heating element is embedded in the upper and lower layers of the core, and the core can be deformed by diffusing ions that increase the refractive index in the core by giving a temperature gradient by heating non-uniformly by resistance heat caused by current. By this method, the PLC element can be easily connected and the degree of integration can be increased.

Description

Core deformation method of waveguide

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core deformation method of a planar waveguide (PLC) called Planar Waveguide (PLC). In particular, in order to facilitate connection between a PLC and an optical fiber or another optical device, the core of the PLC input / output unit may be expanded. It relates to a PLC core deformation method.

The use of single-mode fiber in optical communication has drastically improved the transmission amount, and thus the use of single-mode fiber in the subscriber network as well as the inter-station transmission path is becoming prominent. The use of such a single mode optical fiber not only increases the amount of transmission but also enables various functions by wavelength division multiplexing and phase manipulation of light waves such as optical switches. However, a problem in single mode optical communication is that the diameter of cores in optical fibers and optical devices is very small. Therefore, the connection between the optical fiber, the optical fiber and the optical fiber is very difficult, causing the cost of the optical signal transmission and reception equipment that requires such a connection is very expensive. The present invention is to extend the connection portion in a tapered shape to facilitate the connection of the optical fiber-PLC, PLC-PLC, PLC-optical device (laser diode, photodiode) and the like. In the present invention, unlike the conventional taper forming method, the hot wire is locally buried, thereby non-uniformly heating the PLC by electric resistance heat, thereby forming a taper by diffusing ions such as Ge2 + ions that are doped in the core to increase the refractive index.

Formation of tapered cores is necessary not only for the ease of connection between the PLC and other optical components described above, but also for the fabrication of highly integrated PLCs. The taper in the horizontal direction can be simply formed by the mask pattern, but the effect is halved. Therefore, many studies have been conducted for the formation of taper in the vertical direction as well as horizontal.

Hereinafter, a few embodiments of a modification technique of a tapered core according to the prior art will be described.

1 is an exemplary view for explaining a conventional core expansion technology using an electric furnace.

The method according to FIG. 1 forms a temperature gradient in the waveguide propagation direction by heating the end of the PLC 5 chip by means of a furnace 1 and cooling the other end, thereby spreading the core doping material by diffusion. Mode-Field Diameter (MFD) was extended.

The taper by this method can maintain a single mode condition because the difference in refractive index between the core and the clad decreases as the core size increases.

FIG. 2 is a view illustrating a taper forming method by a conventional Flame Hydrolysis Deposition (FHD) method.

In the method of FIG. 2, the taper in the vertical direction was formed by adjusting the position of the torch 7 when the silica film was deposited by FHD.

That is, in the above method, when gaseous mixture of raw materials (SiCl4-GeCl4-BCl3-POCl3) and hydrogen and oxygen for generating a flame are introduced into the torch 7, hydrolysis due to combustion heat occurs, and thus silica is produced. Glass particles are deposited on the silicon substrate 9, and the composition of the silica particles which determines the refractive index is related to the composition of the source gas to be introduced. Therefore, the components and refractive index of the deposited film can be controlled by the gas flow rate. In this method, the refractive index distribution can be freely formed by moving the torch 7 in the horizontal direction and adjusting the flow rate of the gas during the deposition process.

3 is a schematic diagram for explaining a taper forming technique using a conventional shadow mask.

The method of FIG. 3 uses a shade mask 11 and tapered by sputter deposition. A spacer 13 made of Si chip is placed on the silicon substrate 15, and the shade mask 11 is placed on the spacer 13. When deposition is performed by RF sputtering, a taper is formed in the lower portion of the edge of the shadow mask 11 to gradually increase the thickness of the thin film. In the deposition by this method, since the refractive index cannot be gradually changed, the single mode condition cannot be satisfied.

The conventional vertical taper forming method described above has a problem that the manufacturing method is very complicated and a lot of constraints. In order to solve this problem, a method of three-dimensionally extending a mode-field diameter (MFD) by simply adjusting the pattern of the waveguide horizontally has been proposed.

4 is a view for explaining a core mode expansion method by a conventional core disconnection method.

As illustrated in FIG. 4, the effective MFD is expanded by artificially scattering light traveling along the core by disconnecting the core portion of the waveguide at regular intervals. This method may be simple because the method does not change the refractive index in the vertical direction, but manufacturing is difficult when the core disconnection interval is very small (less than 1 μm), and the loss due to scattering is not small.

