JP2009122606A - Wavelength converter, and detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength converter with which the device is prevented from being complicated and S/N from being deteriorated, and a detector equipped with the wavelength converter. <P>SOLUTION: The wavelength converter 1 has a nonlinear meta-material 10 on which signal light (with a wavelength of λin) and pump light (with a wavelength of λp) with a frequency different from that of the signal light are made incident and the frequency of the signal light is subjected to sum frequency conversion. The signal light and the pump light are made incident on the nonlinear meta-material 10 in propagating directions opposite to each other. The nonlinear meta-material 10 makes a direction of the phase velocity at the frequency of the pump light out of the signal light, the pump light and the wavelength-converted signal light opposite to a propagation direction, and makes the direction of the phase velocity of the pump light identical to the direction of the phase velocity of the signal light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wavelength conversion device and a detection device.

  Quantum information technology using the quantum mechanical state of light and electrons is expected to provide advanced security technologies such as highly secure cryptographic communication and highly confidential authentication. For example, in quantum cryptography communication, information expressed using two quantum degrees of freedom (hereinafter, quantum information) is transmitted on a single photon, thereby ensuring the presence of an eavesdropper on the communication path. It can be detected and a secure private key can be distributed.

  However, there are still some challenges to apply such quantum information technology widely. One of them is a technique for detecting a single photon as signal light or weak light at a single photon level with high efficiency.

  Since quantum communication generally uses a wavelength near 1550 nm where fiber loss is small, a technique for detecting photons with high efficiency in this wavelength band is extremely important. However, photon detection in the 1550 nm band is not so easy as compared to the visible light band where a highly efficient Si photodiode can be used. At present, the following three methods are considered as effective photon detection methods in this wavelength band.

  The most common method is to use an InGaAs avalanche photodiode (APD), which is widely used in current quantum key distribution systems. In this case, weak light of a single photon level is detected by applying a bias voltage higher than the breakdown voltage to the photodiode. However, poor detection efficiency is the first major issue. The quantum efficiency is about 10%, and photons are counted only once in 10 times. The second problem is that there are many processes called dark counts that are erroneously counted when no photons are present, and quantum key distribution leads to an increase in errors. The third problem is that it is necessary to perform a gate operation at a constant time interval due to a transient current (after pulse) after photon detection, and it is difficult to increase the repetition rate of photon detection.

  As a second technique, a superconducting single photon detector has attracted attention in recent years. This means that a part of the superconductor is broken by the incidence of a single photon, and the arrival of the photon is read through the resistance change (see Patent Document 1). This detector is not only expected to have higher quantum efficiency than APD, but also features a very low dark count. Further, since the gate operation is unnecessary and the response speed is as fast as several tens of ps, it is suitable for large-capacity communication. The difficulty is that cooling is required to about the liquid helium temperature (4.2 K) in order to maintain the superconducting state. For this reason, cost reduction is difficult in principle.

  Under such circumstances, the third method that can simultaneously realize high performance and low cost is a photon detection method based on wavelength conversion. FIG. 9 shows a schematic diagram thereof. The basic idea is that it is difficult to detect photons in the 1550nm band directly, so it is converted to wavelengths in the visible light region by frequency up-conversion (up-conversion) and then detected with highly efficient Si APD. Yes (see Patent Document 2).

First, signal light (single photon) _in the communication wavelength band λ _in = 1550 nm is superimposed on the pump light (wavelength λ _p ) emitted from the pump light source 92 by WDM, and is incident on the nonlinear optical medium 90. As a result of the sum frequency conversion that occurs in this crystal, photons with λ _in = 1550 nm are up-converted to photons with a wavelength λ _{out in} the visible light band. Here, 1 / λ _in + 1 / λ _p = 1 / λ _out . In such a visible light wavelength band, for example, Si APD94 having both high quantum efficiency and low dark count can reliably perform photon detection.
Here, if a crystal with good conversion efficiency such as PPLN (periodically poled lithium niobate) is used as the nonlinear optical medium 90, wavelength conversion can be performed with an efficiency of about 90%, so that high photon detection efficiency is obtained as a whole. It is done. Further, in the case of Si APD, since the gate operation is unnecessary, the speed can be increased.

  A technique for performing wavelength conversion of signal light by a non-linear optical process is a key technique for photon detection. In addition to photon detection, such wavelength conversion technology is expected to be applied to quantum relay for long-range quantum communication, and is extremely useful in quantum information processing.

