Optical device

Abstract

The application provides an optical device, comprising: a laser providing a light beam of a first wavelength; a first beam splitter splitting the light beam of the first wavelength; an optical parametric oscillator halving the frequency of a first split light beam with less energy to obtain a wavelength-doubled light beam; a first beam combiner superimposing the wavelength-doubled light beam and the split light beam with the first wavelength; a phase matcher adjusting the relative phase of the wavelength-doubled light beam and the split light beam with the first wavelength so that the energy of the split light beam with the first wavelength is converted into the wavelength-doubled light beam in an optical parametric amplifier; the optical parametric amplifier amplifying the wavelength-doubled light beam; and a harmonic beam splitter separating the wavelength-doubled output light beam. The application can generate a laser beam with a wavelength of 2 microns from a mature laser beam with a wavelength of about 1 micron in industrial high-power material processing, and has the advantages of small realization difficulty, high controllability, high conversion efficiency and suitability for industrial application.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to an optical device. Background Technology

[0002] Absorption is a fundamental process, and because absorption is wavelength-dependent, the processing results also exhibit wavelength dependence. For example, the optimal wavelength for processing copper is a laser beam in the green or blue range; while for processing plastics and polymers, ultraviolet (UV) and deep ultraviolet (DUV) light are more ideal; in medical applications, such as bone tissue processing, laser beams with wavelengths of 2 μm or longer are more suitable due to the absorption characteristics of water; extreme ultraviolet (EUV) light with a wavelength of approximately 10 nm is of great significance for photolithography and metrology technologies. One important method for generating EUV light is through laser-induced plasma, in which a high-energy laser beam is focused onto a target material. Due to its extremely high intensity, the target material atoms are ionized, and the ionized atoms emit EUV radiation. Currently, 10 μm wavelength carbon dioxide lasers are commonly used to generate extreme ultraviolet (EUV) light through laser-induced plasma; however, carbon dioxide lasers are bulky and have poor electro-optical efficiency. Research has found that the conversion efficiency of driving laser to EUV radiation increases with increasing laser wavelength. For example, the conversion efficiency achievable using a 2μm laser beam is twice that of a 1μm laser beam.

[0003] The wavelength of a laser beam is primarily determined by the gain material used, and new wavelengths can be generated through nonlinear processes. These nonlinear processes mainly involve frequency multiplication, such as frequency doubling, third harmonics, and multiple harmonics, as well as optical parameter generation. A special case of optical parameter generation is frequency halving. Laser beams of various wavelengths can be converted into larger wavelength laser beams through corresponding nonlinear media; however, the longer the wavelength, the higher the requirements for optical components (i.e., the greater the difficulty in implementation). Currently, the wavelength of mature lasers suitable for high-power industrial material processing is approximately 1 μm. Therefore, how to generate a 2 μm wavelength laser beam from a 1 μm wavelength laser based on frequency halving technology has become one of the problems urgently needing to be solved by those skilled in the art.

[0004] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an optical device to solve the problems of difficulty in halving the laser beam frequency, low conversion efficiency, and unsuitability for industrial applications in the prior art.

[0006] To achieve the above and other related objectives, the present invention provides an optical device for halving the frequency, the optical device comprising at least:

[0007] Laser, first beam splitter, optical parametric oscillator, first beam combiner, phase matcher, optical parametric amplifier and harmonic beam splitter;

[0008] The laser provides a beam with a first wavelength;

[0009] The first beam splitter is disposed at the output end of the laser and is used to split the beam having a first wavelength, wherein the intensity of the first split beam is less than the intensity of the second split beam.

[0010] The optical parametric oscillator is located at the output end of the first beam splitter, and halves the frequency of the first beam to obtain a beam with double the wavelength.

[0011] The first beam combiner is disposed at the output end of the first beam splitter and the optical parametric oscillator, and superimposes the beam with doubled wavelength with the split beam having the first wavelength;

[0012] The phase matcher receives the beam from the output of the first beam combiner and adjusts the relative phase between the wavelength-doubled beam and the beam splitting beam having the first wavelength, so that the energy of the beam splitting beam having the first wavelength is converted into the wavelength-doubled beam in the optical parametric amplifier.

[0013] The optical parametric amplifier amplifies the light beam by doubling its wavelength;

[0014] The harmonic beam splitter is located at the output of the optical parametric amplifier and is used to separate beams of different wavelengths.

[0015] Optionally, the optical parametric amplifier includes a first mirror, a second mirror, and a first gain medium, and the phase matcher includes a first phase matching unit, a second phase matching unit, and a third phase matching unit;

[0016] The first reflector and the second reflector are positioned opposite each other, and the first gain medium is disposed between the first reflector and the second reflector; the light beam passes through a phase matching unit each time it passes through the first gain medium;

[0017] Wherein, the first reflector and the second reflector are ridge-type reflectors, or the first reflector and the second reflector are curved surface reflectors.

[0018] Optionally, the laser is a crystal doped with Nd or Yb ions, and the first wavelength is 1 μm to 1.1 μm.

[0019] Optionally, the phase matcher employs an optical material, and the relative phase of the two beams is adjusted by adjusting the thickness or orientation of the optical material, or by utilizing the temperature effect, piezoelectric effect, electro-optic effect, or magneto-optic effect within the optical material.

[0020] Optionally, the optical parametric oscillator includes a first curved mirror, a second curved mirror, a first planar mirror, a second planar mirror, and a nonlinear optical crystal;

[0021] The first curved mirror, the second curved mirror, the first flat mirror, and the second flat mirror constitute an optical resonant cavity for doubling the wavelength of the light beam, and the nonlinear optical crystal is disposed within the optical resonant cavity.

[0022] Alternatively, the optical parametric oscillator may further include an optical etalon, which is disposed in the optical path within the optical resonant cavity.

[0023] Alternatively, the first or second planar reflector may be replaced by a grating.

