JP2005132693A - Electro-optical element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electro-optical element containing an optical waveguide by dispersion precipitating ferroelectric microcrystals having high electro-optical effect and nonlinear optical effect inside glass without requiring heat treatment. <P>SOLUTION: This manufacturing method of an electro-optical element comprises a step in which a glass body mainly containing either one of a glass component (a) containing at least one of Li<SB>2</SB>O and K<SB>2</SB>O, at least one of Nb<SB>2</SB>O<SB>5</SB>and Ta<SB>2</SB>O<SB>5</SB>, and at least one of SiO<SB>2</SB>, GeO<SB>2</SB>, and TeO<SB>2</SB>, or a glass component (b) containing at least one of MgO, CaO, SrO, and BaO, at least one of TiO<SB>2</SB>, and ZrO<SB>2</SB>, and at least one of SiO<SB>2</SB>, and GeO<SB>2</SB>, is prepared, a step in which a core part in which microcrystals are dispersed is formed inside the glass body by condensation irradiating a pulse laser having a longer wavelength than the fundamental absorption end wavelength of the glass component, and a step in which an optical waveguide having a two dimensionally or three dimensionally continued core is formed by scanning the focus of a laser two dimensionally or three dimensionally in the glass body while condensation irradiating the pulse laser. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electro-optical element including an optical waveguide in which microcrystals (nanocrystals) are dispersed and a method for manufacturing the same.

A wavelength division multiplexing (WDM) communication system that transmits a signal on a large number of light beams having different wavelengths as a countermeasure against the increase in communication capacity due to an increase in communication demand due to the rapid expansion of the Internet. Is active. However, even the WDM system introduced in the current practical system cannot meet the demand for communication, and therefore, it is necessary to increase the transmission capacity per wavelength, and 40 Gbps (40 Gbit per second) transmission technology has been developed up to now. Has been developed and is about to stand up in a few years. In systems of 40 Gbps or more, since faster response performance is required, it is difficult to apply the existing semiconductor EA (electroabsorption type) modulator, and external modulation based on single crystal LiNbO ₃ using the electro-optic effect is used. The vessel is likely to become mainstream. This electro-optic effect is conventionally unique to single crystal materials typified by LiNbO ₃ , and functional devices using these materials have been researched and developed. However, this single crystal material such as LiNbO ₃ is a different material from the quartz glass fiber provided in the existing network. Therefore, the connection loss between LiNbO ₃ and the silica glass fiber is high, and there are problems such as poor matching with the fiber and high cost, and it has not yet become a main control device of the optical fiber network.

On the other hand, silica glass-based materials are expected as basic materials for optical devices because they are low in cost, have excellent propagation characteristics, have low connection loss with fibers, and have a wide transmission wavelength range. However, silica glass-based materials have essentially no electro-optic effect or non-linear optical effect, and thus have been limited to passive devices such as filters. In the 1980s, since the report of inducing optical nonlinearity in silica glass by the poling method has been made, the search for an effective poling method has been actively conducted. Furthermore, in recent years, it has been found that the electro-optic effect and the nonlinear optical effect comparable to those of a LiNbO ₃ single crystal are exhibited by ultraviolet light poling. A material that has both the electro-optic and non-linear optical effects at practical levels, and the excellent properties inherent in glass materials such as low loss, excellent formability, and cost performance, is expected as a new photonics material with unprecedented characteristics. Yes. However, the electro-optic effect and the nonlinear optical effect induced by poling have a problem in long-term stability of performance, which is a factor that hinders progress to device application.

Hereinafter, the non-patent document and the patent document of the prior examples for forming the crystal having the electro-optic effect and the nonlinear optical effect regardless of the poling will be described. First, as a method for precipitating crystals on glass, there is an example in which nanocrystals having a diameter of 40 to 60 nm are precipitated on the glass surface by irradiating with UV laser light (for example, see Non-Patent Document 1). The composition of the glass used for crystallization in this case is _{15K 2 O-15Nb 2 O 5} -70TeO 2. This glass contains a constituent element of the ferroelectric crystal KNbO ₃ having a large electro-optic effect and nonlinear optical effect in the glass composition, and TeO ₂ for forming a glass skeleton. By irradiating the glass surface with XeCl excimer laser light having a wavelength λ = 308 nm through a phase mask, nanocrystals having a nonlinear optical effect are deposited on the glass surface. When the laser beam passes through the phase mask, interference light is generated, and a high-intensity laser beam is irradiated onto a local region of the glass surface, thereby depositing nanocrystals.

