JPH0774426A - Variable wavelength laser, variable wavelength filter and selective wavelength detection element - Google Patents

Abstract

PURPOSE:To acquire a variable wavelength laser which does not cause mode hop and has wide variable wavelength width by using two directional couplers with wide coupling band width and by forming a narrow wavelength band width coupled to the two directional couplers by shifting a wavelength band region of each directional coupler. CONSTITUTION:A clad layer 102, a first waveguide path layer 103 of a multilayer quantum well and a clad layer 104 are deposited on a substrate 101 by molecular epitaxial method. Then, the clad layer 104 in an active region part is removed and an active layer 111 and a clad layer 112 are deposited selectively by a metal organic vapor phase growth method. Then, after forming grating in a coupling region part, a wavelength control layer 105 of a multiple quantum well is selectively formed. Thereafter, a second waveguide path layer 106 of multiple quantum well, a clad layer 107 and a cap layer 108 are deposited by a metal organic vapor phase growth method. Electrodes 109, 110 are then formed and high reflection rate treatment is performed for a part R1 to make edge face reflection rate of R1>R2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device such as a wavelength tunable laser, a wavelength tunable filter and a wavelength selective detector used for optical wavelength division multiplexing communication.

[0002]

2. Description of the Related Art Conventionally, as a wavelength tunable laser, a wavelength tunable laser utilizing distributed Bragg reflection (Japanese Patent Laid-Open No. 3-214).
683) or a wavelength tunable laser using a grating type directional mode coupler (Japanese Patent Laid-Open No. 2-63012).

The operating principle of a wavelength tunable laser utilizing distributed Bragg reflection will be described. By applying a voltage to the diffraction grating portion, a plasma effect occurs due to the injected electrons and holes, and the refractive index decreases. This decrease in the refractive index changes the Bragg reflection condition, which changes the oscillation wavelength of the laser.

In a wavelength tunable laser using a grating type directional mode coupler, a waveguide and a reflecting mirror are constructed so that only wavelengths coupled by the grating type directional mode coupler oscillate. The wavelength variable method is performed by changing the wavelength to be coupled by the coupler. The coupling wavelength of the grating type directional mode coupler is determined by the grating period. Therefore, as a method for changing the coupling wavelength of the coupler, a voltage is applied to the coupler region, the refractive index there is changed, the grating period is changed, and the coupling wavelength is changed.

Further, conventionally, a wavelength tunable filter utilizing distributed Bragg reflection has been used as the wavelength tunable filter (Japanese Patent Laid-Open No. Sho 6-96).
3-256927, etc.) and a wavelength tunable filter using a grating type directional mode coupler (Japanese Patent Laid-Open No. 2-6).
No. 3012) has been proposed.

The operating principle of the wavelength tunable filter utilizing distributed Bragg reflection is substantially the same as the operating principle of the above wavelength tunable laser. That is, when a voltage is applied to the diffraction grating portion, a plasma effect occurs due to the injected electrons and holes, and the refractive index is reduced. This decrease in the refractive index changes the Bragg reflection condition and changes the selected wavelength.

In the wavelength tunable filter using the grating type directional mode coupler, the waveguide is constructed so that only the wavelengths coupled by the grating type directional mode coupler propagate to one of the waveguides. The wavelength variable method is performed by changing the wavelength to be coupled by the coupler. The coupling wavelength of the grating type directional mode coupler is determined by the grating period. Therefore, as a method of changing the coupling wavelength, a voltage is applied to the coupler region and the refractive index is changed to change the coupling wavelength.

[0008]

The wavelength tunable laser utilizing the distributed Bragg reflection described above does not cause mode hop during stable operation, but has a wavelength tunable range of about several nm. On the other hand, in a wavelength tunable laser using a grating type directional coupler, whether or not mode hop occurs depends on the coupling bandwidth of the coupler, and in order to suppress the mode hop, the coupling bandwidth of the coupler is usually set to fabric. Must be less than or equal to Perot's mode interval.

The wavelength tuning range is determined by the tuning width of the coupler. Here, the full width at half maximum and the tuning width of the coupling wavelength spectrum of the grating type directional coupler have the following relationship.

[0010]

[Equation 1] In this way, the tuning width and the half-value width of the coupled wavelength spectrum are correlated, and the wavelength variable range is limited in order to suppress the half-value width. Actually, when using a directional coupler having a full width at half maximum of about 1 nm that can prevent mode hop, 1.55
Only a wavelength tunable range of about 60 nm has been obtained with a wavelength tunable laser in the μm band (Appl. Phys. Le.
tt. 60 (26), 29 June 1992).

Further, the wavelength tunable filter utilizing the distributed Bragg reflection has a narrow half width at the time of stable operation of less than or equal to angstrom, but has a wavelength tunable range of about several tens of liters. Therefore, the number of wavelengths that can be selected is about 20 to 30.

