KR100875926B1 - Wavelength Multiplexing and Demultiplexing Optical Filter Modules and Manufacturing Method Thereof - Google Patents

Abstract

A wavelength multiplexing and demultiplexing optical filter module and a method of manufacturing the same according to the present invention include at least one input waveguide; An input stage star coupler in the form of a slab waveguide connected to the input waveguide; An arrayed waveguide having an optical path having a predetermined difference therebetween, a plurality of individual waveguides having a heterogeneous waveguide section having different refractive indices of waveguide cores sequentially arranged, and connected to an input star coupler; An output stage star coupler in the form of a slab waveguide connected to the array waveguide; And at least one output waveguide coupled to the output stage star coupler. The present invention introduces a heterogeneous waveguide section in which the existing waveguide and the core material are different in some regions of the arrayed waveguide, thereby reducing polarization and temperature dependence, and at the same time, effectively eliminating the optical coupling loss occurring at both ends of the heterogeneous waveguide section without additional waveguide forming process. Can be removed.

Description

Wavelength Multiplexing and Demultiplexing Optical Filter Modules and Method of Manufacturing the Same {Optical Filter and Manufacturing Method of the Same}

FIG. 1 is a diagram illustrating an embodiment of a wavelength multiplexing and demultiplexing optical filter module having a general configuration of waveguide gratings.

FIG. 2 is a diagram illustrating an embodiment in which hetero waveguide sections are introduced into a wavelength multiplexing and demultiplexing optical filter module having a general configuration of waveguide gratings.

FIG. 3 is a view illustrating an embodiment in which a heterogeneous waveguide section is introduced into a wavelength multiplexing and demultiplexing optical filter module having an arrayed waveguide grating according to the present invention.

4A and 4B are diagrams illustrating an exemplary embodiment of configuring a transition waveguide section of a wavelength multiplexing and demultiplexing optical filter module having an arrayed waveguide grating according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength multiplexing and demultiplexing optical filter module and a method of manufacturing the same. More particularly, the present invention relates to an array waveguide lattice-type wavelength multiplexing and demultiplexing optical beam used in an optical communication system using a wavelength division multiplexing method. The present invention relates to a filter module and a method of manufacturing the same.

FIG. 1 is a diagram illustrating an embodiment of a wavelength multiplexing and demultiplexing optical filter module having a general configuration of waveguide gratings.

Referring to FIG. 1, signal signals multiplexed through the input waveguide 101 are optically coupled to the input stage star coupler 102 in the form of a slab waveguide, and then optically coupled to the arrayed waveguide 103.

The individual waveguides constituting the arrayed waveguide 103 are sequentially arranged so that their optical paths are different at regular intervals, and the signal light traveling through each individual waveguide is optically coupled to the output stage star coupler 104 in the form of a slab waveguide. Then, the optical waveguide is optically coupled with the output waveguide 105.

The wavelength multiplexed signal light entering the input waveguide 101 is separated and outputted by wavelength through each output waveguide 105 through this series of processes.

When signal light having a wavelength corresponding to each output waveguide 105 is input to the output waveguide 105, the wavelength multiplexed signal light is collected through the input waveguide 101, so that the optical filter module performs a wavelength multiplexing function. .

In order for the performance of the optical filter module to be properly exhibited, the optical power loss of the signal light accumulated in the plurality of continuous optical coupling and waveguide processes as described above and the phase error of the signal light accumulated in the process of the arrayed waveguide 103 are maximized. Reduction is required.

The present invention introduces a heterogeneous waveguide section in which the existing waveguide and the core material are different in some regions of the arrayed waveguide, thereby reducing polarization and temperature dependence, and at the same time, effectively eliminating the optical coupling loss occurring at both ends of the heterogeneous waveguide section without additional waveguide forming process. It is a technical subject to remove.

According to an aspect of the present invention, there is provided a wavelength multiplexing and demultiplexing optical filter module including at least one input waveguide; An input stage star coupler in the form of a slab waveguide connected to the input waveguide; An arrayed waveguide having a light path having a predetermined difference therebetween, a plurality of individual waveguides having a heterogeneous waveguide section having different refractive indices of waveguide cores sequentially arranged, the arrayed waveguides connected to the input star coupler; An output stage star coupler in the form of a slab waveguide connected to the arrayed waveguide; And at least one output waveguide coupled to the output stage star coupler.

More preferably, in the wavelength multiplexing and demultiplexing optical filter module according to the present invention for achieving the above technical problem, the hetero waveguide section is a core of a core having a high refractive index.

