JPH0773500A - Waveguide and focus detecting device or step measuring device using the same - Google Patents

Abstract

PURPOSE:To allow a reflected light to be accurately made incident on a waveguide from a surface to be detected by using the waveguide constituted so as to become a single mode waveguide or a double mode waveguide according to a polarization direction of light. CONSTITUTION:The annealing is performed to both side areas 6a, 6b and 3a, 4a of the single mode waveguide 5 after a proton is exchanged, and a second core part is formed. The areas 3a, 4a become the single mode waveguides 3, 4 for distribution, and the areas 5a, 6a, 67b covering first, second core parts become the double mode waveguide 7. Since only abnormal light beam is increased when the proton is exchanged, when the conditions of the proton exchange and the annealing are selected properly, the waveguide 5 and the areas 6a, 6b become the single mode waveguide 7 for a waveguide light of a normal light beam and become the double mode waveguide 7 for the waveguide light of the abnormal light beam. A completely combined length is defined as Lc, and the length L of a double mode area is decided to be a prescribed length, and the arrangement of a laser light beam source and a substrate is decided. When the outgoing light quantities from the waveguides 3, 4 are differential-amplified, the condensing deviation of light is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide and a focus detecting device or a step measuring device using the waveguide.

[0002]

2. Description of the Related Art In recent years, waveguides have been drawing attention in various fields. The reason is that the use of the waveguide has the advantages that the optical system can be made smaller and lighter, and the adjustment of the optical axis becomes unnecessary. The waveguide is a single mode waveguide in which only the 0th mode light is excited due to the difference in the refractive index between the waveguide (core portion) and the substrate (clad portion), the width of the waveguide or the refractive index distribution.
It is classified into a double-mode waveguide in which two modes of the next and first modes are excited, and a multi-mode waveguide in which three or more modes of zero-order, first-order, and second-order and above are excited.

In such a waveguide, the present inventors have proposed a configuration in which the state of an object to be inspected (surface to be inspected) is optically measured using a double mode waveguide (H. Oki).
and J. Iwasaki, Optics Com
communications 85 (1991) 177).
When laser light is incident on the double mode waveguide, the 0th-order mode and the 1st-order mode are excited in the waveguide according to the amplitude distribution of the laser light incident on the waveguide. The two modes interfere in the waveguide. Therefore, the light intensity distribution in the waveguide is asymmetric. Therefore, if the length of the double-mode waveguide is set to an optimum dimension in advance and the branch waveguide is connected after that, the asymmetry of the light intensity distribution in the double-mode region is caused by the amount of light emitted from the two branched waveguides. The difference can be checked by detecting the difference.

Here, two factors are considered to bring about the asymmetry of the light intensity distribution in the waveguide. One is when the intensity distribution of the incident laser light is asymmetric, and the other is when the phase distribution of the incident laser light is asymmetric. If the length of the double mode region is appropriately selected, the asymmetry in any case can be detected efficiently. The asymmetry of the intensity distribution can observe the distribution of the reflectance of the light on the surface to be inspected, and the asymmetry of the phase distribution can observe the distribution of the slope, step, or height of the surface to be inspected.

A focus detection device has been proposed which detects the displacement (focus shift) of the incident laser light in the optical axis direction by using the mode interference in the double mode waveguide (R. Juskaitis and
T. Wilson, Applied Optics
31 (1992) 4569). This is a configuration in which the center of the end face of the double mode fiber and the incident position of the laser spot are displaced. At this time, if the laser spot is out of focus (focus), an inclination occurs in the equiphase surface of the light incident on the fiber. The focus shift can be detected (focus detection) by detecting the asymmetry of the phase distribution caused by this inclination.

[0006]

However, the above-described focus detection device has a problem that it is not possible to accurately detect the shift of the focus. In view of the above problems, it is an object of the present invention to provide a focus detection device capable of accurately detecting a focus shift.

