JP2011198903A - Method and device for controlling wavelength-variable laser array element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of controlling a wavelength-variable laser array element for improving wavelength stability, by suppressing a wavelength drift because of thermal fluctuation caused by a current change in a wavelength change, without adding any special structure, even if an interval of the wavelength-variable laser array is relatively wide.SOLUTION: In a control unit of a wavelength-variable laser array element where a plurality of DFB lasers are disposed in parallel, current is allowed to flow to a control region 23 of a DFB laser operating next after the operating DFB laser during operation of an arbitrary DFB laser from among a plurality of DFB lasers. Then, a current amount I allowed to flow to the control region 23 of the DFB laser to be operated next is controlled within a range where the current amount I becomes larger than a control current amount Iunder operation conditions of the DFB laser to be operated next and smaller than a total current amount I.

Description

  The present invention relates to a control method and a control apparatus for a wavelength tunable laser array element used as a light source for optical fiber communication and a light source for optical measurement, and in particular, covers a light source for optical wavelength (frequency) multiplexing system in optical communication and a broadband wavelength band. The present invention relates to a wavelength control method and a control device for an optical measurement light source.

  In a wavelength division multiplexing communication system in optical fiber communication, laser beams having a plurality of different frequencies (wavelengths) are transmitted through a single optical fiber at intervals determined by a standard. Each frequency is called a channel, and a wavelength tunable laser capable of switching the oscillation frequency at high speed is required for high-speed channel switching.

In communication lasers, lasers that oscillate at a single wavelength, called single-mode lasers, are used, and in order to obtain a single mode, for example, a diffraction grating with periodic irregularities in a waveguide is used. ing. The semiconductor optical waveguide in which the diffraction grating is formed serves as a distributed reflector (DBR) that selectively reflects at a Bragg wavelength λ _B determined by the period Λ of the diffraction grating and the equivalent refractive index n of the optical waveguide. The relationship between λ _B and Λ, n is expressed by the following equation (1).

  A laser manufactured by giving a gain to a distributed reflector is called a distributed feedback (DFB) laser.

  From the above formula (1), it can be seen that the Bragg wavelength can be changed by changing the equivalent refractive index n of the distributed reflector. In other words, the wavelength that can be selectively reflected can be changed, and if a resonator using a distributed reflector is configured, it is possible to configure a wavelength tunable laser that can change the oscillation wavelength by changing the equivalent refractive index. It becomes. As a wavelength tunable laser using a diffraction grating, a DBR laser using a uniform diffraction grating DBR, an SG (Sampled Grating) -DBR laser, an SSG (Super Structure Grating) -DBR laser, and the like are known.

  There is also a distributed active (TDA-) DFB laser capable of continuously changing the wavelength. Here, FIG. 8 shows a cross section of the basic structure of the distributed active DFB laser. As shown in FIG. 8, in the distributed active DFB laser, the active waveguide layer 102 and the inactive waveguide layer (wavelength control region) 103 are alternately cycled at constant lengths La and Lt on the lower clad 101, respectively. As a result, the structure is cascaded. An upper cladding 104 is formed on the active waveguide layer 102 and the inactive waveguide layer 103, and unevenness, that is, a diffraction grating 105 is formed between the active waveguide layer 102 and the inactive waveguide layer 103 and the upper cladding 104. Is formed. Furthermore, an active region electrode 106 and a wavelength control region electrode 107 are provided on the upper clad 104 corresponding to the active waveguide layer 102 and the inactive waveguide layer 103, respectively. A common electrode 108 is provided below the lower clad 101. This distributed active DFB laser emits light and gains by injecting a current Ia into the active waveguide layer 102. A diffraction grating 105 is formed in each waveguide, and the period of the diffraction grating 105 is increased. Only the corresponding wavelength is selectively reflected to cause laser oscillation. On the other hand, since the refractive index is changed by the plasma effect according to the carrier density by injecting the current It into the inactive waveguide layer 103, the optical period of the diffraction grating of the inactive waveguide changes. The equivalent refractive index of the inactive waveguide layer changes, and the resonant longitudinal mode wavelength is shifted to the short wavelength side by the ratio of the length of the wavelength control region to the length of one period. If the active region length is La and the wavelength control region length is Lt, the length of one cycle of the repetitive structure is La + Lt, and the change rate Δλr / λr of the resonance longitudinal mode wavelength is expressed by the following equation (2) It becomes.

  On the other hand, each wavelength of the plurality of reflection peaks is also shifted to the short wavelength side as a result of a change in equivalent refractive index due to current injection. Since the reflection peak wavelength is proportional to the average equivalent refractive index change within one cycle of the repetitive structure, the change ratio Δλs / λs of the reflection peak wavelength is expressed by the following equation (3).

  From the equations (2) and (3), the reflection peak wavelength and the resonance longitudinal mode wavelength are shifted by the same amount. Therefore, in this laser, the wavelength continuously changes while maintaining the first oscillation mode.

  In addition, even in the case of a ring resonator having an optical waveguide in a ring shape, the resonance wavelength is determined by the optical length, which is the product of the physical length of the ring and the equivalent refractive index. It is known that

  As a method for dynamically changing the equivalent refractive index of the semiconductor, there are a method for changing the temperature, a method for changing the semiconductor by an electric current injection, and the like. The change in refractive index with temperature is relatively slow and takes several seconds to stabilize. On the other hand, it is known that the refractive index change due to current injection is caused by the plasma effect and the like, and the refractive index change occurs in a few nanoseconds.

  However, in general, in a semiconductor, heat is generated due to a resistance component when a current flows. When the channel is switched, the amount of heat generated is changed by changing the amount of wavelength control current, so that the temperature of the semiconductor laser chip changes. However, since the refractive index changes due to current injection and at the same time, the refractive index changes slowly due to the temperature change, a shift of about several GHz to several tens GHz occurs compared to the set frequency immediately after the channel switching, and the set frequency is slow. The drift phenomenon of approaching This drift phenomenon is caused by a thermal factor and takes several milliseconds or more. Therefore, it is necessary to suppress the thermal drift phenomenon in order to sufficiently exhibit the high speed of the plasma effect by current injection.

  In Patent Documents 1, 2, and 3, in order to suppress wavelength drift due to heat of the wavelength tunable laser, an electrode for thermal compensation is prepared adjacent to the wavelength control region of the wavelength tunable laser, and the current of the control layer changes. Thermal compensation is performed by changing the current flowing through the electrode for thermal compensation in accordance with the timing.

