JP2006242615A - Pump-probe photometric device and photometric method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pump-probe photometric device and photometric method that can irradiate pump light and probe light to a photosensitive material, accurately measure the time development of a non-linear component of the response signal, and display a waveform on a display. <P>SOLUTION: The pump-probe photometric device comprises a laser beam generating device 11 for generating a laser pulse, a light-splitting device 12 for dividing the laser pulse into pump light and probe light of femto-second order, a light-sweeping device 13 for periodically making one of the optical path of the pump light and the optical path of the probe light shorter or longer than the other, a irradiating device 14 for irradiating the pump light and the probe light to a sample, a response light-receiving device 15 for receiving a response light from the sample of the light irradiated to the sample and generating the detected signals of a plurality of channels, a direct-current component cut device 16 for cutting the direct-current component of the detected signals of the plurality of channels, and a response signal display device 17 for A/D-converting the detected signals of the plurality of channels, of which direct-current components have been removed, and displaying the waveform. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a time-resolved spectroscopic measurement technique, and specifically irradiates a photosensitive material with pump light and probe light, accurately measures the time evolution of a nonlinear component of the response signal, and displays a waveform on a display. The present invention relates to a pump-probe photometry device and a photometry method.

  Conventionally, a photometric technique using pump light and probe light is known in order to detect a photochemical reaction (optical response) of a substance.

  For example, in the pump-probe photometric device 9 shown in FIG. 6, the laser pulse LP generated by the laser generator 91 is separated into the pump light p1 and the femtosecond order probe light p2 by the splitter 92.

  In FIG. 6, the optical path length L1 of the pump light p1 can be changed by the delay device 93, and the sample 100 is irradiated with the pump light p1 and the probe light p2 at different peak timings. A part of the probe light p <b> 2 is incident on the correction light detection device 95 by the splitter 94.

  The response light (transmitted light) of the combined light (indicated by reference sign p3) applied to the sample 100 is detected by the light detection device 96. The light detection device 96 can detect the response light in multiple channels (that is, detect different frequency components). Specifically, the response light is amplified by a lock-in amplifier, and step scan detection is performed by a plurality of photosensors PD (not shown). The detection signal from the light detection device 96 is corrected by the correction light detection device 95, digitized by the AD converter 97, and stored in the data storage device 98 as detection data.

  By the way, in the pump-probe photometry device 9 of FIG. 6, since the time required for step scan detection and one step is about several seconds, it takes time to integrate. Therefore, the entire waveform cannot be measured accurately unless long-term stability of the laser generator is guaranteed. In addition, the correction photodetection device 95 can cancel the DC component, but there is a problem that processing of the detection data becomes complicated.

  An object of the present invention is to provide a pump-probe photometry device and photometry capable of irradiating a photosensitive material with pump light and probe light, accurately measuring the time evolution of the nonlinear component of the response signal, and displaying the waveform on a display. It is to provide a method.

The pump-probe photometry device of the present invention is
A laser beam generator for generating a laser pulse;
A light separation device for separating the laser pulse into pump light and probe light on the order of femtoseconds;
A light sweeping device that periodically shortens and extends one of the optical path of the pump light and the optical path of the probe light with respect to the other;
A response light receiving device that receives the response light from the sample of the pump light and the probe light irradiated on the sample and generates a detection signal of a plurality of channels;
A DC component cut device for cutting the DC component of the detection signals of the plurality of channels;
A response signal display device that AD-converts the detection signals of the plurality of channels from which the DC component has been removed and displays a waveform;
It is provided with.

  In addition, in this invention, the irradiation apparatus which irradiates a sample with the said pump light and the said probe light can also be provided suitably.

The pump-probe photometry method of the present invention comprises:
An optical separation step for separating the laser pulse into pump light and femtosecond order probe light;
A light sweeping step of periodically shortening and extending one of the optical path of the pump light and the optical path of the probe light with respect to the other;
An irradiation step of irradiating the sample with the pump light and the probe light;
A response light receiving step of receiving response light from the sample of the light irradiated on the sample and generating a detection signal of a plurality of channels;
A DC component cutting step for cutting a DC component of the detection signals of the plurality of channels;
A response signal display step of AD-converting the detection signals of the plurality of channels from which the DC component has been removed and displaying a waveform;
It is characterized by having.

  In the present invention, the light sweep is performed to periodically shorten and extend one of the optical path of the pump light and the optical path of the probe light, and the direct current component of the detection signals of a plurality of channels is cut. The nonlinear component of (sample) can be selectively detected. In addition, since continuous sweeping is possible, the waveform can be displayed on a display such as an oscilloscope.

