JP2019140183A - Laser device and method of controlling laser element - Google Patents

Abstract

To provide a laser device capable of suppressing change in oscillation wavelength of a laser element, and to provide a method of controlling a laser element.SOLUTION: A laser device 100 comprises: a laser element 101 that has a plurality of control elements for controlling an oscillation wavelength or an optical output by being supplied with a power; and a controller 102 that controls the power to be supplied to the plurality of control elements. The controller 102, as the power, supplies to at least one control element a power compensated by a compensation amount that is set depending on an index value indicating at least one calorific value of the control elements.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser apparatus and a laser element control method.

  Conventionally, in a laser element such as a semiconductor laser element, various techniques have been disclosed in order to suppress a change in oscillation wavelength caused by a change in heat generation (Patent Documents 1 to 3). These technologies suppress changes in the oscillation wavelength by controlling the drive current and temperature of the laser element.

  On the other hand, in a wavelength tunable laser element, a configuration is disclosed in which the oscillation wavelength is made variable using the vernier effect (Patent Document 4). In this wavelength tunable laser element, the wavelength characteristic is changed by heating a wavelength characteristic variable element such as a diffraction grating or a ring resonator with a heater, thereby changing the oscillation wavelength. In some cases, a semiconductor optical amplifier is integrated in the wavelength tunable laser element.

Japanese Patent No. 6000494 Japanese Patent Laying-Open No. 2015-201549 Japanese Patent No. 5473451 Japanese Patent Laid-Open No. 2006-178283

  A laser element such as a wavelength tunable laser element disclosed in Patent Document 4 has a plurality of heat sources in the laser element such as a heater and a semiconductor optical amplifier. These heat sources are for controlling the oscillation wavelength or optical output of the laser element by supplying electric power, and are hereinafter referred to as control elements.

  As a result of the presence of a plurality of control elements in a laser element, the heat generated by a certain control element may affect other control elements, and the oscillation wavelength of the laser element may change from the set value.

  The present invention has been made in view of the above, and an object of the present invention is to provide a laser device and a laser element control method capable of suppressing a change in the oscillation wavelength of the laser element.

  In order to solve the above-described problems and achieve the object, a laser device according to one embodiment of the present invention includes a laser element having a plurality of control elements that control an oscillation wavelength or an optical output when power is supplied; A control unit that controls the power supplied to the plurality of control elements, and the control unit sets a compensation amount that is set as the power according to an index value that indicates at least one heat generation amount of the control element. The power compensated by is supplied to at least one other control element.

  In the laser device according to one aspect of the present invention, the plurality of control elements include a heater that heats a wavelength characteristic variable element that controls an oscillation wavelength of the laser element, and a semiconductor that controls an optical output of the laser element. An optical amplifier is included.

  A laser apparatus according to an aspect of the present invention includes a plurality of wavelength characteristic variable elements having different wavelength characteristic change periods, and the laser element utilizes a vernier effect by a combination of the plurality of wavelength characteristic variable elements. The oscillation wavelength is controlled.

  The laser apparatus according to an aspect of the present invention is characterized in that the control unit temporally changes the compensation amount in accordance with a temporal change in an index value of the at least one control element.

  A laser device according to one embodiment of the present invention includes a laser element having a plurality of control elements that control oscillation wavelength or optical output when power is supplied, and control that controls the power supplied to the plurality of control elements. A plurality of heaters for heating a plurality of wavelength characteristic variable elements that control an oscillation wavelength of the laser element, and the control unit uses the control element as the power The power determined by the correlation of the power supplied to the plurality of heaters, which is determined according to an index value indicating at least one heat generation amount and a set oscillation wavelength, is supplied to the plurality of heaters. .

  A laser element control method according to an aspect of the present invention is a laser element control method including a plurality of control elements that control an oscillation wavelength or an optical output when electric power is supplied. A control step of controlling the power to be supplied, and in the control step, at least power compensated by a compensation amount set according to an index value indicating at least one heat generation amount of the control element, It supplies to one said other said control element, It is characterized by the above-mentioned.

  A method for controlling a laser element according to one embodiment of the present invention includes a plurality of control elements that control an oscillation wavelength or an optical output when power is supplied, and the plurality of control elements controls the oscillation wavelength. A method of controlling a laser element including a plurality of heaters for heating the wavelength characteristic variable element, comprising: a control step of controlling the power supplied to the plurality of control elements, wherein in the control step, as the power, Supplying the plurality of heaters with electric power determined by a correlation of electric power supplied to the plurality of heaters, which is determined according to an index value indicating at least one calorific value of the control element and a set oscillation wavelength. Features.