  Next, a microcrystal-dispersed glass in which microcrystals are selectively deposited in a predetermined pattern only inside the glass material and a manufacturing method thereof will be described (for example, see Patent Document 1). In this example, pulsed laser light emitted from a light source is condensed and irradiated inside a glass having a predetermined depth by a condensing device such as a lens, so that the metal ions contained in the glass composition are photoreduced and the altered region. Is generated. Next, heat treatment is performed to selectively precipitate microcrystals in the glass with the altered region as a nucleus. The microcrystalline region is patterned at a predetermined position by relative movement of the condensing point and on / off of the laser beam. Metal ions include Au ions, Ag ions, Cu ions, Pt ions, and the like.

“UV-Laser Induced Photoperiodic Structure in Tellurite-Based Glass Ceramics”, X IX International Congress on Glass, ICD X IX, O1g. Japanese Patent Laid-Open No. 11-71139 (pages 4 to 9 and FIGS. 1 and 2)

  In the case of the above prior art in which a ferroelectric crystal having a large nonlinear optical effect is deposited on a part of glass, crystal deposition occurs only on the glass surface, and crystals cannot be deposited inside the glass. The reason why crystal precipitation occurs only on the glass surface is considered to be because the glass having the above composition has a fundamental absorption edge in the vicinity of a wavelength of 400 to 500 nm. Since the wavelength of the irradiated laser beam is in the absorption wavelength region of this glass, it is considered that the laser beam is absorbed near the glass surface and energy is consumed only for crystallization in the local region. Therefore, in this case, it is impossible to cause laser light to enter the glass and to precipitate crystals inside. For this reason, when an electro-optic element is manufactured using this crystal precipitation portion, for example, when an optical waveguide is formed, an etching process for processing the waveguide into a predetermined pattern shape is required. Furthermore, there is a problem that a cladding layer forming step by a film forming process is required.

  Further, in the case of the method for producing a microcrystalline dispersed glass described in the above-mentioned Japanese Patent Application Laid-Open No. 11-71139, pulsed laser light is condensed and irradiated inside the glass in which metal ions are dispersed in advance, and the metal ions are irradiated with light. Reduction is generated to produce an altered region, and then heat treatment is performed to selectively grow microcrystals with the altered region as a nucleus. In this case, it is necessary to perform heat treatment after the pulse laser beam irradiation. However, when the glass is heat-treated, the equivalent refractive index of the core (non-crystalline part), which is increased by laser light irradiation, decreases, and the propagation characteristics of the waveguide deteriorate significantly due to the occurrence or disappearance of the refractive index distribution. .

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to obtain an electro-optic element including an optical waveguide in which ferroelectric microcrystals having a large electro-optic effect and nonlinear optical effect are dispersed and precipitated inside the glass without requiring heat treatment.

The electro-optic element according to the present invention includes (1) at least one component of Li ₂ O and K ₂ O, at least one component of Nb ₂ O ₅ and Ta ₂ O ₅ , and SiO ₂ and GeO. ₂ , a glass component including at least one component of TeO ₂ , (2) at least one component of MgO, CaO, SrO, and BaO, and at least one component of TiO ₂ and ZrO ₂ And a step of preparing a glass body mainly comprising any one of the glass components including at least one component of SiO ₂ and GeO ₂ ;
A step of forming a core part in which fine crystals are dispersed by condensing and irradiating a pulse laser beam having a wavelength longer than the fundamental absorption edge wavelength of the glass component inside the glass body;
While condensing and irradiating the pulsed laser beam, the laser beam condensing point is scanned two-dimensionally or three-dimensionally inside the glass body, and the core portion is two-dimensionally or three-dimensionally continuous. Forming an optical waveguide.

  According to the method for manufacturing an electro-optic element according to the present invention, a core portion in which microcrystals having an electro-optic effect and a non-linear optical effect are dispersed only at the focusing point by the focused irradiation of pulsed laser light can be formed. The core portion can be formed at the location. Further, by scanning the condensing point of the pulse laser beam two-dimensionally or three-dimensionally, an optical waveguide having a complicated two-dimensional or three-dimensional structure in the core portion can be easily formed. Furthermore, according to the composition of the glass used for this invention, a microcrystal can be disperse | distributed and precipitated inside a glass body only by condensing irradiation of a pulsed laser beam. Therefore, no heat treatment is required, the dimensions of the glass body and the core portion are not distorted, and no heat treatment is performed, so that the refractive index of portions other than the microcrystals of the core portion can be kept high. Further, since a heat treatment process is not required, the manufacturing cost can be reduced. Further, in the manufacture of an electro-optic element, a core portion can be formed at a portion scanned with a condensing point of laser light, and the periphery of the core portion becomes a cladding portion. Therefore, a processing process and film formation for forming a cladding layer There is no need to carry out post-processes such as processes, and the manufacturing cost can be greatly reduced.

