JP3962777B2 - Real-time spectrometer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spectroscopic method and a spectroscopic device, and more particularly to a real-time imaging spectroscopic method and a real-time imaging spectroscopic device for obtaining a spectrum of a real-time change in a minute time.
[0002]
[Prior art]
Photoinduced reactions occur in photochemical reactions such as photopolymerization, photolysis, and photosynthesis performed in many organic chemicals and biological systems, and in photoexcitation in semiconductors. These initial processes of photochemical reactions and the relaxation phenomenon of photoexcited carriers in semiconductors are ultrafast phenomena that occur within a time period of several tens of femtoseconds to several tens of picoseconds. It is extremely important to clarify the reaction-induced states and photoinduced phenomena of substances.
[0003]
In order to elucidate the photoinduced phenomenon of a substance, it is necessary to obtain the spectrum (wavelength characteristics) and the change with time. As a method for performing this analysis, various laser spectroscopy methods such as conventional pump-probe transient absorption spectroscopy, four-wave mixing method, and sum-frequency generation spectroscopy as a method for temporal analysis of light emission are used.
[0004]
In these conventional laser spectroscopy methods, in spectrum (wavelength characteristic) measurement, the time is fixed by fixing the stage constituting the optical delay circuit, the spectrum is measured by a spectroscope, and in the time change measurement, the measurement wavelength is measured. The time response is measured by changing the time by moving the stage constituting the optical delay circuit, and each is performed individually. As described above, since the conventional laser spectroscopy is performed by fixing either one of the time and the measurement wavelength, both the spectrum (wavelength characteristic) measurement and the time change measurement cannot be performed simultaneously.
[0005]
[Problems to be solved by the invention]
Conventional laser spectroscopy cannot perform both spectrum (wavelength characteristic) measurement and time change measurement at the same time. Therefore, in order to obtain a time-resolved total absorption (or reflection) spectrum in a measurement sample, It is necessary to repeat the spectrum measurement for each delay time and the time response measurement for each measurement wavelength while changing the optical delay time or the measurement wavelength, respectively.
[0006]
Therefore, there is a problem that it usually takes a long time from several hours to several days to perform a series of measurements of spectrum measurement and time change measurement. In addition, in such a measurement that requires a long time, there are problems in that the laser operates stably over a long period of time and that the sample deteriorates due to the long-time laser irradiation.
[0007]
In addition, in order to measure transients by spectroscopic methods that repeatedly accumulate data while changing the time or wavelength as in the past, it is necessary to always remove reaction products in order to eliminate the influence of past reaction conditions. The object needs to flow like a solution.
[0008]
However, many phenomena in solids are thermally irreversible, such as photochromism and photopolymerization. In such a thermally irreversible phenomenon in the solid, the reaction product accumulates in the sample by excitation light (pump light), and the reaction product cannot be removed by flow like a solution. There is a problem that conventional spectroscopy cannot be applied to the analysis of the phenomenon.
[0009]
For example, solid-state photochromic compounds are expected as optical memory materials, and it is required to evaluate the physical properties of optical functional materials such as optical memory and optical switching, and to establish guidelines for designing these materials. In addition, research on dynamic processes of biological samples weak against strong excitation is also required, but it is currently difficult to analyze the dynamic processes of the photostructural changes of such compounds. Therefore, there is a need for a spectroscopic method and a spectroscopic device that can measure a time-resolved spectrum instantaneously in response to such a demand.
Therefore, the present invention aims to solve the above-described conventional problems and simultaneously perform time resolution and spectrum measurement in spectroscopic measurement.
[0010]
[Means for Solving the Problems]
The present invention irradiates a sample with excitation light to generate a reaction product, irradiates the reaction product with probe light, and spectrally measures transmitted light or reflected light obtained from the sample. The time resolution and the spectrum measurement are performed simultaneously by developing the spectrum along the time axis along with the wavelength axis.
[0011]
In the real-time spectroscopy of the present invention, probe light and excitation light including a plurality of wavelengths are irradiated onto a sample by superimposing the probe light and / or excitation light so that at least the sample surface has an optical delay time. The reaction product information generated by the reaction is read in the form of optical information by irradiating the probe light, and this light is split into two dimensions of the optical delay time axis and the wavelength axis to obtain the actual time width of the optical delay time. By performing time spectroscopy, time resolution and spectrum measurement are performed simultaneously.
[0012]
The source light of the excitation light and the probe light is a femtosecond laser pulse, and the pulse width of this pulse light is a unit of femtosecond. By delaying this light, real time time resolution of picosecond unit is performed. be able to. The excitation light and the probe light can be formed by bisecting the femtosecond laser pulse emitted from one femtosecond laser pulse light source.
[0013]
The spectroscopic method of the present invention can perform time resolution together with spectrum measurement in the following manner.
