A device and method for realizing high repetition rate nonlinear frequency conversion

Abstract

The present invention relates to the technical field of laser nonlinear frequency conversion, and discloses a device and method for realizing high-repetition-rate nonlinear frequency conversion, including: a pulsed light source that emits fundamental frequency light with a linear polarization state; a time-domain beam splitting system that splits the fundamental frequency light into 2n groups of polarized light; the repetition frequency of each group of polarized light with orthogonal polarization directions is 1 / 2<supgt;n+1< / supgt; of the repetition frequency of the fundamental frequency light, where n≥0; a nonlinear frequency conversion system that generates two beams of signal light with the same pulse sequence for each group of polarized light; a time-domain beam combining system that combines the generated 2<supgt;n+1< / supgt> groups of signal light to obtain a combined light output with the same repetition frequency as the fundamental frequency light; the present invention uses an electro-optic modulator and a polarization beam splitter to split the high-repetition-rate fundamental frequency light into two beams of low-repetition-rate pulses, and then combines the wavelengths that generate nonlinear conversion through an optical path with a delay in an annular reflection cavity at equal time intervals, so as to combine the low-repetition-rate pulses into high-repetition-rate pulses, realizing high-energy, high-repetition-rate nonlinear frequency conversion.

Description

Technical Field

[0001] The present invention relates to the technical field of laser nonlinear frequency conversion, and in particular to a device and method for realizing high repetition rate nonlinear frequency conversion. Background Art

[0002] High repetition rate, high energy ultrafast lasers are widely used in advanced medical equipment, laser micro-nano processing, defense laser weapons and other fields. In particular, the research on 1μm band lasers is very mature and has begun to be used in different fields. However, due to material limitations, lasers that can directly generate other bands (such as visible, mid-infrared, etc.) are not so mature.

[0003] Currently, the main technical means used to convert mature 1μm band lasers to the required wavelength are based on nonlinear frequency conversion methods, including frequency doubling, optical parametric amplification, optical parametric oscillation, etc.

[0004] For nonlinear frequency conversion technology, in addition to the mature 1μm band laser as the fundamental frequency light source, the performance of nonlinear crystals is also crucial. A good nonlinear crystal needs to have a large nonlinear coefficient, a high damage threshold and good stability. However, some nonlinear crystals with good nonlinear coefficients (such as BaGa4Se7 crystals) have poor thermal conductivity during high repetition rate nonlinear conversion, which causes the crystal to accumulate heat, and its damage threshold is also lower than that of low repetition rate nonlinear conversion, which affects its nonlinear conversion efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a nonlinear frequency conversion device that can achieve high repetition rate and solve at least one of the above-mentioned technical problems. The specific solution is as follows:

[0006] According to a specific embodiment disclosed in the present invention, a first aspect of the present invention provides a device capable of realizing high repetition rate nonlinear frequency conversion, comprising:

[0007] The pulse light source emits a linear polarization state with a wavelength of The fundamental frequency light;

[0008] The time domain beam splitting system splits the fundamental frequency light into two n A group of polarized light; wherein each group of polarized light includes two beams of first polarized light and second polarized light with orthogonal polarization directions, and the repetition frequency of each polarized light is 1 / 2 of the repetition frequency of the fundamental frequency light n+1 , n≥0;

[0009] A nonlinear frequency conversion system is used to generate two beams of polarized light with the same pulse sequence and a wavelength of signal light;

[0010] The time-domain beam combining system generates 2 n+1 Combining the signal light beams to obtain a synthetic light output having the same repetition frequency as the fundamental frequency light;

[0011] Among them, the time domain beam combining system includes: a delay control unit and a time domain beam combining unit, the delay control unit is configured to make the pulse peak value and the pulse interval of the pulse sequence of two signal lights before synthesis correspond to each other at the same time; the time domain beam combining unit is configured to combine the two pulse sequences whose pulse peak value and pulse interval correspond to each other.

[0012] Preferably, the nonlinear frequency conversion system comprises:

[0013] 2 n+1 A nonlinear frequency conversion unit is provided, each of the nonlinear frequency conversion units is arranged on the optical path of each beam of polarized light, so that each group of polarized light generates a first signal light and a second signal light having a pulse sequence.