  The electro-optical element according to the present invention includes an optical waveguide in which an electro-optic crystal having a particle diameter smaller than the wavelength λ = 800 nm to 1,550 nm of propagation light in the optical waveguide is dispersed and deposited. Specifically, the Mie scattering parameter q (= 2πa / λ) relating to the particle diameter a of the microcrystal and the wavelength λ of the light propagating through the optical waveguide satisfies the following expression: 1 / 5π <q <2π. Therefore, an electro-optic element that suppresses Mie scattering is obtained.

  Hereinafter, an electro-optical element and a manufacturing method thereof according to embodiments of the present invention will be described with reference to the drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

Embodiment 1 FIG.
A method for manufacturing an electro-optical element according to Embodiment 1 of the present invention will be described with reference to FIGS. This method of manufacturing an electro-optical element includes the following steps.
(I) (a) At least one component of Li ₂ O and K ₂ O, at least one component of Nb ₂ O ₅ and Ta ₂ O ₅ , and SiO ₂ , GeO ₂ , and TeO ₂ A glass component containing at least one component, (b) at least one component of MgO, CaO, SrO, BaO, at least one component of TiO ₂ , ZrO ₂ , SiO ₂ , GeO A glass body mainly containing any one of the glass components containing at least one of the _two components is prepared.
The glass composition (a) can be represented by a composite oxide composition of M ⁽¹⁾ ₂ O-M ⁽²⁾ ₂ O ₅ -M ⁽³⁾ O ₂ . Here, M ⁽¹⁾ is at least one element of Li and K, M ⁽²⁾ is at least one element of Nb and Ta, and M ⁽³⁾ is at least one element of Si, Ge, and Te. Represents each. The glass composition (b) can be represented by a composite oxide composition of M ⁽¹⁾ OM ^{( 2)} O ₂ -M ⁽³⁾ O ₂ . Here, M ⁽¹⁾ is at least one element of Mg, Ca, Sr, and Ba, M ⁽²⁾ is at least one element of Ti and Zr, and M ⁽³⁾ is at least one element of Si and Ge. Each element is represented.
(Ii) A pulse laser beam having a wavelength longer than the fundamental absorption edge wavelength of the glass component is focused and irradiated on the inside of the glass body to form a core portion in which microcrystals are dispersed.
(Iii) A light beam in which the core portion is two-dimensionally or three-dimensionally continuous by two-dimensionally or three-dimensionally scanning the inside of the glass body while condensing and irradiating pulsed laser light. A waveguide is formed.

First, a step of preparing a glass body containing a glass component having a predetermined composition will be described. Here, an example in which a glass substrate of 15K ₂ O-15Nb ₂ O ₅ -70TeO ₂ as a glass composition (a) and a glass substrate of 30BaO-15TiO ₂ -55GeO ₂ as a glass composition (b) is prepared I will explain it. First, the manufacturing method of a glass substrate is demonstrated. For the production of the glass having the composition (a), K ₂ CO ₃ : 12.031 g, Nb ₂ O ₅ : 23.138 g, TeO ₂ : 64.832 g are used as raw materials. As raw materials, BaCO ₃ : 45.993 g, TiO ₂ : 9.308 g, and GeO ₂ : 44.698 g were used, and mixed powders each having a total weight of 100 g obtained by treatment with a milling machine were used. In the glass of composition (a), this mixed powder is put in a gold crucible and heat treated at 950 ° C./30 min in an electric furnace, in the glass of composition (b) in a platinum crucible and heat treated at 1300 ° C./30 min in an electric furnace, It was melted. This melt was cast and quenched on an iron plate previously heated to 300 ° C. to obtain glass. Thereafter, re-heat treatment was performed at a temperature around the strain point to remove the strain inside the glass. After cooling, the glass was cut into a plate having a thickness of 2 mm and a 25 mm square, and both surfaces were optically polished to obtain glass substrates 13 having the compositions (a) and (b).

