JP5317122B2 - Single photon generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain high efficiency, high integration and high-control polarization at the same time, in a single-photon generator that uses a 2DPC optical resonator. <P>SOLUTION: The single-photon generator includes a material as a core of two-dimensional photonic crystal optical resonator, a light-emitting body introduced into the material as a core of two-dimensional photonic crystal optical resonator, an optical waveguide using amorphous silicon hydride as a core, a low reflective-index material functioning as a clad of the two-dimensional photonic crystal optical resonator, a low refractive-index material functioning as a clad of amorphous silicon hydride optical waveguide, an adhesive material for joining wafer, and a device substrate. The two-dimensional photonic crystal optical resonator has at least one reflecting surface, and the amorphous silicon hydride optical waveguide has at least one reflecting surface close to the two-dimensional photonic crystal optical resonator. The two-dimensional photonic crystal optical resonator and the amorphous silicon hydride optical waveguide are arranged, in such a manner that the mutual reflecting surfaces overlap. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a single photon generator used for quantum cryptography communication and the like, and more particularly to a single photon generator using a two-dimensional photonic crystal optical resonator.

Currently, in order to realize a safe information communication society, it is expected to realize quantum cryptography communication with extremely high security.
Quantum cryptographic communication is characterized by security guarantees based on physical laws, not security guarantees based on the conventional computational complexity theory.

In particular, quantum cryptography communication using a single photon has attracted attention as one of the leading communication methods. When sending photons one by one, based on quantum theory, it is impossible to eavesdrop without leaving a trace. Therefore, in quantum cryptography communication using a single photon, it is possible to detect the presence or absence of eavesdropping.
By detecting the presence / absence of eavesdropping, the sender and the receiver can share information guaranteed not to be eavesdropped with each other. Quantum cryptographic communication using a single photon is a communication method suitable for sharing information that should not be known to a third party.
Quantum cryptographic communication using a single photon is expected to be applied to common key distribution in a common key cryptosystem.

  In quantum cryptography communication using a single photon, an apparatus for efficiently generating a single photon is required. Conventionally, weak laser light having an average number of photons per pulse attenuated to about 0.1 has been used. However, when a weak laser beam is used, the number of photons follows a Poisson distribution, so that the probability that two or more photons are generated at the same time cannot be sufficiently reduced.

  In recent years, a method using a micro optical resonator has been reported as one of effective methods for realizing an ideal single photon source. In particular, an optical resonator using a two-dimensional photonic crystal (2-Dimensional Photonic Crystal: 2DPC) has attracted a great deal of attention because it can realize an ultra-small and high-performance optical resonator. For example, it has been reported that a single photon source can be realized by introducing a light emitter such as a quantum dot into a 2DPC optical resonator (FIG. 36, Non-Patent Document 1).

However, a single photon source using a 2DPC optical resonator has the following problems.
The first problem is that the 2DPC optical resonator has a vertically symmetric structure, and therefore emits light symmetrically with respect to the vertical direction (FIG. 37).
In the generation of a single photon, the probability of being emitted to the upper surface (or the lower surface) is 50%.
Therefore, when the light receiving optical system is arranged on the upper surface (or the lower surface), the probability that a single photon can be received is 50% at the maximum.
Here, in the 2DPC optical resonator, a countermeasure for introducing a vertical asymmetric structure and making the light emission non-uniform in the vertical direction can be considered. Generally, when a vertical asymmetric structure is introduced, TE (Transverse-Electric) -TM It is known that (Transverse-Magnetic) coupling occurs and the characteristics as an optical resonator deteriorate.

As a second problem, the 2DPC optical resonator is an ultra-compact optical resonator having a size of about several μm, and thus emits light with respect to a wide radiation angle.
For communication, a single photon must be transmitted using an optical fiber. However, since the radiation pattern has a wide radiation angle, efficient coupling with the optical fiber becomes very difficult.

In addition to the 50% loss listed as the first problem, the coupling loss with the optical fiber listed as the second problem causes many of the single photons generated in the 2DPC optical resonator to be transmitted to the optical fiber. Without being lost as a loss.
In a communication system using a single photon, if a single photon is lost due to loss, information held by the single photon is not transmitted at all. Therefore, the realization of a single photon generator capable of efficiently transmitting a single photon to an optical fiber is very important.

  Furthermore, for practical use, the single photon generator is required to have a structure suitable for integration. Examples of integration include high integration of single photon sources, optical / optical integration with other optical devices, and optical / electronic integration with other electronic devices.

  For practical use, it is desirable that the single photon generator can control the polarization direction of the generated single photon. Naturally, it is desirable in the quantum cryptography communication system in which signals 0 and 1 are assigned to two orthogonal polarization directions. Also, in the quantum cryptography communication system that assigns 0 and 1 of the signal to two phases shifted by π, the polarization direction of a single photon is controlled to a desired direction in consideration of the polarization dependence of the optical element It is hoped that it can be done.

