JP3345794B2 - Mode-locked laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mode-locked laser device, such as a mode-locked ultrashort optical pulse laser device used for optical communication and optical measurement, for achieving high stability.

[0002]

2. Description of the Related Art Mode-locked lasers have the advantages of being able to generate optical pulse trains with high repetition and being able to generate ultrashort optical pulses. Research and development are being actively pursued with the aim of applying it to applications.

FIG. 12A shows an example of the configuration of a conventional ring-cavity mode-locked laser. In the figure, reference numeral 2 denotes an optical modulator for modulating light loss or phase at a predetermined frequency, and 1 denotes an optical modulator. A drive power supply for the optical modulator 2, an optical amplifier 3 for amplifying the modulated optical pulse, an optical isolator 4 for defining the traveling direction of the optical pulse and blocking the reflected return light, and a reference numeral 5 for the amplified optical pulse to the outside An optical coupler to be extracted, 6 is a wavelength filter, and 7 is an optical waveguide that optically couples each of the above components (see H. Takara et al., "20 GHz transform").
-limited optical pulse generation and bit-error-ra
te operationusing a tunable, actively mode-locked
Er-doped fiber ring laser ", Electron. Lett., Vol.2
9, No. 13, pp. 1149-1150, 1993).

[0004] Specifically, as the optical modulator 2, LiNbO
A modulator using an electro-optic effect such as ₃ is mainly used. As the wavelength filter 6, a filter using a dielectric multilayer filter is mainly used. An optical fiber is mainly used as the optical waveguide 7. Er as the optical amplifier 3
Rare-earth doped optical fiber amplifiers and semiconductor laser amplifiers doped with rare earths such as Nd and Nd are mainly used.

Here, the operation principle of the conventional mode-locked laser will be described with reference to FIG. FIG. 12 (b)
FIG. 12 is a diagram showing typical spectrum characteristics obtained by mode locking, and FIG. 12C is a diagram showing its time characteristics. In FIG. 12A, the optical modulator 2, the optical amplifier 3,
The optical isolator 4 and the optical coupler 5 are coupled in a ring shape via the optical waveguide 7 to form a ring resonator. Here, the value the optical path length L of the ring resonator, and the refractive index was physical length of each element of the ring resonator and h and n, which is multiplied by the respective refractive index n _i in each of the physical length h _i and ( Sum of the respective optical path lengths).

[0006]

(Equation 1)

In a ring resonator, there are a number of longitudinal modes having a frequency interval given by a fundamental resonance frequency _fr = c / L (c is the speed of light). Here, the repetition frequency in the optical modulator 2 in the ring resonator

[0008]

(Equation 2)

[0009] The addition of light modulation, as shown in FIG. 12 (b), becomes a mode-locked oscillator so that phases are aligned in all longitudinal modes frequency interval N · f _c, as shown in FIG. 12 (c) repetition period 1 / optical pulse train (N · f _c) is obtained. This equation (2) is the mode synchronization condition. Note that the pulse width corresponds to the reciprocal of the oscillation spectrum width δν determined by the envelope of a number of longitudinal mode spectra, and the center of the spectrum envelope is the center wavelength (frequency ν ₀ ).

[0010]

[SUMMARY OF THE INVENTION However, the mode-locked laser is satisfied (2) of the mode-locked conditions to change the longitudinal mode frequency interval f _c when the change in the cavity optical path length occurs due to a temperature change or the like However, there is a problem that the laser operation becomes unstable.

Further, even when changing the oscillation wavelength of the laser λ the wavelength filter, as in the case of temperature changes for changing the optical path length L of the resonator by the wavelength dispersion of the refractive index n _i of equation (1), There is a problem that the laser operation becomes unstable.

The present invention has been made in view of such a conventional problem, and provides a mode-locked laser device which can automatically set the optical path length of a resonator with respect to a change in temperature and a change in oscillation wavelength. With the goal.

