Multi-band multi-line slab co2 laser

Abstract

The disclosure provides a multi-band multi-line slab CO2 laser, comprising two pairs of discharge electrodes, two radio frequency power supplies, two long rectangular concave spherical end mirrors, a first diaphragm, a concave spherical output mirror, a second diaphragm, a reflective plane diffraction grating and a third diaphragm. The concave spherical output mirror, the second diaphragm, the grating and the third diaphragm are located on the central axis of the laser; the two pairs of discharge electrodes and the two end mirrors are symmetrically located on both sides of the central axis; the first diaphragm is arranged in a row on the side of the mirror surface close to the end mirror; the second diaphragm is close to the output mirror; the third diaphragm is close to the grating; the long rectangular concave spherical end mirror, the grating and the concave spherical output mirror form a folded near-axicon stable resonant cavity; the laser beam is output from the concave spherical output mirror along the central axis, and the spectrum of the laser contains multiple transition spectral lines of the CO2 laser in the wavelength range of 9 μm-11 μm, which belong to four transition bands of 10P, 10R, 9P and 9R, namely the P branch and the R branch of the 00°1-10°0 band and the 00°1-02°0 band.

Description

Technical Field

[0001] This disclosure relates to the field of laser technology, and in particular to a multi-band, multi-line slab CO2 laser. Background Technology

[0002] The laser transition lines of a CO2 laser can number around 100 in the 9-11 μm wavelength range, belonging to four transition bands: 10P, 10R, 9P, and 9R (the P and R branches of the 00°1-10°0 band and the 00°1-02°0 band of the CO2 molecule). The distribution of laser transition lines spans 200 cm⁻¹. -1 Spectral width. Conventional CO2 lasers, due to competition among transition lines within a common gain region, can only output a single spectral line with the highest gain (10.6 μm) or randomly output a few high-gain lines. If a laser could operate simultaneously on multiple bands and lines, it would have enormous potential applications in picosecond-scale (Ps) and femtosecond-scale (Fs) ultra-intense laser physics and laser chemistry research. In EUV lithography source development, using four spectral lines (P18, P20, P22, and P24) of the 10P band simultaneously as seed laser sources to control a high-power CO2 laser amplifier can generate high-repetition-rate, high-power 10-20 ns pulsed lasers. Compared to amplifying only on a single spectral line (10.6 μm), the power amplifier can increase the output energy by 20%. Multi-line or multi-band CO2 lasers can avoid competition between transition lines by using internal cavity diffraction gratings or internal cavity prisms to separate specific dedicated gain regions for different transition lines in the gas discharge gain medium region.

[0003] In related technologies, CO2 lasers use internal cavity diffraction gratings to achieve simultaneous oscillation of multiple lines in the 10P band or internal cavity prisms to achieve simultaneous oscillation of one spectral line in each of the 10P and 10R dual bands, but cannot achieve independent and controllable simultaneous oscillation of multiple bands and multiple lines. Summary of the Invention

[0004] To address at least one technical problem mentioned above and in other aspects in the prior art, this disclosure provides a multi-band, multi-line slab CO2 laser capable of achieving independent and controllable simultaneous oscillation of multiple bands and lines.

[0005] According to one aspect of this disclosure, a multi-band multi-line slab CO2 laser is provided, comprising: two pairs of discharge electrodes, two radio frequency power supplies, two elongated rectangular concave spherical end mirrors, a first aperture, a concave spherical output mirror, a second aperture, a reflective plane diffraction grating, and a third aperture (not shown in the figure).

[0006] The concave spherical output mirror, the second aperture, the reflective plane diffraction grating, and the third aperture are located on the central axis of the laser. The two pairs of discharge electrodes and the two long rectangular concave spherical end mirrors are symmetrically located on both sides of the central axis. The first aperture is arranged in a row on one side of the mirror surface of the concave spherical end mirror. The second aperture is close to one side of the mirror surface of the concave spherical output mirror. The third aperture is close to the reflective plane diffraction grating.

[0007] The two long rectangular concave spherical end mirrors, the reflective plane diffraction grating, and the concave spherical output mirror constitute a folded near-concentric stable resonant cavity. The laser beam is output from the concave spherical output mirror along the central axis. The laser spectrum contains multiple transition lines of the CO2 laser in the wavelength range of 9 μm-11 μm, belonging to four transition bands: 10P, 10R, 9P, and 9R, which are the P and R branches of the 00°1-10°0 band and the 00°1-02°0 band of the CO2 molecule.

