JP2021128970A - Laser device and control method thereof - Google Patents

Abstract

To achieve suitable control of the frequency of a laser beam.SOLUTION: A laser device includes a laser unit including a light source unit that makes the frequency of the output laser beam variable and a monitor unit that acquires a frequency equivalent amount corresponding to the frequency of the laser beam, and a control unit that controls the frequency of the laser beam by supplying a control amount to the light source unit according to a set value, and the laser unit has a characteristic in which the frequency of the laser beam changes non-linearly with respect to a set value or a monitor value used when controlling the frequency of the laser beam, and the control unit sets, for a slope of a change in the frequency of the laser beam with respect to a change in the set value or the monitor value or the frequency equivalent amount, a control constant for determining the control amount by referring to a storage unit according to the set value or the monitor value, and sets a control constant in a range in which the absolute value of the slope is small larger than a control constant in a range in which the absolute value of the slope is large in a first range and a second range which are different ranges that the set value or the monitor value can take.SELECTED DRAWING: Figure 4

Description

The present invention relates to a laser device and a control method thereof.

A laser device that changes the frequency of the output laser beam by utilizing the vernier effect is known (see, for example, Patent Document 1). The laser device described in Patent Document 1 has a light source unit in which the frequency of the laser light is variable by utilizing the vernier effect, and light having periodic transmission characteristics with respect to the frequency of the laser light output from the light source unit. It includes a filter, a light receiving element that acquires the intensity of laser light transmitted through the light filter, and a control device that controls the operation of the light source unit.

The control device calculates a monitor value corresponding to the frequency of the laser beam based on the intensity of the laser beam acquired by the light receiving element. Then, the control device controls the operation of the light source unit so that the monitor value converges to the control target value. The control device controls the frequency of the laser beam by supplying electric power corresponding to the controlled amount to the light source unit. The control amount is an amount adjusted for control, for example, an electric current. The electric power is supplied to a heater provided in the light source unit to make the frequency of the laser beam variable.

Japanese Patent No. 6241931

Here, when the configuration related to the control of the frequency of the laser light has a characteristic that the frequency of the laser light changes non-linearly with respect to the set value or the monitor value used when controlling the frequency of the laser light, the convergence time In some cases, frequency control became unstable due to increase, oscillation, overshoot, or undershoot.

The present invention has been made in view of the above, and an object of the present invention is to provide a laser apparatus and a control method thereof that can realize more suitable control when controlling the frequency of a laser beam.

In order to solve the above-mentioned problems and achieve the object, one aspect of the present invention is a light source unit in which the frequency of the output laser light is variable, and a monitor corresponding to a frequency equivalent amount corresponding to the frequency of the laser light. A laser unit including a monitor unit for acquiring a value, a control unit for controlling the frequency of the laser light by supplying a control amount to the light source unit according to a set value, and the set value or the monitor value. Correspondingly, a storage unit for storing a plurality of control constants for determining the control amount is provided, and the laser unit has the set value or the monitor value used when controlling the frequency of the laser light. The control unit has a characteristic that the frequency of the laser light changes non-linearly, and the control unit sets a predetermined control constant with reference to the storage unit according to the set value or the monitor value, and the set value or With respect to the gradient of the change in the frequency or frequency equivalent of the laser beam with respect to the change in the monitor value, the absolute value of the gradient is in the first range and the second range, which are different ranges that the set value or the monitor value can take. This is a laser device that sets the control constant in the smaller range to be larger than the control constant in the range in which the absolute value of the tilt is larger.

The set value or the monitor value may be a current value supplied to the control light source unit.

The monitor unit includes a frequency filter whose transmittance changes periodically with respect to the frequency of the input light, a first detection unit that detects the first intensity of the laser light corresponding to the intensity of the laser light, and the laser. The set value or the monitor value may include a value corresponding to, including a second detection unit that detects a second intensity corresponding to the intensity of the laser light after the light has passed through the frequency filter.

The monitor unit includes a first detection unit that detects a first intensity of laser light corresponding to the intensity of the laser light, and the set value or the monitor value is the second intensity with respect to the first intensity. It may be a value corresponding to the ratio of.

When the control unit performs change control for changing the frequency or frequency equivalent of the laser beam from the first set value to the second set value, the elapsed time from the start time of the change control or the first setting The control constant may be set according to the arrival rate from the value to the second set value.

When the control unit performs change control for changing the frequency or frequency equivalent of the laser beam from the first set value to the second set value, while changing from the first set value to the second set value. When the sign of the change in inclination changes, the control constant smaller than the control constant outside the range of the predetermined range may be set in the predetermined range including the point where the sign changes.

The control constant may be a proportional constant in proportional control.

The frequency of the laser beam may be variable in the light source unit by utilizing the vernier effect.

One aspect of the present invention is a laser unit having a light source unit for varying the frequency of the output laser light and a monitor unit for acquiring a monitor value corresponding to a frequency equivalent amount corresponding to the frequency of the laser light. A method for controlling a laser apparatus including The control step has a characteristic that the frequency of the laser beam changes non-linearly with respect to the set value or the monitor value used when controlling the control amount, and the control step is performed according to the set value or the monitor value. Including a setting step of setting a predetermined control constant with reference to a storage unit that stores a plurality of control constants for determining the above, in the setting step, the frequency of the laser light or the frequency of the laser light with respect to a change of the set value or the monitor value. With respect to the gradient of the change in the frequency equivalent amount, the control constant in the range in which the absolute value of the gradient is smaller in the first range and the second range, which are different ranges that the set value or the monitor value can take, is described. This is a control method for a laser device in which the absolute value of the tilt is set larger than the control constant in the larger range.

According to the present invention, there is an effect that more suitable control can be realized when controlling the frequency of the laser beam.

FIG. 1 is a diagram showing a configuration of a laser device according to the first embodiment. FIG. 2 is a diagram showing a configuration of a laser unit. FIG. 3 is an explanatory diagram of adjusting the frequency of the laser beam. FIG. 4 is a block diagram showing a configuration of a control unit according to the first embodiment. FIG. 5 is an explanatory diagram of a discrimination curve based on the relationship between the frequency and the PD ratio. FIG. 6 is a diagram showing an example of the relationship between the Phase current and the frequency of the laser beam. FIG. 7 is a diagram showing an example of setting a constant of proportionality with respect to the range of Phase current. FIG. 8 is a diagram showing an example of setting a proportionality constant with respect to the elapsed time from the start time of the change control of the PD ratio. FIG. 9 is a flowchart showing a control method by the control unit according to the first embodiment. FIG. 10 is a block diagram showing a configuration of a control unit according to the second embodiment. FIG. 11 is a flowchart showing a control method by the control unit according to the second embodiment. FIG. 12 is a block diagram showing a configuration of a control unit according to the third embodiment. FIG. 13 is a diagram showing an example of setting a proportionality constant with respect to the achievement ratio of the PD ratio to the target PD ratio. FIG. 14 is a flowchart showing a control method by the control unit according to the third embodiment. FIG. 15 is a block diagram showing a configuration of a control unit according to the fourth embodiment. FIG. 16 is an explanatory diagram of an example in which there is a place where the sign of the inclination changes between the set value at the start of the change control of the PD ratio and the set value of the target. FIG. 17 is a flowchart showing a control method by the control unit according to the fourth embodiment.

Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. The present invention is not limited to the embodiments described below. Further, in the description of the drawings, the same parts are appropriately designated by the same reference numerals. In addition, the drawings are schematic, and the relationship between the dimensions of each element, the ratio of each element, and the like may differ from reality. Further, even between the drawings, there may be parts having different dimensional relationships and ratios from each other. In addition, the xyz coordinate axes are appropriately shown in the drawings, and the directions will be described thereby.

