JPH11119186A - Wavelength variable filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength variable filter with which has no dependence on polarization, is high in a response speed and allows high-speed tuning by using a material dispersed with liquid crystal droplates below 150 nm in a light transparent medium as a cavity. SOLUTION: This Fabry-Perot etalon type wavelength variable filter includes the multilayered films formed by laminating first layers 102 which consist of transparent electrodes 105 and optical mirror layers 104, second layers 101 which consist of a material changed in its refractive index by an electric field and third layers 103 which consist of the transparent electrodes and the optical mirror layers in this order. The material which changed in its refractive index by the electric field is a material formed by dispersing the liquid crystal droplets of <=150 nm in diameter into the light transparent medium, such as polymer or quartz glass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength tunable filter, and more particularly to a technique effective when applied to a technique for selectively separating light of a specific wavelength from wavelength multiplexed light.

[0002]

2. Description of the Related Art Optical communication using an optical fiber has recently been rapidly put into practical use because it can transmit a large amount of information at a high speed. However, at the moment, only an optical pulse of a specific wavelength is transmitted. If a large number of optical pulses of different frequencies can be transmitted, a larger amount of information can be transmitted. This is wavelength multiplexed (W
DM) and is currently being actively researched. In wavelength multiplex communication, a wavelength tunable filter for selectively selecting only light having an arbitrary wavelength from optical pulses having a large number of wavelengths is required. Conventional filters of this type include a grating filter that controls the angle with a motor, a tunable filter that moves a dielectric filter with a motor, and an etalon filter that controls the resonator length with a piezo element. The disadvantages are that the speed is slow, the module is large, and the price is high. In order to solve the above-mentioned disadvantages of the wavelength tunable filter, the present applicant has devised a filter in which a nematic liquid crystal is filled in a Fabry-Perot etalon and the optical gap of the etalon is changed by applying a voltage. (Japanese Patent Application No. 2-41273)
No. 6).

[0003]

However, a filter using a nematic liquid crystal has a problem that the tuning speed cannot be further increased because the nematic liquid crystal has a response speed of only a maximum of several milliseconds. A high tuning speed is an essential characteristic for realizing wavelength division multiplexing (WDM) in a high-speed LAN.
Further, since a filter using liquid crystal utilizes the orientation of liquid crystal by voltage, the change in the refractive index is not uniform depending on the polarization state of incident light and the direction of the polarization plane. Therefore,
The so-called polarization dependency, in which the tuning characteristic changes depending on the plane of polarization, occurs, which causes a practical problem. It has been reported that a wavelength tunable filter using a chiral smectic A liquid crystal exhibits a high response speed of 10 μsec in order to increase the response speed. However,
The variable width is narrow and the polarization dependence has not been improved yet (A. Sneh and K. Johnson, “High-speed continuously
tunable liquid crystal filter for WDMnetwork, ”J.
Lightwave.Technol.vol.14, pp.1067, 1996.).

In order to realize WDM in a high-speed optical LAN, it is desired to improve these two disadvantages, that is, to develop a wavelength tunable filter having high speed and high practicability without polarization dependence. There is a demand for higher density, smaller size, and lower cost by arraying. The present invention has been made to solve the problems of the prior art, and an object of the present invention is to use, as a cavity, a material in which a liquid crystal droplet is dispersed in a light transmitting medium in a wavelength tunable filter. Therefore, there is no polarization dependence,
Another object of the present invention is to provide a technology that has a high response speed and enables high-speed tuning. Another object of the present invention is to
In a wavelength tunable filter, as the size of the liquid crystal droplets decreases, the voltage required to drive the liquid crystal droplets tends to increase, but a plasticizer that is effective in plasticizing plastic in the polymer dispersing the liquid crystal droplets It is an object of the present invention to provide a technique capable of driving a liquid crystal droplet at a low voltage and increasing the variable width of a wavelength tunable filter per voltage by adding a liquid crystal droplet. Another object of the present invention is to provide a wavelength tunable filter that is less expensive than a conventional wavelength tunable filter, and can be made higher in density and smaller by combining it with an arrayed optical fiber or the like. It is to provide a new technology. Another object of the present invention is to improve the spectrum by stacking a large number of tunable filters or using a plane mirror or a prism mirror in the tunable filter, and to improve the entire tunable range. It is an object of the present invention to provide a technology that can be extended to a wavelength range. It is another object of the present invention to provide a technology capable of easily configuring a multiplexer / demultiplexer by using a plane mirror in a wavelength tunable filter. The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0005]

In order to solve the above-mentioned problems, the present invention provides a medium whose refractive index is changed by applying a voltage, in a polymer or glass having good light transmittance, having a particle size of 150 nm or less. A medium in which extremely small liquid crystal droplets are dispersed is used. This small liquid crystal droplet has a much faster response than bulk liquid crystal. In addition, a liquid crystal droplet of this size is very small in comparison with the wavelength of light normally used in an optical communication system, so that it does not work as a scatterer and has a small transmission loss. These high speed and low transmission loss of a liquid crystal droplet of 150 nm or less are characteristics not found in liquid crystal particles of the order of μm, which have been studied as display devices using scattering before.

FIG. 2 is a diagram for explaining the structure and operating principle of a medium in which the refractive index changes by applying a voltage according to the present invention. The voltage is applied to the nano-sized liquid crystal droplet 201 in the same direction as the incidence of light. 1 schematically shows the direction of the director of a liquid crystal droplet when is applied, taking a nematic liquid crystal having a positive dielectric anisotropy as an example. In FIG. 2, 202 is a polymer layer, 203 is an electrode,
Reference numeral 204 denotes a driving power supply. When no voltage is applied, the directions of the liquid crystal droplets 201 are random, and the size of the liquid crystal droplets 201 is much smaller than the wavelength of light. There is no. Thus, the medium is considered equivalent for any polarization of the incident light and the index of refraction of the medium is considered equal for any polarization of the incident light. When a voltage is applied, the direction of the director of the liquid crystal droplet 201 tends to be perpendicular to the surface. In this case, the director of the liquid crystal droplet 201 is also directed to any polarization of the incident light. Changes in the same manner, the change in the refractive index of the medium becomes equal for any polarization of the incident light. Therefore, the change in the refractive index of the medium due to the voltage has no polarization dependence, and the characteristics of the tunable filter do not have polarization dependence.