  In Patent Document 3, the sum of input power is always constant in an element in which six wavelength tunable lasers (LDs) are arranged in parallel at intervals of 20 μm and a coupler (coupler) and a semiconductor optical amplifier (SOA) are integrated. Thus, a method is shown in which a current is passed through the control region of the LD other than the light emitting LD so that the heat quantity of the entire chip becomes constant.

Japanese Patent No. 3168855 Japanese Patent No. 3257185 JP 2008-218947 A

  In the current-controlled wavelength tunable laser, it is necessary to provide an electrode for thermal compensation in parallel with the laser in order to suppress thermal drift. In the case of a wavelength tunable laser array in which a plurality of wavelength tunable lasers are arranged in parallel, it is possible to apply current to the control layer of the wavelength tunable laser other than the oscillating wavelength tunable laser to compensate for heat. It was necessary to make the interval close to about 20 μm.

  However, in the case of various DBR lasers, distributed active DFB lasers, and the like, a current to the active waveguide layer that causes gain and a current to the inactive waveguide layer for controlling the wavelength are required. , A space for routing is required. In particular, in a distributed active DFB laser, active waveguides and inactive waveguides are arranged alternately, and electrodes are connected to each other between the active waveguides and the inactive waveguides. Therefore, it is very difficult to bring the electrode to one side. Therefore, it is difficult to provide an electrode for heat compensation in the vicinity of the laser or to narrow the laser interval of the laser array.

  In view of the above, the present invention has been made to solve the above-described problems. Even when the laser interval of the wavelength tunable laser array is relatively wide, wavelength switching can be performed without adding a special structure. It is an object of the present invention to provide a control method and a control apparatus for a wavelength tunable laser array element that suppresses wavelength drift due to thermal fluctuation caused by current change and improves wavelength stability.

A control method of a wavelength tunable laser array element according to the first invention for solving the above-described problem is as follows.
A control method of a wavelength tunable laser array element in which a plurality of current control type wavelength tunable semiconductor lasers having a control region through which a heat compensation current flows are arranged in parallel,
During operation of an arbitrary wavelength tunable semiconductor laser among the plurality of wavelength tunable semiconductor lasers, a current is passed through a control region of the wavelength tunable semiconductor laser that operates next to the wavelength tunable semiconductor laser in operation,
The current I flowing through the control region of the wavelength tunable semiconductor laser operating in the following, greater than the control current amount I _t at the operating conditions of the wavelength tunable semiconductor laser operating in the next, smaller than its total current I _all range It is controlled by.

A method for controlling a wavelength tunable laser array element according to the second invention for solving the above-described problem is as follows.
A plurality of current-controlled wavelength tunable semiconductor lasers having a control region in which a heat compensation current flows are arranged in parallel, and the interval L _LD between adjacent wavelength tunable lasers is other than the control region in which the wavelength tunable semiconductor laser constitutes a resonator. A method for controlling a wavelength tunable laser array element arranged wider than the control region size _LE from
During operation of an arbitrary wavelength tunable semiconductor laser among the plurality of wavelength tunable semiconductor lasers, a current is passed through a control region of the wavelength tunable semiconductor laser that operates next to the wavelength tunable semiconductor laser in operation,
The current I flowing through the control region of the wavelength tunable semiconductor laser operating in the following, greater than the control current amount I _t at the operating conditions of the wavelength tunable semiconductor laser operating in the next, smaller than its total current I _all range It is controlled by.

A method of controlling the wavelength tunable laser array element according to the third invention for solving the above-described problem is as follows.
A plurality of distributed active distributed feedback semiconductor lasers, which are current control type wavelength tunable semiconductor lasers having a control region in which a heat compensation current flows, are arranged in parallel, and an interval L _LD between adjacent wavelength tunable lasers is set as the wavelength tunable semiconductor laser. a method of controlling a wavelength tunable laser element array from the region other than the control area is arranged wider than the size L _E of the control region constituting the resonator Te,
During operation of an arbitrary wavelength tunable semiconductor laser among the plurality of wavelength tunable semiconductor lasers, a current is passed through a control region of the wavelength tunable semiconductor laser that operates next to the wavelength tunable semiconductor laser in operation,
The current I flowing through the control region of the wavelength tunable semiconductor laser operating in the following, greater than the control current amount I _t at the operating conditions of the wavelength tunable semiconductor laser operating in the next, smaller than its total current I _all range It is controlled by.

A method for controlling a wavelength tunable laser array element according to the fourth invention for solving the above-described problem is as follows.
A control method of a wavelength tunable laser array element according to any one of the first to third inventions,
The total current of the plurality of wavelength tunable semiconductor lasers is summed by flowing a current through the wavelength tunable semiconductor laser in operation and a control region of one of the wavelength tunable semiconductor lasers other than the wavelength tunable semiconductor laser that operates next. The amount or the total amount of the total power is controlled to be the same before and after switching from the operating wavelength tunable semiconductor laser to the next operating wavelength tunable semiconductor laser.

A method for controlling a wavelength tunable laser array element according to a fifth invention for solving the above-described problem is as follows.
A method of controlling a wavelength tunable laser array element according to a fourth invention,
A total amount of all currents of the plurality of wavelength tunable semiconductor lasers, or a total amount of total power thereof is stored using a control region of the wavelength tunable semiconductor laser that is not adjacent to the wavelength tunable semiconductor laser to be operated next. To do.

A method for controlling a wavelength tunable laser array element according to a sixth invention for solving the above-described problem is as follows.
A control method of a wavelength tunable laser array element according to any one of the first to fifth inventions,
And a light control element that is integrated on the same semiconductor substrate as the plurality of wavelength tunable semiconductor laser elements, is connected to laser light oscillated from the plurality of wavelength tunable semiconductor lasers, and controls the laser light according to an injection current. ,
The current amount or power amount of the control region of the wavelength tunable semiconductor laser that is not operating is changed in accordance with the current change amount or power change amount of the injection current to the light control element.
Examples of the light control element include a light blocking element, a phase control element, and an optical switch.

In addition, a control device for a wavelength tunable laser array element according to a seventh invention for solving the above-described problem is as follows.
A control device for a wavelength tunable laser array element in which a plurality of current control type wavelength tunable semiconductor lasers having a control region through which a heat compensation current flows are arranged in parallel,
During operation of an arbitrary wavelength tunable semiconductor laser among the plurality of wavelength tunable semiconductor lasers, a current is passed through a control region of the wavelength tunable semiconductor laser that operates next to the wavelength tunable semiconductor laser in operation,
The current I flowing through the control region of the wavelength tunable semiconductor laser operating in the following, greater than the control current amount I _t at the operating conditions of the wavelength tunable semiconductor laser operating in the next, smaller than its total current I _all range And a first thermal compensation control unit that is controlled in step (1).

