JP2012191044A - Semiconductor laser drive control circuit and method of driving semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive control circuit that can obtain a constant wavelength modulation width without depending on a wavelength to be selected, in a wavelength selection light source.SOLUTION: A semiconductor laser drive control circuit comprises a first unit and a second unit. The first unit sets the wavelength of outgoing light of a semiconductor laser device based on a first value in which a first time average value, which is a time average value of the intensity of light that is emitted from the semiconductor laser device and transmits through a wavelength filter 18, is normalized by a second time average value, which is a time average value of the intensity of the light that is emitted from the semiconductor laser device. The second unit decides the wavelength modulation width of the outgoing light of the semiconductor laser device and controls the amplitude of a high-frequency signal supplied to a heater so that the wavelength modulation width is constant.

Description

  The present invention relates to a semiconductor laser drive control circuit and a method for driving a semiconductor laser device.

  Patent Document 1 below describes a laser control device. The laser control device described in Patent Document 1 reduces nonlinear effects that occur when light having a narrow spectral width is input from an semiconductor fiber to an optical fiber. Specifically, the laser control device described in Patent Document 1 widens the spectrum width of the emitted light of the semiconductor laser by superimposing a modulation current (dither signal) on the driving current of the semiconductor laser.

JP 2006-222807 A

  The inventor of the present application has found that when the dither signal is added to the drive current of the semiconductor laser, the wavelength of the emitted light of the semiconductor laser changes greatly.

  Therefore, the inventor of the present application is studying a drive control circuit that superimposes a dither signal on the current applied to the heater in a semiconductor laser device in which the temperature of the diffraction grating can be adjusted by the heater and the wavelength of the emitted light can be selected.

  However, the relationship between the amplitude of the dither signal given from such a drive control circuit and the wavelength modulation width of the emitted light can vary depending on individual differences of the heaters used or the use environment. Also, even if the dither signal is constant, the amount of wavelength modulation can change depending on the selected wavelength.

  Therefore, in this technical field, it is required to obtain a constant wavelength modulation width without depending on the wavelength to be selected.

  The semiconductor laser drive control circuit according to one aspect of the present invention applies wavelength modulation to a wavelength tunable semiconductor laser device that can select the wavelength of the emitted light by adjusting the temperature of the diffraction grating with an integrated heater. The drive control circuit includes a first unit and a second unit. The first unit is the time average value of the intensity of the light emitted from the semiconductor laser device, and the first time average value which is the time average value of the intensity of the light emitted from the semiconductor laser device and transmitted through the wavelength filter. The wavelength of the emitted light from the semiconductor laser device is set based on the first value normalized by the second time average value. The second unit has a first intensity corresponding to the wavelength modulation component of the light emitted from the semiconductor laser device and transmitted through the wavelength filter, and a second intensity corresponding to the wavelength modulation component of the light emitted from the semiconductor laser device. The wavelength modulation width of the emitted light of the semiconductor laser device is determined based on the second value normalized by the wavelength filter and the transmission characteristic of the wavelength filter, and the magnitude of the high-frequency signal given to the heater so that the wavelength modulation width is constant To control.

  This semiconductor laser drive control circuit obtains the wavelength modulation width by using the transmission characteristics of the second value and the wavelength filter. That is, this drive control circuit can determine the wavelength modulation width from the actual outgoing light and the transmission characteristics of the wavelength filter. And this drive control circuit controls the magnitude | size of the high frequency signal given to a heater so that the calculated | required wavelength modulation width may become fixed. Thus, the drive control circuit can obtain a constant wavelength modulation width without depending on the wavelength to be selected.

  In one embodiment, the diffraction grating may be a CSG-DBR (Chirped Sampled Distributed Distributed Bragg Reflector). In one embodiment, the wavelength filter may be an etalon filter.

  Another aspect of the present invention relates to a method of driving a wavelength tunable semiconductor laser device capable of selecting the wavelength of emitted light by adjusting the temperature of a diffraction grating with an integrated heater. The method includes (a) superimposing a high-frequency signal on the electrode of the heater, (b) detecting a high-frequency component corresponding to the high-frequency signal in the emitted light from the semiconductor laser device as a first signal, and (c) ) Detecting a high-frequency component corresponding to the high-frequency signal in the light after the outgoing light has been transmitted through the wavelength filter as a second signal; and (d) the first signal, the second signal, and the wavelength filter. And (e) controlling the magnitude of the high-frequency signal so that the wavelength modulation width is constant.

