CN112670798B - Multi-frequency terahertz wave generating device based on non-collinear cascade optical difference frequency - Google Patents

Abstract

Compared with the existing terahertz radiation source based on the cascaded optical difference frequency effect, the multi-frequency terahertz wave generation device based on non-collinear cascaded optical difference frequency provided by the present invention, (1) by changing the position of the mirror and Angle, the size of θ ₁ , θ ₂ ... θ _n‑1 can be adjusted to obtain multi-frequency terahertz waves. The tuning method is simple and the operation is flexible. (2) By changing the position and angle of the mirror, the size of θ ₁ , θ ₂ ... θ _n‑1 can be adjusted to realize non-collinear cascaded difference frequency and effectively improve the conversion efficiency of terahertz wave.

Description

A multi-frequency terahertz wave generation device based on non-collinear cascaded optical difference frequency

technical field

The invention belongs to the technical field of terahertz wave application, and in particular relates to a terahertz generation device based on cascaded difference frequency.

Background technique

Terahertz waves (Terahertz, THz for short) refer to electromagnetic waves with a frequency in the range of 0.1-10 THz (1THz=10 ¹² Hz). The transitional area from macro theory to micro theory. The special position of terahertz wave makes it widely used in basic research fields such as physics, chemistry, astronomy, molecular spectroscopy, life science and medical science, as well as medical imaging, environmental monitoring, material detection, food detection, radio astronomy, mobile communication, satellite Applied research fields such as communication and military radar have great scientific research value and broad application prospects. Terahertz waves are mainly used in the following fields:

(1) Imaging field

The transient electromagnetic field generated by the terahertz electromagnetic pulse can be directly measured by using the terahertz time-domain spectroscopy technique, and the dielectric constant of the sample can be directly measured.

(2) Biochemical technology field

Since the rotational absorption spectra of many biomacromolecules are in the terahertz frequency range, the molecular motion information in the reaction can be obtained by studying the terahertz absorption spectra of biochemical reactions. It provides a powerful means for further research on chemical reactions.

(3) Astronomy field

In the universe, a large amount of matter is emitting terahertz electromagnetic waves. A large number of molecules such as carbon (C), water (H ₂ O), carbon monoxide (CO), nitrogen (N ₂ ), and oxygen (O ₂ ) can be detected in the terahertz frequency range.

(4) Communication field

Terahertz wave is a good broadband information carrier, which can carry audio or video signals for transmission. The use of terahertz waves for communication can achieve a wireless transmission speed of 10 GB/s, which is hundreds to more than a thousand times faster than the current ultra-wideband technology.

(5) Homeland security field

In the field of homeland security, due to the non-ionization and strong penetrability of terahertz waves, it can provide long-distance and large-scale detection of hidden explosives, contraband, weapons, drugs and other dangerous items in airports, stations and other places. early warning.

The lack of terahertz sources capable of generating high-power, high-quality, high-efficiency terahertz waves at low cost and operating at room temperature is the main problem at present.

Contents of the invention

The purpose of the present invention is to provide a multi-frequency terahertz wave generating device based on non-collinear cascaded optical difference frequency, which can generate terahertz waves of multiple frequencies and improve the conversion efficiency of terahertz waves.

The purpose of the present invention is achieved in the following manner:

A multi-frequency terahertz wave generating device based on non-collinear cascaded optical difference frequency, including a first pump source and a second pump source, APPLN crystal, MgO:LiNbO ₃ crystal, B ₁ reflector B ₁ , B _2nd mirror B ₂ ... B _nth mirror B _n , M _1st mirror M ₁ , M _2nd mirror M ₂ ... M _nth mirror M _n , C _1st mirror C ₁ , C _2th mirror C ₂ ... C nth mirror _{C n ,} beam combiner and phase delay system;

The first pump light emitted from the first pump source enters the beam combiner; the second pump light emitted from the second pump source enters the beam combiner after passing through the phase delay system; the first pump light and the second The pump light is combined into a bundle of mixed light in the beam combining mirror; the mixed light is incident on the APPLN crystal, and the first cascaded light 12 is generated through the cascaded optical difference frequency;

