JPH03277928A - Raman spectrophotometer - Google Patents

Abstract

PURPOSE:To make it possible to remove stray light sufficiently and to facilitate handling by arranging a band removing filter wherein a I-III-VI2 chalcopyrite- type compound semiconducor crystal is arranged between first and second polarizers in the light path of scattered light. CONSTITUTION:A band removing filter 20 is formed by arranging a I-III-VI2 chalcopyrite-type compound semiconductor (single crystal of AgGaSe) 20c be tween Glan-Thompson prism polarizers 20a and 20b. The polarizers 20a and 20b are arranged so that both light polarizing axes are in parallel. In this filter 20, the central wavelength lambdao of the removing band is made to agree approxi mately with the transmitting wavelength lambdae of a laser (AlGaAs diode laser) 14. The most of the scattered light inputted into the filter 20 is Rayleigh scat tered light (stray light). The scattered light having the wavelength in the vicinity of the wavelength lambdae=lambdao is removed in the filter 20. The Raman scattered light which is shifted from this wavelength by the intrinsic amount of a sample is transmitted through the filter 20. Since the stray-light removing ratio is as high as about 10<3> or higher, the Raman shift amount can be measured with sufficient accuracy even if a compact, inexpensive sepctroscope 22 is used.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a Raman spectrophotometer using a band-reject filter.

[Conventional technology]

Raman spectrophotometers are used to obtain structural information of all solid, liquid, and gaseous compounds. Specifically, it is used for basic research in an academic sense and evaluation purposes at the new material development stage, and currently the former accounts for about 1/3 of the total.
The latter accounted for about 273. Traditional Raman spectrophotometers typically use A as the excitation light source.
r'') A gas laser is used, and a double monochromator or triple monochromator in which a plurality of monochromators are arranged in series is used as a spectrometer to remove relatively strong Rayleigh scattered light (stray light).

[Problem to be solved by the invention]

As a result, the device becomes large and expensive, and furthermore, interlocking adjustment tends to deteriorate due to vibrations, etc., and readjustment is required simply by moving the device, making it difficult to handle. There is also a Raman spectrophotometer that uses a notch filter (interference filter) as a band-elimination filter placed between the entrance slit of the spectrometer and the sample cell, but the notch filter has a transmittance of 70-80% and a transmission wavelength width of 1.0-1.0%. 2. Onm, and since the wavefront cannot be aligned in a straight line when it is made into parallel light, stray light cannot be removed sufficiently, and it is hardly used. In addition, as band-removal filters, there are colloid filters and dye filters, but the former is expensive and unstable, and the latter is expensive and cannot align the wavefront in a straight line when parallel light is used. Therefore, stray light cannot be removed sufficiently, and it is not used in Raman spectrophotometers. In view of these problems, it is an object of the present invention to provide a Raman spectrophotometer that is small, inexpensive, can sufficiently remove stray light, and is easy to handle.

[Means to solve the problem]

In order to achieve this objective, the present invention focuses the light emitted from a laser into a sample cell, collects the light scattered by the sample in the sample cell, and makes it incident on a spectrometer. In a Raman spectrophotometer that detects the intensity of light emitted from a spectrometer, a band elimination filter is placed in the optical path of the scattered light between the sample cell and the spectrometer. This band-removal filter includes a first polarizer and a second polarizer whose polarization axis is rotated by 00 rotations around the optical axis with respect to the polarization axis of the first polarizer.
a polarizer and an I- disposed between the first and second polarizers;
I[[-Vl, group chalcopyrite compound semiconductor crystal. The I-II[-VL group chalcopyrite compound semiconductor crystal has optical rotation and birefringence, and the birefringence disappears near the emission wavelength of the laser, and the optical rotation angle of transmitted light at the emission wavelength is The thickness is approximately (θ+90)0. The laser may be, for example, Aj! It is a GaAs diode laser, and the lm-'wa group chalcopyrite type compound semiconductor crystal is, for example, an AgG aSew single crystal. In addition to the im-vr group chalcopyrite type compound semiconductor crystal having the above properties, AgGa (Sx
5er-11-) *, Cu A j! s+Gl
kl-IIs l , Ag G ax I nl −
IF S e=, AgGa (Sex Tea-++)
There are 2. Here, X is an arbitrary value from 0 to 1, and the center wavelength λ of the removal band depends on the value of X. are different.

