WO2020209049A1 - Dispositif optique et son procédé de production - Google Patents

Dispositif optique et son procédé de production Download PDF

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WO2020209049A1
WO2020209049A1 PCT/JP2020/013065 JP2020013065W WO2020209049A1 WO 2020209049 A1 WO2020209049 A1 WO 2020209049A1 JP 2020013065 W JP2020013065 W JP 2020013065W WO 2020209049 A1 WO2020209049 A1 WO 2020209049A1
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optical
layer
electro
material layer
electrode
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PCT/JP2020/013065
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English (en)
Japanese (ja)
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尚徳 増子
宏幸 高木
平澤　拓
寺部　一弥
敬志 土屋
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パナソニック株式会社
国立研究開発法人物質・材料研究機構
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Publication of WO2020209049A1 publication Critical patent/WO2020209049A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/03—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
    • G02F1/035—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect in an optical waveguide structure

Definitions

  • This disclosure relates to an optical device and a method for manufacturing the same.
  • Patent Documents 1 and 2 and Non-Patent Documents 1 to 4 have been proposed (for example, Patent Documents 1 and 2 and Non-Patent Documents 1 to 4).
  • the index of refraction can be varied by various optical effects. For example, by changing the refractive index of the optical waveguide, the phase of the light propagating in the optical waveguide can be modulated.
  • the present disclosure provides an optical device capable of realizing a large refractive index modulation using an electro-optical effect.
  • FIG. 1A is a side view schematically showing the optical phase modulator in the exemplary embodiment of the present disclosure as viewed from the X direction.
  • FIG. 1B is a side view of the optical phase modulator in the exemplary embodiment of the present disclosure schematically shown from the Y direction.
  • FIG. 2A is a diagram schematically showing charge distribution in the pair of electrodes, the electro-optical material layer, and the electrolyte layer when a voltage is applied to the pair of electrodes.
  • FIG. 2B is a diagram schematically showing the relationship between the electric potential and the distance between the pair of electrodes along the Z direction from the upper surface of the first electrode.
  • FIG. 2C is a diagram schematically showing the relationship between the distance between the pair of electrodes from the upper surface of the first electrode along the Z direction and the strength of the electric field.
  • FIG. 4 is a flowchart showing a manufacturing process of the optical phase modulator.
  • FIG. 5 is a plan view schematically showing an example of a Mach-Zehnder type optical switching device.
  • FIG. 6A is a diagram schematically showing a first example of an optical phased array.
  • FIG. 6B is a diagram schematically showing a second example of an optical phased array.
  • Non-Patent Document 1 discloses an optical phase modulator using a stress-optic effect in which the refractive index changes with stress.
  • the piezoelectric body is deformed by applying a voltage to the piezoelectric body laminated on the optical waveguide. Due to the deformation of the piezoelectric body, stress is applied to the optical waveguide, and the refractive index of the optical waveguide changes. Due to the change in refractive index, the phase of light propagating in the optical waveguide is modulated.
  • the amount of change in the refractive index of the optical waveguide due to the piezoelectric material is small, for example, on the order of about 10-6 . Therefore, the phase of light cannot be significantly modulated unless the optical waveguide is lengthened. Lengthening the optical waveguide leads to an increase in the size of the optical phase modulator.
  • Non-Patent Documents 2 and 3 disclose an optical phase modulator using a thermo-optic effect in which the refractive index changes with heat.
  • the amount of change in refractive index due to thermo-optic effect is large, for example, 10 -2 order. Therefore, even when the optical phase modulator is small, the phase of light can be largely modulated.
  • the modulation speed of the refractive index due to the thermo-optical effect is low, and it is not possible to realize high-speed modulation exceeding, for example, several hundred kHz.
  • Non-Patent Document 4 discloses an optical phase modulator using an electro-optic effect in which the refractive index changes by applying an electric field.
  • electro-optical effects the Pockels effect and the Kerr effect are known. When no electric field is applied, the amount of change in the refractive index is zero.
  • the amount of change in the refractive index is determined by the product of the electro-optical constant inherent in the electro-optical material and the strength of the applied electric field.
  • the Kerr effect the amount of change in the refractive index is determined by the product of the electro-optic constant and the square of the strength of the applied electric field.
  • the change in the refractive index modulates the phase of the light propagating through the electro-optical material.
