An ultra-high sensitivity heterodyne detector for terahertz waves

Abstract

The present invention provides a terahertz wave heterodyne detector with ultra-high sensitivity. A heavy metal electrode pair grown on a beat frequency laser absorption layer absorbs the energy of the beat frequency laser, while an antiferromagnetic layer absorbs the resonant terahertz wave, and the spin-to-charge current conversion in the heavy metal electrode pair is realized by the spin-orbit coupling effect, so that mixing occurs in the heavy metal electrode pair, and the frequency conversion of the terahertz wave frequency to the frequency of a conventional electronics radio frequency band that is easy to measure is realized. Finally, the heterodyne signal is obtained through analysis by devices such as a spectrum analyzer. This terahertz wave heterodyne detector with ultra-high sensitivity utilizes the property of the antiferromagnetic oscillator frequency in the terahertz band and combines the heterodyne method, having advantages such as good frequency selectivity and high sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz optoelectronic devices, and more specifically, to a terahertz wave heterodyne detector with ultra-high sensitivity. Background Art

[0002] Terahertz waves refer to a segment of electromagnetic radiation waves between microwaves and far-infrared rays, and are usually defined with a frequency range of 0.1 THz - 10 THz.

[0003] Due to its unique penetrability, low photon energy characteristics, fingerprint spectrum characteristics, high bandwidth and other characteristics, terahertz waves have great application potential and market in the fields of non-destructive testing, security inspection, component detection, communication, etc.

[0004] In addition, the universe is also filled with terahertz electromagnetic radiation waves. These terahertz radiations contain important information about the formation of cosmic galaxies, as well as the atmospheric composition information of planets, satellites, comets, etc. Understanding the information carried by these terahertz radiations has also become a major application of terahertz waves in astronomy.

[0005] However, all these applications are inseparable from the detection of terahertz waves. Therefore, researching and developing terahertz wave detectors is one of the keys for terahertz technology to be widely applied.

[0006] Detecting terahertz waves is mainly divided into two categories: pulsed terahertz signal detectors and continuous wave terahertz signal detectors according to the type of electromagnetic waves. For pulsed terahertz waves, there are mainly methods such as electro-optic sampling, photoconductive sampling, and air detection; for continuous wave terahertz, there are mainly methods such as bolometers, Golay Cells, pyroelectric release, Schottky, and field effect transistors.

[0007] However, for applications with high detection sensitivity, due to the reasons of their own implementation methods, there are currently no very effective room temperature detectors that can be competent. And terahertz wave detectors that reach the quantum measurement limit all require cryogenic superconducting mixers cooled by liquid nitrogen, which brings great challenges to applications, and methods such as bolometry cannot achieve frequency resolution either.

[0008] Therefore, developing terahertz wave detectors with high frequency resolution ability and ultra-high sensitivity will bring significant scientific and application value to the fields of materials science, biomedicine, astronomy, security inspection, military communication, quantum information, etc. Summary of the Invention

[0009] In view of this, to solve the above problems, the present invention provides a terahertz wave heterodyne detector with ultra-high sensitivity, and the technical solution is as follows:

[0010] A terahertz wave heterodyne detector with ultra-high sensitivity, the terahertz wave heterodyne detector includes:

[0011] Relatively arranged beat-frequency laser absorption layer and antiferromagnetic layer;

[0012] At least one pair of heavy metal electrode pairs arranged on the beat-frequency laser absorption layer, and at least one pair of the heavy metal electrode pairs is located between the beat-frequency laser absorption layer and the antiferromagnetic layer;

[0013] Spectrum analyzer connected to the heavy metal electrode pair;

[0014] Wherein, the detected terahertz wave is incident from the side of the beat-frequency laser absorption layer facing away from the antiferromagnetic layer, and the two-beam beat-frequency laser is incident from the side of the antiferromagnetic layer facing away from the beat-frequency laser absorption layer;

[0015] The detected terahertz wave and the two-beam beat-frequency laser are mixed in the beat-frequency laser absorption layer, the heavy metal electrode pair and the antiferromagnetic layer, and the heterodyne radio frequency signal after frequency down-conversion is detected by the spectrum analyzer, realizing ultra-high-sensitivity detection.

