CN107404059B - Method and device for generating terahertz waves by continuously inclined pulse wave surface pumping lithium niobate - Google Patents
Method and device for generating terahertz waves by continuously inclined pulse wave surface pumping lithium niobate Download PDFInfo
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 238000005086 pumping Methods 0.000 title claims abstract description 51
- 238000000034 method Methods 0.000 title claims abstract description 41
- 239000013078 crystal Substances 0.000 claims abstract description 60
- 238000003384 imaging method Methods 0.000 claims abstract description 24
- 230000003287 optical effect Effects 0.000 claims abstract description 15
- 230000005466 cherenkov radiation Effects 0.000 claims description 7
- 230000005540 biological transmission Effects 0.000 claims description 2
- 239000010408 film Substances 0.000 abstract description 16
- 239000010409 thin film Substances 0.000 abstract description 15
- 238000004519 manufacturing process Methods 0.000 abstract 1
- 239000006185 dispersion Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 229910003327 LiNbO3 Inorganic materials 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000010287 polarization Effects 0.000 description 2
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000009022 nonlinear effect Effects 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
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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
- H01S1/00—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range
- H01S1/02—Masers, i.e. devices using stimulated emission of electromagnetic radiation in the microwave range solid
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention relates to a method for generating terahertz waves by a femtosecond laser optical rectification method, which aims to realize continuous tilting of pulse wave surfaces without introducing any distortion of any time, space and frequency domains, can improve the tilting quality of the wave surfaces, and has the characteristics of low manufacturing cost, convenient adjustment, simplicity, high efficiency and strong practicability. The invention relates to a device for generating terahertz waves by continuously tilting pulse wave surface pumping lithium niobate, which consists of a femtosecond laser light source, a beam expander, a focusing lens, a tilting F-P cavity, a beam limiting diaphragm, an imaging lens and lithium niobate crystals, wherein the tilting F-P cavity consists of a full-reflection mirror for pumping laser wave bands and a thin film partial-reflection mirror which are arranged in parallel; the wave surface of the laser pulse generated by the femtosecond laser source is a plane after passing through the beam expander, and the focus is projected onto a film part reflecting mirror of the inclined F-P cavity, and reflected light is projected onto the lithium niobate crystal through an imaging lens. The invention is mainly applied to the occasion of generating terahertz waves.
Description
Technical Field
The invention relates to a method for generating terahertz waves by a femtosecond laser optical rectification method, in particular to a method for generating terahertz waves by adopting an inclined F-P cavity formed by a full-reflection mirror and a thin film partial reflection mirror to realize continuous wave surface inclined pumping of lithium niobate.
Background
The current adoption of an optical rectification method to generate ultra-fast terahertz waves is one of important photonics means in the terahertz technical field [1]. The main mechanism of generating ultra-fast terahertz waves by an optical rectification method is to utilize the second-order nonlinear effect of nonlinear crystals. When the femtosecond pulse is applied to the nonlinear crystal, the monochromatic components in the pulses no longer propagate independently, but rather a mixing phenomenon occurs. The intermediate frequency effect generates light waves with a frequency close to the second harmonic, and the difference frequency effect generates an electric polarization field of low-frequency oscillation, and the electric polarization field can radiate low-frequency electromagnetic waves in a terahertz wave band. Therefore, the energy of terahertz waves generated by the optical rectification effect is mainly derived from the energy of the incident laser pulse, and the energy conversion efficiency thereof is mainly dependent on: the second-order nonlinear coefficient of the medium, the absorption coefficient of the medium to the terahertz wave and the phase matching condition between the laser pulse and the terahertz wave. After the nonlinear crystal is selected, the phase matching condition is the only factor considered to be steerable. The better the phase matching of the femtosecond laser with the nonlinear crystal is, the longer the distance that the pump pulse and the generated terahertz wave can act in the crystal, the higher the light-light conversion efficiency of the terahertz wave is.
