JP2005017410A - Wavelength conversion laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of a state in which intensity of linearly polarized light, being desired output light, is not properly controlled with a wavelength of fundamental light incident on a wavelength conversion element. <P>SOLUTION: When the fundamental light emitted from an optical resonator consisting of a semiconductor amplifying element 1 and an optical fiber 3 is made incident on the wavelength conversion element 5, the wavelength conversion element 5 emits second harmonic light thereof. A polarizer 52 transmits only an extraordinary ray component of the second harmonic light. A beam splitter 56 makes a part of the extraordinary ray component passed through the polarizer 52 branch and a photometric element 57 measures intensity of the branched extraordinary ray component. A laser control part 60 drives the semiconductor amplifying element 1 based on a signal Sd from the photometric element 57. Even when harmonic light containing extraordinary and ordinary ray components is emitted from the wavelength conversion element, output intensity of the extraordinary ray component is adequately controlled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wavelength conversion laser device, and more particularly to a wavelength conversion laser device that prevents a situation in which the intensity of linearly polarized light, which is desired output light, cannot be properly controlled.
[0002]
[Prior art]
Conventionally, a semiconductor laser module in which a laser diode and an optical fiber having a grating portion formed therein are combined to stabilize the wavelength is known (see, for example, Patent Document 1).
Further, a technique for converting the wavelength of laser light whose wavelength is fixed by a grating portion into harmonic light by a wavelength conversion element is known (for example, see Patent Document 2).
Further, a part of the harmonic light output from the wavelength conversion element is branched by a beam splitter, the intensity of the branched light is measured by a detector, and the driving current of the semiconductor laser is adjusted based on the measurement result, and the laser light A technique for controlling the output is known (for example, see Patent Document 3).
[0003]
[Patent Document 1]
Japanese Patent No. 3120828 [Patent Document 2]
Japanese Patent No. 3223648 [Patent Document 3]
JP 2000-138405 A [0004]
[Problems to be solved by the invention]
The inventor of the present application oscillates laser light from the red to the near infrared region with a semiconductor laser, stabilizes the wavelength by using an optical fiber in which a grating part is formed, and nonlinearly uses the laser light emitted from the optical fiber as a fundamental wave. A wavelength conversion laser device has been developed in which a second harmonic is generated by a wavelength conversion element in which a periodically poled structure is formed in an optical crystal to obtain near-ultraviolet or visible laser light. In the bioengineering field and measurement field, linear polarization is often required, so that the crystal axis of the wavelength conversion element and the polarization of the wavelength conversion element are generated so as to generate the second harmonic of the abnormal light with respect to the fundamental wave of the abnormal light. The direction was arranged to generate the second harmonic of linearly polarized light. In addition, a part of the harmonic light output from the wavelength conversion element is branched by a beam splitter, the intensity of the branched light is measured by a detector, the semiconductor laser drive current is adjusted based on the measurement result, and the output light The intensity was controlled.
However, there is a problem that depending on the wavelength of the fundamental wave, the intensity of linearly polarized light, which is desired output light, cannot be properly controlled.
Accordingly, an object of the present invention is to provide a wavelength conversion laser device that prevents a situation in which the intensity of linearly polarized light, which is desired output light, cannot be properly controlled.
[0005]
[Means for Solving the Problems]
In a first aspect, the present invention provides a semiconductor optical amplifying element, an optical fiber having a grating portion formed therein, and light emitted from an optical resonator composed of the semiconductor optical amplifying element and the optical fiber. A wavelength conversion element in which a periodically poled structure is formed in a nonlinear optical crystal that emits harmonic light of the incident light as light, a polarizer that transmits only the extraordinary light component of the harmonic light, and the light that passes through the polarizer Light branching means for branching a part of the extraordinary light component, photometry means for measuring the intensity of the extraordinary light component branched, and intensity of the extraordinary light component branched based on the measurement result of the photometry means becomes a predetermined value Thus, there is provided a wavelength conversion laser device comprising control means for driving the semiconductor optical amplification element.