  In this method, the wavelength modulation width is obtained by using the transmission characteristics of the first signal, the second signal, and the wavelength filter. That is, in this method, the wavelength modulation width can be obtained from the actual outgoing light and the transmission characteristics of the wavelength filter. This method controls the magnitude of the high-frequency signal given to the heater so that the obtained wavelength modulation width is constant. Thereby, this method can obtain a constant wavelength modulation width without depending on the wavelength to be selected.

  In one embodiment, a semiconductor laser device includes a distributed feedback semiconductor laser and a CSG-DBR (Chirped Sampled Distributed Bragg Reflector), and a plurality of heaters including the heater are integrated in a CSG-DBR. The heater electrode on which the high-frequency signal is superimposed may be the heater electrode arranged closest to the distributed feedback semiconductor laser among the plurality of heater electrodes. The heater disposed closest to the distributed feedback semiconductor laser greatly contributes to the adjustment of the wavelength modulation width with respect to the magnitude of the high-frequency signal. Therefore, according to this embodiment, the wavelength modulation width can be controlled efficiently. In one embodiment, the wavelength filter may be an etalon filter.

  As described above, according to the present invention, there are provided a semiconductor laser drive control circuit and a method for driving a semiconductor laser capable of obtaining a constant wavelength modulation width without depending on a selected wavelength. .

1 is a diagram showing a semiconductor laser system including a semiconductor laser drive control circuit according to an embodiment. It is a figure which shows the semiconductor laser apparatus which concerns on one Embodiment. It is a figure which shows the CSG-DBR area | region shown in FIG. It is a figure for demonstrating the control principle of the semiconductor laser drive control circuit which concerns on one Embodiment. It is a figure which shows the semiconductor laser system containing the semiconductor laser drive control circuit which concerns on another embodiment. It is a figure which shows the semiconductor laser system containing the semiconductor laser drive control circuit which concerns on another embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a diagram illustrating a semiconductor laser system including a semiconductor laser drive control circuit according to an embodiment. A semiconductor laser system 100 shown in FIG. 1 includes a semiconductor laser drive control circuit 10 according to an embodiment. Further, the semiconductor laser system 100 can include the semiconductor laser device 12, the optical branching elements 14 and 16, the wavelength filter 18, and the photoelectric conversion elements 20, 24 and 26.

  FIG. 2 is a diagram illustrating a semiconductor laser device according to an embodiment. As shown in FIG. 2, the semiconductor laser device 12 may be a wavelength tunable semiconductor laser device that can select the wavelength of the emitted light. In one embodiment, the semiconductor laser device 12 includes a CSG-DBR (Chirped Sampled Distributed Bragg Reflector) region 30, an SG-DFB region 32, and a semiconductor optical amplifier (SOA) region. .

  The CSG-DBR region 30 has an optical waveguide including a diffraction grating. The optical waveguide of the CSG-DBR region 30 is optically coupled to one end of the optical waveguide of the SG-DFB region 32. Details of the CSG-DBR region 30 will be described later.

  The SG-DFB region 32 constitutes a distributed feedback (DFB) semiconductor laser. The SG-DFB region 32 is made of a semiconductor crystal having a gain with respect to laser oscillation at a target wavelength. An electrode 36 is provided on the SG-DFB region 32. The SG-DFB region 32 generates light in the optical waveguide by the current supplied to the electrode 36. The optical waveguide of the SG-DFB region 32 is optically coupled to the optical waveguide of the SOA region 34 at the other end.

  The SOA region 34 includes an optical waveguide made of a semiconductor crystal for gaining light by current control or for absorbing light. An electrode 38 is provided on the SOA region 34. The SOA region 34 gives gain to light or absorbs light according to the current applied to the electrode 38.

  In one embodiment, the semiconductor laser device 12 may further include a temperature control device 40. The temperature control device 40 includes a Peltier element or the like, and controls the temperatures of the CSG-DBR region 30, the SG-DBR region 32, and the SOA region 34. The temperature control device 40 is controlled by a controller (not shown in FIG. 2) such as a microcomputer.

  Reference is now made to FIG. FIG. 3 is a diagram showing the CSG-DBR region shown in FIG. The CSG-DBR region 30 may include a substrate 30a, a lower cladding layer 30b, a grating layer 30c, an optical waveguide layer 30d, an upper cladding layer 30e, and an insulating film 30f.

