WO2018232689A1

WO2018232689A1 - Time-entangled photon pair generating device

Info

Publication number: WO2018232689A1
Application number: PCT/CN2017/089537
Authority: WO
Inventors: 耿巍; 张臣雄
Original assignee: 华为技术有限公司
Priority date: 2017-06-22
Filing date: 2017-06-22
Publication date: 2018-12-27
Also published as: CN109429509A

Abstract

An entangled photon pair generating device, comprising a substrate, a pump light source, and a first waveguide structure and a second waveguide structure located on the substrate. The pump light source is used for transmitting pump light to the first waveguide structure. The first waveguide structure is used for alternately outputting a first pump light pulse and a second pump light pulse after time division is performed on the pump light. The second waveguide structure is used for converting two pumped photons in the first pump light pulse or in the second pump light pulse into an entangled photon pair. Integrating the first waveguide structure, the second waveguide structure, and the pump light source on one substrate can reduce device size. The first waveguide structure and the second waveguide structure on the substrate are both formed by etching the same waveguide material on the substrate; therefore, a manufacturing process thereof is compatible with a CMOS process, facilitating mass production of devices and cost reduction.

Description

Time entangled photon pair generating device

Technical field

The present application relates to the field of optical communication technologies, and in particular, to a time entangled photon pair generating device.

Background technique

Quantum entanglement refers to a phenomenon in a quantum mechanical system in which the properties of individual particles cannot be described separately due to the quantum association, which can only describe the overall nature of the system. If a pair is in a polarization entangled state

The photon, if the polarization measurement for one of them is H, the polarization of the other photon must be H, and vice versa. The entangled photon pair has important applications in the current quantum knock down (QKD) system. For example, the QKD of the BBM92 protocol can be performed using entangled photon pairs. To achieve ultra-long-distance QKD, it is necessary to realize quantum using entangled photon pairs. Relay (quantum relay or quantum repeater) and so on.

Photons can be entangled in different dimensions. For example, common entanglement coding methods include polarization entanglement, path entanglement, and time entanglement. Most current patent applications are related to polarization entangled photon sources. For the time entangled photon pair, because its quantum state is not easily interfered by the external environment in the optical fiber, it is the most widely used coding method for the actual QKD.

However, the current generation of entangled photon pairs has only been studied academically. The common way to produce time-coupled photon pairs academically is the down-conversion technique: using a laser, an unequal-arm MZ interferometer, a nonlinear material, and a system of multiple optical components, beamsplitters, and couplers to produce entangled photons. Correct. Among them, the laser is used to provide pump light, and the unequal arm MZ interferometer is usually a fiber-optic coded optical path for time-spliting the pump light to form early and late pulses, then early pulse and late pulse pumping. A nonlinear material is used to generate a temporally entangled photon pair, which is then condensed using a plurality of optical elements to entangle the photon pairs, and the entangled photon pairs are split by a beam splitter and a coupler and coupled into the fiber. Commonly used nonlinear materials, such as barium metaborate crystal BBO, periodically poled lithium niobate crystal PPLN, etc., the preparation process or growth process can not be compatible with complementary metal oxide semiconductor (CMOS) process. Materials that are compatible with CMOS processes do not contain these commonly used nonlinear materials, so these nonlinear materials cannot achieve CMOS on-chip integration. Optical components are usually optical lenses. Lasers are usually large-volume independent devices with complex structures. The unequal-arm MZ interferometers, optical lenses, beam splitters and couplers are also large-sized independent devices. The size is too large to achieve on-chip integration. Therefore, due to the limitation of the principle of such entangled photon generation, each device selects an independent device and the size and processing process of each functional device are greatly different, and it is also difficult to be compatible with the CMOS process, so these devices cannot achieve low cost. The on-chip integration results in a large overall size and high processing cost of the time entangled photon pairing system formed by these independent devices.

In summary, in the prior art, a time-entangled photon pair is generated by using a chip-down technique, and there is a large difference in size and on-chip processing technology of a time entangled photon pair generation system composed of a plurality of independent devices, which cannot be miniaturized and cannot be combined with a CMOS process. Compatible technical issues.

Summary of the invention

The embodiment of the present application provides a time entangled photon pair generating device for solving the problem that the size of the time entangled photon pair generating system in the prior art using the under-chip technology to generate a time entangled photon pair cannot be miniaturized, and cannot be combined with CMOS. Process-compatible technical issues.

