JP3923481B2 - Nano optical D / A converter - Google Patents

Description

  The present invention relates to a nano-optical D / A converter and a nano-optical A / D converter that are particularly applied to fields such as a nanoscale optical communication network and optical measurement.

  With the recent development of semiconductor microfabrication technology, a semiconductor element having a fine structure up to a size at which a quantum mechanical effect appears noticeably has been realized (for example, see Non-Patent Document 1). As semiconductor elements utilizing this quantum mechanical effect, for example, HBT (Hetero-junction Bipolar Transistor) and quantum well lasers have been put into practical use. In addition, nanoscale quantum dots that take advantage of the particle properties of electrons by controlling single electrons using quantum mechanical effects have attracted attention.

  Quantum dots are formed by using the above-described semiconductor microfabrication technology to form a box with a potential that is so fine that it gives three-dimensional quantum confinement to excitons. Utilizing this exciton confinement system, the energy levels of carriers in the quantum dot become discrete, and the density of states sharpens in a delta function. Single-electron memories that use light absorption between the sharpened states of this quantum dot and single-electron transistors that turn on / off single electrons that enter and exit the quantum dot have already been studied. Nanoscale manipulation is being realized.

M. Ohtsu, K. Kobayashi, T. Kawazoe, S. Sangu, T. Yatsui, IEEE J. Sel. Top. Quant. Electron., To be published Vol8.No4 2002 July-Aug, P839-P862

  By the way, in order to meet the demand for future large-capacity information processing, a nanoscale nano-optical D / A converter that can perform optical D / A conversion and optical A / D conversion without being controlled by the diffraction limit of light. Realization of a nano-optical A / D converter or the like is desired.

  However, when trying to realize such a nanoscale circuit with an electronic device, problems such as power consumption and heat generation occur, and when trying to realize it with an optical device, miniaturization is still limited by the diffraction limit of light. There is a problem of being done. Furthermore, when trying to realize this with a quantum device, there is a problem that an apparatus for ensuring coherence for a long time becomes large. For this reason, a practical nanoscale optical D / A conversion and optical A / D conversion circuit itself have not yet been devised.

  Therefore, the present invention has been devised in view of the above-described problems, and finds a unique photophysical phenomenon between quantum dots arranged in the nanometer region, and allows light to be controlled without being controlled by the light diffraction limit. An object of the present invention is to provide a nano light D / A converter and a nano light A / D converter capable of performing D / A conversion, light A / D conversion processing, and the like on a nano scale.

  In order to solve the above-described problems, the nano-optical D / A converter according to the present invention is supplied with input light having different frequencies corresponding to the dielectric substrate and each bit of the digital signal to be D / A converted. An input-side quantum dot group in which a plurality of quantum dots having different sizes so that excitons are excited according to the frequency of the supplied input light are formed on the substrate; The resonance energy level in which excitons are injected from each quantum dot constituting the input-side quantum dot group through the substrate according to resonance with the level, and the energy released from the resonance energy level Accordingly, output quantum dots that generate output light having a frequency lower than that of each input light as an analog signal that has been D / A converted are provided.

  In order to solve the above-described problems, a nano-optical A / D converter according to the present invention is supplied with input light having a dielectric substrate and light intensity corresponding to an analog signal to be A / D converted. The quantum dots on the input side formed on the substrate having a plurality of energy levels in which excitons are transitioned according to the light intensity of the supplied light, and the resonance according to the resonance between the energy levels. An output-side quantum dot group comprising a plurality of quantum dots whose resonance energy levels are different from each other so that excitons are injected from the quantum dot on the input side via the substrate, Each quantum dot constituting the group generates output light having a higher frequency than the input light as an A / D converted digital signal in accordance with the energy emitted from the resonance energy level.

  In the nano-optical D / A converter according to the present invention, by controlling the supply state of the input light based on the digital signal to be D / A converted, the energy flowing from the quantum dots constituting the quantum dot group to the output side quantum dots is controlled. Since the sum can be controlled and the light intensity of the output light as the analog signal to be emitted is controlled by this, D / A conversion can be realized. In particular, in the nano-optical D / A converter to which the present invention is applied, optical D / A conversion can be performed between nanometer-sized quantum dots without being controlled by the diffraction limit of light. Can also be realized.