The substrate 30a can be, for example, an Inp semiconductor substrate. The lower cladding layer 30b is provided on the substrate 30a. The lower cladding layer 30b can be an InP semiconductor layer. The grating layer 30c is embedded in the lower cladding layer 30b. The grating layer 30c can be an InGaAsP semiconductor layer. The optical waveguide layer 30d is provided on the lower cladding layer 30b. The optical waveguide layer 30d can be an InGaAsP semiconductor layer. The upper cladding layer 30e is provided on the optical waveguide layer 30d. The upper cladding layer 30e can be an InP semiconductor layer. The insulating film 30f is provided on the upper cladding layer 30e. The insulating film 30f can be, for example, a SiO ₂ film.

  The grating layer 30c may have a structure in which a space portion 30g in which InGaAsP is uniformly arranged and a diffraction grating portion 30h in which InGaAsP and InP are alternately arranged are connected. On the insulating film 30f, heaters 30i, 30j, and 30k are integrated. Electrodes 30m are connected to both ends of each heater.

  As shown in FIG. 3, the CSG-DBR region 30 may have seven segments 301 to 307. The segments 301 to 303 constitute a first segment group, the segments 304 to 305 constitute a second segment group, and the segments 306 to 307 constitute a third segment group.

  The heater 30i is integrated in the first segment group, the heater 30j is integrated in the second segment group, and the heater 30k is integrated in the third segment group. The heater 30i adjusts the equivalent refractive index of the first segment group by adjusting the temperature of the first segment group. The heater 30j adjusts the temperature of the second segment group and adjusts the equivalent refractive index in the second segment group. The heater 30k adjusts the equivalent refractive index of the third segment group by adjusting the temperature of the third segment group. The CSG-DBR region 30 can adjust the wavelength of the emitted light of the semiconductor laser device 12 by controlling the temperature applied to each segment group by the heaters 30i, 30j, and 30k. Further, the wavelength modulation width of the emitted light of the semiconductor laser device 12 can be adjusted by modulating the temperature applied to any one of the heaters. In addition, the selection frequency (selection wavelength) of the emitted light of the semiconductor laser device 12 may be several hundred THz, for example, and the frequency modulation width (wavelength modulation width) may be about ˜1 GHz. For example, when the selected wavelength is 1.5 μm, the frequency is 200 THz, and in this case, the deviation of 1 GHz can correspond to 1.5000075 μm.

  Reference is again made to FIG. The outgoing light from the SOA region 34 is coupled to the optical branching element 14. The optical branching element 14 emits a part of the input light to the outside and outputs the other part of the light to the photoelectric conversion element 20. The photoelectric conversion element 20 is an element that can output an electrical signal corresponding to the power of light, and can be a photodiode. The output electrical signal of the photoelectric conversion element 20 can be used for power control of the optical output of the semiconductor laser device 12, for example.

  The outgoing light from the CSG-DBR region 30 is coupled to the optical branching element 16. The optical branching element 16 outputs part of the input light to the photoelectric conversion element 22 and outputs the other part of the light to the wavelength filter 18. This wavelength filter 18 may be an etalon filter. The light input to the wavelength filter 18 is output to the photoelectric conversion element 24 through the wavelength filter 18. These photoelectric conversion elements 22 and 24 are elements that can output an electrical signal corresponding to the power of light, and can be photodiodes. In addition, when referring to the output electric signal of the photoelectric conversion element, the output electric signal may be an output electric signal from a transimpedance amplifier electrically connected to the photoelectric conversion element. That is, the output electrical signal of the photoelectric conversion element can be a voltage signal obtained by current / voltage conversion of the photocurrent from the photoelectric conversion element by a transimpedance amplifier.

  As shown in FIG. 1, the output electrical signals of the photodiodes 22 and 24 are output to the semiconductor laser drive control circuit 10 of one embodiment. The drive control circuit 10 includes a controller 50 such as a microcomputer. The controller 50 constitutes a first unit and a second unit according to one aspect of the present invention. The drive control circuit 10 may include voltage sources 52a, 52b, and 52c, current sources 54a, 54b, and 54c, a modulation current source 56, and a capacitive element 58.

  The voltage source 52a gives a voltage signal to the current source 54a under the control of the controller 50. The current source 54a supplies a current corresponding to the input voltage signal to one electrode 30m of the heater 30i. The voltage source 52 b gives a voltage signal to the current source 54 b under the control of the controller 50. The current source 54b supplies a current corresponding to the input voltage signal to one electrode 30m of the heater 30j. The voltage source 52 c gives a voltage signal to the current source 54 c under the control of the controller 50. The current source 54c supplies a current corresponding to the input voltage signal to one electrode 30m of the heater 30k. The other electrodes of the heaters 30i, 30j, and 30k can be connected to the ground.

