JP2003083905A - Sample analyzer based on measurement of surface displacement of sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem raised by the conventional method of measuring surface displacement of sample utilizing the Sagnac interferometer that, when three kinds of light having the same wavelength are used as reference light, probe light, and pumping light, unnecessary light reaches a detector and increases the background and, in addition, when a method of properly using two kinds of wavelengths for the three kinds of light is used for solving the problem, another problem arises that a wavelength changing element, such as the SHG, etc., the conversion efficiency of which is low and fluctuates depending upon the ambient environment, such as the temperature, etc., and which deteriorates the shape of a short-pulse, and so on, must be used at wavelength changing time. SOLUTION: A sample analyzer based on the measurement of the surface displacement of a sample adopts such a constitution that makes three kinds of light of pumping light, probe light, and reference light having the same wavelength incident obliquely to the surface of a sample so that the sample may obliquely reflect the light. Consequently, only necessary interference light can be introduced to the detector while the three kinds of light having the same wavelength are used. At the same time, the Sagnac interferometer or another interfering means showing an effect which is close to that shown by the interferometer is utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring an elastic wave excited by pulsed light as a displacement of a sample surface and analyzing the inside of the sample. In particular, it is used for measuring the film thickness of multilayer films in semiconductor products. Further, even if it is not a semiconductor product, any sample provided with a thin film can be a measurement target according to the present invention. Magnetic recording tapes, magnetic recording disks, optical recording disks, coated steel plates and the like are examples thereof.

[0002]

2. Description of the Related Art As a method of nondestructively measuring the thickness of an opaque thin film having a thickness of less than a micron, an elastic wave is generated in the thin film by a pump probe method, and an elastic wave echo reflected at the film interface returns to the surface. A method is used in which the time taken to arrive is measured and the time is converted to a film thickness.

In the pump probe method, at least a short pulse laser light source, a means for separating pump light and probe light, and these lights are used for sampling and measuring the change with time of a sample excited by the short pulse pump light. , A delay optical path for sampling timing adjustment, and a detector are used. Further, it is a conventional means to irradiate pump light intermittently and improve the S / N ratio by utilizing a lock-in amplifier synchronized with its cycle and phase.

As one of the methods for measuring the time until the echo returns, a method of measuring the reflectance change of the sample surface by the echo with a probe light is used, and it is shown in US Pat. No. 4,710,030. In addition, a method of measuring a change in the sample surface due to an echo as a change in the reflection angle of the probe light is also used. B. Writ
e and K.E. Kawashima, Phys. Re
v. Lett. , V69, N11, P1668-167
1 (1992).

As a method of measuring the fluctuation of the sample surface, there is also a method of directly measuring the displacement in the thickness direction of the sample surface. In this method, two types of light, probe light and reference light, are used, and the phase change of the probe light due to the sample surface displacement is measured by interference with the reference light.

The surface displacement can be known from the phase change measured here. For example, Japanese Patent Application Laid-Open No. 5-172739 discloses an example using a Michelson interferometer, a Mach-Zehnder interferometer, and a Fabry-Perot interferometer. Further, as a method of the same kind, an example of using a Sagnac interferometer is described in US Pat. H. Hurr
ey and O. B. Write, Optics L
etters, V24, N18, P1305-1307
(1999).

The principle of a conventional sample surface displacement measuring method using a Sagnac interferometer will be described below with reference to FIG.

The light emitted from the short pulse laser 1 is
By passing through the SHG 21, the light becomes a mixture of the original light and the light whose wavelength is half. The two kinds of light are separated by a dichroic mirror 22, one of which is used as a pump light 20 and the other of which is used as a reference light 18 and a probe light 19. Reference light 1 that has passed through the dichroic mirror 22
The mixed light of 8 and the probe light 19 passes through the mirror 4 and then 2
The ratio of the P-polarized component and the S-polarized component is adjusted by the half-wave plate 5. After that, a quarter-wave plate 6 installed so as to have an axis of 0 degree or 90 degrees with respect to the paper surface of FIG. 2 provides a phase difference of 90 degrees between the P-polarized component and the S-polarized component. To be In this example, P reaching sample 17
The polarization component is used as the reference light 18 and the S polarization component is used as the probe light 19.

The reference beam 18 is composed of a BS (beam splitter) 23, a PBS (polarizing beam splitter) 24, and 4.
Sub-wave plate 28, lens 29, sample 17, lens 2
Proceed in the order of 9, quarter-wave plate 28, PBS 24, mirror 26, mirror 25, BS 23, and then PBS 11.
After that, it goes to the detector 12 and the detector 13. On the other hand, the probe light 19 includes a BS 23, a mirror 25, a mirror 26, a PBS 24, a quarter wavelength plate 28, a lens 29,
Sample 17, lens 29, quarter wave plate 28, PBS2
4 and BS23 in this order, and then to the detector 12 and the detector 13 via the PBS 11. The order of passing through this optical path is achieved by the difference in the polarization state of each light, which will be described in detail later. Therefore, the reference light 18 and the probe light 19 travel in the same optical path in opposite directions from the first passage through the BS 23 to the second arrival at the BS 23. As described above, the Sagnac interferometer is characterized in that two types of light to be interfered share the same optical path on the closed loop and travel in opposite directions. With this configuration, the influence of the disturbance on both lights becomes the same and is canceled at the time of interference. Further, since both lights travel the same optical path length, they exit the closed loop at the same timing and head for the PBS 11. As can be seen from FIG. 2, the probe light 19 bypasses the mirrors 25 and 26 and reaches the sample, so that the reference light 18 precedes the probe light 19 and the sample 17.
Arrive at. As described above, the sample 17 is installed at a position displaced from the midpoint of the total optical path length of the closed loop.

The reference light 18 and the probe light 19 undergo some modulation when reflected by the sample 17 in the middle of the closed loop, and the difference in their influences can be obtained from the detection result of the interference light. In practice, the reference light 18, the pump light 20, and the probe light 19 are arranged in this order so that each light reaches the sample 17, and the reference light 18 is generated by the sample 17 before being affected by the pump light 20. Is reflected, and the probe light 19 is reflected by the sample 17 after being influenced by the pump light 20. In this method, the phase change of the probe light 19 due to the displacement of the sample surface is detected by utilizing the interference with the reference light 18. Since the short-pulse probe light 19 is used, it is possible to capture and sample the sample surface displacement at a certain moment. In the middle of the optical path that guides the pump light 20,
A delay optical path using the retro-reflector 8 is provided. By moving the retro-reflector 8 in the direction in which the optical path length expands and contracts, the time from the arrival of the pump light 20 at the sample 17 to the arrival of the probe light 19 is adjusted.

