WO2014034738A1 - レーザ光源 - Google Patents
レーザ光源 Download PDFInfo
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- WO2014034738A1 WO2014034738A1 PCT/JP2013/073049 JP2013073049W WO2014034738A1 WO 2014034738 A1 WO2014034738 A1 WO 2014034738A1 JP 2013073049 W JP2013073049 W JP 2013073049W WO 2014034738 A1 WO2014034738 A1 WO 2014034738A1
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- lens
- laser light
- collimating lens
- wavelength
- optical fiber
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/30—Collimators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
- B23K26/0648—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/0665—Shaping the laser beam, e.g. by masks or multi-focusing by beam condensation on the workpiece, e.g. for focusing
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
- G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
- G02B19/0009—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only
- G02B19/0014—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only at least one surface having optical power
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
- G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
- G02B19/0047—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
Definitions
- the present invention relates to a laser light source for realizing laser irradiation by including a collimator device for collimating input light having a wide spectral width, and condensing the input light having a wide spectral width after being collimated. .
- the collimated laser light is condensed using a condensing lens, and the laser light is focused on one point of the workpiece.
- a concentrating configuration is used.
- the focal length differs depending on the wavelength of the light.
- the position where the light emitted from the end face of the optical fiber becomes a plane wave after collimating with respect to the end face of the optical fiber (beam waist) also varies depending on the wavelength of the light, and the wavefront of the polychromatic light is concentrated at one point.
- a contrivance is made to reduce chromatic aberration by using an achromatic lens as a condensing lens.
- the inventor discovered the following problems.
- the polychromatic light is a light having a spectral width of several hundreds of nanometers
- chromatic aberration may affect the machining accuracy.
- the difference in the focal position of the wavelength component is as large as 156 ⁇ m for the plano-convex lens, but improved to 60 ⁇ m for the achromatic lens.
- the influence becomes enormous in a processing target having a film thickness of less than 60 ⁇ m.
- the present invention has been made to solve the above-described problems.
- the position difference (depending on the wavelength of the beam waist from which a plane wave is generated) It includes a collimator device that can reduce the amount of variation in the beam waist position depending on the included wavelength, and reduces chromatic aberration (condensation distance difference depending on the wavelength in the polychromatic light) when converging multicolor light. It aims at providing the laser light source which can improve the processing precision of the depth direction markedly by reducing effectively.
- the laser light source includes a single mode optical fiber, a collimating lens, a condenser lens, a laser light incident part, and a collimating lens installation part.
- the single mode optical fiber emits laser light having a spectral width of several hundred nm from the core portion.
- the collimating lens collimates the laser beam emitted from the single mode optical fiber.
- the condensing lens condenses the laser light collimated by the collimating lens.
- the laser beam incident part sets the incident position of the laser beam emitted from the single mode optical fiber.
- the collimating lens installation unit fixes the collimating lens.
- the laser beam path position of the laser light that has passed through the collimator lens is shifted so that the shorter wavelength component of the wavelength component included in the laser beam is shifted to the collimator lens side.
- the installation position of the collimating lens with respect to the light incident part is set.
- the laser light may include a wavelength component whose beam waist position is located on the single mode optical fiber side with respect to the collimating lens.
- the collimating lens includes a light incident surface on which laser light emitted from the single mode optical fiber is incident, A light emitting surface from which laser light is emitted is provided.
- the single mode is set based on the position of the light exit surface of the collimator lens disposed so that the focal point of the collimator lens is positioned on the light exit end surface of the single mode optical fiber at the center wavelength of the laser light.
- the collimating lens is installed within the range of +100 ⁇ m to +1000 ⁇ m along the optical axis of the laser light emitted from the single mode optical fiber. Is preferred.
- the beam waist position on the short wavelength side is relatively shifted to the collimator lens side compared to the beam waist position on the long wavelength side.
- the specific installation position of the collimating lens is from +100 ⁇ m to +1000 ⁇ m, preferably from +125 ⁇ m from a position away from the incident position of the laser beam by f 1.31 ⁇ m (the focal length of the collimating lens with respect to the reference wavelength component having the center wavelength of 1.31 ⁇ m).
- a position of +1000 ⁇ m condenser lens side from a position f 1.31 ⁇ m away from the laser light incident position
- the “center position of the collimating lens” means a position that defines the effective maximum diameter of the lens as shown in FIGS. 6 (A) to 6 (C) and FIG. 9 (A).
