An on-chip double silicon carbide color center HOM interferometer based on stress regulation

Abstract

The present invention relates to an on-chip dual silicon carbide color center HOM interferometer device based on stress regulation. Using this device, a completely monolithic SiC photonic circuit can be realized. Two frequency-matched color center single-photon sources are connected to an on-chip beam splitter via a single-mode ridge waveguide, making it possible to perform two-photon interference experiments on the chip.

Description

Technical Field

[0001] The present invention belongs to the field of quantum information science and technology, and in particular relates to an on-chip double silicon carbide color center HOM interference device based on stress regulation. Background Art

[0002] Silicon carbide (SiC) is an important wide-bandgap semiconductor material with numerous outstanding properties, such as high-temperature stability, high power density, and high electron mobility. Consequently, it has attracted widespread attention in power electronics, energy, and optoelectronics. SiC exists primarily in hexagonal 4H-SiC (bandgap 3.23 eV), 6H-SiC (3.0 eV), and cubic 3C-SiC (2.36 eV). These crystal forms have been commercialized at the wafer level, with established n-type and p-type doping methods compatible with CMOS integrated circuit manufacturing processes. Furthermore, SiC possesses numerous single-photon sources, or color centers, with wavelengths from visible light to near-telecom wavelengths. Most of these single-photon sources are optically addressable and controllable in spin coherence, exhibiting very long coherence times (up to 20 milliseconds). Another unique property of these color centers is that they can be coupled to nuclear spins for quantum storage, and the high-fidelity mechanism at the spin-photon interface can be exploited to achieve long-range entanglement of multiple spins. These color center quantum light sources can be optically excited by continuous light, pulsed light, and electrical excitation, with a lifetime of 1ns to 170ns, depending on the type of color center and the quantum efficiency (up to 70%). In addition, the nano-manufacturing technology of SiC has also matured, and the manufacture of high optical quality factor Q, microresonators and nanoresonators is underway, while the integration of single-photon detectors based on superconducting nanowires in silicon carbide has been achieved. From the perspective of quantum optics, SiC materials have many interesting quantum optical properties, such as the mutual conversion between spin quantum bits and optical quantum bits, single photon emission, etc. These properties make SiC a potential quantum information and quantum computing platform.

[0003] Optical quantum computing and communication based on single-photons and linear optics rely on quantum interference between two photons at a 50:50 beam splitter. This process, known as the Hong-Ou Mandel (HOM) effect, occurs when two identical single photons enter the two input ports of a beam splitter. When the photons become indistinguishable, they merge into a two-photon Fock state, which then emerges from the same but random output port. This process forms the basis for the generation of the simplest nontrivial path-entangled NOON state and introduces an optical nonlinearity that is fundamental to the implementation of more complex photonic gates and protocols in optical quantum integrated circuits. Therefore, scalable optical quantum information technology will require the integration of many identical, indistinguishable single-photon sources with reliable photonic circuits composed of beam splitters. Leveraging advanced integrated photonic technologies can significantly reduce the footprint of quantum devices. Furthermore, the inherent subwavelength stability of the path length, low losses, and near-perfect mode overlap of the integrated beam splitter allow for high-fidelity control of photon states, enabling high-fidelity quantum interference. Advances in integrated photonics have enabled the realization of relatively complex quantum circuits, demonstrating CNOT gate operations, boson sampling, quantum walks, some simple quantum algorithms, and inter-chip quantum teleportation. Integrated photonic circuits have also been combined with spontaneous four-wave mixing (SFMW) photon sources. However, due to the probabilistic nature of the light sources used, their efficiency and scalability are inherently limited. Single-photon sources based on quantum emitters do not have this limitation and have recently been shown to outperform SFMW and down-conversion photon sources in achieving both high photon indistinguishability and brightness. Furthermore, long-range interference between two quantum emitters has been demonstrated using ion beams, quantum dots, organic molecules, or diamond color centers. The vast majority of these experiments were conducted in free space. Performing similar experiments on a chip, utilizing fully integrated quantum emitters and beam-splitting photonic circuits, has not yet been performed and remains a missing component for scaling up these quantum technologies. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an on-chip double silicon carbide color center HOM interferometer device based on stress regulation.

[0005] The present invention discloses an on-chip double silicon carbide color center HOM interference device based on stress regulation, the device comprising: a piezoelectric material, the piezoelectric material being provided with a horizontal groove, and the extension line of the groove passing through the center of the piezoelectric ceramic; a multimode interference coupler MMI being provided on the piezoelectric material, wherein the MMI comprises a first waveguide and a second waveguide, wherein the first waveguide comprises a first part and a second part, and the first part and the second part of the first waveguide are provided with a color center; the piezoelectric material is further provided with metal electrodes, comprising a first metal electrode and a second metal electrode, and the first metal electrode and the second metal electrode are symmetrical along the horizontal groove.

