CN108767650B - Function composite electro-optical Q switch - Google Patents
Function composite electro-optical Q switch Download PDFInfo
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- CN108767650B CN108767650B CN201810616911.5A CN201810616911A CN108767650B CN 108767650 B CN108767650 B CN 108767650B CN 201810616911 A CN201810616911 A CN 201810616911A CN 108767650 B CN108767650 B CN 108767650B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
- H01S3/1123—Q-switching
- H01S3/115—Q-switching using intracavity electro-optic devices
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention discloses a function composite electro-optical Q switch, belonging to the application of crystal material in the photoelectric technical field, the invention is composed of a KDP crystal or L iNbO3The crystal is cut into a certain design to form a functional composite electro-optical Q-switch device. It utilizes natural double refraction effect and electro-optical effect of electro-optical crystalIt can simultaneously function as 1/4 wave plate and traditional electro-optical Q switch, and can independently perform the pressurized electro-optical Q switch. The invention has the advantages that: the 1/4 wave plate or the analyzer is not needed to be used when the Q-switch is switched in a pressurizing mode, the installation and the adjustment are simple and convenient, the compactness and the stability of the laser are improved, and the cost is reduced.
Description
Technical Field
The invention relates to the field of laser devices, in particular to a functional composite electro-optical Q switch.
Background
The Q-switching technology is one of the most commonly used modes for obtaining laser with narrow pulse width and high peak power at present, and is characterized in that the Q value of a cavity is changed according to a certain program by a certain method, the cavity is in a low Q value state at the beginning of pumping, namely, the loss in the cavity is large, laser oscillation cannot be formed, the number of upper level inversion particles in a laser medium is accumulated continuously at the moment, when the maximum value is accumulated, the Q value of the cavity is suddenly increased to the maximum value, namely, the loss is reduced to the minimum value, the laser oscillation is quickly established at the moment, the number of the upper level inversion particles is quickly consumed in a short time, and the upper level inversion particles are converted into laser energy to be output. At present, technologies such as electro-optical Q-switching, acousto-optical Q-switching, passive Q-switching, mechanical Q-switching and the like are mainly available.
Among all the Q-switching techniques, electro-optical Q-switching is widely used as an active Q-switching technique because of its high switching rate and its easy acquisition of narrow pulse width, and because of its easy realization of high-precision synchronization between the laser and other linkage instruments. Electro-optic Q-switch utilizes the electro-optic effect of the electro-optic crystal, changes the polarization state of laser after passing through the electro-optic crystal by applying step voltage on the crystal, and realizes the low Q value and high Q value states of a laser cavity by matching with a polarization element.
Electro-optical Q-switching generally operates in two ways: pressurized and depressurized. The pressurized mode is that when a voltage is applied to the crystal, the Q switch is in an open state, i.e. the cavity is in a high Q value state, and after the voltage is removed, the cavity is in a low Q value state, and the reverse is the reverse. For a traditional electro-optical Q switch, light is generally transmitted along the optical axis direction or two crystals are paired to compensate natural birefringence, so that the polarization state of laser light passing through the electro-optical Q switch can not be changed when no voltage is applied. In order to realize the pressurized electro-optical Q-switching, an analyzer or 1/4 wave plate must be added into the cavity, so that on one hand, the insertion loss is increased, and the compactness and the stability of the laser are not facilitated; and on the other hand, the debugging difficulty and the cost are increased. Although no extra polarization element is needed for the voltage-relief type Q-switching, the time for applying high voltage to the crystal is long, which not only puts high requirements on an electro-optical Q-switching driving source, but also shortens the service life of the Q-switch.
Disclosure of Invention
The invention aims to obtain an electro-optic Q switch which can perform pressurized electro-optic Q switching and does not need an additional optical polarization element.
The invention provides a functional composite electro-optical Q switch, which adopts the technical scheme as follows:
the electro-optic crystal is cut at a special angle into
Theta is an included angle between the laser propagation direction and the crystal optical axis, and the value of theta satisfies the relation:
wherein the content of the first and second substances,
l is the length in the light-transmitting direction, noAnd neThe natural birefringence of the electro-optic crystal, λ is the wavelength of the laser, the electro-optic crystal may be L iNbO3Crystals or KDP-like crystals, for L iNbO3A crystal, an electric field is applied along the direction close to the x axis; for KDP crystal, an electric field is applied along the light passing direction. The direction of the near z axis is the light passing direction, two end faces are polished and plated with laser antireflection films, and laser is incident perpendicular to the end faces. The electro-optic crystal cut can also be
The invention has the advantages that: combines the advantages of the existing pressurized and voltage-relief electro-optical Q-switching technologies, and avoids the disadvantages of the pressurized and voltage-relief electro-optical Q-switching technologies. The laser can not only perform pressurized electro-optic Q-switching, but also does not need to use 1/4 wave plates or polarization elements such as an analyzer and the like, so that the advantages of low requirements of the pressurized electro-optic Q-switching technology on a Q-switching driving source, long service life of an electro-optic Q switch and the like are kept, the problems of high installation and adjustment difficulty, difficulty in stabilizing a laser system and the like caused by the fact that the wave plates are greatly influenced by temperature and stress are avoided, the compactness and stability of the laser are improved, and the cost is reduced.
