CN109856820B - On-chip terahertz wave amplitude modulator based on fin line nested artificial microstructure - Google Patents
On-chip terahertz wave amplitude modulator based on fin line nested artificial microstructure Download PDFInfo
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Abstract
The invention discloses an on-chip terahertz wave amplitude modulator based on a fin line nested artificial microstructure, and belongs to the technical field of electromagnetic functional devices. The invention comprises a rectangular waveguide, a fin line, an external bias filter circuit, a first dielectric substrate and a second dielectric substrate; the input end and the output end of the rectangular waveguide are connected by a fin line, and the fin line comprises a waveguide-fin line transition part, a middle transmission area and a fin line-waveguide transition part; the fin line modulation part is positioned in the middle transmission area and comprises two modulation units, and each modulation unit comprises an artificial microstructure and an HEMT diode; the external bias filter circuit comprises a filter input end, a compact microstrip resonance unit and a filter output end, and the filter output end is connected with the fin line through a bonding line. The modulator has large modulation bandwidth and modulation depth, and can work under the conditions of normal temperature, normal pressure and non-vacuum, so the modulator has good practical application prospect.
Description
Technical Field
The invention belongs to the technical field of electromagnetic functional devices, and particularly relates to an on-chip terahertz wave amplitude modulator based on a fin line nested artificial microstructure.
Background
The terahertz wave state functional device is one of core technologies in a terahertz communication system, and is now the key point in the field of terahertz scientific and technical research. Compared with microwaves, the terahertz waves have higher frequency, so that when the terahertz waves are used as communication carriers, more information can be carried in unit time, and the emission directivity of the terahertz waves is better than that of the microwaves due to the shorter wavelength of the terahertz waves. The research hot tide of terahertz scientific technology is formed worldwide. Since 2004, a plurality of terahertz modulator articles are published in the international natural Science top-level publication such as Nature/Science, the modulation function of the modulator is generally designed based on semiconductor materials, and since the conductivity of the semiconductor materials is sensitive to the applied laser, electric field, temperature and other variables, the modulation function can be achieved by changing the conductivity at a certain position in such a way that the related frequency, amplitude and phase are influenced.
The electronic information industry is an important pillar of the current national economy, and the microelectronic technology is an important foundation of the electronic information industry. Since the end of the 20 th century, third-generation wide bandgap semiconductor materials represented by gallium nitride (GaN) and silicon carbide (SiC) have wide bandgap, high breakdown voltage, high electronic saturation rate, radiation resistance and the like, and thus have wide application prospects in civilian fields such as communication, radar, aviation, internet of things and the like and military fields such as aerospace, electronic equipment and the like. At present, the wide bandgap microwave semiconductor device mainly comprises a SiC device and a GaN device. Later, with the breakthrough of heteroepitaxy technology, GaN HEMT devices have been developed dramatically. The GaN HEMT device not only has the advantage of the inherent characteristics of GaN materials, but also has the more important that the electron transport characteristics of the A1GaN/GaN heterojunction are obviously improved due to the high-concentration two-dimensional electron gas (2-DEG) formed by spontaneous polarization and piezoelectric polarization, and the electron mobility exceeds 2000cm2/V & s. Therefore, the GaN HEMT device has higher radio frequency power output capability. The above advantages of the gan hemt device make it a very important position in the new generation of solid state devices.
Metamaterials (Metamaterials) are artificial composite structures or composite media with extraordinary physical properties not found in natural media, which are often derived from structures other than constituent elements. Since the working frequency of the metamaterial is related to the structural design, the working frequency of the metamaterial can be easily adjusted. People combine novel material through the metamaterial structure of designing not unidimensional, and the external factor of artificial control changes and then adjusts and control terahertz wave transmission, combines together through based on HEMT structure and artifical metamaterial structure, can prepare automatically controlled effective high-speed terahertz modulator, has very big application potential in the wireless communication of terahertz.