On the other hand, the half-width and tuning width of the coupling wavelength spectrum of the grating type directional coupler have the above-described relationship, and the tuning width and the half-width are correlated with each other. Limited range. In addition, the number of wavelengths that can be selected is the tuning width / -10
Assuming dB width (width 10 dB down from the peak value of the combined wavelength spectrum), the number of wavelengths is

[0013]

[Equation 2] Can be expressed as However, the filter characteristic has side lobes as shown in FIG. 2, the number of wavelengths that can be actually taken is reduced to a fraction, and the number of wavelengths is limited to about 30.
After all, the number of wavelengths that can be selected by any filter is as small as about 30.

In view of the above problems, an object of the present invention is to provide a wavelength tunable laser with a wide wavelength tunable width in which no mode hop occurs, a side lob, and a wavelength tunable filter and a wavelength selective detector with a reduced half width. To provide.

[0015]

A tunable laser according to the present invention which achieves the above object comprises a first waveguide, a second waveguide, a first waveguide and a second waveguide. , A plurality of coupling regions provided so as to couple a light wave of a particular wavelength propagating through any one of the waveguides to the other waveguide, and an active region arranged so as to couple with any of the waveguides. And a reflecting portion having an end face arrangement in which light waves of wavelengths coupled in the plurality of coupling regions resonate, and a structure capable of changing coupling wavelengths of the plurality of coupling regions. With such a wavelength tunable laser, a wavelength tunable laser with a wide wavelength tunable width in which mode hop does not occur is realized.

A tunable filter according to the present invention which achieves the above object, comprises a first waveguide, a second waveguide, and
A plurality of coupling regions provided in the first waveguide and the second waveguide so as to couple an optical wave of a specific wavelength propagating through one of the waveguides to the other waveguide; It has a structure capable of changing the coupling wavelengths of a plurality of coupling regions, and a waveguide separation region disposed in either one of the first waveguide and the second waveguide.
Such a wavelength tunable filter solves the above-mentioned problems.

Further, the wavelength selective detector according to the present invention which achieves the above object is provided with any one of the first waveguide, the second waveguide, the first waveguide and the second waveguide. A plurality of coupling regions provided so as to couple light waves of a specific wavelength propagating through the waveguide to the other waveguide, and a structure capable of changing the coupling wavelength of the plurality of coupling regions,
It has a waveguide isolation region arranged in either one of the first waveguide and the second waveguide, and a structure for absorbing and detecting light of a wavelength coupled by the coupling region. The above-mentioned problems are solved by such a wavelength selective detector.

Specifically, the coupling region may be formed by a grating. The plurality of coupling regions may have the same grating structure. The grating structures of the plurality of coupling regions may be different from each other. In the structure of the grating, the depth of the grating may be different. The grating structure may have different grating periods. In the structure of the grating, the recesses and the projections of the grating may have different length ratios. In the structure of the grating, the shape of the grating may be different. A reflecting mirror may be arranged in either one of the first waveguide and the second waveguide. . At least one of the first waveguide and the second waveguide may be bent. An absorption region that absorbs light propagating in a part of the first waveguide and the second waveguide may be arranged. Also,
The number of waveguides is not limited to two. It may be three or more.

Further, the wavelength tunable laser according to the present invention which achieves the above object is provided so as to couple a plurality of waveguides and a light wave of a specific wavelength propagating through one of the waveguides to another waveguide. A plurality of coupling regions, an active region arranged so as to couple with any one of the waveguides, and a plurality of coupling regions are formed on the end face where the light waves of the wavelengths coupled to each other resonate and have a higher reflectance than the other end faces. It is characterized in that it has a certain reflection part and a structure capable of changing the coupling wavelength of the plurality of coupling regions.

A wavelength tunable filter according to the present invention which achieves the above object is provided with a plurality of waveguides and a plurality of waveguides provided so as to couple an optical wave of a specific wavelength propagating through one of the waveguides to another waveguide. Of the coupling region, a structure capable of changing the coupling wavelength of the plurality of coupling regions, and a waveguide separation region disposed in any of the waveguides.

The wavelength selective detector according to the present invention which achieves the above object is provided so as to couple a plurality of waveguides and a light wave of a specific wavelength propagating through one of the waveguides to another waveguide. A plurality of coupling regions, a structure capable of changing the coupling wavelengths of the plurality of coupling regions, a waveguide separation region disposed in any of the waveguides, and absorption of light of wavelengths coupled to the plurality of coupling regions And a structure for detecting.

