JP2002286937A - Dielectric film deposition method to optical fiber end face and dielectric film deposition system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the optical characteristics of a deposited dielectric film from being varied from the desired optical characteristics by a change in atmospheric temperature when the dielectric film is deposited on the end face of an optical fiber. SOLUTION: The dielectric film deposition method to the optical fiber end face comprises starting deposition after preheating the inside of a hermetic space where the deposition to the fiber end face is performed to a prescribed temperature. This dielectric film deposition system has a heating source capable of preheating the inside of a chamber where the deposition is performed to a prescribed temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a dielectric film on an end face of an optical fiber. Another application of the present application relates to an apparatus capable of forming a dielectric film on an end face of an optical fiber.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional apparatus for forming a dielectric film on an end face of an optical fiber (hereinafter referred to as "fiber end face").
There is a dielectric film forming apparatus as shown in FIG. In this dielectric film forming apparatus, at least two electron beam guns (EB guns) B and two containers (crucibles) are placed in a vacuum chamber A.
C, a rotating dome D capable of setting an end of an optical fiber (not shown), and an ion gun F capable of irradiating active molecules.
And a nutrizer G capable of irradiating negatively charged thermoelectrons.

A dielectric film is formed on an end face of a fiber by the dielectric film forming apparatus shown in FIG. 9 as follows.
The end of the optical fiber is set on the rotary dome D via a holder (not shown), and the fiber end face is exposed in the vacuum chamber A. Next, while rotating the rotating dome D, an electron beam is irradiated from one electron beam gun B toward a raw material (high refraction material or low refraction material) of the dielectric film accommodated in one container C. Then, the raw material is melted and evaporated, and the evaporated raw material molecules or atoms are deposited on the end face of the fiber. After a predetermined amount of source molecules or atoms are deposited,
The irradiation of the electron beam from the electron beam gun B is stopped, and the adjacent shutter H is rotated so that the container C
Close. Next, an electron beam is irradiated from the other electron beam gun B ′ toward the raw material (low-refraction material or high-refraction material) of the dielectric film accommodated in the other container C ′, and the same as above. The source molecules or atoms evaporated from the container C ′ are deposited and laminated on the source molecules or atoms deposited on the fiber end face. When a predetermined amount of source molecules or atoms are deposited, the irradiation of the electron beam from the electron beam gun B 'is stopped, and the adjacent shutter H' is rotated to close the container C '. Thereafter, by repeating this, a film made of a high-refractive material (hereinafter referred to as a “high-refractive material film”) and a film made of a low-refractive material (hereinafter referred to as a “film made of a low-refractive material”) are alternately stacked on the end face of the fiber to form A dielectric film is formed.

In the ion gun F shown in FIG. 9, active molecules (O ₂ active molecules, Ar active molecules, He active molecules) are directed toward the fiber end face in order to improve the denseness of the formed dielectric film. , N ₂ active molecules, CO ₂ active molecules, H ₂ O active molecules, etc.) to impart energy to the raw material molecules or atoms deposited on the same end face. The nutrizer G is for irradiating negatively charged thermoelectrons toward the fiber end face during film formation to prevent the fiber end face from being positively charged, thereby maintaining electrical neutrality.

[0005]