FIG. 1 is a diagram for explaining the basic structure of a tunable filter according to the present invention. In FIG.
Is the second layer, 102 is the first layer, 103 is the third layer, 1
04 is an optical mirror (dielectric mirror) film, 105 is a transparent electrode, 106 is a transparent substrate, and 107 is an AR coating film (anti-reflection coating film). As the transparent substrate 106, a synthetic quartz having a surface roughness accuracy of λ / 10 or less is usually used. This second
The layer 101 is a material whose refractive index is changed by an electric field, and is a material in which liquid crystal droplets having a diameter of 150 nm or less are dispersed in a light transmitting medium such as a polymer (polymer) or quartz glass. In this case, the second layer 1
01 needs to be transparent in the used wavelength band. According to the tunable filter of the present invention shown in FIG.
When no voltage is applied and when a voltage is applied, the change in the refractive index of the second layer 101 does not depend on the polarization. Absent. The matrix medium in which the liquid crystal droplets are dispersed may be any material as long as it is a light-transmitting material, and is not particularly limited, but a polymer having good light-transmitting properties and having no optical anisotropy, for example, PMMA System polymers, polystyrene polymers, polycarbonate polymers, thermosetting or photocurable acrylic polymers, epoxy polymers, polyurethane polymers, polyisocyanate systems, polyenepolythiol systems, and glass.

As a method of manufacturing the second layer 101, when the matrix medium is a polymer, for example, the matrix polymer and liquid crystal are dissolved in an organic solvent, and the solvent is removed to form a liquid crystal droplet. A method such as a method of separating liquid crystal from a polymer or a method of dissolving liquid crystal in a thermosetting or photocurable prepolymer and separating liquid crystal droplets from a cured matrix polymer by heat or light irradiation. Alternatively, from a mixture of a polymer precursor and a liquid crystal, a method of obtaining the liquid crystal by layer separation is generally used,
Photocurable polymers are preferred for fabrication. In any method, in order to obtain a liquid crystal droplet having the size specified in the present invention, it is necessary to rapidly remove the solvent or rapidly cure the prepolymer to rapidly perform phase separation. On the other hand, when the matrix medium is glass, it can be produced by immersing porous glass having a pore size corresponding to the size of the liquid crystal droplet specified in the present invention in the liquid crystal.

Examples of the liquid crystal include a nematic liquid crystal, a cholesteric liquid crystal, and a ferroelectric liquid crystal. A nematic liquid crystal having a large change in refractive index due to a change in orientation is desirable. The size of the granular liquid crystal droplet is 150
nm or less is appropriate. This is because if the diameter is larger than 150 nm, scattering due to the difference in the refractive index between the liquid crystal droplet and the medium is large, and the light transmittance is not sufficient, and if it is 100 nm or less, the scattering loss is extremely small. In addition, the response speed tends to increase as the size of the liquid crystal droplet decreases, but the voltage required for driving the liquid crystal increases. Therefore, the liquid crystal droplet size must be several nm or more to maintain a practical applied voltage. Is desirable. This small liquid crystal droplet has an extremely fast response (10 μsec or less) as compared with the bulk liquid crystal. In addition, since the liquid crystal droplet of this size is very small in comparison with the wavelength of light normally used in an optical communication system, it does not work as a scatterer and has a small transmission loss (1 to 2 dB / cm).

The order of lamination of the transparent electrode 105 and the optical mirror film 104 in the first layer 102 and the third layer 103 may be any order, but preferably, the optical mirror film 104 is It is preferably closer to 101, that is, inside. This is the optical mirror film 1
This is because a wavelength tunable filter with better performance can be obtained by reducing the transmission loss of the resonance section from the optical mirror film 104 to the optical mirror film 104. Further, the first layer 102 and the third layer 1
The transparent electrode 105 constituting a part of No. 03 may be the same or a different type, and is not particularly limited.
As a material of the transparent electrode 105, a thin film of indium oxide or tin oxide doped with tin oxide can be used. This is produced by vapor deposition or sputtering.
Further, the optical mirror films 104 constituting a part of the first layer 102 and the third layer 103 may be the same or different types, as long as a desired reflectance can be obtained at a predetermined wavelength. Well, in that case, a reflectivity of 95
% Or more is preferable. For the infrared region, T
e-KBr, Al-Ge-SiO, Cu-Ge-Si
A multilayer film of O, Au-Ge-SiO, TiO ₂ -SiO ₂ is given as an example. These are produced by vapor deposition or sputtering.

The tunable filter of the present invention shown in FIG.
For example, it is manufactured by the following procedure. First, a transparent substrate 106, for example, a glass substrate or a plastic substrate such as PMMA or polycarbonate, is prepared in the wavelength band to be used, and a transparent electrode 105 and an optical mirror film 104 are laminated on the substrate 106 to form a first substrate. Layer 102 (or third layer 103) is formed. Next, on the substrate 106 on which the first layer 102 (or the third layer 103) is formed,
A film of a liquid mixture of a prepolymer and a liquid crystal that can be photopolymerized or thermally polymerized is formed by a method such as spin coating. In this state, the prepolymer is polymerized and solidified by heat or light, and extremely small liquid crystal droplets are generated in the polymer by phase separation. Next, the third layer 103 (or the first layer 10) is added to the liquid crystal droplet dispersed polymer film formed on the first layer 102 (or the third layer 103).
2) That is, the substrate 106 on which the optical mirror film 104 and the transparent electrode 105 are laminated is brought into close contact with each other to manufacture the wavelength tunable filter of the present embodiment. Note that the outer surface of the substrate 106 is desirably covered with the AR coat film 107 from the viewpoint of reducing reflection here.

The transparent electrode 105 and the optical mirror film 10
After laminating the two substrates 106 with the spacers 4 having a predetermined thickness sandwiched therebetween, and filling the gaps formed by the spacers with a liquid mixture of a photopolymerizable or thermally polymerizable prepolymer and a liquid crystal, It is also possible to use a method in which a prepolymer is polymerized by heat or light, and extremely small liquid crystal droplets are formed in the polymer by phase separation. Further, a porous glass substrate having a pore size of 150 nm or less is immersed in liquid crystal, and the pores filled with liquid crystal are sandwiched between two substrates 106 on which an optical mirror film 104 and a transparent electrode 105 are laminated, and adhered and fixed. It is also possible to produce by doing.

The interface roughness, thickness, and size of each film constituting the wavelength tunable filter of the present invention shown in FIG. 1 are not particularly limited as long as they are within a practical range. However, the thickness (cavity length) of the second layer 101 is an important factor that determines the interval between the wavelengths of resonating light (hereinafter, referred to as FSR) and, at the same time, half of the spectrum of light that can be separated. It also affects the price range. Therefore, this thickness is determined in consideration of the variable width of the filter and the like, and is usually several μm to 100 μm.