[0022]

In order to widen the tuning width in the directional coupler, the coupling wavelength spectrum width or the coupling bandwidth becomes wider. Therefore, as shown in FIG. 1, two directional couplers having a wide coupling bandwidth W1 are used, and the wavelength bands of the respective directional couplers are shifted so that the narrow wavelengths coupled to the two directional couplers are obtained. A wavelength tunable laser having a wide wavelength tunable width in which the bandwidth W2 is formed and mode hop does not occur can be realized.

Further, the characteristics of the two directional couplers are made different, the side lobes are suppressed, the bandwidth of the filter itself is narrowed, and the number of selectable wavelengths is increased. For example, as shown in FIG. 3, by combining two couplers having characteristics of A (shown in FIG. 2) and B respectively, a filter having characteristics of C (shown by a thick line) is formed. As a result, side lobes are suppressed and the number of wavelengths that can be selected is increased. Alternatively, as shown in FIG.
By combining two couplers each having the characteristic of D, a filter having the characteristic of E (shown by a thick line) is formed, and side lobes can be suppressed and the half width can be reduced.

[0024]

[Embodiment 1] FIG. 5 is a diagram showing a configuration of a first embodiment of the present invention. The present embodiment relates to a wavelength tunable laser in which two grating portions have the same grating structure. The structure of this embodiment will be described below.

1.5 μm on n-GaAs substrate 101
N-Al _0.5 Ga _0.5 As cladding layer 102, n-Ga
As and n-Al _0.4 Ga _0.6 As are alternately laminated to form a multiple quantum well (MQW) 0.2 μm first waveguide layer 103, _0.5 μm n-Al _0.5 Ga _0.5 As clad layer 104 was deposited by the molecular beam epitaxy (MBE) method. Next, the clad layer 104 of the portion to be the active region is removed, and a 0.1 μm GaAs active layer 111 and a 0.7 μm p-Al _0.4 Ga _0.6 As clad layer 112 are selectively formed by metal organic chemical vapor deposition (MOCVD). It was deposited by the method. Next, a grating having a depth of 0.2 μm was formed in the bonding region. Next, GaAs and Al
_The wavelength control layer 105 made of MQW in which _0.5 Ga _0.5 As was laminated was selectively formed. After that, p- of 0.3 μm
MQW in which GaAs and p-Al _0.4 Ga _0.6 As are laminated
Second waveguide layer 106 consisting of 1.2 μm p-Al
_0.5 Ga _0.5 As clad layer 107, 0.1 μm p-G
The aAs cap layer 108 was deposited by MOCVD. Next, the electrodes 109 and 110 were formed. And
The R ₁ portion was subjected to high reflectance treatment so that the end face reflectance was R ₁ >> R ₂ .

A voltage was applied to each electrode of the wavelength tunable laser having the above structure, and the oscillation wavelength was measured. As a result, wavelength tunability of 90 nm width in 0.8 μm band can be realized,
Mode hop did not occur during stable operation. Also, by providing a voltage difference between A ₁ and C ₁ , the o
It was also confirmed that n and off were possible. Oscillation is possible when the voltages A ₁ and C ₁ are not applied or when the voltages are made equal.

[0027]

[Embodiment 2] FIG. 6 is a diagram showing a configuration of a second embodiment of the present invention. The present embodiment relates to a wavelength tunable laser in which two grating sections have different periods.

The structure of this embodiment will be described below.

A 0.4 μm first waveguide layer 202 made of MQW in which n-InP and n-In _0.4 Ga _0.6 As are laminated on an n-InP substrate 201, and a 1.0 μm n waveguide layer 202 is formed.
-The InP clad layer 203 was deposited by MOCVD. Next, the clad layer 2 in the central portion to be the active region
03 was removed and GaInAsP of 0.1 μm was selectively
Active layer 210, 1.9 μm p-InP clad layer 21
1 was deposited by the MOCVD method. Next, a grating having a depth of 0.4 μm and a period Λ1 and a period Λ2 was formed in the coupling region. Next, InP and In _0.5 Ga _0.5 As
The wavelength control layer 204 made of MQW in which is laminated is selectively formed. Then, 0.6 μm of p-InP and p-I
The second waveguide layer 205 made of MQW in which n _0.5 Ga _0.5 As is laminated, and the p-InP clad layer 20 having a thickness of 1.2 μm
6, 0.1 μm p-GaInAsP cap layer 207
Was deposited by the MOCVD method. Next, the electrode 20
8 and 209 were formed. And the end face reflectance is R ₁ >>
The R1 portion was subjected to high reflectance treatment so as to be R ₂ .

A voltage was applied to each electrode of the wavelength tunable laser having the above structure, and the oscillation wavelength was measured. As a result, wavelength tunability of 100 nm was realized in the 1.55 μm band, and mode hop did not occur during stable operation. Moreover, not occur oscillate when no voltage is applied to the A ₂ and C _2, by providing a voltage difference between A ₂ and C _2, it was confirmed that the oscillation occurs.

