JP2005343702A - Optical material, optical device, and etalon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical material which has a low manufacturing cost, undergoes little change in the direction of a ray even when it has a temperature unevenness, has excellent transmittance to infrared rays, and has controlled temperature dependency of an optical path length, to provide an optical device, and to provide an etalon. <P>SOLUTION: The optical material comprises a crystallized glass in which the main crystal is a deposition of a β-quartz solid solution or a β-eucryptite solid solution, has an infrared transmittance of at least 50% in a thickness of 3 mm at any one of wavelengths in the range of 1,200 to 1,700 nm, has a coefficient of thermal expansion α of -2.0×10<SP>-6</SP>to 2.0×10<SP>-6</SP>/°C at -40 to 100°C, and satisfies the relationship: ϕ-0.5α<19.5×10<SP>-6</SP>(wherein α is the coefficient of thermal expansion, and ϕ is the temperature coefficient of polarizability). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical material made of crystallized glass in which a β-quartz solid solution or a β-eucryptite solid solution is precipitated as a main crystal, and an optical device for optical communication containing the optical material as a part of constituent members, and It is about etalon.

  In recent years, with the development of optical communication technology, networks using optical fibers are being rapidly developed. In this network, wavelength multiplexing technology that transmits light of a plurality of wavelengths at once is used, and wavelength filters, couplers, waveguides, and the like are becoming important devices.

In addition to this type of optical communication device, micro-optical type optical communication devices using lenses and prisms are widely used. In these optical communication devices, quartz glass (SiO ₂ ) having excellent transparency and excellent dimensional stability is widely used as an optical material.

  In addition, some optical communication devices of this type change their characteristics depending on the temperature and interfere with outdoor use. Therefore, the characteristics of such optical communication devices are constant regardless of temperature changes. Therefore, a so-called temperature compensation technique is required.

  Typical optical communication devices that require temperature compensation include waveguide devices such as arrayed wave guides (hereinafter referred to as AWG) and planar optical circuits (hereinafter referred to as PLC), and fiber Bragg gratings (hereinafter referred to as FBGs). And Fabry-Perot etalon (hereinafter referred to as etalon).

  As shown in Formula 1, these optical communication devices have a problem that when the ambient temperature changes, the optical path length changes due to the change in refractive index and thermal expansion coefficient.

  1 / L · dS / dT = (dn / dT) + nα Equation 1

  Here, L represents the thickness (mm) of the substrate, S represents the optical path length (mm), n represents the refractive index, and α represents the thermal expansion coefficient.

  In waveguide devices such as AWG and PLC, and FBG, by using a material having a negative thermal expansion coefficient or a material having a large negative refractive index temperature dependence as a substrate, the temperature dependence of the optical path length of these devices (For example, refer to Patent Document 1).

  However, it is technically difficult to reduce the temperature dependence of the optical path length of the etalon using the technique described in Patent Document 2 because of the structure of the etalon.

Therefore, conventionally, in etalon, quartz glass having a low temperature dependence of the optical path length (see, for example, Patent Document 2), Cs ₂ O—B ₂ O ₃ —SiO ₂ glass having a low temperature dependence of the optical path length (for example, , Patent Document 3), or B ₂ O ₃ —BaO—Al ₂ O ₃ —SiO ₂ glass (for example, see Patent Document 4) has been proposed as a substrate material.
JP 2001-342038 A JP 2000-47029 A JP 2002-20136 A JP 2002-321937 A

  However, the quartz glass described in Patent Document 2 requires a melting temperature of 1700 ° C. or higher in the melting method, which makes melting difficult and requires a special melting furnace that can withstand such high temperatures. And Also, it has been proposed to produce quartz glass at a lower temperature by a special method, but in any case, there is a problem that the production cost is high. Moreover, since the glass of patent document 3 or patent document 4 has a large thermal expansion coefficient, when this glass is used for an etalon, there is a possibility that the direction of the light beam is likely to change if there is temperature unevenness. there were.

  The present invention has been made in view of the above circumstances, and is an optical material that is low in manufacturing cost, hardly changes in the direction of light even if there is temperature unevenness, has excellent infrared transparency, and can suppress the optical path length temperature dependency. An object is to provide an optical device and an etalon.

  The inventors of the present invention can use an optical material having a low thermal expansion coefficient α, a high infrared transmittance, and a crystallized glass in which the thermal expansion coefficient α and the temperature coefficient φ of the polarizability are controlled. The present inventors have obtained the knowledge that the manufacturing cost is low, the direction of the light beam hardly changes even when there is temperature unevenness, the infrared ray transmission is excellent, and the optical path length temperature dependency can be suppressed, and is proposed as the present invention.