[0006]
As a result of intensive studies by the inventor of the present application, it has been found that a second harmonic of ordinary light can be generated simultaneously with the second harmonic of extraordinary light in a wavelength conversion element in which a periodically poled structure is formed in a nonlinear optical crystal. This will be described next.
The periodic domain-inverted structure is a structure in which the spontaneous polarization of the crystal is periodically inverted so as to satisfy the quasi-phase matching condition (for example, “JA Armstrong et. Al, Phys. Rev., 127, p1918). , 1962 "," Kurimura, Solid Physics 29, No. 1, p75, 1994 ").
The quasi phase matching condition is that the polarization inversion period Λ satisfies the following equation.
Λ = 2m × λ / 4 {n (2ω) −n (ω)} (1)
Here, m = 1, 2, 3,..., N (ω) is the refractive index of the fundamental wave, and n (2ω) is the refractive index of the second harmonic.
[0007]
Usually, m = 1 is used because the conversion efficiency is proportional to (1 / m) ² . For example, when the wavelength of the fundamental wave TE (ω) of the extraordinary light propagating in the TE mode is converted to the second harmonic TE (2ω) of the extraordinary light propagating in the TE mode, the refractive indexes n (ω) and n (2ω ), The refractive indexes ne (ω) and ne (2ω) of extraordinary light are used.
FIG. 4A shows the relationship between the wavelength λ of the fundamental wave TE (ω) and the polarization inversion period Λ satisfying the quasi-phase matching condition in this case. Note that MgO: LiNbO ₃ having a periodically poled structure is used as the wavelength conversion element.
[0008]
Next, when m = 1, for example, when the wavelength of the fundamental wave TE (ω) of extraordinary light propagating in the TE mode is converted to the second harmonic TM (2ω) of ordinary light propagating in the TM mode, , M = 1, and refractive indexes n (ω) and n (2ω) may be the refractive index ne (ω) of extraordinary light and the refractive index no (2ω) of the second harmonic of ordinary light, respectively.
FIG. 4B shows the relationship between the wavelength λ of the fundamental wave TE (ω) and the polarization inversion period Λ satisfying the quasi phase matching condition in this case.
[0009]
Next, when m = 2, for example, when the wavelength of the fundamental wave TE (ω) of extraordinary light propagating in the TE mode is converted into the second harmonic TM (2ω) of ordinary light propagating in the TM mode, , M = 2, and the refractive indexes n (ω) and n (2ω) may be the refractive index ne (ω) of extraordinary light and the refractive index no (2ω) of the second harmonic of ordinary light.
FIG. 4C shows the relationship between the wavelength λ of the fundamental wave TE (ω) and the polarization inversion period Λ satisfying the quasi phase matching condition in this case.
[0010]
As can be seen from FIG. 4, when the polarization inversion period Λ of the wavelength conversion element is around 5.3 [μm] and the wavelength λ of the fundamental wave TE (ω) is around 980 [nm], (a) and (c There is a point P where) intersects. This is because the fundamental wave TE (ω) of the extraordinary light propagating in the TE mode is wavelength-converted to the second harmonic TE (2ω) of the extraordinary light at m = 1, and at the same time, the fundamental light TE (ω) at m = 2. It means that the wavelength is converted to the second harmonic TM (2ω).
In addition, at the time of m = 2 pseudo phase matching, when the ratio of the length in the optical axis direction (duty ratio) between the polarization inversion part and the non-inversion part in the polarization inversion period is 1, no second harmonic is generated. (See “Kurimura, Solid State Physics” above.) However, in reality, it is difficult to create a domain-inverted structure with a duty ratio of exactly 1, so the above-mentioned problem occurs. It is.
