Ferroelectric device assembling apparatus and ferroelectric device

Abstract

The purpose of the present application is to provide: a ferroelectric device assembling apparatus that makes it possible to maintain the curing temperature of an adhesive when adhering a ferroelectric device while eliminating static; and a ferroelectric device.　A ferroelectric device assembling apparatus (400) is for assembling a ferroelectric device (20) including a ferroelectric element (304) by using a thermosetting adhesive. The ferroelectric device assembling apparatus comprises: a heating device (301) that cures the thermosetting adhesive; and a static eliminator (402) for neutralizing electrification generated due to heating performed by the heating device (301). At least one of the heating device (301) and the static eliminator (402) is configured to include a temperature maintaining mechanism for maintaining the temperature of the ferroelectric element (304) during static elimination performed by the static eliminator (402).

Description

Ferroelectric device assembly apparatus and ferroelectric device

[0001] The present disclosure relates to a ferroelectric device assembly apparatus and a ferroelectric device, and more particularly to a ferroelectric device assembly apparatus and a ferroelectric device that use a thermosetting adhesive in the assembly process.

[0002] Ferroelectric materials have spontaneous polarization, which can be reversed by an external electric field, and have a high nonlinear optical coefficient under certain conditions. Due to these properties, ferroelectric materials are used in a variety of electronic devices. Ferroelectric devices refer to electronic devices that use ferroelectric materials. Here, we will explain the assembly of ferroelectric devices using a wavelength conversion element as an example.

[0003] Optical waveguides using periodically poled lithium niobate (hereinafter referred to as PPLN) conventionally used in wavelength converters are wavelength conversion elements that can achieve high optical wavelength conversion efficiency by increasing the optical intensity by using the optical waveguide and utilizing quasi-phase matching technology. Therefore, optical waveguides using PPLN are attracting attention as devices that will play an important role in the fields of next-generation optical fiber communications and quantum computers.

[0004] Optical waveguides using PPLN are used as parametric amplifiers and pump light generators in phase-sensitive amplifiers (PSAs), which are capable of low-noise optical amplification, and have achieved high-gain, low-noise optical amplification characteristics. Furthermore, in the field of quantum computing, it has been reported that inserting a PPLN optical waveguide into a fiber ring resonator and using it as a parametric oscillator has enabled extremely high-capacity calculations at extremely high speeds compared to conventional computers. To further improve the performance of these technologies, it is important to realize wavelength conversion devices with higher wavelength conversion efficiency.

[0005] There are also several known methods for fabricating optical elements (hereinafter referred to as wavelength conversion elements) that perform wavelength conversion using quasi-phase matching technology. For example, a method is used in which a crystal (hereinafter referred to as nonlinear optical crystal) substrate that exhibits a nonlinear optical effect is periodically poled, and then a proton exchange waveguide is fabricated using the periodically poled structure. Similarly, a method is used in which a nonlinear optical crystal substrate is periodically poled, and then a ridge-type optical waveguide is fabricated using a photolithography process and a dry etching process.

[0006] Patent Document 1 discloses an example of fabricating a ridge-type optical waveguide. Patent Document 1 describes fabricating a wavelength conversion element by bonding a first substrate made of a nonlinear optical crystal having a periodically poled structure and a second substrate having a refractive index lower than that of the first substrate with an adhesive, in order to improve the light confinement effect of the ridge-type optical waveguide. Patent Document 1 also describes using the same type of nonlinear optical crystal as the first substrate as the second substrate, and applying heat to the first and second substrates for diffusion bonding, in order to avoid cracks due to deterioration of the adhesive or temperature changes.

[0007] Patent No. 3753236

[0008] Thus, the assembly process for the wavelength conversion module includes a step of bonding the wavelength conversion element to the support member with an adhesive, and further bonding the support member to the temperature control element with the adhesive. The adhesive is a thermosetting resin, and the wavelength conversion module, support member, and temperature control element are placed on a heating plate and heated to harden. At this time, the ferroelectric wavelength conversion module has pyroelectric properties, and may be damaged by charging and discharging due to temperature fluctuations. For this reason, the adhesive is hardened while being neutralized with a static eliminator. The static eliminator neutralizes static electricity by, for example, blowing air containing ions generated by causing a corona discharge in a discharge needle onto the wavelength conversion element.