In recent years, as a new category of nonlinear optical media, metamaterials that control the optical response with an artificial fine structure have attracted attention. In metamaterials, a strong electromagnetic field can be created locally due to the fine structure, and the inherent nonlinearity of the substance can be enhanced (see Non-Patent Document 1 and Non-Patent Document 2), so highly efficient wavelength conversion. Can also be expected. In addition, in metamaterials having a negative refractive index (or left-handed light propagation), the second harmonic generation also has a unique property that the generated second harmonic propagates in the opposite direction to the fundamental wave. It is known (see Non-Patent Document 3).
However, in general, metamaterials are known to have a sharp increase in absorption loss at wavelengths where the refractive index is negative (or left-handed), and are not suitable for devices that handle single photons that are vulnerable to loss. It is believed that.

JP2002-94133 JP 2006-98130 M. W. Klein, et al., Opt. Express 15, 5238 (2007) Fukui, Otsu, “Basics of Optical Nanotechnology” Ohm Company (2003) I. V. Shadrivov, et al., J. Opt. Soc. Am. B 23, 529 (2006)

In the method shown in FIG. 9, in the method of converting the wavelength of the signal light, it is necessary to simultaneously enter the non-linear optical medium 90 with the pump light that is stronger than the light at the signal light level together with the signal light. However, at this time, the following two problems arise.
The first problem relates to separation of the converted signal light and pump light. Usually, when wavelength conversion is efficiently performed by PPLN or the like, it is necessary to propagate signal light and pump light in the same direction as shown in FIG. For this reason, after wavelength conversion, it is necessary to separate the wavelength-converted signal light and pump light using the prism 91, the pinhole 93, etc., and finally extract only the signal light.
But this is not so easy. When handling weak light of a single photon level as signal light, the strong pump light component must be completely removed, and slight contamination and scattering are not allowed. This necessitates rigorous optical system design and adjustment, and complicates the system. In addition, when a plurality of prisms and wavelength filters are stacked, a loss of single photons after conversion may be considered, resulting in a decrease in efficiency.

  The second problem is the influence of Raman scattering of pump light in the fiber. In FIG. 9, Raman scattering of the pump light can occur in the fiber until the pump light propagates from the pump light source 92 to the nonlinear optical medium 90. Raman scattering is a kind of inelastic scattering, and the pump light can be scattered at the same wavelength as the signal light, and therefore cannot be removed even by the prism 91 or the pinhole 93. For this reason, dark count will increase.

  Thus, a method for wavelength conversion of weak light at the photon level without complicating the apparatus and deteriorating S / N has not been known so far.

  According to the present invention, there is provided a wavelength conversion device having a nonlinear metamaterial that receives signal light and pump light having a frequency different from that of the signal light and converts the frequency of the signal light into a sum frequency. In the material, the signal light and the pump light are incident in opposite propagation directions, and the nonlinear metamaterial is the pump light out of the signal light, the pump light, and the wavelength-converted signal light. A wavelength conversion device is provided in which the direction of the phase velocity is reversed with respect to the propagation direction at a frequency of 1 to make the direction of the phase velocity of the pump light the same as the direction of the phase velocity of the signal light.

The feature of the present invention, which is different from the conventional wavelength converter, is a nonlinear metamaterial that is a so-called left-handed system in which the direction of phase velocity and the direction of propagation are opposite to each other as the nonlinear optical medium for wavelength conversion. It is a point to use.
Usually, when performing wavelength conversion, a momentum conservation law called a phase matching condition is imposed between a plurality of light waves involved in wavelength conversion. Because of this phase matching condition, efficient wavelength conversion generally occurs when the phase speeds of the signal light and the pump light are in the same direction. PPLN is an example.
For this reason, in the conventional wavelength conversion device, in order to cause efficient wavelength conversion, it is necessary to propagate the signal light and the pump light in the same direction. As a result, the converted signal light and the strong pump light are separated. In order to do so, a complicated apparatus configuration has been essential. In addition, there was concern about the deterioration of the S / N ratio.
On the other hand, when a non-linear metamaterial that is left-handed at the wavelength of the pump light is used as in the present invention, the direction of the phase velocity is opposite to the propagation direction at this wavelength.
On the other hand, in this nonlinear metamaterial, the signal light remains a right-handed system, and the propagation direction of the signal light and the direction of the phase velocity are the same direction.
Therefore, in this case, when the signal light and the pump light are propagated in opposite directions, the phase matching condition is achieved, and efficient wavelength conversion occurs. Thereby, there is no fear that strong pump light is mixed with signal light, and it is possible to avoid complication of the apparatus and deterioration of S / N.
Conventionally, at wavelengths that operate as left-handed materials, loss due to absorption generally increases, so metamaterials were considered unsuitable for devices that handle weak light such as signal light. . However, in the case of the present invention, the signal light before conversion, the signal light after conversion, and the pump light are left-handed at the wavelength of the pump light, and the normal right-handed system is left for the signal light sensitive to loss. It is designed to be. For this reason, the influence of the absorption loss of signal light can be minimized.

