阅读说明：本技术 一种低电压双块晶体电光q开关 (Low-voltage double-crystal electro-optical Q switch ) 是由 商继芳 孙军 杨金凤 周娅玲 郝好山 于 2021-07-12 设计创作，主要内容包括：本发明提供了一种低电压双块晶体电光Q开关,属于晶体材料在光电技术领域中的应用。本发明是由两块铌酸锂或者钽酸锂晶体按照特殊的设计切型和设计晶轴取向制成的一种电光Q开关器件,用于YAG激光器及其他激光器中作电光调Q使用。通过优化设计开关构型,本发明解决了现有技术存在的半波电压高、消光比低、受两晶体温差及长度偏差影响大、对加工精度、温控精度、晶体质量要求苛刻等缺点,设计的双块晶体电光Q开关同时兼顾了半波电压低、温度范围宽、两晶体温差及长度偏差容许范围大、消光比更高等优点,更加有利于实际应用。(The invention provides a low-voltage double-block crystal electro-optical Q switch, belonging to the application of crystal materials in the field of photoelectric technology. The invention relates to an electro-optical Q-switch device which is made by two lithium niobate or lithium tantalate crystals according to special design cutting and design crystal axis orientation and is used for electro-optical Q-switching in YAG lasers and other lasers. By optimally designing the switch configuration, the invention solves the defects of high half-wave voltage, low extinction ratio, large influence caused by the temperature difference and length deviation of the two crystals, harsh requirements on processing precision, temperature control precision and crystal quality and the like in the prior art, and the designed double-crystal electro-optical Q switch simultaneously has the advantages of low half-wave voltage, wide temperature range, large allowable range of the temperature difference and length deviation of the two crystals, higher extinction ratio and the like, and is more beneficial to practical application.)

1. A low-voltage double-crystal electro-optical Q-switch is characterized in that: is formed by combining two same electro-optical crystals according to a certain matching direction, wherein each crystal is cut by adopting a special angle and is cut into。

2. The low voltage two-block crystal electro-optic Q-switch of claim 1, wherein: the electro-optic crystal is a lithium niobate crystal or a lithium tantalate crystal.

3. The low voltage two-block crystal electro-optic Q-switch of claim 1, wherein: the length direction of the crystal is a light passing direction, and two end faces in the light passing direction are polished and plated with laser antireflection films; an electric field is applied in the thickness direction of the crystal, and two crystal faces in the thickness direction are plated with metal films.

4. The low voltage two-block crystal electro-optic Q-switch of claim 1, wherein: the two crystals are fixed by a mechanical clamp or an optical cement according to the thickness/width directions, which are mutually vertical and the length direction orientation is consistent.

5. The low voltage two-block crystal electro-optic Q-switch of claim 1, wherein: the above-mentionedθHas a value range of。

6. The low voltage two-block crystal electro-optic Q-switch of claim 1, wherein: the two crystals are placed according to the same orientation, namely the thickness direction, the width direction and the length direction are respectively parallel, then an 1/2 wave plate applying the wavelength is placed between the two crystals, and the long axis and the short axis of the 1/2 wave plate form an angle of 45 degrees with the thickness direction or the width direction of the crystals.

7. The low voltage two-block crystal electro-optic Q-switch of any of claims 1-6, wherein: the crystal cut can also beAndangle of rotationθAlso has a value range of。

8. The use of a low voltage two-block crystal electro-optic Q-switch as claimed in claim 7, in a laser resonator, wherein: when the crystal is applied to a laser resonant cavity, the light-passing surface is vertical to the propagation direction of laser, the thickness or width direction of the crystal and the transmission direction of the polarizer form an angle of 45 degrees, and the polarities of voltages applied to the two crystals are opposite.

Technical Field

The invention relates to the field of laser devices, in particular to a low-voltage double-crystal electro-optical Q-switch.

Background

The electro-optic Q-switching technology is one of the most commonly used modes for obtaining high-peak-power short pulse laser at present, the electro-optic effect of an electro-optic crystal is utilized, a step-type Q-switching voltage is applied to the crystal, the polarization state of the laser after passing through the crystal is periodically changed, the loss in a laser resonant cavity can be periodically modulated by matching with the use of a polarizer, the energy is greatly stored in a laser working substance during the high loss period, when the energy is accumulated to the maximum value, the loss in the cavity is suddenly reduced to the minimum value, laser oscillation is quickly established at the moment, and a large amount of energy is quickly released in a very short time, so that the output of the high-peak-power narrow-pulse-width laser is realized. As an active Q-switching technology, the electro-optical Q-switching has the advantages of high switching rate, strong turn-off capability and the like, the laser output time can be accurately controlled, and high-precision synchronization can be realized between a laser and other linkage instruments, so that the electro-optical Q-switching technology is widely applied, and electro-optical Q-switching devices are widely applied to pulse lasers.

