A kind of shift frequency based on tunable laser excites the signal strength detection device and method of Raman spectrum
Technical field
The present invention relates to the signal strength detection technical field of Raman spectrum.
Background technology
Raman spectrum be a kind of detection speed fast, without the need to pre-service, to measured matter not damaged and can the detection technique of the intactly significant advantage such as reaction molecular internal structural information, be widely used in the fields such as food security, chemical analysis and material analysis.But can along with the generation of fluorescence signal in most of Raman detection process, hypofluorescence signal meeting severe jamming is to the identification of weak Raman signal, hyperfluorescenceZeng Yongminggaoyingguang signal even can flood Raman signal, so remove fluorescence interference effectively can improve detection efficiency in Raman detection process.
The method of the effective Fluorophotometry be widely adopted at present mainly contains fluorescence quenching method, time resolution method, numerical value facture and shift frequency excitation method.Fluorescence quenching method reduces fluorescent yield by adding specific fluorescent quencher or increase time shutter of sample in testing sample, and the method can only for minority specific sample and the extra condition that measuring process is introduced brings very large uncertainty to measurement result.Time resolution method make use of the characteristic that the Raman light life-span is far smaller than fluorescence lifetime, by adopting ultrashort pulse light or high frequency modulated light source the two to be separated in time domain, but significantly improve cost based on the Raman system that the method builds because needs adopt high-speed response device.Numerical value facture utilizes the different spectral characteristic of Raman signal and fluorescence signal, extracts faint Raman signal by the mode such as Fourier transform and curve from fluorescence background, but the method is comparatively large by the impact of software algorithm, and measurement result consistance is poor.
Shift frequency excitation method is based on fluorescence and the incoherent characteristic of excitation wavelength, under identical collection condition, when having the laser excitation sample of minute differences with two bundle wavelength, in two spectrum of acquisition, fluorescence signal changes hardly, and all Raman signals all can produce minor shifts.Namely the signal subtraction of twice collection can be obtained the difference raman spectral signal removing fluorescence interference, be finally inversed by original raman spectral signal again, and then the analysis realized testing sample, the process computation amount of the original raman spectral signal of inverting is large, and can introduce error.The key that shift frequency excitation method can realize to guarantee to have at least two stable, to have different wave length exciting lights.In existing technology, the laser instrument that employing two different wave lengths export mostly, the wavelength of laser instrument needs to do high-precision Current Control and temperature controls to guarantee the stability that optical maser wavelength exports, and uses branched laser instrument to be unfavorable for the system integration, and adds cost.The another kind of technology widely adopted is the laser instrument adopting single Wavelength tunable, by regulating the working temperature of laser, electric current or being realized the change of excitation wavelength by external cavity feedback, the advantage of this technology only uses a lasing light emitter to reduce system bulk, reduce cost.But the wavelength shift that Current adjustment realizes can only reach 0.5nm usually, can not meet the detection with wide range material; Temperature adjusting wavelength speed is slow, and stable regulation 1nm required time is greater than 30s, causes whole system poor real; External cavity feedback regulates high for mechanical hook-up precision class requirement, and needs strict temperature to control to guarantee Wavelength stabilized output, substantially increases complexity and the cost of system.
The wavelength shift realized by Current adjustment in prior art can only reach 0.5nm usually, and the wavelength tuning range of present embodiment is greater than 10nm, can realize the detection of wide range material.
Summary of the invention
The present invention is to solve shift frequency excitation apparatus complex structure, poor real and wide range material cannot be detected, large according to the method calculated amount of the original raman spectral signal of difference raman spectral signal inverting, and the problem of error can be introduced, thus a kind of shift frequency based on tunable laser is provided to excite the signal strength detection device and method of Raman spectrum.
