JP2004326010A - Thermo-optic phase modulator and thermo-optic intensity modulator - Google Patents

Abstract

A thermo-optic phase modulator capable of changing the phase of light by a small temperature change and a thermo-optic intensity modulator using the thermo-optic phase modulator.
A thermo-optic phase modulator that changes the phase of light propagating through the core by changing the temperature of the core of the optical waveguide, wherein the core is dS ₁₅₅₀ / dT ₋₅ defined by the following equation. _-65 consists of glass which is 3.0 * 10 < ^-5 > / _degreeC or more, The _thermooptic phase modulator characterized by the above-mentioned, and the thermooptic intensity modulator using the same.
dS ₁₅₅₀ / dT _{−5 to 65} = dn ₁₅₅₀ / dT _{−5 to 65} + n ₁₅₅₀ · α _{−5 to 65}
In the above formula, n ₁₅₅₀ represents a refractive index at 25 ° C. with respect to light having a wavelength of 1550 nm. dn ₁₅₅₀ / dT _{−5 to 65} represents an average temperature change rate at −5 to 65 ° C. of the refractive index with respect to light having a wavelength of 1550 nm. α ₋₅ to 65 indicates an average linear expansion coefficient at −5 to 65 ° C.
[Selection figure] None

Description

【００２３】
本発明のｄＳ_１５５０／ｄＴ_{−５〜６５}が３．０×１０^−５／℃以上のガラスは、ΔＴ_１５５０が各段に小さく、小さい消費電力で、速い応答速度で熱光化学位相変調が可能であり、熱光学強度変調器、光熱スイッチ等に応用可能な熱光学位相変調器を提供できることがわかる。
【発明の効果】
本発明の熱光学位相変調器により小さな温度差で光の位相を変化させることが可能であり、本発明の熱光学位相変調器を用いて、消費電力が小さく、応答速度が速い、熱光学強度変調器、光熱スイッチ等を提供することができる。
【図面の簡単な説明】
【図１】熱光学位相変調器である。
【図２】熱光学強度変調器である。
【符号の説明】
１ 光導波路のコア
２ 光導波路のクラッド
３ ヒーター
４ 光導波路アーム
５ ヒーター
６ 方向性結合器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical component used in equipment for optical communication and optical information processing, and more particularly to a thermo-optic phase modulator applicable to a thermo-optic intensity modulator and a thermo-optic switch.
[0002]
[Prior art]
In recent years, research and development related to the enhancement of functionality, miniaturization, and cost reduction of optical functional devices have been actively conducted toward the opticalization of communication networks. In a wavelength division multiplexing (WDM) transmission system that is currently being introduced, an optical cross-connect system and an optical add / drop multiplexing system are being developed. These systems require an optical path switching function in addition to the optical demultiplexing function. At present, such a switching function is performed by converting light into electricity. However, in order to realize a network that takes advantage of the high-speed and broadband characteristics of optical communication, it is necessary to switch light spatially as it is. Such devices include thermo-optic intensity modulators and thermo-optic switches that combine the thermo-optic effect with a Mach-Zehnder interferometer structure. Currently, the proposed thermo-optic switch is a thermo-optic switch using a silica-based glass waveguide, and non-patent documents 1 and 2 report matrix optical switches of 8 × 8 or 16 × 16 scale. .
[0003]
The most basic circuit of the thermo-optic switch is a 2 × 2 switch. The phase difference Δφ between the two waveguide arms can be expressed by the following expression using the length L, the optical path length change dS / dT per unit length, the temperature difference ΔT between the waveguide arms, and the light wavelength λ.
Δφ = 2π · L · dS / dT · ΔT / λ
Further, dS / dT is expressed by the following equation by the thermal expansion coefficient α, the refractive index n, and the refractive index temperature change dn / dT.
dS / dT = dn / dT + n · α
Therefore, in the case of a thermo-optic switch using a silica-based glass waveguide, L = 5 mm, dn / dT = 9 × 10 ⁻⁶ / ° C., n = 1.44, α = 4.3 × 10 ⁻⁷ / ° C., When λ = 1550 nm, about 15 ° C. is required for switching.
Such (M × N) thermo-optic switches can be combined to form an M × N matrix switch. However, when a large-scale matrix switch, for example, a 16 × 16 matrix switch is configured, 256 switches are used. Therefore, an increase in power consumption is a serious problem, and a more power-saving optical switch, that is, a thermo-optical switch capable of switching with a smaller temperature difference is desired.
In the case of a thermo-optic switch using a silica glass waveguide, the response speed is very slow, about 1 to 3 ms. In view of increasing the response speed, a thermo-optic switch that can be switched with a small temperature difference has been desired.
