CN111478154B - Terahertz frequency shifter - Google Patents
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- CN111478154B CN111478154B CN202010460023.6A CN202010460023A CN111478154B CN 111478154 B CN111478154 B CN 111478154B CN 202010460023 A CN202010460023 A CN 202010460023A CN 111478154 B CN111478154 B CN 111478154B
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- H—ELECTRICITY
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Abstract
The application relates to a terahertz frequency shifter, and belongs to the technical field of terahertz. The terahertz frequency shifter comprises: terahertz emission source, dynamic grating device, beam splitter and laser equipment; the terahertz emission source is used for emitting terahertz waves with the first frequency; the beam splitter is used for reflecting part of terahertz waves to the dynamic grating device; the laser device is used for generating two laser beams with frequency difference, and the two laser beams irradiate on the dynamic grating device at a certain included angle and interfere to form laser interference fringes; the dynamic grating device is also used for generating photo-generated carriers which move synchronously with the laser interference fringes after being irradiated by the two laser beams, the terahertz waves irradiated on the dynamic grating device are diffracted by modulation of the photo-generated carriers, and the terahertz waves with the second frequency are output. The terahertz wave diffraction device utilizes the dynamic grating diffraction technology to diffract the terahertz wave on the dynamic grating device, so that the terahertz wave can generate frequency offset only by one set of terahertz emission source.
Description
Technical Field
The application belongs to the technical field of terahertz, and particularly relates to a terahertz frequency shifter.
Background
Terahertz waves (THz waves) are electromagnetic waves whose oscillation frequency is on the order of 0.1THz-10 THz. Terahertz waves have the characteristics of good penetrability to nonpolar materials, high carrier frequency, difficult ionization damage and the like, and have great application potential in the fields of military, public safety, high-speed communication, biological research and the like. The terahertz wave technology has rapid development in recent years, and because the terahertz wave has the characteristic and advantage of good penetrability to nonpolar materials, the research on the Doppler interference speed measurement technology based on the terahertz wave has important application value in dynamic response under material loading.
In the field of terahertz wave interference, a more common method is to transmit and receive non-zero intermediate frequency interference based on terahertz frequency multiplication sources of electronics technology, wherein two sets of frequency multiplication amplifying links must be used, one set of frequency multiplication amplifying links is used for generating and transmitting terahertz waves, the other set of frequency multiplication amplifying links is used for generating terahertz waves of another frequency, and non-zero intermediate frequency interference detection is realized through a mixer or a detector, and a system diagram is shown in fig. 1. The method is used for carrying out phase locking on the terahertz transmitting source and the two detected frequency multiplication amplifying links through the crystal oscillator with the frequency of 10MHz or 100MHz, and the phase stability of two paths of terahertz waves is poor, so that interference signal noise is large, and finally, the accuracy of the motion information of the detected target is poor.
Disclosure of Invention
In view of this, an embodiment of the present application is to provide a terahertz frequency shifter, so as to solve the problems that the existing terahertz interference needs to be implemented by two sets of frequency multiplication amplifying links, resulting in poor phase stability of two paths of terahertz waves, so that interference signal noise is larger, and cost is higher.
Embodiments of the present application are implemented as follows:
The embodiment of the application provides a terahertz frequency shifter, which comprises the following components: terahertz emission source, dynamic grating device, beam splitter and laser equipment; a terahertz transmitting source for transmitting terahertz waves of a specified power and oscillation frequency of a first frequency; the beam splitter is arranged on a light path of the terahertz emission source and is used for reflecting a part of terahertz waves to the first surface of the dynamic grating device; the laser device is used for generating two laser beams with frequency difference, the two laser beams irradiate the second surface of the dynamic grating device at a certain included angle and interfere with each other to form laser interference fringes, and the first surface and the second surface are opposite surfaces; the dynamic rasterizer is further configured to generate a photo-generated carrier that moves synchronously with the laser interference fringes after being irradiated by the two laser beams, and the terahertz waves irradiated onto the dynamic rasterizer are modulated by the photo-generated carrier and diffracted, so as to output terahertz waves with an oscillation frequency of a second frequency, where the second frequency is different from the first frequency. In the embodiment of the application, the terahertz wave is diffracted on the dynamic grating device by utilizing the dynamic grating diffraction technology, so that the frequency of the terahertz wave diffracted from the grating is changed to a certain extent, and therefore, only one set of terahertz emission source is needed to be used, so that the terahertz wave can generate certain frequency offset, the cost is saved, and simultaneously, as the two paths of terahertz waves for terahertz emission source (the terahertz wave with the first frequency) and detection (the terahertz wave with the second frequency) are both from the same emission source, the phase stability of the two paths of terahertz waves is high, and the noise of interference signals can be reduced.