The present application provides an entangled photon pair generating device including a substrate and a pumping source, a first waveguide structure and a second waveguide structure on the substrate; wherein the first waveguide structure and the second waveguide The structure is formed by etching a waveguide material between the pumping source and the second waveguide structure; the pumping source is configured to emit to the first waveguide structure Pumping light; the first waveguide structure for alternately outputting the first pump light pulse and the second pump light pulse after time-splitting the pump light; the second waveguide structure for The pump photons in the first pump light pulse or the second pump light pulse are converted into entangled photon pairs, the entangled photon pair comprising associated first photons and second photons.

The entangled photon pair generating device in the present application comprises at least a pumping light source and a first waveguide structure and a second waveguide structure on the substrate, the first waveguide structure has a time splitting function, and the second waveguide structure has a spontaneous four-wave mixing effect The function of the entangled photon pair, the first waveguide structure and the second waveguide structure are formed by etching the waveguide material on the substrate, and the etching process can be compatible with the CMOS process, and the CMOS process can be used to fabricate the substrate. A waveguide structure and a second waveguide structure can integrate the pump light source with the substrate by a chip process or a CMOS process, so that the size of the entangled photon pair generating device can be miniaturized.

Further, the entangled photon pair generating device further includes: a third waveguide structure on the substrate, the third waveguide structure is formed by etching the waveguide material, the third waveguide structure Located between the first waveguide structure and the second waveguide structure for filtering out noise photons different from the frequency of the pump light in the first pump light pulse and the second pump light pulse.

The entangled photon pair generating device in the present application includes a first waveguide structure and a second waveguide structure on the substrate, and a third waveguide structure on the substrate, and the third waveguide structure has a filtering function, such as The function of the band rejection filter is capable of filtering out the first pump light pulse or the second pump before the first pump light pulse and the second pump light pulse alternately outputted by the first waveguide structure enter the second waveguide structure The noise photons in the pump pulse having different frequency of the pump light are photons generated in the first waveguide structure different from the frequency of the pump light in the first pump light pulse or the second pump light pulse.

Further, the entangled photon pair generating device further includes: a fourth waveguide structure on the substrate, the fourth waveguide structure is formed by etching the waveguide material, the fourth waveguide structure An output end of the second waveguide structure is configured to filter out noise photons output from the output end of the second waveguide structure different from the frequencies of the first photon and the second photon.

The entangled photon pair generating device in the present application includes a pumping light source and a first waveguide structure on the substrate, a second waveguide structure, a third waveguide structure, and a fourth waveguide structure, and the fourth waveguide structure has a filter function. The noise photon entangled in the entangled photon pair generated by the third waveguide structure can be filtered out, and the noise photon refers to a photon generated at a frequency different from the first photon and the second photon generated during the generation of the entangled photon pair. It is beneficial to increase the content percentage of the entangled photon pair, which is beneficial to improve the signal quality when the entangled photon pair is applied in optical communication.

Further, the entangled photon pair generating device further includes: a fifth waveguide structure on the substrate, the fifth waveguide structure is formed by etching the waveguide material, the fifth waveguide structure Located at an output of the fourth waveguide structure for separating the first photon and the second photon output from an output of the fourth waveguide structure.

The entangled photon pair generating device in the present application includes a pumping light source and a first waveguide structure on the substrate, a second waveguide structure, and a fifth waveguide structure, the fifth waveguide structure having the function of a beam splitter, capable of entanglement Photon separation in a photon pair.

Further, the entangled photon pair generating device further includes: a sixth waveguide structure on the substrate, The sixth waveguide structure is formed by etching the waveguide material, and the sixth waveguide structure is located at an output end of the fifth waveguide structure for outputting the output end of the fifth waveguide structure The photons are coupled into the first single mode fiber, and the second photons are coupled into the second single mode fiber. The first single mode fiber and the second single mode fiber are disposed outside the substrate.

The entangled photon pair generating device in the present application includes a pumping light source and a first waveguide structure on the substrate, and a second waveguide structure, further including a sixth waveguide structure. The sixth waveguide structure has the function of a coupler capable of coupling separate photons into a single mode fiber.

The substrate may be, but not limited to, an SOI (Silicon-On-Insulator) substrate. The waveguide material can be, but is not limited to, silicon or silicon nitride. The substrate can be, but is not limited to, an SOI substrate. When the waveguide material on the substrate is silicon or silicon nitride, the pump light can excite spontaneous four-wave mixing effects and convert photons into entangled photons when passing through the second waveguide structure. .

In the embodiment of the present application, the frequencies of the two pump photons are respectively ωp1 and ωp2, and the frequencies of the first photon and the second photon are respectively ωi and ωs, and if ωp1=ωp2, ωs≠ωi, And ωs+ωi=2×ωp1=2×ωp2 is satisfied; if ωp1≠ωp2, ωs=ωi, and ωp1+ωp2=2×ωs=2×ωi is satisfied. The entangled photon pair generating device in the present application can be applied to the principle of time entangled photon pair generation based on non-degenerate spontaneous four-wave mixing effect, and is applicable to the principle of time entangled photon pair generation based on degenerate spontaneous four-wave mixing effect. .

