JP2009192544A - Spectroscopic apparatus and total reflection raman spectrum system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the diameter of a beam and obtain high S/N ratio spectra. <P>SOLUTION: A spectroscopic apparatus includes a light source; an optical fiber (x) for guiding light emergent from the light source; a total reflecting prism for irradiating light emergent from the optical fiber (x) as oozing light to a sample on a total reflection surface; a spectroscopic means for acquiring a spectrum of Raman scatting components of scattering light of light irradiated to the sample; an object lens (w) for collecting light emergent from the light source and making it incident on to an incident end of the optical fiber (x); and an object lens (y) for collecting light emergent from an emergent end of the optical fiber (x) and turning it toward the total reflecting prism. A numerical aperture NAw of the object lens (w); a numerical aperture NAy of the object lens (y); a numerical aperture NAxin of the incident end of the optical fiber (x); and a numerical aperture NAxout of its emergent end have the relation NAw>NAxin and NAxout>NAy or the relation NAw>NAxin, NAxout>NAy, and NAw=NAy. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a spectroscopic device and a total reflection Raman spectroscopic device, and in particular, to a spectroscopic device and a total reflection Raman spectroscopic device using optical elements having different numerical apertures.

First, the NA (numerical aperture) and F value of the optical element are defined. The condensing device is defined as an optical element that changes the size of the beam, such as an objective lens, a convex lens, or a concave mirror, and the optical waveguide device is defined as an optical element that propagates light to another place. FIG. 1 schematically shows a state in which light passes through an objective lens, a convex lens, and an optical waveguide device, which are condensing devices, and the traveling direction of the light changes. The traveling direction of light after passing through each optical element is determined by the angle p shown in FIG. When light travels in the direction opposite to that in FIG. 1, the angle p is the maximum allowable light reception angle of the optical element. The angle p is an angle formed by the optical axis direction and the light traveling direction, and corresponds to an incident angle or an outgoing angle to the incident end face or the outgoing end face of the optical element. Here, the NA (numerical aperture) of the objective lens and the optical waveguide device is defined as NA = sin (p), and the F value of the convex lens is defined as F = f / D (f: focal length, D: diameter). There is a relationship of F = 1/2 tan (p) = (1- (NA) ² ) ^1/2 / 2 (NA) between NA and F value, especially when angle p is sufficiently small, F = 1 / 2 (NA).

  When the light passing through the objective lens is narrowed at a steep angle and the angle p takes a large value, the NA also takes a large value. When the light passing through the core of the optical waveguide device expands at a steep angle and the angle p takes a large value, the NA also takes a large value. Therefore, light is emitted or incident at a steep angle on a high NA objective lens and a high NA optical waveguide device. When the light passing through the convex lens is narrowed at a steep angle and the angle p takes a large value, the focal length f needs to be a small value and the F value becomes small. Therefore, light exits or enters the convex lens having a small F value at a steep angle.

  Optical elements such as an objective lens, an optical waveguide device, and a convex lens are usually connected so as not to lose as much light as possible. For this purpose, according to the description of Non-Patent Document 1, when the lens w, the optical fiber x, and the lens y are connected and light advances in this order, it is necessary to satisfy NAw <NAx <NAy. Therefore, when the numerical aperture NAxin at the incident end and the numerical aperture NAxout at the outgoing end are different in the optical waveguide device x, it is necessary to satisfy NAw <NAxin and NAxout <NAy.

  As a method for evaluating the molecular structure of the film surface, as described in Non-Patent Document 2, a total reflection Raman spectroscopic device using an optical fiber and an objective lens has been proposed. Non-Patent Document 2 does not describe the types of the optical fiber and the objective lens.

Toshiaki Sugawara, Lightwave Engineering, Corona, 1998, p.128. Megumi Maekawa, Masanobu Yoshikawa, Gen Katagiri, Hideyuki Ishida, Ryosuke Shimizu, BUNSEKI KAGAKU, 40, T203 (1991).

  In the total reflection Raman spectroscopic apparatus described in Non-Patent Document 2, when an optical fiber and an objective lens are selected according to the description in Non-Patent Document 1, it becomes difficult to narrow the beam diameter as described later, and a total reflection Raman having a low S / N ratio is obtained. There was a problem that only the spectrum could be acquired.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a spectroscopic device and a total reflection Raman spectroscopic device capable of narrowing the beam diameter and acquiring a spectrum with a high S / N ratio. It is to provide.

  In order to solve the above-described problems, a spectroscopic device according to the present invention condenses an optical waveguide device x whose NA (numerical aperture) at the output end is NAxout, and light emitted from the output end of the optical waveguide device. , NA (numerical aperture) NAy, and a light collecting device y, and NAxout> NAy.

Further, the spectroscopic device according to the present invention condenses light, NA (numerical aperture) is a condensing device w NAw, and the light collected by the condensing device w is incident from the incident end, NA (numerical aperture) at the entrance end is NAxin, NA (numerical aperture) at the exit end is NAxout, and the light emitted from the exit end of the optical waveguide device is collected (NA ( NAg> NAxin and NAxout> NAy
It is characterized by being.

