Light splitting device

Abstract

The present invention suppresses a reduction in accuracy due to the influence of noise light. A spectroscopic device (1) is provided with: a light source (2); a quantum optical system (4) that has one or more nonlinear optical elements (12) that generate photon pairs of idle light and signal light from the pump light by an entangled photon pair generation process, and that is provided with a sample placement tool (35) for disposing a sample (SP) on the optical path of the idle light; a detection unit (6) that detects the light intensity of the light output from the quantum optical system (4); and an analysis device (8). The quantum optical system (4) is configured so as to emit first and second signal light (s1, s2) at different optical paths, the detection unit (6) is provided with a beam splitter (40) that receives the first and second signal light (s1, s2) from the quantum optical system (4), and the detection unit (6) detects the light intensity of each of the two light beams emitted from the beam splitter (40). The analysis device (8) acquires an interference pattern on the basis of the two light beams detected by the detection unit (6).

Description

Technical Field

[0001] The invention relates to a light splitting device. Background Art

[0002] In infrared spectroscopy, a technique has been proposed in which, by using quantum mechanically correlated photon pairs, infrared detection is no longer necessary and spectroscopic analysis can be performed by detecting only visible light (see, for example, Non-Patent Documents 1, 2, and 3).

[0003] Prior art literature

[0004] Non-patent literature

[0005] Non-patent document 1: Anna Paterova, Hongzhi Yang, Chengwu An, Dmitry Kalashnikov and Leonid Krivitsky, "Measurement of infrared optical constants with visible photons", New Journal of Physics, April 2018, Volume 20 043015

[0006] Non-patent document 2: Chiara Lindner, Sebastian Wolf, Jens Kiessling, and Drankkuhnemann, "Fourier transforminfrared spectroscopy with visible light", OpticsExpress, Vol.28, Issue 4, pp.4426-4432 (2020)

[0007] Non-patent document 3: Y.Mukai, M.Arahata, T.Tashima, R.Okamoto, and S.Takeuchi, "Quantum Fourier-Transform Infrared Spectroscopy for Complex TransmittanceMeasurements", PHYSICAL REVIEW APPLIED, Vol.15, Issue 3, March 2021 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] However, in an optical system that generates photon pairs, there is a problem that when noise light such as stray light, disturbance light, and fluorescence of an optical element is generated, the accuracy of spectroscopic analysis is deteriorated due to the influence of the noise light.

[0010] An object of the present invention is to provide a spectroscopic device capable of suppressing a decrease in accuracy due to the influence of noise light.

[0011] Solutions for solving problems

[0012] The present specification includes the entire contents of Japanese Patent Application No. 2022-035693 filed on March 8, 2022.

[0013] One embodiment of the present invention is a spectroscopic device comprising: a light source that emits pump light; a quantum optical system having one or more nonlinear optical elements and a sample configuration device, wherein the pump light is incident on the nonlinear optical element, the nonlinear optical element generates photon pairs of idler light and signal light from the pump light through an entangled photon pair generation process, and the sample configuration device is used to configure the sample on the optical path of the idler light; a detection unit that detects the light intensity of light output from the quantum optical system; and an analysis device that obtains an interference pattern based on the light intensity, wherein the quantum optical system is configured to emit a first signal light and a second signal light with different optical paths, the detection unit has a beam splitter that receives the first signal light and the second signal light from the quantum optical system, the detection unit detects the light intensity of each of the two light beams emitted from the beam splitter, and the analysis device obtains the interference pattern based on the two light beams detected by the detection unit.

[0014] Effects of the Invention

[0015] According to one aspect of the present invention, it is possible to suppress a decrease in accuracy due to the influence of noise light. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a diagram schematically showing the structure of an infrared spectroscopic device according to an embodiment of the present invention.

[0017] Figure 2 It is a schematic diagram of an interference pattern obtained by the infrared spectroscopic device of this embodiment.

[0018] Figure 3 It is an explanatory diagram of the synthesis of the signal lights s1 and s2 in the beam splitter.

[0019] Figure 4 is a diagram schematically showing the structure of a reference structure.

[0020] Figure 5is a schematic diagram of the interference pattern obtained by the reference structure.

[0021] Figure 6 This is a diagram schematically showing the structure of an infrared spectroscopic device according to Modification 1.

[0022] Figure 7 This is a diagram schematically showing the structure of an infrared spectroscopic device according to Modification Example 2.

[0023] Figure 8 This is a diagram schematically showing the structure of an infrared spectroscopic device according to Modification 3.

[0024] Fig. 9 This is a diagram schematically showing the structure of an infrared spectroscopic device according to Modification 4.

[0025] Fig.10 It is a diagram schematically showing the structure of an infrared spectroscopic device according to the second embodiment.

[0026] Fig.11 It is a diagram schematically showing the structure of an infrared spectroscopic device according to the third embodiment. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0028] [First embodiment]

[0029] Figure 1 Schematically shows the structure of the infrared spectroscopic device 1 according to the first embodiment. Figure 1 In the figure, for the convenience of explanation, the light paths superimposed on each other are depicted separately from each other.

[0030] The infrared spectrometer 1 of this embodiment is a measuring device using infrared spectroscopy. Infrared spectroscopy is a method of analyzing the structure and quantification of a sample SP based on an absorption spectrum obtained by irradiating infrared rays to the sample SP. Measuring devices using infrared spectroscopy are classified into dispersion type and Fourier transform type. The infrared spectrometer 1 of this embodiment is a Fourier transform type device, which performs spectroscopic analysis on the sample SP by performing Fourier transform analysis on an interference pattern obtained by interference of light.

[0031] In addition, the infrared spectrometer 1 of this embodiment uses an idler photon in the infrared region and a signal photon in the visible region, which are a photon pair that are quantum mechanically correlated, as light to irradiate the sample SP, and uses quantum interference between the photon pairs that are quantum mechanically correlated, thereby being able to obtain an interference pattern based on the detection of signal photons in the visible region.

[0032] In addition, a “photon pair that is quantum mechanically correlated” is referred to as an “entangled photon pair”, “entangled photon pair”, and is referred to as an “entangled photon pair” in this specification.

[0033] In addition, even when noise light such as disturbance light, stray light, and fluorescence of an optical element is included in a signal photon, the infrared spectroscopic device 1 of this embodiment can obtain an interference pattern without the influence of the noise light and perform high-precision spectroscopic analysis.

[0034] like Figure 1 As shown, such an infrared spectroscopic device 1 includes a light source 2 , a quantum optical system 4 , a detection unit 6 , and an analysis device 8 .

[0035] The light source 2 is a laser device that irradiates continuous-wave laser light of a visible wavelength into the quantum optical system 4. The laser light is used as pump light p for exciting a nonlinear crystal 12 described later in the quantum optical system 4, and in this embodiment, light of a wavelength of 532 nm is used.

[0036] The quantum optical system 4 is an optical system having at least an entangled photon pair generation function, a quantum interference function, a sample action function, an optical path length variable function, and a signal light separation and output function.

[0037] [Entangled photon pair generation function]

[0038] The entangled photon pair generation function is a function of generating an entangled photon pair of an idler photon with a wavelength in the infrared region and a signal photon with a wavelength in the visible region through an entangled photon pair generation process. In this embodiment, the wavelength of the idler photon is 1.5 μm, and the wavelength of the signal photon is 0.824 μm. In addition, these idler photons and signal photons are both continuous waves, and the continuous wave idler photons are referred to as "idler light i" and the continuous wave signal photons are referred to as "signal light s" below.

[0039] In addition, in the process of generating entangled photon pairs, spontaneous parametric down-conversion (SPDC) is used as one of the nonlinear optical processes. Figure 1As shown, the quantum optical system 4 has a nonlinear crystal 12, which is an example of a nonlinear optical element that undergoes spontaneous parametric down-conversion due to the incidence of pump light p. The nonlinear crystal 12 converts the pump light p incident via the focusing lens 10 and the first dichroic mirror 11 into an entangled photon pair (idler light i and signal light s) through spontaneous parametric down-conversion, and outputs the entangled photon pair. The phase matching condition of the nonlinear crystal 12 is appropriately adjusted so that a signal light s with a wavelength of less than 1 μm and an idler light i of infrared light are obtained from the pump light p of visible light. In the present embodiment, as described above, the wavelength of the signal light s is 0.824 μm, and the wavelength of the idler light i is 1.5 μm.

[0040] The condenser lens 10 is a lens whose focal point is located at the nonlinear crystal 12, and condenses the pump light p at the nonlinear crystal 12. The first dichroic mirror 11 transmits the signal light s and reflects the pump light p.

[0041] The nonlinear crystal 12 uses a lithium niobate (LiNbO 3 ) crystal, but other nonlinear crystals such as a silver gallium sulfide (AgGaS 2 ) crystal may also be used.

[0042] In addition, the nonlinear optical element may be a quasi-phase matching element in which polarization is periodically inverted, a silicon resonator, or an optical waveguide formed of silicon (Si) and / or silicon nitride (SiN), etc., instead of the nonlinear crystal 12 .

