JP2013205113A - Multiwavelength measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiwavelength measuring device capable of effectively performing optical measurement at multiwavelengths.SOLUTION: A multiwavelength measuring device includes: an optical resonator; a light emitting member which is arranged in the optical resonator, which has each of a quantum dot and a quantum well, which emits light with a plurality of wavelengths differing from each other, and which is formed by laminating a plurality of structures; optical members choosing the light with any one of the plurality of wavelengths; and a light receiving element receiving the light with the chosen wavelength, which has passed through a measuring object containing a plurality of components.

Description

  The present invention relates to a multi-wavelength measuring apparatus that performs optical measurement at multiple wavelengths.

  Optical measurements at multiple wavelengths are used for various applications. For example, the amount of light transmitted to a material may be measured at a plurality of wavelengths, and the amount of components contained in the material may be calculated. For this reason, for example, light emitted from a light source having a broad wavelength band is spectrally separated by a spectroscope or the like (for example, see Patent Document 1).

JP 2010-072007 A

Here, it is often sufficient to use a plurality of wavelengths corresponding to the components (substances) in the measurement material for the measurement. That is, a substance often exhibits light absorption at a specific wavelength (the substance has a characteristic light absorption spectrum on the wavelength axis such as wavelengths λ1, λ2,...). This is the same even when the light absorption spectrum is broad, and a plurality of wavelengths depending on the components (substances) in the measurement material are often sufficient.
In this case, the light emitted from the light source includes light of a wavelength that is not used for measurement, which causes energy loss.

  In view of the above, an object of the present invention is to provide a multi-wavelength optical measurement apparatus that enables efficient optical measurement at multiple wavelengths.

  A multi-wavelength measurement apparatus according to an aspect of the present invention includes an optical resonator and a plurality of structures that are disposed in the optical resonator and each include a quantum dot or a quantum well and emit light having a plurality of different wavelengths. A light-emitting member formed by laminating, an optical member that selects one of the light beams of a plurality of wavelengths, a light-receiving element that receives light of the selected wavelength that has passed through a measurement target including a plurality of components, It is characterized by comprising.

  Select one of the light of multiple wavelengths from “Light emitting member with multiple quantum dots or quantum wells and emitting multiple wavelengths of light, each of which has a laminated structure” Measure optically. As a result, efficient optical measurement at multiple wavelengths becomes possible.

The light emitting member includes a first layer, a first quantum dot or first quantum well disposed on the first layer, and a second layer covering the first quantum dot or the first quantum well. A first structure that emits light of a first wavelength, a third layer, and a second quantum dot or a second quantum well disposed on the third layer And a fourth layer covering the second quantum dot or the second quantum well, the second layer being stacked on the first structure, and different from the first wavelength A second structure that emits light of a wavelength; a fifth layer; a third quantum dot or third quantum well disposed on the fifth layer; and the third quantum dot or third A sixth layer covering the second quantum well, and disposed in a stacked manner on the second structure, and having a third wavelength different from the first and second wavelengths A third structure that emits may have.
Efficient optical measurement can be performed using the first to third wavelengths of light from the first to third quantum dots or quantum wells in the first to third structures, respectively.

The measurement object includes first to third components, controls the optical member, selects light of the first to third wavelengths, and each of the selected light of the first to third wavelengths. Based on the stored amount of received light of the light receiving element and the absorbance of the first to third components at the first to third wavelengths, A calculation unit that calculates a composition ratio of a plurality of components to be measured.
Based on the measurement results with the light of the first to third wavelengths, the composition ratio of the first to third components can be calculated.

  Here, various methods can be used to vary the wavelength of light emitted from each structure. For example, the wavelength of light emitted from each structure can be varied by the following (1) to (4) and combinations thereof.

(1) At least one of the composition or size (thickness, etc.) of the first to third quantum dots is different.
(2) The thicknesses of the first, third and fifth layers are different.
(3) The lattice constants of the constituent materials of the first, third and fifth layers are different.
(4) The compositions of the second, fourth and sixth layers are different.

  According to the present invention, it is possible to provide a multi-wavelength optical measurement apparatus that enables efficient optical measurement at multiple wavelengths.

