Laser based on single-frequency optical oscillation and laser output method

Abstract

The invention discloses a laser based on single-frequency continuous light oscillation and a laser output method, and the laser comprises a first reference laser which generates a first wavelength laser; the second reference laser generates second wavelength laser, and the second wavelength laser is single-frequency continuous light; the frequency multiplication module is coupled with the first reference laser and is used for converting the first wavelength laser into an up-conversion signal; and the sum frequency module is respectively coupled with the frequency multiplication module and the second reference laser, and is used for carrying out sum frequency on the second wavelength laser and the up-conversion signal to generate a target wavelength laser output signal of 184.13-283.81 nm. According to the laser structure provided by the invention, components are convenient to construct, the power requirement for reference light is low, the conversion efficiency is high during frequency conversion, time matching does not need to be carried out on various reference light during frequency sum, and deep ultraviolet band laser can be output as continuous light or pulsed light.

Description

Technical Field

[0001] The present invention belongs to the technical field of lasers, and in particular relates to a laser based on single-frequency light oscillation and a laser output method. Background Art

[0002] With the advancement of optical technology, the application fields of lasers with wavelengths near 193nm are constantly expanding, including photolithography, defect detection, spectroscopy, etc. Generally, the generation of 193nm wavelength lasers relies on nonlinear optical frequency conversion technology.

[0003] As disclosed in patent CN105191026A, a 193 nm laser and an inspection system are used to generate an output wavelength of about 193.4 nm, including a fundamental laser, an optical parameter generator, a fourth harmonic generator, and a frequency mixing module. The optical parameter generator coupled to the fundamental laser can generate a down-converted signal. The fourth harmonic generator coupled to the optical parameter generator or the fundamental laser can generate the fourth harmonic. The frequency mixing module coupled to the optical parameter generator and the fourth harmonic generator can generate a laser output at a frequency equal to the sum of the fourth harmonic and twice the frequency of the down-converted signal.

[0004] However, as in the above-mentioned prior art, when generating a 193nm pulsed laser, it is difficult to match each reference optical signal, and precise adjustment is required to achieve the coincidence of each reference optical pulse in time and space.

[0005] Therefore, it is an urgent problem to be solved by technical personnel in this field to explore lasers with convenient component assembly, low reference light power requirements, and convenient matching, so as to achieve high reference light frequency conversion efficiency and output of continuous or pulsed lasers in the deep ultraviolet band. Summary of the invention

[0006] In view of the defects existing in the above-mentioned prior art, the present invention provides a laser and a laser output method based on single-frequency light oscillation, wherein the laser specifically comprises: a first reference laser, which generates a first wavelength laser; a second reference laser, which generates a second wavelength laser, and the second wavelength laser is a single-frequency continuous light; a frequency doubling module, which is coupled to the first reference laser and is used to convert the first wavelength laser into an up-conversion signal; and a sum frequency module, which is respectively coupled to the frequency doubling module and the second reference laser and is used to sum frequency the second wavelength laser and the up-conversion signal to generate a target wavelength laser output signal of 184.13-283.81nm.

[0007] The laser structure provided by the present invention has convenient component assembly, low power requirement for reference light, high conversion efficiency during frequency conversion, and no need for spatial matching of various reference lights during frequency summing, thereby enabling the output of deep ultraviolet band laser in the form of continuous light or pulsed light.

[0008] In a first aspect, the present invention provides a laser based on single-frequency light oscillation, specifically comprising:

[0009] A first reference laser generates a laser with a first wavelength;

[0010] A second reference laser generates a second wavelength laser, and the second wavelength laser is a single-frequency continuous light;

[0011] A frequency doubling module, coupled to the first reference laser, for converting the first wavelength laser into an up-conversion signal;

[0012] The frequency summing module is coupled to the frequency doubling module and the second reference laser respectively, and is used to perform frequency summing on the second wavelength laser and the up-conversion signal to generate a target wavelength laser output signal of 184.13-283.81nm.

[0013] Furthermore, the wavelength of the first wavelength laser is 970-1530 nm, and the wavelength of the second wavelength laser is 1530-2200 nm.

[0014] Further, the frequency doubling module includes a first frequency doubling module and a second frequency doubling module, the first frequency doubling module is coupled to the first reference laser, and the second frequency doubling module is coupled to the first frequency doubling module;

[0015] A first frequency doubling module is used to perform a first-stage frequency doubling on the first wavelength laser to generate a primary up-conversion signal, wherein the wavelength of the primary up-conversion signal is 485-765nm;

[0016] The second frequency multiplication module is used to perform a second frequency multiplication on the primary up-conversion signal to generate an up-conversion signal, and the wavelength of the up-conversion signal is 242.5-382.5nm.

[0017] Furthermore, the sum frequency module includes at least one resonant cavity, the resonant cavity includes at least one sum frequency medium, and the sum frequency medium is a nonlinear medium.

[0018] Furthermore, the resonant cavity also includes a light combining and splitting element and a light beam transmission control element;

[0019] The light combining and splitting element is used for combining the second wavelength laser and the up-conversion signal, and / or for combining the second wavelength laser and the sum frequency signal, and / or for splitting the second wavelength laser and the target wavelength laser, and / or for splitting the second wavelength laser and the sum frequency signal;

[0020] The beam transmission control element is used for focusing the second wavelength laser and / or for reflecting the second wavelength laser.