Optionally, in the embodiment of the present application, the pump light source may be disposed on the substrate. In the present application, a pump light source and a plurality of waveguide structures are integrated on a substrate. For example, when the substrate is an SOI substrate, since the thickness of the SOI substrate is on the order of micrometers and the size is on the order of millimeters, the entangled photon pair generating device is used. The size is miniaturized. In addition, the plurality of waveguide structures are formed by etching the waveguide material deposited on the substrate, and the entangled photon pair generating device can be formed directly on the SOI substrate by a CMOS process, which can quantify the production of small devices and is advantageous for cost reduction.

Further, the pumping source is a III-V laser diode or a vertical cavity surface emitting laser array VCSEL bonded to the substrate, or the pumping source is a Ge epitaxially grown on the substrate Laser diode.

In the present application, for the pump light source, whether the III-V laser diode or the vertical cavity surface emitting laser array VCSEL is selected, the size can be guaranteed in the micrometer level, and the pumping light source can be integrated by the patch process. On the substrate, integration of the pumping source and the plurality of waveguide structures on the substrate is achieved, which is advantageous for reducing the volume of the entangled photon pair generating device. If the Ge laser diode is epitaxially grown directly on the substrate, the entangled photons are more controllable to the thickness and length and width of the generating device, and the miniaturization of the entangled photon pair generating device can be realized.

Optionally, the device further includes a carrier, and the substrate and the pumping light source are disposed on the carrier.

In the present application, the pump light source and the substrate are integrated on the carrier, and a plurality of waveguide structures are integrated on the substrate, which is advantageous for miniaturizing the size of the entangled photon pair generating device, for example, when the substrate is an SOI substrate, due to the SOI lining The thickness of the bottom is on the order of microns such that the dimensions of the entangled photon pair generating device are on the order of microns. In addition, the plurality of waveguide structures are formed by etching the waveguide material deposited on the substrate, and the entangled photon pair generating device can be formed directly on the SOI substrate by a semiconductor process, which can quantify the production of small devices and is advantageous in reducing cost.

Further, the pumping source is a III-V laser diode or a vertical cavity surface emitting laser array VCSEL bonded to the carrier.

In the present application, for the pump light source, whether the III-V laser diode or the vertical cavity surface emitting laser array VCSEL is selected, the size can be guaranteed in the micrometer level, and the pumping light source can be integrated by the patch process. On the carrier, on-chip integration of the pump source and the plurality of waveguide structures on the substrate is achieved, which is advantageous for reducing the volume of the entangled photon pair generating device.

Further, the device further includes a seventh waveguide structure, the seventh waveguide structure is located on the carrier and/or the substrate, and the pump light source passes through the seventh waveguide structure and the first waveguide Structural connectivity.

In the present application, the pumping source on the carrier is connected to the first waveguide structure on the substrate through the seventh waveguide structure, so that the positional relationship between the pumping source on the carrier and the plurality of waveguide structures on the substrate is flexible, for example, The positional relationship between the pump source on the carrier and the plurality of waveguide structures on the substrate may be in a horizontal arrangement; for example, the positional relationship between the pump source on the carrier and the plurality of waveguide structures on the substrate may be side by side In this case, the lateral dimension of the carrier can be further reduced.

DRAWINGS

1 is a schematic diagram of a principle of generating a time pulse superposition state and a time entangled photon pair according to an embodiment of the present application;

2 is a schematic diagram of a schematic diagram of a degenerate spontaneous four-wave mixing effect and a non-degenerate spontaneous four-wave mixing effect according to an embodiment of the present application;

3 is a schematic diagram of a principle of an entangled photon pair generating device according to an embodiment of the present application;

4 is a schematic cross-sectional structural view of a first entangled photon pair generating device according to an embodiment of the present application;

5 is a schematic top plan view of a first entangled photon pair generating device according to an embodiment of the present application;

6 is a schematic cross-sectional structural view of a second entangled photon pair generating device according to an embodiment of the present application;

7 is a schematic cross-sectional structural view of a second entangled photon pair generating device according to an embodiment of the present application;

8 is a schematic cross-sectional structural view of a second entangled photon pair generating device according to an embodiment of the present application;

9 is a schematic top plan view of a second entangled photon pair generating device according to an embodiment of the present application;

FIG. 10 is a schematic top plan view of a second entangled photon pair generating device according to an embodiment of the present application.