[0007]

As a result of earnest research, the inventors have found that it is difficult to align the light incident on the fiber because the light source and the fiber are separately arranged.
Furthermore, since the fiber is used, it has been found that it is not possible to "select an appropriate length for the double mode region" as described above. Because of these two causes,
I realized that I couldn't measure accurately.

Therefore, the inventors have considered using a waveguide. The inventors first prototyped a device using the waveguide having the configuration shown in FIG. This is a configuration in which the light emitting waveguide 71 and the light receiving waveguide 72 are formed on the same substrate, and the light emitting position and the light receiving position can be easily and accurately aligned. Further, since the waveguide is used, it is possible to accurately "select the length of the double mode region to an appropriate length" by using a well-known semiconductor manufacturing technique.

This device requires an incident means for guiding the reflected light so that the light emitted from the waveguide 71 is reflected by the surface to be detected and is incident on the waveguide 72. It is difficult to arrange the incident means, the waveguide, the surface to be inspected, etc. so that the reflected light is accurately incident on the waveguide. Further, since such an incident means is arranged, the device becomes large. Therefore, it is not necessary to align the reflected light when entering the waveguide, and a waveguide that does not require such an incident means was considered.

The inventors of the present invention use a waveguide having a structure in which it becomes a single mode waveguide or a double mode waveguide depending on the polarization direction of light, so that the reflected light from the surface to be examined is incident on the waveguide. We found a configuration that eliminates the need for alignment when performing. That is, the first aspect of the present invention is "the outward trip".
A single mode waveguide that propagates the "outgoing path" light in a single mode, and a double mode waveguide that propagates the "return path" light in a double mode for the "return path" light. And a center of the single-mode waveguide and a center of the double-mode waveguide are deviated on at least one end face (claim 1).

Secondly, "a first core portion formed on a substrate and having a refractive index larger than that of the substrate for ordinary rays and extraordinary rays, and the substrate formed for only extraordinary rays on the substrate. A second core portion having a refractive index larger than that of the first core portion, and the first core portion constitutes a single mode waveguide that propagates the ordinary ray in a single mode with respect to the ordinary ray,
A region in which the first core portion and the second core portion are combined constitutes a double mode waveguide that propagates the extraordinary ray in a double mode with respect to the extraordinary ray, and the center of the single mode waveguide and the A waveguide characterized in that the center of the double-mode waveguide is deviated on at least one end face (claim 2).

Third, the waveguide according to claim 1 or 2, wherein the double mode waveguide is provided with an electrode for applying an electric field. (Claim 3) ”is provided. Fourth, “claim 1
Or the waveguide according to 3, wherein a guiding single-mode waveguide for guiding the light in the "outgoing path" to the single-mode waveguide, and the light in the "return path" in the double-mode waveguide The waveguide (claim 4) according to claim 1 or 3, characterized in that at least two distributing single-mode waveguides for distributing the intensity distribution are provided.

Fifth, "The waveguide according to claim 2 or 3, wherein the guiding single mode waveguide for guiding the ordinary ray to the single mode waveguide, and the waveguide in the double mode waveguide are provided. A waveguide (claim 5) according to claim 2 or 3, characterized in that at least two distributing single-mode waveguides for distributing the light intensity distribution of the extraordinary ray are provided.

Sixthly, "a waveguide and polarization control means arranged between the waveguide and the surface to be inspected, for making the polarization direction of the" forward "light and the polarization direction of the" return "light orthogonal to each other. First condensing means for condensing the light emitted from the waveguide on the surface to be inspected, and second condensing means for condensing the reflected light from the surface to be inspected on the waveguide. And at least two detectors for detecting the light intensity distribution of the reflected light in the waveguide,
A focus detection device comprising a detection means for detecting a shift of the focus of the light focused on the surface to be detected from a signal of the detector, wherein the waveguide is a waveguide. A focus detection device (claim 6) ″ is provided.

