CN113721376A - Light-operated terahertz optical fiber modulator and light amplitude modulation method thereof - Google Patents

Light-operated terahertz optical fiber modulator and light amplitude modulation method thereof Download PDF

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CN113721376A
CN113721376A CN202110863050.2A CN202110863050A CN113721376A CN 113721376 A CN113721376 A CN 113721376A CN 202110863050 A CN202110863050 A CN 202110863050A CN 113721376 A CN113721376 A CN 113721376A
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terahertz
light
graphene
optical fiber
metamaterial
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CN113721376B (en
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关贺元
卢惠辉
陈立均
吴岱
李鹏
丘文涛
陈哲
王建新
韩鑫洋
明经渊
梁爱杰
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Jinan University
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    • G—PHYSICS
    • G02—OPTICS
    • 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
    • G02F1/01—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 for the control of the intensity, phase, polarisation or colour 
    • G02F1/0126—Opto-optical modulation, i.e. control of one light beam by another light beam, not otherwise provided for in this subclass
    • G—PHYSICS
    • G02—OPTICS
    • 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
    • G02F1/01—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 for the control of the intensity, phase, polarisation or colour 
    • G02F1/011—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 for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass
    • G02F1/0115—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 for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass in optical fibres
    • G02F1/0118—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 for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass in optical fibres by controlling the evanescent coupling of light from a fibre into an active, e.g. electro-optic, overlay
    • G—PHYSICS
    • G02—OPTICS
    • 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
    • G02F2203/00—Function characteristic
    • G02F2203/13—Function characteristic involving THZ radiation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Nonlinear Science (AREA)
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  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

The invention discloses a light-operated terahertz optical fiber modulator and a light amplitude modulation method thereof, wherein the light-operated terahertz optical fiber modulator comprises: the terahertz optical fiber is used for transmitting terahertz waves, a polishing area is arranged on the side edge of the terahertz optical fiber, and the end face of the terahertz optical fiber, provided with the polishing area on the side edge, is D-shaped; and arranging a metamaterial with a micro-nano structure on the polishing area, and arranging graphene on the metamaterial to form a graphene-metamaterial structure as a light modulation structure. According to the invention, the terahertz optical fiber structure is polished at the side edge, so that the loss of terahertz waves in a free space can be effectively reduced, the contact area between graphene and a terahertz wave evanescent field is increased, and the modulation efficiency is improved. According to the invention, the graphene is used as a modulation medium substance, so that the modulation characteristic of the terahertz modulator can be effectively improved. In a terahertz waveband, a nano periodic structure prepared by adopting a metamaterial has a high resonance factor. The interaction of the metamaterial and the terahertz light is effectively enhanced through resonance enhancement.

Description

Light-operated terahertz optical fiber modulator and light amplitude modulation method thereof
Technical Field
The invention relates to the technical field of terahertz wave modulation, in particular to a light-operated terahertz optical fiber modulator and a light amplitude modulation method thereof.
Background
The terahertz wave is a section of electromagnetic wave with the frequency range of 0.1-10 THz, and the wavelength of the terahertz wave is 3 mm-30 um. In the electromagnetic spectrum, terahertz waves lie between microwaves and far infrared radiation. Since the microwave frequency is the upper limit of the electronic frequency and the far infrared radiation frequency is the lower limit of the optical frequency, it can also be said that the terahertz wave lies between the electronic and optical wavelength ranges. Terahertz science is an emerging interdisciplinary subject spanning macroscopic electronics and microscopic photonics, and links up a macroscopic classical electromagnetic wave theory and a microscopic quantum theory. The terahertz covers characteristic spectral lines of various vibrations including condensed substances and biomacromolecules, so that the terahertz is very suitable for identifying the structure and the variety of substances; meanwhile, the photon energy of the terahertz wave is low, the biological tissue cannot be damaged, and the terahertz wave can be applied to biological living body detection. Just because the terahertz wave has special position and excellent performance in the electromagnetic spectrum, the terahertz technology has important academic value and huge application prospect in the research fields of electronics, information, communication, life, aerospace and the like.
