JPH04278441A - Method for measuring absorption quantity of light - Google Patents

Abstract

PURPOSE:To detect the minute change in the absorption quantity of light to the light incident simultaneously with detection light with high efficiency. CONSTITUTION:A quartz glass pipe 1 with an inner diameter of about 0.3mm is filled with a solution sample S having a refractive index higher than that of said pipe 1 and the light propagating through the solution sample S is totally reflected even at the interface with the quartz glass pipe 1 and propagated from the incident end of the pipe 1 to the emitting end thereof without receiving any loss other than the absorption of light due to the solution sample S to allow a plurality of light axes to perfectly coincide and the transitional absorption quantity being the minute absorption quantity of light is made possible to measure. The mutual acting regions of two different lights are allowed to perfectly coincide by an easy optical adjusting method and this method is optimum to an optical apparatus using a femto-sec region requiring strict optical adjustment up to about 10mum.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention exhibits responsiveness to the incidence of pulsed light, which is second light having a time width of picoseconds, femtoseconds, or shorter, and which exhibits responsiveness to the incidence of pulsed light with respect to the first incident light. This invention relates to improvements in methods for measuring changes in quantity.

0002

[Prior Art] In the measurement of steady-state light absorption in a solution sample, a quartz glass cell with an optical distance of 10 mm is used.
Further, in the case of a dilute solution sample, a quartz glass cell having a length of about 100 mm is used, but in any case, the measurement is often performed by making multiple reflections within the cell and increasing the optical distance. In the measurement of the amount of steady light absorption, since the measurement is performed using a single light beam, there is no practical problem with the above method, but in the measurement of the amount of transient light absorption,
It is necessary to set the amount of light absorption for white light for spectrum measurement in an appropriate range (absorption coefficient: 0.1 to 2.0) and to increase the change in the amount of light absorption due to excitation light. To achieve this, two types of optical arrangements have been devised, called transverse excitation and longitudinal excitation, respectively.

For lateral excitation, as shown in FIG. 4, a solution sample S is filled in a double-sided transparent quartz cell 8, which serves as a container for holding the solution sample and has flat, transparent optical windows on four sides. In FIG. 4, 11A is the first light emitted from the first light source 11, which is focused by a spherical lens 5 with a focal length of 150 mm, for example, arranged so as to be confocal with respect to the double-sided transparent quartz cell 8. be illuminated. 6 is a spherical lens that converges the first incident light 11B that enters the photodetector 13. 12 is a second light source that emits second light 12A. A cylindrical lens pair 9 is composed of a cylindrical convex lens 9a and a cylindrical concave lens 9b, and magnifies the second light 12A in the optical axis direction of the first light 11A or reduces it in a direction perpendicular to the first light 11A. As shown in FIG. 4, the first light 11A whose amount of light absorption is to be measured is optically excited from a direction perpendicular to the first light 11A. At this time, in order to increase the interaction distance for the first light 11A, as shown in the plan view and side view of FIGS. 5(a) and 5(b), the pulsed light that is the second light 12A is The first light 11A expands to the optical path length of the double-sided transparent quartz cell 8 in the optical axis direction (FIG. 5(a)), and decreases to the beam diameter of the first light 11A in the direction perpendicular to this (FIG. 5(a)). 5(b)). Therefore, due to constraints on the optical system of the second light 12A, the optical path length for measuring the amount of light absorption is limited to about 10 mm.

On the other hand, vertical excitation, as shown in FIG.
First light 11A and second light 12A for measuring the amount of light absorption
After aligning the optical axis with the pulsed light, the solution sample S
The light is incident on a single-sided transparent quartz cell 10 that is a flat container that holds the light and has optical windows on two transparent sides.Measurements can be made using the single-sided transparent quartz cell 10, and the amount of light absorbed can be measured. Although there is no limit to the optical path length, the practical limit is more than 10 cm due to restrictions on optical axis adjustment. In addition, 6a
is a spherical lens, and 7 is a semi-transparent mirror or a minute rectangular prism.

In addition, in the multiphoton absorption spectrum measurement method, which is the same type of measurement as transient light absorption measurement, the fluorescence detection excitation spectrometry method has the highest sensitivity for compounds that emit fluorescence; however, for compounds that emit fluorescence, It takes a considerable amount of time to tune the wavelength of the laser beam that is the excitation light source, and the measurement wavelength becomes discrete, making it impossible to obtain a continuous spectrum.

[0006]

As described above, in the conventional steady light absorption measurement for a solution sample S, the optical path length for measuring the amount of light absorption is limited to about 10 mm in the transverse excitation method. Further, even in the longitudinal excitation method, the limit is about 10-odd cm, which is not satisfactory. Furthermore, the multiphoton absorption spectrum measurement method, which is the same type of measurement as the transient light absorption amount measurement, has the disadvantage that the solution sample S is limited to compounds that emit fluorescence.