  Next, the step of irradiating the glass substrate 13 with the pulsed laser light 11 to form the core portion 15 in which the microcrystals are dispersed and precipitated inside the glass substrate 13, A step in which the light condensing point 14 is scanned two-dimensionally or three-dimensionally inside the glass body 13 to form an optical waveguide in which the core portion 15 continues two-dimensionally or three-dimensionally will be described. FIG. 1A shows a process of manufacturing an optical waveguide having a core portion 15 in which a microcrystal (nanocrystal) 17 is dispersed and precipitated inside by condensing and irradiating a pulse laser beam 11 inside a glass substrate 13. FIG. FIG. 1B is a schematic view showing nanocrystals 17 dispersed and precipitated inside the core portion 15. An example in which a femtosecond laser is used as the light source of the pulse laser beam 11 will be described with reference to FIG. FIG. 2 is a block diagram of a basic apparatus for writing an optical waveguide on the glass substrate 13 using a femtosecond laser.

(1) The pulsed laser light 11 emitted from the femtosecond laser device is narrowed down to a spot having a diameter of several μm in the inner region of the glass substrate 13 by the condenser lens 12 installed on the optical axis. The condensing lens 12 may use an objective lens having a magnification of 40 to 100 in order to make the waveguide shape spherical. This condensing irradiation region is set at a depth position of 30 μm or more from the surface in order to prevent ablation of the glass substrate 13. Specifically, as shown in FIG. 2, a laser beam having a wavelength of 810 nm obtained by reproducing and amplifying a mode-locked Ti: Al ₂ O ₃ laser 21 using a YAG laser beam (wavelength λ = 532 nm) 21 as an excitation light source is After being amplified by the amplifier 23, the average output is adjusted to an appropriate value on the order of several hundreds mW by the attenuator 24, and then the condensed light is irradiated onto the region 14 inside the glass substrate 13 through the objective lens 12. Further, in the condensing irradiation inside the glass by the femtosecond laser light irradiation apparatus, the conditions other than the above are as follows: pulse width: 170 to 220 fs, laser beam diameter: 3 mm, repetition frequency: 250 kHz, pulse energy: 4 μJ (one pulse) Energy integrated value).

(2) Next, while condensing and irradiating the inside of the glass, the core portion 15 that is linearly continuous can be formed by translating the glass substrate 13 placed on the movable stage. Note that the pattern of the core portion 15 is not limited to a straight line, and various patterns that are two-dimensionally and three-dimensionally continuous such as a curved line or a Y-shape can be formed. Specifically, as shown in FIG. 2, the movable stage 26 is controlled by a computer 27, and the glass substrate 13 is two-dimensionally parallel and perpendicular to the optical axis of the laser beam, curved, or three-dimensionally. An optical waveguide is formed by moving the optical waveguide. The scanning speed can be performed in the range of 10 μm / sec to 500 μm / sec. Further, the appearance of the optical waveguide can be detected by the CCD camera 28 and observed on the television monitor 29.

Here, the pulse laser beam having a wavelength longer than the fundamental absorption edge wavelength of the glass material constituting the used glass substrate is used. The relationship between the composition of the glass material and the absorption of laser light will be described with reference to FIG. FIG. 3 is a graph showing the transmittance of the glass having the composition (a) and the composition (b) produced. The TeO ₂ -based glass having the composition (a) and the GeO ₂ -based glass having the composition (b) are excellent in infrared transmittance, and are therefore particularly suitable for communication glass materials among nonlinear optical glasses. The glass of composition (a) has a fundamental absorption edge at a wavelength λ = 400 nm to 500 nm, and the glass of composition (b) has a fundamental absorption edge at a wavelength λ = 350 nm to 400 nm. For this reason, it is necessary to use a laser beam having a wavelength longer than the fundamental absorption edge wavelength as the laser beam used for condensing irradiation inside the glass. In the experiment conducted this time, laser light having a wavelength λ = 810 nm was used, so that absorption on the glass surface and inside can be minimized. Although the case where a femtosecond laser is used as the laser light source has been described here, a picosecond laser may be used, and the same effect as described above can be obtained.