[0013]

According to one aspect of the present invention, an optical modulator for modulating light loss or phase at a predetermined frequency, and amplifying a modulated optical pulse. Resonator optically coupled to the outside, and an optical coupler for extracting the optical pulse to the outside, and an optical waveguide that optically couples these components to each other to form a ring resonator. An optical delay device for electrically changing an optical path length inside the resonator, and i number of temperature sensors for detecting the temperature of i (i is an integer of 2 or more ) of the resonator outside the resonator; A thermometer that outputs an electric signal corresponding to each detected temperature of the i temperature sensors, and an average temperature Tave based on the output of the thermometer, Tave = k ₁ T ₁ + k ₂ T ₂ +... + K _i T _{i However,} k n (n = 1,2 ·· i): average temperature Tave and the temperature coefficient relationship between the optical path length is determined to be the linear resonator _{T n (n = 1,2 ··· i} ): determined by the detected temperature becomes equation for each temperature sensor An electrical signal processing circuit that outputs an optical delay device drive signal for driving the optical delay device based on the average temperature, and wherein the electrical signal processing circuit has an optical path length of the resonator due to a change in the temperature of the resonator. An optical delay device drive signal is output so as to suppress the change.

According to a second aspect of the present invention, there is provided an optical modulator for modulating the loss or phase of light at a predetermined frequency, an optical amplifier for amplifying a modulated optical pulse, and two optical devices for reflecting most of incident light. A Fabry-Perot resonator comprising: a light reflector; and an optical waveguide that is disposed at both ends of the two light reflectors, and the optical modulator and the optical amplifier are disposed therebetween and optically coupled to form a Fabry-Perot resonator. In the type-mode-locked laser device, an optical delay device for electrically changing the optical path length is provided inside the resonator, and the i (where i is 2 or less) of the resonator is provided outside the resonator.
I number of temperature sensors that detect the temperature at the above integer ) location;
A thermometer that outputs an electric signal corresponding to each detected temperature of the i temperature sensors, and an average temperature Tave based on the output of the thermometer, Tave = k ₁ T ₁ + k ₂ T ₂ +... + K _i T _{i where, k n (n = 1,2 ···} i): temperature coefficient relationship between the optical path length is determined to be the linear average temperature Tave and the resonator T _{n (n} = 1,2 .. I): an electric signal processing circuit for obtaining an optical delay device drive signal for driving the optical delay device based on the average temperature, which is obtained by the following expression: The electrical signal processing circuit outputs an optical delay device drive signal so as to suppress a change in the optical path length of the resonator due to a change in the temperature of the resonator.

According to a third aspect of the present invention, there is provided an optical modulator for modulating the loss or phase of light at a predetermined frequency, an optical amplifier for amplifying the modulated optical pulse, and an optical coupling for extracting the optical pulse to the outside. Resonator type mode-locked laser device comprising a resonator and an optical waveguide that optically couples these components to each other to form a ring resonator. Filters and
I number of temperature sensors which comprise an optical delay device for electrically changing the optical path length, and which detect the temperature of i (i is an integer of 2 or more ) of the resonator outside the resonator; and a thermometer for outputting an electric signal corresponding to each temperature detected by the sensor, the average temperature Tave based on the output of the _{thermometer, Tave = k 1 T 1 +} k 2 T 2 + ··· + k i T i However, _{k n (n = 1,2 ··· i} ): average temperature coefficient relationship between the optical path length is determined to be the linear temperature Tave the resonator _{T n (n = 1,2 ··· i} ) : A temperature detected by each temperature sensor, and outputs an optical delay device driving signal for driving the optical delay device based on the average temperature and an electric signal for outputting an electric signal for driving the optical filter. A processing circuit, and the electric signal processing circuit has a laser oscillation wavelength. And outputs the optical delay unit driving signal so as to suppress the change in optical path length of the resonator due to temperature changes in the size and the resonator.

According to a fourth aspect of the present invention, there is provided an optical modulator for modulating the loss or phase of light at a predetermined frequency, an optical amplifier for amplifying a modulated optical pulse, and two optical modulators for reflecting most of incident light. A Fabry-Perot resonator comprising: a light reflector; and an optical waveguide that is disposed at both ends of the two light reflectors, and the optical modulator and the optical amplifier are disposed therebetween and optically coupled to form a Fabry-Perot resonator. In the type-mode-locked laser device, an optical filter that changes the transmission wavelength electrically in the resonator and an optical delay device that changes the optical path length electrically are provided inside the resonator. 2 or more
Number ) i number of temperature sensors for detecting the temperature of the location;
A thermometer that outputs an electric signal corresponding to each detected temperature of the temperature sensors; and an average temperature T based on the output of the thermometer.
The _{ave, Tave = k 1 T 1} + k 2 T 2 + ··· + k i T i _{where, k n (n = 1,2 ···} i): the relationship between the average temperature Tave and the optical path length of the resonator A temperature coefficient T _n (n = 1, 2,..., I) determined to be linear: a temperature detected by each temperature sensor is obtained by the following equation, and based on this average temperature, the optical delay unit is driven. An electrical signal processing circuit that outputs an optical signal for driving the optical filter, wherein the electrical signal processing circuit outputs an optical signal that drives the optical filter; An optical delay device drive signal is output so as to suppress a change in the optical path length of the device.

