JP3276939B2 - Near-field optical microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a near-field optical technique, and more particularly to a knock-type near-field optical microscope which controls a near-field distance with high sensitivity.

[0002]

2. Description of the Related Art As is well known, a conventional shearing-field near-field optical microscope includes a light source unit 1, an optical fiber probe 2, an oscillation unit 3, and a signal feedback unit 4, as shown in FIG. The light source unit 1 provides a light source. The oscillating unit 3 is a probe of the optical fiber by resonance.
Drive. When the probe 2 of the optical fiber is in contact with the surface of the sample 7, the amplitude and phase are changed by the van der Waals force and the acting force between the tip of the probe 2 of the optical fiber and the sample surface, and the signal feedback is performed. Unit 4 performs feedback control. Then, since the probe 2 of the optical fiber is projected on the surface of the sample 7 as a height of several nm, a near-field optical image of the sample 7 is obtained.

The oscillating unit 3 in the above-mentioned conventional near-field optical microscope of the shearing force type comprises a fork-shaped column 5 and a piezoelectric ceramic 16. Fork column 5
Is attached to the probe 2 of the optical fiber in the longitudinal axis direction.
That is, the short-axis surface 8 of the fork-shaped column 5 detects and induces a load such as an acting force and a van der Waals force between the surface of the sample 7 and the tip of the probe 2 of the optical fiber. Receive. However, since the area of the short axis surface 8 of the fork-shaped column 5 is small, the external force that can be received is small. Under the precondition that the load does not change, the external force is directly proportional to the area. Then, the amplitude is small due to resonance, and the sensitivity (that is, the inclination rate) is small. Note that both the energy stored in the probe 2 by the amplitude and the external force are directly proportional. Further, since the probe 2 of the optical fiber and the longitudinal axis of the fork-shaped column 5 are stuck flat and the rigidity of the whole structure is larger, the sensitivity of the oscillation induced by the external force is relatively reduced.

[0004] A conventional near-field optical microscope of the shearing force type is left under an environmental condition of being in the air to obtain a sample 7.
During the observation operation of the above, the relationship between the amplitude peak due to resonance and the height of the sample 7 is shown as in FIG. In FIG. 2, the scale of one vertical grid is 0.14 V, and the scale of one horizontal grid is 21.73 nm. As can be seen, the amplitude is minimal when the probe 2 of the optical fiber contacts the sample 7 or when the distance becomes zero. In the amplitude variation section defined by us, an area having a variation value from 10% to 90% is called an action area, and is divided into two stages. The first stage has a very low sensitivity of 66 nm and the second stage has a very low sensitivity of about 0.02 V / nm. In other words, since the sensitivity of the conventional shearing force type near-field optical microscope is not good, feedback control cannot be accurately performed.

[0005]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a near-field optical microscope which has not only excellent sensitivity but also accurate feedback control.

[0006]

A near-field optical microscope according to the present invention for solving the above-mentioned problems includes a light source unit, a probe of an optical fiber, an oscillation unit, and a signal feedback unit. The light source unit provides light. Since one end of the probe of the optical fiber is connected to the light source unit, by the light supplied from the light source of the unit,
At the other tip of the probe of the optical fiber, a point light source having a near field is formed. The oscillation unit has a piezoelectric ceramic and an arm. The probe is located at one end of the arm in the longitudinal direction.
A needle is attached in the short direction of the arm. The piezoelectric ceramic is arranged on the arm. The signal feedback unit changes the amplitude and phase of the probe of the optical fiber by driving the piezoelectric ceramic vibrating with the harmonic waveform, and performs feedback control.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. First, as shown in FIGS. 3 and 4, the near-field optical microscope according to one embodiment of the present invention mainly includes a light source unit 10, an optical fiber probe 20, an oscillation unit 30, and a signal feedback unit 40. It is formed. The light source unit 10 has a laser light source 11 and guides the light source to a probe 20 of an optical fiber for near-field optics via a shield plate 12 and an optical fiber coupling 13.

The optical fiber probe 20 forms a point light source having a near field at the tip by the light supplied from the light source unit 10. As shown in FIG. 4, the oscillation unit 30 includes a two-layer piezoelectric ceramic 31, a magnet 32, and an iron thin piece 3.
3 and arm 34. The piezoelectric ceramic 31 is attached to one end of the magnet 32 with glue, and the thin iron piece 33 is sucked to the other end by magnetic force, so that a layered arrangement is obtained. In addition, a thin piece of iron 33 is set on the arm 34. The design in which the magnet 32 is used as an intermediary material for connection is mainly such that, when the arm 34 is damaged, the thin piece 33 of iron is simply pulled out of the magnet 32. The arm 34 is a tuning fork. One end is attached to the probe 20 and the other end is provided with the piezoelectric ceramic 31 and the like. Note that two electrodes 341 and 342 are formed on the arm 34.

[0009] The signal feedback unit 40 has a control box 41. The signal end is connected to two electrodes 341 and 342 of the arm 34 via a preamplifier 42 to control the vibration of the two-layer piezoelectric ceramic 31. The frequency of the vibration is close to the resonance frequency of the combination of the probe 20 and the arm 34 of the near-field optical fiber. Control box 4
The other end of 1 receives the optical signal. That is, a near-field optical signal is obtained from the tip of the probe 20 of the optical fiber.
After the signal is guided to the photoelectric amplification tube 44 by an optical fiber, the signal is transmitted to the phase lock amplifier 43. The enlarged signal is transmitted to the control box 41 as a near-field optical microscopic image signal. Feedback control can be performed by the other end of the control box 41.