[0006] The first portion and the second portion of the first waveguide are symmetrical along the horizontal groove; an extension line of the horizontal groove passes through the center of the MMI.

[0007] The piezoelectric material is piezoelectric ceramic; a metal bottom electrode is provided on the back of the piezoelectric material.

[0008] The MMI includes a first waveguide and a second waveguide, wherein the first waveguide and the second waveguide are arranged on both sides of the MMI.

[0009] A color center is provided on the first part and the second part of the first waveguide: a color center is provided on the first part and the second part of the first waveguide respectively.

[0010] The present invention provides a method for preparing an on-chip dual silicon carbide color center HOM interferometer device based on stress regulation, comprising:

[0011] (1) Depositing a metal bottom electrode on the back of the piezoelectric material, then drawing a horizontal groove on the front of the piezoelectric material, and depositing a metal top electrode on the piezoelectric material;

[0012] (2) Preparation of silicon carbide color centers: Electron beam photoresist is spin-coated on the surface of SiCOI, and a circular hole array pattern is formed by electron beam exposure. The aforementioned photoresist is used as a template, and a preliminary color center ensemble is formed in the circular holes by electron beam irradiation or plasma injection to obtain a preliminary color center array. The photoresist is then washed off and annealed to stabilize the color centers and form a single color center.

[0013] (3) In step (2), electron beam photoresist is spin-coated on the SiCOI surface, and the MMI pattern is formed by electron beam exposure. The MMI is prepared on the top SiC film using dry etching technology, and the single-point color center is positioned by a laser wide-field imaging device, and the two color centers are respectively located on two sides of one side of the MMI. Then, the lower buried oxide layer is hollowed out and transferred to the piezoelectric ceramic of step (1), thereby obtaining an on-chip double silicon carbide color center HOM interferometer device based on stress regulation.

[0014] The preferred embodiment of the above method is as follows:

[0015] In the step (1), the piezoelectric material is piezoelectric ceramic; the piezoelectric ceramic is PMN-PT piezoelectric ceramic; the bottom electrode is 20nmCr / 200-300nmAu, and the top electrode is 20nmCr / 200-300nmAu; the width of the horizontal groove is 2-10 microns.

[0016] The 20nmCr / 200-300nmAu method is to first deposit 20nmCr and then deposit 200-300nmAu.

[0017] In the step (1), a metal bottom electrode is deposited on the back of the piezoelectric material by electron beam evaporation or magnetron sputtering to deposit metal as the bottom electrode on the back of the piezoelectric material; horizontal grooves are drawn on the front of the piezoelectric material by using carbon dioxide femtosecond laser scribing to draw horizontal grooves on the piezoelectric material; and the metal top electrode is deposited on the piezoelectric ceramic by photolithography and electron beam evaporation.

[0018] In step (2), the SiCOI (silicon carbide on insulator wafer) comprises, from bottom to top, a base layer, a buried oxide layer, and a silicon carbide layer. For example, the base layer is a Si layer, and the buried oxide layer is a silicon dioxide layer.

[0019] The photoresist in steps (2) and (3) is at least one of PMMA, ZEP520A, and HSQ.

[0020] In the step (2), electron beam photoresist is spin-coated on the SiCOI surface, and a circular hole array pattern is formed by electron beam exposure. The method comprises the following steps: spin-coating electron beam photoresist on the SiCOI surface, pre-baking, electron beam exposure, and development to form a circular hole array pattern.

[0021] The electron beam irradiation or plasma injection in step (2) is between 1e11 and 1e15 cm -2 ; The plasma implantation is one or more of H, He, and C plasma implantation.

[0022] The annealing in step (2) is performed at 300-800° C. for 20-30 minutes.

[0023] In the step (3), the SiCOI surface is spin-coated with electron beam photoresist, and the MMI pattern is formed by electron beam exposure: electron beam photoresist spin coating, pre-baking, electron beam exposure, post-baking, and development.

[0024] The dry etching technology in step (3) is reactive ion etching RIE-ICP dry etching technology, wherein the ICP power is 100-180W, the bias power is 80-120W, and the SF6 gas flow rate is 15-32SCCM (standard cubic centimeters per minute), the O2 gas flow rate is 4-8SCCM, and the Ar gas flow rate is 4-8SCCM.

[0025] In the step (3), the lower buried oxide layer is hollowed out by HF dry etching; the transfer is to remove the structure from the substrate using a sticky polymer (such as polydimethylsiloxane (PDMS) or polyvinyl alcohol (PVA)) and transfer it to the piezoelectric ceramic.