- the term “the position of the collimating lens” is simply referred to as the “center position of the collimating lens” without particular mention.
- the “center position of the condensing lens” means a position that defines the effective diameter of the lens as shown in FIG. 9 (A).
- position of the optical lens means “the central position of the condenser lens”.
- the laser light source may include a condensing lens installation unit for fixing the condensing lens.
- the installation position of the condensing lens with respect to the collimating lens is an area where the beam diameter of the laser light that has passed through the collimating lens is equal to or smaller than the effective aperture diameter of the condensing lens and condenses through the condensing lens.
- the chromatic aberration (wavelength-dependent focal length difference) of the laser light is set so as to be within a region where the laser light is minimized. With this configuration, it is possible to perform highly accurate control in the depth direction.
- the distance between the center position of the collimating lens and the central position of the condenser lens is adjusted in addition to the beam diameter of the laser beam being less than the effective aperture diameter of the condenser lens.
- the tolerance is greater when the slope of the graph indicating the relationship between the interval and chromatic aberration (wavelength-dependent focal length difference) is gentler.
- the installation position of the collimating lens with respect to the laser light incident portion is f 1.31 ⁇ m + 125 ⁇ m
- the installation position of the condenser lens with respect to the collimating lens that is, the distance between the central position of the collimating lens and the central position of the condenser lens is 600 mm.
- the installation position of the collimating lens and the installation position of the condenser lens differ depending on whether tolerance is important or miniaturization of the laser head is important.
- a reflection mirror may be disposed in the optical path between the collimating lens and the condenser lens.
- the collimating lens is preferably a lens that reduces chromatic aberration.
- the condenser lens is preferably a lens that reduces chromatic aberration.
- An example of a lens that reduces chromatic aberration is an achromatic lens.
- the laser light source includes a position adjusting unit provided in one of the laser light incident unit and the collimating lens installation unit. May be provided. This position adjustment unit makes it possible to adjust the position of the distance between the incident position of the laser beam and the center position of the collimating lens at a level of 10 ⁇ m or less.
- the collimator device when collimating polychromatic light having a wide spectral width, the collimator device capable of further reducing the difference for each wavelength of the position (beam waist) where the plane wave is generated includes a wide spectral width.
- a laser light source capable of reducing a difference in a condensing position for each wavelength when condensing input light having a wavelength after collimating.
- FIG. 5 is a schematic diagram for explaining a change in focal position when a plane wave having a plurality of wavelength components is incident on a condenser lens ( ⁇ 1 ⁇ 2 ⁇ 3 ). These are the figures for demonstrating the relationship of the focal distance with respect to an incident wave front. These are the figures for demonstrating the concept of this embodiment which suppresses a chromatic aberration by controlling an incident wave front for every wavelength component.
- MFD mode field diameter
- DELTA wavelength and beam waist position
- FIG. 5 is a diagram showing a calculation result of a beam waist position with respect to wavelengths of 1.0 ⁇ m to 1.55 ⁇ m by changing the adjustment position ⁇ of the collimator lens.
- FIG. 4 is a diagram showing a calculation result of a wavelength-dependent focal length difference ⁇ of polychromatic light (wavelength: 1.0 to 1.55 ⁇ m) with respect to a distance A between the collimating lens and the condenser lens by changing the adjustment position ⁇ of the collimating lens. .
- FIG. 5 is a diagram showing measurement results of beam waist positions with respect to wavelengths of 1.0 ⁇ m to 1.55 ⁇ m by changing the adjustment position ⁇ of the collimating lens.
- the collimator device 2 in FIG. 1A includes a laser light incident part 25 for setting the laser light emission position, a collimator lens 30, a collimator lens setting part 35 for fixing the collimator lens 30, and laser light emission from the laser light incident part 25.
- the position adjusting unit 50 is configured to adjust the position of the laser light incident part.
- the position adjustment unit 50 may be installed so that the position of the collimating lens installation unit 35 can be adjusted.
- the 1B includes a light source 10, an optical fiber (delivery fiber) 20, a laser light incident part 25 for fixing the end face 22, a collimating lens 30, a collimating lens installation part 35 for fixing the collimating lens 30,
- the optical lens 40 and the condensing lens installation part 45 which fixes the condensing lens 40 are comprised.
- the laser beam incident part 25, the collimating lens 30, and the collimating lens installation part 35 function as a collimator device.
