Transverse modulation KDP type electro-optical Q switch
阅读说明：本技术 一种横向调制kdp型电光q开关 (Transverse modulation KDP type electro-optical Q switch ) 是由 商继芳 郝好山 杨金凤 陈铃 苏丽霞 于 2020-12-30 设计创作，主要内容包括：本发明提供了一种横向调制KDP型电光Q开关,其特征在于：将两块相同的KDP型晶体组合,所述KDP型晶体切型为,其中x、z代表KDP型晶体的各晶轴,l、b分别代表切割晶体的长度和宽度方向,角度θ的取值范围为,所述KDP型晶体的长度方向为通光方向、厚度方向为加电场方向。本发明电光Q开关的半波电压可调,开关形状和电极均易制备,电场更加均匀,因而消光比更高,并且本发明电光Q开关的自然双折射及其受温度的影响更小,对匹配用两晶体的长度偏差、温度偏差等要求更低,容许范围更大,更加实用。(The invention provides a transverse modulation KDP type electro-optical Q switch, which is characterized in that: combining two identical KDP type crystals, wherein the KDP type crystals are cut into Wherein x、z Represents each crystal axis of KDP type crystal, l、b respectively representing the length and width directions, angles of the cut crystal θ Has a value range of The length direction of the KDP type crystal is a light passing direction, and the thickness direction is an electric field adding direction. The half-wave voltage of the electro-optical Q switch is adjustable, the shape and the electrode of the switch are easy to prepare, and the electric field is more uniform, so the extinction ratio is higher, the natural birefringence of the electro-optical Q switch and the influence of the temperature on the electro-optical Q switch are smaller, the requirements on length deviation, temperature deviation and the like of two matched crystals are lower, the allowable range is larger, and the electro-optical Q switch is more practical.)
1. A transverse modulation KDP type electro-optical Q switch is characterized in that: combining two identical KDP type crystals, wherein the KDP type crystals are cut intoWhereinx、zRepresents each crystal axis of KDP type crystal,l、brespectively representing the length and width directions, angles of the cut crystalθHas a value range ofThe length direction of the KDP type crystal is a light passing direction, and the thickness direction is an electric field adding direction.
2. The transverse-modulating KDP-type electro-optical Q-switch of claim 1, characterized in that: two end faces in the length direction of the KDP type crystal are polished and plated with laser antireflection films, and two crystal faces in the thickness direction are plated with metal films.
3. The transverse-modulating KDP-type electro-optical Q-switch of claim 1, characterized in that: the two KDP type crystals are combined according to the thickness or width directions which are mutually vertical and the length direction orientation is consistent, and are fixed by a mechanical clamp or an optical adhesive.
4. The transverse-modulating KDP-type electro-optical Q-switch of claim 1, characterized in that: the KDP type crystal is KH2PO4(KDP) crystals, KD2PO4(DKDP) crystals or NH4H2PO4(ADP) crystals.
5. The transverse-modulating KDP-type electro-optical Q-switch of claim 1, characterized in that: the electro-optical Q switch is applied to a laser, when the electro-optical Q switch is applied to the laser, the light passing surface is vertical to the propagation direction of laser, the thickness or width direction of a crystal and the transmission direction of a polarizer in the laser form 45 degrees, and the polarities of voltages applied to the two crystals are opposite.
6. The transverse-modulating KDP-type electro-optical Q-switch of claim 1, characterized in that: placing the two KDP type crystals in the same direction, namely the thickness direction, the width direction and the length direction are respectively parallel, then placing an 1/2 wave plate with the applied wavelength between the two crystals, wherein 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; 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 45 degrees, and the polarities of voltages applied to the two crystals are opposite.
Technical Field
The invention relates to the field of Q-switched laser devices, in particular to a transverse modulation KDP type electro-optical Q switch.