Detailed ways

The embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

The principle of time splitting the pump light is that a single photon passes through an unequal arm MZ interferometer to produce a time superposition of individual photons. For example, as shown in Figure 1(a), after passing through the first 50:50 fiber splitter of the unequal arm MZ interferometer, a single photon has a half chance of passing the short arm through the long arm and half the probability. A single pump pulse forms an early pulse and a late pulse after passing through the first fiber splitter, and then merges with the second fiber splitter to form a superposition of the early pulse and the late pulse.

A commonly used principle for generating temporally entangled photon pairs is to pump time-split pump light to excite nonlinear materials to produce temporally entangled photon pairs. As shown in Figure 1(b), after a single pump pulse passes through the same unequal-arm MZ interferometer, pumps nonlinear materials such as BBO, PPLN, etc., in the process, with the same probability in early pulses or Two correlated photons entangled in time are formed in the late pulse, and the probability of simultaneously generating two associated photons in the early pulse and the late pulse is almost zero, which can be ignored. Limited by this principle, each functional device is a separate device, and the manufacturing methods of each functional device are quite different, so these functional devices cannot achieve on-chip integration, and the entire device size cannot be reduced.

The principle of generating a time entangled photon pair used in the present application is: a third-order nonlinearity of a waveguide structure subjected to time-division, in a waveguide structure of a silicon-based material (such as silicon, silicon nitride, silicon dioxide, etc.) Under the influence of the effect, the pump photons of the early pulse pump optical pump are converted into time-entangled correlated photon pairs, or the pump photons of the late pulse pump optical pump are converted into time-entangled correlated photon pairs.

Among them, the silicon-based waveguide structure has a three-order nonlinear effect (spontaneous four-wave-mixing, SFWM), also known as spontaneous four-wave mixing effect. Spontaneous four-wave mixing includes non-degenerate four-wave mixing and degenerate four-wave mixing.

The principle of non-degenerate spontaneous four-wave mixing is: see Figure 2(a), if the two pump photons before the conversion have the same frequency (indicated by ω _p ), then the two pump photons are subjected to the silicon-based waveguide. The third-order nonlinear effect of the silicon line can be converted into two correlated photons with different frequencies (represented by ω _s and ω _i , respectively), and the two associated photons satisfy: 2ω _p = ω _s + ω _i .

The principle of degenerate spontaneous four-wave mixing is as follows: See Figure 2(b). If the two pump photons before the conversion have different frequencies (represented by ω _p1 and ω _p2 respectively), the two pump photons are subjected to silicon. The third-order nonlinear effect of the silicon waveguide of the fundamental waveguide can be converted into two associated photons of the same frequency (represented by ω _{s, i} ), and the two associated photons satisfy: ω _p1 +ω _p2 =2ω _s,i .

The present invention provides a time entangled photon pair generating device suitable for both non-degenerate spontaneous four-wave mixing and degenerate spontaneous four-wave mixing.

Based on the above principle, the present application provides an entangled photon pair generating device including a pumping light source and a plurality of waveguide structures. The pumping source and the plurality of waveguide structures are integrated on the same substrate surface, and the plurality of waveguide structures provide time entanglement. The photon pair produces an optical path and an output optical path. As shown in FIG. 3, the substrate is an SOI substrate, and the pump light source and the plurality of waveguide structures are disposed on the same surface on the SOI substrate, wherein the pump light source provides pump light, and the plurality of waveguide structures are connected to each other and can A beam splitting path for pumping light, a pair of photons to generate an optical path, and a transmission path for entanglement of photon pairs. The process of generating an entangled photon pair by the entangled photon generation device is: after the pump light source generates the pump light, the spectroscopic optical path provided by the waveguide structure performs time splitting on the pump light, and the entangled photon pair generates an optical path to excite the spontaneous four-wave mixing effect. The pump light is converted into an entangled photon pair, and the transmitted optical path of the entangled photon pair filters and splits the associated photons in the entangled photon pair and is respectively coupled into the single mode fiber outside the substrate.

It should be noted that the pumping light source in the present application is capable of generating pump light of a communication band, which is a monochromatic pumping light pulse or an overlapping pump pulse of two different wavelengths.

It should be noted that the plurality of waveguide structures in the present application are silicon-based waveguide structures, such as silicon, silicon nitride or silicon dioxide waveguide structures, to generate spontaneous four-wave mixing effects on the SOI substrate. However, it is not limited to these three types, and waveguide structures having the above functions of other materials are also within the scope of the present application. In addition, the waveguide structure can be etched through the waveguide material on the SOI substrate, and the process can be compatible with the CMOS process.

It should be noted that the SOI substrate in the present application is a silicon-based substrate, and a silicon-insulator-silicon structure SOI substrate can be obtained by ion implantation or wafer bonding.