[0009] However, the air blown by the static eliminator has a problem in that it cools the support member and the wavelength conversion element attached thereto, which means that the adhesive between the support member and the wavelength conversion element, or between the support member and the temperature control element, does not easily rise to its hardening temperature by the air blown, and it becomes necessary to raise the set temperature of the heating plate above the hardening temperature of the adhesive.

[0010] The present disclosure has been made in consideration of these points, and aims to provide a ferroelectric device assembly apparatus and a ferroelectric device that are capable of maintaining the curing temperature of an adhesive when bonding a ferroelectric device while discharging the device.

[0011] In order to achieve the above object, one form of the ferroelectric device assembly apparatus disclosed herein is a ferroelectric device assembly apparatus that assembles a ferroelectric device including a ferroelectric element formed from a ferroelectric material using a thermosetting adhesive, and is equipped with a heating device that hardens the thermosetting adhesive and a static eliminator that neutralizes electrostatic charges generated by heating by the heating device, and at least one of the heating device and the static eliminator includes a temperature maintenance mechanism that maintains the temperature of the ferroelectric element during static elimination by the static eliminator.

[0012] Furthermore, a ferroelectric device according to one embodiment of the present disclosure is a ferroelectric device including a ferroelectric element, which is assembled by a ferroelectric device assembly apparatus including a heating device that hardens a thermosetting adhesive that bonds a ferroelectric element, and a static eliminator that neutralizes the charge of the ferroelectric element heated by the heating device, wherein the static eliminator is an ultraviolet irradiation type or a soft X-ray irradiation type static eliminator, and the ferroelectric element is provided with a shielding film between the adhesive and the static eliminator that blocks ultraviolet light or soft X-rays.

[0013] According to the above-described embodiment, it is possible to provide a ferroelectric device assembling apparatus and a ferroelectric device that can bond a ferroelectric device while removing static electricity, prevent damage to the temperature control element, and do not increase the assembly time.

[0014] FIG. 1 is a perspective view for explaining the basic configuration of a wavelength conversion module. FIG. 2 is a schematic view for explaining an assembly device for a wavelength conversion module of a first embodiment. FIG. 3 is a schematic view for explaining an assembly device for a wavelength conversion module of a second embodiment. FIG. 4 is a schematic view for explaining an assembly device for a wavelength conversion module of a third embodiment. FIG. 5 is a schematic view for explaining an assembly device for a wavelength conversion module of a fourth embodiment. FIG. 6 is a schematic view for explaining an assembly device for a wavelength conversion module as a comparative example.

[0015] Hereinafter, first to fourth embodiments of the present disclosure will be described with reference to the drawings. The drawings used in the present embodiments are for explaining the configuration, arrangement of each part, action, effect, function, and technical concept of the present disclosure, and do not limit the size, aspect ratio, or specific shape of the configuration shown in the present embodiments, but illustrate the present embodiments.

[0016] 1 is a perspective view of a wavelength conversion module 20 (ferroelectric device) for explaining the basic configuration of the wavelength conversion module 20. The wavelength conversion module 20 includes a wavelength conversion device 10 and a metal housing 303 that houses the wavelength conversion device 10. The wavelength conversion device 10 includes a wavelength conversion element 304 (ferroelectric element), a multiplexer 14, a demultiplexer 15, a support member 305, and a temperature control element 306. The wavelength conversion element 304 generates difference frequency light 1c between signal light 1a and control light 1b and performs wavelength conversion using quasi-phase matching (hereinafter referred to as QPM) technology.

