Laser oscillator

Abstract

To provide a laser oscillator capable of emitting a laser beam with high quality.SOLUTION: A laser oscillator (1) comprises: a cylinder-shaped outer electrode (20); an inner electrode (21) that is arranged concentrically with an external electrode, and forms a discharge chamber (25) into which a laser medium is filled between the external electrode and itself; a first resonator mirror (22) that is provided to one end side of the outer electrode (20) and the inner electrode (21), and reflects a laser beam discharged from the discharge chamber (25); a second resonator mirror (23) that is provided to the other end side of the outer electrode (20) and the inner electrode (21), and reflects the laser beam between the first resonator mirror (22) and itself; and a support member (24) supporting the inner electrode (21). The support member (24) includes an open part (244) in which the laser beam passes at a position corresponding to the discharge chamber (25), and in at least one part of the open part (244), an open width becomes space filter parts (2441 and 2442) formed so as to be smaller than a beam diameter of the laser beam discharged from the discharge chamber.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a laser oscillator. [Background technology]

[0002] In recent years, a cylindrical slab type gas laser device has been proposed as a laser oscillator configured to emit a uniform beam having a laser intensity distribution close to a Gaussian distribution and suitable for processing (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-332785 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, even with such a laser oscillator, noise may occur in the pulse waveform of the output laser, which may affect the quality of the laser light. If a laser light with such noise is used to drill a hole in a printed circuit board, for example, the quality of the hole will be degraded.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a laser oscillator capable of emitting high quality laser light. [Means for solving the problem]

[0006] One aspect of the present invention is a laser oscillator comprising: a cylindrical outer electrode; an inner electrode arranged concentrically with the outer electrode and forming a discharge chamber filled with a laser medium between the outer electrode and the inner electrode; a first resonator mirror provided on one end side of the outer electrode and the inner electrode and reflecting laser light emitted from the discharge chamber; a second resonator mirror provided on the other end side of the outer electrode and the inner electrode and reflecting the laser light between the first resonator mirror and the first resonator mirror; and a support member supporting the inner electrode, wherein the support member has an opening at a position corresponding to the discharge chamber through which the laser light passes, and at least a portion of the opening is a spatial filter portion whose opening width is formed smaller than the beam diameter of the laser light emitted from the discharge chamber. Effect of the Invention

[0007] According to the present invention, it is possible to provide a laser oscillator capable of emitting high quality laser light. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is an exploded view for explaining the structure of the laser oscillator according to the embodiment of the present invention. [Diagram 2] FIG. 4 is a view of the right end side of the outer electrode and inner electrode from the bracket side. [Diagram 3] FIG. 2 is a cross-sectional view of the laser oscillator taken in the longitudinal direction. [Figure 4] FIG. [Diagram 5] FIG. 4 is a schematic diagram showing a reflection path of laser light. [Figure 6] FIG. 4A is a diagram showing the relationship between the reflectance of the first resonator mirror and the wavelength of the laser light, and FIG. 4B is a diagram showing the relationship between the oscillation line and wavelength of the laser light emitted from the discharge chamber. [Figure 7] FIG. 2A is a diagram showing a pulse waveform of a laser beam emitted from a laser oscillator in a comparative example, and FIG. 2B is a diagram showing a pulse waveform of a laser beam emitted from a laser oscillator according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a laser oscillator 1 according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the laser oscillator 1 according to the present embodiment is a cylindrical slab type CO2 laser oscillator, and includes an outer electrode 20, an inner electrode 21, resonator mirrors 22, 23, and a bracket 24. More specifically, the laser oscillator 1 includes a cylindrical outer electrode 20 and an inner electrode 21 with different diameters arranged concentrically, and a discharge chamber 25 is formed between the outer electrode 20 and the inner electrode 21 (see also FIG. 2). The discharge chamber 25 is filled with a laser medium such as CO2, and when high-frequency power is applied between the outer electrode 20 and the inner electrode 21, the laser medium is excited to emit laser light L.

[0010] The first resonator mirror 22 is provided at the end of the laser oscillator 1 on the laser light emission side, and its inner surface 222 is spiral-shaped so that the laser light is reflected in a shifted manner. The second resonator mirror 23 is provided at the end opposite to the first resonator mirror 22, and is configured to reflect the laser light toward the first resonator mirror 22. Therefore, the laser light L emitted from the discharge chamber 25 is reflected back and forth between the resonator mirrors 22 and 23, as shown in FIG. 3, and is finally emitted from an output window 221 provided in the first resonator mirror 22.

