JP2012186333A - Laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser device capable of reporting replacement time of an optical fiber according to an actual degradation state of the optical fiber and also capable of securing both economical efficiency and stable operation.SOLUTION: A laser device according to the present invention comprises: a laser light output section having a fiber light amplifier 223; and a wavelength conversion section having a wavelength conversion optical element 34. A laser device LS comprises: an excitation light detector 51 that detects a power of excitation light of the fiber light amplifier 223 and outputs a first detection signal Pa; a second harmonic wave detector 53 that detects a power of light of which wavelength has been converted by the wavelength conversion optical element 34 and outputs a second detection signal Pb; and an FA determination section 58 that determines an operation state of the fiber light amplifier 223. The FA determination section 58 outputs a lifetime determination signal when the second detection signal Pb with respect to the first detection signal Pa (dPb)/(dPa) becomes equal to or lower than a lifetime reference value.

Description

  The present invention includes a laser light output unit that has a fiber optical amplifier and emits fundamental wave laser light, and a wavelength that has a wavelength conversion optical element and wavelength-converts and outputs the fundamental wave laser light emitted from the laser light output unit. The present invention relates to a laser device including a conversion unit.

  The laser apparatus as described above is used as a light source for, for example, a microscope, a shape measuring apparatus, and an exposure apparatus. Such a laser device generally outputs a fundamental laser beam having a wavelength λ = 1.0 to 1.55 μm from a laser beam output unit, and the fundamental laser beam is provided in a plurality of wavelength conversion units. The wavelength is sequentially converted by the wavelength conversion optical element, and for example, an ultraviolet laser beam having a wavelength of λ = 193 nm or λ = 309 nm is output (for example, see Patent Document 1 and Patent Document 2).

JP 2000-200747 A Japanese Patent Laid-Open No. 2002-50815

  In such a laser device, the optical fiber in the fiber optical amplifier provided in the laser light output section is generally composed of a core, a clad, and a resin coating that protects them. A rare earth element is added to the core, and stimulated emission occurs when signal light and excitation light are incident, thereby amplifying the signal light. At this time, due to the heat generation of the optical fiber itself and the generation of up-conversion light with a short wavelength, the resin coating gradually deteriorates over the long term use of the fiber optical amplifier, and the temperature and humidity of the environment where the laser device is placed Since it becomes easy to be influenced by disturbances such as changes, it becomes difficult to output a stable fundamental wave laser beam, and thus a stable wavelength converted light. In addition, light that has been wavelength-converted by the wavelength conversion optical element is generally shorter in wavelength than the fundamental laser beam, and a part of the light becomes return light and enters the optical fiber, which may deteriorate the resin coating. is there. This is also considered to be the same for a single or multi-clad optical fiber using a resin clad.

  Therefore, in the conventional laser device, the replacement life of the optical fiber is determined in consideration of various deterioration factors, and when a set constant operation time (for example, 10,000 hours) has elapsed, a warning or the like is displayed, It was configured to encourage replacement of the fiber optical amplifier. This means that optical fiber deterioration has not progressed so much, and even if it is still fully usable, the fiber optical amplifier must be replaced uniformly. This is a problem in terms of economy and resource protection. was there. In addition, for example, there are many workpieces with high reflectivity, and the wavelength-converted light irradiated to the workpiece from the laser device enters the optical fiber as return light and promotes deterioration of the optical fiber. In the case of use in the above, there is a problem that it may be difficult to ensure a stable operation by reaching the use limit before the elapse of a preset replacement life.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser apparatus capable of achieving both economic efficiency and ensuring stable operation.

  In order to solve the above problems and achieve the object, the inventor firstly reduced the optical output after wavelength conversion output from the laser device (referred to as harmonic output for convenience) from the initial output, and the cause is the fiber What kind of phenomenon is occurring when it is considered to be due to deterioration of the optical amplifier, in other words, about the state change of the fiber optical amplifier that causes a decrease in harmonic output and instability? We conducted intensive research. This will be described below with reference to the drawings. FIG. 9 shows a simplified block diagram of a laser apparatus for explanation.

  The laser device is roughly divided into a laser beam output unit 1 having a fiber optical amplifier 21 and emitting a fundamental laser beam, and a fundamental wave laser having a wavelength conversion optical element 31 and emitted from the laser beam output unit 1. And a wavelength converter 3 that converts the wavelength of the light and outputs the light. FIG. 9 shows a configuration in which the laser light output unit 1 is configured by a laser light source 11 that generates signal light and a fiber optical amplifier 21 that amplifies the signal light generated by the laser light source 11. The signal light (fundamental laser beam) amplified by the fiber optical amplifier 21 is incident on the wavelength converting optical element 31, and the wavelength converting optical element 31 performs predetermined wavelength conversion such as generation of nth-order harmonics and wavelength conversion. Light and fundamental laser light that has been transmitted without being wavelength-converted are emitted.

Here, in the wavelength conversion, it is necessary to make light having a high linear polarization rate incident on the wavelength conversion optical element 31 with the polarization plane set at a predetermined angle with respect to the crystal optical axis. The fundamental laser light whose polarization is adjusted by a polarization controller (not shown) installed after the light source 11 enters the wavelength conversion optical element 31. In FIG. 10, a PPLN (Periodically Poled LiNbO ₃ ) crystal having a periodically polarized structure is used as the wavelength converting optical element 31, and the fundamental wave ω ₁ having a predetermined frequency is wavelength-converted to obtain a second harmonic whose frequency is doubled. The case where (double wave) ω ₂ is generated is illustrated. From the fiber optical amplifier 21, a linearly polarized fundamental wave (fundamental laser beam) ω ₁ is emitted. At this time, the wavelength conversion optical element 31 is s-polarized light whose polarization direction is the crystal optical axis direction (polarization direction) of the wavelength conversion optical element 31 with respect to the polarization direction of the fundamental wave ω ₁ emitted from the fiber optical amplifier 21. The arrangement posture is set so that the conversion efficiency is maximized when the linearly polarized light is incident. In the figure, the polarization state and power of the fundamental wave ω ₁ and the second harmonic ω ₂ are represented by the direction and length of the arrow.

FIG. 11 and FIG. 12 show the operating characteristics of the laser device observed in the normal state before the fiber optical amplifier 21 deteriorates in the laser device configured as described above. Here, FIG. 11 shows the power Pω ₁ of the fundamental wave ω _{1 on} the horizontal axis, the power Pω ₂ of the second harmonic ω ₂ on the vertical axis, and the power Pω ₁ of the fundamental wave incident on the wavelength conversion optical element 31. This represents a change in the second harmonic power Pω ₂ emitted from the wavelength conversion optical element 31 when the wavelength conversion optical element 31 is changed, and the wavelength conversion efficiency when the power of the incident fundamental wave (power density in the crystal) is a predetermined value or more. Is a change in a substantially constant region. FIG. 12 shows the fundamental wave output from the fiber optical amplifier 21 when the pumping light power Ppump is plotted on the horizontal axis and the power Pω of the output light is plotted on the vertical axis, and the pumping light power Ppump of the fiber optical amplifier 21 is changed. The power Pω ₁ and the second harmonic power Pω ₂ output from the wavelength conversion optical element 31 are shown.

From both figures, at the normal time before the fiber optical amplifier 21 deteriorates, the fundamental wave power Pω ₁ increases in proportion to the power Ppump of the pumping light that excites the fiber optical amplifier 21 (with a slope of a predetermined coefficient). In the region where the wavelength conversion efficiency is substantially constant, the power Pω ₂ of the second harmonic increases in proportion to the power Pω _{1 of the} fundamental wave (same as above).