Further, it has been noticed that the focus detecting device can be applied to measure the step of the surface to be inspected. Therefore, seventhly, "a waveguide and polarization control means which is disposed between the waveguide and the surface to be inspected and which makes the polarization direction of the" forward "light and the polarization direction of the" return "light orthogonal to each other, First condensing means for condensing the light emitted from the waveguide onto the surface to be inspected, and second condensing means for condensing the reflected light from the surface to be inspected into the waveguide. The at least two detectors for detecting the light intensity distribution of the reflected light in the waveguide, and the step measuring device for measuring the step of the surface to be inspected from the signal of the detector, wherein the waveguide is provided. Alternatively, there is provided a step measuring device (claim 7) characterized in that it is the waveguide according to 2 or 3 or 4 or 5.

[0016]

According to the present invention, by using a waveguide having a structure in which a single-mode waveguide or a double-mode waveguide is formed depending on the polarization direction of light, alignment of reflected light to the waveguide is unnecessary. Therefore, the reflected light from the surface to be inspected can be accurately incident on the waveguide.

Further, since the double mode region can be easily and accurately manufactured by using the well-known semiconductor manufacturing technique, accurate measurement can be performed. Furthermore, when a substrate having an electro-optical effect is used, by applying an electric field to the waveguide, the complete coupling length of the waveguide can be changed to match the desired complete coupling length.

The complete coupling length is the length at which the phase difference between the 0th-order mode light and the 1st-order mode light propagating in the double mode region is π, and is the minimum length. The length of the double mode region can be generally determined by the length of the double mode waveguide, but when a single mode branching waveguide (single mode waveguide for distribution) is connected to the double mode waveguide (for example, two single modes). If the mode waveguide is connected in Y-branch, and the branch angle of the single mode waveguide is small, a region (coupling region) where the single mode waveguides optically couple with each other is formed. This is because the light propagating through the waveguide leaks into the clad (substrate), and the light is coupled between the waveguides that are close to each other. There are even and odd modes in this coupling region. These two modes are the 0th mode of the double-mode waveguide, 1
Corresponds to the next mode. In this coupling region, the optical power shifts between the two single mode waveguides due to the interference between the even mode and the odd mode. This can be considered similarly to the interference between the 0th-order mode and the 1st-order mode of the double-mode waveguide. Therefore, in such a case, the length of the double mode region is equal to the length of the double mode waveguide and the length of propagation in two modes due to the optical coupling of the branch waveguide.

The length L of the double mode area is
When observing the phase distribution of an object with the complete coupling length as L _c , the equation (1) is used, and L = L _c (2m + 1) / 2 (m = 0, 1, 2, ...) (1) Similarly, when observing the intensity distribution of an object, L = mL _c (m = 1, 2, ...) (2) may be set as in equation (2). Therefore, when the length of the double mode region does not completely match the desired length, it can be adjusted by changing the length of the complete bond length. These are described in detail in JP-A-4-208913.

If the double mode waveguide is connected to the Y-branch single mode waveguide (single mode waveguide for distribution) having a small branch angle, the contrast of the detection signal is improved, and the light intensity distribution in the double mode region is improved. Asymmetry can be detected accurately. This is because when the 0th-order mode and the 1st-order mode interfere with each other in the double-mode waveguide, the positions of the peaks (mountains) of the respective electric field distributions are different in the width direction of the waveguide, whereas the interference does not occur well. Thus, in the region where the single mode waveguides are optically coupled to each other as described above, the peaks (peaks) of the electric field distributions of the even mode (0th order mode) and the odd mode (1st order mode) can be aligned. This is because interference can occur efficiently because it is possible. Therefore, it is preferable to connect the double-mode waveguide and the Y-branch single-mode waveguide (distribution single-mode waveguide) having a small branching angle.

