JPH05158084A - Measuring instrument for linear and nonlinear optical sensing rate - Google Patents

Abstract

PURPOSE:To measures the linear and nonlinear optical sensing ratios by measuring the refractive index and film thickness of a sample and the light intensity distribution of an SHG or THG. CONSTITUTION:This measuring instrument is provided with a light irradiation means 2 in which the sample 3 is irradiated with light, an image sensor 6 which measures light reflected by striking on the sample 3 coupled with a grating coupler 5, and a light intensity detection sensor 7 which measures the intensity of light passed through the sample 3; and the refractive index, the film thickness, and the light intensity distribution of the SHGH or THG are measured from the outputs of the image sensor 6 and light intensity detection sensor 7 and the light output intensity of the light irradiation means 2 is used to measure the linear and nonlinear optical sensing ratios.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring linear and nonlinear optical susceptibility of a sample.

[0002]

BACKGROUND OF THE INVENTION The first experiment in nonlinear optics was performed by Franken et al. On the second harmonic light of a ruby laser. After that, a method for quantifying the second-order and third-order nonlinear optical susceptibility of a material is described by Kurtz,
Each was proposed by Kajar and others. Until now, only the incident angle dependence of the harmonic light intensity of the nonlinear optical material has been measured by the measurement method proposed by Kurz and Kajar.

[0003]

In order to measure the susceptibility of a nonlinear optical material, in addition to the incident light intensity, the thickness of a single crystal, film or thin film sample, the refractive index of the sample due to the fundamental wave, and the harmonic It is necessary to know the refractive index of the sample due to. However, in the past, as a method of accurately measuring the film thickness of film and thin film samples, the refractive index of the sample due to the fundamental wave, and the refractive index of the sample due to the harmonics, in addition to the harmonic light intensity, an interferometric film thickness meter, ellipsometer There are only the measurement method by the metric, the refractive index by the Abbe refractometer, and the refractive index by the mode line method using the pulsum coupler.

Since the interferometric film thickness measuring device has to assume the refractive index, it cannot calculate the accurate film thickness. The measurement method by ellipsometry has a problem that a film thickness region that cannot be measured with respect to incident light periodically exists, and the measurement accuracy deteriorates as the film thickness increases.
The refractive index measurement using the Abbe refractometer has problems that it is difficult to measure a sample having a refractive index of 1.78 or more and that the measurement wavelength cannot be freely selected. The refractive index measurement by the mode line method is used as an optical waveguide, and for thin film samples of submicron to several microns,
The refractive index and the film thickness can be simultaneously measured with high accuracy. However, in the conventional device, since the sample substrate and the photodetector must be rotated by several tens of degrees in cooperation with each other, it takes time to measure the refractive index and a prism for guiding light to the sample is used. Is difficult to couple with the sample,
There is no reproducibility of measurement results. Further, there are problems that the measurement itself is difficult and the expensive prism and the sample itself are often damaged.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to measure the refractive index, film thickness and incident light intensity of crystals, films and thin film samples regardless of whether they are inorganic or organic. , And to provide a linear and nonlinear optical susceptibility measuring device capable of easily measuring the nonlinear optical susceptibility of a sample.

[0006]

The linear and non-linear optical susceptibility measuring apparatus of the present invention comprises a film or thin film sample arranged in contact with a single-crystal or optical waveguide grating coupler, or an arrangement of the grating coupler. Light irradiation means for irradiating a film or thin film sample that has not been irradiated and light for a sample in contact with the grating coupler, and the light is guided once in the sample by the grating coupler and radiated again to the outside of the grating coupler. A linear image sensor for detecting the generated light or Brewster angle, and irradiating the sample on which the grating coupler is not arranged with light, and the second harmonic generation from the sample excited by the incident light,
Alternatively, a light intensity detection sensor for detecting the light intensity distribution of the third harmonic generation, and a refractive index calculating means for calculating the refractive index of the sample from the detection result of the image sensor, a film thickness for measuring the film thickness of the film or thin film sample. Non-linear optical susceptibility of the sample is provided from the refractive index of the sample, the film thickness, the light intensity distribution of the second harmonic generation or the third harmonic generation, and the higher harmonic light output intensity of the light irradiating means. A technical means including a signal processing device including an optical susceptibility calculating means is adopted.