[0024] Optionally, when the beam received by the first beam combiner includes the remaining pump beam from the previous stage, the optical device further includes a phase controller disposed between the first beam splitter and the corresponding first beam combiner. The phase controller is used to adjust the phase of the split beam having a first wavelength so that the phases of the beams having the first wavelength input into the same first beam combiner are consistent.

[0025] Alternatively, the first beam combiner, the phase matcher, and the optical parametric amplifier constitute a frequency division amplification unit, and the optical device includes N frequency division amplification units; the first beam splitter outputs N+1 split beams, and the intensity of the first split beam with a first wavelength is less than the intensity of the other split beams; N is a natural number greater than or equal to 2.

[0026] Each frequency-division amplification unit is cascaded sequentially between the output of the optical parametric oscillator and the input of the harmonic beam splitter. Each frequency-division amplification unit receives the second to the (N+1)th beam splitter output from the first beam splitter, obtains a beam with a first wavelength from the first beam splitter, obtains a beam with doubled wavelength from the previous stage, and converts the energy of the beam with the first wavelength into the beam with doubled wavelength. The energy of the beam with doubled wavelength is gradually enhanced through the cascading of N-stage frequency-division amplification units.

[0027] Alternatively, the N frequency division amplification units include a third curved mirror, a fourth curved mirror, a second gain medium, a third gain medium, a dichroic beam splitter, and N phase matching units;

[0028] The third curved mirror and the fourth curved mirror are arranged opposite to each other to form an off-axis confocal unstable resonant cavity; the second gain medium and the third gain medium are arranged side by side between the third curved mirror and the fourth curved mirror; the light beam passes through a phase matching unit before passing through each gain medium each time;

[0029] The dichroic beam splitter is disposed between each gain medium and the fourth curved mirror; a beam with doubled wavelength is input from between the third curved mirror and the gain medium, and a beam with the first wavelength is input as a pump source through the dichroic beam splitter.

[0030] Alternatively, the third curved mirror is coated with an antireflective coating relative to a light beam having a first wavelength, and a high reflective coating relative to a light beam having twice the wavelength.

[0031] Alternatively, the first beam combiner, the phase matcher, and the optical parametric amplifier constitute a frequency division amplification unit, and the optical device includes M frequency division amplification units and M harmonic beam splitters; the optical device also includes a second beam splitter; the first beam splitter outputs M+1 split beams, and the intensity of the first split beam with a first wavelength is less than the intensity of the other split beams; M is a natural number greater than or equal to 2.

[0032] The second beam splitter is located at the output end of the optical parametric oscillator and is used to split the beam with doubled wavelength into M beams.

[0033] Each frequency division amplifier unit receives the second to M+1 beam splits output from the first beam splitter, and the second input receives the beam split with doubled wavelength output from the second beam splitter. A beam with a first wavelength is obtained from the first beam splitter, and a beam with doubled wavelength is obtained from the second beam splitter. The energy of the beam with the first wavelength is converted into the beam with doubled wavelength through M parallel channels.

[0034] Alternatively, the optical device may further include a coherent combiner and M-1 or M phase controllers;

[0035] Each phase controller is located at the output of a harmonic beam splitter, and the coherent combiner is located at the output of each phase controller.

[0036] The phase controller is used to control the relative phase of the output beams of each channel so that the output beams of each channel can be coherently combined and superimposed.

[0037] Alternatively, the first beam splitter, optical parametric oscillator, first beam combiner, phase matcher, optical parametric amplifier, and harmonic beam splitter constitute a frequency-division oscillation amplification module. The optical device includes P frequency-division oscillation amplification modules, as well as a third beam splitter and a second beam combiner. The laser provides P beams of different wavelengths, where P is a natural number greater than or equal to 2.

[0038] The third beam splitter is located at the output end of the laser and is used to separate beams of different wavelengths and provide them to the corresponding frequency division oscillation amplification module.

[0039] Each frequency division oscillation amplification module doubles the wavelength of the beam provided by the third beam splitter, one by one.

[0040] The second beam combiner is located at the output end of each frequency division oscillation amplification module to combine the beams of different wavelengths output by each frequency division oscillation amplification module.

[0041] Alternatively, the laser may include an oscillator in which beams of different wavelengths are distributed sequentially in the time domain; or the laser may include P oscillators and a third beam combiner, in which each oscillator provides beams of different wavelengths, which are then combined by the third beam combiner and output.

[0042] As described above, the optical device of the present invention has the following beneficial effects:

[0043] The optical device of this invention is based on frequency halving technology. It uses an optical parametric oscillator to convert a portion of the original beam with lower energy into a beam with doubled wavelength, and then uses a portion of the original beam with higher energy as a pump source to amplify the beam with doubled wavelength. It can generate a laser beam with a wavelength of 2μm from a laser beam with a wavelength of about 1μm that is mature in industrial high-power material processing. It is easy to implement, highly controllable, highly efficient in conversion, and suitable for industrial applications. Attached Figure Description

[0044] Figure 1 The diagram shown is a first structural schematic of the optical device of the present invention.

[0045] Figure 2 The diagram shown is a schematic diagram of a first structure of the first beam splitter of the present invention.

[0046] Figure 3 The diagram shown is a second structural schematic of the first beam splitter of the present invention.

[0047] Figure 4 The diagram shown is a first structural schematic of the optical parametric oscillator of the present invention.

[0048] Figure 5 The diagram shown is a second structural schematic of the optical parametric oscillator of the present invention.

[0049] Figure 6 The diagram shown is a third structural schematic of the optical parametric oscillator of the present invention.

[0050] Figure 7 The diagram shown is a schematic diagram of a first structure of the first bundle combiner of the present invention.

[0051] Figure 8 The diagram shown is a second structural schematic of the first bundle combiner of the present invention.

[0052] Figure 9 The diagram shown is a third structural schematic of the first bundle combiner of the present invention.

[0053] Figure 10 The diagram shown is a schematic representation of the phase matcher of this invention.

[0054] Figure 11 This is shown as one implementation of the frequency division amplification unit of the present invention.