A kind of shift frequency based on tunable laser of the present invention excites the signal strength detection device of Raman spectrum, comprises current driver, semiconductor laser, grating, grid controller, catoptron, bandpass filter, the first convex lens, excitation fiber, the second convex lens, sampling receptacle, high-pass filter, coupled lens group, collects optical fiber, spectrometer and spectral analysis module;
The control signal output terminal of current driver connects the control signal input end of semiconductor laser, the collimated light beam that semiconductor laser sends is incident to grating, grating is fixed on grid controller, zero order beam after optical grating diffraction is incident to catoptron, light beam after catoptron reflection is incident to bandpass filter, the light beam of bandpass filter outgoing is incident to the first convex lens, first convex lens are by beams converge and be coupled into one end of excitation fiber, the second convex lens are incident to from the light beam of the other end outgoing of excitation fiber, second convex lens by beams converge to sampling receptacle, in sampling receptacle, the Raman diffused light of sample is incident to coupled lens group after high-pass filter, coupled lens group is by beams converge one end to collection optical fiber, the other end collecting optical fiber connects the optical interface of spectrometer, the signal output part of spectrometer connects the signal input part of spectral analysis module.
The luminous power of above-mentioned zero order beam after optical grating diffraction is greater than 100mW, and live width is less than 0.5nm, and wavelength tuning range is greater than 10nm.
The distance range of above-mentioned first convex lens and excitation fiber is (f
1-5mm) ~ (f
1+ 5mm), f
1it is the focal length of the first convex lens.
The scope that the light beam that above-mentioned semiconductor laser sends is incident to the incidence angle θ of grating is: 10 ° of < θ <80 °, and the space structure cycle d of the output wavelength λ of θ and semiconductor laser and grating meets relational expression: λ=2dsin θ.
Above-mentioned grating pendulum inclination angle variable quantity
wherein △ λ is test substance Raman spectrum live width.
The scope of the luminous power of above-mentioned zero order beam after optical grating diffraction is 100mW ~ 300mW.
Based on the detection method of above-mentioned detection device, comprise signal intensity gatherer process and the analytic process of Raman spectrum:
The signal intensity gatherer process of Raman spectrum comprises the following steps:
Testing sample one by one, is placed in sampling receptacle by step, firing current driver, and wavelength is λ
1laser be radiated on sample;
Step one two, spectrometer collection initial spectrum is also delivered to spectral analysis module, and spectral analysis module does initial analysis to the spectrum received, and judges time degree of stability and the fluorescence background level of spectrum;
Step one three, according to the spectral temporal degree of stability in step one two and fluorescence background level, judge that whether laser power is suitable and namely neither destroy sample molecule structure, the fluorescence excited can not cause again the photo detecting unit of spectrometer saturated, if judged result is yes, then perform step one four, if judged result is no, distance between the incident end face then adjusting the first convex lens and excitation fiber, and return step one two;
Step one four, spectral analysis module acquisition and recording excitation wavelength is λ
1time spectral signal intensity R
1;
The step First Five-Year Plan, by the deflection angle of grating feedback controller adjustment grating, excitation wavelength is made to be λ
2, spectral analysis module acquisition and recording excitation wavelength is λ
2time spectral signal intensity R
2;
The signal strength analysis process of Raman spectrum comprises the following steps:
Step 2 one, by the spectral signal intensity R under two of spectral analysis module acquisition and recording different excitation wavelengths
1and R
2do difference, obtain initial differential raman spectral signal intensity D
0, D
0=R
2-R
1;
Step 2 two, obtains initial differential raman spectral signal intensity D
0the center wave number of the differential signal that middle intensity is maximum
respectively to spectral signal intensity R
1and R
2?