As a result, when the arm 34 of the oscillation unit 30 is used, when the probe 20 of the optical fiber is in contact with the surface of the sample 7, a load such as van der Waals force and surface acting force is applied to the arm 34. ,
The portion receiving the force is the entire surface of the beam and has a larger area, so that the external force that can be received increases. Therefore, the resonance not only has a large amount of energy stored in the probe 20 of the optical fiber, but also has a larger amplitude than that of the conventional shear force method. Further, since only one end of the arm 34 is attached to the probe 20 of the optical fiber, the overall rigidity is small, and excellent oscillation sensitivity can be obtained.

FIG. 5 shows a conventional near-field optical microscope of the shearing force type and a near-field optical microscope of the present embodiment left in different environments, and the output voltage from both electrodes 341 and 342 and the drive amplitude. It is a figure which compares a relationship. (a) when the device of the present embodiment is in a free state, (b) when the device of the present embodiment is left in the air, (c) when the device of the present embodiment is left in the water, (D) is a case where the existing device is left in the air. In other words, the sensitivity of the device of the present embodiment is excellent in air and water because the measured voltage is higher than the voltage from the existing device.

FIG. 6 is a diagram showing the relationship between the amplitude peak due to resonance and the distance altitude from the probe to the sample when the near-field optical microscope of this embodiment is left in the air. As can be seen, the working area from 10% to 90% is 19.5 nm and the sensitivity (gradient) is 0.083V.
/ Nm, which is four times the sensitivity of the conventional one, 0.020 V / nm. FIG. 7 is a diagram illustrating the relationship between the amplitude peak due to resonance and the distance altitude from the probe to the sample when the near-field optical microscope of the present embodiment is left in water.
As can be seen from the figure, the sensitivity (gradient) is 0.072 V /
In nm, it is 3.6 times that of the conventional one. That is, the present embodiment provides excellent sensitivity and can perform more accurate feedback control than the existing one.

The arm in the near-field optical microscope of the present embodiment employs a tuning fork as described above.
Single arm or double arm beams may be employed. Also, the signal feedback unit 40 uses different peripheral equipment according to different feedback designs.

According to the near-field optical microscope according to the present invention, the oscillation sensitivity of the tuning fork induced by external force is excellent, and accurate feedback control can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional near-field optical microscope using a shearing force method.

FIG. 2 is a diagram showing a relationship between amplitude due to resonance and a distance from a probe to a sample when a conventional near-field optical microscope of a shearing force type is left in the air.

FIG. 3 is a diagram illustrating a near-field optical microscope according to an embodiment of the present invention.

FIG. 4 is a perspective view illustrating an oscillation unit according to an embodiment of the present invention.

FIG. 5 is a diagram comparing the relationship between the output voltage and the drive amplitude of the conventional near-field optical microscope of the shearing force type and the near-field optical microscope according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between a peak of amplitude due to resonance and a distance from a probe to a sample when the near-field optical microscope according to the embodiment of the present invention is left in the air.

FIG. 7 is a diagram illustrating a relationship between a peak of amplitude due to resonance and a distance from a probe to a sample when the near-field optical microscope according to the embodiment of the present invention is left in water.

[Explanation of symbols]

 Reference Signs List 10 light source unit 20 probe of optical fiber 30 oscillation unit 31 piezoelectric ceramic 34 arm 40 signal feedback unit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Rd ▲ Fragment ▼ Ying No.20, No.20, 171 Street, Liancheng Road, Zhongcheng City, Taipei, Taiwan JP-A-10-253364 (JP, A) JP-A-4-136743 (JP, A) JP-A-9-229948 (JP, A) JP-A-9-257814 (JP, A) A) JP-A-8-248043 (JP, A) JP-A-8-334520 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 13/10-13/24 G12B 21 / 00-21/24 G02B 21/00 G02B 11/00 JICST file (JOIS)

Claims (7)

(57) [Claims] 1. A light source unit for providing light, one end of which is connected to the light source unit, and the other end of which is a point light source having a near field formed by light supplied from the light source unit. It has a probe, a piezoelectric ceramic and an arm, and the longitudinal direction of the arm.
The probe is attached to one end of the arm in the short direction of the arm, the piezoelectric ceramic is an oscillation unit arranged on the arm and oscillating with a harmonic waveform, and a piezoelectric ceramic oscillating with the harmonic waveform. A signal feedback unit that drives, changes the amplitude and phase of the probe, and performs feedback control. 2. The near-field optical microscope according to claim 1, wherein the arm is a tuning fork. 3. The near-field optical microscope according to claim 1, wherein the arm is a single-arm beam. 4. The near-field optical microscope according to claim 1, wherein the arm is a double-arm beam. 5. The piezoelectric ceramic according to claim 1, wherein one end of a magnet is pasted with glue at one end, and a thin piece of iron is attached to the other end by magnetic force, and the thin piece of iron is installed on the arm. Item 7. A near-field optical microscope according to Item 1. 6. The near light source according to claim 1, wherein the light source unit has a laser light source, and guides the light of the laser light source to the probe via a shield plate and coupling of an optical fiber. Field optical microscope. 7. The signal feedback unit has a control box, and a signal end of the control box is connected to the arm via a preamplifier to control a vibration of the piezoelectric ceramic. The other end can obtain a signal from the tip of the probe, the signal is guided to a photoelectric amplifier tube, transmitted to a phase lock amplifier, and feedback-controlled by the other end of the control box. 2. The near-field optical microscope according to 1.