In the first aspect, the probe light and the excitation light are condensed and irradiated on the sample surface in a linear or belt shape. The probe light and the excitation light are incident on the linear or belt-shaped condensing surface so that there is an optical path difference between them. In this incidence, one of the probe light and the excitation light is incident obliquely on the condensing surface, is incident on the condensing surface so that there is an optical path difference in the length direction, and the other is incident vertically on the condensing surface. In addition to incident on the light collecting surface so that there is no optical path difference in the length direction, both the probe light and the excitation light are obliquely incident on the light collecting surface, and on the light collecting surface in the length direction. By making incident light so that there is an optical path difference, it is possible to cause optical path differences in the lengthwise direction on the condensing surface.
[0014]
This incidence forms a time difference corresponding to the optical delay time on the sample surface. The probe light and / or excitation light can form an optical path difference by being incident at a predetermined angle with respect to the normal direction of the light collecting surface. As a result, the information on the optical delay time after irradiation is included in the linear or belt-shaped light condensing surface along the length direction, and the wavelength component is measured by splitting the linear light or the belt-shaped light. By doing so, time resolution and spectrum measurement can be performed simultaneously.
[0015]
In the second aspect, the probe light and the excitation light are condensed and irradiated in a spot shape on the sample surface. The probe light is passed through time delay forming means for forming a time delay before irradiation. As a result, the information on the optical delay time after the excitation light irradiation is included in the dot-shaped condensing surface. By developing this point light on the time axis of the optical delay time, and dispersing the developed light on the wavelength axis and measuring the wavelength component, time resolution and spectrum measurement can be performed simultaneously. According to the 2nd aspect, since it can measure at one point on a sample, the nonuniformity of the measurement data which arises when the irradiation position of irradiation light changes with nonuniformity of a sample can be prevented.
[0016]
In the third aspect, the probe light and the excitation light are condensed and irradiated in a linear or band shape on the sample surface, and are incident perpendicularly on the condensing surface on the linear or band-shaped condensing surface. , And incident so that there is no optical path difference in the length direction. The probe light and / or excitation light is passed through time delay forming means for forming a time delay before irradiation. Thereby, the information on the optical delay time after irradiation is included in the linear or belt-shaped condensing surface along the length direction of the line or belt. By splitting the linear light or band light and measuring the wavelength component, time resolution and spectrum measurement can be performed simultaneously.
[0017]
The real-time spectroscopic device of the present invention includes an irradiation unit that irradiates a sample with excitation light and probe light including a plurality of wavelengths, and two-dimensional time and wavelength axes of transmitted light or reflected light obtained from the sample by irradiation. And a detecting means for two-dimensionally detecting the spectrum by the spectroscopic means.
[0018]
Here, the probe light and / or excitation light is configured to have an optical delay time at least on the sample surface, and the spectroscopic means disperses the information on the optical delay time on the time axis, and the real time of the time width of the optical delay time. Spectral analysis at the same time resolution and spectral measurement.
[0019]
The irradiation means provided in the present invention includes a light source that generates a femtosecond laser pulse having a pulse width in units of femtoseconds, a wavelength conversion element that forms excitation light from the femtosecond laser pulses, and a plurality of wavelengths from the femtosecond laser pulses. A self-phase modulation element that forms white probe light, and an optical system that forms excitation light and probe light in a linear or belt shape.
[0020]
The real-time spectroscopic device of the present invention forms optical delay time information on the sample surface by providing the probe light and / or excitation light with an optical delay time, and simultaneously performs time resolution and spectrum measurement. The formation of the light delay time can be performed by the irradiation unit, and the present invention can be applied to a plurality of modes of irradiation unit.
[0021]
In the first aspect of the irradiating means, the probe light and the excitation light are condensed on the sample surface in a linear or belt shape. One of the probe light and the excitation light is incident obliquely on the condensing surface at the linear or belt-shaped condensing surface, and incident on the condensing surface so that there is an optical path difference in the length direction, and the other is linear. Alternatively, the light is incident perpendicularly on the light condensing surface at the band-shaped light condensing surface and incident on the light condensing surface so that there is no optical path difference in the length direction. Alternatively, both the probe light and the excitation light are obliquely incident on the condensing surface at the linear or belt-shaped condensing surface and are incident on the condensing surface so that there is an optical path difference in the length direction. Depending on the incident angle of this light, an optical delay time is formed on the sample surface.
[0022]
The second aspect of the irradiating means includes a time delay forming means for forming a time delay in the probe light, an optical system for condensing the probe light that has passed through the time delay forming means on the sample surface in a dot shape, and an excitation light. And an optical system that collects light in a spot shape on the sample surface. Thereby, the spot-like probe light irradiated on the sample surface has an optical delay time. The spectroscopic means is equipped with an optical system that expands the point-like light from the sample in a linear or band-like manner on the time axis of the optical delay time, and the light containing the information on the optical delay time is given a linear or strip-like shape on the time axis of the optical delay time Expand to spectroscopic.
[0023]
The third aspect of the irradiation means is that the time delay forming means for forming a time delay in the probe light and / or the excitation light, and the light passing through the time delay forming means is formed in a linear shape or a belt shape, and the length direction of the irradiation surface And an optical system that irradiates the other light in a linear or belt shape and irradiates perpendicularly to the length direction of the irradiation surface. Accordingly, the linear or belt-like probe light and / or excitation light irradiated on the sample surface has an optical delay time in the length direction of the irradiation surface. The spectroscopic means is equipped with an optical system that expands the transmitted light or reflected light obtained from the sample in a linear or belt shape on the time axis of the optical delay time, and the light including the information on the optical delay time is linear on the optical delay time axis. Expand to spectroscopic.
