JP2008147389A - Laser equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser equipment capable of outputting a laser beam having an intended spectrum width and an intended intensity. <P>SOLUTION: The laser equipment having an optical resonator with at least a reflecting means for selectively reflecting a beam of the predetermined band of wavelength at its one end, and an optical amplifying medium arranged in the optical resonator comprises: a laser beam source part 2 reflecting the laser beam with the spectrum width varied in response to the intensity of the output beam; an optical amplifying unit connected to the laser beam source, amplifying the laser beam output from the laser beam source part, and outputting the amplified laser beam; and an optical output control unit connected to the laser beam source part and the optical amplifying unit, controlling the instensity of the laser beam output from the laser beam source part so that the amplified laser beam output from the optical amplifying unit has the intended spectrum width, and also controlling the amplified laser beam to the intended intensity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser device including a laser light source unit and an optical amplification unit.

  2. Description of the Related Art Conventionally, as a laser device used for laser processing such as semiconductor exposure, a laser device including a laser light source unit and an optical amplification unit connected to the laser light source unit has been disclosed (see Patent Document 1). . This laser device has a so-called MOPA (Master Oscillator Power Amplifier) structure, in which a laser light source unit outputs laser light having a desired wavelength, and an optical amplification unit amplifies the laser light to a desired intensity. Output.

JP 2003-8119 A

  By the way, the spectral width of the laser beam output from the laser device affects the coherence of the laser beam. Therefore, for example, in the field of use such as laser processing, there is a demand to use a laser beam having an optimum spectral width according to the intended use.

  However, the conventional laser apparatus has a problem in that it cannot flexibly change the spectrum width of the laser beam to be output and cannot obtain the laser beam having a desired spectrum width.

  The present invention has been made in view of the above, and an object of the present invention is to provide a laser apparatus capable of outputting laser light having a desired spectral width at a desired intensity.

  In order to solve the above-described problems and achieve the object, a laser apparatus according to the present invention includes an optical resonator including at least one reflecting means for selectively reflecting light in a predetermined wavelength band, and the optical resonance. A laser light source unit having a light amplifying medium disposed in the chamber and outputting a laser beam having a spectrum width that changes in accordance with an output light intensity; and the laser connected to the laser light source unit and output from the laser light source unit An optical amplifying unit that amplifies light and outputs amplified laser light, and is connected to the laser light source unit and the optical amplifying unit, so that the amplified laser light output from the optical amplifying unit has a desired spectral width. And a light output control unit that controls the intensity of the laser beam output from the laser light source unit and controls the amplified laser beam to a desired intensity.

  In the laser device according to the present invention, in the above invention, the optical amplifying medium is an optical amplifying fiber in which a rare earth element is added to a core portion, and the reflecting means is a fiber Bragg grating connected to the optical amplifying fiber. It is characterized by being.

  The laser device according to the present invention is arranged on the light output side of the optical amplification unit in the above invention, and when the amplified laser light output from the optical amplification unit is input, the amplified laser light has a wavelength. A wavelength conversion element that outputs different wavelength conversion light is provided.

  The laser device according to the present invention is characterized in that, in the above invention, the amplified laser beam has a spectral width of 200 pm or less.

  The laser device according to the present invention is characterized in that, in the above invention, the spectrum width of the amplified laser beam is 50 pm or more.

  According to the present invention, there is provided an optical resonator including at least one reflection means for selectively reflecting light in a predetermined wavelength band, and an optical amplification medium disposed in the optical resonator, and the output light intensity A laser light source unit that outputs a laser beam whose spectral width changes in response to the laser light source unit, an optical amplification unit that is connected to the laser light source unit and amplifies the laser beam output from the laser light source unit and outputs an amplified laser beam; The intensity of the laser light output from the laser light source unit is controlled so that the amplified laser beam output from the optical amplification unit is connected to the laser light source unit and the optical amplification unit and has a desired spectral width. Since the optical output control unit that controls the amplified laser beam to a desired intensity is provided, it is possible to realize a laser device that can output a laser beam having a desired spectral width at a desired intensity.

  Embodiments of a laser apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a schematic diagram schematically showing the configuration of the laser apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, the laser device 1 includes a laser light source unit 2, an optical amplification unit 3, a control unit 4 that is an optical output control unit, and an input / output unit 5.

