KR20160120988A - Apparatus for measuring fluorescence lifetime - Google Patents

Abstract

The present invention relates to a device to measure a lifetime of a fluorescence. According to an embodiment of the present invention, the device to measure the lifetime of the fluorescence comprises: a plurality of pump light sources which outputs a pump light of different wavelengths; a pump light combiner which combines the pump lights from the pump light sources, and outputs the result to a first multimode fiber (MMF); the first MMF which delivers the pump light inputted from the pump light combiner; a light isolator which allows the pump light delivered through the first MMF to pass through, blocking light inputted into the first MMF; a wavelength selection reflection filter which allows the pump light passing through the light isolator to pass through and reflects fluorescent light from a specimen; a second MMF which delivers the pump light passing through the wavelength selection reflection filter to the specimen and the fluorescent light from the specimen to the wavelength selection reflection filter; a third MMF which delivers the fluorescent light reflected from the wavelength selection reflection filter; a cut-off filter which absorbs the pump light wavelength from the fluorescent light delivered from the third MMF, allowing the remaining fluorescent light to pass through; and a photodiode which converts the fluorescent light passing through the cut-off filter into an electric signal.

Description

{APPARATUS FOR MEASURING FLUORESCENCE LIFETIME}

The present invention relates to a fluorescence lifetime measuring apparatus.

High-power solid-state lasers are used as a laser oscillation medium in the form of rods or discs, in which rare-earth ions are added in small quantities. At this time, the doping concentration and fluorescence lifetime of the rare earth ions in the laser oscillation medium is a key material characteristic of the medium which determines the laser oscillation characteristics.

In general, the fluorescence lifetime is determined by measuring the temporal behavior of fluorescence intensity attenuation using time resolved fluorescence spectroscopy. However, since the fluorescence lifetime measurement method according to the prior art uses a spectrometer as a method of selecting a specific wavelength of fluorescence, integration and miniaturization of measurement equipment are limited.

The concentration of doping can be measured by measuring the mass of a trace element using an inductively coupled plasma mass spectrometer (ICP-MS), which is a chemical analysis method, and by measuring the light absorption of a specific rare earth ion using optical absorption spectroscopy .

ICP-MS dissolves a single crystal in a specific solvent to measure the mass ratio of the atoms constituting the single crystal. Therefore, the sample to be measured must be destroyed and the average value of the concentration of rare earth ions present in the solution is provided. Therefore, the ICP-MS can not measure the doping concentration with respect to the solid state sample in the form of rod or disk, and the spatial distribution of the doping concentration can not be measured. In addition, the optical absorption spectroscopy can measure the concentration of a disk-shaped solid sample. However, in order to minimize irregular reflection and scattering of light incident on the sample, both surfaces of the disk are processed to an optical quality surface of less than? / 5 There is a problem that a rod-shaped sample can not be measured. Furthermore, since the optical absorption measuring device can precisely measure only at an optical density (OD) of less than 4, there is a limit of the measurable disk thickness (depending on the kind of the rare earth ion and the doping concentration, mm), the optical absorption spectroscope has a problem that the beam size of the light used is about 3 mm or more in diameter and the spatial resolution of the doping concentration measurable in the disk is about 3 mm or more.

An object of the present invention is to provide an apparatus which can accurately and easily measure fluorescence lifetime without destroying a sample.

The apparatus for measuring fluorescence lifetime according to an embodiment of the present invention includes: a plurality of pump light sources for outputting pump lights of different wavelengths; A pump coupler coupling the pump light output from the plurality of pump light sources and outputting the pump light to a first multi-mode fiber (MMF); A first multimode optical fiber for transmitting the pump light received from the pump coupler; An optical isolator that transmits the pump light transmitted from the first multimode optical fiber and blocks light input to the first multimode optical fiber; A wavelength selective reflection filter that transmits the pump light transmitted through the optical isolator and reflects the fluorescence emitted from the sample; A second multimode optical fiber for transmitting the pump light transmitted through the wavelength selective reflection filter to the sample and transmitting the fluorescence generated from the sample to the wavelength selective reflection filter; A third multimode optical fiber for transmitting the fluorescence reflected from the wavelength selective reflection filter; A cut-off filter for absorbing the pump light wavelength from the fluorescence transmitted from the third multimode optical fiber and passing the remaining fluorescence; And a photodiode for converting the fluorescence passing through the blocking filter into an electric signal.