An important technology in terahertz technology is terahertz amplitude regulation. The terahertz wave is further developed, and an excellent high-speed terahertz regulation and control technology is particularly important. Terahertz amplitude modulation techniques can be divided into: an electric control modulation technology, a light control modulation technology, a temperature control modulation technology, a magnetic control modulation technology and the like. The light-operated modulation technology can avoid the influence of parasitic impedance in the electric control technology, provides a new idea for realizing rapid modulation, and has great application potential. The conventional light-operated graphene terahertz amplitude modulator adopts a spatial light modulation mode, graphene is integrated on a semiconductor substrate, terahertz waves and pump light (visible light or near infrared light) are incident in a mode perpendicular to the graphene, semiconductor materials generate photon-generated carriers, terahertz waves are absorbed, and modulation of the terahertz light is finally achieved. However, the conventional graphene optical control terahertz optical fiber modulator has the following problems: (1) terahertz light and external pump light directly and vertically irradiate the modulator, and the required optical power is higher; (2) the interaction length of the vertical incident light and the substance is short, so that the improvement of modulation depth is limited; (3) the electric control mode is influenced by a large resistance-capacitance time constant; (4) terahertz light is modulated in free space, however, terahertz light is transmitted in free space and can be strongly absorbed by water molecules in air, and the loss of terahertz waves is high.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a light-operated terahertz optical fiber modulator and a light amplitude modulation method thereof, so as to solve the problems of low modulation depth, low modulation speed and high terahertz wave loss caused by free space modulation of the traditional light-operated terahertz optical fiber modulator.
The purpose of the invention is realized by the following technical scheme:
an optically controlled terahertz fiber modulator comprising: the terahertz optical fiber is used for transmitting terahertz waves, a polishing area is arranged on the side edge of the terahertz optical fiber, and the end face of the terahertz optical fiber, provided with the polishing area on the side edge, is D-shaped; and the polishing area is provided with a light modulation structure.
Preferably, the polishing area is provided with a metamaterial with a micro-nano structure, and the metamaterial is provided with graphene to form a graphene-metamaterial structure as a light modulation structure.
Preferably, the metamaterial is a metal material or a semiconductor material, and the thickness of the metamaterial is 100-1000 nm.
Preferably, the depth of the polishing area is 30-600 um, and the length of the polishing area is 5-30 mm.
Preferably, the metamaterial is a periodic structure arranged in a patterned array, and the pattern is any one of a stripe column, a square column, a cylinder and a ring column.
Preferably, the graphene is a monolayer or N-layer, N > 1.
Preferably, the diameter of the terahertz optical fiber is 100-2000 um, the material of the terahertz optical fiber is cycloolefin polymer, and an air hole is formed in the middle area of the terahertz optical fiber.
A light amplitude modulation method of a light-operated terahertz optical fiber modulator comprises the following steps: the terahertz waves are incident from one end of the terahertz optical fiber and leak from the polishing area to form an evanescent field, and the evanescent field interacts with the graphene-metamaterial; meanwhile, pump light irradiates a polishing area from the side, the pump light irradiates on the metamaterial to be excited to generate photoacoustic carrier concentration, the photoacoustic carrier concentration is diffused to graphene, the Fermi level of the graphene is improved, the absorption characteristic of the graphene to terahertz light is enhanced, and the amplitude of the terahertz light is modulated efficiently by changing the wavelength and/or power of the pump light.
Preferably, the light amplitude modulation method further includes: the terahertz waves leak out from the side polishing area of the terahertz optical fiber, and the interaction between the terahertz waves and graphene is enhanced under the resonance enhancement of the metamaterial; the length of the side polishing area is larger than the terahertz wavelength and the thickness of graphene, so that the action time of terahertz waves and graphene is prolonged; the external pumping light changes the conductivity of the terahertz surface of the graphene, the metamaterial enhances the action of the graphene and the external pumping light, the absorption of the graphene on terahertz waves is enhanced, and efficient terahertz modulation is finally achieved.