A control apparatus for a wavelength tunable laser array element according to an eighth aspect of the present invention for solving the above-described problem,
A control device for a wavelength tunable laser array element according to a seventh invention,
By passing a current through the wavelength tunable semiconductor laser in operation and a control region of any one of the wavelength tunable semiconductor lasers other than the wavelength tunable semiconductor laser that operates next,
A total amount of all currents of the plurality of wavelength tunable semiconductor lasers or a total amount of the total power thereof is controlled in the same manner before and after switching from the wavelength tunable semiconductor laser in operation to the wavelength tunable semiconductor laser to be operated next; A heat compensation control unit is further provided.

A control apparatus for a wavelength tunable laser array element according to a ninth invention for solving the above-described problems is as follows.
A control device for a wavelength tunable laser array element according to a seventh or eighth invention,
A light control element integrated on the same semiconductor substrate as the plurality of wavelength tunable semiconductor lasers, connected to laser light oscillated from the plurality of wavelength tunable semiconductor lasers, and controlling the laser light according to an injection current;
A third thermal compensation control unit that changes the current amount or power amount of the control region of the wavelength tunable semiconductor laser that is not operating in accordance with the current change amount or power change amount of the injection current to the light control element; It is characterized by that.

  As described above, according to the present invention, it is possible to suppress a change in the amount of heat generated by a current change for controlling the wavelength without adding a special structure to the wavelength tunable laser array, and to stabilize the oscillation wavelength. Can be

It is a figure which shows an example of the wavelength variable laser array element controlled by the control apparatus of the wavelength variable laser array element which concerns on 1st embodiment of this invention. It is a figure for demonstrating the structure of the distributed active DFB laser which a wavelength tunable laser array element comprises, Comprising: The upper surface is shown to Fig.2 (a), and the cross section is shown in FIG.2 (b). It is sectional drawing of the III-III line in FIG. FIG. 4A is a graph showing the characteristics of the oscillation frequency immediately after switching when the wavelength is switched in the same distributed active DFB laser in the wavelength tunable laser array element, and FIG. 4A shows the case where there is no compensation current. (B) shows a case where there is a compensation current. FIG. 5A is a graph showing the characteristics of the oscillation frequency immediately after switching between different distributed active DFB lasers in a wavelength tunable laser array element, and FIG. 5A shows a case where there is no compensation current. FIG. 5B shows a case where there is a compensation current, and FIG. 5C shows a case where there is a thermal compensation current and a local thermal compensation current. It is a figure for demonstrating an example of the structure of the DBR type | mold wavelength tunable semiconductor laser controlled with the control apparatus of the wavelength tunable laser array element which concerns on 2nd embodiment of this invention. It is a figure explaining other examples of the structure of a DBR type tunable semiconductor laser. It is a figure for demonstrating the structure of a distributed active DFB laser.

  A control method and a control apparatus for a tunable laser array element according to the present invention will be specifically described in each embodiment.

[First embodiment]
A wavelength tunable laser array element control method and control apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

A wavelength tunable laser array element (wavelength tunable laser array, optical integrated element) 10 according to the present embodiment is provided on the same substrate as shown in FIG. 6-channel distributed active DFB laser array (LD section) 11 composed of six distributed active DFB lasers (wavelength variable semiconductor lasers, LD1 to LD6) 11a to 11f and waveguides 12a through which their output lights are respectively guided. A multi-mode interferometer (MMI) coupler (coupler) 13 that is an optical coupler for combining the output light guided through the waveguide section 12 into one, It is composed of a semiconductor optical amplifier (SOA) 14 that adjusts the intensity of output light at the final stage. The six distributed active DFB lasers 11a to 11f are arranged in parallel with an interval L _LD between adjacent distributed active DFB lasers of 60 μm. Further, the above-described wavelength tunable laser array element 10 is provided with a control device 15. Controller 15, a current I which then flows to the control region of the wavelength tunable semiconductor laser operating, greater than the control current amount I _t at the operating conditions of the wavelength tunable semiconductor laser operating in the next, the total current I _all The wavelength at which the first thermal compensation control unit that controls in a smaller range, the total amount of the total currents of the plurality of wavelength tunable semiconductor lasers, or the total amount of the total power thereof is operated next from the operating wavelength tunable semiconductor laser. The second thermal compensation control unit that controls the same before and after switching to the tunable semiconductor laser, the control region of the wavelength tunable semiconductor laser that is not operating according to the current change amount or the power change amount of the injection current to the light control element A third thermal compensation controller that changes the amount of current or the amount of power is provided. The control device 15 controls the current or power supplied to the active region electrodes and the control region electrodes, which will be described later, of the six distributed active DFB lasers (LD1 to LD6) by the control method described later.

  First, the basic structure of the distributed active DFB laser integrated in the 6-channel distributed active DFB laser array 11 will be described.

As shown in FIG. 2B, the distributed active DFB laser is composed of a first laser part A ₁ , a phase shift region 20 and a second laser part A ₂ , which are connected in series in this order from the right in the figure. It is a thing.

In the first laser part A ₁ , an active element having an optical gain with respect to the oscillation wavelength band and having a length La _{1 made} of GaInAsP formed on a lower clad (semiconductor substrate) 21 made of n-type InP. A waveguide layer (active region, active layer) 22 _a1 and a non-active waveguide layer (inactive region, having a length L _{t1 made} of GaInAsP having no optical gain and having a composition different from that of the active waveguide layer 22 _a1 . (Wavelength control region, control layer) 23 _t1 has a periodic structure in which a plurality of layers are alternately and repeatedly connected in a cycle L ₁ along the light propagation direction.

In the second laser part A ₂ , an active element having an optical gain with respect to the oscillation wavelength band and having a length La _{2 made} of GaInAsP, which is formed on the lower clad (semiconductor substrate) 21 made of n-type InP. A waveguide layer (active region, active layer) 22 _a2 and a non-active waveguide layer having a length L _{t2 made} of GaInAsP having no optical gain and having a composition different from that of the active waveguide layer 22 _a2 (inactive region, (Wavelength control layer, control layer) 23 _t2 has a periodic structure in which a plurality of layers are alternately connected in a cycle of L ₂ along the light propagation direction.