  • the modulation speed of the refractive index due to the electro-optical effect is high, and for example, modulation of several tens of MHz or more can be realized.
  • the stronger the applied electric field the greater the amount of change in the refractive index.
  • the strength of the applied electric field is limited to a strength lower than the dielectric breakdown electric field strength of the electro-optical material. Therefore, the amount of change in the refractive index is on the order of about 10-4 and does not become so large.
  • Patent Document 1 discloses an optical modulation device using an electro-optical effect.
  • the electro-optical material layer is in contact with the electrolyte layer.
  • an external voltage is applied to the electro-optical material layer and the electrolyte layer, a strong electric field is generated near the interface between the electro-optic material layer and the electrolyte layer.
  • the strength of the electric field exceeds the dielectric breakdown electric field strength of the electro-optical material layer.
  • the state in which light is transmitted through the electro-optical material layer and the state in which light is reflected by the electro-optical material layer are switched by changing the refractive index of the electro-optical material layer.
  • This optical modulation device is used as an optical switching element. It is not envisioned that the electro-optical material layer or electrolyte layer will be used as an optical waveguide. Furthermore, no specific material for the electrolyte layer is mentioned.
  • Patent Document 2 discloses an optical switch using an electrochromic effect.
  • the optical waveguide is surrounded by an electrochromic material layer.
  • the electrochromic material layer is in contact with the electrolyte layer.
  • a voltage is applied to the electrochromic material layer and the electrolyte layer.
  • a redox reaction occurs in the electrochromic material layer, and the electronic structure of the electrochromic material layer changes.
  • the refractive index of the electrochromic material layer changes due to the change in the electronic structure.
  • the oxidation reaction or reduction reaction occurs reversibly depending on the polarity of the voltage applied from the outside. The oxidized or reduced state is maintained even when no voltage is applied.
  • the amount of change in the refractive index is on the order of about 10-3 .
  • the modulation rate is very slow, at most a few Hz.
  • the electrolyte layer is provided to oxidize or reduce the electrochromic material layer.
  • the present inventor has come up with the optical device described in the following item, which can realize a large refractive index modulation using an electro-optical effect by using an electrolyte layer formed of a specific material.
  • the refractive index of the electro-optical material layer can be greatly modulated by a strong electric field generated near the interface between the electro-optical material layer and the electrolyte layer.
  • the optical device according to the second item further includes a control circuit for controlling the voltage in the optical device according to the first item.
  • the control circuit modulates the phase of light propagating through the electro-optical material layer by controlling the voltage to change the refractive index of the electro-optical material layer.
  • the phase of light propagating in the electro-optical material layer can be modulated by a control circuit.
  • the optical device according to the third item is 1 ⁇ x ⁇ 4 in the optical device according to the first or second item.
  • the electrolyte layer has Li ion conductivity effective for generating a strong electric field near the interface between the electro-optical material layer and the electrolyte layer.
  • the electrolyte layer has the above-mentioned effective Li-ion conductivity and has a flat surface.
  • the optical device according to the fifth item is the optical device according to any one of the first to fourth items, in which the electrolyte layer has an amorphous structure.
  • the flatness of the interface between the electro-optical material layer and the electrolyte layer can be improved.
  • the optical device according to the sixth item is the optical device according to any one of the first to fifth items, in which the electro-optical material layer is formed of potassium niobate tantalate.
  • the electro-optical material layer exhibits a high electro-optical effect near room temperature.
  • the method for manufacturing an optical device includes a step of forming a first electrode, a step of forming an electro-optical material layer on the first electrode, and Li x on the electro-optical material layer.
  • a step of forming an electrolyte layer formed from a substance represented by Zr z Si 1-z Oy (x> 0, y x / 2 + 2, 0 ⁇ z ⁇ 1) and a second step on the electrolyte layer. It includes a step of forming an electrode.
  • the step of forming the electrolyte layer is such that the electrolyte layer is charged with electricity at room temperature by a pulse laser deposition method. Includes the step of depositing on the optical material layer.
  • the electrolyte layer can be easily deposited on the electro-optical material layer. Further, the flatness of the interface between the electro-optical material layer and the electrolyte layer can be improved.
  • all or part of a circuit, unit, device, member or part, or all or part of a functional block in a block diagram is, for example, a semiconductor device, a semiconductor integrated circuit (IC), or an LSI (range scale integration). ) Can be performed by one or more electronic circuits.