For an electro-optical Q-switch, low half-wave voltage, high extinction ratio, high temperature stability, high light damage resistance threshold, large light transmission aperture, low cost, easy processing and the like are key indexes for evaluating the practicability of the electro-optical Q-switch, but at present, the electro-optical crystal which can completely meet the requirements is very few, and only potassium dideuterium phosphate (KD) is obtained for practical application₂PO₄DKDP), lithium niobate (LiNbO)₃LN), rubidium titanyl phosphate (RbTiOPO)₄RTP) and each has deficiencies. The DKDP crystal is easy to deliquesce and needs special packaging, the performance of the switch is unstable and even the switch cannot work due to the change of the refractive index of the matching fluid at low temperature, the DKDP electro-optical Q switch adopts a longitudinal modulation mode, the half-wave voltage is high and cannot be adjusted, the annular electrode is complex to prepare, the electric field is not uniform easily, and the dynamic extinction ratio of the switch is low. Although the half-wave voltage of the LN electro-optical Q-switch can be reduced by increasing the aspect ratio, the device caliber is smaller or the length is longer, the extinction ratio of the switch is lower, and the half-wave voltage of the traditional LN Q-switch with the conventional size is higher. The RTP crystal is a crystal newly developed and used in recent years, has the advantages of large electro-optic coefficient, high damage threshold, small piezoelectric coefficient and the like, is a biaxial crystal, needs to be matched for use to compensate natural birefringence, is extremely sensitive to optical quality, processing deviation, temperature deviation and the like of two crystals, is limited by preparation technology, is imported by means of more domestic applications at present, and has price not onlyAre expensive and subject to limitations.

Compared with other crystals, the LN crystal has stable physical and chemical properties, mature growth technology and low growth cost, can meet the requirement of large-caliber photoelectric device preparation, can work in a wide temperature range, and is an electro-optic crystal with good comprehensive properties and high cost performance. Albeit to the traditionzCut LN electro-optical Q-switch, due to the electro-optical coefficient usedγ ₂₂Smaller (about 3.4 pm/V) results in higher half-wave voltage, but larger other electro-optic coefficients of the LN crystal, e.g.γ ₃₃About 30.8 pm/V,γ ₅₁About 28 pm/V, therefore, the half-wave voltage can be further reduced by optimizing the switch configuration and the power-up mode. In the early days, researchers proposedxOryCut LN electro-optical Q-switches, i.e. using edgeszAxial electric field and edgexOryThe modulation mode of the axial light transmission adopts two crystals to compensate natural birefringence in a matching way, and the effective electro-optic coefficient utilized by the mode is larger, so that the half-wave voltage is greatly reduced. For example, under the condition of the same switch size, the dynamic 1/4 wave voltage is reduced to about 1200V from 3600V in the traditional mode. However, in this method, the light transmission direction and the optical axis are 90 °, the natural birefringence is the largest, the influence of the temperature is the largest, the switching performance is extremely unstable, and the method is very sensitive to the temperature difference between two crystals, the processing deviation, the optical quality of the crystals and the like, so that the method is difficult to be used practically.

Disclosure of Invention

The invention provides a low-voltage double-block crystal electro-optic Q switch, which solves the defects of high half-wave voltage, low extinction ratio, large influence by temperature difference and length deviation of two crystals, harsh requirements on processing precision, temperature control precision, crystal quality and the like in the prior art.

The technical scheme for realizing the invention is as follows:

a low-voltage double-crystal electro-optical Q switch is composed of two same electro-optical crystals combined in a certain pairing direction, each crystal cut at a special angle。

The electro-optic crystal is a lithium niobate crystal or a lithium tantalate crystal.

The length direction of the crystal is a light passing direction, and two end faces in the light passing direction are polished and plated with laser antireflection films; an electric field is applied in the thickness direction of the crystal, and two crystal faces in the thickness direction are plated with metal films.

The two crystals are fixed by a mechanical clamp or an optical cement according to the thickness/width directions, which are mutually vertical and the length direction orientation is consistent.

The above-mentionedθHas a value range of。

Besides the above combination mode, two crystals can be placed according to the same orientation, namely the thickness direction, the width direction and the length direction are respectively parallel, then an 1/2 wave plate applying the wavelength is placed between the two crystals, and the long axis and the short axis of the 1/2 wave plate form an angle of 45 degrees with the thickness direction or the width direction of the crystals.

The crystal cut can also beAndangle of rotationθAlso has a value range of。

When the crystal is applied to a laser resonant cavity, the light-passing surface is vertical to the propagation direction of laser, the thickness or width direction of the crystal and the transmission direction of the polarizer form an angle of 45 degrees, and the polarities of voltages applied to the two crystals are opposite.