The formation of a dielectric film on the end face of a fiber as described above has the following problems. The temperature in the vacuum chamber A at the start of vapor deposition of the raw material molecules or atoms on the fiber end surface is almost the same as room temperature. A change occurs in the temperature in A. Due to such a temperature change, the refractive index of the high-refractive material film and the low-refractive material film laminated on the fiber end face change, and as a result, the optical characteristics of the dielectric film become different from the expected optical characteristics. I will. For example, when a Ta ₂ O ₅ film, which is one of the high refraction material films, is formed using the dielectric film forming apparatus shown in FIG. 9, it is represented in a graph shown in FIG. Temperature change. From this graph, it can be seen that the temperature in the vacuum chamber A increases with time after the start of the Ta ₂ O ₅ film formation, and a temperature change of 60 ° C. occurs between the start and end of the film formation. FIG. 11 is a graph showing a light amount change pattern measured by an optical film thickness meter (not shown) provided in the vacuum chamber A. The difference P1 between the peak and the valley of the sine wave at the point A in the graph is shown. 1 from the start of film formation
The refractive index of the Ta ₂ O ₅ film (thickness: 90 nm) after 5 minutes is shown, and the difference P2 between the peak and the valley of the sine wave at point B is the Ta ₂ O ₅ film (film thickness: 270 nm) 42 minutes after the start of film formation. ) Indicates the refractive index. FIG. 12 is a graph showing the refractive index of the Ta ₂ O ₅ film calculated based on the graph shown in FIG. From the graph, originally, the refractive index of the Ta ₂ O ₅ film, which should be constant irrespective thickness, Ta ₂ O at a later point in time 15 minutes from the start of film formation
_It can be seen that the 0.15 difference between the ₅ film (90 nm thick) and the Ta ₂ O ₅ film (270 nm thick) at 42 minutes after the start of film formation.

[0006] The change in the refractive index caused by the temperature change in the vacuum chamber as described above is caused by a high refractive material film (for example, a TiO ₂ film or an Nb ₂ O ₅ film) other than the Ta ₂ O ₅ film and a low refractive index. The same occurs for a material film (for example, a SiO ₂ film or the like). Therefore, when a dielectric film is formed by alternately laminating the high refractive material film and the low refractive material film on the end face of the fiber, the optical characteristics of the formed dielectric film are different from the expected optical characteristics. It will be something.

[0007]

SUMMARY OF THE INVENTION One of the objects of the present invention is as follows.
It is an object of the present invention to provide a method for forming a dielectric film on a fiber end face, in which a change in the ambient temperature is reduced as much as possible, and a dielectric film having desired optical characteristics can be formed.
Another object of the present invention is to provide a dielectric film forming apparatus capable of realizing the above method.

One of the methods of forming a dielectric film on an end face of an optical fiber according to the present application is to dispose an end face of an optical fiber in a closed space and deposit a source atom or molecule of the dielectric film on the end face. In the method of forming a dielectric film on an end face of a fiber, the inside of the closed space is preheated to a predetermined temperature, and then vapor deposition of raw material molecules or atoms on the end face of the optical fiber is started.

Another method of forming a dielectric film on the end face of an optical fiber according to the present application is to reduce the temperature change in a closed space from the start of vapor deposition of material molecules or atoms of a dielectric film to the end of vapor deposition. The temperature in the closed space is controlled so as to be within ° C.

One of the dielectric film forming apparatuses of the present application is a dielectric film capable of forming a dielectric film by depositing raw material molecules or atoms of the dielectric film on an end face of an optical fiber exposed in a chamber. A film forming apparatus is provided with a heating source for preheating the inside of a chamber to a predetermined temperature before starting deposition of source molecules or atoms on an end face of an optical fiber.

Another one of the dielectric film forming apparatuses of the present application is provided with an electron beam gun in a chamber for melting a raw material of the dielectric film and evaporating molecules or atoms thereof,
A heating source for preheating the inside of the chamber to a predetermined temperature is arranged near the electron beam gun.

[0012]

(Embodiment 1) Hereinafter, an example of an embodiment of a dielectric film forming method and an apparatus for forming a dielectric film on an end face of an optical fiber according to the present invention will be described. As shown in FIG. 1, the dielectric film forming apparatus of the present invention shown in FIG. 1 has two electron beam guns (EB guns) 2a and 2b and a dielectric film Two containers (crucibles) 3a and 3b capable of storing raw materials, a rotating dome 4 capable of setting an end of an optical fiber (not shown), an ion gun 5 capable of irradiating active molecules, and a thermoelectric electron having a negative charge. A neutriser 6 capable of irradiation, a temperature control mechanism 7 capable of controlling the temperature in the vacuum chamber 1, and an optical film thickness meter 8 capable of measuring the film thickness of the dielectric film formed on the fiber end face are provided. It is a thing. The electron beam guns 2a and 2b, the containers 3a and 3b, the rotating dome 4, the ion gun 5, and the nut riser 6 have the same structure and have the same functions as those shown in FIG. Is omitted.