[0043] [Quantum interference function]

[0044] The quantum interference function is a function of causing quantum interference between multiple entangled photon pair generation processes. In the quantum optical system 4 of this embodiment, the number of times the entangled photon pair generation process can be generated is two. The first entangled photon pair generation process is referred to as the "first entangled photon pair generation process", and the second entangled photon pair generation process is referred to as the "second entangled photon pair generation process". In addition, the idler light i and the signal light s generated in the first entangled photon pair generation process are respectively marked with the figure marks "i1" and "s1", and the idler light i and the signal light s generated in the second entangled photon pair generation process are respectively marked with the figure marks "i2" and "s2". The figure mark "i1" is sometimes referred to as the first idler light i1, the figure mark "i2" is sometimes referred to as the second idler light i2, the figure mark "s1" is sometimes referred to as the first signal light s1, and the figure mark "s2" is sometimes referred to as the second signal light s2.

[0045] Here, in quantum optics, the first entangled photon pair generation process and the second entangled photon pair generation process are both described by probability amplitudes. Moreover, in quantum interference, when the probability amplitudes of the first entangled photon pair generation process and the second entangled photon pair generation process interfere with each other in the same phase state, the probability amplitude is enhanced (so-called "constructively interfere"). On the contrary, when the probability amplitudes of the first entangled photon pair generation process and the second entangled photon pair generation process interfere with each other in the opposite phase state, the probability amplitude is canceled (so-called "destructively interfere").

[0046] According to quantum optics, when these "constructive interference" and "destructive interference" occur, the detection probability of the photons constituting the entangled photon pair increases or decreases. In contrast, when these quantum interferences are not caused (when the state vector corresponding to the first photon generation process is independent of the state vector corresponding to the second photon generation process and can be distinguished, these quantum interferences will not occur), the above-mentioned increase or decrease in the detection probability will not occur.

[0047] The quantum optical system 4 of this embodiment has a structure in which quantum interference occurs between the first entangled photon generation process and the second entangled photon generation process.

[0048] In detail, Figure 1 As shown, the quantum optical system 4 is provided with a fixed mirror 14 for reflecting the pump light p emitted from the nonlinear crystal 12. The fixed mirror 14 reflects the pump light p incident thereon in such a way that the pump light p reaches the nonlinear crystal 12 through the same optical path and is incident again on the nonlinear crystal 12. Thus, the pump light p passes through the nonlinear crystal 12 twice in opposite directions (i.e., reciprocates), and the first entangled photon pair generation process occurs in the forward path, and the second entangled photon pair generation process occurs in the reverse path.

[0049] That is, in the first embodiment, there is only one nonlinear crystal 12 , and the quantum optical system 4 emits the first signal light s1 and the second signal light s2 along the optical path (optical path) of the pump light p that reciprocates in the one nonlinear crystal 12 .

[0050] In addition, in the present embodiment, the conversion efficiency of spontaneous parametric down conversion in the nonlinear crystal 12 is low, and only a very small part of the pump light p is converted into entangled photon pairs. Therefore, the light amount of the pump light p reciprocating in the nonlinear crystal 12 is roughly the same in the forward path and the reverse path of the same optical path, and the light amount of the entangled photon pairs generated in the first entangled photon pair generation process and the second entangled photon pair generation process is also roughly the same. Moreover, when the sample SP is not configured, quantum interference is caused between the two photon pair generation processes.

[0051] Furthermore, a collimator lens 70 for collimating the pump light p and the signal light s1 is arranged in front of the fixed mirror 14 .

[0052] [Sample function]

[0053] The sample action function is to make the idle light i1 separated from the entangled photon pair generated in the first entangled photon pair generation process pass through the sample SP as the analysis object, thereby generating absorption or reflection (absorption in this embodiment) by the sample SP. Since the sample SP absorbs or reflects the idle light i1, the intensity of quantum interference is weakened compared to the intensity when the sample SP is not configured. The weakening of this intensity is reflected in the detection probability of the signal lights s1 and s2.

[0054] In this embodiment, in order to realize such a sample action function, the quantum optical system 4 includes a second dichroic mirror 32, a movable mirror 34, and a sample arrangement device 35, and the sample arrangement device 35 and a collimating lens 72 are arranged between the second dichroic mirror 32 and the movable mirror 34. The sample arrangement device 35 is a device for holding the sample SP, for example, a sample holding device such as a sample box or a sample stand transparent to the idler light i, and the sample holding device is used to hold the sample SP on the optical path of the idler light i1.

[0055] The second dichroic mirror 32 is an optical member for separating the idler light i1 from the light emitted from the nonlinear crystal 12 (the pump light p, the signal light s1 , and the idler light i1 ).

[0056] The movable mirror 34 is a reflection mirror into which the idler light i1 separated by the second dichroic mirror 32 is incident, and reflects the idler light i1 so as to return to the second dichroic mirror 32 through the same optical path as when the idler light i1 was incident thereon.

[0057] The collimator lens 72 is a lens for collimating the idler light i1.

[0058] By arranging the sample SP on the optical path between the second dichroic mirror 32 and the movable mirror 34, the sample SP acts on the idler light i1 that reciprocates between the second dichroic mirror 32 and the movable mirror 34, thereby reducing the intensity of quantum interference, which is reflected in the detection probability of the signal lights s1 and s2. The signal light s1 is in an entangled state with the idler light i1 after the sample SP acts, and the signal light s2 is in an entangled state with the idler light i2 that the sample SP does not act on. Therefore, the spectroscopic analysis of the sample SP can be performed based on these signal lights s1 and s2.

[0059] Furthermore, by providing a sealed sample chamber for storing the sample SP on the optical path and installing the sample placement tool 35 in the sample chamber, spectroscopic analysis of the sample SP can be performed with the internal ambient pressure of the sample chamber adjusted.

[0060] [Optical path length variable function]

[0061] The optical path length variable function is a function for changing the optical path length from the second dichroic mirror 32 to the movable mirror 34. To achieve this function, the quantum optical system 4 includes an actuator 36 that changes the optical path length by moving the movable mirror 34 at a constant speed in a direction coaxial with the optical path.

[0062] [Signal light separation output function]

[0063] The signal light separation and output function is a function of outputting the signal light s1 and the signal light s2 that can be observed by the sample action function from different optical paths.

[0064] In order to realize this function, the quantum optical system 4 is provided with a bandpass filter 38 and the above-mentioned fixed mirror 14. Both the bandpass filter 38 and the fixed mirror 14 are optical components having an optical characteristic of transmitting light of a target wavelength, and the fixed mirror 14 is used as a first output component for outputting the signal light s1, and the bandpass filter 38 is used as a second output component for outputting the signal light s2.

[0065] More specifically, the bandpass filter 38 is an optical filter that transmits the signal light s2 of the light (pump light p and entangled photon pairs (signal light s2 and idler light i2) based on the second entangled photon pair generation process) that has passed through the second dichroic mirror 32 from the nonlinear crystal 12 side, and blocks other light (pump light p and idler light i2). Thus, the signal light s2 is output from the quantum optical system 4 after passing through the bandpass filter 38. A collimating lens 74 is arranged on the output side of the bandpass filter 38, and the signal light s2 is collimated by the collimating lens 74 and then output.

[0066] The fixed mirror 14 is a reflector having optical properties of reflecting the pump light p and transmitting the signal light s1, and thus, the signal light s1 of the light (the pump light p and the signal light s1) incident on the fixed mirror 14 from the second dichroic mirror 32 passes through the fixed mirror 14 and is output from the quantum optical system 4. The signal light s1 is collimated by the collimating lens 70 as is the case with the signal light s2.

[0067] In addition, in the above-mentioned non-patent documents 1 to 3, the following structure is shown: by making the signal light s1 in a superimposed state with the pump light p enter the nonlinear crystal 12 again through the same optical path, the signal light s1 and the signal light s2 are output in a superimposed state. However, even in the case where the signal light s1 does not enter the nonlinear crystal 12 again due to passing through the fixed mirror 14 as in the present embodiment, quantum interference is generated by synthesizing the two signal lights s1 and s2 at the beam splitter 40 described later (for example, refer to XYZou, LJWang, L.Mandel, "Induced coherence and indistinguishability in optical interference", Physical Review Letters, Volume 67, Issue 3, July 15, 1991, pp.318-321).

[0068] Here, the second dichroic mirror 32, the fixed mirror 14, and the movable mirror 34 of the quantum optical system 4 of this embodiment form a structure similar to a Michelson interferometer. However, such a structure can be replaced with a structure similar to other interferometers such as a Mach-Zehnder interferometer as long as it generates an optical path difference between the optical path between the second dichroic mirror 32 and the fixed mirror 14 and the optical path between the second dichroic mirror 32 and the movable mirror 34.

[0069] The detection unit 6 causes interference between the signal lights s1 and s2 output from the quantum optical system 4 by synthesis and detects the synthesized light. The detection unit 6 includes a beam splitter 40 , a first detector 41 , and a second detector 42 .