  In the nano-optical A / D converter according to the present invention, by controlling the light intensity of the input light based on the analog signal to be A / D converted, it is controlled to which quantum dot the energy is transmitted from the input side quantum dot. Since each bit signal of the emitted digital signal is dominated by this, A / D conversion can be realized. In particular, the nano-optical A / D converter to which the present invention is applied can perform optical A / D conversion between nanometer-sized quantum dots without being controlled by the diffraction limit of light, and make a high-performance optical device nano-sized. Can also be realized.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

The present invention is applied to a nano-optical D / A converter 1 as shown in FIG. The nano-optical D / A converter 1 is a converter that converts a supplied digital signal into an analog signal on a nano scale. For example, a substrate 10 made of a dielectric material such as NaCl, KCl, or CaF _2, and a substrate An output-side quantum dot composed of a quantum dot group 20 composed of a plurality of quantum dots 11, 12, 13 formed on the surface of 10 and a single quantum dot formed in the vicinity of the quantum dot group 20 30.

  The first quantum dot 11, the second quantum dot 12, the third quantum dot 13, and the output side quantum dot 30 constituting the quantum dot group 20 are discretely formed by confining excitons three-dimensionally. Single electron (exciton) is controlled based on the energy level. In these quantum dots 11, 12, 13, and 30, the energy levels of the carriers are made discrete by the exciton confinement system, and the state density can be sharpened in a delta function.

  The quantum dots 11, 12, and 13 formed on the dielectric substrate 10 are supplied with input light having different frequencies corresponding to the bits of the digital signal for transmitting information depending on the presence or absence of a pulse train. That is, the input light whose frequency is allocated to different bits propagates on the substrate 10 as shown in FIG. 1 and is supplied to the quantum dots 11, 12, and 13.

  Here, the input light supplied to the first quantum dot 11 is input light A, the input light supplied to the second quantum dot 12 is input light B, and further supplied to the third quantum dot 13. When the input light is input light C, these input lights A, B, and C are supplied to the quantum dots 11, 12, and 13 by propagating on the substrate 10. At this time, a plasmon waveguide may be formed on the substrate 10, and the input light A, B, C may be supplied to the quantum dots 11, 12, 13 via the plasmon waveguide, or each quantum dot 11, This may be supplied via a near-field optical probe brought close to 12, 13 respectively.

  The quantum dots 11, 12, and 13 and the output-side quantum dot 30 have quantum levels that have substantially the same state density functions. By supplying the input lights A, B, and C to the quantum dots 11, 12, and 13, respectively, excitons at the ground level can be excited. As a result, a dipole interaction occurs between each quantum dot 11, 12, 13 and the output-side quantum dot 30, resulting in resonance with each other via the above-described quantum levels.

  Each quantum dot 11, 12, 13, 30 is made of a material system such as CuCl, GaN, or ZnO. Incidentally, when the material system constituting each quantum dot 11, 12, 13, 30 is CuCl, these are constituted in a cubic shape called a quantum box, and each quantum dot 11, 12, 13, 30 is constituted. When the material system is GaN or ZnO, these are configured as a sphere or a disk. For example, when CuCu is used as the material system constituting each of the quantum dots 11, 12, 13, and 30, the side lengths thereof are nanometer-sized, in other words, the wavelengths of the input light A, B, and C. It forms on the board | substrate 10 so that it may become the following.

  These quantum dots 11, 12, 13, and 30 can be formed on the substrate 10 by using the following Bridgman method. When CuCu is used as the material system constituting each of the quantum dots 11, 12, 13, and 30, the CuCl powder and the NaCl powder are first mixed and melted at a temperature of about 800 ° C. Next, the molten powder mixture is suspended in a furnace having a temperature gradient in the vertical direction, and moved up and down in the furnace at a speed of several mm / h to create a temperature gradient in the mixed powder gradually. To crystallize. When heat treatment is performed at a temperature of about 200 ° C. for several minutes to several tens of minutes, NaCl crystals including CuCl quantum dots 11, 12, 13, and 30 can be produced. Incidentally, in this Bridgman method, the size of the generated quantum dots 11, 12, 13, and 30 can be freely controlled by changing the heat treatment temperature and the heat treatment time, and these are formed side by side in a region of 100 nm or less. It is also possible.