  Moreover, according to this invention, the detection apparatus which has the detector which detects the wavelength converter mentioned above and the signal beam | light converted with the said wavelength converter can also be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the wavelength converter which can prevent the complication of an apparatus and the deterioration of S / N, and a detection apparatus provided with this wavelength converter are provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.
(First embodiment)
First, the outline of the present embodiment will be described with reference to FIG.
The wavelength conversion device 1 of the present embodiment is a non-linear metamaterial that receives signal light (wavelength λin) and pump light (wavelength λp) having a frequency different from that of the signal light and converts the frequency of the signal light to sum frequency. (Nonlinear optical medium) 10 is provided.
Signal light and the pump light are incident on the nonlinear metamaterial 10 in the opposite propagation directions.
The non-linear metamaterial 10 has a phase velocity direction opposite to a propagation direction at a frequency of the pump light among the signal light, the pump light, and the wavelength-converted signal light, and the phase of the pump light The direction of the speed is the same as the direction of the phase speed of the signal light.

Next, the wavelength conversion device 1 and the detection device 3 of this embodiment will be described in detail.
The wavelength conversion device 1 includes the nonlinear metamaterial 10 described above, an optical fiber 13 that guides signal light that is a single photon to the nonlinear metamaterial 10, a pump light source 2 that generates pump light, and pump light into the nonlinear metamaterial. 10 and an optical fiber 14 leading to 10 and separation elements 11 and 12.
The optical fiber 13 and the optical fiber 14 are arranged with the nonlinear metamaterial 10 interposed therebetween, and the signal light and the pump light are incident on the nonlinear metamaterial 10 from opposite directions. In FIG. 1, signal light having a wavelength λin = 1550 nm is incident on the nonlinear metamaterial 10 from the left side to the right side of the drawing.
On the other hand, the pump light generated from the pump light source 2 enters the nonlinear metamaterial 10 from the right side of the drawing to the left.
In the nonlinear metamaterial 10, the direction of the phase velocity of the pump light is opposite to the direction of the group velocity.
On the other hand, the nonlinear metamaterial 10 does not convert the phase velocity and the group velocity direction of the signal light before conversion and the signal light after conversion.
Therefore, in the nonlinear metamaterial 10, the direction of the phase velocity of the pump light and the direction of the phase velocity of the signal light before conversion are the same direction. In this state, the phase matching condition is satisfied, and the signal light is frequency-upconverted to the wavelength λout and propagates rightward in the drawing.

The converted signal light emitted from the non-linear metamaterial 10 of the wavelength conversion device 1 passes through the separation element 12, and only the converted signal light is separated into the detector (Si avalanche photodiode (APD)) 5. It will be incident. The converted signal light is detected by the detector (Si avalanche photodiode (APD)) 5. The detection device 3 includes the wavelength conversion device 1 and the detector 5.
On the other hand, the pump light passes through the nonlinear metamaterial 10, propagates to the left side of the drawing, and enters the separation element 11. This separation element 11 separates the pump light.

  When performing wavelength conversion, a law of conservation of momentum called a phase matching condition is imposed between wave number vectors of light waves involved in wavelength conversion. In general, efficient wavelength conversion occurs when the wave number vector of signal light and the wave number vector of pump light are aligned. In the case of ordinary right-handed materials, the wave vector is directed in the same direction, as shown in FIG. 2 (a), that the signal light and the pump light have the same energy propagation direction (pointing vector direction). I mean. For this reason, in the conventional wavelength conversion device, in order to cause efficient wavelength conversion, it is necessary to propagate the signal light and the pump light in the same direction. As a result, the converted signal light and the strong pump light are separated. Required.

