CN112114463B - Device and method for generating tunable terahertz waves - Google Patents
Device and method for generating tunable terahertz waves Download PDFInfo
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
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- G02B27/1006—Beam splitting or combining systems for splitting or combining different wavelengths
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- G02B27/16—Beam splitting or combining systems used as aids for focusing
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
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Abstract
The embodiment of the invention provides a device and a method for generating tunable terahertz waves, wherein the device comprises: the beam splitting and combining assembly receives input target laser to perform beam splitting and combining treatment to generate a focused laser combined beam comprising frequency doubling light spots and a base frequency hollow light spot array, wherein the radius of the light spots of the base frequency hollow light spot array is variable, the base frequency hollow light spot array is overlapped with the frequency doubling light spots to improve the terahertz generation efficiency of a single hollow light spot, the energy of the whole terahertz wave is effectively improved, the frequency adjustment of the terahertz wave can be realized by adjusting the hollow characteristic, and the energy concentration on a required frequency band is realized; the terahertz wave generating assembly receives the focused laser beam combination emitted into the cavity by the beam splitting and combining assembly, the fundamental frequency hollow light spot array ionizes the inert gas to form a plasma array, the plasma array forms terahertz waves under the action of the uniform electric field and the frequency doubling light spots and radiates the terahertz waves from the cavity, and the output of the terahertz waves with high strength and narrow line width can be realized.
Description
Technical Field
The invention relates to the technical field of terahertz waves, in particular to a device and a method for generating tunable terahertz waves.
Background
The terahertz band, which is generally referred to as electromagnetic radiation in the frequency range of 0.1-10THz, is between the infrared and microwave bands. Is superior to high-energy photon wave bands such as X-rays in biological safety, and has higher spatial resolution characteristic and higher frequency compared with microwaves. In addition, the rotation or vibration energy level of a large number of molecules is in the terahertz wave band, so the terahertz wave has very wide application prospect in the fields of biomedicine, wireless communication, radar imaging, nondestructive testing, safety inspection and the like.
The generation of terahertz waves can be largely divided into two categories, optical and electronic generation, corresponding to up-conversion or down-conversion of the original frequency. For optical techniques to generate terahertz radiation, the following are generally included: photoconduction, photorectification, plasma four-wave mixing, etc. associated with ultrashort laser pulses that produce terahertz radiation. For electronics to generate terahertz wave radiation, typical terahertz wave sources include miniature vacuum electronics, relativistic electronics, semiconductor lasers, and the like.
In recent years, as plasma-based terahertz experimental results are proposed, more and more researchers consider the terahertz wave of the plasma itself to have uniqueness, and the uniqueness is not considered in a simple model. For example, quasi-bound free electrons inside the plasma (although free to move, electrons in the plasma can be bound by plasma boundaries, and electron-ion interactions can cause characteristic oscillations of the plasma) determine that they have very significant differences compared to pure gases or metals. These reasons suggest that the laser-generated plasma oscillation frequency and the terahertz eigen-oscillation frequency cannot be described by a simple model at this time. Also, based on the above understanding, there can be improvements in the generation of terahertz as well.
In the prior art, the terahertz wave generated based on the optical laser field method generally has broadband characteristics, so that the energy in a single required frequency band is relatively low even though the energy conversion efficiency is not low. If the terahertz wave based on the plasma is controlled to realize energy concentration on a required frequency band, the generation of the tunable terahertz wave based on the optical method is expected to be further broken through.
Disclosure of Invention
Aiming at the technical problems in the prior art, the embodiment of the invention provides a device and a method for generating tunable terahertz waves, which aim to solve the technical defects in the prior art.
The embodiment of the invention provides a device for generating tunable terahertz waves, which comprises:
the beam splitting and combining component receives input target laser to perform beam splitting and combining treatment to generate a focused laser combined beam comprising frequency doubling light spots and a fundamental frequency hollow light spot array, wherein the radius of the light spots of the fundamental frequency hollow light spot array is variable;
the terahertz wave generating assembly comprises a cavity filled with inert gas, a uniform electric field is arranged in the cavity, the terahertz wave generating assembly receives the focused laser beam combination injected into the cavity by the beam splitting and combining assembly, the inert gas is ionized by the fundamental frequency hollow light spot array to form a plasma array, and the plasma array forms terahertz waves under the action of the uniform electric field and frequency doubling light spots and radiates the terahertz waves from the cavity.
