CN112595416A - Broadband infrared spectrometer - Google Patents
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- 238000006243 chemical reaction Methods 0.000 claims abstract description 79
- 230000003287 optical effect Effects 0.000 claims abstract description 76
- 239000013078 crystal Substances 0.000 claims abstract description 71
- 230000008859 change Effects 0.000 claims abstract description 37
- 238000001514 detection method Methods 0.000 claims abstract description 21
- 238000012545 processing Methods 0.000 claims abstract description 18
- 238000001228 spectrum Methods 0.000 claims abstract description 12
- 230000008878 coupling Effects 0.000 claims abstract description 11
- 238000010168 coupling process Methods 0.000 claims abstract description 11
- 238000005859 coupling reaction Methods 0.000 claims abstract description 11
- 230000001678 irradiating effect Effects 0.000 claims abstract description 9
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- 230000010287 polarization Effects 0.000 claims description 38
- 230000000737 periodic effect Effects 0.000 claims description 21
- 229910052710 silicon Inorganic materials 0.000 claims description 15
- 239000010703 silicon Substances 0.000 claims description 15
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 14
- 238000006073 displacement reaction Methods 0.000 claims description 10
- 238000005086 pumping Methods 0.000 claims description 7
- 238000001914 filtration Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 claims description 2
- 230000003595 spectral effect Effects 0.000 claims description 2
- 230000035945 sensitivity Effects 0.000 abstract description 6
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 12
- 238000010586 diagram Methods 0.000 description 8
- 238000005516 engineering process Methods 0.000 description 6
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000013307 optical fiber Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229910005540 GaP Inorganic materials 0.000 description 1
- 238000002835 absorbance Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000003745 diagnosis Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- HZXMRANICFIONG-UHFFFAOYSA-N gallium phosphide Chemical compound [Ga]#P HZXMRANICFIONG-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 238000002834 transmittance Methods 0.000 description 1
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
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- G01J3/28—Investigating the spectrum
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Abstract
The embodiment of the invention discloses a broadband infrared spectrometer, which comprises: the signal coupling unit is used for coupling the infrared light signal to be detected into the frequency up-conversion unit; the frequency up-conversion unit is used for combining the infrared light signal to be detected and the pump light and then irradiating the combined beam to a nonlinear crystal with a continuous change period for tunable frequency up-conversion to obtain an up-conversion light signal; the optical splitting and frequency selecting unit is used for determining the corresponding wavelength of the optical signals with different wavelengths contained in the up-conversion optical signals; the detection and data processing unit is used for detecting the signal intensity of each wavelength optical signal contained in the up-conversion optical signal and determining the spectrum of the up-conversion optical signal. The nonlinear of the nonlinear crystal with continuous change period is utilized to convert the incident infrared light signal into visible light or near infrared light, and the converted signal light is detected, so that tunable frequency conversion and spectrum acquisition of the broadband infrared light signal can be realized, and the method has the characteristics of large detection range, high sensitivity and the like.
Description
Technical Field
The invention relates to the technical field of infrared detection, in particular to a broadband infrared spectrometer.
Background
The infrared spectrometer is positioned on an optical signal of a research infrared band, and the middle infrared band corresponds to vibration energy level transition radiation of chemical molecules, so that the infrared spectrometer is widely applied to determining molecular structures of substances and identifying the types of compounds. The sample to be analyzed is irradiated with infrared light of a certain frequency, the absorption bands are recorded by an infrared spectrometer, and the type and structure of the compound can be deduced by the number, position and intensity of the absorption bands. To date, infrared spectrometers have been developed for three generations. The first generation is a prism-type dispersive infrared spectrometer, which uses a prism as a light splitting element, has low resolution and has strict requirements on the environment. In the 60 s, a grating type dispersion spectrometer appeared, and a grating engraving technology is adopted, so that the resolution is greatly improved, and the requirement on the environment is reduced. An interference infrared spectrometer developed in the 70 s belongs to a third-generation infrared spectrometer, and comprises a Fourier transform infrared spectrometer, wherein the Fourier transform infrared spectrometer irradiates a sample by using interference light, the interference light containing sample information reaches a detector, and then signals are processed through Fourier transform, and finally an infrared absorption spectrogram of transmittance or absorbance along with wave number or wavelength is obtained. The Fourier transform infrared spectrometer has wide measurement range, high measurement precision, high resolution and extremely fast measurement speed, thereby being widely applied. With the development of the technology, the sensitivity of the spectroscopic analysis technology is more required by the analysis and detection of trace substances and the research of biophotonic science.
