JP2001066446A - Array waveguide type diffraction grating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an array waveguide type diffraction grating having the small temperature dependency and loss of a transmission light wavelength. SOLUTION: The array waveguide 4 of the array waveguide type diffraction grating which is composed by connecting plural light input waveguides 2, an input side slab waveguide 3, plural array waveguides 4 mutually having different length, an output side slab waveguide 5 and plural light output waveguides 6 in this order on a substrate 1 is cut and separated at the middle of the longitudinal direction to form a first array waveguide 4a and a second array waveguide 4b, respectively. A third slab waveguide 7 is provided in the embodiment that the whole array waveguides 4a, 4b are traversed. The third slab waveguide 7 is formed of quartz glass having a coefficient of linear expansion smaller than that of the array waveguide 4 and having a small refrative index temperature gradient, and moreover the length of a route (the length of a route 8) in the optical axis direction of light propagating from the first array waveguide 4a to the corresponding second array waveguide 4b inside the third slab waveguide 7 is formed into the size by which the temperature dependency of the length of the optical path of the whole array waveguide 4 is nearly cancelled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an arrayed waveguide type diffraction grating used in an optical communication system, and more particularly to a reduction in the temperature dependence of the transmission wavelength of an arrayed waveguide type diffraction grating.

[0002]

2. Description of the Related Art In recent years, attempts have been made to increase the degree of multiplexing and increase the transmission capacity in a wavelength division multiplexing transmission system. To realize this, a plurality of signal lights having a wavelength interval of 1 nm or less are optically combined. There is a need for an optical multiplexer / demultiplexer that can wave. As such an optical multiplexer / demultiplexer, for example, Japanese Patent Application
Array waveguide type diffraction grating (AWG; Arrayed Waveguide G) as proposed in 1-65588.
2. Description of the Related Art An optical multiplexer / demultiplexer that uses rating is known.

As shown in FIG. 6, the arrayed waveguide type diffraction grating is obtained by forming the waveguide configuration shown in FIG. 1 on a substrate 1, and this waveguide configuration is composed of one or more parallel waveguides. The input side slab waveguide 3 as a first slab waveguide is connected to the output side of the optical input waveguide 2, and a plurality of array waveguides arranged in parallel are connected to the output side of the input side slab waveguide 3. The output side slab waveguide 5 as a second slab waveguide is connected to the output side of the plurality of arrayed waveguides (channel waveguides) 4, and the output side of the output side slab waveguide 5 is connected to the output side. A plurality of juxtaposed optical output waveguides 6 are connected and formed.

The array waveguide 4 propagates light derived from the input side slab waveguide 3 and has different lengths. The plurality of array waveguides 4 form a diffraction grating 14. Are formed. The optical input waveguide 2 and the optical output waveguide 6 are provided corresponding to the number of signal lights having different wavelengths, which are split by, for example, an arrayed waveguide type diffraction grating. Usually, a large number of such waveguides are provided, for example, 100. In the same figure, for simplification of the figure, the number of each of the waveguides 2, 4, 6 is simply shown.

[0005] An optical fiber on the transmission side is connected to the optical input waveguide 2 so that wavelength-division multiplexed light is introduced. The optical input waveguide 2 passes through the optical input waveguide 2 to the input side slab waveguide 3. The introduced light spreads due to the diffraction effect, enters the plurality of array waveguides 4, and propagates through the array waveguides 4.

The light propagating through each array waveguide 4 reaches the output side slab waveguide 5 and is further condensed and output by the optical output waveguide 6, but the length of each array waveguide 4 is reduced. Since they are different from each other, a phase shift of each light occurs after propagating through each arrayed waveguide 4, and the wavefront of the converged light is tilted according to the amount of the shift. The light condensing positions of the different lights are different from each other, and by forming the light output waveguides 6 at the positions, lights having different wavelengths can be output from the different light output waveguides 6 for each wavelength.

In this arrayed waveguide type diffraction grating,
Since the wavelength resolution of the diffraction grating is proportional to the difference (ΔL) between the lengths of the array waveguides 4 constituting the diffraction grating, by designing ΔL to be large, it is possible to reduce the wavelength interval which cannot be realized by the conventional diffraction grating. The optical multiplexing / demultiplexing of narrow wavelength multiplexed light becomes possible, and the optical multiplexing / demultiplexing function of a plurality of signal lights required for realizing high-density optical wavelength multiplexing communication, that is, a plurality of optical signals having a wavelength interval of 1 nm or less. Can be divided or combined.