(Embodiment 1)
[Outline configuration of laser device]
FIG. 1 is a diagram showing a configuration of a laser device according to the first embodiment.
The laser device 1 includes a modularized laser unit 2 and a control unit 3 that executes a control step for controlling the operation of the laser unit 2.
Although the laser unit 2 and the control unit 3 are separately configured in FIG. 1, they may be modularized as one.

[Structure of light source unit]
Under the control of the control unit 3, the laser unit 2 changes the frequency of the laser light to be output to a laser light of any one of a plurality of frequencies, and outputs the laser light of the frequency. The laser unit 2 includes a light source unit 4, a semiconductor optical amplifier (SOA) 5, a planar lightwave circuit (PLC) 6, a light detection unit 7, a temperature sensor 8, and temperature control. A vessel 9 and a device 9 are provided. The plane light wave circuit 6 and the light detection unit 7 form a monitor unit 10.

FIG. 2 is a diagram showing the configuration of the laser unit.
The light source unit 4 is, for example, a laser that utilizes the vernier effect, and outputs the laser beam L1 under the control of the control unit 3. The light source unit 4 includes a laser main body unit 41 that changes the frequency of the output laser beam L1 and a changing unit 42. The changing unit 42 has three microheaters that generate heat according to the electric power supplied from the control unit 3, and the laser light L1 output from the laser body 41 by locally heating the laser body 41. Change the frequency of.

The laser main body 41 includes first and second waveguides 43 and 44, respectively, formed on a common base B1. Here, the base B1 is made of, for example, an n-type InP. An n-side electrode 45 is formed on the back surface of the base portion B1 so as to include, for example, AuGeNi, and is in ohmic contact with the base portion B1.

The first waveguide section 43 has an embedded waveguide structure. The first waveguide section 43 includes a waveguide section 431, a semiconductor laminated section 432, and a p-side electrode 433.
The waveguide portion 431 is formed so as to extend in the z direction in the semiconductor laminated portion 432.
Further, in the first waveguide section 43, a gain section 431a and a DBR (Distributed Bragg Reflector) type diffraction grating layer 431b are arranged.

Here, the gain portion 431a is an active layer having a multiple quantum well structure made of InGaAsP and a light confinement layer. Further, the diffraction grating layer 431b is composed of a sampling diffraction grating composed of InGaAsP and InP.

The semiconductor laminated portion 432 is configured by laminating InP-based semiconductor layers, and has a function of a clad portion with respect to the waveguide portion 431.

The p-side electrode 433 is arranged on the semiconductor laminated portion 432 so as to be along the gain portion 431a. A SiN protective film (not shown) is formed on the semiconductor laminated portion 432. The p-side electrode 433 is in contact with the semiconductor laminated portion 432 via an opening (not shown) formed in the SiN protective film.

Here, the DBR heater 421, which is a microheater, is arranged along the diffraction grating layer 431b on the SiN protective film of the semiconductor laminated portion 432. Then, the DBR heater 421 generates heat according to the electric power supplied from the control unit 3, and heats the diffraction grating layer 431b. Further, by controlling the electric power supplied to the DBR heater 421 by the control unit 3, the temperature of the diffraction grating layer 431b changes, and the refractive index thereof changes.

The second waveguide section 44 includes a two-branch section 441, two arm sections 442, 443, and a ring-shaped waveguide 444.

The two-branch portion 441 is composed of a 1 × 2 type bifurcated waveguide including a 1 × 2 type multi-mode interference type (MMI) waveguide 441a, and the two port side is connected to each of the two arm portions 442 and 443. At the same time, the 1 port side is connected to the 1st waveguide section 43 side. That is, one end of the two arm portions 442 and 443 is integrated by the bifurcated portion 441 and optically coupled to the diffraction grating layer 431b.

The arm portions 442 and 443 are all extended in the z direction and are arranged so as to sandwich the ring-shaped waveguide 444. These arm portions 442 and 443 are optically coupled to the ring-shaped waveguide 444 with the same coupling coefficient κ as the ring-shaped waveguide 444. The value of κ is, for example, 0.2. The arm portions 442 and 443 and the ring-shaped waveguide 444 form a ring resonator filter RF1. Further, the ring resonator filter RF1 and the two-branch portion 441 form a reflection mirror M1.

Here, the RING heater 422, which is a microheater, has a ring shape and is arranged on a SiN protective film (not shown) formed so as to cover the ring-shaped waveguide 444. Then, the RING heater 422 generates heat according to the electric power supplied from the control unit 3, and heats the ring-shaped waveguide 444. Further, by controlling the electric power supplied to the RING heater 422 by the control unit 3, the temperature of the ring-shaped waveguide 444 changes, and the refractive index thereof changes.

The above-mentioned two-branch portion 441, arm portion 442, 443, and ring-shaped waveguide 444 all have a high-mesa waveguide structure in which an optical waveguide layer 44a made of InGaAsP is sandwiched by a clad layer made of InP. ..

Here, the Phase heater 423, which is a microheater, is arranged on a part of the SiN protective film (not shown) of the arm portion 443. The region below the Phase heater 423 of the arm portion 443 functions as a phase adjusting portion 445 that changes the phase of light. Then, the Phase heater 423 generates heat according to the electric power supplied from the control unit 3, and heats the phase adjusting unit 445. Further, by controlling the electric power supplied to the Phase heater 423 by the control unit 3, the temperature of the phase adjusting unit 445 changes, and the refractive index thereof changes.

The first and second waveguide sections 43 and 44 described above constitute an optical resonator C1 composed of a diffraction grating layer 431b optically connected to each other and a reflection mirror M1. Further, the gain unit 431a and the phase adjusting unit 445 are arranged in the optical resonator C1.

The diffraction grating layer 431b generates a first comb-shaped reflection spectrum having periodic reflection characteristics at predetermined frequency intervals. On the other hand, the ring resonator filter RF1 generates a second comb-shaped reflection spectrum having periodic reflection characteristics at predetermined frequency intervals.

Here, the second comb-shaped reflection spectrum has a peak with a full width at half maximum narrower than the peak full width at half maximum of the peak of the first comb-shaped reflection spectrum, and has a frequency interval different from the frequency interval of the first comb-shaped reflection spectrum. Has periodic reflection characteristics.

To exemplify the characteristics of each comb-shaped reflection spectrum, the frequency interval (free spectrum region: FSR) between the peaks of the first comb-shaped reflection spectrum is 373 GHz. The full width at half maximum of each peak is 43 GHz. On the other hand, the frequency interval (FSR) between the peaks of the second comb-shaped reflection spectrum is 400 GHz. The full width at half maximum of each peak is 25 GHz. That is, the full width at half maximum (25 GHz) of each peak of the second comb-shaped reflection spectrum is narrower than the full width at half maximum (43 GHz) of each peak of the first comb-shaped reflection spectrum.

In the light source unit 4, in order to realize laser oscillation, one of the peaks of the first comb-shaped reflection spectrum and one of the peaks of the second comb-shaped reflection spectrum can be superposed on the frequency axis. .. In such superposition, at least one of the DBR heater 421 and the RING heater 422 is used to heat the diffraction grating layer 431b by the DBR heater 421 and change its refractive index by the thermo-optical effect to form a first comb shape. The reflection spectrum is moved and changed as a whole on the frequency axis, and the ring-shaped waveguide 444 is heated by the RING heater 422 to change its refractive index to obtain a second comb-shaped reflection spectrum on the frequency axis. This can be achieved by performing at least one of moving and changing the whole.