Further, the point P has a certain width due to subtle variations in the refractive index of the wavelength conversion element, polarization inversion period, and non-uniformity of the waveguide structure. Moreover, it fluctuates also with the temperature change of a wavelength conversion element.
[0011]
In addition, the inventors of the present application diligently studied and confirmed that the change of the extraordinary light component contained in the output light is different from the change of the ordinary light component with respect to the temperature change of the wavelength conversion element. This will be described next.
That is, as shown in FIG. 5, when the fundamental wave of 980 [nm] is wavelength-converted, the extraordinary light component P (2ωe) included in the output light of 490 [nm] is a curve having a maximum peak around 24 ° C. changed. On the other hand, the ordinary light component P (2ωo) contained in the output light became smaller as the temperature increased.
That is, it was found that not only the intensity of the extraordinary light component and the ordinary light component fluctuates due to the temperature fluctuation of the wavelength conversion element, but also the polarization ratio, that is, the ratio of the extraordinary light component to the ordinary light component.
However, since the beam splitter generally has a polarization property, when the polarization ratio changes, the intensity ratio of the reflected light and the transmitted light in the beam splitter changes. Therefore, even if the output light is controlled based on the reflected light, proper control cannot be performed.
[0012]
Thus, a part of the output light is branched by an optical branching element such as a beam splitter, the intensity of the branched light is measured by a detector, and the drive current of the semiconductor laser is adjusted based on the measurement result, and the output of the laser light is adjusted. In the example of FIGS. 4 and 5 described above, when the polarization inversion period Λ of the wavelength conversion element is around 5.3 [μm] and the wavelength of the fundamental wave is around 980 [nm], The component and the ordinary light component are included in the output light, and under the influence of the ordinary light component, a state occurs in which the intensity of the abnormal light that is the desired output light cannot be controlled to be constant.
Therefore, in the wavelength conversion laser device according to the first aspect, only the extraordinary light component of the harmonics emitted from the wavelength conversion element is transmitted and output by the polarizer, and a part of the extraordinary light component is branched to measure the intensity. To control the output. Thereby, even if the extraordinary light component and the ordinary light component are output from the wavelength conversion element, it is possible to prevent a situation in which the intensity of the extraordinary light that is the desired output light cannot be controlled to be constant.
[0013]
In a second aspect, the present invention provides the wavelength conversion laser device having the above-described configuration, including a beam shaping prism that shapes a beam shape of the harmonic light emitted from the wavelength conversion element, and the polarizer and the beam shaping prism. Provides a wavelength conversion laser device characterized by being integrally formed.
In the wavelength conversion laser device according to the second aspect, for example, a polarizer and a beam shaping prism are integrally formed by providing a polarizing film on the inclined surface of the beam shaping prism. Thereby, a structure can be simplified rather than comprising a polarizer and a beam shaping prism separately.
[0014]
In a third aspect, the present invention provides a semiconductor optical amplifying element, an optical fiber having a grating portion formed therein, and light emitted from an optical resonator composed of the semiconductor optical amplifying element and the optical fiber. A wavelength conversion element in which a periodically poled structure is formed in a nonlinear optical crystal that outputs harmonic light of the incident light as light, light branching means for branching a part of the harmonic light, and abnormal light of the branched harmonic light A polarizer that transmits only the component; a photometric means for measuring the intensity of the extraordinary light component; and driving the semiconductor optical amplification element so that the intensity of the extraordinary light component becomes a predetermined value based on a measurement result of the photometric means There is provided a wavelength conversion laser device characterized by comprising a control means.
In the wavelength conversion laser device according to the third aspect, only the extraordinary light component of the harmonics emitted from the wavelength conversion element is transmitted by the polarizer, and the output is controlled by measuring the intensity thereof. Thereby, even if the extraordinary light component and the ordinary light component are output from the wavelength conversion element, it is possible to prevent a situation in which the intensity of the extraordinary light that is the desired output light cannot be controlled to be constant.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to embodiments shown in the drawings. Note that the present invention is not limited thereby.
