JP2902260B2 - Optical wavelength filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength filter.

[0002]

2. Description of the Related Art Conventionally, an optical wavelength filter has been used to separate an optical signal having a specific wavelength from wavelength-multiplexed optical signals. Such a filter is disclosed in, for example, Japanese Patent Application Laid-Open No. 60-121404. FIG. 17 is a plan view schematically showing the configuration of this conventional filter.

The conventional filter shown in FIG.
2 and these waveguides 10 and 12 are made parallel and close to each other in the coupling region 14. A diffraction grating 16 is formed in a coupling region 14 of one of the waveguides 12, and the light is separated according to the wavelength by using the diffraction grating 16. That is,
When the light L1 or L2 is incident on the other waveguide 10, the light L1 having the wavelength to be separated is reflected by the diffraction grating 16 of the coupling region 14, becomes a retrograde wave, and exits from one waveguide 12, and the other wavelengths. L2 passes through the diffraction grating 16 in the coupling region 14 and exits from the other waveguide 10.

In this conventional filter, the light (traveling wave) transmitted through the diffraction grating 16 in the coupling region 14 and the diffraction grating 1
The light reflected by 6 (reverse wave) is coupled, and by utilizing this coupling, the wavelength bandwidth of transmission and reflection is narrowed.

The diffraction grating 16 has a structure in which the waveguide 12 is formed to have an uneven shape and the equivalent refractive index of the waveguide 12 is periodically changed. In addition, the diffraction grating 16 is equivalent to the waveguide 12 using an electro-optic effect. It is possible to consider an electrical device that periodically changes the refractive index. In order to reduce the period of the diffraction grating or increase the reflection efficiency, a structural diffraction grating is more advantageous.

[0006]

However, in the above-described conventional filter, when a structural diffraction grating is used, light of a specific wavelength input to the filter and light of other wavelengths are always separated. Therefore, a case where the light is separated and a case where the light is not separated cannot be selected, and the on / off control of the light separation and non-separation cannot be performed.

On the other hand, when an electric diffraction grating is used,
By electrically generating or extinguishing the diffraction grating, the separation and non-separation of light can be controlled on and off. However, in this case, it is difficult to reduce the period of the diffraction grating or increase the reflection efficiency.

An object of the present invention is to solve the above-mentioned conventional problems by selectively forming a state in which light is reflected by a diffraction grating and a state in which light is not reflected by utilizing light absorption and / or light amplification in a waveguide. An object of the present invention is to provide an optical wavelength filter and a driving method thereof.

[0009]

In order to achieve this object, the optical wavelength filters of the first invention are arranged close to each other so as to form refractive index waveguides and to cause light interaction . A plurality of active layers for transmitting zero-order even-mode light, a diffraction grating provided on at least one of these active layers, and an active layer provided with a diffraction grating (hereinafter, active layer A)
And a second light control structure for electrically variably controlling the amount of light amplification in an active layer having no diffraction grating (hereinafter, active layer B). It is characterized by comprising.

According to the first aspect, the plurality of active layers arranged close to each other constitute one waveguide system. Field distribution of light input to this waveguide system (electric field distribution or magnetic field distribution of light)
Varies depending on the amount of light absorption in the active layer A and the amount of light amplification in the active layer B. Therefore, by variably controlling the amount of light absorption and / or the amount of light amplification, the field distribution of input light of a specific wavelength is controlled to a state in which the input light is reflected by the diffraction grating, or such that the input light is not reflected. State. As a result, input light of a specific wavelength (hereinafter, specific light) and input light of other wavelengths (hereinafter, specific light)
Non-specific light) can be separated or not separated.

In practicing the first invention, the first light control structure is electrically connected to the p-type first clad, the n-type first clad, and the p-type first clad sandwiching the active layer provided with the diffraction grating. N electrically connected to the first side electrode and the n-type first cladding
And a second light control structure electrically connected to the p-type second clad, the n-type second clad, and the p-type second clad sandwiching the active layer having no diffraction grating. It is preferable to have a structure having a p-side second electrode to be connected and an n-side second electrode electrically connected to the n-type second clad. In this case, the first light control structure can electrically variably control the amount of light amplification in addition to the amount of light absorption in the active layer A, and the second light control structure can control the amount of light amplification in addition to the amount of light absorption in the active layer B. Can also be variably controlled electrically.

The driving method of the optical wavelength filter according to the second invention is as follows.
A method for driving an optical wavelength filter according to a first aspect of the present invention, wherein the amount of light absorption and the amount of light amplification are individually controlled for each active layer. As the amount of light absorption in the active layer A increases, the size of the light field distribution generated in the active layer A decreases, and as the amount of light amplification in the active layer B increases, the size of the light field distribution generated in the active layer B increases. It becomes big.

According to the second aspect of the invention, when the input light is not separated, the field distribution of the specific light can be activated by appropriately adjusting the amount of light absorption in the active layer A and / or the amount of light amplification in the active layer B. Layer A does not. Or,
The size of the field distribution of the specific light generated in the active layer B is made larger than the size of the field distribution of the specific light generated in the active layer A. When the field distribution of the specific light is controlled in this manner, a state where the specific light transmits through the diffraction grating can be formed.

When the input light is separated, the amount of light absorption in the active layer A and / or the amount of light amplification in the active layer B are arbitrarily and suitably adjusted, so that the size of the field distribution of the specific light generated in the active layer A is reduced. The size of the field distribution of the specific light generated in the active layer B is made equal. Alternatively, the size of the field distribution of the specific light generated in the active layer A is made larger than the size of the field distribution of the specific light generated in the active layer B. When the field distribution of the specific light is controlled in this manner, a state where the specific light is reflected by the diffraction grating can be formed.

Further, the optical wavelength filter according to the third invention comprises a plurality of gain waveguides which are arranged close to each other so as to cause light interaction , and which propagate light in the zero-order even mode . An active layer, a diffraction grating provided on at least one of these active layers, and a light control structure for electrically variably controlling the amount of light amplification in the active layer.

According to the third aspect, the plurality of active layers arranged close to each other constitute one waveguide system. The field distribution of light input to this waveguide system changes according to the change in the amount of light amplification in each active layer. Therefore, by variably controlling the amount of light amplification, the field distribution of the specific light can be controlled so that the specific light is reflected by the diffraction grating, or the specific light can be transmitted through the diffraction grating. Or you can. As a result, the specific light and the non-specific light can be separated or not separated.

A method for driving an optical wavelength filter according to a fourth aspect of the present invention is as follows.
A method for driving an optical wavelength filter according to a third aspect of the present invention, wherein the amount of light amplification is individually controlled for each active layer during the driving. The active layer forms a gain waveguide,
Therefore, the active layer performs a light guiding action (light confinement action) when optical amplification occurs, and loses the light guiding action when optical amplification is not occurring. Further, as the amount of light amplification increases, the size of the field distribution of specific light generated in the active layer increases.

According to the fourth aspect, when the input light is not separated, the field distribution of the specific light is substantially prevented from occurring in the active layer A by adjusting the amount of light amplification in each active layer as appropriate. To Alternatively, the field distribution of the specific light generated in the active layer B is made larger than the field distribution of the specific light generated in the active layer A. When the field distribution of the specific light is controlled in this manner, a state where the specific light transmits through the diffraction grating can be formed.