Compared with the prior art, the invention has the following advantages:
according to the invention, the terahertz optical fiber structure is polished at the side edge, so that the loss of terahertz waves in a free space can be effectively reduced, the contact area between graphene and a terahertz wave evanescent field is increased, and the modulation efficiency is improved. When the pump light irradiates, the micro-nano structure couples the pump light into the metamaterial, the local electric field enhancement effect of the micro-nano structure can effectively excite photon-generated carriers in the metamaterial, and a large number of photon-generated carriers diffuse into graphene, so that the Fermi level of the graphene is improved, and the modulation effect is enhanced. In a terahertz waveband, a nano periodic structure prepared by adopting a metamaterial has a high resonance factor. The interaction of the metamaterial and the terahertz light is effectively enhanced through resonance enhancement. Therefore, the terahertz wave modulator can effectively solve the problem of terahertz wave loss of other free space terahertz modulators, obtains excellent performance of large modulation depth, high modulation rate and low pump light power, and has outstanding and obvious technical effects.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic structural diagram of an optically controlled terahertz optical fiber modulator according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of an end face of a terahertz optical fiber according to an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a terahertz optical fiber provided with a polished region at a side edge according to an embodiment of the present invention.
Fig. 4 (a) is a top view of a metamaterial having a micro-nano structure according to an embodiment of the present invention.
Fig. 4 (b) is a cross-sectional view of an end face of a terahertz optical fiber provided with a polished region on a side edge thereof according to an embodiment of the present invention.
Fig. 5 is a schematic structural diagram of single-layer graphene according to an embodiment of the present invention.
Fig. 6 is a diagram of a working system of the optically controlled terahertz optical fiber modulator according to the embodiment of the present invention.
Fig. 7 is a frequency domain diagram of an output of the optical terahertz fiber modulator according to the embodiment of the present invention.
Icon: 1-a terahertz optical fiber; 2-a metamaterial; 3-single layer graphene; 4-pump light; 5-air holes; 6-terahertz light source; 7-pump light laser; 8-terahertz detection system.
Detailed Description
The invention is further illustrated by the following figures and examples.
Referring to fig. 1 to 3, (a) of fig. 4, (b) of fig. 4, and fig. 5, an optically controlled terahertz optical fiber modulator includes: the terahertz fiber comprises a terahertz fiber 1 for transmitting terahertz waves, wherein a polishing area is arranged on the side edge of the terahertz fiber 1, and the end face of the terahertz fiber 1, on which the polishing area is arranged, is D-shaped; the polishing and grinding area is provided with a metamaterial 2 with a micro-nano structure, the metamaterial 2 is provided with graphene 3 to form a graphene-metamaterial structure as a light modulation structure, the graphene 3 is a single layer or N layers (few layers), and N is greater than 1. The metamaterial 2 enhances the interaction of the external pump light 4 and the graphene 3 and also enhances the interaction of the terahertz waves and the graphene 3, so that a large modulation depth is obtained. The contact area between the graphene-metamaterial and the terahertz evanescent field can be increased by polishing the flat area on the side edge.
In this embodiment, the polished area of the terahertz fiber 1 is obtained by a physical or chemical side polishing method, and the fiber cladding and the fiber core in a certain length area are removed to make a special fiber structure with a D-shaped end surface. The flat polishing surface (polishing area) of the side polishing optical fiber forms a leakage window for transmitting light in the fiber core, and evanescent field energy is easy to leak out of the polishing area and interacts with the graphene-metamaterial. The depth of the polishing area is 30-600 um, the length of the polishing area is 5-30 mm, the sufficient side polishing length and the sufficient side polishing depth fully increase the contact area of the terahertz waves and the surface of the metamaterial 2, the utilization efficiency of photon-generated carriers is effectively improved, and therefore the terahertz waves are well modulated. The parameters of the fiber wheel type side edge polishing and grinding machine are adjusted, the length and the depth of a polishing and grinding area are changed, the length of the polishing and grinding area is longer, and the effect of leaked terahertz waves and a polishing and grinding surface structure is stronger. In summary, the lateral polishing terahertz optical fiber 1 adopted in the embodiment of the invention can effectively reduce the transmission loss of terahertz waves, and in addition, the interaction between the terahertz waves and the metamaterial 2 on the polishing area can be effectively enhanced by changing the length and the depth of the lateral polishing.
