JPH06268308A - Wavelength converter - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] Power conversion such as wavelength conversion output light power selection and modulation based on data signals without increasing the size of the device, cost, and loss of light. In addition, stable operation is performed without hindering mode locking. [Structure] A wavelength conversion laser section 3 that obtains wavelength conversion output light by making oscillation light from the semiconductor laser 1 incident on a nonlinear optical element 2 is provided, and a minute high-frequency superimposed current is added to an injection current of the semiconductor laser 1 to form a semiconductor laser. Wavelength-converted laser that frequency-modulates the oscillation light of the above and frequency-modulates the wavelength-converted output light from the wavelength conversion laser unit, and pulls the oscillation wavelength of the semiconductor laser to the input fundamental wave wavelength that maximizes the wavelength conversion efficiency of the nonlinear optical element 2. The mode lock circuit section 12 of the section 3, the automatic output control circuit section 13, and the amplitude modulation circuit 14 of the minute high-frequency superposed current to the semiconductor laser 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength conversion device, and more particularly to a semiconductor laser and a wavelength conversion element for generating a second harmonic or a higher harmonic of the semiconductor laser as a fundamental wave. The present invention relates to a wavelength conversion device having a nonlinear optical element.

[0002]

2. Description of the Related Art There is a need for a short wavelength, for example, blue laser light as a light source for optical recording / reproduction of optical disks of high density and optical resolution, optical recording / reproduction such as magneto-optical recording / reproduction, and a light source used in medical equipment. It is rising.

As a light source of this type, as shown in FIG.
The oscillation light of the semiconductor laser 1 as the fundamental wave light is made incident on the nonlinear optical element 2 so-called SHG (second harmonic generation element), THG (third harmonic generation element) as the wavelength conversion element, and the second of the fundamental wave is generated. There is a direction in which a wavelength conversion device using the wavelength conversion laser unit 3 is used in which laser light of a short wavelength such as blue is obtained by generating the next or higher harmonics.

This wavelength converter has, for example, a wavelength of 860n.
The output light of the semiconductor laser 1 by the m single-mode laser is collimated by the collimator lens 4 and is shaped by the anamorphic prism 5 into a beam having a substantially circular cross section. The non-linear optical element 2 of FIG.

At this time, the nonlinear optical element 2 usually needs to be phase-matched with the wavelength of the incident light.

Therefore, the semiconductor laser 1 and the non-linear optical element 2 are kept within the range of the phase matching temperature by a temperature control means such as a Peltier element.

However, in practice, the semiconductor laser used in this wavelength converter is, as described above, generally a single mode laser, and its oscillation wavelength usually changes greatly depending on the ambient temperature and the applied current. Therefore, when the nonlinear optical element 2 having a narrow phase matching range is used, in order to always maintain a good phase matching state and exhibit high conversion efficiency, the oscillation wavelength of the semiconductor laser is set to a wavelength capable of phase matching. High-precision current control is required.

As a mode-locking method for maintaining the current control, that is, the phase matching condition, there is a method called, for example, Drever locking method (paper collection; Proc.SPI).
E 1663, Optical Data Storage, San Jose p410 (1992)).

In this method, when the phase matching condition is satisfied in the configuration of FIG. 9 described above, when the laser beam of the semiconductor laser 1, that is, the fundamental wave is 860 nm, for example, KNb is used.
When the nonlinear optical element 2 made of O ₃ crystal outputs blue light having a wavelength of 430 nm of the second harmonic, at the same time, when the oscillation light of the semiconductor laser 1 is in a phase matching state in the nonlinear optical element 2, this ring is used. Since the resonator is set to be in a resonance state, the fact that the reflected light amount of the laser light of the semiconductor laser from the incident end face of the nonlinear optical element 2 is minimized is used.

That is, in this case, as shown in FIG. 9, a mode lock circuit section 12 is provided, and in this case, the nonlinear optical element 2 oscillates at a wavelength satisfying the phase matching condition with respect to the semiconductor laser 1. a predetermined DC current supplies from the power supply terminal T _b to which a DC bias is supplied, for example, 3 from the high-frequency oscillator 8 to
Frequency modulation (FM) of the optical output of the semiconductor laser 1 by superimposing a minute high frequency superimposed current of 00 MHz or 400 MHz.
To do.