[0070] The beam splitter 40 is an optical element that causes interference between the signal lights s1 and s2 by synthesizing them, and has two incident ports 40A1 and 40A2 and two emission ports 40B1 and 40B2. The signal lights s1 and s2 are incident on the beam splitter 40 from the different incident ports 40A1 and 40A2. Specifically, the signal light s1 is guided from the quantum optical system 4 by the reflector 51 and is incident on the incident port 40A1, and the signal light s2 is guided from the quantum optical system 4 by the reflector 52 and is incident on the other incident port 40A2. These signal lights s1 and s2 are synthesized inside the beam splitter 40, and the synthesized light is branched and output to the two emission ports 40B1 and 40B2, respectively.

[0071] As described above, the signal light s1 is entangled with the idler light i1 after the interaction with the sample SP, and the signal light s2 is entangled with the idler light i2 which has no interaction with the sample SP. Therefore, the light outputted from the emission ports 40B1 and 40B2 respectively becomes the light obtained by interference between the signal light s1 including the information of the interaction with the sample SP and the signal light s2 not including the information of the interaction with the sample SP.

[0072] In this embodiment, the ratio of reflectivity to transmittance of the beam splitter 40 is 1:1, and the light amounts of light output from the two emission ports 40B1 and B2 are substantially equal. However, the ratio of reflectivity to transmittance of the beam splitter 40 is not limited to 1:1.

[0073] In the following description, the light output from the two emission ports 40B1 and 40B2 is referred to as signal light s1' and signal light s2', respectively. However, as described above, signal light s1' and signal light s2' are both lights after interference between signal light s1 and signal light s2, and signal light s1' does not originate only from signal light s1, and signal light s2' does not originate only from signal light s2.

[0074] The first detector 41 is a photodetector that detects the signal light s1' and outputs a first detection signal to the analysis device 8, and the second detector 42 is a photodetector that detects the signal light s2' and outputs a second detection signal to the analysis device 8. These first detectors 41 and second detectors 42 use silicon-based photodetectors having optical properties capable of detecting visible light, for example, image sensors composed of solid semiconductor elements such as CCD (Charged-Coupled Device) and CMOS (Complementary Metal-Oxide-Semiconductor). In addition, a single PD (photodiode) can also be used instead of the image sensor. The first detection signal and the second detection signal are signals that represent the intensity (i.e., light intensity) corresponding to (more accurately, proportional to) the number of detected photons of the signal light s1' and s2'.

[0075] The analyzing device 8 obtains an interference pattern based on the difference between the first detection signal of the first detector 41 and the second detection signal of the second detector 42 during the period when the movable mirror 34 is moved at a certain speed, and performs spectroscopic analysis on the sample SP by performing Fourier transform analysis on the interference pattern. The analyzing device 8 of this embodiment has a computer that realizes such a function. The computer has a processor such as a CPU (Central Processing Unit) and an MPU (Micro-Processing Unit), a memory device such as a ROM (Read Only Memory) and a RAM (Random Access Memory) (also called a main storage device), a storage device such as an HDD (Hard Disk Drive) and an SSD (Solid State Drive) (also called a secondary storage device), and an interface circuit for connecting the light source 2, the quantum optical system 4, and the detection unit 6 in a manner capable of sending and receiving signals, and is realized by the processor executing a program stored in the memory device or the storage device. Figure 1 The functional parts shown.

[0076] That is, Figure 1 As shown, the analysis device 8 includes a moving mirror control unit 60 , an interference pattern acquisition unit 62 , and a spectrum creation unit 64 .

[0077] The movable mirror control unit 60 transmits a control signal for moving the movable mirror 34 to the actuator 36 , thereby controlling the movement of the movable mirror 34 .

[0078] The interference pattern acquisition unit 62 acquires the interference pattern by calculating the difference between the first detection signal of the first detector 41 and the second detection signal of the second detector 42 while the movable mirror 34 is moved at a constant speed.

[0079] The spectrum generating unit 54 generates a wavelength or wave number spectrum by Fourier transforming the interference pattern (for example, fast Fourier transforming), and performs qualitative and quantitative analysis of the sample SP based on the peak wave number (wavelength) and peak intensity of the spectrum.

[0080] In addition, the analyzing device 8 is not limited to the above-mentioned functions, and may control each part of the infrared spectroscopic device 1 such as turning on and off the light source 2 .

[0081] Figure 2 It is a schematic diagram of the interference pattern obtained by the analysis device 8.

[0082] The interference pattern is a signal showing the relationship between the light after the signal lights s1 and s2 are synthesized (signal lights s1', s2') and the movement amount ΔL of the movable mirror 34 (that is, the change amount of the optical path length of the idler light i). In this embodiment, the light after the signal lights s1 and s2 are synthesized is evenly distributed into the signal lights s1' and s2' by the beam splitter 40. In addition, the difference (P2s-P1s) between the light intensities P1s and P2s of the signal lights s1' and s2' is obtained by the interference pattern acquisition unit 62 of the analysis device 8 to generate an interference pattern.

[0083] Figure 3 It is an explanatory diagram of the synthesis of the signal lights s1 and s2 in the beam splitter 40 .

[0084] In the infrared spectroscopic device 1, as Figure 3 As shown, for example, assume that noise (stray light / fluorescence, etc.) is mixed into the path of signal light s2 and that the signal light s2 contains a noise component sx (stray light / fluorescence, etc.). In this case, such signal light s2 is incident on the beam splitter 40, whereby the noise component sx is evenly distributed to the paths of signal light s1' and signal light s2'. Thus, signal light s1' and signal light s2' containing a noise component sx' having a height of 1 / 2 of the noise component sx are output from the beam splitter 40. Here, the signal lights s1 and s2 originating from the crystal cause quantum interference, and therefore, the intensities in the signals s1' and s2' vibrate with opposite phases. Therefore, when the difference (P2s-P1s) between the light intensities P1s and P2s of the signal lights s1' and s2' is taken, as described above Figure 2 As shown in FIG. 1 , the noise component sx' of the signal light s1' and s2' disappears, and only the interference signal remains. In addition, by taking the difference between the light intensities P1s and P2s (P2s-P1s), as described above, Figure 2 As shown, the waveform of the interference pattern is a waveform based on the axis of the difference (P2s-P1s)=0 (zero), that is, a waveform with a shift of "zero".

[0085] As described above, in the infrared spectrometer 1, even if noise light is generated in the period up to the front stage of the detection unit 6 and the noise light is mixed into the signal lights s1 and s2, the influence of the noise light is offset by the difference between the signal lights s1' and s2', and an interference pattern after the influence of the noise light is eliminated is obtained. In particular, when the conversion efficiency of the nonlinear crystal 12 is poor and the light intensity of the signal lights s1, s2, s1', and s2' is weak, the accuracy of the analysis result will be greatly reduced even by a small amount of noise light. In contrast, according to the infrared spectrometer 1 of this embodiment, an interference pattern after the influence of the noise light is eliminated can be obtained, so that the reduction in accuracy caused by the noise light can be suppressed, and high-precision spectroscopic analysis can be performed.

[0086] Next, the quantum interference and the interference pattern in the infrared spectroscopic device 1 will be described in more detail from the viewpoint of quantum optics. In order to facilitate understanding of them, the quantum interference and the interference pattern in the reference structure will be described first.

[0087] [Reference structure]

[0088] Figure 4 1 is a diagram schematically showing a structure of a reference structure 1R relative to the infrared spectroscopic device 1 of this embodiment. Figure 1 The same components as those shown are denoted by the same reference numerals, and description thereof will be omitted.

[0089] like Figure 4 As shown, the reference structure 1R includes a light source 2R, a quantum optical system 4R, a detection unit 6R, and an analysis device 8R, which respectively correspond to the light source 2, the quantum optical system 4, the detection unit 6, and the analysis device 8 of the infrared spectrometer 1. However, there are the following main differences between the infrared spectrometer 1 and the reference structure 1R.

[0090] That is, the first difference is that the quantum optical system 4 of the infrared spectroscopic device 1 outputs the signal lights s1 and s2 separately, whereas the quantum optical system 4R of the reference structure 1R outputs them in a superposition state. That is, in the quantum optical system 4 of the infrared spectroscopic device 1, the fixed mirror 14 allows the signal light s1 to pass through, but in the quantum optical system 4R of the reference structure 1R, the fixed mirror 14R does not allow the signal light s1 to pass through but reflects the signal light s1.

[0091] The second difference is that the detection unit 6 of the infrared spectrometer 1 combines the two signal lights s1 and s2 in the beam splitter 40, whereas the quantum optical system 4R of the reference structure 1R combines and outputs the two signal lights s1 and s2 by superimposing them through the same optical path.