In the research of generating terahertz waves by an optical rectification method, nonlinear crystals with large nonlinear coefficients are required, and nonlinear crystals capable of generating terahertz waves in a matching laser source band are limited at present. Among them, lithium niobate (LiNbO 3) crystals having a high nonlinear coefficient are one of the most widely used crystals at present. However, the refractive index of THz wave band in the crystal is larger than that of pump light, so that terahertz waves can be emitted only in the form of 'Cerenkov radiation' under the conventional pumping condition, and the terahertz waves are guided out by a silicon prism or the crystal surface is cut along the emergent direction of the THz waves. Under such conditions, the generation efficiency of terahertz sources using LiNbO3 crystals is low and the quality of terahertz waves is poor due to the "space walk-off" effect of pump light and terahertz waves and the tapered emission surface of terahertz waves of "cerenkov radiation" [2 ].
Until 2002, hening et al [3] in hungarian proposed a new method of inclined pulse wave surface pumping (TPFP) in LiNbO3 crystals, which can provide pump light with a velocity component in the terahertz wave direction and maintain synchronization with the terahertz wave velocity, thus overcoming the "time-space walk-off effect" and significantly increasing the conversion efficiency; and the conical surface emission of the terahertz wave is changed into unidirectional plane emission from the 'Cerenkov radiation', so that the effective utilization rate of the terahertz wave is greatly improved. From this research and application of this technology, rapid developments have been made. The current method for realizing pulse wave surface tilting in TPFP technology is to utilize angular dispersion provided by diffraction grating and then utilize a lens imaging system to image tilted wave surface pulse on the inner side of the emergent surface of LiNbO3 crystal prism.
Therefore, in the technology of generating terahertz waves by pumping LiNbO3 crystals with oblique pulse wave surfaces, the quality of the oblique pulse wave surfaces is critical to the generation process and quality of the terahertz waves. In principle, the method of tilting the pulse wave surface should not affect the time, space, frequency domain and other characteristics of the original pump pulse, except for providing the effect of tilting the pulse wave surface, otherwise the time, space, frequency domain characteristics of the terahertz wave generated must be different from the method of tilting the pulse wave surface. However, in the process of realizing TPFP by adopting diffraction grating angular dispersion, time and space chirping are necessarily introduced into the original pump femtosecond pulse; meanwhile, due to the existence of the grating structure, the pulse action results in time-frequency dispersion, namely the pulse wave surface after the inclined wave surface is no longer continuous, namely the pulse wave surface is formed by the collection of small pulses separated in time and frequency in the light beam, and the light beam is divergent light, so that the accuracy of the subsequent imaging and the terahertz process are obviously influenced.
In addition, the accurate satisfaction of LiNbO can be realized at present 3 Diffraction grating parameters required for oblique pulse wave surfaces of the exit angle of a crystal prism (the cerenkov wave surface generating terahertz waves in a lithium niobate crystal) are difficult to match with existing commercial grating parameters. If custom gratings are expensive. Commercial gratings with similar parameters are purchased, so that an inclination angle error is necessarily introduced. Therefore, for the technical field of generating terahertz waves by the TPFP lithium niobate crystal, a new technology for continuously tilting the pumping pulse wave surface without causing characteristic distortion of time, space, frequency domain and the like of the pumping pulse is very necessary to be researched and developed.
[1] Xu Jingzhou, zhang Xicheng, terahertz science and technology and application, beijing university Press, 2007.
[2]D.H.Auston,K.P.Cheung,J.A.Valdmanis,and D.A.Kleinman,Cherenkov radiation from femtosecond optical pulses in electro-optic media,Phys.Rev.Lett.1984,53:1555.
[3]Hebling J,Almasi G,Kozma I Z,et al.Velocity matching by pulse front tilting for large-area THz-pulse generation[J].Optics Express,2002,10(21):1161.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a method for generating terahertz by adopting an inclined F-P cavity formed by a reflecting mirror and a film part reflecting mirror to realize continuous wave surface inclined pumping of lithium niobate. The method utilizes a plane mirror and a thin film part mirror which are relatively arranged in parallel to form an inclined F-P cavity. The pump femtosecond pulse after beam expansion is incident on the film part reflector in the inclined F-P cavity through the focus of the focusing lens, and is output after single reflection of the light beam outer edge light, so that continuous inclined pulse wave surface is realized without introducing any distortion of time, space and frequency domain, the inclined quality of the wave surface can be improved, and the device has the characteristics of low cost, convenience in adjustment, simplicity, high efficiency and strong practicability. In order to achieve the purpose, the technical scheme adopted by the invention is that the device for generating terahertz waves by pumping lithium niobate through a continuous inclined pulse wave surface comprises a femtosecond laser light source, a beam expander, a focusing lens, an inclined F-P cavity, a beam limiting diaphragm, an imaging lens and lithium niobate crystals, wherein the inclined F-P cavity is formed by arranging a full reflecting mirror for pumping a laser wave band and a thin film part reflecting mirror in parallel; the laser pulse generated by the femtosecond laser source passes through the beam expander and then the pulse wave surface is a plane, the focus is projected onto the film part reflector of the inclined F-P cavity after passing through the focusing lens, the reflected light passes through the total reflection mirror in the inclined F-P cavity so that the outermost edge light of the reflected light beam is output after being reflected once, the original beam size is maintained unchanged through the beam limiting diaphragm, and then the reflected light is projected onto the lithium niobate crystal through the imaging lens.