Background
In the field of laser technology, Q-switching technology is one of the important ways to obtain pulsed laser, and Q-switching devices are essential critical elements in pulsed lasers. The commonly used Q-switching technology mainly comprises three types of passive Q-switching, acousto-optic Q-switching and electro-optic Q-switching. Compared with other two Q-switching technologies, electro-optical Q-switching as an active Q-switching technology has the advantages of high switching rate, strong turn-off capability, stable working state, convenience for synchronization with other application equipment in time sequence and the like, nanosecond-level short pulse laser is easy to obtain, and the peak power of output laser can reach hundreds of megawatts, so that an electro-optical Q-switching device is widely applied to pulse lasers.
The KDP type crystal is one of a few practical electro-optical crystals and is the earliest practical electro-optical crystal. The crystal growth technology is mature, large-size crystals with high optical quality can be easily grown, the growth cost is low, the electro-optic coefficient is large, and the light damage resistance threshold is high. Therefore, this type of crystal is most widely used in known electro-optic crystal materials, particularly in lasers in the civilian field, and is the only crystal that can currently meet the requirements of laser Inertial Confinement Fusion (ICF) applications.
In order to avoid the influence of natural birefringence, the conventional KDP-type electro-optical Q-switch mainly adopts a longitudinal modulation mode, that is, the directions of light passing and an electric field are the same and are along the optical axis direction. In this way, on one hand, the annular electrode is needed, the switch shape and the electrode preparation difficulty are high, and the electric field is not easy to be uniform, so that the switch is not tight enough, and the dynamic extinction ratio is low; on the other hand, the half-wave voltage is high and not adjustable.
Some researchers have proposed a lateral modulation application mode, in which a crystal is cut at 45 ° -z, an electric field is applied along the z-axis direction, the light-passing direction is in the xoy plane and forms 45 ° with the x and y axes, in this way, half-wave voltage can be reduced by increasing the aspect ratio, but natural birefringence exists, and two-block crystal compensation is required, because the light-passing direction and the optical axis form 90 °, the natural birefringence is the largest and is also the largest affected by temperature, the switching performance is extremely unstable, and the lateral modulation application mode is very sensitive to the temperature difference, the processing deviation, the optical quality of the two crystals, and the like, and thus, the lateral modulation application mode has not been put into practical use.
Disclosure of Invention
The invention provides a transverse modulation KDP type electro-optical Q switch, which utilizes the maximum effective electro-optical coefficient, increases the allowable range of the temperature difference and the processing deviation of two crystals and improves the extinction ratio of the switch to meet the actual application requirement on the premise of ensuring transverse modulation by optimally designing the directions of light and an electric field.
The technical scheme for realizing the invention is as follows:
a transverse modulation KDP type electro-optical Q switch is formed by combining two identical KDP type crystals according to a special design cutting type and a matching direction, wherein each crystal is cut by a special angle, the materials, cutting types, sizes, film layer plating and the like of the two crystals are completely identical, and the KDP type crystal cutting type isWhereinx、zRepresents each crystal axis of KDP type crystal,l、brespectively representing the length and width directions, angles of the cut crystalθHas a value range ofThe length direction of the KDP type crystal is a light passing direction, two end faces of the light passing direction are polished and plated with laser antireflection films, the thickness direction is an electric field adding direction, and two crystal faces of the thickness direction are plated with metal films.
The two KDP type crystals are combined according to the thickness or width directions which are mutually vertical and the length direction orientation is consistent, and are fixed by a mechanical clamp or an optical adhesive.
The KDP type crystal is KH2PO4(KDP) crystals, KD2PO4(DKDP) crystals or NH4H2PO4(ADP) crystals.
The electro-optical Q switch is applied to a laser, when the electro-optical Q switch is applied to the laser, the light passing surface is vertical to the propagation direction of laser, the thickness or width direction of a crystal and the transmission direction of a polarizer in the laser form 45 degrees, and the polarities of voltages applied to the two crystals are opposite.
Preferably, two KDP type 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 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; 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 45 degrees, and the polarities of voltages applied to the two crystals are opposite.