Dirk Englund and et al, “Controlling the Spontaneous Emission Rate of Single Quantum Dots in a Two-Dimensional Photonic Crystal,” Physical Review Letters, vol. 95, pp. 013904-1-4 (2005)

  The present invention has been made in view of the above-mentioned problems of the prior art, and simultaneously achieves high efficiency, high integration, and high polarization control for a single photon generator using a 2DPC optical resonator. It is an object of the present invention to provide a single photon generating device. The details are as follows.

First, a 2DPC optical resonator single photon generator capable of efficiently transmitting a single photon to an optical fiber is provided.
Second, to provide a 2DPC optical resonator single photon generator suitable for integration.
Third, to provide a 2DPC optical resonator single photon generator capable of controlling the polarization direction of a single photon.

The above problem is solved by the following means.
(1) As a component, a material that becomes a core of a two-dimensional photonic crystal optical resonator, a light emitter introduced into a material that becomes a core of a two-dimensional photonic crystal optical resonator, and a light emitter are introduced Hydrogenation that is formed above the core material of the two-dimensional photonic crystal optical resonator, transmits the irradiated excitation light, irradiates the light emitter, and transmits single photons generated from the light emitter . an amorphous silicon emission optical waveguide, a first low refractive index material serving as a clad disposed below the the two-dimensional photonic crystal optical resonators of the core material 2-dimensional photonic crystal optical resonators, hydrogen A second low-refractive-index material that functions as a cladding of the amorphous silicon optical waveguide, a device substrate, and a wafer-bonding adhesive material that bonds the wafer between the first low-refractive-index material and the device substrate , Is a laminated structure,
The two-dimensional photonic crystal optical resonator has at least one mirror surface, and the hydrogenated amorphous silicon optical waveguide has at least one mirror surface in the vicinity of the two-dimensional photonic crystal optical resonator. dimension photonic crystal optical resonators and water hydride amorphous silicon optical waveguide, a single photon generating apparatus characterized by being arranged to have at least one reflection-surfaces that can be shared with each other.
(2) The two-dimensional photonic crystal used in the two-dimensional photonic crystal optical resonator is a triangular lattice two-dimensional photonic crystal or a square lattice two-dimensional photonic crystal. Single photon generator.
(3) The single-photon generator according to (1) or (2), wherein the material serving as the core of the two-dimensional photonic crystal optical resonator is a compound semiconductor.
(4) The single light emitting device according to any one of (1) to (3), wherein the light-emitting body introduced into the material serving as a core of the two-dimensional photonic crystal optical resonator is a quantum dot. Photon generator.
(5) The single photon generator according to any one of (1) to (4), wherein the hydrogenated amorphous silicon optical waveguide has a thin-line optical waveguide structure or a rib-type optical waveguide structure.
(6) The single photon generator according to any one of (1) to (5), wherein the first low refractive index material is SiO ₂ .
(7) The single photon generator according to any one of (1) to (6), wherein the second low refractive index material is SiO ₂ .
(8) The single photon generator according to any one of (1) to (7), wherein the wafer bonding adhesive material is BCB resin or SOG (Spin On Glass).
(9) The single photon generator according to any one of (1) to (8), wherein the device substrate is a Si substrate, an SOI (Silicon On Insulator) substrate, or a quartz substrate.
(10) The amount of misalignment of the mirror surface due to the alignment error that occurs during fabrication between the two-dimensional photonic crystal optical resonator and the hydrogenated amorphous silicon optical waveguide is 100 nm or less. (1) The single photon generator in any one of (9).

  In the present invention, single photons generated using a 2DPC optical resonator are extracted using a hydrogenated amorphous silicon (a-Si: H) optical waveguide. Here, the a-Si: H optical waveguide can be connected to the optical fiber with high efficiency. Accordingly, the present invention firstly provides a 2DPC optical resonator single photon generator capable of efficiently transmitting a single photon to an optical fiber.

  In the present invention, wafer bonding using an adhesive material for wafer bonding is introduced, and optical / optical integration with other optical devices and optical / electronic integration with other electronic devices can be realized. In addition, since single photons are extracted using an a-Si: H optical waveguide, it is possible to realize optical / optical integration with an arbitrary optical element. Therefore, secondly, the present invention provides a 2DPC optical resonator single photon generator suitable for integration.

  In the present invention, the two-dimensional photonic crystal optical resonator and the a-Si: H optical waveguide are arranged so that their mirror surfaces overlap each other. By arranging the mirrored surfaces in this way, it becomes possible to control the polarization direction of a single photon to TE polarization or TM polarization and emit it to an optical fiber. Therefore, thirdly, the present invention provides a 2DPC optical resonator single photon generator capable of controlling the polarization direction of a single photon.