[0017]

[0018]

According to the above configuration, the change in the cavity optical path length due to the change in the mode-locked laser temperature and the oscillation wavelength can be represented by:
Determined from the temperature and the set wavelength of the resonator, and controlling the optical delay device in the resonator to correct the change in the optical path length of the resonator, prevent the change in the optical path length of the laser resonator and achieve stable mode-locking operation. Can be realized.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a mode-locked laser device according to a reference example . In this reference example , the amount of change in the resonator optical path length of the ring resonator mode-locked laser due to temperature change is automatically corrected by detecting the temperature of the resonator,
This is a device that operates a mode-locked laser stably.

In the figure, reference numerals 1 to 6 denote a driving power supply of an optical modulator, an optical modulator, an optical amplifier, an optical isolator, an optical coupler, and a wavelength filter, respectively, as in the conventional example shown in FIG.
Reference numeral 7 denotes an optical waveguide. As the optical waveguide 7, in addition to the conventional optical fiber, a channel type waveguide formed on a flat substrate, for example, a planar lightwave circuit (reference M.Ka
wachi et al .: 'Silica waveguide on silicon and the
ir application to integrated-optical components',
Opt. & Quantnm Electron., 2090, 23, pp. 391-417) may be used. As the optical amplifier 3, in addition to the rare earth-doped optical fiber amplifier and the semiconductor laser amplifier of the conventional example, a rare earth-doped planar waveguide type amplifier in which the above-mentioned planar lightwave circuit is doped with rare earth may be used (reference document K. Hattori et al. al.:'Erbium-doped silica-based
planar-waveduide amplifier integrated with a 980/1
530-nm WDM coupler ', in Optical Fiber Communicatio
n 1993 Technical Digest Series Volume 4, paper FB
2).

8 is a temperature sensor, 9 is a thermometer, 10
Denotes an electric signal processing circuit, and 11 denotes an electric optical delay unit. As the temperature sensor 8, a platinum resistor or a thermistor whose resistance value changes according to the temperature T can be used. The thermometer 9 outputs this resistance value as an electric signal.

FIG. 2 shows a specific example of the motorized optical delay unit 11. FIGS. 2A and 2B show an optical delay device utilizing coupling of two optical waveguides by a lens system. Here, reference numeral 20 denotes an optical lens, 21 denotes an electric stage that electrically changes the position in the direction of the arrow, 22 denotes a right-angle mirror such as a triangular prism, and 23 denotes a drive power supply. FIG. 2A shows an optical stage 21 in which the optical lens and the optical waveguide for either the incoming or outgoing light are used.
By fixing it on the top and moving it along the ray direction,
The optical path length between the two optical waveguides 7 can be changed. Similarly, in FIG. 2B, the optical path length can be adjusted by moving the right-angle mirror 22 along the ray direction.

FIG. 2C shows an example of a motorized optical delay device in which the optical waveguide is extended by tension to change the optical path length. In this method, a relatively long optical waveguide such as an optical fiber is wound around a drum 24 made of a piezo element, and the diameter of the drum 24 is changed by voltage to change the tension on the optical fiber, thereby changing the optical path length. Things. FIG. 2D is an example of a motorized optical delay device that changes the optical path length by electrically changing the refractive index of the optical waveguide. Here, 25 is a substrate, 26 is an optical waveguide whose refractive index changes electrically, and 27 is an electrode. By applying a voltage V between the two electrodes 27, an electric field E is generated in the optical waveguide 26, the refractive index of the optical waveguide changes, and the optical path length changes. As the optical waveguide whose refractive index changes electrically, a ferroelectric material such as LiNbO ₃ having an electro-optical effect is mainly used. By using the motorized optical delay unit 11 shown in FIG. 2, the optical path length of the resonator can be electrically controlled by the electric signal processing circuit 10 shown in FIG.

