CN216981127U - Pockels box with large clear aperture - Google Patents

Abstract

The utility model discloses a Pockels cell with a large clear light aperture, which comprises an electro-optical crystal, wherein the upper part of the electro-optical crystal is connected with a first fixed block through a buffer layer, the lower part of the electro-optical crystal is connected with a second fixed block through a fixed layer, and a first electrode and a second electrode which are used for applying voltage to the electro-optical crystal are respectively arranged on the first fixed block and the second fixed block. According to the embodiment of the utility model, by arranging the buffer layer and the fixed layer, the problems of mechanical vibration of crystals and cooling and heat dissipation caused by a piezoelectric effect can be solved, so that the buffer layer and the fixed layer are suitable for a regenerative amplifier with high power and high energy laser output.

Description

Pockels box with large clear aperture

Technical Field

The utility model relates to the technical field of high-energy ultrafast lasers, in particular to a Pockels cell with a large clear aperture.

Background

The pockels cell is a laser device developed based on the electro-optical effect, and is widely used in high repetition frequency solid state laser Q-switches, cavity emptying of lasers, high frequency optical switches, choppers, optical choppers and high repetition frequency regenerative amplifier control. Pockels cells change the polarization state of light by a change in birefringence of an electro-optic crystal caused by an applied voltage. The refractive index of the electro-optical crystal in a certain direction is changed by applying electric field control on the electro-optical crystal, so that the Pockels cell of the electro-optical modulator can work as a variable wave plate, and the change of the polarization state is realized.

The current mainstream pockels cell has three major problems:

1. the pockels cell can generate an additional piezoelectric ringing effect during operation to cause mechanical vibration of the crystal, and particularly when the driving frequency exceeds kHz, the influence is great;

2. the electro-optic crystal has a certain damage threshold value, so that the electro-optic crystal is small in size, the application requirements of a high-power and high-energy laser cannot be met, and the problem of larger mechanical vibration and heat dissipation can be brought by increasing the size of the crystal;

3. the body fixing structure is mainly made of elastic plastic, since the thickness of the plastic pad must be large enough to ensure sufficient elasticity, such plastic pad may cause thermal problems due to limited thermal conductivity, especially in case of high laser power operation.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides a Pockels cell with a large clear aperture, which aims to solve the problems of mechanical vibration and cooling and heat dissipation of crystals caused by piezoelectric effect and is suitable for a regenerative amplifier with high-power and large-energy laser output and a high-power pulse selector.

The embodiment of the utility model provides a Pockels cell with a large clear aperture, which comprises an electro-optical crystal, wherein the upper part of the electro-optical crystal is connected with a first fixed block through a buffer layer, the lower part of the electro-optical crystal is connected with a second fixed block through a fixed layer, and a first electrode and a second electrode which are used for applying voltage to the electro-optical crystal are respectively arranged on the first fixed block and the second fixed block.

Further, the first fixed block is of a structure with a wide top and a narrow bottom, the second fixed block is of a structure with a narrow top and a wide bottom, at least one first cooling channel is arranged on the narrow side structure of the first fixed block, and at least one second cooling channel is arranged on the narrow side structure of the second fixed block; the mass of the first fixing block and the mass of the second fixing block are both larger than that of the electro-optic crystal, and the first cooling channel and the second cooling channel are both communicated with the external environment of the Pockels cell to realize heat exchange.

Further, the first cooling channel and the second cooling channel are filled with cooling liquid, and the cooling liquid is non-conductive liquid.

Further, the first electrode is an anode, the second electrode is a cathode, the first electrode and the second electrode are respectively communicated with the anode and the cathode of a power supply, the power supply is used for providing an adjustable pulse broadband, the adjustable range is 200ns at minimum, and the rising and falling edges of the pulse are 2-10 ns;

the polarization state of the laser light passing through the electro-optic crystal within the pockels cell is transformed when a voltage is applied.

Further, the electro-optic crystal is a BBO crystal or a KDP crystal, an anti-reflection film with a high damage threshold value is plated on the surface of the BBO crystal or the KDP crystal, and the high damage threshold value is larger than 700MW/cm²。

Further, the number of the electro-optical crystals is 1 or more.