An example of a single photon generator. An example of a 2DPC optical resonator and an a-Si: H optical waveguide that are components of a single photon generator. An example of the 2DPC optical resonator which is a component of a single photon generator. An example of the a-Si: H optical waveguide which is a component of a single photon generator. An example of an arrangement method of a 2DPC optical resonator and an a-Si: H optical waveguide, which are components of a single photon generator. The example of the a-Si: H optical waveguide which is a component of a single photon generator. Explanatory drawing of the alignment error of the 2DPC optical resonator and a-Si: H optical waveguide which arise on manufacture. An example of the board | substrate which has the material used as the core of 2DPC optical resonator, and a device board | substrate. An example of introducing a low refractive index material onto a material that becomes a core of a 2DPC optical resonator. An example of introducing an adhesive material for wafer bonding to the wafer bonding interface. An example of wafer bonding using an adhesive material for wafer bonding. The example which removed the excess member with respect to the board | substrate which has the material used as the core of 2DPC optical resonator. An example of introducing a 2DPC optical resonator structure into a material that becomes a core of a 2DPC optical resonator. An example of introducing a low refractive index material onto a material that becomes a core of a 2DPC optical resonator. An example of introducing an a-Si: H optical waveguide onto a low refractive index material. An example of introducing a low refractive index material onto an a-Si: H optical waveguide. An example of introducing a 2DPC optical resonator structure into a material that becomes a core of a 2DPC optical resonator. An example of introducing a low refractive index material onto a material that becomes a core of a 2DPC optical resonator. An example of introducing an a-Si: H optical waveguide onto a low refractive index material. An example of introducing a low refractive index material onto an a-Si: H optical waveguide. An example of wafer bonding using an adhesive material for wafer bonding. The example which removed the excess member with respect to the board | substrate which has the material used as the core of 2DPC optical resonator. An example of introducing a low refractive index material onto a material that becomes a core of a 2DPC optical resonator. 2DPCL7 optical resonator. Electric field distribution (Ey) of the fundamental resonance mode of the 2DPCL7 optical resonator. Explanatory drawing (overhead view) of the coupling structure of 2DPCL7 optical resonator and a-Si: H optical waveguide. Explanatory drawing (sectional drawing) of the coupling structure of 2DPCL7 optical resonator and a-Si: H optical waveguide. An example of electric field distribution (Ey) on the mirror surface in the coupling structure of 2DPCL7 optical resonator and a-Si: H optical waveguide. Light extraction efficiency when the distance between centers of the 2DPCL7 optical resonator and the a-Si: H optical waveguide is changed. Q value when the distance between the centers of the 2DPCL7 optical resonator and the a-Si: H optical waveguide is changed. Explanatory drawing of the coupling structure of 2DPCL7 optical resonator and a-Si: H optical waveguide. Light extraction efficiency when the position of the a-Si: H optical waveguide is changed in the x direction. Q value when the position of the a-Si: H optical waveguide is changed in the x direction. An example of a coupling structure of a 2DPCL7 optical resonator and an a-Si: H optical waveguide (x = −1765 nm). An example of the coupling structure of a 2DPCL7 optical resonator and an a-Si: H optical waveguide. An example of the single photon source using the 2DPC optical resonator by a conventional method. Explanatory drawing of the emitted light in the 2DPC optical resonator which has a vertically symmetrical structure.

Hereinafter, the present invention will be described in detail based on examples.
FIG. 1 shows an embodiment of a single photon generator according to the present invention.
The single photon generator includes a material that becomes a core of a 2DPC optical resonator as a first component. For example, a compound semiconductor such as GaAs or InP may be used as a material for the core of the 2DPC optical resonator.

  This single photon generator includes a light emitter as a second component in a material that becomes a core of a 2DPC optical resonator. For example, InAs quantum dots may be used as the light emitter.

The single photon generator includes an optical waveguide having a-Si: H as a core as a third component. The a-Si: H optical waveguide is first used to efficiently extract single photons generated in a 2DPC optical resonator (FIG. 2).
Second, a-Si: H optical waveguides are used to efficiently transmit a single photon into an optical fiber. For example, a single photon can be transmitted to the optical fiber without loss by inserting a spot size converter or the like between the a-Si: H optical waveguide and the optical fiber.

Single photon generation requires excitation of the emitter in the 2DPC optical resonator. Here, the influence of the a-Si: H optical waveguide when excitation is performed by general light irradiation will be considered. Here, the thickness of the a-Si: H optical waveguide is smaller than the wavelength of light.
The optical characteristics of a-Si: H depend on the manufacturing method and manufacturing conditions, but generally have an optical band gap larger than that of silicon. Therefore, it is possible to transmit light without absorption over a wider wavelength band than silicon.

When the wavelength of the excitation light is made to correspond to a wide transmission wavelength band of a-Si: H, the a-Si: H optical waveguide can transmit the excitation light without absorption. In this case, the a-Si: H optical waveguide does not disturb excitation by light irradiation at all. Therefore, the a-Si: H optical waveguide is allowed to be freely arranged. For example, the a-Si: H optical waveguide may be disposed immediately above or below the 2DPC optical resonator.
The wide transmission wavelength band of a-Si: H is a great advantage when excitation by light irradiation is performed.