More preferably, in the wavelength multiplexing and demultiplexing optical filter module according to the present invention for achieving the above technical problem, each of the individual waveguides is different from the refractive index of the core and the core material having a small refractive index is a clad of the core having a large refractive index Waveguide section; And a transition waveguide section connected to the hetero waveguide section, wherein a width of the core having a large refractive index gradually decreases in a waveguide direction consisting of a core having a small refractive index.

Array waveguides according to the present invention for achieving the above technical problem are arranged in a plurality of individual waveguides each having a light path having a predetermined difference, each individual waveguide is provided with a heterogeneous waveguide section having a different refractive index of the core In the hetero waveguide section, a core material having a small refractive index is a core of a core having a large refractive index.

More preferably, in the arrayed waveguides according to the present invention for achieving the above technical problem, each of the individual waveguides has different refractive indexes of the cores, and a heterogeneous waveguide section in which a core material having a small refractive index is a clad of the core having a large refractive index; And a transition waveguide section connected to the hetero waveguide section, wherein a width of the core having a large refractive index gradually decreases in a waveguide direction consisting of a core having a small refractive index.

According to an aspect of the present invention, there is provided a method of fabricating a wavelength multiplexing and demultiplexing optical filter module, including: (a) providing at least one input waveguide; (b) connecting an input stage star coupler in the form of a slab waveguide to the input waveguide; (c) forming an arrayed waveguide by sequentially arranging a plurality of individual waveguides having heterogeneous waveguide sections each having a different optical path having a predetermined difference therebetween, and connecting the input waveguide with a star coupler; (d) connecting an output stage star coupler in the form of a slab waveguide with the arrayed waveguide; And (e) connecting at least one output waveguide with the output stage star coupler.

More preferably, in the wavelength multiplexing and demultiplexing optical filter module manufacturing method according to the present invention for achieving the above technical problem, the hetero waveguide section is generated by the core of the core having a large refractive index.

More preferably, in the wavelength multiplexing and demultiplexing optical filter module manufacturing method according to the present invention for achieving the above technical problem, the step (c) is (c1) heterogeneous different refractive index of the core of each individual waveguide A waveguide section, wherein the hetero waveguide section comprises: forming a core material having a low refractive index into a clad of cores having a high refractive index; And (c2) forming a transition waveguide section in which a width of the core having a large refractive index gradually decreases in a waveguide direction made of a core having a small refractive index, and connecting the hetero waveguide section with the hetero waveguide section.

In the method of manufacturing an arrayed waveguide according to the present invention for achieving the above technical problem, (a) each of the individual waveguides has a heterogeneous waveguide section having a different refractive index of the core, the hetero waveguide section is a core having a small refractive index Forming the material into a clad of core having a high refractive index; And (b) forming a transition waveguide section for gradually decreasing the width of the core having the large refractive index in the direction of the waveguide composed of the core having the small refractive index and connecting the hetero waveguide section with the hetero waveguide section.

Hereinafter, a wavelength multiplexing and demultiplexing optical filter module and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram illustrating an embodiment in which hetero waveguide sections are introduced into a wavelength multiplexing and demultiplexing optical filter module having a general configuration of waveguide gratings.

Among the proposed methods, a technique for designing the arrayed waveguide 103 grating by introducing a heterogeneous waveguide section 113 having different waveguide characteristics within the arrayed waveguide 103 as shown in FIG. 2 (for example, Japanese Patent Application Laid-Open No. 1998) The optical waveguide filter according to -307219 and a method for manufacturing the same are preferable in terms of single integration of various optical elements performing different functions on the same substrate.

In addition, the hetero waveguide section 113 is also arranged in sequence so that their optical paths are different at regular intervals, forming a stress relief groove in the side cladding portion of the hetero waveguide (CK Nadler et al , IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, No. 5, p. 1407-1412 (1999)) It is possible to reduce the polarization and temperature dependence of the optical filter module by varying the thermo-optic coefficient of the heterogeneous waveguide (for example, a thermal optical device according to US Pat. No. 6118909). Do.

The thermo-optic coefficient of the waveguide is the degree to which the effective refractive index of the waveguide basic mode changes with temperature, and its sign and size are largely determined by the thermo-optic coefficient of the waveguide core material.

However, if the difference in refractive index between the core material and the clad material is small or the cross-section of the core is small and the degree to which the electromagnetic field of the waveguide is concentrated is small, the core material and the thermo-optic coefficient have opposite signs and have a large absolute value. It is possible to lower the absolute value of the thermo-optic coefficient of the waveguide mode by applying to. In special cases, the sign of the thermo-optic coefficient may be reversed.