[0008] According to embodiments of this disclosure, the laser mixing gas in the multi-band multi-line slab CO2 laser includes either the laser mixing gas of a conventional slab CO2 laser or the isotopic CO2 laser mixing gas.

[0009] According to embodiments of this disclosure, based on the different requirements for the number of spectral lines required by the aforementioned multi-band multi-line slab CO2 laser, the aforementioned long rectangular concave spherical end reflector is replaced by multiple short concave spherical end reflectors; simultaneously, the aforementioned discharge electrode is replaced by multiple narrow discharge electrodes, and the aforementioned radio frequency power supply is replaced by multiple low-power radio frequency power supplies.

[0010] According to embodiments of this disclosure, the above-mentioned multi-band multi-line slab CO2 laser has a dual-band multi-line structure, and the spectrum of the output laser includes 4 to 6 strong spectral lines in both the 9P and 10P bands.

[0011] According to embodiments of this disclosure, the above-mentioned multi-band multi-line slab CO2 laser has a dual-band multi-line structure, and the spectrum of the output laser includes 4 to 6 strong spectral lines in both the 9P and 10R bands.

[0012] According to embodiments of this disclosure, by setting a discharge electrode, a radio frequency power supply, a long rectangular concave spherical end reflector, a first aperture, a concave spherical output mirror, a second aperture, a reflective planar diffraction grating, and a third aperture, the gain regions of multiple transition spectral lines belonging to the four transition bands of 10P, 10R, 9P, and 9R within the wavelength range of 9 μm to 11 μm are spatially separated according to different wavelengths. This avoids competition between transition spectral lines, achieves independent and controllable simultaneous oscillation of multiple bands and lines, and the oscillation of each spectral line can be individually adjusted and controlled. Attached Figure Description

[0013] The foregoing contents, as well as other objects, features, and advantages of this disclosure, will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0014] Figure 1 A schematic diagram of a normalized CO2 laser gain spectrum according to an embodiment of the present disclosure is shown.

[0015] Figure 2 This schematic diagram illustrates the working principle of a multi-band multi-line slab CO2 laser according to an embodiment of the present disclosure.

[0016] Figure 3 A schematic side cross-sectional view of a multi-band, multi-line slab CO2 laser according to an embodiment of the present disclosure is shown; and

[0017] Figure 4 The schematic diagram illustrates the working principle of a multi-band multi-line slab CO2 laser according to another embodiment of the present disclosure.

[0018] The meanings of the reference numerals in the above figures are as follows:

[0019] 1-Discharge electrode;

[0020] 2-RF power supply;

[0021] 3-Reflective planar diffraction grating;

[0022] 4-First aperture;

[0023] 5-Elongated rectangular concave spherical end reflector;

[0024] 6-Second aperture;

[0025] 7-Concave spherical output mirror;

[0026] 8- Narrow discharge electrode;

[0027] 9-Low-power radio frequency power supply;

[0028] 10-Short strip concave spherical end reflector;

[0029] 9R- CO2 molecule's R branch at 00°1-02°0;

[0030] The p-branch of the 00°1-02°0 band in the 9P-CO2 molecule;

[0031] 10R - The R branch of the CO2 molecule's 00°1-10°0 band;

[0032] The P-branch of the 10P-CO2 molecule (00°1-10°0). Detailed Implementation

[0033] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0035] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0036] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0037] CO2 lasers can have approximately 100 laser transition lines in the wavelength range of 9 μm–11 μm, belonging to four transition bands: 10P, 10R, 9P, and 9R (the P and R branches of the 00°1–10°0 and 00°1–02°0 bands of the CO2 molecule). Figure 1 As shown, the laser transition spectral line distribution spans 200 cm⁻¹. -1 Spectrum width.

[0038] In related technologies, CO2 lasers use internal cavity diffraction gratings to achieve simultaneous oscillation of multiple lines in the 10P band or internal cavity prisms to achieve simultaneous oscillation of one spectral line in each of the 10P and 10R dual bands, but cannot achieve independent and controllable simultaneous oscillation of multiple bands and multiple lines.

