CN106770130A - A kind of method for measuring two photon absorption cross section - Google Patents
A kind of method for measuring two photon absorption cross section Download PDFInfo
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- CN106770130A CN106770130A CN201710030738.6A CN201710030738A CN106770130A CN 106770130 A CN106770130 A CN 106770130A CN 201710030738 A CN201710030738 A CN 201710030738A CN 106770130 A CN106770130 A CN 106770130A
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- photon
- fluorescence
- absorption cross
- photon absorption
- photon fluorescence
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6402—Atomic fluorescence; Laser induced fluorescence
Abstract
The invention discloses a kind of method for measuring two photon absorption cross section.Femtosecond laser is introduced scanning microscopic system as light source by the present invention, femtosecond laser excites the two-photon fluorescence signal of detected materials after object lens are focused on, fluorescence signal and then received by sensitive photomultiplier is responded, be imaged on computers by after opto-electronic conversion, data sampling, treatment.The background of material two-photon fluorescence imaging is subtracted again, and the value of fluorescence intensity substitutes into formula and calculate the 2PA sections that can obtain detected materials as two-photon fluorescence intensity signal in then readable two-photon fluorescence imaging figure of drawing materials.2PA section gauges method proposed by the present invention is based on the two-photon fluorescence micro imaging system of stabilization, more traditional 2PA cross sectional testing methods, the error of measurement result is substantially reduced, and measuring method is more easy, reliable, the personnel for being adapted to non-optical specialty are operated.
Description
Technical field
It is a kind of method of new measurement two photon absorption cross section the invention belongs to field of optical detection.This measurement side
Method can be based on any two-photon fluorescence microscope, be measured by the intensity signal of two-photon fluorescence method acquisition fluorescent material
The two photon absorption cross section of material.
Background technology
Two-photon fluorescence (Two-Photon Fluorescence, 2PF) refers to that fluorescent material swashs in high peak power pulse
Two photon transitions of light source are absorbed under light stimulus simultaneously to excitation state, then relaxation returns to ground state and launches a mistake of photon
Journey.The two-photon of material is characterized usually using two-photon action section (Two-PhotonActionCross-Section, η δ)
Fluorescent emission efficiency, it represents that material absorbs incident photon and launches the ability of two-photon fluorescence, equal to the two-photon of material
Absorption cross-section (2PA, Two-PhotonAbsorption Cross-Section, δ) and fluorescence quantum yield (Fluorescence
Quantum Yield, η) product.Wherein, 2PA sections characterize the probability that material molecule occurs two-photon absorption, reflect material
Material carries out the ability of two-photon absorption.The method in measurement 2PA sections can substantially be divided into two major classes, and a class is from absorption cross-section
Definition is set out, and carries out direct measurement, such as nonlinear transmission method.When surveying 2PA sections in this way, incident optical power needs very
Greatly, and material requested concentration it is higher.Additionally, measure 2PA sections with the method to lack a reference to determine used by measurement
Whether incident optical power is in a rational scope with material concentration.Therefore the easy producing ratio of result that transmitance method is measured
Larger error.In addition, the measurement of transmitance method is higher to the power requirement of light source, common femtosecond OPO power is often inadequate,
Need using peak power femtosecond OPA higher as light source.
