A structure and method of use to overcome polarity reversal in a ferroelectric crystal pair optical device

Abstract

The application discloses a structure for overcoming polarity reversal of a double ferroelectric crystal matched electro-optical device, which is a parallelogram and comprises a first crystal, a second crystal, a first reflector and a second reflector; wherein the first crystal, the second crystal, the first reflector and the second reflector are 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 by the first crystal to the second reflector on the lower side of the parallelogram, and the second reflector reflects the light to the light transmission surface of the second crystal. The application only loads the voltage along the spontaneous polarization direction on the first crystal, the voltage connection mode is simple, the problem of polarity reversal of the second crystal is completely overcome, and the device avoids the problem of failure due to polarity reversal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electro-optic crystal device preparation, and more particularly to a structure for overcoming polarity reversal of a double ferroelectric crystal paired electro-optic device and a use method thereof. BACKGROUND

[0002] Electro-optic devices are commonly used to modulate laser amplitude, phase and intensity. Currently available electro-optic devices include KDP (KH2PO4), LN (LiNbO3), BBO (β-BaB2O4), KTP (KTiOPO4) and RTP (RbTiOPO4) electro-optic devices. Among them, KDP, LN and BBO are uniaxial crystals, and electro-optic modulation is usually achieved by using single crystal devices. KTP and RTP are biaxial crystals with natural birefringence. In order to offset the phase difference caused by static birefringence, two crystals are usually paired and compensated [Comparison patents: CN 220709491 U 2024.04.02 vacuum high-pressure-resistant RTP electro-optic switch; CN 112363330B 2023.11.03 double-crystal electro-optic switch assembly system, assembly method and double-crystal electro-optic switch; CN 111817124 A 2020.10.23 novel double-crystal RTP Pockels cell assembly; CN 104858817B 2016.08.24 electro-optic Q-switch double-crystal pairing clamping tool and its use method, (all the above patents are used by applying voltage to two paired crystals at the same time)].

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

[0004] KTP and RTP crystals have ferroelectric properties in addition to electro-optic properties. When used as paired electro-optic devices, the voltage direction of the first crystal is along the positive direction of its polarity Z axis, and the voltage direction of the second crystal is along the reverse direction of its polarity Z axis (see FIG. 1). Figure 1 a, FIG. Figure 2 a). Under the action of a strong electric field, the second crystal may have a polarity reversal, resulting in a failure of the compensation effect and making the device unable to continue to be used. KDP and LN crystals also have ferroelectric properties, and when their large electro-optic coefficients are used, there is also static natural birefringence, so there are also double-crystal paired KDP and LN electro-optic devices, which also face the problem of polarity reversal of one of the crystal devices. SUMMARY

[0005] Therefore, the application provides a structure and a use method for overcoming the polarity reversal of a double ferroelectric crystal paired electro-optical device to overcome the failure of the electro-optical device in application.

[0006] The double crystal pairing has two modes, one is a wave plate type, two crystals are placed on the same flat electrode base, and a half wave plate is inserted therebetween, and the specific structure is shown in the attached Figure 2 b;The other mode is a wave plate-free type, two crystals are placed on the electrode base of a V-shaped support structure, and the specific structure is shown in the attached Figure 1 b. In the two modes, the two crystals need to be plated with electrodes on the polar faces and arranged in series along a straight line, and the positive polar face of the first crystal is connected to the positive electrode of the power supply together with the negative polar face of the second crystal, and at the same time, the other two polar faces of the two crystals are connected to the negative electrode of the power supply. The V-shaped support structure becomes a commonly used pairing mode because it has one less half wave plate. However, the V-shaped support is a special-shaped structure, and is often made of titanium alloy material, which is difficult to process, especially the multiple fixing hole positions on the support, which is more difficult to process, and brings inconvenience to use.