  Each of these quantum dots 11, 12, 13, and 30 may be further formed on the substrate 10 based on a molecular epitaxy (MBE) growth method, or quantum dot formation using near-field light CVD. The position may be accurately controlled.

The quantum confinement level E ( _nx , _ny , _nz ) in each quantum dot 11, 12, 13, 30 is as follows when the particle mass is m and the side length of the quantum dot is L: Defined by equation (1).
E (n _x , n _y , n _z ) = h ² / 8π ² m (π / L) ² (n _x ² + _ny ² + n _z ² ) (1)
Based on this equation (1), E (n _x , n _y , n _z ) of each quantum dot 11, 12, 13, 30 is calculated. Here, the side length ratio of the first quantum dot 11, the second quantum dot 12, the third quantum dot 13, and the output-side quantum dot 30 is approximately 1: √2: 2: 2√2. At some point, as shown in FIG. 2, E (111) when the quantum level in the first quantum dot 11 is (1,1,1), and the quantum level in the output-side quantum dot 30 is (4 , 2, 2) is equal to E (422). Also, E (111) when the quantum level in the second quantum dot 12 is (1,1,1) and when the quantum level in the output side quantum dot 30 is (2,2,2). E (222) becomes equal. When the quantum level in the third quantum dot 13 is (1,1,1) and the quantum level in the output side quantum dot 30 is (2,1,1). E (211) becomes equal. That is, the quantum level (1, 1, 1) of the first quantum dot 11, the quantum level (1, 1, 1) of the second quantum dot 12, and the quantum level (1 of the third quantum dot 13) , 1, 1) are the quantum levels (4, 2, 2), (2, 2, 2), (2, 1, 1) in the output-side quantum dot 30 and the excitation energy levels of the excitons, respectively. Are in a resonating relationship. Actually, in order to cause resonance between them, the input light A having the frequency ω1 corresponding to the quantum level (1,1,1) in the first quantum dot 11 and the quantum level in the second quantum dot 12 are used. By supplying the input light B of the frequency ω2 corresponding to (1,1,1) and the input light C of the frequency ω3 corresponding to the quantum level (1,1,1) in the third quantum dot 13, respectively. Excitons are excited to such quantum levels.

  If the exciton is excited to the quantum level (1,1,1) in the first quantum dot 11 by supplying the input light A having the frequency ω1, the quantum level (1,1,1, A resonance occurs between 1) and the quantum level (4, 2, 2) in the output-side quantum dot 30. As a result, excitons existing at the quantum level (1, 1, 1) in the first quantum dot 11 move to the quantum level (4, 2, 2) of the output side dot 30, and the output side quantum dot Move to 30 quantum levels (1,1,1). As a result, the excitons apparently move from the first quantum dot 11 to the output side quantum dot 30. The excitons that have moved to the quantum level (1, 1, 1) of the output-side quantum dot 30 emit light therefrom. Light emitted from the lower quantum level (1, 1, 1) of the output-side quantum dot 30 is extracted as output light as an analog signal, and its frequency ω4 is the frequency ω1, ω2 of the input light. , it becomes much lower than ω3. This is because the size of the output side quantum dot 30 is larger than that of each quantum dot 11, 12, 13. Therefore, by selectively detecting only the output light of the frequency ω4, it is possible to accurately measure the light intensity of the output light without mixing other frequency components.

  That is, by forming the quantum dots 11, 12, 13, and 30 having different side length ratios on the substrate 10, quantum levels having substantially equal state density functions can be created, and resonance can be generated between them. By causing it to occur, excitons can be injected from the quantum dots 11, 12, 13 having a small volume into the quantum dots 30 having a large volume. In other words, excitons can be transmitted between the quantum dots by making the volumes (sizes) different from one another.