It is a schematic diagram showing the multiwavelength measuring apparatus 10 which concerns on one Embodiment of this invention. It is a figure showing the relationship between the light absorbency spectrum of sample S (measurement object), and the light emission spectrum from the light source. It is a figure showing the laminated | stacked structure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing a multiwavelength measuring apparatus 10 according to an embodiment of the present invention. The multi-wavelength measuring apparatus 10 measures the spectral characteristics of the sample S. The light source 20, the optical fibers 31 to 31e, the optical coupler 32, the lenses 33a and 33b, the cell 34, the optical elements 35a and 35b, and the photodetector 36a. , 36b, and a control / calculation unit 37.

The light source 20 selects and emits light having a plurality of wavelengths suitable for the spectroscopic measurement of the sample S.
FIG. 2 is a diagram illustrating the relationship between the absorbance spectrum of the sample S (measurement target) and the emission spectrum from the light source 20.

  Here, it is assumed that the sample S is a mixture in which three substances f, g, and h are mixed (measurement target including a plurality of components). FIG. 2B shows an outline of light absorption (absorbance) spectra f (λ), g (λ), and h (λ) of these three substances f, g, and h.

  Here, the substances f, g, and h are, for example, polymer substances. For example, as shown in FIG. 2B, the light absorption (absorbance) spectrum by the polymer substance is broad, and there is an overlap between the absorbance spectra f (λ), g (λ), and h (λ). A plurality of components f, g, and so on that overlap in the absorbance spectra f (λ), g (λ), and h (λ) are measured by absorbance measurement using light having a wavelength interval apart (for example, λ1 to λ3 in FIG. 2). It is possible to analyze the component amount of the mixed sample of h. For example, a multi-component analysis (albumin, glucose, etc.) of a living body becomes possible. As an example, when glucose having light absorption in the vicinity of 1.26 microns is determined as the measurement target substance, light having a plurality of wavelengths including the vicinity of 1.26 microns may be prepared.

  At this time, for example, by selectively using light of wavelengths λ1, λ2, and λ3 shown in FIG. 2, the substances f, g, and h can be quantified (calculation of the mixing ratio). The wavelengths λ1, λ2, and λ3 are, for example, in the range of 980 nm to 2000 nm, and the absorbance spectra f (λ), g (λ), and h (λ) can be set in different regions. In particular, the wavelengths λ1, λ2, and λ3 are preferably set in a region where the difference in values of the absorbance spectra f (λ), g (λ), and h (λ) is large. As shown in FIG. 2, when the light absorption (absorbance) spectra f (λ), g (λ), and h (λ) are broad, the wavelengths λ1, λ2, and λ3 have some degree of arbitraryness.

  Here, light other than the wavelengths λ1, λ2, and λ3 is not necessary for measurement of the mixing ratio of the substances f, g, and h. That is, when the light source 20 generates light other than the wavelengths λ1, λ2, and λ3 (broad light generation), energy is lost.

  Therefore, as shown in FIG. 2A, the light source 20 selects and emits light having peaks P1 to P3 having wavelengths λ1, λ2, and λ3 that match the light absorption spectra of the substances to be measured f, g, and h. Like that. As a result, highly efficient measurement with the light source 20 becomes possible. Here, light of peak P1 of wavelength λ1 is emitted, and light of peak P2 of wavelength λ2 and light of peak P3 of wavelength λ3 are not emitted. Details of the light source 20 will be described later.

The optical fibers 31, 31 a to 31 e are light guides that guide light from the light source 20.
The optical coupler 32 is a branching device that branches light from the light source 20 and the optical fiber 31 into two optical fibers 31a and 31b. The optical coupler 32 preferably branches the light from the optical fiber 31 into 1: 1.

  The lens 33a converts the light from the optical fiber 31c into parallel light and passes it through the cell 34. The lens 33b converts the light that has passed through the cell 34 into convergent light and introduces it into the optical fiber 31c.

  The cell 34 is a light transmissive container (for example, a part or all of light in a wavelength range of 980 nm to 2000 nm is passed), and holds the sample S. The sample S is, for example, a mixture in which substances f, g, and h are mixed, and may be any of gas, liquid, and solid.