According to an embodiment of the present invention, an apparatus for generating tunable terahertz waves, the beam splitting and combining assembly includes:
the frequency doubling crystal receives input target laser to carry out frequency doubling radiation and generates collinear laser beams of the base frequency light and the frequency doubling light;
the beam splitter receives the input collinear laser beam for splitting to generate a base frequency beam and a frequency doubling beam;
the wave front phase modulation module receives an input fundamental frequency light beam to perform phase modulation, and generates a fundamental frequency hollow light spot array;
the telescope component receives and processes the input frequency doubling light beam to generate frequency doubling light spots;
the beam combining mirror receives the base frequency hollow light spot array and the frequency doubling light spots for beam combining to generate a laser combined beam comprising the base frequency hollow light spot array and the frequency doubling light spots;
and the focusing mirror receives the laser combination beam to carry out focusing treatment to generate a focused laser combination beam.
According to an embodiment of the present invention, the apparatus for generating tunable terahertz waves, the beam splitting and combining assembly further includes: and the light spot adjusting module is used for adjusting the size of the light spot of the fundamental frequency hollow light spot array and is arranged between the beam splitter and the wavefront phase modulating module.
According to an embodiment of the present invention, an apparatus for generating a tunable terahertz wave, the telescope assembly includes: the first reflector, the concave lens, the convex lens and the second reflector are sequentially arranged;
and the frequency doubling light beam is processed by the first reflector, the concave lens, the convex lens and the second reflector in sequence to generate frequency doubling light spots.
According to the device for generating tunable terahertz waves, the beam splitter is a bicolor beam splitter, and the beam combiner is a bicolor beam combiner.
According to an apparatus for generating a tunable terahertz wave according to an embodiment of the present invention, the terahertz wave generating component further includes:
a pulse power supply for supplying a pulse voltage;
first electrode board and second electrode board, first electrode board and second electrode board arrange in the cavity, just first electrode board and second electrode board all through radio frequency impedance match with pulse power supply connects, with form in the cavity even strong electric field.
An embodiment of the present invention further provides a method for generating a tunable terahertz wave, which is used for the apparatus for generating a tunable terahertz wave as described above, and the method includes:
inputting target laser into a beam splitting and combining component for beam splitting and combining to generate a focused laser combination beam comprising a base frequency hollow light spot array and a frequency doubling light spot;
the beam splitting and combining assembly enables the focused laser combined beam to be injected into a cavity of the terahertz wave generating assembly, the fundamental frequency hollow light spot array ionizes inert gas to form a plasma array, and the plasma array forms terahertz waves under the action of a uniform electric field and frequency doubling light spots and radiates the terahertz waves from the cavity.
According to the method for generating the tunable terahertz wave, disclosed by the embodiment of the invention, target laser is input to a beam splitting and combining component for beam splitting and combining treatment, so that a focused laser combined beam containing a fundamental frequency hollow light spot array and a frequency doubling light spot is generated, and the method comprises the following steps of:
inputting the target laser to a frequency doubling crystal for frequency doubling radiation to generate collinear laser beams of the fundamental frequency light and the frequency doubling light;
inputting the collinear laser beams to a beam splitter for beam splitting to generate fundamental frequency beams and frequency doubling beams;
inputting the fundamental frequency light beam into a wavefront phase modulation module for phase modulation to generate a fundamental frequency hollow light spot array;
inputting the frequency doubling light beam into a telescope component for processing to generate frequency doubling light spots;
inputting the base frequency hollow light spot array and the frequency doubling light spot into a beam combining mirror for beam combining to generate a laser combined beam comprising the base frequency hollow light spot array and the frequency doubling light spot;
and inputting the laser beam combination into a focusing mirror for focusing treatment to generate a focused laser beam combination.
According to the method for generating the tunable terahertz wave, disclosed by the embodiment of the invention, the fundamental frequency hollow light spot array ionizes inert gas to form a plasma array, and the plasma array forms the terahertz wave under the action of a uniform electric field and frequency doubling light spots, and the method comprises the following steps:
the fundamental frequency hollow light spot array is tunneled and ionized in the inert gas to form a plasma array;
the plasma array receives the stored energy of the uniform electric field and forms terahertz waves under the driving of the frequency doubling light spots.
According to the method for generating the tunable terahertz wave, after the fundamental frequency hollow light spot array is generated, the method further comprises the following steps:
and inputting the fundamental frequency hollow light spot array to a light spot adjusting module so as to adjust the light spot size of the fundamental frequency hollow light spot array.