- the laser light source 10 may include an output optical fiber 20.
- the exit end face 22 of the optical fiber 20 has an end cap structure of a coreless fiber that reduces the power density of light guided through the optical fiber 20 in order to avoid damage to the end face of the optical fiber 20 at the end. Also good.
- the multicolor light source 10 is a light source that emits multicolor light having a spectral width of 0.9 to 1.55 ⁇ m.
- the polychromatic light emitted from the polychromatic light source 10 enters the core region of the optical fiber 20 from one end face 21 of the optical fiber 20.
- the optical fiber 20 is composed of a core region in the center portion and a cladding region covering the periphery of the core region, and the polychromatic light incident on the core region from the end surface 21 propagates in the core region and exits from the other exit end surface 22. Is done.
- the diameter of the core region of the optical fiber 20 is, for example, about 10 ⁇ m.
- the emission end face 22 of the optical fiber 20 is made of a coreless fiber or the like that can reduce the power density to avoid end face damage when laser light with high output intensity is emitted from a narrow core region.
- the light is emitted through the end cap fiber.
- the end cap fiber is a coreless glass rod having a length of 500 ⁇ m and a diameter of 125 ⁇ m.
- the laser light source 1 is designed in consideration of the emission diameter and the emission angle with these attached. Below, in order to demonstrate easily, the structure by which the end cap is not provided in the output end surface 22 of the optical fiber 20 is demonstrated.
- the polychromatic light emitted from the emission end face 22 of the optical fiber 20 enters the collimating lens 30 and is emitted after being collimated. Then, the collimated polychromatic light is incident on the condensing lens 40 and passes through the condensing lens 40, so that a point P (point Pmin (shortest focal position) to point Pmax (farthest focal position)) that differs for each wavelength. It is condensed to.
- the outgoing end face 22 of the optical fiber 20 is fixed by a laser light incident part 25.
- the collimating lens 30 is fixed by a collimating lens installation unit 35.
- the relative position of the collimating lens installation unit 35 and the laser beam incident unit 25 can be adjusted by the position adjusting unit 50 in units of ⁇ m.
- the condenser lens 40 is fixed by a condenser lens installation part 45. About the condensing lens 45 and the collimating lens installation part 35, a relative position can be adjusted per 10 mm.
- the collimator lens 30 is provided at a position where the focal length f corresponds to the wavelength, thereby providing light.
- Parallel light can be generated from the light emitted from the fiber 20.
- a plane wave can be generated at a desired position by adjusting the position of the collimating lens 30. Then, by providing the condensing lens 40 at a position where the plane wave is generated, a condensing point where the monochromatic light is most condensed is formed at a focal distance from the condensing lens 40.
- FIG. 2 shows a result of calculating chromatic aberration when an ideal plane wave is incident on each of the planoconvex lens and the achromatic lens (model number: AC050-008-C, manufactured by Thorlab).
- FIG. 2A is a diagram illustrating the focal length difference ⁇ due to chromatic aberration of polychromatic light when a plane wave is incident, and FIG. 2B shows the result.
- FIG. 2A is a diagram illustrating the focal length difference ⁇ due to chromatic aberration of polychromatic light when a plane wave is incident
- FIG. 2B shows the result.
- a graph G210 shows the calculation result of the plano-convex lens
- a graph G220 shows the calculation result of the achromatic lens
- the vertical axis of the graph of FIG. 2 (B) shows the respective points when the position of the focal point after the light in the 0.9 ⁇ m wavelength band passes through the condenser lens (plano-convex lens or achromatic lens) is 0. It refers to the difference in the focal position of light of a wavelength.
- the achromatic lens used in the calculation of FIG. 2B can function as an achromatic lens for polychromatic light of 0.7 ⁇ m to 1.1 ⁇ m.
- the achromatic lens shows lens characteristics (change in focal position) that are almost equivalent to polychromatic light of 0.7 ⁇ m to 1.1 ⁇ m even for light of wavelengths of 1.2 ⁇ m and 1.3 ⁇ m. It was confirmed. Note that the difference in focal position between light with a wavelength of 0.9 ⁇ m and light with a wavelength of 1.3 ⁇ m was about 40 ⁇ m for an achromatic lens, and about 120 ⁇ m for a plano-convex lens. In other words, using an achromatic lens as a condenser lens confirms that the difference from the focal position when the wavelength of incident light changes can be made smaller than when a plano-convex lens is used.