  According to the present invention, it is possible to suppress the change in the oscillation wavelength of the laser element.

FIG. 1 is a configuration diagram of a laser apparatus according to an embodiment. FIG. 2 is a diagram illustrating a control flow of the control example 1. FIG. 3 is a diagram illustrating an example of a temporal change in the SOA current and the compensation amount. FIG. 4 is a diagram illustrating an example of the relationship between the DBR current, the ring current, and the oscillation wavelength. FIG. 5 is a diagram illustrating an example of a change in the relationship between the DBR current, the ring current, and the oscillation wavelength. FIG. 6 is a diagram illustrating a control flow of the control example 2.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In the drawings, the same or corresponding elements are denoted by the same reference numerals as appropriate, and redundant description is omitted.

  FIG. 1 is a configuration diagram of a laser apparatus according to an embodiment. The laser device 100 includes a laser element 101, a control unit 102, and a light receiving element 103.

  The laser element 101 is, for example, a wavelength tunable semiconductor laser element configured by an optical waveguide, which is disclosed in Patent Document 4, and includes a ring-shaped waveguide 101a, arm portions 101b and 101c, a DBR (Distributed Bragg). A reflector 101d, a gain unit 101e, a semiconductor optical amplifier (SOA) 101f, and heaters 101g, 101h, and 101i.

  The combination of the ring-shaped waveguide 101a and the arm portions 101b and 101c functions as a reflection mirror having a first comb-like reflection spectrum having a periodic reflection peak of light in frequency. The DBR diffraction grating 101d is, for example, a sampling diffraction grating, and functions as a diffraction grating having a second comb-like reflection spectrum having a periodic reflection peak of light in frequency. The first comb-like reflection spectrum and the second comb-like reflection spectrum have different reflection peak periods (periods of change in wavelength characteristics). The reflection mirror and the diffraction grating constitute a laser resonator in the laser element 101. The gain unit 101e has an active core layer, emits light when power is supplied, and exhibits an optical amplification function. The laser element 101 oscillates at a wavelength at which the reflection peak of the first comb-like reflection spectrum of the reflection mirror, the reflection peak of the second comb-like spectrum of the diffraction grating, and the longitudinal mode of the laser resonator coincide. The laser beam generated by the laser oscillation has an active core layer, and is optically amplified by the SOA 101f that exhibits an optical amplification function when power is supplied, and is output as the laser beam L.

  The heater 101g is a ring-shaped heater provided in the ring-shaped waveguide 101a, and heats the ring-shaped waveguide 101a when power is supplied from the control unit 102. By heating the ring-shaped waveguide 101a, the reflection peak of the first comb-shaped reflection spectrum is shifted on the wavelength axis.

  The heater 101h is a heater provided in a part of the arm unit 101c, and heats a part of the arm unit 101c when power is supplied from the control unit 102. When a part of the arm portion 101c is heated, the resonator length (optical length) of the laser resonator is changed, and the wavelength of the longitudinal mode is entirely shifted on the wavelength axis. The portion heated by the heater 101h functions as a phase adjustment unit.

  The heater 101i is a heater provided in the DBR diffraction grating 101d, and heats the DBR diffraction grating 101d when power is supplied from the control unit 102. When the DBR diffraction grating 101d is heated, the reflection peak of the second comb-like reflection spectrum is shifted on the wavelength axis.

  By heating at least one of the heater 101g and the heater 101i and the heater 101h, the reflection peak of the first comb-like reflection spectrum of the reflection mirror, the reflection peak of the second comb-like spectrum of the diffraction grating, and the vertical direction of the laser resonator The wavelength that matches the mode, that is, the oscillation wavelength can be changed. As a result, the laser element 101 functions as a wavelength tunable laser element.

  As described above, the oscillation wavelength of the laser element 101 is controlled using the vernier effect by the combination of the diffraction grating and the reflection mirror, which are two wavelength characteristic variable elements. The heaters 101g, 101h, and 101i are control elements that control the oscillation wavelength of the laser element 101 when power is supplied. The SOA 101f is a control element that controls the light output of the laser element 101 (the power of the laser light L) when electric power is supplied. The heaters 101g, 101h, and 101i are heating elements, and the SOA 101f is a heating element that generates heat by using a part of the energy that is not used for optical amplification out of the supplied power energy.

  The control unit 102 controls the power supplied to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e. The light receiving element 103 is, for example, a photodiode, receives a part of the laser light L output from the laser element 101, and outputs a current signal corresponding to the received light intensity to the control unit 102.