[0039] In view of this, the present disclosure provides a multi-band, multi-line slab CO2 laser. By setting up a discharge electrode, a radio frequency power supply, a long rectangular concave spherical end reflector, a first aperture, a concave spherical output mirror, a second aperture, a reflective plane diffraction grating, and a third aperture, the gain regions of multiple transition spectral lines belonging to the four transition bands of 10P, 10R, 9P, and 9R within the wavelength range of 9 μm to 11 μm are spatially separated according to different wavelengths. This avoids competition between transition spectral lines, thus enabling independent and controllable simultaneous oscillation of multiple bands and lines. Furthermore, the oscillation of each spectral line can be individually adjusted and controlled.

[0040] The multi-band, multi-line slab CO2 laser disclosed herein can be used as a seed laser source to control a high-power CO2 laser to generate high-repetition-rate, high-power, narrow-pulse lasers, which has important applications in ultra-intense ps and fs laser physics research and EUV lithography source research. Furthermore, it also has important applications in laser chemistry and optoelectronic countermeasures.

[0041] Figure 1 A schematic diagram of a normalized CO2 laser gain spectrum according to an embodiment of the present disclosure is shown.

[0042] Figure 1 The horizontal axis represents frequency, in cm. -1 , Figure 1 The vertical axis represents the relative gain intensity, which is derived from... Figure 1 The relationship between the frequency of the laser spectral lines generated by the transitions between different energy levels of CO2 molecules and their gain intensity can be observed. The CO2 laser exhibits approximately 100 laser transition lines in the 9-11 μm wavelength range, belonging to four transition bands: 10P, 10R, 9P, and 9R. The distribution of these laser transition lines spans over 200 cm⁻¹. -1 Spectral width; energy level transitions mainly occur between the two vibrational-rotational energy levels of the electronic ground state of the CO2 molecule. The output laser wavelengths include 10.6 μm and 9.6 μm wavelengths.

[0043] Figure 2 This schematic diagram illustrates the working principle of a multi-band multi-line slab CO2 laser according to an embodiment of the present disclosure. Figure 3 A schematic side cross-sectional view of a multi-band multi-line slab CO2 laser according to an embodiment of the present disclosure is shown.

[0044] According to some embodiments of this disclosure, such as Figure 2 and Figure 3As shown, the multi-band multi-line slab CO2 laser includes: two pairs of discharge electrodes 1, two radio frequency power supplies 2, two long rectangular concave spherical end mirrors 5, a first aperture 4, a concave spherical output mirror 7, a second aperture 6, a reflective plane diffraction grating 3, and a third aperture (not shown in the figure); the first aperture 4 is arranged in a row on one side of the mirror surface of the concave spherical end mirror 5; the second aperture 6 is close to one side of the mirror surface of the concave spherical output mirror 7; the third aperture is close to the reflective plane diffraction grating 3; wherein, the concave spherical output mirror 7, the second aperture 6, the reflective plane diffraction grating 3, and the third aperture are located on the central axis of the laser, and the two pairs of discharge electrodes 1 and the two long rectangular concave spherical end mirrors 5 are symmetrically located on both sides of the central axis.

[0045] According to some embodiments of this disclosure, the elongated rectangular concave spherical end mirror 5, the reflective planar diffraction grating 3, and the concave spherical output mirror 7 constitute a folded near-concentric stable resonant cavity. The laser beam is output from the concave spherical output mirror 7 along the central axis. The laser spectrum contains multiple transition lines of the CO2 laser in the wavelength range of 9 μm-11 μm, belonging to four transition bands: 10P, 10R, 9P, and 9R, which are the P and R branches of the 00°1-10°0 band and the 00°1-02°0 band of the CO2 molecule.

[0046] According to some embodiments of this disclosure, the elongated rectangular concave spherical end reflector 5 is a total reflection mirror with a gold-plated film, and its reflectivity is usually above 99%; the concave spherical output mirror 7 is a partial reflectivity mirror, and its reflectivity can vary in a wide range depending on different design purposes; the reflective planar diffraction grating 3 is a gold-plated blazed grating on a copper, molybdenum or silicon substrate, and its reflectivity is usually above 95%.

[0047] According to some embodiments of this disclosure, the radius of curvature of the concave spherical output mirror 7 is approximately the same as that of the concave spherical end reflector 5, but the radius of curvature of the concave spherical output mirror 7 is slightly larger than that of the concave spherical end reflector 5.