  • the LSI or IC may be integrated on one chip, or may be configured by combining a plurality of chips.
  • functional blocks other than the storage element may be integrated on one chip.
  • it is called an LSI or an IC, but the name changes depending on the degree of integration, and it may be called a system LSI, a VLSI (very large scale integration), or a ULSI (ultra large scale integration).
  • a Field Programmable Gate Array (FPGA) programmed after the LSI is manufactured, or a reconfigurable logistic device capable of reconfiguring the junction relationship inside the LSI or setting up the circuit partition inside the LSI can also be used for the same purpose.
  • FPGA Field Programmable Gate Array
  • circuits, units, devices, members or parts can be performed by software processing.
  • the software is recorded on a non-temporary recording medium such as one or more ROMs, optical discs, hard disk drives, etc., and when the software is executed by a processor, the functions identified by the software It is executed by a processor and peripheral devices.
  • the system or device may include one or more non-temporary recording media on which the software is recorded, a processor, and the required hardware devices, such as an interface.
  • light refers to electromagnetic waves including not only visible light (wavelength of about 400 nm to about 700 nm) but also ultraviolet rays (wavelength of about 10 nm to about 400 nm) and infrared rays (wavelength of about 700 nm to about 1 mm). means.
  • an optical phase modulator will be described as an example of an optical device capable of realizing a large refractive index modulation using an electro-optical effect.
  • FIGS. 1A and 1B are diagrams schematically showing the optical phase modulator 100 in the exemplary embodiment of the present disclosure.
  • the coordinate system including the X-axis, the Y-axis, and the Z-axis which are orthogonal to each other shown in FIGS. 1A and 1B is used.
  • the + Z direction is referred to as "upward”
  • the -Z direction is referred to as "downward”.
  • the dimension in the X direction is referred to as "length”
  • the dimension in the Y direction is referred to as "width”
  • the dimension in the Z direction is referred to as "thickness”.
  • FIG. 1A schematically shows the structure of the optical phase modulator 100 as viewed from the + X direction.
  • FIG. 1B schematically shows the structure of the optical phase modulator 100 as viewed from the ⁇ Y direction.
  • the optical phase modulator 100 includes a substrate 10, a first electrode 20a and a second electrode 20b, an electro-optical material layer 30, an electrolyte layer 40, and a control circuit 50.
  • the substrate 10 has a main surface 10s parallel to the XY plane.
  • the first electrode 20a is located on the main surface 10s of the substrate 10.
  • the electro-optical material layer 30 is located on the first electrode 20a.
  • the electrolyte layer 40 is located on the electro-optical material layer 30.
  • the second electrode 20b is located on the electrolyte layer 40. That is, the substrate 10, the first electrode 20a, the electro-optical material layer 30, the electrolyte layer 40, and the second electrode 20b are laminated in this order.
  • the first electrode 20a and the second electrode 20b may be referred to as a "pair of electrodes 20".
  • the substrate 10, the first electrode 20a and the second electrode 20b, the electro-optical material layer 30, and the electrolyte layer 40 have a structure extending at least in the X direction.
  • the substrate 10 supports a pair of electrodes 20, an electro-optical material layer 30, and an electrolyte layer 40.
  • the substrate 10 can be formed from, for example, at least one selected from the group consisting of magnesium oxide (MgO), spinel (MgAl 2 O 4 ), and ⁇ -alumina ( ⁇ -Al 2 O 3 ).
  • the substrate 10 may be omitted if it is unnecessary.
  • the pair of electrodes 20 directly or indirectly sandwich the electro-optical material layer 30 and the electrolyte layer 40 in the Z direction.
  • “Directly sandwiching” means that the first electrode 20a and the electro-optical material layer 30 are in contact with each other, and the second electrode 20b and the electrolyte layer 40 are in contact with each other.
  • “Indirectly sandwiching” means that another member is located between the first electrode 20a and the electro-optical material layer 30 and / or between the second electrode 20b and the electrolyte layer 40. To do.
  • the other member may be a dielectric member, a gas such as air, or a liquid such as water.
  • the X direction may be referred to as a "first direction”.
  • Each of the pair of electrodes 20 has a plane parallel to the XY plane.
  • a DC voltage is applied to the pair of electrodes 20.