In the existing frequency up-conversion technology based on a nonlinear medium, a uniform period polarization nonlinear crystal is adopted to convert the wavelength of a mid-infrared photon into a shorter visible light or short-wave near-infrared range, and then the photon after wavelength conversion is detected.
Disclosure of Invention
Because the existing method has the problems, the embodiment of the invention provides a broadband infrared spectrometer.
The embodiment of the invention provides a broadband infrared spectrometer, which comprises:
the signal coupling unit is used for coupling the infrared light signal to be detected into the frequency up-conversion unit;
the frequency up-conversion unit is used for combining the infrared light signal to be detected and the pump light beam and then irradiating the combined beam onto a nonlinear crystal with a continuous change period to perform tunable frequency up-conversion so as to obtain an up-conversion light signal, wherein the frequency of the up-conversion light signal is greater than that of the infrared light signal to be detected; combining the infrared light signal to be detected and the pump light and then irradiating the combined infrared light signal to the nonlinear crystal with the continuous change period for tunable frequency up-conversion, namely combining the infrared light signal to be detected and the pump light and then irradiating the combined infrared light signal to the nonlinear crystal with the continuous change period, wherein the combined infrared light signal is irradiated to the continuously moving nonlinear crystal with the continuous change period, so that the combined signal passes through different polarization periods of the nonlinear crystal with the continuous change period, and further all frequency components contained in the infrared light signal to be detected are sequentially subjected to frequency up-conversion;
the optical splitting and frequency selecting unit is used for determining optical signals with different wavelengths and corresponding wavelengths contained in the up-conversion optical signals;
and the detection and data processing unit is configured to detect the signal intensity of each wavelength optical signal included in the upconverted optical signal, and determine the spectrum of the upconverted optical signal according to the signal intensity of each wavelength optical signal included in the upconverted optical signal and the corresponding wavelength.
Further, the upconversion optical signal includes one or both of a visible light signal and a near-infrared light signal.
Further, the frequency up-conversion unit includes: the device comprises a pumping source laser, a polarizer, a near infrared band lens, a nonlinear crystal with a continuous change period, an electric displacement platform, a servo motor, a near infrared band lens and a filter plate;
the pump source laser is used for outputting pump light, the polarizer is used for adjusting the pump light into linear polarization, the pump light is focused by a near infrared band lens and then is combined with the infrared light signal to be detected, and the combined signal is incident on the nonlinear crystal with the continuous change period to perform frequency up-conversion so as to obtain an up-conversion light signal; the nonlinear crystal with the continuous change period is positioned on the electric displacement platform, and the electric displacement platform is driven by the servo motor to move so that the polarization period of the nonlinear crystal continuously changes along the horizontal direction vertical to the incident light beam;
the filter is located on one side, close to the up-conversion optical signal output direction, of the nonlinear crystal in the continuous change period and used for filtering pumping light and noise.
Further, the optical splitting and frequency selecting unit includes: the device comprises a reflector, a plane reflection grating, a grating rotation angle control device and a diaphragm; the up-conversion optical signal is reflected by the reflector and then enters the plane reflection grating, and the grating rotation angle control device controls the plane reflection grating to rotate by different angles, so that the up-conversion optical signal can enter the detection and data processing unit through the diaphragm after being reflected by the plane reflection grating; the corresponding relation between the rotation angle of the plane reflection grating and the wavelength of the up-conversion optical signal is calibrated in advance, and the rotation angle of the plane reflection grating when the detection and data processing unit detects the optical signal in the whole rotation process determines the intensity and the corresponding wavelength of the optical signal with different wavelengths contained in the up-conversion optical signal.
