WO2003010519A1

WO2003010519A1 - Time resolution transient absorption measuring device

Info

Publication number: WO2003010519A1
Application number: PCT/JP2002/007394
Authority: WO
Inventors: Haruhisa Saitoh; Motoyuki Watanabe
Original assignee: Hamamatsu Photonics K.K.
Priority date: 2001-07-24
Filing date: 2002-07-22
Publication date: 2003-02-06
Also published as: JP2003035665A

Abstract

A first optical system (2) is connected to the harmonic component output terminal (11) of a laser light source (1) and a second optical system (3) (including a white short-pulse beam generating means (15)) to a basic wave component output terminal (12), the second optical system (3), having two optical paths (3A, 3B) branched by a half mirror (32a), applies a reference beam and a data beam in succession to a sample (40) approximately when a pump beam is applied via the first optical system to generate a streak image obtained by subjecting the fluorescent light and transmitted light of the sample (40) to wavelength resolution and time resolution by means of a spectroscope (5) and a streak camera (6), and the image is sent to a control analyzer (8) via a TV camera (7).

Description

¾ ¾Itoda »

Time-resolved transient absorption measurement device

Technical field

The present invention relates to a time-resolved transient absorption measuring device for measuring a temporal change of a transient absorption spectrum, and more particularly to a time-resolved transient absorption measuring device capable of measuring a femtosecond order transient absorption spectrum.

Background art

Time-resolved transient absorption measurement, which measures transient absorption in a very short time range, is known as a method of tracking the irreversible reaction as well as the process of generating and annihilating reaction intermediates in photochemical reactions such as solutions, solids, and thin films. As a device for performing time-resolved transient absorption measurement, a technique disclosed in Japanese Patent Publication No. 6-178686 is known.

This technique uses a probe light to irradiate a sample that has been photoexcited with pulsed light, and measures the temporal change in transmitted light intensity with a streak camera to measure the temporal change in the transient absorption spectrum. The sample light and the reference light can be measured simultaneously by dividing the probe light and guiding one to the irradiation position of the pump light and the other to the other position. The document states that the sample light and the reference light are emitted from the light source at the same time, so that the effects of the intensity of the probe light and the fluctuation of the spectrum can be eliminated. Disclosure of the invention

However, the time resolution of this device is determined by the time resolution of the streak camera, and both the pump light and the probe light are delayed using optical fibers, so the pulse width is expanded by fiber mode dispersion. And the time resolution is degraded. Also, for the probe light, the short wavelength component is measured later than the long wavelength component due to group velocity dispersion, and the time resolution is degraded. For this reason, even when a camera having a high time resolution is used as a streak camera, it has been difficult to perform measurement in units of femtoseconds to picoseconds with high accuracy. Therefore, an object of the present invention is to provide a time-resolved transient absorption measuring device capable of measuring transient absorption with high accuracy and high time resolution in a time region from femtosecond to nanosecond.

In order to solve the above-mentioned problems, a time-resolved transient absorption measuring apparatus according to the present invention comprises: a laser light source that emits pulse light including harmonics; and a white short pulse light generation that generates white short pulse light from an output pulse of the laser light source. Means, a mirror, a shutter, and a lens. A first optical system that guides the harmonic component output from the laser light source to the sample and irradiates it as pump light, and a mirror, a shutter, a lens, and a half mirror. The half-mirror splits the white short-pulse light output from the white short-pulse light generator into two optical paths with different optical path lengths, returns the same to the same optical path, combines the light with the half mirror, and guides the sample to the sample. A second optical system that sequentially irradiates the sample before and after the pump light irradiation from a direction different from the light, and an extended light of the sample in the second optical system And a streaking camera that is disposed on the top and that spectrally outputs light transmitted through the sample and emitted from the sample, and a streak camera that records a temporal change in light intensity output from the spectral means. And