[0092] The third difference is that the detection unit 6 of the infrared spectrometer 1 uses a beam splitter 40 to split the synthesized light into two signal lights s1' and s2' and outputs them, and the analysis device 8 obtains an interference pattern based on the difference in light intensities P1s and P2s between the signal lights s1' and s2'. In contrast, the reference structure 1R uses a detector 41R to detect the light intensity Ps of the light synthesized from the two signal lights s1 and s2, and the analysis device 8R obtains the interference pattern based on the light intensity Ps.

[0093] Quantum interference and interference pattern in such a reference structure 1R are described as follows using quantum optics. In addition, the meanings of symbols, variables, operators, etc. in the following description are as shown in Table 1.

[0094] [Table 1]

[0095]

[0096] First, in classical optics, light is described using an electric field described by complex numbers. On the other hand, in quantum optics, the state of a system is described using a state vector that is the basis of a complex Hilbert space and physical quantities (operators on the Hilbert space) that act on the state vector.

[0097] In reference structure 1R, if it is assumed for convenience in order to explain the process of deriving the equation that idler light i1 and idler light i2 can be distinguished, and signal light s1 and signal light s2 can be distinguished, the state vector of quantum optical system 4R is expressed by the following equation (1).

[0098] [Number 1]

[0099]

[0100] However, in the quantum optical system 4R of the reference structure 1R, in reality, since the signal light s1 and the signal light s2 overlap on the same axis and have the same polarization and angular frequency, they cannot be distinguished, and the annihilation operators of the signal light s1 and the signal light s2 are connected as shown in the following equation (2). The idler light i1 and the idler light i2 are also indistinguishable. However, since the idler light i1 passes through the sample SP twice, the so-called beam splitter model is used to connect the annihilation operators of the idler light i1 and the idler light i2 as shown in the following equation (3) (for equation (3), refer to non-patent document 1, for example).

[0101] [Number 2]

[0102]

[0103] [Number 3]

[0104]

[0105] Therefore, when the signal light s1 and the signal light s2 are associated by equation (2) and the idler light i1 and the idler light i2 are associated by equation (3), the state vector of the quantum optical system 4R becomes the following equation (4) according to equations (1) to (3).

[0106] [Number 4]

[0107]

[0108] Next, in the reference structure 1R, the electric field of the positive frequency at time t measured by the detector 41R is expressed by the following equation (5).

[0109] [Number 5]

[0110]

[0111] Then, when the electric field of the positive frequency of equation (5) is applied to equation (4) representing the state vector of the quantum optical system 4R, the following equation (6) is obtained.

[0112] [Number 6]

[0113]

[0114] Next, the square of the norm of equation (6) is obtained by taking the inner product of the state vector of equation (6) and the conjugate vector of the state vector (equation (6A)). Using the obtained equation, the time average of the light intensity Ps of the signal light measured by the detector 41R of the reference structure 1R is expressed by the following equation (7). Among them, the "t" at the lower right of "<>" in equation (7) refers to the time average, and "cc" refers to the complex conjugate of its preceding term. The range of the time average is set to at least exceed the response time of the infrared detector.

[0115] [Number 6A]

[0116]

[0117] [Number 7]

[0118]

[0119] Here, if the wavelength center of the signal light s is set to ω 0s , set the wavelength center of the idler light i to ω 0i , then in the spontaneous parametric down-conversion ω s +ω i =ω p = constant is established, so ω in equation (7) s and ω i Each uses an angular frequency Ω and is represented as ω s =ω 0s -Ω、ω i =ω 0i +Ω. If it is used, it becomes F(ω s ,ω i )=F(Ω), formula (7) is expressed by the following formula (8).

[0120] [Number 8]

[0121]

[0122] Furthermore, in the reference configuration 1R, when the movement amount ΔL of the movable mirror 34R is “0”, t 0i =t 0s When the origin of the movement amount ΔL is set in a manner, equation (8) becomes the following equation (9).

[0123] [Number 9]

[0124]

[0125] Here, in order to facilitate comparison with the infrared spectrometer 1 of this embodiment, the light intensity is calculated when there is no loss of the signal light s and the quantum efficiency of the detector 41R is "1". The constant "2" on the right side of the formula (9) corresponds to the average power. If the power of the signal light s generated when the pump light p passes through the nonlinear crystal 12 only once is set to I0, then the average power is appropriate to be 2I0. Therefore, in this case, the formula (9) becomes the following formula (10), and in the reference structure 1R, an interference pattern corresponding to the formula (10) is obtained.

[0126] [Number 10]

[0127]

[0128] Next, quantum interference and interference pattern in the infrared spectroscopic device 1 are described as follows using quantum optics. In addition, the meanings of symbols, variables, operators, etc. in the following description are as shown in Table 2.

[0129] [Table 2]

[0130]

[0131] The signal light s1 and the signal light s2 in the infrared spectrometer 1 are different from the reference structure 1R and are clearly distinguished by passing through completely different paths. Therefore, the above equation (2) does not hold, and the annihilation operators of the signal light s1 and the signal light s2 are independent. On the other hand, the idler light i1 and the idler light i2 in the infrared spectrometer 1 overlap with the reference structure 1R in the same way, and the above equation (3) holds directly. Therefore, the state vector of the quantum optical system 4 of the infrared spectrometer 1 is expressed as equation (11) using equations (1) and (3).

[0132] [Number 11]

[0133]

[0134] In addition, in the detection unit 6 of the infrared spectroscopic device 1, the conversion of light in the beam splitter 40 having a transmittance-reflectance ratio of 1:1 is expressed by the following equation (12) using the annihilation operator of the signal light s1 and the signal light s2 input to the different incident ports 40A1 and 40A2, and the annihilation operator of the signal light s1' and the signal light s2' output from the different emission ports 40B1 and 40B2. In the equation (12), the matrix part of 2 rows and 2 columns represents the conversion action of the beam splitter 40, and each component of the matrix part is determined based on the transmittance and reflectance of the beam splitter 40. In addition, there are several methods for displaying the matrix involved in the beam splitter 40 according to the processing of the phase component, and the equation (12) is used here. For example, there is also a display method in which the matrix involved in the beam splitter 40 is set to the equation (12A), but the final result is only the addition of the phase constant, which is essentially the same as the display method of the equation (12).

[0135] [Number 12]

[0136]

[0137] [Number 12A]

[0138]

[0139] In the infrared spectrometer 1, the positive frequency electric field of the signal light s1' measured by the first detector 41 at time t is expressed by the following equation (13). Similarly, the positive frequency electric field of the signal light s2' measured by the second detector 42 at time t is expressed by the following equation (14).

[0140] [Number 13]

[0141]

[0142] [Number 14]

[0143]

[0144] Furthermore, when equation (13) is applied to equation (11) representing the state vector of the quantum optical system 4, equation (15) is obtained. Similarly, when equation (14) is applied to equation (11), equation (16) is obtained.

[0145] [Number 15]

[0146]

[0147] [Number 16]

[0148]

[0149] Next, the square of the norm of equation (15) is obtained by taking the inner product of the state vector of equation (15) and the conjugate vector of the state vector (equation (16A)). Using the obtained equation, the time average of the light intensity P1s of the signal light s1' measured by the first detector 41 of the infrared spectrometer 1 is expressed by the following equation (17). Among them, the "t" at the lower right of "<>" in equation (17) refers to the time average, and "cc" refers to the complex conjugate of its preceding term. The range of the time average is set to at least a degree exceeding the response time of the infrared detector.

[0150] Similarly, the square of the norm of equation (16) is obtained by taking the inner product of the state vector of equation (16) and its conjugate vector (equation (17A)). Using the obtained equation, the time average of the light intensity P2s of the signal light s2' measured by the second detector 42 of the infrared spectrometer 1 is expressed by the following equation (18). Among them, the "t" at the lower right of "<>" in equation (18) refers to the time average, and "cc" refers to the complex conjugate of its preceding term. The range of the time average is set to at least exceed the response time of the infrared detector.

[0151] [Number 16A]

[0152]

[0153] [Number 17]

[0154]

[0155] [Number 17A]

[0156]

[0157] [Number 18]

[0158]

[0159] In these equations (17) and (18), "1" as the constant part on the right side is considered to represent the average power at each emission port 40B1, 40B2. In the beam splitter 40, the power is evenly branched at a ratio of 1:1, so the average power at each emission port 40B1, 40B2 is equal. Therefore, it is considered that the ratio of the right side to the left side in equations (17) and (18) is equal, and the difference between equations (17) and (18) can be directly calculated to obtain the difference between the light intensity P1s and the light intensity P2s as in equation (19).

[0160] [Number 19]

[0161]

[0162] Similar to equation (8), equation (19) is expressed as the following equation (20) using one angular frequency Ω.

[0163] [Number 20]

[0164]

[0165] Furthermore, in the infrared spectroscopic device 1, when the movement amount ΔL of the movable mirror 34 is “0”, t 0i =t 1s -t 2s When the origin of the movement amount ΔL is set in a manner, equation (20) becomes the following equation (21).

[0166] [Number 21]

[0167]

[0168] Here, if the light intensity of the signal light s1, s2, s1', s2' is calculated when there is no loss and the quantum efficiency of the first detector 41 and the second detector 42 is "1", then equations (17) and (18) become the following equations (22) and (23), respectively.