In one possible embodiment, the laser device includes: a laser, a frequency modulated laser; a laser for generating a first laser light of a certain frequency and irradiating the second surface of the dynamic rasterizer at a first incident angle; and the frequency modulation laser is used for generating second laser with different frequency from the first laser, irradiating the second surface of the dynamic grating device at a second incident angle, and interfering with the first laser to form the laser interference fringes. In the embodiment of the application, two mutually independent lasers are directly utilized to generate two laser beams with frequency difference, so that the required laser beams can be obtained quickly.
In one possible embodiment, the laser device includes: an acousto-optic modulator, a laser and a beam splitter; a laser for generating laser light of a certain frequency and irradiating the second surface of the dynamic rasterizer at a first incident angle; the beam splitter is arranged on an optical path of the laser and is used for reflecting a part of laser light to the acousto-optic modulator; the acousto-optic modulator is used for modulating a part of laser generated by the laser, changing the frequency of the part of laser, and irradiating the part of laser onto the second surface of the dynamic grating device at a second incident angle. In the embodiment of the application, one laser is utilized to generate laser, a beam splitter is utilized to reflect a part of the laser to the acousto-optic modulator, and the acousto-optic modulator is utilized to change the frequency of the part of the laser, so that two laser beams with a certain frequency difference are generated, the phase stability of the generated two laser beams is high, and meanwhile, the applicability of the scheme can be expanded.
In one possible embodiment, the first angle of incidence is not equal to the second angle of incidence. In the embodiment of the application, the incident angles of the two laser beams irradiated on the dynamic grating device are not required to be equal, so that the position relation of the two laser beams is more flexible.
In one possible implementation, the dynamic rasterizer is made of high-resistance silicon, low-temperature grown gallium arsenide or vanadium dioxide thin films. In the embodiment of the application, the material which can generate the photo-generated carriers and has shorter carrier duration is adopted as the material of the dynamic grating device, so that the photo-generated carriers generated by the dynamic grating device can move in the same direction and at the same speed along with the light intensity distribution, thereby forming a moving periodic carrier distribution, and the frequency of terahertz waves diffracted from the grating can be periodically and dynamically changed.
In one possible embodiment, the second surface of the dynamic rasterizer is coated with a conductive film having the property of transmitting laser light and reflecting terahertz waves. In the embodiment of the application, the second surface of the dynamic grating device is coated with the conductive film with the characteristics of transmitting laser and reflecting terahertz waves, so that the terahertz waves irradiated on the dynamic grating device can be prevented from being reflected and diffracted and transmitted and diffracted.
In one possible embodiment, the conductive film is an ITO conductive film. In the embodiment of the application, the common ITO conductive film is coated on the second surface of the dynamic grating device, so that the acquisition difficulty of the conductive film can be reduced, and the practicability and applicability of the scheme are improved.
In one possible embodiment, the thickness of the ITO conductive film is 100 to 300 nanometers. In the embodiment of the application, the thickness of the coated ITO conductive film is between 100 and 300 nanometers, the reflection effect on terahertz waves can be improved to the greatest extent, if the coating is too thick, the transmissivity of laser can be influenced, and if the coating is too few, the reflection effect on terahertz waves can be influenced.