- the incident light to the condenser lens 40 is required to be a plane wave.
- the expanded light passes through the collimating lens 30 and the wavefront incident on the condensing lens 40 has a different wavefront for each wavelength due to the refractive index dispersion of the collimating lens 30, and the condensing position is complicated. It becomes.
- FIG. 3 is a schematic diagram for explaining a change in the focal position when a plane wave having a plurality of wavelength components is incident on the condenser lens ( ⁇ 1 ⁇ 2 ⁇ 3 ).
- the incident light is condensed at the position of the focal length f.
- the wavelength components collected through the condensing lens 40 are f 1 , f 2 , f 3 according to the refractive index dispersion of the material. Concentrate at different positions. That is, the focal length of the wavelength component ⁇ 1 collected through the condenser lens 40 is f 1 , the focal length of the wavelength component ⁇ 2 collected through the condenser lens 40 is f 2 , and the condenser lens 40.
- the focal length of the wavelength component ⁇ 3 collected through is f 3 .
- the difference ⁇ wavelength dependent focal length difference
- the difference ⁇ is simply referred to as a focal length difference.
- FIG. 4 is a diagram for explaining the relationship between the focal length for the incident wavefront, FIG. 4 (A), the relationship of the focal length with respect to a plane wave of wavelength lambda 1, FIG. 4 (B), the negative curvature of the ratio of the focal length with respect to (wavefront convex toward the right side in the drawing) the wavelength lambda 1 of the wavefront with a radius, FIG. 4 (C) towards the wavelength lambda 1 of the wavefront (left side of the drawing has a positive curvature radius convex
- FIG. 4 A
- FIG. 4 (B) the relationship of the focal length with respect to a plane wave of wavelength lambda 1
- FIG. 4 (B) the negative curvature of the ratio of the focal length with respect to (wavefront convex toward the right side in the drawing) the wavelength lambda 1 of the wavefront with a radius
- FIG. 4 (C) towards the wavelength lambda 1 of the wavefront left side of the drawing has a positive curvature radius convex
- FIG. 5 is a diagram for explaining the concept of this embodiment in which chromatic aberration is suppressed by controlling the incident wavefront for each wavelength component
- FIG. 5A shows a wavelength ⁇ having a negative radius of curvature
- FIG. 5B shows the relationship of the focal length with respect to the plane wave of wavelength ⁇ 2
- FIG. 5C shows the positive curvature radius with respect to the wavefront of 1 (convex wavefront toward the right side of the drawing).
- the condensing lens 40 shown in FIGS. 4 and 5 is both an achromatic lens (model number: AC050-008-C) manufactured by Thorlab.
- the wavelength is fixed at ⁇ 1 and the wavefront incident on the condenser lens 40 is a plane wave (A), a wavefront (B) having a negative radius of curvature, There are three types of wavefront (C) having a positive radius of curvature.
- the focal length in FIG. 4A is f 1 as in FIG.
- the light incident on the condenser lens 40 has a predetermined spread angle at an incident angle ⁇ with respect to the normal line of the condenser lens 40 (which coincides with the optical axis of the condenser lens 40). Therefore, the focal length is f 1 + ⁇ f f according to Snell's law occurring on the incident surface side and the exit surface side of the lens.
- the behavior is opposite to that in FIG. 4B, and therefore f 1 ⁇ f n . That is, the focal length is controlled by controlling the wavefront incident on the condenser lens 40.
- each wavelength satisfies the relationship of ⁇ 1 ⁇ 2 ⁇ 3 .
- the focal length of the wavelength ⁇ 2 that is a plane wave is f 2 as in FIG.
- the wavefront of the wavelength ⁇ 3 has a positive radius of curvature and shifts from the focal length f 3 in the plane wave to the f 2 side.
- the main premise here is that the radius of curvature of the wavefronts of the short wavelength side component and the long wavelength side component can be controlled to minus and plus, respectively.
- the collimating lens 30 may be affected by the refractive index dispersion of the broadband spectrum. That is, since the beam propagation characteristics of the light (laser light) that has passed through the collimating lens 30 depends on each wavelength, it is difficult to make all the wavefronts of the respective wavelengths incident on the condenser lens 40 into plane waves, for example. Therefore, in the following, the wavefront control according to the present embodiment for the light that has passed through the collimating lens 30 will be described in detail with reference to FIG.