Disclosure of Invention
The invention aims to provide an on-chip terahertz wave amplitude modulator based on a fin line nested artificial microstructure, which realizes the control of an electromagnetic resonance mode in an artificial electromagnetic resonance unit structure by controlling the electromagnetic characteristic of a HEMT diode through voltage application, so that terahertz waves transmitted in a fin line-waveguide are subjected to amplitude modulation.
The technical problem proposed by the invention is solved as follows:
an on-chip terahertz wave amplitude modulator based on a fin line nested artificial microstructure comprises a rectangular waveguide, a fin line, an external bias filter circuit 5, a first dielectric substrate and a second dielectric substrate; the upper surface and the lower surface of the first dielectric substrate and the second dielectric substrate are plated with metal layers, and the first dielectric substrate and the second dielectric substrate are in the same horizontal position and are connected in a T shape; the width of the first dielectric substrate is larger than that of the rectangular waveguide, and the first dielectric substrate penetrates through the cavity wall of the rectangular waveguide and is placed on the long side (E surface) of the rectangular waveguide;
the input end 1 and the output end 4 of the rectangular waveguide are connected by a fin line, and the fin line is etched on the upper surface of the first dielectric substrate; two gaps vertical to the fin lines are etched on one side of the middle part of the fin lines, and a rectangular metal coating layer (bonding region) is formed between the two gaps; the fin line comprises a waveguide-fin line transition part 2, an intermediate transmission area and a fin line-waveguide transition part; the fin line modulation part 3 is positioned in the middle transmission region and comprises two modulation units, wherein each modulation unit comprises an artificial microstructure 6 and an HEMT diode 7; the artificial microstructure 6 is an I-shaped resonance unit, and the HEMT diode 7 is positioned in the middle of a longitudinal metal rod of the I-shaped resonance unit; the HEMT diode 7 comprises two electrodes 8 and a doped heterojunction 9, wherein the doped heterojunction 9 is connected with the longitudinal metal rod of the I-shaped resonance unit through the two electrodes 8; the upper section and the lower section of the longitudinal metal rod of the adjacent I-shaped resonance unit are respectively connected through two metal wires, the two metal wires are respectively connected with the two sides of the fin line through short branches, one metal wire is grounded, and the other metal wire is connected with the rectangular metal coating layer;
the rectangular waveguide is provided with a rectangular air window at the joint of the first dielectric substrate and the second dielectric substrate, and the width of the rectangular air window is more than or equal to that of the external bias filter circuit 5; the external bias filter circuit 5 is etched on the upper surface of the second dielectric substrate; the external bias filter circuit comprises a filter input end, a Compact microstrip resonance unit (CMRC) and a filter output end; the filter input end and the filter output end are microstrip lines; the width of the filter output end is the same as that of the rectangular metal coating layer; the filtering output end is connected with the rectangular metal coating layer through a bonding wire.
The upper surface of the first dielectric substrate coincides with the middle of the long side (E-plane) of the rectangular waveguide.
The upper edge of the waveguide-fin line transition part 2 extends from the wide edge of the rectangular waveguide input end 1 to the upper edge of the fin line modulation part in a curve mode, and the lower edge of the waveguide-fin line transition part 2 extends from the wide edge of the rectangular waveguide input end 1 to the lower edge of the fin line modulation part in a curve mode.
The material of the first dielectric substrate is SiC or sapphire.
The material of the second dielectric substrate is SiO2。
The doped heterojunction 9 is made of AlGaN/GaN, InGaN/GaN, AlGaAs/GaAs, AlGaAs/InGaAs, or AlGaAs/InGaAs/InP, and the oblique lines indicate the combination of two or three materials.
The electrode 8 is made of Ti, Al, Ni or Au.
The artificial microstructure 6 and the metal wire are made of Au, Ag, Cu or Al.
The rectangular waveguide has dimensions WR2.8, with a specific size of 0.356mm by 0.711 mm.