Further, as shown in FIG. 3, InP is doped with Fe on both sides of the active waveguide layer 22 (22 _a1 , 22 _a2 ) and the inactive waveguide layer 23 (23 _t1 , 23 _t2 ) to increase resistance. A current blocking layer 24 made of is formed.

An upper cladding 25 made of p-type InP is formed on these layers 22 _a1 , 23 _t1 , 22 _a2 , and 23 _t2 as shown in FIGS. 2B and 3, and these layers 22 _a1 , 23 _t1 are formed. , 22 _a2 , 23 _t2 and the upper cladding 25 are formed with a diffraction grating 26 in which periodic irregularities are formed and the equivalent refractive index of the waveguide is periodically modulated. In the phase shift region 20, a phase shift unit 27 that forms the phase of the diffraction grating λ / 4 phase is formed on the lower clad 21 made of n-type InP, and the upper clad 25 made of p-type InP is formed on the phase shift unit 27. Is formed. As a result, the λ / 4 phases of the diffraction gratings 26 of the first laser part A ₁ and the second laser part A ₂ are shifted.

Further, a contact layer 28 made of highly doped p-type InGaAs is provided on the upper cladding 25 for ohmic contact, and an active region electrode 29 and a wavelength control region electrode 30 are formed on the contact layer 28. . By separating the contact layer 28 into two corresponding to the active region electrode 29 and the wavelength control region electrode 30, the active region electrode 29 and the wavelength control region electrode 30 can inject current independently of each other. . As an active region electrode 29, over the region of the active layer waveguide layer 22 _a1, 22 _a2 corresponding to the regions it provided active region electrode 29 _a1, 29 _a2, respectively, all the active region electrode 29 _a1, 29 _a2 The two are short-circuited on each other. As the wavelength control region electrode 30, wavelength control region electrodes 30 _t1 and 30 _t2 are provided above the regions of the inactive waveguide layers 23 _t1 and 23 _t2 corresponding to these regions, respectively, and all the wavelength control region electrodes 30 _t1 are provided. , 30 _t2 are short-circuited on each other. A common lower electrode 31 is formed below the lower clad 21. Since the electrodes are short-circuited on the element, the contact layer 28 is formed only in the region above the active layer region 22 in the lower layer of the active region electrode 29 (the electrode width of FIG. 2A is wide). (Part), an insulating layer 32 is formed in a region above the inactive waveguide layer 23 (refer to FIG. 3 where the electrode width is narrow in FIG. 2A). Similarly, the contact layer 28 is provided only in the region above the inactive waveguide layer 23 in the lower layer of the wavelength control region electrode 30 so that the wavelength control region electrode 30 can inject current only into the inactive waveguide layer 23. An insulating layer 32 is formed in a region above the active waveguide layer 22 (a portion with a narrow electrode width in FIG. 2A, FIG. 3). reference).

When GaInAsP having a band gap wavelength of 1.55 μm is used as the active waveguide layer 22 (22 _a1 , 22 _a2 ), the inactive waveguide layer 23 (23 _t1 , 23 _t2 ) has a shorter band gap wavelength, for example, By using GaInAsP having a band gap wavelength of 1.4 μm, the carrier density does not become constant because it does not contribute to the laser oscillation gain. Thereby, the refractive index can be changed greatly by current injection.

  The active waveguide layer 22 and the inactive waveguide layer 23 do not have to be bulk materials. For example, a quantum well structure, a multilayer quantum well structure in which quantum wells are sandwiched between barrier layers, or a lower-dimensional quantum well It may have a structure. Further, in order to enhance light confinement and carrier confinement in the active layer, a separate confinement heterostructure in which a layer having an intermediate refractive index is introduced between the active layer and the cladding layer may be introduced.

  The semiconductor used in this element is not limited to the combination of InP and GaInAsP, and other semiconductors such as GaAs, GaInNAs, and AlGaInAs may be used. The band gap between the active waveguide layer 22 and the inactive waveguide layer 23 may be used. The combination of wavelengths is not limited to the above.

In the first laser part A ₁ and the second laser part A ₂ , the repetition periods of the active waveguide layer 22 and the inactive waveguide layer 23 are different from L ₁ = 50 μm and L ₂ = 70 μm, respectively. The ratio of the waveguide layer 22 and the inactive waveguide layer 23 (L _a1 / L _t1 and L _a2 / L _t2 ) is the same. In this embodiment, this ratio is set to 1/2. Between the first laser part A ₁ and the second laser part A ₂ , the phase of the diffraction grating 26 is changed by λ / 4 wavelength. Thereby, the phases of the reflected wave at the first laser part A ₁ and the reflected wave at the second laser part A ₂ are matched so as to satisfy the oscillation condition.

The active region electrode 29 and the wavelength control region electrode 30 provided on the active waveguide layer 22 and the wavelength control non-active waveguide layer 23 are separated from each other. As shown in FIG. The active region electrodes 29 _a1 and 29 _a2 on the waveguide layer 22 and the wavelength control region electrodes 30 _t1 and 30 _t2 on the inactive waveguide layer 23 are short-circuited on the element, and have a comb-like electrode shape. Yes. By short-circuiting the electrodes in each region on the element in this way, it is possible to inject current into each region by simply bonding a metal bonding wire one by one.

Here, a method for manufacturing the distributed active DFB laser having the above-described configuration will be briefly described.
(1) First, an active waveguide layer (active layer) 22 (22 _a1 , 22 _a2 ) is not formed on the lower cladding 21 made of n-type InP by using a metal organic vapor phase epitaxial growth method and a selective growth method thereby. An active waveguide layer (wavelength control layer) 23 (23 _t1 , 23 _t2 ) is produced.
(2) Thereafter, the pattern of the diffraction grating 26 is transferred to the applied resist by using an electron beam exposure method, and etching is performed using the transfer pattern as a mask to form the diffraction grating 26.
(3) Next, after growing the upper clad 25 made of p-type InP and the contact layer 28 made of p-type InGaAs, in order to control the transverse mode, the waveguide is processed into a stripe shape having a width of 1.2 μm, A current blocking layer 24 made of InP (semi-insulator) doped with Fe is grown on both sides thereof.
(4) After forming the active region electrode 29 and the wavelength control region electrode 30, in order to electrically separate the active region electrode 29 for driving the active layer and the wavelength control region electrode 30 for wavelength control, The contact layer 28 between the electrodes is removed.
Before the active region electrode 29 is formed, the region above the active waveguide layer 22 is formed so that the electrodes are short-circuited on the element and the active region electrode 29 can inject current only into the active waveguide layer 22. The contact layer 28 is formed on the insulating layer 32 in the region above the non-active waveguide layer 23, and the active region electrode 29 is formed on the insulating layer 32. Similarly, before the wavelength control region electrode 30 is formed, the electrodes are short-circuited on the element and the wavelength control region electrode 30 can inject current only into the inactive waveguide layer 23. A contact layer 28 is formed in a region above 23, an insulating layer 32 is formed in a region above the active waveguide layer 22, and a wavelength control region electrode 30 is formed in an upper layer thereof. Thereafter, a lower electrode 31 is formed below the lower cladding 21.