The light-transmitting incident surface of the lithium niobate crystal is a z-a surface of a crystal optical axis, and the included angle between the emergent surface of the crystal and the z-b surface is 63.5 degrees; the angle may be adjustable according to the incident wavelength.
The pulse wave surface projected to the lithium niobate crystal is parallel to the emergent surface of the lithium niobate crystal, and the emergent surface of the lithium niobate crystal is cut according to the Cerenkov radiation surface generating terahertz waves in the lithium niobate crystal.
A method for generating terahertz wave by continuously tilting pulse wave surface pumping lithium niobate uses a femtosecond laser light source and a beam expander to generate pulse with pulse wave surface as plane, and uses a plane mirror and a thin film part mirror to be placed in parallel to form a tilted F-P cavity, so that the pump femtosecond pulse after beam expansion is projected to the tilted F-P cavity through a focusing lens to realize continuous tilting pulse wave surface, the size of the pump beam is maintained unchanged through a beam limiting diaphragm, and then the pump femtosecond pulse is projected to lithium niobate crystal through an imaging lens.
The pulse wave surface projected to the lithium niobate crystal is parallel to the emergent surface of the lithium niobate crystal, and the emergent surface of the lithium niobate crystal is cut according to the Cerenkov radiation surface generating terahertz waves in the lithium niobate crystal.
The invention has the characteristics and beneficial effects that:
because the method adopts the inclined F-P cavity formed by the total reflection mirror and the film partial reflection mirror to realize the technology of generating terahertz by pumping lithium niobate by wave surface inclination, angular dispersion and diffraction are not involved, compared with the prior method, the method has the following remarkable characteristics:
1. the method realizes the pulse wave surface inclination of the pumping pulse according to the method of beam width wave surface division by expanding, focusing, reflecting and partially transmitting the pumping pulse, and does not introduce other time, space and frequency domain distortions to the original pulse.
2. The method realizes the adjustment of the inclined wave surface angle of the pumping pulse by adjusting the beam expansion ratio, the focal length of the focusing lens and the inclined angle of the F-P cavity, and is simple and convenient to operate.
3. In the method, the beam-limiting diaphragm is used for maintaining the size of the beam emergent beam after the wave surface of the pumping pulse is inclined.
4. In the method, the primary total reflection range of the outermost light of the focused pump beam is defined as the scale of the inclined F-P cavity, so that the continuity of the pump pulse wave-dividing surface is ensured.
5. In the method, the material dispersion and the optical path difference of the film part reflector in the inclined F-P cavity, which are introduced to the pumping pulse, are negligible, and the fraction ratio is 50%, so that the total output efficiency is ensured to reach more than 80%.
Description of the drawings:
FIG. 1 is a schematic diagram of a tilted F-P cavity formed by a mirror and a thin film partially reflecting mirror to realize continuous pulse wavefront tilting.
FIG. 2 is a schematic diagram of a method for generating terahertz by pumping lithium niobate with inclined wave surface using an inclined F-P cavity. The reference numerals in the figures are respectively: the laser comprises a femtosecond laser source 1, a beam expander 2, a focusing lens 3, an inclined F-P cavity 4, a beam limiting diaphragm 4, an imaging lens 5 and a lithium niobate crystal 6.