  The optical elements 35a and 35b have substantially the same optical characteristics and exclude optical lights other than the selected wavelengths λ1, λ2, and λ3 (optical bandpass filters, etalon filters, holographic filters, interference filters, etc.) It is. In other words, the optical elements 35a and 35b correspond to “an optical member that selects one of a plurality of wavelengths of light”. The wavelengths λ1, λ2, and λ3 can be selected by exchanging the optical elements 35a and 35b. That is, the optical elements 35a and 35b (for example, transmit light of wavelength λ1 and block light of wavelengths λ2 and λ3) pass through optical elements 35a and 35b (for example, transmit light of wavelength λ2 and transmit light of wavelength λ2). to block light of λ1 and λ3). Further, optical elements 35a and 35b having variable wavelength selection characteristics may be used. For example, the wavelength of the transmission region can be changed by tilting the etalon filter with respect to the optical path.

  However, the optical elements 35a and 35b can be omitted. This is because the wavelengths λ1, λ2, and λ3 can be selected by the optical element 23 described later. That is, the wavelengths λ1, λ2, and λ3 can be selected using only one or both of the optical element 35 (35a, 35b) and the optical element 23. When both the optical element 35 (35a, 35b) and the optical element 23 are used, the optical element 35 contributes to preventing background light from being mixed into the photodetectors 36a, 36b.

  The photodetectors 36a and 36b receive light that has passed through the cell 34 and light that has not passed through the cell 34, and output signals Sa and Sb corresponding to the intensity of the received light. The photodetector 36a corresponds to a light receiving element that receives light transmitted through the measurement target.

The control / calculation unit 37 performs calculations based on the signals from the photodetectors 36a and 36b.
The control / calculation unit 37 controls “the optical member to select the light of the first to third wavelengths, and the amount of light received by the light receiving element for each of the selected light of the first to third wavelengths. Corresponds to the “control unit for storing”. That is, the control / calculation unit 37 controls the optical elements 23 and 35 (35a and 35b) (control of the optical characteristics of the optical elements 23 and 35 or replacement with optical elements 23 and 35 having different optical characteristics), and the sample. The wavelength of light passing through S is selected. The control / calculation unit 37 has a memory for storing the signals Sa and Sb from the photodetectors 36a and 36b at that time.

The control / calculation unit 37 is configured to read “a plurality of components to be measured based on the stored amount of light received by the light receiving element and the absorbance of the first to third components at the first to third wavelengths. It functions as a “calculation unit that calculates the composition ratio of the composition”. For this purpose, the control / calculation unit 37 uses the light absorbances f (λ1) to f (λ3), g (λ1) to g (λ3), h (λ1) to h (λ3) (or later described) of a plurality of components. Matrix M or inverse matrix M ⁻¹ ), and parameters necessary for calculation (for example, optical path length d described later) are stored.

(Details of the light source 20)
Hereinafter, details of the light source 20 will be described.
The light source 20 includes a mirror (reflector) 21, a light emitting member 22, an optical element 23, and a power source 24.
The mirror (reflector) 21 forms an optical resonator together with the end face 22 a on the opposite side of the light emitting member 22.

  The optical resonator of the present embodiment is a mirror-facing (linear type) optical resonator sandwiched between a mirror 21 and an end face 22a. Light reciprocates along the path between the mirror 21 and the end face 22a. However, a ring type optical resonator may be used instead of the linear type optical resonator.

  In the optical resonator of this embodiment, light (spatial light) propagates in the space between the mirror 21 and the end face 22a (optical resonator using a spatial optical component). On the other hand, light (guided light) may be propagated using a waveguide (semiconductor, dielectric optical waveguide, optical fiber, etc.) (optical resonator using optical waveguide optical components). .

  As the mirror 21, a distributed Bragg reflector, a distributed feedback reflector, or a photonic crystal reflector can be used. The distributed Bragg reflector is a reflector in which layers having different refractive indexes are alternately stacked with a quarter wavelength length. A distributed feedback reflector is a reflector in which reflection points are distributed using a diffraction grating or the like. The photonic crystal reflector is a reflector using a photonic crystal. A photonic crystal is a structure in which materials having different refractive indexes are periodically arranged, and the period of this structure reflects light having a wavelength of 1/2. These can be used for both spatial light and guided light.