[0021] Further, the light combining and splitting element includes a dichroic mirror, and the light beam transmission control element includes at least one of a total reflection mirror, a total reflection concave mirror, and a partial reflection mirror;

[0022] The resonant cavity further includes an adjusting element, which is used to adjust the resonant cavity to match the wavelength of the second wavelength laser.

[0023] Furthermore, the resonant cavity further includes a first sum frequency medium, and a first total reflection concave mirror and a second total reflection concave mirror arranged on both sides of the first sum frequency medium, and a first dichroic mirror arranged between the first total reflection concave mirror and the first sum frequency medium, and a second dichroic mirror arranged between the first sum frequency medium and the second total reflection concave mirror;

[0024] The first total reflection concave mirror is used for reflecting and focusing the second wavelength laser;

[0025] The first dichroic mirror is used for combining the second wavelength laser and the up-conversion signal, or for combining the second wavelength laser and the previous level sum frequency signal;

[0026] The second dichroic mirror is used for beam splitting the second wavelength laser and the target wavelength laser, or for beam splitting the second wavelength laser and the current level sum frequency signal, or for beam splitting the second wavelength laser and the current level sum frequency signal;

[0027] The second total reflection concave mirror is used to reflect the second wavelength laser remaining after the sum frequency treatment of the first sum frequency medium.

[0028] Furthermore, the resonant cavity also includes a partial reflection mirror and a total reflection mirror. The partial reflection mirror is coupled to the photodetector, and the total reflection mirror is fixedly arranged on the adjustment element. The partial reflection mirror is used to couple the second wavelength laser into the resonant cavity, and the total reflection mirror is used to reflect the second wavelength laser to the first total reflection concave mirror.

[0029] Furthermore, the resonant cavity further comprises a partial reflector, a second sum frequency medium, a total reflector, and a third dichroic mirror and a fourth dichroic mirror arranged on both sides of the second sum frequency medium, which are coupled in sequence;

[0030] The third dichroic mirror is used for combining the second wavelength laser and the up-conversion signal;

[0031] The fourth dichroic mirror is used for splitting the second wavelength laser and the current level sum frequency signal, and inputting the second wavelength laser into the total reflection mirror, and inputting the current level sum frequency signal into the first dichroic mirror.

[0032] Furthermore, the sum frequency module includes a first sum frequency module and a second sum frequency module, each of which includes at least one resonant cavity, the first sum frequency module is coupled to the frequency doubling module and the second reference laser, and the second sum frequency module is coupled to the first sum frequency module and the second reference laser;

[0033] The first sum frequency module generates a primary sum frequency signal, and the wavelength of the primary sum frequency signal is 209.32-328.85nm;

[0034] The second frequency addition module generates a target wavelength laser output signal, and the wavelength of the target wavelength laser is 184.13-283.81nm.

[0035] Furthermore, it also includes a beam splitting module coupled to the second laser, which is used to perform beam splitting processing on the second wavelength laser to generate a first-order sum frequency light of the second wavelength laser and a second-order sum frequency light of the second wavelength laser;

[0036] The sum-frequency module includes a first sum-frequency module and a second sum-frequency module, each of which includes at least one resonant cavity, the first sum-frequency module is respectively coupled to the frequency doubling module and the beam splitting module, and the second sum-frequency module is respectively coupled to the first sum-frequency module and the beam splitting module;

[0037] The first sum-frequency module is used to perform sum-frequency operation on the up-converted frequency signal and the primary sum-frequency light of the second wavelength laser to generate a primary sum-frequency signal;

[0038] The second sum frequency module is used to sum the primary sum frequency signal with the secondary sum frequency light of the second wavelength laser to generate a target wavelength laser output signal;

[0039] The wavelength of the primary sum frequency signal is 209.32-325.85 nm, and the wavelength of the target wavelength laser is 184.13-283.81 nm.

[0040] In a second aspect, the present invention further provides a laser output method based on single-frequency light oscillation, using the laser based on single-frequency light oscillation as described above, specifically comprising the following steps:

[0041] Emitting a laser with a first wavelength through a first reference laser;

[0042] The second wavelength laser is emitted by a second reference laser, wherein the second wavelength laser is a single-frequency continuous light;

[0043] Converting the first wavelength laser into an up-conversion signal in a frequency doubling module;

[0044] The second wavelength laser and the up-conversion signal are frequency-added in the frequency addition module to generate a target wavelength laser output signal of 184.13-283.81 nm.

[0045] The present invention provides a laser based on single-frequency light oscillation and a laser output method, which at least include the following beneficial effects:

[0046] (1) The laser structure provided by the present invention has convenient component assembly, low power requirement for reference light, high conversion efficiency during frequency conversion, no need for time matching of various reference lights during frequency summing, and more convenient spatial matching of various reference lights, which can realize the output of deep ultraviolet laser in the form of continuous light or pulsed light.

[0047] (2) The laser provided by the present invention reduces the power requirement for a single laser by coordinating the outputs of multiple wavelength lasers such as the first reference laser and the second reference laser, thereby effectively reducing the difficulty of building and configuring the components in the laser.