In the case of separating the input light, the magnitude of the field distribution of the specific light generated in the active layer A and the field of the specific light generated in the active layer B are adjusted by arbitrarily and suitably adjusting the amount of light amplification in each active layer. Make the size of the distribution equal. Alternatively, the field distribution of the specific light generated in the active layer A is made larger than the field distribution of the specific light generated in the active layer B. When the field distribution of the specific light is controlled in this manner, a state where the specific light is reflected by the diffraction grating can be formed.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. The drawings are only schematically shown to the extent that the invention can be understood, and thus the invention is not limited to the illustrated examples.

FIGS. 1 and 2 are a sectional view and a plan view schematically showing the structure of the first embodiment of the first invention.
(A) and (B) show cross sections taken along lines IA-IA and IB-IB in FIG.

The optical wavelength filter of this embodiment includes a plurality of, for example, two active layers 18 and 20 which constitute refractive index waveguides and are arranged close to each other so as to cause light interaction.
At least one of these active layers, for example, a diffraction grating 22 provided on the active layer 18, a first light control structure 24 for electrically variably controlling the amount of light absorbed in the active layer 18 provided with the diffraction grating 22, and a diffraction grating 22. Light control structure 26 for electrically variably controlling the amount of light amplification in the active layer 20 not provided with
And comprising.

In this embodiment, the first light control structure 24 electrically connects the p-type first clad 28 and the n-type first clad 30 sandwiching the active layer 18 provided with the diffraction grating 22 to the p-type first clad 28. It has a p-side first electrode 32 to be connected, and an n-side first electrode 34 electrically connected to the n-type first clad 30. p-type first cladding 28 and n-type first cladding 30
Is made wider than the band gap of the active layer 18.

According to the first light control structure 24 having such a configuration, the amount of light amplification in addition to the amount of light absorption in the active layer 18 can be electrically variably controlled. By forming a state in which a voltage is applied such that the n-side first electrode 34 has a positive potential with respect to the p-side first electrode 32 or a state in which no current is injected into the active layer 18, the active layer 18 absorbs light. Cause. Further, by forming a state in which a voltage is applied such that the n-side first electrode 34 has a negative potential with respect to the p-side first electrode 32 or a state in which a current is injected into the active layer 18, the Cause amplification. The amount of light absorption (or light absorption rate) and the amount of light amplification (or light amplification rate) in the active layer 18 are determined by these electrodes 3
The larger the voltage difference between 2 and 34, the larger the voltage difference, and the smaller the voltage difference, the smaller the voltage difference.

The second light control structure 26 is a p-type second clad 2 that sandwiches the active layer 20 on which the diffraction grating 22 is not provided.
8 and n-type second cladding 36 and p-type second cladding 28
And an n-side second electrode 38 electrically connected to the n-type second clad 36.
The band gaps of the p-type second cladding 28 and the n-type second cladding 36 are made wider than the band gap of the active layer 20.

According to the second light control structure 26 having such a configuration, the amount of light absorption in addition to the amount of light amplification in the active layer 20 can be electrically variably controlled. n for the p-side second electrode 32
By forming a state in which a voltage is applied so that the second electrode 38 has a negative potential or a state in which a current is injected into the active layer 20, optical amplification occurs in the active layer 20. In addition, by forming a state in which a voltage is applied so that the n-side first electrode 34 has a positive potential with respect to the p-side second electrode 32 or a state in which no current is injected into the active layer 18, light is applied to the active layer 18. Causes absorption. The amount of light absorption and the amount of light amplification in the active layer 18 increase as the voltage difference between the electrodes 32 and 34 increases, and decrease as the voltage difference decreases.

Here, the p-type first cladding 28 is also used as the p-type second cladding 28 (hereinafter, these claddings are
The first p-side electrode 32 is also used as the p-side second electrode 32 (hereinafter referred to as a p-side second electrode 32).
These electrodes are referred to as p-side first and second common electrodes).

Further, in this embodiment, the n-type second clad 36 is an n-InP substrate, and an n-side second electrode 38 is provided on the lower surface of the clad 36. The cladding 36 and the electrode 38 are ohmic-connected.

Then, on the n-type second cladding 36 sequentially,
A striped non-doped GaAsInP active layer 20, a p-InP first and second common cladding 28, a non-doped GaAsInP active layer 18, an n-InP first clad 30, and an n-side first electrode 34 are provided. The electrode 34 and the cladding 30 are ohmic-connected, and the diffraction grating 22 is provided between the claddings 30 and 18. The diffraction grating 22 has a periodic structure in which irregularities are repeated at regular intervals along the stripe direction of the active layer 18.

The active layers 18 and 20 are close to each other to form one waveguide system (hereinafter, referred to as a waveguide system S).
When the amount of light absorption of the active layers 18 and 20 and the amount of light amplification of the active layers 18 and 20 are not electrically changed, the active layer 1
The mode in which the waveguide system S is excited in the arrangement direction of 8, 8 (the direction along the y-axis in FIG. 1A) is preferably an even-order mode of the 0th order. In order to configure the waveguide system S that excites the zero-order even mode, assuming that the refractive index of the n-type second cladding 36 is 3.4, for example, the thickness of the active layers 18 and 20 is set to 0.1. 5 μm, layer thickness of cladding 28 is 2 μm
Hereinafter, the refractive index difference between the active layer 18 and the claddings 28 and 30 may be set to 0.04, and the refractive index difference between the active layer 20 and the claddings 28 and 36 may be set to 0.04. Under such conditions, the coupling coefficient between the active layers 18 and 20 is 0.0138 μm ⁻¹ .

Further, in this embodiment, an i-InP buried layer 40, a p-InP buried layer 42 and an i-InP buried layer 44 are sequentially provided on the n-type second clad 36. Embedded layer 4
0 fills the sides of the active layer 20, the buried layer 42 fills the sides of the p-type first and second claddings 28, and the buried layer 44 fills the sides of the active layer 18 and the n-type first cladding 30. . Then, the buried layer 44 is partially cut out to form the buried layer 42.
And the p-side first and second common electrodes 3
2 is provided. These exposed portions and the electrodes 32 are ohmic-connected.

The p-side first and second common electrodes 32 and the p-type first and
The second common clad 28 is electrically connected via the buried layer 42, and the buried layer 42 and the n-type second clad 36 are electrically insulated and separated by the buried layer 40 therebetween. The buried layers 40 and 44 are also the cladding of the active layers 20 and 18, and make the band gap of these active layers 20 and 18 narrower than the band gap of the buried layers 40 and 44.

The active layers 20 and 18 constitute a refractive index waveguide in which a light guiding action (or a light confining action) is caused by the refractive index. By making the refractive index of the active layer 20 higher than the refractive index of the surrounding medium, here, the claddings 28 and 26 and the buried layer 40, an optical waveguide action is generated in the active layer 20. Similarly, the refractive index of the active layer 18 is
The medium surrounding the periphery of the active layer 1 has a higher refractive index than the claddings 28 and 30 and the buried layer 44.
8 has an optical waveguide effect.