[Effect]

This band rejection filter has a center wavelength λ of the rejection band. Most of the scattered light incident on the band-elimination filter is Rayleigh scattered light (stray light), where λ, = λ, which substantially matches the emission wavelength λ, of the laser. Scattered light at nearby wavelengths, that is, Rayleigh scattered light, is removed by a band elimination filter, and Raman scattered light shifted from this wavelength by an amount specific to the sample is
Pass through a band-rejection filter. For example, the stray light removal ratio is 1
It is high, over 0'. Therefore, even if a small and inexpensive band-elimination filter and spectrometer are used, stray light can be sufficiently removed and the amount of Raman shift can be measured with sufficient accuracy. In addition, since the I m VIH group chalcopyrite compound semiconductor is a solid, it has excellent vibration resistance and almost no performance deterioration is observed, so the Raman spectrophotometer can be used for a long period of time with only initial adjustment. Easy to handle. Nao, I m The group VIi chalcopyrite compound semiconductor 20c was developed as a nonlinear optical crystal for second harmonic generation.

【Example】

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 shows a schematic configuration of a Raman spectrophotometer. A sample 12 in a sample cell 10 is irradiated with laser light emitted from a semiconductor laser 14 through a condensing lens 16 . A part of the light scattered by the sample 12 passes through a condenser lens 18 and a band-removal filter 20 into a spectroscope 2.
The light is condensed and incident on the second incidence slit 22a. The band-rejection filter 20 is arranged between a pair of Glan-Thompson prism polarizers 20a and 2Ob.
A group Il chalcopyrite compound semiconductor 20C is arranged. The Glan-Thompson prism polarizers 20a and 20b are arranged with their plane polarization axes parallel to each other. Further, the I-mVIa group chalcopyrite compound semiconductor 20c is arranged with its main axis parallel to the polarization axis. The I m VIR group chalcopyrite compound semiconductor 20c has optical rotation and birefringence, and the l
-l1l-Vl, group chalcopyrite compound semiconductor 2
0c and/or the material of the semiconductor laser 14 is selected. I m 'The wavelength λ at which the birefringence of the JIQ group chalcopyrite compound semiconductor 20c disappears. is a value specific to the substance, but can be selected depending on the composition ratio of the compound mixed crystal. For example, the wavelength λ of A gG aS e. is 811 nm, and AgGa5. wavelength λ, Ha50
0 nm, but mixed crystal AgGa (s w s el
−, ), the wavelength λ. is the composition ratio x of S and Se: (1-x
), it can be set to any value within the range of 500 to 811 nm. On the other hand, as the semiconductor laser 14, Al
When a GaAs diode laser is used, its emission wavelength can be selected within the range of 775 to 900 nm. Therefore, I-I[I-Vl, the wavelength λ of the group chalcopyrite compound semiconductor 20c. and the wavelength λ of the semiconductor laser 14 can be made to match. Usually, the wavelength λ of the chalcopyrite compound semiconductor 20c for I-III-VI2I2 is set in order to facilitate agreement between the two. Select first,
Next, the wavelength λ of the semiconductor laser 14 is set to this wavelength λ. match. The thickness of the chalcobyrite compound semiconductor 20c for I, -III-VI2I2 is the same as that of the Glan-Thompson prism polarizer 2.
Wavelength λ transmitted through 0a. The linearly polarized light of IIn VI
The angle of rotation is selected to be 90 degrees when transmitted through the s-group chalcopyrite compound semiconductor 20c. The transmission characteristics of the band-rejection filter 20 configured in this way are as follows:
When the material of 0c is AgGaS ex, it becomes as shown in FIG. Band-removal filter 2 in this case
The stray light removal ratio of 0 is 10" or more. The light emitted from the output sleeve 22b of the spectrometer 22 is projected onto the photomultiplier tube 24, and its light intensity is detected. The output of the photomultiplier tube 24 is amplified by the amplifier 26, and the A/D
The converter 28 converts it into a digital value ■ and supplies it to the microcomputer 30. On the other hand, the semiconductor laser 14 is integrated with a monitoring PIN photodiode 32 that detects the laser light output. The output of the PIN photodiode 32 is the A/D
It is converted into a digital value 1 by the converter 34 and supplied to the microcomputer 30. microcomputer 3
0 is also supplied with its scanning wavelength λ from the spectrometer 22. The microcomputer 30 determines the wavelength (λ-λ,) and the relative light intensity 1/1. A value obtained by multiplying by a constant is supplied to the recorder 36 to record a Raman spectrum. Since the emission wavelength of the semiconductor laser 14 depends on its temperature, in order to keep it constant, the temperature of the semiconductor laser 14 is detected by a temperature detector 38, and its output is sent to an amplifier 40,
/D converter 42 to the microcomputer 30, and the microcomputer 30 controls, for example, on/off an electronic cooler 44 that utilizes the Peltier effect.
The temperature of the semiconductor laser 14 is λ,=λ. It is approaching the target temperature. I-n[VI* group chalcobyrite compound semiconductor 20
The wavelength λ0 of c also depends on the temperature, which is 0.3 people/℃
On the other hand, I-In-
Since the band rejection half width of the VIi group chalcopyrite compound semiconductor 20c can be made up to 40, the temperature dependence of the VIm group chalcopyrite compound semiconductor 20c can be reduced in normal use at room temperature. No need to consider. In the above configuration, most of the scattered light incident on the band-rejection filter 20 is Rayleigh scattered light (stray light), but λ
,=λ. Scattered light of a nearby wavelength, that is, Rayleigh scattered light, is removed by the band-elimination filter 20, and Raman scattered light shifted from this wavelength by an amount specific to the sample is transmitted through the band-eliminated filter 20. Band rejection filter 20
As mentioned above, the stray light removal ratio is as high as 10a or more. Therefore, even if a spectrometer 22 with relatively low resolution is used, or in other words, a small and inexpensive spectrometer 22 is used, it is possible to measure the amount of Raman shift with sufficient accuracy. Since the Mata, I III vx Group 2 chalcopyrite compound semiconductor 20c is a solid, it has excellent vibration resistance.
In addition, since almost no performance deterioration is observed, the Raman spectrophotometer can be used for a long period of time with only initial adjustment, and is easy to handle. Incidentally, the present invention includes various other modifications. For example, Glan-Thompson prism polarizers 20a and 2
Instead of 0b, an inexpensive film polarizer or the like may be used. Furthermore, in the above embodiment, a case was explained in which the band-removal filter 20 was arranged between the condenser lens 18 and the entrance sleeve 22a of the spectrometer 22, but the sample 12 and the condenser lens 18
Alternatively, a collimating lens (not shown) may be disposed between the sample 12 and the condensing lens 18, and the band eliminating filter 20 may be disposed between the collimating lens and the condensing lens 18. May be placed. Furthermore, the spectroscope 22 may have a configuration in which a plurality of monochromators are arranged in series. In this case as well, a Raman spectrophotometer with the same performance as a conventional one can be made smaller and provided at a lower cost. Further, the laser is not limited to a semiconductor laser, and for example, when the I-III-VIi group chalcopyrite compound semiconductor 20c is Cu Aim GFll-xsx, an Ar+ gas laser or a He-Ne gas laser can be used. can.