[0031]

Third Embodiment FIG. 7 is a diagram showing the configuration of the third embodiment of the present invention. This embodiment relates to a tunable laser having an active region in the upper waveguide. The structure of this embodiment will be described below.

On the n-InP substrate 301, a _0.4 μm first waveguide layer 302 made of MQW in which n-InP and n-In _0.4 Ga _0.6 As are laminated, and a 1.0 μm n-type waveguide layer 302 is formed.
The InP clad layer 303 was deposited by the MOCVD method. Next, the clad layer 30 in the central portion to be the active region
3 is removed, and the 1.9 μm n-InP cladding layer 308 and the 0.1 μm GaInAsP active layer 309 are selectively removed.
Was deposited by the MOCVD method. Next, a grating having periods Λ ₁ and Λ ₂ was formed in the coupling region with a depth of 0.4 μm. Next, the wavelength control layer 304 made of MQW in which InP and In _0.5 Ga _0.5 As are laminated was selectively formed. After that, 0.6 μm of p-InP and p-In _0.5 G
a second waveguide layer 305 made of MQW in which a _0.5 As is laminated, a 1.2 μm p-InP clad layer 306,
0.1 μm p-GaInAsP cap layer 307
It was deposited by the OCVD method. Next, the electrodes 310, 3
11 was formed. Then, the R ₁ portion was subjected to high reflectance treatment so that the end face reflectance was R ₁ >> R ₂ .

A voltage was applied to each electrode of the wavelength tunable laser having the above structure, and the oscillation wavelength was measured. As a result, wavelength tunability up to 100 nm can be realized in the 1.3 μm band, and mode hop did not occur during stable operation. It was also confirmed that the oscillation can be turned on and off by appropriately setting the voltage difference between A ₃ and C ₃ .

[0034]

[Fourth Embodiment] FIG. 8 is a diagram showing the configuration of a fourth embodiment of the present invention. The present embodiment relates to a wavelength tunable laser having a reflecting mirror in the upper waveguide. The configuration of this embodiment will be described below.

The active region 40 is formed on the GaAs substrate 406.
1, a first grating type directional coupler region 402,
The second grating type directional coupler region 403 is arranged in a plane. In addition, the first waveguide layer 404 and the second waveguide layer 405 are laminated on the substrate 406.
A high reflectance treatment was applied to the R ₃ and R ₄ surfaces. This makes the first
Only the light coupled in the grating type directional coupler region 402 of is reflected by the 45-degree reflecting mirror 407 and can propagate to the second grating type directional coupler region 403. The other layer structure, the grating structure and the like are substantially the same as those in the above-mentioned embodiment.

A constant voltage was applied to the electrode A _4, and a voltage was applied to B ₄ and C ₄ . As a result, it was also confirmed that tuning of 80 nm can be realized in the 0.8 μm band without mode hopping, and oscillation can be turned on and off by providing a voltage difference between B ₄ and C ₄ . Further, it was confirmed that the spontaneous emission light at the time of oscillation off was smaller than that of the third embodiment. At the time of oscillation off, spontaneous emission light is not reflected by the 45-degree reflecting mirror 407 formed in the second waveguide layer 405 of the first grating type directional coupler region 402, and the rightward direction in FIG. The spontaneous emission light travels through the first waveguide layer 404 as it is and goes out.

[0037]

Fifth Embodiment FIG. 9 is a diagram showing the configuration of the fifth embodiment of the present invention. This embodiment relates to a wavelength tunable laser having an absorption layer in the upper waveguide. The configuration of this embodiment will be described below.

0.4 made of MQW in which n-InP and n-GaInAsP are laminated on the n-InP substrate 501.
A μm first waveguide layer 502 and a 1.0 μm n-InP clad layer 503 were deposited by MOCVD. Next, the clad layer 503 in the central portion to be the active region is removed and the 1.9 μm n-InP clad layer 50 is selectively removed.
MOC the GaInAsP active layer 510 of 9, 0.1 μm
It was deposited by the VD method. Next, a grating having a depth of 0.3 μm, a period Λ ₁ , a depth of 0.4 μm, and a period Λ ₂ was formed in the coupling region. Next, InP and InGa
A wavelength control layer 504 made of MQW in which As was laminated was selectively deposited. Then, 0.6 μm of p-InP and p
-Depositing a second waveguide layer 506 composed of MQW in which GaInAsP is laminated, removing the second waveguide layer 506 in one (the right side in this embodiment) coupling region, and light having a wavelength not coupled by a coupler; InGaAsP absorption layer 505, which has the same composition ratio as active layer 510, was selectively deposited by MOCVD in order to absorb. Next, 1.5
μm p-InP clad layer 507, 0.1 μm p-
Liquid layer growth (LPE) of GaInAsP cap layer 508
Formed by the method.