Further, the electro-optical crystal is directly connected with the buffer layer, and the electro-optical crystal is connected with the fixing layer in a gluing mode or welded mode.

Furthermore, the buffer layer has thermal conductivity and electrical conductivity, and is made of a soft metal sheet;

the fixing layer has thermal conductivity, the fixing layer is conductive solder or a non-conductive adhesive, and when the fixing layer is the non-conductive adhesive, the power supply cathode and the second electrode are both grounded.

Furthermore, the first fixed block and the second fixed block are both conductive, and the second fixed block are made of metal materials.

Further, heat dissipation pieces are arranged inside the first fixing block and the second fixing block.

The embodiment of the utility model provides a Pockels cell with a large clear aperture, which comprises an electro-optical crystal, wherein the upper part of the electro-optical crystal is connected with a first fixed block through a buffer layer, the lower part of the electro-optical crystal is connected with a second fixed block through a fixed layer, and a first electrode and a second electrode which are used for applying voltage to the electro-optical crystal are respectively arranged on the first fixed block and the second fixed block. According to the embodiment of the utility model, by arranging the buffer layer and the fixed layer, the problems of mechanical vibration and cooling and heat dissipation of the crystal caused by the piezoelectric effect can be solved, so that the buffer layer and the fixed layer are suitable for a regenerative amplifier with high-power and high-energy laser output.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a pockels cell with a large clear aperture according to an embodiment of the present invention;

fig. 2 is another schematic structural diagram of a pockels cell with a large clear aperture according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the utility model herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the utility model. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

Referring to fig. 1, a pockels cell with a large clear aperture according to an embodiment of the present invention includes an electro-optical crystal 3, an upper portion of the electro-optical crystal 3 is connected to a first fixed block 1a through a buffer layer 2, a lower portion of the electro-optical crystal 3 is connected to a second fixed block 1b through a fixed layer 4, and a first electrode 5a and a second electrode 5b for applying a voltage to the electro-optical crystal 3 are respectively disposed on the first fixed block 1a and the second fixed block 1 b.

In this embodiment, the pockels cell includes an electro-optic crystal 3, and a first fixed block 1a and a second fixed block 1b respectively located above and below the electro-optic crystal 3, wherein the buffer layer 2 is disposed between the first fixed block 1a and the electro-optic crystal 3, a fixed layer 4 is disposed between the second fixed block 1b and the electro-optic crystal 3, and meanwhile, a first electrode 5a and a second electrode 5b are respectively disposed on the first fixed block 1a and the second fixed block 1b and are used for applying voltage to the electro-optic crystal 3 (or canceling the application of voltage).

The integral connection between the first fixed block 1a, the second fixed block 1b and the electro-optical crystal 3 suppresses expansion or compression of the electro-optical crystal 3 in a direction parallel to the crystal plane to which the electrodes are connected. The piezoelectric effect of the electro-optic crystal 3 caused by the expansion or compression in the direction perpendicular to the connecting crystal planes can be fundamentally counteracted by the pressing fixing and buffering layers 2 of the first fixing block 1a and the second fixing block 1 b. In general, the first fixed block 1a and the second fixed block 1b can counteract any vibration of the electro-optical crystal 3 caused by its own mass or the surrounding environment (e.g., an optical platform).

In the prior art, for electro-optic crystals used to drive high laser powers, in addition to producing the desired electro-optic effect, the piezoelectric ringing effect is also relatively large. The high alternating voltage can cause the crystal size to change through the piezoelectric effect, so that the mechanical force generated by the elastic bracket generates voltage, thereby changing the optical characteristic influence of the electro-optical crystal. Especially when the operating frequency of the pockels cell coincides with the resonance frequency of the mechanical vibration of the electro-optic crystal, the performance of the whole system is affected.