[0008]

However, in the arrayed waveguide type diffraction grating, the transmission wavelength greatly changes with changes in the external environment temperature. In order to prevent this, transmission wavelength fluctuations are conventionally suppressed by keeping the arrayed waveguide type diffraction grating at a constant temperature with a Peltier element for temperature control. However, for the Peltier element and its temperature control, an arrayed waveguide type Since the cost of the diffraction grating increases and the power consumption for controlling the temperature increases, it is desired to realize an arrayed waveguide grating that can operate stably without depending on the environmental temperature.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an arrayed waveguide type diffraction grating which can operate stably without depending on the environmental temperature. is there.

[0010]

Means for Solving the Problems In order to solve the above problems, the present invention has the following structure to solve the problems. That is, according to the present invention, the first slab waveguide is connected to the output side of one or more optical input waveguides arranged in parallel, and the first slab waveguide is connected to the output side of the first slab waveguide. A plurality of side-by-side array waveguides of different lengths for transmitting light derived from the waveguide are connected, and a second slab waveguide is connected to an output side of the plurality of array waveguides. The slab waveguide 2 has a waveguide configuration in which a plurality of juxtaposed optical output waveguides are connected to an output side, and a plurality of optical signals having different wavelengths input from the optical input waveguide are transmitted. An arrayed waveguide type light that propagates with a phase difference for each wavelength by the arrayed waveguide, makes it incident on a different optical output waveguide for each wavelength, and outputs light of different wavelengths from different optical output waveguides. In the diffraction grating,
All the array waveguides are cut and separated into a first array waveguide and a second array waveguide at a middle part in the longitudinal direction, and the separated first array waveguide and the second array waveguide are separated. A third slab waveguide is provided in such a manner as to cross all the first and second array waveguides at an interval between the third slab waveguide and the array waveguide. At least one of the linear expansion coefficients is formed to have a different value, and the optical axis direction of light propagating in the third slab waveguide from the first array waveguide toward the corresponding second array waveguide. The path length is a means for solving the problem with a configuration formed so as to substantially cancel the temperature dependence of the optical path length of the entire array waveguide.

In the present invention having the above-described structure, all the array waveguides are connected to the first array waveguide and the second
And the third array waveguide in a manner crossing all of the first and second array waveguides at a distance between the separated first and second array waveguides. Is provided.

In the conventional arrayed waveguide type diffraction grating, the transmission wavelength depends on the external environment temperature because the length of the arrayed waveguide changes with the change of the external environment temperature and the optical path length of the propagation light changes. In the present invention, at least one of the refractive index temperature gradient and the linear expansion coefficient of the third slab waveguide and the arrayed waveguide is different from each other, and the first slab waveguide and the arrayed waveguide have different values. The path length in the optical axis direction of light propagating in the third slab waveguide from the array waveguide toward the corresponding second array waveguide almost cancels the temperature dependence of the optical path length of the entire array waveguide. Due to the third slab waveguide, the temperature dependence of the optical path length of the entire arrayed waveguide can be almost canceled by the third slab waveguide.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same reference numerals are given to the same parts as those in the conventional example, and the overlapping description will be omitted. FIG. 1 is a plan view schematically showing an embodiment of an arrayed waveguide grating according to the present invention.

As shown in FIG. 1, the arrayed waveguide type diffraction grating of this embodiment also has a core waveguide structure formed on a substrate 1 like the arrayed waveguide type diffraction grating of the conventional example.
The waveguide configuration includes a plurality of optical input waveguides 2, an input side slab waveguide 3, a plurality of array waveguides 4, an output side slab waveguide 5, and a plurality of optical output waveguides 6. Further, the optical input waveguide 2, the array waveguide 4, and the optical output waveguide 6 are arranged side by side with a predetermined waveguide interval.