wave-number range in do integration, obtain respectively and characterize the value I of excitation light power
1and I
2;
Step 2 three, to spectral signal intensity R
1and R
2carry out power normalization respectively, then the two is done difference and obtain normalized difference raman spectral signal intensity D, D=R
2/ I
2-R
1/ I
1;
Step 2 four,
evenly normalized difference raman spectral signal intensity is extracted in scope
amount to N number of data point,
for test substance Raman spectrum live width, i=1 ~ N, N be greater than 1 integer;
Step 2 five is right
the N number of data point extracted in scope divides pointwise to take absolute value summation, acquisition raman spectral signal intensity level A,
A kind of shift frequency based on tunable laser of the present invention excites the signal strength detection device of Raman spectrum, utilizes single, without temperature control, without the need to precision optical machinery device and the laser instrument of tunable wave length realize pick-up unit and the method for the Raman signal intensity of hyperfluorescenceZeng Yongminggaoyingguang material in conjunction with spectral signal strength analysis method of the present invention.With a Wavelength tunable laser can make whole shift frequency activating system structure become more simplify and compact, be conducive to miniaturization and the portability of system.Make use of external-cavity semiconductor laser output wavelength and depend on grating feedback angle, to the insensitive physical characteristics of temperature change, and the spectral characteristic that difference spectrum signal amplitude and wavelength difference have nothing to do under excitation wavelength difference is greater than test substance Raman spectrum live width situation, in conjunction with spectroscopic analysis methods of the present invention, laser instrument is without the need to temperature control, real-time is good, the accuracy of measuring can be ensured, reduce system complexity, reduce system bulk and cost, improve level of integrated system and stability, laser output wavelength is regulated by changing grating feedback angle, wavelength tuning range is large, the detection of wide range material can be realized.The adjustment of excitation light power size is that the efficiency by controlling freely to be optically coupled to excitation fiber realizes, and change output power by changing laser Injection Current in nontraditional technology, the output spectrum characteristic not changing exciting light can be guaranteed like this, realize pure optical power adjustment.Device of the present invention and existing commercial miniature spectrometer have good compatibility, are easy to be employed to build novel Raman spectrum detection system.
A kind of shift frequency based on tunable laser of the present invention excites the signal strength detection method of Raman spectrum, to obtain initial differential raman spectral signal integration and normalization, obtain normalized difference raman spectral signal, the N number of data point of even extraction the summation that takes absolute value, obtain raman spectral signal intensity level, and then realize the analysis to testing sample.Need not the original raman spectral signal of inverting, just can realize the analysis to testing sample, calculated amount is little, and result of calculation is accurate.
Accompanying drawing explanation
Fig. 1 is the structural representation that a kind of shift frequency based on tunable laser described in embodiment one excites the signal strength detection device of Raman spectrum.
Fig. 2 is the former medicine of industry of germifuge tricyclazole in embodiment seven excites lower acquisition normalized Raman spectrogram at two kinds of different wave lengths.
Fig. 3 is the normalized difference Raman spectrogram of the former medicine of industry of germifuge tricyclazole in embodiment seven.
Embodiment
Embodiment one: composition graphs 1 illustrates present embodiment, a kind of shift frequency based on tunable laser described in present embodiment excites the signal strength detection device of Raman spectrum, comprises current driver 1, semiconductor laser 2, grating 3, grid controller 4, catoptron 5, bandpass filter 6, first convex lens 7, excitation fiber 8, second convex lens 9, sampling receptacle 10, high-pass filter 11, coupled lens group 12, collects optical fiber 13, spectrometer 14 and spectral analysis module 15;
The control signal output terminal of current driver 1 connects the control signal input end of semiconductor laser 2, the collimated light beam that semiconductor laser 2 sends is incident to grating 3, grating 3 is fixed on grid controller 4, zero order beam after grating 3 diffraction is incident to catoptron 5, light beam after catoptron 5 reflects is incident to bandpass filter 6, the light beam of bandpass filter 6 outgoing is incident to the first convex lens 7, first convex lens 7 are by beams converge and be coupled into one end of excitation fiber 8, the second convex lens 9 are incident to from the light beam of the other end outgoing of excitation fiber 8, second convex lens 9 by beams converge to sampling receptacle 10, in sampling receptacle 10, the Raman diffused light of sample is incident to coupled lens group 12 after high-pass filter 11, coupled lens group 12 is by beams converge one end to collection optical fiber 13, the other end collecting optical fiber 13 connects the optical interface of spectrometer 14, the signal output part of spectrometer 14 connects the signal input part of spectral analysis module 15.