As described above, the reflected light of the oscillation light of the semiconductor laser 1 from the nonlinear optical element 2 is used for this mode locking. That is, as described above, the reflected light has a minimum value at the time of phase matching, but at the same time, includes the above-described high frequency superimposed current signal component (corresponding to the J ₁ component of the Bessel function in FM modulation), and this signal component J ₁ That is, since the FM sideband signal has a phase inversion at the mode lock point as a boundary, the reflected light is detected by the wideband detector D ₁ , and the detected current signal is converted into a voltage signal by the current-voltage converter 9. , Which is input to an analog multiplier, that is, a multiplier 10, and when the multiplier 10 multiplies the high frequency oscillator 8 with a minute high frequency superposed signal to the semiconductor laser 1, an output corresponding to the phase displacement of the reflected light is obtained. This output signal is considered the mode locking error signal.

Therefore, if this output is fed back to the drive current of the semiconductor laser 1 so that this error signal becomes zero, a PLL (phase lock loop) circuit is constructed and the wavelength conversion laser section 3 is mode-locked. Will be applied.

Reference numeral 11 in the figure is a feedback loop filter.

On the other hand, when this type of wavelength conversion device is used as a light source for optical recording / reproducing, for example, at the time of recording,
It is necessary to change and set the power of the wavelength-converted output light in accordance with reproduction, erasing, etc. Further, when it is used as recording light, for example, it is necessary to perform power modulation according to the recording signal, that is, the data signal. come.

In this type of wavelength conversion device, in order to change and set its power, that is, to select a lighting power mode or to perform modulation by a data signal, an external light modulation element by, for example, an acousto-optic effect or an electro-optic effect is used. It is considered that a general method is to arrange them and perform power modulation through the wavelength-converted output light.

However, such provision of the optical modulator to the outside causes the setting of the mutual arrangement position with the wavelength conversion laser section, that is, the complexity of assembly and manufacturing, the increase in size of the apparatus, and the increase in cost, and further. There is a problem such as a loss of light due to the wavelength-converted output light passing through the optical modulator.

Further, since the setting of the change of the power of the output light of the wavelength conversion and the power modulation such as the modulation based on the data signal can be performed by the control of the semiconductor laser of the fundamental wave light source, the drive current of this semiconductor laser is set. However, in this case, the phase matching condition due to the fluctuation of the oscillation wavelength of the semiconductor laser largely fluctuates, and the mode locking is lost, which causes the pulling time of the mode locking to be long. Problems such as inability to perform high-speed modulation and difficulty in stable operation occur.

[0018]

SUMMARY OF THE INVENTION As described above, according to the present invention, the oscillation light of the semiconductor laser as the fundamental wave light source is incident on the nonlinear optical element as the wavelength conversion element and the second or higher harmonics. In a wavelength conversion device obtained by wavelength-converting a wave, power modulation such as power selection and modulation based on a data signal can be performed without causing device size increase, cost increase, light loss, and mode locking. To be able to perform stably without inhibiting.

[0019]

According to the first aspect of the present invention, a semiconductor laser 1 and a oscillating light from a wavelength conversion element, that is, the semiconductor laser 1 are used as an input fundamental wave, as shown in the configuration diagram of FIG. A wavelength conversion laser unit 3 including a non-linear optical element 2 to be incident, and a minute high frequency superimposing current to the injection current of the semiconductor laser 1 to frequency modulate the oscillation light of the semiconductor laser to output wavelength conversion output light from the wavelength conversion laser unit. A frequency-modulating circuit, a mode-lock circuit section 12 of a wavelength conversion laser section 3 for pulling the oscillation wavelength of a semiconductor laser to an input fundamental wave wavelength that maximizes the wavelength conversion efficiency of the nonlinear optical element 2, an automatic output control circuit section 13, The semiconductor laser 1 has an amplitude modulation circuit 14 for a minute high frequency superimposed current.

The automatic output control circuit section 13 detects the wavelength-converted output light and is controlled by this detection signal to control the lighting power mode of the wavelength-converted laser section 3, such as recording, reproducing and erasing in the optical recording and reproducing. The amplitude modulation circuit 14 is supplied with an instruction voltage for setting the maximum (peak) power and the minimum (bottom) power of the wavelength conversion output light of the wavelength conversion laser unit 3 according to the mode.

A data signal is input to the amplitude modulation circuit 14, and the semiconductor laser 1 is supplied with this data signal.
The amplitude of the drive current is modulated.