Next, the principle of the present embodiment will be described. There is a relationship between the temperature T of the resonator and the optical path length L of the resonator as shown in FIG. When the temperature T of the resonator increases (or decreases), the optical path length L of the resonator also increases (or decreases) due to thermal expansion. If the thermal expansion coefficient of the resonator length is α, and a certain reference temperature is Ts, and the resonator optical path length satisfying the mode locking condition is Ls at this time, the relationship between T and L can be generally approximated by the following equation.

[0027]

(Equation 3)

From this equation, the change amount δL of the resonator optical path length due to the temperature change δT can be expressed by the following equation.

[0029]

(Equation 4)

In the operation procedure of this embodiment , first, the optical path length L of the resonator is set to a value Ls satisfying the mode locking condition at a certain reference temperature Ts. Next, the temperature T of the resonator length is detected by the temperature sensor 8. Then, the electric signal processor 10 corrects the optical delay amount D of the motorized optical modulator 11 by the temperature change δT = T−Ts of the resonator and the change amount δL of the resonator optical path length determined by the equation (4). (Note that the amount of change in the optical delay amount D is represented by δD).

[0031]

(Equation 5)

Therefore, according to the present embodiment, the amount of change in the optical path length of the cavity of the mode-locked laser due to temperature change is automatically corrected by detecting the temperature of the resonator, and the mode-locked laser can be operated stably. .

For example, when most of the resonator is formed of an optical fiber like a mode-locked fiber laser, the thermal expansion coefficient α is about 10 ⁻⁵ (1 / ° C.). When the cavity optical path length L _s = 100 m and the temperature change T−T _s of the cavity is 1 (° C.), the cavity optical path length increases by about 1 mm. Therefore, the mode-locking condition can be maintained by reducing the same optical path length by the optical delay unit.

Although the temperature of the optical amplifier in the resonator is detected in FIG. 1, the temperature of other components may be detected. FIG. 4 is a block diagram showing a configuration of an embodiment of the present invention.
FIG. When the temperature distribution of the resonator length is not uniform, the temperature is detected from a plurality of (two or more) positions in the resonator as shown in FIG. 4, and an average temperature is defined as in the following equation.
In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals (or the same reference numerals (the left-side reference numerals) of the same hyphenated codes). In this case, the temperature sensor 8-
1, 8-2 and 8-3 are provided in the optical amplifier 3, the optical modulator 2 and the optical coupler 5, respectively.
To T3 are input to the corresponding thermometers 9-1 to 9-3.

[0035]

(Equation 6)

First, the temperature of each part (T ₁ , T ₂ ,..., T _i )
And the resonator optical path length L are measured, and the temperature coefficients (k ₁ , k ₂ ,..., K _i ) of each part are determined so that the relationship between the average temperature T _ave and the resonator optical path length L becomes linear. Then, by replacing T with T _ave in the equation (5), it is possible to automatically set the cavity optical path length that satisfies the mode locking condition by the average temperature T _ave , similarly to the temperature detection method at one point in FIG. it can.

[0037] FIG. 5 is a diagram showing the configuration of a full Aburipero cavity mode-locked laser device. In the figure, reference numeral 28 denotes a light reflector that reflects most of the incident light. This device is the same as that of FIG. 1 except that the resonator configuration is a Fabry-Perot type, and the amount of change in the resonator optical path length due to temperature change is automatically corrected according to the same principle as that of FIG. The mode-locked laser can be operated. Parts corresponding to the respective parts in FIG. 1 are denoted by the same reference numerals.

Reference Example 1 FIG. 6 is a view showing a ring resonator type mode-locked laser operation stabilization method as a reference example . This example is an apparatus that automatically corrects a change in the cavity optical path length when the oscillation wavelength of the mode-locked laser changes, and operates the mode-locked laser stably. An electric wavelength filter 12 capable of controlling a transmission center wavelength by an electric signal Sλ from an electric signal processor 10 is provided to electrically control an oscillation center wavelength of a mode-locked laser. And the same reference numerals are used.