According to the present invention, the present invention can accurately and easily measure the fluorescence lifetime without destroying the sample.

1 is a view showing a fluorescence lifetime apparatus according to an embodiment of the present invention.
2 is a diagram showing a light absorption spectrum of a sample measured using a conventional technique.
FIG. 3 is a graph showing fluorescence decay dynamics of a sample measured using a fluorescence lifetime apparatus according to an embodiment of the present invention. FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish it, will be described with reference to the embodiments described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. The embodiments are provided so that those skilled in the art can easily carry out the technical idea of the present invention to those skilled in the art.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

1 is a view showing a fluorescence lifetime apparatus according to an embodiment of the present invention.

The fluorescence lifetime apparatus according to an embodiment of the present invention includes a pump light source unit 100, a light transmission unit 200, a light receiving unit 300, and a fluorescence lifetime measurement unit 400. However, this distinction is merely a functional division, and actual components can be modified.

The pump light source unit 100 may include a plurality of pump light sources 111, 113, ..., 11k, a pump light coupler 150 and a first multimode fiber (MMF1, 170). Furthermore, the pump light source unit 100 may further include a pump-light control unit 130.

The plurality of pump light sources 111, 113, ..., 11k output pump lights of different wavelengths. According to an embodiment of the present invention, the plurality of pump light sources 111, 113, ..., and 11k are arranged in the order of light absorption peaks of excitation electrons of various kinds of rare earth ions (Nd ^{3 +} , Er ^{3 +} , Yb ^{3 +} And can output light having a peak wavelength. In addition, the plurality of pump light sources 111, 113, ..., 11k may include laser diodes.

The apparatus for measuring fluorescence lifetime according to an embodiment of the present invention may include a pump control unit 130 for controlling the plurality of pump light sources 111, 113, ..., 11k. The pump control unit 130 can control the plurality of pump light sources 111, 113, ..., 11k to operate in a pulse mode and to drive with a square pulse and a repetition rate . According to an embodiment of the present invention, the pump control unit 130 may vary the repetition rate and the pulse width of the plurality of pump light sources 111, 113, ..., 11k according to the lifetime range of the fluorescence to be measured Can be adjusted.

The pump light combiner 150 combines the pump light output from the plurality of pump light sources 111, 113, ..., 11k and outputs the combined pump light to a first multi-mode fiber (MMF). That is, the pump light coupler 150 provides a means for efficiently inputting pump lights of different wavelengths to the first multimode optical fiber 170. To this end, the pump light coupler 150 according to an embodiment of the present invention may include a waveguide coupler or a free-space coupler using a lens combination.

The first multimode optical fiber 170 transmits the pump light inputted from the pump light coupler 150. According to an embodiment of the present invention, the first multimode optical fiber 170 outputs the pump light received from the pump light coupler 150 to the optical isolator 210. According to an embodiment of the present invention, the first multimode optical fiber 170 may include lenses 171 and 172 for increasing the coupling efficiency of light to the input / output unit.

According to the prior art, in order to excite various kinds of rare earth ions, various kinds of light sources have to be excited. However, according to the present invention, by using a plurality of pump light sources 111, 113, ..., and 11k and a pump light coupler 150 coupling the outputs thereof, one integrated pump light source module can be constructed, , It is possible to generate various wavelengths of pump light and excite various kinds of rare earth ions.

Further, as compared with conventional time-resolved spectroscopic measurement apparatuses which do not require separate optical alignment and are exposed to free space using the first multimode optical fiber 170, (Ingot) production site. Furthermore, in the case of using a laser diode, it is easy to miniaturize the pump light source.

The optical transmission unit 200 may include an optical isolator 210, a wavelength selective reflection filter 230, and a second multimode optical fiber (MMF2, 250).

The optical isolator 210 transmits the pump light transmitted from the first multimode optical fiber 170 and blocks the light input to the first multimode optical fiber 170. The optical isolator 210 transmits the pump light generated from the pump light source unit 100 to the sample 500 and the fluorescence generated from the sample 500 and the scattered light of the second multimode optical fiber MMF2 250, As shown in FIG.