[0048] (3) The sum frequency module provided by the present invention can not only increase the power density of the reference light and effectively improve the power conversion efficiency during nonlinear frequency conversion, but also realize deep ultraviolet band laser output without time matching the two wavelengths of the fundamental frequency light emitted by the first reference laser and the second reference laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic diagram of the structure of a laser based on single-frequency light oscillation provided by the present invention;

[0050] Figure 2 A schematic diagram of the structure of a laser with multiple frequency doubling modules according to an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of the structure of a first single resonant cavity of a certain embodiment provided by the present invention;

[0052] Figure 4 A schematic diagram of the structure of a second single resonant cavity of an embodiment provided by the present invention;

[0053] Figure 5 A schematic diagram of the structure of a first part of a dual-resonance cavity in an embodiment provided by the present invention;

[0054] Figure 6 A schematic diagram of the structure of a second dual-resonance cavity of an embodiment provided by the present invention;

[0055] Figure 7 A schematic diagram of the structure of a laser having a first plurality of sum frequency modules according to an embodiment of the present invention;

[0056] Figure 8 A schematic diagram of the structure of a laser with multiple sum frequency modules of a second embodiment provided by the present invention;

[0057] Fig. 9 A schematic flow chart of a laser output method based on single-frequency light oscillation provided by the present invention. DETAILED DESCRIPTION

[0058] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0060] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0061] It is an urgent problem to be solved by technical personnel in this field to explore lasers with easy component assembly, low reference light power requirements, and convenient matching to achieve high reference light frequency conversion efficiency and output of continuous or pulsed lasers in the deep ultraviolet band.

[0062] At least one beam of single-frequency continuous light is used as the reference light. Through frequency sum processing with other reference lights, there is no need to time match various reference lights, and the spatial matching of various reference lights is more convenient, which can realize the output of deep ultraviolet band laser in the form of continuous light or pulsed light.

[0063] like Figure 1 As shown, the present invention provides a laser based on single-frequency light oscillation, which specifically includes:

[0064] A first reference laser generates a laser with a first wavelength;

[0065] A second reference laser generates a second wavelength laser, and the second wavelength laser is a single-frequency continuous light;

[0066] A frequency doubling module, coupled to the first reference laser, for converting the first wavelength laser into an up-conversion signal;

[0067] The frequency summing module is coupled to the frequency doubling module and the second reference laser respectively, and is used to perform frequency summing on the second wavelength laser and the up-conversion signal to generate a target wavelength laser output signal of 184.13-283.81nm.

[0068] The first reference laser generates a first wavelength laser, the wavelength of the first wavelength laser is 970-1530nm, the first wavelength laser can be continuous light or pulse light, and the pulse time width can be any width.

[0069] The first reference laser may include a seed light source and a single-stage amplifier structure, or a seed light source and a multi-stage amplifier structure. Of course, the first reference laser may also include a laser oscillator cavity, and the first wavelength laser is directly output by the laser oscillator cavity. The laser oscillator cavity that oscillates and outputs the first wavelength laser may be a planar cavity, a plano-concave cavity, a convex cavity, etc., and no further restrictions are made on the mode structure, limited mode characteristics, and output power of the laser oscillator cavity that oscillates and outputs the first wavelength laser.

[0070] The second reference laser generates a second wavelength laser, the wavelength of the second wavelength laser is 1530-2200nm, and the second wavelength laser needs to be single-frequency continuous light.

[0071] The second reference laser may include a seed light source and a single-stage amplifier structure, or a seed light source and a multi-stage amplifier structure. Of course, the second reference laser may also include a laser oscillator cavity, and the second wavelength laser is directly output by the laser oscillator cavity. The laser oscillator cavity that oscillates and outputs the second wavelength laser may be a surface cavity, a plano-concave cavity, a convex cavity, etc., and no further restrictions are made on the mode structure, limited mode characteristics, and output power of the laser oscillator cavity that oscillates and outputs the first wavelength laser.

[0072] The frequency doubling module is used to perform up-conversion processing on the first wavelength laser. The first wavelength laser forms an up-conversion signal after passing through the frequency doubling module, and the up-conversion signal is frequency-summed with the second wavelength laser. The frequency doubling module can include a single frequency doubling module or multiple frequency doubling modules.

[0073] The laser structure provided by the present invention has convenient component assembly, low power requirement for reference light, high conversion efficiency during frequency conversion, no need for time and space matching of various reference lights during frequency summing, and more convenient spatial matching of various reference lights, which can realize the output of deep ultraviolet band laser in the form of continuous light or pulsed light.

[0074] Preferably, Figure 2 As shown, the frequency doubling module includes a first frequency doubling module and a second frequency doubling module, wherein the first frequency doubling module is coupled to the first reference laser, the second frequency doubling module is coupled to the first frequency doubling module, and the second frequency doubling module is also coupled to the sum frequency module.

[0075] By setting up two frequency doubling modules, the first wavelength laser is frequency-doubled in two stages, which can not only improve the conversion efficiency and increase the adjustable range of the wavelength, but also improve the design flexibility and the overall stability of the sum frequency module.

[0076] The first frequency doubling module is used to perform a first-stage frequency doubling on the first wavelength laser to generate a first up-conversion signal, wherein the wavelength of the first up-conversion signal is 485-765nm.

[0077] The first frequency doubling module may adopt a single-pass frequency doubling cavity, or a double-pass frequency doubling cavity, a multi-pass long cavity, a ring-shaped frequency doubling cavity, etc. The specific structure of the first frequency doubling module is not further limited here.