[0011] 1 and 3, in the longitudinal direction of the laser oscillator, the bracket 24 described above is provided between the cylindrical slab portion (electrode portion) formed by the outer electrode 20 and the inner electrode 21 and the second resonator mirror 23, and the spacer 26 is provided between the cylindrical slab portion and the first resonator mirror 22. The bracket 24 and the spacer 26 are members that fix and support the inner electrode 21, and the inner electrode 21 is supported at both ends by the bracket 24 and the spacer 26. The inner electrode 21 is insulated from the outer electrode 20, the bracket 24, the resonator mirrors 22 and 23, and the spacer 26 by insulators not shown.

[0012] Next, the configuration of the bracket 24 will be described. As shown in Fig. 4, the bracket 24 is configured to include an outer support circular portion 241 that is attached to the outer electrode 20, an inner support circular portion 242 to which the inner electrode 21 is attached, and a connection portion (pillar portion) 243 that connects the outer support circular portion 241 and the inner support circular portion 242. The outer support circular portion 241 is formed in a ring shape of a predetermined width to match the shape of the end face of the outer electrode 20, and mounting holes 2411 for mounting the bracket 24 to the outer electrode 20 are formed at multiple locations in the circumferential direction.

[0013] In addition, the inner support circular portion 242 is formed in a ring shape with a smaller diameter than the outer support circular portion 241 to match the end face shape of the inner electrode 21, and mounting holes 2421 for mounting the inner electrode 21 to the bracket 24 are formed at multiple locations in the circumferential direction.

[0014] Furthermore, an opening 244 through which laser light L passes is provided between the outer support circle portion 241 and the inner support circle portion 242 that are concentrically arranged. Fig. 5 is a diagram showing the path of laser light L emitted from the discharge chamber 25, reflected between the resonator mirrors 22 and 23, and emitted from the output window 221. In order to make the path of the laser light L clear, numbers 1 to 8 are assigned in Fig. 5 with different phases in the circumferential direction for convenience.

[0015] 5, the laser light L is emitted from the position of phase number 1, passes through the first filter portion 2441 corresponding to phase number 1 in the opening 244 of the bracket 24, enters the second resonator mirror 23, and is reflected toward the first resonator mirror 22 with a changed phase by the second resonator mirror 23. The laser light L turned back by the second resonator mirror 23 then passes through the second filter portion 2442 corresponding to phase number 2 of the opening 244 and the discharge chamber 25, enters the first resonator mirror 22, and is reflected toward the second resonator mirror 23 with a changed phase.

[0016] The laser light L, which is reflected multiple times by the resonator mirrors 22 and 23 and passes multiple times through the discharge chamber 25 and the first and second filter sections 2441 and 2442, passes through a laser passing window section 2443 (in this case, a section corresponding to phase number 3) which is a part of the opening 244 other than the discharge chamber 25 and the first and second filter sections 2441 and 2442, and proceeds to the first resonator mirror 22. As shown by the arrows in Fig. 5, the laser light L is reflected multiple times at the parts corresponding to phase numbers 4 to 7 between the resonator mirrors 23 and 22, and is emitted to the outside from the output window 221 located at the position of phase number 8.

[0017] Here, the first and second filter sections 2441, 2442 of the opening 244 are spatial filter sections that function as spatial filters by being formed with an opening width smaller than the beam diameter of the laser light emitted from the discharge chamber 25. Hereinafter, the first and second filter sections 2441, 2442 as the spatial filter sections will be described in detail.

[0018] The above-mentioned first resonator mirror 22 is a band selection mirror (wavelength selection element) that selectively reflects laser light in a specific wavelength band (frequency band). FIG. 6(a) is a diagram showing the relationship between the reflectance of the first resonator mirror 22 and the wavelength of the laser light, and FIG. 6(b) is a diagram showing the relationship between the oscillation line and wavelength of the laser light L emitted from the discharge chamber 25. As can be seen from these FIGS. 6(a) and 6(b), the first resonator mirror 22 has a high reflectance for laser light in the wavelength band of the 9R portion, which is a short wavelength band, and a low reflectance for laser light in the wavelength bands of 9P, 10R, and 10P, which are longer than the 9R portion. Therefore, the wavelength of the laser light L emitted from the output window 221 becomes light in the short wavelength band of 9R.