The wavelength selective reflection filter 230 transmits the pump light transmitted through the optical isolator 210 and reflects the fluorescence emitted from the sample 500. That is, when the pump light generated from the pump light source unit 100 is transmitted through the optical isolator 210, the wavelength selective reflection filter 230 transmits the pump light to the sample 500 through the second multimode optical fiber 250, Mode optical fiber 250 and transmits the fluorescence generated in the second multimode optical fiber 250 to the light receiving unit 300.

The second multimode optical fiber MMF2 250 transmits the pump light transmitted through the wavelength selective reflection filter 230 to the sample 500 and transmits the fluorescence generated from the sample 500 to the wavelength selective reflection filter 230. [ According to an embodiment of the present invention, the second multimode optical fiber 250 may include lenses 251 and 252 for increasing the coupling efficiency of light to the input / output unit. The second multimode optical fiber 250 includes a convex lens 252 at an output portion and condenses the pump light having a beam waist less than 0.1 mm through the convex lens 252 and outputs the pump light to the sample 500 can do. Through this process, the rare-earth ion electron state of the sample 500 can be excited to spatial resolution of less than 0.1 mm. At this time, when the sample is moved in the x, y, and z directions and the pump is irradiated, the spatial distribution of fluorescence can be measured and the spatial distribution of the doping concentration can be calculated.

The rare earth ions excited by the pump light emit fluorescence continuously in the pump pulse "ON" state, and exhibit a temporal behavior in which the fluorescence intensity attenuates from the beginning of the pulse "OFF". The fluorescence having such characteristics is transmitted to the light receiving unit 300 through the light transmitting unit 200. Particularly, in the optical transmission unit 200, the wavelength reflection filter 230 and the second multimode optical fiber 250 are sections in which the pump light and the signal light coexist simultaneously. The pump light is input to the sample and the fluorescence generated in the sample 500 To the light receiving unit 300.

According to the present invention, there is a disadvantage in that the spatial resolution is low and the optical alignment is required, which is inconvenient to use. However, according to the present invention, the second multimode optical fiber 250 is used, Compared with conventional time-resolved spectroscopic measurement equipment exposed to space, the equipment operating environment is advantageous in that it can be operated not only in a laboratory environment, but also in a general ingot production site. In addition, the fluorescence lifetime of a sample having various shapes (ingots, rods, disks) can be measured with a spatial resolution of less than 0.1 mm without destroying the sample.

The light receiving unit 300 may include a third multimode optical fiber (MMF 3, 310), a cutoff filter 330, and a photodiode 350.

The third multimode optical fiber 310 transmits the fluorescence reflected from the wavelength selective reflection filter 230. According to an embodiment of the present invention, the third multimode optical fiber 310 receives the fluorescence reflected from the wavelength selective reflection filter 230 and outputs the fluorescence to a cut-off filter 330. According to an embodiment of the present invention, the third multimode optical fiber 310 may include lenses 311 and 312 that increase coupling efficiency of light to the input / output unit.

The blocking filter 330 absorbs or reflects the pump light wavelength from the fluorescence transmitted from the third multimode optical fiber 310, and passes the remaining fluorescence. That is, in order to minimize the optical power of the pump light input to the photodiode 350, the cutoff filter 330 absorbs or reflects the wavelength of the pump light and transmits the fluorescence.

The photodiode 350 serves to convert the fluorescence that has passed through the blocking filter into an electrical signal. That is, it converts the fluorescence into a signal of a type that can be analyzed.

According to the present invention, it is difficult to miniaturize the fluorescence lifetime measuring apparatus by using a monochromator for wavelength selection. However, according to the present invention, the light receiving unit is connected to the third multimode optical fiber (MMF3, 310) The photodiode 350 can be simplified to make it possible to miniaturize the fluorescence lifetime measuring device. Further, as compared with conventional time-resolved spectroscopic measurement apparatuses which do not require separate optical alignment and are exposed to free space using the third multimode optical fiber 310, (Ingot) production site.