With this configuration, the white single pulse is split into two by the second optical system, and the difference in the arrival time at the sample is generated according to the difference in the optical path length of the two split optical paths, and the white light is mixed with the pump light. Can be irradiated. The light that has passed through the sample before irradiation with the pump light, that is, the light that has passed through the sample after light excitation, ie, the light that has passed through the sample after light excitation, is measured as reference light. Since these two lights are obtained by dividing the same white single pulse, their components are the same, and the effect of the temporal fluctuation of the light source can be eliminated. In addition, the first optical system and the second optical system each consist only of a mirror, a shutter, a lens, and a half mirror, and do not use an optical fiber. Never happen. Since the reference light and the data light are introduced on the same optical axis and can be detected by one detector, the effect of the fluctuation of the white light position can be avoided, and the measurement accuracy can be reduced. It is possible to improve the degree. In addition, as compared with the case where the reference light and the data light are incident on different positions of the sample, the influence of the non-uniformity due to the position of the sample can be eliminated.

It is preferable that the second optical system adjusts the difference in arrival time of light guided to the sample via both optical paths by changing the optical path length of at least one of the divided optical paths. This makes it possible to freely set the time interval between the reference light and the data light.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram showing a preferred embodiment of the time-resolved transient absorption measurement device according to the present invention.

FIG. 2 is a diagram for explaining the relationship among the sample arrival time of the reference light, the pump light, and the data light in the apparatus of FIG.

FIG. 3 is a flowchart showing a measurement procedure in the apparatus of FIG.

4A and 4B are schematic diagrams each showing a streak image in the apparatus of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram showing a schematic configuration of a time-resolved transient absorption measurement device according to the present invention. For easy understanding of the explanation, the optical system is shown in a simplified state.

This apparatus 100 is a device for measuring the time-resolved transient absorption of the sample 40 placed on the sample stage 4, and includes a laser light source 1, white short pulse light generating means 15, first and second optical devices. The system consists of systems 2, 3, a sample table 4, a spectroscope 5 as a detection device, a streak camera 6, a television camera 7, a control and analysis device 8, and a monitor 9 for displaying analysis results.

The laser light source 1 is, for example, a femtosecond mode-locked pulse laser light source, and includes an output terminal 12 for outputting a fundamental wave component, and a harmonic that is a pump light for exciting the sample 40. And an output terminal 11 for outputting a component.

The first optical system 2 is configured by arranging a first shutter 21, mirrors 22, 23, and a lens 24 in order from the output terminal 11 side of the harmonic component. The sample 40 is arranged so as to be irradiated from a predetermined direction. Hereinafter, the optical path length of the first optical system 2 from the output end 11 to the sample 40 is represented by 1 ^.

In the second optical system 3, three mirrors 31a to 31c and a half mirror 32a are arranged in order from the output end 12 side of the fundamental wave component, and on one of the branched optical paths 3A, In this order, a motorized reflector reflector 33 and mirrors 34a and 34b, which are arranged so as to be movable in the direction of arrow X by combining mirrors, are arranged at a position intersecting the other optical path 3B. The half mirror 32b is placed on the surface and synthesized. A second shutter 35, a sample stage 4, a slit 36, and a lens 37 are arranged in this order on the combined optical path 3C, and a spectroscope 5 is arranged on the extension of the optical path.

The white short-pulse light generating means 15 is arranged between the mirrors 31b and 31c of the second optical system 3, and is irradiated between the lenses 15a and 15c by irradiation of the fundamental wave component of the laser light. A white short-pulse light generating material 41 b such as a nonlinear optical element for generating short-pulse light is arranged, and a filter 41 d for removing unnecessary light components is arranged at a subsequent stage. Here, the combined optical path 3C and the optical path of the first optical system are arranged so as to intersect at a predetermined angle on the sample 40. Hereinafter, the optical path length through the optical path 3 A side of the second optical science system 2 from the output terminal 1 2 up to the sample 4 0 L _2, to display the optical path length through the optical path 3 B side L _{2 2.}

The spectroscope 5 is, for example, an astigmatism correction type spectroscope that wavelength-decomposes incident light in a predetermined axial direction and outputs the light as output light. The streak camera 6 time-resolves incident light with a direction orthogonal to the wavelength resolution direction of the spectrometer as a time axis direction, and outputs an image. Then, the television camera 7 has a function of acquiring this output image and converting it into an electric signal.