The present application fabricates a plurality of waveguide structures and a pumping light source on the surface of the SOI substrate. Since the thickness of the SOI substrate is on the order of micrometers, the size of the entangled photon pair generating device is miniaturized, and a plurality of waveguide structures having the above functions can pass The waveguide material on the SOI substrate is etched, and the process can be compatible with the CMOS process. Therefore, the entangled photon pair generating device can be formed directly on the SOI substrate by a semiconductor process, which can quantify the production and contribute to cost reduction.

Based on the above inventive concept, an entangled photon pair generating device provided by an embodiment of the present application will be described below with reference to specific embodiments. An entangled photon pair generating device provided by the present application, as shown in FIG. 4, includes a substrate 100, a waveguide structure 200 on the substrate 100, and a pumping light source 300. The waveguide structure 200 includes: a first waveguide structure 201, The second waveguide structure 202, the third waveguide structure 203, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure 206.

The substrate 100 may be, but not limited to, an SOI substrate.

The first waveguide structure 201, the second waveguide structure 202, the third waveguide structure 203, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure 206 are all engraved by the waveguide material deposited on the substrate 100. After the etching, the etching process can be compatible with the CMOS process. Therefore, the entangled photon pair generating device can be formed directly on the substrate 100 by a semiconductor process, which can quantify the production and contribute to cost reduction. Optionally, the waveguide material on the substrate 100 The quality can be, but is not limited to, silicon or silicon nitride.

Taking the substrate 100 as an SOI substrate as an example, the first waveguide structure 201, the second waveguide structure 202, the third waveguide structure 203, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure are combined with FIG. The positional relationship, structural features and functions between 206 are described in detail.

In FIG. 5, a pumping source 300, a first waveguide structure 201, a third waveguide structure 203, a second waveguide structure 202, a fourth waveguide structure 204, a fifth waveguide structure 205, and a sixth waveguide structure 206 on an SOI substrate. (not shown in Fig. 8) is arranged laterally along the inline shape.

The pumping light source 300 is disposed at an edge of the SOI substrate and disposed adjacent to the first waveguide structure 201 for emitting pump light to the first waveguide structure 201. Optionally, the pumping source 300 is a III-V laser diode or a vertical cavity surface emitting laser array VCSEL bonded to an SOI substrate. Optionally, the pump light source 300 is a Ge laser diode epitaxially grown on the SOI substrate. The pumping source 300 is bonded or directly grown on the SOI substrate to ensure that the size of the entangled photon generation device fabricated on the SOI substrate is on the order of millimeters.

The first waveguide structure 201 is directly connected to the pumping light source 300 for alternately outputting the first pumping light pulse and the second pumping light pulse after time-splitting the pumping light. The first waveguide structure 201 provides two optical paths of different lengths. The two optical paths respectively meet at the input end and the output end of the first waveguide structure 201, and the first waveguide structure 201 has an optical path of unequal length, and the first waveguide structure 201 can be The pump light input at the input end is time-divided to alternately output the first pump light pulse and the second pump light pulse, the first pump light pulse is an earlier output pump light pulse, and the second pump light pulse It is a pump light pulse that is output later. The output of the first waveguide structure 201 is in communication with the input of the second waveguide structure 202 via a third waveguide structure 203 having a filtering effect.

The third waveguide structure 203 is located between the first waveguide structure 201 and the second waveguide structure 202, and the third waveguide structure 203 is configured to filter out the third photon in the first pump light pulse or the second pump light pulse. The frequency of the three photons is different from the frequency of the two pump photons before the conversion of the entangled photons. The shape of the third waveguide structure 203 is designed to be in the shape of an optical filter, such as the shape of a band rejection filter, which functions to alternately output the first pump light pulse and the second pump light pulse into the second waveguide structure 202. Previously, noise photons of different frequency from the pump light in the first pump light pulse or the second pump light pulse are filtered out, that is, if two pumps in the first pump light pulse or the second pump light pulse The frequencies of the neutrons are ωp1 and ωp2, respectively, and the third waveguide structure 203 removes noise photons different from ωp1 and ωp2 output from the first waveguide structure 201. This is because the pump light of the first pump light pulse or the second pump light pulse also has a certain probability of generating a four-wave mixing effect or a Raman effect in the first waveguide structure 201, thereby generating photons of other frequencies. Photons are noisy for entangled photons, so they are filtered out before entangled photons are generated.

The second waveguide structure 202 is located at the output end of the third waveguide structure and has a spiral structure. The function of the second waveguide structure 202 is to provide an optical path that is as long as possible, so that the first pump light pulse and the second pump light pulse are alternately output. In the process of passing through the second waveguide structure 202, there is sufficient time to generate an entangled photon pair by a certain probability p in the optical path by the effect of the spontaneous four-wave mixing effect. The specific generation process is to convert two pump photons in the first pump light pulse into entangled photon pairs, or convert two pump photons in the second pump light pulse into entangled photon pairs, and generate entangled photons. The pair includes the associated first photon and second photon.

