Structure for overcoming polarity reversal of electro-optical device paired with double ferroelectric crystals and use method

Abstract

The invention discloses a structure for overcoming polarity reversal of an electro-optical device paired with double ferroelectric crystals, which is in a parallelogram shape and comprises a first crystal, a second crystal, a first reflecting mirror and a second reflecting mirror, wherein the first crystal, the second crystal, the first reflecting mirror and the second reflecting mirror are all arranged on the same metal plate, the first crystal and the first reflecting mirror are located on the upper side of the parallelogram, and the second crystal and the second reflecting mirror are located on the lower side of the parallelogram; the first reflecting mirror reflects laser transmitted by the first crystal to the second reflecting mirror on the lower edge of the parallelogram, and the second reflecting mirror reflects the laser to the light transmitting face of the second crystal. According to the invention, the voltage along the spontaneous polarization direction is only loaded on the first crystal, the voltage connection mode is simple, the problem of polarity reversal of the second crystal is completely overcome, and the problem of failure of the device due to polarity reversal is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of electro-optical crystal device preparation, and more specifically, to a structure and usage method for overcoming the polarity reversal of a paired electro-optical device of a double ferroelectric crystal. Background Art

[0002] Electro-optical devices are a common means of modulating the amplitude, phase, and intensity of lasers. Currently, the practical electro-optical devices are only KDP (KH2PO4), LN (LiNbO3), BBO (β-BaB2O4), and KTP (KTiOPO4), RTP (RbTiOPO4) electro-optical devices. Among them, KDP, LN, and BBO are uniaxial crystals, and electro-optical modulation is often achieved through a single crystal device; while KTP and RTP are biaxial crystals with natural birefringence. In order to cancel the phase difference caused by static birefringence, two crystals are often paired and used for compensation [Comparative patents: CN 220709491 U, a vacuum high-voltage-resistant RTP electro-optical switch on April 2, 2024; CN 112363330B, a double-crystal electro-optical switch assembly system, assembly method, and double-crystal electro-optical switch on November 3, 2023; CN 111817124 A, a new type of double-crystal RTP Pockels cell assembly on October 23, 2020; CN 104858817B, an electro-optic Q-switch double-crystal pairing clamping tooling and its usage method, (the above patents all use two paired crystals with voltage applied simultaneously)].

[0003] The pairing method of two crystals is to connect two crystals with exactly the same size in series, and the second crystal is rotated 90° around the main axis in the light propagation direction or the second crystal is rotated 180° around the main axis in the light propagation direction, and a half-wave plate is inserted between the two crystals.

[0004] Based on the electro-optical properties, KTP and RTP crystals also have ferroelectric properties. When used as paired electro-optical devices, the voltage applied to the first crystal is along the positive direction of its polar Z-axis, while the voltage applied to the second crystal is along the negative direction of its polar Z-axis (see Attachment Figure 1 a, Attachment Figure 2 a). Under the action of a strong electric field, there is a possibility of polarity reversal in the second crystal, resulting in the failure of the compensation effect and the device being unable to continue to be used. KDP and LN crystals also have ferroelectric properties, and there will also be static natural birefringence when using their large electro-optic coefficients. Therefore, there are also applications of paired KDP and LN electro-optical devices, and at this time, the problem of polarity reversal of one of the crystal devices also exists. Summary of the Invention

[0005] In view of this, the present invention provides a structure and a method of use for overcoming the polarization reversal of a paired electro-optic device of double ferroelectric crystals, so as to overcome the failure problem of the electro-optic device during application.

[0006] There are two modes of double-crystal pairing. One is the wave plate type, where two crystals are placed on the same flat electrode base, and a half-wave plate is inserted in the middle. The specific structure is shown in Appendix Figure 2 b; the other way is the non-wave plate type, where two crystals are placed on the electrode base of a V-shaped bracket structure. The specific structure is shown in Appendix Figure 1 b. In both ways, electrodes need to be plated on the polarization surfaces of the two crystals and they are arranged in series along a straight line. When in use, the positive polarization surface of the first crystal and the negative polarization surface of the second crystal are commonly connected to the positive pole of the power supply. At the same time, the other two polarization surfaces of the two crystals are commonly connected to the negative pole of the power supply. Due to the absence of a half-wave plate, the V-shaped bracket structure has become the commonly used pairing mode. However, the V-shaped bracket is a special-shaped structure and is often made of titanium alloy, which is difficult to process. Especially, the processing of multiple fixing holes on the bracket is even more difficult, bringing inconvenience to use.