[0026] The present invention provides an application of the on-chip dual silicon carbide color center HOM interference device based on stress regulation in on-chip dual single-photon source interference research.

[0027] Two color-center single-photon sources were simultaneously pumped using a fiber array and end-face coupling. The emission frequencies of the two color centers were aligned through piezoelectric ceramic stress control. The single photons emitted by the two color centers interfered in the MMI, and the HOM two-photon interference was verified by measuring the second-order correlation function at the collector.

[0028] Beneficial effects

[0029] This invention proposes for the first time an on-chip HOM two-photon interference experiment integrating two color centers on the SiCOI platform, making it possible to develop scalable large-scale multi-quantum state controllable optical quantum integrated circuits based on deterministic quantum single-photon sources.

[0030] The present invention provides a preparation method and structure of an on-chip dual silicon carbide color center HOM interferometer device based on stress regulation. Using this device, a completely monolithic SiC photonic circuit can be realized. Two frequency-matched color center single-photon sources are connected to the on-chip beam splitter through a single-mode ridge waveguide, making it possible to perform two-photon interference experiments on the chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Diagram of a piezoelectric ceramic device used to apply stress;

[0032] Figure 2 (a-b) Flowchart for the preparation of MMI containing a single color center;

[0033] Figure 3 Schematic diagram of the final device;

[0034] Figure 4 Schematic diagram of pulsed laser two-photon interference. DETAILED DESCRIPTION

[0035] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0036] Example 1

[0037] An on-chip double silicon carbide color center HOM interferometer device based on stress regulation includes a piezoelectric ceramic, wherein a horizontal groove is provided on the piezoelectric ceramic, and the extension line of the groove passes through the center of the piezoelectric ceramic; an MMI is provided on the piezoelectric ceramic, wherein the MMI includes a first waveguide and a second waveguide, wherein the first waveguide includes a first part (first path) and a second part (second path), and a color center is respectively provided on the first part and the second part of the first waveguide; the piezoelectric material is also provided with metal electrodes, including a first metal top electrode and a second metal top electrode, and the first metal electrode and the second metal electrode are symmetrical along the horizontal groove.

[0038] The first and second portions of the first waveguide are symmetrically arranged along the horizontal groove; the extension line of the horizontal groove passes through the center of the MMI. A metal bottom electrode is provided on the back of the piezoelectric material. The first and second waveguides are provided on either side of the MMI.

[0039] Example 2

[0040] (1) Preparation of piezoelectric ceramics: First, Au is deposited on the back of the piezoelectric ceramic by electron beam evaporation or magnetron sputtering to deposit 20nmCr / 200nmAu as the bottom electrode. Then, a straight structure with a width of about 2 microns is scratched on one side of the PMN-PT piezoelectric ceramic by carbon dioxide femtosecond laser scribing technology. Then, Au metal electrodes are deposited on the piezoelectric ceramic by photolithography and electron beam evaporation to obtain the following: Figure 1 The specific process is as follows: AZ5214 photoresist is applied at 4000 rpm / 2000 acc, pre-baked at 100°C for 60 seconds, photolithography, AZ300MIF development, electron beam evaporation of 20 nm Cr / 200 nm Au, and acetone metal lift-off.

[0041] (2) Preparation of SiC color centers: First, spin-coat an electron beam photoresist such as ZEP520A or PMMA on the SiCOI surface. Specifically, ZEP520A is used in this embodiment at 6000 rpm / 3000 acc, pre-baked at 180°C for 4 min, and exposed by electron beam with a beam current of 1 nA and a dose of 200 to 340 μC / cm 2 (Example beam current 1nA dose 280μC / cm 2 ), developed with o-xylene for 60s, and obtained Figure 2 The hole array structure is shown in a. Then it is irradiated by 2MeV electron beam or 40keV He + Ion implantation (40keV He+ in this example) is performed using the aforementioned photoresist as a mask to form a preliminary color center ensemble in the circular hole to obtain a preliminary color center array. The irradiation or implantation dose is between 1e11 and 1e15 cm -2The photoresist is then washed off with acetone and annealed at 300-800°C for 30 minutes to stabilize the color center and form a single color center (annealing temperature is 300°C in this embodiment). Photoresist is then spin-coated on the SiCOI surface, and a single color center is obtained through photolithography, Au deposition, and lift-off processes. Figure 2 b) and locate the subsequent color center using a laser wide-field imaging device.