  For this reason, by using the transmission principle of the exciton, the input lights A, B, and C corresponding to the quantum dots 11, 12, and 13 having a small volume are supplied to excite the excitons in the respective quantum levels. This is transmitted to the output-side quantum dot 30 having a large volume. The output-side quantum dot 30 generates output light by emitting such transmitted excitons to a lower level, and transmits this to the outside as an analog signal.

  The light intensity of the output light is governed by the amount of excitons emitted to the lower level in the output-side quantum dot 30, and the amount of excitons emitted is the amount of excitons transmitted from the quantum dots 11, 12, and 13. Depends on. That is, when the input lights A, B, and C are respectively supplied to all the quantum dots 11, 12, and 13, the amount of excitons that are excited correspondingly increases and is transmitted to the output-side quantum dot 30. As the amount of excitons increases, the light intensity of the output light based on these emissions increases. On the other hand, when the input lights A, B, and C are not supplied to all the quantum dots 11, 12, and 13, the amount of excitons that are excited correspondingly decreases, and the output-side quantum dot 30. As the amount of excitons transmitted to the light source decreases, the light intensity of the output light based on these emissions decreases. This means that the light intensity of the output light can be changed by controlling the supply state of the input light A, B, and C to the quantum dots 11, 12, and 13.

That is, the nano-optical D / A converter 1 to which the present invention is applied operates by linking the supply of the input light A, B, C to the quantum dots 11, 12, 13 with the digital signal to be A / D converted. The output light is generated as an analog signal having a light intensity corresponding to. For example, A0 = a ₂ × 2 ² + a ₁ × 2 ¹ + a ₀ × 2 ⁰ (a _{2 to} a ₀ take a value of 1 or 0) and a 3-bit digital signal represented by a binary number ( When converting a ₀ , a ₁ , a ₂ ) into an analog signal, the value of a ₀ is defined by the input light A having the frequency ω1, the value of a ₁ is defined by the input light B having the frequency ω2, and a A value of ₂ is defined by the input light C having the frequency ω3.

FIG. 3 shows the relationship of the light intensity of an analog signal that can be converted by the nano-optical D / A converter 1 with respect to such a 3-bit digital signal. As shown in FIG. 3, A0 (= a ₂ × 2 ² + a ₁ × 2 ¹ + a ₀ ×) is controlled by controlling the supply of the input lights A, B, and C having the frequencies ω1, ω2, and ω3. An analog signal having a magnitude of 2 ⁰ ) can be acquired. Of b0, b1, b2 constituting the strength of the analog signal, b0 is based on the digital signal _{a 0,} b1 is based on the digital signals _{a 1,} b2 is in the digital signal _{a 2} Is based.

Here, when the value of a ₀ is 1, the input light A having the frequency ω1 is supplied. On the other hand, when the value of a ₀ is 0, the supply of the input light A having the frequency ω1 is stopped, or the input light other than the frequencies ω1, ω2, and ω3 is switched to the supply. In the first quantum dot 11 to which the input light A having the frequency ω1 is supplied, excitons are excited to the quantum level (1, 1, 1). Since the light is emitted by moving to the position (4, 2, 2) and further transitioning to the lower level, it contributes to the light intensity of the analog signal as output light. On the other hand, in the first quantum dot 11 to which the input light A having the frequency ω1 is not supplied, the exciton is not excited to the quantum level (1, 1, 1). It does not move to the quantum level (4, 2, 2) of the output-side quantum dot 30, and this does not contribute to the light intensity of the analog signal as output light.

Similarly, when the value of a ₁ is 1, and supplies the input light B frequency .omega.2. On the contrary, if the value of a ₁ is 0, or stops supplying the input light B frequency .omega.2, or frequency .omega.1, .omega.2, it switches to the supply of input light other than [omega] 3. In the second quantum dot 12 to which the input light B having the frequency ω <b> 2 is supplied, excitons are excited to the quantum level (1,1,1). Since the light is emitted by moving to the position (2, 2, 2) and further transitioning to the lower level, it contributes to the light intensity of the analog signal as output light. On the other hand, in the second quantum dot 12 to which the input light B having the frequency ω2 is not supplied, the exciton is not excited to the quantum level (1, 1, 1). It does not move to the quantum level (2, 2, 2) of the output side quantum dot 30, and this does not contribute to the light intensity of the analog signal as output light.