The fluorescence lifetime measuring unit 400 analyzes the electrical signal converted by the photodiode 350 and measures fluorescence lifetime. The fluorescence lifetime measuring unit 400 may include an amplifier 410, an A / D converter 430, and a signal analyzer 450.

The A / D converter 430 converts the amplified analog signal into a digital signal. The signal analyzer 450 converts the digital signal into a digital signal, And the fluorescence lifetime is measured. At this time, the amplifier 410 can use a broadband amplifier of 20 MHZ or more and can measure the fluorescence lifetime by averaging measured values measured several times.

According to the present invention, it is possible to reduce the size of the fluorescence lifetime device by integrating and simplifying the pump light source unit 100 and the light receiving unit 300. By using the multimode optical fibers 150, 250 and 310, the optical path can be simplified, Optical alignment is unnecessary and equipment operation is possible in the general production site.

Further, according to an embodiment of the present invention, the apparatus may further include a doping concentration calculation unit for calculating a doping concentration of the sample using Equation (1) based on the fluorescence lifetime measured by the fluorescence lifetime measuring unit 400 have.

C = Q [(? _O /? _F ) -1] ^1/2 Equation (1)

C is the doping concentration, Q is the quenching parameter, τ _o is the excited electron state lifetime in the absence of the non-radiative energy transfer process, and τ _f is the excitation current in a specific doping conduction condition where fluorescence quenching occurs. Electronic state life

The dopant concentration doped in a solid-state laser host can be measured by analyzing the lifetime of the excited electronic state of the rare-earth ion. In more detail, the excited electron state lifetime can be measured using time resolved fluorescence spectroscopy, the decay dynamics of fluorescence generated during the decay process. That is, the ions in the excited state are activated by the nonradioactive energy transfer process in proportion to the doping concentration, and the fluorescence quenching phenomenon occurs and the fluorescence lifetime becomes shorter as the doping concentration increases I have. With this feature, the doping concentration can be calculated. The Q and τ _o of a rare earth ion doped laser single crystal are inherent constants that are determined when the material and excited electron states are determined, and thus the doping concentration can be determined by measuring the fluorescence lifetime τ _f .

Hereinafter, a method of obtaining the doping concentration using the conventional technique and a method of obtaining the doping concentration according to the embodiment of the present invention will be compared.

2 is a diagram showing a light absorption spectrum of a sample measured using a conventional technique.

In FIG. 2, the X axis represents wavelength and the Y axis represents optical density.

For Nd: YAG crystals having different doping concentrations, the doping concentration of Nd ^{3 +} ions is determined by the conventional light absorption measurement method using equation (2) as follows.

N = 2.3 * [OD / (d *?)] Equation (2)

OD: optical density, d: thickness of the sample, l: absorption cross-section of the ion

The thickness of the sample is 0.31 cm, and the absorption cross-section of the Nd ^{3 +} ion at the wavelength of 808 nm is 7.7 × 10 ²⁰ cm ² . At this time, N = 1.38 x 10 ²⁰ cm ^-3 corresponds to the doping concentration of 1 at% Nd ^{3 +} ions. Based on this, the doping concentration of Nd ^{3 +} ions in Sample A and Sample B can be calculated as follows. Table 1 shows the Nd ^{3 +} ion doping concentration calculated by the equation (2).

Samplee Sample B Doping concentration 1.16 at% 1.58 at%

^{3 shows the} results of measurement of the damping dynamics of Nd ^{3 +} ion fluorescence (1064 nm) by exciting a sample with 808 nm pump light using a fluorescence lifetime measuring apparatus according to an embodiment of the present invention.

FIG. 3 is a graph showing fluorescence decay dynamics of a sample measured using a fluorescence lifetime apparatus according to an embodiment of the present invention. FIG.

In Fig. 3, the X-axis represents time and the Y-axis represents fluorescence intensity.

Table 3 shows the fluorescence lifetime obtained by linearly fitting the measurement data of FIG. Table 2 shows the fluorescence lifetime (τ _f ) of Nd ^{3 +} ions.