[0024]
In the present invention, light including information on the optical delay time is dispersed in the line or band direction, and this spectrum is detected by a two-dimensional detector. The time response is measured from the data in one axial direction of the two-dimensional detector, and the spectrum is measured for the wavelength from the data in the other axial direction. By simultaneously obtaining both time response and spectrum data with a two-dimensional array of two-dimensional detectors, an absorption (or reflection) spectrum obtained by simultaneously resolving the spectrum and time can be obtained as image information.
Further, the measurement time can be adjusted by optically delaying the excitation light to form a time difference with the probe light.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The first embodiment of the present invention will be described with reference to FIGS. 1 to 5, the second embodiment of the present invention will be described with reference to FIGS. 6 and 7, and the first embodiment of the present invention will be described with reference to FIGS. The third aspect will be described.
[0026]
First, the first aspect will be described. 1 to 5 are schematic diagrams for explaining the configuration, schematic diagrams for explaining the spectrum of transmitted light, schematic diagrams for explaining the spectrum of reflected light, time response and spectrum in the first embodiment. FIG. 6 is a schematic signal diagram for explaining a schematic example of measurement data and a relationship between probe light and measurement light.
[0027]
In the first aspect, as the configuration for forming the optical delay time, either the excitation light or the probe light is incident on the sample with a predetermined incident angle, or the excitation light and the probe light Both can be configured to be incident on the sample with a predetermined incident angle.
[0028]
In the following description, the configuration in which the probe light is incident on the sample with a predetermined incident angle will be described. However, the configuration in which the excitation light is incident on the sample with a predetermined incident angle, or the probe light and the excitation light are excited. The same applies to a configuration in which light is incident on the sample with a predetermined incident angle.
[0029]
In FIG. 1, a real-time spectroscopic apparatus 1 according to the present invention includes an irradiation unit 2 that irradiates a sample S with excitation light and probe light, and a transmitted light or reflected light obtained from the sample S by the irradiation light. A spectroscopic means 3 for performing spectroscopic analysis, and a detection means 4 for detecting the spectrally divided time-axis and wavelength-axis signals in two dimensions. In the first aspect, the excitation light and the probe light are linearly collected with respect to the sample S, and an optical delay time is applied to the probe light simultaneously irradiated onto the sample S according to the incident angle of the probe light with respect to the sample S. And time resolution is performed by this optical delay time.
[0030]
The irradiation unit 2 includes a laser light source 2a that generates femtosecond laser pulses having a pulse width of femtosecond units. This femtosecond laser pulse is divided into two by the beam splitter 2b, one femtosecond laser pulse is irradiated to the sample S as excitation light, and the other femtosecond laser pulse is sampled as probe light of femtosecond white light having a plurality of wavelengths. S is irradiated.
[0031]
Excitation light is converted into pulsed light of a specific wavelength by passing a femtosecond laser pulse emitted from the laser light source 2a through the wavelength conversion element 2f. After adjusting the time difference from the probe light by the optical delay stage 2g, an appropriate light is obtained. Collimated to a large beam diameter (for example, about 5 mm diameter), formed into a linear shape by the cylindrical lens 2h2, and condensed on the sample S.
The optical delay stage 2g may be provided on the probe light side, thereby adjusting the time difference between the probe light and the excitation light.
[0032]
On the other hand, the probe light is converted into femtosecond white light having a plurality of wavelengths by passing a femtosecond laser pulse emitted from the laser light source 2a through the self-phase modulation element 2d, and a beam having an appropriate size is obtained by an optical system such as a mirror 2c2. Collimated to a diameter (for example, about 5 mm diameter), formed into a linear shape by the cylindrical lens 2h1, and condensed on the sample S. Note that polarizing elements 2e1 and 2e2 are disposed on the optical path of the probe light with the sample S interposed therebetween. The polarizing elements 2e1 and 2e2 are used when correcting the chirp by the Kerr effect. In this case, the polarization directions are shifted by 90 degrees from each other. On the other hand, at the time of actual measurement, the polarization direction is set to 0 degree and used in parallel.
[0033]
In FIG. 1, 2c1 to 2c7 are mirrors for forming optical paths of excitation light and probe light. For example, sapphire, a quartz substrate, or water can be used as the self-phase modulation element 2d.
[0034]
The cylindrical lenses 2h1 and 2h2 are optical systems that form beam-like light in a linear shape. FIG. 10 shows an example of the cylindrical lens 2h. The illustrated cylindrical lens 2h is a columnar lens having a semicircular cross section, and the length direction of the optical cylindrical lens 2h is the linear direction of the emitted light.
[0035]
The probe light and the excitation light formed in a linear shape by the cylindrical lenses 2h1 and 2h2 are condensed on the sample S in a linear shape. The measurement light excited by the excitation light and extracted from the sample S by the probe light is then shaped into an appropriate size by the lens system, and then is narrowed down on the slit 3a by the cylindrical lens, and is dispersed by the spectroscopic element 3b. It is detected by the detector 4.