  By the above-described manufacturing method, as shown in FIG. 1, an optical waveguide in which a core part in which microcrystals are dispersed and precipitated inside a glass substrate having a predetermined composition is obtained two-dimensionally or three-dimensionally is obtained. Table 1 shows that, on the glass substrates of Example 1 (composition (a)) and Example 2 (composition (b)), the average output of pulsed laser light as the optical waveguide writing conditions: 400 mW, scanning speed: 30 μm / sec, and The average output is 650 mW, and the evaluation results are obtained by measuring the propagation characteristics by propagating infrared light having a wavelength of λ = 1,550 nm to an optical waveguide manufactured at a scanning speed of 30 μm / sec.

  Moreover, as a result of observing the cross section of the core part of the optical waveguide formed in the glass substrate of the said composition (a) and the composition (b) using the transmission electron microscope, 500 nm or less microparticles | fine-particles disperse | distribute in the core part cross section. Confirmed that. As a result of observation of a lattice image by a transmission electron microscope and EDX analysis, the fine particles deposited inside the glass core of the composition (a) are nanocrystals having a K—Nb—Te—O composition. found. On the other hand, it was found that the fine particles deposited inside the glass core of the composition (b) were nanocrystals having a Ba-Ti-Ge-O-based composition.

From the above experimental results, in this electro-optic element manufacturing method, instead of the poling method, nanocrystals are dispersed and precipitated in the glass to induce the electro-optic effect and the nonlinear optical effect. Glass used for crystallization is composed of a composition containing a constituent element of a ferroelectric crystal having a large nonlinear optical effect (for example, LiNbO ₃ , KNbO ₃ , BaTiO _3, etc.), and the electro-optic effect developed from such a glass material In addition, since the nonlinear optical effect originates from the precipitated crystal phase, its performance can be maintained almost permanently. In addition, nanocrystals can be dispersed and precipitated in the glass only by focused irradiation with pulsed laser light, and it is not necessary to perform a heat treatment at 500 ° C. or higher as in the conventional example. In addition, an optical waveguide formed by irradiation with pulsed laser light has a high refractive index region accompanying a defect or density change of the glass structure formed by the energy of the laser light, and nanocrystals are dispersed and precipitated in this region. The core part is constituted by this high refractive index region. Usually, if a heat treatment at 500 ° C. or higher is performed after the core portion is formed, the glass structure in the high refractive index region of the core portion is relaxed, resulting in a decrease in refractive index and a change in the shape of the waveguide. Adversely affects. According to the present invention, nanocrystals can be dispersed and deposited by condensing and irradiating pulsed laser light, and no heat treatment is required, so that a decrease in the refractive index of the core and a change in waveguide shape due to the heat treatment can be suppressed. it can. Further, since a heat treatment process is not required, the manufacturing cost can be reduced.

Further, the characteristics of this electro-optical element and its application examples will be described. The optical path length of the optical waveguide made from the glass of the composition (a) and the composition (b) is set to 0.1 mm, and YAG laser light (wavelength λ = 1,064 nm) is incident from one waveguide cross section. As a result of calculating the nonlinear optical constant d from the output value by the maker fringe method for detecting light of the second harmonic (wavelength λ = 532 nm), electro-optical characteristics almost equivalent to those of the LiNbO ₃ single crystal were obtained. Further, a phase modulator was manufactured using these optical waveguides, and a Mach-Zehnder type optical switch constituted by coupling a silica-based PLC 3 dB coupler on both sides of the waveguide was manufactured. As a result of calculating the electro-optic constant r from these operating characteristics, a maximum of 10 pm / V was obtained for an optical waveguide made from glass of composition (a), and a maximum of 30 pm / V was obtained for an optical waveguide made from glass of composition (b). As a result, almost the same characteristics as those of LiNbO ₃ single crystal were obtained. An electro-optic effect can be obtained by applying an electric field to a pair of electrodes sandwiching a part of the core portion.