According to the device and the method for generating the tunable terahertz waves, the array type fundamental frequency hollow light spot array with the variable radius is obtained through the beam splitting and combining assembly, and then the fundamental frequency hollow light spot array and the frequency doubling light spots are combined in space, so that the terahertz generation efficiency of a single hollow light spot can be further improved, the energy of the whole terahertz waves is effectively improved, the device and the method are superior to the terahertz radiation of a single hollow plasma, the frequency adjustment of the terahertz waves can be realized through the adjustment of the hollow characteristic, and the energy concentration on the required frequency band is realized. And then the terahertz wave generating assembly is used for enabling the fundamental frequency hollow light spot array to generate terahertz waves, the broadband terahertz waves can be generated by utilizing the tunneling ionization action of inert gas under the focused laser beam combination and the driving action of frequency doubling light spots, the energy of a uniform electric field wrapped by the fundamental frequency hollow light spot array can be stored to form terahertz wave band radiation of a target radiation frequency, and the output of the terahertz waves with high strength and narrow line width is realized.
Drawings
Fig. 1 is a schematic structural diagram of a device for tunable terahertz waves according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a terahertz wave generating assembly according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a focused fundamental hollow spot array (3 × 3) according to an embodiment of the present invention;
fig. 4 is a schematic flow chart of a method for tuning a terahertz wave according to another embodiment of the present invention.
Reference numerals
20-a beam splitting and combining assembly;
201-frequency doubling crystal; 202-a beam splitter;
203-wavefront phase modulation module; 204-beam combining mirror;
205 — first mirror; 206-concave lens; 207-convex lens;
208-a second mirror; 209-focusing mirror;
30-a terahertz wave generating assembly;
301-pulse power supply; 302-radio frequency impedance matching;
303 — a first electrode plate; 304 — an exit window; 305-a second electrode plate;
306 — an air intake end; 307-electrode grounding;
308-air outlet end; 309-entrance window.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terminology used in the one or more embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the one or more embodiments of the invention. As used in one or more embodiments of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used in one or more embodiments of the present invention refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It should be understood that, although the terms first, second, etc. may be used herein to describe various information in one or more embodiments of the present invention, such information should not be limited by these terms. These terms are only used to distinguish one type of information from another. For example, a first aspect may be termed a second aspect, and, similarly, a second aspect may be termed a first aspect, without departing from the scope of one or more embodiments of the present invention. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.
First, the noun terms to which one or more embodiments of the present invention relate are explained.
Tuning: in general, the output frequency or wavelength of laser light is determined to be constant under the given conditions of the laser working substance, the excitation mode, the optical resonant cavity, and the like, but the output laser wavelength can be controlled to be continuously changed in a controllable manner to a certain extent or within a certain range by a certain additional technique, which is called a laser tuning technique.
Femtosecond laser: femtosecond (fs) is also called femtosecond, and is a measurement unit for calibrating time length, and femtosecond laser is a common technical means for obtaining strong power short pulse under laboratory conditions at present.
Fundamental frequency light beam: the oscillation frequency of the electromagnetic field output by the femtosecond laser system is a low-frequency light beam in the bicolor complex wave.
Frequency doubling light beam: the second nonlinear effect of the nonlinear crystal under the action of strong laser is utilized to make the fundamental laser with frequency omega pass through the crystal and then become frequency-doubled light beam with frequency 2 omega, which is called frequency doubling technology or second harmonic oscillation. For example, 0.8 micron laser is passed through the frequency doubling crystal to become 0.4 micron blue light.
Fundamental frequency hollow light spot array: and at the fundamental frequency, a plurality of hollow light spots form an array. Based on the fundamental frequency hollow light spot array, the energy of the whole terahertz wave can be effectively improved, and the terahertz wave is superior to the terahertz wave of a single hollow plasma.
Frequency doubling facula: the double frequency light forms a light spot through the telescope system, and the size of the double frequency light spot is much larger than that of the fundamental frequency hollow light spot. The frequency doubling light spots are used for being combined with the base frequency hollow light spot array, the base frequency hollow light spot array is covered by the frequency doubling light spots at the focus position, and the free electron motion characteristics in the generated base frequency hollow light spot array can be regulated and controlled by changing time delay.
A wavefront phase modulation module: the phase control of the wavefront can be realized for the fundamental frequency light beam, a fundamental frequency hollow light spot array is generated, and the complex modulation of the light spot characteristics is realized.
A beam splitter: the surface of the optical glass is coated with one or more layers of films, and after a beam of bicolor laser is projected on the coated glass, the lens usually reflects the laser with one frequency and transmits the laser with the other frequency, so that the beam is divided into two beams, and the coated glass is called a beam splitter.
A beam combining mirror: the coated glass which combines two beams of light with different wave bands into one beam is called a beam combiner.
Achromatic lens: the achromatic lens is used for realizing chromatic aberration correction in the process of focusing optical fibers of different wave bands by combining a plurality of coated lenses and compensating by utilizing an air gap and the like in the middle.