[0078] The second frequency multiplication module is used to perform a second frequency multiplication on the first up-conversion signal to generate a second up-conversion signal, and the wavelength of the second up-conversion signal is 242.5-382.5nm.

[0079] The second frequency doubling module may adopt a single-pass frequency doubling cavity, or a double-pass frequency doubling cavity, a multi-pass long cavity, a ring-shaped frequency doubling cavity, etc., and the specific structure of the first frequency doubling module is not further limited here.

[0080] For the method of outputting the target wavelength laser by coordinating multiple wavelength lasers, the sum frequency module is an important component. The sum frequency module performs sum frequency on the two reference beams from the first reference laser and the second reference laser, and finally outputs the target wavelength laser.

[0081] The frequency summing module is coupled to the frequency doubling module and the second reference laser respectively, and is used to perform frequency summing on the second wavelength laser and the up-conversion signal to generate a target wavelength laser output signal of 184.13-283.81nm.

[0082] The sum frequency module includes at least one resonant cavity, the resonant cavity includes at least one sum frequency medium, the sum frequency medium is a nonlinear medium, the nonlinear medium can be a crystal, a waveguide, or a combination structure of a crystal and a waveguide.

[0083] For crystal nonlinear media, you can choose BBO, KTP, KDP, LBO, LN, LT, etc., and for waveguides, you can choose Ti:LN, LN, LT, etc. In the nonlinear medium, nonlinear frequency conversion occurs. When a resonant cavity is formed by the combination of crystal and waveguide, they can be connected in different ways to form a combined type of sum frequency medium, thereby achieving more efficient frequency conversion or meeting specific scene requirements, such as embedding crystals in waveguides, waveguide-crystal-waveguide combination structures, etc. Different nonlinear media can undergo the same nonlinear frequency conversion process or different nonlinear frequency conversion processes.

[0084] The resonant cavity may also include a light combining and splitting element and a light beam transmission control element;

[0085] The light combining and splitting element is used for combining the second wavelength laser and the up-conversion signal, and / or for combining the second wavelength laser and the sum frequency signal, and / or for splitting the second wavelength laser and the target wavelength laser, and / or for splitting the second wavelength laser and the sum frequency signal;

[0086] The light combining and splitting element may be an integrated element including all the functions mentioned above, or may be separated into a plurality of elements, each of which realizes at least one of the functions mentioned above.

[0087] The beam transmission control element is used to focus the second wavelength laser and / or to reflect the second wavelength laser. The beam transmission control element can ensure the transmission oscillation of the beam in the resonant cavity and ensure that the beam has the maximum power density in the nonlinear medium of the resonant cavity.

[0088] The light combining and splitting element includes a dichroic mirror, and the light beam transmission control element includes at least one of a total reflection mirror, a total reflection concave mirror and a partial reflection mirror;

[0089] The resonant cavity further includes an adjusting element, which is used to adjust the resonant cavity to match the wavelength of the second wavelength laser.

[0090] The relative positions of the sum frequency medium, light combining and splitting elements, light beam transmission control elements, etc. in the resonant cavity can be connected and placed according to the design and requirements of the resonant cavity.

[0091] The sum frequency module is coupled to the frequency doubling module and the second reference laser respectively, wherein the coupling with the frequency doubling module is direct coupling, that is, the sum frequency module is directly connected to the frequency doubling module to receive the up-conversion signal from the frequency doubling module.

[0092] The coupling between the sum frequency module and the second reference laser may be a direct coupling method or an indirect coupling method.

[0093] The direct coupling between the sum frequency module and the second reference laser means that the sum frequency module is directly connected to the second reference laser and receives all the second wavelength laser light from the second laser.

[0094] At this time, the up-conversion signal of 242.5-382.5nm is combined with the second wavelength laser of 1530-2200nm in the sum frequency module to convert the wavelength into a laser output of 184.13-283.81nm. The second wavelength laser is a single-frequency continuous light, which is injected into the resonant cavity of the sum frequency module and oscillates in the cavity, thereby increasing the power density and the sum frequency conversion efficiency, thereby achieving high-efficiency sum frequency laser output.

[0095] When the sum frequency module and the second reference laser are directly coupled, the resonant cavity of the sum frequency module can be as follows: Figure 3 A single resonant cavity is shown.

[0096] A single resonant cavity for sum frequency processing includes a first sum frequency medium (sum frequency medium 2), and a first total reflection concave mirror M3 and a second total reflection concave mirror M4 disposed on both sides of the first sum frequency medium, and a first dichroic mirror L3 disposed between the first total reflection concave mirror M3 and the first sum frequency medium (sum frequency medium 2), and a second dichroic mirror L4 disposed between the first sum frequency medium (sum frequency medium 2) and the second total reflection concave mirror M4;

[0097] The first total reflection concave mirror is used for reflecting and focusing the second wavelength laser;

[0098] The first dichroic mirror is used for combining the second wavelength laser and the up-conversion signal;

[0099] The second dichroic mirror is used for splitting the second wavelength laser and the target wavelength laser;

[0100] The second total reflection concave mirror is used to reflect the second wavelength laser remaining after the sum frequency treatment of the first sum frequency medium.

[0101] The first total reflection concave mirror and the second total reflection concave mirror are used to reflect and focus the second wavelength laser oscillating in the resonant cavity, and form two beam waist positions in the cavity. The sum frequency medium is also located at the two beam waist positions in the cavity, so that the beam diameter at the nonlinear medium is minimized and the energy density is maximized, thereby obtaining the best sum frequency efficiency.