The single photon generator includes a low-refractive index material that functions as a cladding of a 2DPC optical resonator as a fourth component. For example, SiO ₂ may be used as the low refractive index material. Here, the refractive index of SiO ₂ is about 1.45.

This single photon generator includes, as a fifth component, a low refractive index material that functions as a cladding of an a-Si: H optical waveguide. For example, SiO ₂ may be used as the low refractive index material.

  This single photon generator includes a wafer bonding adhesive material as a sixth component. For example, BCB resin may be used as the wafer bonding adhesive material.

  The single photon generator includes a device substrate as a seventh component. For example, a Si substrate may be used as the device substrate.

The first to fifth components are bonded onto the device substrate, which is the seventh component, using the wafer bonding adhesive material, which is the sixth component.
Wafer bonding using a wafer bonding adhesive material is first used to realize integration of a single photon generator. For example, by introducing wafer bonding using an adhesive material for wafer bonding, optical / optical integration with other optical devices and optical / electronic integration with other electronic devices can be realized.
Wafer bonding using an adhesive material for wafer bonding is secondly used to cover the periphery of the 2DPC optical resonator core with a low refractive material. By including the wafer bonding step, it is possible to introduce a low refractive index material on both the upper and lower surfaces of the 2DPC optical resonator core.

Here, a method of introducing a low refractive index material on the upper and lower surfaces of the 2DPC optical resonator core without using the wafer bonding technique is also conceivable. For example, a material that becomes a core of a 2DPC optical resonator is grown on the low refractive index material using a crystal growth technique, and the low refractive index material is introduced on the lower surface of the 2DPC optical resonator. Thereafter, a low refractive index material is formed on the upper surface of the 2DPC optical resonator core. Thus, it is also possible to introduce low refractive index materials on both the upper and lower surfaces of the 2DPC optical resonator core without using the wafer bonding technique.
However, it is generally difficult to grow a high-quality compound semiconductor on a low refractive index material due to a difference in lattice constant or the like.

Therefore, in the production of the single photon generator according to the present invention, a method of introducing a low refractive index material to both the upper and lower surfaces of the 2DPC optical resonator core is adopted through the wafer bonding process.
Since a wafer bonding step using a wafer bonding adhesive material is included, for example, it is easy to realize a 2DPC optical resonator having a high-quality compound semiconductor as a core.
In addition, wafer bonding using an adhesive material for wafer bonding has an advantage that good wafer bonding is possible even when there are irregularities at the wafer bonding interface.

The single photon generator according to the present invention must satisfy the following conditions for the 2DPC optical resonator and the a-Si: H optical waveguide in order to realize control of the polarization direction of the single photon. .
(1) In the single photon generator, the 2DPC optical resonator includes at least one mirror surface (FIG. 3). The a-Si: H optical waveguide includes at least one mirror surface in the vicinity of the 2DPC optical resonator (FIG. 4).
(2) The 2DPC optical resonator and the a-Si: H optical waveguide are arranged so that their mirror surfaces overlap each other (FIG. 5).
By arranging the mirrored surfaces in this way, it becomes possible to control the polarization direction of a single photon to TE polarization or TM polarization and emit it to an optical fiber.

  When the 2DPC optical resonator and the a-Si: H optical waveguide are arranged without considering the conditions regarding the mirror surface, the polarization direction of the single photon is either TE polarization or TM polarization. It becomes a state that can be. That is, a single photon becomes TE polarization or TM polarization according to a certain probability, and is emitted to the optical fiber. Since the polarization direction of a single photon is ambiguous, there is a problem in improving the efficiency of information transmission.

In the above embodiment, a triangular lattice 2DPC is used as the 2DPC (FIG. 3), but other 2DPCs may be used in the present invention. For example, use of square lattice 2DPC and the like can be mentioned.
Moreover, in the said Example, although a circular hole is used as a basic structure of 2DPC (FIG. 3), you may use another basic structure in this invention. For example, utilization of an elliptical hole, a triangular hole, etc. is mentioned.

In the above embodiment, a 2DPC optical resonator in which a plurality of circular holes are embedded is used as the 2DPC optical resonator (FIG. 3). However, in the present invention, other 2DPC optical resonators may be used.
For example, as a method of forming a 2DPC optical resonator, a method of changing the hole size, a method of shifting the position of the hole, a method of hetero-connecting 2DPC line defect waveguides, and a modulation structure on a part of the 2DPC line defect waveguides The method to introduce etc. are mentioned.
However, in the present invention, the 2DPC optical resonator needs to have at least one mirror surface that can be shared with the a-Si: H optical waveguide.