Similarly, when the value of a ₂ is 1, it supplies the input light C of the frequency [omega] 3. In contrast, when the value of a ₂ is 0, or stops supplying the input light C of the frequency [omega] 3, or a frequency .omega.1, .omega.2, switches to the supply of input light other than [omega] 3. In the third quantum dot 13 to which the input light C having the frequency ω3 is supplied, excitons are excited to the quantum level (1, 1, 1). Since the light is emitted by moving to the level (2,1,1) and further transitioning to the lower level, it contributes to the light intensity of the analog signal as output light. On the other hand, in the third quantum dot 13 to which the input light C having the frequency ω3 is not supplied, the exciton is not excited to the quantum level (1, 1, 1). It does not move to the quantum level (2, 1, 1) of the output side quantum dot 30, and this does not contribute to the light intensity of the analog signal as output light.

  FIG. 4 shows the result of measuring the light intensity of the output light from the output-side quantum dot 30 with a near-field optical microscope for each digital signal to be D / A converted. FIG. 5 shows the results of actual measurement of the light intensity of the output light converted into analog signals by the nano-optical D / A converter 1 for all the 3-bit digital signals.

As shown in FIGS. 4 and 5, when D / A conversion is performed on a digital signal represented by a ₂ = 0, a ₁ = 0, a ₀ = 1 (001 in binary notation), The input light A is supplied to only one quantum dot 11, the amount of excitons transmitted to the output-side quantum dot 30 is minimized, and the light intensity of the output light L3 based on these emissions is 0. .05.

On the other hand, in the case of D / A conversion of a digital signal (100 in binary notation) represented by a ₂ = 1, a ₁ = 0, a ₀ = 0, only the third quantum dot 13 is used. The amount of excitons transmitted to the output-side quantum dot 30 is larger than the first quantum dot 11 because the third quantum dot 13 is larger than the first quantum dot 11, The light intensity of the output light L2 based on these emissions also becomes about four times.

Further, when D / A conversion is performed on a digital signal represented by a ₂ = 1, a ₁ = 1, a ₀ = 1 (binary notation 111), all the quantum dots 11, 12, and 13 When the input lights A, B, and C are respectively supplied, the amount of excitons transmitted to the output quantum dot 30 is the largest, and the light intensity of the output light L1 based on these emissions is expressed in binary notation. As compared with that of the digital signal represented by 001, it becomes about 7 times larger. This is because the intensity of the analog signal generated by the output side quantum dot 30 can be expressed by the sum of excitons (energy) flowing from the quantum dots 11, 12, and 13.

  From the results shown in FIGS. 4 and 5 described above, it can be seen that as the input digital signal increases, the light intensity of the analog signal output from the output quantum dot 30 increases, and based on the digital signal. The linearity of the intensity of the generated analog signal can also be confirmed.

  In addition, when the distance from each quantum dot 11,12,13 to the output side quantum dot 30 is equal, the transmission amount of excitons increases as the size of the quantum dots 11,12,13 increases. For this reason, when input lights A, B, and C having the same light intensity are supplied, the amount of excitons transmitted from the third quantum dot 13 is the largest, and then the second quantum dots 12, The amount of transmission decreases in the order of the first quantum dots 11. That is, when the input light A is supplied only to the first quantum dots 11, the light intensity of the output light emitted from the output-side quantum dots 30 is the smallest as described above.

  In order to further secure the linearity of the light intensity of the analog signal with respect to the input digital signal, in addition to the size of each quantum dot 11, 12, 13, the quantum dot 11, 12, 13 and the output This can be realized by optimizing the distance from the side quantum dot 30.

  As described above, in the nano-optical D / A converter 1 to which the present invention is applied, the input lights A, B, and C having different frequencies corresponding to the respective bits of the digital signal to be D / A converted are supplied and supplied. The plurality of quantum dots 11, 12, and 13 having different sizes so that excitons are excited according to the frequencies ω1, ω2, and ω3 of the input lights A, B, and C, respectively, An output side quantum dot 30 having a resonance energy level into which excitons are injected is formed on the substrate.