[0102] In addition, if Figure 4 As shown, based on the above structure ( Figure 3 ), the single resonant cavity may also include a partial reflector M1, a second sum frequency medium (sum frequency medium 1), a total reflector M2, which are coupled in sequence, and a third dichroic mirror L1 and a fourth dichroic mirror L2 arranged on both sides of the second sum frequency medium (sum frequency medium 1), the third dichroic mirror is coupled to the frequency doubling module, the partial reflector M1 is coupled to the photodetector PD, and the total reflector M2 is fixedly arranged on the adjustment element (such as piezoelectric ceramic PZT). The total reflector is fixed on the piezoelectric ceramic, and the piezoelectric ceramic can receive the locking signal and adjust the resonant cavity length in real time to achieve the locking of the cavity mode with the wavelength and frequency of the second wavelength laser, thereby achieving the oscillation and enhancement of the second wavelength laser in the resonant cavity.

[0103] At this time, compared with the single resonant cavity of the above structure ( Figure 3 ), Figure 4 In the single resonant cavity, the first dichroic mirror is used to combine the second wavelength laser and the previous level sum frequency signal, and the previous level sum frequency signal at this time is the current level sum frequency signal input by the fourth dichroic mirror;

[0104] The partial reflector is used to couple the second wavelength laser into the resonant cavity;

[0105] The third dichroic mirror is used for combining the second wavelength laser and the up-conversion signal;

[0106] The fourth dichroic mirror is used for splitting the second wavelength laser and the current level sum frequency signal, and inputting the second wavelength laser into the total reflection mirror, and inputting the current level sum frequency signal into the first dichroic mirror;

[0107] The total reflection mirror is used for reflecting the second wavelength laser to the first total reflection concave mirror.

[0108] Specifically, when the second wavelength laser passes through the partial reflector M1, a portion of it is transmitted and coupled into the resonant cavity, and the other portion is reflected and hits the photodetector PD. The light entering the photodetector generates an error signal.

[0109] The third dichroic mirror L1 combines the part of the second wavelength laser beam entering from the partial reflector M1 and the up-conversion signal input by the frequency doubling module, and enters the second sum frequency medium to obtain the current level sum frequency signal (ie, Figure 4 The first sum frequency signal in the signal), and at the same time, also includes the remaining second wavelength laser.

[0110] The remaining second wavelength laser is totally reflected by the total reflection mirror M2 and reaches the first total reflection concave mirror M3, which reflects and focuses the remaining second wavelength laser. The first sum frequency signal and the remaining second wavelength laser are combined in the first dichroic mirror L3 and then enter the first sum frequency medium for sum frequency. The focusing of the remaining second wavelength laser by the first total reflection concave mirror M3 enables the remaining second wavelength laser to have the maximum light intensity density in the first sum frequency medium, thereby achieving the highest sum frequency efficiency of the remaining second wavelength laser and the first sum frequency signal.

[0111] After being sum-frequency processed by the first sum-frequency medium, it is split by the second dichroic mirror L4 to form a target wavelength laser and a residual second wavelength laser. The target wavelength laser is output from the resonant cavity, and the residual second wavelength laser is reflected by the second total-reflection concave mirror M4 and then input into the partial reflection mirror M1, where it coincides with the second wavelength laser input from outside the resonant cavity, participates in the next or next level of sum-frequency processing, and continues to oscillate in the resonant cavity.

[0112] When the sum frequency module and the second reference laser are directly coupled, the resonant cavity of the sum frequency module can also be used as follows: Figure 5 ,like Figure 6 The dual resonant cavity shown.

[0113] Will be like Figure 5 ,like Figure 6 The resonant cavity structures shown in the figure are combined to form a double resonant cavity, that is, the front end of the sum frequency module selects the first resonant cavity (such as Figure 5 As shown), the back end of the sum frequency module selects the second resonant cavity (as shown Figure 6 shown).

[0114] The first resonant cavity and the second resonant cavity both include a first sum frequency medium (sum frequency medium 1), and a first total reflection concave mirror M3 and a second total reflection concave mirror M4 disposed on both sides of the first sum frequency medium (sum frequency medium 1), and a first dichroic mirror L3 or L1 disposed between the first total reflection concave mirror M3 and the first sum frequency medium, and a second dichroic mirror L4 or L2 disposed between the first sum frequency medium and the second total reflection concave mirror M4;

[0115] The first total reflection concave mirror M3 is used for reflecting and focusing the second wavelength laser;

[0116] The first dichroic mirror L1 is used for combining the second wavelength laser and the up-conversion signal; the first dichroic mirror L3 is used for combining the second wavelength laser and the previous level sum frequency signal, where the previous level sum frequency signal is the current level sum frequency signal generated by the beam splitting of the first dichroic mirror L2;

[0117] The second dichroic mirror L4 is used for splitting the second wavelength laser and the target wavelength laser; the first dichroic mirror L2 is used for splitting the second wavelength laser and the current level sum frequency signal;

[0118] The second total reflection concave mirror is used to reflect the second wavelength laser remaining after the sum frequency treatment of the first sum frequency medium.