In one possible embodiment, the terahertz emission source includes: the device comprises a crystal oscillator, a first frequency multiplier, an amplifier and a second frequency multiplier; the first frequency multiplier is used for multiplying the frequency of the radio frequency signal with the third frequency generated by the crystal oscillator to fourth frequency output, wherein the fourth frequency is N times the third frequency, and N is a positive integer larger than 2; an amplifier for amplifying the power of the radio frequency signal of the fourth frequency input by the first frequency multiplier; and the second frequency multiplier is used for multiplying the frequency of the radio frequency signal with the fourth frequency input by the amplifier to the first frequency output, wherein the first frequency is M times the fourth frequency, and M is a positive integer greater than 2. In the embodiment of the application, the frequency multiplication is carried out on the hundred megahertz radio frequency signals generated by the crystal oscillator by using the first frequency multiplier, the power amplification is carried out on the radio frequency signals subjected to the frequency multiplication by using the amplifier, and finally, the frequency multiplication is carried out on the radio frequency signals of tens of gigahertz which are input by the amplifier by using the second frequency multiplier, so that terahertz waves can be output, and the required device cost is maximally solved on the premise of ensuring the feasibility of the scheme.
In one possible embodiment, the terahertz frequency shifter further includes: and the detector or the mixer is used for mixing the terahertz wave reflected by the detected target with the terahertz wave with the second frequency to generate an interference signal and outputting the interference signal. In the embodiment of the application, the terahertz wave reflected by the detection target and the terahertz wave with the second frequency are mixed by using the detector or the mixer to generate the interference signal, so that the non-zero intermediate frequency interference detection can be realized rapidly.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the embodiments of the application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. The above and other objects, features and advantages of the present application will become more apparent from the accompanying drawings. Like reference numerals refer to like parts throughout the several views of the drawings. The drawings are not intended to be drawn to scale, with emphasis instead being placed upon illustrating the principles of the application.
Fig. 1 is a schematic structural diagram of a conventional terahertz interference system.
Fig. 2 shows a schematic structural diagram of a terahertz frequency shifter according to an embodiment of the present application.
Fig. 3 shows a schematic structural diagram of a laser device according to an embodiment of the present application.
Fig. 4 shows a schematic diagram of the working principle of the terahertz frequency shifter provided by the embodiment of the application.
Fig. 5 shows a schematic structural diagram of another terahertz frequency shifter according to an embodiment of the present application.
Detailed Description
The following description of the technical solutions according to the embodiments of the present application will be given with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the present application, it should be noted that, the azimuth or positional relationship indicated by the terms "front", "back", etc. are based on the azimuth or positional relationship shown in the drawings, or the azimuth or positional relationship that is commonly put in use of the product of this application, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element to be referred to must have a specific azimuth, be configured and operated in a specific azimuth, and therefore should not be construed as limiting the present application. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
In the description of the present application, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
In view of the problems that the existing terahertz interference can be realized only by adopting two sets of frequency multiplication amplifying links, and the phase stability of two paths of terahertz waves is poor, so that interference signal noise is large and the cost is high. The embodiment of the application provides a terahertz frequency shifter, which can enable terahertz waves to generate certain frequency offset by only using one set of terahertz emission sources, thereby realizing interference signal detection of non-zero intermediate frequency.
As shown in fig. 2, the terahertz frequency shifter provided by the embodiment of the application includes: dynamic rasterizer, terahertz emission source, beam splitter and laser equipment. The function of each device will be described below.
And the terahertz transmitting source is used for transmitting terahertz waves with specified power and oscillation frequency of a first frequency (f 1). In one embodiment, the terahertz emission source includes: the device comprises a crystal oscillator, a first frequency multiplier, an amplifier and a second frequency multiplier.
The crystal oscillator is used for generating a radio frequency signal with a third frequency and transmitting the video signal to the first frequency multiplier. For example, the frequency of the RF signal generated by the crystal oscillator is 100MHz.
The first frequency multiplier is used for multiplying the frequency of the radio frequency signal with the third frequency generated by the crystal oscillator to fourth frequency output, wherein the fourth frequency is N times the third frequency, and N is a positive integer larger than 2. For example, the frequency of the radio frequency signal outputted via the first frequency multiplier is several GHz to several tens of GHz, such as 20GHz, where N is 200.
And the amplifier is used for amplifying the power of the radio frequency signal with the fourth frequency input by the first frequency multiplier and outputting the amplified radio frequency signal to the second frequency multiplier.