Drawings
Fig. 1 is a schematic structural diagram of a functional composite electro-optical Q-switch according to the present invention. The x, y and z axes in the figure represent the respective crystal axes of the electro-optic crystal.
Detailed Description
Example 1:
using L iNbO3A crystal is used for preparing a functional composite electro-optical Q-switch, the size of the Q-switch is designed to be 9mm × 9mm × 18.8.8 mm, and the Q-switch is applied to a laser with the laser wavelength of 1064nm
The value of θ was 1.7 ° by substituting k in 2 into the corresponding parameter, and L innbo was added3The crystal is cut according to the cutting type of (xztw) -1.2 degrees/1.2 degrees, two end faces along the length direction are polished and coated with an antireflection film of 1064nm, two near-x faces are coated with Ti/Au electrodes, and an electric field is applied along the direction near-x axis.
When the laser is applied, the laser passing through the polarizer enters perpendicular to the end face of the crystal, and the polarization direction of the polarizer is L iNbO3The x-axis or y-axis of the crystal is parallel. As can be seen from FIG. 1, the angle between the laser propagation direction and the crystal optical axis is θ, i.e. 1.7 °, and the projection on the xoy plane forms an angle of 45 ° with the x-axis
When no voltage is applied, the phase difference generated by natural birefringence after the laser passes through the crystal is 5 pi/2, the included angle between the intrinsic polarization direction and the polarizing direction is 45 degrees, the laser is reflected by the full-reflection mirror and then passes through the electro-optic crystal again to generate the phase difference of 5 pi/2, so the total phase difference is 5 pi, the polarization direction of the laser rotates 90 degrees relative to the original polarization direction at the moment, the laser cannot pass through the polarizer, the Q switch is in an off state, the cavity loss is maximum, and the Q value is minimum.
When 1/4 wave voltage is applied on the crystal, the phase difference generated after the laser passes through the crystal is changed into 3 pi, the total phase difference generated after the laser passes through the crystal twice in a reciprocating way is 6 pi, the polarization direction of the laser is the same as the original polarization direction, the laser can pass through the polarizer, the Q switch is in an open state, the cavity loss is minimum, and the Q value is highest.
The electro-optical Q-switch is applied to Nd: YAG laser realizes the purpose of independently performing pressurized electro-optical Q-switching. The 1/4 wave voltage is 2200V, the repetition frequency is 10Hz, the single pulse output energy is 200mJ, the pulse width is 7 ns.
Claims (2)
1. A functional compound electro-optic Q-switch, characterized by: the electro-optic crystal is cut along a special angle into
Theta is an included angle between the laser propagation direction and the crystal optical axis, and the value of theta satisfies the relation:
wherein the content of the first and second substances,
l is the length in the light-transmitting direction, noAnd neThe natural birefringence of the electro-optic crystal is represented by λ, laser wavelength, near z-axis direction, two end faces polished and coated with laser antireflection film, laser is incident perpendicular to the end faces, and the electro-optic crystal can be represented by L iNbO3Crystals or KDP-like crystals, for L iNbO3A crystal, an electric field is applied along the direction close to the x axis; for KDP crystal, an electric field is applied along the light passing direction.
2. The functional composite electro-optic Q-switch of claim 1, wherein: the electro-optic crystal cut can also be
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| CN112382920B (en) * | 2020-11-28 | 2021-07-23 | 河南工程学院 | Low-voltage laminated lithium niobate electro-optical Q switch |
| CN112421372B (en) * | 2020-12-30 | 2022-03-18 | 河南工程学院 | Transverse modulation KDP type electro-optical Q switch |
| CN113488841B (en) * | 2021-07-12 | 2022-12-09 | 河南工程学院 | Low-voltage independent pressurization type electro-optical Q switch |
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| JP3620024B2 (en) * | 2001-07-06 | 2005-02-16 | 有限会社ピエデック技術研究所 | Width longitudinal piezoelectric crystal resonator |
| CN101499605B (en) * | 2009-02-19 | 2011-08-31 | 福州高意通讯有限公司 | A crystal device |
| RU2013126525A (en) * | 2010-11-09 | 2014-12-20 | ЛОРЕНС ЛИВЕРМОР НЭШНЛ СЕКЬЮРИТИ, ЭлЭлСи | MULTI-CRYSTAL FREQUENCY MOTOR FOR CONVERSION TO THIRD HARMONIC |
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| CN103259182B (en) * | 2013-04-26 | 2014-06-18 | 山东大学 | General electro-optical Q-switching switch and Q-switching laser for broadband passing through optical rotation crystal for single or odd times |
| CN205724360U (en) * | 2016-06-06 | 2016-11-23 | 中国工程物理研究院应用电子学研究所 | A kind of Q-switched pulse laser being switched fast polarization state |
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