Next, the operation will be analyzed using a coupling equation. Considering that light absorption or optical amplification and reflection by the diffraction grating are performed in the waveguide system S as described above, the following expression is used for the waveguide system S.

The coupling equation shown in Equation 1 is obtained. However, the waveguide system S excites the zero-order even mode and cuts off other waveguide modes.

[0035]

(Equation 1)

Hereinafter, when light enters the waveguide system S from one end 20 a of the active layer 20, the light passes through the diffraction grating 22 and moves from one end 20 a to the other end 2 of the active layer 20.
Light propagating through the waveguide system S in the direction P toward 0b is referred to as forward light, and is reflected by the diffraction grating 22 at the other end 2.
0b to the one end 20a in the direction Q
Is referred to as reflected light (see FIG. 1 (A)). The difference in the propagation constant between the active layer 18 provided with the diffraction grating 22 and the active layer 20 provided with no diffraction grating 22 is referred to as the reflected light. Assuming that referred the imaginary component of terms involved in the active layer 20 with the imaginary component of terms related to the layer 18 is referred to as the imaginary component I1 and the imaginary component I2, a _1: forward light of the field distribution formed in the active layer 18 Amplitude B ₁ : Amplitude of field distribution formed by reflected light in active layer 18 A ₂ : Amplitude of field distribution formed by forward light in active layer 20 B ₂ : Amplitude z of field distribution formed by reflected light in active layer 20 : Light propagation distance (see FIG. 1 (A)) i: imaginary unit Δ: Δ = (１ ／) · (Δβ + i · ΔG) where Δβ: refractive index difference between active layers 18 and 20 ΔG = (imaginary number) Component I1)-(Imaginary component I2) K: Active layers 18 and 2 Coupling coefficient between δ: δ = (2 · π · n g) / λ = | ( wave number of forward light) - (wave number of the reflected light) | · (1/2) where, n _g = | (active layer 18 equivalent refractive index of) + (equivalent refractive index of the active layer 20) | · (1/2) λ : wavelength of light K _B: by the diffraction grating 22, the coupling coefficient between the advance light and reflected light other hand, advance light and reflected The optical powers 光_A ⁺ and Ψ _B ⁺ of light can be expressed as shown in the following equation (Equation 2).

F: The size of the field distribution formed by the forward light and the reflected light in the active layer 18 e: The size of the field distribution formed by the forward light and the reflected light in the active layer 20

[0038]

(Equation 2)

By differentiating both sides of the equation (2) and substituting the equation (1) into the equation obtained by the differentiation, the following equation (3) is obtained.

[0040]

(Equation 3)

[0041] As can be seen from equation (3), forward and reflected light is coupled in terms of K _B · f ^2, the reflection efficiency of the diffraction grating 22 is changed according to the magnitude f of the thus field distribution .

The change in the magnitude f of the field distribution will now be considered. As an example, when Δβ = 0 (the active layers 18 and 2
Consider the magnitude f of the field distribution when the refractive index difference is equal to 0). The magnitude f of the field distribution in this case can be expressed as in the following equation (Equation 4).

[0043]

(Equation 4)

In equation (4), when ΔG = + ∞, f
² = 1, f ² = １ ／ when ΔG = 0, and ΔG = −∞
At the time, f ² = 0. As can be understood from this, when ΔG = 0 or ΔG> 0, the size f of the field distribution increases, and thus the forward light can be reflected by the diffraction grating 22. The relationship between the field distribution formed in the waveguide system S by the advancing light and the gain generated in the active layers 18 and 20 is represented by ΔG
FIG. 3 conceptually shows the case where = 0. FIG. 3 (A)
3B, the horizontal axis represents the position y (see FIG. 1A) in the arrangement direction of the active layers 18 and 20, the vertical axis of FIG. 3A represents the electric field of light, and FIG. The vertical axis indicates the gain of the active layer.

When ΔG <0, the size f of the field distribution becomes small, so that the forward light passes through the diffraction grating 22. FIG. 4 conceptually shows the relationship between the field distribution formed in the waveguide system S by the advancing light and the gain generated in the active layers 18 and 20. The vertical and horizontal axes of FIG. 4 are shown in the same manner as FIG.

Here, since the waveguide system S excites the zero-order even mode, when ΔG = 0 (I1 = I2), f = e and Δ
When G> 0 (I1> I2), f> e and ΔG <
When 0 (I1 <I2), f <e. When the amount of light absorption or light amplification in the active layer 18 is increased, I1
Becomes smaller or larger, and I2 becomes smaller or larger when the amount of light absorption or light amplification in the active layer 20 is increased. Therefore, by adjusting the amount of light absorption and / or the amount of light amplification arbitrarily and appropriately, f = e or f> e,
A state in which the forward light is reflected by the diffraction grating 22 can be formed.
Further, by adjusting the light absorption amount and / or the light amplification amount arbitrarily and appropriately so that f <e, it is possible to form a state in which the forward light is transmitted through the diffraction grating 22. By adjusting the amount of light absorption and / or the amount of light amplification in this manner, the reflection function of the diffraction grating 22 can be controlled on / off, and thus the separation and non-separation of light can be controlled on / off.

Next, the optical output characteristics of the optical wavelength filter of this embodiment will be described with reference to an example. FIG. 5 shows an example of optical output characteristics obtained by using the solution of the coupling equation shown in (Equation 1) for this optical wavelength filter.

In FIG. 5, when the input intensity of light input to the waveguide system S from one end 20a of the active layer 20 is 1, the output of light output from the other end 20b of the active layer 20 is assumed. The intensity is shown on the vertical axis and the wavelength of light is shown on the horizontal axis. The _{K B · L = 5, K} · L = 2, G · L = 7 and Δ
The light output specific curve i when a G · L = 9 in solid lines, yet _{K B · L = 5, K} · L = 2, G · L = 7 and .DELTA.G ·
The light output characteristic curve ii when L = -9 is shown by a dotted line (where L is the element length of the optical wavelength filter).

In FIG. 5, focusing on light having a Bragg wavelength λ _B and a wavelength near the same (hereinafter, specific light) and light having other wavelengths (hereinafter, non-specific light), when ΔG · L = 9, In addition, the light output intensity of the specific light output from the end 20b can be sufficiently reduced for practical use, and the light output intensity of the non-specific light output from the end 20b can be sufficiently increased for practical use. Specific light can be separated. Also ΔG
When L = -9, both the light output intensities of the specific light and the non-specific light output from the end 20b can be sufficiently increased for practical use, and therefore, the specific light and the non-specific light are not separated. Can be

According to the analysis of the inventors of the present application, in order to reduce the light output intensity of the specific light output from the end 20b when separating the specific light and the non-specific light, it is necessary to use, for example, It has been found that the size f of the field distribution in the active layer 18 should be larger than the size e of the field distribution in the active layer 20 by a certain ratio or more so that ΔG >> 1. Further, in order to practically sufficiently increase the light output intensity of the specific light output from the end 20b when the specific light and the non-specific light are not separated, for example, ΔG << − 1,
It has been found that the size e of the field distribution in the active layer 20 should be larger than the size f of the field distribution in the active layer 18 by a certain ratio or more.