FIG. 7 shows a specific example of the motor-driven wavelength filter 12. Here, 20 is an optical lens, 30 is an optical filter plate made of a dielectric multilayer film or the like, 31 is an electric stage for rotating the optical filter plate, 32 is a power supply for driving the stage, 33 is a liquid crystal, 34 is a mirror, 35 is a base, 36 is a power supply for driving the liquid crystal. The electric wavelength filter of FIG. 7A can electrically control the transmission wavelength by rotating the optical filter plate 30 with the electric stage 31 and changing the angle θ with respect to the plate surface and the optical axis. The electric wavelength filter shown in FIG. 7B can electrically control the transmission wavelength by changing the electric field applied to the liquid crystal 33 to change the refractive index n of the liquid crystal 33. In addition, "6
Liquid crystal variable wavelength filter capable of selecting 00 channels ", 1
Proceedings of the 992 IEICE Autumn Conference, C-2
46).

Next, the principle of the present embodiment will be described. 8 between the oscillation wavelength λ of the mode-locked laser and the optical path length L of the resonator.
There is a relationship as shown in When the oscillation wavelength λ increases (or decreases), the resonator optical path length L decreases (or increases) due to wavelength dispersion of the refractive index of the resonator. From the equation (1), the change δL of the resonator optical path length can be expressed by the following equation.

[0041]

(Equation 7)

On the other hand, the relationship between the wavelength and the refractive index dispersion is given by the following equation from the Cellmeier equation (GP Ag
rawal, "Nonlinear fiber optics", Academic Press, c
hapter.1, p.7).

[0043]

(Equation 8)

Here, λi is a constant determined by the medium constituting the resonator. In the operation procedure of this embodiment , first, the resonator optical path length L is set to a value Ls that satisfies the mode locking condition at a certain reference oscillation wavelength λs. Then, the physical length hi of each component and the wavelength dispersion ni of the refractive index are measured. Next, the electric wavelength processor 12 is driven by the electric signal processor 10 to set the oscillation wavelength to a desired wavelength λ. Then, the electric optical delay unit 11 is driven by the electric signal processor 10 to change the optical delay amount D into the oscillation wavelength change δλ = λ−λs and (7)
The change amount δL of the resonator optical path length determined from the equation (8) is changed so as to be corrected.

[0045]

(Equation 9)

As a result, the amount of change in the optical path length of the mode-locked laser due to the change in the oscillation wavelength is automatically corrected, and the mode-locked laser can always be operated stably. For example, assuming that most of the resonator is made of an optical fiber like a mode-locked fiber laser and the wavelength dispersion of the refractive index in the resonator is almost constant, the equation (9) can be approximated as follows.

[0047]

(Equation 10)

[0048] 100m the resonator optical path length L _s, the refractive index n as 1.45, the refractive index wavelength dispersion of the optical fiber is assumed to quartz bulk values and comparable with the wavelength 1.5μm band (∂n ( λ) / {λ} −10 ⁻⁵ (1 / nm)), and the change in the oscillation wavelength λ−λ _s = 1 nm results in a cavity optical path length of 0.
It is reduced by about 7 mm. Therefore, the mode locking condition can be maintained by increasing the same optical path length by the optical delay unit.

[0049] (Reference Example 2) FIG. 9 is a diagram showing a full Aburipero cavity mode-locked laser device. This example is the same as Embodiment 3 except that the resonator configuration is a Fabry-Perot type, and the same reference numerals are given to the components corresponding to those shown in FIGS.
According to the same principle as in the third embodiment, the amount of change in the resonator optical path length due to the change in the oscillation wavelength is automatically corrected, and the mode-locked laser can be operated stably.

FIG. 10 is a diagram showing another configuration example of the ring resonator mode-locked laser operation stabilizing method. This configuration example
Automatic setting of the cavity optical path length by temperature detection of the circuit of FIG. 1 ,
And automatic setting of the resonator optical path length in accordance with the change in the set value of the oscillation wavelength described above. In FIG. 10, components corresponding to the components shown in FIGS. 1, 5, 6, and the like are denoted by the same reference numerals.