  The modulation current source 56 applies a modulation current (high frequency signal) having an amplitude and a frequency set by the controller 50 to one electrode 30m of the heater 30i via the capacitive element 58. Since the heater 30i is disposed closest to the SG-DFB region 32 (DFB semiconductor laser), the contribution to the wavelength modulation width of the emitted light of the semiconductor laser device 12 is large. Therefore, the wavelength modulation width can be controlled efficiently by applying a modulation current to the heater 30i. However, the modulation current source 56 may be connected to one electrode of any heater. The amplitude and frequency set by the controller 50 can be initialized from the computer 200, for example.

  As shown in FIG. 1, the drive control circuit 10 may further include a filter 60, an AD converter 62, a filter 64, an AD converter 66, a division circuit 68, a wideband filter 70, and an AD converter 72.

  The input of the filter 60 is electrically connected to the photodiode 24. The filter 60 is an integration filter that removes a wavelength modulation component from the electrical signal from the photodiode 24. The output of the filter 60 is connected to the AD converter 62. The AD converter 62 applies analog-digital conversion to the output electric signal from the filter 60 to generate a digital signal D2. The digital signal D2 is input to the controller 50.

  The input of the filter 64 is electrically connected to the photodiode 22. The filter 64 is an integration filter that removes a wavelength modulation component from the electrical signal from the photodiode 24. The output of the filter 64 is connected to the AD converter 66. The AD converter 66 applies analog-digital conversion to the electrical signal from the filter 64 to generate a digital signal D1. The digital signal D1 is input to the controller 50.

  The input of the divider circuit 68 is electrically connected to the photodiode 22 and the photodiode 24. The division circuit 68 normalizes the electrical signal from the photodiode 24 with the electrical signal from the photodiode 22. The signal normalized by the division circuit 68 is output to the wideband filter 70.

  The broadband filter 70 is a filter having a band larger than the wavelength modulation width of the semiconductor laser device 12, and removes noise of the signal from the division circuit 68. The output signal of the filter 70 is output to the AD converter 72.

  The AD converter 72 applies an analog-digital conversion to the input signal to generate a digital signal. The digital signal generated by the AD converter 72 is output to the controller 50.

  Hereinafter, the control by the controller 50 will be described in detail with reference to FIG. FIG. 4 is a diagram for explaining the control principle of the semiconductor laser drive control circuit according to the embodiment. In FIG. 4, the horizontal axis indicates the wavelength λ of light, and the vertical axis indicates the power of light or the value of an electrical signal corresponding thereto. In FIG. 4, L1 indicates the wavelength characteristic of light incident on the photodiode 22, and L2 indicates the wavelength characteristic of light incident on the photodiode 24. F represents the transmission characteristics of the wavelength filter 18. Further, the selected wavelength of the emitted light from the semiconductor laser device 12 is λT.

  The light incident on the photodiode 22 does not pass through the wavelength filter 18, and therefore has a wavelength characteristic L1 that is relatively flat with respect to the wavelength characteristic L2 in the wavelength band including the wavelength λT. On the other hand, the wavelength characteristic L2 of light incident on the photodiode 24 is affected by the transmission characteristic F of the wavelength filter 18.

  The intensity of the light incident on the photodiode 22 becomes a signal D1 having a value (first time average value) indicated by E1 in FIG. 4 by passing through the integration filter 64 and the AD converter 66. On the other hand, the intensity of the light incident on the photodiode 24 passes through the filter 60 and the AD converter 62 having an integration function, so that the signal D2 having a value (first time average value) indicated by E2 in FIG. Become. As shown in FIG. 4, E2 / E1 is a value corresponding to the wavelength of the emitted light from the semiconductor laser device 12. Therefore, by performing feedback control so that E2 / E1 becomes a predetermined value, the wavelength of the emitted light of the semiconductor laser device 12 can be fixed to the selected wavelength λT.

  The controller 50 of the drive control circuit 10 receives the signal D1 from the AD converter 66 and the signal D2 from the AD converter 62, and supplies a voltage source so that E2 / E1 (first value) becomes a predetermined value. By controlling 52a to 52c, that is, by controlling the current applied to the heaters 30i, 30j, and 30k, the temperature of the heaters 30i, 30j, and 30k is adjusted, and the wavelength of the emitted light of the semiconductor laser device 12 is changed. It can be fixed at the selected wavelength λT.