The temperature control mechanism 7 includes a vacuum chamber 1
A heating source (sheath heater) 10 disposed in the inside, a heater power supply 11 for supplying power to the sheath heater 10, a sensor (thermocouple) 12 for detecting the temperature in the vacuum chamber 1, and a vacuum based on the detection result of the thermocouple 12 The temperature controller 13 measures the temperature in the chamber 1 and controls the heater power supply 11 based on the measurement result.
In the temperature control mechanism 7, the temperature controller 13 outputs a control signal to the heater power supply 11 based on the measured temperature in the vacuum chamber 1, and increases or decreases the amount of power supplied from the power supply 11 to the sheath heater 10 to control the same. The temperature inside the vacuum chamber 1 is controlled by adjusting the calorific value of the heater 10.

The optical film thickness meter 8 includes a glass plate 20, first and second mirrors 21a and 21b, and a light source 2 shown in FIG.
3. It comprises a detector 24. The glass plate 20
Is disposed at the tip of the rotating shaft 25 of the rotating dome 4 so that the raw material molecules or atoms of the dielectric film are deposited on the surface of the glass plate 20 under the same conditions as the fiber end face. The first mirror 21a reflects the light generated from the light source 23 toward the glass plate 20. Specifically, the rotation shaft 25 is hollow, and the light reflected by the first mirror 21a propagates inside the rotation shaft 25 as an optical path, and irradiates the glass plate 20. The second
Mirror 21b of the light applied to the glass plate 20
The reflected light is reflected toward the detector 24 and made incident on the detector 24. The detector 24 detects the amount (film thickness) of raw material molecules or atoms deposited on the surface of the glass plate 20 based on a change in the amount of light of a specific wavelength among the incident light.

The present invention shown here is directed to the end face of the optical fiber.
The dielectric film forming method uses the dielectric film forming apparatus of the present invention.
To form a dielectric film on the fiber end face,
Specifically, it comprises the following steps. (1) The rotating dome 4 of the dielectric film forming apparatus shown in FIG.
Secure the end of the fiber through a holder not shown.
To expose the fiber end face into the vacuum chamber 1.
You. (2) The inside of the vacuum chamber 1 is
Heat the chamber 1 to a temperature of 70 ° C. (the temperature in FIG. 1).
(Measured value by the controller 13). (3) When the temperature in the vacuum chamber 1 reaches 70 ° C.,
Film formation on the fiber end face is started. Specifically, the rotation
While rotating the beam 4, one of the electron beam guns 2a or
2b to the high refractive material in one container 3a or 3b (where
Is Ta_TwoO_FiveIrradiate electron beam toward) to melt the same material
To evaporate the molecules or atoms,
Deposit on the end face. Predetermined amount of Ta_TwoO_FiveMolecule or atom
After vapor deposition on the fiber end face, that is,
Ta_TwoO_FiveAfter the film is formed, the electron beam gun 2a or 2
Stop irradiation of electron beam from b
By rotating the shutter 30a or 30b, the container 3a or
Closes 3b. (4) Then, from the other electron beam gun 2b or 2a to the other
Low refractive material (here, SiO 2) in the container 3b or 3a_TwoTo)
And irradiate it with an electron beam.
Ta deposited on fiber end face_TwoO_FiveThe container on the membrane
SiO evaporated from 3b or 3a_TwoBy depositing atoms or molecules
Laminate. SiO of predetermined thickness_TwoAfter the film is formed, the electron
Stop irradiation of electron beam from beam gun 2b or 2a
At the same time, rotate the adjacent shutter 30b or 30a
To close the container 3b or 3a. In addition, Ta_TwoO_FiveFilm and SiO
_TwoThe thickness of the film should be measured by the optical thickness meter 8 described above.
Of course. (5) Thereafter, the above (3) and (4) are repeated to obtain a fiber
Predetermined film thickness Ta on the end face_TwoO _FiveFilm and SiO_TwoAlternately stack the membranes
A dielectric film having a predetermined thickness is formed.