Next, the traveling directions and polarization states of the reference light 18 and the probe light 19 will be described. The light split by the BS 23 and directed to the PBS 24 is the reference light 18 and the mirror 2.
The light traveling toward 5 becomes the probe light 19. When passing through the BS 23, both lights have both P-polarized component and S-polarized component. The reference light 18 is PBS for the first time.
When passing 24, only the P-polarized component passes. Then, a quarter with an axis tilted 45 degrees with respect to the paper of FIG.
After passing through the wave plate 28 twice, it becomes S-polarized light and the second P
Arrived at BS24. Therefore, the S-polarized reference light 18 is guided toward the mirror 26 by the PBS 24. After that, the mirror 26 and the mirror 2 are kept in the S-polarized state.
5 and BS23 in that order toward PBS11. When the probe light 19 first passes through the PBS 24, only the S-polarized component passes through. After that, the light passes through the quarter-wave plate 28 twice, becomes P-polarized light, and reaches the PBS 24 for the second time. Therefore, the P-polarized probe light 19 is P
It is guided toward BS23 by BS24. afterwards,
In the P-polarized state, the light passes through the BS 23 toward the PBS 11.

The reference light 18 and the probe light 19 passing through the BS 23 toward the PBS 11 for the second time do not interfere as they are because the polarization states are orthogonal to each other, but the PBS 11 tilted 45 degrees with respect to the paper surface of FIG. The interference light 32 and the interference light 33 are obtained by passing through. By the way, the quarter-wave plate 6 provides a phase difference of 90 degrees between the reference light 18 and the probe light 19 in advance. Due to this phase difference, the detector output changes linearly with respect to a minute phase change generated by the displacement of the sample surface. actually,
In the interference light 32 and the interference light 33, the phase difference generated by the quarter-wave plate 6 acts with the opposite sign, and the phase difference between the reference light 18 and the probe light 19 in each interference is 90 degrees and −90. It becomes degree. Further, the outputs of the detector 12 and the detector 13 include information on the change in the reflectance on the sample surface, in addition to the information on the phase change of the probe light 19 due to the displacement of the sample surface. Therefore, by taking the difference between the outputs of the detector 12 and the detector 13, only the information on the phase change of the probe light 19 can be extracted. The above method in which a phase difference of 90 degrees is provided with respect to the light before interference and two types of interference light are obtained and the phase change is measured from the difference is a conventional means for measuring a minute phase change. is there.

The pump light 20 separated by the dichroic beam splitter 22 passes through a mirror 7, a retroreflector 8, a mirror 9, an AOM 10 and a mirror 30 in this order, and then a reference light 18 and a probe light 19 by a dichroic beam splitter 27. And is guided to the sample 17. The pump light 20 reflected by the sample 17 returns to the same optical path in the opposite direction and is separated from the optical paths of the reference light 18 and the probe light 19 by the dichroic beam splitter 27, so that the detectors 12 and 13 are Do not reach

A method of intermittently irradiating the pump light 20 and improving the S / N ratio by utilizing the lock-in amplifier 14 synchronized with the cycle and phase thereof is included in FIG. Here, the optical path of the pump light 20 is periodically opened and closed using the AOM 10, and when the optical path is opened, the above measurement is repeated for each pump light pulse that has passed through the AOM. Pump light 20 when the light path is closed
The above measurement is repeated without reaching the sample. The lock-in amplifier 14 performs measurement in synchronization with this cycle and phase. By using the lock-in amplifier 14,
The S / N ratio is improved by subtracting the measured value when the pump light 20 does not reach the sample as the background signal from the measurement result when the pump light 20 reaches.

This example is an example of a sample surface displacement measuring method using a Sagnac interferometer, and some optical components unnecessary for the above description are omitted. Various optical circuits having the same function can be realized by changing the arrangement order of the optical components, or changing the separation direction of various lights, or partially changing or adding the optical components. The above example is the simplest,
It is also an example of a sophisticated optical circuit.

Finally, the displacement of the sample surface due to the pump light will be described. When the pump light is applied to the opaque thin film,
Since the sample is opaque, the pump light energy is absorbed only in a limited depth range of the outermost surface. In addition, since the pump light has a pulsed shape, energy is absorbed at the moment of irradiation. Therefore, the partially concentrated energy becomes an elastic wave and advances into the sample. This elastic wave is partly reflected at the part where the material such as the thin film interface is non-uniform, returns toward the sample surface, and becomes an echo. When the elastic wave reaches the surface, the outermost surface volume is expanded and contracted, and as a result, the sample surface is changed. The elastic wave that has reached the surface of the sample again travels toward the inside of the sample, is reflected by the non-uniform portion of the material, and becomes a second echo. In this way, echoes periodically reach the sample surface and are observed as displacement of the sample surface.

[0017]

In the conventional sample surface displacement measuring method, when the sample position with respect to the interferometer fluctuates, it cannot be distinguished from the sample surface displacement, and the measurement result is greatly affected. A method using a Sagnac interferometer has been proposed as a method for improving the problem.
The Sagnac interferometer is designed such that the optical path of the probe light and that of the reference light are made common so that the influence of disturbance acts on both lights equally and, as a result, is canceled at the time of interference. Fluctuation of sample position is also one of the factors of disturbance,
The use of Sagnac interferometer can reduce the effect.

However, in the conventional method using the Sagnac interferometer, the three types of incident light and reflected light of the reference light, the probe light, and the pump light share a single optical path immediately before the sample. . Due to its structure, a wavelength conversion element such as SHG had to be used in order to use light of different wavelengths for the pump light and the probe light. In the conventional method, three types of incident light and reflected light of reference light, probe light, and pump light share a single optical path immediately before the sample. The measurement spot size can be reduced to the diffraction limit by making the light sharing the optical path incident perpendicularly to the sample surface. However, when three types of incident / reflected light of the same wavelength share one optical path, it is impossible to separate the light reflected and returned from the sample by only the difference in polarization as it is, and therefore it is detected. Unwanted light other than the coherent light that should reach the detector causes an increase in background. Therefore, in order to separate the three types of light, it is necessary to use light of different wavelengths for the pump light and the probe light. However, there are problems such as low conversion efficiency of wavelength conversion elements such as SHG used for that purpose, fluctuation of conversion efficiency due to external environment such as temperature, deterioration of short pulse shape during conversion, and the like.

It is an object of the present invention to solve the above problems and to realize a measuring method that is tolerant of variations in sample position and that does not require a wavelength conversion element.

[0020]

In order to solve the above-mentioned problems, in the present invention, three kinds of light of pump light, probe light, and reference light are obliquely incident on the surface of the sample, and the light is oblique to the sample. The structure that reflects the light is adopted. That is, immediately before the sample, these three kinds of light share two optical paths. As a result, only the necessary coherent light is guided to the detector while the three types of light having the same wavelength are used. At the same time, I decided to use the Sagnac interferometer, or another interferometer with an effect close to it. As a result, a measurement method that is tolerant of changes in the sample position was realized without using a wavelength conversion element.

[0021]

DETAILED DESCRIPTION OF THE INVENTION In the following description, S-polarized light and P-polarized light will be used.
The expression that the polarization state is different is used for two types of light having polarization states orthogonal to each other such as polarization. Such two kinds of light can be separated by a polarization optical element. In addition, in the following description, the part described as the detection unit includes the PBS 11, the detector 12, and the
And the entire portion corresponding to the detector 13 is included.