When pockels cells are used in regenerative amplifiers for high laser powers, the half-wave voltage of the control voltage is typically in the order of hundreds of volts or even thousands of volts, especially for large aperture pockels cells, tens of kilovolts are required. In order to reduce the power density of the laser radiation within the crystal, in this case an electro-optical crystal of larger aperture is used, which is then operated at a correspondingly higher operating voltage, thereby further amplifying the piezoelectric effect.

Compared with the design in the prior art, the pockels cell provided by the embodiment of the utility model can effectively solve or avoid the problems. The embodiment of the utility model is more suitable for a regenerative amplifier (kilowatt and hundred-millijoule level laser output) with high power and larger energy laser output by arranging the buffer layer 2 and the fixed layer 4, and more simply and effectively solves the problem of mechanical vibration of crystals caused by piezoelectric effect. At high voltage and high frequency modulation, particularly when the pockels cell is subjected to a modulation frequency in which the drive voltage applied to the electrodes is in the range of 1kHz to 10MHz, the piezoelectric ringing effect is minimized.

In one embodiment, the first fixed block 1a is of a structure with a wide top and a narrow bottom, the second fixed block is of a structure with a narrow top and a wide bottom, at least one first cooling channel 6a-6b is arranged on the narrow side structure of the first fixed block 1a, and at least one second cooling channel 6c-6d is arranged on the narrow side structure of the second fixed block 1 b; the mass of the first fixing block 1a and the mass of the second fixing block 1b are both larger than that of the electro-optical crystal 3, and the first cooling channels 6a-6b and the second cooling channels 6c-6d are both communicated with the external environment of the Pockels cell to realize heat exchange.

In this embodiment, the first fixing block 1a and the second fixing block 1b are respectively provided with first cooling channels 6a to 6b and second cooling channels 6c to 6d, and the cooling and heat dissipation problems can be effectively solved through the first cooling channels 6a to 6b and the second cooling channels 6c to 6 d. Here, it should be noted that the number of the first cooling passages 6a to 6b is at least one, and the number of the second cooling passages 6c to 6d is also at least one, so that the cooling effect can be ensured. In addition, the first and second fixed blocks 1a and 1b should have a mass greater than that of the electro-optical crystal 3 so that residual mechanical vibration between the electro-optical crystal 3 and the first and second fixed blocks 1a and 1b can be suppressed or even completely suppressed.

Further, the first cooling passages 6a to 6b and the second cooling passages 6c to 6d are filled with a cooling liquid, and the cooling liquid is a non-conductive liquid.

In the mutually communicated cooling channels, a cooled non-conductive liquid (or air) can pass through the cooling channels to take away heat generated on the first fixed block 1a and the second fixed block 1b due to the strong laser light passing through the electro-optical crystal 3.

In another embodiment, heat dissipation members are disposed inside the first and second fixing blocks 1a and 1 b. For example in the form of ceramic radiators applied to said first and second fixed blocks 1a, 1b, it is also possible to envisage using fins passively cooled by air as said heat sinks.

In one embodiment, the first electrode 5a is an anode, the second electrode 5b is a cathode, the first electrode 5a and the second electrode 5b are respectively communicated with the anode and the cathode of a power supply, the power supply is used for providing an adjustable pulse broadband, the adjustable range is 200ns at minimum, and the rising and falling edges of the pulse are 2-10 ns;

the polarization state of the laser light passing through the electro-optic crystal 3 within the pockels cell is transformed when a voltage is applied.

In this embodiment, the first electrode 5a and the second electrode 5b are connected to the power supply (specifically, a high-voltage power supply) through corresponding lines. In particular, the power supply is characterized by high-voltage pulses with rapid rising edges and falling edges, the pulse bandwidth is adjustable, and the adjustable range can be 200ns to direct current.

When a voltage is applied, the polarization state of the laser light is rotated by 90 ° from s-polarized light to p-polarized light (or vice versa). The laser light is then reflected or transmitted at the thin film polarizer 8 and follows two possible beam propagation paths of s-and p-polarization, depending on the original polarization of the pockels cell front laser light and the applied voltage.