[0016]
-First embodiment-
FIG. 1 is an explanatory diagram illustrating a wavelength conversion laser device 100 according to the first embodiment.
This wavelength conversion laser device 100 includes a semiconductor optical amplification element 1 that generates laser light by injecting current into a light reflection surface 1a, a light emission surface 1b, and a region sandwiched between these surfaces, and a semiconductor optical amplification device 1 , A Peltier element 34 for controlling the temperature of the semiconductor optical amplifying element 1 via the mounting board 33, and a lens 2 for condensing the laser light generated by the semiconductor optical amplifying element 1. And an optical fiber 3 having a grating portion 6 formed therein, a lens 4 for condensing the light emitted from the optical fiber 3, and a second harmonic light of light incident through the lens 4 including the wavelength conversion element 5. A wavelength converting unit 50 that outputs the optical fiber 3, a grating unit extending mechanism 20 having a first fixing unit 14 and a second fixing unit 15 that hold the optical fiber 3 at two positions sandwiching the grating unit 6, and a housing 10 that stores these. The temperature sensing element 31 for detecting the temperature Ti of the grating section 6, the temperature sensing element 32 for detecting the temperature Tc in the wavelength conversion section 50, and the wavelength in the wavelength band of the light incident on the wavelength conversion section 50 A temperature control unit 40 that controls the temperature Tc according to the temperature Ti and a laser control unit 60 are provided so that the convertible wavelength band of the conversion unit 50 is adapted.
[0017]
The semiconductor optical amplifying element 1 generates and amplifies light having a wavelength in the range of 975 [nm] to 1015 [nm], for example. The light reflecting surface 1a is provided with a coating having a high reflectance with respect to the generated light, and the light emitting surface 1b is provided with a coating having a low reflectance with respect to the generated light.
[0018]
The end surface 3a on the incident side of the optical fiber 3 is preferably processed into a taper shape or a wedge shape so that more light emitted from the semiconductor optical amplifier element 1 enters. In this case, the lens 2 may not be provided.
[0019]
The grating portion 6 is formed by processing a part of the optical fiber 3 so that the refractive index periodically varies. For example, an ultraviolet laser such as an excimer laser is split into two light beams by a beam splitter, passes through different optical paths, and is superimposed and irradiated on an optical fiber to generate interference fringes, and an optical fiber photo produced according to the ultraviolet intensity. It is formed by periodically changing the refractive index at the same interval as the interference fringes by the refraction effect. By appropriately setting the period and length of the grating section 6, the bandwidth, center wavelength, and reflectance can be set freely.
[0020]
The grating unit 6 reflects only light in a certain wavelength band. For example, only light having a center wavelength λi between 975 [nm] and 1015 [nm] and having a bandwidth of about 0.5 [nm] is reflected. The bandwidth is determined by the length of the grating portion 6, and the center wavelength λi can be adjusted by adjusting the period in which the refractive index varies by the grating portion extension mechanism 20.
[0021]
The grating portion extending mechanism 20 includes a base 21, a moving nut 22 that can slide on the base 21, a screw rod 23 that is screwed to the moving nut 22, and the screw rod 23 manually or using a tool. And an operation unit 24 that can be rotated. The first fixed portion 14 is provided on the base 21, and the second fixed portion 15 is provided on the moving nut 22. The 1st fixing | fixed part 14 and the 2nd fixing | fixed part 15 hold | maintain the optical fiber 3 fixedly with an adhesive agent or soldering.
[0022]
When the operating portion 24 is turned and the screw rod 23 is turned, the moving nut 22 slides on the base 21 and the interval between the first fixing portion 14 and the second fixing portion 15 changes. Thereby, the grating part 6 expands and contracts, and the cycle in which the refractive index varies is changed. Thereby, the light emitted from the optical fiber 3 to the wavelength conversion element 5 can be matched with the wavelength convertible band of the wavelength conversion element 5.