Next, when the power of the second harmonic ω ₂ output from the laser device starts to decrease from the initial output and is considered to be caused by the deterioration of the fiber optical amplifier 21, for example, the laser light source 11 and the wavelength An example of the operating characteristics of the laser device observed when there is no abnormality in the conversion optical element 31 and the second harmonic power similar to the initial output is obtained when the fiber optical amplifier 21 is replaced with a new one. As shown in FIG. The horizontal and vertical axes in the figure are the same as in FIG. 12, and the fundamental wave power Pω ₁ output from the fiber optical amplifier 21 and the wavelength conversion optical element when the pumping light power Ppump of the fiber optical amplifier 21 is changed. 3 shows a change in the power Pω ₂ of the second harmonic output from 31.

From FIG. 13, when the power Ppump of the pumping light that excites the fiber optical amplifier 21 increases, the power Pω _{1 of the} fundamental wave increases in proportion to this. At this time, the gradient (dPω ₁ ) / (dPpump) of the fundamental wave power with respect to the pumping light power is almost the same as that in the normal state. However, although the power Pω ₂ of the second harmonic increases with the increase of the pumping light power, that is, the fundamental power Pω ₁ , the slopes thereof are (dPω ₂ ) / (dPpump) and (dPω ₂ ) / (DPω ₁ ) becomes smaller than normal, and the second harmonic power Pω ₂ tends to saturate in the high power region.

FIG. 14 is an example of the operating characteristics of the laser device observed from the state shown in FIG. 13 in a state where the deterioration of the fiber optical amplifier 21 has further progressed. The horizontal and vertical axes in the figure are the same as those in FIGS. 12 and 13 and represent changes in the fundamental power Pω ₁ and the second harmonic power Pω ₂ when the pumping light power Ppump is changed. is there.

Even in this state, if the power Ppump of the pumping light that excites the fiber optical amplifier 21 increases, the power Pω _{1 of the} fundamental wave increases in proportion to this. There is no significant change in the slope (dPω ₁ ) / (dPpump) of the fundamental wave power with respect to the pumping light power. On the other hand, the power Pω ₂ of the second harmonic fluctuates so as to wave greatly with respect to the pump light power Ppump and the power Pω _{1 of the} fundamental wave, and the gradients thereof are (dPω ₂ ) / (dPpump) and (dPω ₂ ). / (DPω ₁ ) varies greatly between positive and negative.

The reason why the above phenomenon occurs, that is, even though the fundamental power Pω ₁ has not changed significantly from the normal time, the second harmonic power Pω ₂ is increased with respect to the fundamental power increase. The inventor conducted further research to investigate the cause of whether it fluctuates so as to swell greatly. And I caught the phenomenon that seems to be the cause. For the fiber optical amplifier 21 in the degraded state shown in FIG. 14, the power Pω ₁ of the fundamental wave and the powers Pω _1p and Pω _1s of the two polarization components of the fundamental laser light when the power P pump of the pump light is changed. The result of examining the change is shown in FIG.

As described above, the power Pω ₁ of the fundamental laser light emitted from the fiber optical amplifier 21 increases in proportion to the pumping light power Ppump of the fiber optical amplifier 21 and the slope of the fundamental power with respect to the pumping light power (dPω _1). ) / (DPpump) shows no significant change. However, at this time, the polarization state of the fundamental laser beam has greatly fluctuated. FIG. 15 illustrates this.

That is, as the pumping light power Ppump increases, the power Pω ₁ (= Pω _1p + Pω _1s ) of the entire fundamental wave, which is the sum of the power Pω _1p of the p-polarized component of the fundamental wave and the power Pω _1s of the s-polarized component, increases. However, there is no significant change in the slope of the fundamental wave power with respect to the excitation light power. However, the powers Pω _1p and Pω _1s of the two polarization components of the fundamental wave fluctuate so as to wave greatly with respect to the excitation light power. At this time, since the two polarization components coexist and the composition ratio fluctuates, the fundamental laser beam incident on the wavelength conversion optical element 31 becomes elliptically polarized light as shown in FIG. It seems that the direction is changing.

As already described, it is the s-polarized component that contributes to the second harmonic generation in the wavelength conversion optical element 31, and the power Pω ₂ of the second harmonic varies in response to the variation of the s-polarized component of the fundamental wave. To do. Therefore, even though the fundamental power Pω ₁ is increased in proportion to the pumping light power Ppump, the second harmonic power Pω ₂ output from the laser device is larger than the pumping light power. It fluctuated as a wave. Based on the knowledge obtained by the above research, the inventor completed the following invention.

  An embodiment exemplifying the present invention includes a laser light output unit that has a fiber optical amplifier and emits a fundamental wave laser beam, and a wavelength converter that has a wavelength conversion optical element and emits the fundamental wave laser beam. And a wavelength conversion unit that outputs the output. In addition, this laser apparatus detects the intensity of the fundamental wave laser light or the state quantity corresponding thereto and outputs a first detection signal Pa corresponding to the detected quantity (for example, excitation light detection in the embodiment). 51, fundamental wave detector 52, etc.) and second detection means for detecting the intensity of light wavelength-converted by the wavelength conversion optical element and outputting a second detection signal Pb corresponding to the detection amount (for example, the embodiment) The second harmonic detector 53), the first detection signal Pa output from the first detection means and the second detection signal Pb output from the second detection means to determine the operating state of the fiber optical amplifier. An FA determination unit. When the ratio between the change amount dPa of the first detection signal Pa and the change amount dPb of the second detection signal Pb falls outside the preset life reference range, for example, (FA) (dPb) / (dPa ) Is less than the life reference value, it is configured to output a life judgment signal.

  Note that the state quantity corresponding to the intensity of the fundamental laser beam can be the intensity of the pumping light in the fiber optical amplifier. Alternatively, the state quantity corresponding to the intensity of the fundamental laser beam may be the intensity of the fundamental laser beam transmitted through the wavelength conversion optical element.

  Further, among the light emitted from the wavelength conversion optical element, a mirror that transmits the fundamental wave laser light that has passed through the wavelength conversion optical element and transmits a part of the light that has been wavelength-converted by the wavelength conversion optical element (for example, A mirror 42) in the embodiment, and a spectroscopic element (for example, the spectroscopic element 56 in the embodiment) for separating the fundamental laser beam that has passed through the mirror and the wavelength-converted light that has passed through the mirror. The detection means and the second detection means can be configured to detect the intensities of the fundamental laser beam and the wavelength-converted light, respectively, separated by the spectroscopic element.

  In the laser device having such a configuration, the first detection means for detecting the intensity of the fundamental wave laser light and the like and outputting the first detection signal Pa corresponding to the detection amount, and the light wavelength-converted by the wavelength conversion optical element Second detection means for detecting the intensity of the first detection signal and outputting a second detection signal Pb corresponding to the detection amount, and the FA determination unit changes the change amount dPa of the first detection signal Pa and the change of the second detection signal Pb. When the ratio to the quantity dPb falls outside the preset life reference range, a life determination signal is output. As described above, when the fiber optical amplifier is in a normal state, the output of the wavelength-converted light has a certain slope with respect to an increase in the intensity of the fundamental laser beam, and (dPb) / (dPa) or its The reciprocal is a predetermined finite value. When the fiber optical amplifier is deteriorated, for example, (dPb) / (dPa) decreases, and when the deterioration further proceeds, positive and negative fluctuations occur. Therefore, according to the present configuration in which the ratio of the change amount dPa of the first detection signal Pa and the change amount dPb of the second detection signal Pb is taken and the life determination signal is output when the value is outside the life reference range. Thus, it is possible to appropriately determine whether or not the fiber optical amplifier has actually deteriorated, and it is possible to provide a laser apparatus that can achieve both economic efficiency and ensuring stable operation.