[0036]
2 and 3 show the incident state of the excitation light and the probe light on the sample S, and the detection state of the measurement light obtained from the sample S on the time axis and the wavelength axis, and FIG. 2 detects the transmitted light. FIG. 3 shows a configuration example, and FIG. 3 shows a configuration example for detecting reflected light. 2 and 3 are different from each other in terms of transmitted light and reflected light, and the other configurations are the same. Therefore, the transmitted light in FIG. 2 will be mainly described below.
[0037]
In FIG. 2, the excitation light is incident on the sample S at an angle that does not cause an optical path difference, while the probe light is incident on the sample S so as to overlap the excitation light at an angle that causes an optical path difference. . The broken line shown in the probe light in FIG. 2 represents the wavefront of the same optical delay time. Note that the interval between the wavefronts shown in the figure is arbitrarily determined from the description, and the interval itself does not include any special meaning.
[0038]
The probe light is incident on the surface of the sample S at an angle θ as shown in the figure, so that the arrival time on the sample surface is sequentially shifted depending on the condensing position extending linearly or in a strip shape, and the optical path difference is increased. Will be formed. For example, on the linear or belt-shaped light condensing surface P with a hatched portion in the figure, the probe light first reaches the end A, then reaches the other end B with a delay, and there is an optical path difference between both ends. It is formed. This optical path difference corresponds to the time difference of the optical delay time of Δt. For example, if the length of the linear focusing on the sample S of the probe light is 5 to 6 mm (for example, 5.2 mm) and the incident angle is 30 degrees, the distance between both ends of the end A and the end B The optical path difference is 3 mm, and an optical delay time of about 10 ps (picosecond) is formed as a time difference. The incident angle θ described above is not limited to 30 degrees, and can be arbitrarily set so as to form a predetermined light converging surface P. Usually, 20 degrees to 30 degrees from the beam diameter of the probe light and the optical delay time. Degree is appropriate.
[0039]
When the sample S is relatively uniform and there is no difference in characteristics depending on the position, or is negligible, each of the linear condensing surfaces P obtained by the incidence of the excitation light and the probe light in the line direction. The position state represents a state corresponding to each response time. Therefore, the measurement light emitted from each position in the linear direction of the linear condensing surface P includes information on the state corresponding to each response time, and wavelength components at each response time are obtained by dispersing the measurement light. Can be requested.
[0040]
The transmitted light that has passed through the sample S from the condensing surface P is shaped to an appropriate size by a lens system, and is narrowed down on the slit 3a by a cylindrical lens to be linear or banded along the time axis of the optical delay time. To do. The spectroscopic means 3b splits the measurement light extending linearly or in a strip shape along the time axis of the optical delay time in a predetermined wavelength range. In FIG. 2, only a part of the arrow indicating the spectrum is schematically displayed. The detector 4 includes a two-dimensional detector 4a. One axial direction (x-axis direction in the figure) of the two-dimensional detector 4a is made to correspond to the time axis of the optical delay time of the spectroscopic means 3b, and the other axial direction. (Y-axis direction in the figure) is made to correspond to the wavelength axis of the spectroscopic means 3b, and the dispersed light is detected in two dimensions, the time axis and the wavelength axis. As a result, the two-dimensional detector 4a can simultaneously measure two measurement elements of the optical delay time and the wavelength, and the detected detection signal can image the spectrum in two dimensions using the optical delay time as real time. Can do.
[0041]
FIG. 3 shows a configuration example for detecting reflected light. Similar to the transmitted light in FIG. 2, two measurement elements of optical delay time and wavelength are measured simultaneously, and the spectrum is two-dimensionally using the optical delay time as real time. Can be imaged.
FIG. 4 is an example of two-dimensional imaging of optical delay time and spectrum. The time axis is taken in the x-axis direction, the wavelength axis is taken in the y-axis direction, and the intensity is taken in the z-axis direction. In FIG. 4A, a curve indicated by a solid line indicates a spectrum at each time (t1 to t6), and in FIG. 4B, a curve indicated by a solid line and a broken line indicates a time change at each wavelength (λ1 to λ7). Is shown. In addition, each time (t1-t6) and each wavelength ((lambda) 1- (lambda) 7) to show in figure are examples, Comprising: It can select arbitrarily within a measurement range. In addition, although FIG. 4 is displayed with a curve, the display is not limited to a curve, and can be displayed with a curved surface.
[0042]
Further, the spectroscopic means and the two-dimensional detector can be constituted by a CCD detector spectroscope (for example, 1024 pixels × 1024 pixels) in one apparatus, for example, light after excitation light irradiation in the x-axis direction of the CCD. Information on the delay time is written at once as information on the wavelength separated by the spectrometer in the y-axis direction of the CCD. Note that the accumulation of data in the CCD is determined by the exposure time of the CCD.
[0043]
Moreover, the spectral range to measure can be 400 nm-800 nm as an example, for example, and this spectral range can be adjusted by replacing | exchanging the grating of a spectrometer.