Samplee Sample B Fluorescence lifetime (μs) 124 111

The quenching parameter Q is a constant value that depends on the material. Here, Q is 1.33 ± 0.01 × 10 ²⁰ cm ^-3 , and τ _o is 260 μs as the lifetime value in the absence of fluorescence quenching. The doping concentration calculated by this method is as follows. Table 3 shows the Nd ^{3 +} ion doping concentration.

C _abs [at%] τ _f [μs] Q [10 ²⁰ cm ^-3 ] Samplee 1.16 124 1.32 Sample B 1.58 111 1.34

Table 1 and Table 3 show that the doping concentration calculated by the conventional technique is the same as the doping concentration calculated using the fluorescent lifespan device according to one embodiment of the present invention.

The embodiments of the present invention disclosed in the present specification and drawings are merely illustrative examples of the present invention and are not intended to limit the scope of the present invention in order to facilitate understanding of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

100: pump light source part
111, 113, ... , 11k: a plurality of pump light sources
130: Pump control unit
150: Pump coupler
170: first multimode optical fiber
200:
210: Isolator
230: wavelength selective reflection filter
250: second multimode optical fiber
300:
310: Third multimode optical fiber
330: Cutoff filter
350: photodiode
400: Fluorescence lifetime measuring unit
410: Amplifier
430: A / D converter
450: Signal Analysis Section

Claims (11)

A plurality of pump light sources for outputting pump lights of different wavelengths;
A pump coupler coupling the pump light output from the plurality of pump light sources and outputting the pump light to a first multi-mode fiber (MMF);
A first multimode optical fiber for transmitting the pump light received from the pump coupler;
An optical isolator that transmits the pump light transmitted from the first multimode optical fiber and blocks light input to the first multimode optical fiber;
A wavelength selective reflection filter that transmits the pump light transmitted through the optical isolator and reflects the fluorescence emitted from the sample;
A second multimode optical fiber for transmitting the pump light transmitted through the wavelength selective reflection filter to the sample and transmitting the fluorescence generated from the sample to the wavelength selective reflection filter;
A third multimode optical fiber for transmitting the fluorescence reflected from the wavelength selective reflection filter;
A cut-off filter for absorbing or reflecting the wavelength of the pump light from the fluorescence transmitted from the third multimode optical fiber and allowing the remaining fluorescence to pass therethrough; And
And a photodiode for converting the fluorescence passing through the blocking filter into an electric signal.
The method according to claim 1,
Further comprising a fluorescence lifetime measuring unit for measuring the fluorescence lifetime by analyzing the electric signal converted by the photodiode.
3. The method of claim 2,
And a doping concentration calculation unit for calculating a doping concentration of the sample using Equation (1) based on the fluorescence lifetime measured by the fluorescence lifetime measuring unit.
C = Q [(? _O /? _F ) -1] ^1/2 Equation (1)
C is the doping concentration, Q is the quenching parameter, τ _o is the excited electron state lifetime in the absence of the non-radiative energy transfer process, and τ _f is the excitation current in a specific doping conduction condition where fluorescence quenching occurs. Electronic state life
The method according to claim 1,
Wherein the plurality of pump light sources comprises:
And outputs light having a peak absorption wavelength in the excited state of rare earth ions.
The method according to claim 1,
Wherein the plurality of pump light sources comprises:
A device for measuring fluorescence lifetime comprising a laser diode.
The method according to claim 1,
Further comprising a pump control unit for controlling the plurality of pump light sources.
The method according to claim 6,
Wherein the pump-
Wherein the plurality of pump light sources operate in a pulse mode and are controlled to be driven by a square pulse and a repetition rate.
8. The method of claim 7,
Wherein the pump-
Wherein the repetition rate and the pulse width of the plurality of pump light sources are variably controlled according to the lifetime range of the fluorescence to be measured.
The method according to claim 1,
The pump-
And a free-space coupler using a waveguide coupler or a combination of lenses.
The method according to claim 1,
Mode optical fiber, at least one of the first multimode optical fiber, the second multimode optical fiber, and the third multimode optical fiber,
And a lens for increasing the coupling efficiency of light to the input / output unit.
11. The method of claim 10,
The second multimode optical fiber
Wherein a convex lens is included in the output section, and the pump light having a beam waist less than 0.1 mm is condensed through the convex lens and outputted to the sample.

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