[0169] [Number 22]

[0170]

[0171] [Number 23]

[0172]

[0173] Then, equation (21) is expressed as equations (24) and (25) below using equations (22) and (23). Then, in the analysis device 8 of the infrared spectrometer 1, interference patterns corresponding to equations (24) and (25) are obtained.

[0174] [Number 24]

[0175]

[0176] [Number 25]

[0177]

[0178] When comparing equation (10) for reference structure 1R with equation (25) for infrared spectrometer 1, equation (10) includes a term of "2I0" corresponding to the power of signal light s1 and s2, whereas equation (25) does not include such a term. In quantum optical system 4R of reference structure 1R, noise light (stray light / fluorescence, etc.) reaches infrared detector 41R and is added to the interference pattern, so Figure 5As shown in the figure, an interference pattern of a waveform in which the center of the power amplitude deviates from zero is obtained. This noise light is not the entangled photon pair generated in the nonlinear crystal 12 but the light caused by mixing. In contrast, in the infrared spectrometer 1, since the noise light (stray light / fluorescence, etc.) has nothing to do with quantum interference, it is evenly distributed to the two emission ports 40B1 and 40B2. This noise light is not the entangled photon pair generated in the nonlinear crystal 12 but the light caused by mixing into the quantum optical system 4. Therefore, in the interference pattern obtained by taking the difference, as shown in FIG. Figure 2 As shown, such noise is removed.

[0179] As mentioned in the description of equation (12), the phases of the signal light s1' and the signal light s2' emitted from the beam splitter 40 are opposite to each other. This is described as follows.

[0180] That is, when the light intensity of the signal light s1 is measured on the incident side of the beam splitter 40, the source of the signal light s1 is obviously the first entangled photon pair generation process, so quantum interference will not occur, and the light intensity will not change even if the movable mirror 34 is moved. When the light intensity of the signal light s2 is measured on the incident side of the beam splitter 40, the light intensity will not change due to the movable mirror 34 for the same reason.

[0181] In addition, the sum of the light intensities of the two signal lights s1 and s2 incident on the beam splitter 40 is equal to the sum of the light intensities of the two signal lights s1' and s2' emitted from the beam splitter 40. In addition, as described above, even if the movable mirror 34 is moved, the light intensities of the signal lights s1 and s2 do not change. Therefore, even if the movable mirror 34 is moved, the sum of the light intensities of the signal lights s1' and s2' does not change.

[0182] When the intensity of the signal light s1' is measured on the emission side of the beam splitter 40, the source of the signal light s1' is unclear, so quantum interference occurs and an interference pattern is observed when the movable mirror 34 is moved. The same is true when the intensity of the signal light s2' is measured on the emission side of the beam splitter 40.

[0183] However, as described above, even if the movable mirror 34 is moved, the sum of the light intensities of the signal lights s1 ′ and s2 ′ does not change, and therefore the phases of the two interference patterns observed on the emission side of the beam splitter 40 are opposite to each other.

[0184] The above-described embodiment merely shows one mode of the present invention, and any modification and application are possible without departing from the gist of the present invention.

[0185] For example, in the above-mentioned embodiment, an example of obtaining an interference pattern based on the difference (P2s-P1s) between the light intensities P1s and P2s of the signal lights s1' and s2', respectively. However, the above-mentioned interference pattern can also be obtained based on the difference (αP2s-βP1s) between the values ​​obtained by multiplying at least one of the differences in the light intensities P1s and P2s by a constant (α, β are constants, one of which may also be 1). Thus, for example, when the ratio of the reflectivity and transmittance of the beam splitter deviates from 1:1 and the noise cannot be completely eliminated by a simple difference, the noise can be eliminated by adjusting α and β. In addition, the offset of the interference pattern obtained by such an operation may be as follows: Figure 2 That is not 0, but it can also prioritize noise elimination.

[0186] Furthermore, modified examples of the embodiment of the present invention will be described below.

[0187] (Variant 1)

[0188] The infrared spectroscopic device 1 described above has the following structure: the quantum optical system 4 has a variable optical path length function for changing the optical path length of the optical path from the second dichroic mirror 32 to the movable mirror 34, and the optical path length of the idler light i is changed by the optical path length changing function. However, the quantum optical system 4 may change the optical path length of the signal light s1 instead of changing the optical path length of the idler light i.

[0189] Figure 6 Schematically shows the structure of the infrared spectrometer 100 according to this modification. Figure 1 The components shown are denoted by the same reference numerals, and description thereof will be omitted.

[0190] In the infrared spectroscopic device 100 according to the present modification, the quantum optical system 104 fixes the optical path length of the idler light i1 by using the fixed mirror 114 as a reflector for reflecting the idler light i1. In addition, the quantum optical system 104 includes an optical path length variable mechanism 180 for changing the optical path length of the signal light s1 at the front stage of the detection unit 6. The optical path length variable mechanism 180 includes: the above-mentioned movable mirror 34, which is moved at a certain speed by the actuator 36; a first reflector 181, which reflects the signal light s1 after passing through the fixed mirror 14 toward the movable mirror 34; and a second reflector 182, which reflects the signal light s1 reflected by the movable mirror 34 toward the detection unit 6. The optical path length variable mechanism 180 changes the optical path length of the signal light s1 (the optical path length between the second dichroic mirror 32 and the movable mirror 34) by moving the movable mirror 34.

[0191] As described above, the signal light s1 and the idler light i1 passing through the sample SP are in an entangled state. Since the signal light s1 contains information after interacting with the sample SP, the interference pattern is obtained by changing the optical path length of the signal light s1 and using synthesis to make the signal light s2 that does not contain the information of the sample SP interfere with the signal light s1.

[0192] According to this variation, it is not necessary to extend the optical path length of the idle light i for configuring the sample SP, and the optical path length can be fixed to the minimum required length. Thus, the size of the sample chamber for storing the sample SP can be limited to the minimum required length. Therefore, even if air needs to be sent to the sample chamber for analysis, the amount of air can be limited, thereby suppressing the reduction in analysis accuracy caused by the influence of absorbing moisture in the air.

[0193] (Variant 2)

[0194] In the above-mentioned infrared spectrometer 1, in order to realize the quantum interference function of quantum interference between multiple entangled photon pair generation processes, the quantum optical system 4 has a fixed mirror 14, which reflects the pump light p emitted from the nonlinear crystal 12 and then re-injects it into the nonlinear crystal 12. The quantum optical system 4 generates multiple entangled photon pair generation processes in the same nonlinear crystal 12 by reciprocating the pump light p in the nonlinear crystal 12. However, the quantum optical system 4 can also generate entangled photon pair generation processes in different nonlinear crystals 12.

[0195] Figure 7 Schematically shows the structure of the infrared spectrometer 200 according to this modification. Figure 1 The components shown are denoted by the same reference numerals, and description thereof will be omitted.

[0196] The quantum optical system 204 of the infrared spectroscopic device 200 is configured as follows: a first nonlinear crystal 12A and a second nonlinear crystal 12B that are considered to be identical to each other are provided instead of one nonlinear crystal 12, and in the quantum optical system 204, the pump light p emitted from the light source 2 passes through the first nonlinear crystal 12A and the second nonlinear crystal 12B in sequence, thereby generating a first entangled photon pair generation process and a second entangled photon pair generation process. That is, the modified example 2 includes the first nonlinear crystal 12A and the second nonlinear crystal 12B, and the quantum optical system 204 causes the first signal light s1 to be emitted along the optical path (optical path) of the pump light p incident on the first nonlinear crystal 12A, and causes the second signal light s2 to be emitted along the optical path (optical path) of the pump light p incident on the second nonlinear crystal 12B.

[0197] In addition, in this structure, an optical path length variable mechanism 280 for changing the optical path length of the idler light i1 is arranged between the first nonlinear crystal 12A and the second nonlinear crystal 12B. The optical path length variable mechanism 280 is substantially the same as the optical path length variable mechanism 180 provided in the infrared spectroscopic device 100, and includes a movable mirror 34, a first reflection mirror 281 for reflecting the idler light i1 emitted from the first nonlinear crystal 12A toward the movable mirror 34, and a second reflection mirror 282 for reflecting the idler light i1 reflected by the movable mirror 34 toward the sample SP. In this optical path length variable mechanism 280, the movable mirror 34 is moved at a certain speed by the actuator 36, thereby changing the optical path length of the idler light i1.

[0198] On the other hand, the pump light p and the signal light s1 emitted from the first nonlinear crystal 12A are reflected by the reflector 221 toward the fixed mirror 14, and the signal light s1 passes through the fixed mirror 14 and is output to the detection unit 6. The pump light p is reflected by the fixed mirror 14, passes through the condenser lens 276 and the third dichroic mirror 236, and then enters the second nonlinear crystal 12B.