  • the DC voltage may be a DC pulse voltage.
  • the time average of the voltage value of the DC pulse voltage may be treated as the value of the DC voltage. By changing the duty ratio of the DC pulse voltage, the time average value of the voltage can be adjusted.
  • Each of the pair of electrodes 20 may be a metal electrode or a transparent electrode.
  • the thickness of the first electrode 20a can be, for example, 100 nm or more and 200 nm or less.
  • the second electrode 20b was formed from, for example, at least one selected from the group consisting of SnO 2- doped In 2 O 3 (ITO), F-doped SnO 2 (FTO), and Sb-doped TiO 2 (ATO). It can be a transparent electrode.
  • the thickness of the second electrode 20b can be, for example, 100 nm or more and 200 nm or less.
  • the electro-optical material layer 30 functions as an optical waveguide layer that propagates light 32 along the X direction by total reflection.
  • the ellipse shown in FIG. 1A indicates that the intensity of the light 32 is high within the ellipse.
  • the refractive index of the electro-optical material layer 30 is higher than the refractive index of the medium around the optical phase modulator 100 and the refractive index of each of the substrate 10 and the electrolyte layer 40.
  • the first electrode 20a is a transparent electrode
  • the refractive index of the electro-optical material layer 30 is higher than the refractive index of the first electrode 20a.
  • the refractive index of the first electrode 20a is higher than that of the substrate 10.
  • the substrate 10 does not function as an optical waveguide layer.
  • the loss of light 32 can be ignored.
  • the refractive index of the electro-optical material layer 30 changes according to the strength of the applied electric field due to the Pockels effect or the Kerr effect. The stronger the applied electric field, the greater the amount of change in the refractive index of the electro-optical material layer 30. When no electric field is applied, the amount of change becomes zero.
  • the apparatus of this embodiment is different from the apparatus utilizing the electrochromic effect described above.
  • the refractive index changes from the initial value only when a voltage is applied, it is easy to turn on and off the optical phase modulator 100.
  • the phase of the light 32 propagating in the electro-optical material layer 30 can be modulated by the change in the refractive index of the electro-optical material layer 30 due to the application of an electric field. Due to the fast response of the electro-optic effect, the phase modulation rate can be high, for example, several tens of MHz or higher.
  • the wavelength of the light 32 in the air is ⁇
  • the refractive index of the electro-optical material layer 30 when no electric field is applied is n 0
  • the amount of change in the refractive index of the electro-optical material layer 30 due to the application of an electric field is ⁇ n
  • electricity is applied.
  • the length of the optical material layer 30 is L
  • each of the first electrode 20a and the second electrode 20b may be a transparent electrode or a metal electrode.
  • the loss of light 32 can be ignored. If the thickness of the electrolyte layer 40 is sufficiently large, the evanescent light of the light 32 does not reach the second electrode 20b. Therefore, when the thickness of the electrolyte layer 40 is sufficiently large, the loss of light 32 can be ignored even if the second electrode 20b is a metal electrode.
  • the electro-optical material layer 30 may be formed from a bulk or a thin film.
  • the thickness of the thin film can be, for example, 0.1 ⁇ m or more and 10 ⁇ m or less.
  • the cost of thin films is lower than the cost of bulk.
  • the electro-optical material layer 30 is composed of, for example, lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), potassium dihydrogen phosphate (KH 2 PO 4 ), and ammonium dihydrogen phosphate (KH 2 PO 4 ). It can be formed from at least one selected from the group consisting of NH 4 H 2 PO 4 ).
  • the electro-optical material layer 30 is, for example, for example, barium titanate (BaTiO 3), strontium titanate (SrTiO 3), potassium titanate (KTaO 3), zirconate lead lanthanum titanate ((Pb 1-x La x) (Zr y Ti 1-y) 1-x / 4 O 3: PLZT), and potassium tantalate niobate (KTa 1-x Nb x O 3: is selected from the group consisting of KTN) It can be formed from at least one. Among these, KTN exhibits a high electro-optical effect near room temperature by setting the composition ratio of Nb and Ta to an appropriate ratio.
  • KTN is transparent at a wavelength of 1550 nm for light used in optical communication. Therefore, application of KTN to optical devices is expected.
  • the electro-optical material layer 30 may be formed of a material exhibiting other electro-optical effects such as the electrochromic effect.
