A superconducting quantum capacitance detector with large saturated power

Abstract

The application discloses a superconducting quantum capacity detector with large saturated power, which comprises a reference ground, a coplanar waveguide transmission line, a superconducting microwave resonator based on a tantalum film and a single Cooper pair box based on aluminum, the superconducting microwave resonator comprises a double helix inductor and an interdigital capacitor, the single Cooper pair box is connected to the interdigital capacitor through aluminum metal wires, the single Cooper pair box and the double helix inductor are located on the same side of the interdigital capacitor, and the single Cooper pair box is located above the double helix inductor, so that the detector unit is more compact, the space utilization is increased, and the number of pixels of a multi-pixel focal plane detector array is increased; the gate capacitor is designed in the shape of a tuning fork, compared with an existing parallel wire structure, double capacitance values can be obtained without increasing the volume of a superconducting island, the smaller the volume of the superconducting island is, the more significant the quantum capacity effect of the detector is, and the more obvious the response is, the larger the gate capacitor is, and the larger the saturated power of the detector is, so that the saturated power can be increased without losing sensitivity.

Description

Technical Field

[0001] This invention relates to the field of terahertz astronomical detection, and more particularly to a high-saturation-power superconducting quantum capacitor detector. Background Technology

[0002] Terahertz detection technology has irreplaceable scientific value for the development of astronomical observation. More than half of the energy in the universe is distributed in the terahertz band (0.1–10 THz), which covers a large number of important astrophysical radiation processes, such as molecular rotation lines in the interstellar medium, thermal radiation from cold dust, and terahertz radiation from high-redshift galaxies. Therefore, developing highly sensitive terahertz detectors is of great significance for revealing key physical processes such as star formation, galaxy evolution, and the cosmic cycle of matter.

[0003] The superconducting quantum capacitance detector, based on the superconducting tunnel junction and quantum capacitance effect, is recognized internationally as one of the most sensitive terahertz detectors. Its noise-equivalent power reaches the order of 10⁻²⁰ W / Hz¹ / ², and it has achieved single-photon-level detection capability in the terahertz band. This detector exhibits outstanding performance in deep-space low-background observations, and has potential applications in cutting-edge fields such as cosmic microwave background radiation detection and indirect dark matter detection.

[0004] However, the dynamic range of superconducting quantum capacitor detectors is limited by their low saturation power. In actual astronomical observations, the intensity of terahertz radiation from different celestial bodies (such as planets, star-forming regions, and active galactic nuclei) can vary by several orders of magnitude. When the signal power approaches or exceeds the detector's saturation threshold, the detector response will become nonlinear or even saturated, leading to distorted observational data and making it difficult to accurately reconstruct the radiation characteristics of celestial bodies. This limitation particularly affects the imaging and spectroscopic observation of bright celestial bodies, thus restricting the widespread application of this technology in comprehensive, multi-objective astronomical research. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a superconducting quantum capacitor detector that improves saturation power without sacrificing sensitivity.

[0006] Technical solution: The high-saturation-power superconducting quantum capacitor detector of the present invention includes a reference ground, a coplanar waveguide transmission line, a tantalum-based superconducting microwave resonator, and an aluminum-based single Cooper pair. The tantalum-based superconducting microwave resonator includes a double-helix inductor and an interdigital capacitor. The aluminum-based single Cooper pair is connected to the interdigital capacitor through an aluminum metal wire. The aluminum-based single Cooper pair and the double-helix inductor are located on the same side of the interdigital capacitor, and the aluminum-based single Cooper pair is located above the double-helix inductor.

[0007] Furthermore, the aluminum-based single Cooper pair cell includes a grid-like absorber, an aluminum Josephson junction, and a tuning fork-shaped gate capacitor.

[0008] Furthermore, one end electrode of the interdigitated gate capacitor is in the shape of a tuning fork and is connected to the interdigitated capacitor via an aluminum metal wire, while the other end electrode is a single aluminum wire serving as a superconducting island.