[0014] Preferably, the time domain beam combining system comprises: n+1 -1 delay control unit and 2 n+1 -1 time domain beam combining unit;

[0015] When n=0, the delay control unit is arranged on the optical path of a beam of the signal light, so that the pulse peaks and pulse intervals of the two pulse sequences at the same time correspond to each other;

[0016] When n>0, the delay control unit is respectively arranged on the optical path of any beam of the signal light so that at the same time, the delay control unit with 1 / 2 n+1 The first signal light and the second signal light can be combined into a beam having a repetition frequency of 1 / 2 n The signal light of the repetition frequency makes the adjacent two paths have 1 / 2 n The signal light with repetition frequency can be combined into a beam with 1 / 2 n-1 Repeat the signal light of the frequency until 2 n+1 - The repetition frequency of the combined signal light is the same as the repetition frequency of the fundamental frequency light;

[0017] 2 n+1 -1 time domain beam combining unit, so that the generated 2 n+1 The signal light beams are combined to obtain a signal light output having the same repetition frequency as the fundamental frequency light.

[0018] Preferably, the time domain beam splitting system comprises:

[0019] A first electro-optical modulator changes the fundamental frequency light from a linear polarization state to an orthogonal linear polarization state;

[0020] The first polarization beam splitter is used to split the fundamental frequency light into transmitted light and reflected light according to the polarization state of the fundamental frequency light modulated by the first electro-optical modulator; the transmitted light is the first polarized light with the first polarization direction, and the reflected light is the second polarized light with the second polarization direction.

[0021] Preferably, the nonlinear frequency conversion system is a nonlinear frequency conversion system based on a second-order nonlinear optical effect;

[0022] The type of nonlinear frequency conversion includes at least one of the following: second harmonic generation, optical parametric generation, optical parametric oscillation and optical parametric amplification.

[0023] Preferably, the delay control unit comprises:

[0024] The annular reflection cavity comprises: a second polarization beam splitter, which makes the first signal light or the second signal light with a first polarization direction to be cyclically reflected in the annular reflection cavity; and makes the first signal light or the second signal light with a second polarization direction to be transmitted;

[0025] The second photoelectric modulator is arranged in the annular reflection cavity and on the optical path where the second polarization beam splitter is incident. By changing the polarization state of the first signal light or the second signal light, the first signal light or the second signal light can be circularly reflected in the annular reflection cavity, so that the output first signal light or the second signal light has a second polarization direction.

[0026] Preferably, the annular reflection cavity further comprises: a second total reflection mirror, a third total reflection mirror and a fourth total reflection mirror;

[0027] The first signal light or the second signal light having the first polarization direction is circularly reflected in the annular reflection cavity.

[0028] Preferably, the delay control unit further comprises: a position adjustment mechanism;

[0029] By synchronously changing the positions of the second total reflective mirror and the third total reflective mirror, the optical path of the first signal light or the second signal light in the annular reflective cavity is adjusted;

[0030] Or by synchronously changing the positions of the third total reflection mirror and the fourth total reflection mirror, the optical path of the first signal light or the second signal light in the annular reflection cavity is adjusted so that the pulse peaks and pulse intervals of the two pulse sequences before synthesis at the same time correspond to each other.

[0031] Preferably, the time domain beam combining unit comprises:

[0032] A half-wave plate, which makes the polarization directions of the two signal lights before synthesis orthogonal;

[0033] The third polarization beam splitter is used to combine two adjacent signal beams with the same repetition frequency.

[0034] According to the specific implementation mode disclosed in the present invention, the second aspect of the present invention provides a method for realizing high repetition rate nonlinear frequency conversion, comprising:

[0035] The pulse fundamental frequency light with linear polarization state is split to obtain 2 n A group of polarized light, wherein each group of polarized light includes two beams of first polarized light and second polarized light with orthogonal polarization directions, and the repetition frequency of each polarized light is 1 / 2 of the repetition frequency of the fundamental frequency light n+1 , n≥0;

[0036] Using nonlinear frequency conversion technology, 2 n Group polarization conversion to 2 n groups of signal lights having the same pulse sequence, wherein each group of signal lights having the same pulse sequence comprises two beams of first signal light and second signal light having the same polarization direction;

[0037] Adjust the polarization state of the first signal light or the second signal light in each group, and the optical path of the signal light in the delay control unit where it is located, so that at the same time, the two signal lights with 1 / 2 n+1 The first signal light and the second signal light can be combined into a beam having a repetition frequency of 1 / 2 n The signal light of the repetition frequency; adjusting any one of the channels having 1 / 2 n The optical path of the signal light of the repetition frequency in the delay control unit is such that the two adjacent paths have 1 / 2 n The signal light with repetition frequency can be combined into a beam with 1 / 2 n-1 Repeat the signal light of the frequency until 2 n+1 - The repetition frequency of the combined signal light is the same as the repetition frequency of the fundamental frequency light;

[0038] Adjust the polarization direction of the signal light so that the polarization directions of the two signal lights before beam combination are orthogonal, so that the generated 2 n+1 The signal lights are combined to obtain signal lights having the same repetition frequency as the fundamental frequency light.