[0007]

The film-shaped sample on which the grating coupler is arranged is irradiated with light by the light irradiation means. The light guided by the grating coupler is detected by the linear image sensor, the refractive index calculation means of the signal processing device calculates the refractive index of the sample, and the film thickness calculation means of the signal processing device calculates the film thickness of the sample. To do. In addition, according to the order for which the nonlinear optical susceptibility is to be obtained, light of different wavelengths and fundamental waves are applied to the sample with the grating coupler, and the light guided by the grating coupler is applied by the linear image sensor. The refractive index of the sample is calculated and the refractive index of the sample is calculated by the refractive index calculating means of the signal processing device. In the case of a park single crystal whose sample thickness is known, the Brewster angle is detected by a linear image sensor and the refractive index of the sample is calculated by the refractive index calculating means of the signal processing device.

Light is applied to the sample on which the grating coupler is not arranged by the light irradiation means. The light intensity distribution of SHG or THG transmitted through the sample is detected by the light intensity detection sensor.

Then, the nonlinear optical susceptibility calculating means of the signal processing device is adapted to the refractive index, film thickness and SH of the sample obtained above.
The nonlinear optical susceptibility of the sample is calculated from the light intensity distribution of G or THG and the light output intensity of the light irradiation means.

[0010]

As described above, the linear and nonlinear optical susceptibility measuring apparatus of the present invention has a refractive index of a sample, a film thickness, a light intensity distribution of SHG or THG, and a light output of a light irradiation means. From the intensity, the nonlinear optical susceptibility of the sample can be measured.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the linear and nonlinear optical susceptibility measuring apparatus of the present invention will be explained based on an embodiment shown in the drawings.

[Configuration of Embodiment] FIGS. 1 to 4 show an embodiment of the present invention, and FIGS. 1 and 2 are schematic configuration diagrams of a linear and nonlinear optical susceptibility measuring apparatus. The linear and non-linear optical susceptibility measuring apparatus 1 detects light guided by a film-shaped sample 3 which is in contact with a stage 4, which automatically supports the light irradiating means 2 and the sample 3, and whose orientation is automatically aligned, and a grating coupler 5. Linear image sensor 6, or linear image sensor 6 for detecting the Brewster angle of a single crystal, light intensity detection sensor 7 for detecting the light intensity distribution of SHG or THG transmitted through sample 3 in which grating coupler 5 is not arranged, electrical It comprises a circuit box 8, a polarizer 9 for guiding the light emitted by the light irradiation means 2 to the sample 3, and an analyzer 10 for guiding the light transmitted through the sample 3 to the light intensity detection sensor 7.

The light irradiating means 2 emits a He-Ne laser and an Nd: YAG laser, and a wavelength of light emitted by the light irradiating means 2 is halved by mounting a harmonic crystal on the light emitting portion. To It is needless to say that the laser shown in this embodiment is an example, and other light sources may be used.

The polarizer 9 guides the light emitted from the light irradiation means 2 to the sample 3. In this embodiment, the two mirrors 1 are used.
1, 12, UV visible light cut filter 13, 1/2
It includes a wave plate 14, a polarizing plate 15, and a lens 16.

The analyzer 10 guides the light passing through the sample 3 to the light intensity detection sensor 7. In this embodiment, the lens 17, two filters 18, 19 for transmitting only SHG or THG, and a polarizing plate 20. , Focusing lens 21.

As shown in the schematic view of FIG. 3, the stage 4 supports the first goniometer stage 22 on which the sample 3 is mounted and which tilts the mounted sample 3 in the plane direction of the sample 3, and the first goniometer stage 22. Then, the second goniometer stage 23 that tilts the first goniometer stage 22 in a direction orthogonal to the plane direction of the sample 3 and the second goniometer stage 23 is supported.
The gonio stage 23 is composed of a rotary stage 24 that rotates. Further, the rotary stage 24 is provided with a slide portion 25 that slides the sample mounted via the second goniometer stage 23 and the first goniometer stage 22. The slide portion 25 is for applying the light guided through the polarizer 9 to the sample on which the grating coupler 5 is arranged or to the sample on which the grating coupler 5 is not arranged. Each of the first goniometer stage 22, the second goniometer stage 23, the rotary stage 24, and the slide portion 25 is provided with an electric actuator (not shown) such as an electric motor, which is controlled by the electric circuit box 8. It

The sample 3 is, as shown in FIG. 4, 1 μm to 3 μm held between two transparent substrates 26 and 27.
A film-like one having a grating coupler 5 in which a large number of grooves having a depth of about 0.5 μm are formed in a part of one substrate, or a single crystal. The transparent substrate 26 on the side where light is incident is provided with a smaller refractive index than the other transparent substrates 27. Further, the sample may be filled between the two transparent substrates 26 and 27, and if the sample can be coupled with the grating coupler 5, one of the substrates may be omitted. The grating coupler 5 does not have to have a plurality of grooves, but may be another one as long as it can obtain guided light.