[0016] Optionally, in the above terahertz wave heterodyne method detector, the terahertz wave heterodyne method detector further includes:

[0017] At least one preamplifier, and the number of the preamplifiers is the same as the number of the heavy metal electrode pairs;

[0018] One of the preamplifiers is respectively arranged on the connection path between each pair of the heavy metal electrode pairs and the spectrum analyzer.

[0019] Optionally, in the above terahertz wave heterodyne method detector, the terahertz wave heterodyne method detector further includes:

[0020] A first laser for emitting a first beam of beat-frequency laser;

[0021] A second laser for emitting a second beam of beat-frequency laser.

[0022] Optionally, in the above terahertz wave heterodyne method detector, at least one of the first laser and the second laser is a wavelength-tunable laser.

[0023] Optionally, in the above terahertz wave heterodyne method detector, the terahertz wave heterodyne method detector further includes:

[0024] A magnet for generating an external magnetic field.

[0025] Optionally, in the above terahertz wave heterodyne method detector, the heavy metal electrode pair is a heavy metal electrode pair made of Pt or Ta or W material.

[0026] Optionally, in the above terahertz heterodyne detector, the antiferromagnetic layer is an antiferromagnetic layer of NiO or Cr2O3 or BiFeO3 material.

[0027] Optionally, in the above terahertz heterodyne detector, the antiferromagnetic resonance frequency of the antiferromagnetic layer falls in the terahertz band and can be regulated by an external magnetic field.

[0028] Optionally, in the above terahertz heterodyne detector, the antiferromagnetic transition temperature of the antiferromagnetic layer is above room temperature, and the bandgap width is larger than the photon energy corresponding to the beat-frequency laser.

[0029] Optionally, in the above terahertz heterodyne detector, each pair of the heavy metal electrode pairs includes: a first electrode unit and a second electrode unit;

[0030] The first electrode unit and the second electrode unit have the same shape and are T-shaped electrode structures;

[0031] The horizontal parts of the two T-shaped electrode structures are arranged oppositely, and the distance therebetween is 0.05 μm - 50 μm;

[0032] The width of the vertical part of the T-shaped electrode structure is 0.1 μm - 100 μm, and the length is 50 μm - 2000 μm;

[0033] The length of the horizontal part of the T-shaped electrode structure is 1 μm - 500 μm;

[0034] The sum of the width of the horizontal part of the T-shaped electrode structure and the distance between the horizontal parts of the two T-shaped electrode structures is 0.1 μm - 100 μm.

[0035] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0036] A terahertz heterodyne detector with ultra-high sensitivity provided by the present invention utilizes the gap between heavy metal electrode pairs grown on a beat-frequency laser absorption layer to absorb the energy of the beat-frequency laser. At the same time, the antiferromagnetic layer absorbs the resonant terahertz wave, and the spin-orbit coupling effect realizes the conversion of spin flow to charge flow in the heavy metal electrode pairs, thereby generating mixing in the heavy metal electrode pairs and realizing the down-conversion of the terahertz wave frequency to the frequency of a conventional electronics radio frequency band that is easy to measure. Finally, the heterodyne signal is analyzed through devices such as a spectrum analyzer.

[0037] The ultra-high sensitivity terahertz heterodyne detector utilizes the property that the antiferromagnetic oscillator frequency is in the terahertz band and combines the heterodyne method, having advantages such as good frequency selectivity and high sensitivity. Description of the Drawings

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on the provided drawings.

[0039] Figure 1 Schematic structural diagram of a terahertz wave heterodyne detector with ultra-high sensitivity provided for an embodiment of the present invention;

[0040] Figure 2 Schematic structural diagram of a heavy metal electrode pair provided for an embodiment of the present invention. Detailed implementation manners

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0042] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0043] Refer to Figure 1 , Figure 1 Schematic structural diagram of a terahertz wave heterodyne detector with ultra-high sensitivity provided for an embodiment of the present invention.