[0023]
The semiconductor optical amplifying element 1 and the grating unit 6 constitute an optical resonator. That is, the light emitted from the semiconductor optical amplifying element 1 is collected by the lens 2 and is incident on the incident side end face 3 a of the optical fiber 3. The light incident on the optical fiber 3 is reflected in the wavelength band determined by the grating unit 6, returns to the semiconductor optical amplifier 1, is amplified by the semiconductor optical amplifier 1, and then exits the semiconductor optical amplifier 1 again. , Enters the optical fiber 3. By repeating this, light in the wavelength band determined by the grating section 6 is emitted from the emission side end face 3 b of the optical fiber 3. The end face 3b is polished with an inclination of, for example, 8 ° in order to suppress the reflected return light. The end face 3b is preferably provided with an antireflection film.
[0024]
The light emitted from the emission side end face 3 b of the optical fiber 3 is condensed by the lens 4 onto the end face 5 a of the wavelength conversion element 5 in the wavelength conversion unit 50. The lens 4 is provided with an antireflection film.
[0025]
The wavelength conversion element 5 is, for example, an optical waveguide formed on LiNbO ₃ , MgO: LiNbO ₃ , LiTaO ₃ , MgO: LiTaO ₃ , KNbO ₃ , KTiOPO ₄ , or those subjected to polarization inversion processing. . The wavelength conversion element 5 is, for example, light having a wavelength of 975 [nm] to 1015 [nm] incident thereon, and light having a second harmonic wave having a wavelength of 487.5 [nm] to 507.5 [nm]. Is generated.
[0026]
The temperature detected by the temperature sensing element 31 is a temperature in the vicinity of the grating section 6 in the housing 10, but is regarded as the temperature Ti of the grating section 6.
The temperature detected by the temperature sensing element 32 is the temperature of the internal space of the wavelength conversion unit 50, but is regarded as the temperature Tc of the wavelength conversion element 5.
The temperature sensitive elements 31 and 32 are, for example, thermistors.
[0027]
The temperature control unit 40 includes a Peltier element 41, a conversion circuit 42 that converts the temperature Ti of the grating unit 6 into a voltage Vi, a conversion circuit 43 that converts the temperature Tc of the wavelength conversion element 5 into a voltage Vc, and a reference to the voltage Vi. It has an adder circuit 44 that outputs a voltage Vs obtained by adding the voltage Vo, and a drive circuit 45 that outputs a drive current Ip of the Peltier element 41 based on the difference between the voltage Vs and the voltage Vc.
Therefore, there is the following relationship.
Vi = A1 · Ti (2)
Vc = A2 · Tc (3)
Vs = Vi + Vo (4)
Ip = A3 · (Vs−Vc) (5)
A1, A2, and A3 are conversion coefficients.
[0028]
When the temperature Ti of the grating 6 and the temperature Tc of the wavelength conversion element 5 are both the reference temperature To, the center wavelength λio of the fundamental wavelength band incident from the optical fiber 3 to the wavelength conversion element 5 and the wavelength conversion element 5 If the center wavelength λco of the wavelength band that can be wavelength-matched coincides with Ti (Tc = To, Ip = 0) in the equations (1) to (4), the following relationship can be obtained.
0 = A3 · (A1 · To + Vo−A2 · To) (6)
[0029]
FIG. 2 is a block diagram illustrating a control loop of the temperature control unit 40.
A block B1 represents conversion functions of the conversion circuit 42, the conversion circuit 43, the addition circuit 44, and the drive circuit 45. This conversion function can be derived from equations (2) to (6).
Block B <b> 2 represents a current-temperature conversion function in the Peltier element 41. This current-temperature conversion function is expressed by the following equation using A4 as a conversion coefficient.
Tc = A4 · Ip (7)
[0030]
From the equations (2) to (7), the following equation is derived.