A voltage was applied to each electrode of the wavelength tunable laser having the above structure, and the oscillation wavelength was measured. As a result, wavelength tunability of 110 nm could be realized in the 1.55 μm band, and mode hop did not occur during stable operation. It was also confirmed that oscillation can be turned on and off by controlling the voltage applied to the B ₅ and C ₅ electrodes.
Further, since there is the absorption layer 505, it was confirmed that the spontaneous emission light at the time of oscillation off was smaller than that in the third embodiment.

[0040]

[Embodiment 6] FIG. 6 is a diagram showing the structure of a sixth embodiment of the present invention. This embodiment relates to a wavelength tunable filter in which two grating sections have the same grating structure. The structure of this embodiment will be described below.

1.5 μm on the n-GaAs substrate 601
N-Al _0.5 Ga _0.5 As cladding layer 602, n-Ga
0.2 μm first waveguide layer 603 and _0.5 μm n-Al _0.5 Ga _0.5 As clad layer in which As and n-Al _0.4 Ga _0.6 As are alternately laminated to form a multiple quantum well (MQW). 604 was deposited by the molecular beam epitaxy (MBE) method. Next, a grating having a depth of 0.2 μm was formed in the bonding region. Next, GaAs and Al _0.5
Wavelength control layer 6 made of MQW laminated with Ga _0.5 As
05 was formed. After that, a second waveguide layer 606 made of MQW in which 0.3 μm of p-GaAs and p-Al _0.4 Ga _0.6 As are laminated, and 1.2 μm of p-Al _0.5 Ga _0.5.
An As clad layer 607 and a 0.1 μm p-GaAs cap layer 608 were deposited by MOCVD. Then, a V groove 620 is formed in a part of the second waveguide layer 606.
Separated. Next, electrodes 609 and 610 were formed.

A voltage was applied to each of the electrodes 609 and 610 of the wavelength tunable filter having the above structure, and the filter characteristics were measured. As a result, it was possible to realize wavelength tunability of 90 nm in the 0.8 μm band, obtain a half-width value of 8Å, and confirm that the number of wavelengths of about 60 waves can be selectively detected. Further, the half width of the filter was changed from 1.9 nm to 0 (no transmitted light) by providing the voltage difference between A ₁ and C ₁ . It was also confirmed that the side lobes were also suppressed.

[0043]

[Seventh Embodiment] FIG. 11 is a diagram showing the structure of a seventh embodiment of the present invention. The present embodiment relates to a wavelength tunable filter in which two grating sections have different periods. The structure of this embodiment will be described below.

A 0.4 μm first waveguide layer 702 made of MQW in which n-InP and n-In _0.4 Ga _0.6 As are laminated on an n-InP substrate 701, and a 1.0 μm n-type waveguide layer 702.
The InP clad layer 703 was deposited by MOCVD. Next, a depth of 0.4 μm and a period Λ in the coupling region portion.
1 and Λ2 gratings were formed. Next, InP
To form a wavelength control layer 704 made of MQW in which In _0.5 Ga _0.5 As and In _0.5 Ga _0.5 As are stacked. Then, p-I of 0.6 μm
A second waveguide layer 705 made of MQW in which nP and p-In _0.5 Ga _0.5 As are stacked, a 1.2 μm p-InP clad layer 706, and a 0.1 μm p-GaInAsP cap layer 707 are deposited by MOCVD. Let After that, a V groove 720 was formed in a part of the substrate, and the second waveguide layer 705 was separated. Next, electrodes 708 and 709 were formed.

A voltage was applied to each of the electrodes 708 and 709 of the wavelength tunable filter having the above structure, and the filter characteristics were measured. As a result, 100 nm in the 1.55 μm band
It was confirmed that the wavelength variability of 1 was realized, and the half width thereof was 1 nm, and that the number of wavelengths of about 50 waves could be selectively detected. Further, the half width of the filter was changed from 2.2 nm to 0 (no transmitted light) by providing the voltage difference between A ₂ and C ₂ . It was also confirmed that the side lobes were also suppressed. Also, each electrode 708, 709
It was confirmed that no light was transmitted through the filter when no voltage was applied to the filter.

[0046]

[Embodiment 8] FIG. 12 is a diagram showing the structure of an eighth embodiment of the present invention. This embodiment relates to a wavelength tunable filter having an absorption region. The structure of this embodiment will be described below.