  The total reflection Raman spectroscopic device according to the present invention collects light, an objective lens w having NA (numerical aperture) NAw, and light collected by the objective lens w is incident from an incident end. An optical fiber x with NA (numerical aperture) at the end is NAxin and NA (numerical aperture) at the output end is NAxout, and the light emitted from the output end of the optical fiber is condensed. NA (numerical aperture) is NAy An objective lens y, and NAw> NAxin and NAxout> NAy.

  In the total reflection Raman spectroscopic apparatus, the excitation light is preferably visible light (wavelength: 400 nm to 680 nm).

  Further, the spectroscopic device according to the present invention condenses the light, NA (numerical aperture) NAw NA, and the light collected by the light collecting device w is incident from the incident end, NA (numerical aperture) at the entrance end is NAxin, NA (numerical aperture) at the exit end is NAxout, and the light emitted from the exit end of the optical waveguide device is collected (NA ( And NAw <NAxin, NAxout> NAy, and NAw = NAy.

  Further, the total reflection Raman spectroscopic device according to the present invention condenses light, an objective lens w having NA (numerical aperture) NAw, and light collected by the objective lens w is incident from an incident end. , NA (numerical aperture) at the entrance end is NAxin, NA (numerical aperture) at the exit end is NAxout, and the light emitted from the exit end of the optical fiber is condensed, NA (numerical aperture) is NAy The objective lens y is NAw <NAxin, NAxout> NAy, and NAw = NAy.

  In the total reflection Raman spectroscopic apparatus, the excitation light is preferably visible light (wavelength: 400 nm to 680 nm).

  In the total reflection Raman spectroscopic apparatus, the excitation light is preferably near infrared light (wavelength 700 nm to 850 nm).

  Furthermore, the total reflection Raman spectroscopic device according to the present invention comprises a light source, a light guide means x for guiding the light emitted from the light source, and the light emitted from the light guide means x as a sample on the total reflection surface. In the total reflection Raman spectroscopic apparatus, comprising: a total reflection prism that irradiates as a protruding light; and a spectroscopic unit that splits a Raman scattering component of the scattered light of the light irradiated on the sample in the total reflection prism. A lens w that condenses the emitted light and enters the incident end of the light guide means x, and a lens y that condenses the light emitted from the exit end of the light guide means x and directs it to the total reflection prism Between the numerical aperture NAw of the lens w, the numerical aperture NAy of the lens y, the numerical aperture NAxin at the entrance end of the light guide means x, and the numerical aperture NAxout at the exit end, “NAw> NAxin and NAxout > NAy ”or“ NAw <NAxin, NAxout> NAy and NA It is characterized by the relationship “w = NAy”.

  In the total reflection Raman spectroscopic apparatus, the light guide means x is preferably an optical fiber.

  In the total reflection Raman spectroscopic apparatus, it is preferable that the excitation light emitted from the light source is visible light (wavelength: 400 nm to 680 nm).

  In the total reflection Raman spectroscopic device, the excitation light emitted from the light source is preferably near infrared light (wavelength 700 nm to 850 nm).

  If the total reflection Raman spectroscopic device of the present invention is used, the beam diameter of the excitation light can be narrowed and a spectrum can be acquired with a high S / N ratio.

  Further, the total reflection optical system in the total reflection Raman spectroscopic device of the present invention is a case where an objective lens and an optical fiber are used in a total reflection fluorescence spectroscopic device (Japanese Patent Laid-Open No. 4-337447) and a nonlinear Raman spectroscopic device (Japanese Patent Laid-Open No. 10-115573). If it is also used, the generation efficiency of weak signals can be increased by narrowing the beam diameter.

It is a schematic diagram showing a mode that the light passes through the inside of the optical element placed in the air. It is a schematic diagram of the total reflection optical system in the total reflection Raman spectroscopy apparatus used for implementation of this invention. FIG. 4 is a diagram showing a beam image on the prism bottom surface of Example 1. In Example 1, it is the figure which showed the Raman spectrum of the polystyrene / polyvinyl methyl ether laminated film when visible light incident angle is 70 degrees. FIG. 6 is a diagram showing a beam image on the prism bottom surface of Example 2. In Example 2, it is the figure which showed the Raman spectrum of the polystyrene / polyvinyl methyl ether laminated film when visible light incident angle is 70 degrees. In Example 2, it is the figure which showed the Raman spectrum of the polystyrene / polyvinyl methyl ether laminated film with respect to each incident angle of visible light. In Example 2, it is the figure which showed the Raman intensity | strength of the polystyrene / polyvinyl methyl ether laminated film with respect to each incident angle of visible light. In Example 3, it is the figure which showed the Raman spectrum of the polystyrene / polyvinyl methyl ether laminated film with respect to each incident angle of near-infrared light. In Example 3, it is the figure which showed the Raman intensity | strength of the polystyrene / polyvinyl methyl ether laminated film with respect to each incident angle of near-infrared light. 10 is a diagram showing a beam image on the prism bottom surface of Comparative Example 1. FIG. In the comparative example 1, it is the figure which showed the Raman spectrum of the polystyrene / polyvinyl methyl ether laminated film when visible light incident angle is 70 degrees. 10 is a diagram showing a beam image on the prism bottom surface of Comparative Example 2. FIG. In the comparative example 2, it is the figure which showed the Raman spectrum of the polystyrene / polyvinyl methyl ether laminated film when visible light incident angle is 70 degrees.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 schematically shows a total reflection optical system in the total reflection Raman spectroscopic apparatus of the present embodiment. In the total reflection optical system of FIG. 2, the basic skeleton is designed and manufactured by Horiba, Ltd., and the types of the objective lens w, the optical fiber x, and the objective lens y are provided by the present embodiment as follows.