[0044]
FIG. 5 is a schematic signal diagram for explaining the relationship between the probe light and the measurement light. FIG. 5A shows a femtosecond laser pulse having a pulse width generated from a laser light source in units of femtoseconds. The pulse width is, for example, about 100 fs (femtosecond), and the repetition of the pulse is about 1 ms. FIG. 5B shows a change over time of measurement light obtained from the sample by irradiation with excitation light and probe light. Photoinduced reactions such as the initial process of photochemical reaction and the relaxation phenomenon of carriers photoexcited in a semiconductor are ultrafast phenomena that occur within a period of several tens of femtoseconds to several tens of picoseconds. In the real-time spectroscopy according to the present invention, by using the above-described optical delay time, it is possible to measure this ultrafast time change of about 10 ps (picoseconds).
[0045]
In addition, the present invention can cope with not only an ultrafast time change of about 10 ps (picoseconds) but also a longer time change. FIGS. 5C to 5E show measurement examples of this relatively long time change.
[0046]
FIG. 5C shows an example in which the time change of the measurement light obtained from the sample by the irradiation of the excitation light and the probe light is relatively long. In the real-time spectroscopy according to the present invention, the irradiation timing of the probe light is changed by adjusting the optical delay time between the excitation light and the probe light, and the time change of about 10 ps (picosecond) during a relatively long time change. Can be measured. FIGS. 5D and 5E show time changes of about 10 ps (picoseconds) from the times t1 and t2. In the real-time spectroscopy according to the present invention, the time changes are obtained by including the optical delay time in the probe light. Can be obtained in one measurement.
[0047]
5C is obtained by repeating the pulse light shown in FIG. 5D (FIG. 5E) at a predetermined time interval (for example, a unit of about 10 ps). Can do.
[0048]
This time adjustment has a configuration in which an optical delay stage is disposed on one of the optical paths of the probe light and the excitation light, or a configuration in which an optical delay stage is disposed on the optical paths of both the probe light and the excitation light. You can also.
[0049]
In addition, when changing the time which measures a time change, time adjustment is performed between probe light and excitation light by an optical delay stage. For example, in order to measure a time change of about 10 ps (picosecond) from the time t2 instead of the measurement change from the time t1 (FIG. 5 (e)), the optical path length of the optical delay stage 2g is set to the time t1 and the time t2. The time is adjusted between the probe light and the excitation light by extending the length corresponding to this time interval.
[0050]
Note that femtosecond white light obtained by self-phase modulation on sapphire, a quartz substrate, water, or the like is positively chirped on the sample, resulting in a difference in group velocity depending on the wavelength. This positive chirp is a phenomenon in which when the light passes through the dispersion medium, the refractive index of the dispersion medium increases as the wavelength becomes shorter, so that the white light generated simultaneously on the sapphire substrate arrives with a shorter wavelength when reaching the sample. It is. Therefore, the polarizing plate 2e1 and the polarizing plate 2e2 are arranged with the sample S interposed therebetween, and the amount of chirp is measured using the Kerr effect with the polarizations being perpendicular to each other, and the measurement result is data-corrected based on the measured amount of chirp. Thus, the measurement error in the femtosecond region can be corrected.
[0051]
Next, the second aspect of the present invention will be described. 6 and 7 are a schematic diagram for explaining the configuration and a schematic diagram for explaining spectroscopy in the second mode. In addition, description is abbreviate | omitted about the part which is common in a 1st aspect.
[0052]
In FIG. 6, the real-time spectroscopic device 1 according to the second aspect of the present invention is similar to the first aspect in that the irradiation means 2 that irradiates the sample S with excitation light and probe light, and the sample S by irradiation light. A spectroscopic unit 3 that splits the obtained light into a time axis and a wavelength axis, and a detection unit 4 that detects the split time axis and wavelength axis signals in two dimensions.
[0053]
In the first aspect described above, the excitation light and the probe light are linearly collected on the sample S, and an optical delay time is formed on the light simultaneously irradiated on the sample S according to the incident angle with respect to the sample S. The second mode is a mode in which excitation light and probe light are collected in a dot-like manner with respect to the sample S. The probe light passes through a time delay forming means for forming a time delay before irradiation, and the probe light formed on the spot-like light condensing surface has a light delay time due to the formation of the time delay, thereby performing time resolution. .
[0054]
The second mode is a mode in which time-resolved and spectrum measurement are simultaneously performed by expanding the point light on the light collecting surface in the direction of the optical delay time, and measuring the wavelength component by dispersing the expanded light. According to the second aspect, since measurement can be performed at one point on the sample, it functions particularly effectively in the case of a non-uniform sample having a characteristic difference depending on the position of the sample, as in the first aspect. In addition, it is possible to prevent the non-uniformity included in the measurement data caused by the difference in the collection position of the irradiation light.
[0055]
Note that the irradiating means 2 of the second aspect has a configuration in which the excitation light and the probe light are focused on the sample S in the form of dots, and a condensing lens 2j2 that condenses the excitation light on the sample S, and the probe A condensing lens 2j1 for condensing the light on the sample S, and a time delay forming means 2i for forming a time delay on the optical path of the probe light before irradiating the sample S as a configuration for forming an optical delay time; A condensing lens 2j3 is provided between the sample S and the spectroscopic means 3 as a configuration for expanding the spot light on the condensing surface in the direction of the optical delay time.