FIGS. 2 to 4 show that a dielectric film having desired optical characteristics is formed by starting film formation on the fiber end face after preheating the inside of the vacuum chamber 1 shown in FIG. It is a figure showing the result of an experiment performed in order to confirm that a film is possible. FIG. 2 shows the vacuum chamber 1 shown in FIG.
After preheating the inside to 70 ° C, the above-mentioned Ta
₅ is a graph showing a temperature change in the vacuum chamber 1 when only a ₂ O ₅ film is formed. From this graph, it can be seen that by preheating the inside of the vacuum chamber 1, the temperature change in the vacuum chamber 1 from the start to the end of the film formation is suppressed to within 10 ° C. FIG. 3 shows a change in light quantity measured by the optical film thickness meter 8 shown in FIG. 1 at point C (42 minutes after the start of film formation) and point D (66 minutes after the start of film formation) in the graph shown in FIG. 5 is a graph showing a pattern, wherein a difference P1 between a peak and a valley of a sine wave at point C in the graph indicates the refractive index of the Ta ₂ O ₅ film (thickness: 90 nm) 15 minutes after the start of film formation, and point D Ta ₂ O ₅ difference P2 of sinusoidal peaks and valleys in the 66 minutes after the start of film formation in
The refractive index of the film (thickness: 360 nm) is shown. FIG.
4 is a graph showing the refractive index of the Ta ₂ O ₅ film calculated based on the graph shown in FIG. The graph shows that the Ta ₂ O ₅ film (thickness: 90 nm) at 15 minutes after the start of film formation and 66 minutes after the start of film formation.
It can be seen that the difference in the refractive index from the Ta ₂ O ₅ film (thickness: 360 nm) at the minute point is 0.03.

As described above, when the inside of the vacuum chamber 1 shown in FIG. 1 is preheated, the temperature change in the chamber 1 during the film formation is suppressed within a certain range, and a Ta ₂ O ₅ film having a predetermined refractive index can be formed. It can be seen that it is. The same applies to a high-refractive material film (for example, a TiO ₂ film or an Nb ₂ O ₅ film) and a low-refractive material film (for example, an SiO ₂ film) other than the Ta ₂ O ₅ film. Therefore, if the inside of the vacuum chamber 1 is pre-heated as in the present invention, a high refractive material film and a low refractive material film having a predetermined refractive index are formed on the end face of the fiber, and a dielectric film having an intended optical property is formed. Can be formed.

(Embodiment 2) Hereinafter, another embodiment of the dielectric film forming apparatus of the present invention will be described. The basic configuration of the dielectric film forming apparatus of the present invention shown here is the same as that shown in FIG. The difference is that, as shown in FIG. 5, a heating source (halogen lamp) 40 different from the sheath heater 10 is provided in the vacuum chamber 1, and the temperature in the vacuum chamber 1 can be controlled by both the sheath heater 10 and the halogen lamp 40. It was that. The halogen lamp 40
Is a vacuum chamber 1 mainly before the start of film formation on the fiber end face.
It works to preheat the inside. In addition, since the temperature change is greatest in the vicinity of the electron beam guns 2a and 2b, from the viewpoint of minimizing the temperature change in the vacuum chamber 1, the halogen lamp 40 is connected to the electron beam guns 2a and 2b.
Is desirably arranged in the vicinity of. Further, when the halogen lamp 40 is disposed near the electron beam guns 2a and 2b, degassing around the electron beam guns 2a and 2b can be performed.
However, the heating source 40 may be other than a halogen lamp.