  This total reflection Raman spectroscopic device is provided facing a light source (not shown) such as a laser that emits light of a predetermined wavelength as excitation light, and an incident end of an optical fiber x, and the light emitted from the light source is transmitted to the optical fiber x. Objective lens w with a numerical aperture NAw that converges and enters the incident end of the optical fiber, and a flexible optical fiber x that guides the light incident from the incident end in the axial direction and exits from the exit end (incidence-side numerical aperture NAxin, exit Side numerical aperture NAxout) and an objective lens y having a numerical aperture NAy that is provided opposite to the output end of the optical fiber x and collects light emitted from the output end of the optical fiber x.

  The total reflection Raman spectroscopic apparatus also includes a hemispherical total reflection prism that radiates excitation light onto the sample on the total reflection surface and irradiates the sample as light (evanescent light), and excitation light on the sample on the total reflection surface. A diaphragm lens for condensing the light emitted from the objective lens y so as to converge, and a spectroscopic device (not shown) for spectroscopically observing Raman scattering components from scattered light from the sample irradiated with the excitation light And have.

  In this total reflection Raman spectroscopic device, the light emitted from the light source is converted into substantially parallel light by a collimator lens (not shown) and then incident on the incident end of the optical fiber x by the objective lens w. The light incident on the optical fiber x travels along the axis of the optical fiber x, exits from the exit end thereof, and becomes substantially parallel light by the objective lens y. The light emitted from the objective lens y is collected by the diaphragm lens so as to converge on the sample on the total reflection surface of the total reflection prism.

  Here, as shown in position (a) and position (b) in the figure, the objective lens y and the aperture lens are arbitrarily selected within a predetermined range for the incident angle q of the excitation light with respect to the total reflection surface of the total reflection prism. can do.

  Specifically, in FIG. 2, in the total reflection optical system from the objective lens w to the total reflection prism, the optical fiber x has a length of 60 cm, FC connectors are attached to both ends, the diaphragm lens has an F value of 4, prism Is made of non-fluorescent sapphire and hemispherical with a diameter of 20 mm. (1) Excitation light oscillates from the laser, (2) Excitation light enters the total reflection optical system in Fig. 2, (3) Total reflection Raman scattered light generated from the sample reaches the detector through the spectrometer Thus, a total reflection Raman spectrum is measured.

  In (1) above, a diode-pumped visible laser (Spectra Physics Millenia) is used as a light source for visible light (wavelength 532 nm) excitation, and a diode-pumped visible laser (Spectra Physics Millenia) is used for near-infrared light (wavelength 752 nm) excitation. A titanium: sapphire laser (Spectra Physics Model 3900S) pumped in 1 was used as the light source.

  In (2) above, if the objective lens w, the optical fiber x, and the objective lens y corresponding to this embodiment are used, the excitation light focused by the objective lens w enters the optical fiber x and is emitted while being magnified from the optical fiber x. Then, it becomes parallel light by the objective lens y, and is narrowed on the prism bottom surface by the diaphragm lens.

  As described above, in the total reflection optical system shown in FIG. 2, the objective lens y and the aperture lens rotate as a unit, and the excitation light is transmitted as shown at positions (a) and (b) in FIG. The incident angle q can be changed. If the incident angle q at the position (b) is greater than or equal to the critical value, the excitation light that has reached the bottom surface of the prism is not refracted toward the sample side, and all is reflected in the direction of (c) in FIG. Such total reflection generates light that oozes from the prism bottom to a sample surface depth of about 100 nm. As a result, only the sample surface depth of about 100 nm is excited, and only this part generates total reflection Raman scattered light. Will do.

  In (3) above, the generated total reflection Raman scattered light is condensed by the camera lens (F value 1) to become parallel light, passes through the Rayleigh light cut filter, and is collected by the condensing lens (F value 7.5). After being focused on the slit of (Jobin Yvon Ramanor T-64000, F value 7.5), it is spectrally separated by a diffraction grating (number of grooves 600 grooves / mm) and charged coupled device detector (Princeton Instruments, LN / CCD- 1024EHRB) is reached.

As the above-mentioned Rayleigh light cut filter, Kaiser Holographic Notch Filter HNPF-532-1.5 for visible light (532 nm) excitation, Kaiser Holographic Notch Filter HNPF-752-1.5 for near infrared light (752 nm) excitation, Each is preferably used. The slit width is preferably a width corresponding to a resolution of 10 cm- ¹ , and is preferably 120 μm for visible light (532 nm) excitation and 240 μm for near infrared light (752 nm) excitation.