That is, the optical material of the present invention precipitates β-quartz solid solution or β-eucryptite solid solution as a main crystal, has a thickness of 3 mm, and has an infrared transmittance of 50% or more at any wavelength of wavelengths 1200 to 1700 nm. The thermal expansion coefficient α at −40 ° C. to 100 ° C. is −2.0 to 2.0 × 10 ⁻⁶ / ° C., and the temperature coefficient φ of the polarizability is φ−0.5α. It is characterized by comprising crystallized glass having a relationship of <19.5 × 10 ⁻⁶ .

Further, the optical device of the present invention precipitates β-quartz solid solution or β-eucryptite solid solution as a main crystal, has a thickness of 3 mm, and has an infrared transmittance of 50% or more at any wavelength of wavelengths 1200 to 1700 nm. The thermal expansion coefficient α at −40 ° C. to 100 ° C. is −2.0 to 2.0 × 10 ⁻⁶ / ° C., and the temperature coefficient φ of the polarizability is φ−0.5α. An optical material made of crystallized glass having a relationship of <19.5 × 10 ⁻⁶ is included in a part of the constituent members.

Moreover, the etalon of the present invention precipitates β-quartz solid solution or β-eucryptite solid solution as a main crystal, has a thickness of 3 mm, and has an infrared transmittance of 50% or more at a wavelength of 1200 to 1700 nm. Yes, the thermal expansion coefficient α at −40 ° C. to 100 ° C. is −2.0 to 2.0 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient α and the temperature coefficient φ of the polarizability are φ−0.5α < An optical material made of crystallized glass having a relationship of 19.5 × 10 ⁻⁶ is included in a part of the constituent members.

The optical material of the present invention precipitates β-quartz solid solution or β-eucryptite solid solution as a main crystal, has a thickness of 3 mm, and has an infrared transmittance of 50% or more at any wavelength of wavelengths 1200 to 1700 nm. In order to obtain a crystallized glass having a thermal expansion coefficient α at −40 ° C. to 100 ° C. of −2.0 to 2.0 × 10 ⁻⁶ / ° C., this optical material is made of a material (base When used as a prism or a lens used for a micro-optical type optical communication device, the direction of the light beam hardly changes even if there is temperature unevenness. In addition, the crystallized glass original glass (mother glass) is lower in temperature than quartz glass (at 1700 ° C. or lower) and can be easily melted in a generally used melting furnace, so that the manufacturing cost is reduced.

  Moreover, since the optical material of the present invention has a thickness of 3 mm and an infrared transmittance at any wavelength of 1200 to 1700 nm is 50% or more, an optical material such as an etalon substrate material, a prism, or a lens is used. The optical loss of the optical device can be suppressed. The infrared transmittance is preferably 70% or more, and more preferably 80% or more. Further, it is particularly preferable that the infrared transmittance is 50% or more over the entire wavelength range of 1200 to 1700 nm with a thickness of 3 mm.

  In general, the optical path length temperature coefficient of the optical material is expressed by the above-described formula 1, and the refractive index temperature coefficient dn / dT is expressed by the following formula 2.

dn / dT = (n ² −1) (n ² +2) / 6n × (φ−3α) Equation 2

  Here, φ represents the polarizability temperature coefficient.

  Since the above-mentioned crystallized glass has a refractive index of about 1.5, the optical path length temperature coefficient 1 / L · dS / dT can be approximated from Equation 1 and Equation 2 as Equation 3 below.

  1 / L · dS / dT = 0.62 × (φ−0.5α) Equation 3

  From Equation 3, it can be seen that the smaller the (φ−0.5α), the smaller the optical path length temperature coefficient.

Since the optical material of the present invention is made of crystallized glass having (φ−0.5α) smaller than 19.5 × 10 ⁻⁶ , the optical path length temperature coefficient is small, specifically, 1 / L · dS / dT. Becomes smaller than 12.0 × 10 ⁻⁶ / ° C., and the selection wavelength of an optical device such as an etalon is difficult to shift. Further, (φ−0.5α) is preferably smaller than 19.0 × 10 ⁻⁶ .

  When the optical material of the present invention has a refractive index of 1.54 or less at a wavelength of 1550 nm, when an optical device using an optical material such as an etalon substrate material, a prism, or a lens is bonded to an optical fiber, Light reflection at the joint surface can be suppressed. The refractive index is preferably 1.53 or less, and more preferably 1.52 or less.