As in the prior art, the present invention uses a short pulse laser light source, a delay optical path for adjusting the timing of sampling, and a detector. Further, a modulator for periodically modulating the intensity of pump light and a lock-in amplifier synchronized with the modulation are used. (See Figure 1). Less than,
In the description of the embodiments of the present invention, the description of the same parts as those in the related art will be omitted. Therefore, taking FIG. 2 or FIG. 1 as an example, the beam transport system from when the reference light 18 and the probe light 19 pass through the quarter-wave plate 6 to the detection unit and the pump light is the AOM 10 The beam transport system after passing through will be described focusing on its embodiment. The explanation will be central.

First, the optical paths immediately before the sample for the three kinds of light of the reference light, the probe light and the pump light will be described. The conventional technique has three components: reference light, probe light, and pump light.
In the present invention, these three types of light are obliquely incident on the sample surface, whereas the three types of light are perpendicularly incident on the sample surface. (See Figures 2 and 1). Therefore, in the prior art, there was only one optical path immediately before the sample, but in the present invention, there are two optical paths immediately before the sample. The two optical paths have a non-perpendicular angle with respect to the sample surface, and are in a positional relationship such that the light incident from one optical path is reflected along the other optical path. Therefore, each of the three types of light passes through one of the optical paths when it is incident on the sample, and after reflection from the sample, passes through the other optical path that is different from the one upon incidence.
By using two optical paths, it is possible to separate three types of light of the same wavelength that are reflected back from the sample surface and returned from the combination of the traveling directions and polarization states of the three types of light. This eliminates the need for a wavelength conversion element such as SHG used to obtain light of different wavelengths. Therefore, in the present invention, BS or PBS is used to extract the mixed light of the reference light and the probe light and the pump light from one light source. To adjust the separation ratio, 2
A method in which the ratio of P-polarized light and S-polarized light is adjusted through a one-half wavelength plate and then separated with PBS is preferable.

Immediately before the sample, a lens for condensing each parallel light coming toward the sample on the sample surface and a lens for returning the light reflected from the irradiation spot on the sample surface to the parallel light are required. Become. It is possible to use separate lenses for the two optical paths immediately before the sample, but it is preferable to share one lens. In that case, the two optical paths that connect the lens and the optical element on the side opposite to the sample as viewed from the lens have a positional relationship that is parallel to the optical axis of the lens and symmetrical with respect to the optical axis of the lens. preferable. This lens has an aspherical lens specialized for one wavelength, or an equivalent function, so that even if light parallel to the optical axis enters at a position deviated from the optical axis, it focuses on the same position. It is preferable to have a compound lens.

In order to separate the three kinds of light, one of the following three kinds of patterns is required between the polarization direction of each light and the above two optical paths. In the first pattern, the reference light 18 and the probe light 19 having different polarization states travel in opposite directions on the two optical paths (see FIG. 3A). At this time, the pump light 20 has the same traveling direction as the reference light 18 and has a polarization state different from that of the reference light 18. Alternatively, probe light 1
It has the same traveling direction as 9 and a polarization state different from that of the probe light. In the second pattern (see FIG. 3A), the reference light 18 and the probe light 19 having the same polarization state travel in opposite directions along the two optical paths (see FIG. 3B). At this time, the pump light 20 has the same traveling direction as the reference light 18 and has a polarization state different from that of the reference light 18. Alternatively, it has the same traveling direction as the probe light 19 and has a polarization state different from that of the probe light 19. In the third pattern (see FIG. 3B), the reference light 18 and the probe light 19 having different polarization states travel along the two optical paths in the same direction (see FIG. 3C). At this time, the pump light 20 travels in the opposite direction to the reference light 18 and the probe light 19, and has the same polarization state as the reference light or the probe light. (Refer to FIG. 3C) Although FIG. 3 shows a diagram only when the reference light is P-polarized light, the reference light may be S-polarized light. Hereinafter, an embodiment of the beam transport system will be described for each of these three types of patterns.

An example of the first pattern is shown in FIGS. 4 and 5, but a more general embodiment will be described here. In this pattern, the reference light and the probe light are separated by the PBS, travel in opposite directions in the closed loop of the Sagnac interferometer, then are mixed again by the same PBS and are guided to the detection unit. The reference light and the probe light traveling in opposite directions on the closed loop have different polarization states.
The pump light is superposed by the BS on the same optical path as the reference light and the probe light, and is guided to the sample. This BS is installed somewhere in the optical path forming the closed loop or between the PBS and the detector. The pump light reflected by the sample is
When passing through the above PBS and exiting from the closed loop, it does not reach the detector because it goes to the light source side rather than the detector side.
Since the pump light directed to the sample needs to have the same polarization state as the reference light or the probe light that faces the pump light,
When it arrives at, it must be in that polarization state. The reference light and the probe light are set to 1 above the BS before reaching the detection unit.
As they pass once, their intensity is halved. Since the pump light passes through the BS 36 once before reaching the sample, its intensity is halved. The sample is installed in the middle of the closed loop, and a lens is used so that the light in both directions traveling on the closed loop is condensed at the same position on the surface of the sample.

An example of the second pattern is shown in FIGS. 6 and 7, but a more general embodiment will be described here. In this pattern, the reference light and the probe light are separated by the PBS, travel in opposite directions in the closed loop of the Sagnac interferometer, and then are mixed by the same PBS again, and the optical path is reversed toward the light source and installed in the middle. B
It is guided to the detection part by S. Also, in the middle of the closed loop,
An optical element for converting the polarization state, for example, a half-wave plate is installed. Light incident on this optical element is converted into a polarization state different from that at the time of incidence. The reference light and the probe light traveling in opposite directions on the closed loop have the same polarization state on the optical path on the same side with the polarization state converting optical element interposed therebetween. The pump light is superposed on the same light path as the reference light and the probe light by the above PBS or another PBS installed in the closed loop, and is guided to the sample. The pump light reflected by the sample is deviated from the optical paths of the reference light and the probe light by the PBS passing next, and does not reach the detector. The pump light directed to the sample needs to have a polarization state different from that of the reference light and the probe light traveling in the same direction or in the opposite direction, and therefore has to be in that polarization state when arriving at the PBS. Since the reference light and the probe light pass through the BS twice before reaching the detection portion, their intensities become ¼. On the other hand, since the pump light does not pass through the BS even once, its intensity does not change. The sample is installed in the middle of the closed loop, and a lens is used so that the light in both directions traveling on the closed loop is condensed at the same position on the surface of the sample.