On the other hand, in the light source unit 4, there is a resonator mode by the optical resonator C1. Then, in the light source unit 4, the resonator length of the optical resonator C1 is set so that the interval between the resonator modes (longitudinal mode interval) is 25 GHz or less. In the case of this setting, the resonator length of the optical resonator C1 is 1800 μm or more, and it can be expected that the line width of the oscillating laser beam is narrowed. As for the frequency of the resonator mode of the optical resonator C1, the phase heater 423 is used to heat the phase adjusting unit 445 to change its refractive index, and the frequency of the resonator mode is moved as a whole on the frequency axis. This can be fine-tuned. That is, the phase adjusting unit 445 is a part for actively controlling the optical path length of the optical resonator C1.

When the light source unit 4 injects a current from the n-side electrode 45 and the p-side electrode 433 into the gain unit 431a by the control unit 3 and causes the gain unit 431a to emit light, the peak of the spectral component of the first comb-shaped reflection spectrum, The peak of the spectral component of the second comb-shaped reflection spectrum and one of the resonator modes of the optical resonator C1 are configured to oscillate the laser at a matching frequency, for example, 193.4 THz, and output the laser beam L1. ..

In the light source unit 4, the frequency of the laser beam L1 can be changed by utilizing the vernier effect. FIG. 3 is an explanatory diagram of adjusting the frequency of the laser beam. The upper row shows the first comb-shaped reflection spectrum of the diffraction grating layer 431b (DBR), the middle row shows the second comb-shaped reflection spectrum of the reflection mirror M1 (RING), and the lower row shows the spectrum of the resonator mode. show.

When the DBR heater 421 is controlled by adjusting the power to be supplied, the comb-shaped reflection spectrum shifts from the shape shown by the solid line to the shape shown by the broken line on the frequency axis as shown by the thick arrow line. Similarly, when the RING heater 422 is controlled, its comb-shaped reflection spectrum shifts from the shape shown by the solid line to the shape shown by the broken line on the frequency axis. Similarly, when the Phase heater 423 is controlled, the spectrum shifts from the shape shown by the solid line to the shape shown by the broken line on the frequency axis.

In the state shown by the solid line, the laser oscillates at a frequency f1 in which the reflected peak of the DBR, the resonator mode of the optical resonator C1 and the reflected peak of the RING coincide with each other. In order to achieve this state, the DBR heater 421 and the RING heater 422 set frequency positions at which the reflection spectra of the DBR and RING peak, respectively, based on the supplied electric power. Further, the Phase heater 423 sets the frequency position at which the resonator mode peaks based on the supplied electric power. When the state shown by the broken line is set by controlling each heater, the frequency at which the reflected peak of the DBR, the resonator mode of the optical resonator C1 and the reflected peak of the RING coincide with each other can be set to the frequency f2, so that the frequency of the laser beam L1 is set to the frequency f2. Can be adjusted to. The power supplied to each heater can be controlled by using the current as a control amount. That is, the control unit 3 controls the frequency of the laser beam L1 by supplying electric power corresponding to the current, which is a controlled amount, to the light source unit 4. Current or power is an example of a controlled quantity.

When changing the frequency of the laser beam L1 from the first frequency to the second frequency, for example, the DBR heater 421 and the RING heater 422 are feed-forward controlled so that the comb-shaped reflection spectra of the DBR and the RING overlap at the second frequency. Then, the Phase heater 423 is feedback-controlled so that any one of the resonator modes matches the second frequency. However, the control method is not limited to this.

The explanation will be continued by returning to FIG. Although not specifically shown, the semiconductor optical amplifier 5 has an embedded waveguide structure including an active core layer made of the same material and structure as the first waveguide 43. However, the diffraction grating layer 431b is not provided. The semiconductor optical amplifier 5 is optically coupled to the light source unit 4 by a space-coupling optical system (not shown). Then, the laser beam L1 output from the light source unit 4 is input to the semiconductor optical amplifier 5. The semiconductor optical amplifier 5 amplifies the laser beam L1 and outputs it as the laser beam L2. The semiconductor optical amplifier 5 may be monolithically configured with the light source unit 4 on the base portion B1.

The plane light wave circuit 6 is optically coupled to the arm portion 442 by a space-coupling optical system (not shown). Then, a part of the laser light L3 generated by the laser oscillation in the light source unit 4 is input to the plane light wave circuit 6 via the arm unit 442 as in the laser light L1. The laser beam L3 has the same frequency as the frequency of the laser beam L1 and has an intensity corresponding to the intensity of the laser beam L1. The plane lightwave circuit 6 includes an optical branching portion 61, an optical waveguide 62, and an optical waveguide 63 having a frequency filter 63a which is a ring resonator type optical filter.

The optical branching unit 61 branches the input laser beam L3 into two laser beams L4 and L5.
Then, the optical waveguide 62 guides the laser beam L4 to the PD (Photo Diode) 71 described later in the photodetector 7. Further, the optical waveguide 63 guides the laser beam L5 to the PD 72 described later in the photodetector 7.

Here, the frequency filter 63a has a characteristic that the transmittance changes periodically with respect to the frequency of the input light, and transmits the laser light L5 at a transmittance corresponding to the frequency of the laser light L5. Then, the laser beam L5 transmitted through the frequency filter 63a is input to the PD 72. That is, the frequency filter 63a is a waveguide type frequency filter. As the frequency filter 63a, an etalon filter or an MZI (Mach-Zehnder Interferometer) filter having a periodic transmission characteristic with respect to the frequency of the input light may be used.

The photodetector 7 includes PDs 71 and 72. The PD71 receives the laser light L4 (having the same frequency as the laser light L1 output from the light source unit 4 and having an intensity corresponding to the intensity of the laser light L1), and corresponds to the intensity of the laser light L4. The electric signal is output to the control unit 3. The PD 72 receives the laser beam L5 that has passed through the frequency filter 63a, and outputs an electric signal corresponding to the intensity of the laser beam L5 to the control unit 3. The electric signals output from the PDs 71 and 72 are used for frequency lock control by the control unit 3 (control for setting the frequency of the laser beam L1 output from the light source unit 4 to the target frequency).

PD71 is an example of a first detection unit that detects the first intensity, which is the intensity of the laser beam L4 corresponding to the intensity of the laser beam L1. PD72 is an example of a second detection unit that detects the second intensity, which is the intensity of the laser light L5, which corresponds to the intensity after the laser light L1 has passed through the frequency filter 63a.

The temperature sensor 8 is composed of, for example, a thermistor or the like, and detects the ambient temperature of the light source unit 4 and the planar light wave circuit 6. The temperature sensor 8 may be arranged outside the temperature controller 9 and detect the temperature of the environment in which the laser device 1 is arranged as the ambient temperature. The temperature sensor 8 outputs an electric signal including the detected temperature information to the control unit 3.

The temperature controller 9 is composed of, for example, a TEC (Thermo Electric Cooler) including a Perche element or the like. A light source unit 4, a semiconductor optical amplifier 5, a planar light wave circuit 6, a photodetector unit 7, and a temperature sensor 8 are mounted on the temperature controller 9. Then, the temperature controller 9 adjusts the temperatures of the light source unit 4, the semiconductor optical amplifier 5, the planar light wave circuit 6, the photodetector unit 7, and the temperature sensor 8 according to the supplied power. In this case, the control unit 3 controls the electric power supplied to the temperature controller 9 so that the light source unit 4 mainly has a constant temperature based on the temperature information detected by the temperature sensor 8. It is preferable to control the light source unit 4 so that the temperature becomes constant in order to suppress fluctuations in the frequency of the laser beam L1 depending on the operating conditions and the external environmental temperature.