  The laser light source unit 2 is a double-clad type optical fiber laser that can output extremely high intensity light, and is a semiconductor laser that outputs pumping light having a wavelength of 900 to 980 nm, where LD 21-1 to 21-n (n is an integer). ), A constant current source 22 that supplies driving power of a constant current value to the LDs 21-1 to 21-n, and multimode optical fibers 23-1 to 23-1 that guide the pumping light output from the LDs 21-1 to 21-n. 23-n, a TFB (Tapered Fiber Bundle) 23 that is an optical multiplexer for coupling the pumping light guided by the multimode optical fibers 23-1 to 23-n to the double-clad optical fiber 251, and the double-clad optical fiber 251. The input side FBG (Fiber Bragg Grating) 261 which is a reflection means connected to the input side F, and the input side F An amplification double-clad optical fiber 252 that is an optical amplification medium connected to the BG 261, an output-side FBG 262 that is reflection means connected to the amplification double-clad optical fiber 252, and a standard single-mode optical fiber 253 connected to the output-side FBG 262 And an optical coupler 27 which is an optical branching means connected to the output side FBG 262 via a single mode optical fiber 253, and a PD (PhotoDetector) 27 which is a photoelectric conversion means connected to the optical coupler 27. Here, the input side FBG 261 and the output side FBG 262 have wavelength selectivity. The input side FBG 261 has a reflectance band of 5 nm of 99% or more with the wavelength of 1083 nm as the center. The output side FBG 262 is centered on light having a wavelength of 1083 nm and has a full width at half maximum (FWHM) of 10% peak reflectance of 0.02 nm. The input-side FBG 261 and the output-side FBG 262 constitute a Fabry-Perot type optical resonator in which an amplifying double-clad optical fiber 252 is disposed for light having a wavelength of 1083 nm.

  FIG. 2 is a diagram showing a schematic cross section of the amplifying double clad optical fiber 252 shown in FIG. 1 and a corresponding refractive index profile. As shown in FIG. 2, the amplifying double-clad optical fiber 252 has a refractive index higher than that of the core portion 252a to which ions of the rare earth element ytterbium (Yb) are added and the core portion 252a formed on the outer periphery of the core portion 252a. A low inner clad portion 252b and an outer clad portion 252c having a lower refractive index than the inner clad portion 252b formed on the outer periphery of the inner clad portion 252b are provided and have a refractive index profile 252d. The double clad optical fiber 251 has the same configuration as that of the amplifying double clad optical fiber 252, but Yb is not added to the core portion.

  The optical amplifying unit 3 is a double clad type optical amplifier connected to the laser light source unit 2 through a single mode optical fiber 253, and outputs LD 31-1 to 31-m (m is an integer) that outputs pumping light. A constant current source 32 that supplies driving power having a constant current value to the LDs 31-1 to 31-m, and multimode optical fibers 33-1 to 33 that guide the pumping light output from the LDs 31-1 to 31-m. -m, a TFB 34 for coupling the pumping light guided by the multimode optical fibers 33-1 to 33-m to the double clad optical fiber 351, an optical isolator ISO connected to the single mode optical fiber 253, an optical isolator ISO, Standard single-mode optical fiber 353 connecting to TFB 34, and double-clad light for amplification connected to TFB 34 via double-clad optical fiber 351 An optical coupler 37 connected to the amplifying double-clad optical fiber 352 via the single mode optical fiber 353, an optical output terminal 39 connected to the optical coupler 37 via the single mode optical fiber 353, and an optical coupler 37. And a PD 38 connected to the. The double clad optical fiber 351 has the same configuration as the double clad optical fiber 251, and the amplification double clad optical fiber 352 has the same configuration as the amplification double clad optical fiber 252.

  The control unit 4 is connected to the constant current sources 22 and 32 and the PDs 28 and 38, and stores a control unit 41 that stores control data described later, a calculation unit 42 that performs control calculations described later, and a constant current. And a current control unit 43 that repeatedly controls the current value output from the sources 22 and 32. Further, the input / output unit 5 is connected to the control unit 4 to input and display various set values.

  Next, the operation of the laser device 1 will be described. In the laser light source unit 2, the LDs 21-1 to 21-n are supplied with driving power from the constant current source 22, output pumping light with a wavelength of 900 to 980 nm, and the multimode optical fibers 23-1 to 23-n are The excitation light output from the LDs 21-1 to 21-n is guided to the TFB 24. The TFB 24 couples the guided pumping light to the amplifying double clad optical fiber 252 via the double clad optical fiber 251 and the input side FBG 261. The excitation light coupled to the amplifying double-clad optical fiber 252 optically excites Yb ions added to the core part 252a while propagating through the core part 252a and the inner cladding 252b in multimode. As a result, although Yb ions generate fluorescence, the input side FBG 261 and the output side FBG 262 constitute an optical resonator in which the amplifying double-clad optical fiber 252 is disposed inside the light with a wavelength of 1083 nm. Light with a wavelength of 1083 nm is amplified while reciprocating in the optical resonator to cause laser oscillation, and laser light is output from the output side FBG 262 side.