This embodiment is different from the conventional example in that all the arrayed waveguides 4 are cut and separated into a first arrayed waveguide 4a and a second arrayed waveguide 4b at an intermediate portion in the longitudinal direction. The distance between the separated first and second arrayed waveguides 4a and 4b is
A third slab waveguide 7 is provided so as to cross the first and second array waveguides 4a and 4b. By providing the third slab waveguide 7, the temperature of the optical path length of the entire array waveguide 4 is increased. That is, we almost offset the dependence.

That is, the third slab waveguide 7 and the arrayed waveguide 4 are formed so that at least one of the refractive index temperature gradient and the linear expansion coefficient is different from each other (specifically, the third slab waveguide 7 and the arrayed waveguide 4 have different values).
The slab waveguide 7 is formed of silica-based glass having a smaller linear expansion coefficient and a smaller refractive index temperature gradient than the arrayed waveguide 4), and a corresponding second arrayed waveguide from the first arrayed waveguide 4a. The path length of the light propagating in the third slab waveguide 7 toward the wave path 4b in the optical axis direction (path 8)
Is set to a size that almost cancels the temperature dependence of the optical path length of the entire array waveguide 4.

In FIG. 1, for the sake of simplicity, the inside of the third slab waveguide 7 is divided into the first arrayed waveguides 4.
Although only three paths 8 in the optical axis direction of the light propagating from the a to the corresponding second array waveguide 4b are shown in FIG.
Is a path connecting each array waveguide 4a and the corresponding second array waveguide 4b, and there are at most the number of array waveguides 4. The third slab waveguide 7 has a thickness of 10 μm and a width (length in the Y direction in the drawing) of 3500 μm.
(Uniform), a trapezoidal shape formed so that the length in the X direction in the figure increases toward the upper side.

FIG. 1 conceptually shows the arrayed waveguide type diffraction grating of this embodiment. Therefore, the second arrayed waveguide 4b corresponding to the length of the first arrayed waveguide 4a is shown. Is shown to be longer from the inner side to the outer side of the array, but in fact, conversely, the sum of the lengths becomes shorter from the inner side to the outer side of the array of the arrayed waveguide 4. ing. That is, as shown in FIG. 2, for example, the length of the i-th array waveguide 4 (the length of the i-th first array waveguide 4a and the length of the i-th second array) counted from the inside of the array shown in FIG. The sum of the length of the (i + 1) -th array waveguide 4 (the length of the (i + 1) -th first array waveguide 4a and the length of the (i + 1) -th second array waveguide 4b) is greater than the sum of the lengths of the waveguides 4b. Sum) is formed short.

In this embodiment, the optical input waveguide 2
For example, the number of optical output waveguides 6 is set to 16, for example, and the number of arrayed waveguides 4 is set to 100. The core size of each waveguide 2, 4, 6 is 6μm thick
× The width is 6 μm.

Further, in the present embodiment, as described above, the third slab waveguide 7 is interposed between the array waveguides 4 so that the third slab waveguide 7 is diffracted by the array slab waveguide 7 and the third slab waveguide 7. Grid 14 and a corresponding first
Array waveguide 4a and second array waveguide 4b, and
In the meantime, the waveguide length between the channel waveguides formed by the path 8 in the third slab waveguide 7 (the length of the first array waveguide 4 + the length of the corresponding second array waveguide 4+ The difference ΔL in the length of the corresponding path 8) was set to 64 μm. The diffraction order m was 61, the refractive index n of the core forming the waveguide configuration was 1.4698, and a wavelength multiplexing interval of 0.8 nm was obtained in the wavelength band of 1.55 μm used in optical communication.

The inventor of the present invention has determined the characteristics of the third slab waveguide 7 and the array waveguides 4 such as the composition and linear expansion coefficient, and the length of the propagating light in the optical axis direction. Was examined based on the following examination.

In an arrayed waveguide type diffraction grating having a waveguide configuration as shown in FIG. 6, (Equation 1) holds.

[0023]

(Equation 1)

Here, n is the effective refractive index of the arrayed waveguide 4, ΔL is the difference between the lengths of the adjacent arrayed waveguides 4, m is the diffraction order (integer), and λ is the transmission wavelength. Differentiating this (Equation 1) with respect to temperature gives (Equation 2).