In this embodiment, the terahertz fiber 1 is a micro-structured fiber for transmitting terahertz waves, and the diameter of the terahertz fiber 1 is 100 to 2000 um. The material of the terahertz optical fiber 1 is cycloolefin polymer, and the middle area is an air hole 5. The diameter of the optical fiber is 1mm, and the optical fiber is suitable for transmitting terahertz waves with the frequency of 0.1-2.5 THz. The terahertz waves are strongly absorbed by water molecules in free space, so that the transmission loss of the terahertz waves is large. Therefore, the proper waveguide is adopted to transmit the terahertz waves, the loss of the terahertz waves can be effectively reduced, and the absorption coefficient of the optical fiber to the terahertz waves is lower than 3cm-1The water absorption is less than 0.01%. By adopting the terahertz optical fiber 1, the terahertz wave loss problem of other free space terahertz modulators can be effectively solved.
The metamaterial 2 is a periodic structure arranged in a graphical array, and the graph is any one of a strip column, a square column, a cylinder, an annular column and a polygonal column. In visible light and near-infrared wave bands, the micro-nano structure generates a strong local electric field enhancement effect, and the local electric field enhancement effect can effectively enhance the interaction between light and graphene 3. The metamaterial 2 has a high resonance factor in the terahertz waveband. The reasonable micro-nano structure of the metamaterial 2 can effectively enhance the interaction between the external pump light 4 and the terahertz wave and the graphene 3, and reduce the modulation power required by the external pump light 4. The metamaterial 2 is made of a metal material or a semiconductor material, and the thickness of the metamaterial 2 is 100-1000 nm. The semiconductor material is silicon or germanium, and in this embodiment, the metamaterial 2 is a gold cylinder, and the arrangement of the gold cylinder is a periodic structure. The 800nm golden cylinder structure is prepared by oblique incidence deposition technology. The metamaterial 2 has many novel characteristics in the optical field, and the nano-scale microstructure of the metamaterial can generate obvious anisotropic modulation on incident light waves, so that the structure has birefringence characteristics similar to those of anisotropic crystal materials.
In this embodiment, the ultra-fast modulation rate can be obtained by using the graphene 3 with ultra-high electron mobility. The terahertz wave can be effectively regulated and controlled under the excitation of the pump light 4. Specifically, as shown in fig. 5, the two-dimensional material graphene 3 is adopted as the modulation mediator substance in the technical solution of the present invention. The two-dimensional material graphene 3 has a unique structure, and has excellent performance when being applied to the preparation of a light-operated terahertz amplitude modulation device:
(1) the graphene 3 has good response to visible light, near infrared light and terahertz light, and the carrier concentration of the graphene 3 can be effectively modulated by adopting the visible pump light and the near infrared pump light 4, so that the absorption characteristic of the graphene 3 on the terahertz light is changed, and the amplitude of the terahertz light is modulated efficiently;
(2) the light-operated response time of the graphene 3 is 1 ps;
(3) the graphene 3 has ultrahigh thermal conductivity, so that heat accumulation can be reduced, and thermal damage can be reduced.