In the embodiments of the present invention, an apparatus and a method for generating a tunable terahertz wave are provided, which are described in detail in the following embodiments one by one.
An embodiment of the present invention provides a device for generating a tunable terahertz wave, as shown in fig. 1, including: a beam splitting and combining assembly 20 and a terahertz wave generating assembly 30. The beam splitting and combining component 20 is configured to split an incident target laser beam to generate a fundamental frequency beam and a frequency doubling beam respectively, process the fundamental frequency beam and the frequency doubling beam respectively to generate a fundamental frequency hollow light spot array and a frequency doubling light spot respectively, and combine the beams to generate a focused laser combined beam including the frequency doubling light spot and the fundamental frequency hollow light spot array; a cavity filled with inert gas is formed in the terahertz wave generating assembly 30, a uniform electric field is arranged in the cavity, the terahertz wave generating assembly 30 receives the focused laser beam combination emitted into the cavity by the beam splitting and combining assembly 20, the base frequency hollow light spot array ionizes the inert gas to form a plasma array, and the plasma array forms terahertz waves under the action of the uniform electric field and frequency doubling light spots and radiates the terahertz waves from the cavity.
Wherein the spot radius of the fundamental frequency hollow spot array is variable. In the embodiment, the cut-off frequency of the equivalent waveguide can be regulated and controlled by regulating the radius of the hollow light spot array, and band-pass filtering is provided for a uniform electric field in a subsequent stage, so that narrow-linewidth high-strength terahertz wave output is realized.
In addition, the hollow light spot array and the frequency doubling pulse are overlapped in space to realize array terahertz waves, the array terahertz waves can realize the modulation of the cut-off frequency of the fundamental frequency hollow light spot array by adjusting the hollow size in the hollow light spots, and the terahertz waves with narrow line width are realized.
Specifically, referring to fig. 1, the structure of the beam splitting and combining assembly includes: frequency doubling crystal 201, beam splitter 202, wavefront phase modulation module 203, telescope component, beam combiner 204 and focusing mirror 209.
In this embodiment, the target laser may be various, and in this embodiment, a femtosecond laser is preferable, and since the femtosecond laser has very high instantaneous power, high-intensity terahertz wave output can be realized.
The frequency doubling crystal 201 can be barium metaborate crystal (BBO crystal) or other crystals for frequency doubling, and realizes frequency doubling radiation through phase matching. The frequency doubling crystal 201 is used for receiving input target laser to perform frequency doubling radiation, and generating collinear laser beams of the base frequency light and the frequency doubling light.
The collinear laser beam generated by the frequency doubling crystal 201 through frequency doubling radiation is incident into the beam splitter 202 to realize beam splitting and generate a fundamental frequency beam and a frequency doubling beam.
In this embodiment, the beam splitter 202 may be a dichroic beam splitter, or may be a multi-color beam splitter, and in this embodiment, a dichroic beam splitter is preferred to transmit fundamental frequency light to form a fundamental frequency light beam, and reflect frequency doubling light to form a frequency doubling light beam. Correspondingly, the beam combiner 204 is preferably a two-color beam combiner.
Generally, the frequency doubling generation efficiency of femtosecond laser is approximately 20%, so that when the two-color field scheme is applied to the generation process of terahertz waves, the field intensity of fundamental frequency beams is stronger and is used for generating plasma.
After the fundamental frequency light beam and the frequency doubling light beam are generated, the generated fundamental frequency light beam is input to the wavefront phase modulation module 203 for phase modulation, and a fundamental frequency hollow light spot array is generated.
In this embodiment, the reason why the wavefront phase modulation is performed after passing through the frequency doubling crystal 201 is that the fundamental frequency light beam and the frequency doubling light beam are separated, so that the two beams of light can be modulated respectively; if the phase modulation is performed first and then the frequency doubling crystal 201 is passed, the phase characteristics of the wavefront are complex, which may affect the phase matching in the frequency doubling process, resulting in complex phase of the frequency doubling light, and at the same time, the focal position space of the fundamental frequency light beam and the frequency doubling light beam may not coincide in the focusing process.
In addition, the generation of the fundamental frequency hollow light spot array is superior to the terahertz wave of a single hollow plasma, and the adjustment of the frequency of the terahertz wave can be realized by adjusting the hollow characteristic, so that the energy concentration on the required frequency band is realized.
Optionally, a light spot adjusting module may be further disposed between the beam splitter 202 and the wavefront phase modulating module 203, and is configured to adjust the size of the light spot of the fundamental frequency hollow light spot array.