[0055] Figure 12 The diagram shown is a structural schematic of the harmonic beam splitter of the present invention.

[0056] Figure 13 The diagram shown is a second structural schematic of the optical device of the present invention.

[0057] Figure 14 The diagram shown is a fourth structural schematic of the first bundle combiner of the present invention.

[0058] Figure 15 The diagram shown is a fifth structural schematic of the first bundle combiner of the present invention.

[0059] Figure 16 The diagram shown is a sixth structural schematic of the first bundle combiner of the present invention.

[0060] Figure 17 The diagram shown is a third structural schematic of the optical device of the present invention.

[0061] Figure 18 This is shown as one implementation of the three-stage frequency divider amplifier unit of the present invention.

[0062] Figure 19 This is a schematic diagram of the fourth structure of the optical device of the present invention.

[0063] Figure 20 This is a schematic diagram of the fifth structure of the optical device of the present invention.

[0064] Figure 21 This is a schematic diagram of the sixth structure of the optical device of the present invention.

[0065] Component designation explanation

[0066] 1 Optical device

[0067] 10 Lasers

[0068] 11 First beam splitter

[0069] 111 First Thin Film Beam Spectroscope

[0070] 112 First Wave Film

[0071] 113 First Thin Film Polarizing Mirror

[0072] 12 Optical Parametric Oscillators

[0073] 121, 122 First and second curved surface reflecting mirrors

[0074] 123, 124 First and second plane mirrors

[0075] 125 Nonlinear optical crystal

[0076] 126 Optical etalon

[0077] 127 gratings

[0078] 13 First bundle combiner

[0079] 13a, 13b, 13c, 13d, 13e: Second to Sixth Thin Film Beam Spectroscopes

[0080] 13f, 13m First and second half-wave plates

[0081] 13g, 13j second and third wave films

[0082] 13h, 13i, 13k, 13l - Second to Fifth Thin Film Polarizing Mirrors

[0083] 14 Phase Matcher

[0084] 141~146 First to sixth phase matching units

[0085] 15 Optical Parametric Amplifier

[0086] 151, 152 First and second reflecting mirrors

[0087] 153, 156, 157 First, Second, and Third Gain Mediums

[0088] 154, 155 Third and fourth curved surface reflecting mirrors

[0089] 158 Dihedral Beam Splitter

[0090] 15a Folding Reflector

[0091] 15b Faraday Isolator

[0092] 16, 16a, 16b Harmonic Beam Splitter

[0093] 161 Seventh Thin Film Beam Spectroscope

[0094] Phase controllers 17, 17a, and 17b

[0095] 18 Second beam splitter

[0096] 19 Coherent Combiner

[0097] 2, 2a, 2b, 2c, 2d frequency divider amplifier units

[0098] 3, 3a, 3b Frequency division oscillation amplification modules

[0099] 4 Third beam splitter

[0100] 5 Second bundle combiner Detailed Implementation

[0101] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0102] Please see Figures 1 to 21 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0103] To address the aforementioned problems, the present invention provides an optical device, preferably for converting a 1μm laser beam into a 2μm laser beam, and capable of extending to obtain a laser beam with a longer wavelength. The optical device of the present invention will be described in detail below.

[0104] Example 1

[0105] like Figure 1 As shown, this embodiment provides an optical device 1, which includes:

[0106] Laser 10, first beam splitter 11, optical parametric oscillator 12, first beam combiner 13, phase matcher 14, optical parametric amplifier 15, and harmonic beam splitter 16.

[0107] like Figure 1 As shown, laser 10 provides a beam with a first wavelength λ1.

[0108] Specifically, in this embodiment, the laser 10 is implemented using a crystal doped with Nd or Yb ions, and the first wavelength λ1 is set to around 1 μm, for example, 1 μm to 1.1 μm, preferably 1 μm; in actual use, the first wavelength can be set as needed.

[0109] like Figure 1 As shown, the first beam splitter 11 is disposed at the output end of the laser 12 and is used to split the beam with a first wavelength λ1, wherein the intensity of the first split beam is less than the intensity of the second split beam.

[0110] Specifically, the first beam splitter 11 splits a beam with a first wavelength λ1 into two beams of different intensities. Typically, the energy of the first beam is much less than the energy of the second beam, and the wavelengths of both beams remain the first wavelength λ1. Any structure capable of achieving the above function is applicable to the first beam splitter of this invention, and will not be elaborated upon here. For example... Figure 2 As shown, as an example, the first beam splitter 11 includes a first thin-film beam splitter 111. For example, 90% of the intensity of the incident beam is reflected and output through the reflecting surface of the first thin-film beam splitter 111, and 10% of the intensity of the beam is output through the transmitting surface of the first thin-film beam splitter 111. Figure 3 As shown, as another example, the first beam splitter 11 includes a first waveplate 112 and a first thin-film polarizer 113. After the incident beam passes through the first waveplate 112, the polarization direction of 10% of the beam intensity is set to a preset polarization direction and output through the first thin-film polarizer 113; the remaining 90% of the beam intensity is reflected by the first thin-film polarizer 113. In practical use, the transmitted and reflected beam energies can be interchanged, and the intensity ratio can be set according to actual needs, not limited to this embodiment.

[0111] like Figure 1 As shown, the optical parametric oscillator 12 is located at the output end of the first beam splitter 11, and the frequency of the first beam splitter is halved to obtain a beam with a wavelength doubled by 2λ1.