It should be noted that the probability of simultaneously generating entangled photon pairs in the first pump light pulse and the second pump light pulse is negligible, because the first pump light pulse and the second pump light pulse simultaneously generate entanglement. The probability of a photon pair is p ² , which is a minimum value. Therefore, it can be considered that in the case where an entangled photon pair is generated in the first pump light pulse, no entangled photon pair is generated in the second pump light pulse, and vice versa. Also.

Wherein, the entangled state of the generated entangled photon pair can be used

Represented where e indicates that an entangled photon pair was detected in an earlier first pump light pulse position and l indicates that an entangled photon pair was detected in a later second pump light pulse.

Wherein, the frequency relationship between the two pump photons before conversion and the converted entangled photon pair is: the frequencies defining the two pump photons are respectively ωp1, ωp2, and the frequencies of the first photon and the second photon are respectively ωi, ωs Then, if an entangled photon pair is generated according to the non-degenerate spontaneous four-wave mixing principle, then ωp1=ωp2, ωs≠ωi, and satisfy ωs+ωi=2×ωp1=2×ωp2; if the four-wave mixing is performed according to degenerate spontaneous The principle produces an entangled photon pair, then ωp1 ≠ ωp2, ωs = ωi, and satisfies ωp1 + ωp2 = 2 × ωs = 2 × ωi.

Furthermore, the output of the second waveguide structure 202 is in communication with the input of the fifth waveguide structure 205 through the fourth waveguide structure 204.

The fourth waveguide structure 204 is located between the second waveguide structure 202 and the fifth waveguide structure 205 and has a structural feature similar to an optical filter, and functions to pass the second waveguide after the entangled photon pair enters the fifth waveguide structure 205. The doping of the output of the structure 202 is filtered out of noise photons in the entangled photon pair, wherein the noise photons are photons that are different in frequency from the first photon and the second photon generated during the generation of the entangled photon pair.

The fifth waveguide structure 205 is located at the output end of the fourth waveguide structure 204, and has a structural feature similar to a beam splitter, and functions as the first photon and the second photon in the entangled photon pair outputted by the fourth waveguide structure 204, according to The optical path of the fifth waveguide structure 205 separates the first photon from the second photon. The output end of the fifth waveguide structure 205 includes a first output end and a second output end. The first output end of the fifth waveguide structure 205 outputs a first photon, and the second output end of the fifth waveguide structure 205 outputs a second photon. .

The sixth waveguide structure 206 is located at the output end of the fifth waveguide structure 205 and has a structural feature similar to a coupler for coupling the first photon outputted from the first output end of the fifth waveguide structure 205 into the first single mode fiber. The second photon outputted from the second output end of the fifth waveguide structure 205 is coupled into the second single mode fiber, and the first single mode fiber and the second single mode fiber are disposed outside the substrate 100.

In the above entangled photon pair generating device provided by the present application, the pumping light source 300, the first waveguide structure 201 having a spectroscopic effect, and the third waveguide structure 203 having a filtering effect have an exciting four-wave mixing effect to generate an entangled photon pair. a second waveguide structure 202, a fourth waveguide structure 204 having a filtering effect, a fifth waveguide structure 205 having a splitting effect, and a sixth waveguide structure 206 having a coupling function may be integrated on the SOI substrate due to the SOI substrate The thickness is on the order of micrometers, and the size is on the order of millimeters, so that the size of the entangled photon pair generating device is miniaturized, and the first waveguide structure 201, the second waveguide structure 202, the third waveguide structure 203, the fourth waveguide structure 204, and the fifth The waveguide structure 205 and the sixth waveguide structure 206 are both formed by etching a waveguide material deposited on the SOI substrate. The etching process can be compatible with the CMOS process. Therefore, the entangled photon pair generating device can be directly on the SOI substrate. Through the formation of a semiconductor process, it is possible to quantify production and contribute to cost reduction.

Based on the same inventive concept, the present application further provides an entangled photon pair generating device, as shown in FIG. 6, comprising:

The substrate 100 includes a waveguide structure 200 on the substrate 100 and a pumping source 300. The waveguide structure 200 includes a first waveguide structure 201, a second waveguide structure 202, a third waveguide structure 203, and a fourth waveguide structure 204. The fifth waveguide structure 205, the sixth waveguide structure 206, further includes a carrier 400, the substrate 100 and the pumping light source 300 are disposed on the carrier 400, and further includes a seventh waveguide structure 401, and the pumping light source 300 passes through the seventh waveguide structure 401 and A waveguide structure 201 is in communication.