The first cascade light 12 becomes the second cascade light G ₁ after being transmitted by the B ₁ reflector B ₁ , and the second cascade light G ₁ is reflected by the M ₁ reflector M ₁ and the C ₁ reflector C ₁ Rear incident MgO:LiNbO ₃ crystal; the first cascade light is reflected by the B ₁ mirror B ₁ and then reflected by the B ₂ mirror B ₂ to become the third cascade light G ₂ , the third cascade light G ₂ After being reflected by the M ₂ reflector M ₂ and the C ₂ reflector C ₂ , it enters the MgO:LiNbO ₃ crystal 13; the first cascade light 12 is transmitted by the B ₂ reflector B ₂ and then passes through the B ₃ reflector After B ₃ is reflected, it becomes the fourth cascade light G ₃ , and the fourth cascade light G ₃ enters the MgO:LiNbO ₃ crystal after being reflected by the M ₃ reflector M ₃ and the C ₃ reflector C ₃ ;

By analogy, _the first cascade light 12 becomes the _{n+1th cascade light Gn after being transmitted by the Bn-1th} reflector Bn _-1 and then reflected by the _Bnth reflector _Bn , and the n+th 1 The cascade light G _n is reflected by the M _nth reflector M _n and the C nth reflector _{C n} and then enters the MgO:LiNbO ₃ crystal 13, the n+1th cascade light G _n is not the second cascade light G ₁ Or the third cascade light G ₂ .

The second cascade light G ₁ , the third cascade light G ₂ ...the n+1th cascade light G _n is incident on the MgO:LiNbO ₃ crystal, thereby generating terahertz waves through the MgO:LiNbO ₃ crystal;

The frequencies of the first pump light and the second pump light are different; the plane of beam propagation is the plane determined by the X axis and the Y axis, and the Z axis is perpendicular to the plane of beam propagation. The first beam emitted from the first pump source The initial propagation direction of the pump light is the positive direction of the X axis, the initial propagation direction of the second pump light emitted from the second pump source is the positive direction of the Y axis, and the propagation direction of the mixing light is the positive direction of the X axis; The included angle between the propagation direction of the Hertzian wave and the vertical direction of the exit surface of the MgO:LiNbO ₃ crystal is 0°-10°.

The first pumping source uses a pulsed laser, the second pumping source uses a pulsed laser, and the polarization directions of the two pumping lights are both Z-axis.

The phase delay system consists of a first reflector, a second reflector, a third reflector and a fourth reflector, the second pump light emitted from the second pump source passes through the first reflector, the second reflector, The phase delay system composed of the third reflector and the fourth reflector is incident on the beam combiner.

The first reflecting mirror, the second reflecting mirror, the third reflecting mirror and the fourth reflecting mirror are all plane mirrors, and totally reflect the second pumping light, the B _1st reflecting mirror B ₁ , the B _2nd reflecting mirror B ₂ ...the B _nth reflector B _n partially transmits the first cascade light 12, the _M1th reflector _M1 , the _M2th reflector _M2 ... the _Mnth reflector _Mn , the _C1th reflector C _1. The C _{2 th} reflector C ₂ . . . the C _n th reflector C _n totally reflects the first cascade light 12 .

The APPLN crystal is a cuboid, a rectangle in the XY plane, and the optical axis is along the Z axis. The MgO:LiNbO ₃ crystal is an isosceles trapezoid in the XY plane, and the optical axis of the crystal is along the Z axis.

The second cascade light G ₁ , the third cascade light G _{2 .} . . the n+1th cascade light G _n is incident from the oblique plane of the MgO:LiNbO ₃ crystal in the XY plane.

The cascaded light is a kind of mixed frequency light in which cascaded lights of multiple frequencies are mixed, and they propagate collinearly. The frequency difference between adjacent cascade lights in the cascade lights is equal to the frequency difference between the first pump light and the second pump light.

The angle between the direction of the second cascade light G ₁ , the third cascade light G ₂ ... the n+1th cascade light G _n incident on the MgO:LiNbO ₃ crystal and the vertical direction of the incident MgO:LiNbO ₃ crystal plane is 0°-10°, the angle between the second cascade light G ₁ and the third cascade light G ₂ is θ ₁ , the angle between the third cascade light G ₂ and the fourth cascade light G ₃ is θ ₂ , and the angle between the nth cascade light G _n-1 and the n+1th cascade light G _n is θ _n-1 . Changing the position and angle of the C _1st reflector C ₁ , the _C2th reflector C ₂ ... the _Cnth reflector C _n can change the size of θ ₁ , θ ₂ ... θ _n-1 , through the non-collinear Cascaded difference frequencies generate high power terahertz waves.