[0112] Specifically, the optical parametric oscillator 12 converts the input laser (i.e., the pump beam) into lower-frequency output light through nonlinear optical interactions; in this example, the output light frequency is halved. Any structure capable of achieving the above function is applicable to this invention. Figure 4As shown, as an example, the optical parametric oscillator 12 includes a first curved mirror 121, a second curved mirror 122, a first flat mirror 123, a second flat mirror 124, and a nonlinear optical crystal 125. The first curved mirror 121, the second curved mirror 122, the first flat mirror 123, and the second flat mirror 124 are arranged opposite to each other to form an optical resonant cavity (ring cavity) for doubling the wavelength of the beam. The nonlinear optical crystal 125 is disposed within the optical resonant cavity. After a beam with a first wavelength λ1 enters the optical parametric oscillator 12, its frequency is halved (wavelength multiplied), resulting in a beam with a wavelength doubled by 2λ1. A small amount of beam with the first wavelength λ1 remains in the output beam. Figure 5 As shown, as an example, the optical parametric oscillator 12 also includes an optical etalon 126, which is disposed in the optical path within the optical resonant cavity to limit the spectral range of the output beam with a wavelength doubled by 2λ1 to a narrower range. Figure 6 As shown, as an example, in Figure 4 Based on this, the first plane mirror 123 or the second plane mirror 124 is replaced with a grating 127, and the grating 127 limits the spectral range of the output beam with a wavelength doubled by 2λ1.

[0113] like Figure 1 As shown, the first beam combiner 13 is disposed at the output end of the first beam splitter 11 and the optical parametric oscillator 12, and superimposes the beam with a wavelength doubled by 2λ1 with the second beam split having a first wavelength λ1.

[0114] Specifically, any structure capable of combining a beam with a wavelength doubled by 2λ1 with a second beam splitting having a first wavelength λ1 is suitable for the first beam combiner of the present invention. For example... Figure 7 As shown, as an example, the first beam combiner 13 is implemented based on a thin-film beam splitter, including a second thin-film beam splitter 13a and a third thin-film beam splitter 13b; the second thin-film beam splitter 13a reflects a second beam splitting beam with a first wavelength λ1 (a reflector can be used instead); the third thin-film beam splitter 13b reflects the beam with a first wavelength λ1 output from the optical parametric oscillator 12 on the first surface, and transmits a beam with a wavelength doubled by 2λ1 output from the optical parametric oscillator 12, and reflects the second beam splitting beam with a first wavelength λ1 output from the second thin-film beam splitter 13a on the second surface, thereby combining the beam with wavelength λ1 and the beam with wavelength 2λ1 (it should be noted that the beam with the first wavelength λ1 in the output beam is the second beam splitting beam output from the first beam splitter 11). Figure 8As shown, as another example, the first beam combiner 13 includes a fourth thin-film beam splitter 13c, a fifth thin-film beam splitter 13d, and a sixth thin-film beam splitter 13e. A beam with a first wavelength λ1 output from the optical parametric oscillator 12 is reflected by the fourth thin-film beam splitter 13c, and a beam with a wavelength doubled by 2λ1 output from the optical parametric oscillator 12 is transmitted through the fourth thin-film beam splitter 13c. The fifth thin-film beam splitter 13d reflects a second beam with a first wavelength λ1 (which can be replaced by a reflector). The sixth thin-film beam splitter 13e transmits the beam with a wavelength doubled by 2λ1 output from the fourth thin-film beam splitter 13c based on its first surface, and reflects the second beam with a first wavelength λ1 output from the fifth thin-film beam splitter 13d based on its second surface, thereby combining the beam with wavelength λ1 and the beam with wavelength 2λ1 (similarly, the beam with the first wavelength λ1 in the output beam is the second beam output from the first beam splitter 11). Figure 9 As shown, as yet another example, in Figure 8 Based on this, a first half-wave plate 13f is also provided on the output side of the sixth thin-film beam splitter 13e for adjusting the polarization direction.

[0115] It should be noted that in this embodiment, the beam with the first wavelength λ1 output by the optical parametric oscillator 12 is removed by the first beam combiner 13. At this time, there is no need to adjust the phase of the second beam with the first wavelength λ1.

[0116] like Figure 1 As shown, the phase matcher 14 receives the beam from the output of the first beam combiner 13 and adjusts the relative phase between the beam with a wavelength doubled by 2λ1 and the beam split with a first wavelength λ1, so that the energy of the second beam split with the first wavelength λ1 is converted into the beam with a wavelength doubled by 2λ1 in the optical parametric amplifier 15; the optical parametric amplifier 15 amplifies the beam with doubled wavelength.

[0117] Specifically, in this embodiment, the phase matcher 14 is formed of an optical material. The methods for adjusting the relative phase of the two beams include, but are not limited to: due to chromatic aberration, the phases of beams of different wavelengths change differently after passing through an optical material of a certain thickness. Adjusting the thickness of the optical material alters the relative phases of the beams of different wavelengths, thus achieving phase matching. After passing through the phase matcher 14 with materials of different thicknesses, the optical path lengths of the beams of different wavelengths are different, thereby generating different phases within the optical material. Alternatively, for an optical material of a certain thickness, adjusting the orientation of the optical material (rotating it in a certain direction) is equivalent to a change in thickness when the beam passes through the phase matcher 14, resulting in a change in relative phase. Figure 10As shown, in this example, the phase matcher 14 is a dispersive optical medium with a given thickness, and the relative phase of the two beams can be adjusted by changing its direction. Alternatively, the temperature effect within the optical material can be utilized; the refractive index of the optical material has a certain wavelength-dependent relationship with temperature, and the relative phase of the two beams can be changed when the temperature coefficients are different. Alternatively, the piezoelectric effect within the optical material can be utilized; typically, the polarization directions of the second beam with a first wavelength λ1 and the beam with a wavelength doubled to 2λ1 are different, and the polarization-dependent refractive index can be adjusted through the piezoelectric effect, thereby achieving relative phase adjustment. Alternatively, the electro-optic effect within the optical material can be utilized; the refractive index of the optical material can be changed by an electric field to achieve relative phase adjustment. Alternatively, the magneto-optic effect within the optical material can be utilized; the refractive index of the optical material can be changed by a magnetic field to achieve relative phase adjustment. Any method that can adjust the relative phase is applicable to this invention, and the implementation of the phase matcher 14 is not limited to the several methods listed in this embodiment.