  Therefore, by controlling the supply state of the input lights A, B, and C based on the digital signal to be D / A converted, the total energy flowing from the quantum dots 11, 12, and 13 to the output side quantum dots 30 is controlled. Since the intensity of the output light as an analog signal to be emitted is governed by this, D / A conversion can be realized. In particular, in the nano-optical D / A converter 1 to which the present invention is applied, optical D / A conversion can be performed between nanometer-sized quantum dots without being controlled by the light diffraction limit, and by using this, It is also possible to realize high-performance optical devices with nano dimensions.

  The present invention is not limited to the embodiment described above. For example, the present invention may be applied to a nano A / D converter 5 that converts a supplied analog signal into a digital signal on a nano scale.

  As shown in FIG. 6, the nano A / D converter 5 includes a substrate 10, a quantum dot group 20 including a plurality of quantum dots 11, 12, and 13 formed on the surface of the substrate 10, and the quantum dots And an input-side quantum dot 40 composed of a single quantum dot formed in the vicinity of the group 10. In addition, in this nano A / D converter 5, about the same structure as the nano optical D / A converter 5 mentioned above, description here is abbreviate | omitted by citing description of FIG.

  The input-side quantum dot 40 has the same configuration as the output-side quantum dot 30 described above. The input side quantum dot 40 is supplied with input light D as an analog signal to be A / D converted.

The quantum dot group 20 emits output light as a digital signal in the nano A / D converter 5. The first quantum dot 11 constituting the quantum dot group 20, a value of a ₀ constituting the digital signal is defined by the output light U1, and the second quantum dot 12 is of a ₁ constituting the digital signal defining a value at the output light U2, and the third quantum dots 13 define the value of a ₂ constituting the digital signal at the output light U3.

  Next, an A / D conversion operation by the nano A / D converter 5 will be described.

  First, as shown in FIG. 7, the input light D having the frequency ω5 corresponding to the quantum level Q1 that is optically forbidden between the other quantum dots 11, 12, and 13 is supplied to the input-side quantum dot 40. To do. As a result, excitons are excited to the quantum level Q1.

  Next, the exciton excited to this quantum level Q1 transitions to the lower quantum level R1. Since this quantum level R1 is optically forbidden in the input side quantum dot 40, light cannot be emitted therefrom. However, when the exciton is transmitted to the first quantum dot 11 having the quantum level R1 ′ that resonates with the quantum level R1, the output light U1 having the frequency ω6 is emitted from the first quantum dot 11. Will do.

  Further, by increasing the light intensity of the input light D supplied to the input-side quantum dot 40, the amount of excitons excited to the quantum level Q1 increases, and excitation that transits to the lower quantum level R1. The amount of children increases accordingly. As a result, excitons cannot be swept to the first quantum dot 11 side only from the quantum level R1. For this reason, the surplus of excitons transitions to the quantum level R2 that is higher than the quantum level R1 and is optically forbidden in the input-side quantum dot 40. The excitons that have transitioned to the quantum level R2 are transmitted to the second quantum dot 12 having the quantum level R2 ′ that resonates with the exciton, whereby the output light U2 having the frequency ω7 is output from the second quantum dot 12. Will emit light. The frequency of the output light U1, U2,... Emitted by the exciton emission is higher than the frequency ω5 of the input light, and they are different from each other, so that they can be selectively detected.

  Further, by increasing the light intensity of the input light D supplied to the input side quantum dot 40, the output light U3 can be emitted from the third quantum dot in the same manner.

  By increasing the light intensity of the input light D in this way, the amount of excitons to be emitted is increased, and the quantum level R1 ′ that resonates with the lower quantum levels R1, R2,. , R2 ′,... Can be emitted through the first quantum dots 11, the second quantum dots 12,. This suggests that the presence or absence of output light U1, U2,... Emitted from each quantum dot 11, 12, 13 is governed by the light intensity of the input light D supplied.