This phenomenon may occur when a positive sign of thermo-optic coefficient such as inorganic silica and a negative sign of thermo-optic coefficient such as organic polymer are used as waveguide cores and clads, respectively. by introducing on the whole or partial region of 103), there have been attempts to reduce the temperature dependence of the optical filter module (gimdeokjun et al , Optical Fiber Communications Conference 2003, vol. 1, p. 61-62 (2003) and Korean Patent No. 10-0597232).

This method using an organic polymer as a clad has the advantage that the waveguide forming process is relatively simple and easy to implement, but has a disadvantage in that the subsequent process temperature cannot be sufficiently increased due to the low pyrolysis temperature of the organic polymer.

For this reason, unlike organic polymers, a material that can withstand high temperatures and has a negative thermo-optic coefficient is required, but it is difficult to find such a material in reality. However, in the case where a waveguide having a relatively large difference in thermo-optic coefficient of core material itself is applied to the hetero waveguide section 203, it is necessary to remove the temperature dependency of the optical filter even when both the core and clad materials have positive thermo-optic coefficient codes. In theory, it is possible.

However, as described above, reducing the temperature dependence due to the difference in thermo-optic coefficient of core material itself, as proposed by H. Tanobe, et al. It has been implemented only in waveguides with the same rib structure as Q (H. Tanobe et. al , IEEE Photonics Technology Letters, Vol. 10, No. 2, p. 235-237 (1998)), in a channel or buried waveguide in which the entire core is clad, it is difficult to realize in reality because of the complexity of the waveguide forming process.

On the other hand, the optical filter module is implemented by forming an optical waveguide on the substrate of a material such as silicon or glass in the manufacturing process, the larger the difference in refractive index between the waveguide core material and the clad material, the smaller the radius of curvature of the curved waveguide can be designed For this reason, it is preferable that the refractive index difference between the waveguide core material and the clad material is large in terms of miniaturization and integration of the optical device.

Such a large difference in refractive index between the waveguide core material and the clad material formed on the substrate is preferable in terms of miniaturization and improvement of the degree of integration of the optical device. However, the actual waveguide loss of the waveguide that is manufactured has a difference in refractive index between the core material and the clad material. It tends to increase rapidly as it gets larger.

As the difference in the refractive index between the waveguide core and the cladding increases, the cross-sectional area of the waveguide core satisfying the single mode condition decreases. In this case, the physical roughness of the core side caused by the etching process contributes to an increase in the loss of the waveguide light. have.

In addition, this roughness increases the optical loss of the arrayed waveguide itself in the arrayed waveguide grating type optical filter module, and also increases the phase error between individual waveguides, resulting in further deterioration of the optical crosstalk characteristics of the optical filter module. .

On the other hand, when materials with a very large refractive index difference of 2 or more, such as silicon and silica, are used as cores and clads in a channel or buried single mode waveguide, respectively, the thickness of the silicon core is about 220 nm than that of the square form, which is 300 nm thick And a rectangular shape with a width of about 500 nm is preferred.

As such, the technique of increasing the width relative to the thickness of the core has the effect of suppressing the increase in light loss due to the side roughness, whereas the effective refractive index of the waveguide between the TE mode and the TM mode is a major cause.

In addition, since the filter wavelength is directly determined by the effective refractive index of the waveguide constituting the arrayed waveguide, the polarization dependence of the filter wavelength in the arrayed waveguide lattice type optical filter module implemented with the rectangular silicon waveguide becomes a serious problem.

As such, in the arrayed waveguide grating type optical filter module, the method of changing the optical characteristics of the waveguide only for a part of the arrayed waveguide 103 may perform a different function as well as design to reduce polarization and temperature dependency of the optical filter module. It is desirable for single integration of various optical devices.

In addition, the method of changing the clad material for a portion of the arrayed waveguide is relatively easy to implement in the waveguide forming process, but considering that the energy of the waveguide is concentrated in the core, it is effective to change the core material itself to suppress polarization and temperature dependency. It is advantageous from the side.

However, considering the channel or the embedded waveguide in which the entire core is surrounded by cladding, it is practically difficult to introduce heterogeneous waveguide sections having different core materials into the arrayed waveguide region due to the complexity of the waveguide forming process.

And even after being introduced, there is a problem in that the optical coupling loss is additionally generated at the boundary between the existing waveguide section and the heterogeneous waveguide section.