[0007] The application provides a double crystal pairing compensation scheme without loading voltage on the second crystal, and a pairing compensation structure is also provided. In the application, the voltage is only loaded on the first crystal, and the electric field direction is along the spontaneous polarization direction of the crystal during use, so that the polarization reversal of the crystal does not occur. However, in order to reduce the requirement for high repetition frequency power supply, the length of the single crystal needs to be greater than the length of the commonly used single crystal, so that the size of the device increases after the two crystals are arranged in series, which breaks through the length of the original laser, and the application provides a structure in which the two crystals are arranged in parallel.

[0008] In order to achieve the above object, the application adopts the following technical scheme:

[0009] A structure for overcoming the polarity reversal of a double ferroelectric crystal paired electro-optical device, characterized in that the structure is a parallelogram, comprising a first crystal, a second crystal, a first mirror and a second mirror.

[0010] The first crystal, the second crystal, the first mirror and the second mirror are 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 by the first crystal to the second mirror on the lower side of the parallelogram, and the second mirror reflects the light to the light transmission face of the second crystal.

[0012] The two mirrors need to be precisely adjusted so that the laser reflected by the second mirror can be perpendicular to the light transmission face of the second crystal.

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

[0014] Preferably, the first crystal and the second crystal are placed in parallel along the light transmission direction.

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

[0016] Preferably, the first crystal is plated with metal electrodes on the positive and negative polar faces respectively.

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

[0018] Another object of the present application is to provide a method for using the above-mentioned structure for overcoming the polarity reversal of the electro-optic device of the ferroelectric crystal pair, comprising:

[0019] (1) a metal block electrode with the same size as the negative polar face of the first crystal is fixed on the negative polar face by using conductive glue, and a lead wire is drawn on the metal block;

[0020] (2) the positive polar face of the first crystal is fixed on the metal plate by using conductive glue, and a lead wire is drawn on the edge of the metal plate;

[0021] (3) the first mirror is fixed on the metal plate behind the first crystal by using epoxy resin glue;

[0022] (4) the non-polar face of the second crystal is fixed on the metal plate below the first mirror by using epoxy resin glue;

[0023] (5) the second mirror is fixed on the metal plate in front of the second crystal by using epoxy resin glue;

[0024] (6) the first crystal and the second crystal, the first mirror and the second mirror are precisely adjusted synchronously, so that there is only one light spot after passing through the second KTP crystal;

[0025] (7) the assembled device is placed in a laser cavity, the negative polar face of the first crystal is connected to the positive pole of the power supply, the positive polar face of the first crystal is connected to the negative pole of the power supply, then 1 / 2 wave voltage or 1 / 4 wave voltage is loaded 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] According to the above technical solution, compared with the prior art, the present application has the following beneficial effects:

[0028] This invention applies a voltage along the spontaneous polarization direction only to the first crystal. The voltage connection method is simple and completely overcomes the polarity reversal problem of the second crystal, thus preventing device failure due to polarity reversal. Simultaneously, the second crystal does not require electrode plating and is fixed with epoxy resin, which cures at room temperature, reducing stress in the device and improving overall device performance and extinction ratio. All components of this invention are placed on a metal plate, which is easier to process and fix than a V-shaped bracket. The structure of this invention uses a parallel approach; compared to existing technologies, the device length is almost identical, thus having little impact on the laser's size. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 The diagram shows the pairing principle (a) and structure (b) of the V-shaped scaffold bicrystalline crystal.

[0031] Figure 2 The diagram shows the pairing principle (a) and structure (b) of a waveplate-type bicrystalline crystal.

[0032] Figure 3 The principle (a) and structure (b) of pairing a single crystal with pressure on a dual crystal are shown.

[0033] Figure 3 In a, 1 is the first ferroelectric crystal, 2 is the first reflector, 3 is the second ferroelectric crystal, and 4 is the second reflector. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] Figure 3 The principle of pairing two crystals under pressure on a single crystal (see appendix) Figure 3 a) and structural diagram (see appendix) Figure 3 b). As shown in the figure, the first crystal of the present invention is Figure 3 As shown in 'a', the first reflecting mirror is...Figure 3 a shows 2, the second crystal is Figure 3 a shows 3, the second mirror is Figure 3 a shows 4.