Examples of the third pattern are shown in FIGS. 8, 9 and 10, but a more general embodiment will be described here. In this pattern, the reference light and the probe light are separated by the PBS, pass through the optical paths having different lengths, are mixed by the PBS, and are guided to the sample. The reference light and the probe light reflected by the sample are PB
After being separated by S and passing through optical paths having different lengths, they are mixed by PBS and guided to a detector. (See Figure 8). Between the light source and the detector, the reference light and the probe partially travel different optical paths, but their total optical path lengths must be the same. Further, the reference light and the probe light traveling between the PBSs have different polarization states. The sample is placed between the second and third PBS.
Further, a lens for condensing the mixed light from the PBS of the second time on the sample surface and a lens for returning the light reflected from the irradiation spot on the sample surface to the parallel light toward the PBS of the third time are used. PBS for both reference light and probe light
Although it passes once, it is preferable that the first PBS and the fourth PBS can be substituted by one PBS, and the second PBS and the third PBS can be simultaneously substituted by another PBS. (See Figure 9). At this time, there are two long optical paths and two short optical paths between the two PBSs. These two long optical paths do not overlap and, never once, come close and parallel. Is preferred. At the same time, these two short optical paths do not overlap, and should not be, but close and parallel. Is preferred. Alternatively, all four PBSs can be replaced with one PBS. (See Figure 10). At this time, there are three closed loops that exit this PBS and return to this PBS again. The two optical paths that do not pass through the sample do not overlap and should not be, but they are close and parallel. Is preferred. As described above, when the four PBSs are replaced with the two PBSs or the one PBS, the half-wave plate is inserted into one of the two optical paths between the sample and the PBS. There is a need. When the two optical paths between the lens and the PBS are made parallel, or instead of the above-mentioned half-wave plate, a quarter-wave plate is inserted so as to span both optical paths. You can also The pump light is superposed on the same optical path as the reference light or the probe light by the BS and guided to the sample. This BS is preferably an optical path between the sample and the detection unit, and is preferably installed on the optical path shared by the reference light and the probe light. Further, this BS can be installed on one optical path of the reference light or the probe light in the optical path between the sample and the detector. The pump light reflected by the sample travels in the direction opposite to the traveling directions of the reference light and the probe light, and therefore does not reach the detector. The pump light heading for the sample needs to have the same polarization state as the reference light or the probe light that faces it, so it must have that polarization state when it reaches the BS. The pump light passes through the BS once before reaching the sample, so its intensity is halved. on the other hand,
The reference light and the probe light both pass through the BS once before reaching the detection unit, and one of the lights passes through the B.
It may pass S once. The intensity of light that has passed through the BS is halved, and the intensity of light that has not passed through does not change.

[0029]

EXAMPLES Examples will be described with reference to the drawings. However, the following examples do not limit the present invention. Actually, various optical circuits having the same function can be realized by changing the arrangement order of the optical components, the separation direction of various lights, changing some of the optical components, or adding them. Further, unlike the embodiment, it is not necessary to form all the optical paths on one plane. Also, in an actual device, the apparent optical path may be complicated in order to provide an appropriate optical path length or to match the direction of the optical path connecting the respective functions.

FIG. 1 is a diagram showing common constituent parts in each embodiment described later. Half of the light emitted from the short pulse laser 1 is installed at an appropriate angle
The wave plate 2 adjusts the intensity ratio of the S polarization component for the pump light 20 and the P polarization component for the reference light 18 and the probe light 19. The mixed light of the reference light 18 and the probe light 19 and the pump light 20 are separated by the PBS 3. The separated pump light 20 passes through the delay optical path formed by the mirror 7, the retroreflector 8, and the mirror 9, and is then intensity-modulated by the AOM or the chopper 10, and the beam transport system 31
Be led to. The AOM or the chopper 10 is driven by the driver 15. The output of the driver 15 is also supplied to the lock-in amplifier 14. on the other hand,
After the mixed light of the reference light 18 and the probe light 19 passes through the mirror 4, the half-wave plate 5 adjusts the ratio of the S-polarized component and the P-polarized component. The ratio of the components is not necessarily 1: 1. Depending on the relationship between the change intensity of the interference light due to the surface displacement of the sample 17 and the intensity of the background noise, it may be better to make it asymmetric. Then, Figure 1
The quarter-wave plate installed so that it has an axis of 0 degree or 90 degree with respect to the plane of the paper, creates a 90 degree phase difference between the S-polarized component and the P-polarized component, and transports the beam. It is led to the system 31. The reference light 18, the probe light 19, and the pump light 20 that have passed through the beam transport system 31 obliquely enter the sample 17 at different timings, are obliquely reflected, and return to the beam transport system 31. After that, the reference light 18 and the probe light 19 again come out of the beam transport system 31, and next, BS
Head to 43. One of the lights split by the BS 43 is the reference light 1 having a phase difference of 90 degrees by the polarizing plate 46.
8 and the probe light 19 are converted into interference light 32. The other light is converted into interference light 33 between the reference light 18 and the probe light 19 having a phase difference of −90 degrees by the polarizing plate 47. In order to realize such a relationship between phase and polarization,
Both the polarizing plate 46 and the polarizing plate 47 need to have an axis of 45 degrees with respect to the paper surface of FIG. 1, and the axes of both polarizing plates must have a right angle relationship. Here, the outputs of the detector 12 and the detector 13 include information on the change in reflectance on the sample surface in addition to the information on the phase change of the probe light 19 due to the displacement of the sample surface. Therefore, by taking the difference between the outputs of the detector 12 and the detector 13, information on the phase change of the probe light 19 can be mainly extracted. The same function is performed by PBS1 in FIG.
It can also be realized by a combination of 1, the detector 12, and the detector 13. However, it is not possible to consider the possibility that the 90-degree phase difference provided by the quarter-wave plate 6 may shift due to repeated reflection and transmission thereafter. In order to compensate for the shift, in this embodiment, the phase compensating plate 44 and the phase compensating plate 45 are provided immediately before the interference light is extracted from the mixed light of the reference light 18 and the probe light 19.

In the embodiment shown in FIG. 4, a specific example of the portion shown as the beam transport system 31 in FIG. 1 is shown together with the sample 17. Further, FIG. 4 is an embodiment of the first pattern of the present invention. The mixed light of the reference light 18 and the probe light 19 is separated into the P-polarized component and the S-polarized component by the PBS 34, and becomes the reference light 18 and the probe light 19, respectively.
The reference light 18 and the probe light 19 after separation go around the closed loop in different directions while maintaining their respective polarization states,
At the same time, it reaches PBS 34. When passing through the PBS 34, the reference light 18 and the probe light 19 are mixed and guided to the detection unit. A BS 36 for guiding the pump light 20 to the sample 17 is installed between the PBS 34 and the detection unit. Pump light 20 must be either P-polarized or S-polarized. An optical path connecting the mirror 35 and the lens 29, and PB
The optical path connecting S34 and the lens 29 is the lens 29
Is set in a position that is parallel to the optical axis of the lens and is symmetrical with respect to the optical axis of the lens 29. In this embodiment, since the reference light and the probe light pass through the BS 36 once before reaching the detection portion, their intensities are halved. Pump light is sample 17
Since it passes through the BS 36 once before reaching, the intensity is halved. Moreover, since the probe light and the reference light pass through the closed loop in different polarization states, the influence of disturbance may be different for each polarization state.