FIG. 3 is a diagram for explaining the structure and operating principle of the tunable filter of the present invention. The basic structure of the wavelength tunable filter of the present invention shown in FIG. 3 is a Fabry-Perot etalon type wavelength tunable filter in which a polymer is used as a matrix medium and minute liquid crystal droplet dispersed polymers are sandwiched in the cavity. In the figure,
Reference numeral 301 denotes a nematic liquid crystal droplet having a particle diameter of 150 nm or less, 302 denotes a polymer layer that confines the liquid crystal,
03 is an optical mirror (dielectric mirror) film, 304 is a transparent electrode, 305 is a transparent substrate, and 306 is an AC power supply. 307 indicates a transmission spectrum when no voltage is applied, and 308 indicates a transmission spectrum when voltage is applied. As shown in FIG. 3A, when no voltage is applied, the liquid crystal molecules in the liquid crystal droplet 301 are oriented in random directions, and the refractive index of light incident on the minute liquid crystal droplet dispersed polymer layer is reduced. is the average refractive index of the refractive index of the nematic liquid crystal (n _e, n _o). Further, as shown in FIG. 3 (b), aligned liquid crystal molecules in the applied electric field direction to apply a voltage, the refractive index approaches the n _o.

[0015] Normally, the wavelength 633 nm, the value of n _e, n _o is 1.7174,1.532, the refractive index of the average 1.5
It is about 55. Therefore, as shown in the lower part of FIG. 3, the wavelength of the transmitted light, which is the resonance wavelength of the Fabry-Perot etalon, is the wavelength of the transmitted light when no voltage is applied (3 in FIG. 3).
07) to a shorter wavelength (308 in FIG. 3). The change in the refractive index of the minute liquid crystal droplet dispersed polymer is expressed by the following equation (1) (S. Matsumoto, M. Houl)
bert, T.Hayashi and K.Kubodera, ”Fine dropletsof LC
s in a transparent polymer and their response to a
n electric field, ”Appl.phys.Lett., vol.69 (8), pp.10
44, 1996, and S. Matsumoto et al; Organic Thin Fil
ms for Photonic Applications, Technical Digest, P90
(1997)).

[0016]

Δn = kE ² (E is in V / μm) (1) where k is a constant of proportionality, the size of the liquid crystal droplet,
It depends on the density of the liquid crystal droplet. k is usually 1 × 1
It is 0 ~ ⁵ ~2 × 10 ~ about ^4. The relationship between the change in the refractive index and the wavelength shift amount Δλ is represented by the following equation.

[0017]

[Number 2] Δλ = 1550 × Δn / n ( nm) ············ (2) For example, when k = 4 × 10 ~ ^5, small liquid crystal drops having a thickness of 20μm When a voltage of 600 V is applied to the let dispersion polymer layer, an electric field of 30 V / μm is applied, the refractive index change Δn is 0.036, and a wavelength tunability of 37 nm can be expected. However, this electric field is the dielectric breakdown limit, and the variable width can be expected to be about 15 nm at maximum when 400 V is applied. That is, the present invention provides a first layer composed of a transparent electrode and an optical mirror layer, a second layer composed of a material whose refractive index changes with an electric field, and a third layer composed of a transparent electrode and an optical mirror layer.
Is a Fabry-Perot etalon type wavelength tunable filter including a multilayer film formed by laminating layers in this order, wherein a material whose refractive index changes by an electric field has a diameter of 150 nm in a light transmitting medium such as a polymer or quartz glass. It is a material in which the following liquid crystal droplets are dispersed. In addition, the present invention provides a transparent layer having substantially the same refractive index as the second layer at the interface between the second layer and the first layer or the interface between the second layer and the third layer. It is characterized by including. Further, the present invention is characterized in that the liquid crystal droplet is a nematic liquid crystal droplet. Further, the present invention is characterized in that the polymer contains a plasticizer. Further, the present invention is characterized in that the polymer is a photocurable polymer. Further, the present invention is characterized in that the photocurable polymer is a polyenepolythiol-based polymer. Further, the present invention is characterized in that two or more tunable filters having different cavity gaps are stacked.

The present invention further comprises a prism mirror or a flat mirror provided on the other side of the tunable filter, wherein the light beam or the light beam array incident from one side of the tunable filter is After passing through the wavelength tunable filter, the light is reflected by the prism mirror or the plane mirror, is incident on the wavelength tunable filter, passes through the wavelength tunable filter again, and is emitted from one side of the wavelength tunable filter. Features. Further, the present invention further comprises two plane mirrors provided on both sides of the tunable filter so as to be displaced from each other, and a light beam or a light beam array obliquely incident from one side of the tunable filter. However, after passing through the wavelength tunable filter, the light is reflected by the first plane mirror and is incident on the wavelength tunable filter. After passing through the wavelength tunable filter again, the light is reflected by the second plane mirror and is reflected by the second plane mirror. The light is incident on the tunable filter, passes through the tunable filter again, and is emitted from the other side of the tunable filter. Further, the present invention includes a plane mirror installed on one side of the tunable filter, and a light beam or a light beam array obliquely incident from one or the other side of the tunable filter,
The multi-reflection proceeds between the plane mirror and the optical mirror layer of the liquid crystal wavelength tunable filter, and a light beam or a light beam array corresponding to the transmission wavelength of the wavelength tunable filter is interposed therebetween. The light is emitted from the other side.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments, components having the same functions are denoted by the same reference numerals, and repeated description thereof will be omitted.

[First Embodiment] A tunable filter according to a first embodiment of the present invention is a Fabry-Perot etalon type tunable filter having the same structure as that shown in FIG. 3 and is produced by the following method. First, a transparent electrode made of ITO (30 in FIG. 3) is formed on a substrate (305 in FIG. 3) such as quartz glass.
4) A substrate is prepared by laminating an optical mirror film (303 in FIG. 3) by vapor deposition. The optical mirror film is a dielectric multilayer mirror film having a reflectance of 97% for light having a wavelength of 1.5 μm, and the substrate surface polishing accuracy is desirably λ / 10 or less. On this substrate, a film of a mixture of a liquid ultraviolet curable prepolymer (for example, NOA81 manufactured by Norland) and a nematic liquid crystal (BL24 manufactured by Merck) is formed by spin coating. Here, the mixing ratio of the prepolymer and the nematic liquid crystal is 50 g of the liquid crystal with respect to 100 g of the resin, and the film thickness is about 20 μm. This is irradiated with a metal halide lamp to polymerize and cure the resin and form liquid crystal droplets in the resin. A Fabry-Perot etalon type tunable filter having the same structure as that shown in FIG.

FIG. 4 shows a transmission spectrum of a wavelength tunable filter according to the present embodiment when a laser beam of a 1.5 μm band having a wide bandwidth is incident on the substrate in a perpendicular direction. It was confirmed that this transmission spectrum did not change even if the polarization direction of the incident light was rotated. FSR of transmitted light is 37.4n
m and the half width was 0.6 nm. The transmission loss is 2.
It was 37 dB.

Next, a voltage was applied to the wavelength tunable filter of the present embodiment, and a change in the wavelength of transmitted light was observed. FIG. 5 is a graph showing the voltage dependence of the wavelength of light transmitted by the wavelength tunable filter of the present embodiment. As is apparent from FIG. 5, in the wavelength tunable filter of the present embodiment, 50
It can be seen that the applied light changes the wavelength of the transmitted light by 12.7 nm. Further, even if the polarization direction of the incident light was rotated, the amount of change in the wavelength of the transmitted light did not change at all. These results indicate that a Fabry-Perot etalon using a material in which liquid crystal droplets are dispersed as a cavity functions as a tunable filter having no polarization dependence. When a rectangular pulse of 400 V was applied to this filter and the response waveform of the filter was observed, the rise time and fall time were several tens to several hundreds μ.
sec and fast response.