Further, the detection and data processing unit comprises: the system comprises a silicon single photon detector, a data acquisition card and a processing unit;
the silicon single photon detector is used for detecting the intensities of optical signals with different wavelengths contained in the up-conversion optical signals; the silicon single-photon detector is connected with the data acquisition card, and the optical signal intensities of different wavelengths contained in the up-conversion optical signal detected by the silicon single-photon detector are sent to the processing unit through the data acquisition card;
the processing unit is configured to determine a spectrum of the upconverted optical signal according to the signal intensity of each wavelength optical signal included in the upconverted optical signal and the corresponding wavelength.
Further, the signal coupling unit includes: an achromatic lens and a dichroic mirror in a middle infrared band;
and the infrared light signal to be detected is focused by the mid-infrared band achromatic lens and is incident into the nonlinear crystal with a continuous change period through the dichroic mirror.
Furthermore, the front end face of the nonlinear crystal with the continuous change period is plated with antireflection films in a middle infrared band and a near infrared band, and the rear end face of the nonlinear crystal with the continuous change period is plated with an antireflection film in a near infrared band.
Further, the frequency up-conversion unit further includes: an achromatic lens in the near infrared band or the visible band;
the near infrared band or visible light band achromatic lens is located in front of the filter, and the up-conversion light passes through the filter after being changed into parallel light through the near infrared band or visible light band achromatic lens.
Further, the filter is a band-pass filter.
Further, the pump source laser outputs narrow linewidth near infrared light.
According to the technical scheme, the broadband infrared spectrometer provided by the embodiment of the invention enables the infrared signal to be detected and the pump light to be combined and then to be incident on the continuously moving nonlinear crystal with the continuous change period, so that the combined signal passes through different polarization periods of the continuously changing nonlinear crystal, and further all frequency components contained in the infrared signal to be detected are sequentially subjected to frequency up-conversion. The broadband infrared spectrometer provided by the embodiment of the invention converts an incident mid-infrared light signal into a visible light or near-infrared band by utilizing the nonlinear crystal with a continuous change period, detects the converted light signal, can realize frequency conversion and spectrum acquisition of broadband signal light, and has the characteristics of large detection range, high sensitivity and short response time.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a block diagram of a broadband infrared spectrometer according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a broadband infrared spectrometer according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a lithium niobate crystal structure with sector-shaped periodic polarization characteristics according to an embodiment of the present invention;
fig. 4 is a corresponding relationship between the wavelength of the infrared light signal to be detected and the polarization period of the lithium niobate crystal with the sector period polarization characteristic according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a block diagram illustrating a structure of a broadband infrared spectrometer according to an embodiment of the present invention, and fig. 2 is a schematic structural diagram of a broadband infrared spectrometer according to an embodiment of the present invention, where the reference numerals in the diagram indicate: 1-intermediate infrared objective lens, 2-intermediate infrared multimode fiber, 3-collimator, 4-intermediate infrared band achromatic lens, 5-dichroic mirror, 6-ytterbium-doped fiber laser, 7-polarizer, 8-near infrared band lens, 9-fan-shaped lithium niobate crystal with periodic polarization characteristic, 10-electric displacement platform and driver, 11-near infrared band achromatic lens, 12-filter set, 13-diffraction grating, 14-piezoelectric ceramic and driver, 15-diaphragm, 16-silicon single photon detector, 17-data acquisition card and 18-computer. FIG. 3 is a schematic diagram of a lithium niobate crystal structure with sector-shaped periodic polarization characteristics according to an embodiment of the present invention; fig. 4 is a corresponding relationship between the wavelength of the infrared light signal to be detected and the polarization period of the lithium niobate crystal with the sector period polarization characteristic according to an embodiment of the present invention. The broadband infrared spectrometer provided by the embodiment of the invention is explained and explained in detail with reference to fig. 1, fig. 2, fig. 3 and fig. 4.
