JP2003084216A - Fabry-perot filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Fabry-Perot filter in element structure which can make an initial gap large and is easy to manufacture. SOLUTION: The Fabry-Perot filter which has a fixed mirror and a movable mirror arranged opposite the fixed mirror across a size-variable gap and selects and transmits light with arbitrary desired wavelength corresponding to the gap has a fixed substrate where the fixed mirror is formed, a movable substrate which is connected to the fixed substrate across spacers, a plurality of hinge parts which are formed thinly by etching a plural places of the surface of the movable substrate on the opposite side from the fixed substrate into a groove shape, a projection part which is formed thickly between the plurality of hinge parts of the movable substrate and connected to the hinge parts and where the movable mirror is formed, and a metal heater which is connected to the hinge parts to form a bimetal structure; and the metal heater is electrified to generate heat and the movable substrate is driven through the bimetal effect between the hinge parts and metal heater to vary the gap.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fabry-Perot filter that selects and transmits light of any desired wavelength.

[0002]

2. Description of the Related Art FIG. 3 is a vertical sectional view of a conventional Fabry-Perot filter. In FIG. 3, 20 is a Si substrate, 21
Is a fixed mirror, and SiO2 formed on the Si substrate 20.
/ TiO2 and the like.
Reference numeral 22 denotes a movable mirror that is arranged to face the fixed electrode, and is composed of a multilayer optical thin film made of, for example, SiO2 / TiO2.

Reference numeral 23 is a fixed electrode formed on the fixed mirror 21 so that the central portion of the fixed mirror 21 is exposed as an optically active region 24, and is made of, for example, an Au film. 25
Is a support film that supports the movable mirror 22, and is connected to the fixed electrode 23 via spacers 26a and 26b made of, for example, polyimide for forming a gap between the fixed mirror 21 and the movable mirror 22. The support film 25 is composed of a multilayer film of a movable electrode 25a made of an Al film and a SiN film 25b.

Then, by applying an arbitrary desired wavelength selection voltage (driving voltage) between the fixed electrode 23 and the movable electrode 25a to generate an electrostatic force, the movable mirror 22 is driven to move the fixed mirror 21 and the movable mirror 22. By changing the size of the gap formed between the two, the Fabry-Perot filter selectively transmits light of any desired wavelength corresponding to the size of the gap.

In manufacturing the Fabry-Perot filter, a multilayer optical thin film forming the fixed mirror 21 is deposited on the Si substrate 20, an Au film to be the fixed electrode 23 is deposited, and then the central portion of the Au film is deposited. Are etched away to form the optically active region 24. And the spacers 26a, 2
After the polyimide 6b is coated on the entire surface, an Al film 25a and a SiN film 25b which will be the support film 25 are deposited and the central portion is removed by etching, and the movable mirror 22 is attached to the removed central portion.
A multilayer optical thin film to be formed is deposited and supported by the support film 25. Then, the polyimide is removed by etching, leaving the spacers 26a and 26b, to produce an air gap structure.

[0006]

However, such a Fabry-Perot filter has the following problems. (1) Since two electrodes (the fixed electrode 23 and the movable electrode 25a) are required to drive the movable mirror, the element structure and the wiring structure are complicated. (2) When the initial gap is increased, the reflectivity of the fixed mirror and the movable mirror can be lowered and the film thickness thereof can be reduced, which facilitates the design and manufacture of the optical thin film. But,
If the initial gap is increased, the drive voltage of the Fabry-Perot filter also increases, and there is a risk that the high voltage may destroy the device, and there is a limit to increasing the initial gap.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to realize a Fabry-Perot filter having an element structure which can increase the initial gap and is easy to manufacture.

[0008]

According to a first aspect of the present invention, there is provided a fixed mirror and a movable mirror which is disposed opposite to the fixed mirror with a variable size gap, and corresponds to the gap. In a Fabry-Perot filter that selectively transmits light of any desired wavelength, a fixed substrate on which the fixed mirror is formed, a movable substrate connected to the fixed substrate via a spacer, and the fixed substrate of the movable substrate. A plurality of hinge portions formed in a groove shape at a plurality of positions not facing each other to be thinly formed, and a thick portion formed at a position sandwiched by the plurality of hinge portions of the movable substrate to be connected to the hinge portion. And a metal heater that is connected to the hinge portion to form a bimetal structure and that has a protrusion on which the movable mirror is formed. The metal heater is energized to heat the hinge portion and the hinge portion. By driving the movable substrate by the bimetal effect of the genus heater is Fabry-Perot filters, characterized in that a variable the gap.