In the temperature controller 9, the light source unit 4 and the semiconductor optical amplifier 5 provide an installation surface 91 on which the light source unit 4, the semiconductor optical amplifier 5, the plane lightwave circuit 6, the light detection unit 7, and the temperature sensor 8 are mounted. When the temperature sensor 8 is divided into two regions, a first region Ar1 on which the light wave circuit 6 is mounted and a second region Ar2 on which the plane lightwave circuit 6 and the light detection unit 7 are mounted, the temperature sensor 8 has a second region. It is placed on Ar2. That is, the temperature sensor 8 is arranged close to the plane light wave circuit 6. However, the temperature sensor 8 may be placed in the first region Ar1 and may be arranged close to the light source unit 4.

[Structure of control unit]
Next, the configuration of the control unit 3 will be described. FIG. 4 is a block diagram showing the configuration of the control unit. The control unit 3 is connected to, for example, a higher-level control device (not shown) provided with a user interface, and controls the operation of the laser unit 2 according to an instruction from the user via the higher-level control device.

In the following, frequency lock control by the control unit 3 which is the main part of the present invention will be mainly described. Further, in FIG. 4, for convenience of explanation, a configuration for executing frequency lock control is mainly shown as a configuration of the control unit 3.

The control unit 3 includes analog-to-digital converters (ADCs) 31 and 32, a calculation unit 33, a storage unit 34, and a current source 35.

The ADC 31 converts the analog electric signal input from the PD 72 into a digital signal and outputs it to the calculation unit 33. The ADC 32 converts the analog electric signal input from the PD 71 into a digital signal and outputs it to the calculation unit 33.

The calculation unit 33 performs various calculation processes for control executed by the control unit 3, and is composed of, for example, a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array). The storage unit 34 has a portion composed of, for example, a ROM (Read Only Memory) in which various programs and data used by the arithmetic unit 33 for performing arithmetic processing are stored, and when the arithmetic unit 33 performs arithmetic processing. It is provided with a portion composed of, for example, a RAM (Random Access Memory), which is used for storing the work space of the above, the result of the arithmetic processing of the arithmetic unit 33, and the like. The control function of the control unit 3 is realized by software by the functions of the calculation unit 33 and the storage unit 34.

The current source 35 supplies electric power for controlling the frequency of the laser beam L1 to the light source unit 4 based on the instruction from the calculation unit 33. In the present embodiment, the calculation unit 33 instructs the current source 35 to indicate the current value as a control amount. The current source 35 supplies the current of the instructed current value to the light source unit 4.

Next, the configuration of the calculation unit 33 will be described in detail. As functional units, the calculation unit 33 includes a PD ratio calculation unit 331, a target frequency setting unit 332, a target PD ratio setting unit 333, a difference acquisition unit 334, a current acquisition unit 335, and a control constant determination unit 336. It includes a PID control unit 337 and a DBR / RING power setting unit 338. These functional parts are realized by the cooperation of software and hardware resources.

The PD ratio calculation unit 331 calculates the PD ratio from the digital signals input from the ADCs 31 and 32. The PD ratio is the ratio of the second intensity detected by PD72 to the first intensity detected by PD71. This PD ratio is a monitor value and is also called a monitor PD ratio.

The PD ratio will be described. FIG. 5 is an explanatory diagram of a discrimination curve based on the relationship between the frequency and the PD ratio. The PD ratio changes periodically with respect to the frequency corresponding to the transmission characteristic of the frequency filter 63a. In the example shown in FIG. 5, the PD ratio is standardized so as to change between 0 and 1, but the PD ratio may be standardized so as to change between -1 and +1. Further, the monitor value may be calculated only from the second intensity detected by the PD 72 and transmitted through the frequency filter 63a. Even in such a case, the subsequent processing can be performed with the monitor value as the PD ratio. In addition, the monitor value of the PD71 at each frequency is acquired in advance and stored in the storage unit 34 or the like, and the monitor of the PD71 acquired in advance according to the value or range of the target frequency when calculating the PD ratio. The PD ratio may be calculated using the value. As described above, the set value or the monitor value may include a value corresponding to the second intensity.

In FIG. 5, when the frequency of the laser beam L1 is f3 as shown by the point P3 indicated by the black circle, the PD ratio calculated by the PD ratio calculation unit 331 is R3. This means that if the light source unit 4 is controlled so that the PD ratio becomes R3, a frequency lock that locks the frequency of the laser beam L1 to f3 is realized. The PD ratio is an amount corresponding to the frequency of the laser beam L1, and is an example of a monitor value corresponding to the frequency equivalent amount. The point P3 is a control target point when the frequency of the laser beam L1 is controlled to f3, and is also called a lock point.

Since the discrimination curve changes periodically, the same PD ratio may be obtained for different frequencies. In the laser device 1, when a target frequency is set, electric power corresponding to the target frequency is supplied to each of the DBR heater 421 and the RING heater 422 according to the target frequency. As a result, the first comb-shaped reflection spectrum and the second comb-shaped reflection spectrum overlap in the frequency range including the target frequency, and the frequency range in which laser oscillation is possible is limited.

The explanation will be continued by returning to FIG. The target frequency setting unit 332 sets the target frequency as the target value of the frequency of the laser beam L1 by, for example, instructing from a higher-level control device. The target value of the frequency of the laser beam L1 is an example of the set value. The set value determines the control amount accordingly.

The target PD ratio setting unit 333 sets a target PD ratio, which is an amount equivalent to the target frequency, based on the target frequency set by the target frequency setting unit 332. The target PD ratio is set by using table data or a relational expression showing the correspondence between the frequency stored in the storage unit 34 and the PD ratio. This correspondence is determined based on the discrimination curve generated by the frequency filter 63a.

The difference acquisition unit 334 calculates and acquires the difference between the monitor PD ratio calculated by the PD ratio calculation unit 331 and the target PD ratio set by the target PD ratio setting unit 333.

The current acquisition unit 335 acquires a current value as a set value set by the PID control unit 337, which will be described later, or acquires a current value flowing through the current source 35 as a monitor value, and determines the acquired current value as a control constant. Output to unit 336.

The control constant determination unit 336 performs a setting step of setting a control constant for determining a control amount according to the current value and the target frequency (or target PD ratio). In the first embodiment, the proportionality constant Kp in the proportional control for determining the current value, which is the control amount instructed to the light source unit 4, is set. The storage unit 34 stores a plurality of control constants for determining the control amount according to the set value or the monitor value. The control constant determination unit 336 reads an appropriate control constant from the storage unit 34, refers to the control constant, and sets the control constant.

The PID control unit 337 sets the current value based on the differential constant Kd and the integral constant Ki corresponding to the difference between the monitor PD ratio and the target PD ratio, and the proportional constant Kp determined by the control constant determining unit 336. The instruction of the current value can be output to the current source 35 to perform proportional integral differentiation (PID) control. However, in this embodiment, PI control is performed.

The DBR / RING power setting unit 338 sets the power to be supplied to each of the DBR heater 421 and the RING heater 422 based on the target frequency set by the target frequency setting unit 332. The DBR / RING power setting unit 338 can set a current value based on the set power, output an instruction of the current value to the current source 35, and perform feedforward control of the DBR heater 421 and the RING heater 422. ..

[Control method]
Next, the control method executed in the laser device 1 will be described. The laser unit 2 has a characteristic that the frequency of the laser beam L1 changes non-linearly with respect to a set value or a monitor value used when controlling the frequency of the laser beam L1.

FIG. 6 is a diagram showing an example of the relationship between the Phase current as an example of the set value or the monitor value and the frequency of the laser beam L1. Here, the Phase current is a current supplied to the Phase heater 423. As shown in FIG. 6, the frequency of the laser beam L1 has a characteristic of changing non-linearly with respect to the Phase current. The reason may be, for example, the calorific value with respect to the current value of the Phase heater 423, the change in the frequency of the resonator mode with respect to the calorific value, or the correlation between the calorific value and the change may be non-linear.