[0044] The terahertz wave heterodyne detector includes:

[0045] A beat frequency laser absorption layer 1 and an antiferromagnetic layer 3 arranged oppositely;

[0046] At least one pair of heavy metal electrode pairs 2 arranged on the beat frequency laser absorption layer 1, and at least one pair of the heavy metal electrode pairs 2 is located between the beat frequency laser absorption layer 1 and the antiferromagnetic layer 3;

[0047] A spectrum analyzer connected to the heavy metal electrode pair 2;

[0048] Wherein, the detected terahertz wave is incident from the side of the beat frequency laser absorption layer 1 facing away from the antiferromagnetic layer 3, and two beams of beat frequency lasers are incident from the side of the antiferromagnetic layer 3 facing away from the beat frequency laser absorption layer 1;

[0049] The detected terahertz wave and the two-beam beat-frequency laser are mixed in the beat-frequency laser absorption layer 1, the heavy metal electrode pair 2, and the antiferromagnetic layer 3, and the heterodyne radio frequency signal after frequency down-conversion is detected by the spectrum analyzer, realizing ultra-high-sensitivity detection.

[0050] In this embodiment, the antiferromagnetic layer 3 has become an important part of the terahertz-band response device because its intrinsic antiferromagnetic spin resonance frequency falls in the terahertz and sub-terahertz bands and the resonance response is extremely fast.

[0051] This application uses the "sandwich" structure composed of the beat-frequency laser absorption layer 1, the heavy metal electrode pair 2, and the antiferromagnetic layer 3 to realize heterodyne mixing and obtain the frequency down-conversion signal in the terahertz band.

[0052] Specifically, the magnon spin resonance characteristic of the antiferromagnetic layer 3 absorbs terahertz (ω THz ) of a specific wavelength. Through the spin-orbit coupling effect, the conversion of spin flow to charge flow is realized in the heavy metal electrode pair 2; at the same time, the beat-frequency laser absorption layer 1 absorbs the two-beam beat-frequency laser (ω Laser ), and the mixing of the terahertz wave frequency and the laser beat frequency (ω THz , ω Laser , ω Laser + ω THz and ω Laser - ω THz ) is realized in the gap between the heavy metal electrode pairs 2. The heterodyne signal (ω Laser - ω THz ) after frequency down-conversion is extracted by the radio frequency spectrum analyzer.

[0053] In the radio frequency band, it can be amplified and measured very precisely by electronic methods. Therefore, the terahertz wave heterodyne detector provided by the present invention has extremely high sensitivity.

[0054] That is to say, the detected terahertz wave is incident from the side of the beat-frequency laser absorption layer 1 facing away from the antiferromagnetic layer 3, acts on the antiferromagnetic layer 3 to form a net spin current, and is converted into a charge current through spin-orbit coupling in the heavy metal electrode pair 2.

[0055] The two-beam beat-frequency laser is incident from the side of the antiferromagnetic layer 3 facing away from the beat-frequency laser absorption layer 1 and enters the gap position between the heavy metal electrode pairs 2. Due to the absorption of the energy of the two-beam beat-frequency laser by the beat-frequency laser absorption layer 1, a high-frequency plasma electric field containing the beat component is formed between the heavy metal electrode pairs 2.

[0056] Finally, the high-frequency charge current generated by the terahertz wave and the high-frequency electric field generated by the beat-frequency laser are mixed in the heavy metal electrode pair 2, and the heterodyne signal can be obtained through subsequent radio frequency spectrum analysis.

[0057] Furthermore, based on the above embodiments of the present invention, the beat-frequency laser absorption layer 1 is a terahertz wave highly transparent layer, and absorption materials corresponding to different lasers can be selected.

[0058] For example, for a laser of about 800 nm, the beat-frequency laser absorption layer 1 can be selected as a low-temperature grown GaAs layer, and its thickness can be 0.3 mm.

[0059] For example, for a laser of about 1560 nm, a multi-layer structure of InGaAs / InAlAs can be selected.

[0060] Furthermore, based on the above embodiments of the present invention, the heavy metal electrode pair 2 is a heavy metal electrode pair made of Pt or Ta or W material.

[0061] In this embodiment, the heavy metal electrode pair 2 can be selected from non-magnetic metals with a relatively large atomic number, including but not limited to Pt or Ta or W, etc.

[0062] When the heavy metal electrode 2 is made of Pt material, its thickness can be selected as 3 nm.

[0063] By using heavy metal electrode pairs made of different materials, reverse control of the spin-orbit coupling signal voltage from spin current to charge current can be achieved.