In the embodiment shown in FIG. 5, a specific example of the portion shown as the beam transport system 31 in FIG. 1 is shown together with the sample 17. FIG. 5 shows another embodiment of the first pattern of the present invention. Reference light 18 and probe light 19
The mixed light of is separated into an S-polarized component and a P-polarized component by the PBS 34 and becomes the reference light 18 and the probe light 19, respectively. The separated reference light 18 and probe light 19 make one round in different directions in the closed loop while maintaining their respective polarization states, and at the same time reach the PBS 34. When passing through the PBS 34, the reference light 18 and the probe light 19 are mixed and guided to the detection unit. During the closed loop, the pump light 20 was applied to the sample 1
BS 36 for guiding to 7 is installed. Pump light 20
Must be S-polarized. Mirror 25 and lens 2
The optical path connecting 9 and the optical path connecting the PBS 34 and the lens 29 are both parallel to the optical axis of the lens 29, and the lens 2
It is set at a position symmetrical with respect to the optical axis of 9. In this embodiment, the reference light and the probe light are transmitted to BS3 before reaching the detection unit.
Since 6 passes once, their intensity is halved. Before pump light reaches the sample 17, BS36 once,
As it passes, its intensity is halved. Moreover, since the probe light and the reference light pass through the closed loop in different polarization states, the influence of disturbance may be different for each polarization state.

In the embodiment shown in FIG. 6, a specific example of the portion shown as the beam transport system 31 in FIG. 1 is shown together with the sample 17. Further, FIG. 6 shows an embodiment of the second pattern of the present invention. The mixed light of the reference light 18 and the probe light 19 is separated into the P-polarized component and the S-polarized component by the PBS 34, and becomes the reference light 18 and the probe light 19, respectively.
The separated reference light 18 and probe light 19 travel in different directions in the closed loop. The reference light 18 is a half-wave plate 3 installed so as to have an axis of 45 degrees with respect to the paper surface of FIG.
The P polarized light is converted into the S polarized light by 8, and travels through the remaining closed loop to reach the PBS 34. On the other hand, probe light 1
9 travels in a closed loop in the opposite direction to the reference light 18, is converted from S-polarized light into P-polarized light by the same half-wave plate 38, and travels in the remaining closed loop, and P at the same time as the reference light 18.
Reach BS34. Since the reference light 18 and the probe light 19 that have gone around the closed loop are both converted to different polarization states, they travel in the direction opposite to the light source direction by the PBS 34 and are guided to the detection unit side by the BS 37. The pump light 20 is guided into the closed loop through the PBS 34, makes a circuit around the closed loop, and is then ejected by the PBS 34 in a direction different from the detector side. The pump light 20 is P-polarized,
Or must be S-polarized. Mirror 3
The optical path connecting the lens 5 and the lens 29 and the optical path connecting the half-wave plate 38 and the lens 29 are both set parallel to the optical axis of the lens 29 and symmetrical to the optical axis of the lens 29. It In this embodiment, since the reference light and the probe light pass through the BS 37 twice before reaching the detection portion, their intensities become 1/4. On the other hand, pump light sets BS37 to 1
Since it does not pass even times, its intensity does not change. Further, since the probe light and the reference light pass through most of the common optical path in the same polarization state, the influence of disturbance is smaller than that of the first pattern.

In the embodiment shown in FIG. 7, a specific example of the portion shown as the beam transport system 31 in FIG. 1 is shown together with the sample 17. FIG. 7 shows another embodiment of the second pattern of the present invention. Reference light 18 and probe light 19
The mixed light of is separated into an S-polarized component and a P-polarized component by the PBS 34 and becomes the reference light 18 and the probe light 19, respectively. The separated reference light 18 and probe light 19 travel in different directions in the closed loop. The reference light 18 is converted from S-polarized light into P-polarized light by the half-wave plate 38 installed so as to have an axis of 45 degrees with respect to the paper surface of FIG. Reach On the other hand, the probe light 19 travels in a closed loop in the opposite direction to the reference light 18,
Similarly, the half-wave plate 38 converts the P-polarized light into S-polarized light, travels through the remaining closed loop, and reaches the PBS 34 at the same time as the reference light 18. Reference beam 18 that goes around the closed loop
Since both the probe light 19 and the probe light 19 have been converted into different polarization states, they travel in a direction opposite to the light source direction by the PBS 34, and are guided to the detection unit side by the BS 37. The pump light 20 is guided into the closed loop through the PBS 39, passes through the sample, and is then ejected by the PBS 34 in a direction different from the detector side. Pump light 20 must be P-polarized. The optical path that connects the PBS 39 and the lens 29 and the optical path that connects the PBS 34 and the lens 29 are both set parallel to the optical axis of the lens 29 and symmetrical to the optical axis of the lens 29. In this embodiment, the reference light and the probe light are transmitted to the BS 37 twice before reaching the detector.
As they pass, their intensity is ¼. On the other hand, since the pump light does not pass through BS37 even once, its intensity does not change. Further, since the probe light and the reference light pass through most of the common optical path in the same polarization state, the influence of disturbance is smaller than that of the first pattern.

In the embodiment shown in FIG. 8, a specific example of the portion shown as the beam transport system 31 in FIG. 1 is shown together with the sample 17. Further, FIG. 8 shows an embodiment of the third pattern of the present invention. The mixed light of the reference light 18 and the probe light 19 is separated into the P-polarized component and the S-polarized component by the PBS 34, and becomes the reference light 18 and the probe light 19, respectively.
After that, the reference light 18 includes the PBS 40, the lens 29, the sample 17, the lens 50, the PBS 51, the mirror 48, and the mirror 4.
Pass through the order 9 and reach PBS 52. On the other hand, the probe light 19 passes through the mirror 25, the mirror 26, the PBS 40, the lens 29, the sample 17, the lens 50, and the PBS 51 in this order, and reaches the PBS 52 at the same time as the reference light 18. P
The reference light 18 and the probe light 19 reaching the BS 52 are mixed and travel toward the detection unit. B for guiding the pump light 20 to the sample 17 between the PBS 51 and the lens mirror 50
S36 is installed. Since the pump light 20 is guided to the light source side after passing through the sample 17, it does not return to the optical path toward the detection unit. There is no limitation on the polarization state of the pump light 20. In this embodiment, since the reference light and the probe light pass through the BS 36 once before reaching the detection portion, their intensities are 1 /
It becomes 2. Since the pump light passes through the BS 36 once before reaching the sample 17, its intensity is halved. Also,
Since the probe light and the reference light are incident on the sample in the same optical path, when the sample surface is tilted, the deviation of the reflected light with respect to the designed optical path acts equally and cancels the influence. This is shown in FIG. FIG. 11A shows a state in which the sample is tilted in the first pattern and the second pattern. It can be seen that the positions of the reference light 18 and the probe light 19 after reflection on the lens after reflection are displaced by a and b, respectively. In this case, a and b are not equal to each other, which causes a shift of the optical path at the time of interference. On the other hand, FIG. 11B
Indicates that the deviation (a) of the reference light 18 and the deviation (b) of the probe light 19 in the third pattern are always equal. Therefore, in the case of the third pattern, the inclination of the sample surface does not cause the optical path shift at the time of interference.