  Moreover, it is preferable that the crystal grain size of the crystallized glass is 0.5 μm or less because the infrared transmittance at any wavelength among the wavelengths of 1200 to 1700 nm tends to be 50% or more with a thickness of 3 mm.

The optical material of the present invention is a Li ₂ O—Al ₂ O ₃ —SiO ₂ based crystallized glass having a mol% of Li ₂ O, Na ₂ O, K ₂ O of 9% or less, or mol%. It is desirable that it is made of Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass having a B ₂ O ₃ content of 0.5 to 10%. The reason is as follows.

An alkali metal oxide of Li ₂ O, Na ₂ O, or K ₂ O is a component that increases the polarizability temperature coefficient. If the total amount of Li ₂ O, Na ₂ O, and K ₂ O is more than 9%, the crystallinity glass has a large polarizability temperature coefficient and an optical path length temperature coefficient, which is not preferable. A preferable range of the total amount of Li ₂ O, Na ₂ O, and K ₂ O is 8.5% or less, and a more preferable range is 8% or less.

B ₂ O ₃ is a component that lowers the polarizability temperature coefficient. If B ₂ O ₃ is less than 0.5%, the crystallinity glass has a large polarizability temperature coefficient and an optical path length temperature coefficient, which is preferable. Absent. When B ₂ O ₃ is more than 10%, it becomes difficult to precipitate β-quartz solid solution or β-eucryptite solid solution as a main crystal, and a thermal expansion coefficient of 2.0 × 10 ⁻⁶ / ° C. or less is obtained. It becomes difficult to be. In addition, the crystal grain size becomes large, and the infrared transmittance becomes lower than 50%, which is not preferable. A preferable range of B ₂ O ₃ is 0.8 to 8%, and a more preferable range is 1 to 6%.

The Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass in which the total amount of Li ₂ O, Na ₂ O, and K ₂ O is 9% or less in terms of mol%, ₂ 67-79%, Al ₂ O ₃ 8-18%, Li ₂ O 2-8%, ZrO ₂ + TiO ₂ 0.5-4.5%, P ₂ O ₅ 0-10%, MgO + ZnO 2-8% It is desirable to contain this, and the reason for this limitation is as follows.

SiO ₂ is a main component constituting the glass network and a constituent component of the precipitated crystal, and reduces the polarizability temperature coefficient. When SiO ₂ is less than 67%, the polarizability temperature coefficient becomes large, the glass becomes unstable, and β-quartz solid solution or β-eucryptite solid solution having a desired crystal grain size is precipitated as a main crystal. It becomes difficult. On the other hand, if it exceeds 79%, it becomes difficult to melt the glass. A preferable range of SiO ₂ is 68 to 77%, and a more preferable range is 69 to 75%.

Al ₂ O _{3 is} also a network component of glass and a crystal component. When Al ₂ O ₃ is less than 8%, it becomes difficult to precipitate a desired crystal, and it becomes difficult to obtain a thermal expansion coefficient of 2.0 × 10 ⁻⁶ / ° C. or less. On the other hand, if it exceeds 18%, the glass tends to be devitrified. A preferable range of Al ₂ O ₃ is 9 to 16%, and a more preferable range is 10 to 15%.

Li ₂ O is a constituent component of β-quartz solid solution crystal or β-eucryptite solid solution crystal. When Li ₂ O is less than 2%, it becomes difficult to precipitate a desired crystal, and it becomes difficult to obtain a thermal expansion coefficient of 2.0 × 10 ⁻⁶ / ° C. or less. On the other hand, if it exceeds 8%, the temperature coefficient of polarizability becomes too large. A preferable range of Li ₂ O is 3 to 7%, and a more preferable range is 4 to 6%.

ZrO ₂ and TiO ₂ are components having an action of forming crystal nuclei. If the total amount of ZrO ₂ and TiO ₂ is less than 0.5%, the nucleation action becomes insufficient, and crystals having a desired particle size cannot be uniformly deposited. On the other hand, if it exceeds 4.5%, melting of the glass becomes difficult and devitrification tends to occur, which is not preferable. A preferable range of the total amount of ZrO ₂ and TiO ₂ is 0.7 to 4.2%, and a more preferable range is 1 to 4%.

P ₂ O ₅ has the effect of promoting the nucleation action. If it exceeds 10%, the viscosity of the glass becomes high and melting becomes difficult. A preferable range of P ₂ O ₅ is 0 to 7%, and a more preferable range is 0 to 5%.