As shown in fig. 1, an embodiment of the present invention provides a broadband infrared spectrometer, including:
the signal coupling unit 1 is used for coupling an infrared light signal to be detected into the frequency up-conversion unit;
the frequency up-conversion unit 2 is configured to combine the infrared light signal to be detected with the pump light, and then irradiate the combined beam onto a nonlinear crystal with a continuous change period to perform tunable frequency up-conversion, so as to obtain an up-converted optical signal, where the frequency of the up-converted optical signal is greater than the frequency of the infrared light signal to be detected; combining the infrared light signal to be detected and the pump light and then irradiating the combined infrared light signal to the nonlinear crystal with the continuous change period for tunable frequency up-conversion, namely combining the infrared light signal to be detected and the pump light and then irradiating the combined infrared light signal to the nonlinear crystal with the continuous change period, wherein the combined infrared light signal is irradiated to the continuously moving nonlinear crystal with the continuous change period, so that the combined signal passes through different polarization periods of the nonlinear crystal with the continuous change period, and further all frequency components contained in the infrared light signal to be detected are sequentially subjected to frequency up-conversion;
a light splitting and frequency selecting unit 3, configured to determine optical signals with different wavelengths and corresponding wavelengths included in the upconverted optical signal;
and the detection and data processing unit 4 is configured to detect the signal intensity of each wavelength optical signal included in the upconverted optical signal, and determine the spectrum of the upconverted optical signal according to the signal intensity of each wavelength optical signal included in the upconverted optical signal and the corresponding wavelength.
In this embodiment, the signal coupling unit 1 includes a mid-infrared achromatic objective lens, a mid-infrared multimode optical fiber, a collimator, a mid-infrared achromatic lens, and a dichroic mirror. The infrared light signal to be detected is a weak signal transmitted in a space with the wavelength of 3-5 microns, is coupled to the intermediate infrared multimode optical fiber through the intermediate infrared achromatic objective lens, and is collimated by the collimator to emit spatial parallel light, the parallel light is focused by the intermediate infrared waveband achromatic lens with the focal length of 100mm, and is incident into the nonlinear crystal with the continuous change period through the dichroic mirror, wherein the intermediate infrared waveband signal is transmitted by the dichroic mirror, and the near infrared light is reflected.
In this embodiment, the frequency up-conversion unit 2 includes a pumping source laser, a polarizer, a near-infrared band lens, a continuously variable periodic nonlinear crystal, an electric displacement platform and driver, a near-infrared band achromatic lens, and a filter set, where the pumping source laser is an ytterbium-doped fiber laser, and outputs narrow-linewidth near-infrared light, i.e., pumping light, with a central wavelength of 1064nm and an average output power greater than 10W. The pump light is changed into vertically polarized linear polarization light through the polarizer, is focused through a near infrared band lens with the focal length of 100mm, is reflected by the dichroic mirror and then is focused into the nonlinear crystal with a continuous change period, and the pump light and the focus of the intermediate infrared signal light coincide inside the crystal.