In the embodiment shown in FIG. 9, a specific example of the portion shown as the beam transport system 31 in FIG. 1 is shown together with the sample 17. FIG. 9 is another embodiment of the third pattern of the present invention. Reference light 18 and probe light 19
The mixed light of is separated into a P-polarized component and an S-polarized component by the PBS 34 and becomes the reference light 18 and the probe light 19, respectively. After that, the reference light 18 is reflected by the PBS 40, the lens 29,
Sample 17, lens 29, half-wave plate 41, PBS4
0, mirror 26, mirror 25 in that order, and then P
Reach BS34. On the other hand, the probe light 19 is reflected by the mirror 2
5, mirror 26, PBS 40, lens 29, sample 17,
The light passes through the lens 29, the half-wave plate 41, and the PBS 40 in this order, and reaches the PBS 34 at the same time as the reference light 18. P
Between BS34 and PBS40, between PBS40 and mirror 26,
Between mirror 26 and mirror 25, and between mirror 25 and PBS3
Between the four, there are two optical paths, which are parallel and close to each other. Reference light 18 from P polarized light to S
The half-wave plate 41 is installed so as to have an axis of 45 degrees with respect to the paper surface of FIG. 9 so as to convert it into polarized light and convert the probe light 19 from S-polarized light into P-polarized light. PBS for the second time
The reference light 18 and the probe light 19 reaching 34 are mixed,
It progresses in the direction opposite to the direction of the light source. However, the optical path when the mixed light first enters the PBS 34 and the mixed light
The optical path from S34 toward the detection unit is parallel, but the position is slightly different. Pump light 2 is provided between the PBS 34 and the detector.
BS36 for guiding 0 to the sample 17 is installed. The pump light 20 passes through the sample 17 and then the second PBS3.
Since it is guided to the light source side when passing through 4, it does not return to the optical path toward the detector. Pump light 20 must be either P-polarized or S-polarized. The optical path that connects the PBS 40 and the lens 29 and the optical path that connects the half-wave plate 41 and the lens 29 are both set parallel to the optical axis of the lens 29 and symmetrical to the optical axis of the lens 29. It In this embodiment, since the reference light and the probe light pass through the BS 36 once before reaching the detection portion, their intensities are halved. Pump light B before reaching sample 17
Since it passes once through S36, its intensity is halved. Also, it is not possible to have a Sagnac interferometer because it is impossible for the probe light and reference light to have a common closed-loop optical path. can get. Also,
In the parallel portion of the optical path, the probe light and the reference light travel in the same polarization state, and therefore, like the second pattern, the influence of disturbance is smaller than that of the first pattern. Further, since the probe light and the reference light are incident on the sample in the same optical path, when the sample surface is tilted, the deviation of the reflected light with respect to the designed optical path acts equally and cancels the influence. (See Figure 11B). Therefore, it is not affected by the inclination of the sample surface as compared with the first pattern and the second pattern.

In the embodiment shown in FIG. 10, a concrete example of the portion shown as the beam transport system 31 in FIG.
Shown with sample 17. Further, FIG. 10 shows a third embodiment of the present invention.
It is another example of a pattern. The mixed light of the reference light 18 and the probe light 19 is separated into the S-polarized component and the P-polarized component by the PBS 34, and becomes the reference light 18 and the probe light 19, respectively. After that, the reference light 18 passes through the quarter-wave plate 28, the lens 29, the sample 17, the lens 29, the quarter-wave plate 28, the PBS 34, the mirror 25, the mirror 26, and the mirror 35 in this order, and then again. Reach PBS 34. On the other hand, the probe light 19 includes a mirror 35, a mirror 26, a mirror 25, a PBS 34, a quarter-wave plate 28, and a lens 2.
9, the sample 17, the lens 29, the quarter wavelength plate 28, and the reference light 18, and reaches the PBS 34 at the same time.
Between PBS 34 and mirror 35, between mirror 35 and mirror 26
, Between mirror 26 and mirror 25, and between mirror 25 and PB
There are two optical paths between S34, which are parallel and close to each other. In order to convert the reference light 18 from S polarized light to P polarized light and the probe light 19 from P polarized light to S polarized light, the quarter wave plate 28 has an axis of 45 degrees with respect to the paper surface of FIG. Is installed in. The reference light 18 and the probe light 19 that have reached the PBS 34 for the third time are mixed and travel in a direction opposite to the light source direction. However, the optical path when the mixed light first enters the PBS 34 and the optical path when the mixed light travels from the PBS 34 to the detection unit are parallel, but the positions are slightly different. A BS 36 for guiding the pump light 20 to the sample 17 is installed in the optical path for reference light between the PBS 34 and the mirror 25. The pump light 20 is the sample 17
After passing through, the light beam is guided to the light source side when passing through the PBS 34 for the second time, and therefore does not return to the optical path toward the detection unit.
Pump light 20 must be P-polarized. PBS3
The two optical paths from the 4 to 1/4 wave plate 28 toward the lens 29 are both parallel to the optical axis of the lens 29,
Moreover, it is set at a position symmetrical with respect to the optical axis of the lens 29. In this embodiment, the reference light is transmitted to the BS before reaching the detector.
Since it passes through 36 once, its intensity is halved.
On the other hand, since the probe light never passes through BS36,
Its intensity does not change. Since the pump light passes through the BS 36 once before reaching the sample 17, its intensity is halved. In addition, since it is impossible for the probe light and the reference light to have a common optical path, it does not serve as a Sagnac interferometer, but since each light travels in parallel in spatially close positions, an effect similar to that of a Sagnac interferometer can be obtained. . Further, in the parallel portions of the optical paths, the probe light and the reference light travel in the same polarization state, and therefore, like the second pattern, the influence of disturbance is smaller than that of the first pattern. Further, since the probe light and the reference light are incident on the sample in the same optical path, when the sample surface is tilted, the deviation of the reflected light with respect to the designed optical path acts equally and cancels the influence. (Fig. 1
1B). Therefore, it is not affected by the inclination of the sample surface as compared with the first pattern and the second pattern.

[0038]

The present invention is carried out in the form as described above, and has the following effects. The reference light, the probe light, and the pump light of the same wavelength are obliquely incident on the sample surface, and two optical paths are shared immediately before the sample, so that Sagnac interference can be achieved without using a wavelength conversion element such as SHG. It is possible to measure the sample surface displacement using an interferometer or an interferometer having an effect close to that, and to measure the film thickness by the method. By substituting a lens for condensing each parallel light coming toward the sample on the sample surface and a lens for returning the light reflected from the irradiation spot on the sample surface to the parallel light, one lens can be used. An optical system that makes effective use of space can be assembled. Also, by disposing two optical paths connecting the lens and the optical element on the side opposite to the sample as viewed from the lens in parallel to the optical axis of the lens and symmetrically with respect to the optical axis of the lens, The influence of aberration can be reduced.