MgO and ZnO are constituent components of β-quartz solid solution crystal or β-eucryptite solid solution crystal. When the total amount of MgO and ZnO is less than 2%, it becomes difficult to precipitate a desired crystal, and it becomes difficult to obtain a thermal expansion coefficient of 2.0 × 10 ⁻⁶ / ° C. or less. On the other hand, if it exceeds 8%, the polarizability temperature coefficient becomes too large. A preferable range of the total amount of MgO and ZnO is 2.5 to 6%, and a more preferable range is 3 to 5%.

Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass having a B ₂ O ₃ content of 0.5% or more by mol% is SiO ₂ 60-79%, Al ₂ O _{3 in} mol%. It is desirable to contain 8 to 18%, Li ₂ O 2 to 15%, ZrO ₂ + TiO ₂ 0.5 to 4.5%, and the reason for such limitation is as follows.

SiO ₂ is a main component constituting the glass network and a constituent component of the precipitated crystal, and reduces the polarizability temperature coefficient. When SiO ₂ is less than 60%, the polarizability temperature coefficient becomes large, the glass becomes unstable, and β-quartz solid solution or β-eucryptite solid solution having a desired crystal grain size is precipitated as a main crystal. It becomes difficult. On the other hand, if it exceeds 79%, it becomes difficult to melt the glass. A preferable range of SiO ₂ is 62 to 77%, and a more preferable range is 65 to 75%.

Al ₂ O _{3 is} also a network component of glass and a crystal component. When Al ₂ O ₃ is less than 8%, it becomes difficult to precipitate a desired crystal, and it becomes difficult to obtain a thermal expansion coefficient of 2.0 × 10 ⁻⁶ / ° C. or less. On the other hand, if it exceeds 18%, the glass tends to be devitrified. A preferable range of Al ₂ O ₃ is 9 to 17%, and a more preferable range is 10 to 16%.

Li ₂ O is a constituent component of β-quartz solid solution crystal or β-eucryptite solid solution crystal. When Li ₂ O is less than 2%, it is difficult to precipitate a desired crystal, and it becomes difficult to obtain a thermal expansion coefficient of 2.0 × 10 ⁻⁶ / ° C. or less. On the other hand, if it exceeds 15%, the polarizability temperature coefficient becomes too large. A preferable range of Li ₂ O is 3 to 13%, and a more preferable range is 4 to 12%.

ZrO ₂ and TiO ₂ are components having an action of forming crystal nuclei in the glass. If the total amount of ZrO ₂ and TiO ₂ is less than 0.5%, the nucleation action becomes insufficient, and crystals having a desired particle size cannot be uniformly deposited. On the other hand, if it exceeds 4.5%, melting of the glass becomes difficult and devitrification tends to occur, which is not preferable. A preferable range of the total amount of ZrO ₂ and TiO ₂ is 0.7 to 4.2%, and a more preferable range is 1 to 4%.

In the present invention, other components such as As ₂ O ₃ , SnO ₂ , BaO, Sb ₂ O ₃ , CaO, and SrO can be added as necessary.

As ₂ O ₃ is generally used as a glass refining agent, but has an action of promoting crystal transition. Therefore, if As ₂ O ₃ exceeds 1%, β-spodumene solid solution is likely to precipitate, and it becomes difficult to obtain a thermal expansion coefficient of 2.0 × 10 ⁻⁶ / ° C. or less. A preferred range for As ₂ O ₃ is 0.8% or less, and a more preferred range is 0.6% or less.

SnO ₂ can be added up to 5%. That is, even if SnO ₂ is added up to 5%, unlike As ₂ O ₃ , there is almost no effect of promoting crystal transition. Furthermore, since SnO ₂ also has a nucleation ability, the amount of nucleating agent used can be reduced.

  Hereinafter, the present invention will be described in detail based on examples.

Table 1 shows Examples 1 to 5 of the present invention and Comparative Examples 6 to 8.

  Examples and Comparative Examples in Table 1 were produced as follows.

  First, batch materials prepared so as to have the composition shown in the table were placed in a platinum crucible and melted at 1580 ° C. for 20 hours. Next, this molten glass was poured onto a carbon plate and roll-formed to form a glass plate having a thickness of 5 mm and gradually cooled to room temperature.

  Next, each glass plate was subjected to nucleation treatment at 780 ° C. for 3 hours, then subjected to crystallization treatment at the crystallization temperature in the table for 1 hour, and cooled to room temperature. Examples 1 to 5 and Comparative Examples 6-8 crystallized glass was produced.

  For the crystallized glass thus obtained, the main crystal seed, the thermal expansion coefficient (α), the refractive index (n), the refractive index temperature coefficient (dn / dT), the optical path length temperature coefficient (1 / L · dS / dT), The polarizability temperature coefficient (φ), infrared transmittance at 1550 nm, and crystal grain size were measured.