The linear image sensor 6 uses a monitor means such as a CCD in order to linearly analyze the light guided to the sample 3 or the light reflected by the sample 3. The output of the linear image sensor 6 is output to the electric circuit box 8.

Since the light intensity detection sensor 7 detects the intensity of the light passing through the sample 3, an element capable of detecting the light intensity such as a photomultisensor, a photoelectric tube, or a photodiode is used. The output of the light intensity detection sensor 7 is output to the electric circuit box 8.

The electric circuit box 8 includes an interface 8a, a signal processing device 8b, a display means 8c for displaying a result to a user by a display or printing, and a drive control device 8.
It consists of d. In addition, the signal processing device 8b includes the harmonic crystal 28
Based on the output of the linear image sensor 6 and the output of the light intensity detection sensor 7 depending on the presence / absence of the refractive index, the film thickness and the nonlinear optical susceptibility of the sample 3, the refractive index calculating unit 29, the film thickness calculating unit 30, the nonlinear optical The susceptibility calculating means 32 is provided.
In addition, the drive control device 8d includes the first goniometer stage 22, the second goniometer stage 23, and the rotary stage 2 of the stage 4.
4 and the electric actuator of the slide portion 25 are driven and controlled.

[Operation of Embodiment] Next, the operation of the above embodiment will be briefly described. First, only the film sample 3 or the single crystal sample 3 sandwiched between the transparent substrates 26 and 27 is set on the stage 4. When the sample is a single crystal, the light irradiating means 2 irradiates the sample 3 with light. Then, the light intensity detection sensor 7 detects the intensity of the light transmitted through the analyzer 10 placed behind the sample 3. At this time, the first goniometer stage 2
2 is tilted to the left and right, and the sample 3 is oriented at the position where the transmitted light intensity is the weakest.

Next, the sample 3 is rotated by 90 °, and the light irradiation means 2 irradiates the sample 3 with guide light. Then, the light intensity detection sensor 7 detects the intensity of the light transmitted through the analyzer 10 placed behind the sample 3. At this time, the second gonio stage 23 is tilted to the left and right, and the sample 3 is oriented again at the position where the transmitted light intensity is the weakest.

As a result, the dielectric main axis of the single crystal sample 3 becomes parallel to the polarization direction of the incident light. That is, the dielectric main axis of the sample 3 is found. In this way, when the dielectric main axis is in the crystal growth plane, the dielectric main axis can be automatically found. When the dielectric main axis is not in the crystal growth plane, the sample 3 is processed so that the incident optical axis is perpendicular to the dielectric main axis and set on the first goniometer stage 22, and the minimum value of the transmitted light intensity is set. The dielectric principal axis can be determined by measurement. Next, the reflected light from the single crystal and the film sample is detected by the linear image sensor, and the stage is rotated so that an important plane is exposed with respect to the optical axis.

Next, when the sample is in the form of a film and is sandwiched between the transparent substrates 26 and 27, the sample surface is rotated so that the guided light from the sample 3 strikes the linear image sensor 6.

The light from the light irradiation means 2 is applied to the sample 3 on which the grating coupler 5 is arranged (see FIG. 1). Then, the mode line of the light guided by the grating coupler 5 is measured using the linear image sensor 6. Then, the signal processing device 8b calculates the refractive index and the film thickness from the mode line obtained by the linear image sensor 6 by the refractive index calculating means 29 and the film thickness calculating means 30. Next, a harmonic crystal 28 is arranged in the light output portion of the light irradiation means 2,
The sample 3 in which the grating coupler 5 is arranged is again irradiated with the light of 1/2 or 1/3 wavelength. Then, the mode line generated by the light guided by the grating coupler 5 is measured by using the linear image sensor 6, and the refractive index calculation means 29 of the signal processing device 8b measures the refraction at 1/2 or 1/3 wavelength. Calculate the rate. In the case of a single crystal of which the thickness of the sample 3 is known, first, the 1/2 deflection plate 14
The sample 3 is irradiated with the light of the light irradiating means 2 changed by P. Then, the stage 24 is rotated, and the rotation angle (Brewster angle) at which the reflected light from the sample surface disappears is measured using the linear image sensor 6. Then, the signal processing device 8b calculates the refractive index by the refractive index calculating means 29 from the Brewster angle obtained by the linear image sensor 6. Next, the harmonic crystal 28 is arranged in the light output portion of the light irradiation means 2, and the sample 3 is irradiated again with the light of 1/2 or 1/3 wavelength. Then, the Brewster angle is measured using the linear image sensor 6, and the refractive index calculation means 29 of the signal processing device 8b calculates the refractive index at the time of 1/2 or 1/3 wavelength.