It is a schematic block diagram of the whole laser apparatus shown as an example of application of this invention. It is drawing which illustrates the connection structure of the fiber optical amplifier in an amplification part. It is drawing for demonstrating the structure and effect | action of a wavelength conversion optical system. It is a schematic block diagram of 50 A of FA lifetime judgment apparatuses of a 1st structure form. It is a graph which shows the example of a setting of the lifetime reference value in 50 A of FA lifetime judgment apparatuses. It is a schematic block diagram of FA lifetime judgment apparatus 50B of a 2nd structure form. It is a graph which shows the example of a setting of the lifetime reference value in FA lifetime judgment apparatus 50B. It is a schematic block diagram of FA lifetime judgment apparatus 50C of a 3rd structure form. It is the block diagram of the simplified laser apparatus. It is explanatory drawing for demonstrating the state of the fundamental wave (omega) _{1 which} injects into a wavelength conversion optical element, and the 2nd harmonic wave (omega) ₂ inject | emitted from a wavelength conversion optical element in a fiber optical amplifier in a normal state. Fiber optical amplifiers are observed in a normal state, is a graph showing the relationship between the second harmonic power Pomega ₂ emitted from the fundamental wave of the power Pomega ₁ and the wavelength conversion optical element that is incident on the wavelength conversion optical element. The pump light power Ppump of the fiber optical amplifier, the fundamental wave power Pω ₁ output from the fiber optical amplifier, and the second harmonic power output from the wavelength conversion optical element, observed in the normal state of the fiber optical amplifier. is a graph showing the relationship between Pω _2. Fiber optical amplifier pumping light power Ppump, fundamental wave power Pω ₁ output from the fiber optical amplifier, and second harmonic power output from the wavelength conversion optical element, observed in the initial deterioration state of the fiber optical amplifier is a graph showing the relationship between Pω _2. The pumping light power Ppump of the fiber optical amplifier, the fundamental wave power Pω ₁ output from the fiber optical amplifier, and the second harmonic output from the wavelength conversion optical element, observed in a state where the deterioration of the fiber optical amplifier has progressed. is a graph showing the relationship between the power Pomega ₂ of. The pumping light power Ppump of the fiber optical amplifier, the fundamental wave power Pω ₁ output from the fiber optical amplifier, and the powers Pω _1p of the two polarization components of the fundamental wave, which were observed in a state where the degradation of the fiber optical amplifier progressed. It is a graph which shows the relationship with Pomega _1s . In a state in which the fiber optical amplifier is deteriorated is an explanatory diagram for explaining a second state of the harmonic omega ₂ emitted from the fundamental omega ₁ and the wavelength conversion optical element enters the optical wavelength conversion element.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an entire laser apparatus LS to which the present invention is applied. The laser device LS has a fiber optical amplifier and outputs a laser beam output unit 1 that emits a fundamental laser beam, and a wavelength conversion optical element that converts the wavelength of the fundamental laser beam emitted from the laser beam output unit 1 and outputs it. And a control unit 8 that controls the operation of the wavelength conversion unit 3, the laser beam output unit 1, and the wavelength conversion unit 3.

The laser light output unit 1 and the wavelength conversion unit 3 can be appropriately set according to the use and function of the system configured using the laser device LS. In the present embodiment, a fundamental laser beam La (La ₁ , La ₂ , La ₃ ) having a wavelength of 1547 nm is output from the laser beam output unit 1, and this is wavelength-converted by the wavelength conversion unit 3, and an ultraviolet having the shortest wavelength of 193 nm. A case where the laser beam Lv is output will be described as an example.

FIG. 1 shows a configuration in which the laser beam output unit 1 is configured by three laser beam output units 1a, 1b, and 1c. That is, the laser beam output unit 1 includes a first laser beam output unit 1a for outputting a first fundamental wave laser light La _1, second second laser beam output unit 1b for outputting a fundamental wave laser beam La ₂ and, The third laser beam output unit 1c that outputs the _third fundamental wave laser beam La3 is used.

In FIG. 1, the laser light output unit 1 includes a laser light generation unit 10 that outputs signal light Ls (Ls ₁ , Ls ₂ , Ls ₃ ), and an amplification that amplifies the signal light output from the laser light generation unit 10. The form comprised by the part 20 is shown. That is, the first laser beam output section 1a includes a first laser light generator 10a for outputting a signal light Ls ₁ of the first fundamental wave having a laser light source 11, a first laser light generator having a fiber optical amplifier 21 is constituted by a first amplifying part 20a for amplifying the signal light Ls ₁ of the first fundamental wave output from the section 10a, the fundamental wave laser light La ₁ of the amplified signal light or first is by first amplifying unit 20a Is output.

Similarly, the second laser beam output unit 1b, a second fundamental wave and a second laser light generator 10b for outputting a signal light Ls ₂ of the second fundamental wave having a laser light source 12, the fiber optical amplifier 22 is constituted by a second amplifier 20b for amplifying the signal light Ls _2, the second is the fundamental laser beam La ₂ output from the second amplifying section 20b. The third laser light output unit 1c includes a third laser beam generating unit 10c for outputting a third signal light Ls ₃ of the fundamental wave has a laser light source 13, the third fundamental signal light having a fiber optical amplifier 23 is constituted by a third amplifier unit 20c for amplifying the ls _3, the third fundamental laser beam La ₃ is outputted from the third amplifying unit 20c.

Laser light sources 11 to 13 that are provided in the laser light generator 10 (10a to 10c) and generate signal light having a wavelength of 1547 nm include, for example, a DFB (Distributed Feedback) semiconductor laser or fiber laser having an oscillation wavelength of 1.5 μm. Can be used. These lasers can be oscillated and pulsed, and the pulse waveform can be controlled at a high speed on the order of nanoseconds by controlling the excitation current. The laser beam generator 10 is provided with an external modulator such as an EOM (Electro Optic Modulator) or AOM (Acousto Optic Modulator), and the output light of the laser light source generated by CW or pulse oscillation is cut out by the external modulator. The pulse light may be output. Further, in the above configuration, the signal lights Ls ₁ , Ls ₂ , and Ls ₃ are output from the individual laser light sources 11 to 13, but the output from one laser light source is branched by a coupler and Ls ₁ , Ls ₂ , Ls ₃ may be used.

  The fiber optical amplifiers 21 to 23 that are provided in the amplifying unit 20 (20a to 20c) and amplify signal light having a wavelength of 1547 nm are, for example, erbium-doped fiber optical amplifiers (EDFAs) whose core is doped with erbium (Er) Are preferably used. Each of the first to third amplification units 20a to 20c can be configured by providing a single or a plurality of fiber optical amplifiers. In the present embodiment, a configuration form in which three fiber optical amplifiers 221, 222, and 223 are connected in series will be described, as shown in FIG. 2 as an example of the connection configuration of the fiber optical amplifier 22 taking the second amplifying unit 20b as an example.

  That is, the second amplifying unit 20b is configured by connecting a first-stage fiber optical amplifier 221, a second-stage fiber optical amplifier 222, and a third-stage fiber optical amplifier 223 in series. At this time, the first-stage fiber optical amplifier 221, the second-stage fiber optical amplifier 222, and the third-stage fiber optical amplifier 223 include erbium-doped fibers (EDF) 221a, 222a, and 223a. The pumping light used and output from the pumping light sources 221b, 222b, 223b is coupled to the core of each fiber via the WDM couplers 221c, 222c, 223c. The first amplifying unit 20a and the third amplifying unit 20c are configured similarly.

The first fundamental wave laser beam La ₁ emitted from the first amplification unit 20a, the second fundamental wave laser beam La ₂ emitted from the second amplification unit 20b, and the third fundamental wave emitted from the third amplification unit 20c. The laser beam La ₃ is output from the laser beam output unit 1 (1a, 1b, 1c) and input to the wavelength conversion unit 3.

  The wavelength conversion unit 3 is provided with a wavelength conversion optical system 30 including a plurality of wavelength conversion optical elements and mirrors. A schematic configuration of the wavelength conversion optical system 30 is shown in FIG. In FIG. 3, the ones indicated by ellipses on the optical path are collimator lenses and condenser lenses, and their descriptions are omitted. Also, in the figure, the polarization state of light incident on each wavelength conversion optical element is added, and the s-polarized light described above is indicated by a circle with a dot, and the p-polarized light whose polarization plane is orthogonal to the vertical direction. Indicated by an arrow. Further, the fundamental wave is represented by ω, and its n-order harmonic is represented by nω.