[0019] However, even when the oscillation of 9P, 10R, and 10P is suppressed by the first resonator mirror 22, noise may occur in the laser light L as shown in FIG. 7(a). Specifically, in the example of FIG. 7(a), the oscillation line 9R(22) that oscillates from the middle of the pulse becomes noise. That is, the oscillation line 9R(20) and the oscillation line 9R(24) oscillate from the beginning of one pulse, but the oscillation line 9R(22) oscillates from the middle of one pulse. Since the output laser pulse waveform is a superposition of the oscillation line 9R(20), the oscillation line 9R(22), and the oscillation line 9R(24), if noise occurs in the oscillation line 9R(22), this noise is carried on the laser pulse waveform, distorting the pulse waveform and degrading the quality of the laser pulse.

[0020] Here, the beam diameter of the laser light L varies depending on the wavelength, and the longer the wavelength of the oscillation line, the larger the beam diameter. For this reason, in this embodiment, the opening width of the above-mentioned first and second filter sections 2441, 2442 is formed narrower than the beam diameter of the laser light L before passing through these filter sections, so that the laser light L with a long wavelength is effectively attenuated. Specifically, in this embodiment, the widths of the first and second filter sections 2441, 2442 are determined so that the laser light L with a wavelength of 9R(22) or more is effectively attenuated.

[0021] That is, the first resonator mirror 22 is a band-selective mirror having a high reflectance for laser light in a specific wavelength band 9R. The specific wavelength band 9R includes a first wavelength 9R(24) and a second wavelength 9R(22) that is longer than the first wavelength 9R(24). The aperture widths of the spatial filter sections 2441 and 2442 are set so as to effectively attenuate laser light L having a wavelength equal to or longer than the second wavelength 9R(22).

[0022] 4 and 5, the opening 244 of the bracket 24 is formed by two arc-shaped openings whose circumference is divided by two connecting parts 243, and the spatial filter parts 2441 and 2442 are formed at one end of each of the arc-shaped openings 244. As described above, these one ends are the phase positions through which the laser light L emitted from the discharge chamber 25 passes first and second among the openings 244 of the arc-shaped bracket 24, and the long-wavelength laser light L is effectively attenuated immediately after the laser light L is emitted. In this embodiment, the opening width of the laser passing window part 2443 is formed larger than the opening width of the spatial filter parts 2441 and 2442 and the beam diameter of the laser light in order not to attenuate the laser light more than necessary after the spatial filter parts 2441 and 2442.

[0023] The laser light L of the second wavelength 9R(22) is oscillated using the energy remaining in the oscillator even after the energy is consumed for the laser oscillation of the laser light L of the wavelengths 9R(20) and 9R(24). If the spatial filter units 2441 and 2442 are present, the loss exceeds the gain, and the laser light L of the second wavelength 9R(22) can hardly oscillate. In particular, in the case of this embodiment, the spatial filter units 2441 and 2442 are provided at the start position of the laser as described above, so stimulated emission of the laser light L of the second wavelength 9R(22) is effectively inhibited and the laser light L can hardly oscillate.

[0024] In this case, the laser light L of the oscillation line 9R(20) is also attenuated, but since the gain of the laser light L of the oscillation line 9R(20) is high, no problem occurs in the output pulse waveform.

[0025] <Summary> [Configuration 1] A cylindrical outer electrode (20); an inner electrode (21) arranged concentrically with the outer electrode (20) and forming a discharge chamber (25) filled with a laser medium between the inner electrode (21) and the outer electrode (20); a first resonator mirror (22) provided on one end side of the outer electrode (20) and the inner electrode (21) and configured to reflect the laser light emitted from the discharge chamber (25); a second resonator mirror (23) provided on the other end side of the outer electrode (20) and the inner electrode (21) and configured to reflect the laser light between itself and the first resonator mirror (22); a support member (24) for supporting the inner electrode (21), The support member (24) has an opening (244) through which the laser light passes at a position corresponding to the discharge chamber (25), and at least a part of the opening (244) is a spatial filter section (2441, 2442) whose opening width is smaller than the beam diameter of the laser light emitted from the discharge chamber (25). A laser oscillator (1).