[0119] In addition, the first resonant cavity and the second resonant cavity also include a partial reflection mirror M1 and a total reflection mirror M2. The partial reflection mirror M1 is coupled to the photodetector PD, and the total reflection mirror M2 is fixedly arranged on the piezoelectric ceramic PZT. The partial reflection mirror M1 is used to couple the second wavelength laser into the resonant cavity, and the total reflection mirror M2 is used to reflect the second wavelength laser to the first total reflection concave mirror M3.

[0120] Specifically, when the second wavelength laser of the second reference laser passes through the partial reflector M1 of the first resonant cavity, a portion of it is transmitted and coupled into the interior of the resonant cavity, and the other portion is reflected and hits the photodetector PD. The light entering the photodetector generates an error signal.

[0121] The second wavelength laser entering the resonant cavity is totally reflected by the total reflection mirror M2 and reaches the first total reflection concave mirror M3, which reflects and focuses the second wavelength laser. The up-converted signal and the second wavelength laser are combined in the first dichroic mirror L1 and then enter the first sum frequency medium for sum frequency. The focusing of the second wavelength laser by the first total reflection concave mirror M3 enables the second wavelength laser to have the maximum light intensity density in the first sum frequency medium, thereby achieving the highest sum frequency efficiency of the second wavelength laser and the up-converted signal.

[0122] After passing through the sum frequency of the first sum frequency medium, it is split by the second dichroic mirror to form the current level sum frequency signal and the remaining second wavelength laser. The current level sum frequency signal is output from the resonant cavity, and the remaining second wavelength laser is reflected by the second total reflection concave mirror and then input into the partial reflection mirror, overlaps with the second wavelength laser input from the resonant cavity, participates in the next sum frequency processing, and continues to oscillate in the resonant cavity.

[0123] The second wavelength laser from the first resonant cavity or the second reference laser passes through the partial reflector M1 of the second resonant cavity, a portion of which is transmitted and coupled into the resonant cavity, and the other portion is reflected and hits the photodetector PD. The light entering the photodetector generates an error signal.

[0124] The second wavelength laser light entering the resonant cavity is totally reflected by the total reflection mirror M2 and reaches the first total reflection concave mirror M3. The first total reflection concave mirror M3 reflects and focuses the second wavelength laser light.

[0125] Afterwards, the current level sum frequency signal (for this sum frequency, it belongs to the previous level sum frequency signal, Figure 4 The first sum frequency signal in the first dichroic mirror L3 is combined with the second wavelength laser and then enters the first sum frequency medium for sum frequency. The first total reflection concave mirror M3 focuses the second wavelength laser so that the second wavelength laser has the maximum light intensity density in the first sum frequency medium, achieving the highest sum frequency efficiency of the second wavelength laser and the previous sum frequency signal.

[0126] After being sum-frequency processed by the first sum-frequency medium, it is split by the second dichroic mirror L4 to form a target wavelength laser signal and a residual second wavelength laser. The target wavelength laser signal is output from the resonant cavity, and the residual second wavelength laser is reflected by the second total-reflection concave mirror M4 and then input into the partial reflection mirror M1, where it overlaps with the second wavelength laser input from outside the resonant cavity, participates in the next sum-frequency processing, and continues to oscillate in the resonant cavity.

[0127] The direct coupling of the sum frequency module and the second reference laser is carried out by selecting and determining the resonant cavity type of the sum frequency module to meet the requirements of different application scenarios.

[0128] After determining whether the resonant cavity is a single resonant cavity or a double resonant cavity, multiple sum frequencies can be set. For example, it can be set to two sum frequencies, with the first sum frequency passing through a first sum frequency module and the second sum frequency passing through a second sum frequency module.

[0129] The first frequency summing is to sum the up-converted signal output by the frequency doubling module with the second wavelength laser output by the second reference laser to obtain a 209.32-328.85nm laser. After summing, it is then summed with the second wavelength laser to finally obtain a 184.13-283.81nm wavelength laser output.

[0130] Specifically, if Figure 7 As shown, the sum frequency module includes a first sum frequency module and a second sum frequency module, each of which includes at least one resonant cavity, the first sum frequency module is coupled to the frequency doubling module and the second reference laser, and the second sum frequency module is coupled to the first sum frequency module;

[0131] The first sum frequency module generates a primary sum frequency signal, and the wavelength of the primary sum frequency signal is 209.32-328.85m;

[0132] The second frequency addition module generates a target wavelength laser output signal, and the wavelength of the target wavelength laser output signal is 184.13-283.81 nm.

[0133] The above embodiment shows the case where the sum frequency module is directly coupled to the second reference laser. In practical applications, the sum frequency module may also be indirectly coupled to the second reference laser.

[0134] For the indirect coupling method between the sum frequency module and the second reference laser, beam splitting is generally performed at the output end of the second reference laser. At this time, for the second wavelength laser after beam splitting, the sum frequency module can choose to perform two sum frequencies. That is, the second reference laser is first coupled with the beam splitting module, and then coupled with the sum frequency module. Among them, the first sum frequency is to perform sum frequency on the up-conversion signal output by the frequency doubling module and the second wavelength laser output by the second reference laser to obtain a 209.32-325.85nm laser. After the sum frequency, it is then sum frequency with the second wavelength laser to finally obtain a laser output with a wavelength of 184.13-283.81nm.