  Here, the spectrum width of the laser light output from the laser light source unit 2 changes according to the output light intensity. Specifically, the spectrum width becomes wider as the output light intensity increases. The characteristics of the laser beam output from the laser light source unit 2 are, for example, a center wavelength of 1083 nm, a spectrum width of 30 to 160 pm, and an intensity of 2 to 8 W.

  On the other hand, in the optical amplifying unit 3, the LDs 31-1 to 31 -m are supplied with driving power from the constant current source 32, output pumping light having a wavelength of 900 to 980 nm, and multimode optical fibers 33-1 to 33- m guides the excitation light output from the LDs 31-1 to 31-m to the TFB 34. The TFB 34 couples the pumping light guided through the double clad optical fiber 351 to the amplification double clad optical fiber 352. Here, the excitation light coupled to the amplification double-clad optical fiber 352 optically excites Yb ions added to the core portion while propagating through the amplification double-clad optical fiber 352 in multimode. At the same time, the TFB 34 couples the laser light output from the laser light source unit 2 and input through the optical isolator ISO to the amplifying double clad optical fiber 352 via the double clad optical fiber 351. The laser beam coupled to the amplifying double-clad optical fiber 352 interacts with the excited Yb ions while propagating through the core portion in a single mode, and is optically amplified by the stimulated emission action and amplified from the output terminal 39. Output as laser light L1. Here, the spectrum width of the amplified laser beam L1 differs from the spectrum width of the laser beam output from the laser light source unit 2 in accordance with the output light intensity of the amplified laser beam L1, and for example, the spectrum width becomes wider.

  In the laser apparatus 1 according to the first embodiment, the control unit 4 controls the constant current source 22 of the laser light source unit 2 and also controls the constant current source 32 of the optical amplification unit 3, thereby amplifying laser light. In consideration of the fact that the spectral width of L1 is wider than the spectral width of the laser light output from the laser light source section 2, the laser light output from the laser light source section 2 so that the amplified laser light L1 has a desired spectral width. Is controlled so that the amplified laser beam L1 has a desired intensity. As a result, the amplified laser beam L1 output from the laser device 1 has a desired spectral width and a desired intensity. The characteristics of the amplified laser beam L1 are, for example, a spectrum width of 100 to 600 pm and an intensity of 40W.

  Moreover, the control which the control part 4 performs is performed in the following procedures, for example. That is, in the laser light source unit 2, the optical coupler 27 branches a part of the laser light at a predetermined branching ratio of about 1 to 10%, and the PD 28 receives the branched laser light and has a magnitude corresponding to the light intensity. This current is output to the control unit 4. On the other hand, in the optical amplifying unit 3, the optical coupler 37 branches a part of the amplified laser light with a predetermined branching ratio of about 1 to 10%, and the PD 38 receives the branched laser light and responds to its light intensity. A current having a magnitude is output to the control unit 4. Here, the control unit 4 receives the currents output from the PDs 28 and 38 and measures the respective current values, and receives the set spectral width and the set intensity values input from the input / output unit 5. Next, the control unit 4 reads from the storage unit 41 data of combinations of target current values for the laser light source unit 2 and the optical amplification unit 3 corresponding to the set spectral width and the set intensity. Next, the control unit 4 causes the calculation unit 42 to calculate the difference between the measured current value from the PD 28 and the target current value for the laser light source unit 2, the measured current value from the PD 38, and the target current value for the optical amplification unit 3. Each difference is calculated. Next, the control unit 4 causes the current control unit 43 to repeatedly control the current values of the driving power output from the constant current sources 22 and 32 so that the calculated differences are equal to or less than a predetermined control error. As a result, the LDs 21-1 to 21-n and 31-1 to 31-m are controlled so as to output excitation light having a predetermined intensity, and the intensity of the laser light output from the laser light source unit 2 has a predetermined spectral width. The intensity of the laser beam output from the optical amplifying unit 3 is controlled to have a desired spectral width and intensity.

  By the way, the spectral width of the laser beam output from the laser light source unit 2 changes according to the output light intensity when the light having a wavelength of 1083 nm is amplified while reciprocating in the optical resonator. This is considered to be due to the influence of nonlinear optical effects such as self-phase modulation (SPM) generated in the optical fiber such as the amplification double-clad optical fiber 252 disposed in the resonator. Also in the optical amplifying unit 3, it is considered that the spectral width of the amplified laser light L1 is changed by the influence of the nonlinear optical effect generated in the optical fiber such as the amplifying double clad optical fiber 352.