[0007] The present invention proposes a method of not applying voltage to the second crystal to implement a pairing compensation scheme for the double crystals, and thus proposes a pairing compensation structure. In the present invention, since the voltage is only applied to the first crystal, when in use, the electric field direction is along the spontaneous polarization direction of the crystal, so the polarization reversal of this crystal will not occur; but in order to reduce the requirements for the high-repetition-rate power supply, the length of a single crystal in the present invention needs to be greater than the length of the currently commonly used single crystal, which leads to an increase in the device size after the two crystals are arranged in series, breaking through the length of the original laser. Therefore, the present invention proposes a structure in which the two crystals are arranged in parallel.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A structure for overcoming the polarization reversal of a paired electro-optic device of double ferroelectric crystals, characterized in that the structure is in the shape of a parallelogram and includes a first crystal, a second crystal, a first mirror and a second mirror;

[0010] Wherein, the first crystal, the second crystal, the first mirror and the second mirror are all arranged on the same metal plate, and the first crystal and the first mirror are located on the upper side of the parallelogram, and the second crystal and the second mirror are located on the lower side of the parallelogram;

[0011] The first mirror reflects the laser transmitted through the first crystal to the second mirror at the lower side of the parallelogram, and the second mirror reflects the light to the light-transmitting surface of the second crystal.

[0012] The two mirrors need to be precisely adjusted so that the laser reflected by the second mirror can be perpendicularly incident on the light-transmitting surface of the second crystal.

[0013] Preferably, the first crystal and the second crystal are dimensionally consistent along the direction of using the electro-optic effect.

[0014] Preferably, the first crystal and the second crystal are placed parallel to each other along the optical path direction.

[0015] Preferably, the positive-polarity surface of the first crystal is placed on the metal plate, and the non-polarity surface of the second crystal is placed on the metal plate.

[0016] Preferably, metal electrodes are plated on the positive and negative polarity surfaces of the first crystal respectively.

[0017] Preferably, the first crystal and the second crystal are electro-optic crystals with ferroelectric properties.

[0018] Another object of the present invention is to provide a method of using the above-mentioned structure for overcoming the polarity inversion of the paired electro-optic device of double ferroelectric crystals, including:

[0019] (1) Fix a metal block electrode with the same size as the negative-polarity surface on the negative-polarity surface of the first crystal using conductive glue, and lead out a wire from the metal block.

[0020] (2) Fix the positive-polarity surface of the first crystal on the metal plate using conductive glue, and lead out a wire from the edge of the metal plate.

[0021] (3) Fix the first mirror on the metal plate behind the first crystal using epoxy resin glue.

[0022] (4) Fix the non-polarity surface of the second crystal on the metal plate below the first mirror using epoxy resin glue.

[0023] (5) Fix the second mirror on the metal plate in front of the second crystal using epoxy resin glue.

[0024] (6) Synchronously and precisely adjust the first crystal and the second crystal, and the first mirror and the second mirror, so that there is only one light spot after passing through the second KTP crystal.

[0025] (7) Place the assembled device into the laser cavity, connect the negative-polarity surface of the first crystal to the positive pole of the power supply, connect the positive-polarity surface of the first crystal to the negative pole of the power supply, and then apply a 1 / 2 wave voltage or a 1 / 4 wave voltage to perform electro-optic modulation on the laser.

[0026] Although the second crystal is not loaded with voltage, there is still natural birefringence, which can compensate for the natural birefringence of the first crystal.

[0027] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention only applies a voltage along the direction of spontaneous polarization to the first crystal. The voltage connection method is simple, completely overcoming the problem of the polarity reversal of the second crystal, so that the device avoids the problem of failure due to polarity reversal. At the same time, the second crystal does not need to be plated with electrodes, and the second crystal is fixed with epoxy resin glue, which can be cured at room temperature, reducing the stress in the device and improving the overall performance of the device and the extinction ratio. All components of the present invention are placed on a metal plate, and the metal plate is easier to process and fix than the V-shaped bracket. The structure of the present invention adopts a parallel mode. Compared with the prior art, there is almost no difference in the length of the device, so it has little impact on the size of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0030] Figure 1 It is a diagram of the principle (a) and structure (b) of the double-crystal pairing with a V-shaped bracket.

[0031] Figure 2 It is a diagram of the principle (a) and structure (b) of the double-crystal pairing with a wave plate.

[0032] Figure 3 It is a diagram of the principle (a) and structure (b) of the double-crystal pairing with a single crystal under pressure.

[0033] Figure 3 In a, 1 is the first ferroelectric crystal, 2 is the first mirror, 3 is the second ferroelectric crystal, and 4 is the second mirror. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] Embodiment 1

[0036] Figure 3 It is the principle of double-crystal pairing with a single crystal under pressure (see Appendix Figure 3 a) and the structure diagram (see Appendix Figure 3 b). As shown in the figure, the first crystal of the present invention is Figure 3 1 shown in a, and the first mirror isFigure 3 2 as shown in a, and the second crystal is Figure 3 3 as shown in a, and the second mirror is Figure 3 4 as shown in a.

[0037] As an example, the paired ferroelectric crystals are KTP crystals, and the sizes of the two crystals are both 4mm×4mm×20mm.