[0048] According to some embodiments of this disclosure, the laser mixing gas in a multi-band multi-line slab CO2 laser includes either the laser mixing gas of a conventional slab CO2 laser or an isotopic CO2 laser mixing gas.

[0049] According to some embodiments of this disclosure, the laser mixing gas of a conventional slab CO2 laser mainly includes CO2 gas, nitrogen, and helium, and also includes other gases such as CO, oxygen, xenon, and hydrogen. The isotopic CO2 laser mixing gas includes isotopes of C and O elements in the CO2 molecule.

[0050] The following analysis explains the mechanism by which the spectral structure of the laser beam output from the concave spherical output mirror 7 includes multiple spectral lines from the aforementioned four spectral bands (i.e., the four transition bands of 10P, 10R, 9P, and 9R):

[0051] First, the transmission law of natural light after passing through the reflective plane diffraction grating 3 in ordinary optics is determined by the grating equation, which is expressed as formula (1):

[0052] (1),

[0053] in, The grating constant; The wavelength of light; Angle of incidence The diffraction angle (conversely, if) Let be the angle of incidence, then (for the angle of incidence); when fixed When unchanged, Follow Increase. The condition where the incident and incident beams coincide is called the Littrow condition. The incident angle and diffraction angle at this point are defined as the Littrow angle. ,

[0054] Formula (2) can be derived from the above formula (1):

[0055] (2),

[0056] For a given The Littrow angle can be determined using formula (2) based on the Littrow wavelength. The value. Figure 2 In the example, g = 120 / mm, take Figure 1 If the wavelength of 10 μm where the gain is zero between the two bands is the Littrow wavelength, then the Littrow angle θ is 37°.

[0057] The following analyzes the function of the reflective planar diffraction grating 3 in the embodiments of this disclosure:

[0058] like Figure 2 As shown, the elongated rectangular concave spherical end mirror 5, the reflective plane diffraction grating 3, and the concave spherical output mirror 7 form a folded near-concentric stable resonant cavity. The reflective plane diffraction grating 3 and the concave spherical output mirror 7 form one arm of the resonant cavity, with the laser beam output from the concave spherical output mirror 7 along the central axis. The second arm is composed of the reflective plane diffraction grating 3 and the elongated rectangular concave spherical end mirror 5. Since the reflective plane diffraction grating 3 has diffraction and beam splitting capabilities, the second arm is actually separated into multiple directions according to wavelength, determined by formula (1). The second arms for the 9 μm and 10 μm spectral bands are distributed on both sides of the laser's central axis. Therefore... Figure 1More than 80 spectral lines of different wavelengths will be separated in the gain region. This folded near-concentric stable resonator is actually a combination of more than 80 independent V-shaped folded near-concentric stable resonators, where each independent V-shaped folded near-concentric stable resonator corresponds to... Figure 1 The image shows a spectral line and a small region within the long rectangular concave spherical end mirror 5. Each spectral line has a corresponding dedicated gain region, which avoids competition between transition spectral lines.

[0059] When the RF power supply 2 of the multi-band, multi-line slab CO2 laser is turned on, photons of each specific spectral line oscillate and amplify back and forth in a specific V-shaped folded near-concentric stable resonant cavity, only... Figure 1 Only those spectral lines with sufficiently high gain can form laser beams, which are output from the concave spherical output mirror 7 along the central axis. The intensity of the output laser beam for each line can be adjusted independently by changing the aperture size of the first aperture 4 near the concave spherical end mirror 5. Figure 2 The illustrated embodiment shows four sets of intensity lines for four spectral bands. It is important to note that all these laser spectral lines of different wavelengths are generated independently in their respective dedicated gain regions and resonant cavities, and there is no coupling between these laser beams.

[0060] According to some embodiments of this disclosure, such as Figure 4 As shown, according to the different requirements of the number of spectral lines required by the multi-band multi-line slab CO2 laser, the long rectangular concave spherical end mirror 5 is replaced by multiple short concave spherical end mirrors 10; at the same time, the discharge electrode 1 is replaced by multiple narrow discharge electrodes 8, and the RF power supply 2 is replaced by multiple low-power RF power supplies 9.