In this embodiment, it should be noted that the continuously periodic nonlinear crystal includes, but is not limited to, a periodically polarized lithium niobate crystal having a fan-shaped grating structure, an oriented patterned gallium phosphide crystal having a fan-shaped grating structure, and the like, and the description is given in the embodiment of the present invention as a lithium niobate crystal having a fan-shaped periodic polarization characteristic. After being combined by a dichroic mirror, an infrared light signal to be detected and pump light are incident on a lithium niobate crystal with a sector periodic polarization characteristic for tunable frequency up-conversion, and the infrared light signal to be detected is subjected to phase matching in the lithium niobate crystal with the sector periodic polarization characteristic to obtain sum frequency light, namely up-conversion light, of which the frequency is greater than that of the infrared light signal to be detected, so that the mid-infrared light is converted into visible light or near-infrared light. Note that the polarization period of the lithium niobate crystal having the sector period polarization characteristic continuously changes in the horizontal direction perpendicular to the incident light, and the schematic structural diagram thereof is shown in fig. 3. The lithium niobate crystal with the sector periodic polarization characteristic is positioned on an electric displacement platform, and the electric displacement platform is driven by a servo motor to move along the horizontal direction vertical to incident light, so that the incident signal light to be detected and the pump light pass through different polarization periods of the lithium niobate crystal with the sector periodic polarization characteristic, and further all frequency components contained in the infrared light signal to be detected are sequentially subjected to frequency up-conversion. The front end face of the crystal is plated with an antireflection film with a middle infrared wave band and 1064nm, and the rear end face is plated with an antireflection film with a near infrared wave band.
In this embodiment, it should be noted that, the frequency up-conversion of the infrared light signal to be detected in the nonlinear crystal with periodic polarization characteristic needs to satisfy the corresponding phase matching condition, where the phase matching condition is as follows:
Δk＝k2-k1-kp-kΛ，
where Δ k is the amount of phase mismatch, k1For the infrared light signal to be detected, k2For the converted up-converted optical signal, kpFor pump light, kΛIs the wavevector of a nonlinear crystal with periodic polarization characteristics.
When Δ k is equal to 0, the infrared signal to be detected and the pump light perform optical frequency conversion in the nonlinear crystal with periodic polarization characteristic, and at this time, the relationship between the wavelength of the infrared signal to be detected and the polarization period of the nonlinear crystal with periodic polarization characteristic is as follows:
wherein λ is1For the wavelength, lambda, of the infrared light signal to be detected2For up-conversion of the wavelength, λ, of the optical signalpIs the wavelength of the pump light, n1Refractive index of wavelength of infrared light signal to be detected in nonlinear crystal with periodic polarization characteristic, n2Refractive index n in nonlinear crystal with periodic polarization characteristic for up-conversion of optical signal wavelengthpLambda is the polarization period of the nonlinear crystal with periodic polarization characteristic.
In this embodiment, the up-converted light is emitted from the nonlinear crystal, then enters the near-infrared achromatic lens with a focal length of 100mm, becomes parallel light, and then passes through the filter, wherein the filter consists of a 780-.
In this embodiment, the wavelength of the upconversion light signal is determined by the spectrum-dividing and frequency-selecting unit, specifically, the upconversion light is reflected by the reflector and then enters the plane reflection grating, the reflection wavelength range of the plane reflection grating is 700nm to 900nm, and the grating rotation angle control device, such as a computer, drives the piezoelectric ceramic to control the plane reflection grating to rotate at different angles, so that the upconversion light can be detected by the silicon single photon detector through the diaphragm after being reflected by the plane reflection grating. The corresponding relation between the rotation angle of the plane reflection grating and the wavelength of the up-conversion light which can pass through the diaphragm is calibrated in advance, different angles of the plane reflection grating correspond to different wavelengths of the up-conversion light, and the up-conversion light wavelength can be determined through the angle of the plane reflection grating.
In this embodiment, the upconversion optical signal that passes through the diaphragm after being reflected by the planar reflection grating with different angles is detected by the silicon single photon detector, and the signal intensity of each wavelength optical signal and the wavelength of each wavelength optical signal contained in the infrared optical signal to be detected are determined according to the wavelength determined by the angle of the planar reflection grating, the silicon single photon detector is connected with the data acquisition card, the optical signal intensity of different wavelengths contained in the upconversion optical signal detected by the silicon single photon detector is sent to the processing unit through the data acquisition card, and the processing unit can directly determine the spectrum of the upconversion optical signal, and can also determine the spectrum of the upconversion optical signal according to the relationship between the upconversion optical signal and the infrared optical signal to be detected.