The purpose of the present invention is to eliminate these drawbacks, and in principle, in the longitudinal excitation method, which has no limitation on the optical path length, the first light and the second light for measuring the amount of light absorption are used. The aim is to automatically and completely match pulsed light within a cell, and to provide an optimal light absorption measurement method for measuring light absorption up to the femtosecond region.

[0008]

[Means for Solving the Problems] The method for measuring the amount of light absorption according to the present invention is to completely match the interaction region of the detected light from the substance to be measured and the pulsed light which is the second light, and to In order to efficiently detect minute changes in light absorption due to light, the interaction distance is made sufficiently long for measurement.

[0009]

[Operation] According to the present invention, a quartz glass tube with an inner diameter of 0.3 to 0.5 mm is filled with a solution sample having a higher refractive index than the quartz glass tube, and light propagating through the solution sample is caused to interact with the quartz glass tube. Due to total reflection at the interface, the two optical axes are perfectly aligned by propagating from the input end to the output end without suffering any loss other than light absorption by the solution sample, and transient light with a small amount of light absorption is generated. Make it possible to measure absorption amount, etc.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an apparatus for carrying out the present invention. In Fig. 1, the same reference numerals as in Figs. 4, 5, and 6 indicate the same parts, and 1 is formed with an inner diameter of 0.3 mm and a length of 2 m with the end face as perpendicular to the optical axis as possible. A quartz glass tube with optically flat surfaces at both ends,
A sample reservoir 2 having a smooth optical window 3 is installed. The distance between the optical window 3 and the end face of the silica glass tube 1 is set to a minimum value of 2 mm due to the numerical aperture (0.12) of the condensing optical system coupled thereto. The sample container 4 for holding the solution sample S is configured as described above. The sample volume at this time was 1 ml. The refractive index of the quartz glass tube 1 is n(58
9.3nm)=1.458, (n(1.06μm)=1
．． 449), and the refractive index of benzene used as a solvent is n (589.3 nm) = 1.4979, which satisfies the light transmission conditions for an optical fiber. At this time, the concentration of naphthalene, which is a solute, is 3.4 x 10-4 mo
Since it is dilute (1/l) and its contribution to the refractive index is small, it can be ignored. The absorption spectrum when transmitting white light was consistent with measurements using a conventional 10 mm cell.

Next, in addition to white light, a wavelength of 1 is used as excitation light.
．． FIG. 2 shows the spectrum when a laser beam of 0.06 μm is passed through. This shows that a continuous spectrum was obtained and the wavelength resolution was much better than the measurement results using fluorescence detection excitation spectroscopy (Fig. 3), demonstrating the usefulness of measuring minute light absorption using this method.

[0012] The method for measuring the amount of light absorption according to the present invention is not limited to the above-mentioned embodiments. For example, instead of the quartz glass tube 1, it is also possible to use other optical glasses or polymer tubes with a low refractive index.

[0013]

Effects of the Invention The light absorption measurement method of the present invention allows the interaction region of the detected light from the substance to be measured and the pulsed light, which is the second light, to completely match, and also allows the detection light from the pulsed light to In order to efficiently detect changes in absorption, the interaction distance is made sufficiently long for measurement, making it suitable for perfectly matching the interaction regions of two different lights using a simple optical adjustment method. As mentioned above, it is particularly suitable as an optical device for use in the femtosecond region, which requires precise optical adjustment down to about 10 microns.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of a measuring device for implementing the light absorption amount measuring method of the present invention.

FIG. 2 is a simultaneous two-photon absorption spectrum diagram of naphthalene.

FIG. 3 is a fluorescence-detected two-photon absorption spectrum diagram of naphthalene.

FIG. 4 is a configuration diagram of a measuring device for explaining a conventional method for measuring light absorption using lateral excitation.

5 is a diagram for explaining the action of the cylindrical lens pair in FIG. 4. FIG.

FIG. 6 is a configuration diagram of a measuring device for explaining a conventional method for measuring light absorption using longitudinal excitation.

[Explanation of symbols]

1 Quartz glass tube 2 Sample reservoir 3 Optical window 4 Sample container 5 Spherical lens 6 Spherical lens 7 Semi-transparent mirror or minute right angle prism 8
Double-sided transparent quartz cell 9 Cylindrical lens pair 10 Single-sided transparent quartz cell 11 First light source 12 Second light source 13 Photodetector 11A First light 11B First incident light 12A Second light S Solution sample

Claims (1)

[Claims] 1. Shows responsiveness to the incidence of first light for measuring the amount of light absorption and pulsed light that is second light having a time width of picoseconds, femtoseconds or shorter,
In a method for measuring the amount of light absorption of a substance to be measured that interacts with incident light, the interaction region of the detection light from the substance to be measured and the pulsed light that is the second light is made to completely match, and A method for measuring light absorption amount, characterized in that measurement is performed with a sufficiently long interaction distance in order to efficiently detect minute changes in light absorption amount due to pulsed light.