Next, an embodiment of the second invention will be described. This embodiment is an example of driving the optical wavelength filter of the above-described first embodiment of the present invention. In the driving, the amount of light absorption or the amount of light amplification in the active layer 18 provided with the diffraction grating 22 is determined. The amount of light absorption or the amount of light amplification in the active layer 20 where the diffraction grating 22 is not provided is individually controlled for each of the active layers 18 and 20. In each active layer, one of three states of light absorption> 0, light amplification> 0, and light absorption = light amplification = 0 is generated.

When the specific light and the non-specific light are not separated,
The amount of light absorption or the amount of light amplification of each active layer is adjusted as appropriate and individually. 1) Prevents a specific light field distribution from being substantially generated in the active layer 18; The field distribution of the specific light generated in 20 is set to be larger than the field distribution of the specific light generated in the active layer 18. When controlling the field distribution of the specific light in this way, the specific light passes through the diffraction grating 22, so that the optical wavelength filter can be driven so as not to separate the specific light and the non-specific light.

In order to sufficiently increase the light output intensity of the specific light output from the end 20b when the specific light and the non-specific light are not separated, the field distribution of the specific light generated in the active layer 20 must be controlled by the active layer. It is preferable to make the specific light larger than the field distribution of the specific light 18 by a certain ratio or more.

The amount of light absorption and the amount of light amplification may be adjusted as long as 1) and / or 2) can be realized. However, for example, when 1) or 2) is realized by causing only light absorption in the active layer 18, or when 2) is realized by causing only optical amplification in the active layer 20, the light of the optical wavelength filter is The output intensity cannot be equal to the light input intensity of the filter.
Therefore, preferably, light absorption is caused in the active layer 18 and light amplification is caused in the active layer 20 so that the light output intensity and the light input intensity of the optical wavelength filter are made equal to each other. Good to achieve.

When the specific light and the non-specific light are separated from each other, the light absorption amount or the light amplification amount of each active layer is arbitrarily and suitably adjusted individually. 3) Field distribution of the specific light generated in the active layer 18 Or the size of the specific light field distribution generated in the active layer 20 is made equal, or 4) the specific light field distribution generated in the active layer 18 is made smaller than the specific light field distribution generated in the active layer 20. To be larger. When controlling the field distribution of the specific light in this way, the specific light is reflected by the diffraction grating 22, so that the optical wavelength filter can be driven so as to separate the specific light and the non-specific light.

In order to reduce the light output intensity of the specific light output from the end 20b when the specific light and the non-specific light are separated from each other, the field distribution of the specific light generated in the active layer 18 must be reduced. It is preferable that the field distribution of the specific light generated at 20 is made larger than a certain ratio or more.

The amount of light absorption and the amount of light amplification may be adjusted as long as 3) or 4) can be realized. However, for example, when 4) is realized by causing only the optical amplification in the active layer 18 or 4) is realized by causing only the light absorption in the active layer 20, the light output intensity of the optical wavelength filter is reduced. It cannot be equal to the light input intensity of the filter. Therefore, preferably, 4) is realized while causing light amplification in the active layer 18 and light absorption in the active layer 20 so that the optical output intensity and the optical input intensity of the optical wavelength filter are equalized. Is good.

In this embodiment, the active layers 18 and 20
When neither light absorption nor light amplification occurs in both cases, the waveguide system S excites the even mode, and thus 3) can be realized.
However, 3) may not always be realized due to design errors and other factors. In this case, preferably, light amplification is caused in the active layer 18 and light absorption is caused in the active layer 20.
At 0, light amplification is caused and light absorption is caused at the active layer 18, so that the light output intensity and light input intensity of the light wavelength filter are made equal.
It is better to realize 3).

FIGS. 6 and 7 are sectional views schematically showing the structure of the second embodiment of the first invention, and FIG. 8 is a plan view schematically showing the structure of the second embodiment of the first invention. . FIG.
Sections taken along the line VI-VI, FIGS. 7 (A), (B) and (C) show lines VIIA-VIIA, VIIB-VIIB and VIIC- in FIG.
The cross section taken along the VIIC line is shown. The components corresponding to those in the first embodiment of the first invention described above are denoted by the same reference numerals, and detailed description of the same points as those in the first embodiment of the first invention will be omitted.

In this embodiment, a plurality of, for example, three diffraction grating areas 46 are arranged along the stripe direction of the active layer 18.
a, 46b, and 46c are provided, and these regions 46a, 46
The diffraction gratings 22a,
22b and 22c are provided. Each diffraction grating 22a, 22b
And 22c have different periods in the direction along the active layer 18, and these diffraction gratings 22a, 22b and 2c have different periods.
The wavelength of the specific light separated by 2c is made different.

Further, first light control structures 24a, 24b and 24c are provided in the diffraction grating arrangement areas 46a, 46b and 46c, respectively, and second light control structures 26a and 26b are provided.
And 26c.

The first light control structure 24a is for electrically variably controlling the amount of light absorption in the active layer 18 in the diffraction grating arrangement region 46a and the amount of light amplification in addition thereto. For this reason, the n-side first electrode 34a and the p-side first and second common electrodes 32a are provided on the n-type first clad 30 and the buried layer 42 in the arrangement region 46a, and the portions corresponding to the arrangement region 46a are provided. The first light control structure 24a is constituted by the n-type first clad 30, the p-type first and second common clad 28, the n-side first electrode 34a, and the p-side first and second common electrodes 32a.

The first light control structure 24b is for electrically variably controlling the amount of light absorption and the amount of light amplification in the active layer 18 in the diffraction grating arrangement region 46b. Therefore, the n-side first electrode 34b and the p-side first and second common electrodes 32b are provided on the n-type first clad 30 and the buried layer 42 in the arrangement region 46b, and the portions corresponding to the arrangement region 46b are provided. The first light control structure 24b is composed of the n-type first clad 30, the p-type first and second common clad 28, the n-side first electrode 34b, and the p-side first and second common electrodes 32b.

The first light control structure 24c is for electrically variably controlling the amount of light absorption in the active layer 18 in the diffraction grating arrangement region 46c and the amount of light amplification in addition thereto. For this reason, the n-side first electrode 34c and the p-side first and second common electrodes 32c are provided on the n-type first clad 30 and the buried layer 42 in the arrangement region 46c, and the portions corresponding to the arrangement region 46c are provided. The first light control structure 24c is composed of the n-type first clad 30, the p-type first and second common clads 28, the n-side first electrode 34c, and the p-side first and second common electrodes 32c.

The second light control structure 26a is for electrically variably controlling the amount of light amplification and the amount of light absorption in the active layer 20 in the diffraction grating area 46a.
For this reason, the n-side second electrode 38 is provided on the n-type second clad 36 by extending from the diffraction grating disposition area 46a to the diffraction grating disposition area 46c, and the n-type second electrode 38 corresponding to the disposition area 46a is provided. The second light control structure 26a includes the two claddings 36, the p-type first and second common claddings 28, the n-side second electrode 38, and the p-side first and second common electrodes 32a.
The n-side second electrode 38 is an n-side electrode common to the second light control structures 26a, 26b and 26c, and the p-side first and second common electrodes 32a are the second light control structure 26a and the first light control structure 24.
This is a common p-side electrode for a.