The invention has the beneficial effects that:

(1) the half-wave voltage is greatly reduced. The invention optimizes the modulation mode with the maximum electro-optical effect by analyzing and calculating the electro-optical effect when an electric field is applied along any direction and light is transmitted along any direction, further reasonably designs the optimal crystal cut type, and the half-wave voltage of the designed double-block crystal electro-optical Q switch is greatly reduced. For example, forThe half-wave voltage of the cut double-block crystal LN electro-optical Q switch is traditionalzAbout 25% of cut LN electro-optical Q-switchxCutting oryThe cut LN electro-optical Q-switch is about 30% lower. In addition, the half-wave voltage of the electro-optical Q-switch of the present invention is lower than that of an RTP electro-optical Q-switch of the same size, about half of the same. Compared with RTP crystal, LN and LT crystal has mature growth technology and lower cost, can meet the requirement of preparing large-caliber devices, and is more beneficial to practical application.

(2) In addition to the half-wave voltage reduction, withxOryCompared with a cut-twin crystal LN electro-optical Q switch, the electro-optical Q switch has the included angle between the light-passing direction and the crystal optical axisθMuch less than 90 deg., and natural birefringence and its temperature effectsThe electro-optical Q-switch has smaller natural birefringence, larger tolerance range for length deviation, temperature deviation and the like of two crystals, and is more practical. In addition, what is often used in practice is a rimzAxial growth of crystals, the optical inhomogeneities being predominantly alongzIn the axial direction, analysis shows that the smaller the included angle between the light passing direction and the optical axis is, the smaller the influence of optical nonuniformity on the extinction ratio is, and therefore, the extinction ratio of the electro-optical Q-switch is higher. It can be calculated by theory that, in the case of the same optical inhomogeneity,the extinction ratio of the cut double-block crystal LN electro-optical Q switch is aboutxOryCut 2.4 times of LN electro-optical Q-switch.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 shows a monolithic crystal cut ofIn whichx、y、zThe axes represent the respective crystal axes of the electro-optic crystal,l、b、trespectively representing the length, width and thickness directions of the cut crystal.

Fig. 2 is a schematic diagram of a structure of a low-voltage two-block crystal electro-optical Q-switch of the present invention, each of which is cut as shown in fig. 1.

FIG. 3 is a schematic diagram of a structure of a low-voltage two-block crystal electro-optical Q-switch of the present invention, each of which is cut as shown in FIG. 1, wherein P is₁、P₂Representing the fast and slow axes of the 1/2 wave plate.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.

Example 1

The low-voltage double-crystal electro-optical Q-switch is prepared by LN crystal, and the crystal cut type of the Q-switch is designed asThe size of the monolithic crystal is 9 mm by 10 mm (thickness)tX widthbX lengthl) The method is applied to lasers with laser wavelength of 1064 nm. Two LN crystals are arranged in accordance withCutting, polishing two end faces along the length direction, plating an antireflection film with the thickness of 1064 nm, plating Au/Ti electrodes on two crystal faces along the thickness direction, and applying an electric field along the thickness direction. The two crystals are combined and fixed together by using a mechanical clamp, so that the length directions of the two crystals are parallel to each other, and the thickness (width) directions of the two crystals are vertical to each other. Electrodes are led out of the two crystals to apply Q-switching high voltage, the two crystals adopt a parallel power-up mode, and the polarities of the applied voltages are opposite.

When the Q-switch is applied to a laser, the light-passing surface is vertical to the propagation direction of laser, and the thickness and width directions of the Q-switch form an angle of 45 degrees with the transmission direction of a polarizer in the laser.

The double-block crystal electro-optical Q switch is applied to an Nd-YAG laser, and an 1/4 wave voltage pressurization type Q switching mode is adopted, so that the purpose of electro-optical Q switching is achieved. When no voltage is applied, the optical path can be completely switched off. When 1/4 wave Q-switched high voltage is applied, stable pulse laser output is obtained. The 1/4 wave voltage is 720V, the output energy of single pulse is about 200mJ, the pulse width is about 7ns when the repetition frequency is 10 Hz. The extinction ratio of the Q-switch was measured to be 120:1 using the cross-polarization method.