In addition, in the second invention, as shown in the configuration diagram of one example in FIG. 2, in the above-described first invention configuration, the direct current applied to the semiconductor laser 1 is scanned to scan the semiconductor laser. An error signal that changes the oscillation wavelength to change the wavelength of the input fundamental wave to the nonlinear optical element 2 and derives an error signal corresponding to the deviation from the wavelength of the input fundamental wave that maximizes the wavelength conversion efficiency of the nonlinear optical element 2. Drawer circuit section 15
And a switching means 16 for switching the error signal extraction circuit section 15 and the mode lock circuit section 12 to the semiconductor laser 1.

A third aspect of the present invention is based on each of the above configurations.
The frequency modulation index β of the output light from the wavelength conversion laser unit 3 is selected to be 0 to 2.4.

[0024]

In the present invention, the superposition of a minute high frequency superposition current for mode locking of the wavelength conversion laser section 3, that is, the output light of the wavelength conversion laser section 3 is frequency-modulated,
Then, the fact that the power of the output light of the wavelength conversion laser section 3 changes by changing the modulation index β of this frequency modulation is utilized.

That is, when mode locking is performed by superimposing the minute high frequency superimposed current as described above,
That is, in the case where the output light of the wavelength conversion laser 3 is FM-modulated, the modulation index β of the FM modulation is given by the following mathematical expression 1.

[0026]

[Equation 1]

Here, λ is the fundamental wave oscillation wavelength due to the DC bias current of the semiconductor laser, Δλ is the displacement with respect to the current wavelength,
For example, given by Δλ≈0.005 nm / mA, f _M is the minute high-frequency superimposed current frequency, eg, 300 MHz, c is the speed of light, and ΔA is the minute high-frequency superimposed current amplitude.

Since the output light from the wavelength conversion laser unit 3 is proportional to the J ₀ component of the Bessel function in FM modulation, the output light is arbitrarily changed by changing the amplitude ΔA of the minute high frequency superimposed current. It becomes possible to control.

Then, the amplitude Δ of the minute high frequency superimposed current is now.
By changing A, the FM modulation index β becomes 0.1,
Measures the intensity of each reflected light from the front end face (incident end face) of the nonlinear optical element 2 when the incident light from the oscillation light of the semiconductor laser 1 enters the nonlinear optical element 2 when changed to 0.5, 1.0, 1.5, 2.0. Then, it becomes as shown by the solid line curves in FIGS.

In each figure, the horizontal axis shows the phase, and the vertical axis shows the maximum value of the intensity normalized to 1. The error signal in each case is shown by a broken line curve in each of these figures.

Here, since the reflected light is in a phase matching state and is in a resonance state when the wavelength conversion output light is generated from the wavelength conversion laser section 3, the intensity of the reflected light is small and phase matching is not performed. Since the reflected light intensity becomes large when the wavelength-converted output light is small, the magnitude of the wavelength output light can be known from this reflected light intensity.

By the way, according to FIGS. 3 to 7, in the phase matching state, the minimum value of the reflected light is the smallest when β = 0.1 shown in FIG. 3, and the wavelength conversion output light intensity, that is, the power is the largest. On the other hand, it can be seen that when the value of β is increased, the minimum value level of the reflected light increases and the wavelength-converted output light decreases. And β = 2.
At 0, the output light becomes almost zero, which is not shown, but β = 2.4
No wavelength-converted output light was generated.

In other words, the power of the wavelength-converted output light can be controlled by controlling β and therefore by controlling the high frequency superimposed current amplitude ΔA.

Incidentally, in order to set β = 0.2 under the above conditions, it is sufficient to carry out the current amplitude control in the order of ΔA≈29.6 μm, that is, sub-mA.

In the present invention, the power of the wavelength-converted output light is controlled by controlling the high frequency superimposed current amplitude ΔA by the amplitude modulation circuit 14. According to the present invention, according to the lighting power mode, Moreover, analog modulation can be performed by the data signal, including digital modulation such as ON / OFF of the wavelength-converted output light.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the present invention will be described with reference to FIG. Also in this example, the semiconductor laser 1 and, for example, KNbO as a wavelength conversion element for obtaining the second or higher harmonics of the fundamental wave by making the oscillation light from the semiconductor laser 1 incident as the fundamental wave light. _A wavelength conversion laser unit 3 having a ring resonator formed by a non-linear optical element 2 composed of ₃ crystals is constructed.

The semiconductor laser 1 has a wavelength of 860 nm, for example.
Single mode lasers are used.