The control signal output terminal of current driver 1 connects the control signal input end of semiconductor laser 2, for semiconductor laser 2 provides current excitation, for the gain media in semiconductor laser 2 chip provides energy, makes its outgoing optimum output power.Be incident to grating 3 after the collimating mirror collimation that the laser that semiconductor laser 2 is launched is carried by it, grating 3 is arranged on grid controller 4.The beat of grating 3 and pitch attitude is controlled to ad-hoc location by grid controller 4, the first order light beam of grating 3 diffraction can be fed back to the resonator cavity of semiconductor laser 2, thus realize the effect of longitudinal mode selection and linewidth compression, the outgoing wavelength of semiconductor laser 2 is changed by the deflection angle changing grating 3.The relation met between the deflection angle θ of the grating 3 and space structure cycle d of semiconductor laser 2 output wavelength λ and grating 3 is determined by grating equation: λ=2dsin θ.Zero order beam after grating 3 diffraction is incident to catoptron 5, and catoptron 5 and grating are arranged on same base, can guarantee that the direction of propagation of laser beam does not change because of the adjustment of grating 3 deflection angle.Light beam after catoptron 5 reflects is incident to bandpass filter 6, bandpass filter 6 allows the light of about 10nm wavelength coverage near optical maser wavelength to pass through, the transmitance of its all band is less than per mille, effectively suppresses the spontaneous radiation fluorescence of semiconductor laser 2 to the interference of measuring.Light beam through bandpass filter 6 is incident to the first convex lens 7, the one end being coupled into excitation fiber 8 is converged through the first convex lens 7, after the outgoing of excitation fiber 8 other end, be incident to the second convex lens 9 again, the light beam after the second convex lens 9 converge is incident to sampling receptacle 10.Sampling receptacle can hold solid matter also can hold fluent meterial, can realize the detection of solid-liquid two kinds of form materials.In sampling receptacle 10, the Raman diffused light of sample is incident to coupled lens group 12 after high-pass filter 11, high-pass filter 11 is cut-off type optical filter, the transmitance being less than the light of excitation wavelength is less than per mille, and the spontaneous radiation fluorescence of semiconductor laser 2 and other bias lights can be suppressed further to the interference of measuring.Sample scattering light is incident to the one end of collecting optical fiber 13 after being converged by coupled lens group 12, the other end collecting optical fiber 13 is connected to the optical interface of spectrometer 14, and the signal output part of spectrometer 14 is connected to the signal input part of spectral analysis module 15.Spectrometer 14 is the common microgratings spectrometer in market.
Embodiment two: present embodiment excites the signal strength detection device of Raman spectrum to be described further to a kind of shift frequency based on tunable laser described in embodiment one, in present embodiment, the luminous power of the zero order beam after grating 3 diffraction is greater than 100mW, live width is less than 0.5nm, and wavelength tuning range is greater than 10nm.
Embodiment three: present embodiment excites the signal strength detection device of Raman spectrum to be described further to a kind of shift frequency based on tunable laser described in embodiment one, in present embodiment, the distance range of the first convex lens 7 and excitation fiber 8 is (f
1-5mm) ~ (f
1+ 5mm), f
1it is the focal length of the first convex lens 7.
The distance of the first convex lens 7 and excitation fiber 8 is at (f
1-5mm) ~ (f
1+ 5mm) in scope time light beam just can be coupled into excitation fiber 8, almost do not have light beam coupling to enter optical fiber when distance exceedes this scope.
Embodiment four: present embodiment excites the signal strength detection device of Raman spectrum to be described further to a kind of shift frequency based on tunable laser described in embodiment one, in present embodiment, the scope that the light beam that semiconductor laser 2 sends is incident to the incidence angle θ of grating 3 is: 10 ° of < θ <80 °, and the space structure cycle d of the output wavelength λ of θ and semiconductor laser 2 and grating 3 meets relational expression: λ=2dsin θ.
Embodiment five: present embodiment excites the signal strength detection device of Raman spectrum to be described further to a kind of shift frequency based on tunable laser described in embodiment one, and in present embodiment, grating 3 puts inclination angle variable quantity
wherein △ λ is test substance Raman spectrum live width.