[0025]

(Equation 2)

Here, α indicates the coefficient of linear expansion of the core. In general, the quartz-based glass forming the arrayed waveguide 4 has positive values of the temperature differential coefficient of the refractive index and the linear expansion coefficient.
As is clear from (Equation 2), the temperature derivative of the transmitted wavelength also has a positive value. Therefore, the transmission wavelength of the arrayed waveguide 4 shifts to the longer wavelength side as the temperature rises.

If the length of the array waveguide 4 before and after the temperature rise is equal in all the array waveguides 4, the transmission wavelength should be constant without depending on the temperature. As described above, since the lengths of the array waveguides 4 are different from each other, the amount of extension of the lengths also differs, and as described above, the transmission wavelength of the array waveguide 4 changes depending on the temperature. Will be.

The inventor of the present invention has proposed that the array waveguides should be arranged in the middle of the length of all the arrayed waveguides 4 in the longitudinal direction so as to correspond to the difference in the amount of expansion of each arrayed waveguide 4 and to offset the difference in the amount of expansion. A third slab waveguide 7 having a refractive index temperature gradient and a linear expansion coefficient different from that of the waveguide 4 is provided (the first arrayed waveguide 4).
A third slab waveguide 7 is provided at a distance between the first array waveguide 4a and the second array waveguide 4b so as to cross all the first and second array waveguides 4a and 4b). By satisfying (Equation 3) of the phase matching condition and (Equation 4) that satisfies the condition that the waveguide length difference does not change due to a temperature change, the temperature dependence of the optical path length of all arrayed waveguides 4 is offset. I thought.

[0029]

(Equation 3)

[0030]

(Equation 4)

[0031] (Equation 3), the equation (4), n _a is the effective refractive index of the arrayed waveguide 4, _{n b} is the third slab waveguide 7
As shown in FIG. 2 _, the effective refractive index _{La, i} of the i-th array waveguide 4 (i-th first array waveguide 4a) is counted from the inside of the array (see FIG. 1). And the ith second
Sum of the lengths of the arrayed waveguides 4b), _{Lb, i} in the third slab waveguide 7 from the i-th first arrayed waveguide 4a to the i-th second arrayed waveguide 4b. Is the length of the path 8 _{i in} the optical axis direction of the light propagating through (the distance between the i-th first arrayed waveguide 4 a and the i-th second arrayed waveguide 4 b in the optical axis direction), and m is the diffraction order (Integer) and λ is the transmission wavelength. Further, La _{, i + 1} , _{Lb, i + 1} are in accordance with the above.

Based on the above idea, in this embodiment,
With the temperature rise, the extension amount of the i-th first arrayed waveguide 4a, the extension amount of the i-th second arrayed waveguide 4b,
From the i-th first arrayed waveguide 4a to the i-th arrayed waveguide 4b, the sum of the amount of elongation of the path 8 in the optical axis direction of the light propagating in the third slab waveguide 7 is i = 1 To M (M is the total number of the arrayed waveguides 4, and in this embodiment, 10
The composition of the silica-based glass of the cores of the arrayed waveguides 4 (4a, 4b) and the third slab waveguide 7 to be equal in all cases up to 0) was studied as follows.

First, in (Equation 3) and (Equation 4),
In order to reduce the loss of the arrayed waveguide 4, if the refractive indices of the arrayed waveguide 4 and the third slab waveguide 7 at room temperature (25 ° C.) are equal (n _a = n _b = n), 5),
(Equation 6) is obtained. The refractive index of the core forming the arrayed waveguide 4 and the third slab waveguide 7 was set to be 0.80% larger than the refractive index of the lower clad and the upper clad.

[0034]

(Equation 5)

[0035]

(Equation 6)

Here, α _a and α _b are the linear expansion coefficients of the array waveguide 4 and the third slab waveguide 7, respectively. ΔL _a is the difference between the waveguide lengths of the adjacent array waveguides 4 (the difference between the waveguide lengths of the adjacent array waveguides 4a + the difference between the waveguide lengths of the adjacent array waveguides 4b), and ΔL _b is A path 8 _{i in} the optical axis direction of light propagating from the i-th first arrayed waveguide 4 a to the i-th arrayed waveguide 4 b in the third slab waveguide 7 and the inside of the third slab waveguide 7. i + 1st first
From the array waveguide 4a to the (i + 1) th array waveguide 4b
And the difference from the path 8 _{i + 1 in} the optical axis direction of the light propagating to
It is shown by (Equation 7) and (Equation 8).

