JP3309355B2 - Micro aperture evaluation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating a small aperture, and more particularly to an apparatus for evaluating the accuracy of a light passing aperture having a diameter shorter than the wavelength of light.

[0002]

2. Description of the Related Art In a near-field optical microscope such as a photon scanning tunneling microscope, a micro-aperture probe having a light passage opening having a diameter smaller than the wavelength of light at its tip is used.
In many cases, the micro-aperture probe is formed by sharpening the tip of an optical fiber by etching, depositing a metal film thereon, and then removing the tip metal film to form an opening.

In such a small aperture probe,
The propagation loss of light varies depending on the shape of the opening, and accordingly, the intensity distribution pattern of the near-field light, which is the evanescent wave emitted from the opening, also changes. Conventionally, a technique of observing the shape of the opening with an electron microscope has been used to inspect the performance of the probe.

Further, since the intensity distribution pattern of the evanescent light has a correspondence with the polarization state of the light incident on the probe, when the probe is used, it is necessary to determine this correspondence in advance and select an optimum polarization state. Is required. For that purpose, it is necessary to actually detect the intensity distribution pattern of the near-field light. Conventionally, a method of detecting this pattern by scanning another probe has been used.

[0005]

However, since the above inspection method using an electron microscope is a destructive inspection, there is a problem that it cannot be used for inspection of a micro aperture probe actually used.

[0006] Further, the above-described method of measuring an intensity distribution pattern by scanning another probe requires skill in measurement and takes a long time, so that the yield is poor and is not suitable for practical use.
In addition, in this method, since the measurement probe affects the intensity distribution pattern of the near-field light emitted from the probe to be measured, there is also a problem that the reliability of the evaluation is low.

[0007] In addition to the near-field optical microscope, a device having a minute aperture is also used in various apparatuses utilizing near-field light, and it may be necessary to evaluate the minute aperture.

Accordingly, an object of the present invention is to provide a micro-aperture evaluation apparatus capable of accurately and easily evaluating the intensity distribution pattern of near-field light emitted from a micro-aperture, the optimum polarization state of incident light, and the like. And

[0009]

A micro-aperture evaluation device according to the present invention is a micro-aperture evaluation device for evaluating a light-passing aperture having a diameter shorter than the wavelength of light, comprising: a light source for emitting light for evaluation;
An incident optical system that causes the light to enter the light passage opening, a diffusion plate that receives the light emitted from the light passage opening, and visualizes an intensity distribution pattern of the light, and the intensity distribution that is visualized by the diffusion plate It is characterized by comprising imaging means for imaging a pattern, and display means for displaying the imaged intensity distribution pattern.

That is, the present invention relates to an apparatus for evaluating a minute aperture such as a minute aperture probe used in a near-field optical microscope apparatus and a planar recording head using near-field light, and which is incident on the aperture. The light intensity distribution pattern of the light emitted from the aperture as the propagation light is visualized by a diffusion plate, imaged, and displayed.

It is preferable that the micro-aperture evaluation device has a polarization control means for changing a polarization state of the light incident on the light passage aperture.

[0012]

It is known that the intensity distribution pattern has a correlation between the propagation light emitted from the minute aperture and the near-field light. This correlation can be obtained by electromagnetic analysis such as Bethe's calculation formula. Further, since it is possible to directly observe the intensity distribution pattern of the near-field light with the near-field optical microscope, the observation pattern can be correlated in advance with the intensity distribution pattern of the propagating light.

According to the micro-aperture evaluation device of the present invention, the intensity distribution pattern of the light emitted from the micro-aperture, which is the light passage aperture, is visualized by the diffusion plate, and the visualized intensity distribution pattern is imaged by the image sensor. Therefore, the intensity distribution pattern of the near-field light can be known based on the display pattern and the above-described correlation determined in advance.

[0014] The apparatus further comprises a polarization control means, and obtains an intensity distribution pattern in each polarization state by changing a polarization state of the light incident on the light passage opening, thereby obtaining an optimum polarization of the incident light with respect to the light passage opening. The state can be determined.

Therefore, for example, even when the above-mentioned minute aperture of the optical fiber probe is evaluated, it is not necessary to perform the conventional destructive inspection using an electron microscope.

Further, even when the optimum polarization state of the incident light is determined, the measurement can be performed more easily and with a higher yield as compared with the above-described conventional method of scanning another measuring probe. In addition, since the problem that such a measurement probe affects the intensity distribution pattern of the near-field light does not occur, the reliability of evaluation is improved.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a micro-aperture evaluation apparatus according to an embodiment of the present invention.

The micro-aperture evaluation apparatus is used to evaluate the performance of a micro-aperture probe 10 used in, for example, a near-field optical microscope or the like, and a laser that emits a light (laser beam) 11 for evaluation. 12 and collimator lens for collimating this divergent laser beam 11
13, a condensing lens 14 for converging the collimated laser beam 11 to the base end (the left end of the probe in the figure) of the micro-aperture probe 10, and a polarized light disposed between these lenses 13 and 14. Λ / 2 plate 15 as a control element.