Detailed Description
The invention aims to overcome the limitation of the method for generating terahertz waves by adopting grating inclined pulse wave surface pumped lithium niobate in the prior art, and provides a method for generating terahertz waves by adopting an inclined F-P cavity formed by a total reflection mirror and a thin film partial reflection mirror to realize continuous wave surface inclined pumped lithium niobate. The method utilizes a plane total reflection mirror and a thin film partial reflection mirror which are arranged in parallel to form an inclined F-P cavity. The pump femtosecond pulse after beam expansion is refocused into the inclined F-P cavity through the focusing lens, so that continuous inclined pulse wave surface is realized, no distortion of any time, space and frequency domains is introduced, and the inclined quality of the wave surface is improved. The invention has the characteristics of low cost, convenient adjustment, simplicity, high efficiency and strong practicability.
The solution scheme of the method of the invention is as follows:
a method for generating terahertz by continuous wave surface inclined pumping of lithium niobate by adopting an inclined F-P cavity formed by a total reflection mirror and a film partial reflection mirror comprises a femtosecond laser light source, a beam expander, a focusing lens, an inclined F-P cavity, a beam limiting diaphragm, an imaging lens and a lithium niobate crystal. Characterized in that the method comprises the following steps:
(2) the femtosecond laser source outputs femtosecond pulse with the wavelength of 1040nm, and the laser pulse passes through the beam expander;
(3) and the beam diameter of the pumping laser beam is expanded to 2-4 times by the beam expander. The pump pulse after beam expansion passes through the focusing lens;
(4) projecting a focal point to a thin film partial mirror in the tilted F-P cavity through the focusing lens; so that the pump beam's extreme light line passes through the tilt the reflector in the F-P cavity emits after primary reflection;
(5) the beam size of the emergent beam is limited to the original beam expansion size by the expanded pumping pulse passing through the inclined F-P cavity and the beam limiting diaphragm;
(6) the pumping pulse passing through the beam limiting diaphragm enters the lithium niobate crystal through the imaging lens.
The 1040nm pump laser pulse can meet the following conditions:
(1) the 1040nm femtosecond laser can be pulse lasers with other wavelengths;
(2) the 1040nm femtosecond laser pulse width is fs-ps magnitude.
The focusing lens meets the following requirements:
(7) the focusing lens is an achromatic lens;
(8) the focal length F of the focusing lens is determined by the size A of the expanded pump beam and the incidence angle beta formed by converging the outermost light rays to the film part reflecting mirror in the inclined F-P cavity: f=a/tan β.
The inclined F-P cavity the following requirements are satisfied:
(1) the inclined F-P cavity is formed by arranging a full reflecting mirror for pumping laser wave bands and a thin film partial reflecting mirror in parallel;
(2) the thickness of the film part reflecting mirror in the inclined F-P cavity is smaller than 200 micrometers, and the intensity spectroscopic ratio is 1:1;
(3) the distance, the parallelism and the integral rotation angle between the two cavity mirrors of the inclined F-P cavity are adjustable. The tilt angle of the tilted F-P cavity is selected according to the requirement on the pump tilt angle.
(4) The transverse dimension delta of the inclined F-P cavity is determined by the distance m between the two cavity mirrors, the inclination angle alpha of the F-P cavity and the incidence angle beta formed by converging the outermost light rays to the thin film partial reflecting mirror in the inclined F-P cavity according to the requirement that the outermost light rays of the pumping light beams are emitted after being reflected once by the total reflecting mirror in the inclined F-P cavity and neglecting the influence of the thin film partial reflecting mirror in the F-P cavity on the optical path and the chromatic dispersion: delta=2m×tan (α+β).
The imaging lens meets the following requirements:
(1) the imaging lens can be single lens imaging or multi-lens combined imaging.
The lithium niobate crystal meets the following requirements:
(2) the light-transmitting incident surface of the lithium niobate crystal is a z-a surface of a crystal optical axis, and the included angle between the emergent surface of the crystal and the z-b surface is 63.5 degrees; the angle may be adjustable according to the incident wavelength.