And the second frequency multiplier is used for multiplying the frequency of the radio frequency signal with the fourth frequency input by the amplifier to the first frequency (f 1) for output, wherein the first frequency is M times the fourth frequency, and M is a positive integer greater than 2. For example, the fourth frequency RF signal (if the frequency is 20 GHz) is processed by the second frequency multiplier, and then the frequency is multiplied to 0.1THz to 10THz, such as 0.1THz, where M is 5.
It should be noted that, the number of the amplifiers and/or frequency multipliers may be increased appropriately, so as to reduce the performance requirements of the amplifiers and/or frequency multipliers, for example, in one embodiment, the terahertz emission source further includes a third frequency multiplier located after the second frequency multiplier, where the second frequency multiplier is used to multiply the frequency of the rf signal with the fourth frequency input by the amplifier to the fifth frequency output, and the third frequency multiplier is used to multiply the frequency of the rf signal with the fifth frequency input by the second frequency multiplier to the first frequency (f 1) output, so the structure of the terahertz emission source cannot be understood as a limitation of the present application.
The beam splitter is arranged on an optical path of the terahertz emission source and is used for reflecting a part of terahertz waves onto a first surface (such as the front surface) of the dynamic grating device, and the rest of the terahertz waves which are generated by the terahertz emission source and are not reflected by the beam splitter are normally emitted.
The laser device is used for generating two laser beams with frequency difference, the two laser beams irradiate on a second surface (such as a back surface) of the dynamic grating device at a certain included angle and interfere on the second surface to form laser interference fringes, and the first surface and the second surface are opposite surfaces.
In one embodiment, a laser apparatus includes: a laser, and a frequency modulated laser, as shown in fig. 3. In this embodiment, a laser is configured to generate a first laser light of a frequency (omega 1) and impinge on a second surface of the dynamic rasterizer at a first angle of incidence (beta).
The frequency modulation laser is used for generating second laser (the frequency is omega 1 +delta omega) with different frequency from the first laser, and irradiating the second laser onto the second surface of the dynamic grating device at a second incidence angle (alpha), and interfering with the first laser to form laser interference fringes. Wherein the first incident angle (β) and the second incident angle (α) may be the same or different.
In yet another embodiment, a laser apparatus includes: a laser, an acousto-optic modulator, and a beam splitter. In this embodiment, the laser is configured to generate laser light at a frequency (ω 1) and impinge on the second surface of the dynamic rasterizer at a first angle of incidence (β).
The beam splitter is disposed on the optical path of the laser and is used for reflecting a part of the laser light onto the acousto-optic modulator, and the rest part (unreflected laser light) irradiates onto the second surface of the dynamic grating device at a first incident angle (beta).
An acousto-optic modulator for modulating a portion of the laser light generated by the laser (the portion reflected by the beam splitter) such that the frequency of the portion of the laser light is changed (to ω 1 +Δω) and impinges (α) on the second surface of the dynamic rasterizer at a second angle of incidence. Wherein the first incident angle (β) and the second incident angle (α) may be the same or different.
The dynamic grating device is also used for generating photo-generated carriers which move synchronously with the laser interference fringes after being irradiated by two beams of laser generated by the laser equipment, the terahertz waves irradiated on the dynamic grating device are modulated by the photo-generated carriers and are diffracted, and terahertz waves with the oscillation frequency of (f 1 +delta f) are output, wherein the second frequency is different from the first frequency, and the frequency difference is delta f. The dynamic rasterizer is made of a material which can generate photo-generated carriers and has a short carrier duration, such as high-resistance silicon (HRFZ-Si), gallium arsenide (LT-GaAs) grown at low temperature, a vanadium dioxide (VO 2) film on a substrate, and the like.