FIG. 6 shows the vacuum chamber 1 shown in FIG. 5 after preheating to 75 ° C. by a halogen lamp 40 and then forming only a Ta ₂ O ₅ film on the fiber end face. It is a graph showing a temperature change. From this graph, it can be seen that the temperature change in the vacuum chamber 1 is suppressed within 5 ° C. from the start to the end of the film formation.
FIG. 7 shows point E (3 from the start of film formation) in the graph shown in FIG.
2 minutes) and at point F (56 minutes after the start of film formation),
6 is a graph showing a light amount change pattern measured by the optical film thickness meter 8 shown in FIG. 5, wherein a difference P1 between a peak and a valley of a sine wave at a point E is Ta ₂ O 32 minutes after the start of film formation.
₅ indicates the refractive index of the film (film thickness 90 nm), and the difference P2 between the peak and the valley of the sine wave at the point F is Ta
_It shows the refractive index of a ₂ O ₅ film (260 nm thick). FIG. 8 is a graph showing the refractive index of the Ta ₂ O ₅ film calculated based on the graph shown in FIG. From the graph, the difference in the refractive index between the Ta ₂ O ₅ film (thickness: 90 nm) 32 minutes after the start of the film formation and the Ta ₂ O ₅ film (thickness: 270 nm) 56 minutes after the start of the film formation It turns out that it is 0.01 or less.

From the graphs shown in FIGS. 6 to 8, when the halogen lamp 40 is provided in addition to the sheath heater 10, the temperature change in the vacuum chamber 1 during the film formation is smaller than when only the sheath heater 10 is provided. It can be seen that the refractive index of the high refractive material film and the low refractive material film can be further suppressed.

The use of the dielectric film forming apparatus shown in FIG. 5 is, of course, included in the method of forming a dielectric film on the end face of an optical fiber according to the present invention. In short, regardless of whether the dielectric film forming apparatus of the present invention is used or another dielectric film forming apparatus is used, the periphery of the fiber end face is pre-heated, and the end face of the same end face during film formation is heated. In the case of suppressing the change in the refractive index of the high-refractive material film and the low-refractive material film formed on the same end surface by suppressing the change in the ambient temperature, the dielectric film is formed on the end surface of the optical fiber according to the present invention. Included in the method.

Further, in alternately forming the high-refractive material film and the low-refractive material film, these films are formed not intermittently but intermittently. The case where the temperature change in the vacuum chamber is suppressed within a certain range is also included in the method of forming a dielectric film on the end face of the optical fiber of the present invention. For example, when forming a dielectric film in which four layers of high-refractive material films and low-refractive material films are alternately laminated on the end face of a fiber, the first layer and the first layer are preheated to 70 ° C. or 75 ° C. in the vacuum chamber. A second layer is formed. afterwards,
After the film formation is temporarily stopped and the temperature in the raised vacuum chamber is lowered to 70 ° C. or 75 ° C., the film formation of the third and fourth layers is started. The reflectivity of the dielectric film thus formed is 0.003% against the design value of 0.001%.
%Met.

In the dielectric film forming apparatus shown in FIGS. 1 and 5, the temperature in the vacuum chamber 1 is measured based on the detection result of the thermocouple 12, but instead of the thermocouple 12, or the thermocouple is used. A radiation thermometer provided in the vacuum chamber 1 in addition to the pair 12 and capable of directly measuring the temperature on the rotary dome 4 is also included in the dielectric film forming apparatus of the present invention. The case where the dielectric film is formed on the end face of the optical fiber is also included in the method of forming a dielectric film on the end face of the optical fiber of the present invention. Under the same conditions, there is a difference of about 20 ° C. between the chamber temperature measured based on the detection result of the thermocouple 12 shown in FIGS. 1 and 5 and the chamber temperature measured by the radiation thermometer. is there. For example, the former is 70
In the case of ° C, the latter is 90 ° C. Therefore, when the temperature in the preheated vacuum chamber is measured by the radiation thermometer, it is preferable to determine the film formation start timing in consideration of the measured temperature difference.