[0061] According to some embodiments of this disclosure, the multi-band multi-line slab CO2 laser includes: multiple narrow discharge electrodes 8, multiple low-power radio frequency power supplies 9, multiple short concave spherical end reflectors 10, a first aperture 4, a reflective plane diffraction grating 3, a third aperture (not shown in the figure), a concave spherical output mirror 7, and a second aperture 6, wherein the third aperture is disposed close to the reflective plane diffraction grating 3.

[0062] According to some embodiments of this disclosure, the radius of curvature of the concave spherical output mirror 7 is approximately the same as that of the short strip concave spherical end reflector 10, but the radius of curvature of the concave spherical output mirror 7 is slightly larger than that of the short strip concave spherical end reflector 10.

[0063] According to some embodiments of this disclosure, both the elongated rectangular concave spherical end reflector 5 and the short concave spherical end reflector 10 are rectangular in shape.

[0064] According to some embodiments of this disclosure, the short concave spherical end mirror 10, the reflective planar diffraction grating 3, and the concave spherical output mirror 7 together form a folded near-concentric stable resonant cavity.

[0065] According to some embodiments of this disclosure, the multi-band multi-line slab CO2 laser has a dual-band multi-line structure, and the output laser spectrum includes 4 to 6 strong spectral lines from both the 9P and 10P bands. For example... Figure 4 As shown, each transition band includes four laser spectral lines, forming two sets of laser spectral lines. This laser can output eight laser spectral lines in total: 10P18, 10P20, 10P22, and 10P24 of the 10P band and 9P16, 9P18, 9P20, and 9P22 of the 9P band. These lines are output along the central axis by a concave spherical output mirror 7.

[0066] According to some embodiments of this disclosure, a structure similar to the dual-band multi-line slab CO2 laser can also be designed such that the spectrum of the output laser contains 4 to 6 strong spectral lines in both the 9P and 10R bands.

[0067] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0068] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A multi-band, multi-line slab CO2 laser, characterized in that, include: Two pairs of discharge electrodes, two radio frequency power supplies, two long rectangular concave spherical end reflectors, a first aperture, a concave spherical output mirror, a second aperture, a reflective plane diffraction grating, and a third aperture; The concave spherical output mirror, the second aperture, the reflective planar diffraction grating, and the third aperture are located on the central axis of the laser. The two pairs of discharge electrodes and the two elongated rectangular concave spherical end mirrors are symmetrically located on both sides of the central axis. The first aperture is arranged in a row on one side of the mirror surface of the elongated rectangular concave spherical end mirror. The third aperture is arranged close to the reflective planar diffraction grating. The two long rectangular concave spherical end mirrors, the reflective planar diffraction grating, and the concave spherical output mirror together form a folded near-concentric stable resonant cavity. The laser beam is output from the concave spherical output mirror along the central axis. The laser spectrum contains multiple transition lines of the CO2 laser in the wavelength range of 9 μm-11 μm, belonging to four transition bands: 10P, 10R, 9P, and 9R, which are the P and R branches of the 00°1-10°0 band and the 00°1-02°0 band of the CO2 molecule.

2. The multi-band, multi-line slab CO2 laser according to claim 1, characterized in that, The laser mixing gas in the multi-band multi-line slab CO2 laser includes either the laser mixing gas of a conventional slab CO2 laser or the isotopic CO2 laser mixing gas.

3. The multi-band, multi-line slab CO2 laser according to claim 1, characterized in that, Depending on the different requirements for the number of spectral lines required by the multi-band multi-line slab CO2 laser, the long rectangular concave spherical end mirror is replaced by multiple short concave spherical end mirrors; at the same time, the discharge electrode is replaced by multiple narrow discharge electrodes, and the radio frequency power supply is replaced by multiple low-power radio frequency power supplies.

4. The multi-band, multi-line slab CO2 laser according to claim 3, characterized in that, The multi-band, multi-line slab CO2 laser has a dual-band, multi-line structure, and the output laser spectrum contains 4 to 6 strong spectral lines in both the 9P and 10P bands.

5. The multi-band, multi-line slab CO2 laser according to claim 3, characterized in that, The multi-band, multi-line slab CO2 laser has a dual-band, multi-line structure, and the output laser spectrum contains 4 to 6 strong spectral lines in both the 9P and 10R bands.

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