That is, a thermo-optic phase modulator that enables these thermo-optic switches to change the phase of light with a smaller temperature difference has been desired.
[0004]
[Non-Patent Document 1]
Journal of Lightwave Technology (IEEE Photonics Technology Letters), 1999, Vol. 17, No. 7, p. 1192-1199
[Non-Patent Document 2]
IEE Photonics Technology Letters, 1998, Vol. 10, No. 6, p. 810-812
[0005]
[Problems to be solved by the invention]
A thermo-optic phase modulator capable of changing the phase of light by a small temperature change and a thermo-optic intensity modulator using the thermo-optic phase modulator.
[0006]
[Means for Solving the Problems]
(1) A thermo-optic phase modulator that changes the phase of light propagating through the core by changing the temperature of the core of the optical waveguide,
The thermo-optic phase modulator, wherein the core is made of an oxide glass in which dS ₁₅₅₀ / dT ^{−5 to} ₆₅ defined by the following formula is 3.0 × 10 ⁻⁵ / ° C. or more.
dS ₁₅₅₀ / dT _{−5 to 65} = dn ₁₅₅₀ / dT _{−5 to 65} + n ₁₅₅₀ · α _{−5 to 65}
In the above formula, n ₁₅₅₀ represents a refractive index at 25 ° C. with respect to light having a wavelength of 1550 nm. dn ₁₅₅₀ / dT _{−5 to 65} represents an average temperature change rate at −5 to 65 ° C. of the refractive index with respect to light having a wavelength of 1550 nm. α ₋₅ to 65 indicates an average linear expansion coefficient at −5 to 65 ° C.
(2) A thermo-optic intensity modulator having the thermo-optic phase modulator of (1) above.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The thermo-optic phase modulator of the present invention has a refractive index n _{1550 at} 25 ° C. (hereinafter referred to as n ₁₅₅₀ ) for light having a wavelength of 1550 nm and an average temperature change rate dn at −5 to 65 ° C. of the refractive index for light having a wavelength of 1550 nm. ₁₅₅₀ / dT _{−5 to 65} (hereinafter referred to as dn ₁₅₅₀ / dT _{−5 to 65} ) and an average linear expansion coefficient α _{−5 to 65} (hereinafter referred to as α _{−5 to 65} ) at −5 to 65 ° C. DS ₁₅₅₀ / dT _{−5 to 65} (hereinafter referred to as “dS ₁₅₅₀ / dT ^{−5 to} ₆₅ ”) represented by the following formula is 3.0 × 10 ⁻⁵ / ° C. or higher (hereinafter referred to as the present invention). It has an optical waveguide having a core made of glass.
dS ₁₅₅₀ / dT _{−5 to 65} = dn ₁₅₅₀ / dT _{−5 to 65} + n ₁₅₅₀ · α _{−5 to 65}
The optical waveguide is a medium for propagating light, and an optical fiber, a planar optical waveguide formed on or inside the substrate is exemplified, and the shape is not limited.
[0008]
In the glass of the present invention, dS ₁₅₅₀ / dT ^{−5 to} ₆₅ is 3.0 × 10 ⁻⁵ / ° C. or more, and the change due to temperature change of the optical path length with respect to light having a wavelength of 400 to 1800 nm is large. dS ₁₅₅₀ / dT _{−5 to 65} is preferably 3.2 × 10 ⁻⁵ / ° C. or more, more preferably 3.5 × 10 ⁻⁵ / ° C. or more, and particularly preferably 4.0 × 10 ⁻⁵ / ° C. or more. It is.
In the glass of the present invention, α-5 to ₆₅ is preferably 170 × 10 ⁻⁷ / ° C. or less. If it _exceeds 170 × 10 ⁻⁷ / ° C., dn ₁₅₅₀ / dT ₋₅ to ₆₅ becomes small, and as a result, high dS ₁₅₅₀ / dT ₋₅ to ₆₅ becomes difficult to obtain. More preferably alpha _-5～65 is 150 × ^{10 -7} / ℃ less, particularly preferably 130 × 10 ^- is ⁷ / ° C. or less. Moreover, it is preferable that (alpha) _-5-65 is 30 * 10 < ^-7 > / _degreeC or more. If it is less than 30 × ^{10 -7} / ℃, which may result _dS 1550 _{/ dT -5~65} decreases as. More preferably, it is 50 × 10 ⁻⁷ / ° C. or more.