Here, when one value is applied to all the current values for the control constant, for example, the proportionality constant Kp, for example, in the region A on the left side of the broken line DL in FIG. 6, the frequency change with respect to the current value change Since the absolute value of the slope is small, the convergence time for controlling to the target frequency may increase. Further, in the region B on the right side of the broken line DL in FIG. 6, since the absolute value of the slope of the frequency change with respect to the change of the current value is large, oscillation, overshoot, or undershoot may occur.

Therefore, in this control method, different proportionality constants Kp are set according to the range of possible current values. In the example shown in FIG. 7, different proportional constants Kp1, Kp2, Kp3, and Kp4 are set for the ranges I1, I2, I3, and I4 of different current values. In the case of FIG. 7, the ranges I1, I2, I3, and I4 are all ranges in which the frequency changes by 1 GHz, but the ranges I1, I2, I3, and I4 are different in magnitude from each other due to non-linearity. ..

At this time, in the ranges I1, I2, I3, and I4, the absolute value of the slope of the curve gradually increases in this order. Therefore, the values of the proportionality constants Kp1, Kp2, Kp3, and Kp4 are set so that Kp1> Kp2> Kp3> Kp4.

That is, when the first range and the second range are arbitrarily selected from the ranges I1, I2, I3, and I4, which are different ranges in which the current value can be taken, the control constant in the range in which the absolute value of the slope is smaller is tilted. The absolute value of is set larger than the control constant in the larger range. For example, when the absolute value of the slope in the first range is smaller than the absolute value of the slope in the second range, the proportionality constant in the first range is set to be larger than the proportionality constant in the second range. As a result, it is possible to reduce the dependence of the amount of frequency change with respect to the amount of change of the current value, which is the control amount, on the range of the current value, so that the convergence time is increased, oscillation, or overshoot or undershoot occurs. It is suppressed. As a result, more suitable control is realized when controlling the frequency of the laser beam.

In FIG. 7, the change in frequency is the same and the range of the current value corresponding to 1 GHz is set, but the change in frequency may be different for each range. Further, the widths of the current value ranges may be equal to each other.

Further, in this control method, when performing change control for changing the frequency or frequency equivalent of the laser beam L1 from the first set value to the second set value, a proportional constant is used according to the elapsed time from the start time of the change control. To set.

FIG. 8 is a diagram showing an example of setting a proportionality constant with respect to the elapsed time from the start time of the change control of the PD ratio, which is a frequency equivalent amount. In this example, when changing the PD ratio from the current PD ratio, which is the first set value, to the target PD ratio, which is the second set value, Kpt1 is set as a proportional constant until the passage of time t1, and the time t1 After the lapse, Kpt2 is set. For example, Kpt1 can be determined from the current Phase current value, and Kpt2 can be determined from the target frequency or the second set value corresponding to the target frequency.

As described above, since the discrimination curve changes periodically, if the PD ratio is changed suddenly, the lock point will overshoot beyond the frequency range specified on the discrimination curve, and the frequency will be different from the target frequency. May be locked by. Therefore, if Kpt2 is set smaller than Kpt1, a sudden change in the PD ratio when the PD ratio is close to the target PD ratio can be suppressed, so that the occurrence of overshoot and the occurrence of frequency lock at a different frequency can be suppressed. .. In this example, the set value of the proportionality constant is changed before and after the elapse of the time t1, but the reference time for changing the set value of the proportionality constant is set in addition to the time t1, and more steps are taken. You may change the set value with.

〔flowchart〕
FIG. 9 shows the frequency or frequency equivalent of the laser beam L1 by the control unit 3 described above from the first set value (current set frequency or current PD ratio) to the second set value (target frequency or target PD ratio). It is a flowchart which shows the control method of the change control which changes to).

First, in step S101, the target frequency setting unit 332 sets the target frequency as the target value of the frequency of the laser beam L1.

Subsequently, in step S102, the control constant determination unit 336 determines the proportional constant Kpt2 based on the target frequency set by the target frequency setting unit 332.

Subsequently, in step S103, the DBR / RING power setting unit 338 sets the power to be supplied to each of the DBR heater 421 and the RING heater 422 based on the target frequency set by the target frequency setting unit 332.

Subsequently, in step S104, the current acquisition unit 335 acquires the current Phase current value (set value or monitor value).

Subsequently, in step S105, the control constant determination unit 336 determines the proportionality constant Kpt1 based on the current Phase current value acquired by the current acquisition unit 335. The proportionality constant already used for controlling the Phase current value may be determined as Kpt1. This Kpt1 is determined to be equal to any of Kp1, Kp2, Kp3, and Kp4, for example, depending on which of the ranges I1, I2, I3, and I4 shown in FIG. 7 includes the Phase current. ..

Subsequently, in step S106, the target PD ratio setting unit 333 sets the target PD ratio, which is an amount equivalent to the target frequency, based on the target frequency set by the target frequency setting unit 332 in step S101.

Subsequently, in step S107, the PD ratio calculation unit 331 calculates and acquires the monitor PD ratio.

Subsequently, in step S108, the difference acquisition unit 334 acquires the difference between the target PD ratio and the monitor PD ratio (target PD ratio-monitor PD ratio).

Subsequently, in step S109, the PID control unit 337 determines whether or not the elapsed time from the start time of the change control is t1 (for example, 1 second) or more. When it is determined that the value is less than t1 (step S109, No), Kpt1 is set as the proportionality constant in step S110. When it is determined that it is t1 or more (step S109, Yes), Kpt2 is set as a proportionality constant in step S111.

Subsequently, in step S112, the PID control unit 337 uses Kpt1 or Kpt2 and a preset integration constant Ki so that the absolute value of the difference | target PD ratio-monitor PD ratio | becomes smaller. , Performs PI control on the Phase current.

Subsequently, in step S113, the PID control unit 337 determines whether or not | target PD ratio-monitor PD ratio | is within the target error. If it is determined that the error is not within the target error (step S113, No), the control returns to step S107. When it is determined that the target error is within the target error (step S113, Yes), the control ends.

(Embodiment 2)
Next, the laser apparatus according to the second embodiment will be described. The laser apparatus according to the second embodiment has a configuration in which the control unit 3 of the laser apparatus 1 of the first embodiment is replaced with the control unit 3A. The control unit 3A will be described in detail below.

[Structure of control unit]
FIG. 10 is a block diagram showing the configuration of the control unit 3A according to the second embodiment. The control unit 3A is connected to, for example, a higher-level control device (not shown) provided with a user interface, and controls the operation of the laser unit 2 according to an instruction from the user via the higher-level control device.

The control unit 3A has a configuration in which the calculation unit 33 of the control unit 3 is replaced with the calculation unit 33A. The calculation unit 33A has a configuration in which the current acquisition unit 335 is deleted from the configuration of the calculation unit 33.

As described above, in the relationship between the frequency and the PD ratio, the PD ratio has the characteristic of a discrimination curve that changes periodically and smoothly with respect to the frequency corresponding to the transmission characteristic of the frequency filter 63a. The slope of such a discrimination curve differs depending on the frequency. That is, the frequency of the laser beam L1 changes non-linearly with respect to the PD ratio, which is a set value or a monitor value used when controlling the frequency of the laser beam L1.

Therefore, in the control in the control unit 3A, the target PD ratio or the monitor PD ratio is set by utilizing the fact that the slope of the corresponding discrimination curve differs depending on the target PD ratio which is the set value or the monitor PD ratio which is the monitor value. Set the control constant accordingly.

