Laser oscillator

Abstract

The invention provides a laser oscillator capable of emitting laser light with high quality. The laser oscillator includes: an external electrode; an inner electrode forming a discharge chamber between the inner electrode and the outer electrode; a first resonator mirror provided on one end side of the outer electrode and the inner electrode; a second resonator mirror which is provided on the other end side of the outer electrode and the inner electrode, and which reflects the laser light between the second resonator mirror and the first resonator mirror; and a support member that supports the inner electrode. The support member has, at a position corresponding to the discharge chamber, an opening through which the laser beam passes, and at least a portion of the opening is a spatial filter portion in which the opening width is formed smaller than the beam diameter of the laser beam emitted from the discharge chamber.

Description

Technical Field

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

[0002] In recent years, as a laser oscillator, a cylindrical plate type gas laser device configured to have a laser intensity distribution close to a Gaussian distribution and to emit a uniform beam suitable for processing has been developed (see Patent Document 1). [Prior technical literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-332785 Summary of the invention [Problems to be solved by the invention]

[0004] However, even such a laser oscillator sometimes generates noise in the pulse waveform of the laser light output, which may affect the quality of the laser light. When a laser light generating such noise is used to drill a hole in a printed circuit board, for example, the processing quality of the hole may be reduced.

[0005] Therefore, the present invention provides a laser oscillator capable of emitting high-quality laser light.

Solutions to Solve the Problem

[0006] One embodiment of the present invention is a laser oscillator, characterized in that it comprises: a cylindrical outer electrode; an inner electrode, which is arranged concentrically with the outer electrode and forms a discharge chamber filled with a laser medium between the inner electrode and the outer electrode; a first resonator mirror, which is provided on one end side of the outer electrode and the inner electrode and reflects the laser light emitted from the discharge chamber; a second resonator mirror, which is provided on the other end side of the outer electrode and the inner electrode and reflects the laser light between the first resonator mirror; and a supporting member that supports the inner electrode, the supporting member having an opening portion for passing the laser light at a position corresponding to the discharge chamber, at least a portion of the opening portion forming a spatial filter portion whose opening width is formed to be smaller than the beam diameter of the laser light emitted from the discharge chamber. [Effects of the invention]

[0007] According to the present invention, a laser oscillator capable of emitting high-quality laser light can be provided.

[0008] Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. In addition, in the accompanying drawings, the same reference numerals are used for the same or similar components. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1It is an exploded view for explaining the structure of the laser oscillator according to the embodiment of the present invention. Figure 2 This is a diagram showing the right end side of the outer electrode and the inner electrode as viewed from the holder side. Figure 3 This is a cross-sectional view when the laser oscillator is cut along the longitudinal direction. Figure 4 is a schematic diagram showing a bracket. Figure 5 is a schematic diagram showing the reflection path of laser light. Figure 6 (a) is a diagram showing the relationship between the reflectivity of the first cavity mirror and the wavelength of the laser light, and (b) is a diagram showing the relationship between the oscillation line of the laser light emitted from the discharge chamber and the wavelength. Figure 7 (a) is a diagram showing a pulse waveform of laser light emitted from a laser oscillator in a comparative example, and (b) is a diagram showing a pulse waveform of laser light emitted from a laser oscillator according to the present embodiment. DETAILED DESCRIPTION

[0010] Hereinafter, a laser oscillator 1 according to an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 As shown in FIG. 1 , the laser oscillator 1 according to the present embodiment is a cylindrical plate-type CO2 laser oscillator, and includes an outer electrode 20, an inner electrode 21, resonator mirrors 22 and 23, and a support 24. More specifically, the laser oscillator 1 is provided with cylindrical outer electrodes 20 and inner electrodes 21 having different diameters arranged in a concentric circle, and a discharge chamber 25 (also referred to in the accompanying drawings) is formed between the outer electrode 20 and the inner electrode 21. Figure 2 The discharge chamber 25 is filled with a laser medium such as CO 2 . When high-frequency power is applied between the outer electrode 20 and the inner electrode 21 , the laser medium is excited and emits laser light L.

[0011] The first resonator mirror 22 is provided at the end of the laser oscillator 1 on the laser emitting side, and is configured so that the laser light is deflected and reflected by making its inner side surface 222 spiral. In addition, the second resonator mirror 23 is provided at the end on the side opposite to the first resonator mirror 22, and is configured so as to reflect the laser light toward the first resonator mirror 22. Figure 3 As shown, the laser light L emitted from the discharge chamber 25 is folded back and reflected between the resonator mirrors 22 and 23 , and finally emitted from the output window 221 provided in the first resonator mirror 22 .