In the present invention, the thermal diffusion method of a predetermined metal is combined with the proton exchange method or the Li ₂ O external diffusion method,
We constructed a waveguide that can be a single-mode waveguide or a double-mode waveguide depending on the polarization direction of light. Among the methods described above, in the thermal diffusion method, than the substrate relative to the ordinary ray and extraordinary ray can be formed core portion is larger refractive index (first core portion), the proton exchange method and Li ₂
The O-out diffusion method can form a core portion (second core portion) having a higher refractive index than the substrate only for extraordinary rays.
As the metal used for this thermal diffusion, transition metals such as Ti, V, Ni and Cu are often used in the lithium niobate substrate. Also, in the case of lithium tantalate substrate, Cu, T
Transition metals such as i and Nb are often used. These are described in detail in the specification and drawings of Japanese Patent Application No. 4-262725.

By combining the above waveguide with a quarter wave plate, the polarization direction of the "outgoing" light and the polarization direction of the "returning" reflected light are orthogonal to each other. In the present invention, the "outgoing path" indicates the direction in which the light from the light source propagates to the object to be inspected (surface to be inspected), and the "return path" means that the reflected light from the object to be inspected propagates to the photodetector. Indicates the direction to go.

According to the present invention, it is possible to obtain a focus detection device capable of detecting a focus shift accurately and accurately. Furthermore, it is also possible to measure the level difference on the surface to be inspected by applying this focus detection device. Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0024]

1 and 2 are schematic configuration diagrams of a waveguide according to a first embodiment of the present invention. Hereinafter, a method for manufacturing a waveguide will be described with reference to FIGS. This manufacturing method is described in detail in the specification and drawings of Japanese Patent Application No. 4-262725. Here, the region 2a means the single mode waveguide 2
The region 3a is the single mode waveguide 3 and the region 4a is
Is a region in which the single-mode waveguide 4 is formed, the region 5a is a region in which the single-mode waveguide 5 is formed, and the regions 6a, 6b, and 5a are regions in which the double-mode waveguide 7 is formed.

The first core portion is formed on the regions 5a and 2a of the lithium niobate substrate 10 by using the well-known thermal diffusion method of Ti. The regions 2a and 5a are the single mode waveguides 2 (single mode waveguide for guiding) and 5. The single-mode waveguide 5 is smoothly bent from the single-mode waveguide 2 (single-mode waveguide for guiding) to the region 3a side (may be bent to the region 4a side).
It is manufactured so as to form a linear waveguide.

After that, the waveguide shown in FIG. 1 has the regions 6a and 6b on both sides of the single mode waveguide 5 and the region 3a.
4a is annealed after proton exchange (proton exchange method) to produce a second core portion (a cross-sectional view of the waveguide taken along the line AA in FIG. 1 is shown in FIG. 3). The areas 3a and 4a are
It becomes single mode waveguides 3 and 4 (single mode waveguide for distribution). Further, the regions (regions 5a, 6a, 6b) where the first core portion and the second core portion are combined become the double mode waveguide 7. Further, although FIG. 3 shows the overlapping of the Ti diffusion region and the proton exchange region, the illustration of this region is omitted in FIG.

Further, in FIG. 2, the regions 3a, 4a, 5a,
Annealing after proton exchange is performed on 6a and 6b (proton exchange method) to produce a second core portion (a cross-sectional view taken along line BB in FIG. 2 is shown in FIG. 4). The regions 3a and 4a become the single mode waveguides 3 and 4 (single mode waveguide for distribution). In addition, the region (regions 5a, 6a, 6b) where the first core portion and the second core portion are combined is a double mode waveguide 7
Becomes

Thermal diffusion of Ti increases both the refractive index for ordinary rays and the extraordinary ray, but for proton exchange, only the refractive index for extraordinary rays increases. Therefore, the waveguide manufactured in this manner is disclosed in Japanese Patent Application No. 4-262.
As proposed in the specification and drawings of No. 725, by appropriately selecting the conditions of the proton exchange and the annealing, the single mode waveguide 5 can be used for the guided light of the ordinary ray.
Therefore, for the extraordinary ray guided light, the waveguide 5 and the region 6
The double mode waveguide 7 is a combination of a and 6b.