The on-off state of the HEMT diode is controlled by loading a voltage signal through the external bias filter circuit, so that the resonance state of the artificial microstructure is controlled, and amplitude modulation of terahertz waves transmitted inside the rectangular waveguide is realized.
The invention has the beneficial effects that:
the invention utilizes the high electron mobility characteristic of two-dimensional electron gas in the HEMT diode to rapidly control the resonance characteristic of the artificial electromagnetic medium, thereby realizing rapid modulation of terahertz waves. Through the ingenious design of the resonant structure and the organic combination of the resonant structure and the transistor, the structure has strong plasticity: the size of the modulation bandwidth and the position of the modulation frequency band can be effectively adjusted by changing the parameters of the resonance unit (such as the length of the transverse bar and the longitudinal bar of the I-shaped bar). The modulation unit formed by Meta materials design is a two-dimensional plane structure, can be realized by a micro-machining means, has mature process and easy manufacture, and avoids high-difficulty machining caused by a design scheme of a complex three-dimensional structure. The modulator has large modulation bandwidth and modulation depth, and the device can work under the conditions of normal temperature, normal pressure and non-vacuum, so that the modulator has good practical application prospect.
Drawings
Fig. 1 is a schematic diagram of an overall structure of a terahertz wave amplitude modulator according to the present invention;
FIG. 2 is a schematic structural view of a fin line according to the present invention;
FIG. 3 is a schematic diagram of a modulation unit according to the present invention;
FIG. 4 is a schematic diagram of an external bias filter circuit according to the present invention;
FIG. 5 is a schematic diagram of the transmission state of a fin line when no voltage is applied (HEMT is on) in the modulator according to the embodiment;
FIG. 6 is a simulation graph of the transmission curve when a voltage is applied (HEMT cut) in the modulator according to the embodiment;
FIG. 7 is a simulation diagram of the transmission curve of the modulator according to the embodiment when no voltage is applied (HEMT is on);
fig. 8 is a simulation diagram of the transmission curve when a voltage is applied (HEMT cut) in the modulator according to the embodiment.
Detailed Description
The invention is further described below with reference to the figures and examples.
The embodiment provides an on-chip terahertz wave amplitude modulator based on a fin line nested artificial microstructure, the overall structure schematic diagram of which is shown in fig. 1, and the modulator comprises a rectangular waveguide, a fin line, an external bias filter circuit 5, a first dielectric substrate and a second dielectric substrate; the size of the rectangular waveguide is WR2.8, and the specific size is 0.356mm by 0.711 mm; the upper surface and the lower surface of the first dielectric substrate and the second dielectric substrate are plated with metal layers, and the first dielectric substrate and the second dielectric substrate are in the same horizontal position and are connected in a T shape; the material of the first dielectric substrate is SiC, and the material of the second dielectric substrate is SiO 2; the width of the first dielectric substrate is larger than that of the rectangular waveguide, and the first dielectric substrate penetrates through the cavity wall of the rectangular waveguide and is placed on the long side (E surface) of the rectangular waveguide; the upper surface of the first dielectric substrate is superposed with the middle part of the long side (E surface) of the rectangular waveguide;