The light emitting member 22 has an end face 22 a and a light emitting unit 25.
The end face 22a corresponds to the mirror 21 and functions as a mirror constituting an optical resonator. The end face 22a has reflectivity and transparency (semi-transparency), and emits part of the light resonated by the optical resonator as output light.

  The light emitting unit 25 emits light having a plurality of wavelengths. That is, the light emitting section 25 corresponds to “a light emitting member that is disposed in an optical resonator and emits light having a plurality of different wavelengths”.

  As the light emitting unit 25, a quantum dot structure can be used. FIG. 3 shows an example of the quantum dot structure 40 as an example of the light emitting member 22. The quantum dot structure 40 includes quantum dot partial structures 41a to 41c and intermediate layers 42a and 42b.

  The quantum dot partial structures 41a to 41c correspond to “a plurality of structures (first to third structures) each including a quantum dot or a quantum well and emitting light having a plurality of different wavelengths”. As will be described later, quantum wells may be used instead of quantum dots.

  The quantum dot partial structure 41a includes a quantum dot 43a, a cap layer 44a, a sub-nano interlayer separation layer 45a, and a background layer (underlayer) 46a. The quantum dot partial structure 41b includes a quantum dot 43b, a cap layer 44b, a sub-nano interlayer separation layer 45b, and a background layer (underlayer) 46b. The quantum dot partial structure 41c includes a quantum dot 43c, a cap layer 44c, a sub-nano interlayer separation layer 45c, and a background layer (underlayer) 46c.

  The quantum dots 43a to 43c, the cap layers 44a to 44c, the sub-nano interlayer separation layers 45a to 45c, the background layers (underlying layers) 46a to 46c, and the intermediate layers 42a and 42b are group III elements (for example, In, Ga, Al). And a mixed crystal semiconductor of group V elements (for example, As, Sb, N, P). Combinations of Group III elements and Group V elements can be selected as appropriate.

The quantum dot partial structures 41a to 41c are bonded and stacked by the intermediate layers 42a and 42b.
Light is generated from each of the quantum dot partial structures 41a to 41c due to the quantum dots 43a to 43c. The light emission wavelengths of the quantum dot partial structures 41a to 41c can be made different to ensure the light output of a plurality of wavelengths.

  For example, the light emission from each of the quantum dot partial structures 41a to 41c is set to peaks P1 to P3 (wavelengths λ1, λ2, and λ3) (see FIG. 2A), and the light emission member 22 emits light at the wavelengths λ1, λ2, and λ3. Is possible. As will be described later, the wavelengths of the peaks P1 to P3 can be appropriately varied.

  The quantum dots 43a to 43c confine electrons therein, and the electron density of states is discretized. The quantum dots 43a to 43c are arranged in a predetermined layer and have a shape whose size is limited from any three-dimensional direction. FIG. 3 shows a state in which one quantum dot 43a to 43c is arranged in one layer for easy understanding. Actually, a plurality of (multiple) quantum dots are arranged in one layer.

The cap layers 44a to 44c cover the quantum dots 43a to 43c, respectively.
Quantum dots 43a to 43c are arranged on the sub-nano interlayer separation layers 45a to 45c.

  The structure and composition of the quantum dot partial structures 41a to 41c (quantum dots 43a to 43c, cap layers 44a to 44c, sub-nano interlayer separation layers 45a to 45c, background layers (underlayers) 46a to 46c) are closely related to the emission characteristics. Have a relationship. In particular, the constituent materials and sizes of the quantum dots 43a to 43c, the cap layers 44a to 44c surrounding them, and the sub-nano interlayer separation layers 45a to 45c have a great influence on the light emission characteristics (light emission wavelength).

  In order to make the light emission wavelengths different in the quantum dot partial structures 41a to 41c, the respective structures and compositions are adjusted as follows.

(1) The compositions of the quantum dots 43a to 43c are made different. By selecting a composition that lowers the energy band gap of the quantum dots 43a to 43c, the emission wavelength of the quantum dot partial structures 41a to 41c can be increased.

(2) The quantum dots 43a to 43c are made different in film thickness. Increasing the film thickness of the quantum dots 43a to 43c can increase the emission wavelength of the quantum dot partial structures 41a to 41c.