[0056]
With this configuration, the collimated excitation light is condensed on the sample S by the condenser lens 2j2, and the femto white light collimated by the optical system such as the curved mirror 2c2 forms the optical delay time by the time delay forming means 2i. After that, the light is condensed in a dot shape on the sample S by the condenser lens 2j1. The time delay forming means 2i can provide the optical delay time to the probe light at the condensing point on the sample S by changing the width of the time delay to be formed.
[0057]
The measurement light excited by the excitation light and extracted by the probe light having an optical delay time is linearly focused on the slit 3 a of the spectroscopic means 3, and then dispersed by the spectroscopic element 3 b and detected by the detector 4. Is done.
[0058]
FIG. 7 shows a time delay formation and a light delay time formation state by the time delay formation means, and a detection state of the measurement light obtained from the sample S on the time axis and the wavelength axis. In FIG. 7, the excitation light is condensed at a condensing point on the sample S by a condensing lens (not shown), while the probe light is caused to form a time delay by the time delay forming means 2i and the width of the time delay to be formed. And the light is condensed on the sample S by the condensing lens 2j1.
[0059]
As the time delay forming means 2i, for example, an optical element called echelon can be used. Echelon has a plurality of optical path lengths, the pulse width of the pulsed light incident on the echelon is expanded, and a time difference is formed at the time of emission due to the optical path length, giving an optical delay time to the probe light condensed on the sample S. For example, about 150 fs (femtoseconds) of pulse width is about 150 fs (femtoseconds) in an optical material having a length of about 30 mm and a width of about 25 mm and an echelon formed by forming about 1000 pixels each having a length of about 30 μm and a width of about 25 μm When the probe white light is incident, probe white light having a pulse width extended to about 5 ps (picosecond) is emitted.
[0060]
This formation of the optical delay time can give the probe light an optical delay time along the lateral direction of the echelon. In FIG. 7, the light emitted from the right end of the echelon corresponds to the initial light with the delayed pulse width, and the light emitted from the left end of the echelon corresponds to the late light with the delayed pulse width.
[0061]
The pulse light delayed in the width direction of the echelon is condensed by the condenser lens 2j1 at a point on the sample S where the excitation light is condensed. The probe light focused on the point on the sample S again spreads along the optical delay time. The condensing lens 2j3 collects the light spreading along the optical delay time, collimates it, and guides it to the spectroscope and the detector. Here, a slit (not shown) provided in the spectroscope squeezes incident light along the optical delay time and separates light extending linearly along the time axis. As in the first embodiment, the detector 4 uses the two-dimensional detector 4a, and one axial direction (x-axis direction in the figure) of the two-dimensional detector is set to the time axis of the optical delay time of the spectrometer. The other axis direction (y-axis direction in the figure) is made to correspond to the wavelength axis of the spectrometer, and the dispersed light is detected in two dimensions, the time axis and the wavelength axis. As a result, the two-dimensional detector can simultaneously measure two measurement elements of the optical delay time and the wavelength, and the detected detection signal can image the spectrum in two dimensions using the optical delay time as real time. it can.
[0062]
Next, a third aspect of the present invention will be described. FIG. 8 and FIG. 9 are a schematic diagram for explaining the configuration and a schematic diagram for explaining spectroscopy in the third mode. In addition, description is abbreviate | omitted about the part which is common in a 1st aspect.
[0063]
In FIG. 8, the real-time spectroscopic device 1 according to the third aspect of the present invention is similar to the first aspect in that the irradiation means 2 for irradiating the sample S with excitation light and probe light, and the sample S from the sample S by irradiation light. A spectroscopic unit 3 that splits the obtained light into a time axis and a wavelength axis, and a detection unit 4 that detects the split time axis and wavelength axis signals in two dimensions.
[0064]
In the first aspect described above, excitation light and probe light are linearly collected with respect to the sample S, and optical delay is applied to the probe light that is simultaneously irradiated onto the sample S according to the incident angle of the probe light with respect to the sample S. In contrast to the mode in which time is formed and the time resolution is performed by the optical delay time, the third mode is a method in which the excitation light and the probe light are similarly collected linearly on the sample S. In this case, the probe light and / or excitation light passes through time delay forming means for forming a time delay before irradiation, and the probe light and / or excitation formed on the linear condensing surface by the time delay formation. This is a mode in which light is given a light delay time and time resolution is thereby performed.
[0065]
In the third aspect, the light that forms the time delay through the time delay forming means can be either excitation light or probe light, or both excitation light and probe light.
[0066]
In the following, a configuration for forming a time delay in the excitation light by passing the excitation light through the time delay forming unit will be described. However, a configuration for forming a time delay in the probe light by passing the probe light through the time delay forming unit, or The same can be applied to the configuration in which the time delay is formed in the excitation light and the probe light by passing both the excitation light and the probe light through the time delay forming means.