In the operation procedure of this configuration example , first, the optical path length L of the resonator is set to a value Ls satisfying the mode locking condition at a certain reference oscillation wavelength λs and a reference temperature Ts. Then, the physical length hi of each component and the wavelength dispersion ni of the refractive index are measured. Next, the electric wavelength processor 12 is driven by the electric signal processor 10 to set a desired center wavelength λ, and the temperature T of the resonator detected by the temperature sensor 8 is input to the electric signal processor 10. At this time, assuming that the change amount of the resonator optical path length due to the temperature change is δLT and the change amount of the resonator optical path length due to the oscillation wavelength change is δLλ, the total change amount is δLtota
l = δLT + δLλ. Then, the electric signal processor 10
Drives the optical type optical delay device 11 to calculate the total change amount δ
It is changed so as to correct Ltotal. The optical delay amount δD at this time is expressed by the following equation from the equations (5) and (9).

[0052]

[Equation 11]

As a result, the amount of change in the cavity optical path length of the mode-locked laser due to temperature change and oscillation wavelength change can be automatically corrected, and the mode-locked laser can be operated stably. In FIG. 10, the temperature of the optical amplifier in the resonator is detected, but the temperature of other components may be detected.

When the temperature distribution of the resonator length is not uniform, as in the case of FIG.
(At least two positions), and the average temperature of equation (6) is defined so that the relationship between the average temperature T _ave and the cavity optical path length L becomes linear. Then, in equation (11), T is T _ave
As in the temperature detection method at one point in FIG. 10, the resonator optical path length satisfying the mode locking condition can be automatically set by the average temperature T _ave .

[0055] Figure 11 is a diagram showing a configuration example of a full Aburipero cavity mode-locked laser device. This configuration example is the same as the circuit in FIG. 10 except that the resonator configuration is a Fabry-Perot type, and the operation can be stabilized by the same principle as the circuit in FIG.

[0056]

As described above, according to the present invention, the optical delay device in the resonator is controlled so as to correct the change in the optical path length of the resonator due to the change in the set value of the oscillation wavelength and the temperature of the resonator. By doing so, a stable mode-locked laser operation can be realized quickly and automatically at an arbitrary oscillation wavelength and temperature.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a mode-locked laser device according to a reference example .

FIG. 2 is a view showing specific examples (a) to (d) of the electric optical delay unit 11 shown in FIG.

FIG. 3 is a diagram illustrating a relationship between a resonator temperature T and a resonator optical path length L;

FIG. 4 shows a mode-locked laser according to an embodiment of the present invention .
FIG. 2 is a block diagram illustrating a configuration of the device .

5 is a block diagram showing another configuration example of the mode-locked laser device.

FIG. 6 is a block diagram illustrating a configuration example of a mode-locked laser device according to a reference example.

FIGS. 7A and 7B are diagrams showing specific examples (a) and (b) of the electric wavelength filter 12 shown in FIG.

FIG. 8 is a diagram showing a relationship between an oscillation wavelength λ of a mode-locked laser and a resonator optical path length L.

FIG. 9 is a block diagram illustrating a configuration example of a mode-locked laser device according to a reference example.

10 is a block diagram showing another configuration example of the mode-locked laser device.

11 is a block diagram showing another configuration example of the mode-locked laser device.

FIG. 12 is a block diagram illustrating a configuration example of a conventional mode-locked laser device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive power supply 2 Optical modulator 3 Optical amplifier 5 Optical coupler 6 Wavelength filter 7 Optical waveguide 8 Temperature sensor 9 Thermometer 10 Electric signal processor 11 Motorized optical delay unit 12 Motorized wavelength filter 28 Optical reflector

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-252482 (JP, A) JP-A-6-13691 (JP, A) JP-A-2-105483 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01S 3/00-3/30

Claims (4)