Wavelength converting optical system 30, the first fundamental wave laser light La ₁ output from the first laser beam output section 1a is output from the first series I, the second laser beam output unit 1b propagating incident A second series II in which the _second fundamental laser beam La ₂ is incident and propagated; a third series III in which the third fundamental laser beam La ₃ output from the third laser beam output unit 1c is incident and propagated; And the fourth series IV in which the laser beams propagated through the first, second, and third series are superimposed and propagated, and are mainly composed of a total of six wavelength converting optical elements 31 to 36 provided in each series. The

  In the wavelength conversion unit 3, the fundamental laser beam having a wavelength of 1547 nm output from each laser beam output unit is sequentially wavelength-converted, and an ultraviolet laser beam Lv having a wavelength of 193 nm is output. First, an overall outline of the wavelength conversion optical system 30 that converts a fundamental laser beam having a wavelength of 1547 nm into an ultraviolet laser beam Lv having a wavelength of 193 nm will be described, followed by the configuration of the first to fourth series and the laser light propagating through each series. The state of will be described. Note that the fundamental laser beam may be referred to as a fundamental wave.

The first fundamental wave laser light La ₁ having a wavelength of 1547 nm and a frequency ω incident on the first series I is sequentially wavelength-converted from ω → 2ω → 3ω → 5ω by wavelength conversion optical elements 31 to 33 provided in this series. The generated fifth harmonic 5ω is incident on the fourth series IV. The second fundamental wave laser beam La ₂ having a wavelength of 1547 nm and a frequency ω incident on the second series II is wavelength-converted from ω → 2ω by the wavelength conversion optical element 34 provided in this series, and the generated second harmonic wave. 2ω is incident on the fourth series IV. The third fundamental wave laser beam La ₃ having a wavelength of 1547 nm and a frequency ω incident on the third series III enters the fourth series IV without being wavelength-converted.

In the fourth series IV, in the wavelength conversion optical element 35, the seventh harmonic 7ω is generated by the sum frequency generation of the fifth harmonic 5ω generated in the first series and the second harmonic 2ω generated in the second series, In the wavelength conversion optical element 36, by generating the sum frequency of the seventh harmonic 7ω and the fundamental wave ω (third fundamental laser beam La ₃ ) incident from the third series III, the frequency is 8 times the fundamental wave ω, An eighth harmonic 8ω having a wavelength of 193 nm and having a wavelength that is 1/8 of the fundamental wave is generated. Then, an ultraviolet laser beam Lv having a wavelength of 193 nm generated by the wavelength conversion optical element 36 is output from the laser device LS. Hereinafter, the configuration of each series and the state of the propagating laser beam will be described.

In the first series I, wavelength conversion optical elements 31, 32, and 33 are arranged. The first fundamental laser beam La ₁ output from the first laser beam output unit _{1 a} is focused and incident on the wavelength conversion optical element 31 as s-polarized light, and s is generated by the second harmonic generation in the wavelength conversion optical element 31. A second harmonic 2ω of polarized light is generated. The generated second harmonic 2ω of s-polarized light and the fundamental wave ω of s-polarized light transmitted through the wavelength converting optical element 31 are focused and incident on the wavelength converting optical element 32, and the third harmonic 3ω of p-polarized light is generated by sum frequency generation. generate. The wavelength conversion optical elements 31 and 32 are, for example, a PPLN (Periodically Poled LiNbO ₃ ) crystal as the second harmonic generation wavelength conversion optical element 31, and an LBO (LiB ₃ ) as the third harmonic generation wavelength conversion optical element 32. O ₅ ) crystals are preferably used. In addition, as the wavelength conversion optical element 31 for generating the second harmonic, an LBO crystal or the like can be used in addition to a quasi phase matching crystal (QPM) such as a PPKTP crystal and a PPLT crystal.

  The third harmonic 3ω of p-polarized light generated in the wavelength conversion optical element 32 and the second higher harmonic 2ω of s-polarized light transmitted through the wavelength conversion optical element 32 are transmitted through the two-wavelength wave plate 45 and second harmonic 2ω. Only to p-polarized light. As the two-wavelength wave plate 45, for example, a wave plate made of a uniaxial crystal flat plate cut parallel to the optical axis of the crystal is used. This wave plate rotates the polarization plane for light of one wavelength (second harmonic 2ω) and prevents the polarization plane from rotating for light of the other wavelength (third harmonic 3ω). The thickness of the wave plate is cut so as to be an integral multiple of λ / 2 for light of one wavelength, and to be an integral multiple of λ for light of the other wavelength.

The second harmonic wave 2ω and the third harmonic wave 3ω, both of which are p-polarized light, are condensed and incident on the wavelength conversion optical element 33, and the frequency is 5 times the fundamental wave and the wavelength is 1/5 (309 nm) by sum frequency generation. A fifth harmonic 5ω is generated. As the wavelength converting optical element 33 for generating the fifth harmonic, for example, a BBO (β-BaB ₂ O ₄ ) crystal is preferably used. As the wavelength conversion optical element 33, it is also possible to use an LBO crystal or a CLBO (CsLiB ₆ O ₁₀ ) crystal. Since the fifth harmonic wave 5ω emitted from the BBO crystal has an elliptical beam cross section due to the walk-off, the beam cross section is shaped into a circular shape by the two cylindrical lenses 46v and 46h, and is reflected on the mirror 41. Make it incident.

  The mirror 41 has a wavelength selectivity that transmits the laser light in the wavelength band of the fundamental wave ω and the second harmonic 2ω and reflects the laser light in the wavelength band of the fifth harmonic 5ω. The fifth harmonic 5ω of s-polarized light reflected by the mirror (dichroic mirror) 41 is incident on the wavelength conversion optical element 35 of the fourth series IV.

A wavelength converting optical element 34 is disposed in the second series II. The second fundamental laser beam La ₂ output from the second laser beam output unit 1b is condensed and incident on the wavelength conversion optical element 34 with s-polarized light, and generates the second harmonic 2ω of s-polarized light. A PPLN crystal is preferably used as the wavelength converting optical element 34 for generating the second harmonic. As the wavelength conversion optical element 34, another QPM crystal similar to the above can be used. The second harmonic 2ω of s-polarized light generated in the wavelength conversion optical element 34 is incident on the mirror 42.

  The mirror 42 is configured to have wavelength selectivity that transmits laser light in the wavelength band of the fundamental wave ω and reflects laser light in the wavelength band of the second harmonic 2ω, and is a mirror (dichroic mirror) 42. The reflected second harmonic 2ω of the s-polarized light is transmitted through the mirror 41, superimposed on the same axis as the fifth harmonic 5ω, and enters the fourth series IV wavelength conversion optical element 35.

The third series III is not provided with a wavelength conversion optical element. The p-polarized third fundamental laser beam La ₃ output from the third laser beam output unit 1 c and incident on the third series is incident on the mirror 43 without being wavelength-converted. Then, the p-polarized fundamental wave ω reflected by the mirror 43 passes through the mirror 42 and the mirror 41, and is reflected by the second harmonic 2ω reflected by the mirror 42 and the fifth harmonic 5ω reflected by the mirror 41. The light is superimposed on the same axis and enters the wavelength conversion optical element 35 of the fourth series IV.

  In the fourth series IV, a wavelength conversion optical element 35 and a wavelength conversion optical element 36 are disposed. Further, in each of the optical paths of the fundamental wave ω, the second harmonic 2ω, and the fifth harmonic 5ω described above, the light of each wavelength is condensed and incident on the wavelength conversion optical elements 35 and 36 with a predetermined spot size. A set lens is provided. In the wavelength conversion optical element 35, the sum frequency is generated by the fifth harmonic 5ω of s-polarized light incident from the first series I and the second harmonic 2ω of s-polarized light incident from the second series II, and the frequency is fundamental. A seventh harmonic wave 7ω having a wavelength 7 times that of 1/7 (221 nm) is generated. The wavelength conversion optical element 35 for generating the seventh harmonic uses a CLBO crystal.