ΔTc = k · ΔTi (8)
However,
ΔTc = Tc−To (9)
ΔTi = Ti−To (10)
k = A1, A3, A4 / (1 + A2, A3, A4) (11)
And
[0031]
Here, the temperature coefficient of the wavelength band of the fundamental wave incident on the wavelength conversion element 5 from the optical fiber 3 is δλi [nm / ° C.], and the temperature coefficient of the convertible wavelength band of the wavelength conversion element 5 is δλc [nm / ° C. ]
k = δλi / δλc
Or
k≈δλi / δλc
The conversion coefficients A1 to A4 are determined so that.
For example, if δλi = 0.01 [nm / ° C.] and δλc = 0.06 [nm / ° C.],
k = 1/6
Or
k = 0.1-0.2
The conversion coefficients A1 to A4 are determined so that.
[0032]
Since the temperature Tc is controlled according to the temperature Ti as described above, the convertible wavelength band of the wavelength conversion element 5 at the temperature Tc always matches the reflection wavelength band of the grating section 6 at the temperature Ti.
[0033]
Returning to FIG. 1, the wavelength converter 50 emits the wavelength conversion element 5 that outputs the second harmonic light of the incident light (fundamental wave), the lens 51 that collimates the output second harmonic light, and the lens 51. A polarizer 52 that transmits only the extraordinary light component from the second harmonic, prisms 53 and 54 that shape the beam shape of light emitted from the polarizer 52 from an ellipse to a circle, and only the second harmonic component are transmitted. A filter 55 that absorbs or reflects the fundamental wave component, a beam splitter 56 that branches part of the light emitted from the filter 55 and transmits the other, and a photometric element 57 that outputs a photometric signal Sd representing the intensity of the branched light The housing 11 in which these are housed, and the Peltier element 41 for controlling the temperature inside the housing 11 (in particular, the wavelength conversion element 5) are provided.
[0034]
The incident side end face 5a and the emission side end face 5b of the wavelength conversion element 5 are polished with an inclination of, for example, 10 ° from the viewpoint of suppressing reflected return light. The end faces 5a and 5b are preferably provided with an antireflection film.
[0035]
The prisms 53 and 54 are a pair of wedge-shaped prisms having apex angles of 20 ° to 45 °. By independently adjusting the mounting angles of the prisms 53 and 54, variations in ellipticity due to individual differences in the waveguide of the wavelength conversion element 5 can be corrected, and the beam shape of the emitted light can be made circular.
[0036]
From the viewpoint of simplifying the structure, the polarizer 52 may be configured integrally with the prism 53 or 54. For example, instead of providing the polarizer 52, a polarizing film is formed on at least one surface of the prism 53 or 54. Since the inclined surfaces of the prisms 53 and 54 have a slight degree of polarization, it is effective to apply the polarizing film to the surface on which the laser light is incident at a shallow angle, for example, the first surface of the prism 53.
[0037]
The photometric element 57 is, for example, a GaAsP photodiode.
[0038]
Based on the photometric signal Sd from the photometric element 57, the laser control unit 60 drives the semiconductor optical amplifying element 1 by outputting a drive current Id so that the intensity of light incident on the photometric element 57 becomes a predetermined value. In this way, the intensity of the extraordinary light component of the second harmonic output from the wavelength conversion laser device 100 is appropriately controlled.
[0039]
According to the wavelength conversion laser device 100 according to the first embodiment, it is possible to output linearly polarized light having only abnormal light components required in the bioengineering field and the measurement field. Further, the output can be appropriately controlled without being affected by the ordinary light component.
[0040]
-Second Embodiment-
FIG. 4 is a configuration explanatory view showing a wavelength conversion laser device 200 according to the second embodiment.
In this wavelength conversion laser device 200, a polarizer is not inserted between the lens 51 and the prism 53, but a polarizer 58 is inserted between the beam splitter 56 and the photometric element 57 instead. The configuration is the same as that of the wavelength conversion laser device 100 according to the first embodiment.