[0017] The core material of the waveguide of the wavelength conversion element 304 is LiNbO3 (lithium niobate), KNbO3 (potassium niobate), LiTaO3 (lithium tantalate), LiNb(x)Ta( 1-x )O3 (0≦x≦1) (non-stoichiometric lithium tantalate), or KTiOPO4 (potassium titanyl phosphate), and further containing at least one additive selected from Mg (magnesium), Zn (zinc), Sc (scandium), or In (indium),

[0018] 1, in a wavelength conversion device 10, a signal light 1a having a low optical intensity and a control light 1b having a high optical intensity are input to a multiplexer 14 and multiplexed. The signal light 1a multiplexed with the control light 1b travels toward a wavelength conversion element 304 and enters one end of an optical waveguide core 11 having a periodically poled structure disposed on a substrate 12. As the signal light 1a passes through the optical waveguide core 11, it is converted by a nonlinear optical effect into difference frequency light 1c having a wavelength different from that of the signal light 1a, and is output from the other end of the optical waveguide core 11 together with the control light 1b. The difference frequency light 1c and control light 1b output from the optical waveguide core 11 enter a demultiplexer 15 and are separated from each other.

[0019] The metal housing 303 houses the wavelength conversion device 10 and prevents its characteristics from deteriorating due to changes in the operating environment during practical use. The metal housing 303 has an input port 200 and an output port 201 that allow light to be input and output, and houses the wavelength conversion element 304 along with the multiplexer 14 and demultiplexer 15. In particular, the wavelength conversion efficiency of the wavelength conversion element 304 is temperature-dependent, and controlling the temperature of the wavelength conversion element 304 is necessary to maximize the wavelength conversion efficiency. Therefore, the wavelength conversion device 10 further houses a temperature control element 306 inside the metal housing 303. A support member 305 is provided between the wavelength conversion element 304 and the temperature control element 306. The support member 305 is a metal member that uniformly controls the temperature of the entire wavelength conversion element 304, including the optical waveguide core 11 and the substrate 12. The temperature control element 306 is interposed between the support member 305 and the bottom surface of the metal housing 303.

[0020] (Wavelength Conversion Module Assembly Apparatus) FIG. 2 is a schematic diagram for explaining an assembly apparatus 400 for the wavelength conversion module 20 of the first embodiment, showing a side view of the assembly apparatus 400. Note that the multiplexer 14 and demultiplexer 15 shown in FIG. 1 are not shown in FIG. 2 . The assembly apparatus 400 includes a heating plate 301 for heating a wavelength conversion element 304, a support member 305, and a temperature control element 306 housed in a metal housing 303, and a static eliminator 402 for eliminating static electricity from the wavelength conversion element 304. In the assembly apparatus 400, the metal housing 303 is bonded to the temperature control element 306. Furthermore, the wavelength conversion element 304 is bonded to the support member 305. Thereafter, the support member 305 and the temperature control element 306 are bonded with an adhesive, thereby directly or indirectly bonding the wavelength conversion element 304, the support member 305, and the temperature control element 306 to the metal housing 303. In the first embodiment, the static eliminator 402 in this configuration is an ultraviolet ray irradiating or soft X-ray irradiating static eliminator, and functions as a temperature maintaining mechanism for maintaining the temperature of the wavelength conversion element 304 .

[0021] In the first embodiment, the wavelength conversion module in the metal housing 303 is heated by the heating plate 301 to harden the adhesive. In the first embodiment, the heating is performed while the wavelength conversion element 304 is irradiated with ultraviolet light (deep UV) or soft X-rays by the static eliminator 402. In this way, the first embodiment eliminates pyroelectricity of the wavelength conversion element 304 that occurs when the wavelength conversion element 304 is heated.

[0022] In the first embodiment, when the static eliminator 402 is a deep UV irradiation type static eliminator, the light 407 emitted from the static eliminator 402 is deep UV light with a wavelength of 200 nm or less. Electrons are emitted from the surface of the wavelength conversion element 304 irradiated with deep UV light, and the emitted electrons collide with oxygen or nitrogen in the environment to generate ions. The emitted electrons and generated ions neutralize static electricity and eliminate the pyroelectric wavelength conversion element 304. A deep UV irradiation type static eliminator can eliminate static electricity from the wavelength conversion element 304 by light irradiation without using air flow, thereby preventing a decrease in the temperatures of the wavelength conversion element 304 and the heating plate 301 and maintaining the heating temperature.