The method in another kind measurement 2PA sections is the effect from 2PA sections, is measured indirectly.As two-photon is glimmering
Light method surveys 2PA sections, its substantially thinking：
The relation of the two-photon fluorescence intensity F and 2PA section δ that material is produced is represented by：
F=δ NAcηLnI2K (1)
Wherein, NAIt is avogadros constant, c is the molar concentration of material, and η is the fluorescence quantum yield of material, and L is represented
The thang-kng length of material, I is the intensity of incident light, and K is relevant with the collection efficiency of an optical system constant.It is this
Method can be by measuring the two-photon fluorescence intensity of material so as to the anti-2PA sections for releasing it.Due to being difficult directly to try to achieve light
The collection efficiency of system, therefore generally measured using comparison method, that is, find one connects with testing sample two-photon fluorescence spectrum
Closely and reference material known to 2PA sections, their two-photon fluorescence is measured respectively under identical optical environment, then pass through
Extrapolate the 2PA sections of sample in the 2PA sections of reference material.Its computing formula：
Wherein subscript 1 and 0 distinguishes representative sample and reference material.Due to K be one with the thang-kng length of optical system with
The relevant constant of collection efficiency, therefore under identical optical measurement environment, K values are identicals, i.e. K1=K2.So, as long as
Under identical optical environment, both two-photon fluorescence intensity F are measured respectively1、F0, and know their molar concentration c1、
c0, fluorescence quantum yield η1、η0, the refractive index n of solution1、n0, and reference material 2PA sections δ0, it is possible to obtain sample
2PA sections δ1.Compared to nonlinear transmission method, the advantage of two-photon fluorescence method mainly has at 2 points.First, two-photon fluorescence intensity
With incident intensity into quadratic relationship, the shadow that other non-linear absorptions and linear absorption are brought can be reduced in experimentation
Ring.2nd, incident optical power used in fluorescence method measurement and material concentration are more much lower than transmitance method respectively, and this also greatly reduces
The contributions of other non-linear absorptions and linear absorption.Disturbed by reducing these, two-photon fluorescence method can generally compare non-thread
Property transmitance method measures more accurate 2PA sections.
2PA sections can use without ripe commercialization instrument, are typically necessary and oneself build light path and measure material
Fluorescence spectrum, and then wavelength integration is carried out to spectral intensity, and calculated with formula (2).However, being surveyed by spectrometer
Amount be fluorescent material transmitting the part that is scattered of fluorescence signal, and this part fluorescence is very weak, and is easily subject to environment
In other veiling glares influence, therefore measured signal has than larger error.In order to solve this problem, further improve
The precision of detection, the present invention devises a kind of method of new measurement two photon absorption cross section, i.e., directly aobvious with two-photon fluorescence
Micro mirror obtains the two-photon fluorescence light intensity signal of testing sample, and then is calculated its 2PA section with formula (2).
The content of the invention
The present invention is based on two-photon fluorescence microscope, it is proposed that a kind of brand-new two photon absorption cross section measuring method.This
Femtosecond laser is introduced scanning microscopic system as light source for invention, and femtosecond laser is by exciting the double of detected materials after object lens focusing
Photon fluorescence signal, fluorescence signal so that responded sensitive photomultiplier (Photonmultiplier Tube, referred to as
PMT) receive, be imaged on computers by after opto-electronic conversion, data sampling, treatment.Material two-photon fluorescence imaging is subtracted again
Background, the value of fluorescence intensity is used as two-photon fluorescence intensity signal, generation in then readable two-photon fluorescence imaging figure of drawing materials
Enter formula (2) and calculate the 2PA sections that can obtain detected materials.
The technical solution adopted by the present invention is：
2PA section gauges system is based on two-photon fluorescence micro imaging system, mainly including femtosecond laser light source, dichroic
Mirror, PMT, signal amplifier, computer etc..
Two-photon fluorescence micro imaging system can be directed to the characteristic of excited fluorescent material, select flying for suitable wavelength
Second LASER Light Source and suitable PMT receive fluorescence signal, and intensity signal is read by program, and substituting into computing formula (2) can
To calculate the 2PA sections of material.
Benefit of the invention：2PA section gauges method proposed by the present invention is based on the two-photon fluorescence micro-imaging of stabilization
System, more traditional 2PA cross sectional testing methods substantially reduce the error of measurement result, and measuring method it is more easy, can
Lean on, the personnel for being adapted to non-optical specialty (such as material, chemistry, biology) are operated.
Brief description of the drawings
Fig. 1 is the two-photon micro imaging system schematic diagram for measuring fluorescent material 2PA sections；
Fig. 2 is the two-photon fluorescence imaging figure of fluorescent material in the capillary measured with two-photon micro imaging system.