- FIG. 6 shows the distance f 2 ′ from the collimating lens 30 to the beam waist (plane wave) in a state where the distance between the end face of the optical fiber 20 and the center position of the collimating lens 30 is fixed to the focal length at the wavelength ⁇ 2.
- FIG. 5 is a diagram schematically showing how the position of the beam waist varies according to the output light wavelength. 6A to 6C, the wavelengths have a relationship of ⁇ 1 ⁇ 2 ⁇ 3 .
- FIG. 6D is a reference diagram showing beam waist positions virtually formed in FIG.
- FIG. 6A shows the beam waist position of the light having the wavelength ⁇ 1 , and the collimating lens 30 is located at a distance of f 2 (focal length of the wavelength ⁇ 2 ) from the emission end face 22 of the optical fiber 20. is set up.
- the beam waist position (represented by the waist position in the figure) of the light of wavelength ⁇ 1 that has passed through the collimating lens 30 is assumed to be f 1 ′.
- 6B shows the beam waist position of the light of wavelength ⁇ 2.
- the collimating lens 30 is located at the position f 2 from the light emitting end face 22 of the optical fiber 20.
- FIG. 6C shows the beam waist position of the light having the wavelength ⁇ 3 , and the distance from the emission end face 22 of the optical fiber 20 to f 2 as in the case of FIGS. 6A and 6B.
- the collimating lens 30 is installed in the front.
- Such a waist position in FIG. 6C does not exist. Therefore, in FIG. 6D, the beam waist position in the case of FIG. 6C is virtually shown as the position of f 3 ′.
- the positive value of the adjustment position ⁇ refers to a region of the condenser lens 40 side with respect to the installation position L 1
- negative values of the adjustment position ⁇ refers to a region of the light emitting face 22 side with respect to the installation position L 1 Shall.
- FIG. 7 shows the relationship of the mode field diameter (MFD) wavelength of the optical fiber that propagates the laser light from the multicolor light source.
- the relationship of FIG. 7 is the result of calculating the MFD for the wavelength (1.0 ⁇ m to 1.55 ⁇ m) when using a Nufern's large mode area (LMA) fiber.
- the model number of the LMA fiber is PLMA-YDF-10 / 125-VIII, and the LMA fiber has a core diameter of 11.0 ⁇ m and a numerical aperture NA of 0.075.
- FIG. 8 is a diagram showing the relationship between the wavelength and the beam waist position ⁇ f ′. The relationship of FIG.
- FIG. 8 is a result of calculating the waist position of light having a wavelength (1.0 ⁇ m to 1.55 ⁇ m) that has passed through the collimating lens 30.
- FIG. 8 shows a calculation result when the LMA fiber (using the MFD of FIG. 7 for calculation) is used.
- FIG. 7 shows the MFD calculation results of the LMA fiber for wavelengths of 1.0 ⁇ m, 1.06 ⁇ m, 1.1 ⁇ m, 1.31 ⁇ m, and 1.55 ⁇ m, and these long waves are shown in the verification optical system (FIG. 13) is the center wavelength of the bandpass filter (BPF) used in 13).
- BPF bandpass filter
- the collimating lens 30 employs a communication band achromatic doublet (model number: AC050-008-C) manufactured by Thorlab, which is the same lens as the condenser lens 40 in FIG.
- f 1.31 ⁇ m 5.2407 mm
- the ⁇ f ′ values of the respective lights are +201.0 mm and ⁇ 153.8 mm.
- ⁇ f ′ of light having a wavelength of 1.55 ⁇ m is a waist position in the virtual space.
- FIG. 9 shows a state in which the center position of the collimator lens 30 and the condenser lens 40 are fixed in a state where the distance between the exit end face 22 of the optical fiber 20 and the center position of the collimator lens 30 is fixed to the focal length of the collimator lens 30 at a wavelength of 1.31 ⁇ m. It is a figure which shows the relationship of the wavelength-dependent focal distance difference (DELTA) (alpha) with respect to the space
- 9A is a schematic diagram when the condenser lens 40 is arranged under the conditions of FIG. 8, and FIG. 9B is a condenser lens for light with a wavelength of 1.0 ⁇ m to 1.55 ⁇ m.
- DELTA wavelength-dependent focal distance difference
- the calculation result of the relationship of the focal distance difference ⁇ of 40 is shown.
- the MFD value of FIG. 7 is used.