[0039] Compared with the prior art, the above solution disclosed in the present invention has at least the following beneficial effects:

[0040] The present invention utilizes an electro-optic modulator and a polarization beam splitter to divide a high repetition rate fundamental frequency light into multiple low repetition rate pulses, which are then injected into nonlinear crystals respectively to generate wavelengths of nonlinear conversion and then combined at equal time intervals through a time domain beam combining system with a delayed light path, thereby synthesizing the low repetition rate pulses into the previous high repetition rate pulses, and ultimately achieving high energy, high repetition rate nonlinear frequency conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the disclosure of the present invention, and together with the specification, are used to explain the principles disclosed in the present invention. Obviously, the drawings described below are only some embodiments disclosed in the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0042] Figure 1 This is a principle diagram of an optical path of a device for realizing a high repetition rate nonlinear frequency conversion provided by the first embodiment of the present invention;

[0043] Figure 2 It is a schematic diagram of the optical path of a multi-channel high repetition rate nonlinear frequency conversion device according to the second embodiment of the present invention.

[0044] Reference numerals:

[0045] P: polarization beam splitter; P1: first polarization beam splitter; P2: second polarization beam splitter; P3: third polarization beam splitter;

[0046] M1: 45° total reflector; M2: second total reflector; M3: third total reflector; M4: fourth total reflector;

[0047] PC: photoelectric modulator; PC1: first photoelectric modulator; PC2: second photoelectric modulator;

[0048] : Half-wave plate. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages disclosed in the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments disclosed in the present invention, rather than all the embodiments. Based on the embodiments disclosed in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection disclosed in the present invention.

[0050] The terms used in the embodiments disclosed in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the disclosure of the present invention. The singular forms "a", "said" and "the" used in the embodiments disclosed in 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.

[0051] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0052] It should be understood that although the terms first, second, third, etc. may be used to describe in the disclosed embodiments of the present invention, these descriptions should not be limited to these terms. These terms are only used to distinguish the descriptions. For example, without departing from the scope of the disclosed embodiments of the present invention, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0053] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0054] 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.

[0055] The optional embodiments disclosed in the present invention are described in detail below with reference to the accompanying drawings.

[0056] Mid-infrared nonlinear optical crystals have important applications in mid-infrared laser technology, and different crystals have different transmittance ranges and performance characteristics. The selection of suitable crystal materials requires comprehensive consideration of factors such as its nonlinear coefficient, transmittance range, laser damage threshold and thermal conductivity. For example, BaGa4Se7 (BGSe, barium gallium selenide) crystal is a mid-infrared nonlinear crystal with excellent optical properties and thermal stability. It is suitable for mid-infrared laser frequency conversion, terahertz wave generation and nonlinear optical research, but due to its poor thermal conductivity, it cannot be used in high repetition rate, high energy nonlinear frequency conversion. Therefore, the present invention provides a device that can achieve high repetition rate nonlinear frequency conversion, such as Figure 1-Figure 2 As shown, including:

[0057] Pulse light source, emitting linearly polarized light with a wavelength of The fundamental frequency light;

[0058] A time domain beam splitting system is used to split the base frequency light into 2n groups of polarized light; each group of polarized light includes two beams of first polarized light and second polarized light with orthogonal polarization directions, and the repetition frequency of each polarized light is 1 / 2 of the repetition frequency of the base frequency light. n+1 , n≥0.

[0059] In this embodiment, the time domain beam splitting system is composed of multiple groups of photoelectric modulation PC, polarization beam splitter P1 and 45° total reflection mirror M1, which are used to obtain 2 n Group of polarized light.

[0060] Specifically, Figure 2 As shown, the fundamental frequency light is split into two polarized lights after passing through the first photoelectric modulation PC, polarization beam splitter P1 and 45° total reflection mirror M1. Each polarized light is passed through the half-wave plate and the second photoelectric modulation PC, polarization beam splitter P1 and 45° total reflection mirror M1 to obtain a group of first polarized light and second polarized light with orthogonal polarization directions. At this time, the repetition frequency of each polarized light is 1 / 2 of the repetition frequency of the fundamental frequency light. n+1 .

[0061] The nonlinear frequency conversion system enables each group of polarized light to generate two signal lights with the same pulse sequence.

[0062] In this embodiment, the nonlinear frequency conversion system is a nonlinear frequency conversion based on the second-order nonlinear optical effect, so that each wavelength is The fundamental frequency light can be converted into a beam with a wavelength of Signal light. Includes 2 n+1 A nonlinear frequency conversion unit is provided, each of which is arranged on the optical path of each polarized light beam, so that the nonlinear frequency conversion system emits 2 n Group signal light (2 n+1 The generated idler light is reflected out of the system.