  Here, as the structure of the 2DPC optical resonator, the structure of a region sufficiently away from the center of the 2DPC optical resonator, that is, a region where the electromagnetic field in the resonance mode of the 2DPC optical resonator is attenuated to be negligible is not considered It's okay. Actually, there is no problem as long as the conditions of the mirror surface are satisfied in an effective range for the operation of the 2DPC optical resonator.

  In the above embodiment, a rectangular parallelepiped thin wire optical waveguide structure is used as the a-Si: H optical waveguide (FIGS. 1 and 2), but other optical waveguide structures may be used in the present invention. For example, an optical waveguide structure in which a new material (for example, SiN) is added between the core and the clad in the C-shaped thin-line optical waveguide structure, the rib-type optical waveguide structure, and the thin-line optical waveguide structure (FIG. 6). .

In the above embodiment, the a-Si: H optical waveguide has a uniform optical waveguide structure up to the tip (FIGS. 1 and 2). However, in the present invention, a non-uniform optical waveguide structure may be used. Good.
For example, an optical waveguide structure with a thin tip portion, an optical waveguide structure with a thick tip portion, an optical waveguide structure in which the waveguide width is arbitrarily modulated, and the like.
However, in the present invention, the a-Si: H optical waveguide needs to have at least one mirror surface that can be shared with the 2DPC optical resonator.

  Here, the mirror surface of the a-Si: H optical waveguide is required to exist only in the vicinity of the 2DPC optical resonator. That is, an optical waveguide structure having no mirror surface is allowed in a region sufficiently away from the center of the 2DPC optical resonator, that is, in a region where the electromagnetic field in the resonance mode of the 2DPC optical resonator is attenuated to a negligible level. . Examples of the optical waveguide structure having no mirror surface include a bent optical waveguide.

In the above embodiment, the 2DPC optical resonator and the a-Si: H optical waveguide are arranged so that their mirror surfaces overlap each other (FIG. 5). However, when the single photon generator is actually manufactured, a slight misalignment Δr occurs between the mirror surfaces due to the alignment error that occurs during the manufacturing (FIG. 7).
In the present invention, it is ideal that the positional deviation Δr between the two mirror surfaces is zero, but even if Δr deviates from zero, it does not suddenly cause malfunction. If Δr is sufficiently small, normal operation is guaranteed. This is the same as the discussion on the manufacturing error in a normal optical device.

  In the present invention, it is desirable that the positional deviation Δr between the two mirror surfaces is a sufficiently small value. For example, if the latest photolithography technique is used, the positional deviation Δr can be suppressed to a sufficiently small value of several tens of nm or less.

In the above embodiment, a compound semiconductor such as GaAs or InP is used as the material for the core of the 2DPC optical resonator, but other materials may be used in the present invention.
In the above embodiment, InAs quantum dots are used as the light emitters to be introduced into the material that becomes the core of the 2DPC optical resonator, but other light emitters may be used in the present invention.

For example, a case where a compound semiconductor is used as a material for a core of a 2DPC optical resonator and a quantum wire or quantum well is used as a light emitter to be introduced into the material for a core of a 2DPC optical resonator.
Further, there is a case where Si is used as the material for the core of the 2DPC optical resonator, and Ge quantum dots are used as the light emitter to be introduced into the material for the core of the 2DPC optical resonator.

In the above embodiment, it has been described that single photons can be efficiently transmitted by inserting a spot size converter or the like between the a-Si: H optical waveguide and the optical fiber. Here, in the present invention, any spot size converter may be used.
In the present invention, any optical element may be inserted between the a-Si: H optical waveguide and the optical fiber. For example, insertion of an optical modulator, a directional coupler, a polarization rotation element, an optical switch, etc. can be mentioned.
Here, the present invention is not only suitable for high integration of single photon sources, but also because single photons are extracted using an a-Si: H optical waveguide. There is a great advantage that it is suitable for optical and optical integration.

In the above embodiment, SiO ₂ is exemplified as the low refractive material, but other low refractive index materials may be used in the present invention. A plurality of low refractive index materials may be used in combination. For example, SiOF, SiOCH, SiON, SOG (Spin On Glass), SiN, an organic polymer, resin, etc. are mentioned.

  In the above embodiment, the BCB resin is used as the wafer bonding adhesive material. However, in the present invention, other wafer bonding adhesive materials may be used. For example, SOG, organic polymer, resin, metal material, etc. are mentioned.

  In the above embodiment, the Si substrate is used as the device substrate. However, in the present invention, other substrates may be used. Moreover, arbitrary devices (for example, an optical device, an electronic device, etc.) may be produced on the device substrate. For example, an SOI (Silicon on Insulator) substrate, a quartz substrate, a compound semiconductor substrate, and the like can be given.

Next, an example of a method for manufacturing a single photon generator according to the present invention will be briefly described.
First, a substrate having a material that becomes a core of a 2DPC optical resonator and a device substrate are prepared (FIG. 8). For example, a compound semiconductor is mentioned as a material used as the core of a 2DPC optical resonator. For example, the device substrate includes a Si substrate.
A low-refractive-index material that forms the cladding of the 2DPC optical resonator is formed on the material that forms the core of the 2DPC optical resonator (FIG. 9). For example, as the low refractive index material, SiO ₂ and the like.