- the collimating lens 30 is installed at a position of 5.2407 mm from the emission end face 22 of the optical fiber 20 so as to have a focal length f of 1.31 ⁇ m with a wavelength of 1.31 ⁇ m.
- the interval between the collimating lens 30 and the condensing lens 40 was A, and the chromatic aberration (wavelength dependent focal length difference) of the collected light was ⁇ .
- the simulation condition in the present embodiment is a case where 1.31 ⁇ m, which is the central wavelength in the wavelength range of 1.0 ⁇ m to 1.55 ⁇ m, is used as a reference. From the viewpoint of suppressing chromatic aberration, the direction in which chromatic aberration is further expanded. It can be assumed that it is difficult to suppress even if it leads to (see FIG. 5). Note that the simulation conditions of this embodiment, FIG. 5 wavefront condition (A) (a wavefront having a negative radius of curvature) is applied to the wavelength lambda 3 of the light, the wavefront shown in FIG.
- FIG. 5 (B) to the wavelength lambda 2 of light condition is (a plane wave) is applied, wavefront condition (wavefront having a positive radius of curvature) is applied shown in FIG. 5 (C) to the wavelength lambda 1 of the light ( ⁇ 1 ⁇ 2 ⁇ 3). That is, the focal position of the short wavelength side wavelength ( ⁇ 1 ) is a position (f 1 ⁇ f 1 ) away from f 2 due to the wavefront condition of FIG. On the other hand, the focal position of the long wavelength side wavelength ( ⁇ 3 ) is a position (f 3 + ⁇ f 3 ) away from f 2 due to the wavefront condition of FIG. That is, as shown in FIG.
- the beam waist position ⁇ f ′ indicates that it is difficult to suppress chromatic aberration with the characteristic of decreasing to the right as the wavelength increases.
- the suppression of chromatic aberration is a state in which the characteristic of ⁇ f ′ in FIG. 8 increases as the wavelength increases.
- propagation characteristics depending on each wavelength exist and the wavefront state changes at the interval A, it is important to confirm the characteristics at each interval A.
- the beam waist position ⁇ f ′ mentioned here indicates “f n ′ ( ⁇ ) ⁇ f 1.31 ⁇ m ′ ( ⁇ )”, and f n ′ ( ⁇ ) indicates the installation position of the collimating lens “f 1. This indicates the distance from the collimating lens 30 at the wavelength ⁇ n to the beam waist position after collimation when “ 31 ⁇ m + ⁇ ”.
- the radius of curvature of each wavelength at the position of the condenser lens 40 is all negative, which is different from the conditions of the radius of curvature necessary for suppressing chromatic aberration (short wavelength: minus, long wavelength: plus, see FIG. 5). . Therefore, it is expected that it is difficult to suppress chromatic aberration when the adjustment position ⁇ is in the range of ⁇ 3030 ⁇ m to ⁇ 130 ⁇ m. In the simulation of FIG. 10, calculation over a wide range is performed in order to grasp the entire image of ⁇ f ′ with respect to the wavelength.
- the condensing optical system is formed by only the collimating lens 30, and the meaning of the condensing lens 40 becomes extremely small. Therefore, in the actual optical system, f is about 1.31 ⁇ m + 1000 ⁇ m.
- the specific installation position of the collimating lens 30 is suitably a position of +100 ⁇ m to +1000 ⁇ m from a position f 1.31 ⁇ m away from the incident position of the laser beam, preferably from +125 ⁇ m to +1000 ⁇ m.
- FIG. 11 shows the calculation result of the wavelength-dependent focal length difference ⁇ of polychromatic light (wavelength 1.0 to 1.55 ⁇ m) with respect to the distance A between the collimating lens 30 and the condenser lens 40 by changing the adjustment position ⁇ of the collimating lens 30.
- FIG. 12 is a diagram showing the relationship between the distance A between the collimating lens 30 and the condenser lens 40 and the tolerance thereof with respect to the adjustment position ⁇ of the collimating lens 30.
- FIG. 12A shows the collimating lens 30 and the condensing lens 40 with respect to ⁇ (adjustment position of the collimating lens 30) when the installation tolerance ⁇ T of the condensing lens 40 is zero, that is, ⁇ is almost zero.
- FIG. 12B shows the tolerance of the interval A so that the installation tolerance ⁇ T of the condenser lens 40 is ⁇ 5 ⁇ m or less ( ⁇ ⁇ ⁇ 5 ⁇ m) when the interval A of FIG. 12A is used as a reference.