[0012] In addition, if Figure 1 and Figure 3As shown, in the longitudinal direction of the laser oscillator, the above-mentioned support 24 is provided between the cylindrical plate portion (electrode portion) composed of the external electrode 20 and the internal electrode 21 and the second resonator mirror 23, and the spacer 26 is provided between the cylindrical plate portion and the first resonator mirror 22. These support 24 and spacer 26 are components for fixing and supporting the internal electrode 21, respectively, and the internal electrode 21 is supported in a double-supported manner by the above-mentioned support 24 and spacer 26. In addition, the internal electrode 21 is insulated from the external electrode 20, the support 24, the resonator mirrors 22 and 23, and the spacer 26 by an insulator not shown in the figure.

[0013] Next, the structure of the bracket 24 will be described. Figure 4 As shown in FIG. 1 , the bracket 24 is composed of the following components: an outer supporting circular portion 241, which is mounted on the outer electrode 20; an inner supporting circular portion 242, on which the inner electrode 21 is mounted; and a connecting portion (column portion) 243, which connects the outer supporting circular portion 241 and the inner supporting circular portion 242. The outer supporting circular portion 241 is formed in a ring shape with a predetermined width in accordance with the shape of the end surface of the outer electrode 20, and mounting holes 2411 for mounting the bracket 24 on the outer electrode 20 are formed at multiple locations in the circumferential direction.

[0014] The inner supporting circle 242 is formed in a ring shape with a smaller diameter than the outer supporting circle 241 to match the end surface shape of the inner electrode 21 , and mounting holes 2421 for mounting the inner electrode 21 on the bracket 24 are formed at multiple locations in the circumferential direction.

[0015] Furthermore, an opening 244 through which the laser light L passes is formed between the outer supporting circular portion 241 and the inner supporting circular portion 242 which are arranged concentrically. Figure 5 2 is a diagram showing the path of the laser light L emitted from the discharge chamber 25 until it is reflected between the cavity mirrors 22 and 23 and emitted from the output window 221. Figure 5 In FIG. 1 , for convenience, the phase is changed along the circumferential direction and numbers 1 to 8 are marked to facilitate understanding of the path of the laser light L.

[0016] like Figure 5 As shown, the laser light L is emitted from the position of phase number 1, passes through the first filter portion 2441 corresponding to the phase number 1 in the opening 244 of the holder 24, and is incident on the second resonator mirror 23, and is reflected toward the first resonator mirror 22 while its phase is changed by the second resonator mirror 23. The laser light L reflected by the second resonator mirror 23 then passes through the second filter portion 2442 corresponding to the phase number 2 of the opening 244 and the discharge chamber 25, and is incident on the first resonator mirror 22, and is reflected toward the second resonator mirror 23 while its phase is changed.

[0017] The laser light L, which is reflected multiple times by the resonator mirrors 22 and 23 and passes through the discharge chamber 25 and the first filter portion 2441 and the second filter portion 2442 multiple times, passes through the discharge chamber 25 and the portion of the opening 244 other than the first filter portion 2441 and the second filter portion 2442, i.e., the laser light passing window portion 2443 (in this case, the portion corresponding to phase number 3), and moves toward the first resonator mirror 22. Figure 5 As shown by the arrows, the laser light L is reflected multiple times by the portions between the resonator mirrors 23 and 22 corresponding to phase numbers 4 to 7, and is emitted to the outside from the output window 221 at the position of phase number 8.

[0018] Here, the first filter portion 2441 and the second filter portion 2442 of the opening 244 serve as a spatial filter portion that functions as a spatial filter by forming the opening width smaller than the beam diameter of the laser light emitted from the discharge chamber 25. The first filter portion 2441 and the second filter portion 2442 serving as the spatial filter portion will be described in detail below.