  In the drive control circuit 10, the electric signal from the photodiode 24 and the electric signal from the photodiode 22 are input to the dividing circuit 68 without passing through the integration filter. In the division circuit, the electrical signal from the photodiode 24 (second strength electrical signal) is normalized by the electrical signal from the photodiode 22 (first strength electrical signal), and the standardized signal is converted to the wideband filter. AD conversion is performed in the AD converter 72 via 70. In this operation, assuming that the maximum value and the minimum value of the electric signal from the photodiode 24 are E2max and E2min, and the maximum value and the minimum value of the electric signal from the photodiode 22 are E1max and E1min, Ave (E2max / E1max−E2min / E1min) is being processed. Here, “Ave” represents an average value calculation. Ave (E2max / E1max−E2min / E1min) is equivalent to ΔE2 / ΔE1 in FIG. Here, ΔE2 is a value corresponding to the difference between the maximum value and the minimum value of the wavelength characteristic L2 in the wavelength modulation width, and ΔE1 is a value corresponding to the difference between the maximum value and the minimum value of the wavelength characteristic L1 in the wavelength modulation width. It is.

  As is apparent from FIG. 4, the value (second value) obtained by dividing the slope of the transmission characteristic F by ΔE2 / ΔE1 is a value reflecting the wavelength modulation width ΔλT. Therefore, the controller 50 obtains a value obtained by dividing the slope of the transmission characteristic F stored in the controller 50 based on the output signal from the AD converter 72, and the modulation current source 56 so that the value becomes a predetermined value. By performing feedback control (controlling the amplitude of the modulation current), the wavelength modulation width ΔλT can be controlled to a desired value.

  Hereinafter, a semiconductor laser drive control circuit according to another embodiment will be described. FIG. 5 is a diagram showing a semiconductor laser system including a semiconductor laser drive control circuit according to another embodiment. A semiconductor laser system 100A shown in FIG. 5 includes a semiconductor laser drive control circuit 10A. Hereinafter, differences of the semiconductor laser drive control circuit 10A from the semiconductor laser drive control circuit 10 will be described.

  In the semiconductor laser drive control circuit 10 </ b> A, the electric signal from the photodiode 24 is input to the AD converter 62 without passing through the filter 60. Further, the electric signal from the photodiode 22 is input to the AD converter 62 without passing through the filter 64. The electrical signal from the photodiode 22 is input to the AD converter 72 via the high pass filter 80. Furthermore, the electrical signal from the photodiode 24 is input to the AD converter 72A via the high-pass filter 82. The AD converter 72 </ b> A is a 2-channel simultaneous sampling AD converter, and generates two digital signals corresponding to the electrical signal from the photodiode 22 and the electrical signal from the photodiode 24.

  In the drive control circuit 10A, a filtering process similar to the filter 60 is performed on the signal from the AD converter 62 in the controller 50A. Further, the filtering process similar to the filter 64 is performed on the signal from the AD converter 66 in the controller 50A. Further, the division processing of the division circuit 68 and the filtering processing similar to the broadband filter 70 are performed in the controller 50A for the two digital signals from the AD converter 72A. That is, the functions of the filters 60 and 64, the dividing circuit 68, and the wideband filter 70 are realized by digital processing in the controller 50A. The feedback control by the controller 50A is the same as the feedback control of the controller 50.

  Hereinafter, a semiconductor laser drive control circuit according to still another embodiment will be described. FIG. 6 is a diagram showing a semiconductor laser system including a semiconductor laser drive control circuit according to still another embodiment. A semiconductor laser system 100B shown in FIG. 6 includes a semiconductor laser drive control circuit 10B.

  The semiconductor laser drive control circuit 10B is different from the semiconductor laser drive control circuit 10 in that it does not include the AD converters 62 and 66, the filters 60 and 64, the division circuit 68, and the broadband filter 70. In the semiconductor laser drive control circuit 10B, the electrical signals from the photodiodes 22 and 24 are output to the AD converter 72A. The AD converter 72A outputs two digital signals corresponding to the electrical signals from the photodiodes 22 and 24 to the controller 50B.