[0042] (3) MMI preparation: HSQ spin coating at 2000 rpm / 2000 acc, pre-baking at 150°C for 10 min, electron beam exposure, beam current 1 nA, dose 1000 to 5000 μC / cm 2 , post-baking at 170℃ for 10min, TMAH development for 60s, RIE-ICP dry etching was used to obtain the structure (ICP power: 150W, bias power: 100W and SF6 gas flow: 32SCCM (standard cubic centimeters / minute), O2 gas flow: 8SCCM, Ar gas flow is 8SCCM), 10% HF etching for 5-10min to hollow out the silicon oxide, and high polymers such as polydimethylsiloxane (PDMS) or polyvinyl alcohol (PVA) were used to transfer the MMI to the piezoelectric ceramic to obtain Figure 3 The final structure is shown in Figure 2. The on-chip HOM test results are shown in Figure 2. Figure 4 As shown, when two photons arrive at the MMI at the same time, that is, when the time delay is 0 ns, interference occurs, g 2 HOM (0)<0.5, verifying the occurrence of two-photon interference.

Claims

1. An on-chip double silicon carbide color center HOM interferometer based on stress regulation, characterized in that: The device includes: a piezoelectric material, wherein the piezoelectric material is provided with a horizontal groove, and the extension line of the groove passes through the center of the piezoelectric material; an MMI is provided on the piezoelectric material, wherein the MMI includes a first waveguide and a second waveguide, wherein the first waveguide includes a first part and a second part, and the first part and the second part of the first waveguide are provided with a color center; the piezoelectric material is also provided with a metal electrode, including a first metal electrode and a second metal electrode, and the first metal electrode and the second metal electrode are symmetrical along the horizontal groove; wherein the first part and the second part of the first waveguide are respectively located on both sides of the horizontal groove.

2. The stress-controlled on-chip dual silicon carbide color center HOM interferometer device according to claim 1, characterized in that: The first part and the second part of the first waveguide are symmetrical along the horizontal groove; the extension line of the horizontal groove passes through the center of the MMI; the first waveguide and the second waveguide are arranged on both sides of the MMI.

3. The stress-controlled on-chip dual silicon carbide color center HOM interferometer device according to claim 1, characterized in that: The piezoelectric material is piezoelectric ceramic; a metal bottom electrode is provided on the back of the piezoelectric material; and a color center is provided on the first part and the second part respectively.

4. A method for preparing the stress-controlled on-chip dual silicon carbide color center HOM interferometer device according to claim 1, comprising: Step (1) depositing a metal bottom electrode on the back of the piezoelectric material, then scratching a horizontal groove on the front of the piezoelectric material, and depositing a metal top electrode on the piezoelectric material; Step (2) spin-coating electron beam photoresist on the SiCOI surface, forming a circular hole array pattern by electron beam exposure, using the photoresist as a template, obtaining a preliminary color center array by electron beam irradiation or plasma implantation, washing off the photoresist, and annealing; Step (3) spin-coating electron beam photoresist on the surface of SiCOI in step (2), forming the pattern of MMI by electron beam exposure, preparing MMI on the top SiC film by dry etching technology, and making the two color centers on two sides of the MMI respectively, then hollowing out the lower buried oxide layer and transferring it to the piezoelectric material in step (1), thereby obtaining an on-chip double silicon carbide color center HOM interferometer device based on stress regulation.

5. The preparation method according to claim 4, characterized in that: In the step (1), the piezoelectric material is a piezoelectric ceramic, which is a PMN-PT piezoelectric ceramic; the bottom electrode is 20 nm Cr / 200-300 nm Au, and the top electrode is 20 nm Cr / 200-300 nm Au; and the width of the horizontal groove is 2-10 microns.

6. The preparation method according to claim 4, characterized in that: The photoresist in steps (2) and (3) is at least one of PMMA, ZEP520A, and HSQ.

7. The preparation method according to claim 4, characterized in that: The electron beam irradiation or plasma injection amount in step (2) is 1e11-1e15 cm -2 ; The plasma implantation is one or more of H, He, and C plasma implantation.

8. The preparation method according to claim 4, characterized in that: The annealing in step (2) is performed at 300-800° C. for 20-30 minutes.

9. The preparation method according to claim 4, characterized in that: The dry etching technology in step (3) is reactive ion etching (RIE)-ICP dry etching technology, wherein the ICP power is 100-180 W, the bias power is 80-120 W, the SF6 gas flow rate is 15-32 SCCM, the O2 gas flow rate is 4-8 SCCM, and the Ar gas flow rate is 4-8 SCCM.

10. Application of the stress-controlled on-chip dual silicon carbide color center HOM interferometer device according to claim 1 in on-chip dual single-photon source interferometry.

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