[0063] The time domain beam combining system combines the generated 2n+1 groups of signal light to obtain a synthetic light output having the same repetition frequency as the fundamental frequency light.

[0064] Specifically, the time domain beam combining system includes: n+1 -1 delay control unit and 2 n+1 -1 time domain beam combining unit.

[0065] When n=0, the delay control unit is arranged on the optical path of a beam of signal light, so that the pulse peak value of the pulse sequence of the beam of signal light corresponds to the pulse interval of the pulse sequence of the other beam of signal light at the same time.

[0066] When n>0, the delay control unit is respectively arranged on the optical path of any one of the signal beams of each group of signal beams, so that at the same time, the delay control unit has 1 / 2 n+1 The first signal light and the second signal light can be combined into a beam having a repetition frequency of 1 / 2 n The signal light of repetition frequency; and arranged in two adjacent paths and having 1 / 2 n On the optical path of any signal beam with a repetition frequency of 1 / 2 n The signal light with repetition frequency can be combined into a beam with 1 / 2 n-1 The signal light with a repetition frequency, and so on, until two signal lights with a repetition frequency of 1 / 2 of the fundamental frequency light can be combined, so that the repetition frequency of the combined signal lights is the same as the repetition frequency of the fundamental frequency light.

[0067] 2 n+1 -1 time domain beam combining system, so that the generated 2 n+1 The signal light beams are combined to obtain a signal light output having the same repetition frequency as the fundamental frequency light. Example 1

[0068] by Figure 1 Taking the implementation method when n=0 as an example, the fundamental frequency light is a pulsed laser wavelength with a linear polarization state and a high repetition frequency. The pulse laser has an average power of 10W, a pulse width of 800ps, and a repetition frequency of 1KHz. The nonlinear crystal used to generate nonlinear frequency conversion using optical parameters is BaGa4Se7 crystal.

[0069] The time domain beam splitting system includes: a first electro-optical modulator PC1 and a first polarization beam splitter P1.

[0070] When the linearly polarized pulse fundamental frequency light passes through the first electro-optical modulator, the electro-optical modulator periodically changes the polarization state of the incident light under the action of voltage to form fundamental frequency light with both vertical polarization direction and horizontal polarization direction.

[0071] The first polarization beam splitter P1 splits the fundamental frequency light into two beams of light, a transmitted light and a reflected light, according to the polarization state of the fundamental frequency light. The light having the same polarization direction as the transmission axis of the first polarization beam splitter is the first polarized light with horizontal polarization in this embodiment; the light having the polarization direction orthogonal to the transmission axis of the first polarization beam splitter is the second polarized light with vertical polarization in this embodiment.

[0072] Furthermore, the first photoelectric modulator PC1 is a Pockels cell, which is a laser modulator based on the electro-optical effect. When a high voltage is applied to it, the polarization state of the linear polarized light incident therein will change. Therefore, the polarization state of the fundamental frequency light can be controlled in real time by the Pockels cell to obtain the fundamental frequency light in the vertical polarization direction and the horizontal polarization direction. At the same time, by setting the parameters of the Pockels cell and making its trigger signal and the fundamental frequency light use the same trigger source, the synchronization of the pulse time domain is guaranteed.

[0073] Furthermore, the first polarization beam splitter P1 is used to separate the two pulsed fundamental frequency lights of different polarization states, so that the transmitted light and the reflected light respectively contain a portion of pulses of the fundamental frequency light with a high repetition rate. Therefore, the repetition frequency of the first polarized light and the second polarized light is half of the repetition frequency of the fundamental frequency light, realizing the conversion of the fundamental frequency light from high repetition rate to low repetition rate, and reducing the heat load on the single nonlinear crystal.

[0074] In this embodiment, the pressurization time of the Pockels cell is set to be 500us later than the pulse time of the laser, the duration is 1ms, the period is 500Hz, and its trigger signal and the base frequency light use the same trigger source to ensure the synchronization of the pulse time domain, and obtain linear polarized light with orthogonality. Then, the first polarized light of the horizontal polarization component in the base frequency light is transmitted through the first polarization beam splitter, and the second polarized light of the vertical polarization component in the base frequency light is reflected, wherein the repetition frequency of the first polarized light and the second polarized light is 500Hz.

[0075] In order to achieve the final beam combination, a 45° total reflection mirror M1 is arranged on the optical path of the reflected light to reflect the second polarized light so that it propagates in a direction parallel to the first polarized light. In other embodiments, the 45° total reflection mirror M1 can also be arranged after the second nonlinear frequency conversion system.