The structure of the light spot adjusting module can be various, for example, under a specific use scene, the light spot adjusting module is formed by the convex lens, the divergent cone prism and the focusing cone prism, the distance between the convex lens and the divergent cone prism and the distance between the convergent cone prism and the focusing cone prism are adjusted, and the light spot size of the base frequency hollow light spot array can be adjusted.
In addition, the generated frequency doubling light beam is input to the telescope component for processing, and frequency doubling light spots are generated. Specifically, referring to fig. 1, the telescope assembly comprises: a first reflecting mirror 205, a concave lens 206, a convex lens 207, and a second reflecting mirror 208 arranged in this order. The frequency-doubled light beam is processed by the first reflector 205, the concave lens 206, the convex lens 207 and the second reflector 208 in sequence to generate a frequency-doubled light spot.
In this embodiment, the frequency doubling light spot can be amplified by adjusting the focal length ratio of the concave lens 206 and the convex lens 207. Wherein, the frequency doubling light spots cover the base frequency hollow light spot array.
Then, the beam combining mirror 204 receives the fundamental frequency hollow light spot array and the frequency doubling light spots for beam combining, and a laser combined beam containing the fundamental frequency hollow light spot array and the frequency doubling light spots is generated. In this embodiment, the beam combiner 204 is preferably a two-color beam combiner, so as to combine the fundamental frequency light spot and the frequency doubling light spot.
After the generated laser beam is combined, the fundamental frequency light energy is strong, but the plasma array cannot be generated yet, and the plasma can be generated only by focusing. In this embodiment, the amplified frequency-doubled light spot is reflected by the second reflecting mirror 208, and then is combined with the fundamental frequency hollow light spot array after wavefront phase modulation by the dichroic beam combiner 204, and is focused on the terahertz wave generating assembly 210 by the focusing mirror 209. The frequency doubling light is at the focal plane position and needs to be covered with the fundamental frequency hollow light spot array in space.
Specifically, the focusing mirror 209 may be various, such as a convex lens, an achromatic lens, etc., and the present embodiment is preferably an achromatic lens, so as to be used in combination with a dichroic beam splitter and a dichroic beam combiner.
By focusing, the combination of the fundamental frequency light spot and the frequency doubling light spot can drive electrons in the plasma array to move, so that radiation energy is obtained.
Specifically, a cavity filled with inert gas is formed in the terahertz wave generating assembly 30, and a uniform electric field is arranged in the cavity. The focused laser beam is emitted into the cavity, the fundamental frequency hollow light spot array forms terahertz waves under the action of inert gas, a uniform electric field and frequency doubling light spots, and the terahertz waves are emitted.
Specifically, referring to fig. 2, the terahertz-wave generating assembly 30 includes:
and a pulse power supply 301 for supplying a pulse voltage. The breakdown threshold of the plasma in the plasma array can be improved by using the pulse voltage, and the electromagnetic energy storage is supplied for the premise of forming the plasma array.
The plasma display panel comprises a first electrode plate 303 and a second electrode plate 305, wherein the first electrode plate 303 and the second electrode plate 305 are arranged in a cavity, and the first electrode plate 303 and the second electrode plate 305 are both connected with a pulse power supply 301 through a radio frequency impedance matching 302 so as to form a uniform electric field in the cavity.
The electrode ground 307 is connected to the second electrode plate 305 to form a loop.
Specifically, the terahertz-wave generating assembly 30 includes:
an entrance window 309 through which the focused laser beam is injected into the cavity 309;
an exit window 304 through which the terahertz waves exit.
The exit window 304 is a silicon lens exit window, the focal length of the silicon lens is located between the first electrode plate 303 and the second electrode plate 305, and the emitted terahertz waves are converted from divergence to planar light output by the silicon lens.
In addition, the terahertz-wave generating assembly 30 further includes: the gas inlet end 306 and the gas outlet end 308, the gas inlet end 306 and the gas outlet end 308 are respectively connected with the cavity, and the gas inlet end 306 inputs inert gas into the cavity.
Specifically, the inert gas can be argon gas, xenon gas and other gases which are easy to ionize, so that the focused laser beam emitted into the cavity can generate tunneling ionization in the inert gas to generate a plasma array.
Assuming that the intensity of the fundamental optical field is E0Then for having an ionization threshold IpThe main mechanism of ionization will be the tunneling ionization mechanism, and the ADK formula according to tunneling ionization is as follows:
Γ∝exp[-2(2Ip)3/2/3E0](1)
wherein Γ is the ionization rate; i ispIs the ionization threshold; e0Is the fundamental frequency optical field intensity.