[0019] The first resonator mirror 22 described above serves as a band-selective mirror (wavelength selection element) that selectively reflects laser light in a specific wavelength band (frequency band). Figure 6 (a) is a diagram showing the relationship between the reflectivity of the first resonator mirror 22 and the wavelength of the laser light. Figure 6 (b) is a diagram showing the relationship between the oscillation line and the wavelength of the laser light L emitted from the discharge chamber 25. Figure 6 (a) and Figure 6 As can be understood from the figure (b), the first resonator mirror 22 has a high reflectivity of laser light in the wavelength band of the 9R portion, which is a short wavelength band, and a low reflectivity of laser light in the wavelength bands of 9P, 10R, and 10P, which are longer wavelengths 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.

[0020] However, even when the oscillation of 9P, 10R, and 10P is suppressed by the first resonator mirror 22, Figure 7 As shown in (a), noise may also be generated in the laser light L. Specifically, Figure 7 In the example of (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. The output laser pulse waveform becomes a shape in which the oscillation lines 9R(20), oscillation lines 9R(22), and oscillation lines 9R(24) overlap. Therefore, if the noise of the oscillation line 9R(22) is generated, the noise is attached to the laser pulse waveform, the pulse waveform is deformed, and the quality of the laser pulse is reduced.

[0021] Here, regarding the laser light L, the beam diameter varies depending on the wavelength, and the longer the wavelength of the oscillation line, the larger the beam diameter. Therefore, in this embodiment, the lateral widths of the first filter portion 2441 and the second filter portion 2442 are formed to be narrower than the beam diameter of the laser light L before passing through these filter portions, and the long-wavelength laser light L is effectively attenuated. Specifically, in this embodiment, the widths of the first filter portion 2441 and the second filter portion 2442 are determined so that the laser light L with a wavelength of 9R (22) or more is effectively attenuated.

[0022] That is, the first resonator mirror 22 is a band selective mirror having a high reflectivity for laser light in a specific wavelength band 9R, wherein the specific wavelength band 9R includes a first wavelength 9R (24) and a second wavelength 9R (22) having a longer wavelength than the first wavelength 9R (24), and the opening width of the spatial filter parts 2441 and 2442 is set in such a manner that laser light L having a wavelength longer than the second wavelength 9R (22) is effectively attenuated.

[0023] In addition, if Figure 4 and Figure 5 As shown, the opening 244 of the bracket 24 is formed by two arc-shaped openings whose circumferences are divided by two connecting portions 243, and each filter portion of the spatial filter portion 2441, 2442 is formed at one end of each arc-shaped opening 244. As described above, these one ends are phase positions where the laser light L emitted from the discharge chamber 25 passes through the first and second phases in the opening 244 of the arc-shaped bracket 24, and the laser light L is emitted and the long wavelength laser light L is immediately and effectively attenuated. In addition, in this embodiment, after the above-mentioned spatial filter portions 2441, 2442, in order to prevent the laser light from being attenuated more than necessary, the opening width of the laser light passing window portion 2443 is formed to be larger than the opening width of the spatial filter portions 2441, 2442 and the beam diameter of the laser light.

[0024] Regarding the laser light L of the second wavelength 9R(22), even if energy is consumed in the laser oscillation of the laser light L of the wavelength 9R(20) or 9R(24), when there is still energy remaining in the oscillator, the energy is used for oscillation. If the spatial filter portions 2441 and 2442 are present, the loss exceeds the gain, and the laser light L of the second wavelength 9R(22) hardly oscillates. In particular, in the case of the present embodiment, as described above, the spatial filter portions 2441 and 2442 are provided at the starting position of the laser light, and therefore, the stimulated emission of the laser light L of the second wavelength 9R(22) is effectively blocked, and the laser light hardly oscillates.

[0025] In this case, the laser light L of the oscillation line 9R(20) is also attenuated. However, since the laser light L of the oscillation line 9R(20) has a high gain, no problem occurs in the output pulse waveform.

[0026] <Conclusion> [Composition 1] A laser oscillator (1), characterized by comprising: A cylindrical outer electrode (20); An inner electrode (21) is arranged concentrically with the outer electrode (20) and forms a discharge chamber (25) filled with a laser medium between the inner electrode (21) and the outer electrode (20); a first resonator mirror (22) which is disposed on one end side of the outer electrode (20) and the inner electrode (21) and reflects the laser light emitted from the discharge chamber (25); a second resonator mirror (23) which is disposed on the other end side of the outer electrode (20) and the inner electrode (21) and reflects the laser light between the second resonator mirror (23) and the first resonator mirror (22); and a supporting member (24) which supports the inner electrode (21), The supporting member (24) has an opening (244) for allowing the laser to pass through at a position corresponding to the discharge chamber (25), and at least a portion of the opening (244) is a spatial filter portion (2441, 2442) whose opening width is formed smaller than a beam diameter of the laser light emitted from the discharge chamber (25).