  The control unit 102 includes at least a calculation unit 102a, a recording unit 102b, an input unit 102c, an output unit 102d, and a power supply unit 102e. The calculation unit 102a includes, for example, a CPU, and performs various calculation processes for control. The recording unit 102b includes a recording unit such as a ROM that stores various programs and data used by the arithmetic unit 102a to perform arithmetic processing, a work space when the arithmetic unit 102a performs arithmetic processing, and the arithmetic unit 102a. And a recording unit such as a RAM used for recording the result of the arithmetic processing.

  The input unit 102c receives an input of an instruction signal from a host device of the laser device 100, a current signal from the light receiving element 103, and a current monitor signal of the SOA 101f. Information included in the received signal is recorded in the recording unit 102b. The input unit 102c includes, for example, an analog-digital converter (ADC). The output unit 102d receives the instruction signal generated by the arithmetic processing unit 102a through the arithmetic processing, converts the instruction signal into an appropriate instruction signal, and outputs it to the power supply unit 102e. An output unit 102d, for example, a digital-analog converter (DAC) is provided. The power supply unit 102e supplies power to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e based on the instruction signal, and includes, for example, a DC power source.

(Control example 1)
Next, a control example 1 of the laser element 101 executed by the control unit 102 will be described with reference to the flowchart of FIG. First, in step S101, the calculation unit 102a sets power to be supplied to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e based on an instruction signal from the host device of the laser device 100 or the like. This power is a reference power for compensation. In this example, since the voltage is constant, it is assumed that a current is set instead of the power, and the power and the current can be appropriately converted. These supplied current values may be included as information in the instruction signal, or are recorded in the recording unit 102b as table data. The set oscillation wavelength and the setting light for the laser element 101 are included in the instruction signal. It may be selected from table data based on output value information.

  Subsequently, in step S102, the calculation unit 102a acquires a compensation amount. In this example, as shown in Table 1, the current compensation amount (DBR current compensation amount) for the current set in the heater 101i and the heater 101g corresponding to the current (SOA current) value set in the SOA 101f are set. The current compensation amount (ring current compensation amount) for the current that has been set and the current compensation amount (phase current compensation amount) for the current set in the heater 101h are recorded as table data in the recording unit 102b. The calculation unit 102a reads and acquires the compensation amount from the table data recorded in the recording unit 102b. The SOA current is an index value indicating the heat generation amount of the SOA 101f, and each compensation amount is set according to the current value that is the index value. Specifically, each compensation amount is determined by the inflow of heat generated by the SOA 101f in order to obtain a set oscillation wavelength, the ring-shaped waveguide 101a, a part of the arm part 101c (phase adjustment part), the DBR diffraction grating 101d. This is for offsetting the influence of excessive heat on the amount of heat that should be received. As can be seen from Table 1, the greater the SOA current, the greater the amount of heat generated by the SOA 101f, and thus the greater the compensation amount. When the set SOA current is not in the table data, a compensation amount obtained by complementing the SOA current in the table data by linear interpolation or the like may be used.

  Subsequently, in step S103, the calculation unit 102a calculates how to increase the compensation amount. When changing the SOA current, the current value before the change is not changed stepwise from the current value before the change to the target value after the change, but gradually increased from time zero at the start of the change as shown in FIG. There is a case where the time is changed so as to reach the target value at t1. In this case, it is preferable that the compensation amount is continuously changed from the current value to the target value according to the time change of the SOA current. In such a case, when any one of the DBR current compensation amount, the ring current compensation amount, and the phase current compensation amount is changed with time according to the change in the SOA current, it is changed with a different time constant. You may do it. Thereby, the optimal compensation amount according to the time change of the SOA current can be applied at each time.

  Subsequently, in step S104, the calculation unit 102a calculates an instruction value as information included in the instruction signal output to the power supply unit 102e. In step S105, the calculation unit 102a transmits the instruction signal including the instruction value information to the power supply unit. To 102e. The power supply unit 102e supplies current to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e based on the instruction value.

  Here, the current supplied by the power supply unit 102e to the heaters 101g, 101h, and 101i, which are other control elements other than the SOA 101f, is supplied to the heaters 101g, 101h, and 101i based on an instruction signal from a host device of the laser device 100 or the like. This is a compensated current obtained by subtracting the amount of compensation from the current value set for the value (a reference value for compensation). When the SOA current is changed over time as shown in FIG. 3, the instruction values in steps S104 and S105 are also changed over time. As a result, the ring waveguide 101a, a part of the arm portion 101c (phase adjusting portion), and the DBR diffraction grating 101d are given the amount of heat originally received in order to obtain the set oscillation wavelength. Thereby, the change of the oscillation wavelength of the laser element 101 due to the influence of heat generated by the SOA 101f can be suppressed.