According to a second aspect of the present invention, in the Fabry-Perot filter according to the first aspect, a drive electrode connected to the metal heater and energized to the metal heater is provided on the movable substrate. It is a Fabry-Perot filter.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a Fabry-Perot filter according to the present invention, FIG. 2 (a) is a top view thereof, and FIG. 2 (b) is an enlarged view of a main part of FIG. 2 (a). still,
FIG. 1 is a sectional view taken along the line AA ′ in FIG.

In FIGS. 1 and 2A and 2B, 1
Is a fixed substrate made of Si, 2 is a fixed mirror formed on the fixed substrate, 3a, 3b, 3c and 3d are spacers, 4 is a movable substrate made of Si, for example, 5a, 5b, 5c and 5d are hinge portions, and 6 is Protrusion, 7 is a movable mirror, 8a, 8b, 8c, 8d
Is a metal heater formed of a metal having a coefficient of thermal expansion different from that of the hinge portions 5a, 5b, 5c, 5d, and 9a ₁ , 9a ₂ , 9b.
_{1, 9b 2, 9c 1,} 9c 2, 9d 1, 9d 2 is a driving electrode.

The fixed mirror 2 is a quarter of the center wavelength λ of the filter.
Single layer or SiO having an optical film thickness corresponding to the wavelength
The movable substrate 4 is formed of a multilayer film made of 2 / TiO 2 or the like, and is arranged to face the surface of the fixed substrate 1 on which the fixed mirror 2 is formed.
The spacers 3a, 3b, 3c and 3d are connected to the fixed substrate 1.

The movable substrate 4 has a center boss structure, and a plurality of thin hinge portions 5a, 5b are formed by anisotropically etching a plurality of portions of the surface of the movable substrate 4 not facing the fixed substrate 1 into grooves. , 5c, 5d are formed,
A thick protrusion 6 (boss) is formed at a position (center) sandwiched by the hinges 5a, 5b, 5c, 5d. That is, the protrusion 6 is provided at the center of the movable substrate 4 and the hinge 5 is formed.
It is a structure connected by a, 5b, 5c and 5d.

A movable mirror 7 is formed at a portion of the protrusion 6 facing the fixed mirror 2, and hinges 5a, 5b, 5 are formed.
A metal heater 8 is provided at a portion facing the fixed mirror 2 of c and 5d.
a, 8b, 8c and 8d are formed respectively. still,
The movable mirror 7 is a multilayer-film reflective mirror that transmits a specific wavelength by interference with the fixed mirror 2.

Then, as shown in FIGS. 2A and 2B, drive electrodes 9a ₁ , 9a ₂ , 9b ₁ , 9b ₂ , 9 are formed.
c ₁ , 9c ₂ , 9d ₁ and 9d ₂ are formed on a fixed substrate, the drive electrodes 9a ₁ and 9a ₂ are on the metal heater 8a, the drive electrodes 9b ₁ and 9b ₂ are on the metal heater 8b, and the drive electrode 9c.
₁ , 9c ₂ are metal heaters 8c and drive electrodes 9d ₁ , 9d
₂ The metal heater 8d, are connected by a respective conductively conductive wiring pattern _{9a 3, 9b 3, 9c 3} , 9d 3. The fixed substrate 1 and the movable substrate 4 are connected by spacers 3a, 3b, 3c and 3d so that the fixed mirror 2 and the movable mirror 7 face each other to form a gap.

Next, the operation of the Fabry-Perot filter shown in FIGS. 1 and 2 will be described. Drive electrodes 9a ₁ , 9
metal heater 8a is heated when energized from the outside to a _2. When the metal heater 8a is heated, the hinge portion 5
Although a is heated, since the metal heater 8a and the hinge portion 5a have different coefficients of thermal expansion, the metal heater 8 is attached to the hinge portion 5a.
Deflection occurs due to the bimetal effect with a.

Similarly, when the drive electrodes 9b ₁ and 9b ₂ are energized from the outside, a deflection is generated due to the bimetal effect of the metal heater 8b and the hinge portion 5b, and the drive electrodes 9c ₁ and 9c ₂
When an electric current is applied from the outside to the driving electrode 9d, the metal heater 8c and the hinge portion 5c are bent due to the bimetal effect.
_When electricity is applied to ₁ and 9d _{2 from} the outside, the metal heater 8d and the hinge portion 5d are bent due to the bimetal effect.