[0037]

(Equation 7)

[0038]

(Equation 8)

As described above, the array waveguide type diffraction grating
In order to eliminate the temperature dependency, the array waveguide 4 and the third
Linear expansion coefficient of each core glass forming slab waveguide 7
α_a, Α _bAnd the refractive index temperature gradient dn / dT, (Equation 5),
ΔL to satisfy (Equation 6)_a , ΔL _bCan be determined
I understand.

Next, the method of obtaining the linear expansion coefficients α _a and α _b and the refractive index temperature gradients dn / dT and ΔL _a and ΔL _b of each core glass of the array waveguide 4 and the third slab waveguide 7 will be described. State. The refractive index temperature gradient dn / dT can be obtained by subjecting the Lorenz-Lorentz equation to temperature differentiation (Equation 9).

[0041]

(Equation 9)

Here, β is the body expansion coefficient. In the case of an isotropic body such as glass, the relationship between the linear expansion coefficient α and β is β ≒ 3α
Holds. Ψ is the temperature coefficient of the polarizability.

It is known that α and ψ have additive properties due to glass composition components (for example, “Temperature coefficient of polarizability of optical glass”, Optics, 8 (1979) p.
α and ψ can be determined from the glass composition. If ψ is obtained, dn / dT is obtained from (Equation 9), and ΔL _a and ΔL _b satisfying (Equation 5) and (Equation 6) may be obtained from α and dn / dT obtained above. Become.

Therefore, in the present embodiment, in order to cancel the temperature dependence of the optical path length of the entire arrayed waveguide 4, the composition of the arrayed waveguide 4 and the composition of the third slab waveguide 7 are made of quartz glass. The values shown in Table 1 are determined so that the linear expansion coefficient and the refractive index temperature gradient of the arrayed waveguide 4 and the third slab waveguide 7 become predetermined values by using the additivity of the constituent components. did.

[0045]

[Table 1]

The thickness (about 10 μm) of each of the core films 21 and 22 forming the array waveguide 4 and the third slab waveguide 7.
Since the thicknesses of the substrates 1 and 13 (about 1 mm) are thicker than those in Table 1, in Table 1, the linear expansion coefficients α of the arrayed waveguide 4 and the third slab waveguide 7 are both additive properties of the glass component. , The linear expansion coefficient of the array waveguide 4 is approximated by the linear expansion coefficient α of the silicon substrate α = 26 × 10 ⁻⁷ / ° C., and the linear expansion coefficient of the third slab waveguide 7 is the linear expansion coefficient of the quartz substrate. Coefficient α =
Approximation was performed using 5.5 × 10 ⁻⁷ / ° C.

Using the values in Table 1, the elongation amounts ΔL _a and ΔL _b of the arrayed waveguide 4 and the third slab waveguide 7 of the arrayed waveguide type diffraction grating of this embodiment are given by Calculating from (Equation 6), the extension amount of each array waveguide 4 (the extension amount of the first array waveguide 4a + the corresponding second array waveguide 4b)
ΔL _a = −41 μm, while the extension of the third slab waveguide 7 (the extension of the path 8 of each propagating light) ΔL _b = 1
It becomes 05 μm. Then, the sum of the extension amount of each array waveguide 4 and the extension amount of the third slab waveguide 7 (specifically, the first
Of the array waveguide 4a + the corresponding extension of the second array waveguide 4b + the corresponding extension of the propagation light path 8) is ΔL = ΔL _a + ΔL _b = 64 μm.

In this embodiment, since the number of array waveguides is set to 100, the length of the slab waveguide 7 connected to the outermost (uppermost in the figure) array waveguide 4 needs to be 10.5 mm. Therefore, in this embodiment, the length of the third slab waveguide 7 connected to the outermost arrayed waveguide 4 is fixed to 15 mm, and the core of the arrayed waveguide 4 is set to 41 μm from the inside to the outside. On the other hand, the third slab waveguide 7 was manufactured so as to be longer by 105 μm from the inside to the outside so as to correspond to the arrayed waveguide 4.