【Effect of the invention】

As explained above, the Raman spectrophotometer according to the present invention is small and inexpensive, can sufficiently remove stray light, and is easy to handle. 1. It greatly contributes to the expansion of use in development.

[Brief explanation of drawings]

1 and 2 relate to an embodiment of the Raman spectrophotometer according to the present invention, FIG. 1 is a schematic configuration diagram of the Raman spectrophotometer, and FIG. 2 is an I
It is a transmission characteristic diagram showing the transmittance of a band-elimination filter with respect to wavelength when AgGaS e2 is used as a -I-VIi group chalcopyrite compound semiconductor. In the figure, 10 is a sample cell 12, a sample 14 is a semiconductor laser 16, 18 is a condensing lens 20, a band elimination filter 20a, 20b is a Glan-Thompson prism, a polarizer 20c is l-111-Vl, a group chalcopyrite compound semiconductor crystal 22 is a spectrometer 22a is an entrance slit 22b is an output slit 24 is a photomultiplier tube 26.40 is an amplifier 28.34.42 is an A/D converter 30 is a microcomputer 32 is a PIN photodiode 36 is a recorder 38 is a temperature detector 44 is the electronic cooler type

Claims (1)

[Claims] 1) The light emitted from the laser (14) is transmitted to the sample cell (
Raman spectroscopy in which the light scattered by the sample (12) in the sample cell is focused into a spectrometer (22), and the intensity of the light emitted from the spectrometer is detected. In the photometer, a first polarizer (20a) is provided in the optical path of the scattered light between the sample cell and the spectrometer, and the polarization axis is set at θ around the optical axis with respect to the polarization axis of the first polarizer. A second polarizer (20b) arranged with a rotation angle of 20°, and a second polarizer (20b) arranged between the first and second polarizers, having optical rotation and birefringence, and having the birefringence near the emission wavelength of the laser. The optical rotation angle of the transmitted light of the emission wavelength is approximately (θ+90
)° and a group I-III-VI_2 chalcopyrite compound semiconductor crystal (20b) having a thickness of A Raman spectrophotometer characterized by: 2), the laser (14) is an AlGaAs diode laser, and the I-III-VI_2 group chalcopyrite compound semiconductor crystal (20c) is AgGaSe_2
The Raman spectrophotometer according to claim 1, wherein the Raman spectrophotometer is a single crystal.