A wafer bonding adhesive material is applied to the wafer bonding interface (FIG. 10). For example, BCB resin is mentioned as an adhesive material for wafer bonding.
Wafer bonding using an adhesive material for wafer bonding is performed (FIG. 11).
Excess members are removed from the substrate having the material that becomes the core of the 2DPC optical resonator (FIG. 12).

A 2DPC optical resonator structure is fabricated in the material that becomes the core of the 2DPC optical resonator (FIG. 13).
A low-refractive-index material to be a cladding of the 2DPC optical resonator and the a-Si: H optical waveguide is formed (FIG. 14). For example, as the low refractive index material, SiO ₂ and the like.

An a-Si: H optical waveguide is formed (FIG. 15).
A low-refractive-index material that forms the cladding of the a-Si: H optical waveguide is formed (FIG. 16). For example, as the low refractive index material, SiO ₂ and the like.
By using the above manufacturing steps, the single photon generator according to the present invention shown in FIG. 1 can be actually manufactured.

In manufacturing the single photon generator according to the present invention, the following manufacturing process may be used.
In the above embodiment, the 2DPC optical resonator structure is manufactured after wafer bonding (FIG. 13). However, the 2DPC optical resonator structure may be manufactured in the material that becomes the core of the 2DPC optical resonator in the first stage.
In the above embodiment, the wafer bonding adhesive material is applied on the substrate having the material that becomes the core of the 2DPC optical resonator (FIG. 10). However, even if the wafer bonding adhesive material is applied to the device substrate side, Good.
In the above-described embodiment, the sacrificial layer is used when removing the extra member on the substrate having the material that becomes the core of the 2DPC optical resonator (FIGS. 11 and 12), but other substrate removal methods may be used. . Examples thereof include a method using an etch stop layer, a CMP (Chemical Mechanical Polishing) method, a method using hydrogen ion implantation, and the like.

In the above embodiment, the a-Si: H optical waveguide is formed immediately above the 2DPC optical resonator (FIG. 16), but the a-Si: H optical waveguide may be formed immediately below the 2DPC optical resonator. .
As a manufacturing process in the case of forming an a-Si: H optical waveguide directly under a 2DPC optical resonator, an a-Si: H optical waveguide is manufactured on a substrate having a material to be a core of the 2DPC optical resonator, and thereafter And a step of integrating on a device substrate using wafer bonding.
FIG. 17-23 is an explanatory diagram of the manufacturing process. However, in this manufacturing process, it is assumed that the 2DPC optical resonator structure is manufactured in the material that becomes the core of the 2DPC optical resonator in the first stage.
The manufacturing process will be briefly described below.

First, a substrate having a material that becomes a core of a 2DPC optical resonator and a device substrate are prepared. A compound semiconductor is mentioned as a material used as the core of 2DPC optical resonator. An example of the device substrate is a Si substrate.
A 2DPC optical resonator structure is fabricated in the material that becomes the core of the 2DPC optical resonator (FIG. 17).
A low-refractive-index material that forms the cladding of the 2DPC optical resonator and the a-Si: H optical waveguide is formed on the material that becomes the core of the 2DPC optical resonator (FIG. 18). For example, as the low refractive index material, SiO ₂ and the like.

An a-Si: H optical waveguide is formed (FIG. 19).
A low-refractive-index material that forms the cladding of the a-Si: H optical waveguide is formed (FIG. 20). For example, as the low refractive index material, SiO ₂ and the like.
A wafer bonding adhesive material is applied to the wafer bonding interface. For example, BCB resin is mentioned as an adhesive material for wafer bonding.
Wafer bonding using an adhesive material for wafer bonding is performed (FIG. 21).
Excess members are removed from the substrate having the material that becomes the core of the 2DPC optical resonator (FIG. 22).
A low-refractive-index material that forms the cladding of the 2DPC optical resonator is formed (FIG. 23). For example, as the low refractive index material, SiO ₂ and the like.
By using the above manufacturing steps, a single photon generator according to the present invention in which an a-Si: H optical waveguide is formed immediately below a 2DPC optical resonator can be actually manufactured.

  In addition to the above-described manufacturing steps, for example, an a-Si: H optical waveguide is formed on a device substrate after the a-Si: H optical waveguide is formed immediately below the 2DPC optical resonator. There is also a manufacturing process in which a substrate having a material that becomes a core of a 2DPC optical resonator is integrated on a device substrate using wafer bonding.

  Examples of the single photon generator according to the present invention will be described with specific numerical values. In the following, an example of a single photon generator that emits a single photon with an optical communication wavelength of 1.55 μm and TE polarized light to an optical fiber will be described.