Then, the arrayed waveguide type diffraction grating is cut and divided into a desired shape (a trapezoidal shape in the present embodiment) so as to separate a middle part (a central portion in the present embodiment) of the array waveguide 4 in the longitudinal direction. By disposing and connecting the third slab waveguide 7 having the desired shape between the cut and divided first and second array waveguides 4a and 4b, the array waveguide type diffraction grating of this embodiment can be obtained. Formed.

The present embodiment is configured as described above. Next, a method for forming an arrayed waveguide type diffraction grating of this embodiment will be described with reference to FIGS. In addition, (a) ′ to (c) ′ in FIG. 3 respectively correspond to (a) in FIG.
5A to 5C are shown, and FIG.
(D) ′ shows cross-sectional views (a) to (d) of FIG.

First, as shown in FIGS. 3A and 3A ', a lower cladding film 11 and a core film 21 are formed on a silicon substrate 1 by a flame deposition method, similarly to the conventional arrayed waveguide type diffraction grating. And vitrification sintering, and FIG.
As shown in (b) ′, the core film 21 is subjected to reactive ion etching (RIE) to remove unnecessary portions of the core film 21 to form a desired waveguide pattern. Thereafter, as shown in FIGS. 3C and 3C ', the upper clad film 12 is formed on the upper side of the core film 21 by a flame deposition method and vitrification sintering.

Then, a cutting marker 31 as shown in FIG. 4 is formed on the conventional arrayed waveguide type diffraction grating thus formed, and the formed substrate is cut along the cutting marker.

On the other hand, as shown in FIGS. 5A and 5A ′, a slab waveguide 7 is formed by forming a core film 22 on a quartz substrate 13 by flame deposition and vitrification sintering. As shown in (b) and (b) ′ of the same figure, the core film 22 is formed into a desired core shape using reactive ion etching, and as shown in (c) and (c) ′ of the same figure. , Upper cladding film 1
5 is formed by flame deposition and vitrification sintering. Thereafter, the formed substrate is cut into a predetermined shape 100 as shown in (d) and (d) ′ of FIG.

Then, the third slab waveguide 7 cut in FIG. 5 is arranged between the arrayed waveguides 4a and 4b cut and divided in the manufacturing process of FIG. 4, and bonded using an adhesive or the like. Thus, the arrayed waveguide type diffraction grating shown in FIG. 1 is manufactured.

The arrayed waveguide type diffraction grating of this embodiment performs an optical multiplexing / demultiplexing operation such as splitting of wavelength-division multiplexed light by the same operation as the conventional arrayed waveguide type diffraction grating.
In this embodiment, each arrayed waveguide 4 is cut and separated into a first arrayed waveguide 4a and a second arrayed waveguide 4, and between these arrayed waveguides 4a and 4b, as shown in Table 1. A third slab waveguide 7 having a refractive index temperature dependency and a linear expansion coefficient different from that of the arrayed waveguide 4 having an appropriate composition;
In addition, a path length of the light propagating in the third slab waveguide 7 from the first array waveguide 4a to the corresponding second array waveguide 4b in the optical axis direction (length of the path 8). Is formed to have a size that almost cancels the temperature dependence of the optical path length of the entire array waveguide 4, so that the temperature dependence of the entire array waveguide 4 can be made very small.

Therefore, the arrayed waveguide type diffraction grating of this embodiment can be an arrayed waveguide type diffraction grating in which the temperature dependence of the transmitted light wavelength is very small. In fact, when the inventor measured the temperature dependence of the transmission wavelength in the arrayed waveguide type diffraction grating of the present embodiment, the temperature variation width
The fluctuation width of the transmission wavelength of the present arrayed waveguide type diffraction grating at 0 to 80 ° C. was a very small value of 0.04 nm, and it was confirmed that the temperature dependence of the transmission wavelength could be significantly reduced.

The transmission loss of the arrayed waveguide type diffraction grating of the present embodiment and the conventional arrayed waveguide type diffraction grating formed without the third slab waveguide 7 were compared. In the arrayed waveguide type diffraction grating of the embodiment, the transmission loss is increased by only 1 dB as compared with the conventional arrayed waveguide type diffraction grating, and the connection loss between the arrayed waveguide 4 and the third slab waveguide 7 is reduced. There was little excess loss.