Graphene 3 has a number of unique advantages over other materials: (1)106cm2V · s, fast response; (2) the conductivity of the graphene 3 can be modulated by external modulation, such as changing the gate voltage and adding external pump light 4. In general, the absorption of an electromagnetic wave can be described in terms of the imaginary part of the material's dielectric constant, which is related to the real part of the material's surface conductivity. The surface conductivity of the graphene 3 is formed by the intra-band transition conductivity and the inter-band conductivity, and the expression is as follows:
σgraphene(ω)＝σintra(ω)+σinter(ω)
in the formula sigmaintra(omega) and sigmainterAnd (ω) indicates the in-band and inter-band conductivities, respectively. The in-band conductivity is simplified to Drude model, and the conductivity is:
Figure RE-GDA0003318278450000071
wherein E, EFAnd h are the electron charge, fermi level, and planck constant, respectively. τ is the carrier relaxation time of graphene 3 due to scattering. Photon energy higher than 2E in near infrared and visible light rangeFThe graphene 3 conductivity is mainly controlled by the band-to-band conductivity. In the terahertz wave band, the photon energy is lower than 2EFThe 3-interband transition of graphene is forbidden, and the surface conductivity is mainly determined by the interband transition. The terahertz waves are normally incident to the single-layer or few-layer graphene 3 prepared by the CVD method, and the terahertz wave absorption rate of the graphene 3 can reach nearly 40%. When the interlayer metamaterial 2 is not considered in the embodiment of the invention, and only the structures of the single-layer or few-layer graphene 3 and the lateral polished terahertz optical fiber 1 are considered, and then the pump light 4 is added, the terahertz surface conductivity of the graphene 3 is expressed as:
σpump(ω)＝σnopump(ω)-Δσ(ω)
here σnopump(ω) i.e. graphene 3 in-band conductivity as described above simplifies the Drude model. Δ σ (ω) changes in surface conductivity caused by the external pump light 4. When the light intensity of the near-infrared or visible light pump light 4 reaches a certain range, the surface conductivity of the graphene 3 can be changed, and therefore the purpose that the terahertz waves are absorbed and modulated by the graphene 3 is achieved.
The manufacturing process of the light-operated terahertz optical fiber modulator of the embodiment is as follows:
the terahertz optical fiber 1 with polished side edge is selected and fixed on a transfer substrate, meanwhile, a mask is fixed on the side polished surface of the terahertz optical fiber 1, gold columns of 800nm are stacked by an inclined deposition method and are arranged into I-shaped gold cylindrical metamaterials 2 with the length of 10um according to a periodic structure, gold is directly deposited in the polished area of the terahertz optical fiber 1 through a hole structure of the mask, a photoetching process is not needed, and therefore chemical pollution is avoided. The electron beam evaporation inclined deposition method is adopted, the proper uniform nano-structure gold cylinder is selected through substrate rotation and inclination angle control, parameters such as temperature, vacuum degree and air pressure in the incident process are strictly controlled, and finally the shape of the metamaterial 2 is effectively improved through an annealing process. The graphene 3 film with the circumference is formed by growing on a copper foil through a Chemical Vapor Deposition (CVD) method, the process can generate few layers or multiple layers of graphene 3, the graphene 3 is etched into the same size and shape through femtosecond laser, and finally the graphene 3 is transferred to the gold cylindrical metamaterial 2 through wet transfer.
Referring to fig. 6, a light amplitude modulation method of the light-controlled terahertz optical fiber modulatorA method, comprising: the terahertz waves are incident from one end of the terahertz optical fiber 1 and leak from the polishing area to form an evanescent field, and the evanescent field interacts with the graphene-metamaterial; meanwhile, the pump light 4 irradiates the polishing area from the side, the pump light 4 irradiates the metamaterial 2 to be excited to generate the concentration of the photoacoustic carriers, the concentration of the photoacoustic carriers is diffused to the graphene 3, the Fermi level of the graphene 3 is improved, the absorption characteristic of the graphene 3 to the terahertz light is enhanced, and the amplitude of the terahertz light is efficiently modulated by changing the wavelength and/or the power of the pump light 4. On one hand, the metamaterial 2 has sensitive photoelectric sensing capacity, a large number of photon-generated carrier electron hole pairs can be generated under the excitation of low-power near-infrared pump light 4, a foundation is laid for efficient terahertz amplitude regulation, in addition, the graphene 3 material has good mobility through calculation of a graphene 3 material Drude model, namely the carrier concentration and the conductivity of the graphene 3 film 3 can be increased through the injection of a small amount of electrons and holes, and the modulation depth is further improved. In addition, the modulator adopts a side-polished fiber 1 structure, as shown in fig. 7, which is a transmission diagram of the embodiment, and adopts a finite element method to modulate the single-layer graphene-metamaterial to receive the pump light 4 with different powers, and as can be seen from fig. 7, the single-layer graphene-metamaterial is selected respectively, without adding the graphene 3, with adding the graphene 3, and with 0.32mJ/cm2When the pump light 4 is used, the resonant frequency of the graphene-metamaterial and the terahertz wave is changed, the formed transmission spectrum is reduced, and the modulation depth is increased.