[0067]
The irradiation means 2 of the third aspect includes a time delay forming means 2i that forms a time delay on the optical path of the excitation light before irradiating the sample S as a configuration for forming an optical delay time. The passed excitation light is formed into a linear shape by the cylindrical lens 2h2, and is superposed on the probe light irradiated on the sample S and condensed.
[0068]
With this configuration, the excitation light is formed in a linear shape by the cylindrical lens 2h2 after being time-delayed by the time-delay forming means 2i, and is condensed on the sample S. On the other hand, the femto white light collimated by the optical system such as the curved mirror 2c2 is condensed on the sample S by the cylindrical lens 2h1. The time delay forming means 2i can provide the optical delay time to the excitation light at the condensing point on the sample S by changing the width of the time delay to be formed.
[0069]
The measurement light excited by the excitation light having the optical delay time and taken out from the sample S by the probe light is linearly focused on the slit 3a of the spectroscopic means 3, and then spectrally separated by the spectroscopic element 3b, and the detector 4 Is detected.
[0070]
FIG. 9 shows the time delay formation and the light delay time formation state by the time delay formation means, and the detection state of the measurement light obtained from the sample S on the time axis and the wavelength axis. In FIG. 9, the probe light is collected on the sample S, while the excitation light forms a time delay by the time delay forming means 2 i and the width of the time delay to be formed is made different. Condensate linearly.
[0071]
The time delay forming means 2i can use an optical element such as echelon similar to the second embodiment, and the formed time delay gives the excitation light an optical delay time along the lateral direction of the echelon. In FIG. 9, the light emitted from the left end of the echelon corresponds to the initial light with the delayed pulse width, and the light emitted from the right end of the echelon corresponds to the latter light with the delayed pulse width.
[0072]
The pulsed light delayed in the width direction of the echelon is condensed linearly at a point on the sample S where the probe light is condensed by the cylindrical lens 2h2. The slit provided in the spectroscope squeezes incident light along the optical delay time and separates light extending linearly along the time axis. As in the first embodiment, the detector 4 uses the two-dimensional detector 4a, one axial direction (x-axis direction in the figure) of the two-dimensional detector is made to correspond to the time axis of the spectrometer, and the other The axis direction (y-axis direction in the figure) is made to correspond to the wavelength axis of the spectrometer, and the dispersed light is detected in two dimensions, the time axis and the wavelength axis. As a result, the two-dimensional detector can simultaneously measure two measurement elements of the optical delay time and the wavelength, and the detected detection signal can image the spectrum in two dimensions using the optical delay time as real time. it can.
[0073]
In addition, although it can be set as the aspect which forms an optical delay time in probe light by providing echelon on the optical path of probe light, since probe light has a wide wavelength range normally, composition which provides echelon on the optical path of probe light Then, when passing through Echelon, chirp is likely to occur, and it is necessary to correct this chirp. On the other hand, according to the configuration in which the echelon is provided on the optical path of the excitation light, since the excitation light is monochromatic light, there is an advantage that the generation of chirp when passing through the echelon can be suppressed.
[0074]
According to the first aspect, the time width to be measured can be adjusted by adjusting the incident angle of the probe light and / or the excitation light.
According to the second aspect, by collecting the excitation light and the probe light at one point on the sample, measurement data at one point on the sample can be obtained, and non-uniformity due to the position of the sample can be eliminated. It can be applied to samples having different characteristics and states depending on positions, minute samples, and analysis regions.
[0075]
Further, according to the present invention, in the spectroscopic measurement, the time can be shortened by simultaneously performing the time resolution and the spectrum measurement. In addition, it solves the problems of laser instability due to long-time measurement and sample deterioration due to long-term laser irradiation, and can perform measurement in a stable laser state, and minimizes sample deterioration due to laser irradiation. Can be suppressed.
[0076]
Even if the object to be measured is a solid, it is possible to measure a transient phenomenon of a thermally irreversible phenomenon such as photochromism or photopolymerization.
By applying the real-time spectroscopy of the present invention to the analysis of the dynamic process of the optical structure change of the compound, evaluation of the physical properties of optical functional materials such as optical memory and optical switching, establishment of design guidelines for these materials, Alternatively, it can be applied to the study of dynamic processes of biological samples that are vulnerable to strong excitation, and the time-resolved spectrum can be measured in a short time.
[0077]
【The invention's effect】
As described above, according to the real-time spectroscopy of the present invention, time resolution and spectrum measurement can be performed simultaneously in spectroscopic measurement.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining a configuration of a first aspect of the present invention.
FIG. 2 is a schematic view for explaining spectroscopy by transmitted light according to the first embodiment of the present invention.
FIG. 3 is a schematic diagram for explaining spectroscopy by reflected light according to the first embodiment of the present invention.
FIG. 4 is a schematic example of time-resolved and spectrum measurement data according to the first aspect of the present invention.
FIG. 5 is a schematic signal diagram for explaining the relationship between the probe light and the measurement light according to the first aspect of the present invention.
FIG. 6 is a schematic diagram for explaining a configuration of a second aspect of the present invention.
FIG. 7 is a schematic diagram for explaining spectroscopy of a second aspect of the present invention.
FIG. 8 is a schematic diagram for explaining a configuration of a third aspect of the present invention.