Next, when the sample is a film-like substance, the sample 3 is slid so that the light irradiation position is a portion where the grating coupler 5 is not arranged (see FIG. 2). If the sample 3 is a single crystal that is not in contact with the grating, this operation is not performed. Then, the light of the light irradiation means 2 is applied to the film sample or the single crystal sample 3 in which the grating coupler 5 is not arranged. Then, the light intensity distribution of SHG or THG from the sample excited by the light incident on the sample 3 is measured by the light intensity detection sensor 7.

Then, the non-linear optical susceptibility calculating means 32 of the signal processing device 8b uses the respective data (refractive index, film thickness, refractive index at 1/2 or 1/3 wavelength, S
The nonlinear optical susceptibility is calculated from the light intensity distribution of HG or THG) and the light output intensity of the light irradiation means 2. The non-linear optical susceptibility calculating means 32 has a calculation function of comparing the experimental value fringe obtained by the calculation with the theoretical fringe and setting the experimental value closest to the theoretical fringe as the non-linear optical susceptibility. Then, the refractive index calculated by the signal processing device 8b, the refractive index at the time of 1/2 or 1/3 wavelength, the film thickness, the non-linear optical susceptibility, the light intensity distribution of SHG or THG, the light output of the light irradiation means 2. The intensity is displayed to the user by the display means 8c.

[Effects of Embodiment] In the linear and nonlinear optical susceptibility measuring apparatus 1 of this embodiment, the sample 3 is placed on the first goniometer stage 22 and the apparatus is activated, without destroying the sample 3. The reproducibility is also easy, and the refractive index of the sample 3, the film thickness, the light intensity distribution of SHG or THG, the nonlinear optical susceptibility, etc. can be automatically measured. That is, since each value can be easily obtained, it will be easier to find a material superior to the conventionally known optical materials. Further, the nonlinear susceptibility, refractive index, etc. of a material are indispensable parameters for designing each device, and by using the linear and nonlinear optical susceptibility measuring apparatus 1 of the present invention,
In order to develop the optoelectronic technology in the future, its practical effect will be great.

[0029]

[Modification] In the above embodiment, the sample 3 was rotated,
The sample 3 may be fixed and other optical systems such as the light irradiation means 2, the linear image sensor 6, and the light intensity detection sensor 7 may be rotated.

Further, as shown in FIG. 5, the light generated by the sample 3 is multi-split and irradiated on different positions of the sample 3 to generate S.
It is also possible to simultaneously measure HG or THG to measure a plurality of harmonic light intensity distributions in one sample 3, or to measure the harmonic light intensities of a plurality of materials at once.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a linear and nonlinear optical susceptibility measuring device.

FIG. 2 is a schematic view of a linear and nonlinear optical susceptibility measuring device.

FIG. 3 is a schematic perspective view of a stage.

FIG. 4 is a partial cross-sectional view of a sample sandwiched between two transparent substrates.

FIG. 5 is a schematic view of a non-linear optical susceptibility measuring apparatus showing another modification.

[Explanation of symbols]

 1 linear and non-linear optical susceptibility measuring device 2 light irradiation means 3 sample 6 linear image sensor 7 light intensity detection sensor 8b signal processing device 29 refractive index calculating means 30 film thickness calculating means 32 non-linear optical susceptibility calculating means

Claims (1)

[Claims] 1. A light for irradiating a film or thin film sample arranged in contact with (a) a single crystal or an optical waveguide grating coupler, or a film or thin film sample without the grating coupler. Irradiation means, (b) irradiating light to the sample in contact with the grating coupler, linearly detecting light or Brewster angle emitted to the outside of the grating coupler once again guided in the sample by the grating coupler. An image sensor, and (c) Light intensity detection to detect the light intensity distribution of the second harmonic generation or the third harmonic generation from the sample excited by the incident light by irradiating the sample on which the grating coupler is not arranged. Sensor, and (d) the detection result of the image sensor. , A refractive index calculating means for calculating the refractive index of the sample, a film thickness calculating means for measuring the film thickness of the film or thin film sample, and the refractive index of the sample, the film thickness, the light of the second harmonic generation or the third harmonic generation Intensity distribution,
And a signal processing device comprising a nonlinear optical susceptibility calculating means for calculating the nonlinear optical susceptibility of the sample from the harmonic light output intensity of the light irradiating means.