[0037] As an example, the pair of ferroelectric crystals are KTP crystals, and the size of each crystal is 4mm x 4mm x 20mm.

[0038] As an example, the positive and negative polarity faces of the first KTP crystal are determined by using quasi-static testing method. When the piezoelectric coefficient d 33 > 0, the crystal face on which the electrode of the contact piezoelectric coefficient tester is negative polarity face; when the piezoelectric coefficient d 33 < 0, the crystal face on which the electrode of the contact piezoelectric coefficient tester is 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 non-polar face of the second KTP crystal is determined by using quasi-static testing method. When the piezoelectric coefficient d 33 ≠ 0, the crystal face along the testing direction of the piezoelectric coefficient tester is polar face; when the piezoelectric coefficient d 33 = 0, the crystal face along the testing direction of the piezoelectric coefficient tester is non-polar face.

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

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

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

[0044] As an example, the second KTP crystal is placed below the first KTP crystal and is 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, the matched KTP electro-optical device is placed in a laser cavity, the positive pole of a power supply is connected with the negative polarity surface of the first KTP crystal, the negative pole of the power supply is connected with the positive polarity surface of the first KTP crystal, then a 1 / 2 wave voltage or a 1 / 4 wave voltage is loaded to electro-optically modulate the laser.

[0048] The embodiment of the present application can solve the problem of KTP electro-optical device that the polarity of KTP crystal is reversed in use, and effectively prolong the service life of the KTP electro-optical device.

[0049] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts of each embodiment can be referred to each other. For the device disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

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

Claims

1. A structure for overcoming polarity reversal in paired biferroelectric crystal electro-optic devices, characterized in that, The structure is parallelogram-shaped and includes a first crystal, a second crystal, a first mirror, and a second mirror. The first crystal, the second crystal, the first reflector, and the second reflector are all disposed on the same metal plate, with the first crystal and the first reflector located on the upper side of the parallelogram, and the second crystal and the second reflector 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 bottom edge of the parallelogram, and the second reflector reflects the light to the light-transmitting surface of the second crystal. The first crystal and the second crystal are electro-optic crystals with ferroelectric properties, and metal electrodes are plated only on the positive and negative polarity surfaces of the first crystal, and a voltage is applied thereon.

2. The structure for overcoming polarity reversal in paired biferroelectric crystal electro-optic devices according to claim 1, characterized in that, The first crystal and the second crystal maintain the same size along the direction of electro-optic effect.

3. The structure for overcoming polarity reversal in paired biferroelectric crystal electro-optic devices 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 reversal in paired biferroelectric crystal electro-optic devices according to claim 1, characterized in that, The positive polarity of the first crystal is placed on a metal plate, and the non-polarity of the second crystal is placed on the metal plate.

5. A method of using the structure for overcoming polarity reversal in paired biferroelectric crystal electro-optic devices as described in any one of claims 1-4, comprising: (1) A metal block electrode with the same size as the negative polarity surface is fixed on the negative polarity surface of the first crystal using conductive adhesive, and wires are led out from the metal block. (2) The positive polarity surface of the first crystal is fixed to the metal plate with conductive adhesive, and wires are led out from the edge of the metal plate; (3) The first reflector is fixed to the metal plate behind the first crystal with epoxy resin adhesive; (4) The non-polar surface of the second crystal is fixed to the metal plate below the first reflector with epoxy resin; (5) Fix the second reflector to the metal plate in front of the second crystal with epoxy resin adhesive; (6) Synchronously and precisely adjust the first crystal and the second crystal, the first mirror and the second mirror, so that only one light spot is visible after passing through the second crystal; (7) Place the assembled device into the laser cavity, connect the negative polarity of the first crystal to the positive polarity of the power supply, connect the positive polarity of the first crystal to the negative polarity 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.

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