[0026] In this way, it is possible to effectively attenuate long wavelength components contained in the laser light by making at least a part of the opening 244 smaller than the beam diameter of the laser light emitted from the discharge chamber 25 before passing through the spatial filter units 2441, 2442. This effectively attenuates light with wavelengths that become noise, and it is possible to output high-quality laser light having a laser pulse waveform with little distortion, and by using this laser light, for example, in a laser processing device, it is possible to drill high-quality holes in a workpiece such as a printed circuit board with little variation in the processed hole diameter.

[0027] [Configuration 2] the first resonator mirror (22) is a band selection mirror having a high reflectance for laser light in a specific wavelength band (9R); The specific wavelength band (9R) includes a first wavelength (9R(24)) and a second wavelength (9R(22)) that is longer than the first wavelength (9R(24)), The aperture width of the spatial filter unit (2441, 2442) is set so as to effectively attenuate the laser light having the second wavelength or longer. 2. A laser oscillator (1) according to configuration 1.

[0028] With this configuration, it becomes possible for the spatial filter units 2441 and 2442 to effectively attenuate laser light having wavelengths that cause noise.

[0029] [Configuration 3] The opening (244) has a width wider than that of the spatial filter sections (2441, 2442) and has a portion (2443) through which the laser light reflected between the first and second resonator mirrors passes. 3. A laser oscillator (1) according to configuration 1 or 2.

[0030] In this way, since a spatial filter is not formed over the entire opening, the laser light is not attenuated more than necessary.

[0031] [Configuration 4] the support member (24) has an outer diameter side support circular portion (241) to be attached to the outer electrode (20) and an inner diameter side support circular portion (242) to which the inner electrode (21) is attached, The opening (244) is formed in an arc shape between the outer diameter side support circular portion (241) and the inner diameter side support circular portion (242) when viewed in the axial direction, The spatial filter section (2441, 2442) is formed at one end of the arc-shaped opening (244). 4. A laser oscillator (1) according to any one of configurations 1 to 3.

[0032] With this configuration, the long wavelength components of the laser light can be effectively attenuated by the spatial filter at an early stage in the reflection path of the laser light.

[0033] In the above-described embodiment, the spatial filter sections 2441 and 2442 are formed on the second resonator mirror 23 side of the electrode sections 20 and 21, but the present invention is not limited to this. For example, the spatial filter sections may be formed on the support section (e.g., the spacer 26) on the first resonator mirror 22 side of the electrode sections 20 and 21. Also, the inventions described in the above-described embodiment may be combined in any manner. [Explanation of symbols]

[0034] 1: Laser oscillator 20: Outer electrode 21: Inner electrode 22: First cavity mirror 23: Second cavity mirror 24: Support member (bracket) 25:Discharge chamber 2441, 2442: Spatial filter section

Claims

1. A cylindrical outer electrode; an inner electrode that is arranged concentrically with the outer electrode and forms a discharge chamber filled with a laser medium between the outer electrode and the inner electrode; a first resonator mirror provided on one end side of the outer electrode and the inner electrode and configured to reflect the laser light emitted from the discharge chamber; a second resonator mirror provided on the other end side of the outer electrode and the inner electrode and configured to reflect the laser light between the second resonator mirror and the first resonator mirror; a support member for supporting the inner electrode, the support member has an opening through which the laser light passes at a position corresponding to the discharge chamber, and at least a part of the opening is a spatial filter portion having an opening width smaller than a beam diameter of the laser light emitted from the discharge chamber. A laser oscillator comprising:

2. the first resonator mirror is a band selection mirror having a high reflectance for laser light in a specific wavelength band; the specific wavelength band includes a first wavelength and a second wavelength that is longer than the first wavelength, an aperture width of the spatial filter unit is set so as to attenuate laser light having a wavelength equal to or longer than the second wavelength; 2. The laser oscillator according to claim 1.

3. the opening has a width wider than that of the spatial filter section and has a portion through which the laser light reflected between the first and second resonator mirrors passes.

3. The laser oscillator according to claim 1 or 2.

4. the support member has an outer diameter side support circular portion to be attached to the outer electrode and an inner diameter side support circular portion to which the inner electrode is attached, The opening is formed in an arc shape when viewed in the axial direction between the outer diameter side support circular portion and the inner diameter side support circular portion, The spatial filter portion is formed at one end of the arc-shaped opening.

4. The laser oscillator according to claim 3.

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