The output light of the semiconductor laser 1 is collimated by the collimator lens 4 and then beam-shaped by the anamorphic prism 5 to have a substantially circular cross-section. The condensing lens 7 condenses and enters the nonlinear optical element 2 of the wavelength conversion element having the configuration.

At this time, if the phase matching condition is satisfied, the blue light of the wavelength 430 nm of the second harmonic of the fundamental wave is output from the nonlinear optical element 2 of KNbO ₃ crystal.

As described with reference to FIG. 9, the semiconductor laser 1 directed to the nonlinear optical element 2 detects the reflected light of the laser light from the nonlinear optical element 2 by the broadband first detector D ₁ . , This detected current signal,
It is converted into a voltage signal by the current-voltage converter 9, and this is input to the analog multiplier, that is, the multiplier 10,
The multiplier 10 multiplies the high frequency oscillator 8 with the minute high frequency superimposed signal to the semiconductor laser 1 to obtain an output according to the phase displacement of the reflected light, that is, a mode locking error signal.

Reference numeral 11 is a feedback loop filter.

On the other hand, the automatic output control circuit (APC) unit 13
And an amplitude modulation circuit 14 for a minute high frequency superimposed current of the semiconductor laser 1.

Then, a predetermined DC drive current for oscillating a wavelength satisfying the phase matching condition of the nonlinear optical element 2 is supplied to the semiconductor laser 1 from the power supply terminal T _b to which the DC bias is supplied, and a high frequency is supplied to this drive current. Oscillator 8
For example, the optical output of the semiconductor laser 1 is frequency-modulated (FM) by superimposing a minute high-frequency superimposed current of, for example, 300 MHz or 400 MHz, but in the present invention, this minute high-frequency superimposed current is further amplitude-modulated by the amplitude modulation circuit 14. And supply. In this case, first, it is selected to feed back to the drive current of the semiconductor laser 1 an output such that the mode-locking error signal becomes zero in a state where the minute high-frequency superimposed current is not amplitude-modulated, that is, in the state where only FM modulation is performed. To do.

The amplitude modulation circuit 14 has an AM having a peak power and a bottom power specified by the automatic output control circuit unit 13 for the minute high frequency superimposed current from the high frequency oscillator 8.
In addition to the modulation, the data signal, for example, the recording signal is input to the data signal from the terminal T _s to perform the AM modulation based on the data signal.

The automatic output control circuit section 13 has a terminal T
_The control voltage according to the lighting power mode is given from _M , and the reference power is switched and set in each mode in the state where the data signal is not given.

That is, for example, in an optical recording / reproducing apparatus, the reference power is different depending on each mode of recording, reproducing, erasing, etc. Generally, for example, high power is used for recording, low power is used for reproducing and erasing is used for erasing. Since high power is required, switching of lighting power modes is selected.

The automatic output control circuit section 13 is supplied with a predetermined control voltage by the above-mentioned mode switching, so that the automatic output control circuit section 13 outputs the amplitude modulation circuit 1.
4, the command voltage Φ _p is set so that the wavelength-modulated output light has a power corresponding to each mode, that is, AM modulation for obtaining a predetermined peak power and bottom power in each mode is performed by the amplitude modulation circuit 14. Φ _b is supplied.

Further, in the automatic output control circuit 13, the above-mentioned instruction voltages Φ _p and Φ _b are held at predetermined values in the selected power mode without depending on the fluctuation of the wavelength-converted output light. Is automatically controlled. That is, in the illustrated example, the output light of the nonlinear optical element 2, that is, the wavelength-converted output light is converted into parallel light by the collimator lens 21, and a part of the light is converted into second light by the beam splitter 22.
To the detector D ₂ 23, and a detection current signal corresponding to the magnitude of the output light is taken out by the detector D ₂ 23, and this is converted into a voltage signal containing no high frequency component by the current-voltage converter 24, and the automatic output control circuit section is provided. It is fed back to 13 so that the indicated voltages Φ _p and Φ _b are held at the selected constant values.

Then, in this way, the amplitude modulator 14
The minute high-frequency superimposed current that has been AM-modulated is, for example, as shown in FIG.
The waveform shown in A is generated, and the wave driven by superposition
The wavelength-amplitude output light of the long conversion laser unit 3 is as shown in FIG. 8B.
become. That is, in FIG.₀, Τ
₂ .., the high frequency superimposed current amplitude ΔA is a large value ΔA
₀At this time, for example, the wavelength amplitude output light is turned off.
And, for example, the interval τ ₁, Τ₃... in high frequency superposition
The current amplitude ΔA is a small value ΔA₁And at this time
For example, the wavelength amplitude output light is turned on.