Regarding the two optical paths immediately before the sample, the reference light and the probe light having orthogonal polarization states travel in opposite directions in the two optical paths, and the pump light having a polarization state orthogonal to the reference light is the same as the reference light. By proceeding in the direction, the first pattern of the measuring method of the present invention can be realized. Alternatively, with respect to the two optical paths immediately before the sample, the reference light and the probe light whose polarization states are orthogonal to each other travel in opposite directions in the two optical paths, and the pump light having a polarization state orthogonal to the probe light has the same direction as the probe light. Then, the first pattern of the measuring method of the present invention can be realized. PBS for separating the reference light and the probe light, a closed loop in which the separated reference light and the probe light travel in opposite directions while maintaining their polarization states, a sample installed in the middle of the closed loop, and a reference light and a probe light. With the BS that guides the pump light to the optical path, the beam transport system of the first pattern can be realized.

Regarding the two optical paths immediately before the sample, the reference light and the probe light having the same polarization state travel in opposite directions in the two optical paths, and the pump light having a polarization state orthogonal to the reference light has the same direction as the reference light. To the second of the measuring method of the present invention.
The pattern can be realized. Alternatively, with respect to the two optical paths immediately before the sample, the reference light and the probe light having the same polarization state travel in opposite directions in the two optical paths, and the pump light having a polarization state orthogonal to the probe light is in the same direction as the probe light. By proceeding, the second pattern of the measuring method of the present invention can be realized. PB for separating reference light and probe light
S, a closed loop in which the reference light and the probe light after separation travel in opposite directions, a half-wave plate that converts each polarization state of the ongoing reference light and probe light into orthogonal states, and in the middle of the closed loop The beam transport system of the second pattern can be realized by the sample to be installed and the BS that guides the pump light to the optical paths of the reference light and the probe light.

Regarding the two optical paths immediately before the sample, the reference light and the probe light whose polarization states are orthogonal to each other travel along the two optical paths in the same direction, and the pump light having the same polarization state as the reference light is opposite to the reference light. By proceeding in the direction, the third pattern of the measuring method of the present invention can be realized. Alternatively, with respect to the two optical paths immediately before the sample, the reference light and the probe light whose polarization states are orthogonal to each other travel in the same optical path in the two optical paths, and the pump light having the same polarization state as the probe light is opposite to the probe light. Then, the third pattern of the measuring method of the present invention can be realized. PBS for separating the reference light and the probe light from the light of the light source, a PBS for mixing the reference light and the probe light that have passed through different optical paths, a means for guiding the mixed light to the sample surface, and a mixed light reflected by the sample for the next optical path. , PBSA for re-separating the reference light and the probe light from the mixed light after the reflection, a PBS for mixing the reference light and the probe light that have passed through different optical paths after the re-separation, and a pump for the optical paths of the reference light and the probe light. The BS that guides the light can realize the above-described beam transport system of the third pattern. By constructing an optical path having the same total optical path length between the light source and the detector for the reference light and the probe light, both lights can reach the detector at the same time and interfere with each other. In the above third pattern, one PBS for separating the reference light and the probe light from the light of the light source, and one PBS for mixing the reference light and the probe light that have passed through different optical paths after the re-separation are used.
, And at the same time, the PBS that mixes the reference light and the probe light that have passed through different optical paths and the PBS that re-separates the reference light and the probe light from the mixed light after reflection is replaced by another PBS. The system can be simplified. In the above beam transportation system, 2
By arranging two long optical paths in parallel between the PBSs so as not to overlap with each other, and at the same time arranging two short optical paths in parallel with each other so as not to overlap with each other, an effect close to that of the Sagnac interferometer is obtained. Can be made. In the above third pattern, a PBS for separating the reference light and the probe light from the light of the light source, a PBS for mixing the reference light and the probe light that have passed through different optical paths, and a PBS for mixing the reflected light with the reference light and the probe light. PBS for separation, and PBS for mixing reference light and probe light that have passed through different optical paths after re-separation
The beam transport system can be simplified by substituting one polarization beam splitter for. In the above beam transport system, by arranging two optical paths of the three closed loops passing through the PBS that do not pass through the sample in parallel and so as not to overlap, an effect close to that of a Sagnac interferometer can be obtained. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a common part in an embodiment of the present invention.

FIG. 2 is a diagram showing the principle of a sample surface displacement measuring method using a conventional Sagnac interferometer.

FIG. 3 is a diagram showing incident light paths of a reference light, a probe light, and a pump light on a sample, and polarization states.

FIG. 4 is a diagram showing an example of a first pattern in the present invention.

FIG. 5 is a diagram showing another embodiment of the first pattern of the present invention.

FIG. 6 is a diagram showing an embodiment of a second pattern in the present invention.

FIG. 7 is a diagram showing another embodiment of the second pattern in the present invention.

FIG. 8 is a diagram showing an example of a third pattern in the present invention.

FIG. 9 is a diagram showing another embodiment of the third pattern of the present invention.

FIG. 10 is a diagram showing still another embodiment of the third pattern of the present invention.

FIG. 11 is a diagram showing a comparison of influences of sample inclinations.

[Explanation of symbols]

1 Short pulse laser 2, 5, 38, 41 Half-wave plate 3, 11, 24, 34, 39, 40, 51, 52 Polarizing beam splitter 4, 7, 9, 25, 26, 30, 35, 42 , 48, 4
9 mirror 6, 28 quarter wave plate 8 retroreflector 10 AOM or chopper 12, 13 detector 14 lock-in amplifier 15 driver 16 data acquisition system 17 sample 18 reference light 19 probe light 20 pump light 21 wavelength conversion element ( SHG, etc.) 22, 27 Dichroic beam splitter 23, 36, 37, 43 Beam splitter 29, 50 Lens 31 Beam transport system 32, 33 Interfering light 44, 45 Phase compensation plate 46, 47 Polarizing plate

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F065 AA30 AA65 BB13 BB17 CC02                       CC03 CC31 EE00 FF51 GG04                       GG25 LL12 LL33 LL35 LL37                 2G051 AA32 AA37 AA41 AA71 AB02                       AB06 BA10 BA11 BC01 CA03                       CB01 CB10 EA04                 2H052 AA01 AA04 AB24 AC04 AC09                       AC14 AC27 AD02 AD34 AF04

Claims (7)