[Second Embodiment] A tunable filter according to a second embodiment of the present invention is also a Fabry-Perot etalon type tunable filter having the same structure as that shown in FIG. 3, and is manufactured by the following method. FIG. 6 is a diagram for explaining a method of manufacturing the wavelength tunable filter according to the present embodiment. At the beginning,
As shown in FIG. 6A, a transparent electrode 602 made of ITO and an optical mirror film 6 are formed on a substrate 601 made of quartz glass or the like.
03 is prepared by vapor deposition. The optical mirror film 603 has a reflectance of 9 μm for light having a wavelength of 1.5 μm.
A dielectric multilayer mirror film of 7%;
Is preferably λ / 10 or less. On this substrate, a mixture of an ultraviolet-curable resin and a nematic liquid crystal is spin-coated with a spinner to form a film of a mixture of the ultraviolet-curable resin and the nematic liquid crystal having a thickness of about 20 μm. Here, the mixing ratio of the ultraviolet-curable resin and the nematic liquid crystal is 100 g of the resin and 50 g of the liquid crystal. Then, a uniform ultraviolet ray 606 is applied using a metal halide lamp.
To polymerize and cure the resin, and form liquid crystal droplets 604 in the resin (polymer) layer 605 to form fine liquid crystal droplet dispersed polymer layers. Next, as shown in FIG. 6B, the green portion of the substrate of the fine liquid crystal droplet dispersed polymer layer (6 in FIG. 6).
07 part).

Next, as shown in FIG. 6C, an adhesive 608 is applied to a part of the portion where the fine liquid crystal droplet dispersed polymer layer has been removed, and a pair of substrates is further placed thereon. Then, while observing interference fringes generated between the opposing optical mirror films 603 so that the optical mirror films 603 are parallel to each other, adhesion is performed so that the interference fringes are reduced. This paired substrate is a substrate in which a transparent electrode 602 made of ITO and an optical mirror film 603 are laminated on a substrate 601 made of quartz glass or the like by vapor deposition. At this time, depending on the case, a gap is formed between the upper substrate and the fine liquid crystal droplet dispersed polymer layer, and a portion 607 from which the fine liquid crystal droplet dispersed polymer is removed becomes a void. Therefore, as shown in FIG. 6D, an adhesive (or matching oil) having the same refractive index as the minute liquid crystal droplet dispersed polymer is provided in the gap between the minute liquid crystal droplet dispersed polymer layer and the surface of the optical mirror film 603. 609 is poured by capillary reduction. Finally, as shown in FIG. 6E, the periphery is sealed with a sealant 610. As described above, in the present embodiment, a transparent layer (adhesive or matching) having substantially the same refractive index as the minute liquid crystal droplet dispersed polymer is provided on one interface between the minute liquid crystal droplet dispersed polymer layer and the optical mirror film 603. Since the oil 609) is inserted, it is possible to prevent unnecessary light reflection and improve the characteristics.

[Third Embodiment] In the wavelength tunable filter of the first embodiment, that is, a Fabry-Perot etalon type tunable filter using a polymer in which nano-sized liquid crystal droplets are dispersed as a cavity material, a liquid crystal drop As the size of the droplet decreases, the voltage required to drive the liquid crystal droplet tends to increase. Therefore, in the wavelength tunable filter of the present embodiment,
By adding a substance (plasticizer) that has the effect of plasticizing plastic to the polymer that disperses the liquid crystal droplet, the liquid crystal droplet is driven at a low voltage, and the variable width of the wavelength tunable filter per voltage is increased. It was made. Examples of the plasticizer include dibutyl phthalate, di-n-octyl phthalate, di (2-ethylhexyl) phthalate, dinonyl flate, dilauryl phthalate, butyl benzyl phthalate, di (2-ethylhexyl) adipate, and di (2-ethylhexyl) sebacate. 2-ethylhexyl), tricresyl phosphate, tri (2-ethylhexyl) phosphate, polyethylene glycol esters, epoxy fatty acid esters and the like.

The tunable filter of the present embodiment is created by the following method. First, a transparent electrode (FIG. 3) made of ITO is formed on a substrate (305 in FIG. 3) such as quartz glass.
(304) and an optical mirror film (303 in FIG. 3) are prepared by vapor deposition. The optical mirror film is a dielectric multilayer mirror film having a reflectance of 97% for light having a wavelength of 1.5 μm, and the surface polishing accuracy of the substrate is λ / 1.
0 or less is desirable. On this substrate, a film of a mixture composed of a liquid ultraviolet-curable polyenepolythiol-based prepolymer (for example, NOA81 manufactured by Norland), a nematic liquid crystal (for example, BL24 manufactured by Merck), and a plasticizer is formed by spin coating. I do. This is irradiated with a metal halide lamp to polymerize and cure the resin,
A liquid crystal droplet is formed in the resin. A Fabry-Perot etalon type tunable filter having the same structure as that shown in FIG.

The wavelength tunable filter of the present embodiment was actually prepared, a voltage was applied to the prepared wavelength tunable filter, and the amount of wavelength shift of transmitted light was measured. FIG. 7 shows the measurement results. FIG. 7 is a graph showing the voltage dependence of the wavelength shift amount of light transmitted by the wavelength tunable filter of the present embodiment. In FIG. 7, the graph indicated by-●-is a wavelength tunable filter of the present embodiment to which di (2-ethylhexyl) adipate is added as a plasticizer, and the graph indicated by-□-is tricresyl phosphate as a plasticizer. The tunable filter of the present embodiment to which the additive is added, and the graph indicated by-▲-are the tunable filters without the addition of the plasticizer (the tunable filter of the first embodiment). Here, in the wavelength tunable filter of the present embodiment to which di (2-ethylhexyl) adipate is added as a plasticizer, the mixing ratio of the polyenepolythiol-based prepolymer and the nematic liquid crystal is such that the liquid crystal is 60 g per 100 g of the resin, The mixing ratio of the polyenepolythiol prepolymer and di (2-ethylhexyl) adipate is 100 g of the resin, 7 g of the liquid crystal, and the film thickness is about 20 μm. Similarly,
In the wavelength tunable filter of the present embodiment to which tricresyl phosphate is added as a plasticizer, the mixing ratio of the polyene polythiol-based prepolymer and the nematic liquid crystal is such that the liquid crystal 60 g per 100 g of the resin, the polyene polythiol-based prepolymer and the phosphorus The mixing ratio with tricresyl acid is 100 g of resin, 7 g of liquid crystal, and the film thickness is about 20 μm. In the wavelength tunable filter according to the first embodiment without the addition of a plasticizer, the mixing ratio of the polyene polythiol-based prepolymer and the nematic liquid crystal is 100 g of the resin, and 60 g of the liquid crystal.
The thickness is about 20 μm. As is apparent from FIG. 7, in the wavelength tunable filter of this embodiment to which a plasticizer such as di (2-ethylhexyl) adipate and tricresyl phosphate is added, the first embodiment in which no plasticizer is added is used. As compared with the wavelength tunable filter described above, a large wavelength shift amount can be obtained at a low voltage.