  The semiconductor growth method is not limited to the metal organic vapor phase epitaxial growth method, and a molecular beam epitaxial growth method or other means may be used. The method of forming the diffraction grating is not limited to the electron beam exposure method, and a two-bundle interference exposure method or other means may be used.

  The current blocking layer 24 is not limited to an InP layer doped with Fe, but may be an InP layer doped with another dopant such as Ru to increase the resistance. Alternatively, a multilayer structure in which p-type semiconductors and n-type semiconductors are alternately stacked may be used.

  The waveguide structure employs a buried structure in this embodiment, but the principle of the present invention can also be used in a general ridge structure or high mesa structure.

In the present embodiment, the number of repetitions of the active waveguide layer 22 and the inactive waveguide layer 23 in each of the first laser part A ₁ and the second laser part A ₂ is six. Since the first laser part A ₁ and the second laser part A ₂ use the diffraction grating 26 having the same coupling coefficient, the second laser having a long repetition period of the active waveguide layer 22 and the inactive waveguide layer 23 is used. reflectivity for better parts a ₂ becomes larger the coupling coefficient and the product of length increases. Therefore, when the number of repetitions is the same, the output is naturally asymmetric, and the output from the first laser unit A ₁ having a low reflectivity is larger than the output from the second laser unit A ₂ having a high reflectivity. Therefore, the output can be efficiently extracted from the first laser part A ₁ side. Note that the number of repetitions of the active waveguide layer 22 and the inactive waveguide layer 23 is not limited to 6, and the number of repetitions does not have to be the same in the first laser part A ₁ and the second laser part A _2. Therefore, the repetition period and the number of repetitions may be designed according to the required reflectance.

In the wavelength tunable semiconductor laser according to the present embodiment, laser light oscillates by passing a current between the active region electrode 29 and the lower electrode 31 shown in FIGS. 2 (a) and 2 (b). The oscillation wavelength at this time is determined by the diffraction grating 26 of the first laser part A ₁ and the second laser part A ₂ shown in FIG. In addition, by injecting current into the wavelength control region electrode 30 shown in FIGS. 2A and 2B, the equivalent refractive index of the inactive waveguide layer 23 changes, and the resonant longitudinal mode wavelength becomes shorter. Accordingly, the oscillation wavelength is also shifted to the short wavelength side. At this time, as will be described later, in addition to the wavelength tunable laser in operation, power is supplied to the control region of the wavelength tunable laser that operates next to the wavelength tunable laser in operation, or after the wavelength tunable laser in operation. Control was performed such that power was applied to the control region of the wavelength tunable laser that is not adjacent to the wavelength tunable laser that operates at the same time.

<Control method>
In the wavelength tunable laser array, there are two patterns when changing the channel. In the first case, the oscillating LD is the same, and the channel is changed only by the change of the wavelength control current It. The second is a case where a channel is switched between different LDs.

  In the case of channel switching within the same LD, the active layer current Ia is kept substantially constant, and the oscillation wavelength changes only with the control current It. For example, consider switching from channel 1 of Ia = 75 mA, It = 1.56 mA to channel 2 of Ia = 75 mA, It = 52.3 mA in LD1. In this case, channel 1 and channel 2 have a difference of about 50 mA in total current. If the total calorific value is constant between the two channels, wavelength temperature drift does not occur, and wavelength switching without error in a few ns determined purely by the plasma effect of the carrier or the like is possible. Therefore, a current is passed through the wavelength control region of LD 2 that is not used in channel 1 and channel 2. More strictly, it is necessary to measure the voltage or the like and control the input power to be constant. However, simply, the wavelength control current of the LD 2 is set as the thermal compensation current, and the channel 1 is operated at 52.3 mA and the channel 2. In operation, 1.56 mA, which is the opposite of the wavelength control current of the LD 1, flows to the current, so that the total current amount can be made constant and the heat generation amount can be made almost constant. As a result, the chip temperature change can be suppressed, and the refractive index change due to the temperature change can be suppressed.

  Here, FIG. 4 shows the result of measuring the oscillation frequency deviation immediately after the switching when the channel 1 and the channel 2 are switched at a cycle of 100 ms in the LD 1. The horizontal axis in FIG. 4 indicates time and is 0 when switching. The vertical axis in FIG. 4 indicates the deviation of the oscillation frequency from the frequency during continuous operation. That is, the frequency when operated continuously under the operating condition of channel 2 is set to zero. FIG. 4A shows the result of switching when the thermal compensation current of LD2 is not used, and FIG. 4B shows the result of switching when the thermal compensation current of LD2 is used. When the thermal compensation current is not used, as shown in FIG. 4 (a), the deviation from the set frequency (frequency during continuous operation) is 5 GHz or more, and a time of 2 ms or more until the frequency deviation is within 1 GHz. However, by using the thermal compensation current, as shown in FIG. 4B, the frequency deviation can be suppressed to about 2 GHz or less, and the frequency deviation within 1 GHz can be reached in 0.2 ms or less. The switching time has been improved by an order of magnitude.

  In order to stabilize the chip temperature, it is not always necessary to use an adjacent LD, and an amount of current flowing through LD2 is input to another LD (for example, LD3, LD4, LD5, or LD6) as necessary ( Distribution).