  The p-polarized seventh harmonic wave 7ω generated by the wavelength conversion optical element 35 and the p-polarized fundamental wave ω incident from the third wavelength series III and transmitted through the wavelength conversion optical element 35 are incident on the wavelength conversion optical element 36. As a result of the sum frequency generation, an eighth harmonic 8ω having a frequency eight times that of the fundamental wave and a wavelength of 1/8 (193 nm) is generated. The wavelength converting optical element 36 for generating the eighth harmonic uses a CLBO crystal.

Then, the eighth harmonic wave 8ω generated in the wavelength conversion optical element 36 is emitted from the wavelength conversion unit 3, and an ultraviolet laser beam Lv having a wavelength of 193 nm is output from the laser device LS. In the laser device LS configured as described above, the fundamental wave laser light La (La ₁ , La ₂ , La, which is output from the laser light output unit 1 (1a, 1b, 1c) and enters the wavelength conversion unit 3 is provided. The polarization state of ₃ ) has a great influence on the wavelength conversion efficiency in the wavelength conversion unit 3, and in turn the output of the ultraviolet laser beam.

  For example, as shown in FIG. 15, when the fiber optical amplifier deteriorates and the polarization state of the fundamental laser beam changes, the harmonic output changes as shown in FIG. 14, and the wavelength 193 nm finally output is changed. The output of the ultraviolet laser beam Lv becomes unstable. Further, for example, the output value of the ultraviolet laser beam Lv having a wavelength of 193 nm emitted from the wavelength conversion optical element 36 is monitored, and the power of the ultraviolet laser beam is stabilized by controlling the power of the fundamental laser beam according to the output value. Such power feedback control (auto power control) becomes difficult.

  Therefore, the laser device LS is provided with an FA life determination device 50 (50A, 50B, 50C) that observes the deterioration state of the fiber optical amplifier and outputs a life determination signal when it is determined that the replacement life has been reached. ing. FIG. 4 shows a schematic configuration diagram of the FA life determination device 50A of the first configuration form. In addition, in FIG. 4, the structure of the FA lifetime judgment apparatus provided in the 2nd series II in the 2nd laser beam output part 1b-the wavelength converter 3 in the laser beam output part 1 is illustrated as a representative example.

[First configuration]
The FA lifetime determination device 50A detects the intensity of the second harmonic wave 2ω that is output after being converted by the wavelength conversion optical element 34 and the excitation light detector 51 that detects the intensity of the excitation light in the fiber optical amplifier 223. Based on the harmonic detector 53, the first detection signal Pa output from the excitation light detector 51 and the second detection signal Pb output from the second harmonic detector 53, the operating state of the fiber optical amplifier 223 is determined. The FA determination unit 58 is configured.

  The excitation light detector 51 can use a power sensor that detects the power Ppump of the excitation light output from the excitation light source 223b and outputs a first detection signal Pa having a magnitude corresponding to the detected excitation light power. . As such an excitation light detector 51, a known power sensor having detection sensitivity in a wavelength band including the wavelength (1480 nm) of excitation light can be used. For example, as shown in the drawing, the excitation light output from the excitation light source 223b. It is configured by deriving a part of light (for example, about 1%) and detecting its power. When a Raman laser or the like is used as the excitation light source 223b, a power monitor sensor provided in the Raman laser can be used as the excitation light detector 51.

The second harmonic detector 53 detects the power Pω ₂ of the second harmonic 2ω emitted from the wavelength conversion optical element 34, and the second detection signal Pb having a magnitude corresponding to the detected second harmonic power. Can be used. As such a second harmonic detector 53, a known power sensor having detection sensitivity in a wavelength band including the wavelength (774 nm) of the second harmonic 2ω can be used. The second series II of the wavelength conversion unit 3 includes a wavelength selective partial reflection mirror 55 that transmits a fundamental wave having a wavelength of 1547 nm and reflects a part (for example, about 1%) of a second harmonic having a wavelength of 774 nm. A part of the second harmonic generated by the wavelength conversion optical element 34 is incident on the second harmonic detector 53 via the partial reflection mirror 55.

  The FA determination unit 58 includes a memory 58 a in which the life reference value of the fiber optical amplifier 223 is set and stored in advance, the first detection signal Pa output from the excitation light detector 51, and the first output from the second harmonic detector 53. 2 is configured by a processing unit 58b that performs arithmetic processing on the operating state of the fiber optical amplifier 223 based on the detection signal Pb, an output unit 58c that outputs a life determination signal based on the calculation result in the processing unit 58b, and the like.

The FA determination unit 58 receives the first detection signal Pa output from the excitation light detector 51 and the second detection signal Pb output from the second harmonic detector 53, and the processing unit 58b (DPb) / (dPa), which is a ratio of the change amount (dPb) of the second detection signal Pb to the change amount (dPa) of one detection signal Pa, specifically, the change amount (dPpump) of the pumping light power Ppump (DPω ₂ ) / (dPpump), which is the ratio of the second harmonic power variation (dPω ₂ ), is calculated, and when this value falls below the life reference value set and stored in the memory 58a, the output section A command signal is output to 58c to output a life determination signal.

As described with reference to FIGS. 11 to 15, the power Pω ₁ of the fundamental laser light increases in proportion to the power P pump of the pumping light in a normal state before the fiber optical amplifier is deteriorated. The power Pω ₂ of the second harmonic increases in proportion to the power Pω ₁ of the fundamental wave (see FIGS. 11 and 12). That is, the second harmonic power Pω ₂ increases with a certain slope corresponding to the increase of the pumping light power P pump. This inclination (dPω ₂ ) / (dPpump) has a substantially constant value (predetermined inclination) corresponding to the configuration of the fiber optical amplifier. Now, let α be the initial value of (dPω ₂ ) / (dPpump) in the laser device LS.

When the EDF 223a of the fiber optical amplifier 223 begins to deteriorate (for example, the resin coating of the fiber deteriorates), the fundamental power Pω ₁ increases in a first-order proportional to the increase of the pumping power Ppump, but the second harmonic The power Pω ₂ tends to increase and the value of (dPω ₂ ) / (dPpump) becomes smaller than the normal value α (see FIG. 13). As the EDF 223a further deteriorates, the fundamental wave power Pω ₁ increases in proportion to the pumping light power Ppump, but the second harmonic power Pω ₂ becomes the pumping light power Ppump and the fundamental wave power Pω ₁ . On the other hand, it fluctuates so as to be greatly undulated, and (dPω ₂ ) / (dPpump) changes greatly between positive and negative (see FIG. 14).

As described above, when the degradation of the EDF 223a proceeds, the value of (dPω ₂ ) / (dPpump) gradually decreases from the initial value α, and finally greatly varies positively and negatively. Accordingly, (dPb) / (dPa) corresponding to (dPω ₂ ) / (dPpump) is observed in the FA determination unit 58, and when this value becomes a predetermined value or less, a life determination signal is output, and the fiber optical amplifier By notifying the deterioration state of 223, the lifetime of the fiber optical amplifier 223 can be appropriately determined.

FIG. 5 shows an example of setting the life reference value. In the figure, the horizontal axis of the graph is the power Ppump of the excitation light, the vertical axis is the power Pω ₂ of the second harmonic, and the initial value of (dPω ₂ ) / (dPpump) = α is shown by a solid line in the figure. . FIG. 5 shows a configuration example in which the life reference value has two stages, in which the first stage life reference value Tw is indicated by a one-dot chain line, and the second stage life reference value Ta is indicated by a two-dot chain line. The two life reference values Tw and Ta are set and stored in the memory 58a.

In this configuration example, the first stage is a warning that prompts replacement of the fiber optical amplifier 223, and the second stage is an alarm or an interlock that protects the laser device. The processing unit 58b calculates (dPω ₂ ) / (dPpump) from the first detection signal Pa input from the excitation light detector 51 and the second detection signal Pb input from the second harmonic detector 53. When it is determined that the value is equal to or less than the first stage life reference value Tw set and stored in the memory 58a, a command signal is output to the output unit 58c to output a first stage life determination signal.