Then, for example, in this case, if these ΔA ₀ and ΔA ₁ are amplitudes giving the maximum or peak power and the minimum or bottom power in each lighting mode, these are designated by the automatic output control circuit 13. is there.

According to this configuration, the wavelength conversion laser section 3 performs the selection of the lighting mode power and the power modulation based on the data signal.
Since AM modulation is applied to the high frequency superposed current superposed on the drive current of the semiconductor laser 1 for performing the mode locking of A, high speed modulation is possible and the characteristic A
M modulation can be performed.

The selection range of the FM modulation index β of the wavelength-converted output light by the AM modulation is practically 0 to 2.4, which is the peak in the power selection in each of the above lighting power modes and the power modulation by the data signal. Power and bottom power can be set sufficiently.

By the way, in the above-mentioned present invention, the power of the wavelength-converted output light is controlled by amplitude-modulating the minute high-frequency superimposed current for performing mode-locking. As shown by the broken line in FIGS. 3 to 7, since it exists only in the vicinity of the mode lock point, it becomes impossible to pull in the mode locking in the case where the state of leaving the mode lock point occurs.

That is, when the mode is locked, the wavelength conversion element, that is, the nonlinear optical element 2 acts as a resonator, so that, for example, the nonlinear optical element 2 has a crystal length L of 7.0 m.
Assuming that m and the refractive index n are 2.277, the resonance frequency interval F
SR becomes the following expression 2.

[0055]

[Equation 2]

Further, since the finesse F of this resonator is considered to be about 40, the full width at half maximum Δf at the resonance point is given by the following expression 3.

[0057]

[Equation 3]

That is, the mode-lock points are present at a FWHM of 235 MHz at intervals of 9.4 GHz (about 0.023 nm in wavelength) at the oscillation frequency of the semiconductor laser, and therefore the error signal only appears in a discrete manner. It becomes a continuous waveform.

Therefore, an error signal is not always obtained only by applying a constant DC bias current to the semiconductor laser 1. Further, as is usual, it cannot be said that a feedback circuit that makes the error signal zero is sufficient.

The second aspect of the present invention avoids such an inconvenience, and an example thereof will be described with reference to FIG.
In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals and redundant description will be omitted.

In this case, a drive current scanning circuit 17 for scanning the drive current of the semiconductor laser 1 and an error signal extraction circuit section 15 having a pull-in logic circuit 18 are added to the above feedback circuit system, and the error signal extraction circuit is added. A switching means 16 is provided for mechanically or electrically switchingly connecting the section 15 and the mode lock circuit section 12 to the semiconductor laser 1.

That is, in this case, in the initial state of the wavelength conversion operation, the switching means 16 is switched to the contact a side in the figure, and the error signal extraction circuit section 15 is connected to the semiconductor laser 1.

Then, a current for oscillating a laser beam having a wavelength satisfying the phase matching condition from the semiconductor laser 1 is supplied from the DC bias current supply terminal T _b, and the current is applied to the semiconductor laser 1 by the current scanning circuit 17 centered on this value. A direct current is scanned, that is, a current search is performed to change the oscillation wavelength of the semiconductor laser 1 to change the wavelength of the input fundamental wave to the nonlinear optical element 2.

In this state, the pull-in logic circuit 18 pulls out an error signal corresponding to the deviation from the wavelength of the input fundamental wave that maximizes the wavelength conversion efficiency of the nonlinear optical element 2, that is, satisfies the phase matching condition.

Since the wavelength displacement Δλ with respect to the current in the semiconductor laser 1 is given by Δλ≈0.005 nm / mA, for example,
In order to reliably obtain the above-mentioned error signal, it is desirable that the current amplitude be about the resonance frequency interval of the resonator formed by the non-linear optical element, 0.023 nm / 0.005 nm = 4.6 mA or more in this example.

Next, since the intensity of the reflected light from the nonlinear optical element 2 becomes a minimum in the vicinity of the mode lock point, the current-voltage converter for converting the detection signal from the detector D ₁ for detecting this reflected light into a voltage signal. The low frequency component of the reflected light intensity is extracted from 9 and this signal is drawn by the pull-in logic circuit 18.
A range below a certain threshold value is regarded as a retractable range, and by this, the switching means 16 is switched to the other contact b in FIG. 2 to disconnect the error signal extraction circuit section 15 from the semiconductor laser 1 and The lock circuit section 12 is switched and connected to the semiconductor laser 1, and the above-described operation is performed thereafter.