Compared with the prior art, the multi-frequency terahertz wave generating device based on non-collinear cascaded optical difference frequency provided by the present invention has the following advantages compared with the existing terahertz radiation source based on the cascaded optical difference frequency effect:

(1) By changing the position and angle of the reflector, the size of θ ₁ , θ ₂ ... θ _n-1 can be adjusted to obtain multi-frequency terahertz waves. The tuning method is simple and the operation is flexible.

(2) By changing the position and angle of the mirror, the size of θ ₁ , θ ₂ ... θ _n-1 can be adjusted to realize non-collinear cascaded difference frequency and effectively improve the conversion efficiency of terahertz wave.

Description of drawings

Fig. 1 is a structural schematic diagram of an embodiment of the present invention.

Fig. 2 is a diagram of the corresponding relationship between the phase matching angle and the wavelength of the cascaded light when a terahertz wave with a frequency of 0.5 THz is generated.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and should not be construed as limiting the protection scope of the present invention. , those skilled in the art can make some non-essential improvements and adjustments based on the contents of the present invention described below. In the present invention, unless otherwise clearly specified and limited, the technical terms used in the present application shall have the usual meanings understood by those skilled in the present invention.

As shown in Figure 1, a multi-frequency terahertz wave generating device based on non-collinear cascaded optical difference frequency includes a first pump source 1 and a second pump source 3, APPLN crystal 11, MgO:LiNbO ₃ Crystal 13 _{, B1th} reflector _B1 , _B2th reflector _B2 ...Bnth reflector _Bn , _M1th reflector _M1 , _M2th reflector _M2 ... _Mnth reflector M _n , C ₁ th mirror C ₁ , C ₂ th mirror C _{2 .} . . C _n th mirror C _n , beam combiner 9 and a phase delay system.

The first pump light 2 emitted from the first pump source 1 enters the beam combiner 9 . The second pump light 4 emitted from the second pump source 3 enters the beam combiner 9 after passing through the phase delay system. The first pump light 2 and the second pump light 4 are combined into a bundle of mixed light 10 in the beam combining mirror 9 . The mixed frequency light 10 is incident on the APPLN crystal 11, and the first cascaded light 12 is generated through the cascaded optical difference frequency. The first cascaded light 12 becomes cascaded light G ₁ after being transmitted by the B ₁ reflector B ₁ , and the second cascade light G ₁ is incident after being reflected by the M ₁ reflector M ₁ and the C ₁ reflector C ₁ MgO: LiNbO ₃ crystal 13; the first cascade light 12 is reflected by the B ₁ mirror B ₁ and then reflected by the B ₂ mirror B ₂ to become the third cascade light G ₂ , the third cascade light G ₂ After being reflected by the M ₂ reflector M ₂ and the C ₂ reflector C ₂ , it enters the MgO:LiNbO ₃ crystal 13; the first cascade light 12 is transmitted by the B ₂ reflector B ₂ and then passes through the B ₃ reflector After B ₃ is reflected, it becomes the fourth cascade light G ₃ , and the fourth cascade light G ₃ enters the MgO:LiNbO ₃ crystal 13 after being reflected by the M ₃ reflector M ₃ and the C ₃ reflector C ₃ ; and so on , the first cascade light 12 is transmitted by the Bn _-1th mirror Bn _-1 and then reflected by the _Bnth mirror _Bn to become the n+1th cascade light G _n , the n+1th cascade light The light _Gn is reflected by the _Mnth reflector _Mn and the _Cnth reflector _Cn and is incident on the MgO:LiNbO ₃ crystal 13. The n+1th cascade light _Gn is not the second cascade light _G1 or the third cascaded light _G2 ;

The second cascade light _{G 1 ,} the third cascade light G _{2 .}

Since the frequency difference between adjacent cascade lights in the first cascade light 12 is equal to the frequency difference between the first pump light 2 and the second pump light 4, by adjusting the first pump light 2 and the second pump light The frequency difference of the light 4 can generate the first cascade light 12 with different frequency differences of adjacent cascade lights.