[0118] Specifically, as an example, such as Figure 11 As shown, the optical parametric amplifier 15 includes a first reflector 151, a second reflector 152, and a first gain medium 153. The phase matcher 14 includes a first phase matching unit 141, a second phase matching unit 142, and a third phase matching unit 143. The first reflector 151 and the second reflector 152 are arranged opposite to each other, and the first gain medium 153 is disposed between the first reflector 151 and the second reflector 152. The input beam can be repeatedly refracted between the first reflector 151 and the second reflector 152, and thus passes through the first gain medium 153 multiple times. In this example, the first reflector 151 and the second reflector 152 are configured as roof mirrors (with a 90° angle between them, and the two mutually perpendicular reflecting surfaces are called roof surfaces). In practical applications, they can also be configured as curved mirrors. The first gain medium 153 has nonlinear characteristics and includes, but is not limited to, barium β-borate crystal (BBO), lithium triborate crystal (LBO), or potassium titanyl phosphate (KTP). Each time the light beam passes through the first gain medium 153, it passes through a phase matching unit (141, 142, 143) to ensure that the light beam with the first wavelength λ1 and the light beam with a wavelength doubled by 2λ1 that pass through the first gain medium 153 always maintain a relative phase relationship. In the optical parametric amplifier 15, the light beam with the first wavelength λ1 serves as a pump source, and its energy is converted into the light beam with a wavelength doubled by 2λ1, thereby increasing the energy of the light beam with a wavelength doubled by 2λ1.

[0119] like Figure 1 As shown, the harmonic beam splitter 16 is located at the output of the optical parametric amplifier 15 and is used to separate beams of different wavelengths.

[0120] Specifically, any optical element capable of separating light beams of different wavelengths is applicable to this invention. For example... Figure 12 As shown, as an example, the harmonic beam splitter 16 is implemented using a seventh thin-film beam splitter 161, which reflects a beam with a wavelength doubled by 2λ1 and transmits a beam with a first wavelength λ1.

[0121] This invention can generate a laser beam with a wavelength of 2μm from a laser with a wavelength of 1μm, which has great industrial value.

[0122] Example 2

[0123] like Figure 13 As shown, this embodiment provides an optical device 1, which differs from the first embodiment in that it further includes a phase controller 17.

[0124] like Figure 13 As shown, the phase controller 17 is disposed between the first beam splitter 11 and the first beam combiner 13, and is used to adjust the phase of the split beam (second split beam) with the first wavelength λ1 so that the phase of the beam with the first wavelength λ1 input to the same first beam combiner 13 is consistent; that is, the phase of the beam with the first wavelength λ1 output by the phase controller 17 is consistent with the phase of the beam with the first wavelength λ1 output by the optical parametric oscillator 12, so as to make full use of the beam with the first wavelength λ1 as the pump source of the amplifier.

[0125] It should be noted that, at this time, the first beam combiner 13 does not need to remove the beam with the first wavelength λ1 output by the optical parametric oscillator 12. For example... Figure 14 As shown, as an example, the first beam combiner 13 includes a second waveplate 13g, a second thin-film polarizer 13h, and a third thin-film polarizer 13i. A beam with a first wavelength λ1 passes through the second waveplate 13g and is reflected by the second thin-film polarizer 13h. The beam with a first wavelength λ1 output from the optical parametric oscillator 12 and a beam with a wavelength doubled by 2λ1 pass through the third thin-film polarizer 13i and are combined with the beam with a first wavelength λ1 reflected by the third thin-film polarizer 13i (at this time, the combined beam includes both the second beam with a first wavelength λ1 output from the first beam splitter 11 and the beam with a first wavelength λ1 output from the optical parametric oscillator 12, and there is a phase difference between the two). Figure 15As shown, as another example, the first beam combiner 13 includes a third waveplate 13j, a fourth thin-film polarizer 13k, and a fifth thin-film polarizer 13l. A beam with a first wavelength λ1 and a beam with a wavelength doubled by 2λ1 output from the optical parametric oscillator 12 pass through the third waveplate 13j and then through the fourth thin-film polarizer 13k. The beam with the first wavelength λ1 is reflected by the fifth thin-film polarizer 13l and then reflected again by the fourth thin-film polarizer 13k, thus combining with the beam with the first wavelength λ1 and the beam with a wavelength doubled by 2λ1 transmitted through the fourth thin-film polarizer 13k. Figure 16 As shown, as yet another example, in Figure 14 Based on this, a second half-wave plate 13m is also provided on the output side of the third thin-film polarizer 13i to adjust the polarization direction.

[0126] The other structures are the same as in Embodiment 1, and will not be described in detail here.

[0127] Example 3

[0128] like Figure 17 As shown, this embodiment provides an optical device 1. The difference between this embodiment and Embodiment 1 and Embodiment 2 is that this embodiment further increases the energy of the beam with a wavelength doubled by 2λ1 by cascading multi-stage frequency division amplification units.

[0129] like Figure 17 As shown, the first beam combiner 13, the phase matcher 14, and the optical parametric amplifier 15 constitute a frequency divider amplification unit 2. The optical device 1 includes N frequency divider amplification units 2. The first beam splitter 11 outputs N+1 beams, and the intensity of the first beam with a first wavelength λ1 is less than the intensity of the other beams; N is a natural number greater than or equal to 2. Each frequency divider amplification unit 2 is cascaded sequentially between the output of the optical parametric oscillator 12 and the input of the harmonic beam splitter 16. Each frequency divider amplification unit receives the second to the N+1th beams output by the first beam splitter 11, obtains a beam with a first wavelength λ1 from the first beam splitter 11, obtains a beam with a wavelength doubled by 2λ1 from the previous stage, and converts the energy of the beam with the first wavelength λ1 into the beam with a wavelength doubled by 2λ1. The energy of the beam with a wavelength doubled by 2λ1 is gradually enhanced through the cascading of N frequency divider amplification units.