FIG. 1 is a block diagram showing an embodiment of the pump-probe photometric device of the present invention.
In FIG. 1, a pump-probe photometric device 1 includes a laser light generator 11, a light separation device 12, a light sweep device 13, a multiplexing device 14, a combined light irradiation device 15, and a sample response light receiving device 16. A high-pass filter 17 and a response signal display device 18.

  The laser beam generator 11 generates a laser pulse LP. The laser beam generator 11 generates a laser pulse LP having an energy of 310 pJ / pulse, a repetition frequency of 3.78 MHz, and a half width of 20 fs.

The light separation device 12 is a beam splitter BS, and separates the laser pulse LP into pump light p1 and probe light p2 (femtosecond order).
Of the light separated by the light separation device 12, the pump light p <b> 1 is reflected by the first pump light reflection mirror M <b> 11 and enters the light sweep device 13. The light incident on the light sweep device 13 is reflected by the second pump light reflecting mirror M12 and the third pump light reflecting mirror M13.
The reflected light of the third pump light reflecting mirror M13 (that is, the outgoing light of the light sweep device 13) is reflected by the fourth pump light reflecting mirror M14 and is incident on the multiplexing device 14.

On the other hand, the probe light p <b> 2 out of the light separated by the light separation device 12 is reflected by the first probe light reflection mirror M <b> 21, the second probe light reflection mirror M <b> 22, and the third probe light reflection mirror M <b> 23 to the multiplexing device 14. Incident.
The optical path length L2 of the probe light p2 (in this embodiment, the optical path length is defined as the distance from the beam splitter BS to the sample 100 described later) so as to be substantially the same as the optical path length L1 of the pump light p1. It has been adjusted.

  As described above, the light sweep device 13 has the second pump light reflection mirror M12 and the third pump light reflection mirror M13, which are arranged at 90 ° and reciprocate at a predetermined cycle by the movable stage 131. It is configured. In the present embodiment, the movable stage 131 reciprocates to periodically shorten and extend the optical path L1 of the pump light p1 with respect to the optical path L2 of the probe light p2. The reciprocating period of the movable stage 131 is on the order of 20 Hz to several kHz (in this embodiment, 20 Hz). A drive signal for the movable stage 131 (reciprocating synchronization signal) is output to a response signal display device 18 to be described later.

The multiplexing device 14 includes a mirror M31, and combines the pump light p1 and the probe light p2 (the combined light is indicated by a symbol p3).
The combined light irradiation device 15 includes a condensing mirror M32 and irradiates the sample 100 with the combined light p3. The combined light p3 irradiated on the sample 100 passes through the sample 100 and enters the sample response light receiving device 16 via the slit member SLT.

  In this embodiment, the sample response light receiving device 16 is a monochromator, receives response light (transmitted light) p4 from the sample 100, and generates response signals of channels corresponding to a plurality of frequencies. That is, the sample response light receiving device 16 includes a photosensor PD (photosensitive element) corresponding to the number of channels, and can detect light intensity for a plurality of channels. In this embodiment, the number of channels is 16. The sample response light receiving device 16 transmits the light intensity output signal of each photosensor PD to the high-pass filter 17.

The high-pass filter 17 is a DC cut filter amplifier, which receives detection signals for a plurality of channels, removes the DC component DC from this signal, amplifies it, and outputs it.
The response signal display device 18 is a digital oscilloscope, and AD-converts the response signals of a plurality of channels from which the DC component DC has been removed and displays the waveform on the display. As described above, the response signal display device 18 receives the drive signal (reciprocating timing signal) from the optical sweep device 13 and can output a waveform corresponding to the sweep operation of the optical sweep device 13.

Hereinafter, a specific operation example of the pump-probe photometry device 1 will be described with reference to the flowchart of FIG. First, the laser beam LP is separated into the pump light p1 and the probe light p2 by the light separation device 12 (light separation step: S101), and the optical path L1 of the pump light p1 is made to the optical path L2 of the probe light p2 by the light sweep device 13. Are periodically shortened and extended (light sweep step: S102). FIG. 3 illustrates the timing of the pump light p1 and the probe light p2.
4A and 4B are diagrams showing two frequency components EP21 and EP22 of the probe light p2. Each figure shows a phase shift of each frequency component when the optical path L1 of the pump light p1 is periodically shortened and extended with respect to the optical path L2 of the probe light p2. 4A shows a state in which one of the two frequency components EP21 and EP22 of the probe light p2 is slightly advanced, and FIG. 4B shows the state of the two frequency components EP21 and EP22 of the probe light p2. It shows the same state.