  • the electrolyte layer 40 is in contact with at least a part of the electro-optical material layer 30.
  • the electrolyte layer 40 has a structure extending at least in the X direction.
  • the electrolyte layer 40 is formed of an ionic conductor. In an ionic conductor, at least one of a positive ion and a negative ion moves by applying an electric field from the outside.
  • the electrolyte layer 40 is typically a solid electrolyte layer.
  • the solid electrolyte layer depending on its composition, may have a 10 -2 S / cm order of the order of the ion conductivity of 10 -8 S / cm. The material of the electrolyte layer 40 will be described later.
  • the control circuit 50 applies a DC voltage to the pair of electrodes 20.
  • the broken line with an arrow shown in FIG. 1A indicates that a signal is input from the control circuit 50 to the pair of electrodes 20.
  • the control circuit 50 modulates the phase of the light 32 propagating in the electro-optical material layer 30 by applying a voltage to the pair of electrodes 20 to change the refractive index of the electro-optical material layer 30.
  • the control circuit 50 includes a programmable logic device (PLD) such as a digital signal processor (DSP) or a field programmable gate array (FPGA), or a central processing unit (CPU) or an image processing arithmetic processor (GPU) and a computer program. It may be realized by the combination of. In the following figure, the control circuit 50 may be omitted.
  • FIG. 2A is a diagram schematically showing the charge distribution in the pair of electrodes 20, the electro-optical material layer 30, and the electrolyte layer 40 when a voltage is applied to the pair of electrodes 20.
  • the upper part of FIG. 2A represents the optical phase modulator 100 shown in FIG.
  • the lower figure of FIG. 2A schematically shows an example of charge distribution in the region surrounded by the thick line shown in the upper figure.
  • the potential of the second electrode 20b is higher than the potential of the first electrode 20a, a downward electric field is generated between the pair of electrodes 20.
  • FIG. 2A shows the negative charge ( ⁇ ) in the first electrode 20a, the positive charge (+) in the second electrode 20b, and the polarization (+ ⁇ ) in the electro-optical material layer 30 at this time. ), And the distribution of positive ions (+) and negative ions ( ⁇ ) in the electrolyte layer 40 is schematically shown.
  • the negative charge contained in the first electrode 20a is distributed on the side of the electro-optical material layer 30.
  • the positive charge contained in the second electrode 20b is distributed on the side of the electrolyte layer 40. Due to the downward electric field generated between the pair of electrodes 20, positive ions among the ions contained in the electrolyte layer 40 move toward the electro-optical material layer 30, and negative ions move to the side of the second electrode 20b. Move to the side.
  • polarization of a pair of positive and negative charges occurs. Due to the movement of positive and negative ions in the electrolyte layer 40, an electric double layer surrounded by a broken line is formed at the interface 35 between the electro-optical material layer 30 and the electrolyte layer 40. Similarly, an electric double layer surrounded by a broken line is formed at the interface between the electrolyte layer 40 and the second electrode 20b.
  • the electric double layer functions as a capacitor.
  • the strengths of the electric potentials and electric fields generated in the electro-optical material layer 30 and the electrolyte layer 40 will be described. However, it is assumed that the electro-optical material layer 30 is formed from carrier-injected KTN.
  • FIG. 2B is a diagram schematically showing the relationship between the potential V and the distance Z along the Z direction from the upper surface of the first electrode 20a between the pair of electrodes 20.
  • V 1 represents the potential of the first electrode 20a, and V 2 represents the potential of the second electrode 20b.
  • the potential V sharply increases as the distance Z increases due to the formation of the electric double layer.
  • the potential V increases substantially parabolic with the increase in distance Z due to the carrier injection described above.
  • the potential V is substantially constant.
  • FIG. 2C is a diagram schematically showing the relationship between the distance Z between the pair of electrodes 20 along the Z direction from the upper surface of the first electrode 20a and the strength E of the electric field.
  • the electric field strength E shown in FIG. 2C corresponds to the absolute value of the gradient of the potential V shown in FIG. 2B.
  • the electric field strength E increases substantially linearly as the distance Z increases.
  • the electric field strength E sharply decreases as the distance Z increases.