FIG. 5 shows a focus detecting device according to the second embodiment of the present invention used for detecting a focus error signal of an optical disk or the like. In the second embodiment, the waveguide used in the first embodiment is used. Further, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 5, X-cut Y-propagation lithium niobate (LiNb
O ₃ ) substrate 10 is used.

In the focus detection, it is observed that the focus shifts due to the distribution of the inclination of the surface to be inspected. Therefore, the length of the double mode region is set so that the asymmetry of the phase distribution can be measured. This length is obtained by the equation (1). When the light propagates in the waveguide, the laser light source 1 and the lithium niobate substrate 10 are arranged so that the light emitted from the semiconductor laser 1 becomes an ordinary ray and the light in the polarization direction orthogonal to this becomes an extraordinary ray. Laser light is emitted from the end face 9 through the single mode waveguides 2 (guide single mode waveguides) and 5. The emitted laser light is collimated by the collimator lens 11, passes through the quarter-wave plate 12, and is condensed by the objective lens 13 onto the optical disc (test surface) 14 (first condensing means). . Optical disc (test surface)
The laser light (the light on the “return path”) reflected on 14 is again transmitted through the objective lens 13 and the quarter-wave plate 12 and converted into a polarization direction orthogonal to the polarization direction of the light on the “outgoing path”, and the collimator lens The light is focused on the end face 9 at 11. The light reflected by the optical disk (surface to be inspected) 14 (the light on the “return path”) becomes an extraordinary ray with respect to the lithium niobate substrate 10, and therefore passes through the double mode waveguide 7 and the single mode waveguide 3 at the branch 8.
4 (single mode waveguide for distribution). At this time, the light reflected by the optical disc (test surface) 14 (“return path”)
Light is shifted from the center of the entrance of the double mode waveguide 7, so that the double mode waveguide 7 is set to an appropriate length as described above, and the single mode waveguides 3, 4
The amount of light emitted from the (distribution single-mode waveguide) is detected by the photodetectors 15 and 16, and the photodetector 1 is detected by the differential amplifier 17.
By taking the difference between the signals from 5 and 16, it is possible to detect the focus shift of light. In FIG. 5, the reproduction system for signals recorded on the disc and the optical system for auto-tracking are omitted.

When the waveguide substrate is a substrate having an electro-optical effect, an electrode is provided on the substrate, and an electric field is applied to the waveguide by applying a voltage to this electrode, so that the complete coupling length of the double mode region is increased. Can be changed. In this way, when the length of the double mode region deviates from the preferable length for measuring, it becomes possible to measure under the preferable condition by changing the perfect bond length.

FIG. 6 shows a diagram in which electrodes are provided. In the second embodiment, the X-cut Y-propagation lithium niobate substrate 10 is used. The refractive index of this substrate can be efficiently changed by applying an electric field in the Z-axis direction. Therefore, the electrodes 18 and 19 are applied so that the electric field is applied in the Z-axis direction (lateral direction).
To place. When a Z-cut X- or Y-propagation lithium niobate substrate is used, the electrodes may be arranged so that an electric field is applied in the Z-axis direction (longitudinal direction). Electrode 18,
A power source (not shown) is connected to 19.

Further, when an electric field is applied to the waveguide, it is preferable to apply the electric field at a location where the refractive index distribution is symmetrical. Therefore, in FIG. 6, the electrode is arranged at the location before bending the single mode waveguide 5. Needless to say, the configurations of FIGS. 5 and 6 are not limited to the optical disc, and can be applied to a general optical focus detection device.

When the semiconductor laser 1 has a returning light,
The operation of the semiconductor laser 1 becomes unstable. Further, when the polarization direction of the light from the semiconductor laser 1 is deviated, the ordinary ray and the extraordinary ray may propagate through the waveguide, and the "outgoing" light may not propagate in a single mode. In such a case, single mode waveguide 2 (single mode waveguide for guiding)
A publicly known mode splitter may be provided. This mode splitter separates light by the polarization direction [ordinary light (TE mode), extraordinary light (TM mode)].