As can be seen from formula (1), for a particular gas, the ionization threshold I of that gaspBeing a fixed value, the variable affecting the ionization rate is mainly the fundamental optical field strength. Therefore, the generation of plasma relies mainly on the fundamental frequency array of spots. Electrons ionized in the plasma show group motion characteristics under the combined field of fundamental frequency and frequency multiplication, and the group electron motion is the main reason of terahertz waves.
Referring to fig. 3, the fundamental frequency hollow light spot array is focused to a position between two electrode plates 303 and 305 through a focusing mirror 209 to form the focused fundamental frequency hollow light spot array as shown in fig. 3, the focusing field intensity of the fundamental frequency hollow light spot array is close to the coulomb field intensity of inert gas atoms or molecules, and a plasma array in space can be realized through ionization. The characteristic output frequency can be adjusted and controlled by changing the radius of the hollow ring of the fundamental frequency hollow light spot through different plasma waveguide radii. Simulation results show that the characteristic center frequency of the hollow plasma with the inner diameter of 0.1mm is about 0.6THz, and the characteristic center frequency of the hollow plasma with the inner diameter of 0.2mm is about 0.4 THz. The output regulation and control of the terahertz waveband of the characteristic frequency can be realized by changing the hollow radius of the hollow plasma. At the moment, the terahertz waveguide characteristic of the hollow plasma is mainly embodied, and the terahertz energy source is the group motion of plasma electrons under a bicolor laser field and the pulse voltage energy bound by the plasma waveguide. The annular plasma can be approximately used as a waveguide for processing (only when the frequency of the plasma is far away from the terahertz waveband, if the frequency is close to the terahertz waveband, a resonance effect can occur), the cut-off frequency of the equivalent waveguide can be regulated by regulating the hollow radius of the hollow plasma array, band-pass filtering is provided for the double-color field and the uniform electric field, and the terahertz waveband output with narrow line width and high strength is realized.
According to the device for generating the tunable terahertz wave, the array type fundamental frequency hollow light spot array with the variable radius is obtained through the beam splitting and combining assembly, and then the fundamental frequency hollow light spot array and the frequency doubling light spots are combined in space, so that the terahertz generation efficiency of a single hollow light spot can be further improved, the energy of the whole terahertz wave is effectively improved, the device is superior to the terahertz wave radiation of a single hollow plasma, the adjustment of the frequency of the terahertz wave can be realized through the adjustment of the hollow characteristic, and the energy concentration on the required frequency band is realized. And then the terahertz wave generating assembly is used for enabling the fundamental frequency hollow light spot array to generate terahertz waves, so that broadband terahertz waves can be generated by utilizing the tunneling ionization action of inert gas under the focused laser beam and the driving action of frequency doubling light spots, and terahertz wave band radiation of target radiation frequency can be formed by utilizing the stored energy of a uniform electric field wrapped by the fundamental frequency hollow light spot array, and the output of the terahertz waves with high strength and narrow line width is realized.
The following describes an apparatus for generating a tunable terahertz wave according to an embodiment of the present invention, and the apparatus for generating a tunable terahertz wave described below and the method for generating a tunable terahertz wave described above may be referred to in correspondence with each other.
The embodiment of the invention discloses a method for generating a tunable terahertz wave, which is used for the device for generating the tunable terahertz wave, and referring to fig. 4, the method comprises the following steps:
401. the target laser is input to the beam splitting and combining assembly 20 for beam splitting and combining to generate a focused laser combined beam comprising a base frequency hollow light spot array and frequency doubling light spots.
Wherein, the step 401 comprises the following steps S41-S46:
and S41, inputting the target laser to the frequency doubling crystal 201 for frequency doubling radiation, and generating collinear laser beams of the fundamental frequency light and the frequency doubling light.
And S42, inputting the collinear laser beams to the beam splitter 202 for beam splitting to generate fundamental frequency beams and frequency doubling beams.
And S43, inputting the fundamental frequency light beam into the wavefront phase modulation module 203 for phase modulation, and generating a fundamental frequency hollow light spot array.
Optionally, after generating the fundamental frequency hollow spot array, the method further comprises:
and inputting the fundamental frequency hollow light spot array to a light spot adjusting module so as to adjust the light spot size of the fundamental frequency hollow light spot array.
And S44, inputting the frequency doubling light beam into a telescope component for processing to generate frequency doubling light spots.
Specifically, the telescope assembly includes: a first reflecting mirror 205, a concave lens 206, a convex lens 207, and a second reflecting mirror 208 arranged in this order. The frequency-doubled light beam is processed by the first reflector 205, the concave lens 206, the convex lens 207 and the second reflector 208 in sequence to generate a frequency-doubled light spot.