[0130] Specifically, in this embodiment, N is set to 2. For example... Figure 17As shown, the first-stage frequency divider amplification unit 2a converts the energy of the second beam with a wavelength doubled by 2λ1, provided by the optical parametric oscillator 12 (the pre-stage optical path of the first-stage frequency divider amplification unit 2a), and the second beam with a wavelength of the first wavelength λ1, provided by the first beam splitter 11, into a beam with a wavelength doubled by 2λ1. The second-stage frequency divider amplification unit 2a converts the energy of the third beam with a wavelength of the first wavelength λ1, provided by the first-stage frequency divider amplification unit 2a (the pre-stage circuit of the second-stage frequency divider amplification unit 2b), and the third beam with a wavelength of the first wavelength λ1, provided by the first beam splitter 11, into a beam with a wavelength doubled by 2λ1. The larger the value of N, the greater the energy of the beam with a wavelength doubled by 2λ1 output from the final harmonic beam splitter 16.

[0131] Specifically, in this example, the first beam combiner 13 in each frequency division amplification unit 2 removes the remaining pump beam (with a first wavelength λ1) from the previous stage; for example, using... Figure 7 , Figure 8 , Figure 9 The beam combiner structure. In other examples, before each first beam combiner 13 receives the beam with the first wavelength λ1, the phase of the beam with the first wavelength λ1 can be adjusted based on the phase controller (N) so that the phase of the beam with the first wavelength λ1 input to the same first beam combiner 13 is consistent. See Embodiment 2, which will not be described in detail here.

[0132] Specifically, the N frequency-division amplification units 2 can be implemented based on the third curved surface mirror 154, the fourth curved surface mirror 155, the second gain medium 156, the third gain medium 157, the dichroic beam splitter 158, and the N phase matching units. For example... Figure 18The diagram illustrates the implementation of three frequency-division amplification units 2. The third curved mirror 154 and the fourth curved mirror 155 are positioned opposite each other, forming an off-axis confocal unstable resonant cavity. The second gain medium 156 and the third gain medium 157 are arranged side-by-side between the third curved mirror 154 and the fourth curved mirror 155 (in this example, the distances from the second gain medium 156 and the third gain medium 157 to the third curved mirror 154 are the same, meaning their perpendicular projections to the optical axis are at the same point). Each time the beam passes through each gain medium, it passes through a phase-matching unit (denoted as the fourth phase-matching unit 144, the fifth phase-matching unit 145, and the sixth phase-matching unit 146). A dichroic beam splitter 158 is positioned between each gain medium and the fourth curved mirror 155. A beam with a wavelength doubled by 2λ1 is input between the third curved reflector 154 and the gain medium (156, 157). A beam with a first wavelength λ1 serves as the pump source and is input through the dichroic beam splitter 158. In this example, there are three pump sources (with the first wavelength λ1): the beam with the highest energy on the left with the first wavelength λ1 is the pump source of the third-stage frequency divider amplifier unit 2; the beam with the lowest energy in the middle with the first wavelength λ1 is the pump source of the first-stage frequency divider amplifier unit 2; and the beam with the first wavelength λ1 on the right, with energy between the two, is the pump source of the second-stage frequency divider amplifier unit 2. This example also includes a folding reflector 15a for adjusting the optical path; and a Faraday isolator 15b, through which the pump source of the third-stage frequency divider amplifier unit 2 is input.

[0133] Furthermore, to avoid interference, the third curved mirror 154 is coated with an anti-reflection coating (AR) and a high-reflection coating (HR), wherein the anti-reflection coating is used to fully transmit a light beam with a first wavelength λ1, and the high-reflection coating is used to fully reflect a light beam with a wavelength doubled by 2λ1.

[0134] It should be noted that the phase matching unit 14 and the optical parametric amplifier 15 in each stage of the frequency division amplification unit 2 can also be adopted. Figure 11 The structural implementation will not be elaborated here.

[0135] Example 4

[0136] like Figure 19 As shown, this embodiment provides an optical device 1. The difference between this embodiment and embodiments one, two and three is that this embodiment achieves higher power and energy by connecting multiple frequency division amplification units in parallel, because the maximum power and energy that can be obtained from each amplification unit is limited.

[0137] like Figure 19As shown, the optical device includes M frequency-division amplification units 2 and M harmonic beam splitters; it also includes a second beam splitter 18; the first beam splitter 11 outputs M+1 beams, and the intensity of the first beam with a first wavelength λ1 is less than the intensity of the other beams; M is a natural number greater than or equal to 2. The second beam splitter 18 is disposed at the output end of the optical parametric oscillator 12 and is used to split the beam with a wavelength doubled by 2λ1 into M beams; the first input end of each frequency-division amplification unit 2 receives the second to the M+1 beams output by the first beam splitter 11, and the second input end receives the beams with doubled wavelengths output by the second beam splitter 18. The beam with the first wavelength λ1 is obtained from the first beam splitter 11, and the beam with a wavelength doubled by 2λ1 is obtained from the second beam splitter 18. The energy of the beam with the first wavelength λ1 is converted into the beam with a wavelength doubled by 2λ1 through M parallel channels.

[0138] Specifically, in this embodiment, M is set to 2. For example... Figure 19 As shown, the second beam splitter 18 splits the beam with a wavelength doubled by 2λ1 output from the optical parametric oscillator 12 into two beams. The first frequency-dividing amplification unit 2c, based on the first beam with a wavelength doubled by 2λ1 provided by the second beam splitter 18 and the second beam with a first wavelength λ1 provided by the first beam splitter 11, converts the energy of the beam with the first wavelength λ1 into the beam with a wavelength doubled by 2λ1. The first harmonic beam splitter 16a splits the beams of different wavelengths output from the first frequency-dividing amplification unit 2c. The second frequency-dividing amplification unit 2d, based on the second beam with a wavelength doubled by 2λ1 provided by the second beam splitter 18 and the third beam with a first wavelength λ1 provided by the first beam splitter 11, converts the energy of the beam with the first wavelength λ1 into the beam with a wavelength doubled by 2λ1. The second harmonic beam splitter 16b splits the beams of different wavelengths output from the second frequency-dividing amplification unit 2d.