[0023] The static eliminator 402 may also be a soft X-ray irradiation type static eliminator. When the static eliminator 402 is a soft X-ray irradiation type static eliminator, the light 407 emitted from the static eliminator 402 is X-rays with a wavelength ranging from approximately 0.1 nm to 10 nm. When soft X-rays are irradiated into the environment, oxygen and nitrogen in the air are ionized, generating positive ions and free electrons, which neutralize the charge accumulated in the wavelength conversion element 304. The soft X-rays also act on the surface of the wavelength conversion element 304 and can directly discharge the charge accumulated on the surface. Like deep UV light, soft X-ray irradiation can eliminate static on the wavelength conversion element 304 without using air flow, thereby preventing a decrease in the temperatures of the wavelength conversion element 304 and the heating plate 301 and maintaining the heating temperature.

[0024] However, when the static eliminator 402 is a soft X-ray irradiating static eliminator, the assembling device 400 preferably includes a soft X-ray shielding plate 401 that shields the static eliminator 402 from the wavelength conversion module.

[0025] As described above, in the first embodiment, air is not blown directly onto the wavelength conversion element 304 or the heating plate 301, so the temperatures of the wavelength conversion element 304 and the heating plate 301 are not lowered. According to the first embodiment, the heating plate 301 does not reach a temperature higher than that required for thermal curing of the adhesive, and the temperature control element 306 is prevented from being exposed to a temperature high enough to damage it. Furthermore, in the first embodiment, the temperatures of the wavelength conversion element 304 and the heating plate 301 can be maintained at a temperature at which the temperature control element 306 is not damaged, so the time required for curing the adhesive is not prolonged. Therefore, the first embodiment can provide a wavelength conversion module assembly device that bonds wavelength conversion modules while removing static electricity, prevents damage to the temperature control element, and does not prolong assembly time.

[0026] [Second embodiment] Fig. 3 is a schematic diagram for explaining an assembly apparatus 500 for an assembly apparatus for a wavelength conversion module 20 according to a second embodiment, showing a side view of the assembly apparatus 500. In Fig. 3, components similar to those shown in Fig. 2 are denoted by the same reference numerals, and some of the descriptions thereof may be omitted. In the second embodiment, too, the wavelength conversion element 304 bonded to the support member 305 is bonded to the metal housing 303 via the temperature control element 306 with a thermosetting adhesive. The static eliminator 302 of the assembly apparatus is a corona discharge type static eliminator that emits air 307 containing a corona toward the wavelength conversion element 304.

[0027] The assembly apparatus 500 of the second embodiment includes a heating furnace 501 instead of the heating plate 301 shown in FIG. 2 . In the second embodiment, the heating furnace 501 functions as a temperature maintaining mechanism. The heating furnace 501 heats the entire wavelength conversion element 304, so that the temperature distribution of the wavelength conversion element 304 can be made uniform without relying on air blowing from the corona discharge type static eliminator 302. Even if the temperature of the wavelength conversion element 304 drops due to air blowing, the heating temperature of the heating furnace 501 can be increased to maintain the temperature of the wavelength conversion element 304. Furthermore, the temperature control element 306 can be positioned at a sufficient distance from the heating furnace 501, so that the temperature control element 306 can be prevented from being damaged by exposure to high temperatures.

[0028] [Third Embodiment] Figure 4 is a schematic diagram for explaining an assembly apparatus 600 for the wavelength conversion module 20 according to a third embodiment, showing a side view of the assembly apparatus 600. In Figure 4, components similar to those shown in Figure 2 are designated by the same reference numerals, and some of their descriptions may be omitted. In the third embodiment, the wavelength conversion element 304 bonded to the support member 305 is bonded to the metal housing 303 via the temperature control element 306 with a thermosetting adhesive. The static eliminator 402 is a deep UV irradiation type or soft X-ray irradiation type static eliminator. In the third embodiment, as in the first embodiment, the deep UV irradiation type or soft X-ray irradiation type static eliminator 402 functions as a temperature maintenance mechanism.