(57) [Claims] An optical modulator for modulating a loss or phase of light at a predetermined frequency, an optical amplifier for amplifying a modulated optical pulse, an optical coupler for extracting the optical pulse to the outside,
In a ring resonator type mode-locked laser device including: an optical waveguide that optically couples these components to each other to form a ring resonator, an optical delay device that electrically changes an optical path length is provided in the resonator. And i number of temperature sensors for detecting a temperature of i (i is an integer of 2 or more ) of the resonator outside the resonator; and outputting an electric signal corresponding to each detected temperature of the i number of temperature sensors. and a thermometer for the average temperature Tave based on the output of the _{thermometer, Tave = k 1 T 1 +} k 2 T 2 + ··· + k i T i _{where, k n (n = 1,2 ···} i ): Temperature coefficient T _n (n = 1, 2,..., I) determined so that the relationship between the average temperature Tave and the optical path length of the resonator becomes linear. An optical delay device for driving the optical delay device based on the average temperature. An electrical signal processing circuit that outputs a dynamic signal, and the electrical signal processing circuit outputs an optical delay device drive signal so as to suppress a change in the optical path length of the resonator due to a change in the temperature of the resonator. Mode-locked laser device. 2. An optical modulator for modulating the loss or phase of light at a predetermined frequency, an optical amplifier for amplifying a modulated optical pulse, two optical reflectors for reflecting most of incident light, A Fabry-Perot cavity mode-locked laser device comprising: a light reflector that is disposed at both ends and the optical modulator and the optical amplifier are disposed therebetween and optically coupled to form a Fabry-Perot resonator. An optical delay device for electrically changing an optical path length in the resonator, and i number of temperature sensors for detecting a temperature of i (i is an integer of 2 or more ) of the resonator outside the resonator; and a thermometer for outputting an electric signal corresponding to each temperature detected by the i number of temperature sensors, the average temperature Tave based on the output of the _{thermometer, Tave = k 1 T 1 +} k 2 T 2 + ··· + k i T _i where k _n (n = 1, 2 · .. I): Temperature coefficient T _n (n = 1, 2,... I) determined so that the relationship between the average temperature Tave and the optical path length of the resonator becomes linear. And an electric signal processing circuit that outputs an optical delay device drive signal for driving the optical delay device based on the average temperature. A mode-locked laser device for outputting an optical delay device drive signal so as to suppress a change in optical path length. 3. An optical modulator for modulating a loss or phase of light at a predetermined frequency, an optical amplifier for amplifying the modulated optical pulse, an optical coupler for extracting the optical pulse to the outside,
A ring resonator mode-locked laser device comprising: an optical waveguide that optically couples these components to each other to form a ring resonator; an optical filter that changes a transmission wavelength electrically in the resonator; An optical delay device for electrically changing an optical path length, and i number of temperature sensors for detecting a temperature of i (i is an integer of 2 or more ) of the resonator outside the resonator; and a thermometer for outputting an electric signal corresponding to each temperature detected by the sensor, the average temperature Tave based on the output of the _{thermometer, Tave = k 1 T 1 +} k 2 T 2 + ··· + k i T i However, _{k n (n = 1,2 ··· i} ): average temperature coefficient relationship between the optical path length is determined to be the linear temperature Tave the resonator _{T n (n = 1,2 ··· i} ) : Detected temperature of each temperature sensor An optical signal processing circuit for outputting an optical delay device driving signal for driving the optical delay device, and outputting an electrical signal for driving the optical filter, and wherein the electrical signal processing circuit has a laser oscillation wavelength. A mode-locked laser device that outputs an optical delay device drive signal so as to suppress a change in the optical path length of the resonator due to a change in the optical path length and a temperature change in the resonator. 4. An optical modulator for modulating light loss or phase at a predetermined frequency, an optical amplifier for amplifying a modulated optical pulse, two optical reflectors for reflecting most of incident light, A Fabry-Perot cavity mode-locked laser device comprising: a light reflector that is disposed at both ends and the optical modulator and the optical amplifier are disposed therebetween and optically coupled to form a Fabry-Perot resonator. An optical filter that changes the transmission wavelength electrically in the resonator, and an optical delay device that changes the optical path length electrically are provided inside the resonator, and outside the resonator, i (i is an integer of 2 or more ) locations of the resonator I temperature sensors for detecting temperature, a thermometer for outputting an electric signal corresponding to each detected temperature of the i temperature sensors, an average temperature Tave based on an output of the thermometer, Tave = k _{1 T 1} + _{k 2} T 2 ··· ₊ k _{i T} i _{where, k n (n = 1,2 ···} i): Temperature coefficient relationship between the optical path length is determined to be the linear average temperature Tave and the resonator T _n (n = 1, 2,... I): detected temperature of each temperature sensor, and outputs an optical delay device drive signal for driving the optical delay device based on the average temperature. An electric signal processing circuit for outputting an electric signal to be driven, and an optical delay unit driven so that the electric signal processing circuit suppresses a change in the optical path length of the resonator due to a change in laser oscillation wavelength and a change in the temperature of the resonator A mode-locked laser device for outputting a signal.