Example 2

The low-voltage double-crystal electro-optical Q-switch is prepared by LN crystal, and the crystal cut type of the Q-switch is designed asMonolithic crystal sizes of 9 mm by 5 mm (thickness)tX widthbX lengthl) The method is applied to lasers with laser wavelength of 1064 nm. Two LN crystals are arranged in accordance withCutting, polishing two end faces along the length direction, plating an antireflection film with the thickness of 1064 nm, plating Au/Ti electrodes on two crystal faces along the thickness direction, and applying an electric field along the thickness direction. The two crystals are respectively arranged on the two adjusting brackets, so that the two crystals are placed in the same direction, namely the thickness,The width direction and the length direction are respectively parallel. A1064 nm half-wave plate is placed between the two crystals, and the long and short axis directions of the half-wave plate are adjusted to form an angle of 45 DEG with the thickness or width direction of the crystal. Electrodes are led out of the two crystals to apply Q-switching high voltage, the two crystals adopt a parallel power-up mode, and the polarities of the applied voltages are opposite.

When the Q-switch is applied to a laser, the light-passing surface is perpendicular to the laser propagation direction, and the thickness and width directions of the Q-switch form an angle of 45 degrees with the transmission direction of a polarizer in the laser.

The double-block crystal electro-optical Q switch is applied to an Nd-YAG laser, and an 1/4 wave voltage pressurization type Q switching mode is adopted, so that the purpose of electro-optical Q switching is achieved. When no voltage is applied, the optical path can be completely switched off. When 1/4 wave Q-switched high voltage is applied, stable pulse laser output is obtained. The 1/4 wave voltage is 1400V, the output energy of single pulse is about 200mJ, and the pulse width is about 7ns when the repetition frequency is 10 Hz. The extinction ratio of the Q-switch was measured to be 200:1 using the cross-polarization method.

Example 3

The low-voltage double-crystal electro-optical Q-switch is prepared by LN crystal, and the crystal cut type of the Q-switch is designed asThe size of the monolithic crystal is 9 mm by 10 mm (thickness)tX widthbX lengthl) The method is applied to lasers with laser wavelength of 1064 nm. Two LN crystals are arranged in accordance withCutting, polishing two end faces along the length direction, plating an antireflection film with the thickness of 1064 nm, plating Au/Ti electrodes on two crystal faces along the thickness direction, and applying an electric field along the thickness direction. The two crystals are combined and fixed together by using a mechanical clamp, so that the length directions of the two crystals are parallel to each other, and the thickness (width) directions of the two crystals are vertical to each other. Electrodes are led out of the two crystals to apply Q-switching high voltage, the two crystals adopt a parallel power-up mode, and the polarities of the applied voltages are opposite.

When the Q-switch is applied to a laser, the light-passing surface is vertical to the propagation direction of laser, and the thickness and width directions of the Q-switch form an angle of 45 degrees with the transmission direction of a polarizer in the laser.

The double-block crystal electro-optical Q switch is applied to an Nd-YAG laser, and an 1/4 wave voltage pressurization type Q switching mode is adopted, so that the purpose of electro-optical Q switching is achieved. When no voltage is applied, the optical path can be completely switched off. When 1/4 wave Q-switched high voltage is applied, stable pulse laser output is obtained. The 1/4 wave voltage is 800V, the output energy of single pulse is about 200mJ, and the pulse width is about 7ns when the repetition frequency is 10 Hz. The extinction ratio of the Q-switch was measured to be 130:1 using the cross-polarization method.

Example 4

The low-voltage double-crystal electro-optical Q-switch is prepared by LN crystal, and the crystal cut type of the Q-switch is designed asThe size of the monolithic crystal is 9 mm by 10 mm (thickness)tX widthbX lengthl) The method is applied to lasers with laser wavelength of 1064 nm. Two LN crystals are arranged in accordance withCutting, polishing two end faces along the length direction, plating an antireflection film with the thickness of 1064 nm, plating Au/Ti electrodes on two crystal faces along the thickness direction, and applying an electric field along the thickness direction. The two crystals are combined and fixed together by using a mechanical clamp, so that the length directions of the two crystals are parallel to each other, and the thickness (width) directions of the two crystals are vertical to each other. Electrodes are led out of the two crystals to apply Q-switching high voltage, the two crystals adopt a parallel power-up mode, and the polarities of the applied voltages are opposite.

When the Q-switch is applied to a laser, the light-passing surface is vertical to the propagation direction of laser, and the thickness and width directions of the Q-switch form an angle of 45 degrees with the transmission direction of a polarizer in the laser.

The double-block crystal electro-optical Q switch is applied to an Nd-YAG laser, and an 1/4 wave voltage pressurization type Q switching mode is adopted, so that the purpose of electro-optical Q switching is achieved. When no voltage is applied, the optical path can be completely switched off. When 1/4 wave Q-switched high voltage is applied, stable pulse laser output is obtained. The 1/4 wave voltage is 1300V, the repetition frequency is 10Hz, the output energy of single pulse is about 200mJ, and the pulse width is about 7 ns. The extinction ratio of the Q-switch was measured to be 150:1 using the cross-polarization method.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.