When the substrate is a Z-cut X- or Y-propagating lithium niobate substrate, a polarizer using a known metal cladding on the single-mode waveguide 2 (single-mode waveguide for induction). Should be provided. This polarizer absorbs TM mode (extraordinary light) light and
The light of mode (ordinary light) is transmitted. This is described in detail in the specification and drawings of Japanese Patent Application No. 4-313198.

FIG. 7 shows a laser scanning microscope using the step measuring apparatus according to the third embodiment of the present invention. This apparatus includes a first measuring unit that measures a step on the surface 39 to be inspected and a second measuring unit that measures a phase distribution or intensity distribution of the surface 39 to be inspected. Similar to the first and second embodiments,
The same reference numerals as in the first and second embodiments are given and detailed description thereof is omitted.

A waveguide similar to that of the first embodiment is used for the first measuring section. The second measurement section includes a double mode waveguide 27, a single mode waveguide 28 that is a branch waveguide,
A waveguide to which 29 (single mode waveguide for distribution) is connected is used. This waveguide is manufactured by using the Ti diffusion method, the Li ₂ O outdiffusion method, or the proton exchange method. Light emitted from the semiconductor laser 1 (light in the "outgoing path") is emitted from the end face 9 through the single mode waveguides 2 (single mode waveguide for guidance) and 5. This light is collimator lens 1
1 to make parallel light, and polarization-selective diffraction gratings 20 and 1/4
The objective lens 13 passes through the λ plate 12 and the XY scanner 21.
The light is focused on the surface 39 to be inspected by (first focusing means).

The polarization-selective diffraction grating 20 is constructed so as to transmit light in the polarization direction of the "outward path" and diffract the light in the polarization direction of the "return path". The XY scanner 21
The spot of the light focused on the test surface 39 is moved relative to the test surface 39. The reflected light from the surface to be inspected 39 (the “return light”) is collimated by the objective lens 13, passes through the ¼ λ plate 12, is converted into the polarization direction orthogonal to the “outgoing light”, and the polarization is selected. The diffraction grating 20 diffracts the light. Of the diffracted light, the polarization-selective diffraction grating is configured so that the 0th-order light enters the waveguide for step measurement detection and the 1st-order light enters the waveguide for measuring the phase distribution and intensity distribution of the surface 39 to be measured. Place 20. The 0th-order light is condensed by the collimator lens 11 (second condensing means) to the waveguide for detecting the step difference and the 1st-order light is condensed to the waveguide for measuring the phase distribution and the intensity distribution of the surface 39 to be measured. .

The 0th order light enters the double mode waveguide 7 as in the second embodiment and is detected by the photodetectors 15 and 16. In addition, the photodetectors 15 and 16 include the photodetectors 15 and 1
6, a differential circuit 22 for obtaining the difference between the optical signals detected by 6, a sum calculation circuit 23 for obtaining the sum of the signals detected by the photodetectors 15, 16, and a sum calculation circuit for the signals output from the differential circuit 22. And a divider 24 that divides by the signal output from 23. The focus shift amount is calculated by the differential circuit 22, the sum calculation circuit 23, and the divider 24.

When the distribution of the reflectance of the surface 39 to be tested is not constant, the amount of light incident on the waveguide changes. Therefore,
In the third embodiment, the corrected signal from the divider 24 is used. This is because the photodetectors 15 and 16 obtained by the differential circuit 22 are the signals of the total amount of light obtained by the sum calculation circuit 23.
This is a correction for eliminating the nonuniformity of the total amount of light by dividing by the signal of the difference in the amount of light incident on. Although it is preferable to make this correction, if no correction is made, the signal obtained by the differential circuit 22 may simply be used.