[0029] In the third embodiment, attention is focused on the fact that high-energy light 407 such as deep UV light or soft X-rays passes through the transparent wavelength conversion element 304 and deteriorates the adhesive (not shown) between the support member 305 and the wavelength conversion element 304. The inventors of the present disclosure have found that, in order to prevent deterioration of the adhesive, the wavelength conversion element 304 is neutralized by irradiating it with deep UV light or soft X-rays at the minimum necessary irradiation dose.

[0030] 4 , the third embodiment includes an electrometer 603 which is a pyroelectric monitor that monitors the amount of charge caused by pyroelectricity of the wavelength conversion element 304, and a static eliminator control device 604 which is a static elimination control unit that controls the timing of static elimination by the static eliminator 402 based on the amount of charge observed by the electrometer 603. For example, when the amount of charge of the wavelength conversion element 304 reaches a predetermined threshold, the static eliminator control device 604 may send a control signal to the static eliminator control device 604 to drive the static eliminator 402.

[0031] The electrometer 603 can be realized by an instrument such as an electrometer, an electrostatic voltmeter, a field meter, a Hall effect measurement system, a charge plate monitor (CPM), or a Kelvin probe.

[0032] According to the third embodiment, the inventors have confirmed that the wavelength conversion module assembled by the assembly device 600 has high reliability, with the wavelength conversion element 304 not coming off the support member 305.

[0033] [Fourth Embodiment] (Wavelength Conversion Module) Fig. 5 is a diagram for explaining a wavelength conversion element 704 according to a fourth embodiment, showing a side view of an assembly apparatus 700. In Fig. 4, components similar to those shown in Fig. 2 are denoted by the same reference numerals, and some of the descriptions thereof may be omitted. In the fourth embodiment, the static eliminator 402 is a deep UV irradiation type or soft X-ray irradiation type static eliminator. In the assembly apparatus 700 according to the fourth embodiment, the deep UV irradiation type or soft X-ray irradiation type static eliminator 402 functions as a temperature maintenance mechanism, as in the first embodiment.

[0034] The wavelength conversion element 704 includes a shielding film 701 on the back surface of the wavelength conversion element 304 (the surface on which the adhesive is applied) that blocks ultraviolet light (deep UV) or soft X-rays. The shielding film 701 may be a metal plating film containing at least one of lead, copper, iron, and aluminum. Here, the term "containing" refers to an alloy containing at least two of lead, copper, iron, and aluminum, or an alloy of at least one of lead, copper, iron, and aluminum with another material. Note that the shielding film 701 is not limited to being provided on the back surface of the wavelength conversion element 704, but may be located in a position that prevents the adhesive from being irradiated with deep UV light or soft X-rays. Therefore, the shielding film 701 may be located between the static eliminator 402 and the adhesive.

[0035] The inventors have confirmed that the wavelength conversion module assembled by the assembly apparatus 600 has high reliability, with the wavelength conversion element 704 not coming off the support member 305 .

[0036] As described above, the first to fourth embodiments have been described using a wavelength conversion module as an example of a ferroelectric device including a ferroelectric element. However, the ferroelectric element in the first to fourth embodiments is not limited to a wavelength conversion element, and any ferroelectric device formed by bonding another component to the ferroelectric element using a thermosetting resin as an adhesive may be used. The ferroelectric element may be made of, for example, barium titanate (BaTiO) or lead zirconium oxide titanium (PZT: lead zirconate titanate). Examples of other ferroelectric elements include ferroelectric memories, ferroelectric capacitors, piezoelectric elements, and ferroelectric tunnel junctions. A ferroelectric device may be formed by assembling such a ferroelectric element together with other components necessary for achieving its function.