[Embodiment 4] FIG. 8 is a perspective view showing a configuration of a wavelength tunable filter according to another embodiment of the present invention. The tunable filter of the present embodiment is a tunable filter having an array configuration utilizing the fact that the tunable filter of the present invention is a planar device. In FIG.
Reference numeral 01 denotes a wavelength tunable filter having an array configuration, 702 and 703.
Is an optical collimator array to which the light beam array is input / output,
704 is an input side fiber array, and 705 is an output side fiber array. The wavelength tunable filter 701 having the array configuration according to the present embodiment includes a material whose refractive index changes due to an electric field between a pair of transparent substrates on which a transparent electrode and an optical mirror film are formed (the microscopic filter described in each of the above embodiments). Liquid crystal droplet dispersed polymer layer).

FIG. 9 is a diagram showing an example of a transparent electrode pattern formed on a pair of transparent substrates in the tunable filter 701 having the array configuration of the present embodiment. In the figure, reference numeral 801 denotes a pair of transparent substrates, 802 denotes a stripe-shaped transparent electrode, 803 denotes a square (hereinafter referred to as a square) transparent electrode arranged in a matrix, and 804 denotes an entire surface of the substrate. A transparent electrode 806 is a □ -shaped transparent electrode 803
Electrode 807 is a thin film resistor, 808
Is a thin film transistor for adjusting the voltage applied to each of the □ -shaped transparent electrodes 803. In the transparent electrode pattern shown in FIG. 9A, the striped transparent electrodes 802 are formed so as to be orthogonal to each other, and the striped transparent electrodes 802 intersect by driving the striped transparent electrodes 802 in a matrix. A voltage can be applied to each of the points independently. In the transparent electrode pattern shown in FIG. 9B, the extraction electrodes 806 are respectively drawn out from the respective □ -shaped transparent electrodes 803 to the end face of the substrate, and it is possible to apply a voltage to each □ -shaped transparent electrode 803 independently. it can.

In the transparent electrode pattern shown in FIG.
Each of the □ -shaped transparent electrodes 803 is connected in series by a thin film resistor 807, and when the voltage to be applied to the □ -shaped transparent electrode 803 at the front end and the □ -shaped transparent electrode 803 at the terminal end is determined, The voltage applied to the □ -shaped transparent electrode 803 is determined by the resistance value of each thin film resistor 807. FIG. 9D
In the transparent electrode pattern shown in FIG.
Are formed, and the thin film transistor 808 in the row (or column) direction is turned on, and in accordance with that, a voltage is applied to the source (or drain) of the thin film transistor 808 in the column (or row) direction. A voltage can be independently applied to the □ -shaped transparent electrode 803. In the transparent electrode pattern shown in FIG. 9E, a stripe-shaped transparent electrode 802 is formed on one transparent substrate 801, and a voltage can be applied independently to each stripe-shaped transparent electrode 802. FIG.
In the transparent electrode pattern shown in FIG.
01, a stripe-shaped transparent electrode 802 is formed, and the stripe-shaped transparent electrodes 802 are connected in series by a thin-film resistor 807. Therefore, the stripe-shaped transparent electrode 802 at the leading end and the stripe-shaped transparent electrode 802 at the terminal end are formed.
Is determined, the voltage applied to each stripe-shaped transparent electrode 802 is determined by the resistance value of each thin-film resistor 807.

FIG. 10 is a perspective view showing a schematic configuration of an example of the optical collimator array (702, 703) of the present embodiment. FIG. 10A shows a one-dimensional optical collimator array, 901 is a fiber array, 902 is a V-groove substrate having V-groove arrays formed at equal intervals, 903 is a microlens array, and 904 is an output light beam array. It is.
In this optical collimator array, optical fibers are arranged in a V-groove in a V-groove substrate 902,
Is attached to the tip to form a collimator array.
FIG. 10B shows a two-dimensional optical collimator array, 901 is a fiber array, 903 is a microlens array, 904 is an output light beam array, 905 is a frame for containing a microferrule, 906 is a microferrule, 907 Is an optical fiber. In this optical collimator array, an optical fiber 90
7 are inserted, the microferrules 906 are arranged two-dimensionally, and a planar microlens array 903 is attached to form a two-dimensional collimator array. in this way,
In the present embodiment, one wavelength tunable filter can be arrayed, and the cost per channel can be significantly reduced. Conventional liquid crystal tunable filters are polarization dependent and have a slow response speed, and lack practicality, whereas liquid crystal tunable filters using fine liquid crystal droplet dispersed polymers are polarization independent and have a fast response. It has excellent features such as

[Embodiment 5] FIG. 11 is a cross-sectional view of a principal part showing a configuration of a wavelength tunable filter according to another embodiment of the present invention. In the figure, reference numeral 1001 denotes a nematic liquid crystal droplet having a particle size of 150 nm or less;
Is a polymer layer, 1003 is an optical mirror (dielectric mirror)
Film, 1004 is a transparent electrode, 1005 is a transparent glass substrate,
Reference numeral 1006 denotes an AR coat film (anti-reflection coat film). The wavelength tunable filters described in the above embodiments have the disadvantage that the tunable width is as small as about 10 nm and the driving voltage is as high as 500 V as it is. The tunable filter according to the present embodiment improves the above-described disadvantage. As shown in FIG. 11A, the tunable filter of the present embodiment is obtained by superposing two tunable filters, that is, a first tunable filter 1020 and a second tunable filter 1021. is there. The cavity gaps of the two tunable filters (1020, 1021) are slightly different. FIG. 11B shows one spectrum of each of the stacked tunable filters and one spectrum of the stacked filters. 1007 shows one transmission spectrum of the first wavelength tunable filter 1020, 1008 shows one transmission spectrum of the second wavelength tunable filter 1021, and , 1009 show one transmission spectrum passing through two filters. As is apparent from FIG. 11, when the two transmission spectra overlap, the transmission spectrum of the output becomes sharp, crosstalk can be reduced, and the tip of the peak becomes flat. With this effect, as the number of tunable filters increases, the spectrum becomes steeper, and crosstalk can be reduced. Further, as compared with a single filter having the same half width, there is an advantage that the front end of the spectrum is flat and the tolerance for wavelength selection is increased.