[0199] In addition, the idler light i1 after passing through the sample SP passes through the focusing lens 277 and the third dichroic mirror 236 and is incident on the second nonlinear crystal 12B in a state of superposition with the pump light p. As a result, quantum interference occurs between the second entangled photon pair generation process and the first entangled photon pair generation process in the second nonlinear crystal 12B. In addition, in this case, the idler light i1 passes through the sample SP only once. Therefore, the formula corresponding to formula (3) is the following formula (25A), and the formula corresponding to formula (10), formula (25), etc. is: *2 " is replaced by "τ * " and the resulting formula.

[0200] [Number 25A]

[0201]

[0202] When the sample SP has a large absorption, the amplitude of the obtained interference pattern becomes larger, so the infrared spectrometer 200 according to this modification can measure a larger absorbance. -4 When the sample SP is the measurement object, the amplitude of the obtained interference pattern becomes 100 times

[0203] In addition, according to the infrared spectrometer 200 of this modification, since it is not necessary to return the pump light p to the same nonlinear crystal 12 ( Figure 1 ), therefore, the degree of freedom in the layout of the quantum optical system 204 is improved.

[0204] (Variant 3)

[0205] The infrared spectroscopic device 200 according to the second modification is configured such that the quantum optical system 204 changes the optical path length of the idler light i1 . However, the infrared spectroscopic device 200 may be configured to change the optical path length of the signal light s1 similarly to the first modification.

[0206] Figure 8 Schematically shows the structure of the infrared spectrometer 300 according to this modification. Figure 7 The components shown are denoted by the same reference numerals, and description thereof will be omitted.

[0207] In the quantum optical system 304 of the infrared spectroscopic device 300, an optical path length variable mechanism 380 for changing the optical path length of the signal light s1 is provided instead of the optical path length variable mechanism 280 for changing the optical path length of the idler light i1. The optical path length variable mechanism 380 has a structure substantially the same as the optical path length variable mechanism 180 provided in the infrared spectroscopic device 100, and includes a movable mirror 34; a first reflecting mirror 381 for reflecting the signal light s1 emitted from the nonlinear crystal 12A and passing through the fixed mirror 14 toward the movable mirror 34; and a second reflecting mirror 382 for reflecting the signal light s1 reflected by the movable mirror 34 toward the detection unit 6. In the optical path length variable mechanism 380, the movable mirror 34 is moved at a certain speed by the actuator 36, thereby changing the optical path length of the signal light s1.

[0208] (Variant 4)

[0209] The infrared spectrometer 100 according to Modification 1 and the infrared spectrometer 300 according to Modification 3 have been described in which the optical path length of the signal light s1 is changed. When the optical path length of the signal light s1 is changed, it is preferable to change the optical path length of the pump light p by the same amount as the optical path length of the signal light s1.

[0210] Specifically, the interference pattern based on the difference between the light intensities P1s and P2s of the two signal lights s1' and s2' output from the beam splitter 40 is a waveform corresponding to the above equation (21). The equation (21) is the product of the integral operation part shown in the following equation (26) and the variable factor part shown in the following equation (27).

[0211] [Number 26]

[0212]

[0213] [Number 27]

[0214] ω p t 0p -ω 0i t 0i -ω0s t 0s …(27)

[0215] Moreover, the integral operation part is a slowly changing envelope factor, and the variable factor part is a factor that oscillates violently with the phase shown in equation (27).

[0216] In the infrared spectroscopic device 1 according to the embodiment and the infrared spectroscopic device 200 according to the second modification, when the optical path length of the idler light i1 is changed by ΔL, t 0i It changes at 2ΔL / c, so the phase change is as shown in the following equation (28).

[0217] [Number 28]

[0218]

[0219] Here, λ oi is the central wavelength of the idler light i, so the interference pattern is based on the idler central wavelength λ oi The sample SP vibrates with a period of half of the wavelength, and by processing the interference pattern, the transmittance of the sample SP for the idle frequency wavelength can be calculated.

[0220] In contrast, in the infrared spectrometer 100 according to Modification 1 and the infrared spectrometer 300 according to Modification 3, the optical path length of the signal light s1 is changed. However, according to the same explanation as when the optical path length of the idler light i1 is changed, the interference pattern in this case vibrates at half the central wavelength of the signal light s1. Therefore, when the interference pattern is processed, the relationship between the "signal wavelength" and the "transmittance for the idler wavelength corresponding to the signal wavelength" is directly obtained. In this case, when the wavelength of the pump light p is regarded as a constant value, the relationship between the idler wavelength and the transmittance corresponding to the idler wavelength is derived. However, when the wavelength of the pump light p drifts and the wavelength cannot be regarded as a constant value, the wavelength of the pump light p needs to be measured separately.

[0221] Therefore, when the optical path lengths of the signal light s1 and the pump light p are changed by the same amount, the phase is expressed by the following equation (29).

[0222] [Number 29]

[0223]

[0224] In this case, when the movable mirror 34 is moved by the amount ΔL, the interference pattern vibrates at a period of half the wavelength of the idler light i1, similarly to the infrared spectroscopic device 1 according to the embodiment and the infrared spectroscopic device 300 according to Modification 3. Therefore, it is known that even when the wavelength of the pump light p is changed, the spectral characteristics (transmittance, etc.) of the sample SP with respect to the wavelength of the idler light can be directly obtained based on the interference pattern.

[0225] Fig. 9 Schematically shows the structure of the infrared spectrometer 400 according to this modification. Figure 8 The components shown are denoted by the same reference numerals, and description thereof will be omitted.

[0226] As shown in the figure, in the quantum optical system 404 of the infrared spectrometer 400, the optical path length variable mechanism 380 ( Figure 8 ) is arranged between the nonlinear crystal 12A and the fixed mirror 14, thereby causing the path length of the pump light p to change by the same amount as that of the signal light s1.

[0227] It will be understood by those skilled in the art that the above-described exemplary embodiments and various modifications are specific examples of the following aspects.

[0228] A spectroscopic device according to one embodiment comprises: a light source that emits pump light; a quantum optical system into which the pump light is incident; a detection unit that detects the light intensity of light output from the quantum optical system; and an analysis unit that obtains an interference pattern based on the light intensity, wherein the quantum optical system comprises: a nonlinear optical element that generates a first entangled photon pair generation process by the incidence of pump light from the light source, thereby generating photon pairs of idler light and signal light; a moving mirror that changes the optical path length of the idler light or the signal light; and a fixed mirror that causes the pump light emitted from the nonlinear optical element to be reflected and then incident again on the nonlinear optical element, thereby causing the nonlinear optical element to generate a second entangled photon pair that undergoes quantum interference with the first entangled photon pair generation process. An entangled photon pair generation process; a sample configuration device, which configures the sample on the optical path of the idler light generated in any one of the first entangled photon pair generation process and the second entangled photon pair generation process; a first output component, which outputs the signal light generated in the first entangled photon pair generation process; and a second output component, which outputs the signal light generated in the second entangled photon pair generation process, the detection unit comprises: a beam splitter, each signal light outputted by the first output component and the second output component of the quantum optical system is incident on the beam splitter; and two detectors, the two detectors detect the light intensity of each of the two beams emitted from the beam splitter, the analysis device obtains the interference pattern according to the difference between the light intensities detected by the two detectors.

[0229] According to the spectroscopic device of the above aspect, an interference pattern is obtained in which the influence of noise light is eliminated.

[0230] A spectroscopic device according to one embodiment comprises: a light source that emits pump light; a quantum optical system into which the pump light is incident; a detection unit that detects the light intensity of light output from the quantum optical system; and an analysis unit that obtains an interference pattern based on the light intensity, wherein the quantum optical system comprises: a first nonlinear optical element that generates a first entangled photon pair generation process by the incidence of pump light from the light source, thereby generating photon pairs of idler light and signal light; a moving mirror that changes the optical path length of the idler light or the signal light; a fixed mirror that reflects the pump light emitted from the first nonlinear optical element; and a second nonlinear optical element that generates a quantum entangled photon pair between the first entangled photon pair generation process and the pump light reflected by the fixed mirror. A second entangled photon pair generation process of interference; a sample configuration device, which configures the sample on the optical path of the idle frequency light generated in any one of the first entangled photon pair generation process and the second entangled photon pair generation process; a first output component, which outputs the signal light generated in the first entangled photon pair generation process; and a second output component, which outputs the signal light generated in the second entangled photon pair generation process, the detection unit comprises: a beam splitter, each signal light outputted by the first output component and the second output component of the quantum optical system is incident on the beam splitter; and two detectors, the two detectors detect the light intensity of each of the two beams emitted from the beam splitter, and the analysis device obtains the interference pattern according to the difference between the light intensities detected by the two detectors.

[0231] According to the spectroscopic device of one embodiment described above, an interference pattern is obtained in which the influence of noise light is eliminated. In addition, since it is not necessary to return the pump light to the same nonlinear optical element, the degree of freedom in the layout of the quantum optical system is improved.

[0232] In each of the above-mentioned spectroscopic devices, in the quantum optical system, the signal light and the pump light are incident on the movable mirror, and the optical path lengths of the signal light and the pump light are changed by the same amount by movement of the movable mirror.