[0038] As an example, the quasi-static test method is adopted to determine the positive and negative polarity faces of the first KTP crystal. When the piezoelectric coefficient d 33 >0, the crystal face in contact with the upper electrode of the piezoelectric coefficient tester is the negative polarity face; when the piezoelectric coefficient d 33 <0, the crystal face in contact with the upper electrode of the piezoelectric coefficient tester is the positive polarity face.

[0039] As an example, electrodes are plated on the two polarity faces of the first KTP crystal.

[0040] As an example, the quasi-static test method is adopted to determine the non-polarity face of the second KTP crystal. When the piezoelectric coefficient d 33 ≠0, the crystal face along the test direction of the piezoelectric coefficient tester is the polarity face; when the piezoelectric coefficient d 33 =0, the crystal face along the test direction of the piezoelectric coefficient tester is the non-polarity face.

[0041] As an example, the positive polarity face of the first KTP crystal is fixed to the base metal plate through conductive silver paste, and a metal block made of the same material as the metal plate is bonded to the negative polarity face, with a size of 4mm×20mm×1.5mm.

[0042] As an example, wires are led out from the metal base and the metal block electrode of the first KTP crystal respectively.

[0043] As an example, the non-polarity face of the second KTP crystal is fixed to the base metal plate through epoxy resin glue.

[0044] As an example, the second KTP crystal is placed below the first KTP crystal and placed completely parallel.

[0045] As an example, the first mirror is placed behind the first KTP crystal, and the second mirror is placed in front of the second KTP crystal.

[0046] As an example, the two KTP crystals and the two mirrors are precisely adjusted so that there is only one light spot after passing through the second KTP crystal.

[0047] In use, place the paired KTP electro-optic device in the laser cavity. Connect the positive pole of the power supply to the negative-polarity surface of the first KTP crystal and the negative pole of the power supply to the positive-polarity surface of the first KTP crystal, and then apply a 1 / 2 wave voltage or a 1 / 4 wave voltage to perform electro-optic modulation on the laser.

[0048] According to the embodiments of the present invention, the problem that the polarity of the KTP crystal is reversed when the KTP electro-optic device is in use can be solved, and the device length is almost unchanged, effectively improving the service life of the KTP electro-optic device.

[0049] In this specification, the various embodiments are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.

[0050] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A structure for overcoming polarity reversal of a dual ferroelectric crystal paired electro-optical device, characterized in that: The structure is in the shape of a parallelogram and includes a first crystal, a second crystal, a first reflector and a second reflector; The first crystal, the second crystal, the first reflector and the second reflector are all arranged on the same metal plate, and the first crystal and the first reflector are located on the upper side of the parallelogram, and the second crystal and the second reflector are located on the lower side of the parallelogram; The first reflector reflects the laser light transmitted through the first crystal to the second reflector at the lower side of the parallelogram, and the second reflector reflects the light to the light-transmitting surface of the second crystal.

2. A structure for overcoming polarity inversion of a biferroelectric crystal paired electro-optical device according to claim 1, characterized in that: The first crystal and the second crystal keep the same size along the direction of using the electro-optical effect.

3. The structure for overcoming polarity inversion of a biferroelectric crystal paired electro-optical device according to claim 1, characterized in that: The first crystal and the second crystal are placed parallel to each other along the light transmission direction.

4. The structure for overcoming polarity inversion of a biferroelectric crystal paired electro-optical device according to claim 1, characterized in that: The positive polarity surface of the first crystal is placed on the metal plate, and the non-polarity surface of the second crystal is placed on the metal plate.

5. The structure for overcoming polarity inversion of a biferroelectric crystal paired electro-optical device according to claim 1, characterized in that: The first crystal is plated with metal electrodes on the positive and negative polarity surfaces respectively.

6. The structure for overcoming polarity inversion of a biferroelectric crystal paired electro-optical device according to claim 2, characterized in that: The first crystal and the second crystal are electro-optical crystals with ferroelectric properties.

7. A method for using the structure for overcoming polarity inversion of a biferroelectric crystal paired electro-optical device as claimed in any one of claims 1 to 6, comprising: (1) A metal block electrode having the same size as the negative polarity surface is fixed to the negative polarity surface of the first crystal using conductive glue, and a wire is led out from the metal block; (2) Fixing the positive polarity surface of the first crystal to the metal plate with conductive adhesive, and leading out a wire at the edge of the metal plate; (3) fixing the first reflector to the metal plate behind the first crystal using epoxy resin glue; (4) fixing the non-polar surface of the second crystal to the metal plate below the first reflector using epoxy resin glue; (5) Fix the second reflector to the metal plate in front of the second crystal using epoxy resin glue; (6) synchronously and precisely adjusting the first crystal and the second crystal, the first reflector and the second reflector so that there is only one light spot after passing through the second KTP crystal; (7) Place the assembled device into the laser cavity, connect the negative polarity surface of the first crystal to the positive pole of the power supply, and connect the positive polarity surface of the first crystal to the negative pole of the power supply, and then load a 1 / 2 wave voltage or a 1 / 4 wave voltage to perform electro-optical modulation on the laser.

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