Accordingly, the present invention is to solve the above problems, an object of the present invention is to provide a PLC core deformation method for extending the connection portion in the tapered form in order to facilitate the connection between the PLC and the optical fiber or other optical device. There is this.

1 is an exemplary view for explaining a conventional core expansion technology using an electric furnace.

2 is a view showing a taper forming method by a conventional Flame Hydrolysis Deposition (FHD) method

Figure 3 is a schematic diagram for explaining a taper forming technique by a conventional shadow mask (shadow mask)

4 is a view for explaining a core mode expansion method according to the conventional core breaking method.

5A-5I are manufacturing process diagrams for forming a hot wire in accordance with the techniques of the present invention.

6 shows a tapered state of a PLC core according to the method of the present invention.

<Description of Symbols for Main Parts of Drawings>

1: electric furnace 3: specimen holder

5: PLC 7: Torch

9,15: substrate 11: shadow mask

13 spacer 21 silicon substrate

23,29: oxide film 25: hot wire film

27,37: heating wire 31: core film

33: core 35: upper cladding

PLC core modification method of the present invention for achieving the above object,

In the core deformation method of the PLC for smoothly connecting the input / output of the PLC,

Non-uniformly adjusting the temperature gradient by embedding the heating wire locally in the PLC to expand the core in the outward direction of the PLC;

And generating electric resistance heat by flowing a current through the inlet terminal of the heating wire above and below the PLC core layer, and deforming the PLC core by thermal diffusion accordingly.

Hereinafter, a description will be given of an embodiment of a PLC core modification method according to the present invention with reference to the accompanying drawings.

5A-5I are manufacturing process diagrams for forming hot wires in accordance with the techniques of the present invention.

In the PLC core deformation method according to the present invention, a temperature wire is non-uniformly increased by embedding a hot wire in the upper and lower layers around the core where the silica needs to be deformed. The core is thereby deformed by diffusing ions (such as Ge 2+) which increase the refractive index present in the core.

First, referring to FIG. 5A, a silica film 23 is formed on a Si substrate 21.

5B and 5C, after depositing a metal film 25 to be used as a hot wire, a hot wire 27 is formed by etching.

Referring to FIG. 5D, a silica cladding layer 29 is formed on the entire structure.

5E and 5F, the core layer 31 is deposited and etched to form a core 33.

Referring to FIG. 5G, after the upper cladding layer 35 is formed, the hot wire 37 is formed in the same manner as in FIGS. 5B and 5C as shown in FIG. 5H. Again covered with a silica film 39 as shown in FIG. 5I.

At this time, the arrangement of the heating wires 27 and 37 may vary according to the deformation shape of the core 33.

FIG. 6 is a diagram showing a tapered state of the PLC core 33 according to the method of the present invention.

(a) is a plan view of a modified core, (b) is a side view, (c) is a front view.

In the figure, the heating wires 33 and 33 'arranged for deformation into a tapered shape are shown. In order to enlarge the core 33 'in the outward direction, the heating wires 27 and 37 were densely arranged in the outer part, and less densely arranged inwardly. By flowing a current 41 through the inlet terminal of the hot wire above and below the core layer 33, electric resistance heat can be generated and the core 33 can be deformed as shown in FIG. 6 by diffusion.

As described above, according to the method of the present invention described above, the heating wire is embedded in the upper and lower layers of the core, a temperature gradient is generated by the non-uniform resistance heat caused by the current, and the ion which increases the refractive index in the core is expanded. By inducing the deformation of the core by inducing the core, the optical waveguide core of the PLC can be transformed into a tapered shape, thereby facilitating the connection between the PLC-optical fiber and the PLC-optical device, and also the cladding and core of the PLC. The degree of integration can be increased by increasing the refractive index difference between them.

Claims (2)

In the core deformation method of the PLC for smoothly connecting the input / output of the PLC, Non-uniformly adjusting the temperature gradient by embedding the heating wire locally in the PLC to expand the core in the outward direction of the PLC; And generating an electric resistance heat by flowing a current through an inflow terminal of a heating wire above and below the PLC core layer, and deforming the PLC core by thermal diffusion accordingly. The method of claim 1, When the hot wire is locally buried, the hot wire is densely arranged in the outer portion of the PLC, and less densely arranged toward the inside of the PLC.