[0233] According to this spectroscopic device, even when the wavelength of the pump light varies, the spectroscopic characteristics of the sample with respect to the wavelength of the idler light can be directly obtained based on the interference pattern.

[0234] [Second embodiment]

[0235] Fig.10 504 is a diagram schematically showing the structure of an infrared spectroscopic device 500 according to the second embodiment. 504 represents a quantum optical system. Figure 1The same components are denoted by the same reference numerals, and their descriptions are omitted. Fig.10 In the figure, for the convenience of explanation, the light paths superimposed on each other are depicted separately from each other.

[0236] and Figure 7 to Figure 9 As in Modifications 2 to 4 shown, the quantum optical system 504 of the second embodiment includes a first nonlinear crystal 12A and a second nonlinear crystal 12B that are considered to be identical to each other, instead of one nonlinear crystal 12. Here, the first nonlinear crystal 12A and the second nonlinear crystal 12B have equivalent characteristics.

[0237] In the second embodiment, as a structure different from modifications 2 to 4, a pump light branching beam splitter (pump light branching member) 210 having a transmittance to reflectance ratio of 1:1 is provided in the front stage of the first nonlinear crystal 12A. The pump light p is branched into two pump lights p1 and p2 by the pump light branching beam splitter 210. The pump light p1 on one side is incident on the first nonlinear crystal 12A to generate a first entangled photon pair generation process, and the pump light p2 on the other side is incident on the second nonlinear crystal 12B to generate a second entangled photon pair generation process. In addition, in the second embodiment, a movable mirror (signal light reflecting mirror for adjusting the signal light path length) 134 is provided, and the movable mirror 134 constitutes an optical path length variable mechanism for changing the optical path length of the signal light s1.

[0238] When describing the quantum optical system 504 in detail, the pump light p1 on one side passes through the condenser lens 10 and enters the first nonlinear crystal 12A, and a small part of the pump light p1 is converted into the first signal light s1 and the first idler light i1 by spontaneous parametric down conversion.

[0239] The pump light p1 and a small portion of the converted first signal light s1 and first idler light i1 pass through the collimating lens 76 and are incident on the first idler light reflector 150. The pump light p1 and the first signal light s1 pass through the first idler light reflector 150, and the first idler light i1 is reflected by the first idler light reflector 150.

[0240] The pump light p1 and the first signal light s1 transmitted through the first idler light reflector 150 are incident on the bandpass filter (BPS) 151. The first signal light s1 separated by the bandpass filter 151 is reflected by the first signal light reflector 153, the movable mirror (signal light reflector for adjusting the signal light path length) 34, and the second signal light reflector 154 in sequence, and then introduced into the first incident port of the signal light mixing beam splitter 240 having a transmittance and reflectance ratio of 1:1. The first incident port is connected to the first detector 41, and the first signal light s1' is measured by the first detector 41.

[0241] In addition, the first idler light i1 reflected by the first idler light reflecting mirror 150 is incident on the sample placement device 35 .

[0242] The other pump light p2 branched by the pump light branching beam splitter 210 is reflected by the pump reflector 155 and then passes through the second idler light reflector 156. The first idler light i1 mentioned above after passing through the sample arrangement device 35 is reflected at the second idler light reflector 156, and the other pump light p2 and the first idler light i1 pass through the condenser lens 10 and are incident on the second nonlinear crystal 12B.

[0243] In the second nonlinear crystal 12B, a small portion of the pump light p2 is converted into the second signal light s2 and the second idler light i2 by spontaneous parametric down conversion. Since the conversion efficiency is low, the power of the pump light p2 can be set equal before and after the incident.

[0244] The second signal light s2, pump light p2, first idler light i1 and second idler light i2 emitted from the second nonlinear crystal 12B pass through the collimating lens 78 and enter the signal light reflecting mirror 157. At this time, the optical path of the first idler light i1 strictly coincides with the optical path of the second idler light i2.

[0245] The pump light p2, the first idler light i1, and the second idler light i2 pass through the signal light reflector 157, and the second signal light s2 is reflected by the signal light reflector 157. The reflected second signal light s2 is introduced into the second incident port of the signal light mixing beam splitter 240. The second incident port is connected to the second detector 42, and the second signal light s2' is measured by the second detector 42.

[0246] In the analysis device 8, the difference between the signal light intensity of the first signal light s1' measured by the first detector 41 and the signal light intensity of the second signal light s2' measured by the second detector 42 is recorded, and an interference pattern is obtained by moving the movable mirror (signal light reflecting mirror for adjusting the signal light path length) 34. The sample SP is subjected to spectral analysis by performing Fourier transform analysis on the interference pattern.

[0247] That is, according to the second embodiment, a beam splitter 210 for branching pump light is provided in the front stage of the nonlinear crystal 12, and the nonlinear crystal 12 is a first nonlinear crystal 12A and a second nonlinear crystal 12B. The quantum optical system 504 is structured so that the pump light p1 on one side branched by the beam splitter 210 is incident on the first nonlinear crystal 12A, and the pump light p2 on the other side is incident on the second nonlinear crystal 12B, thereby increasing the degree of freedom in designing the quantum optical system 504.

[0248] According to the second embodiment, a movable mirror 34 is provided for changing the optical path length of the signal light s1. Therefore, an interference pattern can be obtained based on the difference between the light intensity of the first signal light s1' measured by the first detector 41 and the light intensity of the second signal light s2' measured by the second detector 42 while the movable mirror 34 is moved at a certain speed. By performing Fourier transform analysis on the interference pattern, the sample SP can be spectroscopically analyzed.

[0249] [Third Embodiment]

[0250] Fig.11 604 is a diagram schematically showing the structure of an infrared spectroscopic device 600 according to the third embodiment. 604 represents a quantum optical system. Figure 1 , Fig.10 The components shown are denoted by the same reference numerals and their descriptions are omitted. Fig.11 In the figure, for the convenience of explanation, the light paths superimposed on each other are depicted separately from each other.

[0251] In the second embodiment, a movable mirror (signal light reflection mirror for adjusting the signal light path length) 34 is used to adjust the signal light path length, but in the third embodiment, a movable mirror (idle reflection mirror for adjusting the idle light path length) 34 is used to adjust the idle light path length, and the movable mirror 34 constitutes a variable light path length mechanism for changing the light path length of the idle light i1.

[0252] One of the pump light p1 branched by the pump light branching beam splitter 210 enters the first nonlinear crystal 12A after passing through the condenser lens 10, and a small part of the pump light p1 is converted into the first signal light s1 and the first idler light i1.

[0253] The pump light p1 and a small portion of the converted first signal light s1 and first idler light i1 pass through the collimating lens 76 and are incident on the first idler light reflector 150. The pump light p1 and the first signal light s1 pass through the first idler light reflector 150, and the first idler light i1 is reflected by the first idler light reflector 150.

[0254] The pump light p1 and the first signal light s1 transmitted through the first idle light reflector 150 are incident on the bandpass filter 151. The first signal light s1 separated by the bandpass filter 151 is reflected by the first signal light reflector 161 and the second signal light reflector 162 and then introduced into the first incident port of the signal light mixing beam splitter 240 having a transmittance to reflectance ratio of 1:1. The first incident port is connected to the first detector 41, and the first signal light s1' is measured by the first detector 41.

[0255] In addition, the first idler light i1 reflected by the first idler light reflecting mirror 150 is incident on the sample placement device 35 .

[0256] The other pump light p2 branched by the pump light branching beam splitter 210 is reflected by the pump reflector 155 and then passes through the second idler light reflector 156. The first idler light i1, which has passed through the sample arrangement device 35, is sequentially reflected by the third idler light reflector 163, the movable mirror (idler light reflector for adjusting the idler light path length) 34, and the fourth idler light reflector 164 and then reflected by the second idler light reflector 156. The other pump light p2 and the first idler light i1 emitted from the second idler light reflector 156 pass through the condenser lens 10 and are incident on the second nonlinear crystal 12B.

[0257] In the second nonlinear crystal 12B, a small portion of the pump light p2 is converted into the second signal light s2 and the second idler light i2. Since the conversion efficiency is low, the power of the pump light p2 can be set equal before and after the incident.

[0258] The second signal light s2 , the pump light p2 , the first idler light i1 , and the second idler light i2 emitted from the second nonlinear crystal 12B pass through the second collimating lens 78 and are incident on the signal light reflecting mirror 157 .

[0259] The pump light p2, the first idler light i1, and the second idler light i2 pass through the signal light reflector 157, and the second signal light s2 is reflected by the signal light reflector 157. The reflected second signal light s2 is introduced into the second incident port of the signal light mixing beam splitter 240. The second incident port is connected to the second detector 42, and the second signal light s2' is measured by the second detector 42.