FIG. 24 shows the structure of the 2DPC optical resonator used in this embodiment. Since this 2DPC optical resonator is formed by embedding seven circular holes, it is generally called a 2DPCL7 optical resonator.
Here, the refractive index of the core of the 2DPC optical resonator is assumed to be 3.4 assuming a compound semiconductor such as GaAs or InP. The refractive index of the cladding of the 2DPC optical resonator is 1.445 assuming SiO ₂ .
At this time, when the thickness of the core of 2DPC is 275 nm, the interval between the circular holes is 392 nm, and the radius of the circular holes is 122 nm, the resonance wavelength of the fundamental resonance mode of the 2DPCL7 optical resonator is 1.55 μm.
Here, the fundamental resonance mode of the 2DPCL7 optical resonator has a sufficiently high Q value of 24,300.
FIG. 25 shows the electric field distribution (Ey) of the fundamental resonance mode of the 2DPCL7 optical resonator.

FIG. 26 shows an overhead view when a 2DPCL7 optical resonator and an a-Si: H optical waveguide are coupled. The 2DPCL7 optical resonator and the a-Si: H optical waveguide are arranged so that their mirror surfaces coincide with each other.
FIG. 27 shows a cross-sectional view when a 2DPCL7 optical resonator and an a-Si: H optical waveguide are coupled.
The refractive index of the core of the a-Si: H optical waveguide is 3.5. The refractive index of the clad is 1.445 assuming SiO ₂ . The structure of the a-Si: H optical waveguide is set to a lateral width of 400 nm and a height of 200 nm in consideration of transmission of a single photon having an optical communication wavelength of 1.55 μm and TE polarization.

FIG. 28 shows a numerical analysis result when a 2DPCL7 optical resonator and an a-Si: H optical waveguide are coupled. FIG. 28 shows the electric field distribution (Ey) on the mirror surface.
As a numerical analysis method, a 3DFDTD (Finite-Difference Time-Domain) method, which is a general three-dimensional electromagnetic field analysis method, was used.

From FIG. 28, it can be seen that light is well extracted from the 2DPCL7 optical resonator to the a-Si: H optical waveguide.
Here, the light propagating in the a-Si: H optical waveguide is only TE polarized light. This is due to the fact that the resonance mode of the 2DPCL7 optical resonator is TE polarization on the mirror plane shared by the 2DPCL7 optical resonator and the a-Si: H optical waveguide.
In polarization control, it is very important to match the mirror planes of the 2DPC optical resonator and the a-Si: H optical waveguide.

Next, the light extraction efficiency and the Q value when the distance between the centers of the 2DPCL7 optical resonator and the a-Si: H optical waveguide (FIG. 27) is changed are shown. Here, the tip of the a-Si: H optical waveguide is disposed immediately above the center of the 2DPCL7 optical resonator.
FIG. 29 shows the light extraction efficiency when the distance between the centers of the 2DPCL7 optical resonator and the a-Si: H optical waveguide is changed. A light extraction efficiency of 50% or more is realized at a center-to-center distance of 310 to 560 nm. In addition, a light extraction efficiency of 71% is realized at a center-to-center distance of 365 nm.

FIG. 30 shows the Q value when the distance between the centers of the 2DPCL7 optical resonator and the a-Si: H optical waveguide is changed. When the center-to-center distance is 310 to 560 nm, the Q value is 140 to 6200.
In general, it is known that a relatively low Q value is suitable for generating a single photon. For example, if the Q value is too large, single photons will be stored in the optical resonator for a long time. In this case, a single photon is not emitted outside the optical resonator but is absorbed by the light emitter. Therefore, a relatively low Q value is desirable for single photon generation.
Therefore, Q values 140 to 6200 can be said to be reasonable Q values for the purpose of generating single photons.

Next, the light extraction efficiency and the Q value when the position of the a-Si: H optical waveguide is changed in the x direction (FIG. 31) are shown. Here, the distance between the centers of the 2DPCL7 optical resonator and the a-Si: H optical waveguide was 480 nm.
Here, when the position of the a-Si: H optical waveguide is changed in the x direction, the coincidence of the mirror surfaces of the 2DPC optical resonator and the a-Si: H optical waveguide is not broken. That is, even when the position of the a-Si: H optical waveguide is changed in the x direction, generation of a TE-polarized single photon is realized as described above.

FIG. 32 shows the light extraction efficiency when the position of the a-Si: H optical waveguide is changed in the x direction. Here, the position where the tip of the a-Si: H optical waveguide is directly above the center of the 2DPCL7 optical resonator is x = 0.
Even when the position of the a-Si: H optical waveguide is changed in the x direction, a high light extraction efficiency of 50% or more can be realized by selecting an appropriate position.

FIG. 33 shows the Q value when the position of the a-Si: H optical waveguide is changed in the x direction.
Here, it should be noted that a light extraction efficiency of 50% or more can be realized even when the tip of the a-Si: H optical waveguide is not directly above the 2DPCL7 optical resonator. For example, a high light extraction efficiency of 68% can be realized at x = −1765 nm (FIG. 34).
In the above, the specific Example of the single photon generator which emits the single photon of optical communication wavelength 1.55micrometer and TE polarization to an optical fiber was demonstrated.