The second light control structure 26b is for electrically variably controlling the amount of light amplification and the amount of light absorption in the active layer 20 in the diffraction grating arrangement region 46b. For this reason, the n-type second cladding 36, the p-type first and second common claddings 28 and the n-side second electrode 38 of the portion corresponding to the arrangement region 46b, and the p-side first and second common electrodes 32b The second light control structure 26b is configured. The p-side first and second common electrodes 32b are p-side electrodes common to the second light control structure 26b and the first light control structure 24b.

The second light control structure 26c is for electrically variably controlling the amount of light amplification and the amount of light absorption in the active layer 20 in the diffraction grating arrangement region 46c. For this reason, the n-type second cladding 36, the p-type first and second common claddings 28 and the n-side second electrode 38 at portions corresponding to the disposition region 46c, and the p-side first and second common electrodes 32c Constitutes the second light control structure 26c. The p-side first and second common electrodes 32c are p-side electrodes common to the second light control structure 26c and the first light control structure 24c.

Since the amount of light amplification and the amount of light absorption are controlled electrically independently for each of the diffraction grating arrangement regions 46a, 46b and 46c, the n-side first electrodes 34a, 34b,
34c, p-side first and second common electrodes 32a, 32b and 3
2c are provided separately electrically.

According to this embodiment, the diffraction gratings 22a,
The reflection action of 2b and 22c is independent for each diffraction grating,
ON / OFF control is possible. The on / off control may be performed individually for each diffraction grating in the same manner as in the above-described embodiment of the second invention. Accordingly, it is possible to independently or separately separate a plurality of types of specific light corresponding to the periods of the diffraction gratings, here, three types of wavelengths.

FIGS. 9 and 10 are a sectional view and a plan view, respectively, schematically showing the structure of the first embodiment of the third invention. FIG. 9 is a sectional view taken along line IX-IX of FIG. Show.

The optical wavelength filter of this embodiment is, for example, a filter in which a filter is provided in a twin stripe injection type semiconductor laser structure, and is arranged close to each other so as to constitute a gain waveguide and cause light interaction. The plurality of, for example, two active layers 48, 50, the diffraction grating 52 provided in at least one of the active layers, for example, the active layer 48, and the optical amplification amount (or optical amplification factor) in the active layers 48, 50 are electrically measured. Control structure 5 variably controlled
4 and 56. In the figure, the active layers 48 and 50 are shown with dots. The laser structure used to construct the optical wavelength filter of this embodiment is not limited to the illustrated example, and various known laser structures can be used in the configuration.

In this embodiment, the light control structure 54 is a p-type clad 58 that sandwiches the active layer 48 provided with the diffraction grating 52.
And an n-type cladding 60, a p-side electrode 62 electrically connected to the p-type cladding 58, and an n-side electrode 64 electrically connected to the n-type cladding 60. p-type cladding 58 and n
The band gap of the mold cladding 60 is made wider than the band gap of the active layer 48.

The light control structure 56 includes a p-type clad 66 and an n-type clad 66 that sandwich the active layer 50 on which the diffraction grating 52 is not provided.
Mold clad 68 and p electrically connected to p-type clad 66
It has a side electrode 70 and an n-side electrode 64 electrically connected to the n-type cladding 68. The band gaps of the p-type cladding 66 and the n-type cladding 68 are made wider than the band gap of the active layer 50. Here, the n-side electrode 64 of the light control structure 54 is also used as the n-side electrode 64 of the light control structure 56 (hereinafter, these electrodes are referred to as the n-side common electrode 64).

Further, in this embodiment, n
-InP substrate is used, and n
A side common electrode 64 is provided. In addition, an n-InP clad 74 and a non-doped Ga
An AsInP active layer 76 and a p-InP cladding 78 are provided.

The area 80 where the active layers 48 and 50 are provided
And 82 are provided side by side in the direction along the substrate surface. The active layer disposition regions 80 and 82 are stripe-shaped regions in plan view. NI of a portion corresponding to active layer disposition region 80
nP cladding 74, non-doped GaAsInP active layer 7
6 and the p-InP cladding 78, the n-type cladding 6
0, an active layer (active region) 48 and a p-type clad 58 are formed. Further, the nI of the portion corresponding to the active layer
nP cladding 74, non-doped GaAsInP active layer 7
6 and the p-InP cladding 78, the n-type cladding 6
8. The active layer (active area) 50 and the p-type cladding 66 are formed. The n-type claddings 60 and 68
It is electrically connected to the side common electrode 64.

Further, a striped p-GaAsInP cap layer 84 and a p-side electrode 62 are sequentially provided on a portion of the p-InP cladding 78 corresponding to the active layer providing region 80. The p-side electrode 62 is electrically connected to the p-type cladding 58 via the cap layer 84. Also, the p-InP cladding 78 corresponding to the active layer disposition region 82
P-GaAsI in the form of stripes
An nP cap layer 86 and a p-side electrode 70 are provided. The p-side electrode 70 is electrically connected to the p-type cladding 66 via the cap layer 86.

Further, the diffraction grating 52 is provided in the active layer disposition area 80. The arrangement position of the diffraction grating 52 can be any suitable position where the field distribution of the specific light that seeps out of the active layer 48 when the specific light is separated can reach the diffraction grating 52. The diffraction grating 52 is provided on the other substrate surface at a portion corresponding to the arrangement region 80. The diffraction grating 52 has a periodic structure in which irregularities are repeated in the stripe direction of the active layer 48.

The active layers 48 and 50 constitute a gain waveguide in which light is guided (or light is confined) by gain. The light control structures 54 and 56 act to selectively inject current into the active layers 48 and 50 in the disposition regions 80 and 82 of the active layer 76 and not to inject current into other portions of the active layer 76. I do. As a result, the active layers 48 and 5
In the active layer 48 and 50, a state can be formed in which no gain is generated at 0 and no gain is generated in the other portions of the active layer 76.
A light guiding action occurs. Anti-reflection films (not shown) are provided on the end faces of the active layers 48 and 50 in order to prevent laser oscillation due to optical amplification from occurring in the active layers 48 and 50 or to make laser oscillation less likely to occur.

When the light guide action is generated, the active layer 4
8 and 50 constitute one waveguide system (hereinafter, referred to as a waveguide system T). At this time, the formation conditions of the active layers 48 and 50, such as the current flowing to the active layers 48 and 50, are set so that the mode in which the waveguide system T is excited in the arrangement direction of the active layers 48 and 50 is preferably a zero-order even mode. The injection amount, the layer thickness of the active layers 48 and 50, and the spacing are set.

Next, an embodiment of the fourth invention will be described. This embodiment is an example of driving the optical wavelength filter of the first embodiment of the third invention described above. In driving the optical wavelength filter, the amount of light amplification in the active layer 48 provided with the diffraction grating 52 and the diffraction grating The amount of light amplification in the active layer 50 where the 52 is not provided is individually controlled for each of the active layers 48 and 50. In each active layer, one of two states, that is, the amount of light amplification> 0 and the amount of light amplification = 0, is generated. By increasing or decreasing the amount of light amplification in the active layer 48, the size of the field distribution of light generated in the active layer 48 can be increased or decreased. Similarly, by increasing or decreasing the amount of light amplification in the active layer 50,
Can be made larger or smaller.