  The life determination at the first stage is a warning that prompts replacement of the fiber optical amplifier 223. For example, character information, a pictogram, a code number, and the like indicating that the fiber optical amplifier 223 is deteriorated and needs to be replaced are stored in the control unit 8. A life determination signal is output such as displaying on a display device or turning on a yellow display lamp that indicates a warning among the three-color rotary display lamps representing the state of the laser device LS.

At this time, the lifetime reference value Tw in the first stage is preferably set within the range of 0.3α to 0.7α with respect to the value α of (dPω ₂ ) / (dPpump) in the initial stage. .About.5α. If (dPω ₂ ) / (dPpump) is less than 0.3α, the convergence time of auto power control (APC) for controlling the pumping light power of the fiber optical amplifier 223 based on the power of the ultraviolet laser light Lv becomes excessive, and ( This is because if dPω ₂ ) / (dPpump) exceeds 0.7α, the replacement life of the fiber optical amplifier 223 is shortened, which is contrary to economic efficiency.

  The second stage life determination is an alarm or an interlock for protecting the laser device. For example, text information, pictogram, code number, etc. indicating that the optical fiber amplifier 223 is deteriorated and auto power control is difficult are displayed. A life determination signal for an alarm that is displayed on the display unit of the control unit 8 or blinks a red indicator lamp that indicates an abnormal state among the three-color rotary indicator lamps that indicate the state of the laser device LS, or In addition to the alarm as described above, for example, an interlock lifetime determination signal that prohibits the operation of the laser device in the auto power control state is output.

The lifetime reference value Ta in the second stage is set within a range of 0.1α to 0.3α with respect to the value α of (dPω ₂ ) / (dPpump) in the initial stage, for example, about 0.2α. It is preferable. 0.1α is a lower limit value that is operated by auto power control in consideration of fluctuation of the second harmonic power, power detection error, and the like. When 0.3α or more, auto power control becomes uncontrollable. This is because the fear is low.

  According to the FA life determination device 50A having such a configuration, a life determination signal corresponding to the deterioration state of the fiber optical amplifier 223 is output. Therefore, it is possible to appropriately determine whether or not the fiber optical amplifier 223 is actually deteriorated and needs to be replaced, and it is possible to provide a laser apparatus that achieves both economy and stable operation. it can.

[Second configuration]
Next, the FA life determination device 50B of the second configuration form will be described with reference to FIG. FIG. 6 is a schematic configuration diagram in the case where the FA lifetime determination device is provided in the second series II of the second laser light output unit 1b to the wavelength conversion unit 3 as in FIG. In addition, the same number is attached | subjected to the part of a structure similar to FA lifetime judgment apparatus 50A of 1st structure form, and duplication description is abbreviate | omitted.

The FA lifetime determination device 50B is wavelength-converted by the fundamental wave detector 52 for detecting the intensity of the fundamental laser beam La ₂ emitted from the fiber optical amplifier 223 and incident on the wavelength conversion optical element 34, and the wavelength conversion optical element 34. The second harmonic detector 53 for detecting the intensity of the emitted second harmonic 2ω, the first detection signal Pa output from the fundamental wave detector 52, and the second detection output from the second harmonic detector 53 And an FA determination unit 58 that determines the operating state of the fiber optical amplifier 223 based on the signal Pb.

The fundamental wave detector 52 detects the power Pω ₁ of the fundamental wave laser beam emitted from the fiber optical amplifier 223 and outputs a first detection signal Pa having a magnitude corresponding to the detected fundamental wave power Pω _1. A power sensor can be used. As such a fundamental wave detector 52, a known power sensor having detection sensitivity in a wavelength band including the wavelength (1547 nm) of the fundamental wave laser beam can be used. The second series II of the wavelength conversion unit 3 is provided with a partial reflection mirror 54 that reflects a part of the fundamental laser beam (for example, about 1%), and the wavelength conversion optical element via the partial reflection mirror 54. A portion of the fundamental laser beam incident on 34 enters the fundamental wave detector 52.

The second harmonic detector 53 and the partial reflection mirror 55 are as described above. That is, the second harmonic detector 53 detects the power Pω ₂ of the second harmonic 2ω emitted from the wavelength conversion optical element 34, and the second detection having a magnitude corresponding to the detected power of the second harmonic. A power sensor that outputs the signal Pb can be used. The partial reflection mirror 55 is a partial reflection mirror having wavelength selectivity that transmits a fundamental wave having a wavelength of 1547 nm and reflects a part (eg, about 1%) of the second harmonic having a wavelength of 774 nm. Part of the second harmonic generated by the wavelength conversion optical element 34 is incident on the second harmonic detector 53 via 55.

  The FA determination unit 58 is fundamental except that the type of the first detection signal to be input and the specific numerical value of the life reference value set and stored in the memory 58a are different from the FA determination unit of the first configuration form. The configuration is the same. That is, the FA determination unit 58 outputs from the memory 58 a in which the life reference value of the fiber optical amplifier 223 is set and stored in advance, the first detection signal Pa output from the fundamental wave detector 52, and the second harmonic detector 53. The processing unit 58b that calculates the operating state of the fiber optical amplifier 223 based on the second detection signal Pb, and the output unit 58c that outputs a life determination signal based on the calculation result in the processing unit 58b.

The FA determination unit 58 receives the first detection signal Pa output from the fundamental wave detector 52 and the second detection signal Pb output from the second harmonic detector 53, and the processing unit 58b (DPb) / (dPa), which is the ratio of the change amount (dPb) of the second detection signal Pb to the change amount (dPa) of one detection signal Pa, specifically, the fundamental wave power incident on the wavelength conversion optical element 34 is the ratio of the amount of change Pomega ₁ variation of the second harmonic power to _{(dPω 1) (dPω 2)} (dPω 2) / (dPω 1) is calculated, and this value is set and stored in the memory 58a life When the reference value is below the reference value, a command signal is output to the output unit 58c to output a life determination signal.

As described above, in the normal previous to deterioration in fiber optical amplifiers seen, power Pomega ₁ of the fundamental wave laser beam is increased in proportion to the power Ppump of the excitation light, the power Pomega ₁ of this fundamental wave The power Pω ₂ of the second harmonic increases proportionally (see FIGS. 11 and 12). That is, the power Pω ₂ of the second harmonic increases with a certain slope corresponding to the increase of the power Pω ₁ of the fundamental wave. This inclination (dPω ₂ ) / (dPω ₁ ) has a substantially constant value (predetermined inclination) corresponding to the configuration of the fiber optical amplifier 223. Now, let β be the initial value of (dPω ₂ ) / (dPω ₁ ) in the laser device LS.

When the EDF 223a of the fiber optical amplifier 223 starts to deteriorate, the fundamental power Pω ₁ increases in a linear proportion to the increase in the pumping light power Ppump, but the second harmonic power Pω ₂ decreases in an increasing trend. The value of (dPω ₂ ) / (dPω ₁ ) is smaller than the normal value β (see FIG. 13). As the EDF 223a further deteriorates, the fundamental wave power Pω ₁ increases in proportion to the pumping light power Ppump, but the second harmonic power Pω ₂ becomes the pumping light power Ppump and the fundamental wave power Pω ₁ . On the other hand, it fluctuates so as to wave greatly, and (dPω ₂ ) / (dPω ₁ ) changes greatly between positive and negative (see FIG. 14).

As described above, when the degradation of the EDF 223a proceeds, the value of (dPω ₂ ) / (dPω ₁ ) gradually decreases from the initial value β, and finally greatly varies positively and negatively. Accordingly, (dPb) / (dPa) corresponding to (dPω ₂ ) / (dPω ₁ ) is observed in the FA determination unit 58, and when this value becomes a predetermined value or less, a life determination signal is output, and the fiber light By notifying the deterioration state of the amplifier 223, the lifetime of the fiber optical amplifier 223 can be appropriately determined.