  • the electro-optic material layer 30 in the portion near the interface 35, a strong electric field having an intensity of E m is generated. Even if the strength of the electric field locally exceeds the strength of the dielectric breakdown electric field, the electro-optical material layer 30 is not destroyed. Since there is no limitation on the dielectric breakdown electric field, the amount of change in the refractive index of the portion of the electro-optical material layer 30 near the interface 35 can be expected to be on the order of, for example, 10-2 or more. The amount of change in the refractive index is larger than that in the case without the electrolyte layer 40. On the other hand, the amount of change in the refractive index of the portion away from the interface 35 is on the order of about 10-3 on average.
  • the amount of change in the refractive index of the electro-optical material layer 30 varies depending on the location.
  • the average value of the change in the refractive index of the electro-optical material layer 30 in space may be the change ⁇ n in the refractive index of the electro-optical material layer 30.
  • the optical phase modulator 100 can modulate the phase of the light 32 propagating through the electro-optical material layer 30 at a large speed and at high speed by using a fast-responsive electro-optical effect.
  • the interface 35 between the electro-optical material layer 30 and the electrolyte layer 40 in this embodiment is flat.
  • the interface 35 does not necessarily have to be strictly flat and may have a portion having some inclination or recesses or protrusions.
  • the electric fields generated in the concave portion or the convex portion may weaken each other, and a strong electric field may not be concentrated in the vicinity of the interface 35. In that case, the amount of change in the refractive index of the portion of the electro-optical material layer 30 near the interface 35 may be small. Further, the light 32 may be lost due to the scattering of the light 32 by the concave or convex portion of the interface 35.
  • the interface 35 when the interface 35 is flat, a strong electric field is concentrated in the Z direction near the interface 35. As a result, the amount of change in the refractive index of the portion of the electro-optical material layer 30 near the interface 35 can be increased. Further, the flat interface 35 suppresses the loss of light 32.
  • the amount of change in the refractive index of the electro-optical material layer 30 is described by a tensor. Therefore, the refractive index of the electro-optical material layer 30 can change in a plurality of directions depending on the direction of the applied electric field. The amount of change in the refractive index of the electro-optical material layer 30 differs depending on the plurality of directions.
  • the refractive index of the electro-optical material layer 30 changes in the X direction and Y. It changes in the direction and the Z direction.
  • the amount of change in the refractive index of the electro-optical material layer 30 becomes maximum in the Z direction.
  • the phase of the light 32 in the TM (transverse magnetic) mode can be greatly modulated.
  • the light 32 in the TM mode has an electric field parallel to the Z direction.
  • a waveguide mode exists when the electro-optical material layer 30 has a width and thickness equal to or greater than a predetermined value. As a result, the electro-optical material layer 30 functions as an optical waveguide layer.
  • the width and thickness of the electro-optical material layer 30 are set to values that form an optical waveguide layer that propagates light 32 along the X direction.
  • LZSO Li x Zr z Si 1-z O y
  • z 0.5.
  • PLD Pulsed Laser Deposition
  • the surface of the LZSO layer becomes rough. This is because carbonates such as lithium carbonate are precipitated on the surface of the LZSO layer by the reaction between Li and CO 2 in the air. Therefore, if the amount of Li in the LZSO layer is small, the flatness of the surface of the LZSO layer can be improved. On the other hand, if the amount of Li in the LZSO layer is too small, the Li ion conductivity decreases. If the Li ion conductivity of the LZSO layer is on the order of about 10-8 S / cm or more, a strong electric field can be generated near the interface 35. From the above, when 1 ⁇ x ⁇ 4, at least the effectiveness of Li ion conductivity is satisfied.
  • the LZSO layer can be formed in an amorphous phase on both the Si substrate and the KTN layer.
  • the Li ion conductivity and surface roughness of the LZSO layer are determined by the amount of Li in the LZSO layer regardless of whether the base of the LZSO layer is a Si substrate or a KTN layer.
  • the LZSO layer has a crystal structure
  • temperature control is performed in order to deposit the LZSO layer having a crystal structure on the KTN layer. Due to the temperature control, the KTN layer and the LZSO layer may be thermally diffused. As a result, the interface 35 can be rough.
  • the LZSO layer has an amorphous structure
  • the LZSO layer can be deposited on the KTN layer at room temperature without controlling the temperature of heating or cooling. As a result, heat diffusion between the KTN layer and the LZSO layer is suppressed. As a result, the interface 35 becomes flat. Since no temperature control is required, the LZSO layer can be easily deposited on the KTN layer. As described above, when the interface 35 is flat, a strong electric field is likely to be generated in the vicinity of the interface 35. Further, the loss of light 32 due to scattering can be suppressed.