Specifically, the terahertz waves leak out from the side polishing area of the terahertz optical fiber 1, interaction between the terahertz waves and the graphene 3 is enhanced under the resonance enhancement of the metamaterial 2, the length of the side polishing area is far larger than the wavelength of the terahertz waves and the thickness of the graphene 3, and the acting time of the terahertz waves and the graphene 3 is effectively prolonged. The external pump light 4 intervenes to cause the terahertz surface conductivity of the graphene 3 to change, and the metamaterial 2 further enhances the effects of the graphene 3 and the external pump light 4, so that the absorption of the graphene 3 on terahertz waves is further enhanced. Under the combined action of the four, a high-efficiency terahertz modulator is finally realized.
As can be seen from the above. The invention can effectively solve the problem of terahertz wave loss of other free space terahertz modulators, obtains the graphene-metamaterial-based enhanced light-operated terahertz optical fiber modulator with high modulation depth, high modulation rate and low pump light 4 power excellent performance, and has outstanding and obvious technical effects.
The above-mentioned embodiments are preferred embodiments of the present invention, and the present invention is not limited thereto, and any other modifications or equivalent substitutions that do not depart from the technical spirit of the present invention are included in the scope of the present invention.

Claims (9)

1. An optically controlled terahertz fiber modulator, comprising: the terahertz optical fiber is used for transmitting terahertz waves, a polishing area is arranged on the side edge of the terahertz optical fiber, and the end face of the terahertz optical fiber, provided with the polishing area on the side edge, is D-shaped; and the polishing area is provided with a light modulation structure.
2. The light-operated terahertz optical fiber modulator of claim 1, wherein a metamaterial with a micro-nano structure is arranged on the polishing area, and graphene is arranged on the metamaterial to form a graphene-metamaterial structure as a light modulation structure.
3. The light-operated terahertz optical fiber modulator of claim 2, wherein the metamaterial is a metal material or a semiconductor material, and the thickness of the metamaterial is 100-1000 nm.
4. The light-operated terahertz optical fiber modulator of claim 3, wherein the depth of the polished area is 30-600 um, and the length of the polished area is 5-30 mm.
5. The light-operated terahertz optical fiber modulator of claim 2, wherein the metamaterial is a periodic structure arranged in a patterned array, and the structure is any one of a stripe column, a square column, a cylinder, an annular column and a polygonal column.
6. The optically controlled terahertz fiber modulator of claim 2, wherein the graphene is a single layer or N-layer, N > 1.
7. The light-operated terahertz optical fiber modulator according to claim 1, wherein the diameter of the terahertz optical fiber is 100-2000 um, the material of the terahertz optical fiber is a cyclic olefin polymer, and the middle region of the terahertz optical fiber is an air hole.
8. A light amplitude modulation method of a light-operated terahertz optical fiber modulator is characterized by comprising the following steps: the terahertz waves are incident from one end of the terahertz optical fiber and leak from the polishing area to form an evanescent field, and the evanescent field interacts with the graphene-metamaterial; meanwhile, pump light irradiates the polishing area from the side, the pump light irradiates the metamaterial to be excited to generate photon-generated carriers, the photon-generated carriers are diffused to the graphene, the Fermi level of the graphene is improved, the absorption characteristic of the graphene to terahertz light is enhanced, and the wavelength and/or power of the pump light are changed to finally realize efficient broadband modulation of the amplitude of the terahertz light.
9. The optical amplitude modulation method according to claim 8, further comprising: the terahertz waves leak out from the side polishing area of the terahertz optical fiber, and the interaction between the terahertz waves and graphene is enhanced under the resonance enhancement of the metamaterial; the contact area between the side-polished terahertz optical fiber evanescent field and the graphene-metamaterial is increased, and the action time of terahertz waves and graphene is prolonged; the external pumping light changes the conductivity of the terahertz surface of the graphene, the metamaterial enhances the action of the graphene and the external pumping light, the absorption of the graphene on terahertz waves is enhanced, and efficient terahertz modulation is finally achieved.
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