In implementing this embodiment with the total reflection optical system of FIG. 2, in order to confirm that the total reflection condition is satisfied, polystyrene (hereinafter abbreviated as PS) on the prism (Aldrich 18,242-7, M _w = 2.8 × 10 ⁵ ) And polyvinyl methyl ether (hereinafter abbreviated as PVME) (TCI P0384, 30% in water) were formed in this order, and the sample shown in FIG. 2 was used as a PS / PVME laminated film.

  Specifically, (1) PS Spectrozol toluene solution (3 wt%) 0.3 mL was spin coated on the prism bottom (3000 rpm / 30 s), (2) vacuum dried at room temperature for 1 hour, (3) PS On the layer, 0.8 mL of a PVME distilled aqueous solution (10 wt%) was cast, and (4) vacuum-dried at room temperature for 24 hours. The film thickness of the PS film is 130 nm (measured by the optical probe method at Toray Research Center, Inc.), and the film thickness of the PVME film is 250 μm (estimated from the PVME weight and cast area).

  As will be described later, the type of objective lens w, optical fiber x, and objective lens y are changed using visible light (wavelength 532 nm) as excitation light in the total reflection optical system of FIG. The beam diameter and the total reflection Raman spectrum were compared when the shape was not applicable. At this time, the diaphragm lens shown in FIG. 2 was fixed at the position where the beam diameter on the prism bottom surface is minimized, but the position of the diaphragm lens is not limited to the types of the objective lens w, the optical fiber x, and the objective lens y. It was the same.

  In the comparison of the above beam diameters, a camera was installed behind the camera lens (F value 1), and a beam image on the bottom surface of the prism was taken. In photographing, the excitation light output and the brightness of the light installed obliquely in front of the prism were adjusted so that the brightness of the image was appropriate for beam identification.

  In comparing the total reflection Raman spectra, the cosmic ray spike noise mixed in the measured Raman spectrum was removed, and the detector sensitivity was corrected to obtain the final experimental result.

  When implementing this embodiment using near-infrared light (wavelength 752 nm) as excitation light in the total reflection optical system shown in Fig. 2, use of IR converter A-3R / T (Phototechnica Co., Ltd.) and beam image display By adjusting the color tone of the TV, the optical axis was adjusted and the beam diameter was confirmed, and the total reflection Raman spectrum was measured. This is because the near-infrared light (wavelength 752 nm) is difficult to see, and the Raman intensity in the near-infrared light excitation is reduced to 20% of that in the visible light excitation (edited by the Chemical Society of Japan, 4th edition, Experimental Chemistry Course 6). The relative intensity at the excitation wavelength of 750 nm and the excitation wavelength of 500 nm is calculated using the fourth power rule described in Spectroscopic I, Maruzen, 1991, p.429, and a more precise alignment is required than in the case of visible light excitation. It is to become. In order to implement this embodiment using near-infrared light (wavelength 752 nm) as excitation light, in addition to the objective lens for near-infrared light, which will be described later, the operation procedure described above is different from that for visible light excitation. Required.

  The Raman spectrum measured as described above was subjected to removal of cosmic ray spike noise and correction of detector sensitivity in the same manner as in the case of excitation with visible light (wavelength 532 nm), and the final experimental results were obtained.

  In Examples and Comparative Examples described in detail below, it is assumed that the numerical apertures of all optical fibers x used in the total reflection optical system of FIG. 2 satisfy NAxin = NAxout. However, the present invention is not limited to the case of NAxin = NAxout, and can be similarly implemented when NAxin and NAxout are different.

  As Example 1, the numerical aperture NAw / NAx / NAy of the objective lens w, the optical fiber x, and the objective lens y is 0.46 / 0.20 / 0.15 (NAxin = NAxout = NAx, NAx = 0.20) in the total reflection optical system of FIG. , NAw> NAxin and NAxout> NAy are satisfied). At this time, the excitation light is visible light (wavelength 532 nm). In detail, the objective lens above is Olympus MSPlan20 (infinity correction, magnification 20 times, numerical aperture 0.46), Olympus UNPLFL5 × (infinity correction, magnification 5 times, numerical aperture 0.15), and the above optical fiber is detailed Mitsubishi Electric Industries ST200D (step index type multimode optical fiber, core diameter 200 μm, numerical aperture 0.20) or Mitsubishi Electric Industries ST100C (step index type multimode optical fiber, core diameter 100 μm, numerical aperture 0.20) is there.

  FIG. 3 shows a beam image on the bottom surface of the prism coated with the PS / PVME laminated film in the total reflection optical system shown in FIG. Here, the excitation light incident angle is q = 70 °, and the excitation light intensity is (40 ± 5) mW.

  As will be described later, when the incident angle q is 70 °, the excitation light is totally reflected on the prism bottom surface (prism / PS interface).

  In the image of FIG. 3, the beam has a shape close to a distortion ellipse on the left and right. This is due to the incidence of excitation light from an oblique direction. When the incident angle of excitation light increases, the length of the minor axis of the ellipse is substantially constant, but the length of the major axis of the ellipse increases. In this specification, the length of the minor axis of the ellipse is regarded as a substantial beam diameter.