Embodiment six: present embodiment excites the signal strength detection device of Raman spectrum to be described further to a kind of shift frequency based on tunable laser described in embodiment two, in present embodiment, the scope of the luminous power of the zero order beam after grating 3 diffraction is 100mW ~ 300mW.
Embodiment seven: composition graphs 2 and Fig. 3 illustrate present embodiment, present embodiment is the detection method exciting the signal strength detection device of Raman spectrum based on a kind of shift frequency based on tunable laser described in embodiment one, comprises signal intensity gatherer process and the analytic process of Raman spectrum:
The signal intensity gatherer process of Raman spectrum comprises the following steps:
Testing sample one by one, is placed in sampling receptacle 10, firing current driver 1 by step, and wavelength is λ
1laser be radiated on sample;
Step one two, spectrometer 14 gathers initial spectrum and is delivered to spectral analysis module 15, and spectral analysis module 15 does initial analysis to the spectrum received, and judges time degree of stability and the fluorescence background level of spectrum;
Step one three, according to the spectral temporal degree of stability in step one two and fluorescence background level, judge that whether laser power is suitable and namely neither destroy sample molecule structure, the fluorescence excited can not cause again the photo detecting unit of spectrometer 14 saturated, if judged result is yes, then perform step one four, if judged result is no, distance between the incident end face then adjusting the first convex lens 7 and excitation fiber 8, and return step one two;
Step one four, spectral analysis module 15 acquisition and recording excitation wavelength is λ
1time spectral signal intensity R
1;
The step First Five-Year Plan, adjusted the deflection angle of grating 3 by grating feedback controller 4, make excitation wavelength be λ
2, spectral analysis module 15 acquisition and recording excitation wavelength is λ
2time spectral signal intensity R
2;
The signal strength analysis process of Raman spectrum comprises the following steps:
Step 2 one, by the spectral signal intensity R under two different excitation wavelengths of spectral analysis module 15 acquisition and recording
1and R
2do difference, obtain initial differential raman spectral signal intensity D
0, D
0=R
2-R
1;
Step 2 two, obtains initial differential raman spectral signal intensity D
0the center wave number of the differential signal that middle intensity is maximum
respectively to spectral signal intensity R
1and R
2?
wave-number range in do integration, obtain respectively and characterize the value I of excitation light power
1and I
2;
Step 2 three, to spectral signal intensity R
1and R
2carry out power normalization respectively, then the two is done difference and obtain normalized difference raman spectral signal intensity D, D=R
2/ I
2-R
1/ I
1;
Step 2 four,
evenly normalized difference raman spectral signal intensity is extracted in scope
amount to N number of data point,
for test substance Raman spectrum live width, i=1 ~ N, N be greater than 1 integer;
Step 2 five is right
the N number of data point extracted in scope divides pointwise to take absolute value summation, acquisition raman spectral signal intensity level A,
Raman spectral signal intensity characterizes the concentration of testing sample, and raman spectral signal intensity can be used for implementing quantitative test to testing concentration.The Raman spectrum analysis method of spectral analysis module 15 is based on 2 points: 1) output wavelength of semiconductor laser 2 depends on the deflection angle of grating 3, and insensitive to temperature change; 2) under excitation wavelength difference is greater than test substance Raman spectrum live width situation, difference spectrum signal amplitude and wavelength difference have nothing to do.Therefore, as long as ensure that excitation wavelength difference is greater than test substance Raman spectrum live width, even if optical maser wavelength has floating of nm rank, under the guarantee of the novel Raman spectrum analysis method in spectral analysis module 15, noise spectra of semiconductor lasers 2 also controls without the need to implementing temperature.Fig. 2 is the former medicine of industry of germifuge tricyclazole excites lower acquisition normalized Raman spectrogram at two kinds of different wave lengths, visible under two kinds of wavelength normalized Raman spectrogram almost overlap, by poor for spectral signal intensity under two kinds of wavelength, obtain normalized difference Raman spectrogram, as shown in Figure 3.