(3) The cap layers 44a to 44c have different lattice constants. By making the lattice constants of the cap layers 44a to 44c closer to the quantum dots 43a to 43c, the emission wavelength of the quantum dot partial structures 41a to 41c can be increased.

(4) The cap layers 44a to 44c are made different in film thickness. Increasing the film thickness of the cap layers 44a to 44c can increase the emission wavelength of the quantum dot partial structures 41a to 41c.

(5) Different compositions of the sub-nano interlayer separation layers 45a to 45c are made. By reducing the number of composition elements of the sub-nano interlayer separation layers 45a to 45c, for example, the light emission wavelength in the quantum dot partial structures 41a to 41c can be increased.

  In this manner, a light source 20 that emits light only at wavelengths λ1 to λ3 by selectively producing a light emitting material or an optical gain material such as quantum dots can be produced. In the present embodiment, a plurality of narrow emission peaks P1 to P3 having wavelengths λ1 to λ3 are caused to emit light in accordance with such a broad light spectrum unique to the substances f, g, and h to be measured. Low power consumption and high intensity light can be generated according to the shape of the optical spectrum of the target substance to be measured.

The quantum dot structure can be created as follows, for example.
(1) Formation of Background Layer (Underlayer) 46c A background layer 46c (for example, an InGaAs layer) is epitaxially grown on a GaAs substrate by MBE (Molecular Beam Epitaxy) method.

(2) Formation of sub-nano interlayer isolation layer 45c A sub-nano interlayer isolation layer 45c (for example, a GaAs layer) is epitaxially grown on the background layer 46c by MBE.

(3) Formation of quantum dots 43c Quantum dots 43c (for example, InAs layers) are epitaxially grown on the sub-nano interlayer separation layer 45c by MBE. Due to lattice mismatch between the constituent material of the sub-nano interlayer separation layer 45c and the constituent material of the quantum dot 43c (inconsistency of lattice constant), island-shaped (island) structure quantum dots 43c are formed (formation by self-organization). . For example, the ratio of In to As is controlled when the quantum dots 43c are formed so that the lattices of the sub-nano interlayer separation layer 45c and the quantum dots 43c are mismatched.

(4) Formation of Cap Layer 44c A cap layer 44c (for example, an InGaAs layer) is epitaxially grown on the quantum dots 43c by MBE. As a result, the quantum dots 43c are covered (embedded) with the cap layer 44c.

(5) Formation of intermediate layer 42b to cap layer 44a Thereafter, intermediate layer 42b, background layer 46b, sub-nano interlayer separation layer 45b, quantum dot 43b, cap layer 44b, intermediate layer 42a, background layer 46a, sub-nano interlayer separation layer 45a, quantum dots 43a, and cap layer 44a were sequentially formed by the MBE method. In this way, a quantum dot structure is formed.
An electrode for current injection is formed on the cap layer 44a and below the background layer 46c.

  In the above production process, the MBE method is used, but MOCVD (Metal Organic Chemical Vapor Deposition method) can also be used.

  The optical element 23 corresponds to “an optical member that selects one of a plurality of wavelengths of light”, and is an optical filter that excludes light other than the selected wavelengths λ1, λ2, and λ3 (an optical bandpass filter, an etalon filter, Holographic filter, interference filter, etc.). The wavelengths λ1, λ2, and λ3 can be selected by exchanging the optical element 23. That is, the optical element 23 (for example, transmits light of wavelength λ1 and blocks light of wavelengths λ2 and λ3) passes through optical element 23 (for example, transmits light of wavelength λ2 and transmits light of wavelengths λ1 and λ3). Replace the light. An optical element 23 having variable wavelength selection characteristics may be used. For example, the wavelength of the transmission region can be changed by tilting the etalon filter with respect to the optical path.

  However, the optical element 23 can be omitted. This is because the wavelengths λ1, λ2, and λ3 can be selected even in the optical element 35 (35a, 35b). That is, the wavelengths λ1, λ2, and λ3 can be selected using only one or both of the optical element 23 and the optical element 35 (35a, 35b).

  The power source 24 supplies a current (electric power) for light emission to the light emitting unit 25.