As described above, according to the second aspect of the present invention, the mode-lock error signal can be reliably extracted, and the mode-locking and the power modulation can be reliably performed.

In the above example, the nonlinear optical element 2 is made of KNbO ₃ crystal, but it is also possible to use a nonlinear optical element as another wavelength conversion element. This is the case where the lock error signal is obtained by detecting the reflected light from the fundamental wave incident end face of the resonator of the nonlinear optical element, but the fundamental wave from the emission end for extracting the wavelength converted output light, that is, the oscillation light of the semiconductor laser Various changes can be made such that the error signal is taken out by the separate detection.

[0069]

As described above, according to the present invention, since the power modulation can be performed by the internal circuit, the power modulation can be performed by providing the modulator with the acousto-optic effect or the electro-optic effect outside. Compared with the case where it is performed, it is possible to achieve size reduction, simplification, mass production, and reduction of optical loss.

Further, since the modulation is performed by the amplitude modulation of a minute high frequency superimposed current for mode locking, the complexity of the circuit configuration can be considerably reduced, the high speed operation is excellent, and the amplitude modulation is applied to the high frequency current. Since it has excellent modulation characteristics, it is possible to reliably and accurately perform power modulation, especially peak power and bottom power setting, so reliable recording using as a light source for high density, high resolution optical recording and reproduction, It has many practical advantages such as being able to reproduce and erase.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an example of a device of the present invention.

FIG. 2 is a block diagram of an example of the device of the present invention.

FIG. 3 is a diagram showing a reflected light intensity and an error signal intensity from a nonlinear optical element of the wavelength conversion laser unit.

FIG. 4 is a diagram showing a reflected light intensity and an error signal intensity from a nonlinear optical element of the wavelength conversion laser unit.

FIG. 5 is a diagram showing reflected light intensity and error signal intensity from the nonlinear optical element of the wavelength conversion laser unit.

FIG. 6 is a diagram showing reflected light intensity and error signal intensity from the nonlinear optical element of the wavelength conversion laser unit.

FIG. 7 is a diagram showing reflected light intensity and error signal intensity from the nonlinear optical element of the wavelength conversion laser unit.

FIG. 8 is an amplitude modulation waveform diagram and a wavelength conversion output waveform diagram of a minute high frequency superimposed current.

FIG. 9 is a configuration diagram of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Nonlinear optical element 3 Wavelength conversion laser 12 Mode lock circuit section 13 Automatic output control circuit section 14 Amplitude modulation circuit 15 Error signal extraction circuit section

Claims (3)

[Claims] 1. A wavelength conversion laser section comprising a semiconductor laser and a non-linear optical element for making oscillation light from the semiconductor laser incident as an input fundamental wave; The oscillation light of the semiconductor laser is frequency-modulated, and the wavelength-converted output light from the wavelength conversion laser unit is frequency-modulated, and the oscillation wavelength of the semiconductor laser is adjusted to the input fundamental wavelength that maximizes the wavelength conversion efficiency of the nonlinear optical element. A mode-locking circuit section of the wavelength conversion laser section that draws in, an automatic output control circuit section, and an amplitude modulation circuit of a minute high-frequency superimposed current to the semiconductor laser, wherein the automatic output control circuit section is the wavelength conversion output light. Of the maximum wavelength conversion output light of the wavelength conversion laser unit according to the lighting power mode of the wavelength conversion laser unit Power and an instruction voltage for setting a minimum power are supplied to the amplitude modulation circuit, and a data signal is input to the amplitude modulation circuit, and the drive current of the semiconductor laser is amplitude-modulated by the data signal. A wavelength conversion device. 2. The direct current applied to the semiconductor laser is scanned to change the oscillation wavelength of the semiconductor laser to change the wavelength of the input fundamental wave to the nonlinear optical element, and the wavelength conversion efficiency of the nonlinear optical element. An error signal extraction circuit section for extracting an error signal corresponding to a deviation from the input fundamental wavelength at which the maximum is obtained, and switching means for switching the error signal extraction circuit section and the mode lock circuit section to the semiconductor laser. The wavelength conversion device according to claim 1, wherein the wavelength conversion device comprises. 3. The frequency modulation index β of the wavelength converted output light
Was selected from 0 to 2.4. 3. The wavelength conversion device according to claim 1, wherein