A _0.4 μm first waveguide layer 802 made of MQW in which n-InP and n-In _0.4 Ga _0.6 As are laminated on an n-InP substrate 801, and a 1.0 μm n-type waveguide layer 802.
The InP clad layer 803 was deposited by MOCVD method. Next, in the coupling region, with a depth of 0.4 μm, a period Λ ₁ ,
A Λ ₂ grating was formed. Next, InP and I
A wavelength control layer 804 made of MQW laminated with n _0.5 Ga _0.5 As, 0.6 μm p-InP and p-In _0.5 Ga
Second waveguide layer 8 made of MQW laminated with _0.5 As
05 was formed using the MOCVD method. After that, a part of the second waveguide layer 805 in the central part where the grating is not formed is removed, and a GaInAsP absorption layer 808 that selectively absorbs the light not coupled by the grating is deposited on the part using the MOCVD method. It was Next,
1.2 μm p-InP clad layer 806, 0.1 μm
Of p-GaInAsP cap layer 807 was deposited by MOCVD. Next, electrodes 810 and 811 were formed.

A voltage was applied to each of the electrodes 810 and 811 of the wavelength tunable filter having the above structure, and the filter characteristics were measured. As a result, 100 nm in the 1.55 μm band
It was confirmed that the wavelength variability of 1 was realized, and the half width thereof was 1 nm, and that the number of wavelengths of about 50 waves could be selectively detected. Further, the half value width of the filter was changed from 2.2 nm to 0 (no transmitted light) by providing the voltage difference between A ₃ and C ₃ . It was also confirmed that the side lobes were also suppressed. In addition, each electrode 810, 811
It was confirmed that no light was transmitted through the filter when no voltage was applied to the filter. The element surface is flat.

[0049]

[Ninth Embodiment] FIG. 13 is a diagram showing the structure of a fourth embodiment of the present invention. This embodiment relates to wavelength selective detection. The configuration of this embodiment will be described below.

A 0.4 μm first waveguide layer 902 made of MQW in which n-InP and n-In _0.4 Ga _0.6 As are laminated on an n-InP substrate 901, and a 1.0 μm n waveguide layer 902.
-The InP clad layer 903 was deposited by the MOCVD method. Next, a grating having periods Λ ₁ and Λ ₂ was formed in the coupling region with a depth of 0.4 μm. Next, InP
To form a wavelength control layer 904 made of MQW in which In _0.5 Ga _0.5 As and In _0.5 Ga _0.5 As are stacked. After that, 0.6 μm −p−
A second waveguide layer 905 made of MQW in which InP and p-In _0.5 Ga _0.5 As were laminated was deposited by MOCVD. After that, the second waveguide layer 905, the wavelength control layer 904, and the clad layer 903 of the detection section are removed, and n−I
The nP cladding layer 906 and the GaInAsP absorption layer 907 were selectively deposited using the MOCVD method. Next,
1.2 μm p-InP clad layer 908, 0.1 μm
Of p-GaInAsP cap layer 909 was deposited by MOCVD. After that, a V groove 920 was formed in a part of the substrate, and the second waveguide layer 905 was separated. Next, electrodes 910, 911, and 912 were formed.

A voltage was applied to each of the electrodes 911 and 912 of the wavelength tunable filter having the above structure, and the filter characteristic and the detection characteristic were measured. As a result, 1.55 μm
A wavelength of 100 nm can be tuned in the band and its half-value width is 1
A value of nm was obtained, and it was confirmed that the number of wavelengths of about 50 waves can be selectively detected by making the detection current at B ₄ have a difference of 10 dB. Further, the half width of the filter was changed from 2.2 nm to 0 (no transmitted light) by providing the voltage difference between A ₄ and C ₄ . It was also confirmed that the side lobes were also suppressed. In addition, each electrode 91
It was confirmed that when no voltage was applied to Nos. 1 and 912, the light passing through the filter was 0.

[0052]

[Embodiment 10] FIG. 14 is a diagram showing the structure of a tenth embodiment of the present invention. This embodiment relates to a wavelength tunable filter in which a reflecting mirror is arranged between two grating parts. The configuration of this embodiment will be described below.

A first grating type directional coupler region 1001 and a second grating type directional coupler region 1002 are two-dimensionally arranged on a GaAs substrate 1006. Further, the first waveguide layer 1003 and the second waveguide layer 1004 are stacked on the substrate 1006. R ₃ ,
Antireflection treatment was applied to the R ₄ surface. As a result, only the light coupled in the first grating type directional coupler region 1001 is reflected by the 45-degree reflecting mirror 1010 and can propagate to the second grating type directional coupler region 1002. The other layer structure, the grating structure and the like are substantially the same as those in the above-mentioned embodiment.

A voltage was applied to each electrode of the wavelength tunable filter having the above structure, and the filter characteristics were measured.
As a result, it was possible to realize wavelength tunability of 80 nm in the 0.8 μm band, obtain a half width of 0.7 nm, and confirm that the number of wavelengths of about 50 waves can be selectively detected. Further, the half width of the filter was changed from 1.9 nm to 0 (no transmitted light) by providing the voltage difference between A ₅ and C ₅ . It was also confirmed that the side lobes were also suppressed. Further, it was confirmed that the light passing through the filter was 0 when no voltage was applied to each electrode.