FIG. 3 is a view illustrating an embodiment in which a heterogeneous waveguide section is introduced into a wavelength multiplexing and demultiplexing optical filter module having an arrayed waveguide grating according to the present invention.

Accordingly, the present invention provides a method for reducing the polarization and temperature dependence of wavelength multiplexing and demultiplexing optical filter modules in the form of an arrayed waveguide grating simultaneously or separately. Additional waveguide forming process in the process of forming the heterogeneous waveguide section 113 in the transition waveguide section 123 for lossless conversion of the waveguide mode at the boundary with the existing arrayed waveguide while introducing the hetero waveguide section 113 composed of cores To form naturally.

The present invention adopts a structure in which a core having a small refractive index acts as a cladding of another waveguide among two kinds of cores, and the width of the core having a relatively large refractive index gradually decreases in the direction of the relative waveguide to allow lossless conversion of the waveguide mode. Hereinafter, this will be described in detail with reference to FIGS. 4A and 4B.

4A and 4B are diagrams illustrating an exemplary embodiment of configuring a transition waveguide section of a wavelength multiplexing and demultiplexing optical filter module having an arrayed waveguide grating according to the present invention.

4A and 4B illustrate a transition waveguide section formed on a substrate 401 such as silicon, and a low refractive index core 404 film and a large refractive index core 403 film are sequentially formed on the lower clad 402 film. After the formation, the core 403 film having a large refractive index is etched into a desired shape, and then a core 406 film having a small refractive index is further formed, and then etched again into a desired shape, and finally, a series of layers for depositing the upper clad 405 film. It can be implemented through the waveguide formation process.

As described above, the present invention has a heterogeneous waveguide section having different waveguide characteristics and a transition waveguide section for lossless conversion of the waveguide mode in the existing arrayed waveguide, and in the process of forming the heterogeneous waveguide section without the additional waveguide forming process. Allow it to form naturally.

If a silicon core waveguide having a rectangular cross-sectional shape is applied to an arrayed waveguide, and the polarization dependence of the filter wavelength is severe, the filter wave length is applied to a square waveguide core constituting a heterogeneous waveguide section by applying a silicon nitride-based material having a smaller refractive index than silicon. Can weaken the polarization dependence.

Of course, in this case, the optical path lengths of the individual waveguides constituting the existing arrayed waveguides are all the same as in the transition waveguide section, whereas the waveguides constituting the heterogeneous waveguide sections are sequentially arranged so that their optical paths differ at regular intervals. It must be designed to perform the wavelength filter function.

In addition, when the thermo-optic coefficient of the waveguide core constituting the heterogeneous waveguide section is larger or smaller than the thermo-optic coefficient of the waveguide core constituting the arrayed waveguide section, the temperature dependence of the filter wavelength may be weakened by an appropriate arrayed waveguide temperature compensation design. have.

The effective refractive index of the basic mode is n _1, and the optical optical coefficients of the waveguides defined by dn ₁ / dT, which represent the degree to which the effective refractive index changes with temperature T, are arranged in sequence so as to be different by ΔL ₁ . Heterogeneous waveguides with different thermo-optic coefficients of dn ₂ / dT in some regions of the existing arrayed waveguides are sequentially arranged such that their optical paths are different by ΔL ₂ to form a lattice of arrayed waveguides having a diffraction order of m. In a situation where the effective refractive index n ₂ of the waveguide is larger than the effective refractive index n ₁ of the existing waveguide, the center wavelength λ ₀ of the arrayed waveguide grating type optical filter module may be expressed by Equation 1 below.

n ₁ ΔL _1- (n ₂ -n ₁ ) ΔL ₂ = mλ ₀

In order for the center wavelength λ ₀ of Equation 1 to have a temperature-independent characteristic, the above-mentioned two types of thermo-optic coefficients and optical paths must be designed to satisfy Equation 2.

ΔL ₁ / ΔL ₂ = (dn ₂ / dT) / (dn ₁ / dT) -1

On the other hand, in the situation where the effective refractive index n ₂ of the heterogeneous waveguide is smaller than the effective refractive index n ₁ of the existing waveguide, Equations 1 and 2 are expressed as Equations 3 and 4, respectively.

n ₁ ΔL ₁ + (n ₂ -n ₁ ) ΔL ₂ = mλ ₀

ΔL ₁ / ΔL ₂ = 1-(dn ₂ / dT) / (dn ₁ / dT)

As described above, the present invention introduces a hetero waveguide section composed of cores of a material having a larger or smaller refractive index than a core of an existing waveguide in a portion of the arrayed waveguide, and among the two kinds of cores mentioned above, a core having a small refractive index acts as a cladding of another waveguide. And the width of the core with a relatively large refractive index is gradually reduced in the direction of the relative waveguide.