The first waveguide structure 201, the second waveguide structure 202, the third waveguide structure 203, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure 206 are all engraved by the waveguide material deposited on the substrate 100. After the etch, the etch process can be compatible with the CMOS process, so the entangled photon pair generating device can be directly in the SOI lining The bottom is formed by a semiconductor process, which can quantify production and help reduce costs. Alternatively, the waveguide material on the substrate 100 is made of silicon or silicon nitride to produce a spontaneous four-wave mixing effect.

Optionally, when the substrate 100 is an SOI substrate, the first waveguide structure 201, the second waveguide structure 202, the third waveguide structure 203, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure 206 are in the SOI. The specific content on the substrate is as described in the foregoing embodiment, and will not be described here.

Optionally, the seventh waveguide structure 401 is located on the substrate 100. Referring to FIG. 7, the substrate 100 is an SOI substrate, and a seventh waveguide structure 401 is disposed at an edge of the SOI substrate. The pump light source 300 on the carrier is disposed adjacent to the seventh waveguide structure 401. The pump light source 300 and the seventh waveguide structure 401 are provided. The first waveguide structure 201, the third waveguide structure 203, the second waveguide structure 202, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure 206 (not shown in FIG. 7) are disposed laterally along the inline shape. The seventh waveguide structure 401 is also fabricated together with the first waveguide structure 201, the second waveguide structure 202, the third waveguide structure 203, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure 206, both of which pass through the SOI. The waveguide material on the substrate is etched, and the waveguide material is a waveguide layer deposited on the SOI substrate. Optionally, the waveguide material on the SOI substrate is silicon, silicon nitride or silicon dioxide to generate a spontaneous four-wave mixing effect of the pump light in the waveguide material on the SOI substrate, and on the SOI substrate The etching process of the waveguide material is compatible with the CMOS process, which is advantageous for the quantitative production of the entangled photon generation device and reduces the cost.

Optionally, the seventh waveguide structure 401 is located on the carrier 400. Referring to FIG. 8, the substrate 100 is an SOI substrate, and the seventh waveguide structure 401 and the pump light source 300 are both disposed on a carrier, and the seventh waveguide structure 401, the pumping light source 300, and the first waveguide structure 201 on the SOI substrate. The third waveguide structure 203, the second waveguide structure 202, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure 206 (not shown in FIG. 8) are disposed laterally along the inline shape. A seventh waveguide structure 401 is disposed adjacent the edge of the SOI substrate in communication with the first waveguide structure 201 at the edge of the SOI substrate. The seventh waveguide structure 401 is formed by etching a waveguide material on the carrier. The waveguide material on the carrier may be the same as or different from the waveguide material on the SOI substrate. Optionally, the waveguide material on the carrier is silicon or silicon nitride.

Optionally, a portion of the seventh waveguide structure 401 is located on the carrier 400 and another portion is located on the substrate 100. Referring to FIG. 9, the substrate 100 is an SOI substrate, the pumping source 300 is disposed on the carrier, a portion of the seventh waveguide structure 401 is located on the carrier 400, and another portion is located on the SOI substrate, and the optical path of the seventh waveguide structure 401 is divided. The front optical path and the rear optical path, the front optical path is located on the carrier 400, and the rear optical path is located on the substrate 100. a seventh waveguide structure 401, a pumping light source 300 and a first waveguide structure 201 on the SOI substrate, a third waveguide structure 203, a second waveguide structure 202, a fourth waveguide structure 204, a fifth waveguide structure 205, and a sixth waveguide structure 206 (not shown in Fig. 8) is disposed laterally along the inline shape.

Alternatively, in order to reduce the lateral dimension of the chip, the pumping source 300 and the substrate 100 are arranged side by side on the carrier 400. As shown in FIG. 10, the substrate 100 is an SOI substrate, and the SOI substrate and the pumping light source 300 are arranged side by side on the carrier, and the shape of the seventh waveguide structure 401 for connecting the pumping light source 300 and the first waveguide structure 201 is C shape. The first waveguide structure 201, the second waveguide structure 202, the third waveguide structure 203, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure 206 (not shown in FIG. 8) on the SOI substrate are along a word Horizontal setting.

Optionally, the pump light source 300 is a III-V laser diode or a vertical cavity surface emitting laser array VCSEL bonded to the carrier 400. Alternatively, the material of the carrier may be silica or a polymer.