Here, light is input to the waveguide system T from one end 70a of the active layer 48, and when the specific light and the non-specific light are not separated, both the specific light and the non-specific light are converted into the active layer 48.
In the case where the specific light and the non-specific light are separated, the specific light is output from one end 70a of the active layer 48 and the non-specific light is output from the other end 70a. And The diffraction grating 52 can act as a Bragg resonator depending on the amount of light amplification,
By utilizing the wavelength selectivity of the resonator, it is possible to output specific light from the end 70b and attenuate and eliminate non-specific light.

When the specific light and the non-specific light are not separated,
The optical amplification amount of each active layer is adjusted as appropriate and individually. 5) The field distribution of specific light is substantially not generated in the active layer 48, or 6) The specific field generated in the active layer 50 is formed. The field distribution of light is set to be larger than the field distribution of specific light generated in the active layer 48. When controlling the field distribution of the specific light in this way, the specific light passes through the diffraction grating 52, so that the optical wavelength filter can be driven so as not to separate the specific light and the non-specific light.

In order to increase the light output intensity of the specific light output from the end portion 70b when the specific light and the non-specific light are not separated from each other, the field distribution of the specific light generated in the active layer 50 must be equal to the active layer. It is preferable that the specific light be larger than the field distribution of the specific light generated at 48 by a certain ratio or more.

As long as 5) and / or 6) can be realized, the optical amplification amount of each active layer may be adjusted in any manner.
However, for example, when 6) is realized by increasing only the amount of optical amplification in the active layer 50 from the state where the waveguide system T is excited in the 0th-order even mode, or by reducing only the amount of optical amplification in the active layer 48. When 5) or 6) is realized, the optical output intensity of the optical wavelength filter cannot be made equal to the optical input intensity of the filter. Therefore, preferably, the optical amplification amount of the active layer 48 is reduced and the optical amplification amount of the active layer 50 is increased from the state where the waveguide system T excites the zero-order even mode, so that the optical output intensity of the optical wavelength filter and the light 5) and / or 6) may be realized while keeping the input intensity equal.

When the specific light and the non-specific light are separated, the amount of light distribution of the specific light generated in the active layer 48 and the activity can be adjusted by individually and suitably adjusting the amount of light amplification of each active layer. Either make the size of the field distribution of the specific light generated in the layer 50 equal, or 8) make the field distribution of the specific light generated in the active layer 48 larger than the field distribution of the specific light generated in the active layer 50. To When controlling the field distribution of the specific light in this way, the specific light is reflected by the diffraction grating 52, so that the optical wavelength filter can be driven to separate the specific light and the non-specific light. In this embodiment, the waveguide system T is configured so as to realize 7) when the waveguide system T excites the zero-order even mode.

In order to reduce the light output intensity of the specific light output from the end portion 70b when separating the specific light and the non-specific light, the field distribution of the specific light generated in the active layer 48 must be controlled by the active layer. It is preferable that the field distribution of the specific light generated at 50 be larger than a certain ratio or more.

As long as 7) or 8) can be realized, the optical amplification amount of each active layer may be adjusted in any manner. However, for example, when the waveguide system T excites the 0th-order even mode and increases only the optical amplification amount in the active layer 48 or decreases only the optical amplification amount in the active layer 50, 8) is realized. The optical output intensity of the optical wavelength filter cannot be made equal to the optical input intensity of the filter.
Therefore, it is preferable to increase the optical amplification amount of the active layer 48 and decrease the optical amplification amount of the active layer 50 from the state where the waveguide system T excites the zero-order even mode, so that the optical output intensity of the optical wavelength filter is reduced. It is preferable to realize 4) while making the light input intensity equal.

FIGS. 11 and 12 are sectional views schematically showing the structure of the second embodiment of the third invention, and FIG. 13 is a plan view schematically showing the structure of the second embodiment of the third invention. . FIG.
12 is a cross section taken along line XI-XI in FIG.
(A), (B) and (C) show XIIA-XIIA line, XI in FIG.
2 shows a cross section taken along the lines IB-XIIB and XIIC-XIIC. The components corresponding to those in the first embodiment of the third invention described above are denoted by the same reference numerals, and detailed description of the same points as in the first embodiment of the third invention is omitted.

In this embodiment, a plurality of, for example, three diffraction grating areas 88 are arranged along the stripe direction of the active layer 48.
a, 88b and 88c are provided, and these regions 88a, 88
b and 88c on the active layer 48, diffraction gratings 52a,
52b and 52c are provided. Each diffraction grating 52a, 52b
And 52c have different periods in the direction along the active layer 48, and these diffraction gratings 52a, 52b and 5c have different periods.
The wavelength of the specific light separated by 2c is made different.

Light control structures 54a, 54b and 54c for independently controlling the amount of light amplification of the active layer 48 provided with the diffraction grating for each of the arrangement regions 88a, 88b and 88c.
Is provided. A p-side first electrode 62a provided with the light control structure 54a on the cap layer 84 in the disposition region 88a;
A portion corresponding to 8a includes the p-type clad 58, the n-type clad 60, and the n-side common electrode 64. Similarly, the p-side first electrode 62b in which the light control structure 54b is provided on the cap layer 84 in the disposition region 88b, and the p-type clad 58, the n-type clad 60, and the n-side common electrode corresponding to the region 88b 64, and further, the light control structure 54c is provided on the cap layer 84 in the disposition region 88c, and the p-type cladding 58 and the n-type cladding 60 in the portions corresponding to the region 88c. and an n-side common electrode 64. Each of the p-side first electrodes 62a, 62b and 62
c are electrically separated from each other, so that the optical amplification amount of the active layer 48 can be reduced by the respective arrangement regions 88a, 88b and 88.
Control is performed independently for each c.

Light control structures 56a, 56b and 5 for independently controlling the amount of light amplification of the active layer 50 having no diffraction grating for each of the arrangement regions 88a, 88b and 88c.
6c is provided. The light control structure 56a is formed from the p-side first electrode 70a provided on the cap layer 86 in the arrangement region 88a, and the p-type clad 66, the n-type clad 68, and the n-side common electrode 64 corresponding to the region 88a. Constitute. Similarly, the light control structure 56b is connected to the cap layer 8 in the arrangement region 88b.
6, a p-type first electrode 70b provided on the first electrode 6 and a p-type cladding 66, an n-type cladding 68 and an n-side common electrode 64 corresponding to the region 88b.
6c and the p-side first electrode 70c provided on the cap layer 86 in the arrangement region 88c, and the p-side first electrode 70c corresponding to the region 88c.
Clad 66, n-type clad 68 and n-side common electrode 6
And 4. By providing each of the p-side first electrodes 70a, 70b and 70c electrically separated from each other,
The light amplification amount of the active layer 50 is controlled independently for each of the arrangement regions 88a, 88b and 88c.

Further, an n-side common electrode 64 is provided extending from the arrangement regions 88a to 88c, and this electrode 64 is provided with the light control structures 54a, 54b, 56c, 56a, 56b and 5c.
6c is a common n-side electrode.