Further, a thin-film polarizing plate 8 is provided on the side of the electro-optical crystal 3 away from the first electrode 5a and the second electrode 5b, so that s-polarized light and p-polarized light are separated.

In a specific embodiment, the electro-optic crystal 3 is a BBO crystal or a KDP crystal, an antireflection film with a high damage threshold is plated on the surface of the BBO crystal or the KDP crystal, and the high damage threshold is greater than 700MW/cm². The light-transmitting wave band of the BBO crystal is 200 nm-2.5 um, and the BBO crystal is mainly characterized by having low thermal lens and low depolarization loss under high laser power. Meanwhile, the BBO crystal is plated with an anti-reflection film with a high damage threshold, so that the service life of the device is prolonged while high transmittance is ensured. The light transmission waveband of the KDP crystal is 178 nm-1.45 um, the KDP crystal is negative optical uniaxial crystal, and the nonlinear optical coefficient d36(1.064um) is 0.39 pm/V.

Here, the number of the electro-optical crystals 3 is 1 or more. For example, as shown in fig. 2, 2 electro-optical crystals 3 are disposed in the pockels cell, and the upper and lower portions of the 2 electro-optical crystals 3 are connected to the buffer layer 2 and the fixed layer 4, but of course, the number of the buffer layer 2 and the fixed layer 4 may be two, or when the number is 1, the areas of the buffer layer 2 and the fixed layer 4 are larger.

In one embodiment, the electro-optical crystal 3 is directly connected with the buffer layer 2, and the electro-optical crystal 3 is glued or welded with the fixing layer 4.

In this embodiment it is advantageous if the electro-optical crystal 3 is firmly bonded to the two electrodes, i.e. in this way mechanical vibrations between the first fixed block 1a, the second fixed block 1b and said electro-optical crystal 3 can be completely suppressed. In particular, the integral connection effectively cancels the expansion change of the electro-optical crystal 3 in the direction parallel to the connection surfaces of the electro-optical crystal 3 and the first fixed block 1a and the second fixed block 1 b. Specifically, the electro-optical crystal 3 is directly connected with the buffer layer 2, and is arranged by gluing or welding with the fixing layer 4.

In addition, the integral connection of the electro-optical crystal 3 and the first fixed block 1a and the second fixed block 1b can also be realized by welding. Similarly, since the buffer layer 2 and the fixing layer 4 are respectively arranged between the electro-optical crystal 3 and the first fixing block 1a and the second fixing block 1b, the electro-optical crystal 3 and the first fixing block 1a and the second fixing block 1b are arranged by welding because the surface of the electro-optical crystal 3 is metallized, and thus the material connection between the electro-optical crystal 3 and the welding can be established by using a proper solder. A very strong connection with high thermal conductivity can be achieved by such a weld.

In one embodiment, the buffer layer 2 has thermal conductivity and electrical conductivity, and the material of the buffer layer 2 is a soft metal sheet;

the fixing layer 3 has thermal conductivity, the fixing layer 3 is conductive solder or a non-conductive adhesive, and when the fixing layer 3 is a non-conductive adhesive, the power supply cathode and the second electrode 5b are both grounded.

In order to enable the first cooling channels 6a to 6b and the second cooling channels 6c to 6d on the first fixed block 1a and the second fixed block 1b to absorb heat generated by the electro-optical crystal 3, it is first necessary to transfer the heat on the electro-optical crystal 3 to the first fixed block 1a and the second fixed block 1 b. This requires good thermal conductivity of the buffer layer 2 and the anchor layer 4. Meanwhile, the buffer layer 2 and the fixed layer 4 also need to conduct the voltage applied by the first electrode 5a and the second electrode 5b on the first fixed block 1a and the second fixed block 1b to the electro-optical crystal 3, so that the buffer layer 2 is required to have good conductivity, and therefore, a soft metal sheet is selected as the buffer layer 2. Here, it is understood that when the fixing layer 4 is a solder, which has conductivity, it can conduct a voltage to the electro-optical crystal 3, and when the fixing layer 4 is an adhesive, it has no conductivity, and therefore both the negative electrode of the power supply and the second electrode 5b are grounded. In particular embodiments, the soft metal sheet may be a platinum sheet, a lead sheet, an indium sheet, or the like. The solder may be a tin-lead solder, a silver solder, or the like. The adhesive is a UV adhesive, a two-component or multi-component adhesive, or the like.