[0027] Thus, by making at least a portion 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 portions 2441 and 2442, it is possible to effectively attenuate the long wavelength component included in the laser light. Thus, light of a wavelength that becomes noise is effectively attenuated, and high-quality laser light having a laser pulse waveform with little deformation can be output, and the laser light can be used, for example, in a laser processing device to drill holes with little deviation in the processing hole diameter and high quality in a workpiece such as a printed substrate.

[0028] [Composition 2] The laser oscillator (1) described in configuration 1 is characterized in that: The first resonator mirror (22) is a band-selective mirror having a high reflectivity 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)) longer than the first wavelength (9R(24)). The opening width of the spatial filter portion (2441, 2442) is set so as to effectively attenuate the laser light having a wavelength longer than the second wavelength.

[0029] With this configuration, laser light having a wavelength that becomes noise can be effectively attenuated by the spatial filter portions 2441 and 2442 .

[0030] [Composition 3] The laser oscillator (1) described in configuration 1 or 2 is characterized in that: The opening (244) has a portion (2443) having an opening width wider than that of the spatial filter portions (2441, 2442) and through which the laser light reflected between the first resonator mirror and the second resonator mirror passes.

[0031] In this way, a spatial filter is not formed over the entire opening, so that the laser light is not attenuated more than necessary.

[0032] [Composition 4] The laser oscillator (1) according to any one of configurations 1 to 3 is characterized in that: The support member (24) includes an outer diameter side support circular portion (241) mounted on the outer electrode (20) and an inner diameter side support circular portion (242) for mounting the inner electrode (21). 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 from the axial direction. The spatial filter portion (2441, 2442) is formed at one end of the arc-shaped opening (244).

[0033] With this configuration, the long wavelength component of the laser light can be effectively attenuated by the spatial filter at the initial stage within the reflection path of the laser light.

[0034] In the above-described embodiment, the spatial filter portions 2441 and 2442 are formed on the second resonator mirror 23 side of the electrode portions 20 and 21, but the present invention is not limited thereto. For example, the spatial filter portion may be formed on the support portion (e.g., the spacer 26, etc.) on the first resonator mirror 22 side of the electrode portions 20 and 21. The inventions described in the above-described embodiments may be combined in any manner.

[0035] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to disclose the scope of the present invention, the following claims are attached.

Explanation of symbols

[0036] 1: Laser oscillator 20: External electrode 21: Inner electrode 22: 1st resonator mirror 23: Second resonator mirror 24: Support component (bracket) 25: Discharge chamber 2441, 2442: Spatial filter part.

Claims

1. A laser oscillator, characterized in that: have: A cylindrical outer electrode; an inner electrode, which is arranged concentrically with the outer electrode and forms a discharge chamber filled with a laser medium between the inner electrode and the outer electrode; a first resonator mirror disposed on one end side of the outer electrode and the inner electrode and reflecting 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 reflecting the laser light between the second resonator mirror and the first resonator mirror; as well as a supporting member that supports the inner electrode, The support member has an opening for passing the laser light at a position corresponding to the discharge chamber, and at least a part of the opening serves as a spatial filter portion having an opening width smaller than a beam diameter of the laser light emitted from the discharge chamber.

2. The laser oscillator according to claim 1, characterized in that The first cavity mirror is a band-selective mirror having a high reflectivity for laser light in a specific wavelength band. The specific wavelength band includes a first wavelength and a second wavelength longer than the first wavelength, The opening width of the spatial filter portion is set so as to attenuate the laser light having a wavelength longer than the second wavelength.

3. The laser oscillator according to claim 1 or 2, characterized in that: The opening portion has a portion having an opening width wider than that of the spatial filter portion and through which the laser beam reflected between the first resonator mirror and the second resonator mirror passes.

4. The laser oscillator according to claim 3, characterized in that The support member includes an outer diameter side support circular portion mounted on the outer electrode and an inner diameter side support circular portion on which the inner electrode is mounted. The opening portion is formed in an arc shape between the outer diameter side support circular portion and the inner diameter side support circular portion when viewed from the axial direction, The spatial filter portion is formed at one end of the arc-shaped opening.

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