In the glass of the present invention, dn ₁₅₅₀ / dT ^{−5 to} ₆₅ is preferably 1.0 × 10 ⁻⁵ / ° C. or higher. If it is less than 1.0 * 10 < ^-5 > / degreeC, the change by the temperature change of the optical path length with respect to the light whose wavelength is 400-1800 nm will become small. More preferably, it is 1.3 × 10 ⁻⁵ / ° C. or more, further preferably 1.5 × 10 ⁻⁵ / ° C. or more, and particularly preferably 1.8 × 10 ⁻⁵ / ° C. or more.
N ₁₅₅₀ of the glass of the present invention is preferably 1.7 or more. If it is less than 1.7, dS ₁₅₅₀ / dT ₋₅ to ₆₅ may be small. More preferably, it is 1.8 or more, More preferably, it is 1.9 or more, Most preferably, it is 2.0 or more.
In the glass of the present invention, α ₋₅ to ₆₅ is _preferably 50 × 10 ⁻⁷ / ° C. or higher, and dn ₁₅₅₀ / dT ^{−5 to} ₆₅ is preferably 1.5 × 10 ⁻⁵ / ° C. or higher.
[0009]
The glass of the present invention preferably contains Bi ₂ O ₃ .
The content of Bi ₂ O ₃ is preferably 10 mol% or more, more preferably 20 mol% or more, particularly preferably 35 mol% or more, and most preferably 40 mol% or more in terms of mol% based on oxide. . Moreover, from the point of favorable vitrification and transparency, it is preferable that it is 80 mol% or less, It is more preferable that it is 75 mol% or less, It is especially preferable that it is 70 mol or less.
[0010]
Moreover, as a component which the glass of this invention may contain,
Examples include Ga ₂ O ₃ , Al ₂ O ₃ , B ₂ O ₃ , SiO ₂ , In ₂ O ₃ , BaO, ZnO, GeO ₂ , WO ₃ and TeO ₂ . The content of these components is preferably 30 mol% or less.
_{Also, TiO 2, ZrO 2, SnO} 2, Li 2 O, Na 2 O, K 2 O, may contain Rb ₂ O and Cs ₂ O, are each 10 mol% or less for these components preferably.
[0011]
Further, BeO, MgO, CaO, SrO, Y ₂ O ₃ , La ₂ O ₃ , CdO and PbO may be contained, but these components are preferably 10 mol% or less in total.
[0012]
The glass of the present invention preferably has the following composition on an oxide basis.
Bi ₂ O _3: 30~75 mol%
SiO ₂ + B ₂ O ₃ : 10 to 60 mol%
_{Al 2 O 3 + Ga 2 O} 3 + In 2 O 3: 5~25 mol%
ZnO + BaO: 0 to 20 mol%
_{Li 2 O + Na 2 O +} K 2 O: 0~15 mol%
CeO ₂ : 0 to 3 mol%
In addition, you may contain components other than these components in the range which does not impair the objective of this invention. For example, “ZnO + BaO: 0 to 20 mol%” means that ZnO and BaO are not essential, but may be contained up to 20 mol% in total.
[0013]
(Glass production method)
The method for producing the glass of the present invention is not particularly limited, and a predetermined raw material is mixed and placed in a platinum crucible, an alumina crucible, a quartz crucible or an iridium crucible, for example, melted in air at 800 to 1300 ° C. It can produce by casting the obtained melt into a predetermined mold. Moreover, you may produce by methods other than melting methods, such as a sol-gel method and a vapor deposition method.
[0014]
(Calculation method of dS ₁₅₅₀ / dT _{-5 to 65} )
n ₁₅₅₀ , dn ₁₅₅₀ / dT _{−5 to 65} and α ₋₅ to ₆₅ are measured, for example, as follows to calculate dS ₁₅₅₀ / dT ₋₅ to ₆₅ .
n ₁₅₅₀ and dn ₁₅₅₀ / dT _{−5 to 65} : Each glass is processed to prepare a regular triangular prism having a thickness of 10 mm and a side of 20 mm. A precision spectrometer GMR-1 manufactured by Kalnew Optical Co., Ltd. is used for this prism. The refractive index for light having a wavelength of 1550 nm is measured at intervals of 10 ° C. within a range of −5 to + 65 ° C., and the average temperature change rate dn ₁₅₅₀ / n of refractive index n _{1550 at} 25 ° C. and n of −5 to 65 ° C. dT _-5 to ₆₅ is obtained.
[alpha _{] -5} to _65: Measurement is performed in the range of -70 to +200 [deg.] C. using a thermomechanical analyzer (TMA) TAS100 manufactured by RIGAKU, and average linear expansion coefficients [alpha] _-5 to ₆₅ at _-5 to ₆₅ [deg.] C. are obtained.