The invention has the beneficial effects that:
(1) by researching the magnitude of the electro-optical effect when the KDP type crystal is electrified along any direction, the configuration mode with the maximum electro-optical effect is preferably selected on the premise of ensuring the transverse modulation, and the reasonable switch configuration is designed.
(2) Compared with a transverse modulation KDP type electro-optical Q switch cut by 45-z, the electro-optical Q switch has the advantages that the effective electro-optical coefficient is larger, and the half-wave voltage is lower. For example, forThe half-wave voltage of the cut electro-optical Q switch is reduced by about 22 percent compared with that of the electro-optical Q switch cut by 45-z with the same size. Besides, the included angle between the light passing direction and the optical axis of the inventionθMuch less than 90 deg., due to natural birefringence and its temperature effectThe natural birefringence of the electro-optical Q switch is less influenced by temperature, the requirements on length deviation, temperature deviation and the like of two matched crystals are lower, the allowable range is larger, and the electro-optical Q switch is more practical.
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 crystal cut ofIn whichx、y、zThe axes represent the respective crystal axes of a KDP type 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 transverse modulation KDP-type electro-optical Q-switch of the present invention, each crystal cut is as shown in fig. 1.
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
In the embodiment, a DKDP crystal is adopted to prepare a transverse modulation electro-optical Q switch, and the Q switch crystal is designed to be cut intoThe size of the monolithic crystal is 9mm by 10mm (thickness)tX widthbX lengthl) The method is applied to lasers with laser wavelength of 1064 nm.
Cutting two DKDP crystals with the same specification according to the design and size, polishing and plating 1064nm laser antireflection films on two end faces in the length direction, plating Au/Ti electrodes on two crystal faces in the thickness direction, combining the two crystals together by using a mechanical clamp, enabling the length directions of the two crystals to be parallel, the thickness direction or the width direction to be mutually vertical, enabling the polarities of voltages applied to the two crystals to be opposite, as shown in figure 2, packaging the crystals in a mechanical shell with light-transmitting windows at two ends, and plating 1064nm laser antireflection films on the surfaces of the two light-transmitting windows.
The transverse modulation DKDP electro-optical Q switch is applied to an Nd-YAG laser, so that a light passing surface is perpendicular to the propagation direction of laser, and the thickness or width direction of the switch forms 45 degrees with the transmission direction of a polarizer in the laser. The purpose of electro-optical Q-switching is achieved in an 1/4 wave voltage-pressurization Q-switching mode. 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 2200V, the repetition frequency is 10Hz, the output energy of single pulse is about 160mJ, and the pulse width is about 10 ns.
Example 2
In the embodiment, a DKDP crystal is adopted to prepare a transverse modulation electro-optical Q switch, and the Q switch crystal is designed to be cut intoThe size of the monolithic crystal is 9mm by 10mm (thickness)tX widthbX lengthl) The method is applied to lasers with laser wavelength of 1064 nm.
Cutting two DKDP crystals with the same specification according to the design and size, polishing and plating 1064nm laser antireflection films on two end faces in the length direction, plating Au/Ti electrodes on two crystal faces in the thickness direction, combining the two crystals together by using a mechanical clamp, enabling the length directions of the two crystals to be parallel, the thickness direction or the width direction to be mutually vertical, enabling the polarities of voltages applied to the two crystals to be opposite, as shown in figure 2, packaging the crystals in a mechanical shell with light-transmitting windows at two ends, and plating 1064nm laser antireflection films on the surfaces of the two light-transmitting windows.
The transverse modulation DKDP electro-optical Q switch is applied to an Nd-YAG laser, so that a light passing surface is perpendicular to the propagation direction of laser, and the thickness or width direction of the switch forms 45 degrees with the transmission direction of a polarizer in the laser. The purpose of electro-optical Q-switching is achieved in an 1/4 wave voltage-pressurization Q-switching mode. 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 2800V, the repetition frequency is 10Hz, the output energy of single pulse is about 160mJ, and the pulse width is about 10 ns.
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.