[0135] Specifically, if Figure 8 As shown, the sum-frequency module includes a first sum-frequency module and a second sum-frequency module, each of which includes at least one resonant cavity, the first sum-frequency module is respectively coupled to the frequency doubling module and the beam splitting module, and the second sum-frequency module is respectively coupled to the first sum-frequency module and the beam splitting module;

[0136] The first sum-frequency module is used to perform sum-frequency operation on the up-converted frequency signal and the primary sum-frequency light of the second wavelength laser to generate a primary sum-frequency signal;

[0137] The second sum frequency module is used to perform sum frequency on the primary sum frequency signal and the secondary sum frequency light of the second wavelength laser to generate a target wavelength laser output signal.

[0138] The wavelength of the primary sum frequency signal is 209.32-325.85 nm, and the wavelength of the target wavelength laser output signal is 184.13-283.81 nm.

[0139] At this time, in the first frequency addition module, the up-conversion signal of 242.5-382.5nm is frequency-added with the second wavelength laser of 1530-2200nm to convert the wavelength into a primary frequency addition signal of 209.32-325.85nm. In the second frequency addition module, the primary frequency addition signal of 209.32-325.85nm is frequency-added with the second wavelength laser of 1530-2200nm to convert the wavelength into a laser output with a wavelength of 184.13-283.82nm.

[0140] The method of indirectly coupling the sum frequency module with the second reference laser is selected, and the sum frequency module for performing the sum frequency twice can also be selected as follows in each sum frequency module. Figure 3 or Figure 4 A single resonant cavity as shown. Alternatively, Figure 5 , Figure 6 Combined dual resonant cavity.

[0141] The laser provided by the present invention is described below by taking a laser with an output wavelength of 193 nm as an example.

[0142] In this embodiment, the wavelength of the target wavelength laser is 193 nm. At this time, the wavelength of the first wavelength laser generated by the first reference laser is 1030 nm, the wavelength of the second wavelength laser generated by the second reference laser is 1560 nm, and the second wavelength laser is single-frequency continuous light.

[0143] The first wavelength laser of 1030nm is up-converted in the frequency doubling module, and the specific up-conversion method is quadruple frequency doubling to obtain an up-converted signal of 257nm.

[0144] The 257nm up-converted signal is frequency-summed twice with the second wavelength laser of 1560nm from the second reference laser to generate a 193nm target wavelength laser output signal.

[0145] like Fig. 9 As shown, the present invention also provides a laser output method based on single-frequency light oscillation, using the laser based on single-frequency light oscillation as described above, specifically comprising the following steps:

[0146] Emitting a laser with a first wavelength through a first reference laser;

[0147] The second wavelength laser is emitted by a second reference laser, wherein the second wavelength laser is a single-frequency continuous light;

[0148] Converting the first wavelength laser into an up-conversion signal in a frequency doubling module;

[0149] The second wavelength laser and the up-conversion signal are frequency-added in the frequency addition module to generate a target wavelength laser output signal of 184.13-283.81 nm.

[0150] The present invention provides a laser based on single-frequency light oscillation and a laser output method, which at least include the following beneficial effects:

[0151] (1) The laser structure provided by the present invention has convenient component assembly, low power requirement for reference light, high conversion efficiency during frequency conversion, no need for time matching of various reference lights during frequency summing, and more convenient spatial matching of various reference lights, which can realize the output of deep ultraviolet laser in the form of continuous light or pulsed light.

[0152] (2) The laser provided by the present invention reduces the power requirement for a single laser by coordinating the outputs of multiple wavelength lasers such as the first reference laser and the second reference laser, thereby effectively reducing the difficulty of building and configuring the components in the laser.

[0153] (3) The sum frequency module provided by the present invention can not only increase the power density of the reference light and effectively improve the power conversion efficiency during nonlinear frequency conversion, but also realize deep ultraviolet band laser output without time matching the two wavelengths of the fundamental frequency light emitted by the first reference laser and the second reference laser.

[0154] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A laser based on single-frequency light oscillation, characterized in that: Specifically include: A first reference laser generates a laser with a first wavelength; A second reference laser generates a second wavelength laser, and the second wavelength laser is a single-frequency continuous light; A frequency doubling module, coupled to the first reference laser, for converting the first wavelength laser into an up-conversion signal; The frequency summing module is coupled to the frequency doubling module and the second reference laser respectively, and is used to perform frequency summing on the second wavelength laser and the up-conversion signal to generate a target wavelength laser output signal, wherein the wavelength of the target wavelength laser is 184.13-283.81nm.

2. The laser based on single-frequency light oscillation as claimed in claim 1, characterized in that: The wavelength of the first wavelength laser is 970-1530 nm, and the wavelength of the second wavelength laser is 1530-2200 nm.

3. The laser based on single-frequency light oscillation as claimed in claim 1, characterized in that: The frequency doubling module includes a first frequency doubling module and a second frequency doubling module, the first frequency doubling module is coupled to the first reference laser, and the second frequency doubling module is coupled to the first frequency doubling module; A first frequency doubling module is used to perform a first-stage frequency doubling on the first wavelength laser to generate a primary up-conversion signal, wherein the wavelength of the primary up-conversion signal is 485-765nm; The second frequency multiplication module is used to perform a second frequency multiplication on the primary up-conversion signal to generate an up-conversion signal, and the wavelength of the up-conversion signal is 242.5-382.5nm.