the input end 1 and the output end 4 of the rectangular waveguide are connected by a fin line, and the fin line is etched on the upper surface of the first dielectric substrate (at the moment, the rest part with the metal coating is a grounding fin); the fin line is symmetrical about a vertical central axis, the structural schematic diagram of the fin line is shown in fig. 2, two gaps perpendicular to the fin line are etched on one side of the middle of the fin line, the width of each gap is 15 micrometers, and a rectangular metal coating layer (bonding region) is formed between the two gaps; the fin line comprises a waveguide-fin line transition part 2, an intermediate transmission area and a fin line-waveguide transition part; the fin line modulation part 3 is positioned in the middle transmission region and comprises two modulation units, the structural schematic diagram of the modulation units is shown in fig. 3, and each modulation unit comprises an artificial microstructure 6 and an HEMT diode 7; the artificial microstructure 6 is an I-shaped resonance unit, and the HEMT diode 7 is positioned in the middle of a longitudinal metal rod of the I-shaped resonance unit; the HEMT diode 7 comprises two electrodes 8 and a doped heterojunction 9, wherein the doped heterojunction 9 is connected with the longitudinal metal rod of the I-shaped resonance unit through the two electrodes 8, and the length of the electrodes is about 10 mu m; the upper section and the lower section of the longitudinal metal rod of the adjacent I-shaped resonance unit are respectively connected through two metal wires, the two metal wires are respectively connected with the two sides of the fin line through short branches, the distance between the metal wires and the electrodes is about 40 mu m, one metal wire is connected with the grounding fin and grounded through the wall of the rectangular waveguide cavity, and the other metal wire is connected with the rectangular metal coating layer (bonding region); the two metal wires are symmetrical about a horizontal central axis of the middle transmission area;
the rectangular waveguide is provided with a rectangular air window at the joint of the first dielectric substrate and the second dielectric substrate, and the width of the rectangular air window is more than or equal to that of the external bias filter circuit 5; the external bias filter circuit 5 is etched on the upper surface of the second dielectric substrate, and the schematic structural diagram thereof is shown in fig. 4; the external bias filter circuit comprises a filter input end, a Compact Microstrip resonance unit (CMRC) and a filter output end which are connected in sequence; the filter input end and the filter output end are microstrip lines; the width of the filter output end is the same as that of the rectangular metal coating layer; the filtering output end is connected with the rectangular metal coating layer through a bonding wire.
The working mechanism of the modulator is that the concentration of two-dimensional electron gas in the HEMT diode is controlled through external voltage, so that the resonance state of the artificial microstructure is controlled, and the on-off characteristic of a fin line transmission part is controlled. The specific modulation process is as follows: the cathode (ohmic contact) in the modulator is connected to one side of the fin line by a grounding wire and to ground through the wall of the cavity, while the anode (schottky contact) is applied with a voltage through an external bias filter circuit.
When the difference between the positive voltage and the negative voltage is 0V, the HEMT diode is in a conducting state, the HEMT diode in the "i" structure is communicated into a whole through the HEMT diode, the resonator is in a working state at the moment, the resonant frequency of the structure is 0.34THz, and as can be seen from fig. 5 and 7, the resonance can block the transmission of terahertz waves, so that the terahertz waves at the frequency cannot be transmitted through the fin line at the moment. When the voltage difference between the positive voltage and the negative voltage is 4-10V, in the process that the applied voltage difference is gradually increased from zero, the concentration of the two-dimensional electron gas in the HEMT diode is gradually reduced until the two-dimensional electron gas in the HEMT diode is exhausted, the HEMT diode is in a pinch-off state, at the moment, the electrodes of the I-shaped resonator are in a disconnected state, as can be seen from fig. 6 and 8, the resonator is in a non-working state, and at the moment, the terahertz wave of 0.34THz can be transmitted to the output waveguide through the fin line.
The modulator can achieve the modulation depth of more than 95% and the transmission bandwidth of 20GHz, and the insertion loss of the terahertz waves can be smaller than-1.0B.