[0076] In this embodiment, the nonlinear frequency conversion system is a nonlinear frequency conversion based on the second-order nonlinear optical effect. After being injected into the nonlinear crystal, the signal light is generated through nonlinear frequency conversion. Idle light .

[0077] Furthermore, the type of nonlinear frequency conversion can be: second harmonic generation SHG, optical parametric generation OPG or optical parametric oscillation OPO. In other embodiments, it can also be nonlinear frequency conversion of optical parametric amplifier OPA. At this time, the incident light is the fundamental frequency light. and the signal light to be amplified , so you need to set up a separate one for reflection The signal light of wavelength is totally reflected by the mirror.

[0078] Furthermore, the nonlinear frequency conversion system of this embodiment includes: a first nonlinear frequency conversion unit, a second nonlinear frequency conversion unit, and a 45° dichroic mirror DM1 for reflecting the transmission signal light of the idler light, which can pass the signal light having a wavelength of The signal light with reflected wavelength is and The idler frequency light and fundamental frequency light.

[0079] In this embodiment, the first polarized light and the second polarized light are respectively passed through the first nonlinear frequency conversion unit and the second nonlinear frequency conversion unit to generate The signal light and The idler light is respectively Fundamental frequency light and The idler light is reflected, and the wavelength is At this time, the first signal light is in a horizontal polarization state, and the second signal light is in a vertical polarization state.

[0080] Furthermore, since the phase matching condition of the nonlinear crystal usually requires that the polarization directions of the input light and the output light satisfy a certain relationship, and in order to enable the first signal light emitted through the delay control system to be combined with the second signal light, a half-wave plate can be set after the first nonlinear frequency conversion unit to adjust the polarization state of the signal light entering the delay control system according to the polarization direction of the first signal light.

[0081] In this embodiment, the time-domain beam combining system includes one delay control unit and one time-domain beam combining unit.

[0082] The delay control unit includes: an annular reflective cavity and a second photoelectric modulator PC2, which controls the polarization state of the first signal light in the annular reflective cavity in real time through the second photoelectric modulator PC2, so that the first signal light is circularly reflected in the annular reflective cavity. Then, by adjusting the optical path of the first signal light reflected in the annular reflective cavity, the first signal light is regulated, thereby strictly controlling the beam combining time of the first signal light and the second signal light.

[0083] Furthermore, the annular reflection cavity is composed of a second polarization beam splitter P2, a second total reflection mirror M2, a third total reflection mirror M3 and a fourth total reflection mirror M4. By symmetrically arranging them in pairs, the first signal light incident through the second polarization beam splitter P2 is reflected in turn by the second total reflection mirror M2, the third total reflection mirror M3 and the fourth total reflection mirror M4, and the first signal light emitted from the fourth total reflection mirror M4 is reflected again by the second polarization beam splitter P2 to form a delayed light path.

[0084] In this embodiment, the second polarization beam splitter P2 is a polarization beam splitter acting on the signal light. The second polarization beam splitter P2 transmits the vertically polarized first signal light and reflects the horizontally polarized first signal light.

[0085] The second photoelectric modulator is arranged in the annular reflection cavity and on the light path where the second polarization beam splitter P2 is incident. By changing the polarization state of the first signal light, the first signal light can be circularly reflected in the annular reflection cavity, so that the output first signal light has a second polarization direction. Preferably, the second photoelectric modulator is a Pockels cell.

[0086] Taking the first signal light emitted from the first nonlinear frequency conversion unit with a horizontal polarization direction and the second signal light emitted from the second nonlinear frequency conversion system with a vertical polarization direction as an example, the polarization direction of the first signal light is first adjusted to a vertical direction through a half-wave plate and enters the delay control unit. At this time, the polarization direction of the first signal light with a vertical polarization direction does not change when it is reflected by the second total reflection mirror M2, the third total reflection mirror M3 and the fourth total reflection mirror M4. In order to enable the first signal light to be cyclically reflected in the annular reflection cavity, a voltage is applied to the second photoelectric modulator PC2 to make it at a high potential, and the polarization direction of the first signal light is horizontal. At this time, the first signal light with a horizontal polarization direction is reflected by the second polarization beam splitter P2, and is reflected again by the second total reflection mirror M2, the third total reflection mirror M3 and the fourth total reflection mirror M4. When passing through the second photoelectric modulator PC2 again, the polarization state of the first signal light does not change because it is at a low potential. In this way, the number of cycles of the first signal light in the annular reflection cavity can be controlled.