Embodiment 2. FIG.
A method for manufacturing an electro-optical element according to Embodiment 2 of the present invention will be described. In this electro-optical element manufacturing method, the composition range of the composition (a) of the glass substrate used will be described with reference to FIG. As a result of intensive studies by the present inventor, M ⁽¹⁾ ₂ O is contained in a proportion of 5 to 20 mol%, M ⁽²⁾ O is contained in a proportion of 5 to 20 mol%, and M ⁽³⁾ glass material manufactured in the composition range of the shaded portion in FIG. 4, including the components of O ₂ at a rate of 60～90Mol% was found to be preferred glass composition nanocrystals precipitated. FIG. 4 shows M ⁽¹⁾ ₂ O-M ⁽²⁾ ₂ O ₅ -M ⁽³⁾ O ₂ , [M ⁽¹⁾ : at least one component of Li or K, M ⁽²⁾ : 3 is a ternary phase diagram of at least one component of Nb or Ta, M ⁽³⁾ : at least one component of Te, Si, or Ge], and shows a composition range in which nanocrystals are precipitated. The composition range of the shaded portion is a composition range in which glass is obtained by quenching treatment, and at the same time, a composition range in which nanocrystals are precipitated by focused irradiation of pulsed laser light. In the figure, white circles indicate a glass composition in which a large amount of nanocrystals are deposited, hatched circles indicate a glass composition in which the precipitation of nanocrystals is small, and black circles indicate a glass composition in which nanocrystals are not precipitated. A glass substrate mainly composed of a glass material having the above composition range can disperse and precipitate nanocrystals inside the glass only by focused irradiation of pulsed laser light, and does not require heat treatment as in the conventional example. In the second embodiment, each M ⁽¹⁾ , M ⁽²⁾ , M ⁽³⁾ of the composition (a) is not limited to one type of component, and may include two or more types of components. Good.

Embodiment 3 FIG.
A method for manufacturing an electro-optic element according to Embodiment 3 of the present invention will be described. In this electro-optic element manufacturing method, the composition range of the composition (b) of the glass substrate used will be described with reference to FIG. The present inventors have studied ^intensively, wherein ^M a ⁽¹⁾ O component in a proportion of 25 mol% 40 ^mol%, wherein the components of the ^{M (2)} _{O 2} at a ratio of ^{10mol% ~20mol%, M (3} ) glass material manufactured in the composition range of the shaded portion of Figure 5 comprising the components of O ₂ at a rate of 45～60Mol% was found to be preferred glass composition nanocrystals precipitated. FIG. 5 shows M ⁽¹⁾ OM ^{( 2)} O ₂ -M ⁽³⁾ O ₂ as the glass composition (b), [M ⁽¹⁾ : at least one component of Mg, Ca, Sr, Ba, M ⁽²⁾ : At least one component of Ti or Zr, M ⁽³⁾ : At least one component of Si or Ge], showing a composition range in which nanocrystals are precipitated. . The composition range of the shaded portion is a composition range in which glass is obtained by quenching treatment, and at the same time, a composition range in which nanocrystals are precipitated by focused irradiation of pulsed laser light. In the figure, white circles indicate a glass composition in which a large amount of nanocrystals are deposited, hatched circles indicate a glass composition in which the precipitation of nanocrystals is small, and black circles indicate a glass composition in which nanocrystals are not precipitated. A glass substrate mainly composed of a glass material having the above composition range can disperse and precipitate nanocrystals inside the glass only by focused irradiation of pulsed laser light, and does not require heat treatment as in the conventional example. In the third embodiment, M ⁽¹⁾ , M ⁽²⁾ , and M ⁽³⁾ are not limited to one type of component, and two or more types of components may be included.

Embodiment 4 FIG.
An electro-optical element according to Embodiment 4 of the present invention will be described with reference to FIG. FIG. 6A is a schematic view of the electro-optical element 10 having an optical waveguide including a core portion 15 having a structure in which nanocrystals 17 of the electro-optical element according to the fourth embodiment are dispersed. FIG. 6B is a cross-sectional view showing a cross-sectional structure of the core portion 15. The core portion 15 is composed of a glass structure defect formed by laser light irradiation and a high refractive index region 16 that accompanies density change, and nanocrystals 17 dispersed in this region.

Hereinafter, an electro-optic element using a glass substrate in the case of 15K ₂ O-15Nb ₂ O ₅ -70TeO ₂ as the glass composition (a) will be specifically described. Table 2 shows the crystal of an electro-optic element having an optical waveguide including a core part formed by dispersing and precipitating nanocrystals under six condensing irradiation conditions of femtosecond laser light (Examples 3 to 8) inside the glass. It is evaluation results, such as a particle size and scattered light intensity.