The plane of beam propagation is the plane determined by the X-axis and the Y-axis, the Z-axis is perpendicular to the plane of beam propagation, and the initial propagation direction of the first pump light 2 emitted from the first pump source 1 is the positive direction of the X-axis. The initial propagation direction of the second pumping light 4 emitted from the second pumping source 3 is the positive direction of the Y axis, and the propagation direction of the mixing light 10 is the positive direction of the X axis.

The purpose of one pump light passing through the phase delay system is to synchronize the phases of the two pump lights.

The second cascade light G ₁ , the third cascade light G _{2 .} . . the n+1th cascade light is incident from the oblique plane of the MgO:LiNbO ₃ crystal 13 in the XY plane. The included angle between the propagation direction of the terahertz wave 14 and the vertical direction of the exit surface of the MgO:LiNbO ₃ crystal 13 is 0°-10°.

In this embodiment, the first pumping source 1 adopts a Yb:YAG pulsed laser, the frequency of the first pumping light 2 is 291.76 THz, the second pumping source 3 adopts a Yb:YAG pulsed laser, and the frequency of the second pumping light 4 The frequency is 291.26THz. The repetition frequency of the two pump sources is 10Hz, the single pulse energy is 100mJ, the beam diameter is 1mm, and the polarization direction is the Z axis.

In this embodiment, the phase delay system is composed of a first reflector 5, a second reflector 6, a third reflector 7 and a fourth reflector 8, and the second pump light 4 emitted from the second pump source 3 After passing through the phase delay system composed of the first reflector 5 , the second reflector 6 , the third reflector 7 and the fourth reflector 8 , it enters the beam combiner 9 . The propagation direction of the light is not changed when the pump light passes through the phase delay system, and the pump light can pass through more than one phase delay system.

The first reflecting mirror 5, the second reflecting mirror 6, the third reflecting mirror 7 and the fourth reflecting mirror 8 are all plane mirrors, and totally reflect the second pumping light 4, the _B1 reflecting mirror _B1 , the Bth reflecting mirror ₂ reflectors B ₂ ... B _nth reflector B _n has a transmittance of 50% for the first cascade light 12, and the M _1st reflector M ₁ , the _M2th reflector M ₂ ... the _Mnth reflector The mirror M _n , the C _{1 th} mirror C ₁ , the C ₂ th mirror C _{2 .} . . the C _{n th} mirror C _n totally reflect the first cascaded light 12 .

In this embodiment, the APPLN crystal 11 is a cuboid, which is a rectangle in the XY plane, and the optical axis of the crystal is along the Z axis. The size X×Y×Z of APPLN crystal 11 is 60mm×6mm×1.5mm. The MgO:LiNbO ₃ crystal 13 is an isosceles trapezoid in the XY plane, the MgO doping concentration is 5 mol %, and the optical axis of the crystal is along the Z axis. The waist length of the MgO:LiNbO ₃ crystal 13 in the XY plane is 20 mm, the length of the upper base is 37.4 mm, the length of the lower base is 20 mm, and the thickness along the Z axis is 5 mm.

In this embodiment, the frequency difference between adjacent cascade lights in the first cascade light 12 is equal to 0.5 THz.

_{In this} embodiment, the direction in which the second cascaded light G ₁ , the third cascaded light G _{2 .} . . The angle in the vertical direction is 0°-10°, the angle between the second cascade light G ₁ and the third cascade light G ₂ is θ ₁ , the third cascade light G ₂ and the fourth cascade light The included angle between G ₃ is θ ₂ , and the included angle between the nth cascaded light G _n-1 and the n+1th cascaded light G _n is θ _n-1 . Changing the position and angle of the C _1st reflector C ₁ , the _C2th reflector C ₂ ... the _Cnth reflector C _n can change the size of θ ₁ , θ ₂ ... θ _n-1 , through the non-collinear Cascaded difference frequencies generate high power terahertz waves. As shown in Figure 2, when the wavelength of the cascaded light and the corresponding size of θ ₁ , θ ₂ ... θ _n-1 are changed, a terahertz wave with a frequency of 0.5 THz can be generated through the non-collinear cascaded difference frequency.