FIG. 11C shows two liquid crystal tunable filters (1020, 1020) having slightly different cavity gaps.
21) One of the wavelength tunable filters obtained by laminating two liquid crystal wavelength tunable filters each having a plurality of transmission spectra, a tunable state thereof, and a slightly different cavity gap.
7 shows how the wavelength of a transmission spectrum of a book is variable. 1
Reference numeral 011 denotes a transmission spectrum group appearing at equal intervals of the first tunable filter 1020.
Reference numeral 012 denotes a group of transmission spectra appearing at equal intervals of the second wavelength tunable filter 1021.
Reference numeral 1013 denotes one transmission spectrum when two wavelength tunable filters are superimposed. In the Fabry-Perot etalon filter, transmission wavelength peaks appear at equal intervals, as shown in the upper two parts of FIG. The larger the cavity gap, the narrower the peak interval (FSR). Therefore, the two wavelength tunable filters (1020, 1021) having different cavity gaps have different peak intervals (FSR).

Two tunable filters (1020, 1020)
If one of the peaks in 21) is adjusted to the same wavelength, the other transmission peaks do not match.
Only book transmission peaks appear. In the first wavelength band, if the two transmission wavelength peaks are matched and varied, the transmission wavelength peak can be varied over the entire first wavelength band. Next, when the same operation is performed in the second wavelength band, the entire wavelength range of the second wavelength band can be changed. Similarly, it can be varied in the third and fourth wavelength bands. Each tunable filter has at most one
Although only 0 nm can be changed, by stacking two tunable filters with slightly different cavity gaps,
The apparent wavelength range of several tens of nm can be varied. In this embodiment, an example is shown in which two tunable filters (1020, 1021) having different cavity gaps are stacked, but the same effect can be obtained with three or more filters. As described above, in the present embodiment, by stacking a large number of tunable filters, it is possible to sharpen the spectrum to reduce crosstalk and to flatten the front end of the spectrum. Further, by controlling the combination of the transmission wavelengths of the respective filters, the wavelength variable width can be greatly increased.

[Embodiment 6] FIG. 12 is an exploded perspective view showing a configuration of a wavelength tunable filter according to another embodiment of the present invention. The tunable filter of the present embodiment is different from the fiber array collimator of the fourth embodiment in that
In the figure, a core-expanded (TEC) fiber is used for the input / output unit.
02 is a transparent electrode, 1103 is an optical mirror (dielectric mirror) film, 1105 is a minute liquid crystal droplet dispersed polymer layer, 1106 is an SC connector sleeve, 1107
Is an input optical fiber, 1108 is an output optical fiber, 1
109 is an extraction electrode, 1110 is a ferrule, 111
Reference numeral 1 denotes a metal portion at the rear of the ferrule 1110, and 1112 denotes a hole formed in the sleeve 1106 to fill a minute liquid crystal droplet dispersed polymer. This transparent electrode 11
02 covers the entire ferrule 1110 and is connected to the metal part 1111. When the core-enlarged fibers are opposed to each other with a gap, the gap may be several tens μm to 100 μm.
In the case of about μm, with very low coupling loss,
It is possible to couple light between optical fibers by propagating light to free space without a lens. Utilizing this characteristic, the TEC fiber and the SC connector sleeve 11
06 can be used to realize an ultra-small tunable filter.

The tunable filter according to the present embodiment is prepared as follows. First, the TEC fiber (11
07, 1108) is inserted into the ferrule 1110 and the tip is polished. Next, the ferrule 1110 is set in the sputtering apparatus.
A transparent electrode 1102 made of ITO is formed so as to cover the whole and the metal part 1111 at the rear of the ferrule 1110. Next, an optical mirror film 1103 is provided on the tip of the ferrule 1110 and the TEC fiber (1107, 1108).
Coat. Next, the sleeve 1106 of the SC connector is used.
The ferrules 1110 of the input side optical fiber 1107 and the output side optical fiber 1108 are inserted from both sides, and the gap is adjusted so that the gap is several μm to several tens μm in parallel. Next, a mixture of liquid crystal and ultraviolet curable resin is inserted into the liquid crystal insertion hole 1112 on the SC connector sleeve 1106, and the resin is cured by ultraviolet irradiation and the liquid crystal droplets are dispersed. Further, an extraction electrode 1109 is attached to the metal portion 1111 at the rear of the ferrule 1110. As described above, in the present embodiment, a polarization-independent, high-speed modulation variable filter having a simple structure can be easily and inexpensively manufactured using the core-expanded fiber and the SC connector.

[Seventh Embodiment] A tunable filter according to another embodiment of the present invention is a tunable filter having an array configuration using a fiber array composed of TEC fibers. FIG. 13 is a diagram for explaining a method of manufacturing the tunable filter having the array configuration according to the present embodiment. Hereinafter, a method for manufacturing the wavelength tunable filter according to the present embodiment will be described with reference to FIG. First, as shown in FIG. 13A, a TEC fiber 1201 is prepared, cut at the enlarged core portion, and its end surface is polished. Next, by the sputtering method, the tip of the core-enlarged fiber and several cm from it
Transparent electrode 12 made of ITO so as to cover the portion
02 is formed. Further, an optical mirror (dielectric mirror) film 1203 is formed on the tip of the TEC fiber 1201. Next, as shown in FIG. 13B, a V-groove substrate 1204 having V-groove arrays formed at equal intervals is prepared.
The V-groove of the V-groove substrate 1204 has TEC fiber 1201
Are arranged such that the TEC fiber 1201 and the end face of the V-groove substrate 1204 are on the same plane, and are bonded and fixed with an adhesive. Next, as shown in FIG.
Four fiber arrays in which the TEC fibers 1201 are arranged and fixed in the V groove of No. 4 are prepared, and the two fiber arrays are opposed to each other with a spacer 1205 interposed therebetween. Adjust so that it is parallel and fix. The gap is 20 to 30μ
m. Next, as shown in FIG. 13D, a mixture of an ultraviolet curable resin and a nematic liquid crystal is poured into a gap formed by the spacer 1205, and is irradiated with ultraviolet light to be solidified, and a minute liquid crystal drop is formed. A let dispersed polymer layer 1206 is formed. Further, an extraction electrode 1207 is attached to the side surface of the TEC fiber 1201. As described above, in the present embodiment, the structure is simple using the fiber array constituted by the core expanded fibers,
A polarization-independent, high-speed modulation variable filter having an array configuration can be manufactured easily and at low cost.