The application utilizes the dynamic grating diffraction technology to diffract the terahertz wave on the dynamic grating device, and the frequency of the terahertz wave diffracted from the grating is changed to a certain extent, thereby achieving the purpose of terahertz frequency shift. Since two paths of terahertz waves for terahertz transmission source (terahertz wave with the first frequency) and detection (terahertz wave with the second frequency) are both from the same transmission source, the phase stability of the two paths of terahertz waves is very high, so that the noise of interference signals can be reduced. The principle that terahertz waves are diffracted in a dynamic grating device to generate frequency changes will be described below. As shown in fig. 4, the main principle of generating terahertz frequency shift based on dynamic grating is:
As shown in fig. 4 (a), two continuous lasers (laser 1 with the frequency ω 1 +Δω and laser 2 with the frequency ω 1) with different frequencies are respectively irradiated onto the dynamic rasterizer at a certain incident angle (α, β), so as to generate an interference light intensity pattern I (x) with a periodic distribution (period ∈) and excite photo-generated carriers on the dynamic rasterizer, and the period of the photo-generated carrier concentration distribution n e (x) is the same as the period of the interference light intensity. On the other hand, since the frequencies of the two laser beams are different, the laser interference pattern moves at a certain speed in one direction Wherein a=i 1+I2,I 1 is the intensity of the laser 1, I 2 is the intensity of the laser 2, so that the generated photo-generated carrier concentration distribution also moves n e (x) in the same direction and at the same speed along with the intensity distribution, thereby forming a periodically moving photo-generated carrier distribution.
For terahertz waves, the reflection efficiency R and the transmission efficiency T of the grating device on the terahertz waves are changed due to different carrier concentrations, and the periodically moving carrier concentration n e (x) forms a terahertz wave periodic dynamic reflection grating R (x) or transmission grating T (x). According to the fourier series theory, any one periodic function can be decomposed into a sum of a plurality of simple sinusoidal functions. Thus, the periodic dynamic reflection or transmittance function can be decomposed into a sum of sine or cosine functions based on the fundamental period Λ. As shown in FIG. 4 (b), taking the reflective example, the dynamic periodic reflectivity R (x) can be decomposed intoAccording to the optical diffraction theory, for a sine function type transmission or reflection type grating, the diffraction beam is divided into three directions, and the directions are respectively corresponding to 0-order diffraction and + -1-order diffraction. Each of the above-mentioned reflectances decomposed by fourier can be regarded as a sinusoidal grating, and thus the diffraction thereof is also divided into three (0 th order and ±1 st order diffraction), the frequency offsets of terahertz diffraction waves are 0,The diffraction direction is determined according to the formula of ∈θ in+cosθin)＝nλTHz since the diffraction angle can be within 90 °, each sine function after the resolution of the reflectivityThere are a limited number of angles that satisfy the above diffraction direction formula. The fundamental period Λ of the dynamic rasterizer can be adjusted by changing the frequency difference of the two laser beams, so that diffraction can occur only in the case of n= +1 (except n=0, namely specular reflection light), and the situation that a plurality of diffraction orders possibly overlap each other is avoided.
Taking the reflective diffraction effect as an example, the dynamic grating periodically modulates the reflectivity R (x) of the terahertz wave, the terahertz wave forms a coherent diffraction intensity in a certain direction, and the frequency of the diffracted terahertz wave changes to a certain extent due to the dynamic grating, wherein the change amount is related to the frequency difference (Δω) between the laser 1 and the laser 2, the incident angles (α, β) and the incident angle (θ in) of the terahertz wave. The frequency shift can be achieved by changing the frequency difference between the two laser beams, such as changing the output frequency of the frequency modulation laser, or changing the included angle of the two laser beams irradiated on the dynamic rasterizer.
Wherein, Wherein Δf is the frequency difference between the second frequency (f 1 +Δf) and the first frequency (f 1), ω 1 +Δω is the frequency of laser 1, ω 1 is the frequency of laser 2, θ out is the angle of the reflected diffracted terahertz wave with respect to the vertical direction, and θ in is the angle of the incident terahertz wave with respect to the vertical direction.
The dynamic grating device can diffract terahertz waves in a mode of reflecting the terahertz waves or in a mode of transmitting the terahertz waves, and the two methods have certain differences on specific optical paths, but the terahertz frequency shift effects can be the same. In order to prevent both reflection diffraction and transmission diffraction of the terahertz wave irradiated onto the dynamic rasterizer, as such an embodiment, a conductive film may be coated on the second surface of the dynamic rasterizer to prevent this, for example, the coated conductive film has a characteristic of transmitting laser light, reflecting terahertz waves.