  On the other hand, if the so-called left-handed nonlinear metamaterial 10 as in the present embodiment is used, the direction of the phase velocity (that is, the direction of the wave vector) and the direction of the group velocity (the direction in which energy flows) at the wavelength of the pump light. ) Is reversed. Therefore, as shown in FIG. 2B, when the pump light is incident in the opposite direction with respect to the propagation direction of the signal light, the directions of the two wave number vectors are aligned, and efficient wavelength conversion occurs. With such a configuration, there is no concern that strong pump light is mixed with the converted signal light, and the complexity of the apparatus and the deterioration of S / N can be avoided.

  As the nonlinear metamaterial 10, there are several configurations such as a configuration using a split ring resonator (see Non-Patent Document 1) and utilization of a material having chirality (see JB Pendry, et al., Science 306, 1353 (2004)). Although an approach is conceivable, here, a realization method using a waveguide-type metamaterial is shown below because of the ease of the microfabrication process.

A basic configuration of the waveguide metamaterial is a slab type plasmon waveguide as shown in FIG. 3, and has a structure in which the upper and lower sides of the dielectric layer 102 are sandwiched between the metal layers 101 and 103. In other words, a flat dielectric layer 102 in contact with the metal layer 103 is laminated on the flat metal layer 103, and a flat metal layer 101 in contact with the dielectric layer 102 is laminated on the dielectric layer 102. ing.
The signal light and the pump light propagate through the interface between the metal layer 101 and the dielectric layer 102 and the interface between the metal layer 103 and the dielectric layer 102 as a surface plasmon mode.

  At this time, the thickness d of the dielectric layer 102 is designed to be the same as or smaller than the spatial spread of the surface plasmon mode. Practically, d is preferably 50 nm or more and 100 nm or less. In such a situation, the upper and lower surface plasmon modes are coupled, and the coupled plasmon mode becomes the fundamental propagation mode. In such a coupled plasmon mode, it is known that anomalous dispersion having a negative dispersion slope appears near the plasma frequency (Phys. Rev. B 73, 035407 (2006)). In the frequency band where such anomalous dispersion occurs, the direction of the phase velocity and the group velocity are reversed, and left-handed light propagation is realized. Such coupling between the plasmon waveguide and the outside can be efficiently performed by a method using a prism, a diffraction grating, or the like (see Non-Patent Document 2).

  4 indicates the propagation direction of the signal light, and the dotted arrow B indicates the vibration direction of the electric field. Furthermore, the curve C in FIG. 4 shows the electric field distribution, and the z-axis shows the position where the electric field becomes zero. The electric field is strongest at the interface between the metal layer 103 and the dielectric layer 102 and at the interface between the metal layer 101 and the dielectric layer 102. Note that the electric field is opposite in phase between the interface between the metal layer 103 and the dielectric layer 102 and between the metal layer 101 and the dielectric layer 102.

Here, in the waveguide type metamaterial of FIG. 3, it is necessary to use a noble metal having a plasma frequency in the vicinity of the visible light band as the metal layers 101 and 103, and in particular, gold (Au) for operating at a visible light wavelength. Use is preferred. On the other hand, various materials can be used as the dielectric layer 102. Among them, a material that exhibits a second-order nonlinear optical effect is preferable. By using a material that exhibits a second-order nonlinear optical effect in this way, the phase velocity direction of the pump light can be reliably reversed with respect to the propagation direction, and sum frequency conversion can be performed.
For example, in addition to ferroelectric materials such as lithium niobate (LiNbO ₃ ), which are common as wavelength conversion elements, organic materials such as MNA (2-methyl-4-nitroaniline) and dye molecules are used as PMMA (polymethyl methacrylate). Those dispersed in a polymer resin such as are suitable.

  In the case of the waveguide type metamaterial as shown in FIG. 4, a strong electric field is generated locally (interface between the metal layer 103 and the dielectric layer 102, interface between the metal layer 101 and the dielectric layer 102). The optical effect is enhanced. Therefore, it is expected that efficient wavelength conversion occurs even when a material that does not have a large nonlinear effect in the bulk is used.