According to this embodiment, the diffraction gratings 52a, 52
The reflection action of 2b and 52c is independent for each diffraction grating,
ON / OFF control is possible. This on / off control may be performed individually for each diffraction grating in the same manner as in the above-described fourth embodiment of the present invention. Accordingly, it is possible to independently or separately separate a plurality of types of specific light corresponding to the periods of the diffraction gratings, here, three types of wavelengths.

FIGS. 14 and 15 are a sectional view and a plan view schematically showing the structure of the third embodiment of the third invention.
4 shows a cross section taken along line XIV-XIV in FIG.
The components corresponding to the components of the first embodiment of the third invention are denoted by the same reference numerals, and detailed description of the same points as those of the first embodiment of the third invention is omitted. .

In this embodiment, three active layer disposing regions 8
0, 82 and 90, and these areas 8
0, 82, and 90 each have a stripe shape and are arranged in parallel at a distance from each other. Then, active layers (active areas) 48, 50, and 92 constituting a gain waveguide are provided in these arrangement regions 80, 82, and 90, respectively.

Further, these arrangement areas 80, 82 and 92
Are provided with light control structures 54, 56 and 94 for variably controlling the amounts of light amplification of the active layers 48, 50 and 90. The light control structure 94 includes a p-type cladding 96 and an n-type cladding 98 sandwiching the active layer 92, a p-side electrode 100 electrically connected to the p-type cladding 96, and an n-side electrode 64 electrically connected to the n-type cladding 98. Have. The n-side electrode 64 is a light control structure 5
An electrode common to 4, 56, and 94, which is electrically connected to the n-type cladding 98 via the substrate 72.

The n- of the portion corresponding to the active layer
The InP cladding 74, the non-doped GaAsInP active layer 76 and the p-InP cladding 78 constitute an n-type cladding 98, an active layer 92 and a p-type cladding 96. p
The band gaps of the mold cladding 96 and the n-type cladding 98 are made wider than the band gap of the active layer 92. Then, on the p-InP cladding 78 at the portion corresponding to the active layer disposing region 90, the stripe-shaped p-Ga
An AsInP cap layer 102 and a p-side electrode 100 are provided. The p-side electrode 100 is electrically connected to the p-type cladding 96 via the cap layer 102.

The diffraction grating 104 is provided in the active layer disposition area 90.
Is provided. The arrangement position of the diffraction grating 104 can be any suitable position at which the field distribution of the specific light that seeps out of the active layer 92 when separating the specific light can reach the diffraction grating 104. A diffraction grating 104 is provided on a portion of the other substrate surface corresponding to the arrangement region 90. The diffraction grating 104 has a periodic structure in which irregularities are repeated in the stripe direction of the active layer 92. Diffraction grating 10 provided on active layer 92
The period of 4 and the period of the diffraction grating 52 provided in the active layer 48 are made different, and the wavelength of the specific light separated by the diffraction gratings 104 and 52 is made different.

The light control structures 54, 56, and 94 selectively inject current into portions of the active layer 76 corresponding to the disposition regions 80, 82, and 92, that is, the active layers 48, 50, and 92. It acts so as not to inject current into a part of the active layer 76. As a result, the active layers 48, 50 and 92
In this case, a state can be formed in which a gain is generated and no gain is generated in the other portions of the active layer 76. Therefore, a light guiding action occurs in the active layers 48, 50 and 90, and thus these active layers 48, 5
0 and 90 function as gain waveguides. Active layer 48,
An antireflection film (not shown) is provided on the end faces of the active layers 48, 50, and 92 in order to prevent laser oscillation due to optical amplification from occurring in the optical layers 50 and 92 or to reduce the occurrence of laser oscillation.

When the light guiding action is occurring, the active layer 4
8, 50 and 92 constitute one waveguide system. At this time, the formation conditions of the active layers 48, 50, and 92, such as the active layers 48, 50, and 92, are set such that the mode in which the waveguide system is excited in the arrangement direction of the active layers 48, 50, and 92 is preferably a zero-order even mode. And 92, the active layer 4
The layer thicknesses and separation intervals of 8, 50 and 92 are set.

According to this embodiment, the diffraction gratings 52 and 1
The on / off control of the reflection action of the light emitting element 04 can be performed independently for each diffraction grating. This on / off control may be performed individually for each diffraction grating in the same manner as in the above-described fourth embodiment of the present invention. Therefore, a plurality of types of specific light corresponding to the periods of these diffraction gratings, here, two types of specific light,
Can be separated or not separated.

FIG. 16 is a plan view schematically showing the configuration of the fourth embodiment of the third invention. The components corresponding to the components of the second embodiment of the third invention are denoted by the same reference numerals, and the detailed description of the same points as those of the second embodiment of the third invention is omitted. .

In the second embodiment of the third invention, each of the installation areas 8
8a, 88b and 88c diffraction grating 52 having a constant period
Although a, 52b and 52c are provided, in this embodiment, chirped gratings 106a, 106b and 106c are provided in the arrangement regions 88a, 88b and 88c, respectively. Therefore, the diffraction gratings 106a, 106
The periods of b and 106c correspond to the corresponding arrangement regions 88, respectively.
a, 88b and 88c, the diffraction grating 10
Specific light having a wavelength corresponding to the average period of 6a, 106b and 106c can be separated.

According to this embodiment, the diffraction grating 106a,
The reflection action of 106b and 106c can be controlled on / off independently for each diffraction grating. This on / off control
What is necessary is just to carry out similarly to the above-mentioned embodiment of the fourth invention individually for each diffraction grating. Therefore, a plurality of types of specific light corresponding to the average period of these diffraction gratings, here three types of specific light, can be separated or not separated independently.

The present invention is not limited to the above-described embodiment, and accordingly, the forming material, shape, arrangement position, number of arrangement, structure, and others of each component can be arbitrarily and suitably changed. For example, the conductivity type p-type may be changed to the opposite conductivity type n-type and the conductivity type n-type may be changed to the opposite conductivity type p-type. Further, in the third invention, diffraction gratings may be individually provided on all of the plurality of active layers constituting the waveguide system.

[0106]

As is clear from the above description, according to the optical wavelength filter of the first invention, the light absorption of the active layer provided with the diffraction grating and the light amplification of the active layer not provided with the diffraction grating. Can be individually variably controlled, so that the field distribution of light input to the waveguide system formed by these active layers can be changed in accordance with the amount of light absorption and / or the amount of light amplification. As a result, the field distribution of the input light can be controlled such that the input light of a specific wavelength is reflected by the diffraction grating, or the light of the specific wavelength is transmitted through the diffraction grating, and therefore, the specific wavelength can be controlled. A state in which the input light (specific light) is separated from an input light (non-specific light) having a wavelength other than that can be selectively formed.

Since the field distribution of the input light is controlled by using light absorption and / or light amplification, the drive current required to separate and non-separate the specific light can be reduced. Further, even when the diffraction grating is structurally formed in order to reduce the period of the diffraction grating or increase the reflection efficiency, the specific light can be selectively separated and non-separated.