[0024]

According to the method of forming a dielectric film on the end face of an optical fiber according to the present invention, film formation is started after preheating the enclosed space where the film is formed on the end face of the fiber. Temperature change in the closed space is suppressed within a certain range. As a result, the refractive indices of the high refractive index film and the low refractive index film constituting the dielectric film do not change due to the temperature conversion, and a dielectric film having an intended optical specification can be formed. Can be.

The dielectric film forming apparatus of the present application provides a method for starting deposition of source molecules or atoms on the end face of an optical fiber.
Since a heating source capable of preheating the chamber to a predetermined temperature is provided, a temperature change in the chamber during film formation is suppressed within a certain range. As a result, the refractive indices of the high refractive index film and the low refractive index film constituting the dielectric film do not change due to the temperature conversion, and a dielectric film having an intended optical specification can be formed. Can be.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of an embodiment of a dielectric film forming apparatus of the present invention.

FIG. 2: Ta ₂ O ₅ in a chamber preheated to 70 ° C.
FIG. 5 is a diagram showing a change in a temperature in a chamber when a film is formed.

FIG. 3. Ta ₂ O ₅ in a chamber preheated to 70 ° C.
The figure which shows the light amount change pattern measured by the optical film thickness meter at the time of forming a film.

FIG. 4 is a diagram showing a refractive index of a Ta ₂ O ₅ film formed in a chamber preheated to 70 ° C.

FIG. 5 is an explanatory view showing another example of the embodiment of the dielectric film forming apparatus of the present invention.

FIG. 6: Ta ₂ O ₅ in a chamber preheated to 75 ° C.
FIG. 5 is a diagram showing a change in a temperature in a chamber when a film is formed.

FIG. 7: Ta ₂ O ₅ in a chamber preheated to 75 ° C.
The figure which shows the light amount change pattern measured by the optical film thickness meter at the time of forming a film.

FIG. 8 is a diagram showing a refractive index of a Ta ₂ O ₅ film formed in a chamber preheated to 75 ° C.

FIG. 9 is an explanatory view showing an example of a conventional dielectric film forming apparatus.

FIG. 10: Ta ₂ O _{5 in a} chamber not preheated
FIG. 5 is a diagram showing a change in a temperature in a chamber when a film is formed.

FIG. 11: Ta ₂ O _{5 in a} chamber not preheated
The figure which shows the light amount change pattern measured by the optical film thickness meter at the time of forming a film.

FIG. 12 is a diagram showing a refractive index of a Ta ₂ O ₅ film formed in a chamber that is not preheated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Electron beam gun 3 Container 4 Rotating dome 5 Ion gun 6 Nutriser 7 Temperature control mechanism 8 Optical film thickness meter

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H038 BA23 BA24 2H048 GA04 GA32 GA60 GA62 2H050 AC89 AD00 4K029 AA08 AA23 BA43 BB02 BC01 BC07 BD00 DB21 FA09

Claims (4)

[Claims] 1. A method of forming a dielectric film on an end face of an optical fiber in which an end face of an optical fiber is disposed in a closed space and material atoms or molecules of the dielectric film are deposited on the end face. A method for forming a dielectric film on an end face of an optical fiber, comprising: starting to deposit material molecules or atoms on the end face of the optical fiber after preheating to a predetermined temperature. 2. The method according to claim 1, wherein the temperature in the sealed space is controlled so that the temperature change in the sealed space from the start of the deposition of the molecules or atoms of the dielectric film to the end of the deposition is within 10 ° C. The method for forming a dielectric film on an end face of an optical fiber according to claim 1. 3. A dielectric film forming apparatus capable of forming a dielectric film by depositing raw material molecules or atoms of a dielectric film on an end face of an optical fiber exposed in a chamber. A heating source for preheating the inside of the chamber to a predetermined temperature before starting the deposition of the raw material molecules or atoms. 4. An electron beam gun for melting a raw material of a dielectric film and evaporating molecules or atoms in a chamber, and preheating the inside of the chamber to a predetermined temperature near the electron beam gun. 4. The dielectric film forming apparatus according to claim 3, wherein said heating source is disposed.