  The minor axis length and major axis length of the beam are 220 μm and 580 μm. The brightness near the center of the beam is high.

  As described above, the reason why the beam diameter is small and the luminance near the beam center is high can be explained as follows.

The combination of numerical apertures is 0.46 / 0.20 / 0.15, and the excitation light is emitted from the optical fiber x at a divergence angle of 23 ° (= 2 × sin ⁻¹ 0.20) and the divergence angle is 17 ° (= 2 × sin ⁻¹ 0.15). Only the following light is incident on the objective lens y.

  The pump light propagating in the optical fiber x includes (1) low-order mode light (light having a small angle p in the optical waveguide device in FIG. 1), and (2) high-order mode light (angle p in the optical waveguide device in FIG. 1). Light), and (3) clad mode light (light propagating through the clad that is not the original optical path in the optical waveguide device in FIG. 1).

  Accordingly, the low-order mode light is located near the center of the light flux having a divergence angle of 23 ° and can enter the objective lens y. However, the high-order mode light and the cladding mode light are located at the end of the light flux and cannot enter the objective lens y. Since only the low-order mode light whose spatial intensity distribution can be approximated by a Gaussian function is incident on the objective lens y, a beam having a small diameter and a high luminance near the center can be formed as shown in FIG.

  In general, the signal in Raman spectroscopic measurement is weak, and it is necessary to increase the intensity of excitation light per unit area. Since total reflection Raman spectroscopy is targeted at a sample surface depth of around 100 nm, the signal light is much weaker than in general Raman spectroscopy, and it is important to increase the excitation light intensity per unit area. Become. The state of FIG. 3 has a high excitation light intensity per unit area, and is effective in obtaining a total reflection Raman spectrum with a high S / N ratio as described below.

  The total reflection Raman spectrum of the PS / PVME laminated film corresponding to the image of FIG. 3 is shown in FIG. In FIG. 4, the measurement time is 20 s, and the excitation light intensity is (135 ± 5) mW.

  As a result of comparison with separately measured PS bulk and prism Raman spectra, it was found that all observed in FIG. 4 were PS Raman bands except * (prism Raman band). This is because excitation light (incident angle q = 70 °) is totally reflected on the prism bottom surface (prism / PS interface), and only the PS film (surface layer 130 nm) is selectively excited.

In FIG. 4, the 1603 cm ⁻¹ band (PS band) is clearly observed with almost the same intensity as the * band (prism band). Further, the peak intensity of the 1002 cm ⁻¹ band (PS band) in FIG. 4 is 0.061.

  As described above with reference to FIGS. 3 and 4, the total reflection optical system in the total reflection Raman spectroscopic device provided by the present embodiment reduces the beam diameter by making the excitation light visible light (wavelength 532 nm) and reducing the S / N It was possible to obtain a total reflection Raman spectrum with an excellent ratio.

  As Example 2, in the total reflection optical system of FIG. 2, the numerical aperture NAw / NAx / NAy of the objective lens w, the optical fiber x, and the objective lens y is 0.15 / 0.20 / 0.15 (NAxin = NAxout = NAx, NAx = 0.20) , NAw <NAxin, NAxout> NAy and NAw = NAy are satisfied). At this time, the excitation light is visible light (wavelength 532 nm). In detail, the objective lens is Olympus UNPLFL5 × (infinity correction, magnification 5 ×, numerical aperture 0.15), and the optical fiber is as described in Example 1. Note that description of portions common to the first embodiment will be omitted.

  FIG. 5 shows a beam image on the bottom surface of the prism coated with the PS / PVME laminated film in the total reflection optical system shown in FIG. Here, the excitation light incident angle is q = 70 °, and the excitation light intensity is (30 ± 5) mW.

  The minor axis length and major axis length of the beam are 230 μm and 750 μm. The brightness near the center of the beam is high.

  As described above, the reason why the beam diameter is small in FIG. 5 and the luminance near the beam center is high is the same as in the first embodiment.

  FIG. 6 shows the total reflection Raman spectrum of the PS / PVME laminated film corresponding to the image of FIG. In FIG. 6, the measurement time is 20 s and the excitation light intensity is (170 ± 5) mW.

  As a result of comparison with the separately measured PS bulk and the Raman spectrum of the prism, it was found that all observed in FIG. 6 were the PS Raman bands except for * (the Raman band of the prism). This is because excitation light (incident angle q = 70 °) is totally reflected on the prism bottom surface (prism / PS interface), and only the PS film (surface layer 130 nm) is selectively excited.

In FIG. 6, the 1603 cm ⁻¹ band (PS band) is clearly observed with almost the same intensity as the * band (prism band). The peak intensity of the 1002 cm ⁻¹ band (PS band) in FIG. 6 is 0.059.

  As described above with reference to FIGS. 5 and 6, the total reflection optical system in the total reflection Raman spectroscopic device provided by the present embodiment narrows the beam diameter by making the excitation light visible light (wavelength 532 nm), and the S / N It was possible to obtain a total reflection Raman spectrum with an excellent ratio.