[0015]
The wavelength of light used by the optical component of the present invention is not particularly limited, but the optical component of the present invention is suitable for optical communication, optical information processing, temperature sensor, and the like using light having a wavelength of 500 to 1800 nm.
[0016]
(Method for manufacturing thermo-optic phase modulator)
By providing a heating means capable of heating the core, such as a heater, in the vicinity of the optical waveguide having a core made of oxide glass having dS ₁₅₅₀ / dT ^{−5 to} ₆₅ of 3.0 × 10 ⁻⁵ / ° C. or more. A thermo-optic phase modulator can be made. FIG. 1 shows a thermo-optic phase modulator. In FIG. 1, a heater 3 is installed in the vicinity of the optical waveguide formed by the core 1 and the clad 2.
The production method of the thermo-optic phase modulator of the present invention is not particularly limited. For example, plasma method, sputtering method, sol-gel method, MOCVD method, vacuum deposition method, flame deposition method (VAD method, OVD method, MCVD method, etc.) , Etc., and a combination of processing methods such as dry etching, wet etching, laser processing, and cutting. Moreover, you may produce using the casting of glass, press molding, drawing, etc.
[0017]
For example, after producing an optical waveguide having a core made of oxide glass with dS ₁₅₅₀ / dT ^{−5 to} ₆₅ of 3.0 × 10 ⁻⁵ / ° C. or more by a known optical waveguide production method, reaction with photolithography is performed. It can be produced by forming a thin film heater by reactive ion etching. Further, in order to prevent oxidation and scratches of the heater, a glass film such as SiO ₂ may be formed in a heater shape. In addition, the heat of a heater should just be transmitted through the medium which contacts an optical waveguide, and the medium is not limited.
The optical waveguide is produced by, for example, a convex process. That is, a lower clad layer is formed on a substrate by sputtering, plasma CVD, laser ablation, electron beam evaporation (hereinafter simply referred to as sputtering). Next, a core layer is formed on the lower cladding layer by sputtering or the like, and the core layer is processed into a desired pattern by etching or the like to form a core. The upper clad layer is formed by sputtering or the like with the core formed on the lower clad layer. Here, the upper clad layer and the lower clad layer constitute a clad.
[0018]
The optical waveguide can also be produced by a two-step thermal ion exchange method. That is, it is suitable for forming an optical amplification waveguide by applying a known two-stage thermal ion exchange method according to Japanese Patent Laid-Open No. 6-194533. The two-stage thermal ion exchange method is a method in which a glass (ion exchange glass) with a mask other than the portion that should constitute the waveguide is immersed in the melt A for ion exchange and the portion that is not masked is highly refracted. An ion exchange layer (hereinafter referred to as a high refractive index layer) is formed, and then the glass is immersed in another ion exchange melt B in order to move the high refractive index layer into the glass, and an electric field is applied. To do. For example, the glass contains Na, the ion exchange melt A is an AgNO ₃ melt, and the ion exchange melt B is a NaNO ₃ melt.
The optical fiber is manufactured, for example, as follows. That is, a preform having a core / cladding structure is prepared using a well-known glass manufacturing method, the preform is placed in an electric furnace, softened, and drawn while being controlled to have a desired outer diameter. When the resin layer is formed around the clad glass, for example, the core / clad structure glass fiber obtained by the drawing process is coated with a UV curable resin and then irradiated with UV to form the resin layer.
[0019]
(Method for manufacturing thermo-optic intensity modulator)
Using the thermo-optic phase modulator of the present invention, a thermo-optic intensity modulator that is a basic unit of a thermo-optic switch can be produced.
A thermo-optic intensity modulator is a device that changes the intensity of light using a thermo-optic effect, and is typically known as a Mach-Zehnder interference thermo-optic intensity modulator.
FIG. 2 shows a Mach-Zehnder interference type thermo-optic intensity modulator. It has a Mach-Zehnder interferometer configuration composed of two directional couplers 6 and two optical waveguide arms 4 connecting them, and a thin film heater 5 is provided as a thermo-optic effect phase shifter on one optical waveguide arm. ing.
By configuring an optical waveguide arm having a thermo-optic effect phase shifter in the vicinity with the thermo-optic phase modulator of the present invention, a thermo-optic intensity modulator capable of changing the light intensity with a small temperature change can be obtained.
[0020]
The thermo-optic intensity modulator can provide a thermo-optic switch that can be switched with a small temperature difference and has a high response speed.