Further, the primary light is incident on the center of the end face of the double mode waveguide 25, and the single mode waveguides 28, 29.
The light is distributed by the (distribution single mode waveguide) as in the second embodiment, and the asymmetry of the light intensity is detected by the photodetector 3.
It is detected at 0 and 31, respectively. Here, since the light incident end of the double mode waveguide 25 functions the same as a pinhole, this configuration constitutes a confocal laser scanning microscope. The differential circuit 32 takes the difference between the signals of the photodetectors 30 and 31. The signal from the differential circuit 32 is used to detect the surface 3 to be measured.
The 9 phase (tilt or step) distribution or intensity (reflectance) distribution is measured.

When measuring the phase distribution of the surface to be inspected 39, the length of the double mode region is set to the length obtained by the equation (1),
When measuring the intensity distribution of the surface 39 to be inspected, the length of the double mode region is set to the length obtained by the equation (2). By applying a voltage to the electrodes 26 and 27 as in the second embodiment,
Since the length of the complete bond length can be changed, it is also possible to select the phase distribution and the intensity distribution to be measured by keeping the length of the double mode region constant and changing the applied voltage.

To measure the step difference measured by the first measuring section, the signal from the divider 24 is read out, and the signal from the divider 24 and the focus position of the objective lens 13 of the object 39 shown in FIG. 9 are read. It is converted from the relationship of the amount of deviation. The relationship in FIG. 9 is measured in advance. Further, a means for moving a stage or the like on which the object to be inspected is moved in the optical axis direction by a piezo actuator or the like is provided so that the signal of the divider 24 becomes 0 (the deviation of the focus becomes 0). ) Move the stage. The level difference of the surface 39 to be tested may be measured by measuring the amount of movement of this stage. In this case, it is not necessary to measure the relationship of FIG. 9 in advance.

In the third embodiment, one light source (semiconductor laser 1) is used to measure the level difference and the inclination or the inclination of the reflectance of the surface to be inspected 39, but as shown in FIG. You may measure it. In this, the waveguide used in the second measuring section is manufactured by the same manufacturing method as that of the waveguide used in the first measuring section. However, in this case, the center of the single mode waveguide and the center of the double mode waveguide are aligned at the end face 37.

The light from the semiconductor laser 1 is focused on the surface 39 to be detected and the reflected light is focused on the end face 9 of the waveguide in the same manner as described above. Similarly, with respect to the light from the semiconductor laser 33, the “outgoing light” propagates in the waveguide in a single mode,
The reflected light is condensed on the surface 39 to be inspected, the reflected light is condensed on the end surface 37, and the reflected light on the “return path” propagates in the waveguide in the double mode.

The other structure is similar to that of FIG. In the third embodiment, the step measuring device is used for the microscope, but the focus detecting device as in the second embodiment may be used instead of the step measuring device. Needless to say, the step measuring device can be used alone. When the step measuring device is used alone, the XY scanner 21 may be omitted.

[0047]

As described above, according to the present invention, since the waveguide in which the light emitting portion and the light receiving portion are integrated can be formed on the single substrate, the "return path" light or extraordinary ray (for example,
When the (reflected light from the surface to be inspected in this embodiment) is incident on the waveguide, it is possible to accurately and accurately perform focus detection and step measurement without alignment of the “return path” light or the extraordinary ray.

According to the embodiment of the present invention, since the Y-branch waveguide is connected to the double mode waveguide, the light can be detected with a very high contrast.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a waveguide according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a waveguide according to a first embodiment of the present invention.

FIG. 3 is a schematic sectional view of a waveguide according to a first embodiment of the present invention.

FIG. 4 is a schematic sectional view of a waveguide according to a first embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a focus detection device according to a second embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of an electrode provided in a focus detection device according to a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram in which a step measuring apparatus according to a third embodiment of the present invention is used in a laser scanning microscope.

FIG. 8 is a schematic configuration diagram in which a step measuring apparatus according to a third embodiment of the present invention is used in a laser scanning microscope.