  In the optical fiber laser, since the resonator length is as long as 10 m or more, for example, the output laser light has a spectrum including many longitudinal modes. For example, when the resonator length is 10 m, the longitudinal mode interval is 0.04 pm. In the case of laser light including many longitudinal modes as described above, the spectrum width is defined as the full width at half maximum obtained from the envelope of the spectrum.

  In order to effectively generate the nonlinear optical effect described above in the optical fiber, it is preferable that the light intensity of the laser light output from the laser light source unit 2 is 1 W or more. Further, if the nonlinear constant of the optical fiber in which the nonlinear optical effect is generated is adjusted, the amount of change in the spectral width with respect to the intensity of the output light can be appropriately adjusted.

  Next, specific characteristics of the laser device 1 according to the first embodiment will be described. FIG. 3 shows the spectral width and optical amplification of the amplified laser beam L1 with respect to the intensity of the laser beam output from the laser light source unit 2 when the intensity of the amplified laser beam L1 output from the laser device 1 is controlled to be 40 W. FIG. 6 is a diagram showing a drive current in part 3. The spectral width of the laser light output from the laser light source unit 2 was 34 pm, 48 pm, and 74 pm when the intensity of the laser light was 2.17 W, 5.18 W, and 8 W, respectively. In the laser apparatus 1, as shown in FIG. 3, for example, when the amplified laser light L1 having a wide spectral width is to be output, the intensity of the laser light output from the laser light source unit 2 is controlled to be high, while the optical amplifying unit 3 By controlling the drive current at a low value, the intensity of the amplified laser beam L1 could be controlled to a constant value while realizing a desired spectral width, as shown in FIG. FIG. 5 is a diagram showing a spectrum of the amplified laser beam L1 output from the laser device 1. In FIG. 5, the horizontal axis indicates the light intensity, the vertical axis indicates the light intensity normalized by the peak value, and the spectra S1, S2, and S3 each have a light intensity of 40 W, and the spectrum widths are about 100 pm, about 200 pm, and about This is a case where the control is performed to be 265 pm. Thus, the laser apparatus 1 was able to output laser light having a desired spectral width with desired intensity.

  As described above, in the laser apparatus 1 according to the first embodiment, the laser light source unit 2 outputs the laser light whose spectral width changes according to the output light intensity, and the control unit 4 includes the optical amplification unit 3. The intensity of the laser beam output from the laser light source unit 2 is controlled so that the amplified laser beam L1 to be output has a desired spectral width, and the desired spectral width is controlled by controlling the amplified laser beam L1 to a desired intensity. It is possible to output the laser beam having a desired intensity.

(Embodiment 2)
Next, a laser apparatus according to Embodiment 2 of the present invention will be described. The laser device according to the second embodiment includes a wavelength conversion element on the light output side of the laser light output unit having the same configuration as the laser device according to the first embodiment.

  FIG. 7 is a schematic diagram schematically showing the configuration of the laser apparatus according to the second embodiment. As shown in FIG. 1, the laser device 6 has the same configuration as the laser device 1, and a laser light output unit 7 that outputs amplified laser light L <b> 5 from the light amplification unit, and the light output of the laser light output unit 7. A wavelength conversion element 8 made of a periodically poled lithium niobate (PPLN) crystal, which is a nonlinear optical crystal, and a wavelength conversion element 8 are placed on the side, and the temperature of the wavelength conversion element 8 and the angle with respect to the amplified laser beam L5 And an adjustment mechanism 9 for adjusting the above. The adjustment mechanism 9 includes, for example, an optical stage on which the wavelength conversion element 8 is placed, and a Peltier element attached to the optical stage so as to be in contact with the wavelength conversion element 8.

  In this laser device 6, the center wavelength of the amplified laser beam L5 output from the laser beam output unit 7 is about 1083 nm. When the amplified laser beam L5 is input, the wavelength conversion element 8 is 1 / wavelength of the amplified laser beam L5. 2 is output as a wavelength-converted light L6 having a wavelength of 541.5 nm.

  The adjustment mechanism 9 adjusts the temperature of the wavelength conversion element 8 and the angle with respect to the amplified laser light L5 in order to optimize the wavelength conversion efficiency, which is the ratio of the intensity of the wavelength converted light L6 to the intensity of the amplified laser light L5. Here, if the spectrum width of the amplified laser beam L5 is too narrow, the wavelength conversion efficiency is improved, but the wavelength conversion efficiency becomes unstable unless the adjustment accuracy of the temperature and angle of the wavelength conversion element 8 is increased, and the amplified laser If the spectral width of the light L5 is too wide, the accuracy of adjusting the temperature and angle of the wavelength conversion element 8 is relaxed, but the wavelength conversion efficiency is lowered.