For example, in the first range and the second range, which are different ranges in which the target PD ratio or the monitor PD ratio can be taken, the control constant in the range in which the absolute value of the slope is smaller is set in the range in which the absolute value of the slope is larger. Set larger than the control constant. For example, when the absolute value of the slope in the first range is smaller than the absolute value of the slope in the second range, the control constant in the first range is set larger than the control constant in the second range. For example, in FIG. 5, when the PD ratio is 0.7, for example, the absolute value of the slope of the discrimination curve is smaller than the absolute value of the slope when the PD ratio is 0.5. Set larger than the proportionality constant when is 0.5. The relationship between the PD ratio and the setting of the proportionality constant is stored in the storage unit 34 as table data or a relational expression, and is appropriately called and used by the control constant determination unit 336.

As a result, the dependence of the amount of frequency change with respect to the PD ratio on the PD ratio can be reduced, so that an increase in convergence time, oscillation, or occurrence of overshoot or undershoot is suppressed. As a result, more suitable control is realized when controlling the frequency of the laser beam.

〔flowchart〕
FIG. 11 shows the frequency or frequency equivalent of the laser beam L1 by the control unit 3A described above from the first set value (current set frequency or current PD ratio) to the second set value (target frequency or target PD ratio). It is a flowchart which shows the control method of the change control which changes to).

First, in step S201, the target frequency setting unit 332 sets the target frequency as the target value of the frequency of the laser beam L1.

Subsequently, in step S202, the target PD ratio setting unit 333 sets the target PD ratio, which is an amount equivalent to the target frequency, based on the target frequency set by the target frequency setting unit 332 in step S201.

Subsequently, in step S203, the control constant determination unit 336 determines the proportionality constant Kpt2 based on the target PD ratio set by the target PD ratio setting unit 333. The proportionality constant Kpt2 is a proportionality constant set based on the slope of the discrimination curve at the target PD ratio.

At any timing from the execution of step S201 to before the execution of step S204, the DBR / RING power setting unit 338 uses the DBR heater 421 and the RING heater based on the target frequency set by the target frequency setting unit 332. The power to be supplied to each of the 422s is set.

Subsequently, in step S204, the PD ratio calculation unit 331 calculates and acquires the monitor PD ratio as the current PD ratio.

Subsequently, in step S205, the control constant determination unit 336 determines the proportionality constant Kpt1 based on the monitor PD ratio acquired by the PD ratio calculation unit 331. The proportionality constant already used for controlling the Phase current value may be determined as Kpt1. The proportionality constant Kpt1 is a proportionality constant set based on the slope of the discrimination curve in the monitor PD ratio.

Subsequently, in step S207, the difference acquisition unit 334 acquires the difference between the target PD ratio and the monitor PD ratio (target PD ratio-monitor PD ratio).

Subsequently, in step S208, the PID control unit 337 determines whether or not the elapsed time from the start time of the change control is t1 (for example, 1 second) or more. When it is determined that the value is less than t1 (step S208, No), Kpt1 is set as the proportionality constant in step S209. When it is determined that it is t1 or more (step S208, Yes), Kpt2 is set as a proportionality constant in step S210.

Subsequently, in step S211 the PID control unit 337 uses Kpt1 or Kpt2 and a preset integration constant Ki so that the absolute value of the difference | target PD ratio-monitor PD ratio | becomes smaller. , Performs PI control on the Phase current.

Subsequently, in step S212, the PID control unit 337 determines whether or not | target PD ratio-monitor PD ratio | is within the target error. If it is determined that the error is not within the target error (step S212, No), the control returns to step S206. When it is determined that the target error is within (step S212, Yes), the control ends.

(Embodiment 3)
Next, the laser apparatus according to the third embodiment will be described. The laser apparatus according to the third embodiment has a configuration in which the control unit 3 of the laser apparatus of the first embodiment is replaced with the control unit 3B. The control unit 3B will be described in detail below.

[Structure of control unit]
FIG. 12 is a block diagram showing a configuration of the control unit 3B according to the third embodiment. The control unit 3B is connected to, for example, a higher-level control device (not shown) provided with a user interface, and controls the operation of the laser unit 2 according to an instruction from the user via the higher-level control device.

The control unit 3B has a configuration in which the calculation unit 33 of the control unit 3 is replaced with the calculation unit 33B. The calculation unit 33B has a configuration in which a compensation amount determination unit 339 as a functional unit is added to the configuration of the calculation unit 33.

As described in the description of the second embodiment, the frequency of the laser beam L1 changes non-linearly with respect to the PD ratio which is a set value or a monitor value used when controlling the frequency of the laser beam L1.

In the control in the control unit 3B, similarly to the control in the control unit 3A, the control is performed according to the target PD ratio or the monitor PD ratio by utilizing the fact that the slope of the discrimination curve is different according to the target PD ratio or the monitor PD ratio. Set a constant. For example, in the first range and the second range, which are different ranges in which the target PD ratio or the monitor PD ratio can be taken, the control constant in the range in which the absolute value of the slope is smaller is set in the range in which the absolute value of the slope is larger. Set larger than the control constant. For example, when the absolute value of the slope in the first range is smaller than the absolute value of the slope in the second range, the control constant in the first range is set larger than the control constant in the second range. For example, in FIG. 5, when the PD ratio is 0.7, for example, the absolute value of the slope of the discrimination curve is smaller than the absolute value of the slope when the PD ratio is 0.5. Set larger than the proportionality constant when is 0.5.

However, in the control unit 3B of the third embodiment, the setting of the proportionality constant is different from the control in the control unit 3A. For example, if the proportionality constant when the PD ratio is 0.5 is Kp as the reference proportionality constant, the compensation amount α is determined for Kp, and α is added, divided, multiplied, or subtracted according to the range of the PD ratio. To set the proportionality constant when the PD ratio is, for example, 0.7. For example, when α is a positive number, the proportionality constants may be set as Kp, Kp + α, Kp + 2α, ... As the absolute value of the slope of the discrimination curve becomes smaller. The relationship between the PD ratio and the α to be determined and the calculation such as addition, subtraction, multiplication and division thereof is stored in the storage unit 34 as table data and a relational expression, and the compensation amount determination unit 339 and the control constant determination unit are stored. 336 calls and uses it as appropriate.

As a result, the dependence of the amount of frequency change with respect to the PD ratio on the PD ratio can be reduced, so that an increase in convergence time, oscillation, or occurrence of overshoot or undershoot is suppressed. As a result, more suitable control is realized when controlling the frequency of the laser beam. In addition, Kp as a reference proportionality constant may be determined according to the current Phase current or the set value of the Phase current corresponding to the target frequency by the control method shown in the first embodiment.

Further, in this control method, when performing change control for changing the frequency or frequency equivalent of the laser beam L1 from the first set value to the second set value, the rate of arrival from the first set value to the second set value is reached. Set the proportionality constant accordingly.

FIG. 13 is a diagram showing an example of setting a proportionality constant with respect to the elapsed time from the start time of the change control of the PD ratio, which is a frequency equivalent amount. In this example, when changing the PD ratio from the current PD ratio, which is the first set value, to the target PD ratio, which is the second set value, as a proportional constant until the PD ratio reaches 50% of the target PD ratio. Kp% 1 is set, and after reaching 50%, Kp% 2 is set. When the PD ratio is the current PD ratio, the arrival rate is 0%, and when the PD ratio is the target PD ratio, the arrival rate is 100%. For example, Kp% 1 can be determined from the value of the current Phase current value, and Kp% 2 can be determined from the target frequency or the second set value corresponding to the target frequency.