[Eighth Embodiment] FIG. 14 is a cross-sectional view of a principal part showing a configuration of a wavelength tunable filter according to another embodiment of the present invention. The wavelength tunable filter of the present embodiment combines one wavelength tunable filter and a mirror film to achieve sharpening of the spectrum, reduction of crosstalk, and flattening of the peak end, similarly to the fifth embodiment. It is intended. In the figure, reference numeral 1301 denotes a wavelength tunable filter including a fine liquid crystal droplet dispersed polymer layer having a liquid crystal droplet of 150 nm or less, 1302 denotes a prism mirror, 1303 denotes an input collimate fiber, 13
Reference numeral 04 denotes an output side collimating fiber, and reference numeral 1305 denotes a plane mirror. FIG. 14A shows a case where a prism mirror 1304 is used, and FIG. 14B shows a case where a plane mirror 1305 is used. The light beams incident on both are reflected by mirrors (1304, 1305) and
It has the same effect as stacking multiple sheets. However, in FIG. 14B, since the light beam is obliquely incident on the wavelength tunable filter 1301, the polarization dependence is slightly (less than 0.1 dB).
However, this is not a serious problem. In addition, since the angle of refraction changes due to the change in the refractive index of the liquid crystal droplet dispersed polymer layer due to oblique incidence, the position of the output beam shifts. However, the beam diameter is 200 μm for the thickness of the tunable filter of about 5 mm. There is a margin of about 2 degrees for the angle, and in FIG. 14B, the incident angle is set between 88 degrees and 89 degrees, so that the beam position shift hardly causes a problem.

FIG. 14C shows a plane mirror 1305 whose two positions are slightly shifted from each other, sandwiching the wavelength tunable filter 1301 and causing the light beam to be slightly inclined and
1 is a plane mirror 1 in which the positions of the two mirrors are slightly shifted
The wavelength tunable filter 13 is reflected twice by 305 and is totally three times.
01. As a result, three wavelength tunable filters 1 are
There is an effect that a filter is superimposed on 301. Although only one collimating fiber is shown here, the same effect can be obtained by forming an array using a filter array and a collimating fiber array. As described above, in the present embodiment, by using the plane mirror and the prism mirror, the number of times that the incident light passes through the wavelength tunable filter is set to two or more times.
It is possible to sharpen the spectrum to reduce crosstalk and to flatten the front end of the spectrum.

[Embodiment 9] FIG. 15 is a cross-sectional view of a principal part showing the configuration of a wavelength tunable filter according to another embodiment of the present invention. This embodiment uses a wavelength tunable filter including a fine liquid crystal droplet dispersed polymer layer,
A variable multiplexer / demultiplexer was created. Referring to FIG. 14, reference numeral 1401 denotes a wavelength tunable filter including an arrayed minute liquid crystal droplet dispersed polymer layer;
Denotes an input side collimating fiber, 1403 denotes an output side collimating fiber array, and 1404 denotes a wavelength tunable filter 14.
Reference numeral 1405 denotes a light beam which has passed through 01, and a plane mirror. In the present embodiment, a light beam is incident on the tunable filter 1401 having an array configuration slightly obliquely from the input side collimating fiber 1402. Tunable filter 140
The light having the wavelength matching the transmission peak of No. 1 passes through the wavelength tunable filter 1401 and enters the output side collimating fiber array 1403.

The light that does not coincide is reflected by the wavelength tunable filter 1401, further reflected by the plane mirror 1405 again, and enters the wavelength tunable filter 1401. Similarly, only light having a wavelength that matches the wavelength of the second tunable filter 1401 passes and the rest is reflected. The same is repeated. In this way, the incident light is split into the collimating fiber array 1403 on the output side. Since a voltage can be independently applied to each electrode of the wavelength tunable filter 1401 having an array configuration including a fine liquid crystal droplet dispersed polymer layer, the wavelength of the multiplexer / demultiplexer can be variably set. In this embodiment, the collimated fiber is used on the incident side. However, the same effect can be obtained by using a collimated fiber array.

[Embodiment 10] FIG. 16 is a cross-sectional view showing a main part of a schematic configuration of a wavelength tunable filter according to another embodiment of the present invention. In the figure, 1501 is a thin film resistor, 1502 is a current source, 1503 is a heater, 1504 is a liquid crystal droplet, 1505 is a polymer layer, 1506 is an optical mirror film, 1507 is a transparent electrode, and 1508 is a substrate. In each of the above embodiments, the transmission wavelength is changed by applying a high voltage between the transparent electrodes. However, a voltage as high as several hundred volts is required as the high voltage. The wavelength tunable filter according to the present embodiment varies the transmission wavelength by changing the temperature. The tunable filter shown in FIG.
By passing a current through one or both of the transparent electrodes 1507 of the wavelength tunable filter having a fine liquid crystal droplet dispersed polymer layer having a normal structure, the temperature of the fine liquid crystal droplet dispersed polymer layer is increased. The transmission wavelength is changed by changing the refractive index of the liquid crystal droplet dispersed polymer layer. The wavelength tunable filter shown in FIG. 16 (b) is a wavelength tunable filter having a fine liquid crystal droplet dispersed polymer layer having a normal structure. By passing a current through the resistor 1501, the temperature of the fine liquid crystal droplet dispersed polymer layer is raised, thereby changing the refractive index of the fine liquid crystal droplet dispersed polymer layer to change the transmission wavelength. It is. In the wavelength tunable filter shown in FIG. 16C, a heater 1503 is attached outside a wavelength tunable filter having a fine liquid crystal droplet dispersed polymer layer having no transparent electrode.
By passing an electric current through 503, the temperature of the fine liquid crystal droplet dispersed polymer layer is raised, whereby the refractive index of the fine liquid crystal droplet dispersed polymer layer is changed to change the transmission wavelength. is there. As described above, the invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and can be variously modified without departing from the gist of the invention. Of course, it is.

[0043]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows. (1) According to the present invention, by using a material in which liquid crystal droplets are dispersed in a light-transmitting medium as a cavity, there is no polarization dependence, a high response speed, and high-speed tuning is possible. (2) According to the present invention, since a plasticizer is added to the polymer in which the liquid crystal droplet is dispersed, the liquid crystal droplet can be driven at a low voltage, and the variable width of the wavelength variable filter per voltage can be increased. Can be. (3) According to the present invention, it is possible to achieve a higher density and a smaller size by combining with an arrayed optical fiber and the like while being less expensive than the conventional tunable filter. (4) According to the present invention, the spectrum is improved by laminating a large number of tunable filters or by using a plane mirror or a prism mirror, and the tunable range is extended to the entire wavelength range. It becomes possible. (5) According to the present invention, it is possible to easily configure a multiplexer / demultiplexer by using a plane mirror. (6) According to the present invention, it is possible to construct a high-speed RAN wavelength division multiplexing transmission system.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a basic structure of a tunable filter of the present invention.

FIG. 2 is a diagram for explaining the structure and operating principle of a medium in which the refractive index changes by applying a voltage according to the present invention.

FIG. 3 is a diagram for explaining the structure and operation principle of the wavelength tunable filter of the present invention.

FIG. 4 is a graph showing a transmission spectrum of the tunable filter according to the first embodiment of the present invention.

FIG. 5 is a graph showing the voltage dependence of the wavelength of light transmitted by the wavelength tunable filter according to the first embodiment.