[0087] Furthermore, the position adjustment mechanism is used to synchronously change the positions of the second total reflection mirror M2 and the third total reflection mirror M3, or synchronously change the positions of the third total reflection mirror M3 and the fourth total reflection mirror M4, so as to adjust the optical path of the first signal light in the annular reflection cavity, thereby controlling the time required for the first signal light to reflect one circle in the annular reflection cavity, that is, regulating the pulse delay of the first signal light.

[0088] At the same moment, when a pulse peak in the pulse sequence of the first signal light corresponds to any pulse interval in the pulse sequence of the second signal light, the pulses in the two pulse sequences are staggered, and the pulse peak of the first signal light is just located in the middle of the two pulses of the second signal light, a voltage is applied to the second photoelectric modulator PC2 again to adjust the first signal light from horizontal polarization to vertical polarization, and the first signal light is output after being transmitted through the second polarization beam splitter P2 and enters the time domain beam combining unit.

[0089] Furthermore, the time domain beam combining unit includes: a third polarization beam splitter P3, which is used to combine the first signal light and the second signal light, thereby combining two low repetition rate pulses into the previous high repetition rate pulse, and finally realizing high energy, high repetition rate nonlinear frequency conversion.

[0090] In this embodiment, it is taken as an example that the third polarization beam splitter P3 transmits vertically polarized light and reflects horizontally polarized light.

[0091] When the first signal light emitted from the delay control unit is vertically polarized, a half-wave plate is used to adjust it to horizontal polarization in order to enable beam combining, so that the first signal light and the second signal light are combined by the third polarization beam splitter P3.

[0092] When the first signal light emitted from the delay control unit is horizontally polarized, the first signal light and the second signal light are combined on the third polarization beam splitter P3, that is, two pulse signal lights with a repetition frequency of 500 Hz are combined into the previous 1 kHz high repetition rate pulse signal light, ultimately achieving high energy, high repetition rate nonlinear frequency conversion.

[0093] Example 3

[0094] The wavelength of the fundamental frequency light with linear polarization The pulse laser has an average power of 10W, a pulse width of 800ps, and a repetition frequency of 1KHz. The nonlinear crystal used to generate nonlinear frequency conversion using optical parameters is BaGa4Se7 crystal, and n=1.

[0095] The time domain beam splitting system uses a combination of multiple polarization beam splitters and a 45° total reflection mirror M1 to split the fundamental frequency light into two groups of polarized light. Figure 2 As shown, the fundamental frequency light first enters the Pockels cell PC, and the Pockels cell pressurization time is set to be 500us later than the laser pulse time, the duration is 1ms, the period is 500Hz, and its trigger signal and the fundamental frequency light use the same trigger source to ensure the synchronization of the pulse time domain and obtain orthogonal linear polarized light.

[0096] Then, the first polarized light of the horizontal polarization component in the fundamental frequency light is transmitted through the first polarization beam splitter P1, and the second polarized light of the vertical polarization component in the fundamental frequency light is reflected, wherein the repetition frequency of the first polarized light and the second polarized light is 500 Hz.

[0097] The first polarized light with horizontal polarization in the first path is converted into polarized light with both horizontal and vertical polarization directions after passing through the half-wave plate and the Pockels cell PC again; the first polarization beam splitter P1 is then used to transmit the polarized light of the horizontal polarization component and reflect the polarized light of the vertical polarization component to obtain a group of first polarized light and second polarized light with two beams of orthogonal polarization directions, and the repetition frequency of each beam of polarized light is 1 / 4 of the repetition frequency of the fundamental frequency light.

[0098] Similarly, after beam splitting, the second polarized light with vertical polarization will also obtain a group of first polarized light and second polarized light with two orthogonal polarization directions, and the repetition frequency of each polarized light is 1 / 4 of the repetition frequency of the fundamental frequency light.

[0099] Four polarized beams enter the nonlinear frequency conversion system and generate four The signal light and The idler light is respectively Fundamental frequency light and The idler light is reflected, and the wavelength is That is, the four polarized lights pass through the nonlinear frequency conversion system to generate the first signal light, the second signal light, the third signal light and the fourth signal light.

[0100] Using the first delay control unit to adjust the pulse delay and polarization direction of the first signal light, so that the first signal light and the second signal light are combined in the first time domain combining unit to obtain a 12th signal light with a repetition frequency of 500 Hz;

[0101] The pulse delay and polarization direction of the fourth signal light are adjusted by using the second delay control unit, so that the third signal light and the fourth signal light are combined in the second time domain combining unit to obtain the 34th signal light with a repetition frequency of 500 Hz;

[0102] The third delay control unit is then used to adjust the pulse delay and polarization direction of the 12th signal light, so that the 12th signal light and the 34th signal light are combined in the third time domain combining unit to synthesize the previous 1KHz high repetition rate pulse signal light, and finally achieve high energy, high repetition rate nonlinear frequency conversion.