As in the case of Kpt, if Kp% 2 is set smaller than Kp% 1, a sudden change in the PD ratio when the PD ratio is close to the target PD ratio can be suppressed, so that the frequency is different from the occurrence of overshoot. It is possible to suppress the occurrence of frequency lock. In this control, the set value of the proportionality constant is changed when the arrival rate is around 50%, but the arrival rate, which is the reference for changing the set value of the proportionality constant, is set in addition to 50% to increase the number. The set value may be changed at the stage of.

〔flowchart〕
FIG. 14 shows the frequency or frequency equivalent of the laser beam L1 by the control unit 3B described above from the first set value (current set frequency or current PD ratio) to the second set value (target frequency or target PD ratio). It is a flowchart which shows the control method of the change control which changes to).

First, in step S301, the target frequency setting unit 332 sets the target frequency as the target value of the frequency of the laser beam L1.

Subsequently, in step S302, the control constant determination unit 336 determines the proportionality constant Kp% 2 based on the target frequency set by the target frequency setting unit 332.

Subsequently, in step S303, the DBR / RING power setting unit 338 sets the power to be supplied to each of the DBR heater 421 and the RING heater 422 based on the target frequency set by the target frequency setting unit 332.

Subsequently, in step S304, the current acquisition unit 335 acquires the current Phase current value (set value or monitor value).

Subsequently, in step S305, the control constant determination unit 336 determines the proportionality constant Kp% 1 based on the current Phase current value acquired by the current acquisition unit 335. The proportionality constant already used for controlling the Phase current value may be determined as Kp% 1. This Kp% 1 is determined to be equal to any of Kp1, Kp2, Kp3, and Kp4, for example, depending on which of the ranges I1, I2, I3, and I4 shown in FIG. 7 includes the Phase current. Will be done.

Subsequently, in step S306, the target PD ratio setting unit 333 sets the target PD ratio, which is an amount equivalent to the target frequency, based on the target frequency set by the target frequency setting unit 332 in step S301.

Subsequently, in step S307, the PD ratio calculation unit 331 calculates and acquires the monitor PD ratio.

Subsequently, in step S308, the compensation amount determination unit 339 sets the compensation amount α according to the target PD ratio or the monitor PD ratio.

Subsequently, in step S309, the control constant determination unit 336 compensates for Kp% 1 and Kp% 2 using the compensation amount α.

Subsequently, in step S310, the difference acquisition unit 334 acquires the difference between the target PD ratio and the monitor PD ratio (target PD ratio-monitor PD ratio).

Subsequently, in step S311 the PID control unit 337 determines whether or not the arrival rate is less than 50%. If it is determined that it is less than 50% (step S311, Yes), Kp% 1 is set as the proportionality constant in step S312. When it is determined that it is 50% or more (step S311, No), Kp% 2 is set as the proportionality constant in step S312.

Subsequently, in step S314, the PID control unit 337 uses Kp% 1 or K% 2 and a preset integration constant Ki to set the absolute value of the difference | target PD ratio-monitor PD ratio | PI control regarding the Phase current is performed so as to be small.

Subsequently, in step S315, the PID control unit 337 determines whether or not | target PD ratio-monitor PD ratio | is within the target error. If it is determined that the error is not within the target error (step S315, No), the control returns to step S307. When it is determined that the target error is within (step S315, Yes), the control ends.

(Embodiment 4)
Next, the laser apparatus according to the fourth embodiment will be described. The laser apparatus according to the fourth embodiment has a configuration in which the control unit 3B of the laser apparatus according to the third embodiment is replaced with the control unit 3C. The control unit 3C will be described in detail below.

[Structure of control unit]
FIG. 15 is a block diagram showing the configuration of the control unit 3C according to the fourth embodiment. The control unit 3C is connected to, for example, a higher-level control device (not shown) provided with a user interface, and controls the operation of the laser unit 2 according to an instruction from the user via the higher-level control device. The control unit 3C has a configuration in which the calculation unit 33B of the control unit 3B is replaced with the calculation unit 33C. The calculation unit 33B and the calculation unit 33C have the same configuration, but the control methods to be executed are different from each other.

As described in the description of the second embodiment, the frequency of the laser beam L1 changes non-linearly with respect to the PD ratio which is the set value or the monitor value used when controlling the frequency of the laser beam L1, and the target PD ratio or the monitor. The slope of the corresponding discrimination curve differs depending on the PD ratio.

FIG. 16 is an explanatory diagram of an example in which the sign of the change in inclination changes between the set value for starting the change control of the PD ratio and the set value for the target. In FIG. 16, in the discrimination curve whose frequency is on the horizontal axis, from the point P5 showing the current value which is the current PD ratio value to the point P6 which is the target PD ratio value, the point P7 which is the median PD ratio. It shows the case where change control is performed via. Further, the change control for changing the frequency in this way corresponds to the case where the change control is performed from the point P5 to the point P6 via the point P7 when the horizontal axis is represented as the time t as shown by the thick arrow. ..

As shown in FIG. 16, the absolute value of the slope of the discrimination curve at points P5 and P6 is smaller than the absolute value of the slope of the discrimination curve at point P7. This corresponds to a change in the sign of the change in the slope of the discrimination curve while changing the PD ratio from the point P5 corresponding to the first set value to the point P6 corresponding to the second set value. In the example shown in FIG. 16, the slope changes so as to have a negative value and an absolute value as the frequency increases from the point P5, and the change in the slope has a negative value, but from the vicinity of the point P7 to the point P6. As the frequency increases, the slope changes so that it has a negative value and an absolute value, and the change in slope is a positive value. That is, the discrimination curve has an inflection point between the points P5 and P6.

If the sign of the change in slope changes while changing from the first set value to the second set value in this way, the following situations may occur. That is, it is preferable that the slope of the discrimination curve is relatively small and the control constant is relatively large at the first set value and the second set value. However, it is preferable that the slope of the discrimination curve is larger in the vicinity of the inflection point than in the case of the first set value and the second set value, and the control constant is set relatively small. As a result, if control is performed using the control constant suitable for the first set value or the second set value as it is in the vicinity of the inflection point, the control constant becomes larger than the suitable value, and overshoot or undershoot occurs. Instability of control may occur.

Therefore, in the method of this example, in the change control, when the sign of the change in the slope of the discrimination curve changes while changing from the first set value to the second set value, a predetermined range including the point where the sign changes. In, a control constant smaller than the control constant outside the predetermined range is set. The predetermined range is, for example, a range of 0.4 to 0.6 when the discrimination curve is a sinusoidal curve and the value is standardized to change from 0 to 1. Since the inflection point is 0.5, 0.4 to 0.6 is in the range of ± 10% from the inflection point with respect to the amplitude of the discrimination curve.

When setting a control constant smaller than the control constant outside the range in the predetermined range, the control constants set separately within the predetermined range and outside the range may be used, or the same control constant may be used. On the other hand, the one to which the compensation amount is applied may be used.

〔flowchart〕
FIG. 17 shows the frequency or frequency equivalent of the laser beam L1 by the control unit 3C described above from the first set value (current set frequency or current PD ratio) to the second set value (target frequency or target PD ratio). It is a flowchart which shows the control method of the change control which changes to).

First, in step S401, the target frequency setting unit 332 sets the target frequency as the target value of the frequency of the laser beam L1.

Subsequently, in step S402, the control constant determination unit 336 determines the proportionality constant Kp% 2 based on the target frequency set by the target frequency setting unit 332.

Subsequently, in step S403, the DBR / RING power setting unit 338 sets the power to be supplied to each of the DBR heater 421 and the RING heater 422 based on the target frequency set by the target frequency setting unit 332.

Subsequently, in step S404, the current acquisition unit 335 acquires the current Phase current value (set value or monitor value).