[0064] For example, by changing the Pt material to Ta material, reversal of the direction of the induced charge current can be achieved.

[0065] Furthermore, based on the above embodiments of the present invention, the antiferromagnetic layer 3 is an antiferromagnetic layer made of NiO or Cr2O3 or BiFeO3 material.

[0066] In this embodiment, the antiferromagnetic layer 3 is a material layer with an antiferromagnetic magnon resonance frequency in the terahertz band, including but not limited to NiO or Cr2O3 or BiFeO3 material layers.

[0067] When the antiferromagnetic layer 3 is made of NiO material, its thickness can be selected as 20 nm.

[0068] By using antiferromagnetic layers made of different materials, coverage measurements at different frequencies can be achieved.

[0069] For example, by changing the NiO material to Cr2O3 material, the resonance absorption measurement at about 1 THz of the original NiO can be changed to the resonance absorption measurement in the sub-terahertz band of 0.2 THz.

[0070] Furthermore, based on the above embodiments of the present invention, the antiferromagnetic transition temperature (Neel temperature) of the antiferromagnetic layer 3 is above room temperature, and the band gap is larger than the photon energy corresponding to the beat-frequency laser.

[0071] Further, based on the above embodiments of the present invention, the antiferromagnetic resonance frequency of the antiferromagnetic layer 3 falls in the terahertz band and can be regulated by an external magnetic field.

[0072] In this embodiment, by replacing the material of the antiferromagnetic layer 3 and coordinating with the adjustment of the external magnetic field, terahertz wave detection with adjustable frequency and high frequency resolution can be obtained.

[0073] Further, based on the above embodiments of the present invention, as Figure 1 shown, the terahertz heterodyne detector further includes:

[0074] At least one preamplifier, the number of the preamplifiers being the same as the number of the heavy metal electrode pairs 2;

[0075] One of the preamplifiers is respectively arranged on the connection path between each pair of the heavy metal electrode pairs 2 and the spectrum analyzer.

[0076] It should be noted that all the heavy metal electrode pairs 2 can also be connected in parallel and then share a preamplifier.

[0077] In this way, all the heavy metal electrode pairs 2 are equivalent to a large total electrode pair structure, and each electrode pair cannot be distinguished, but the signal and the receiving area will increase accordingly.

[0078] Further, based on the above embodiments of the present invention, the terahertz heterodyne detector further includes:

[0079] A first laser for emitting a first beat-frequency laser beam;

[0080] A second laser for emitting a second beat-frequency laser beam.

[0081] In this embodiment, at least one of the first laser and the second laser is a laser with adjustable wavelength.

[0082] The first beat-frequency laser beam and the second beat-frequency laser beam are laser beams in different optical bands with close frequencies, and their beat frequency is in the terahertz band.

[0083] For example, the wavelength of the first beat-frequency laser beam is 780 nm, and the wavelength of the second beat-frequency laser beam is 785 nm.

[0084] Further, based on the above embodiments of the present invention, as Figure 1 shown, the terahertz heterodyne detector further includes:

[0085] A magnet for generating an external magnetic field.

[0086] Further, based on the above embodiments of the present invention, referring to Figure 2 ,Figure 2 The figure is a schematic structural diagram of a pair of heavy metal electrodes provided by an embodiment of the present invention.

[0087] Each pair of the heavy metal electrode pairs 2 includes: a first electrode unit and a second electrode unit;

[0088] The first electrode unit and the second electrode unit have the same shape and are T-shaped electrode structures;

[0089] The horizontal parts of the two T-shaped electrode structures are arranged oppositely, and the distance g therebetween is 0.05 μm - 50 μm;

[0090] The width t of the vertical part of the T-shaped electrode structure is 0.1 μm - 100 μm, and the length l is 50 μm - 2000 μm;

[0091] The length w of the horizontal part of the T-shaped electrode structure is 1 μm - 500 μm;

[0092] The sum p of the width of the horizontal part in the T-shaped electrode structure and the distance between the horizontal parts of the two T-shaped electrode structures is 0.1 μm - 100 μm.

[0093] In this embodiment, the selection of the above parameters for different heavy metal electrode pairs can also be different.