  On the other hand, in the case of channel switching between different LDs, both the active layer current Ia and the wavelength control current It change. For example, when switching from channel 3 operating at LD6 Ia = 75 mA and It = 1.14 mA to channel 4 operating at LD5 Ia = 75 mA and It = 17.47 mA, the change in the amount of current in the entire chip Is 16.33 mA, which is smaller than the above-described channel switching in the same LD. However, since the current change in the LD also includes the change in the active layer current Ia, the current of 76.14 mA in LD6 and 92.47 mA in LD5 are locally switched. In general, in order to obtain a stable oscillation operation, the active layer current Ia is often made larger than the wavelength control current It. In the channel switching between the LDs, the total value of the active layer current Ia and the wavelength control current It is switched at a time. Therefore, even if the input power of the entire chip is constant using the compensation current, It will be a big fluctuation. For example, if only the total current amount is to be constant, the wavelength control current It may simply be kept flowing even when the channel 6 and the channel 4 are both in the LD 6 and LD 5. That is, only the active layer current Ia has to be switched from LD6 to LD5 in the channels 3 and 4. As a result, the total amount of current becomes constant, and the total heat generation amount becomes substantially constant.

  Here, FIG. 5 shows the result of measuring the oscillation frequency deviation immediately after switching when the channel 3 operating in the LD 6 and the channel 4 operating in the LD 5 are switched at a cycle of 100 ms. The horizontal axis in FIG. 5 indicates time and is 0 when switching. The vertical axis in FIG. 5 indicates the deviation of the oscillation frequency from the frequency during continuous operation. That is, the frequency when operating continuously under the operating condition of channel 4 is set to zero. FIG. 5A shows the result when switching is performed without using the thermal compensation current. As shown in FIG. 5A, a frequency shift of about 4 GHz occurs immediately after switching, and it takes 1 ms or more for the frequency shift to be within 1 GHz. FIG. 5B shows the result of the switching operation for making the total current amount simply constant, and the wavelength control current It is continuously supplied to both channels LD6 and LD5, and only the active layer current Ia is switched. As a result, the frequency shift immediately after switching is suppressed to about 2 GHz, and is shortened to about 0.3 ms to enter within 1 GHz, and the effect of the heat compensation current is obtained. In particular, the frequency shift that gradually changes after the rapid change immediately after switching is greatly improved.

  However, the wavelength shift immediately after the switching is larger than the channel switching in the same LD, and it takes time to enter the shift within 1 GHz, and it is difficult to say that the heat compensation is completely performed. This is because the total heat quantity of the chip is compensated and the average temperature of the chip is stable, but the amount of change in the amount of current in the LD is increasing. This is because it has occurred. That is, in FIG. 5B, the wavelength control current It of the LD 5 is constant and the active layer current Ia is switched. Therefore, when the current amount is viewed only by the LD 5, the current amount increases by the active layer current 75 mA. Yes. Therefore, the amount of heat generated in the LD 5 increases immediately after switching. This is also due to the LD interval. In the case where heater mesas are formed at intervals of 20 μm or less or laser arrays are formed at intervals of about 20 μm, heat is transmitted from the heater mesas and adjacent LDs so that the temperature of the operating LD is high. Compared to this, the LD interval is wide as 60 μm in this embodiment. Therefore, even if the adjacent LD is used for heat compensation, the heat generated there is not sufficiently transmitted to the operating LD. As a result, temperature distribution occurs in the chip and it takes time until the operating LD reaches a stable temperature.

  In order to solve this, the wavelength control current It of the LD that operates next to the operating LD is made to flow larger so that the LD that operates next is set to an appropriate temperature in advance. That is, a current for locally compensating for heat flows. Specifically, when channel 3 is operating, Ia = 75 mA, It = 1.14 mA through LD6, It = 65 mA through LD5, It = 2.47 mA through LD3, and when channel 4 is operating, It = 1.14 mA through LD6. LD5 was passed with Ia = 75 mA, It = 17.47 mA, and LD3 with It = 75 mA. A current was passed through the wavelength control region of the LD 3 because the total amount of current was constant. FIG. 5C shows the result. This measurement was performed with a time resolution of 40 μs, but no wavelength shift of 1 GHz or more was observed within that range. Further, as a result of experimenting by changing the amount of control current to be supplied to the LD 5 in advance, a positive frequency deviation occurs as shown in FIG. 5B when the current amount is 60 mA or less, and a negative frequency deviation occurs when the current amount is 70 mA or more. occured. The reason why local thermal compensation can be performed with a current amount lower than the total current amount of the LD 5 is due to the influence of heat from the adjacent LD. That is, it means that the distance between adjacent LDs is important, and even if the distance between adjacent LDs changes, appropriate local thermal compensation can be performed by adjusting the current amount. That is, control is performed so that the sum of the amount of heat P1 transmitted from the surroundings and the amount of heat P2 generated by itself becomes constant.

  This is simply because if the operating condition of the LD that operates next is the active layer current Ia0 and the control region current It0, the range for adjusting the current amount It of the control layer of the LD that operates next is It0 <It This can be realized by satisfying <Ia0 + It0. More specifically, the voltage Vt in the wavelength control region of the next operating LD and the active layer voltages Va0 and Vt0 under the operating conditions of the next operating LD are considered together, and Vt0 × It0 <Vt × It <Va0. What is necessary is just to make it xIa0 + Vt0xIt0.

  In the present embodiment, the current amount is described as constant for simplification of control, but more strictly, the control accuracy can be further improved by making the power constant. In addition, an important point of the present invention is that the control accuracy is further improved by appropriately using the local thermal compensation current even when the LD interval is long.

  Also, although LD3 is used to compensate for the total chip current, it is 180 μm away from LD6 and 120 μm away from LD5. It shows that it is not always necessary to use the adjacent LD for the compensation of the total chip heat quantity. Rather, the heat generated from the adjacent LD affects the amount of current for local thermal compensation. Therefore, depending on the conditions, it is often desirable to use a distant LD for compensation of the total chip heat amount.

The structure of the distributed active DFB laser used in the laser array of the present invention is not limited to the structure of the present embodiment, and the active layer and the wavelength control layer are repeated with a uniform period, or the active layer and the wavelength control layer Two or more combinations of periods may be used. In the case of the distributed active DFB laser, the active layer and the wavelength control layer are alternately arranged, and has a structure suitable for local heat compensation. Since the active region is warmed by the wavelength control regions adjacent to the front and rear in the resonator direction, the effect of local thermal compensation can be obtained if half of the active region length L _a1 or L _a2 is shorter than the laser interval. If the laser structure described in this embodiment, as shown in FIG. 2 (b), the first end surface of the laser part A ₁ has become an active waveguide layer 22 _a1, sandwiched in the control area 23 _t1 It does not have a structured structure and cannot be heated from both the front and rear sides. However, in this laser, since the active layer 22 and the control layer 23 each have six cycles in the first and second laser parts A ₁ and A ₂ , active conduction on the end face side of the first laser part A ₁ is performed. Since the proportion of the waveguide layer 22 _a1 occupies 1/12 or less of the total active waveguide layer 22 and is small, as described above, the active region 22 is formed by the control region 23 adjacent to the front and rear in the resonator direction. Since it is heated, if the half of the length L _a1 or L _a2 of the active region 22 is shorter than the laser interval, the effect of local thermal compensation can be obtained.