[0103] The present invention also provides method embodiments corresponding to the above embodiments. The explanations based on the same name meanings are the same as those of the above embodiments, and have the same technical effects as the above embodiments, which will not be repeated here.

[0104] The present invention discloses a method for realizing high repetition rate nonlinear frequency conversion, comprising the following steps:

[0105] Step S102: split the pulse fundamental frequency light with linear polarization state to obtain 2 n A group of polarized light, wherein each group of polarized light includes two beams of first polarized light and second polarized light with orthogonal polarization directions, and the repetition frequency of each polarized light is 1 / 2 of the repetition frequency of the fundamental frequency light n+1 , n≥0.

[0106] Step S104: Using nonlinear frequency conversion technology to convert 2 n Group polarization conversion to 2 n The signal lights of the plurality of groups have the same pulse sequence, wherein each of the signal lights of the plurality of groups has the same pulse sequence comprises a first signal light and a second signal light with the same polarization direction.

[0107] Step S106: adjust the polarization state of the first signal light or the second signal light in each group, and the optical path of the signal light in the delay control unit where it is located, so that at the same time, the polarization state of the first signal light or the second signal light is 1 / 2 n+1The first signal light and the second signal light can be combined into a beam having a repetition frequency of 1 / 2 n The signal light of the repetition frequency; adjusting any one of the channels having 1 / 2 n The optical path of the signal light of the repetition frequency in the delay control unit is such that the two adjacent paths have 1 / 2 n The signal light with repetition frequency can be combined into a beam with 1 / 2 n-1 Repeat the signal light of the frequency until 2 n+1 The repetition frequency of the signal light after the -1 channel is combined is the same as the repetition frequency of the fundamental frequency light.

[0108] Step S108: Adjust the polarization direction of the signal light so that the polarization directions of the two signal lights before beam combination are orthogonal, so that the generated 2 n+1 The signal lights are combined to obtain signal lights having the same repetition frequency as the fundamental frequency light.

[0109] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the system or device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0110] The above embodiments are only used to illustrate the technical solutions disclosed in the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments disclosed in the present invention.

Claims

1. A device capable of realizing high repetition rate nonlinear frequency conversion, characterized in that: include: The pulse light source emits a linear polarization state with a wavelength of The fundamental frequency light; The time domain beam splitting system splits the fundamental frequency light into two n A group of polarized light; wherein each group of polarized light includes two beams of first polarized light and second polarized light with orthogonal polarization directions, and the repetition frequency of each polarized light is 1 / 2 of the repetition frequency of the fundamental frequency light n +1 , n≥0; A nonlinear frequency conversion system is used to generate two beams of polarized light with the same pulse sequence and a wavelength of signal light; The time-domain beam combining system generates 2 n+1 The signal lights are combined to obtain a synthetic light output having the same repetition frequency as the fundamental frequency light; Among them, the time domain beam combining system includes: a delay control unit and a time domain beam combining unit, the delay control unit is configured to make the pulse peak value and the pulse interval of the pulse sequence of two signal lights before synthesis correspond to each other at the same time; the time domain beam combining unit is configured to combine the two pulse sequences whose pulse peak value and pulse interval correspond to each other.

2. The device capable of realizing high repetition rate nonlinear frequency conversion according to claim 1, characterized in that: The nonlinear frequency conversion system comprises: 2 n+1 A nonlinear frequency conversion unit is provided, each of the nonlinear frequency conversion units is arranged on the optical path of each beam of polarized light, so that each group of polarized light generates a first signal light and a second signal light having a pulse sequence.

3. The device for realizing high repetition rate nonlinear frequency conversion according to claim 2, characterized in that: The time domain beam combining system comprises: n+1 -1 delay control unit and 2 n+1 -1 time domain beam combining unit; When n=0, the delay control unit is arranged on the optical path of a beam of the signal light, so that the pulse peaks and pulse intervals of the two pulse sequences at the same time correspond to each other; When n>0, the delay control unit is respectively arranged on the optical path of any beam of the signal light so that 1 / 2 n+1 The first signal light and the second signal light can be combined into a beam having a repetition frequency of 1 / 2 n The signal light of the repetition frequency makes the adjacent two paths have 1 / 2 n The signal light with repetition frequency can be combined into a beam with 1 / 2 n-1 Repeat the signal light of the frequency until 2 n+1 - The repetition frequency of the combined signal light is the same as the repetition frequency of the fundamental frequency light; 2 n+1 -1 time domain beam combining unit, so that the generated 2 n+1 The signal light beams are combined to obtain a signal light output having the same repetition frequency as the fundamental frequency light.