  • the thickness of the electrolyte layer 40 can be, for example, 500 nm or more and 2.5 ⁇ m or less. If the thickness of the electrolyte layer 40 is less than 500 nm, the evanescent light of the light 32 may reach the second electrode 20b. When the thickness of the electrolyte layer 40 is thicker than 2.5 ⁇ m, the strength of the electric field applied to the electro-optical material layer 30 and the electrolyte layer 40 may decrease due to the increase in the internal resistance of the electrolyte layer 40.
  • the LZSO layer has (1) a flat surface, (2) effective Li ion conductivity can be obtained, and (3) the LZSO layer can be easily deposited on the KTN layer. Has advantages.
  • FIG. 4 is a flowchart showing the manufacturing process of the optical phase modulator 100.
  • the method for manufacturing the optical phase modulator 100 includes the following steps S101 to S104.
  • step S101 an MgO substrate formed from an MgO (100) single crystal is prepared.
  • the MgO substrate corresponds to the substrate 10 shown in FIGS. 1A and 1B.
  • the LSSO layer and the KTN layer are formed on the main surface of the MgO substrate by epitaxial growth in this order.
  • the LSSO layer corresponds to the first electrode 20a shown in FIGS. 1A and 1B.
  • the LSSO layer exhibits electrical conductivity.
  • the LSSO layer is oriented in the [100] direction.
  • the thickness of the LSSO layer is 200 nm.
  • the KTN layer corresponds to the electro-optical material layer 30 shown in FIGS. 1A and 1B.
  • the thickness of the KTN layer is 500 nm.
  • the PLD method is used to form the LSSO layer and the KTN layer.
  • the MgO substrate and the target formed from LSSO are arranged to face each other.
  • the facing distance is 40 mm.
  • O 2 gas By injecting O 2 gas after evacuating the inside of the vacuum chamber, the pressure inside the vacuum chamber becomes 10 Pa.
  • the MgO substrate is heated to 700 ° C.
  • the target formed from the LSSO is irradiated with an ArF excimer laser. As a result, the LSSO layer is deposited on the main surface 10s of the MgO substrate.
  • the MgO substrate on which the LSSO layer is formed on the main surface 10s is heated to 700 ° C., and the target formed from KTN is irradiated with an ArF excimer laser. As a result, the KTN layer is deposited on the LSSO layer. After cooling, the MgO substrate containing the LSSO layer and the KTN layer is removed from the vacuum chamber.
  • the amount of carbonate deposited on the surface of the LZSO layer is small.
  • the LZSO layer has an amorphous structure. Due to the small amount of Li and the amorphous structure, the surface of the LZSO layer is flat.
  • the LZSO layer corresponds to the electrolyte layer 40 shown in FIGS. 1A and 1B.
  • the thickness of the LZSO layer is 600 nm.
  • the PLD method is used to form the LZSO layer.
  • the MgO substrate containing the LSSO layer and the KTN layer and the target formed from LZSO are arranged to face each other.
  • the facing distance is 40 mm.
  • Targets formed from LZSO are irradiated with an ArF excimer laser at room temperature.
  • the LZSO layer is deposited on the KTN layer.
  • step S103 includes a step of depositing the electrolyte layer 40 on the electro-optical material layer 30 by the PLD method at room temperature.
  • an ITO layer formed of 10 wt% SnO 2- doped In 2 O 3 is formed on the LZSO layer at room temperature.
  • the ITO layer corresponds to the second electrode 20b shown in FIGS. 1A and 1B.
  • the thickness of the second electrode 20b is 100 nm.
  • a sputtering method is used to form the ITO layer.
  • an MgO substrate containing an LSSO layer, a KTN layer, and an LZSO layer and a target formed of ITO are arranged so as to face each other.
  • the facing distance is 45 mm.
  • Ar gas By injecting Ar gas after evacuating the inside of the vacuum chamber, the pressure inside the vacuum chamber becomes 1.5 Pa.
  • the ITO layer is deposited on the LZSO layer by sputtering for 12 minutes at an RF power of 50 W.