  In the case of a tunable laser array element, a separation groove may be formed between the lasers depending on the laser structure. In that case, even if the laser interval is narrow, the amount of heat transmitted from the adjacent lasers is smaller than when there is no separation groove. The present invention is effective even in such a case.

  In the present embodiment, as shown in FIG. 1, the configuration using a plurality of wavelength tunable semiconductor lasers LD1 to LD6, the coupler 13, and the SOA 14 has been described. However, in order to realize the present invention, at least two lasers are arranged in parallel. It only has to be arranged in. That is, the coupler 13 may not be an MMI coupler, and may be another coupler such as a funnel type. Even if the light from the semiconductor laser array is coupled by a lens without integrating the coupler 13 and the SOA 14 or the optical path is changed using MEMS (Micro Electro Mechanical Systems), the semiconductor laser array is not fully integrated. The invention can be applied.

  In the case of an integrated wavelength tunable laser array element integrated with an SOA or the like, the region through which current flows is not limited to the laser unit. For example, in order to keep the output constant, a current is also passed through the SOA, but it may be necessary to adjust the output by switching channels. In that case, the amount of heat generated by the entire chip changes because the amount of SOA current changes. In order to compensate for this, the chip temperature can be stabilized by compensating the amount of change in the current in the SOA using the control region of the wavelength tunable laser unit. In addition, even in the case where other current-carrying elements, for example, a light blocking element such as a variable attenuator, a phase control element, and a light control element that controls light output such as an optical switch are integrated, the current value is the same as that of the SOA. Can be compensated for in the control region of the tunable laser. That is, by controlling the current amount of the entire chip, more precisely, the amount of heat generation to be constant, the temperature can be stabilized and an accurate wavelength switching operation can be performed.

[Second Embodiment]
A control method and control apparatus for a wavelength tunable laser array element according to the present embodiment will be described with reference to FIGS.

  The wavelength tunable semiconductor laser used in the wavelength tunable laser array element of the first embodiment described above is a distributed active DFB laser, but can also be applied to other wavelength tunable semiconductor lasers controlled by current injection. The present invention is effective if the maximum value of the distance between the wavelength control region of the wavelength tunable semiconductor laser and the portion where the temperature is to be locally stabilized is smaller than the distance from another wavelength tunable semiconductor laser arranged in parallel. It is. In this embodiment, a case where a DBR laser is used as the wavelength tunable semiconductor laser will be described.

DBR lasers, as shown in FIG. 6, formed on the lower clad 61, the first non-active waveguide layer 63 _t1 length L _t1, the active waveguide layer 62 of length L _a, A second inactive waveguide layer 63 _t2 having a length L _t2 is cascade-connected in this order from the right in the figure. An upper clad 64 is formed on the active waveguide layer 62 and the inactive waveguide layers 63 _t1 and 63 _t2 , and periodic irregularities, that is, periodic irregularities, are formed between the layers 63 _t1 and 63 _t2 and the upper clad 64. Each diffraction grating 65 is formed. On the upper cladding 64, there are active region electrodes 66 and inactive region electrodes 67 _t1 and 67 _t2 corresponding to the active waveguide layer 62 and the first and second inactive waveguide layers 63 _t1 and 63 _t2. Each is formed. In the case of a DBR laser array in which a plurality of DBR lasers having such a configuration are integrated, the first and second inactive waveguide layers 63 _t1 and 63 _t2 that are wavelength control regions are used as local heaters. Locally, the temperature of the laser resonator only needs to be stabilized, but the active waveguide layer 62 is formed by both the first inactive waveguide layer 63 _t1 and the second inactive waveguide layer 63 _t2 at both ends. Since temperature stabilization is achieved, the non-active waveguide on one side only needs to warm half of the active waveguide layer 62. In this case, the half of the length of the active waveguide layer 62 sandwiched between the first inactive waveguide layer 63 _t1 and the second inactive waveguide layer 63 _t2 is larger than the interval L _LD between adjacent lasers. Is short (L _LD > L _a / 2), the effect as a local heater appears. Conversely, if L _LD <L _a / 2, the center portion of the active waveguide can be warmed more efficiently by using the control region of the adjacent LD as a heater.

  Also, depending on the configuration of the DBR laser, when an inactive waveguide that does not have a diffraction grating for phase adjustment is installed in the resonator, for example, between the diffraction grating formation region and the active waveguide layer Although this is also an inactive waveguide layer, it can be used as a local heater.

Moreover, as shown in FIG. 7, it is also possible to apply a DBR laser having one side as an end face mirror. DBR lasers, as shown in FIG. 7, formed on the lower clad 71, an active waveguide layer 72 of length L _a, and the inactive waveguide layer 73 of length L _t1, from the left in the drawing The structure is cascaded in this order. An upper clad 74 is formed on the active waveguide layer 72 and the non-active waveguide layer 73, and periodic unevenness, that is, a diffraction grating 75 is formed between the layer 73 and the upper clad 74. . An active region electrode 76 and an inactive region electrode 77 are formed on the upper clad 74 corresponding to the active waveguide layer 72 and the inactive waveguide layer 73, respectively. The DBR laser having such a structure, it is impossible to warm from both sides of the active waveguide layer 72 with respect to the direction of the resonator, in the case of L _LD> L _a, it appears effective as a topical heater. That is, it is only necessary that the distance from the control region used for heat compensation to the location where heat is to be locally applied is shorter than the array interval of the wavelength tunable laser array. In this way, it is possible to determine whether or not the present invention can be applied not only to the DBR laser but also to other current injection type tunable semiconductor lasers.

  According to the control method and control device for a wavelength tunable laser array element according to the present invention, even when the laser interval of the wavelength tunable laser array is relatively wide, the current change at the time of wavelength switching can be achieved without adding a special structure. Since the wavelength drift due to the resulting thermal fluctuation can be suppressed and the wavelength stability can be enhanced, it can be used effectively in the communication industry and the like.