Further, in the present embodiment, when the compositions of the arrayed waveguide 4 and the third slab waveguide 7 are determined, as described above, the additive properties of the constituent components of the silica-based glass are used. Since the linear expansion coefficient and the refractive index temperature gradient of the arrayed waveguide 4 and the third slab waveguide 7 were determined to be predetermined desired values, the compositions of the arrayed waveguide 4 and the third slab waveguide 7 were determined. Can be determined very easily, and an arrayed waveguide type diffraction grating can be easily designed.

Further, according to the present embodiment, since a temperature controller such as a Peltier element is not used, a small arrayed waveguide type diffraction grating can be obtained.

Next, a description will be given of an array waveguide type diffraction grating according to a second embodiment of the present invention. The present embodiment is configured substantially in the same manner as the first embodiment. The present embodiment is different from the first embodiment in that the array waveguide 4 and the third slab waveguide are different. The composition of 7
The composition shown in Table 2 was used, ΔL _a = −31 μm, ΔL _b = 95
μm.

[0061]

[Table 2]

Also in this embodiment, the array waveguide 4 and the third
The composition of the slab waveguide 7 is such that the linear expansion coefficient and the refractive index temperature gradient of the arrayed waveguide 4 and the third slab waveguide 7 are set to predetermined values by using the additive properties of the constituent components of the silica-based glass. The values shown in Table 2 are determined so that Table 2
Arrayed waveguide 4 using the values, the elongation amount [Delta] L _a third slab waveguide 7, the [Delta] L _b (5), is calculated from (6), wherein as the elongation of the arrayed waveguide 4 Quantity ΔL _a = -31μ
m, the elongation ΔL _b = 95 μm of the third slab waveguide 7,
The sum of the extension amount of each array waveguide 4 and the extension amount of the third slab waveguide 7 is ΔL = ΔL _a + ΔL _b = 64 μm.

The thickness (about 10 μm) of each of the core films 21 and 22 forming the array waveguide 4 and the third slab waveguide 7.
Since the thicknesses of the substrates 1 and 13 (approximately 1 mm) are larger than those in Table 1, the linear expansion coefficients α of the arrayed waveguide 4 and the third slab waveguide 7 are both the same in Table 2 as in Table 1. Without using the additivity of the glass component, the linear expansion coefficient of the arrayed waveguide 4 approximates the linear expansion coefficient of the silicon substrate α = 26 × 10 ⁻⁷ / ° C., and the linear expansion coefficient of the third slab waveguide 7. Was approximated using the linear expansion coefficient α of the quartz substrate = 5.5 × 10 ⁻⁷ / ° C.

The present embodiment is configured as described above. In this embodiment, substantially the same characteristics and effects as those of the first embodiment are obtained.

It should be noted that the present invention is not limited to the above-described embodiment, but can adopt various embodiments. For example,
The core composition forming the arrayed waveguide 4 and the third slab waveguide 7 is not limited to the core composition of each of the above embodiments, but the refractive index of the third slab waveguide 7 and the arrayed waveguide 4 At least one of the temperature gradient and the linear expansion coefficient is formed to have different sizes, and the light propagating in the third slab waveguide 7 from the first array waveguide 4a to the corresponding second array waveguide 4b is formed. By setting the path length in the optical axis direction to an appropriate length, various compositions can be applied so that the temperature dependence of the optical path length of the entire arrayed waveguide 4 is almost canceled.

Further, in each of the above embodiments, the substrate 1 is a silicon substrate, but the material for forming the substrate 1 is not particularly limited, and a quartz substrate may be used.

Further, in each of the above embodiments, the arrayed waveguide type diffraction grating is formed on the substrate by the flame hydrolysis method using quartz glass, but the present invention is limited to the flame hydrolysis method. Not a quartz-based glass waveguide formed by other deposition methods, such as electron beam evaporation,
Alternatively, an arrayed waveguide type diffraction grating may be formed by a silica-based glass waveguide manufactured by ion exchange or proton exchange.