Specific embodiment
Below in conjunction with accompanying drawing, the invention will be further described.
As shown in figure 1, the measuring system in the present invention is based on two-photon fluorescence micro imaging system, mainly swash including femtosecond
Radiant, galvanometer scanning unit, dichroic mirror, PMT, signal amplifier, data collecting card, computer etc..Galvanometer scanning unit, two
Look mirror, PMT etc. are constituted scanning microscopic system and [are just being put scanning microscopy imaging system (Olympus, BX61+ with Olympus here
FV1200 as a example by)]
First, external femtosecond laser introduces Olympus and is just putting scanning microscopy imaging system (Olympus, BX61+
FV1200), expand into being formed with tube lens (tube lens) through scanning lens (scan lens) after galvanometer scanning unit
Light beam is again through the anti-short logical (cutoff wavelength of a block length：980nm) dichroscope reflection, is assembled by object lens and excites fluorescent material, is produced
Two-photon fluorescence signal, the fluorescence that material is inspired is returned along original optical path, by 980nm anti-short logical dichroscopes long, Yi Jixiang
Sensitive PMT is responded after the optical filter (further filtering out femtosecond exciting light) answered to receive；PMT converts analog signals into numeral
Signal, is also connected with reality by computer acquisition, the galvanometer scanning unit in system by after signal amplifier amplification with computer
The synchronization of existing signal scanning.By such set of system, the two-photon fluorescence micro-imaging figure (such as Fig. 2) of material can be obtained.
Fluorescence intensity F in Fig. 21Bias light first can be subtracted with program 1, then be calculated with MATLAB programs 2.Obtained with same method
To the two-photon fluorescence intensity F with reference to fluorescent dyes rhodamine Rh6G0.Afterwards by detected materials and the intensity signal of reference material
F1And F0Substituting into formula (2) can calculate the 2PA sections of material.
The photon that big mode field area (large-mode-area) mixes Yb (ytterbium-doped) is employed in this example
Crystal optical fibre (Photonic Crystal Fiber, PCF) laser (pulsewidth:140fs, repetition rate:50MHz, wavelength:
1040nm) as femtosecond light source.Dichroic mirror is off the length anti-short logical dichroscope, the filter after dichroic mirror that wavelength is 980nm
Mating plate is the pass filter long of 590nm；Object lens are 25 times of hydroscopes of Olympus, and operating distance is 2mm, and 400nm~
1600nm optical bands have good transmitance；PMT can respond the optical signal of 185-800nm wave bands.Selected two-photon
Fluorescent material selects semi-conducting polymer nano particle (Semiconducting Polymer Dots, P-dots), and it absorbs light
Spectrum is located at 350-450nm, and fluorescence peak is in 650nm or so.Rhodamine Rh6G is with reference to fluorescent material.
1. the program of background is subtracted
clear；
Const=1；
I0=imread (background is imaged .bmp')；
I1=imread (' Fig. 2 .bmp')；
J1=rgb2gray (I1)；
K=(J1-J0)*const；
Imwrite (K, ' Fig. 2 actual strength .bmp')；
2. the program of Fig. 2 fluorescence intensity information is read
clear；
I=imread (' Fig. 2 .bmp')；
J=rgb2gray (I)；
K=J (find (J>=0))；
s0=sum (sum (K))
To sum up, present invention sets forth a kind of method in novel measurement 2PA sections.Present invention selection Olympus is just put and is swept
Microscope (Olympus, BX61+FV1200) is retouched, external 1040nm femtosecond lasers is introduced as excitation source, excites P-dots to send out
Two-photon fluorescence signal (with rhodamine Rh6G as reference) is projected, two-photon fluorescence imaging figure has been obtained.Pass through MATLAB again
The formula (2) for calculating 2PA sections is substituted into after reading the fluorescence intensity of image, you can calculate the 2PA sections of detected materials.This
The method for applying mechanically two-photon fluorescence micro imaging system measurement fluorescent material 2PA sections, compared to traditional measuring method, collects
In hgher efficiency, more convenient operation, error is less, and stability is higher, more reliable performance.