The micro-aperture probe 10 is made of, for example, an optical fiber and has a flat end 10a at one end.
The other end has a sharpened tip 10b (right end of the probe in the figure), and this tip 10b has a light passage opening (small opening) having a diameter shorter than the wavelength of light. The laser beam 11 converged on the base end 10a of the small aperture probe 10 as described above
Enters the probe from the base end 10a, propagates, and exits from the opening 10b in a divergent light state.

At this time, evanescent light as near-field light is emitted from the aperture 10b together with the laser beam 11 as normal propagation light. In a near-field optical microscope or the like, this near-field light is used for observation, analysis, processing, and the like of a sample, but this near-field light is not directly used when evaluating a probe.

A diffusing plate 16 is disposed at a position where the laser beam (propagating light) 11 emitted in a diverging light state from the probe opening 10b is incident, and behind the diffusing plate 16 (right side in the figure), A cooled CCD image sensor 17 for imaging a light intensity distribution pattern of the propagation light 11 projected on the diffusion plate 16 is provided.
The image signal S output from the cooled CCD imaging device 17 is input to an image display means 19 such as a CRT via an image processing device 18.

When the micro-aperture probe 10 is evaluated, the laser beam 11 enters the probe 10 as described above, and the laser beam (propagating light) 11 emitted from the micro-aperture of the probe 10 at that time is diffused. The image is projected onto the plate 16 and the projected image is captured by the cooled CCD image sensor 17. This projected image shows the intensity distribution pattern in the beam cross section of the laser beam 11. The image signal S indicating this intensity distribution pattern is input to the image processing device 18, where the image signal S is subjected to predetermined image processing and then output to the image display means 19. In this way, the image display means 19 displays the intensity distribution pattern of the propagation light 11 emitted from the probe 10.

As described above, there is a correlation of the intensity distribution pattern between the propagating light emitted from the tip of the microaperture probe 10 and the near-field light. Therefore, based on the previously obtained correlation, the intensity distribution pattern of the near-field light is known from the intensity distribution pattern of the laser beam (propagating light) 11 displayed on the image display means 19, and the performance of the minute aperture, that is, The performance of the probe 10 can be evaluated.

In this embodiment, the λ / 2 plate
By rotating 15, the direction of linearly polarized light of the laser beam 11 before entering the micro aperture probe 10 can be changed, and the intensity distribution pattern of the laser beam 11 in each polarization state can be confirmed. Thereby, it is possible to know the polarization state in which the optimum intensity distribution pattern of the propagation light (that is, the near-field light) is obtained.

It should be noted that the above-described micro-aperture evaluation device not only evaluates the performance of the micro-aperture probe as described above, but also
For example, the present invention can be used as an evaluation device for a planar type device having a minute opening in a flat substrate, such as a recording head using near-field light. As shown in FIG. 2, the planar type device has a plurality of minute openings. In the above-described evaluation apparatus, while moving in the direction of the arrow, the intensity distribution pattern of the laser beam emitted from each minute opening is applied to the diffusion plate. The projection enables evaluation of each minute aperture.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

 10 Micro aperture probe 11 Laser beam 12 Laser 13 Collimator lens 14 Condenser lens 15 λ / 2 plate 16 Diffusion plate 17 Cooled CCD image sensor 18 Image processor 19 Image display

Continuation of front page (56) References JP-A-5-172695 (JP, A) JP-A-62-299738 (JP, A) JP-A-6-74861 (JP, A) JP-A-11-101715 (JP, A) JP-A-11-132904 (JP, A) JP-A-11-101743 (JP, A) JP-A-11-134301 (JP, A) JP-A-5-332288 (JP, A) JP-A-7-174770 (JP, A) JP-A-11-68338 (JP, A) JP-A-6-213909 (JP, A) JP-A-9-236610 (JP, A) A) Japanese Patent Publication No. 3-10065 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01M 11/00-11/08 G01N 13/10-13/24 G01N 21/47 JICST File (JOIS)

Claims (2)

(57) [Claims] 1. A micro-aperture evaluation device for evaluating a light-passing aperture having a diameter shorter than the wavelength of light, comprising: a light source that emits light for evaluation; and an incident optical system that causes the light to enter the light-passing aperture. A diffuser plate that receives the light emitted from the light passage opening and visualizes an intensity distribution pattern of the light; an imaging unit that captures the intensity distribution pattern visualized on the diffuser plate; and the imaged intensity distribution A micro-aperture evaluation device, comprising: display means for displaying a pattern. 2. The micro-aperture evaluation device according to claim 1, further comprising a polarization controller for changing a polarization state of the light incident on the light-passing aperture.