[0041]
In this wavelength conversion laser device 200, only the extraordinary light component of the light branched by the beam splitter 56 passes through the polarizer 58 and reaches the photometric element 57. For this reason, the output is controlled only by the abnormal light component.
[0042]
According to the wavelength conversion laser device 200 according to the second embodiment, the output light includes the extraordinary light component and the ordinary light component, but the output intensity of the extraordinary light component required in the bioengineering field and the measurement field is appropriately set. Can be controlled. Further, there is an advantage that no output loss or aberration occurs due to the polarizer.
[0043]
【The invention's effect】
According to the wavelength conversion laser device of the present invention, even if the harmonic light including the extraordinary light component and the ordinary light component is emitted from the wavelength conversion element, the output intensity of the extraordinary light component required in the bioengineering field and the measurement field is appropriately adjusted. Can be controlled.
[Brief description of the drawings]
FIG. 1 is a configuration explanatory view showing a wavelength conversion laser device 100 according to a first embodiment.
FIG. 2 is a block diagram showing a control loop of a temperature control unit according to the first embodiment.
FIG. 3 is an explanatory diagram showing a configuration of a wavelength conversion laser device 200 according to a second embodiment.
FIG. 4 is a graph showing the relationship between the wavelength λ of the fundamental wave and the polarization inversion period Λ that satisfies the quasi phase matching condition.
FIG. 5 is a graph showing temperature changes of an extraordinary light component and an ordinary light component included in the second harmonic output.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Semiconductor optical amplification element 2, 4, 51 Lens 3 Optical fiber 5 Wavelength conversion element 6 Grating part 10, 11 Case 20 Grating part expansion | extension mechanism 31, 32 Temperature sensitive element 34, 41 Peltier element 40 Temperature control part 50 Wavelength conversion part 52, 58 Polarizers 53, 54 Prism 55 Filter 56 Beam splitter 57 Photometric element 60 Laser controller 100, 200 Wavelength conversion laser device

Claims (4)

A semiconductor optical amplifier, an optical fiber having a grating portion formed therein, and light emitted from an optical resonator composed of the semiconductor optical amplifier and the optical fiber are used as incident light, and harmonic light of the incident light is emitted. A wavelength conversion element having a periodically poled structure formed in a nonlinear optical crystal, a polarizer that transmits only the extraordinary light component of the harmonic light, and light that branches a part of the extraordinary light component that has passed through the polarizer A branching means; a photometric means for measuring the intensity of the branched abnormal light component; and driving the semiconductor optical amplification element so that the intensity of the abnormal light component branched based on a measurement result of the photometric means becomes a predetermined value. A wavelength conversion laser device comprising a control means. The wavelength conversion laser device according to claim 1, further comprising a beam shaping prism that shapes a beam shape of the harmonic light emitted from the wavelength conversion element, wherein the polarizer and the beam shaping prism are integrally configured. A wavelength conversion laser device characterized by comprising: A semiconductor optical amplifier, an optical fiber having a grating portion formed therein, and light emitted from an optical resonator composed of the semiconductor optical amplifier and the optical fiber is used as incident light, and harmonic light of the incident light is output. A wavelength conversion element in which a periodically poled structure is formed in the nonlinear optical crystal, a light branching unit that branches a part of the harmonic light, a polarizer that transmits only the extraordinary light component of the branched harmonic light, and Photometric means for measuring the intensity of the extraordinary light component; and control means for driving the semiconductor optical amplifier so that the intensity of the extraordinary light component becomes a predetermined value based on the measurement result of the photometry means. A wavelength conversion laser device. 4. The wavelength conversion laser device according to claim 1, wherein the wavelength conversion element is formed by forming a periodically poled structure in a LiNbO ₃ crystal doped with MgO. 5. Laser device.

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