As is clear from the table, in Examples 1 to 5, β-quartz solid solution was precipitated as the main crystal, and the thermal expansion coefficient was small. Further, the infrared transmittance at 1550 nm was 85% or more. Furthermore, the value of (φ−0.5 × α) is low, 19.2 × 10 ⁻⁶ / ° C. or less, and the temperature dependence of the optical path length (dS / dT) is 12.0 × 10 ⁻⁶ / ° C. It was the following. The refractive index at 1550 nm was also 1.506 to 1.518.

On the other hand, in Comparative Examples 6 and 7, since the value of (φ−0.5 × α) is as high as 19.6 × 10 ⁻⁶ / ° C. or more, the temperature dependence (dS / dT) of the optical path length is also 12. It was as high as 6 × 10 ⁻⁶ / ° C. In Comparative Example 8, the main crystal is a β-spodumene solid solution and the crystal grain size is larger than 0.5 μm, so the infrared transmittance at 1550 nm is 10%, and the temperature dependence of the refractive index and the optical path length is measured. I couldn't. Therefore, it cannot be used as a constituent material (base material) of an optical device such as an etalon, an optical material such as a lens or a prism.

  The main crystal species in the table were identified by a well-known X-ray diffraction method. The thermal expansion coefficient was measured using a dilatometer. Furthermore, the infrared transmittance was measured using a spectrophotometer (Shimadzu Corporation UV3100), with the thickness of each sample being 3 mm and the infrared transmittance at 1550 nm. The temperature dependence of the refractive index was evaluated by changing the temperature of the sample and measuring the refractive index, and the polarizability temperature coefficient was obtained from Equation 2. Further, the temperature dependence of the optical path length is the change in interference fringes observed when a sample is placed in one optical path in an interference optical system using light in the wavelength range of 1100 to 1700 nm and the sample temperature is changed. Evaluation was made based on the largest value of the temperature dependence of the optical path length obtained from the above.

  As described above, the optical material of the present invention is low in manufacturing cost, is less likely to change the direction of light even if there is temperature unevenness, is excellent in infrared transparency, and can suppress optical path length temperature dependence. Not only is it suitable as a constituent material for optical devices such as etalon that require stability, infrared transparency, and optical path length athermal properties, but also is a micro-optical type that requires dimensional stability and infrared transparency. It is also suitable as a component material for devices (for example, optical materials such as lenses and prisms).

Claims (9)

A β-quartz solid solution or β-eucryptite solid solution is precipitated as a main crystal, has a thickness of 3 mm, and has an infrared transmittance of 50% or more at a wavelength of 1200 to 1700 nm, and is −40 ° C. to 100 ° C. The thermal expansion coefficient α in the range of −2.0 to 2.0 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient α and the temperature coefficient φ of the polarizability are φ−0.5α <19.5 × 10 ⁻⁶ . An optical material comprising a crystallized glass having a relationship. _2. The optical material according to claim 1, wherein the crystallized glass is mol%, and a total amount of Li ₂ O, Na ₂ O, and K ₂ O is 9% or less. Crystallized glass is mol%, SiO ₂ 67-79%, Al ₂ O ₃ 8-18%, Li ₂ O 2-8%, ZrO ₂ + TiO ₂ 0.5-4.5%, P ₂ O ₅ The optical material according to claim 1, comprising 0 to 10% and MgO + ZnO 2 to 8%. Crystallized glass, in _{mol%, SiO 2 69~75%, Al} 2 O 3 10~15%,
It contains Li ₂ O 4-6%, ZrO ₂ + TiO ₂ 1-4%, P ₂ O ₅ 0-5%, MgO + ZnO 3-5%. Optical material. _2. The optical material according to claim 1, wherein the crystallized glass is mol% and the content of B ₂ O ₃ is 0.5 to 10%. The crystallized glass contains, in mol%, SiO ₂ 60 to 79%, Al ₂ O ₃ 8 to 18%, Li ₂ O 2 to 15%, ZrO ₂ + TiO ₂ 0.5 to 4.5%. The optical material according to claim 1 or 5, characterized in that Crystallized glass, in _{mol%, SiO 2 65~75%, Al} 2 O 3 10~16%,
The optical material according to claim 1, 5 or 6, comprising B ₂ O ₃ 0.8 to 8%, Li ₂ O 4 to 12%, ZrO ₂ + TiO ₂ 1 to 4%.   An optical device comprising the optical material according to claim 1 as a part of a constituent member.   An etalon comprising the optical material according to claim 1 as a part of a constituent member.