  In the semiconductor laser drive control circuit 10B, the functions of the filters 60 and 64, the divider circuit 68, and the broadband filter 70 are realized in the controller 50B. That is, the processing of the filters 60 and 64 is executed by digital processing in the controller 50B for the two signals from the AD converter 72A. Further, the processing of the division circuit 68 and the broadband filter 70 is executed by digital processing on the two signals from the AD converter 72A. The feedback control by the controller 50B is the same as the feedback control of the controller 50.

  The semiconductor laser drive control circuit of the above-described embodiment can arbitrarily select the wavelength of the emitted light of the semiconductor laser device, and is a CSG that is a diffraction grating so as to fix the wavelength of the emitted light to the selected wavelength. -Feedback control can be applied to the current applied to the heater integrated in the DBR. In addition, the semiconductor laser drive control circuits of these embodiments are fed back to the modulation current applied to the heater integrated in the CSG-DBR so as to give a desired wavelength modulation width to the emitted light of the semiconductor laser device at the selected wavelength. Control can be applied. Therefore, the semiconductor laser drive control circuit of the above-described embodiment can control the wavelength and the wavelength modulation width of the emitted light of the semiconductor laser device with high accuracy without depending on the individual difference of the semiconductor laser device or the use environment. It is.

  Although various embodiments have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, since the wavelength modulation component in the output electric signal from the photoelectric conversion element 22 is small, synchronous detection may be performed in order to detect the wavelength modulation component.

  DESCRIPTION OF SYMBOLS 10 ... Semiconductor laser drive control circuit, 12 ... Semiconductor laser apparatus, 14, 16 ... Optical branching element, 18 ... Wavelength filter (etalon filter), 20, 24, 26 ... Photoelectric conversion element (photodiode), 30 ... CSG- DBR region, 30i, 30j, 30k ... heater, 32 ... SG-DFB region, 34 ... semiconductor optical amplification region, 50 ... controller, 56 ... modulation current source, 60, 64 ... filter, 62, 66, 72 ... AD converter 68: Dividing circuit, 70: Broadband filter, 100: Semiconductor laser system.

Claims (6)

A semiconductor laser drive control circuit that modulates the temperature of a diffraction grating by an integrated heater and applies wavelength modulation to a wavelength tunable semiconductor laser device capable of selecting the wavelength of emitted light,
The first time average value that is the time average value of the intensity of the light emitted from the semiconductor laser device and transmitted through the wavelength filter is the second time that is the time average value of the intensity of the light emitted from the semiconductor laser device. A first unit for setting a wavelength of emitted light of the semiconductor laser device based on a first value normalized by an average value;
The first intensity corresponding to the wavelength modulation component of the light emitted from the semiconductor laser device and transmitted through the wavelength filter is normalized by the second intensity corresponding to the wavelength modulation component of the light emitted from the semiconductor laser device. The wavelength modulation width of the emitted light of the semiconductor laser device is determined based on the second value and the transmission characteristic of the wavelength filter, and the magnitude of the high frequency signal applied to the heater so that the wavelength modulation width is constant A second unit for controlling the thickness;
A semiconductor laser drive control circuit.   2. The semiconductor laser drive control circuit according to claim 1, wherein the diffraction grating is a CSG-DBR (Chirped Sampled Distributed Bragg Reflector). 3.   The semiconductor laser drive control circuit according to claim 1, wherein the wavelength filter is an etalon filter. A method of driving a wavelength tunable semiconductor laser device capable of selecting the wavelength of the emitted light by adjusting the temperature of the diffraction grating with an integrated heater,
Superimposing a high frequency signal on the electrode of the heater;
Detecting a high-frequency component corresponding to the high-frequency signal in the emitted light of the semiconductor laser device as a first signal;
Detecting a high-frequency component corresponding to the high-frequency signal, as a second signal, of the light after passing the emitted light through a wavelength filter;
Determining a wavelength modulation width of the emitted light based on transmission characteristics of the first signal, the second signal, and the wavelength filter;
Controlling the magnitude of the high-frequency signal so that the wavelength modulation width is constant;
Including methods. The semiconductor laser device includes a distributed feedback semiconductor laser and a CSG-DBR (Chirped Sampled Distributed Distributed Bragg Reflector),
A plurality of heaters including the heater are integrated in the CSG-DBR,
The heater electrode on which the high-frequency signal is superimposed is a heater electrode disposed closest to the distributed feedback semiconductor laser among the plurality of heater electrodes.
The method of claim 4.   The method according to claim 4 or 5, wherein the wavelength filter is an etalon filter.

Images