And S45, inputting the base frequency hollow light spot array and the frequency doubling light spot into the beam combining mirror 207 for beam combining to generate a laser combined beam containing the base frequency hollow light spot array and the frequency doubling light spot.
S46, the laser beam is input to the focusing mirror 209 to be focused, thereby generating a focused laser beam.
For specific explanation of steps S41-S46, reference may be made to the foregoing embodiments, and details are not repeated here.
402. The beam splitting and combining assembly enables the focused laser combined beam to be injected into a cavity of the terahertz wave generating assembly, the fundamental frequency hollow light spot array ionizes inert gas to form a plasma array, and the plasma array forms terahertz waves under the action of a uniform electric field and frequency doubling light spots and radiates the terahertz waves from the cavity.
According to the device for generating the tunable terahertz wave in the embodiment, the cavity is filled with the inert gas, so that the focused laser beam emitted into the cavity can generate tunneling ionization in the inert gas to generate the plasma array.
A first electrode plate and a second electrode plate are arranged in the cavity to generate a uniform electric field to supply electromagnetic energy storage for the premise of forming the plasma array.
The base frequency hollow light spot array in the step 402 ionizes the inert gas to form a plasma array, and the plasma array forms terahertz waves under the action of the uniform electric field and the frequency doubling light spots, and the method comprises the following steps: the fundamental frequency hollow light spot array is tunneled and ionized in the inert gas to form a plasma array; and the plasma array receives the stored energy of the uniform electric field and forms terahertz waves under the driving of the frequency doubling light spots.
Specifically, terahertz wave radiation is formed by the plasma array under the drive of the frequency doubling light spot, and meanwhile, stored energy in the instantaneous uniform electric field is released by the plasma array, so that stronger terahertz radiation is realized compared with a common generation method of fundamental frequency light and frequency doubling light.
According to the method for generating the tunable terahertz wave, provided by the embodiment of the invention, the array type fundamental frequency hollow light spot array with the variable radius is obtained through the beam splitting and combining assembly, and then the fundamental frequency hollow light spot array and the frequency doubling light spots are combined in space, so that the terahertz generation efficiency of a single hollow light spot can be further improved, the energy of the whole terahertz wave can be effectively improved, the method is superior to the terahertz wave generation mode of a single hollow plasma, the frequency adjustment of the terahertz wave can be realized by adjusting the hollow characteristic, and the energy concentration on the required frequency band can be realized. Then, the terahertz wave generating assembly enables the fundamental frequency hollow light spot array to perform tunneling ionization on inert gas to obtain a plasma environment and enable free electrons in the driving plasma of the frequency doubling light spots to act to form terahertz waves of a target radiation frequency, and the terahertz waves can also radiate electromagnetic field energy storage in a uniform strong electric field to achieve terahertz wave output with high strength and narrow line width.
The embodiment of the invention can realize amplification and output of terahertz pulse transmission with specific wavelength based on the waveguide characteristic of the plasma array. By preparing the hollow plasma array, the terahertz wave generated by laser can be optimized, and the understanding of the complex dynamic process in the plasma for the terahertz wave is facilitated. In addition, by modulating plasma by using the device of the embodiment of the invention, terahertz wave enhancement of obtaining specific point frequency from terahertz wave of gas plasma in a broadband mode can be realized, and terahertz wave with high output energy, good monochromaticity (narrow frequency spectrum) and room-temperature operation can be obtained. The technical breakthroughs of terahertz nonlinear effects, terahertz communication, terahertz radars, terahertz remote sensing, terahertz biology and the like are facilitated. The embodiment of the invention is the cross fusion of the multidisciplinary knowledge of optics, plasma science, electromagnetic field and microwave technology and the like, and has important research significance and use value.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (6)
1. An apparatus for generating a tunable terahertz wave, comprising:
the beam splitting and combining component receives input target laser to perform beam splitting and combining treatment, and generates a focused laser combined beam comprising frequency doubling light spots and a fundamental frequency hollow light spot array, wherein the radius of the light spots of the fundamental frequency hollow light spot array is variable, and the beam splitting and combining component comprises: the frequency doubling crystal receives input target laser to carry out frequency doubling radiation and generates collinear laser beams of the base frequency light and the frequency doubling light; the beam splitter receives the input collinear laser beam for splitting to generate a base frequency beam and a frequency doubling beam; the wave front phase modulation module receives an input fundamental frequency light beam to perform phase modulation, and generates a fundamental frequency hollow light spot array; the telescope component receives and processes the input frequency doubling light beam to generate frequency doubling light spots; the beam combining mirror receives the base frequency hollow light spot array and the frequency doubling light spots for beam combining to generate a laser combined beam comprising the base frequency hollow light spot array and the frequency doubling light spots; the focusing mirror receives the laser combination beam for focusing treatment to generate a focused laser combination beam; the light spot adjusting module is used for adjusting the size of a light spot of the fundamental frequency hollow light spot array and is arranged between the beam splitter and the wavefront phase modulating module;
the terahertz wave generating assembly comprises a cavity filled with inert gas, a uniform electric field is arranged in the cavity, the terahertz wave generating assembly receives the focused laser beam combination injected into the cavity by the beam splitting and combining assembly, the inert gas is ionized by the fundamental frequency hollow light spot array to form a plasma array, and the plasma array forms terahertz waves under the action of the uniform electric field and frequency doubling light spots and radiates the terahertz waves from the cavity.