4. The device for realizing high repetition rate nonlinear frequency conversion according to claim 1, characterized in that: The time domain beam splitting system comprises: A first electro-optical modulator changes the fundamental frequency light from a linear polarization state to an orthogonal linear polarization state; The first polarization beam splitter is used to split the fundamental frequency light into transmitted light and reflected light according to the polarization state of the fundamental frequency light modulated by the first electro-optical modulator; the transmitted light is the first polarized light with the first polarization direction, and the reflected light is the second polarized light with the second polarization direction.

5. The device capable of realizing high repetition rate nonlinear frequency conversion according to claim 1, characterized in that: The nonlinear frequency conversion system is a nonlinear frequency conversion based on the second-order nonlinear optical effect; The type of nonlinear frequency conversion includes at least one of the following: second harmonic generation, optical parametric generation, optical parametric oscillation and optical parametric amplification.

6. The device capable of realizing high repetition rate nonlinear frequency conversion according to claim 2, characterized in that: The delay control unit comprises: The annular reflection cavity comprises: a second polarization beam splitter, which makes the first signal light or the second signal light with a first polarization direction to be cyclically reflected in the annular reflection cavity; and makes the first signal light or the second signal light with a second polarization direction to be transmitted; The second photoelectric modulator is arranged in the annular reflection cavity and on the optical path where the second polarization beam splitter is incident. By changing the polarization state of the first signal light or the second signal light, the first signal light or the second signal light can be circularly reflected in the annular reflection cavity, so that the output first signal light or the second signal light has a second polarization direction.

7. The device capable of realizing high repetition rate nonlinear frequency conversion according to claim 6, characterized in that: The annular reflection cavity further includes: a second total reflection mirror, a third total reflection mirror and a fourth total reflection mirror; The first signal light or the second signal light having the first polarization direction is circularly reflected in the annular reflection cavity.

8. The device capable of realizing high repetition rate nonlinear frequency conversion according to claim 7, characterized in that: The delay control unit further includes: a position adjustment mechanism; By synchronously changing the positions of the second total reflective mirror and the third total reflective mirror, the optical path of the first signal light or the second signal light in the annular reflective cavity is adjusted; Or by synchronously changing the positions of the third total reflection mirror and the fourth total reflection mirror, the optical path of the first signal light or the second signal light in the annular reflection cavity is adjusted so that the pulse peaks and pulse intervals of the two pulse sequences before synthesis at the same time correspond to each other.

9. The device capable of realizing high repetition rate nonlinear frequency conversion according to claim 1, characterized in that: The time domain beam combining unit comprises: A half-wave plate, which makes the polarization directions of the two signal lights before synthesis orthogonal; The third polarization beam splitter is used to combine two adjacent signal beams with the same repetition frequency.

10. A method for realizing high repetition rate nonlinear frequency conversion, characterized in that: include: The pulse fundamental frequency light with linear polarization state is split to obtain 2 n A group of polarized light, wherein each group of polarized light includes two beams of first polarized light and second polarized light with orthogonal polarization directions, and the repetition frequency of each polarized light is 1 / 2 of the repetition frequency of the fundamental frequency light n+1 , n≥0; Using nonlinear frequency conversion technology, 2 n Group polarization conversion to 2 n groups of signal lights having the same pulse sequence, wherein each group of signal lights having the same pulse sequence comprises two beams of first signal light and second signal light having the same polarization direction; Adjust the polarization state of the first signal light or the second signal light in each group, and the optical path of the first signal light or the second signal light in the delay control unit where it is located, so that at the same time, the first signal light or the second signal light has 1 / 2 n+1 The first signal light and the second signal light can be combined into a beam having a repetition frequency of 1 / 2 n The signal light of the repetition frequency; adjusting any one of the channels having 1 / 2 n The optical path of the signal light of the repetition frequency in the delay control unit is such that the two adjacent paths have 1 / 2 n The signal light with repetition frequency can be combined into a beam with 1 / 2 n-1 Repeat the signal light of the frequency until 2 n+1 - The repetition frequency of the combined signal light is the same as the repetition frequency of the fundamental frequency light; Adjust the polarization direction of the signal light so that the polarization directions of the two signal lights before beam combination are orthogonal, so that the generated 2 n+1 The signal lights are combined to obtain signal lights having the same repetition frequency as the fundamental frequency light.

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