  In the above embodiment, the DBR current compensation amount, the ring current compensation amount, and the phase current compensation amount are recorded as table data in the recording unit 102b corresponding to the set value of the SOA current, but as shown in Table 2, The DBR power compensation amount, ring power compensation amount, and phase power compensation amount may be recorded in the recording unit 102b as table data corresponding to the set value of the SOA current.

  In the table data of Tables 1 and 2, the SOA current is a set value, but it may be a current monitor value of the SOA 101f instead of the set value. Corresponding to the optical output of the SOA 101f, the DBR current compensation amount, the ring current compensation amount, the phase current compensation amount, or the corresponding power compensation amount is recorded as table data in the recording unit 102b. Alternatively, the optical output of the SOA 101f may be monitored based on the current signal from and the compensation amount corresponding to the monitored SOA optical output may be acquired from the table data.

  In the above embodiment, the SOA current is used as an index value indicating the heat generation amount of the SOA 101f, and each compensation amount is set according to the current value as the index value. However, the present invention is not limited to this, and as shown in Table 3, the DBR current and the ring current are set as index values indicating the heat generation amounts of the heaters 101i and 101g, and the phase compensation amount is set according to each current value. You may make it do. In addition, any one of the DBR current, the ring current, and the phase current may be used as an index value, and another compensation amount may be set according to each current.

(Control example 2)
Next, a control example 2 of the laser element 101 executed by the control unit 102 will be described. The oscillation wavelength of the laser element 101 is mainly determined by the coincidence between the reflection peak of the first comb-like reflection spectrum of the reflection mirror and the reflection peak of the second comb-like spectrum of the diffraction grating. Since the first comb-like reflection spectrum changes according to the ring current and the second comb-like spectrum changes according to the DBR current, the oscillation wavelength is set with the DBR current and the ring current as parameters, for example, as shown in FIG. It can be shown as a curved surface. It can be said that this curved surface represents the correlation between the DBR current and the ring current.

  This curved surface changes depending on the operating state of the laser element 101. The operating state of the laser element 101 is determined by the operating states of the heaters 101g, 101h, 101i, the SOA 101f, the gain unit 101e, and the like, and the power supplied to each element also varies depending on the operating state of each element.

  FIG. 5 is a diagram showing an example of a change in the relationship between the DBR current, the ring current, and the oscillation wavelength, and shows a curve as shown in FIG. 4 in another form. A similar graph is obtained even when DBR power and ring power are used as parameters instead of DBR current and ring current.

  In FIG. 5, λa1, λa2, ..., λak, ..., λb1, λb2, ..., λbk, ..., λn1, λn2, ..., λnk, ... are specific rings. The oscillation wavelengths obtained by the combination of the current and the DBR current are shown and are different from each other. For example, λa1, λa2,..., Λak,... Correspond to set wavelengths adjacent to each other. Similarly, λb1, λb2,..., Λbk,... Correspond to set wavelengths adjacent to each other, and λn1, λn2,..., Λnk,. . Therefore, to continuously change the oscillation wavelength, for example, the combination of the ring current and the DBR current is changed along an inclined broken line connecting λa1, λa2,..., Λak,. You can do it.

  Here, when the operating state of the laser element 101 is changed, the shape of the curved surface changes, and the inclination angle of the inclined broken lines connecting λa1, λa2,..., Λak,. This means that the correlation between the DBR current and the ring current changes depending on the operating state of the laser element 101. The reason why the correlation changes depending on the operation state in this way is considered as follows. That is, for example, the SOA current supplied to the SOA 11f and the phase current supplied to the heater 101h change depending on the operating state of the laser element 101, and the amount of generated heat also changes. And the correlation changes.

  In this control example 2, the DBR current and the ring current are determined using the correlation between the DBR current and the ring current, which is determined according to the index value indicating at least one calorific value of the control element and the set oscillation wavelength. , Supplied to the heaters 101i and 101g, respectively.

  Hereinafter, the control example 2 of the laser element 101 executed by the control unit 102 will be described with reference to the flowchart of FIG. First, in step S201, the calculation unit 102a sets power to be supplied to the heater 101h, the SOA 101f, and the gain unit 101e based on an instruction signal from a higher-level device of the laser device 100 or the like. Also in this example, since the voltage is constant, the current is set instead of the power. These supplied current values may be included as information in the instruction signal, or are recorded in the recording unit 102b as table data. The set oscillation wavelength and the setting light for the laser element 101 are included in the instruction signal. It may be selected from table data based on output value information.