Further, the first fixed block 1a and the second fixed block 1b both have conductivity, and the second fixed block 1a and the second fixed block 1b are made of a metal material. Such as a metallic material such as copper.

In addition, the first and second fixing blocks 1a and 1b should be dimensionally stable so as to be able to offset the crystal stress accordingly. This can be achieved by choosing a suitable material (e.g. copper) and sufficient cross-sectional area. The electro-optical crystal 3 then establishes a mechanical connection with at least one stationary main structure. It is very advantageous if the integral connection surfaces between said first holding block 1a, second holding block 1b and electro-optical crystal 3 comprise the entire surface of the crystal. In this way, the first and second holding blocks 1a, 1b can withstand any pressure inside the crystal over its entire length and counteract and effectively suppress the transmission of tensile or compressive forces to the crystal through the material connection.

The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description. It should be noted that, for those skilled in the art, it is possible to make several improvements and modifications to the present application without departing from the principle of the present application, and such improvements and modifications also fall within the scope of the claims of the present application.

It should also be noted that, in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Claims (10)

1. The utility model provides a pockels box of big clear light bore, its characterized in that includes the electro-optical crystal, the top of electro-optical crystal is connected with first fixed block through a buffer layer, the below of electro-optical crystal is connected with the second fixed block through a fixed layer, be provided with respectively on first fixed block and the second fixed block and be used for right the first electrode and the second electrode that the electro-optical crystal applyed voltage.

2. The large clear aperture pockels cell of claim 1, wherein the first fixed block is a wide-top and narrow-bottom structure, the second fixed block is a narrow-top and wide-bottom structure, the narrow-side structure of the first fixed block is provided with at least one first cooling channel, and the narrow-side structure of the second fixed block is provided with at least one second cooling channel; the mass of the first fixing block and the mass of the second fixing block are both larger than that of the electro-optic crystal, and the first cooling channel and the second cooling channel are both communicated with the external environment of the Pockels cell to realize heat exchange.

3. A pockels cell of claim 2, wherein the first and second cooling channels are filled with a cooling fluid, which is a non-conductive liquid.

4. The large-aperture pockels cell of claim 1, wherein the first electrode is a positive electrode, the second electrode is a negative electrode, the first electrode and the second electrode are respectively communicated with a positive electrode and a negative electrode of a power supply, the power supply is used for providing an adjustable pulse broadband, the adjustable range is at least 200ns, and the rising and falling edges of the pulse are 2-10 ns;

the polarization state of the laser light passing through the electro-optic crystal in the pockels cell is transformed when a voltage is applied.

5. The large clear aperture pockels cell of claim 1, wherein the electro-optic crystal is a BBO crystal or a KDP crystal, and an anti-reflection film with a high damage threshold is plated on the surface of the BBO crystal or the KDP crystal, and the high damage threshold is greater than 700MW/cm²。

6. A large clear aperture pockels cell according to claim 1, wherein the number of the electro-optical crystals is 1 or more.

7. A large clear aperture pockels cell as claimed in claim 1, wherein said electro-optic crystal is directly attached to said buffer layer, said electro-optic crystal being glued or soldered to said anchoring layer.

8. The large clear aperture pockels cell of claim 4, wherein the buffer layer is thermally and electrically conductive, the buffer layer being made of a soft metal sheet;

the fixing layer has thermal conductivity, the fixing layer is conductive solder or non-conductive adhesive, and when the fixing layer is the non-conductive adhesive, the negative electrode of the power supply and the second electrode are both grounded.

9. The pockels cell of claim 1, wherein the first and second fixed blocks are both conductive, and the second and fixed blocks are made of a metal material.

10. The large clear aperture pockels cell of claim 1, wherein heat sinks are provided inside the first and second fixed blocks.

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