[0139] Furthermore, such as Figure 20As shown, the optical device 1 also includes a coherent combiner 19 and M-1 or M phase controllers; in this example, M=2; the phase controllers are denoted as the first phase controller 17a and the second phase controller 17b. Each phase controller is located at the output end of a harmonic beamsplitter (i.e., the first phase controller 17a is located at the output end of the first harmonic beamsplitter 16a, and the second phase controller 17b is located at the output end of the second harmonic beamsplitter 16b), and is used to control the phase of the output beams of the corresponding channel, so that the phases of the output beams of each channel are consistent. The coherent combiner 19 is located at the output end of each phase controller and is used to combine the beams output by each phase controller. Of course, phase controllers can also be set one by one after the M-1 harmonic beamsplitters. In this case, taking the beam of the channel without a phase controller as a reference, each phase controller adjusts the phase of the corresponding beam, and by controlling the relative phase of the output beams of each channel, the output beams of each channel are coherently combined and superimposed; this will not be described in detail here.

[0140] It should be noted that for different first beam combiner structures, a phase controller 17 may be set between the first beam splitter 11 and each first beam combiner 13 or not; these will not be elaborated here.

[0141] Example 5

[0142] like Figure 21 As shown, this embodiment provides an optical device 1, which differs from Embodiments 1, 2, 3, and 4 in that this embodiment generates and amplifies light beams of different wavelengths by doubling their wavelengths based on a parallel frequency division oscillation amplification module.

[0143] like Figure 21 As shown, the first beam splitter 11, optical parametric oscillator 12, first beam combiner 13, phase matcher 14, optical parametric amplifier 15, and harmonic beam splitter 16 constitute a frequency-division oscillation amplification module 3. The optical device 1 includes P frequency-division oscillation amplification modules 3, as well as a third beam splitter 4 and a second beam combiner 5. The laser 10 provides P beams of different wavelengths; P is a natural number greater than or equal to 2. The third beam splitter 4 is located at the output end of the laser 10 and is used to separate beams of different wavelengths and provide them to the corresponding frequency-division oscillation amplification module 3. Each frequency-division oscillation amplification module 3 doubles the wavelength of each beam provided by the third beam splitter 4. The second beam combiner 5 is a spectral beam combiner, which is located at the output end of each frequency-division oscillation amplification module 3 and combines the beams of different wavelengths output by each frequency-division oscillation amplification module.

[0144] Specifically, in this embodiment, P is set to 2. The laser 10 provides two beams of different wavelengths: a beam with a first wavelength λ1 and a beam with a second wavelength λ2. As an example, the laser 10 includes an oscillator, with the beams of different wavelengths sequentially distributed in the time domain. As another example, the laser 10 includes two oscillators (P in total) and a third beam combiner (not shown in the figure), each oscillator providing a beam of different wavelengths, which are then combined by the third beam combiner and output. The third beam splitter 4 separates the beams of the first wavelength λ1 and the second wavelength λ2. The first frequency-division oscillation amplification module 3a multiplies the wavelength of the beam of the first wavelength λ1; the second frequency-division oscillation amplification module 3b multiplies the wavelength of the beam of the second wavelength λ2. The second beam combiner 5 combines the wavelength-multiplied beams of different wavelengths output by the first frequency-division oscillation amplification module 3a and the second frequency-division oscillation amplification module 3b and outputs the combined beam.

[0145] It should be noted that the frequency division oscillation amplification module can also adopt the structure in Embodiments 2, 3, and 4, and is not limited to this embodiment.

[0146] In summary, the present invention provides an optical device comprising: a laser, a first beam splitter, an optical parametric oscillator, a first beam combiner, a phase matcher, an optical parametric amplifier, and a harmonic beam splitter; the laser provides a beam having a first wavelength; the first beam splitter is disposed at the output end of the laser and is used to split the beam having the first wavelength, wherein the intensity of the first split beam is less than the intensity of the second split beam; the optical parametric oscillator is disposed at the output end of the first beam splitter and halves the frequency of the first split beam to obtain a beam with doubled wavelength; the first beam combiner is disposed at the output end of the first beam splitter. The optical device of this invention uses a frequency halving technique to convert a portion of the original beam with lower energy into a beam with doubled wavelength using an optical parametric oscillator. Then, a portion of the original beam with higher energy is used as a pump source to amplify the beam with doubled wavelength. This allows a 2μm laser beam to be generated from a 1μm wavelength laser beam, a technology matured in industrial high-power material processing. The device is characterized by low implementation difficulty, high controllability, high conversion efficiency, and suitability for industrial applications. Therefore, this invention effectively overcomes the shortcomings of existing technologies and possesses high industrial applicability.

[0147] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An optical device for frequency halving, characterized by The optical device includes at least: Laser, first beam splitter, optical parametric oscillator, first beam combiner, phase matcher, optical parametric amplifier and harmonic beam splitter; The laser provides a beam with a first wavelength; The first beam splitter is disposed at the output end of the laser and is used to split the beam having a first wavelength, wherein the intensity of the first split beam is less than the intensity of the second split beam. The optical parametric oscillator is located at the output end of the first beam splitter, and halves the frequency of the first beam to obtain a beam with double the wavelength. The first beam combiner is disposed at the output end of the first beam splitter and the optical parametric oscillator, and superimposes the beam with doubled wavelength with the split beam having the first wavelength; The phase matcher receives the beam from the output of the first beam combiner and adjusts the relative phase between the wavelength-doubled beam and the beam splitting beam having the first wavelength, so that the energy of the beam splitting beam having the first wavelength is converted into the wavelength-doubled beam in the optical parametric amplifier. The optical parametric amplifier amplifies the light beam by doubling its wavelength; The harmonic beam splitter is located at the output of the optical parametric amplifier and is used to separate beams of different wavelengths.