[0021]
【Example】
Glasses 1 to 5 having the compositions shown in Table 1 were produced. About glass 1-4 and glass 5 (quartz glass), n ₁₅₅₀ , dn ₁₅₅₀ / dT _{−5 to 65} (unit: 10 ⁻⁶ / ° C.) and α _{−5 to 65} (unit: 10 ⁻⁷ / ° C.) are as follows: As a result, dS ₁₅₅₀ / dT _{−5 to 65} (unit: 10 ⁻⁶ / ° C.) was calculated.
n ₁₅₅₀ and dn ₁₅₅₀ / dT _{−5 to 65} : Each glass was processed to prepare a regular triangular prism having a thickness of 10 mm and a side of 20 mm. About this prism, the refractive index with respect to light with a wavelength of 1550 nm was measured at intervals of 10 ° C. in the range of −5 to + 65 ° C. using a precision spectrometer GMR-1 manufactured by Kalnew Optical Industry Co., Ltd., and the refractive index n _{1550 at} 25 ° C. The average temperature change rate dn ₁₅₅₀ / dT _-5 to 65 of n at -5 to 65 ° C was determined.
α-5 to ₆₅ : Glasses 1 to 4 are measured in the range of −70 to + 200 ° C. using a thermomechanical analyzer (TMA) TAS100 manufactured by RIGAKU, and the average linear expansion coefficient α at −5 to 65 ° C. _-5 to ₆₅ were obtained. Since quartz glass of glass 5 has a small thermal expansion coefficient, it is measured in a range of −150 to + 200 ° C. using a laser dilatometer LIX-1 manufactured by ULVAC, and an average linear expansion coefficient α at −5 to 65 ° C. _-5 to ₆₅ were obtained.
Further, as described above, the phase difference Δφ between the two waveguide arms of the thermo-optic switch is the length L, the optical path length change dS / dT per unit length, the temperature difference ΔT between the waveguide arms, the light Can be expressed by the following equation.
Δφ = 2π · L · dS / dT · ΔT / λ
Therefore, as an index of the temperature difference necessary for switching, _LS = 5mm, λ = 1550nm, and dS ₁₅₅₀ / dT _{−5 to 65} (unit: 10 ⁻⁶ / ° C.) obtained in dS / dT in the above formula. By substituting, a temperature ΔT ₁₅₅₀ (unit: ° C.) at which Δφ becomes π was calculated.
The results are shown in Table 1.
[0022]
[Table 1]

[0023]
The glass with dS ₁₅₅₀ / dT ^{−5 to} ₆₅ of 3.0 × 10 ⁻⁵ / ° C. of the present invention has a small ΔT ₁₅₅₀ in each stage, small power consumption, and thermophotochemical phase modulation with a fast response speed. It can be seen that a thermo-optic phase modulator applicable to a thermo-optic intensity modulator, a photothermal switch, etc. can be provided.
【The invention's effect】
The thermo-optic phase modulator of the present invention can change the phase of light with a small temperature difference. Using the thermo-optic phase modulator of the present invention, the power consumption is small and the response speed is fast. A modulator, a photothermal switch, or the like can be provided.
[Brief description of the drawings]
FIG. 1 is a thermo-optic phase modulator.
FIG. 2 is a thermo-optical intensity modulator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Core of optical waveguide 2 Clad of optical waveguide 3 Heater 4 Optical waveguide arm 5 Heater 6 Directional coupler

Claims (4)

A thermo-optic phase modulator that changes the phase of light propagating through the core by changing the temperature of the core of the optical waveguide,
The thermo-optic phase modulator, wherein the core is made of an oxide glass having dS ₁₅₅₀ / dT ^{−5 to} ₆₅ defined by the following formula of 3.0 × 10 ⁻⁵ / ° C. or more.
dS ₁₅₅₀ / dT _{−5 to 65} = dn ₁₅₅₀ / dT _{−5 to 65} + n ₁₅₅₀ · α _{−5 to 65}
In the above formula, n ₁₅₅₀ represents a refractive index at 25 ° C. with respect to light having a wavelength of 1550 nm. dn ₁₅₅₀ / dT _{−5 to 65} represents an average temperature change rate at −5 to 65 ° C. of the refractive index with respect to light having a wavelength of 1550 nm. α ₋₅ to 65 indicates an average linear expansion coefficient at −5 to 65 ° C. The thermo-optic phase modulator according to claim 1, wherein the oxide glass contains Bi ₂ O ₃ . The thermo-optic phase modulator according to claim 1 or 2, wherein the content of Bi ₂ O ₃ in the oxide glass is 10 to 80 mol%. A thermo-optic intensity modulator comprising the thermo-optic phase modulator according to claim 1.

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