The above-mentioned embodiments are only examples and descriptions of the technical solutions of the present invention, which are convenient for those skilled in the art to understand the technical solutions of the present application, rather than all implementation modes, and the protection scope of the present invention is not limited thereto. The various technical features of the above-mentioned embodiments can be combined arbitrarily. For the sake of concise description, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification. When the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, nor is it within the protection scope of the present invention. The basic idea of the present invention lies in the above-mentioned basic scheme. For those skilled in the art and any person familiar with the technical field, without departing from the overall concept of the invention and the spirit of the principles of the present invention, according to the teachings of the present invention, design It does not require creative labor to produce models, formulas, and parameters of various deformations. Changes, modifications, replacements, equivalent replacements and variants made to the embodiments without departing from the principle and spirit of the present invention should also be regarded as the protection scope of the present invention.

Claims (8)

1. Non-collinear cascade opticsThe difference frequency multi-frequency terahertz wave generation device is characterized in that: comprises a first pump source (1) and a second pump source (3), an APPLN crystal (11), mgO: liNbO ₃ Crystal (13), item B ₁ Reflecting mirror (B) ₁ ) The second one, B ₂ Reflecting mirror (B) ₂ ) 823080, 823030a _n Reflecting mirror (B) _n ) M th ₁ Reflecting mirror (M) ₁ ) M th ₂ Reflecting mirror (M) ₂ ) 823060, 823030M _n Reflecting mirror (M) _n ) C, C ₁ Reflecting mirror (C) ₁ ) (ii) C ₂ Reflecting mirror (C) ₂ ) 823060 _n Reflecting mirror (C) _n ) A beam combining mirror (9) and a phase delay system;

a first pump light (2) emitted from a first pump source (1) enters a beam combining mirror (9); second pump light (4) emitted from the second pump source (3) enters the beam combiner (9) after passing through the phase delay system; the first pump light (2) and the second pump light (4) passing through the phase delay system are combined into a mixed light beam (10) in a beam combining mirror (9); mixed light (10) is incident on an APPLN crystal (11) and first cascade light (12) is generated through a cascade optical difference frequency effect; the first cascade light (12) passes through the second cascade light ₁ Reflecting mirror (B) ₁ ) Becomes second cascade light (G) after transmission ₁ ) Second cascade light (G) ₁ ) Through M ₁ Reflecting mirror (M) ₁ ) C, C ₁ Reflecting mirror (C) ₁ ) Incident MgO LiNbO after reflection ₃ A crystal (13); the first cascade light (12) passes through the second cascade light ₁ Reflecting mirror (B) ₁ ) After reflection, the light passes through the second lens ₂ Reflecting mirror (B) ₂ ) After reflection, the light becomes third cascade light (G) ₂ ) Third cascade (G) ₂ ) Through M ₂ Reflecting mirror (M) ₂ ) (ii) C ₂ Reflecting mirror (C) ₂ ) Incident MgO LiNbO after reflection ₃ A crystal (13); the first cascade light (12) passes through the second cascade light ₂ Reflecting mirror (B) ₂ ) After transmission, the second layer passes through the second layer ₃ Reflecting mirror (B) ₃ ) After reflection, becomes the fourth-order coupled light (G) ₃ ) Fourth order of luminescence (G) ₃ ) Through M ₃ Reflecting mirror (M) ₃ ) (ii) C ₃ Reflecting mirror (C) ₃ ) Incident MgO LiNbO after reflection ₃ A crystal (13);

by analogy, the first cascade light (12) passes through the B-th _n-1 Reflecting mirror (B) _n-1 ) After transmission, the second layer passes through the second layer _n Reflecting mirror (B) _n ) After reflection, the light becomes the n +1 cascade light (G) _n ) The n + 1th cascade light (G) _n ) Through M _n Reflecting mirror (M) _n ) (ii) C _n Reflecting mirror (C) _n ) Incident MgO LiNbO after reflection ₃ Crystal (13), n +1 cascade light (G) _n ) Not second cascade light (G) ₁ ) Or third cascade (G) ₂ ）；

Second cascade light (G) ₁ ) And third cascade light (G) ₂ ) \8230A \8230an +1 cascade light (G) _n ) Incident MgO LiNbO ₃ Crystal (13) so as to pass MgO LiNbO ₃ The crystal (13) generates terahertz waves (14);

the frequencies of the first pump light (2) and the second pump light (4) are different; the plane of light beam propagation is a plane determined by an X axis and a Y axis, a Z axis is vertical to the plane of light beam propagation, the initial propagation direction of first pump light (2) emitted from a first pump source (1) is an X-axis forward direction, the initial propagation direction of second pump light (4) emitted from a second pump source (3) is a Y-axis forward direction, and the propagation direction of mixed light (10) is the X-axis forward direction; propagation direction of terahertz wave (14) and LiNbO ₃ The vertical included angle of the emergent surface of the crystal (13) is 0-10 degrees.