In the above entangled photon pair generating device provided by the present application, the pumping light source 300 and the SOI substrate are integrated on the same surface of the carrier, and the first waveguide structure 201 having the light splitting effect is integrated on the SOI substrate, and has a filtering effect. The third waveguide structure 203 has a second waveguide structure for exciting an entangled photon pair to excite an spontaneous four-wave mixing effect, a fourth waveguide structure 204 having a filtering effect, and a fifth waveguide structure 205 having a splitting effect, having a coupling effect The sixth waveguide structure, the thickness of the SOI substrate is on the order of micrometers, and the size is on the order of millimeters, so the above integrated structure makes the entangled photon pair The size of the device is miniaturized, and the first waveguide structure 201, the second waveguide structure 202, the third waveguide structure 203, the fourth waveguide structure 204, the fifth waveguide structure 205, and the sixth waveguide structure 206 are all deposited on the SOI lining. After the waveguide material on the bottom is etched, the etching process can be compatible with the CMOS process. Therefore, the entangled photon pair generating device can be formed directly on the SOI substrate by a semiconductor process, which can quantify the production and is advantageous for cost reduction.

Claims

An entangled photon pair generating device, comprising: a substrate and a pumping source, a first waveguide structure and a second waveguide structure on the substrate;

Wherein the first waveguide structure and the second waveguide structure are formed by etching a waveguide material on the substrate, the first waveguide structure being located at the pumping source and the second waveguide Between structures;

The pumping light source for transmitting pump light to the first waveguide structure;

The first waveguide structure is configured to alternately output the first pump light pulse and the second pump light pulse after performing time splitting on the pump light;

The second waveguide structure is configured to convert two pump photons of the first pump light pulse or the second pump light pulse into an entangled photon pair, the entangled photon pair including an associated first Photons and second photons.
The entangled photon pair generating apparatus according to claim 1, further comprising: a third waveguide structure on said substrate, said third waveguide structure being formed by etching said waveguide material The third waveguide structure is located between the first waveguide structure and the second waveguide structure for filtering out the first waveguide structure output and the first pump light pulse, the second The noise photons of different pump light frequencies in the pump light pulse.
The entangled photon pair generating apparatus according to claim 1, further comprising: a fourth waveguide structure on said substrate, said fourth waveguide structure being formed by etching said waveguide material The fourth waveguide structure is located at an output end of the second waveguide structure, and is configured to filter out a frequency different from a frequency of the first photon and the second photon output from an output end of the second waveguide structure. Noise photons.
The entangled photon pair generating apparatus according to claim 3, further comprising: a fifth waveguide structure on said substrate, said fifth waveguide structure being formed by etching said waveguide material The fifth waveguide structure is located at an output end of the fourth waveguide structure for separating the first photon and the second photon outputted from an output end of the fourth waveguide structure.
The entangled photon pair generating device according to claim 4, further comprising: a sixth waveguide structure on the substrate, wherein the sixth waveguide structure is formed by etching the waveguide material The sixth waveguide structure is located at an output end of the fifth waveguide structure for coupling a first photon outputted from an output end of the fifth waveguide structure into the first single mode fiber, and the second photon is Coupled into the second single mode fiber, the first single mode fiber and the second single mode fiber are disposed outside of the substrate.
The entangled photon pair generating apparatus according to any one of claims 1 to 5, wherein the substrate is an SOI substrate.
The entangled photon pair generating device according to any one of claims 1 to 6, wherein the waveguide material is silicon or silicon nitride.
The entangled photon pair generating device according to any one of claims 1 to 6, wherein the frequencies of the two pump photons are ωp1, ωp2, respectively, of the first photon and the second photon The frequencies are ωi, ωs, respectively.

If ωp1=ωp2, then ωs≠ωi, and satisfy ωs+ωi=2×ωp1=2×ωp2;

If ωp1 ≠ ωp2, ωs = ωi, and ωp1 + ωp2 = 2 × ωs = 2 × ωi is satisfied.
The entangled photon pair generating apparatus according to claim 1, wherein said pumping light source is disposed on said substrate.
The entangled photon pair generating device according to claim 9, wherein said pumping source is a III-V laser diode or a vertical cavity surface emitting laser array VCSEL bonded to said substrate, or said Pump source A Ge laser diode for epitaxial growth on the substrate.
The entangled photon pair generating apparatus according to claim 1, wherein said apparatus further comprises a carrier, and said substrate and said pumping light source are disposed on said carrier.
The entangled photon pair generating apparatus according to claim 11, wherein said pumping source is a III-V laser diode or a vertical cavity surface emitting laser array VCSEL bonded to said carrier.
The entangled photon pair generating apparatus according to claim 12, wherein said apparatus further comprises a seventh waveguide structure, said seventh waveguide structure being located on said carrier and/or said substrate, said pump A light source is in communication with the first waveguide structure through the seventh waveguide structure.