FIG. 9 is a conceptual diagram showing a relationship between a focus shift amount and an output signal of a divider, which is used in a step measuring apparatus according to a third embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a focus detection device using a waveguide.

[Explanation of symbols]

1, 33 ... Semiconductor laser 2, 34 ... Induction single-mode waveguide 3, 4, 28, 29, 35, 36 ... Distributing single-mode waveguide 5 ... Single-mode waveguide 7, 25, 38 ... Double mode waveguide 10 ... Substrate 11 ... Collimator lens 12 ... Quarter wave plate 13 ... Objective lens 14 ... Optical disc 15, 16, 30, 31, ... Photodetector 17 ... Differential amplifier 18, 19, 26, 27 ... Electrode 20 ... Polarization-selective diffraction grating 21 ... XY scanner 22, 32 ... Differential circuit 23. .... Sum calculation circuit 24 ... Divider 39 ... Test sample

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G02B 7/28 (72) Inventor Hiroshi Oki 3-2 Marunouchi, Chiyoda-ku, Tokyo Stock company In Nikon

Claims (7)

[Claims] 1. A single mode waveguide for propagating the "outgoing path" light in a single mode for "outgoing path" light, and a double mode for the "returning path" light for "return path". And a center of the single mode waveguide and a center of the double mode waveguide are deviated from each other on at least one end face. 2. A first core portion formed on a substrate and having a refractive index larger than those of the substrate with respect to ordinary rays and extraordinary rays,
A second core portion formed on the substrate and having a refractive index larger than that of the substrate only for extraordinary rays, and the first core portion propagates the ordinary ray in a single mode with respect to the ordinary ray. Configuring a single mode waveguide, a region where the first core portion and the second core portion are combined constitutes a double mode waveguide that propagates the extraordinary ray in a double mode with respect to the extraordinary ray, A waveguide, wherein the center of the single mode waveguide and the center of the double mode waveguide are deviated on at least one end face. 3. The waveguide according to claim 1 or 2, wherein the double mode waveguide is provided with an electrode for applying an electric field. 4. The waveguide according to claim 1 or 3, wherein a guiding single mode waveguide for guiding the “outgoing path” light to the single mode waveguide, and 4. The waveguide according to claim 1, wherein at least two splitting single-mode waveguides for splitting the light intensity distribution of the "return path" light are provided. 5. The waveguide according to claim 2, wherein the guiding single mode waveguide for guiding the ordinary ray to the single mode waveguide, and the extraordinary ray in the double mode waveguide. 4. The waveguide according to claim 2, wherein at least two splitting single-mode waveguides for splitting the light intensity distribution are provided. 6. A waveguide, polarization control means arranged between the waveguide and the surface to be inspected, for making the polarization direction of the “forward” light and the polarization direction of the “return” light orthogonal to each other, and the guide. First condensing means for condensing the light emitted from the waveguide onto the surface to be inspected, and second condensing means for condensing the reflected light from the surface to be inspected into the waveguide. From at least two detectors that detect the light intensity distribution of the reflected light in the waveguide, and a detection unit that detects the shift of the focus of the light focused on the surface to be detected from the signal of the detector. The focus detection device according to claim 1, wherein the waveguide is the waveguide according to claim 1, 2 or 3 or 4 or 5. 7. A waveguide, polarization control means arranged between the waveguide and the surface to be inspected, for making the polarization direction of the "forward" light and the polarization direction of the "return" light orthogonal to each other, and First condensing means for condensing the light emitted from the waveguide onto the surface to be inspected, and second condensing means for condensing the reflected light from the surface to be inspected into the waveguide. At least two detectors that detect a light intensity distribution of the reflected light in the waveguide, and a step measuring device that measures a step of the surface to be detected from a signal of the detector, wherein the waveguide is the above-mentioned. A step measuring device, which is the waveguide according to 2 or 3 or 4 or 5.