[0009] Furthermore, the Josephson junction is located between the superconducting island and the grid absorber, and the size of the Josephson junction is 100-200 nm.

[0010] Furthermore, the coplanar waveguide transmission line is a straight coplanar waveguide transmission line, with a center conductor width of 10-15 μm and a distance of 6-10 μm between the center conductor and the reference ground.

[0011] Furthermore, the thickness of the tantalum superconducting microwave resonator is 100-200 nm.

[0012] Furthermore, the grid-like absorber has a size of 100 μm × 100 μm, a linewidth of 70 nm, and a unit spacing of 5 μm.

[0013] Furthermore, the linewidth of the interdigital capacitor is 2-4 μm, the interdigit spacing is 2-10 μm, and the interdigitation number is 40-100 pairs.

[0014] Furthermore, the double-helix inductor has a linewidth of 2-4 μm, a line spacing of 2-16 μm, and 5-20 helix turns.

[0015] Furthermore, the two electrodes of the tuning fork gate capacitor are formed in one photolithography process, with a length of 2-8 μm and a gap of 200-300 nm.

[0016] Beneficial Effects: Compared with the prior art, the significant advantages of this invention are: 1. This invention places the aluminum-based single Cooper pair cell and the double-helix inductor of the superconducting microwave resonator on one side of the interdigital capacitor, making the detector unit design more compact, increasing space utilization, and facilitating an increase in the number of pixels in the multi-pixel focal plane detector array; 2. This invention uses a linear coplanar waveguide transmission line to achieve bilateral symmetrical mounting of detector pixels, increasing the number of pixels in the detector array and imaging quality; 3. The gate capacitor of this invention is designed in the shape of a tuning fork. Compared with the existing parallel wire structure, it can obtain double the capacitance value without increasing the volume of the superconducting island. The smaller the volume of the superconducting island, the more significant the quantum capacitance effect of the detector should be and the more obvious the response should be. The larger the gate capacitance, the greater the saturation power of the detector. This invention can improve the saturation power without sacrificing sensitivity; 4. The tuning fork-shaped gate capacitor of this invention is independent of the superconducting microwave resonator and the grid absorber. Compared with the existing scheme that uses a part of the resonator interdigital capacitor as one end electrode of the gate capacitor, the tuning fork-shaped gate capacitor of this invention can be formed in one step in the process, precisely controlling the distance between the two electrodes and avoiding dimensional errors introduced by overlay. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 These are experimental photographs of the present invention; Figure 3 The diagram shows the response of detector 1 and detector 2 under the same radiative power. Detailed Implementation

[0018] The high-saturation-power superconducting quantum capacitor detector of this invention includes a tantalum-based reference ground 1, a tantalum-based coplanar waveguide transmission line 2, tantalum-based superconducting microwave resonators 3 and 4, and aluminum-based single Cooper pairs 5, 6, and 7. The tantalum-based superconducting microwave resonator includes a double-helix inductor 3 and an interdigital capacitor 4. The aluminum-based single Cooper pairs are connected to the interdigital capacitor 4 via aluminum metal wires. The aluminum-based single Cooper pairs 5, 6, and 7 and the double-helix inductor 3 are located on the same side of the interdigital capacitor 4, and the aluminum-based single Cooper pairs 5, 6, and 7 are located above the double-helix inductor 3. The center conductor width of the linear coplanar waveguide transmission line 2 is 10 μm, and the distance between the center conductor and the reference ground 1 is 6 μm. The superconducting microwave resonator is a lumped resonator, including an interdigital capacitor 4 and a double-helix inductor 3. The linewidth of the interdigitated capacitor is 2 μm, the interdigit spacing is 2 μm, and the number of interdigit pairs is 60; the linewidth of the double-helix inductor is 2 μm, the inductor line spacing is 2 μm, and the number of helical turns is 15.