At this time, the life reference value can be set in the same manner as in the configuration example shown in FIG. A similar setting example is shown in FIG. In the figure, the horizontal axis of the graph is the fundamental wave power Pω ₁ , the vertical axis is the second harmonic power Pω ₂ , and the solid line indicates the initial value of (dPω ₂ ) / (dPω ₁ ) = β. ing. In addition, the first stage life reference value Tw is indicated by a one-dot chain line, and the second stage life reference value Ta is indicated by a two-dot chain line. The two life reference values Tw and Ta are set and stored in the memory 58a.

In this configuration example, the first stage is a warning prompting the replacement of the fiber optical amplifier 223, and the second stage is an alarm or an interlock that protects the laser device. The processing unit 58b calculates (dPω ₂ ) / (dPω ₁ ) from the first detection signal Pa input from the fundamental wave detector 52 and the second detection signal Pb input from the second harmonic detector 53, When it is determined that the calculated value is less than or equal to the first stage life reference value Tw set and stored in the memory 58a, a command signal is output to the output unit 58c to output a first stage life determination signal. .

  The life determination at the first stage is a warning that prompts replacement of the fiber optical amplifier 223. For example, character information, a pictogram, a code number, and the like indicating that the fiber optical amplifier 223 is deteriorated and needs to be replaced are stored in the control unit 8. A life determination signal is output such as displaying on a display device or turning on a yellow display lamp that indicates a warning among the three-color rotary display lamps representing the state of the laser device LS.

At this time, the lifetime reference value Tw in the first stage is preferably set within a range of 0.3β to 0.7β with respect to the value β of (dPω ₂ ) / (dPω ₁ ) in the initial stage. It is set to about 0.5β. If (dPω ₂ ) / (dPω ₁ ) is less than 0.3β, the convergence time of auto power control (APC) for controlling the pumping light power of the fiber optical amplifier 223 based on the power of the ultraviolet laser light Lv becomes excessive, This is because if (dPω ₂ ) / (dPω ₁ ) exceeds 0.7β, the replacement life of the fiber optical amplifier 223 is shortened, which is contrary to economic efficiency.

  The second stage life determination is an alarm or an interlock for protecting the laser device. For example, text information, pictogram, code number, etc. indicating that the optical fiber amplifier 223 is deteriorated and auto power control is difficult are displayed. A life determination signal for an alarm that is displayed on the display unit of the control unit 8 or blinks a red indicator lamp that indicates an abnormal state among the three-color rotary indicator lamps that indicate the state of the laser device LS, or In addition to the alarm as described above, for example, an interlock lifetime determination signal that prohibits the operation of the laser device in the auto power control state is output.

The lifetime reference value Ta in the second stage is set within a range of 0.1β to 0.3β with respect to the value β of (dPω ₂ ) / (dPω ₁ ) in the initial stage, for example, about 0.2β. It is preferable to do. 0.1β is a lower limit value that is operated by auto power control in consideration of second harmonic power fluctuation, power detection error, and the like. When 0.3β or more, auto power control becomes uncontrollable. This is because the fear is low.

  Also in the FA life determination device 50B having such a configuration, a life determination signal corresponding to the deterioration state of the fiber optical amplifier 223 is output in the same manner as the FA life determination device 50A described above. Therefore, it is possible to appropriately determine whether or not the fiber optical amplifier 223 is actually deteriorated and needs to be replaced, and it is possible to provide a laser apparatus that achieves both economy and stable operation. it can.

[Third configuration]
Next, the FA life determination device 50C of the third configuration form will be described with reference to FIG. FIG. 8 is a schematic configuration diagram in the case where the FA life determination device is provided in the second series II of the wavelength conversion unit 3 as in FIGS. 4 and 6. In addition, the same number is attached | subjected to the part of a structure similar to the already-described structure form, and duplication description is abbreviate | omitted.

  The FA life determination device 50C includes a fundamental wave detector 52 that detects the intensity of the fundamental wave laser beam that has passed through the wavelength conversion optical element 34 without being wavelength-converted, and a second wavelength that has been wavelength-converted by the wavelength conversion optical element 34 and emitted. Based on the second harmonic detector 53 that detects the intensity of the harmonic 2ω, the first detection signal Pa output from the fundamental wave detector 52, and the second detection signal Pb output from the second harmonic detector 53. And an FA determination unit 58 that determines the operating state of the fiber optical amplifier 223. That is, the FA life determination device 50C of the present configuration form is the same as the FA life determination device 50B of the second configuration form described above in that the fundamental wave intensity is detected by the fundamental laser beam transmitted through the wavelength conversion optical element 34. Is different.

  The fundamental wave detector 52 and the second harmonic detector 53 can use the same power sensors as the fundamental wave detector 52 and the second harmonic detector 53 described above, respectively. As the mirror 42 of the wavelength conversion unit 3, a partial reflection mirror having a wavelength selectivity that transmits a fundamental wave having a wavelength of 1547 nm and transmits a part of the second harmonic having a wavelength of 774 nm (for example, about 1%) is used. The fundamental wave that has passed through the wavelength conversion optical element 34 without being wavelength-converted and the second harmonic generated by the wavelength conversion optical element 34 pass through the mirror 42.

  Behind the mirror 42 is provided a spectroscopic element 56 that splits the fundamental wave having a wavelength of 1547 nm and the second harmonic wave having a wavelength of 774 nm transmitted through the mirror, and the fundamental wave separated by the spectroscopic element 56 is the fundamental wave. The light enters the detector 52, and the second harmonic enters the second harmonic detector 53. As shown in the figure, the spectroscopic element 56 may be a prism, or may be configured using a dichroic mirror, a diffractive optical element, or the like.

  The FA determination unit 58 has the same basic configuration except that the specific value of the life reference value set and stored in the memory 58a is different from the FA determination unit of the second configuration form. That is, the FA determination unit 58 outputs from the memory 58 a in which the life reference value of the fiber optical amplifier 223 is set and stored in advance, the first detection signal Pa output from the fundamental wave detector 52, and the second harmonic detector 53. The processing unit 58b that calculates the operating state of the fiber optical amplifier 223 based on the second detection signal Pb, and the output unit 58c that outputs a life determination signal based on the calculation result in the processing unit 58b.

The FA determination unit 58 receives the first detection signal Pa output from the fundamental wave detector 52 and the second detection signal Pb output from the second harmonic detector 53, and the processing unit 58b (DPb) / (dPa), which is the ratio of the change amount (dPb) of the second detection signal Pb to the change amount (dPa) of one detection signal Pa, specifically, the fundamental wave power transmitted through the wavelength conversion optical element 34 Pω is the ratio of 'variation of (dPω _{1' 1} variation of the second harmonic power _{to) (dPω 2) (dPω 2} ) / (dPω 1 ') is calculated, setting storage this value in the memory 58a When the life is less than the life reference value, a command signal is output to the output unit 58c to output a life determination signal.

Here, the power Pω ₁ ′ of the fundamental wave (referred to as a transmitted fundamental wave) transmitted through the wavelength conversion optical element 34 is the power of the fundamental wave (referred to as an incident fundamental wave for convenience) incident on the wavelength conversion optical element 34. The magnitude is obtained by subtracting the power of the fundamental wave that has contributed to wavelength conversion from Pω ₁ . The contribution ratio of light of the s-polarized component that contributes to wavelength conversion, that is, wavelength conversion efficiency, is substantially constant in a region where the power of the incident fundamental wave (power density in the crystal) is not less than a predetermined value, and the power Pω _{1 of the} incident fundamental wave. Proportionally increases the power Pω ₁ ′ of the transmitted fundamental wave. Therefore, the power Pω ₁ ′ of the transmitted fundamental wave can be handled as a state quantity corresponding to the power Pω ₁ of the incident fundamental wave.