Subsequently, in step S405, the control constant determination unit 336 determines the proportionality constants Kp% 1 and Kp% 3 based on the current Phase current value acquired by the current acquisition unit 335. The proportionality constants already used to control the Phase current value may be determined as Kp% 1 and Kp% 3. This Kp% 1 is determined to be equal to any of Kp1, Kp2, Kp3, and Kp4, for example, depending on which of the ranges I1, I2, I3, and I4 shown in FIG. 7 includes the Phase current. Will be done. Further, Kp% 3 can be determined based on the target frequency and the current Phase current value.

Subsequently, in step S406, the target PD ratio setting unit 333 sets the target PD ratio, which is an amount equivalent to the target frequency, based on the target frequency set by the target frequency setting unit 332 in step S301.

Subsequently, in step S407, the PD ratio calculation unit 331 calculates and acquires the monitor PD ratio.

Subsequently, in step S408, the compensation amount determination unit 339 sets the compensation amount α according to the target PD ratio or the monitor PD ratio.

Subsequently, in step S409, the control constant determination unit 336 compensates for Kp% 1, Kp% 2, and Kp% 3 using the compensation amount α.

Subsequently, in step S410, the difference acquisition unit 334 acquires the difference between the target PD ratio and the monitor PD ratio (target PD ratio-monitor PD ratio).

Subsequently, in step S411, the PID control unit 337 determines whether or not the monitor PD ratio is within the range of 0.4 to 0.6. When it is determined that the range is in the range of 0.4 to 0.6 (step S411, Yes), Kp% 3 is set as the proportionality constant in step S412. If it is determined that the range is out of the range of 0.4 to 0.6 (step S411, No), the flow proceeds to step S413.

In step S413, the PID control unit 337 determines whether or not the arrival rate is less than 50%. If it is determined that it is less than 50% (step S413, Yes), Kp% 1 is set as the proportionality constant in step S414. When it is determined that the content is 50% or more (step S413, No), Kp% 2 is set as the proportionality constant in step S415.

Subsequently, in step S416, the PID control unit 337 is the absolute value of the difference using Kp% 1, K% 2 or Kp% 3 and the preset integration constant Ki | Target PD ratio-monitor. PI control related to the Phase current is performed so that the PD ratio | becomes small.

Subsequently, in step S417, the PID control unit 337 determines whether or not | target PD ratio-monitor PD ratio | is within the target error. If it is determined that the error is not within the target error (step S417, No), the control returns to step S407. When it is determined that the target error is within (step S417, Yes), the control ends.

In any of the above embodiments, in the setting of the control constant in the case of change control, it may be set according to either one or both of the elapsed time and the arrival rate. Further, in setting the control constant in the case of change control, the control constant may be set in multiple stages based on the current frequency and the target frequency instead of the elapsed time and the arrival rate. Further, in the above embodiment, the case where the feedback control is PI control and the control constant is a proportional constant has been described, but the feedback control may be PID control, and the above control constants are used with respect to the integral constant and the differential constant. The settings may be applied.

Moreover, the present invention is not limited by the above-described embodiment. The present invention also includes a configuration in which the above-mentioned components are appropriately combined. Further, 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.

1 Laser device 2 Laser unit 3, 3A, 3B, 3C Control unit 4 Light source unit 5 Semiconductor optical amplifier 6 Plane light wave circuit 7 Light detection unit 8 Temperature sensor 9 Temperature controller 10 Monitor unit 33, 33A, 33B, 33C Calculation unit 34 Storage unit 35 Current source 41 Laser main unit 42 Change unit 43 First waveguide unit 44 Second waveguide unit 44a Optical waveguide layer 45 n-side electrode 61 Optical branching unit 62, 63 Optical waveguide 63a Frequency filter 91 Installation surface 331 PD ratio calculation unit 332 Target frequency setting unit 333 Target PD ratio setting unit 334 Difference acquisition unit 335 Current acquisition unit 336 Control constant determination unit 337 PID control unit 338 DBR / RING Power setting unit 339 Compensation amount determination unit 421 DBR heater 422 RING heater 423 Phase heater 431 Waveguide section 431a Gain section 431b Diffraction grating layer 432 Semiconductor lamination section 433 p-side electrode 441a waveguide section 442, 443 Arm section 444 Ring-shaped waveguide section 445 Phase adjustment section A, B Region Ar1 First region Ar2 First Region B1 Base C Optical Resonator I1, I2, I3, I4 Range L1, L2, L3, L4, L5 Laser Light M1 Reflection Mirror RF1 Ring Resonator Filter

Claims (9)

A laser unit including a light source unit that makes the frequency of the output laser light variable, and a monitor unit that acquires a monitor value corresponding to a frequency equivalent amount corresponding to the frequency of the laser light.
A control unit that controls the frequency of the laser beam by supplying a control amount to the light source unit according to a set value, and a control unit.
A storage unit that stores a plurality of control constants for determining the control amount according to the set value or the monitor value.
With
The laser unit has a characteristic that the frequency of the laser beam changes non-linearly with respect to the set value or the monitor value used when controlling the frequency of the laser beam.
The control unit
A predetermined control constant is set with reference to the storage unit according to the set value or the monitor value.
With respect to the slope of the change in the frequency or frequency equivalent of the laser beam with respect to the change in the set value or the monitor value, in the first range and the second range, which are different ranges that the set value or the monitor value can take. A laser device that sets the control constant in the range in which the absolute value of inclination is small to be larger than the control constant in the range in which the absolute value of inclination is large. The laser device according to claim 1, wherein the set value or the monitor value is a current value supplied to the light source unit. The monitor unit detects a frequency filter whose transmittance changes periodically with respect to the frequency of the input light and a second intensity corresponding to the intensity of the laser light after the laser light has passed through the frequency filter. Equipped with a second detection unit
The set value or the monitor value includes a value corresponding to the second intensity.
The laser apparatus according to claim 1 or 2. The monitor unit includes a first detection unit that detects the first intensity of the laser light corresponding to the intensity of the laser light.
The laser device according to claim 3, wherein the set value or the monitor value is a value corresponding to the ratio of the second intensity to the first intensity. When the control unit performs change control for changing the frequency or frequency equivalent of the laser beam from the first set value to the second set value, the elapsed time from the start time of the change control or the first setting The laser device according to any one of claims 1 to 4, wherein the control constant is set according to the arrival rate from the value to the second set value. When the control unit performs change control for changing the frequency or frequency equivalent of the laser beam from the first set value to the second set value, while changing from the first set value to the second set value. In claims 1 to 5, when the sign of the change in inclination changes, the control constant smaller than the control constant outside the range of the predetermined range is set in the predetermined range including the point where the sign changes. The laser apparatus according to any one. The laser device according to any one of claims 1 to 6, wherein the control constant is a proportional constant in proportional control. The laser device according to any one of claims 1 to 7, wherein the light source unit has a variable frequency of the laser beam by utilizing the vernier effect. A control method of a laser device including a light source unit for varying the frequency of the output laser light and a monitor unit for acquiring a monitor value corresponding to a frequency equivalent amount corresponding to the frequency of the laser light. And
A control step of controlling the frequency of the laser beam by supplying a control amount to the laser unit according to a set value is included.
The light source unit has a characteristic that the frequency of the laser beam changes non-linearly with respect to the set value or the monitor value used when controlling the frequency of the laser beam.
The control step
A setting step of setting a predetermined control constant by referring to a storage unit that stores a plurality of control constants for determining the control amount according to the set value or the monitor value is included.
In the setting step, the first range and the first range, which are different ranges that the set value or the monitor value can take, with respect to the slope of the change in the frequency or frequency equivalent of the laser beam with respect to the change in the set value or the monitor value. A control method for a laser device in which the control constant in the range in which the absolute value of the inclination is smaller in the two ranges is set larger than the control constant in the range in which the absolute value of the inclination is larger.

Images