The method has the advantages that high signal light conversion efficiency can be realized under the condition that frequency up-conversion is carried out on an infrared light signal to be detected in a nonlinear crystal with periodic polarization characteristics to meet phase matching conditions, for the existing general uniform periodic polarization nonlinear crystal, when the wavelength of pump light is fixed, the wavelength of the signal light capable of being converted is correspondingly fixed, the conversion efficiency of the signal light with other wavelengths is extremely low or cannot be converted, so tunable signal light conversion and detection cannot be realized, the existing infrared spectrometer based on the uniform periodic polarization nonlinear crystal can only convert one signal light wavelength, tunable signal light conversion cannot be realized, the detection range is small, and the sensitivity is low. The frequency up-conversion technology of the nonlinear crystal based on the continuous change period, which is provided by the embodiment of the invention, can be used for converting the wavelength of the mid-infrared photon into the near-infrared or visible light range in a tunable manner, so that the spectrum detection is realized.
In this embodiment, it should be noted that the frequency up-conversion technology based on the nonlinear crystal with the continuous change period, which is provided by the embodiment of the present invention, has the highest conversion efficiency of approximately 100% under ideal conditions, and in combination with the high detection efficiency of the silicon single photon detector in the visible light and short-wave near-infrared bands, the spectrometer can achieve the ultra-sensitive spectral resolution of single photon horizontal signals, has a large detection coverage bandwidth, has higher sensitivity compared with the current fourier transform infrared spectrometer, and can achieve the highest single photon level detection.
In this embodiment, it should be noted that both the frequency up-conversion unit and the silicon single photon detector do not need to be refrigerated, and the spectrometer operates in a normal temperature environment, so that compared with a spectrometer using an intermediate infrared detector, the system is greatly simplified, the size is reduced, the stability of the system is improved, and the application in a complex environment is expanded.
According to the technical scheme, the broadband infrared spectrometer provided by the embodiment of the invention enables the infrared signal to be detected and the pump light to be combined and then to be incident on the continuously moving nonlinear crystal with the continuous change period, so that the combined signal passes through different polarization periods of the continuously changing nonlinear crystal, and further all frequency components contained in the infrared signal to be detected are sequentially subjected to frequency up-conversion. The broadband infrared spectrometer provided by the embodiment of the invention converts an incident mid-infrared light signal into a visible light or near-infrared band by utilizing the nonlinear crystal with a continuous change period, detects the converted light signal, can realize frequency conversion and spectrum acquisition of broadband signal light, has the characteristics of large detection coverage wavelength range, high sensitivity and capability of working in a normal temperature environment, and has important application value in the aspects of trace chemical substance spectral analysis, molecular diagnosis, laser radar and the like.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A broadband infrared spectrometer, comprising:
the signal coupling unit is used for coupling the infrared light signal to be detected into the frequency up-conversion unit;
the frequency up-conversion unit is used for combining the infrared light signal to be detected and the pump light beam and then irradiating the combined beam onto a nonlinear crystal with a continuous change period to perform tunable frequency up-conversion so as to obtain an up-conversion light signal, wherein the frequency of the up-conversion light signal is greater than that of the infrared light signal to be detected; combining the infrared light signal to be detected and the pump light and then irradiating the combined infrared light signal to the nonlinear crystal with the continuous change period for tunable frequency up-conversion, namely combining the infrared light signal to be detected and the pump light and then irradiating the combined infrared light signal to the nonlinear crystal with the continuous change period, wherein the combined infrared light signal is irradiated to the continuously moving nonlinear crystal with the continuous change period, so that the combined signal passes through different polarization periods of the nonlinear crystal with the continuous change period, and further all frequency components contained in the infrared light signal to be detected are sequentially subjected to frequency up-conversion;
the optical splitting and frequency selecting unit is used for determining optical signals with different wavelengths and corresponding wavelengths contained in the up-conversion optical signals;
and the detection and data processing unit is configured to detect the signal intensity of each wavelength optical signal included in the upconverted optical signal, and determine the spectrum of the upconverted optical signal according to the signal intensity of each wavelength optical signal included in the upconverted optical signal and the corresponding wavelength.