Using the above combination (NAw / NAx / NAy is 0.15 / 0.20 / 0.15), and further changing the excitation light incident angle q in the total reflection optical system shown in FIG. 2, the Raman spectrum of the PS / PVME multilayer film is obtained. It was measured. FIG. 7 shows the result. The excitation light intensity is (200 ± 5) mW and the measurement time is 20 s. In Fig. 7, S, V, and * represent Raman bands of PS, PVME, and prism, respectively. V (1458), V (1110), and S (1000) are bands of PS wave number 1458 cm ^-1 and PVME wave numbers, respectively. A band of 1110 cm ^{−1 and} a band of PS wave number 1000 cm ⁻¹ are represented.

  In FIG. 7, the PVME Raman band is mainly observed when the excitation light incident angle is small, but only the PS Raman band is observed when the excitation light incident angle is large (excluding the Raman band of the prism). Do). This fact means that only the surface PS layer (thickness 130 nm) is excited by total reflection at a large excitation light incident angle.

  The above results can be explained as follows. Since the refractive indices for visible light are sapphire 1.77, PS 1.59, and PVME 1.46, the critical angle at the PS / PVME interface is 56 ° and the critical angle at the prism / PS interface is 64 ° (Harrick.NJ, Internal Reflection Spectroscopy, John Wiley & Sons, 1967, p.15 (Calculated using equation (6)). Therefore, when the incident angle is less than 57 °, the excitation light passes through the PS layer and the PVME layer, and the Raman band of the PVME layer whose film thickness is 1000 times that of the PS layer is mainly observed. When the incident angle is 57 ° or more, the excitation light is totally reflected at the PS / PVME interface and does not enter the PVME layer, so only the Raman band of the PS layer is observed. When the incident angle is 64 ° or more, the excitation light is totally reflected at the sapphire / PS interface, and the seepage light generated along with it is the excitation light, so that only the Raman band of the PS layer is observed.

FIG. 8 shows the relationship between the intensity of the Raman band in FIG. 7 and the excitation light incident angle. Specifically, the intensity of V (1458), V (1110), and S (1000) is I ₁₄₅₈ (V), I ₁₁₁₀ (V), and I ₁₀₀₀ (S). It was.

In FIG. 8, I ₁₄₅₈ (V) and I ₁₁₁₀ (V) decrease to 1% or less and 2% or less, respectively, around an incident angle of 56 ° (the critical angle of the PS / PVME interface). This is because the excitation light does not enter the PVME layer.

Also, I ₁₀₀₀ (S) is much smaller than I ₁₄₅₈ (V) and I ₁₁₁₀ (V) at all incident angles because the film thickness is smaller than the PVME layer, especially when the incident angle is 64 ° or more. This is because the excitation light oozes out and becomes light. I ₁₀₀₀ (S) gradually decreases at an incident angle of 64 ° or more because the penetration depth of the leaked light decreases with increasing incident angle (Harrick.NJ, Internal Reflection Spectroscopy, John Wiley & Sons, 1967, p.30 (22)).

  As described above with reference to FIGS. 7 and 8, the total reflection optical system in the total reflection Raman spectroscopic device provided by this embodiment changes the excitation light incident angle by changing the excitation light to visible light (wavelength 532 nm). By measuring the total reflection Raman spectrum, it became possible to detect weak Raman scattered light from the PS layer with a thickness of 130 nm.

  As Example 3, in the total reflection optical system of FIG. 2, the numerical aperture NAw / NAx / NAy of the objective lens w, the optical fiber x, and the objective lens y is 0.10 / 0.20 / 0.10 (NAxin = NAxout = NAx, NAx = 0.20) , NAw <NAxin, NAxout> NAy and NAw = NAy are satisfied). At this time, the excitation light is near-infrared light (wavelength 752 nm). The above objective lens is Olympus LMPL5 × IR (for near infrared light, 5 × magnification, numerical aperture 0.10) in detail, and the above optical fiber is as described in Example 1.

In the total reflection optical system shown in FIG. 2, the numerical aperture was changed to the above combination, and the Raman spectrum of the PS / PVME laminated film was measured by changing the incident angle of the excitation light. FIG. 9 shows the result. The excitation light intensity is (56 ± 5) mW and the measurement time is 180 s. In Fig. 9, S, V, and * represent the Raman bands of PS, PVME, and prism, respectively. V (1458), V (1110), and S (1000) represent the PS wavenumber 1458 cm ^-1 band and PVME wavenumber, respectively. A band of 1110 cm ^{−1 and} a band of PS wave number 1000 cm ⁻¹ are represented.

  In FIG. 9, the PVME Raman band is mainly observed when the excitation light incident angle is small, but only the PS Raman band is observed when the excitation light incident angle is large (excluding the prism Raman band). Do). This fact means that only the surface PS layer (thickness 130 nm) is excited by total reflection at a large excitation light incident angle.