As described above, in the normal previous to deterioration in fiber optical amplifiers seen, power Pomega ₁ incident fundamental wave in proportion to the power Ppump of the excitation light is increased, proportional to the power Pomega ₁ of the incident fundamental wave As a result, the power Pω ₂ of the second harmonic increases (see FIGS. 11 and 12). At this time, the power Pω ₁ ′ of the transmitted fundamental wave increases in proportion to the power Pω ₁ of the incident fundamental wave. Therefore, the power Pω ₂ of the second harmonic increases with a certain slope in response to the increase of the power Pω ₁ ′ of the transmitted fundamental wave. This inclination (dPω ₂ ) / (dPω ₁ ′) is a value (predetermined inclination) corresponding to the configuration of the fiber optical amplifier 223 and the wavelength conversion optical element 34. Now, let γ be the initial value of (dPω ₂ ) / (dPω ₁ ′) in the laser device LS.

When the EDF 223a of the fiber optical amplifier 223 starts to deteriorate, the power Pω ₁ of the incident fundamental wave increases linearly with respect to the increase of the power P pump of the pumping light, and accordingly, the power Pω ₁ ′ of the transmitted fundamental wave also increases. Although increasing, the tendency of increasing the power Pω ₂ of the second harmonic is reduced, and the value of (dPω ₂ ) / (dPω ₁ ′) is smaller than the normal value γ (see FIG. 13). As the EDF 223a further deteriorates, the incident fundamental wave power Pω ₁ and the transmitted fundamental wave power Pω ₁ ′ increase in proportion to the pumping light power P pump, but the second harmonic power Pω ₂ undulates greatly. Thus, (dPω ₂ ) / (dPω ₁ ′) changes greatly between positive and negative (see FIG. 14).

As described above, when the degradation of the EDF 223a progresses, the value of (dPω ₂ ) / (dPω ₁ ′) gradually decreases from the initial value γ, and finally greatly fluctuates positively and negatively. Accordingly, (dPb) / (dPa) corresponding to (dPω ₂ ) / (dPω ₁ ′) is observed in the FA determination unit 58, and when this value becomes a predetermined value or less, a life determination signal is output, and the fiber By notifying the deterioration state of the optical amplifier 223, the lifetime of the fiber optical amplifier 223 can be appropriately determined.

At this time, the life reference value can be set in the same manner as in the configuration examples shown in FIGS. That is, with reference to the initial value of (dPω ₂ ) / (dPω ₁ ′) = γ, the first stage life reference value Tw is set within a range of 0.3γ to 0.7γ, for example, about 0.5γ, The second stage life reference value Ta is set within a range of 0.1γ to 0.3γ, for example, about 0.2γ and stored in the memory 58a, and the same warning, alarm, interlock, etc. are executed. can do.

  Also in the FA life determination device 50C having such a configuration, in accordance with the degradation state of the fiber optical amplifier 223, similarly to the FA life determination device 50A in the first configuration form and the FA life determination device 50B in the second configuration form described above. A life judgment signal is output. Therefore, it is possible to appropriately determine whether or not the fiber optical amplifier 223 is actually deteriorated and needs to be replaced, and it is possible to provide a laser apparatus that achieves both economy and stable operation. it can. Further, according to this configuration mode, there is no need to arrange an optical element such as a partial reflection mirror in the optical path of the laser light output unit 1 or the wavelength conversion unit 3, and the initial and long-term generated by inserting the optical element. Loss and adjustment man-hours can be reduced.

  In the embodiment described above, an erbium-doped fiber optical amplifier (EDFA) is shown as an example of a fiber optical amplifier, but the laser medium doped in the core and the cladding structure of the optical fiber are arbitrary. For example, a single or multi-clad yttrium-doped fiber optical amplifier (YDFA) doped with yttrium (Yb) in the core or a single or multi-clad thulium doped fiber doped with thulium (Tm) in the core The same effect can be obtained by applying the same to a laser device having an optical amplifier (TDFA) or the like.

  Moreover, although the PPLN crystal which performs 2nd harmonic generation was illustrated as an example of a wavelength conversion optical element, the effect | action of the crystal to be used and wavelength conversion is arbitrary. For example, a nonlinear optical crystal that generates third-order or higher harmonics, a nonlinear optical crystal that generates a sum frequency of a fundamental wave and other harmonics (for example, the wavelength conversion optics 36 in the embodiment), or a difference frequency generation. The same effect can be obtained by applying the same to a laser device having a nonlinear optical crystal or the like.

1 (1a, 1b, 1c) Laser light output unit 3 Wavelength conversion unit 8 Control unit 10 (10a, 10b, 10c) Laser light generation unit 11, 12, 13 Laser light source 20 (20a, 20b, 20c) Amplification unit 21, 22, 23 Fiber optical amplifier 30 Wavelength conversion optical system 31 to 36 Wavelength conversion optical elements 41, 42, 43 Mirror 50 (50a, 50b, 50c) FA life determination device 51 Excitation light detector 52 Fundamental wave detector 53 Second harmonic Wave detector 54 Partial reflection mirror 55 Partial reflection mirror 56 Spectroscopic element 58 FA determination unit 58a Memory 58b Processing unit 58c Output units 221, 222, 223 Fiber optical amplifiers 221a, 222a, 223a EDF
221b, 222b, 223b Excitation light sources 221c, 222c, 223c WDM coupler LS laser device La (La ₁ , La ₂ , La ₃ ) fundamental laser light Ls (Ls ₁ , Ls ₂ , Ls ₃ ) signal light Lv ultraviolet laser light ω ₁ fundamental wave ω ₂ second harmonic wave P pump pumping power Pω ₁ fundamental wave (incident fundamental wave) ω ₁ power Pω _1p fundamental wave ω ₁ p-polarized component power Pω _1s fundamental wave ω ₁ s-polarized component Power Pω ₁ ′ Fundamental wave (transmitted fundamental wave) transmitted through the wavelength conversion optical element Power Pω ₂ Second harmonic power Pa First detection signal Pb Initial value of second detection signal α (dPω ₂ ) / (dPpump) β (dPω ₂ ) / (dPω ₁ ) initial value γ (dPω ₂ ) / (dPω ₁ ′) initial value Tw First stage life reference value Ta Second stage life reference value

Claims (4)

A laser light output section that has a fiber optical amplifier and emits fundamental laser light; and a wavelength conversion section that has a wavelength conversion optical element and converts the wavelength of the fundamental laser light emitted from the laser light output section and outputs the wavelength conversion optical element. A laser device comprising:
First detection means for detecting the intensity of the fundamental wave laser light or a state quantity corresponding thereto and outputting a first detection signal Pa corresponding to the detection quantity;
Second detection means for detecting the intensity of light wavelength-converted by the wavelength conversion optical element and outputting a second detection signal Pb corresponding to the detection amount;
An FA determination unit that determines the operating state of the fiber optical amplifier based on the first detection signal Pa output from the first detection unit and the second detection signal Pb output from the second detection unit;
The FA determination unit outputs a life determination signal when the ratio of the change amount dPa of the first detection signal Pa and the change amount dPb of the second detection signal Pb is outside a preset life reference range. A laser apparatus configured to   2. The laser device according to claim 1, wherein the state quantity corresponding to the intensity of the fundamental laser beam is an intensity of pumping light in the fiber optical amplifier.   2. The laser device according to claim 1, wherein the state quantity corresponding to the intensity of the fundamental laser beam is the intensity of the fundamental laser beam transmitted through the wavelength conversion optical element. Of the light emitted from the wavelength conversion optical element, a mirror that transmits the fundamental laser light that has passed through the wavelength conversion optical element, and transmits a part of the light that has been wavelength-converted by the wavelength conversion optical element;
A spectral element for separating the fundamental laser beam transmitted through the mirror and the wavelength-converted light transmitted through the mirror;
4. The laser according to claim 3, wherein the first detection unit and the second detection unit detect intensities of the fundamental laser beam and the wavelength-converted light, respectively, separated by the spectroscopic element. apparatus.