- the tolerance of the interval A at which ⁇ of ⁇ 5 ⁇ m or less is reduced and there is a trade-off between miniaturization and the tolerance of the interval A. It is made up. For example, when the tolerance of the interval A is about 10 mm, the value of ⁇ is about 200 ⁇ m, and the interval A is found to be two points of ⁇ 400 mm (graph G1210B) and ⁇ 210 mm (G1220B). If the laser interferometer is used, the condenser lens 40 can be installed sufficiently even if the tolerance of the interval A is on the order of several hundred microns, so the interval A can be set to 200 mm or less. Note that the head box can be reduced in size by folding back with two mirrors during the interval A.
- FIG. 13 is a diagram showing a configuration of the verification optical system of the present embodiment.
- the verification optical system for suppressing chromatic aberration shown in FIG. 13 includes a structure corresponding to the laser light source 1 of FIG. 1B and a measurement system. That is, the laser light source of the verification optical system in FIG. 13 includes a super continuum light source 11 that is a polychromatic light source 10, a Nufern's LMA fiber 21 (corresponding to the optical fiber 20 that is a delivery fiber), and an antenna that corresponds to the collimating lens 30.
- a chromatic lens 31 and a condenser lens 40 are provided.
- this laser light source is installed on a pedestal 70 that holds the Nufern's LMA fiber 21 and the achromatic lens 31, a pedestal 80 that holds the condenser lens 40, and the pedestal 70, and adjusts the installation position of the achromatic lens 31.
- An XYZ stage 75 is provided.
- the XYZ stage 75 includes a Z direction micrometer 76.
- the Nufern's LMA fiber 21 is a Nufern's large mode area fiber (model number: PLMA-YDF-10 / 125-VIII), and has a core diameter of 11 ⁇ m and a numerical aperture NA of 0.075.
- the Z-direction micrometer 76 employs a coarse / fine movement micrometer head (manufactured by Suruga Seiki: B83-1, minimum graduation fine movement: 0.5 ⁇ m).
- the measurement system includes a mid-infrared camera 60 and an objective lens 65.
- the mid-infrared camera 60 employs XenlCs (InGaAs).
- the objective lens 65 is selectively used according to the interval A because of the relationship of the beam diameter. That is, the objective lens 65 employed when the distance A is 200 to 400 mm is NIKON M PlanApo 200 / 0.95, 210/0.
- the objective lens 65 employed when the distance A is 500 to 700 mm is MITSUTOYO M Plan NIR 100 / 0.50, ⁇ / 0.
- a band-pass filter was used to extract a predetermined wavelength from the polychromatic light source.
- the center wavelengths of the bandpass filters are 1.0 ⁇ m, 1.1 ⁇ m, 1.2 ⁇ m, 1.31 ⁇ m, and 1.55 ⁇ m, respectively, and the half widths are all 10 nm.
- the laser light emitted from the Superumcontinuum light source 11 is emitted to the achromatic lens 31 via the Nufern's LMA fiber 21. Since the interval between the Nufern's LMA fiber 21 and the achromatic lens 31 needs to be controlled in units of several ⁇ m, the fine adjustment micrometer head 76 (minimum scale fine movement: 0.5 ⁇ m) can be adjusted in the Z direction of the achromatic lens 31. Is performed by an XYZ stage 75 to which is attached. The measurement of ⁇ is performed by measuring the light collected by the condenser lens 40 with the mid-infrared camera 60. Since the measurement software of the mid-infrared camera 60 (XenICs) was only the beam profile image, ⁇ was obtained from the camera position where the minimum beam profile for each wavelength was obtained.
- FIG. 14 shows the measurement result of the beam waist position for wavelengths of 1.0 ⁇ m to 1.55 ⁇ m by changing the adjustment position ⁇ of the achromatic lens 31 by the optical system of FIG.
- this embodiment makes it possible to suppress chromatic aberration in the case where light is collected after collimating multicolor light having a wide spectral width.
- the distance between the exit end face of the delivery fiber and the collimating lens is controlled in units of several tens of micrometers, and the chromatic aberration can be reduced to zero in principle by arranging the condenser lens at a desired position. It is.
- the optical system (FIG. 13) used for the simulation was prepared, and the verification experiment was performed. As a result, a good agreement with the calculation result was obtained. Proven.