[0019] The aluminum-based single Cooper pair includes a grid absorber 5, an aluminum Josephson junction 6, and a tuning fork-shaped gate capacitor 7. One electrode of the tuning fork-shaped gate capacitor 7 is shaped like a tuning fork and connected to an interdigital capacitor 4 via an aluminum metal wire. The other electrode is a single aluminum wire serving as a superconducting island. The Josephson junction is located between the superconducting island and the grid absorber 5. The Josephson junction has a size of 100-200 nm. The grid absorber 5 has a size of 100 μm × 100 μm, a linewidth of 70 nm, and a unit spacing of 5 μm. The tuning fork-shaped gate capacitor of detector 1 is 1 μm long with a gap of 300 nm; the tuning fork-shaped gate capacitor of detector 2 is 6 μm long with a gap of 250 nm.

[0020] like Figure 3 As shown, the response curves of two superconducting quantum capacitor detectors with different gate capacitances are displayed under the same radiation power. The detector with the smaller gate capacitance, i.e., detector 1, has a smaller amplitude and is already saturated; while the detector with the larger gate capacitance, i.e., detector 2, has a larger amplitude and is not yet saturated.

Claims

1. A high-saturation-power superconducting quantum capacitor detector, characterized in that, The system includes a reference ground (1), a coplanar waveguide transmission line (2), a tantalum-based superconducting microwave resonator, and an aluminum-based single Cooper pair. The tantalum-based superconducting microwave resonator includes a double-helix inductor (3) and an interdigital capacitor (4). The aluminum-based single Cooper pair is connected to the interdigital capacitor (4) via aluminum metal wires. The aluminum-based single Cooper pair and the double-helix inductor (3) are located on the same side of the interdigital capacitor (4), and the aluminum-based single Cooper pair is located above the double-helix inductor (3).

2. The high-saturation-power superconducting quantum capacitor detector according to claim 1, characterized in that, The aluminum-based single Cooper pair cell includes a grid absorber (5), an aluminum Josephson junction (6), and a tuning fork-shaped gate capacitor (7).

3. The high-saturation-power superconducting quantum capacitor detector according to claim 2, characterized in that, One end electrode of the interdigitated gate capacitor (7) is in the shape of a tuning fork and is connected to the interdigitated capacitor (4) through an aluminum metal wire. The other end electrode is a single aluminum wire serving as a superconducting island.

4. The high-saturation-power superconducting quantum capacitor detector according to claim 3, characterized in that, The Josephson junction is located between the superconducting island and the grid absorber (5), and the size of the Josephson junction is 100-200 nm.

5. The high-saturation-power superconducting quantum capacitor detector according to claim 1, characterized in that, The coplanar waveguide transmission line (2) is a straight coplanar waveguide transmission line with a center conductor width of 10-15 μm and a distance of 6-10 μm between the center conductor and the reference ground.

6. The high-saturation-power superconducting quantum capacitor detector according to claim 1, characterized in that, The thickness of tantalum superconducting microwave resonators is 100-200 nm.

7. The high-saturation-power superconducting quantum capacitor detector according to claim 2, characterized in that, The grid absorber (5) has a size of 100 μm × 100 μm, a linewidth of 70 nm, and a unit spacing of 5 μm.

8. The high-saturation-power superconducting quantum capacitor detector according to claim 1, characterized in that, The linewidth of the interdigital capacitor (4) is 2-4 μm, the interdigit spacing is 2-10 μm, and the number of interdigit pairs is 40-100.

9. The high-saturation-power superconducting quantum capacitor detector according to claim 1, characterized in that, The double-helix inductor (3) has a line width of 2-4 μm, a line spacing of 2-16 μm, and a helix number of 5-20 turns.

10. The high-saturation-power superconducting quantum capacitor detector according to claim 2, characterized in that, The two electrodes of the tuning fork gate capacitor (7) are formed in one photolithography process, with a length of 2-8 μm and a gap of 200-300 nm.

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