  Here, the grain size of the crystals precipitated in each optical waveguide in Table 2 was measured by observing the waveguide cross section with a transmission electron microscope. The scattered light intensity of the optical waveguide is such that an optical signal having a wavelength λ = 1, 550 nm is propagated through an optical waveguide having a linear core portion, and the tip that is close to the waveguide using an optical fiber as a probe is guided with an angle. The scattered light intensity distribution was measured and detected along the propagation of the guided light while keeping the distance from the waveguide constant. From the results in the table, when crystals having a particle size larger than the wavelength of propagating light were deposited (Example 6), the scattered light intensity increased. In other irradiation conditions (Examples 3 to 5, Examples 7 and 8), the scattered light intensity was generally low. Further, in Example 4, the particle diameter was 1/10 or less of the wavelength of propagating light and was in the Rayleigh scattering region, but the influence was small because the optical path length of the waveguide was short. From the above results, it is possible to extremely reduce the scattering of propagating light by making the grain size of the crystal formed inside the optical waveguide smaller than the wavelength λ = 800 nm to 1,550 nm of the light propagating through the optical waveguide. it can. Therefore, the diameter “a” of the nanocrystal 17 is preferably smaller than the wavelength λ = 800 to 1,550 nm of the optical signal propagated through the optical waveguide, and has a particle size distribution in a particle size range in which Mie scattering does not occur. Specifically, it is preferable that the following formula, 1 / 5π <q <2π, is satisfied with respect to the Mie scattering parameter q (= 2πa / λ) regarding the particle diameter a of the nanocrystal and the wavelength λ of the light propagating through the optical waveguide.

Embodiment 5 FIG.
An electro-optic element according to Embodiment 5 of the present invention will be described with reference to FIG. This electro-optical element is an application example of the electro-optical element according to the first to fourth embodiments. FIGS. 7A and 7B are schematic views showing examples of the electro-optical element according to this embodiment. FIG. 7A shows an optical circuit 30 having a Mach-Zehnder structure composed of two directional coupling type 3 dB couplers 31 a and 31 b fabricated inside the glass substrate 13. The optical circuit 30 includes directional coupling type 3 dB couplers 31 a and 31 b in which two arms 32 a and 32 b are formed close to each other at two locations. Furthermore, control electrodes 33a, 33b, 33c, and 33d for applying an electric field to a part of each of the arms 32a and 32b between the two 3 dB couplers 31a and 31b are provided. The characteristics of the optical circuit 30 were an element loss of 1.0 dB or less and a branching ratio of 3 dB ± 0.5 dB.

  FIG. 7B similarly shows an optical circuit 40 having a Mach-Zehnder structure having two Y-branch type 3 dB couplers 41 a and 41 b fabricated inside the glass substrate 13. In this optical circuit 40, one arm is branched to two arms 42a and 42b by one Y-branch type 3dB coupler 41a, and two arms 42a and 42b are one by another Y-branch type 3dB coupler 41b. Is coupled to the arm. Furthermore, control electrodes 43a, 43b, 43c, and 43d for applying an electric field to a part of each of the arms 42a and 42b between the two 3 dB couplers 41a and 41b are provided. The characteristics of this optical circuit 40 were a propagation loss of 1.0 dB or less and a branching ratio of 3 dB ± 0.5 dB.

  The optical circuit having the Mach-Zehnder structure applies a control electrical signal from the control electrodes 33a, 33b, 33c, 33d, 43a, 43b, 43c, and 43d formed on the arms 32a, 32b, 42a, and 42b. The present invention can be applied to an electro-optic element such as an optical modulator that controls a signal, an optical switch, a wavelength tunable grating using a grating, and an Add-Drop type optical filter. In the fifth embodiment, the case where the Mach-Zehnder type optical circuit is manufactured has been described. However, the optical circuit can be formed three-dimensionally in the glass substrate, and the functions of the electro-optical element are further integrated. A structure can also be made.