The control analysis device 8 is, for example, a personal computer, the laser light source 1, 1st shutter 2 1st, 2nd shutter 35, electric retro-reflector 33, spectroscope 5, streak camera 6, TV camera 7 Has the function of performing analysis. The monitor 9 is a display device for displaying the analysis result and the like.

Here, the relationship between the optical path length of each optical _{_{path, L 2 1 1 ^> 2}} 2 and is set to be, by further moving the motorized retroreflector 3 3 in the arrow X direction, a longer optical path length It is possible to set.

FIG. 2 is a diagram showing a temporal relationship of light guided to the sample by each optical path. The light guided to the second optical system via the optical path _3B (hereinafter referred to as reference light L _Ref ), the pump light L _pump entering the sample 40 via the first optical system 1, and the light passing through the optical path 3A. FIG. 2 is a diagram illustrating the relationship between the light guided to an optical system (hereinafter, referred to as data light L _data ) and the arrival time at a sample 40.

As shown in FIG. 2, in the present apparatus 100, the light reaches the sample 40 in the order of the reference light L _Ref , the pump light L _pump , and the data light L _data , and also reaches the data light L _data . The time can be adjusted by adjusting the position of the motorized retroreflector 33. Hereinafter, the operation of the present apparatus 100, that is, the measurement of the time-resolved transient absorption characteristics of the sample 40 using the present apparatus 100 will be specifically described. FIG. 3 is a flowchart illustrating the measurement procedure, and FIGS. 4A and 4B are schematic diagrams illustrating an example of a streak image acquired in the measurement.

First, in a state where the sample 40 is not set on the sample stage 4 (if the sample 40 is a liquid or the like, only the container for holding the sample 40 is arranged), the electric retroreflector 33 is driven to drive the optical path length L. _2. Set ₁ to a predetermined optical path length (step S l).

Then, the first shutter 21 and the second shutter 35 are closed (step S2). In this state, any light emitted from the laser light source 1 reaches the sample stage 4 part, so that the streak image in the state where the laser light is not irradiated into the optical systems 2 and 3 of the apparatus 100 (Hereinafter, referred to as a dark current image) can be obtained (step S3). In this state, the streak image of the output of the spectroscope 5 by the streak camera 6 is taken into the control analysis device 8 by the television camera 7.

Next, with the first shutter 21 closed, the second shutter 35 is opened (step S4). In this state, a fundamental wave component is emitted from the output terminal 12 of the laser beam 11. This light is guided to white short pulse light generating means 15 via mirrors 31a and 31b, and is incident on white short pulse light generating substance 15b via lens 15a. The white short-pulse light-generating substance 15b emits a white light pulse with a pulse width of about 100 fmt in accordance with the incidence of the light (step S5). The emitted white light pulse is output from the white short pulse light generating means 15 via the lens 41c and the filter 41d, is split into two by the half mirror 32a via the mirror 31c, The light (reference light Lref) having passed through the optical path 3 B having a short optical path length reaches the sample stage 4 first through the half mirror 32 b and the second shutter 35. Then, the light transmitted through the sample 4 is guided to the spectroscope 5 by the slit 36 and the lens 37, wavelength-resolved, and introduced into the streak camera 6. On the other hand, the other light (data light L _data ) branched by the half mirror _32a is guided to the long optical path 3A, and the motorized retroreflector 33, the mirrors 34a and 34b are after it enters the half mirror 3 2 b, reaching the sample stage 4 portions at a Reference light L _ref reaches after a predetermined time difference through the second shutter 35. Then, the light transmitted through the sample 4 is guided to the spectroscope 5 by the slit 36 and the lens 37, wavelength-resolved, and introduced into the streak camera 6.

The streak camera 6 time-resolves the wavelength-resolved light corresponding to the introduced reference light L _ref and data light L _data to output a strike image as shown in FIG. 4A. . The output image is sent by the television camera 7 to the control analysis device 8 (step S6).