[Claims] 1. A short pulse laser light source, a reference light / probe light / pump light separation means, a means for transporting these lights, a delay optical path for adjusting sampling timing, and a detector. Sample analyzer. The sample analyzer is a sample analyzer including a sample surface displacement measuring means for measuring an echo of an elastic wave excited by the pump light. This sample surface displacement measuring means includes the following. (A) A means that guides the reference light, the probe light, and the pump light having the same wavelength to the sample, separates the lights reflected by the sample, and guides only the reference light and the probe light to the detector to cause interference. (B) Further, the sample surface displacement measuring means makes each of the reference light, the probe light, and the pump light obliquely incident on the sample, and the two optical paths are shared by the incident and reflected lights of these three kinds of light. Including means to make. 2. A lens for converging each parallel light coming toward the sample on the sample surface, and a lens for returning the light reflected from the irradiation spot on the sample surface to the parallel light.
In addition, this sample analyzer includes means for substituting one lens for the above two types of lenses. The means includes two optical paths connecting the lens and an optical element on the side opposite to the sample as viewed from the lens, parallel to the optical axis of the lens and symmetric with respect to the optical axis of the lens. The sample analyzer according to claim 1, further comprising means arranged in a positional relationship. 3. A polarization beam splitter for separating the reference light and the probe light, a closed loop in which the separated reference light and probe light travel in opposite directions while maintaining their polarization states,
Includes a sample installed in the middle of the closed loop and a beam splitter that guides the pump light to the optical paths of the reference light and the probe light, and the polarization state and the optical path of the reference light, the probe light and the pump light immediately before the sample have the following relationship. The sample analyzer according to claim 1, which is present. (A) The reference light and the probe light whose polarization states are orthogonal to each other travel in opposite directions on the two optical paths, and the pump light having a polarization state orthogonal to the reference light travels in the same direction as the reference light. (B) Alternatively, reference light and probe light whose polarization states are orthogonal to each other travel in opposite directions in two optical paths, and pump light having a polarization state orthogonal to the probe light travels in the same direction as the probe light. The device consists of a polarized beam splitter that separates the reference light and the probe light, a closed loop in which the separated reference light and probe light travel in opposite directions while maintaining their polarization states, a sample installed in the middle of the closed loop, and a reference. The sample analyzer according to claim 1, further comprising a beam splitter that guides the pump light to the optical paths of the light and the probe light. 4. A polarization beam splitter for separating the reference light and the probe light, a closed loop in which the separated reference light and the probe light travel in opposite directions, and a polarization state of the reference light and the probe light in the closed loop orthogonal to each other. Half to convert to state
It includes a wave plate, a sample installed in the middle of a closed loop, and a beam splitter that guides the pump light to the optical paths of the reference light and probe light, and the polarization state and the optical path of the reference light, probe light, and pump light immediately before the sample are as follows. The sample analyzer according to claim 1, which is in a relationship. (A) The reference light and the probe light having the same polarization state travel in opposite directions on the two optical paths, and the pump light having a polarization state orthogonal to the reference light travels in the same direction as the reference light. (B) Alternatively, the reference light and the probe light having the same polarization state travel in opposite directions on the two optical paths, and the pump light having a polarization state orthogonal to the probe light travels in the same direction as the probe light. This sample analyzer is a polarization beam splitter that separates the reference light and the probe light, a closed loop in which the separated reference light and probe light travel in opposite directions, and orthogonal polarization states of the reference light and probe light that are running in the closed loop. Half-wave plate for converting into a closed state, sample installed in the middle of the closed loop,
And a beam splitter that guides the pump light to the optical paths of the reference light and probe light. 5. A polarization beam splitter for separating reference light and probe light from light from a light source, a polarization beam splitter for mixing reference light and probe light that have passed through different optical paths, means for guiding the mixed light to a sample surface, and a sample A means for guiding the reflected mixed light to the next optical path, a polarization beam splitter that re-separates the reference light and the probe light from the reflected mixed light, and a polarization that mixes the reference light and the probe light that have passed through different optical paths after the re-separation. A beam splitter, and a beam splitter that guides pump light to the optical paths of the reference light and the probe light,
For the reference light and the probe light, including the optical path with the same total optical path length between the light source and the detector, the polarization state and the optical path of the reference light, the probe light and the pump light immediately before the sample have the following relationship. 1. The sample analyzer according to 1. (A) The reference light and the probe light whose polarization states are orthogonal to each other travel along the two optical paths in the same direction, and the pump light having the same polarization state as the reference light travels in the opposite direction to the reference light. (B) Alternatively, the reference light and the probe light whose polarization states are orthogonal to each other travel along the two optical paths in the same direction, and the pump light having the same polarization state as the probe light travels in the opposite direction to the probe light. (A) This sample analyzer is a polarization beam splitter that separates the reference light and the probe light from the light of the light source, a polarization beam splitter that mixes the reference light and the probe light that have passed through different optical paths, and guides the mixed light to the sample surface. Means, means for guiding the mixed light reflected by the sample to the next optical path, a polarizing beam splitter for re-separating the reference light and probe light from the mixed light after reflection, reference light and probe light that have passed through different optical paths after re-separation And a beam splitter that guides the pump light to the optical paths of the reference light and the probe light. This sample analyzer includes an optical path having the same total optical path length between the light source and the detector with respect to the reference light and the probe light. 6. The sample analyzer according to claim 5, wherein
A device that shares a polarization beam splitter as shown below. (B) The polarization beam splitter that separates the reference light and the probe light from the light from the light source and the polarization beam splitter that mixes the reference light and the probe light that have passed through different optical paths after re-splitting are replaced with a single polarization beam splitter. (B) At the same time, a polarizing beam splitter that mixes the reference light and the probe light that have passed through different optical paths, and a polarizing beam splitter that re-separates the reference light and the probe light from the mixed light after reflection is another polarizing beam splitter. Replace with. (C) This sample analyzer includes two long optical paths and two short optical paths between the two polarization beam splitters. These two long optical paths have a parallel and non-overlapping positional relationship. Further, these two short optical paths are characterized in that they have a parallel and non-overlapping positional relationship. 7. The sample analyzer according to claim 5, which is a sample analyzer according to claim 5, wherein the polarizing beam splitter is shared as follows. , The three closed loops that come out of the polarization beam splitter and return to the polarization beam splitter again, and the two optical paths of the three closed loops that do not pass through the sample are parallel and do not overlap each other. An apparatus having the sample analyzer of claim 5. (A) A polarization beam splitter that separates the reference light and the probe light from the light of the light source, a polarization beam splitter that mixes the reference light and the probe light that have passed through different optical paths, and a reference beam and a probe light from the mixed light after reflection. The polarization beam splitter for splitting and the polarization beam splitter for mixing the reference light and the probe light that have passed through different optical paths after re-splitting are replaced with one polarization beam splitter. (B) Including the three closed loops that come out of the polarization beam splitter and return to the polarization beam splitter, the two optical paths of the three closed loops that do not pass through the sample are parallel and do not overlap. Have a positional relationship.
This sample analyzer exits from this polarization beam splitter and returns to this polarization beam splitter again. 3
Contains a closed loop of books. Of the three closed loops, the two optical paths that do not pass through the sample have a parallel and non-overlapping positional relationship.