4. The laser based on single-frequency light oscillation as claimed in claim 1, characterized in that: The sum frequency module includes at least one resonant cavity, the resonant cavity includes at least one sum frequency medium, and the sum frequency medium is a nonlinear medium.

5. The laser based on single-frequency light oscillation as claimed in claim 4, characterized in that: The resonant cavity also includes a light combining and splitting element and a light beam transmission control element; The light combining and splitting element is used for combining the second wavelength laser and the up-conversion signal, and / or for combining the second wavelength laser and the sum frequency signal, and / or for splitting the second wavelength laser and the target wavelength laser, and / or for splitting the second wavelength laser and the sum frequency signal; The beam transmission control element is used for focusing the second wavelength laser and / or for reflecting the second wavelength laser.

6. The laser based on single-frequency light oscillation as claimed in claim 5, characterized in that: The light combining and splitting element includes a dichroic mirror, and the light beam transmission control element includes at least one of a total reflection mirror, a total reflection concave mirror and a partial reflection mirror; The resonant cavity further includes an adjusting element, which is used to adjust the resonant cavity to match the wavelength of the second wavelength laser.

7. The laser based on single-frequency light oscillation as claimed in claim 6, characterized in that: The resonant cavity further includes a first sum frequency medium, and a first total reflection concave mirror and a second total reflection concave mirror arranged on both sides of the first sum frequency medium, and a first dichroic mirror arranged between the first total reflection concave mirror and the first sum frequency medium, and a second dichroic mirror arranged between the first sum frequency medium and the second total reflection concave mirror; The first total reflection concave mirror is used for reflecting and focusing the second wavelength laser; The first dichroic mirror is used for combining the second wavelength laser and the up-conversion signal, or for combining the second wavelength laser and the previous level sum frequency signal; The second dichroic mirror is used for beam splitting the second wavelength laser and the target wavelength laser, or for beam splitting the second wavelength laser and the current level sum frequency signal, or for beam splitting the second wavelength laser and the current level sum frequency signal; The second total reflection concave mirror is used to reflect the second wavelength laser remaining after the sum frequency treatment of the first sum frequency medium.

8. The laser based on single-frequency light oscillation as claimed in claim 7, characterized in that: The resonant cavity also includes a partial reflector and a total reflector. The partial reflector is coupled to a photodetector. The total reflector is fixedly arranged on an adjusting element. The partial reflector is used to couple a second wavelength laser into the resonant cavity. The total reflector is used to reflect the second wavelength laser to the first total reflective concave mirror.

9. The laser based on single-frequency light oscillation as claimed in claim 8, characterized in that: The resonant cavity further includes a partial reflector, a second sum frequency medium, a total reflector, and a third dichroic mirror and a fourth dichroic mirror arranged on both sides of the second sum frequency medium, which are coupled in sequence. The third dichroic mirror is coupled to the frequency doubling module. The third dichroic mirror is used for combining the second wavelength laser and the up-conversion signal; The fourth dichroic mirror is used for splitting the second wavelength laser and the current level sum frequency signal, and inputting the second wavelength laser into the total reflection mirror, and inputting the current level sum frequency signal into the first dichroic mirror.

10. The laser based on single-frequency light oscillation as claimed in any one of claims 4 to 9, characterized in that: The sum frequency module includes a first sum frequency module and a second sum frequency module, each of which includes at least one resonant cavity, the first sum frequency module is coupled to the frequency doubling module and the second reference laser, and the second sum frequency module is coupled to the first sum frequency module and the second reference laser; The first sum frequency module generates a primary sum frequency signal, and the wavelength of the primary sum frequency signal is 209.32-328.85nm; The second frequency addition module generates a target wavelength laser output signal, and the wavelength of the target wavelength laser is 184.13-283.81nm.

11. The laser based on single-frequency light oscillation as claimed in any one of claims 4 to 9, characterized in that: It also includes a beam splitting module coupled to the second laser, which is used to perform beam splitting processing on the second wavelength laser to generate a first-order sum frequency light of the second wavelength laser and a second-order sum frequency light of the second wavelength laser; The sum-frequency module includes a first sum-frequency module and a second sum-frequency module, each of which includes at least one resonant cavity, the first sum-frequency module is respectively coupled to the frequency doubling module and the beam splitting module, and the second sum-frequency module is respectively coupled to the first sum-frequency module and the beam splitting module; The first sum-frequency module is used to perform sum-frequency operation on the up-converted signal and the primary sum-frequency light of the second wavelength laser to generate a primary sum-frequency signal; The second sum frequency module is used to sum the primary sum frequency signal with the secondary sum frequency light of the second wavelength laser to generate a target wavelength laser output signal; The wavelength of the primary sum frequency signal is 209.32-325.85 nm, and the wavelength of the target wavelength laser is 184.13-283.81 nm.

12. A laser output method based on single-frequency light oscillation, characterized in that: Using a laser based on single-frequency light oscillation as claimed in any one of claims 1 to 11, specifically comprising the following steps: Emitting a laser with a first wavelength through a first reference laser; The second wavelength laser is emitted by a second reference laser, wherein the second wavelength laser is a single-frequency continuous light; Converting the first wavelength laser into an up-conversion signal in a frequency doubling module; The second wavelength laser and the up-conversion signal are frequency-added in the frequency addition module to generate a target wavelength laser output signal, wherein the wavelength of the target wavelength laser is 184.13-283.81 nm.

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