(A) is the schematic of the manufacturing method of the electro-optic element which concerns on Embodiment 1 of this invention, (b) is sectional drawing of a core part. 1 is a block diagram of a laser irradiation apparatus used in a method for manufacturing an electro-optic element according to Embodiment 1 of the present invention. It is a graph which shows the wavelength dependence of the transmittance | permeability of the glass material used for the electro-optic element which concerns on Embodiment 1 of this invention. It is a ternary phase diagram showing the composition range of the composition (a) of the glass material used in the method for manufacturing an electro-optic element according to Embodiment 2 of the present invention. It is a ternary phase diagram showing the composition range of the composition (b) of the glass material used in the method for manufacturing an electro-optic element according to Embodiment 3 of the present invention. (A) is the schematic which shows the optical waveguide structure of the electro-optic element which concerns on Embodiment 4 of this invention, (b) is sectional drawing of a core part. (A) is the schematic of the optical circuit provided with the directional coupling type 3 dB coupler which is an electro-optical element which concerns on Embodiment 5 of this invention, (b) is the light provided with the Y branch type 3 dB coupler. It is the schematic of a circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electro-optical element, 11 Pulse laser beam, 12 Condensing lens, 13 Glass substrate, 14 Condensing point, 15 Core part, 16 High refractive index area | region, 17 Nanocrystal, 20 Pulse laser irradiation system, 21 YAG laser, 22 Ti : Al ₂ O ₃ laser, 23 amplifier, 24 attenuator, 25 mirror, 26 movable stage, 27 computer, 28 CCD camera, 29 TV monitor, 30 directional coupler, 31a, 31b directional coupled 3 dB coupler, 32a, 32b Arm, 33a, 33b, 33c, 33d Control electrode 40 Mach-Zehnder type optical circuit, 41a, 41b Y-branch type 3 dB coupler, 42a, 42b Arm, 43a, 43b, 43c, 43d Control electrode

Claims (9)

(A) At least one component of Li ₂ O and K ₂ O, at least one component of Nb ₂ O ₅ and Ta ₂ O ₅ , and at least one of SiO ₂ , GeO ₂ , and TeO ₂ (B) at least one component of MgO, CaO, SrO, BaO, at least one component of TiO ₂ , ZrO ₂ , and SiO ₂ , GeO ₂ A step of preparing a glass body mainly comprising any one of the glass components including at least one component; and
A step of forming a core part in which fine crystals are dispersed by condensing and irradiating a pulse laser beam having a wavelength longer than the fundamental absorption edge wavelength of the glass component inside the glass body;
While condensing and irradiating the pulsed laser beam, the laser beam condensing point is scanned two-dimensionally or three-dimensionally inside the glass body, and the core portion is two-dimensionally or three-dimensionally continuous. Forming an optical waveguide. A method for manufacturing an electro-optical element. The glass component (a) contains at least one component of Li ₂ O and K ₂ O at a ratio of ₅ to 20 mol%, and contains at least one component of Nb ₂ O ₅ and Ta ₂ O _5. 2. The electro-optic element according to claim 1, wherein the electro-optic element is contained at a rate of 5 to 20 mol% and contains at least one component of SiO ₂ , GeO ₂ , and TeO ₂ at a rate of 60 to 90 mol%. Production method. The glass component (b) is, MgO, CaO, SrO, at least one component of BaO in a proportion of _25~40mol%, TiO _2, at least one component of the ZrO ₂ 10 to 20% _2. The method of manufacturing an electro-optic element according to claim 1, wherein at least one component of SiO ₂ and GeO ₂ is contained in a proportion of 45 to 60 mol%.   The method of manufacturing an electro-optical element according to claim 1, further comprising providing a pair of electrodes sandwiching a part of the core portion. An electro-optic element manufactured by the manufacturing method according to any one of claims 1 to 4,
The Mie scattering parameter q (= 2πa / λ) relating to the particle diameter a of the microcrystal and the wavelength λ of light propagating through the optical waveguide is expressed by the following equation:
1 / 5π <q <2π
An electro-optic element characterized by satisfying (A) At least one component of Li ₂ O and K ₂ O, at least one component of Nb ₂ O ₅ and Ta ₂ O ₅ , and at least one of SiO ₂ , GeO ₂ , and TeO ₂ (B) at least one component of MgO, CaO, SrO, BaO, at least one component of TiO ₂ , ZrO ₂ , and SiO ₂ , GeO ₂ Of the glass component containing at least one component, a glass body mainly containing any one of the glass components is used as a cladding portion, and a core portion in which microcrystals are dispersed inside the glass body is two-dimensional or Comprising a three-dimensional continuous optical waveguide;
The electro-optic element, wherein a refractive index of a portion other than the microcrystal of the core portion is higher than a refractive index of the cladding portion. The Mie scattering parameter q (= 2πa / λ) related to the particle diameter a of the microcrystal and the wavelength λ of the light propagating through the optical waveguide is expressed by the following formula 1 / 5π <q <2π.
The electro-optic element according to claim 6, wherein:   The electro-optical element according to claim 6, wherein the core portion includes a pattern including at least one of a straight line, a curve, a coupler, and a Y branch.   The electro-optic element according to claim 6, further comprising a pair of electrodes that apply an electric field across a part of the core portion.

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