As a specific example, FIG. 5 shows a dispersion curve of the fundamental propagation mode (TM ₀ ) of the coupled surface plasmon obtained by assuming that the dielectric constant ε of the nonlinear dielectric is 2 in the waveguide metamaterial of FIG. Show. Here, the solid line graph is calculated with the width d = 50 nm, and the broken line graph is calculated with the width d = 100 nm. In this figure, the horizontal axis is the propagation constant (the real part of the wave number) β, and the vertical axis is the emission energy (corresponding to the frequency). As can be seen from this figure, the dispersion slope (the slope of the graph) is negative in the vicinity of the emission energy of 2.45 eV (wavelength 506 nm). Here, the group velocity is represented by v _g = dω / dβ, and the phase velocity is represented by v _p = ω / β. When the slope of the graph of FIG. 5 is positive, the group velocity is positive, and when the slope of the graph of FIG. 5 is negative, the group velocity is negative.
The fact that the dispersion slope (the slope of the graph) is negative in the vicinity of the emission energy of 2.45 eV (wavelength 506 nm) indicates that the phase velocity v _p = ω / β and the group velocity v _g = dω / dβ in this wavelength band. This corresponds to the fact that the sign is reversed and left-handed light propagation is realized.

Therefore, when frequency up-conversion of photons in the communication wavelength band is performed, sum frequency conversion as shown in FIG. 6 is possible. Here, the pump wavelength is selected as λp = 506 nm so that only the pump light propagates as a left-handed system. In this way, the pump light is propagated in the opposite direction with respect to the input photon of λin = 1550 nm, so that the sum frequency conversion in the nonlinear metamaterial 10 occurs efficiently, and the photon has a visible light band of λout = 382 nm. Converted to. If it is this wavelength, photon detection with high quantum efficiency is possible by using Si APD5 for short wavelengths.
Further, in the configuration of the present embodiment, the pump light propagates in a direction away from the Si APD 5, so that it is not necessary to have a complicated device configuration using a prism, a pinhole, or the like as in the conventional method of FIG. The device configuration is simplified. Furthermore, since the Raman scattered light generated in the optical fiber 14 between the pump light source 2 and the nonlinear metamaterial 10 does not directly propagate to the Si APD 5, dark count due to Raman scattering is also reduced.

(Second embodiment)
In the embodiment, the nonlinear metamaterial was a waveguide type. On the other hand, in this embodiment, the nonlinear metamaterial is formed in a wire shape (fiber shape).
FIG. 7 shows the structure. The basic configuration is a nanowire 20 in which a three-layer structure of a metal layer 201-dielectric layer 202-metal layer 203 is concentrically stacked, and includes an interface between the metal layer 201 and the dielectric layer 202, a metal layer 203 and a dielectric. A surface plasmon mode propagates on the interface with the layer 202.
More specifically, a wire-like metal layer 201 is used as a central layer, and the periphery of the metal layer 201 is covered with a tubular dielectric layer 202, and the periphery of the dielectric layer 202 is covered with a tubular metal layer 203. It is covered. The metal layer 201 is in contact with the dielectric layer 202, and the dielectric layer 202 is in contact with the metal layer 203.
Again, noble metal layers are preferred as the metal layers 201 and 203, and Au is particularly preferred. As the dielectric layer 202, a material having non-linearity similar to that of the above embodiment is employed. The thickness of the dielectric layer 202 needs to be small enough to couple the inner and outer plasmon modes, and d is preferably 50 nm or more and 100 nm or less as in the first embodiment.

When such a nanowire-like non-linear metamaterial 20 is used, mode coupling through leaching out of a near field, such as that used in a directional coupler, with respect to an optical fiber that propagates signal light and pump light. The method is suitable (for example, see Phys. Rev. Lett. 97, 053002 (2006)).
As shown in FIG. 8, an optical fiber 24 through which signal light propagates and an optical fiber 25 through which pump light propagates are arranged with a nonlinear metamaterial 20 interposed therebetween. The propagation direction of the pump light and the propagation direction of the signal light are opposite.
As shown in FIG. 8, the non-linear metamaterial 20 and the optical fiber 24 through which the signal light propagates are brought close to each other by a certain distance L at an interval a equal to or less than the wavelength of the signal light before conversion, so that the optical fiber from the non-linear metamaterial 20 is obtained. The transfer of light energy to 24 or from the optical fiber 24 to the non-linear metamaterial 20 occurs. Here, when a and L satisfy a certain relationship defined by the mode coupling equation, the transfer efficiency of light energy is maximized.

On the other hand, the nonlinear metamaterial 20 and the optical fiber 25 through which the pump light propagates are brought close to each other by a fixed distance L ′ at an interval a ′ that is equal to or less than the wavelength of the pump light.
As a result, transfer of light energy from the nonlinear metamaterial 20 to the optical fiber 25 or from the optical fiber 25 to the nonlinear metamaterial 20 occurs. At this time, the phase velocity of the pump light incident on the nonlinear metamaterial 20 is opposite to the propagation direction of the pump light, and is the same direction as the phase velocity of the signal light.