According to the optical wavelength filter driving method of the second invention, when driving the optical wavelength filter of the first invention, the amount of light absorption and the amount of optical amplification are individually controlled for each active layer.

By individually controlling each active layer, a specific light field distribution is prevented from being generated in the active layer provided with the diffraction grating, or a specific light field distribution generated in the active layer not provided with the diffraction grating is provided. The size of the distribution can be made larger than the size of the field distribution of the specific light generated in the active layer provided with the diffraction grating. When the field distribution is controlled in this way, the specific light passes through the diffraction grating, so that the optical wavelength filter can be driven so as not to separate the specific light and the non-specific light.

Further, by individually controlling each active layer, the size of the field distribution of the specific light generated in the active layer provided with the diffraction grating and the size of the field distribution of the specific light generated in the active layer not provided with the diffraction grating can be improved. Or the magnitude of the field distribution of the specific light generated in the active layer provided with the diffraction grating can be made larger than the magnitude of the field distribution of the specific light generated in the active layer not provided with the diffraction grating. . When controlling the field distribution in this manner, the specific light is reflected by the diffraction grating, so that the optical wavelength filter can be driven so as to separate the specific light and the non-specific light.

Further, according to the optical wavelength filter of the third invention, the optical amplification amounts of the active layer provided with the diffraction grating and the active layer not provided with the diffraction grating can be individually and variably controlled. The field distribution of light input to the waveguide system can be changed according to the amount of light amplification. As a result, the field distribution of the specific light can be controlled so that the specific light is reflected by the diffraction grating, or the specific light is transmitted through the diffraction grating. A separated state and a non-separated state can be selectively formed.

Since the field distribution of the input light is controlled by using the optical amplification, the drive current required for separating and not separating the specific light can be reduced. In addition, even if the diffraction grating is structured to reduce the period of the diffraction grating or increase the reflection efficiency,
Separation and non-separation of specific light can be selectively performed.

According to the optical wavelength filter driving method of the fourth invention, when driving the optical wavelength filter of the third invention, the amount of optical amplification is individually controlled for each active layer.

By individually controlling each active layer, a specific light field distribution is prevented from being generated in the active layer provided with the diffraction grating, or a specific light field distribution generated in the active layer not provided with the diffraction grating is provided. The distribution can be made larger than the field distribution of the specific light generated in the active layer provided with the diffraction grating. When the field distribution is controlled in this way, the specific light passes through the diffraction grating, so that the optical wavelength filter can be driven so as not to separate the specific light and the non-specific light.

Also, by individually controlling each active layer, the size of the specific light field distribution generated in the active layer provided with the diffraction grating and the specific light field distribution generated in the active layer not provided with the diffraction grating can be reduced. Alternatively, the field distribution of the specific light generated in the active layer provided with the diffraction grating can be made larger than the field distribution of the specific light generated in the active layer provided with no diffraction grating. When the field distribution of the specific light is controlled in this way, the specific light is reflected by the diffraction grating, so that the optical wavelength filter can be driven to separate the specific light and the non-specific light.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views schematically showing a configuration of a first embodiment of the first invention.

FIG. 2 is a plan view schematically showing the configuration of the first embodiment of the first invention.

FIGS. 3A and 3B are diagrams showing a relationship between a field distribution generated in an active layer and a gain in the first embodiment of the first invention.

FIGS. 4A and 4B are diagrams showing a relationship between a field distribution generated in an active layer and a gain in the first embodiment of the first invention.

FIG. 5 is a diagram showing light output characteristics of the first embodiment of the first invention.

FIG. 6 is a sectional view schematically showing a configuration of a second embodiment of the first invention.

FIGS. 7A, 7B, and 7C are cross-sectional views schematically showing a configuration of a second embodiment of the first invention.

FIG. 8 is a plan view schematically showing a configuration of a second embodiment of the first invention.

FIG. 9 is a sectional view schematically showing the configuration of the first embodiment of the third invention.

FIG. 10 is a plan view schematically showing the configuration of the first embodiment of the third invention.

FIG. 11 is a sectional view schematically showing a configuration of a second embodiment of the third invention.

FIGS. 12 (A), (B) and (C) are cross-sectional views schematically showing the configuration of a second embodiment of the third invention.

FIG. 13 is a plan view schematically showing the configuration of a second embodiment of the third invention.

FIG. 14 is a sectional view schematically showing a configuration of a third embodiment of the third invention.

FIG. 15 is a plan view schematically showing a configuration of a third embodiment of the third invention.

FIG. 16 is a plan view schematically showing a configuration of a fourth embodiment of the third invention.

FIG. 17 is a plan view schematically showing a configuration of a conventional filter element.

[Explanation of symbols]

18, 20, 48, 50: Active layers 22, 22a to 22c, 52, 52a to 52c, 106
a to 106c: diffraction grating 24, 24a to 24c: first light control structure 26, 26a to 26c: second light control structure 28: p-type first and second common cladding 30: n-type first cladding 32: p-side First and second common electrodes 34, 34a to 34c: n-side first electrode 36: n-type second clad 38, 38a to 38c: n-side second electrode 46a to 46c, 88a to 88c: diffraction grating arrangement region 54 , 56, 54a to 54c: light control structure 58, 66: p-type cladding 60, 68: n-type cladding 62, 70, 62a to 62c: p-side electrode 64: n-side common electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/025 G02F 1/35

Claims (6)

(57) [Claims] 1. A zero-order even mode, wherein refractive index waveguides are respectively arranged and arranged close to each other so as to cause light interaction.
A plurality of active layers for transmitting the light of the light source, a diffraction grating provided on at least one of the active layers, and a first light control for electrically variably controlling the amount of light absorption in the active layer provided with the diffraction grating. An optical wavelength filter, comprising: a structure; and a second light control structure for electrically variably controlling the amount of light amplification in an active layer having no diffraction grating. 2. A first light control structure comprising: a p-type first clad sandwiching an active layer provided with a diffraction grating; an n-type first clad; a p-side first electrode electrically connected to the p-type first clad; An n-side first electrode electrically connected to the first mold clad; and a second light control structure, wherein the p-type second clad and the n-type second clad sandwich the active layer having no diffraction grating. The optical wavelength filter according to claim 1, further comprising a p-side second electrode electrically connected to the second clad and an n-side second electrode electrically connected to the n-type second clad. 3. A method for driving an optical wavelength filter according to claim 1, wherein the amount of light absorption and the amount of optical amplification are individually controlled for each active layer when driving the optical wavelength filter according to claim 1. 4. A 0th order even mode, wherein each of the gain waveguides is arranged close to each other so as to cause light interaction.
A plurality of active layers for transmitting light of the same mode, a diffraction grating provided on at least one of the active layers, and a light control structure for electrically variably controlling the amount of light amplification in the active layer. An optical wavelength filter. 5. The light control structure comprises a p-type clad sandwiching an active layer, an n-type clad, a p-side electrode electrically connected to the p-type clad, and an n-side electrode electrically connected to the n-type clad. The optical wavelength filter according to claim 1, wherein: 6. A method of driving an optical wavelength filter according to claim 4, wherein the amount of light amplification is individually controlled for each active layer when driving the optical wavelength filter according to claim 4.