[0037] [Comparative Example] Next, the results of comparing the first to fourth embodiments described above with a comparative example will be described. FIG. 6 is a diagram illustrating an assembly apparatus 300 for a wavelength conversion module of the comparative example. In the assembly apparatus 300, the static eliminator 302 is a corona discharge type static eliminator. The corona discharge type static eliminator 302 blows air containing ions onto the wavelength conversion element 304. This blown air cools the wavelength conversion element 304 and the support member 305. Therefore, the configuration of the comparative example has a problem in that the adhesive that fixes the support member 305 and the temperature control element 306 does not sufficiently harden even when the temperature of the heating plate 301 is set to the hardening temperature of the adhesive.

[0038] In a wavelength conversion module assembled using the assembly device 300 of the comparative example, the temperature of the temperature control element 306 close to the heating plate 301 may exceed its heat resistance temperature, resulting in damage. Furthermore, in a wavelength conversion module assembled using the assembly device 300, if the adhesive is cured at a low temperature, the curing time becomes long, resulting in a long module assembly time. According to the first to fourth embodiments of the present disclosure, the problems of the assembly device 300 of the comparative example can be solved, damage to the wavelength modulation element can be prevented, and the yield of wavelength conversion modules can be improved. Furthermore, an increase in the assembly time can be avoided, and a decrease in assembly efficiency can also be avoided.

[0039] REFERENCE SIGNS LIST 1a Signal light 1b Control light 1c Difference frequency light 10 Wavelength conversion device 11 Optical waveguide core 12 Substrate 14 Multiplexer 15 Demultiplexer 20 Wavelength conversion module 29 Metal housing 200 Input port 201 Output port 300, 400, 500, 600, 700 Assembly device 301 Heating plate 302, 402 Neutralizer 303 Metal housing 304, 704 Wavelength conversion element 305 Support member 306 Temperature control element 307 Air 401 X-ray shielding plate 407 Light 501 Heating furnace 603 Electrometer 604 Neutralizer control device 701 Shielding film

Claims

1. A ferroelectric device assembly apparatus that uses a thermosetting adhesive to assemble a ferroelectric device including a ferroelectric element formed from a ferroelectric material, the ferroelectric device assembly apparatus comprising: a heating device that hardens the thermosetting adhesive; and a static eliminator that neutralizes charge generated by heating by the heating device, wherein at least one of the heating device and the static eliminator includes a temperature maintaining mechanism that maintains the temperature of the ferroelectric element during static elimination by the static eliminator.

2. A ferroelectric device assembly apparatus according to claim 1, wherein said temperature maintaining mechanism is an ultraviolet ray irradiating or soft X-ray irradiating static eliminator.

3. A ferroelectric device assembly apparatus according to claim 1, wherein said temperature maintaining mechanism includes a furnace that houses said ferroelectric device.

4. The ferroelectric device assembly apparatus according to claim 3, wherein the static eliminator is of a corona discharge type.

5. A ferroelectric device assembly apparatus as described in claim 1, further comprising: a charge monitor that monitors the amount of charge on the ferroelectric element; and a charge elimination control unit that controls the timing of charge elimination by the charge eliminator based on the amount of charge observed by the charge monitor.

6. A ferroelectric device including a ferroelectric element, assembled by a ferroelectric device assembling apparatus having a heating device for hardening a thermosetting adhesive that bonds a ferroelectric element, and a static eliminator for neutralizing the charge of the ferroelectric element heated by the heating device, wherein the static eliminator is an ultraviolet ray irradiation type or a soft X-ray irradiation type static eliminator, and the ferroelectric element is provided with a shielding film between the adhesive and the static eliminator that blocks ultraviolet light or soft X-rays.

7. The ferroelectric device according to claim 6, wherein the shielding film contains at least one of lead, copper, iron, and aluminum.

8. The ferroelectric device according to claim 6, wherein the ferroelectric device is a wavelength conversion module that includes a wavelength conversion element and generates light having a wavelength different from that of the input signal light when the signal light is input.

9. The core of the wavelength conversion element is made of LiNbO3 (lithium niobate), KNbO3 (potassium niobate), LiTaO3 (lithium tantalate), LiNb(x)Ta( 1-x 10. The ferroelectric device of claim 8, wherein the material contains at least one of: Mg (magnesium), Zn (zinc), Sc (scandium), or In (indium) as an additive.

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