According to the design requirement of the pulse inclination angle of 63.5 degrees in the lithium niobate crystal, specific parameters are selected as follows:
tilting F-P cavity: the interval m between the two mirrors is 10mm, and the transverse dimension delta is 4.7cm; the thickness d of the film partial reflector is 0.1mm, and the refractive index n g Taking 1.52, and taking 1:1 of the light intensity beam splitting ratio of the pumping pulse; the beam expansion pump beam size A is 2mm; the focal length f of the focusing lens is 60mm; the tilt angle α of the tilted F-P cavity is taken to be 65 °.
The principle of the invention is as follows:
the inclined F-P cavity generating the inclination of the wave surface of the pumping pulse is formed by parallel arrangement of a total reflecting mirror for the wavelength of pumping laser and a film part reflecting mirror, and the whole inclined F-P cavity is inclined at an angle, and the structure of the inclined F-P cavity is shown in figure 1. The pulse wave surface of the expanded pumping pulse is a plane at the beginning, all parts in the same time and space are focused on a film part reflecting mirror which inclines an F-P cavity according to the design requirement through a focusing lens, and the incidence angle and the inclination angle determined under the condition that the outermost light of the pumping beam is directly output through the film part reflecting mirror and a total reflecting mirror twice reflecting cavity are ensured, so that all the light of the expanded pumping beam can be reflected and transmitted in the range; because of the expanded beam, the incidence angle of the light rays of each part of each space is gradually reduced, so that the delay (optical path difference) passing through the parallel inclined F-P cavity is gradually reduced, namely the inclination of the pulse wave surface relative to the bit phase surface is generated; particularly, the reflection and transmission processes by means of the inclined F-P cavity cannot be like the optical grating method in terms of the hollow chirp when the original pumping pulse is introduced by the angular dispersion; the inclination angle introduced to the pumping pulse is related to the beam expansion ratio, the focal length of the focusing lens and the inclination angle of the F-P cavity, so that the final inclination angle of the pumping pulse can be controlled by adjusting the parameters; because the pulse emitted by the inclined F-P cavity is divergent light, a beam limiting diaphragm is required to maintain the same beam size as the pumping light; the pump light of the inclined pulse wave surface enters the lithium niobate crystal through the lens imaging system, and the pulse wave surface is parallel to the emergent surface of the lithium niobate crystal (the surface is cut according to the Cerenkov radiation surface generating terahertz waves in the crystal). As described above, the schematic configuration of the entire system is shown in fig. 2.
The invention relates to a method for generating terahertz by adopting an inclined F-P cavity to realize wave-surface inclined pumping lithium niobate, and referring to fig. 2, fig. 2 is a light path diagram of the method for generating terahertz by adopting the inclined F-P cavity to realize wave-surface inclined pumping lithium niobate, and the adopted devices comprise a femtosecond laser source, a beam expander, a focusing lens, an inclined F-P cavity, a beam limiting diaphragm, an imaging lens and a lithium niobate crystal.
The method comprises the following steps:
a) The femtosecond laser source (1) outputs a laser pulse with the wavelength of 1040nm of 50fs-150fs, and the laser pulse passes through the beam expander (2);
b) The diameter of the pumping laser pulse beam is 2mm-4mm through the beam expander (2), and then the pumping laser pulse beam passes through the focusing lens (3);
c) And the pump beam is focused on a film part reflector in the inclined F-P cavity (34) through the focusing lens (3), so that the most light of the pump beam is emitted after being reflected once by a total reflection mirror in the inclined F-P cavity.
d) The original size of the pump beam is maintained through the beam limiting diaphragm (5) by the divergent oblique pulse wave surface emitted by the oblique F-P cavity (4).
e) The pump beam passing through the inclined wave surface of the beam limiting diaphragm (5) passes through an imaging lens (6).
f) The imaging lens (6) couples pumping pulse with inclined pulse wave surface into the lithium niobate crystal (7) to generate terahertz wave.
The 1040nm pump laser pulse meets the following conditions:
(1) the 1040nm femtosecond laser can be pulse lasers with other wavelengths;
(2) the 1040nm femtosecond laser pulse width is fs-ps magnitude.
The focusing lens meets the following requirements:
the focusing lens is an achromatic lens;
(2) the focal length F of the focusing lens is determined by the size A of the expanded pump beam and the incidence angle beta formed by converging the outermost light rays to the film part reflecting mirror in the inclined F-P cavity: f=a/tan β.