2. The device for generating tunable terahertz waves of claim 1, wherein the telescope assembly comprises: the first reflector, the concave lens, the convex lens and the second reflector are sequentially arranged;
and the frequency doubling light beam is processed by the first reflector, the concave lens, the convex lens and the second reflector in sequence to generate frequency doubling light spots.
3. The device for generating tunable terahertz waves of claim 1, wherein the beam splitter is a dichroic beam splitter and the beam combiner is a dichroic beam combiner.
4. The apparatus of generating tunable terahertz waves of claim 1, wherein the terahertz wave generating assembly further comprises:
a pulse power supply for supplying a pulse voltage;
first electrode board and second electrode board, first electrode board and second electrode board arrange in the cavity, just first electrode board and second electrode board all through radio frequency impedance match with pulse power supply connects, with form in the cavity even strong electric field.
5. A method of generating a tunable terahertz wave for use in the apparatus for generating a tunable terahertz wave according to any one of claims 1 to 4, characterized in that the method comprises:
inputting target laser into a beam splitting and combining component for beam splitting and combining to generate a focused laser combination beam comprising a base frequency hollow light spot array and a frequency doubling light spot; inputting the target laser into a frequency doubling crystal for frequency doubling radiation to generate collinear laser beams of the fundamental frequency light and the frequency doubling light; inputting the collinear laser beams to a beam splitter for beam splitting to generate fundamental frequency beams and frequency doubling beams; inputting the fundamental frequency light beam into a wavefront phase modulation module for phase modulation to generate a fundamental frequency hollow light spot array; inputting the fundamental frequency hollow light spot array into a light spot adjusting module to adjust the light spot size of the fundamental frequency hollow light spot array; inputting the frequency doubling light beam into a telescope component for processing to generate frequency doubling light spots; inputting the base frequency hollow light spot array and the frequency doubling light spot into a beam combining mirror for beam combining to generate a laser combined beam comprising the base frequency hollow light spot array and the frequency doubling light spot; inputting the laser beam combination into a focusing mirror for focusing treatment to generate a focused laser beam combination;
the beam splitting and combining assembly enables the focused laser combined beam to be injected into a cavity of the terahertz wave generating assembly, the fundamental frequency hollow light spot array ionizes inert gas to form a plasma array, and the plasma array forms terahertz waves under the action of a uniform electric field and frequency doubling light spots and radiates the terahertz waves from the cavity.
6. The method for generating tunable terahertz waves according to claim 5, wherein the fundamental frequency hollow light spot array ionizes inert gas to form a plasma array, and the plasma array forms terahertz waves under the action of a uniform electric field and frequency doubling light spots, and comprises the following steps:
the fundamental frequency hollow light spot array is tunneled and ionized in the inert gas to form a plasma array;
the plasma array receives the stored energy of the uniform electric field and forms terahertz waves under the driving of the frequency doubling light spots.
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| CN113552097A (en) * | 2021-07-23 | 2021-10-26 | 昆山丘钛微电子科技股份有限公司 | Prism test fixture and spectrometer |
| CN113872022B (en) * | 2021-09-03 | 2023-06-23 | 广东大湾区空天信息研究院 | Terahertz wave generation device and generation method |
| CN114136915B (en) * | 2021-11-05 | 2024-08-27 | 清华大学 | System and method for generating broadband terahertz waves with arbitrary polarization angles |
| CN115000785B (en) * | 2022-05-16 | 2023-12-01 | 中国人民解放军军事科学院国防科技创新研究院 | Terahertz radiation regulation and control device and method based on laser pulse width modulation |
| CN114900234B (en) * | 2022-07-14 | 2022-10-21 | 四川太赫兹通信有限公司 | Terahertz frequency spectrum environment map construction method and equipment |
| CN116699858B (en) * | 2023-08-08 | 2023-11-03 | 深圳赛陆医疗科技有限公司 | Dodging device and gene sequencer |
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