  The multiplexing device 14 combines the pump light p1 and the probe light p2 (combining step: S103), and the combined light irradiation device 15 irradiates the sample 100 with the combined light p3 (combined light irradiation step S104). This is to detect the optical response (time evolution of the non-linear component (time change)) when the sample 100 is irradiated with the pump light p1 and the frequency component of the probe light p2 is irradiated while changing the phase difference. means.

  An example of the change state of the sample 100 at this time is shown in FIGS. Here, the sample 100 is a cyanine organic dye molecule (DTTCI), and shows a probability distribution of electrons confined in the potential well. As the sample 100 is irradiated with the pump light p1 and the phase changes, as shown in FIGS. 5A and 5B, torsional vibration occurs in the cyanine organic dye molecules.

The optical response of the sample 100 can be detected by irradiating the probe light p2 almost simultaneously with the irradiation of the pump light p1 (before the torsional vibration is attenuated).
The direction of twisting changes according to the probability distribution of intramolecular electrons. By irradiating the sample 100 with the frequency component of the probe light p2 before the influence of the irradiation with the pump light p1 disappears, the response light depending on the magnitude and direction of the twist is received by the sample response light receiving device 16.

  The sample response light receiving device 16 receives the response light of the combined light p3 irradiated on the sample 100 and generates a response signal of a plurality of channels (sample response light receiving step: S105). Each of these channels is a response signal extracted for a component having a different phase, and is sent to the DC component removing device 17.

  The DC component removing device 17 removes the DC components of the response signals of a plurality of channels (DC component removing step S106). Of the frequency components, the DC component has a strong influence on the detection of the linear component for the material 100. By removing the DC component, only the response of the nonlinear component can be extracted, and the response signal of the nonlinear component is sent to the response signal display device 18. An example of this response signal is shown in FIG.

  The response signal display device 18 performs AD conversion on the response signals of the plurality of channels from which the DC component has been removed, and displays the waveform (response signal display step S107).

It is a block diagram which shows one Embodiment of the pump-probe photometry apparatus of this invention. It is a flowchart which shows the specific operation example of a pump-probe photometry apparatus. It is a figure which shows the timing of pump light and probe light. It is a figure which shows two frequency components of probe light, (A) shows the state in which one phase of two frequency components of probe light has advanced a little, (B) shows the phase of two frequency components of probe light. Indicates the same state. (A), (B) is a figure which shows a mode that the molecule | numerator twisted as the establishment distribution and phase of the electron by which the electron of the cyanine organic pigment | dye molecule | numerator (DTTCI) was confined in the potential well changed. It is a block diagram which shows the conventional pump-probe photometry apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump-probe photometry apparatus 11 Laser light generator 12 Light separation apparatus 13 Optical sweep apparatus 14 Multiplexing apparatus 15 Combined light irradiation apparatus 16 Sample response light receiving apparatus 17 High pass filter 18 Response signal display apparatus p1 Pump light p2 Probe light M11 1st 1 pump light reflecting mirror M12 second pump light reflecting mirror M13 third pump light reflecting mirror M14 fourth pump light reflecting mirror M21 first probe light reflecting mirror M22 second probe light reflecting mirror M23 third probe light reflecting mirror M31 mirror M32 Condensing mirror BS Beam splitter 100 Sample L1 Optical path of pump light L2 Optical path of probe light

Claims (2)

A laser beam generator for generating a laser pulse;
A light separation device for separating the laser pulse into pump light and probe light on the order of femtoseconds;
A light sweeping device that periodically shortens and extends one of the optical path of the pump light and the optical path of the probe light with respect to the other;
A response light receiving device that receives the response light from the sample of the pump light and the probe light irradiated on the sample and generates a detection signal of a plurality of channels;
A DC component cut device for cutting the DC component of the detection signals of the plurality of channels;
A response signal display device that AD-converts the detection signals of the plurality of channels from which the DC component has been removed and displays a waveform;
A pump-probe photometric device comprising: An optical separation step for separating the laser pulse into pump light and femtosecond order probe light;
A light sweeping step of periodically shortening and extending one of the optical path of the pump light and the optical path of the probe light with respect to the other;
Irradiating the sample with the pump light and the probe light; and
A response light receiving step of receiving response light from the sample of the light irradiated on the sample and generating a detection signal of a plurality of channels;
A DC component cutting step for cutting a DC component of the detection signals of the plurality of channels;
A response signal display step of AD-converting the detection signals of the plurality of channels from which the DC component has been removed and displaying a waveform;
A pump-probe photometry method characterized by comprising:

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