2. The multi-frequency terahertz wave generating apparatus based on the non-collinear cascade optical difference frequency according to claim 1, wherein: the first pump source (1) adopts a pulse laser, the second pump source (3) adopts a pulse laser, and the polarization directions of the two beams of pump light are Z-axis.

3. The multi-frequency terahertz wave generating device based on the non-collinear cascade optical difference frequency according to claim 1, wherein: the phase delay system is composed of a first reflector (5), a second reflector (6), a third reflector (7) and a fourth reflector (8), and second pump light (4) emitted from a second pump source (3) enters the beam combiner (9) after passing through the phase delay system composed of the first reflector (5), the second reflector (6), the third reflector (7) and the fourth reflector (8).

4. The multi-frequency terahertz wave generating apparatus based on the non-collinear cascade optical difference frequency according to claim 3, wherein: the first reflector (5), the second reflector (6), the third reflector (7) and the fourth reflector (8) are plane mirrors and are used for totally reflecting the second pump light (4), and the B < th > is ₁ Reflecting mirror (B) ₁ ) The second one, B ₂ Reflecting mirror (B) ₂ ) 823080, 823030a _n Reflecting mirror (B) _n ) Partially transmitting the first cascade light (12), mth ₁ Reflecting mirror (M) ₁ ) M, M ₂ Reflecting mirror (M) ₂ ) 823060 _n Reflecting mirror (M) _n ) C, C ₁ Reflecting mirror (C) ₁ ) C, C ₂ Reflecting mirror (C) ₂ ) 823060 _n Reflecting mirror (C) _n ) Totally reflecting the first cascade light (12).

5. The multi-frequency terahertz wave generating device based on the non-collinear cascade optical difference frequency according to claim 1, wherein: the APPLN crystal (11) is a cuboid which is rectangular in an X-Y plane, and the optical axis is along the Z axis; mgO LiNbO ₃ The crystal (13) is in an isosceles trapezoid shape in an X-Y plane, and the optical axis of the crystal is along the Z axis.

6. The multi-frequency terahertz wave generating apparatus based on the non-collinear cascade optical difference frequency according to claim 5, wherein: mgO LiNbO ₃ The crystal (13) is isosceles trapezoid in the X-Y plane and has a second cascade (G) ₁ ) And third cascade light (G) ₂ ) \8230A \8230an +1 cascade light (G) _n ) Incident from the plane where the oblique sides of the isosceles trapezoid are located.

7. The multi-frequency terahertz wave generating device based on the non-collinear cascade optical difference frequency according to claim 1, wherein: said first cascade light (12) is a mixed light of a cascade light mixture of frequencies and they propagate co-linearly; the frequency difference of the adjacent cascade light in the first cascade light (12) is equal to the frequency difference between the first pump light (2) and the second pump light (4).

8. The multi-frequency terahertz wave generating apparatus based on the non-collinear cascade optical difference frequency according to claim 1, wherein: second cascade light (G) ₁ ) And third cascade light (G) ₂ ) 823060 \ 8230a, the n + 1th cascade light (G) _n ) Incident MgO LiNbO ₃ Direction of crystal (13) and incident MgO LiNbO ₃ The included angle of the vertical direction of the crystal (13) surface is 0-10 DEG, and the second cascade light (G) ₁ ) In cascade with a third stage (G) ₂ ) Included angle therebetween isθ ₁ Third cascade (G) ₂ ) With fourth order light (G) ₃ ) At an included angle ofθ ₂ N cascade light (G) _n-1 ) Cascade light (G) with n +1 _n ) At an included angle ofθ _n-1 (ii) a Change of the C ₁ Reflecting mirror (C) ₁ ) C, C ₂ Reflecting mirror (C) ₂ ) 823060 _n Reflecting mirror (C) _n ) Can change the position and angle ofθ ₁ 、θ ₂ ……θ _n-1 The high-power terahertz waves are generated through the non-collinear cascade difference frequency.

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