The hinge portions 5a, 5b, 5
The deflection of c and 5d drives the movable substrate 4 to change the size of the gap between the fixed mirror 2 and the movable mirror 7.
In this case, the current flowing through the drive electrodes 9a ₁ and 9a ₂ , the current flowing through the drive electrodes 9b ₁ and 9b ₂ , the drive electrode 9
Currents flowing through c ₁ and 9c ₂ , drive electrodes 9ad and 9d ₂
It is possible to obtain a desired size of the gap by controlling the size of the electric current that is applied to each.

When light having a wavelength of 1.55 μm for communication enters through the optical fiber from above the movable substrate 4, Si is transparent to the light having a wavelength of 1.55 μm. Light having a desired wavelength corresponding to the size of the gap that passes through is selected by the Fabry-Perot filter and emitted from the lower portion of the fixed mirror 2. (Wavelength that minimizes the optical transmission loss of the optical fiber)

Further, a current flowing through the driving electrodes 9a ₁ and 9a ₂ , a current flowing through the driving electrodes 9b ₁ and 9b ₂ , a current flowing through the driving electrodes 9c ₁ and 9c ₂ and the driving electrodes 9ad and 9
The tilt of the movable mirror 7 can be controlled by individually controlling the magnitude of the current flowing to d ₂ .

According to the Fabry-Perot filter as described above, the drive electrodes 9a ₁ and 9a for driving the movable mirror are provided.
₂ , 9b ₁ , 9b ₂ , 9c ₁ , 9c ₂ , 9d ₁ , 9d ₂
Since all are formed on the fixed substrate 1, the element structure and the wiring structure are simplified.

Further, since the movable mirror 7 is driven by the current passing through the drive electrode, the size of the gap does not depend on the voltage, and there is no fear of destroying the element by the voltage. Therefore, the initial Fabry-Perot filter is used. The gap can be increased. Therefore, the reflectance of the fixed mirror 2 and the movable mirror 7 can be lowered to reduce the film thickness, which facilitates the design and manufacture of the optical thin film.

Further, since the movable mirror 7 is formed on the thick projection 6, it does not warp, and the movable mirror 7 has a multi-layer structure for controlling optical performance (half-value width, etc.). It is possible to increase the number of layers of the optical thin film.

[0024]

As described above, according to the present invention,
To realize a Fabry-Perot filter with an element structure that can increase the initial gap by driving the movable mirror by utilizing the bimetal effect due to the difference in the coefficient of thermal expansion between the hinge part and the metal heater, and which is easy to manufacture. You can

[Brief description of drawings]

1 is a cross-sectional view of a Fabry-Perot filter according to the present invention.

FIG. 2 is a top view of a Fabry-Perot filter according to the present invention.

FIG. 3 is a sectional view of a conventional Fabry-Perot filter.

[Explanation of symbols]

1 Fixed Substrate 2 Fixed Mirrors 3a, 3b, 3c, 3d Spacer 4 Movable Substrates 5a, 5b, 5c, 5d Hinge 6 Protrusion 7 Movable Mirrors 8a, 8b, 8c, 8d Metal Heaters 9a ₁ , 9a ₂ , 9b ₁ , 9b ₂ , 9c ₁ , 9c ₂ , 9
d ₁ , 9d ₂ drive electrode

Claims (2)

[Claims] 1. A Fabry which has a fixed mirror and a movable mirror which faces the fixed mirror and has a variable size gap, and which selectively transmits light having a desired wavelength corresponding to the gap. In the Perot filter, a fixed substrate on which the fixed mirror is formed, a movable substrate connected to the fixed substrate through a spacer, and a plurality of portions of a surface of the movable substrate that does not face the fixed substrate are etched in a groove shape. A plurality of hinge portions that are thinly formed, and a projection portion that is thickly formed at a position sandwiched by the plurality of hinge portions of the movable substrate and that is connected to the hinge portions and that forms the movable mirror. A metal heater that is connected to the hinge portion to form a bimetal structure, and is energized to heat the metal heater, and the metal heater is movable by a bimetal effect of the hinge portion and the metal heater. Fabry-Perot filters, characterized in that a variable the gap by driving the plate. 2. The Fabry-Perot filter according to claim 1, wherein a drive electrode connected to the metal heater and energizing the metal heater is provided on the movable substrate.