[0094] Optionally, g = 5 μm, t = 10 μm, l = 200 μm, w = 50 μm, p = 10 μm.

[0095] In the present invention, the number of the heavy metal electrode pairs 2 is at least one pair. By adding an incident terahertz focusing lens or arranging multiple pairs of heavy metal electrode pairs 2 in an array, two-dimensional surface detection can be realized, and the detection ability is improved.

[0096] The above has introduced in detail a terahertz wave heterodyne detector with ultra-high sensitivity provided by the present invention. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

[0097] It should be noted that the embodiments in this specification are all described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0098] It should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that the elements inherent in a process, method, article or device comprising a series of elements, or further include elements inherent in these process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0099] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A terahertz wave heterodyne detector with ultra-high sensitivity, characterized in that, The terahertz wave heterodyne detector includes: A beat-frequency laser absorption layer and an antiferromagnetic layer arranged oppositely; At least one pair of heavy metal electrode pairs arranged on the beat-frequency laser absorption layer, and at least one pair of the heavy metal electrode pairs is located between the beat-frequency laser absorption layer and the antiferromagnetic layer; A spectrum analyzer connected to the heavy metal electrode pairs; Wherein, the detected terahertz wave is incident from the side of the beat-frequency laser absorption layer departing from the antiferromagnetic layer, and two beams of beat-frequency laser are incident from the side of the antiferromagnetic layer departing from the beat-frequency laser absorption layer; The detected terahertz wave and the two beams of beat-frequency laser are mixed in the beat-frequency laser absorption layer, the heavy metal electrode pairs and the antiferromagnetic layer, and the heterodyne radio frequency signal after frequency down-conversion is detected by the spectrum analyzer, realizing ultra-high-sensitivity detection.

2. The terahertz wave heterodyne detector according to claim 1, characterized in that, The terahertz wave heterodyne detector further includes: At least one preamplifier, and the number of the preamplifiers is the same as the number of the heavy metal electrode pairs; One of the preamplifiers is respectively arranged on the connection path between each pair of the heavy metal electrode pairs and the spectrum analyzer.

3. The terahertz wave heterodyne detector according to claim 1, characterized in that, The terahertz wave heterodyne detector further includes: A first laser for emitting a first beam of beat-frequency laser; A second laser for emitting a second beam of beat-frequency laser.

4. The terahertz wave heterodyne detector according to claim 3, characterized in that, Among the first laser and the second laser, at least one laser is a wavelength-tunable laser.

5. The terahertz wave heterodyne detector according to claim 1, characterized in that, The terahertz wave heterodyne detector further includes: A magnet for generating an external magnetic field.

6. The terahertz wave heterodyne detector according to claim 1, characterized in that, The heavy metal electrode pairs are heavy metal electrode pairs made of Pt or Ta or W materials.

7. The terahertz wave heterodyne detector according to claim 1, characterized in that, The antiferromagnetic layer is an antiferromagnetic layer made of NiO or Cr2O3 or BiFeO3 materials.

8. The terahertz wave heterodyne detector according to claim 1, characterized in that, The antiferromagnetic resonance frequency of the antiferromagnetic layer falls in the terahertz band and can be regulated by the external magnetic field.

9. The terahertz wave heterodyne detector according to claim 1, characterized in that, The antiferromagnetic transition temperature of the antiferromagnetic layer is above room temperature, and the band gap is larger than the photon energy corresponding to the beat-frequency laser.

10. The terahertz wave heterodyne detector according to claim 1, characterized in that, Each pair of the heavy metal electrode pairs includes: a first electrode unit and a second electrode unit; The first electrode unit and the second electrode unit have the same shape and are T-shaped electrode structures; The horizontal parts in the two T-shaped electrode structures are arranged oppositely, and the distance therebetween is 0.05 μm - 50 μm; The width of the vertical part in the T-shaped electrode structure is 0.1 μm - 100 μm, and the length is 50 μm - 2000 μm; The length of the horizontal part in the T-shaped electrode structure is 1 μm - 500 μm; The sum of the width of the horizontal part in the T-shaped electrode structure and the distance between the horizontal parts in the two T-shaped electrode structures is 0.1 μm - 100 μm.

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