- SYMBOLS 1 Laser light source, 10 ... Light source, 20 ... Optical fiber, 25 ... Laser beam incident part, 26 ... Pinhole mask, 30 ... Collimating lens, 35 ... Collimating lens installation part, 40 ... Condensing lens, 45 ... Condensing lens Installation part, 50 ... Position adjustment part.
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Abstract
Description
Claims (7)
- スペクトル幅が数百nmであるレーザ光をコア部から出射するシングルモード光ファイバと、
前記シングルモード光ファイバから拡光して出射されたレーザ光をコリメートするコリメートレンズと、
前記コリメートレンズによりコリメートされたレーザ光を集光する集光レンズと、
前記シングルモード光ファイバから出射されるレーザ光の入射位置を設定するレーザ光入射部と、
前記コリメートレンズを固定するコリメートレンズ設置部と、を備え、
前記コリメートレンズを通過した前記レーザ光のビームウエスト位置が、前記レーザ光に含まれる波長成分のうち短波長側波長成分ほど前記コリメートレンズ側へシフトするように、前記レーザ光入射部に対する前記コリメートレンズの設置位置が、設定されている
ことを特徴とするレーザ光源。 - 前記レーザ光は、前記ビームウエスト位置が前記コリメートレンズを基準にして前記シングルモード光ファイバ側に位置する波長成分を含むことを特徴とする請求項1に記載のレーザ光源。
- 前記コリメートレンズは、前記シングルモード光ファイバから出射される前記レーザ光が入射される光入射面と、前記レーザ光が出射される光出射面を有し、
前記レーザ光の中心波長において前記シングルモード光ファイバの光出射端面上に前記コリメートレンズの焦点が位置するよう配置された前記コリメータレンズの前記光出射面の位置を基準とし、前記シングルモード光ファイバ側をマイナス領域、前記集光レンズ側をプラス領域と規定するとき、
前記シングルモード光ファイバから出射される前記レーザ光の光軸に沿って、前記コリメートレンズは、+100μm~+1000μmの範囲内に設置されることを特徴とする請求項1に記載のレーザ光源。 - 前記集光レンズを固定する集光レンズ設置部を備え、
前記コリメートレンズに対する前記集光レンズの設置位置は、前記集光レンズを介して集光するレーザ光の色収差が最小となる領域内に収まるよう、設定されていることを特徴とする請求項1に記載のレーザ光源。 - 前記コリメートレンズは、色収差を低減するレンズであることを特徴とする請求項1に記載のレーザ光源。
- 前記集光レンズは、色収差を低減するレンズであることを特徴とする請求項1に記載のレーザ光源。
- 前記レーザ光入射部と前記コリメートレンズ設置部のいずれか一方に設けられた位置調整部であって、前記レーザ光の入射位置と前記コリメートレンズの中心位置との距離を、10μmレベル以下で位置調整可能にする位置調整部を備えたことを特徴とする請求項1
記載のレーザ光源。
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DE201311004303 DE112013004303T5 (de) | 2012-08-30 | 2013-08-28 | Laserlichtquelle |
JP2014533054A JPWO2014034738A1 (ja) | 2012-08-30 | 2013-08-28 | レーザ光源 |
US14/418,344 US9395550B2 (en) | 2012-08-30 | 2013-08-28 | Laser light source |
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JP2017026660A (ja) * | 2015-07-16 | 2017-02-02 | 住友金属鉱山株式会社 | 光ファイバ端末 |
KR20200005664A (ko) * | 2017-05-17 | 2020-01-15 | 쇼오트 아게 | 펄스 다색 레이저 빔 및 필터를 사용하여 소정의 가공 라인을 따라 공작물을 가공하기 위한 장치 및 방법 |
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US9742492B2 (en) | 2015-12-30 | 2017-08-22 | Surefire Llc | Systems and methods for ad-hoc networking in an optical narrowcasting system |
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JP6959073B2 (ja) * | 2017-08-30 | 2021-11-02 | 株式会社ディスコ | レーザー加工装置 |
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US10236986B1 (en) | 2018-01-05 | 2019-03-19 | Aron Surefire, Llc | Systems and methods for tiling free space optical transmissions |
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US11307367B2 (en) * | 2020-08-17 | 2022-04-19 | X Development Llc | Method of precision beam collimation using fiber-optic circulator and wavelength tunable source |
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