  However, in the laser device 6 according to the second embodiment, the spectral width of the amplified laser beam L5 is controlled to a value that balances the wavelength conversion efficiency of the wavelength conversion element 8 and the temperature and angle adjustment accuracy. Therefore, the wavelength conversion element 8 can output wavelength-converted light having a stable intensity while maintaining a predetermined wavelength conversion efficiency. Note that the wavelength conversion efficiency can be sufficiently improved by setting the spectral width of the amplified laser beam L5 to 200 pm or less, and the adjustment accuracy of temperature and angle can be sufficiently relaxed by setting it to 50 pm or more. Is possible.

  In the second embodiment, the wavelength conversion element is not limited to a PPLN crystal, but a nonlinear optical crystal such as PPLN (PPMgLN) added with MgO, periodically poled lithium tantalate (PPLT), or periodically poled KTP (PPKTP). It may be.

  In the first and second embodiments, the reflecting means constituting the optical resonator is not limited to the FBG, and a Bragg grating portion whose refractive index changes periodically is formed in the optical waveguide portion of the planar lightwave circuit (PLC). It may be a reflection mirror using a dielectric multilayer film.

  In the first and second embodiments, the optical amplifying medium is an amplifying double-clad optical fiber, but may be an amplifying single mode optical fiber in which a rare earth element is added to the core, and the rare earth element is erbium (Er). Or Er and Yb may be added together. The wavelength of the laser light output from the laser device is not limited to 1083 nm, and a desired wavelength can be obtained by setting the reflection wavelength band of the reflection means constituting the optical resonator in the laser light source unit.

It is the schematic which represented typically the structure of the laser apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the typical cross section of the double clad optical fiber for amplification shown in FIG. 1, and a corresponding refractive index profile. When the intensity of the amplified laser beam output from the laser device shown in FIG. 1 is controlled to be 40 W, the spectral width of the laser beam and the drive current in the optical amplifier with respect to the intensity of the laser beam output from the laser light source unit FIG. In the laser apparatus shown in FIG. 1, it is the figure which showed the intensity | strength of the amplified laser beam with respect to spectrum width. It is the figure which showed the spectrum of the amplified laser beam output from the laser apparatus shown in FIG. It is the schematic which represented typically the structure of the laser apparatus concerning Embodiment 2 of this invention.

Explanation of symbols

1, 6 Laser device 2 Laser light source unit 21-1 to 21-n, 31-1 to 31-m LD
22, 32 Constant current source 23-1 to 23-n, 33-1 to 33-m Multimode optical fiber 24, 34 TFB
251, 351 Double clad optical fiber 252, 352 Amplification double clad optical fiber 253, 353 Single mode optical fiber 261 Input side FBG
262 Output side FBG
27, 37 Optical coupler 28, 38 PD
39 Optical Output Terminal 4 Control Unit 41 Storage Unit 42 Calculation Unit 43 Current Control Unit 5 Input / Output Unit 7 Laser Light Output Unit 8 Wavelength Conversion Element 9 Adjustment Mechanism

Claims (5)

An optical resonator having at least one reflecting means for selectively reflecting light in a predetermined wavelength band, and an optical amplification medium disposed in the optical resonator, and having a spectral width according to the output light intensity A laser light source unit that outputs a changing laser beam;
An optical amplifying unit connected to the laser light source unit and amplifying the laser light output from the laser light source unit to output amplified laser light;
The intensity of the laser light output from the laser light source unit is controlled so that the amplified laser beam output from the optical amplification unit is connected to the laser light source unit and the optical amplification unit and has a desired spectral width. A light output controller for controlling the amplified laser light to a desired intensity;
A laser device comprising:   2. The laser device according to claim 1, wherein the optical amplification medium is an optical amplification fiber in which a rare earth element is added to a core portion, and the reflection means is a fiber Bragg grating connected to the optical amplification fiber. .   A wavelength conversion element that is disposed on the light output side of the optical amplification unit and that outputs wavelength-converted light having a wavelength different from that of the amplified laser light when the amplified laser light output from the optical amplification unit is input; The laser apparatus according to claim 1 or 2, characterized in that:   The laser apparatus according to claim 1, wherein a spectrum width of the amplified laser light is 200 pm or less.   The laser apparatus according to claim 4, wherein the spectrum width of the amplified laser light is 50 pm or more.

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