Claims (6)
1. it is a kind of measure two photon absorption cross section method, the device for being used include femtosecond laser light source, galvanometer scanning unit,
Dichroic mirror, photomultiplier, signal amplifier and computer, it is characterised in that：
The laser that external femtosecond laser light source is sent with tube lens through scanning lens into forming after galvanometer scanning unit
Light beam is expanded, then is reflected through the anti-short logical dichroscope of a block length, assembled by object lens and excite fluorescent material, produce two-photon fluorescence letter
Number, the fluorescence that material is inspired is returned along original optical path, by anti-short logical dichroscope long, and for filtering femtosecond exciting light
Sensitive photomultiplier is responded after optical filter to receive；Photomultiplier converts analog signals into data signal, by letter
Number amplifier amplify after by computer acquisition；Described galvanometer scanning unit is connected to realize the same of signal scanning with computer
Step；
By said process, the two-photon fluorescence micro-imaging figure of material is obtained, then fluorescence intensity is obtained from the micro-imaging figureF 1 ；Then the two-photon fluorescence intensity with reference to fluorescent dyes rhodamine Rh6G is obtained in the same wayF 0 ；Thus it is calculated double
Photon absorption cross sections.
2. it is according to claim 1 it is a kind of measure two photon absorption cross section method, it is characterised in that：Two-photon fluorescence shows
Micro- image also needs to do the treatment of background subtraction light.
3. it is according to claim 1 it is a kind of measure two photon absorption cross section method, it is characterised in that：Long anti-short logical two to
The cutoff wavelength of Look mirror is 980nm.
4. it is according to claim 1 it is a kind of measure two photon absorption cross section method, it is characterised in that：Optical filter is
The pass filter long of 590nm.
5. it is according to claim 1 it is a kind of measure two photon absorption cross section method, it is characterised in that：Photomultiplier can
Respond the optical signal of 185-800 nm wave bands.
6. it is according to claim 1 it is a kind of measure two photon absorption cross section method, it is characterised in that：Object lens are Olympic bars
This 25 times of hydroscopes, operating distance is 2mm.
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| US20040061072A1 (en) * | 2002-09-30 | 2004-04-01 | Swinburne University Of Technology | Apparatus |
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| CN203164119U (en) * | 2012-11-14 | 2013-08-28 | 深圳大学 | Two-photon absorption section spectrometer |
| CN105004704A (en) * | 2015-07-09 | 2015-10-28 | 华南师范大学 | New use of neodymium ion sensitized up-conversion nanocrystal, and high-resolution multi-photon microscopic system |
| CN106066318A (en) * | 2016-06-14 | 2016-11-02 | 中国科学院长春光学精密机械与物理研究所 | A kind of method and device of on-line testing optical element laser damage |
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2017
- 2017-01-16 CN CN201710030738.6A patent/CN106770130A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040061072A1 (en) * | 2002-09-30 | 2004-04-01 | Swinburne University Of Technology | Apparatus |
| JP2008069294A (en) * | 2006-09-15 | 2008-03-27 | Ricoh Co Ltd | pi CONJUGATED COMPOUND AND USE THEREOF, AND ELEMENT AND DEVICE USING THE SAME |
| CN203164119U (en) * | 2012-11-14 | 2013-08-28 | 深圳大学 | Two-photon absorption section spectrometer |
| CN105004704A (en) * | 2015-07-09 | 2015-10-28 | 华南师范大学 | New use of neodymium ion sensitized up-conversion nanocrystal, and high-resolution multi-photon microscopic system |
| CN106066318A (en) * | 2016-06-14 | 2016-11-02 | 中国科学院长春光学精密机械与物理研究所 | A kind of method and device of on-line testing optical element laser damage |
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| 何国华等: "双光子吸收截面的测量方法", 《激光杂志》 * |
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