[0260] In the analysis device 8, the difference between the signal light intensity of the first signal light s1' measured by the first detector 41 and the signal light intensity of the second signal light s2' measured by the second detector 42 is recorded, and the interference pattern is obtained by moving the movable mirror (idle light reflecting mirror for adjusting the idle light path length) 34, and the sample SP is subjected to spectral analysis by performing Fourier transform analysis on the interference pattern.

[0261] According to the third embodiment, similarly to the second embodiment, the degree of freedom in design of the quantum optical system 604 is increased, and since it is provided with a movable mirror 234 that changes the optical path length of the first idle light i1, an interference pattern can be obtained based on the difference between the light intensity of the first signal light s1' measured by the first detector 41 and the light intensity of the second signal light s2' measured by the second detector 42 while the movable mirror 234 is moved at a certain speed, and the sample SP can be spectroscopically analyzed by performing Fourier transform analysis of the interference pattern.

[0262] (Other Modifications)

[0263] In each of the above-mentioned embodiments and modifications, the combination of wavelengths of the pump light p, the signal lights s1 and s2, and the idler lights i1 and i2 can be arbitrarily changed according to the spectroscopic device to which the present invention is applied.

[0264] In each of the above-mentioned embodiments and modifications, the structure of each quantum optical system 4, 104, 204, 304, 404 can be replaced with another structure equivalent in classical optics or another structure equivalent in quantum optics.

[0265] Unless otherwise specified, the horizontal and vertical directions, various numerical values, shapes, and materials in the above-mentioned embodiments and various modifications include ranges (all equal ranges) that have the same effects as those directions, numerical values, shapes, and materials.

[0266] [Way]

[0267] It will be understood by those skilled in the art that the above-described exemplary embodiments and various modifications are specific examples of the following aspects.

[0268] (Item 1) A spectroscopic device according to one embodiment comprises: a light source that emits pump light; a quantum optical system having one or more nonlinear optical elements and a sample configuration device, wherein the pump light is incident on the nonlinear optical element, the nonlinear optical element generates photon pairs of idler light and signal light from the pump light through an entangled photon pair generation process, and the sample configuration device is used to configure the sample on the optical path of the idler light; a detection unit that detects the light intensity of light output from the quantum optical system; and an analysis device that obtains an interference pattern based on the light intensity, wherein the quantum optical system is configured to emit a first signal light and a second signal light with different optical paths, the detection unit has a beam splitter that receives the first signal light and the second signal light from the quantum optical system, the detection unit detects the light intensity of each of the two light beams emitted from the beam splitter, and the analysis device obtains the interference pattern based on the two light beams detected by the detection unit.

[0269] According to the spectroscopic device described in the first item, an interference pattern is obtained in which the influence of noise light is eliminated.

[0270] (Item 2) In the spectroscopic device described in Item 1, the number of the nonlinear optical element may be one, and the quantum optical system may emit the first signal light and the second signal light along an optical path of the pump light that reciprocates in the one nonlinear optical element.

[0271] According to the spectroscopic device described in the second item, the quantum optical system is constructed using one nonlinear optical element, so the structure is simple.

[0272] (Item 3) In the spectroscopic device described in Item 1, the nonlinear optical element may include a first nonlinear optical element and a second nonlinear optical element, and the quantum optical system causes the first signal light to be emitted along the optical path of the pump light incident on the first nonlinear optical element, and causes the second signal light to be emitted along the optical path of the pump light incident on the second nonlinear optical element.

[0273] According to the spectroscopic device described in the third aspect, since it is not necessary to return the pump light to the same nonlinear optical element, the degree of freedom in the layout of the quantum optical system is improved.

[0274] (Item 4) In the spectroscopic device described in Item 3, a pump light branching element may be provided in the front stage of the nonlinear optical element, so that one side of the pump light branched by the pump light branching element is incident on the first nonlinear optical element, and the other side of the pump light is incident on the second nonlinear optical element.

[0275] According to the spectroscopic device described in the fourth aspect, the degree of freedom in the layout of the quantum optical system is improved.

[0276] (Item 5) In the spectroscopic device described in any one of Items 1 to 4, it may further include an optical path length variable mechanism that changes the optical path length of the signal light.

[0277] According to the spectroscopic device described in the fifth item, the interference pattern can be acquired based on the two beams of light during a period in which the optical path length of the signal light is changed.

[0278] (Item 6) In the spectroscopic device described in any one of Items 1 to 4, it may further include an optical path length variable mechanism that changes the optical path length of the idler light.

[0279] According to the spectroscopic device described in item 6, the interference pattern can be acquired based on the two lights detected by the detection unit while the optical path length of the idler light is changed.

[0280] (Item 7) In the spectroscopic device described in Item 5 or Item 6, the optical path length variable mechanism may include a movable mirror, and the analyzing device may obtain the interference pattern based on the two beams of light detected by the detecting unit while the movable mirror is moved at a constant speed.

[0281] According to the spectroscopic device described in item 7, the interference pattern can be acquired based on the two lights detected by the detection unit while the movable mirror is moved at a constant speed.

[0282] (Item 8) In the spectroscopic device described in any one of Items 1 to 7, the analyzing device may acquire the interference pattern based on the difference in light intensity of the two light beams detected by the detecting unit.

[0283] According to the spectroscopic device described in the eighth aspect, the interference pattern can be acquired easily and with high accuracy.

[0284] (Item 9) In the spectroscopic device described in any one of Items 1 to 7, the analyzing device may obtain the interference pattern based on a difference between values ​​obtained by multiplying the light intensity of at least one of the two light beams detected by the detecting unit by a constant.

[0285] According to the spectroscopic device described in item 9, the interference pattern can be acquired easily and with high accuracy.

[0286] Description of Reference Numerals

[0287] 1, 100, 200, 300, 400, 500, 600: infrared spectrometer (spectrometer); 2, 2R: light source; 4, 4R, 104, 204, 304, 404, 504, 604: quantum optical system; 6, 6R: detection unit; 8, 8R: analysis device; 12: nonlinear crystal (nonlinear optical element); 12A: first nonlinear crystal (first nonlinear optical element); 12B: second nonlinear crystal (second nonlinear optical element); 14, 14R: fixed mirror; 3 2: second dichroic mirror; 34, 34R: movable mirror; 35: sample configuration device; 40, 240: beam splitter; 40A1, 40A2: incident port; 40B1, 40B2: emission port; 41: first detector; 42: second detector; 62: interference pattern acquisition unit; 210: beam splitter for pump light branching (pump light branching component); Ps, P1s, P2s: light intensity; SP: sample; i, i1, i2: idle light; p, p1, p2: pump light; S, s1, s2: signal light.

Claims

1. A spectroscopic device, comprising: a light source that emits pump light; A quantum optical system having one or more nonlinear optical elements and a sample arrangement device, wherein the pump light is incident on the nonlinear optical element, the nonlinear optical element generates a photon pair of idler light and signal light from the pump light through an entangled photon pair generation process, and the sample arrangement device is used to arrange the sample on the optical path of the idler light; a detection unit that detects the light intensity of light output from the quantum optical system; as well as an analysis device for acquiring an interference pattern based on the light intensity, The quantum optical system is configured to emit the first signal light and the second signal light at different optical paths. The detection unit includes a beam splitter that receives the first signal light and the second signal light from the quantum optical system, and the detection unit detects the light intensity of each of the two beams emitted from the beam splitter. The analyzing device acquires the interference pattern based on the two beams of light detected by the detecting unit.

2. The spectroscopic device according to claim 1, wherein: The nonlinear optical element is one, The quantum optical system emits the first signal light and the second signal light through the optical path of the pump light that reciprocates in a nonlinear optical element.

3. The spectroscopic device according to claim 1, wherein: The nonlinear optical element comprises a first nonlinear optical element and a second nonlinear optical element. The quantum optical system emits the first signal light along an optical path of the pump light incident on the first nonlinear optical element, and emits the second signal light along an optical path of the pump light incident on the second nonlinear optical element.

4. The spectroscopic device according to claim 3, wherein: A pump light branching element is provided at a front stage of the nonlinear optical element. One of the pump lights branched by the pump light branching element is incident on the first nonlinear optical element, and the other of the pump lights is incident on the second nonlinear optical element.

5. The spectroscopic device according to claim 1, wherein: The optical path length variable mechanism is further provided, and the optical path length variable mechanism changes the optical path length of the signal light.

6. The spectroscopic device according to claim 1, wherein: The optical path length variable mechanism is further provided, and the optical path length variable mechanism changes the optical path length of the idler light.

7. The spectroscopic device according to claim 5 or 6, wherein: The optical path length variable mechanism includes a movable mirror, The analyzing device acquires the interference pattern based on the two lights detected by the detecting unit while the movable mirror is moved at a constant speed.

8. The spectroscopic device according to claim 1, wherein: The analyzing device acquires the interference pattern based on the difference in light intensity of the two light beams detected by the detecting unit.

9. The spectroscopic device according to claim 1, wherein: The analyzing device acquires the interference pattern based on a difference between values ​​obtained by multiplying a constant by the light intensity of at least one of the two lights detected by the detecting unit.

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