  For this reason, the light intensity of the input light D is made to correspond to the intensity of the analog signal, and the output light U1, U2,. Optical A / D conversion can be realized between nanometer-sized quantum dots.

  In the above-described embodiment, A / D conversion and D / A conversion of a 3-bit digital signal have been described as examples. However, the present invention is not limited to this case, and a digital signal of 2 bits or more is used. It can be applied to any A / D conversion and D / A conversion. If A / D conversion and D / A conversion of a 2-bit digital signal is realized, a quantum dot group 20 including only the first quantum dots and the second quantum dots 12 is formed on the substrate 10. You can do it. When a digital signal having a number of bits of 4 bits or more is handled, input lights having different frequencies corresponding to the bits are supplied, and excitons are excited according to the frequencies of the supplied input lights. In addition, four or more quantum dots having different energy levels (sizes) may be formed on the substrate.

  In the above-described embodiment, A / D conversion and D / A conversion of a digital signal represented by a binary number have been described as examples. However, the present invention is not limited to this case, and a quaternary number, Of course, the present invention may be applied to A / D conversion and D / A conversion of a digital signal represented by a hexadecimal number or the like.

  Furthermore, in the present invention, the case where excitons are transmitted between quantum levels that resonate with each other has been described as an example. However, the present invention is not limited to such a case. By utilizing the fact that excitons move between quantum levels that do not resonate with each other by raising the temperature of the substrate 10, the frequency of the input light A, B, C supplied to each quantum dot 11, 12, 13 is constant. Of course, it can also be given a width.

It is a figure for demonstrating per structure of the nano optical D / A converter to which this invention is applied. It is a figure for demonstrating about operation | movement of the nano optical D / A converter to which this invention is applied. It is a figure which shows the relationship of the optical intensity of the analog signal which can convert with this nano optical D / A converter 1 about a 3-bit digital signal. It is a figure which shows the result of having measured the optical intensity of the output light from an output side quantum dot for every digital signal which should be D / A converted with a near field optical microscope. It is a figure which shows the result of having actually measured the optical intensity of the output light converted into the analog signal by this nano optical D / A converter about all the 3-bit digital signals. It is a figure for demonstrating per structure of the nano optical A / D converter to which this invention is applied. It is a figure for demonstrating about operation | movement of the nano optical A / D converter to which this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Nano optical D / A converter, 10 Substrate, 11 1st quantum dot, 12 2nd quantum dot, 13 3rd quantum dot, 20 Quantum dot group, 30 Output side quantum dot

Claims (4)

A dielectric substrate;
The input lights having different frequencies corresponding to the respective bits of the digital signal to be D / A converted are supplied, and the excitons are excited according to the frequency of the supplied input lights, and the sizes are made different from each other. An input-side quantum dot group in which a plurality of quantum dots are formed on the substrate;
According to resonance with each energy level, each quantum dot constituting the input-side quantum dot group has a resonance energy level in which excitons are injected through the substrate, and is emitted from the resonance energy level. A nano-optical D / A converter comprising: an output-side quantum dot that generates an output signal having a frequency lower than that of each of the input lights as an analog signal subjected to D / A conversion in accordance with the energy input. 2. The nano light D according to claim 1, wherein an interval between each of the quantum dots constituting the input-side quantum dot group and the output-side quantum dot is adjusted according to the light intensity of the output light. / A converter. 2. The nano light D / 2 according to claim 1, wherein each of the quantum dots constituting the input-side quantum dot group and the output-side quantum dots are adjusted in size according to the light intensity of the output light. A converter. A dielectric substrate;
On the substrate having a plurality of energy levels to which input light having light intensity corresponding to an analog signal to be A / D converted is supplied and excitons are transitioned according to the light intensity of the supplied light. An input-side quantum dot formed on
An output side composed of a plurality of quantum dots whose resonance energy levels are different from each other so that excitons are injected from the quantum dot on the input side through the substrate in response to resonance with each energy level. With a quantum dot group,
Each quantum dot constituting the output-side quantum dot group generates output light having a frequency higher than that of the input light as an A / D-converted digital signal in accordance with energy emitted from a resonance energy level. Nano optical A / D converter.

Images