Further, in each of the above embodiments, as shown in FIG. 2, the length of the (i + 1) -th array waveguide 4 is made shorter than the length of the i-th array waveguide 4, and the i-th array waveguide 4 is formed. than the length of the first arrayed waveguide 4a from the i-th second toward the arrayed waveguide 4b of the light propagating the third slab waveguide 7 in the optical axis direction of the path 8 _i, i + 1 th Although the length of the optical axis direction path 8 _{i + 1} of light propagating in the third slab waveguide 7 from the first array waveguide 4 a to the (i + 1) -th second array waveguide 4 b is formed longer, On the contrary, depending on the composition of the waveguide 4 and the third slab waveguide 7, the length of the i-th arrayed waveguide 4 is larger than the length of the i-th arrayed waveguide 4.
The length of the + 1st arrayed waveguide 4 is increased, and
It may be formed shorter the length of the path 8 _{i + 1} than _i.

[0069]

According to the present invention, the first and second arrayed waveguides are cut and separated at the middle part in the longitudinal direction of the arrayed waveguide, and all of the first and second arrayed waveguides are crossed. A third slab waveguide is provided, and the third slab waveguide and the array waveguide have at least one of a refractive index temperature gradient and a linear expansion coefficient different from each other. The path length in the optical axis direction of the light propagating in the third slab waveguide toward the second array waveguide is formed to have a size that almost cancels the temperature dependence of the optical path length of the entire array waveguide. Therefore, the slab waveguide can substantially offset the temperature dependence of the optical path length of the entire arrayed waveguide.

Further, according to the present invention, as described above, the temperature dependence of the optical path length of the entire arrayed waveguide can be almost cancelled. Therefore, it is not necessary to use a temperature controller such as a Peltier element, and the size An array waveguide type diffraction grating can be obtained.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing a plan view of an embodiment of an arrayed waveguide type diffraction grating according to the present invention.

FIG. 2 is an explanatory diagram showing the relationship between the length of an adjacent arrayed waveguide 4 and the length of a path 8 of propagating light propagating in a third slab waveguide 7 in the arrayed waveguide type diffraction grating of the embodiment. It is.

FIG. 3 is an explanatory diagram showing a plan view and a cross-sectional view of a part of an arrayed waveguide type diffraction grating manufacturing process of the embodiment.

FIG. 4 is an explanatory diagram showing, in a plan view, a manufacturing process subsequent to FIG. 3 for the arrayed waveguide grating of the embodiment.

FIG. 5 is an explanatory diagram showing a plan view and a cross-sectional view of a third slab waveguide manufacturing step in the array waveguide type diffraction grating manufacturing step of the embodiment.

FIG. 6 is an explanatory view of a main part of a conventional arrayed waveguide type diffraction grating in a plan view.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 first slab waveguide (input side slab waveguide) 3 input side slab waveguide 4, 4a, 4b array waveguide 5 second slab waveguide (output side slab waveguide) 6 optical output waveguide 7 Third slab waveguide 31 Marker

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazutaka Nara 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Takeshi Nakajima 2-6-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Furukawa Electric Co., Ltd. (reference) 2H047 KA03 KA12 LA19 PA04 PA05 QA04 TA00

Claims (1)

[Claims] 1. A first slab waveguide is connected to an output side of one or more optical input waveguides arranged side by side, and the first slab waveguide is connected to an output side of the first slab waveguide. A plurality of array waveguides having different lengths for transmitting light derived from the array waveguides are connected, and a second slab waveguide is connected to an output side of the plurality of array waveguides. The output side of the slab waveguide has a waveguide configuration in which a plurality of side-by-side optical output waveguides are connected, and a plurality of optical signals of different wavelengths input from the optical input waveguide, Array waveguide type optical diffraction that propagates with a phase difference for each wavelength by the array waveguide, makes it incident on a different optical output waveguide for each wavelength, and outputs light of different wavelengths from different optical output waveguides. In the grating, all of the array waveguides are in the middle of the longitudinal direction. Are cut and separated into a first array waveguide and a second array waveguide.
A third slab waveguide is provided at a distance between the array waveguide and the second array waveguide so as to cross all of the first and second array waveguides. The arrayed waveguide is formed so that at least one of a refractive index temperature gradient and a linear expansion coefficient is different from each other, and the third slab is moved from the first arrayed waveguide to a corresponding second arrayed waveguide. An arrayed-waveguide type diffraction grating, wherein a path length of light propagating in the waveguide in the optical axis direction is formed to have a size that almost cancels the temperature dependence of the optical path length of the entire arrayed waveguide.