Through this, the present invention can individually or simultaneously weaken the polarization and temperature dependence of the optical filter module by optimizing the arrayed waveguide grating design to match the polarization and temperature characteristics of the heterogeneous waveguide itself.

In addition, the transition waveguide section for lossless conversion of the waveguide mode at the boundary with the existing arrayed waveguide is naturally formed without an additional waveguide forming process in the process of forming the heterogeneous waveguide section.

On the other hand, when the refractive index of the core constituting the conventional arrayed waveguide is very large compared to the core constituting the heterogeneous waveguide section, the present invention increases the optical loss of the arrayed waveguide itself due to the physical roughness of the core side and phase error between the individual waveguides. Suppress the increase.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

The wavelength multiplexing and demultiplexing optical filter module and a method for fabricating the same according to the present invention introduce heterogeneous waveguide sections having different waveguides and core materials into a portion of an arrayed waveguide, thereby reducing polarization and temperature dependence, and at the same time both ends of the heterogeneous waveguide section. The optical coupling loss occurring at can be effectively removed without additional waveguide formation process.

Claims (7)

At least one input waveguide; An input stage star coupler in the form of a slab waveguide connected to the input waveguide; An arrayed waveguide having an optical path having a different length and having a plurality of waveguide sections each having a different waveguide section having different refractive indices, the arrayed waveguides connected to the input star coupler; An output stage star coupler in the form of a slab waveguide connected to the arrayed waveguide; And And at least one output waveguide connected to the output stage star coupler. The hetero waveguide section is a wavelength multiplexing and demultiplexing optical filter module, characterized in that the core material having a small refractive index is a clad of the core having a large refractive index. The method of claim 1, wherein each of the individual waveguides A heterogeneous waveguide section in which a core material having a different refractive index and having a smaller refractive index is a clad of the core having a larger refractive index; And And a transition waveguide section connected to the hetero waveguide section, wherein a width of the core having a large refractive index gradually decreases in a direction of the waveguide composed of a core having a small refractive index. 2. In an arrayed waveguide in which a plurality of individual waveguides having optical paths of different lengths are sequentially arranged, Each of the individual waveguides includes a hetero waveguide section having different refractive indices of cores, and the core material having a small refractive index in the hetero waveguide section is a clad of cores having a large refractive index. The method of claim 3, wherein each of the individual waveguides A heterogeneous waveguide section in which cores have different refractive indices and core materials having a small refractive index are clads of cores having a large refractive index; And And a transition waveguide section connected to the hetero waveguide section, wherein a width of the core having a large refractive index gradually decreases in a direction of the waveguide made of a core having a small refractive index. (a) having at least one input waveguide; (b) connecting an input stage star coupler in the form of a slab waveguide to the input waveguide; (c) forming an arrayed waveguide by sequentially arranging a plurality of individual waveguides having heterogeneous waveguide sections having different refractive indices of waveguide cores and forming an arrayed waveguide, and connecting the input stage star couplers; (d) connecting an output stage star coupler in the form of a slab waveguide with the arrayed waveguide; And (e) connecting at least one output waveguide with the output stage star coupler; The hetero waveguide section is a method of manufacturing a wavelength multiplexing and demultiplexing optical filter module, characterized in that to generate a core material having a small refractive index as a clad of the core having a large refractive index. The method of claim 5, wherein step (c) (c1) a heterogeneous waveguide section in which the refractive indices of the cores of the individual waveguides are formed differently from each other, wherein the heterogeneous waveguide sections are formed of a clad of a core having a high refractive index; And (c2) forming a transition waveguide section in which a width of the core having a large refractive index gradually decreases in a waveguide direction consisting of the core having a small refractive index, and connecting the hetero waveguide section to the multiplexing waveguide section; Manufacturing method of multiplexed optical filter module. In the method of manufacturing an arrayed waveguide in which a plurality of individual waveguides having optical paths of different lengths are sequentially arranged, (a) each of the individual waveguides has a heterogeneous waveguide section in which the refractive indices of the cores are formed differently from each other, wherein the hetero waveguide sections form a core material having a small refractive index as a clad of cores having a large refractive index; And (b) forming a transition waveguide section for gradually reducing the width of the core having a large refractive index in the direction of the waveguide made of the core having a small refractive index, and connecting the hetero waveguide section with the hetero waveguide section. Way.

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