  The above behavior in FIG. 9 is almost the same as in FIG. Assuming that the refractive index for near-infrared light (wavelength 752 nm) is almost the same as that for visible light (532 nm), the critical angle at the prism / PS interface is 64 °. The 65 ° and 70 ° Raman spectra are total reflection Raman spectra.

FIG. 10 shows the relationship between the intensity of the Raman band in FIG. 9 and the incident angle of the excitation light. Specifically, the intensity of V (1458), V (1110), and S (1000) is I ₁₄₅₈ (V), I ₁₁₁₀ (V), and I ₁₀₀₀ (S). It was.

In FIG. 10, I ₁₄₅₈ (V) and I ₁₁₁₀ (V) decrease to 3% or less and 1% or less, respectively, around an incident angle of 56 ° (critical angle at the PS / PVME interface). Also, I ₁₀₀₀ (S) takes much smaller values than I ₁₄₅₈ (V) and I ₁₁₁₀ (V) at all incident angles. The above behavior in FIG. 10 is almost the same as in FIG.

  As described above with reference to FIGS. 9 and 10, the total reflection optical system in the total reflection Raman spectroscopic device provided by this embodiment changes the excitation light incident angle to the near infrared light (wavelength 752 nm). By measuring the total reflection Raman spectrum, it was possible to detect weak Raman scattered light from the 130 nm thick PS layer.

[Comparative Example 1]
As Comparative Example 1, in the total reflection optical system shown in FIG. 2, the numerical aperture NAw / NAx / NAy of the objective lens w, the optical fiber x, and the objective lens y is 0.46 / 0.20 / 0.46 (NAxin = NAxout = NAx, NAx = 0.20) Yes, NAw> NAxin, NAxout <NAy and NAw = NAy are satisfied). At this time, the excitation light is visible light (wavelength 532 nm).

  FIG. 11 shows a beam image on the bottom surface of the prism coated with the PS / PVME laminated film in the total reflection optical system shown in FIG. Here, the excitation light incident angle was q = 70 °, and the excitation light intensity was (50 ± 5) mW.

  The minor axis length and major axis length of the beam are 700 μm and 1500 μm or more. In FIG. 11, a part of the beam protrudes from the image. There is no tendency for the brightness near the center of the beam to increase.

  The NAw / NAx / NAy combinations 0.25 / 0.20 / 0.25, 0.46 / 0.37 / 0.46, 0.46 / 0.22 / 0.46 (NAw> NAxin, NAxout <NAy and NAw = NAy under NAxin = NAxout = NAx) The beam image was taken in (Satisfying), and the result was almost the same as FIG.

  Here, the objective lens is specifically the Olympus LMPLFL10 × (infinite correction, magnification 10 ×, numerical aperture 0.25) and the objective lens described in Example 1. The optical fiber is Newport F-MBE (step index type multimode optical fiber, core diameter 1000μm, numerical aperture 0.37), Fiberguide Industries SFS600 / 660N (multimode optical fiber, core diameter 600μm, numerical aperture 0.22), Fiberguide Industries SFS800 / 880N (multimode optical fiber, core diameter 800 μm, numerical aperture 0.22) and the optical fiber described in Example 1.

  Like the beam in FIG. 11, the luminance near the center does not increase and the diameter is large. In addition to the low-order mode light, the high-order mode light and the clad mode light are incident on the objective lens y, This is probably because the influence of the clad mode light was great.

  FIG. 12 shows the total reflection Raman spectrum of the PS / PVME laminated film corresponding to the image of FIG. In FIG. 12, the measurement time is 20 s, and the excitation light intensity is (160 ± 5) mW.

As a result of comparison with the separately measured PS bulk and the Raman spectrum of the prism, it was found that all observed in FIG. 12 were the PS Raman bands except for * (the Raman band of the prism). The peak intensity of the 1002 cm ⁻¹ band (PS band) in FIG. 12 is 0.020.

[Comparative Example 2]
As Comparative Example 2, in the total reflection optical system shown in FIG. 2, the numerical aperture NAw / NAx / NAy of the objective lens w, the optical fiber x, and the objective lens y is 0.15 / 0.20 / 0.46 (NAxin = NAxout = NAx, NAx = 0.20) And NAw <NAxin and NAxout <NAy). This corresponds to a combination according to the prior art. At this time, the excitation light is visible light (wavelength 532 nm).

  FIG. 13 shows a beam image on the bottom surface of the prism coated with the PS / PVME laminated film in the total reflection optical system shown in FIG. Here, the excitation light incident angle was q = 70 °, and the excitation light intensity was (60 ± 5) mW.

  The length of the minor axis and the length of the major axis of the beam are 3000 μm or more and 3000 μm or more. Part of the beam protrudes from the image. There is no tendency for the brightness near the center of the beam to increase.

  Here, the objective lens and the optical fiber are as described in the first embodiment.

  In FIG. 13, the luminance near the center is not increased and the diameter is large as in FIG. 11, and the cause is as described in the description of FIG. 11.

  FIG. 14 shows the total reflection Raman spectrum of the PS / PVME laminated film corresponding to the image of FIG. In FIG. 14, the measurement time is 20 s, and the excitation light intensity is (160 ± 5) mW.