  Subsequently, in step S202, the calculation unit 102a acquires a correlation. In this example, the correlation between the DBR current and the ring current, which is determined according to the SOA current and the set oscillation wavelength, is recorded in the recording unit 102b as table data or a function. The SOA current is an index value indicating the heat generation amount of the SOA 101f. The amount of heat generated by the SOA 101f affects the correlation between the DBR current and the ring current when realizing the set oscillation wavelength. If the set SOA current is not in the table data, a correlation obtained by complementing the SOA current in the table data by linear interpolation or the like may be used.

  Subsequently, in step S204, the calculation unit 102a calculates an instruction value as information included in the instruction signal output to the power supply unit 102e, and in step S205, the instruction signal including the instruction value information is transmitted to the power supply unit. To 102e. The power supply unit 102e supplies current to the heaters 101g, 101h, 101i, the SOA 101f, and the gain unit 101e based on the instruction value.

  Currents supplied to the heaters 101g and 101i by the power supply unit 102e (ring current and DBR current, respectively) are currents determined by a correlation determined according to the SOA current and the set oscillation wavelength. As a result, each of the ring-shaped waveguide 101a and the DBR diffraction grating 101d is given an appropriate amount of heat to obtain the set oscillation wavelength. Thereby, the change of the oscillation wavelength of the laser element 101 due to the influence of heat generated by the SOA 101f can be suppressed.

  In the control example 2 described above, the correlation between the DBR current and the ring current, which is determined according to the SOA current that is an index value indicating the heat generation amount of the SOA 101f and the set oscillation wavelength, is used. The correlation between the DBR current and the ring current, which is determined according to the phase current that is the index value to be shown and the set oscillation wavelength, may be used.

  Further, the present invention is not limited by the above embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

DESCRIPTION OF SYMBOLS 100 Laser apparatus 101 Laser element 101a Ring-shaped waveguide 101b, 101c Arm part 101d DBR diffraction grating 101e Gain part 101g, 101h, 101i Heater 102 Control part 102a Calculation part 102b Recording part 102c Input part 102d Output part 102e Electric power supply part 103 Light reception Element L Laser light

Claims (7)

A laser element having a plurality of control elements for controlling oscillation wavelength or optical output by being supplied with power;
A control unit for controlling the power supplied to the plurality of control elements;
With
The control unit supplies power compensated by a compensation amount set according to an index value indicating at least one heat generation amount of the control element to the at least one other control element as the power. A laser device characterized.   The plurality of control elements include a heater that heats a wavelength characteristic variable element that controls an oscillation wavelength of the laser element, and a semiconductor optical amplifier that controls an optical output of the laser element. The laser apparatus described.   A plurality of wavelength characteristic variable elements having different wavelength characteristic change periods are included, and the laser element has an oscillation wavelength controlled using a vernier effect by a combination of the plurality of wavelength characteristic variable elements. The laser device according to claim 1.   4. The laser device according to claim 1, wherein the control unit changes the compensation amount with time according to a change with time of an index value of the at least one control element. . A laser element having a plurality of control elements for controlling oscillation wavelength or optical output by being supplied with power;
A control unit for controlling the power supplied to the plurality of control elements;
With
The plurality of control elements include a plurality of heaters that heat a plurality of wavelength characteristic variable elements that control an oscillation wavelength of the laser element,
The control unit determines, as the power, power determined by a correlation of power supplied to the plurality of heaters, which is determined according to an index value indicating at least one heat generation amount of the control element and a set oscillation wavelength. A laser device that supplies the plurality of heaters. A method of controlling a laser element having a plurality of control elements that control oscillation wavelength or optical output by being supplied with power,
A control step of controlling the power supplied to the plurality of control elements,
Supplying power compensated by a compensation amount set according to an index value indicating at least one heat generation amount of the control element to the at least one other control element in the control step. A method for controlling a laser element. A laser having a plurality of control elements that control an oscillation wavelength or an optical output by being supplied with power, and the plurality of control elements heating a plurality of wavelength characteristic variable elements that control the oscillation wavelength An element control method comprising:
A control step of controlling the power supplied to the plurality of control elements,
In the control step, as the power, power determined by a correlation between power supplied to the plurality of heaters, which is determined according to an index value indicating at least one heat generation amount of the control element and a set oscillation wavelength. A method of controlling a laser element, wherein the laser element is supplied to the plurality of heaters.

Images