(Operation of multi-wavelength measuring apparatus 10)
Hereinafter, an example of the operation procedure of the multi-wavelength measuring apparatus 10 will be shown.
(1) Measurement The light of wavelength λ1, λ2, λ3 from the light source 20 is switched. For example, the optical elements 23 and 35 are switched to emit light having a wavelength λ 1 from the light source 20. This light is branched into optical fibers 31 a and 31 b by an optical coupler 32. The light from the optical fiber 31a passes through the sample S, and the light from the optical fiber 31b does not pass through the sample S. The former is measurement light, and the latter is reference light. These lights pass through the optical elements 35a and 35b, respectively, and are received by the photodetectors 36a and 36b.

As described above, the signals Sa and Sb from the photodetectors 36a and 36b represent the intensity of light received by the photodetectors 36a and 36b. The signals Sa and Sb are expressed by the following equation (1).
Sa = K * I1 = K * I0 * T (λ1)
= K * I0 * (e− ^{A (λ1) * d} )
Sb = K * I0 Formula (1)

I1: Amount of light incident on the photodetector 36a (passing through the sample S) I0: Amount of light incident on the photodetector 36b (not passing through the sample S) K: Light incident on the photodetectors 36a, 36b Proportionality constant representing the relationship between the intensity of the light and the intensity of the signals Sa and Sb (corresponding to the sensitivity of the photodetectors 36a and 36b)
T (λ1): Transmittance of sample S at wavelength λ1 A (λ1): Absorbance of sample S at wavelength λ1 d: Optical path length (distance) of light passing through sample S

The ratio R of the signals Sa and Sb corresponds to the transmittance T (λ1) of the sample S at the wavelength λ1, as shown in the following equation (2).
R = Sa / Sb = T (λ1) = e ^{−A (λ1) * d} (2)

From the above, the absorbance A (λ1) can be expressed as in the following formula (3).
A (λ1) = − Log (T (λ1)) / d
= Log (Sb / Sa) / d Formula (3)

  As described above, the absorbance A (λ1) can be calculated using the signals Sa and Sb from the photodetectors 36a and 36b and the optical path length d.

  Similar to the absorbance A (λ1), the absorbances A (λ2) and A (λ3) of the sample S at wavelengths λ2 and λ3 can be calculated.

  In the above, it is assumed that the branching ratio in the optical coupler 32 is 1: 1. For this reason, the ratio R of the signals Sa and Sb and the transmittance T (λ) are equal. If the branching ratio is not 1: 1, some calibration is required.

  If the intensity of light emitted from the light source 20 is stable over time, the photodetector 36b is not necessarily required. When a material with practically negligible absorbance A (λ) is used as the sample S, the signal Sa0 from the light detector 36a is used in place of the signal Sb in equation (3), so that the absorbance A (λ) is obtained. It can be calculated. The photodetector 36b is for monitoring the intensity of light from the light source 20.

(2) Analysis The absorbance A (λ) is the mixing ratio m, n, p of the substances to be measured f, g, h, the absorbances per unit quantity f (λ), g (λ), h (λ) and It has such a relationship.
A (λ) = m * f (λ) + n * g (λ) + p * h (λ)
Here, when λ = λ1, λ2, and λ3, the following relationship is established.
A (λ1) = m * f (λ1) + n * g (λ1) + p * h (λ1)
A (λ2) = m * f (λ2) + n * g (λ2) + p * h (λ2)
A (λ3) = m * f (λ3) + n * g (λ3) + p * h (λ3)

This relationship can be expressed by the following equation (1)

As shown in the following equation (2), the mixing ratios m, n, and p can be calculated from the inverse matrix M ^{−1 of} the matrix M and the absorbances A (λ 2) and A (λ 3) of the sample S.

  As described above, in the multi-wavelength measuring apparatus 10 according to the present embodiment, only the lights of the peaks P1 to P3 having specific wavelengths λ1 to λ3 are emitted and selected. As a result, the energy consumption of the multi-wavelength measuring apparatus 10 (particularly the light source 20) can be reduced. Since the light source 20 does not emit light having a wavelength that is not necessary for the measurement target substance, the energy consumption of the light source 20 is reduced. For example, when the multi-wavelength measuring apparatus 10 is battery-driven, it can operate for a long time.

(Other embodiments)
Embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.