Claims (10)
1. An on-chip terahertz wave amplitude modulator based on a fin line nested artificial microstructure is characterized by comprising a rectangular waveguide, a fin line, an external bias filter circuit (5), a first dielectric substrate and a second dielectric substrate; the upper surface and the lower surface of the first dielectric substrate and the second dielectric substrate are plated with metal layers, and the first dielectric substrate and the second dielectric substrate are in the same horizontal position and are connected in a T shape; the width of the first dielectric substrate is larger than that of the rectangular waveguide, and the first dielectric substrate penetrates through the cavity wall of the rectangular waveguide and is placed on the long side of the rectangular waveguide;
the input end (1) and the output end (4) of the rectangular waveguide are connected by a fin line, and the fin line is etched on the upper surface of the first dielectric substrate; two gaps perpendicular to the fin lines are etched on one side of the middle of the fin lines, and a rectangular metal coating layer is formed between the two gaps; the fin line comprises a waveguide-fin line transition part (2), an intermediate transmission area and a fin line-waveguide transition part; the fin line modulation part (3) is positioned in the middle transmission area and comprises two modulation units, and each modulation unit comprises an artificial microstructure (6) and an HEMT diode (7); the artificial microstructure (6) is an I-shaped resonance unit, and the HEMT diode (7) is positioned in the middle of a longitudinal metal rod of the I-shaped resonance unit; the HEMT diode (7) comprises two electrodes (8) and a doped heterojunction (9), wherein the doped heterojunction (9) is connected with the longitudinal metal rod of the I-shaped resonance unit through the two electrodes (8); the upper section and the lower section of the longitudinal metal rod of the adjacent I-shaped resonance unit are respectively connected through two metal wires, the two metal wires are respectively connected with the two sides of the fin line through short branches, one metal wire is grounded, and the other metal wire is connected with the rectangular metal coating layer;
the rectangular waveguide is provided with a rectangular air window at the joint of the first dielectric substrate and the second dielectric substrate, and the width of the rectangular air window is more than or equal to that of the external bias filter circuit (5); the external bias filter circuit (5) is etched on the upper surface of the second dielectric substrate; the external bias filter circuit comprises a filter input end, a compact microstrip resonance unit and a filter output end; the filter input end and the filter output end are microstrip lines; the width of the filter output end is the same as that of the rectangular metal coating layer; the filtering output end is connected with the rectangular metal coating layer through a bonding wire.
2. The on-chip terahertz wave amplitude modulator based on the fin-line nested artificial microstructure of claim 1, wherein the upper surface of the first dielectric substrate coincides with the middle of the long side of the rectangular waveguide.
3. The on-chip terahertz wave amplitude modulator based on fin-line nested artificial microstructure according to claim 1, wherein an upper edge of the waveguide-fin-line transition portion (2) extends from a wide-side upper edge curve of the rectangular waveguide input end (1) to an upper edge of the fin-line modulation portion, and a lower edge of the waveguide-fin-line transition portion (2) extends from a wide-side lower edge curve of the rectangular waveguide input end (1) to a lower edge of the fin-line modulation portion.
4. The on-chip terahertz wave amplitude modulator based on fin-line nested artificial microstructure of claim 1, wherein the first dielectric substrate is made of SiC or sapphire.
5. The on-chip terahertz wave amplitude modulator based on fin-line nested artificial microstructure of claim 1, wherein the second dielectric substrate is made of SiO2。
6. The fin-line nested artificial microstructure based on an on-chip terahertz wave amplitude modulator of claim 1, characterized in that the material of the doped heterojunction (9) is AlGaN/GaN, InGaN/GaN, AlGaAs/GaAs, AlGaAs/InGaAs or AlGaAs/InGaAs/InP, and the oblique lines indicate the combination of two or three materials.
7. The on-chip terahertz wave amplitude modulator based on fin-line nested artificial microstructure of claim 1, characterized in that the material of the electrode (8) is Ti, Al, Ni or Au.
8. The on-chip terahertz wave amplitude modulator based on fin-line nested artificial microstructures of claim 1, wherein the material of the artificial microstructures (6) and the metal line is Au, Ag, Cu or Al.
9. The on-chip terahertz wave amplitude modulator based on fin-line nested artificial microstructures of claim 1, wherein the rectangular waveguide has dimensions WR2.8, and a specific size is 0.356mm by 0.711 mm.
10. The on-chip terahertz wave amplitude modulator based on the fin-line nested artificial microstructure of claim 1, wherein a voltage signal is loaded through an external bias filter circuit to control the on-off state of a HEMT diode, so as to control the resonance state of the artificial microstructure, and thus the amplitude modulation of terahertz waves transmitted inside the rectangular waveguide is realized.
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