When the transmitted light is 0, the 45-degree reflecting mirror 1010 formed in the second waveguide layer 1004 of the first grating type directional coupler region 1001 does not reflect the light, and FIG. Light is directed to the right of (a) as it is
And goes out of the waveguide layer 1003.

[0056]

According to the present invention, the following effects can be confirmed.

1) A wide-band wavelength tunable laser having a wavelength tunable width of about 90 nm in the 0.8 μm band and a wavelength tunable width of 100 nm in the 1.55 μm band could be realized without mode hopping. 2) It was possible to realize a structure in which oscillation was turned on and off by switching the end face reflectance, and a wavelength tunable laser with a built-in intensity modulation was realized. 3) The side lobe of the filter can be suppressed and the number of selectable wavelengths can be increased. 4) The filter bandwidth can be narrowed and the number of selectable wavelengths can be increased without changing the wavelength variable width.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of a wavelength tunable laser according to the present invention.

FIG. 2 is an explanatory diagram of a problem of a conventional filter.

FIG. 3 is a diagram for explaining the principle of the wavelength tunable filter of the present invention.

FIG. 4 is a diagram illustrating the principle of the wavelength tunable filter of the present invention.

FIG. 5 is a structural diagram of the first embodiment of the present invention.

FIG. 6 is a structural diagram of a second embodiment of the present invention.

FIG. 7 is a structural diagram of a third embodiment of the present invention.

FIG. 8 is a plan view and a cross-sectional view showing the structure of a fourth embodiment of the present invention.

FIG. 9 is a structural diagram of a fifth embodiment of the present invention.

FIG. 10 is a structural diagram of a sixth embodiment of the present invention.

FIG. 11 is a structural diagram of a seventh embodiment of the present invention.

FIG. 12 is a structural diagram of an eighth embodiment of the present invention.

FIG. 13 is a structural diagram of a ninth embodiment of the present invention.

FIG. 14 is a plan view and a sectional view showing the structure of a tenth embodiment of the present invention.

[Explanation of symbols]

101, 406 n-GaAs substrate 102 lower clad layer 103, 202, 302, 404, 502 first waveguide layer 104, 112, 203, 211, 303, 308, 5
03, 509 Intermediate clad layer 105, 204, 304, 504 Wavelength control layer 106, 205, 305, 405, 506 Second waveguide layer 107, 206, 306, 507 Upper clad layer 108, 207, 307, 508 Cap layer 109, 110, 208, 209, 310, 311, 5
11, 512 electrode 111, 210, 309, 510 active layer 201, 301, 501 n-InP substrate 401 active region 402 first grating type directional coupler region 403 second grating type directional coupler region 407 reflector 505 absorption layer 601, 1006 n-GaAs substrate of filter 602 lower clad layer 603, 702, 802, 902, 1003 first waveguide layer 604, 703, 803, 903 intermediate clad layer 605, 704, 804, 904 wavelength control Layers 606, 705, 805, 905, 905, 1004 Second waveguide layers 607, 706, 806 Upper cladding layers 608, 707, 807, 909 Cap layers 609, 610, 708, 709, 810, 811, 9
11, 912 Electrodes 620, 720 V-grooves 701, 801, 901 Filter n-InP substrate 808 Absorption layer 906 Detection part intermediate clad layer 907 Detection layer 908 Detection part upper clad layer 910 Detection part electrode 1001 First filter Grating type directional coupler region 1002 Second grating type directional coupler region 1010 Filter reflector

Claims (33)