In this state, the phase matching condition is satisfied, the signal light is frequency-upconverted to the wavelength λout, and propagates in the same direction as the signal light before conversion. The converted signal light returns to the optical fiber 24 and is detected by the detector 5 as in the above embodiment.
In addition, it is preferable to adjust parameters, such as a fiber diameter and the wire diameter of the nonlinear metamaterial 20, so that the propagation constant of the fibers 24 and 25 and the propagation constant of the nonlinear metamaterial 20 may become equal.
By aligning the propagation constants in this way, the light energy transfer efficiency between the two modes can be optimized.
According to such this embodiment, there can exist an effect similar to 1st embodiment.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the above-described embodiment, the separation element is disposed with the nonlinear metamaterial 10 interposed therebetween, but this separation element may not be provided. By doing in this way, the apparatus structure of a wavelength converter can be simplified.
Furthermore, in the said embodiment, although the wavelength of the signal light which injects into a nonlinear metamaterial was made into the 1.55 micrometer band, it is good not only in this but a 1.3 micrometer band.

It is a figure which shows typically the structure of the detection apparatus concerning 1st embodiment of this invention. It is a figure which shows a mode that wavelength conversion is performed with the nonlinear medium used as a right-handed system, and the nonlinear metamaterial used as a left-handed system in the wavelength of pump light. It is a figure which shows a nonlinear metamaterial. It is a figure which shows the fundamental propagation mode of a nonlinear metamaterial. It is a figure which shows the relationship between the wave number at the time of using a nonlinear metamaterial, and light emission energy. It is a figure which shows the mode of wavelength conversion at the time of using a nonlinear metamaterial. It is a figure which shows the nonlinear metamaterial concerning 2nd embodiment. It is a figure which shows the wavelength converter concerning 2nd embodiment. It is a figure which shows the conventional wavelength converter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wavelength converter 2 Pump light source 3 Detector 5 Detector 10 Non-linear metamaterial 11 Separation element 12 Separation element 13 Optical fiber 14 Optical fiber 20 Non-linear metamaterial 24 Optical fiber 25 Optical fiber 90 Non-linear optical medium 91 Prism 92 Pump light source 93 Pin Hall 94 Si APD
DESCRIPTION OF SYMBOLS 101 Metal layer 102 Dielectric layer 103 Metal layer 201 Metal layer 202 Dielectric layer 203 Metal layer
d width
a interval a 'interval L distance L' distance A arrow B arrow C curve

Claims (8)

A wavelength converter having a nonlinear metamaterial that receives signal light and pump light having a frequency different from that of the signal light and converts the frequency of the signal light to sum frequency,
The nonlinear metamaterial is incident in the propagation direction in which the signal light and the pump light are opposed to each other,
The nonlinear metamaterial is configured to reverse the direction of phase velocity with respect to the propagation direction at the frequency of the pump light out of the signal light, the pump light, and the wavelength-converted signal light, and the phase speed of the pump light. The wavelength conversion device in which the direction of is the same as the direction of the phase velocity of the signal light. In the wavelength converter of Claim 1,
The nonlinear metamaterial is a wavelength conversion device having a first metal layer, a dielectric layer in contact with the first metal layer, and a second metal layer in contact with the dielectric layer. In the wavelength converter of Claim 2,
The wavelength conversion device, wherein the first metal layer and the second metal layer are noble metal layers. In the wavelength converter of Claim 2 or 3,
The wavelength conversion device, wherein the dielectric layer is made of a material having a second-order nonlinear optical effect. In the wavelength converter in any one of Claims 2 thru | or 4,
The nonlinear metamaterial has a structure in which a flat plate-like dielectric layer is laminated on a flat plate-like first metal layer, and a flat plate-like second metal layer is laminated on the dielectric layer. A wavelength converter. In the wavelength converter in any one of Claims 2 thru | or 4,
The nonlinear metamaterial has a structure in which the first metal layer is a central layer, the first metal layer is covered with the dielectric layer, and the dielectric layer is covered with a second metal layer. The wavelength converter. In the wavelength converter in any one of Claims 1 thru | or 6,
The wavelength conversion device wherein the wavelength of the signal light incident on the nonlinear metamaterial is a communication wavelength band of 1.55 μm band or 1.3 μm band.   8. A detection apparatus comprising: the wavelength conversion apparatus according to claim 1; and a detector that detects signal light converted by the wavelength conversion apparatus.

Images