FIG. 6 is a diagram for explaining a method of manufacturing the wavelength tunable filter according to the second embodiment of the present invention.

FIG. 7 is a graph showing a voltage dependence of a wavelength shift amount of transmitted light in an example of the wavelength tunable filter according to the third embodiment of the present invention.

FIG. 8 is a perspective view illustrating a configuration of a wavelength tunable filter according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing an example of a transparent electrode pattern formed on a pair of transparent substrates in the tunable filter having an array configuration according to the fourth embodiment.

FIG. 10 is a perspective view illustrating a schematic configuration of an example of an optical collimator array according to a fourth embodiment.

FIG. 11 is a sectional view of a main part showing a configuration of a wavelength tunable filter according to a fifth embodiment of the present invention.

FIG. 12 is an exploded perspective view illustrating a configuration of a tunable filter according to a sixth embodiment of the present invention.

FIG. 13 is a diagram for explaining a method of manufacturing a wavelength tunable filter having an array configuration according to the seventh embodiment of the present invention.

FIG. 14 is a fragmentary cross-sectional view showing a configuration of a wavelength tunable filter according to an eighth embodiment of the present invention.

FIG. 15 is a fragmentary cross-sectional view showing a configuration of a tunable filter according to Embodiment 9 of the present invention.

FIG. 16 is a fragmentary cross-sectional view showing a schematic configuration of a tunable filter according to a tenth embodiment of the present invention.

[Explanation of symbols]

101: second layer, 102: first layer, 103: third layer, 104, 303, 603, 1003, 1103, 1
203, 1506: Optical mirror (dielectric mirror) film, 1
05,203,304,602,802,803,80
4,1004,1102,1202,1507 ... transparent electrode, 106,305,601,801,1005,15
08: substrate, 107, 1006: AR coat film (anti-reflection coat film), 201, 301, 604, 1001, 15
04: Liquid crystal droplet, 202, 302, 605
1002, 1505: polymer layer for confining liquid crystal droplets, 204: drive power supply, 606: ultraviolet light, 607
… The part where the minute liquid crystal droplet dispersed polymer layer is removed, 608… adhesive, 609… matching oil,
610: Sealant, 701, 1020, 1021, 130
1,1401 wavelength variable filter, 702, 703 optical collimator array, 704, 705, 901 fiber array, 806 extraction electrode, 807 thin film resistor, 8
08: thin film transistor, 902, 1204: V-groove substrate, 903: micro lens array, 904: light beam array, 905: frame for containing micro ferrule, 90
6. Micro ferrule, 907, 1107, 1108
... optical fiber, 1101 ... core of optical fiber, 110
5, 1206: Fine liquid crystal droplet dispersed polymer layer, 1106: SC connector sleeve, 1109, 1
207: extraction electrode, 1110: ferrule, 111
DESCRIPTION OF SYMBOLS 1 ... Metal part at the rear part of ferrule 1110, 1112 ... Hole made in sleeve 1106, 1201 ... TEC fiber, 1205 ... Spacer, 1302 ... Prism mirror
1303, 1304, 1402: Collimated fiber, 1305, 1405: Planar mirror, 1403: Collimated fiber array, 1501: Thin film resistor, 150
2 ... current source, 1503 ... heater.

Continuing on the front page (72) Takayoshi Hayashi Inventor, Nippon Telegraph and Telephone 3-2-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo (72) Inventor Katsuhiko Hirabayashi 3- 19-2, Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph Telephone Co., Ltd.

Claims (15)

[Claims] A first electrode comprising a transparent electrode and an optical mirror layer;
And a second layer made of a material whose refractive index is changed by an electric field.
Is a Fabry-Perot etalon type wavelength tunable filter including a multilayer film in which a third layer composed of a transparent electrode and an optical mirror layer is laminated in this order, and a material whose refractive index is changed by an electric field is A wavelength tunable filter comprising a material in which liquid crystal droplets having a diameter of 150 nm or less are dispersed in a light transmitting medium such as a polymer or quartz glass. 2. A transparent layer substantially equal to the refractive index of the second layer is provided at the interface between the second layer and the first layer or at the interface between the second layer and the third layer. 2. The tunable filter according to claim 1, wherein: 3. The tunable filter according to claim 1, wherein the liquid crystal droplet is a nematic liquid crystal droplet. 4. The tunable filter according to claim 1, wherein the polymer contains a plasticizer. 5. The tunable filter according to claim 1, wherein the polymer is a photocurable polymer. 6. The tunable filter according to claim 5, wherein the photocurable polymer is a polyenepolythiol-based polymer. 7. The tunable filter according to claim 1, wherein at least one of the transparent electrodes is patterned in a stripe shape or a dot shape. 8. The tunable filter according to claim 1, wherein two or more tunable filters having different cavity gaps are laminated. 9. A tunable filter comprising the tunable filter according to claim 1 sandwiched between a core-expanded fiber or a core-expanded fiber array. 10. A tunable filter provided with a prism mirror or a flat mirror provided on the other side of the tunable filter, wherein a light beam or a light beam array incident from one side of the tunable filter is used to control the tunable filter. After passing through, the light is reflected by the prism mirror or the plane mirror, is incident on the tunable filter, passes through the tunable filter again, and is emitted from one side of the tunable filter. The tunable filter according to any one of claims 1 to 7. 11. A tunable filter comprising: two planar mirrors disposed on both sides of the tunable filter so as to be displaced from each other, wherein a light beam or a light beam array obliquely incident from one side of the tunable filter is provided. After passing through the wavelength tunable filter, is reflected by the first plane mirror and is incident on the wavelength tunable filter. After passing through the wavelength tunable filter again, the light is reflected by the second plane mirror and is reflected by the second plane mirror. 8. The tunable filter according to claim 1, wherein the light enters the tunable filter, passes through the tunable filter again, and is emitted from the other side of the tunable filter.
The wavelength tunable filter according to any one of the above. 12. A flat mirror provided on one side of the wavelength tunable filter, wherein a light beam or a light beam array obliquely incident from one or the other side of the wavelength tunable filter is connected to the flat mirror. Travels through multiple reflection between the optical mirror layer of the liquid crystal wavelength tunable filter and a light beam or a light beam array corresponding to the transmission wavelength of the wavelength tunable filter during the other side. The tunable filter according to any one of claims 1 to 7, wherein the tunable filter is emitted from a light source. 13. An input collimating fiber or a collimating fiber array that emits the light beam or the light beam array to the tunable filter, and an output collimator that receives the light beam or the light beam array from the tunable filter. The tunable filter according to any one of claims 10 to 12, further comprising a fiber or a collimated fiber array. 14. The tunable filter according to claim 1, further comprising a current supply unit for supplying a current for heating the second layer to the transparent electrode. . 15. A heating device for heating the second layer, in place of the transparent electrode.
A tunable filter according to any one of claims 13 to 13.