2. The broadband infrared spectrometer of claim 1, wherein the upconverted light signal comprises one or both of a visible light signal and a near infrared light signal.
3. The broadband infrared spectrometer of claim 1, wherein the frequency up-conversion unit comprises: the device comprises a pumping source laser, a polarizer, a near infrared band lens, a nonlinear crystal with a continuous change period, an electric displacement platform, a servo motor, a near infrared band lens and a filter plate;
the pump source laser is used for outputting pump light, the polarizer is used for adjusting the pump light into linear polarization, the pump light is focused by a near infrared band lens and then is combined with the infrared light signal to be detected, and the combined signal is incident on the nonlinear crystal with the continuous change period to perform frequency up-conversion so as to obtain an up-conversion light signal; the nonlinear crystal with the continuous change period is positioned on the electric displacement platform, and the electric displacement platform is driven by the servo motor to move so that the polarization period of the nonlinear crystal continuously changes along the horizontal direction vertical to the incident light beam;
the filter is located on one side, close to the up-conversion optical signal output direction, of the nonlinear crystal in the continuous change period and used for filtering pumping light and noise.
4. The broadband infrared spectrometer of claim 3, wherein the spectral frequency selection unit comprises: the device comprises a reflector, a plane reflection grating, a grating rotation angle control device and a diaphragm; the up-conversion optical signal is reflected by the reflector and then enters the plane reflection grating, and the grating rotation angle control device controls the plane reflection grating to rotate by different angles, so that the up-conversion optical signal can enter the detection and data processing unit through the diaphragm after being reflected by the plane reflection grating; the corresponding relation between the rotation angle of the plane reflection grating and the wavelength of the up-conversion optical signal is calibrated in advance, and the rotation angle of the plane reflection grating when the detection and data processing unit detects the optical signal in the whole rotation process determines the intensity and the corresponding wavelength of the optical signal with different wavelengths contained in the up-conversion optical signal.
5. The broadband infrared spectrometer of claim 1, wherein the detection and data processing unit comprises: the system comprises a silicon single photon detector, a data acquisition card and a processing unit;
the silicon single photon detector is used for detecting the intensities of optical signals with different wavelengths contained in the up-conversion optical signals; the silicon single-photon detector is connected with the data acquisition card, and the optical signal intensities of different wavelengths contained in the up-conversion optical signal detected by the silicon single-photon detector are sent to the processing unit through the data acquisition card;
the processing unit is configured to determine a spectrum of the upconverted optical signal according to the signal intensity of each wavelength optical signal included in the upconverted optical signal and the corresponding wavelength.
6. The broadband infrared spectrometer of claim 1, wherein the signal coupling unit comprises: a mid-infrared achromatic lens and a dichroic mirror;
and the infrared light signal to be detected is focused by the intermediate infrared achromatic lens and is incident into the nonlinear crystal with the continuous change period through the dichroic mirror.
7. The broadband infrared spectrometer of claim 1, wherein the front facet of the continuously variable periodic nonlinear crystal is coated with an anti-reflection film in the mid-infrared band and near-infrared band, and the back facet is coated with an anti-reflection film in the near-infrared or visible band.
8. The broadband infrared spectrometer of claim 3, wherein the frequency up-conversion unit further comprises: an achromatic lens in the near infrared band or the visible band;
the near infrared band or visible light band achromatic lens is located in front of the filter, and the up-conversion light passes through the filter after being changed into parallel light through the near infrared band or visible light band achromatic lens.
9. The broadband infrared spectrometer of claim 3, wherein the filter is a band pass filter.
10. The broadband infrared spectrometer of claim 3, wherein the pump source laser outputs narrow linewidth near infrared light.
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|---|---|---|---|---|
| WO2023112909A1 (en) * | 2021-12-13 | 2023-06-22 | 国立大学法人東京大学 | Time-stretch optical measurement instrument and time-stretch spectroscopy |
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