The inclined F-P cavity meets the following requirements:
(1) the inclined F-P cavity is formed by arranging a full reflecting mirror for pumping laser wave bands and a thin film partial reflecting mirror in parallel;
(2) the thickness of the film part reflecting mirror in the inclined F-P cavity is smaller than 200 micrometers, and the intensity spectroscopic ratio is 1:1;
(3) the distance, the parallelism and the integral rotation angle between the two cavity mirrors of the inclined F-P cavity are adjustable. The tilt angle of the tilted F-P cavity is selected according to the requirement on the pump tilt angle.
(4) The transverse dimension delta of the inclined F-P cavity is determined by the distance m between the two cavity mirrors, the inclination angle alpha of the F-P cavity and the incidence angle beta formed by converging the outermost light rays to the thin film partial reflecting mirror in the inclined F-P cavity according to the requirement that the outermost light rays of the pumping light beams are emitted after being reflected once by the total reflecting mirror in the inclined F-P cavity and neglecting the influence of the thin film partial reflecting mirror in the F-P cavity on the optical path and the chromatic dispersion: delta=2m×tan (α+β).
The imaging lens meets the following requirements:
(1) the imaging lens can be single lens imaging or multi-lens combined imaging, such as a telescope system.
The lithium niobate crystal meets the following requirements:
(1) the light-transmitting incident surface of the lithium niobate crystal is a z-a surface of a crystal optical axis, and the included angle between the emergent surface of the crystal and the z-b surface is 63.5 degrees; the angle may be adjustable according to the incident wavelength.
Claims (4)
1. The device for generating terahertz waves by continuously tilting pulse wave surface pumping lithium niobate is characterized by comprising a femtosecond laser light source, a beam expander, a focusing lens, a tilting F-P cavity, a beam limiting diaphragm, an imaging lens and lithium niobate crystals, wherein the tilting F-P cavity is formed by arranging a full-reflection mirror for pumping laser wave bands and a film part-reflection mirror in parallel; the laser pulse generated by the femtosecond laser source is focused to an inclined F-P cavity through a focusing lens by taking the pulse wave surface as a plane after passing through the beam expander, continuously reflected and transmitted out of the inclined F-P cavity, kept unchanged in size after passing through a beam limiting diaphragm, and projected into a lithium niobate crystal through an imaging lens.
2. The device for generating terahertz waves by continuously inclined pulse wave surface pumping lithium niobate according to claim 1, wherein the method for generating terahertz waves by continuously inclined pulse wave surface pumping lithium niobate uses a femtosecond laser light source and a beam expander to generate pulses with pulse wave surfaces being planes, uses a focusing lens to convert the spatial distribution of the expanded pumping beam into continuous changes of incident angles projected to an inclined F-P cavity, and then realizes the continuous inclined pulse wave surfaces through average time delay introduced by reflection and transmission of the inclined F-P cavity.
3. The device for generating terahertz waves by continuously inclined pulse wave surface pumping of lithium niobate according to claim 1, wherein the pulse wave surface projected to the lithium niobate crystal is parallel to the exit surface of the lithium niobate crystal, and the exit surface of the lithium niobate crystal is cut according to the cerenkov radiation surface generating terahertz waves in the lithium niobate crystal.
4. The device for generating terahertz waves by continuously inclined pulse wave surface pumping lithium niobate according to claim 1, wherein the light incident surface of the lithium niobate crystal is the z-a surface of the crystal optical axis, and the included angle between the emergent surface of the crystal and the z-b surface is 63.5 degrees; the angle may be adjustable according to the incident wavelength.
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| CN105652554A (en) * | 2016-03-24 | 2016-06-08 | 中国工程物理研究院流体物理研究所 | Strong terahertz pulse emission source with stepped structure and design method |
| CN106953224A (en) * | 2017-05-09 | 2017-07-14 | 天津大学 | Continuous tilt impulse wave face-pumping lithium niobate produces the method and device of THz wave |
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| CN105652554A (en) * | 2016-03-24 | 2016-06-08 | 中国工程物理研究院流体物理研究所 | Strong terahertz pulse emission source with stepped structure and design method |
| CN106953224A (en) * | 2017-05-09 | 2017-07-14 | 天津大学 | Continuous tilt impulse wave face-pumping lithium niobate produces the method and device of THz wave |
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