2. The optical device of claim 1, wherein: The optical parametric amplifier includes a first reflector, a second reflector, and a first gain medium; the phase matcher includes a first phase matching unit, a second phase matching unit, and a third phase matching unit. The first reflector and the second reflector are positioned opposite each other, and the first gain medium is disposed between the first reflector and the second reflector; the light beam passes through a phase matching unit each time it passes through the first gain medium; Wherein, the first reflector and the second reflector are ridge-type reflectors, or the first reflector and the second reflector are curved surface reflectors.

3. The optical device of claim 1, wherein: The laser uses a crystal doped with Nd or Yb ions, and the first wavelength is 1 μm to 1.1 μm.

4. The optical device of claim 1, wherein: The phase matcher uses an optical material, and the relative phase of two beams is adjusted by adjusting the thickness or orientation of the optical material, or by utilizing the temperature effect, piezoelectric effect, electro-optic effect or magneto-optic effect within the optical material.

5. The optical device of claim 1, wherein: The optical parametric oscillator includes a first curved mirror, a second curved mirror, a first flat mirror, a second flat mirror, and a nonlinear optical crystal; The first curved mirror, the second curved mirror, the first flat mirror, and the second flat mirror constitute an optical resonant cavity for doubling the wavelength of the light beam, and the nonlinear optical crystal is disposed within the optical resonant cavity.

6. The optical device of claim 5, wherein: The optical parametric oscillator also includes an optical etalon, which is disposed in the optical path within the optical resonant cavity.

7. The optical device of claim 5, wherein: The first or second planar reflector is replaced by a grating.

8. The optical device of claim 1, wherein: When the beam received by the first beam combiner contains the remaining pump beam from the previous stage, the optical device further includes a phase controller disposed between the first beam splitter and the corresponding first beam combiner. The phase controller is used to adjust the phase of the split beam having a first wavelength so that the phases of the beams having the first wavelength input into the same first beam combiner are consistent.

9. The optical device according to any one of claims 1, 3-8, wherein: The first beam combiner, the phase matcher, and the optical parametric amplifier constitute a frequency division amplification unit, and the optical device includes N frequency division amplification units; the first beam splitter outputs N+1 split beams, and the intensity of the first split beam with a first wavelength is less than the intensity of the other split beams; N is a natural number greater than or equal to 2; Each frequency-division amplification unit is cascaded sequentially between the output of the optical parametric oscillator and the input of the harmonic beam splitter. Each frequency-division amplification unit receives the second to the (N+1)th beam splitter output from the first beam splitter, obtains a beam with a first wavelength from the first beam splitter, obtains a beam with doubled wavelength from the previous stage, and converts the energy of the beam with the first wavelength into the beam with doubled wavelength. The energy of the beam with doubled wavelength is gradually enhanced through the cascading of N-stage frequency-division amplification units.

10. The optical device of claim 9, wherein: The N frequency division amplification units include a third curved mirror, a fourth curved mirror, a second gain medium, a third gain medium, a dichroic beam splitter, and N phase matching units; The third curved mirror and the fourth curved mirror are arranged opposite to each other to form an off-axis confocal unstable resonant cavity; the second gain medium and the third gain medium are arranged side by side between the third curved mirror and the fourth curved mirror; the light beam passes through a phase matching unit before passing through each gain medium each time; The dichroic beam splitter is disposed between each gain medium and the fourth curved mirror; a beam with doubled wavelength is input from between the third curved mirror and the gain medium, and a beam with the first wavelength is input as a pump source through the dichroic beam splitter.

11. The optical device of claim 10, wherein: The third curved mirror is coated with an antireflective film relative to a light beam having a first wavelength, and a high reflective film relative to a light beam having twice the wavelength.

12. The optical device according to any one of claims 1-8, characterized in that: The first beam combiner, the phase matcher, and the optical parametric amplifier constitute a frequency division amplification unit. The optical device includes M frequency division amplification units and M harmonic beam splitters. The optical device also includes a second beam splitter. The first beam splitter outputs M+1 split beams, and the intensity of the first split beam with a first wavelength is less than the intensity of the other split beams. M is a natural number greater than or equal to 2. The second beam splitter is located at the output end of the optical parametric oscillator and is used to split the beam with doubled wavelength into M beams. Each frequency division amplifier unit receives the second to M+1 beam splits output from the first beam splitter, and the second input receives the beam split with doubled wavelength output from the second beam splitter. A beam with a first wavelength is obtained from the first beam splitter, and a beam with doubled wavelength is obtained from the second beam splitter. The energy of the beam with the first wavelength is converted into the beam with doubled wavelength through M parallel channels.

13. The optical device of claim 12, wherein: The optical device also includes a coherent combiner and M-1 or M phase controllers; Each phase controller is located at the output of a harmonic beam splitter, and the coherent combiner is located at the output of each phase controller. The phase controller is used to control the relative phase of the output beams of each channel so that the output beams of each channel can be coherently combined and superimposed.

14. The optical device of any of claims 1-8, wherein: The first beam splitter, optical parametric oscillator, first beam combiner, phase matcher, optical parametric amplifier, and harmonic beam splitter constitute a frequency-division oscillation amplification module. The optical device includes P frequency-division oscillation amplification modules, as well as a third beam splitter and a second beam combiner. The laser provides P beams of different wavelengths; P is a natural number greater than or equal to 2. The third beam splitter is located at the output end of the laser and is used to separate beams of different wavelengths and provide them to the corresponding frequency division oscillation amplification module. Each frequency division oscillation amplification module doubles the wavelength of the beam provided by the third beam splitter, one by one. The second beam combiner is located at the output end of each frequency division oscillation amplification module to combine the beams of different wavelengths output by each frequency division oscillation amplification module.

15. The optical device of claim 14, wherein: The laser includes an oscillator, with beams of different wavelengths distributed sequentially in the time domain; or the laser includes P oscillators and a third beam combiner, with each oscillator providing beams of different wavelengths, which are then combined by the third beam combiner and output.

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