(1) In the above embodiment, the mixing ratio of the substances f, g, and h is measured by measuring the absorbances A (λ1), A (λ2), and A (λ3) of the sample S at the wavelengths λ1, λ2, and λ3. m, n, and p can be calculated. In other words, by measuring the absorbance A at three wavelengths corresponding to the three kinds of substances, the mixing ratio of these three kinds of substances is calculated.

  This can be generalized. That is, by measuring the absorbance A at N wavelengths corresponding to N kinds of substances, the mixing ratio of these N kinds of substances can be calculated. In this case, the light source 20 needs to be able to select and emit light of N wavelengths, and the number of quantum dot partial structures is preferably N or more. N can be an integer of 1 or more. When there is one kind of substance (N = 1), the concentration of the substance can be calculated.

  Further, the number of types of substances and the number of wavelengths that can be emitted by the light source 20 do not necessarily need to match. For example, it is allowed that the number of wavelengths is larger than the number of types of substances. In this case, a part of the wavelength that can be emitted can be used. In addition, it is possible to calculate the mixing ratio more accurately by measuring using a larger number of wavelengths than the number of types of substances (a kind of statistical processing).

(2) In the above embodiment, quantum dots are used for the light source 20. On the other hand, it is also possible to use quantum wells instead of quantum dots. That is, a light emitting member (and thus the light source 20) can be configured by laminating structures having “quantum dots or quantum wells”.

(3) In the above embodiment, the wavelength is selected using both of the optical elements 23 and 35 (35a and 35b). On the other hand, only one of the optical elements 23 and 35 can be used. That is, the wavelength can be selected with an optical element (an optical filter) arranged either inside or outside the resonator.

DESCRIPTION OF SYMBOLS 10 ... Multi-wavelength measuring apparatus, 20 ... Light source, 21 ... Mirror, 22 ... Light emitting member, 22a ... End surface, 23 ... Optical element, 24 ... Power supply, 25 ... Light emission part, 31-31e ... Optical fiber, 33a, 33b ... Lens , 34 ... cells, 35a and 35b ... optical elements, 36a and 36b ... photodetectors, 37 ... control and calculation section, 40 ... quantum dot structure, 41a-41c ... quantum dot partial structure, 42a, 42b ... intermediate layer, 43a -43c ... Quantum dot, 44a-44c ... Cap layer, 45a-45c ... Sub-nano interlayer separation layer, 46a-46c ... Background layer

Claims (6)

An optical resonator,
A light emitting member formed by laminating a plurality of structures disposed in the optical resonator, each including a quantum dot or a quantum well, and emitting light having a plurality of different wavelengths;
An optical member for selecting any one of the plurality of wavelengths of light;
A light receiving element that receives light of the selected wavelength that has passed through a measurement target including a plurality of components;
A multi-wavelength measuring apparatus comprising: The light emitting member is
A first layer; a first quantum dot or first quantum well disposed on the first layer; and a second layer covering the first quantum dot or first quantum well. A first structure that emits light of a first wavelength;
A third layer; a second quantum dot or second quantum well disposed on the third layer; and a fourth layer covering the second quantum dot or second quantum well. A second structure that emits light of a second wavelength different from the first wavelength, and is disposed on the first structure;
A fifth layer, a third quantum dot or third quantum well disposed on the fifth layer, and a sixth layer covering the third quantum dot or third quantum well; A third structure that emits light of a third wavelength that is different from the first and second wavelengths and is stacked on the second structure;
Have
The multi-wavelength measuring apparatus according to claim 1. The measurement object includes first to third components;
A controller that controls the optical member to select the light of the first to third wavelengths, and stores the amount of light received by the light receiving element for each of the selected light of the first to third wavelengths;
Calculation for calculating a composition ratio of a plurality of components to be measured based on the stored amount of light received by the light receiving element and the absorbance of the first to third components at the first to third wavelengths Part,
The multi-wavelength measuring apparatus according to claim 2, comprising:   4. The multi-wavelength measuring apparatus according to claim 3, wherein at least one of the composition or size of the first to third quantum dots is different from each other.   4. The multiwavelength measuring apparatus according to claim 3, wherein at least one of the thicknesses of the first, third, and fifth layers and the lattice constant of the constituent material are different. The compositions of the second, fourth and sixth layers are different;
The multi-wavelength measuring apparatus according to claim 3.

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