  In the above embodiment, a single photon generator that emits a TE-polarized single photon to an optical fiber has been described. In the present invention, a single photon that emits a TM-polarized single photon to an optical fiber is described. It is also possible to realize a generator.

The polarization of a single photon is determined by the polarization direction of the resonance mode of the 2DPC optical resonator on the mirror plane shared by the 2DPC optical resonator and the a-Si: H optical waveguide.
When the resonance mode of the 2DPC optical resonator is TE polarization on the mirror surface shared by the 2DPC optical resonator and the a-Si: H optical waveguide as in the above embodiment, the a-Si: H optical waveguide A single photon propagating through the beam is also TE polarized.

On the other hand, when the resonance mode of the 2DPC optical resonator is TM polarization on the mirror plane shared by the 2DPC optical resonator and the a-Si: H optical waveguide, the single propagation through the a-Si: H optical waveguide is performed. The photon is also TM polarized.
In the above embodiment, the fundamental resonance mode that becomes TE polarization is used on the mirror plane shared by the 2DPC optical resonator and the a-Si: H optical waveguide. Focusing on the higher-order resonance mode, a single photon generator that emits a TM-polarized single photon to an optical fiber can be realized.

When the 2DPCL7 optical resonator and the a-Si: H optical waveguide are arranged as shown in FIG. 35, the fundamental resonance mode is on the mirror plane shared by the 2DPCL7 optical resonator and the a-Si: H optical waveguide. TM polarized wave. Therefore, also in this case, it is possible to realize a single photon generator that emits a TM polarized single photon to an optical fiber.
The present invention provides a single photon generator that simultaneously achieves high efficiency, high integration, and high polarization control with respect to a single photon generator using a 2DPC optical resonator.

  As described above, the single photon generator according to the present invention is considered to be most suitable for the realization of the single photon generator. It can also be used as a device for generating photons. For example, application to LED (Light Emitting Diode) light source device, laser light source device, etc. is mentioned.

Claims (10)

As a component, a material comprising a two-dimensional photonic crystal optical resonators core, a light emitting body that is introduced into the material to be the two-dimensional photonic crystal optical resonators of the core, the said light emitter is introduced Formed above the core material of the two-dimensional photonic crystal optical resonator, transmits the excitation light irradiated with light, irradiates the light emitter, and transmits a single photon generated from the light emitter first low refractive index to function as hydrogenated amorphous silicon emission optical waveguide, as cladding of the two-dimensional photonic crystal optical resonators are core material disposed below by the two-dimensional photonic crystal optical resonators weather between the material and the second low refractive index material serving as a cladding of the hydrogenated amorphous silicon optical waveguide, and the device substrate, and the first low refractive index material and the device substrate An adhesive material for a wafer bonding performing bonding a are stacked,
The two-dimensional photonic crystal optical resonators has at least one mirror Utsumen, the hydrogenated amorphous silicon optical waveguide, in the two-dimensional photonic crystal optical resonators vicinity, having at least one mirror Utsumen with, single photon said two-dimensional photonic said hydrogenated amorphous silicon optical waveguide and the crystal optical resonator, characterized in that it is arranged to have at least one reflection-surfaces that can be shared with each other Generator. 2. The single unit according to claim 1, wherein the two-dimensional photonic crystal used in the two-dimensional photonic crystal optical resonator is a triangular lattice two-dimensional photonic crystal or a square lattice two-dimensional photonic crystal. Photon generator. Wherein the two-dimensional photonic crystal optical resonators of the core material, single photon generating apparatus according to claim 1 or 2, characterized in that a compound semiconductor. 4. The single photon generator according to claim 1, wherein the light-emitting body introduced into the material serving as a core of the two-dimensional photonic crystal optical resonator is a quantum dot. 5. . The single-photon generator according to any one of claims 1 to 4, wherein the hydrogenated amorphous silicon optical waveguide has a thin-line optical waveguide structure or a rib-type optical waveguide structure. The single-photon generator according to any one of claims 1 to 5, wherein the first low-refractive-index material is SiO ₂ . The single photon generator according to any one of claims 1 to 6, wherein the second low refractive index material is SiO ₂ . The single photon generator according to any one of claims 1 to 7, wherein the wafer bonding adhesive material is BCB resin or SOG (Spin On Glass). The single-photon generator according to any one of claims 1 to 8, wherein the device substrate is a Si substrate, an SOI (Silicon On Insulator) substrate, or a quartz substrate. Claim 1, wherein between the two-dimensional photonic crystal optical resonators and the hydrogenated amorphous silicon optical waveguide, the positional deviation amount of the mirror plane by the positioning error caused on producing, characterized in that at 100nm or less The single photon generator according to any one of claims 1 to 9.