DESCRIPTION OF SYMBOLS 10 Wavelength variable laser array element 11 LD part 12 Waveguide part 13 Multimode interference coupler 14 Semiconductor optical amplifier (SOA)
15 Control device 20 Phase shift region 21 Lower cladding 22 Active waveguide layer 23 Inactive waveguide layer (wavelength control region)
24 Current blocking layer 25 Upper clad 26 Diffraction grating 27 Phase shift part 28 Contact layer 29 Active region electrode 30 Wavelength control region electrode 31 Lower electrode 32 Insulating layer 33 Core layer 61 Lower clad 62 Active waveguide layer 63 Inactive waveguide layer 64 Upper cladding 65 Diffraction grating 66 Active region electrode 67 Inactive region electrode 68 Lower electrode 71 Lower cladding 72 Active waveguide layer 73 Inactive waveguide layer 74 Upper cladding 75 Diffraction grating 76 Active region electrode 77 Inactive region electrode 78 Lower electrode

Claims (9)

A control method of a wavelength tunable laser array element in which a plurality of current control type wavelength tunable semiconductor lasers having a control region through which a heat compensation current flows are arranged in parallel,
During operation of an arbitrary wavelength tunable semiconductor laser among the plurality of wavelength tunable semiconductor lasers, a current is passed through a control region of the wavelength tunable semiconductor laser that operates next to the wavelength tunable semiconductor laser in operation,
The current I flowing through the control region of the wavelength tunable semiconductor laser operating in the following, greater than the control current amount I _t at the operating conditions of the wavelength tunable semiconductor laser operating in the next, smaller than its total current I _all range A method for controlling a wavelength tunable laser array element, wherein A control region in which a plurality of current-controlled wavelength tunable semiconductor lasers having a control region in which a thermal compensation current flows are arranged in parallel, and the interval L _LD between adjacent wavelength tunable semiconductor lasers constitutes a resonator with the wavelength tunable semiconductor laser A method for controlling a wavelength tunable laser array element arranged from a region other than the region _LE larger than the size LE of the control region,
During operation of an arbitrary wavelength tunable semiconductor laser among the plurality of wavelength tunable semiconductor lasers, a current is passed through a control region of the wavelength tunable semiconductor laser that operates next to the wavelength tunable semiconductor laser in operation,
The current I flowing through the control region of the wavelength tunable semiconductor laser operating in the following, greater than the control current amount I _t at the operating conditions of the wavelength tunable semiconductor laser operating in the next, smaller than its total current I _all range A method for controlling a wavelength tunable laser array element, wherein A plurality of distributed active distributed feedback semiconductor lasers, which are current control type wavelength tunable semiconductor lasers having a control region in which a heat compensation current flows, are arranged in parallel, and an interval L _LD between adjacent wavelength tunable lasers is set as the wavelength tunable semiconductor laser. a method of controlling a wavelength tunable laser element array from the region other than the control area is arranged wider than the size L _E of the control region constituting the resonator Te,
During operation of an arbitrary wavelength tunable semiconductor laser among the plurality of wavelength tunable semiconductor lasers, a current is passed through a control region of the wavelength tunable semiconductor laser that operates next to the wavelength tunable semiconductor laser in operation,
The current I flowing through the control region of the wavelength tunable semiconductor laser operating in the following, greater than the control current amount I _t at the operating conditions of the wavelength tunable semiconductor laser operating in the next, smaller than its total current I _all range A method for controlling a wavelength tunable laser array element, wherein A method for controlling a wavelength tunable laser array element according to any one of claims 1 to 3,
The total current of the plurality of wavelength tunable semiconductor lasers is summed by flowing a current through the wavelength tunable semiconductor laser in operation and a control region of one of the wavelength tunable semiconductor lasers other than the wavelength tunable semiconductor laser that operates next. A method for controlling a wavelength tunable laser array element, wherein the amount or the total amount of the total power is controlled to be the same before and after switching from an operating wavelength tunable semiconductor laser to a next operating wavelength tunable semiconductor laser. A method for controlling a wavelength tunable laser array element according to claim 4,
A total amount of all currents of the plurality of wavelength tunable semiconductor lasers, or a total amount of total power thereof is stored using a control region of the wavelength tunable semiconductor laser that is not adjacent to the wavelength tunable semiconductor laser to be operated next. For controlling a wavelength tunable laser array element. A method for controlling a wavelength tunable laser array element according to any one of claims 1 to 5,
A light control element that is integrated on the same semiconductor substrate as the plurality of wavelength tunable semiconductor lasers, is connected to laser light oscillated from the plurality of wavelength tunable semiconductor lasers, and controls the laser light according to an injection current;
A wavelength tunable laser array element characterized by changing a current amount or power amount in a control region of a wavelength tunable semiconductor laser that is not operating according to a current change amount or a power change amount of an injection current to the light control element. Control method. A control device for a wavelength tunable laser array element in which a plurality of current control type wavelength tunable semiconductor lasers having a control region through which a heat compensation current flows are arranged in parallel,
During operation of an arbitrary wavelength tunable semiconductor laser among the plurality of wavelength tunable semiconductor lasers, a current is passed through a control region of the wavelength tunable semiconductor laser that operates next to the wavelength tunable semiconductor laser in operation,
The current I flowing through the control region of the wavelength tunable semiconductor laser operating in the following, greater than the control current amount I _t at the operating conditions of the wavelength tunable semiconductor laser operating in the next, smaller than its total current I _all range A wavelength control apparatus for a wavelength tunable laser array element, comprising: a first thermal compensation control unit that is controlled in step (1). A control device for a wavelength tunable laser array element according to claim 7,
By passing a current through the wavelength tunable semiconductor laser in operation and a control region of any one of the wavelength tunable semiconductor lasers other than the wavelength tunable semiconductor laser that operates next,
A total amount of all currents of the plurality of wavelength tunable semiconductor lasers or a total amount of the total power thereof is controlled in the same manner before and after switching from the wavelength tunable semiconductor laser in operation to the wavelength tunable semiconductor laser to be operated next; A wavelength tunable laser element control apparatus, further comprising a thermal compensation control unit. A control device for a wavelength tunable laser element according to claim 7 or 8,
A light control element integrated on the same semiconductor substrate as the plurality of wavelength tunable semiconductor lasers, connected to laser light oscillated from the plurality of wavelength tunable semiconductor lasers, and controlling the laser light according to an injection current;
A third thermal compensation control unit that changes the current amount or power amount of the control region of the wavelength tunable semiconductor laser that is not operating in accordance with the current change amount or power change amount of the injection current to the light control element; A wavelength control device for a wavelength tunable laser element, characterized in that:

Images