As a result of comparison with separately measured PS bulk and prism Raman spectra, it was found that all observed in FIG. 14 were PS Raman bands except * (prism Raman band). The peak intensity of the 1002 cm ⁻¹ band (PS band) in FIG. 12 is 0.019.

Here, when the spectra of FIG. 4 of Example 1, FIG. 6 of Example 2, FIG. 12 of Comparative Example 1, and FIG. 14 of Comparative Example 2 are compared, the S / N ratios of FIGS. It can also be seen that it is higher than FIG. Specifically, in FIGS. 4 and 6, the 1603 cm ⁻¹ band (PS band) is clearly observed with almost the same intensity as the band (prism band), whereas in FIGS. The intensity of the cm ⁻¹ band (PS band) is weak and is much smaller than the * band (prism band). Since the intensity ratio of the 1002 cm ⁻¹ band (PS band) in FIGS. 4, 6, 12, and 14 is 0.061: 0.059: 0.020: 0.019, the relative value of the S / N ratio is (61) ^1/2 : (59) ^1/2 : (20) ^1/2 : (19) ^1/2 = 1.8: 1.8: 1.0: 1.0 Thus, it was shown that the example of the present invention is superior to the comparative example including the example corresponding to the conventional technique.

  As described above, the examples and comparative examples of the total reflection optical system in the total reflection Raman spectroscopic apparatus provided by the present embodiment have been described. However, the above examples can be extended as follows.

  The total reflection Raman spectrum can be measured by changing the wavelength of visible excitation light from 532 nm to 400 nm to 680 nm. For this purpose, in the embodiment of the present invention, an argon ion laser, a helium-neon laser, a helium-cadmium laser, a laser diode, or the like may be used as a light source.

  The wavelength of near-infrared excitation light can be changed from 700 nm to 850 nm in addition to 752 nm, and the total reflection Raman spectrum can be measured. Since the near-infrared light oscillated by the titanium: sapphire laser is tunable in the range of 700 nm to 850 nm, this function may be utilized in the embodiment of the present invention.

  The numerical apertures of the objective lens and the optical fiber are not limited to those shown in this embodiment, as long as they satisfy “NAw> NAxin and NAxout> NAy” or “NAw <NAxin, NAxout> NAy and NAw = NAy”. The total reflection Raman spectrum can be measured.

  The essence of the present invention lies in the establishment of NAxout> NAy. That is, in order to narrow the beam diameter, only the low-order mode light among the light emitted from the optical fiber x needs to enter the objective lens y. Therefore, more generally, if the numerical apertures of the objective lens and the optical fiber satisfy NAxout> NAy, the total reflection Raman spectrum can be measured.

  The objective lens and optical fiber shown in this example are used in a total reflection fluorescence spectrometer (Japanese Patent Laid-Open No. 4-337447) and a nonlinear Raman spectrometer (Japanese Patent Laid-Open No. 10-115573), and numerical apertures of “NAw> NAxin and NAxout> NAy” Or “NAw <NAxin, NAxout> NAy and NAw = NAy”, the generation efficiency of weak signals can be increased by narrowing the beam diameter.

  As described above, the total reflection optical system in the total reflection Raman spectroscopic apparatus of the present invention includes a total reflection Raman spectroscopic apparatus, a spectroscopic apparatus capable of saving the space of the optical system and controlling the incident angle of light by using an objective lens and an optical fiber. It can also be applied to. At this time, instead of the objective lens and the optical fiber, a condensing device such as a lens and an optical waveguide device having a function of propagating light may be used.

  The total reflection optical system in the total reflection Raman spectroscopic apparatus of the present invention is premised on the presence of three optical elements, that is, a condensing device w, an optical waveguide device x, and a condensing device y. The concept of the present invention can be applied to a single optical element such as an optical waveguide device having a function.

  Note that NAw <NAxout and NAxin> NAy and NAw ≠ NAy, especially when NAxout = NAxin, the same effect as in the above-described embodiment can be obtained by setting NAw <NAx and NAx> NAy and NAw ≠ NAy. Can do.

Claims (6)

Condensing device w that collects light, NA (numerical aperture) is NAw,
The light collected by the condensing device w is incident from the incident end, the NA (numerical aperture) of the incident end is NAxin, and the NA (numerical aperture) of the output end is NAxout, and an optical waveguide device x,
Condensing light emitted from the emission end of the optical waveguide device, NA (numerical aperture) has a condensing device y NAy,
NAw <NAxin, NAxout> NAy and NAw = NAy
A spectroscopic device characterized by   2. The spectroscopic apparatus according to claim 1, wherein the excitation light is visible light (wavelength: 400 nm to 680 nm).   2. The spectroscopic apparatus according to claim 1, wherein the excitation light is near infrared light (wavelength: 700 nm to 850 nm).   A total reflection Raman spectroscopic apparatus comprising the spectroscopic apparatus according to claim 1.   A total reflection fluorescence spectrometer comprising the spectrometer according to any one of claims 1 to 3.   A nonlinear spectroscopic apparatus comprising the spectroscopic apparatus according to claim 1.