FIG. 9 is a schematic diagram for explaining spectroscopy of a third aspect of the present invention.
FIG. 10 is a diagram illustrating an example of a cylindrical lens.
[Explanation of symbols]
1 Real-time spectrometer
2 Irradiation means
2a Laser light source
2b beam splitter,
2c mirror
2d self-phase modulation means
2e Polarizing plate
2f Wavelength conversion element
2g optical delay stage
2h Cylindrical lens
2i Time delay formation means
2j condenser lens
3 Spectroscopic means
3a slit
3b Spectroscopic element
4 detection means
4a Two-dimensional detector
S sample

Claims (10)

Irradiation means for irradiating a sample with femtosecond white light probe light and / or excitation light of a specific wavelength pulsed light including a plurality of wavelengths,
A spectroscopic means for splitting the transmitted light or reflected light obtained from the sample by the irradiation in two dimensions of the time axis and wavelength axis;
Detection means for two-dimensionally detecting the two-dimensional spectrum;
Two polarizing plates arranged such that the polarization directions are perpendicular to each other with the sample interposed therebetween,
The probe light and / or excitation light has an optical delay time on the sample surface,
The spectroscopic means splits the light delay time as the time axis,
Spectral the time width of the optical delay time in real time,
A real-time spectroscopic device, wherein the time width is corrected based on a chirp amount obtained by the polarizing plate. Irradiation means for irradiating a sample with femtosecond white light probe light and / or excitation light of a specific wavelength pulsed light including a plurality of wavelengths,
A spectroscopic means for splitting the transmitted light or reflected light obtained from the sample by the irradiation in two dimensions of the time axis and wavelength axis;
Detection means for two-dimensionally detecting the two-dimensional spectrum;
A time delay forming means disposed on the excitation light path,
The probe light and / or excitation light has an optical delay time on the sample surface,
The spectroscopic means splits the light delay time as the time axis,
A real-time spectroscopic device characterized in that the time width of the optical delay time is spectroscopically analyzed in real time. Irradiation means for irradiating a sample with femtosecond white light probe light and / or excitation light of a specific wavelength pulsed light including a plurality of wavelengths,
A spectroscopic means for splitting the transmitted light or reflected light obtained from the sample by the irradiation in two dimensions of the time axis and wavelength axis;
Detection means for two-dimensionally detecting the two-dimensional spectrum;
A time delay forming means disposed on the excitation light path;
Two polarizing plates arranged such that the polarization directions are perpendicular to each other with the sample interposed therebetween,
The probe light and / or excitation light has an optical delay time on the sample surface,
The spectroscopic means splits the light delay time as the time axis,
Spectral the time width of the optical delay time in real time,
A real-time spectroscopic device, wherein the time width is corrected based on a chirp amount obtained by the polarizing plate.   The irradiation means includes a light source that generates a femtosecond laser pulse having a pulse width in units of femtoseconds, a wavelength conversion element that forms excitation light from the femtosecond laser pulses, and a plurality of wavelengths from the femtosecond laser pulses. The real-time spectroscopic device according to any one of claims 1 to 3, further comprising a self-phase modulation element that forms white probe light.   The irradiating means condenses the probe light and excitation light in a linear or strip shape on the sample surface, and lengthens either one of the probe light or the excitation light on the linear or strip condensing surface. The light beam is incident with an optical path difference in the vertical direction, and the other is incident on the linear or belt-shaped light collecting surface so that there is no optical path difference in the length direction. The real-time spectroscopic apparatus according to claim 1, wherein a time difference is formed.   The irradiation means forms the optical path difference in the length direction of the light collecting surface by making the probe light or the excitation light incident at a predetermined angle with respect to the normal direction of the light collecting surface. The real-time spectroscopic apparatus according to claim 5.   The irradiation means includes a time delay forming means for forming a time delay in the probe light, an optical system for condensing the probe light that has passed through the time delay forming means on a sample surface, and the excitation light as a sample. An optical system that collects light in a spot shape on a surface, and the spectroscopic unit includes an optical system that splits light obtained from a sample in a linear or belt-like manner on the time axis of the optical delay time. The real-time spectroscopic device according to any one of claims 1 to 3.   The irradiation means forms a time delay forming means for forming a time delay in the probe light, and forms the probe light that has passed through the time delay forming means in a linear shape or a belt shape, and irradiates it perpendicularly to the length direction of the irradiation surface. 2. An optical system, wherein the spectroscopic means includes an optical system that splits transmitted light or reflected light obtained from a sample in a linear or belt-like manner on a time axis of the optical delay time. The real-time spectroscopic device described in 1.   9. The detection unit according to claim 1, wherein the detection unit includes a two-dimensional detector, and detects a spectrum on a time axis by an arrangement in a uniaxial direction, and detects a spectrum on a wavelength axis by an arrangement in another axis direction. A real-time spectroscopic device according to any one of the above.   The said irradiation means is provided with the optical delay means which optically delays probe light and / or excitation light, and forms the time difference between excitation light and probe light, and adjusts measurement time. The real-time spectroscopic device according to any one of 1 to 9.

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