In one embodiment, the coated conductive film having the characteristics of transmitting laser light and reflecting terahertz waves may be an ITO (Indium Tin Oxide) conductive film. Alternatively, the thickness of the ITO conductive film coated thereon may be 100 to 300 nm.
In one embodiment, the terahertz frequency shifter further includes: a detector or mixer as shown in fig. 5. The detector or the mixer is used for mixing the terahertz wave (with the frequency of f 1+fdoppler) reflected by the detection target with the terahertz wave with the frequency of the second frequency (f 1 +delta f), generating an interference signal and outputting the interference signal. f doppler is the Doppler frequency.
It should be noted that, in the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described as different from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. A terahertz frequency shifter, characterized by comprising:
a dynamic rasterizer;
A terahertz transmitting source for transmitting terahertz waves of a specified power and oscillation frequency of a first frequency;
The beam splitter is arranged on the light path of the terahertz emission source and is used for reflecting a part of terahertz waves onto the first surface of the dynamic grating device;
The laser device is used for generating two laser beams with frequency difference, the two laser beams irradiate the second surface of the dynamic grating device at a certain included angle and interfere with each other to form laser interference fringes, and the first surface and the second surface are opposite surfaces;
The dynamic grating device is also used for generating photo-generated carriers which move synchronously with the laser interference fringes after being irradiated by the two laser beams, the terahertz waves irradiated on the dynamic grating device are modulated by the photo-generated carriers to be diffracted, and the terahertz waves with the oscillation frequency being the second frequency are output, wherein the second frequency is different from the first frequency, and the frequency difference of the second frequency is the quotient of the frequency difference of the two laser beams and 2 pi.
2. The terahertz frequency shifter according to claim 1, wherein the laser device comprises:
A laser for generating a first laser light of a certain frequency and irradiating the second surface of the dynamic rasterizer at a first incident angle;
And the frequency modulation laser is used for generating second laser with different frequency from the first laser, irradiating the second surface of the dynamic grating device at a second incident angle, and interfering with the first laser to form the laser interference fringes.
3. The terahertz frequency shifter according to claim 1, wherein the laser device comprises:
an acousto-optic modulator;
a laser for generating laser light of a certain frequency and irradiating the second surface of the dynamic rasterizer at a first incident angle;
the beam splitter is arranged on an optical path of the laser and is used for reflecting a part of laser light to the acousto-optic modulator;
the acousto-optic modulator is used for modulating a part of laser generated by the laser, changing the frequency of the part of laser, and irradiating the part of laser onto the second surface of the dynamic grating device at a second incident angle.
4. The terahertz frequency shifter according to claim 2 or 3, wherein the first incident angle is not equal to the second incident angle.
5. The terahertz frequency shifter according to claim 1, wherein the dynamic grating device is made of high-resistance silicon, low-temperature grown gallium arsenide or vanadium dioxide thin films.
6. The terahertz frequency shifter according to claim 1, wherein the second surface of the dynamic rasterizer is coated with a conductive film having a characteristic of transmitting laser light and reflecting terahertz waves.
7. The terahertz frequency shifter according to claim 6, wherein the conductive film is an ITO conductive film.
8. The terahertz frequency shifter according to claim 7, wherein the thickness of the ITO conductive film is 100 to 300 nm.
9. The terahertz frequency shifter according to claim 1, wherein the terahertz emission source includes:
A crystal oscillator;
The first frequency multiplier is used for multiplying the frequency of the radio frequency signal with the third frequency generated by the crystal oscillator to fourth frequency output, wherein the fourth frequency is N times the third frequency, and N is a positive integer larger than 2;
An amplifier for amplifying the power of the radio frequency signal of the fourth frequency input by the first frequency multiplier;
And the second frequency multiplier is used for multiplying the frequency of the radio frequency signal with the fourth frequency input by the amplifier to the first frequency output, wherein the first frequency is M times the fourth frequency, and M is a positive integer greater than 2.
10. The terahertz frequency shifter according to any one of claims 1 to 3 or 5 to 8, further comprising:
and the detector or the mixer is used for mixing the terahertz wave reflected by the detected target with the terahertz wave with the second frequency to generate an interference signal and outputting the interference signal.
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