The sensitivity correction data at each wavelength (or wave number) position is calculated from the streak image corresponding to the reference light Lref and the data light L _data thus obtained and the previously obtained dark current image (step S7). Next, the sample 40 is placed on the sample stage 4 (step S8), and the first shutter 21 is opened (step S9). As a result, both shutters 21 and 35 are opened. In this state, by outputting the harmonic component and the fundamental component of the laser light from the output terminals 11 and 12 of the laser light source 1, respectively, the sample is irradiated with the harmonic component and the white light pulse one after another ( Step S10).

To Sample 4 0, the reference light L _Re f having passed through the optical path 3 B of the second optical system 3 shines first input, the first pump light Lp _Ump passing through the optical system 2 is incident from a different direction thereafter, Finally, the data light L _data having passed through the optical path 3 A of the second optical system 3 enters. Then, the light emitted from the sample 40 and the light transmitted through the sample 40 in the meantime are wavelength-resolved by the spectroscope 5 and time-resolved by the streak camera 6, as shown in FIG. 4B. The image is captured as a streak image by the television camera 6 and sent to the control analysis device 8 (step S11).

The control analyzer calculates the transient absorption change of the sample 40 based on the acquired streak image data (step S12), and displays the result on the monitor 9 (step S13). The measurement result may be printed using a printer.

In the present apparatus 100, by using the streak camera 6, the time position can be confirmed in the obtained streak image data, so that the measurement can be performed with high accuracy. In addition, measurements with good time resolution can be performed from the femtosecond to the nanosecond level.

In addition, although the spectrum and intensity of the laser light source 1 can vary for each pulse, the present apparatus 100 uses the same pulse as the reference light and the data light, and further provides a time difference at the same position on the sample 40. In this case, the influence of light position intensity fluctuations and position fluctuations can be eliminated, and more accurate measurement can be performed.

Furthermore, since the measurement system (spectrometer 5, streak camera 6, TV camera 7) can be configured as a single unit, the adjustment is easy, and unlike the case where reference light and data light are measured by separate measurement devices, It is possible to completely eliminate fluctuations in measurement ability due to instruments. Measurement can be performed with high accuracy.

Then, the second optical system 3 is configured by a mirror / half mirror without using an optical member such as an optical fiber which may be accompanied by pulse width deformation, and by providing an optical path length difference, the pulse of the reference light and the data light is provided. The width can be maintained at an extremely short pulse width, preventing its deformation and enabling measurement with a high time resolution of femtosecond level. Further, by making one optical path length of the second optical system 3 variable, the time change of transient absorption can be efficiently measured by one device.

In the above description, an example in which white short-pulse light is generated from a fundamental wave component of laser light has been described. However, white short-pulse light may be generated from a harmonic component. Further, the arrangement of the white short-pulse light generating means 15 is not limited to the arrangement shown in FIG. 1, and may be arranged at any position on the laser light source 1 side from the optical path branching position in the second optical system. .

Industrial applicability

The time-resolved transient absorption measurement device according to the present invention can measure the resolved transient absorption characteristics with high accuracy and high time resolution in a time range from femtosecond to nanosecond, and can be used for biological, scientific, physical, and physical properties. It can be widely applied as a measurement device in basic science fields such as.

Claims

The scope of the claims

1. A laser light source that emits pulsed light including harmonics,

White short pulse light generating means for generating white short pulse light from an output pulse of the laser light source,

A first optical system that includes a mirror, a shutter, and a lens, guides a harmonic component output from the laser light source to the sample, and irradiates the sample with pump light;

It is composed of a mirror, a shutter, a lens, and a half mirror. The white short pulse light output from the white short pulse light generating means has a different optical path length by the half mirror.

After splitting into two optical paths, returning to the same optical path, combining by a half mirror, and guiding to the sample, the sample is successively irradiated before and after irradiation of the pump light from a direction different from the pump light. A second optical system,

Spectroscopic means disposed on an extended optical axis of the sample of the second optical system, for spectrally outputting light transmitted through the sample and emitted from the sample,

A streak camera that records a temporal change in the light intensity output from the spectroscopic means,

A time-resolved transient absorption measurement device comprising:

2. The second optical system adjusts a difference in arrival time of light guided to the sample via both optical paths by changing an optical path length of at least one of the divided optical paths. 1. The time-resolved transient absorption measurement device according to 1.