[Claims] 1. A first waveguide, a second waveguide, and an optical wave of a specific wavelength propagating in any one of the first waveguide and the second waveguide. A plurality of coupling regions provided so as to be coupled to one of the waveguides, an active region arranged so as to couple with any one of the waveguides, and an end face on which a light wave of a wavelength coupled in the plurality of coupling regions resonates. 2. A wavelength tunable laser, comprising: a reflection part formed on the end face having a higher reflectivity than other end faces; and a structure capable of changing a coupling wavelength of the plurality of coupling regions. 2. The tunable laser according to claim 1, wherein each of the plurality of coupling regions is formed by a grating. 3. The wavelength tunable laser according to claim 2, wherein the structures of the gratings of the plurality of coupling regions are the same as each other. 4. The wavelength tunable laser according to claim 2, wherein the structures of the gratings of the plurality of coupling regions are different from each other. 5. The tunable laser according to claim 2, wherein the depths of the gratings of the plurality of coupling regions are different from each other. 6. The wavelength tunable laser according to claim 2, wherein the grating periods of the plurality of coupling regions are different from each other. 7. The wavelength tunable laser according to claim 2, wherein the recesses and the projections of the plurality of coupling regions have different length ratios. 8. The tunable laser according to claim 2, wherein the shapes of the gratings of the plurality of coupling regions are different from each other. 9. The wavelength tunable laser according to claim 1, wherein a reflecting mirror is disposed in either one of the first waveguide and the second waveguide. 10. The wavelength tunable laser according to claim 1, wherein an absorption region for absorbing propagating light is arranged in a part of the first waveguide and the second waveguide. 11. A first waveguide, a second waveguide, and an optical wave of a specific wavelength propagating in any one of the first waveguide and the second waveguide. A plurality of coupling regions provided so as to be coupled to one of the waveguides, a structure capable of changing the coupling wavelength of the plurality of coupling regions, and the first waveguide or the second waveguide A wavelength tunable filter having a waveguide isolation region arranged in one of the waveguides. 12. The coupling region is formed of a grating, respectively.
The tunable filter described. 13. The structure of the gratings of the plurality of coupling regions is the same as each other.
The tunable filter described. 14. The tunable filter according to claim 12, wherein structures of the gratings of the plurality of coupling regions are different from each other. 15. The wavelength tunable filter according to claim 12, wherein the depths of the gratings of the plurality of coupling regions are different from each other. 16. The wavelength tunable filter according to claim 12, wherein the periods of the gratings of the plurality of coupling regions are different from each other. 17. The wavelength tunable filter according to claim 12, wherein the concave portions and the convex portions of the grating of the plurality of coupling regions have different length ratios. 18. The wavelength tunable filter according to claim 12, wherein the shapes of the gratings of the plurality of coupling regions are different from each other. 19. The wavelength tunable filter according to claim 11, wherein at least one of the first waveguide and the second waveguide is bent. 20. The wavelength tunable filter according to claim 11, wherein an absorption region for absorbing propagating light is arranged in a part of the first waveguide and the second waveguide. 21. A first waveguide, a second waveguide, and an optical wave of a specific wavelength propagating in any one of the first waveguide and the second waveguide. A plurality of coupling regions provided so as to be coupled to one of the waveguides, a structure capable of changing the coupling wavelength of the plurality of coupling regions, and the first waveguide or the second waveguide A wavelength selective detector comprising: a waveguide separation region arranged in one of the waveguides; and a structure for absorbing and detecting light of wavelengths coupled to a plurality of coupling regions. 22. The plurality of coupling regions are each formed by a grating.
The wavelength selective detector described. 23. The grating structures of the plurality of coupling regions are the same as each other.
The wavelength selective detector described. 24. The wavelength selective detector according to claim 22, wherein the structures of the gratings of the plurality of coupling regions are different from each other. 25. The wavelength selective detector according to claim 22, wherein the grating depths of the plurality of coupling regions are different from each other. 26. The wavelength selective detector according to claim 22, wherein the grating periods of the plurality of coupling regions are different from each other. 27. The wavelength selective detector according to claim 22, wherein the ratios of the lengths of the concave portion and the convex portion of the grating of the plurality of coupling regions are different from each other. 28. The wavelength selective detector according to claim 22, wherein the shapes of the gratings of the plurality of coupling regions are different from each other. 29. The wavelength selective detector according to claim 21, wherein at least one of the first waveguide and the second waveguide is bent. 30. The wavelength selective detector according to claim 21, wherein an absorption region for absorbing propagating light is arranged in a part of the first waveguide and the second waveguide. 31. A plurality of waveguides, a plurality of coupling regions provided so as to couple an optical wave of a specific wavelength propagating through any one of the waveguides to another waveguide, and any one of the waveguides. The active region arranged so as to be coupled to each other, the reflective portion formed on the end face where the light waves of the wavelengths coupled to each other in the plurality of coupling regions resonate and having a higher reflectance than the other end face, and the plurality of coupling regions are coupled to each other. A wavelength tunable laser having a structure capable of changing a wavelength. 32. A plurality of waveguides, a plurality of coupling regions provided to couple an optical wave of a specific wavelength propagating through any one of the waveguides to another waveguide, and the plurality of coupling regions. A wavelength tunable filter having a structure capable of changing wavelengths to be coupled and a waveguide separation region arranged in any of the waveguides. 33. A plurality of waveguides, a plurality of coupling regions provided to couple an optical wave of a specific wavelength propagating through any one of the waveguides to another waveguide, and the plurality of coupling regions. A structure capable of changing the wavelength to be coupled, a waveguide separation region arranged in any of the waveguides, and a structure for absorbing and detecting light of wavelengths coupled to a plurality of coupling regions, Selective wavelength detector.