  • the refractive indexes of the LSSO layer, the KTN layer, and the LZSO layer are about 2.0, 2.2, and 1.7, respectively. Therefore, the KTN layer having the highest refractive index functions as an optical waveguide layer.
  • the refractive index of the KTN layer can be changed in the range of about 2.0 to about 2.2. As a result, the phase of the light 32 propagating in the KTN layer can be modulated.
  • the following materials may be selected for the substrate 10, the pair of electrodes 20, and the electro-optical material layer 30.
  • step S101 instead of the MgO substrate may be prepared MgAl 2 O 4 substrate, or ⁇ -Al 2 O 3 ⁇ - Al 2 O 3 substrate formed from, formed from MgAl 2 O 4.
  • An LSSO layer can be formed as the first electrode 20a on the MgAl 2 O 4 substrate and the a—Al 2 O 3 substrate by epitaxial growth.
  • the MgAl 2 O 4 substrate and the a-Al 2 O 3 substrate are transparent at a wavelength of 1550 nm.
  • the refractive index of the MgAl 2 O 4 substrate and the a-Al 2 O 3 substrate is lower than that of the LSSO layer.
  • a KTN layer can be formed on the layer by epitaxial growth.
  • the layer is transparent at a wavelength of 1550 nm.
  • the refractive index of the layer is lower than that of the KTN layer.
  • the layer has electrical conductivity.
  • step S102 instead of the KTN layer, a layer formed from an electro-optical material exhibiting the Pockels effect or the Kerr effect described above may be formed.
  • a material capable of epitaxially growing the layer is selected for the first electrode 20a.
  • an FTO layer formed of F-doped SnO 2 (FTO) or an ATO layer formed of Sb-doped TiO 2 (ATO) may be formed.
  • the FTO layer and the ATO layer are transparent at a wavelength of 1550 nm.
  • the FTO and ATO layers can be deposited at room temperature.
  • the laminated structure produced by steps S101 to S104 can be patterned into an arbitrary shape by photolithography and dry etching.
  • the width of the laminated structure is designed to be, for example, 1 ⁇ m because there is a 0th-order TM mode in which the wavelength in air is 1550 nm.
  • the laminated structure may be patterned on a Mach-Zehnder type optical switching device or an optical phased array described later.
  • the control circuit 50 changes the refractive index of the electro-optical material layer 30 by changing the value of the DC voltage applied to the pair of electrodes 20. As a result, the phase of the light 32 propagating in the electro-optical material layer 30 is modulated.
  • An application example using the phase modulation of the light 32 will be described below.
  • the optical phase modulator 100 in this embodiment can be applied to, for example, a Mach-Zehnder type optical switching device.
  • FIG. 5 is a plan view schematically showing an example of a Mach-Zehnder type optical switching device 200.
  • the optical switching device 200 includes an input waveguide 200a, two branched optical waveguides 200b, and an output waveguide 200c.
  • the two branched optical waveguides 200b are located between the input waveguide 200a and the output waveguide 200c.
  • the reflection of light at the branch point A on the input waveguide 200a side and the branch point B on the output waveguide 200c side is not considered.
  • one of the optical waveguides includes the optical phase modulator 100 in this embodiment.
  • ⁇ 2 ⁇ / ⁇
  • ⁇ nL 2 ⁇ / ⁇
  • the phases of the light output from the two branched optical waveguides 200b are in phase with each other. Therefore, when two lights having the same phase are input to the output waveguide 200c, the two lights overlap each other. Therefore, the intensity I out of the light output from the output waveguide 200c is equal to the intensity I in of the light input to the input waveguide 200a.
  • ⁇ ⁇ can be set by adjusting the value of the DC voltage applied to the pair of electrodes 20 in the optical phase modulator 100.
  • the phases of the light output from the two branched optical waveguides 200b are opposite to each other. Therefore, when two lights having opposite phases are input to the output waveguide 200c, the two lights cancel each other out. Therefore, the intensity I out of the light output from the output waveguide 200c becomes 0.
  • the intensity I out of the light output from the output waveguide 200c of the optical switching device 200 is changed from I in to 0. Can be adjusted continuously.
  • the optical phase modulator 100 capable of modulating the refractive index at a large speed and at a high speed enables the optical switching device 200 to be miniaturized and the intensity modulation of the light output from the optical switching device 200 to be accelerated.
  • optical phase modulator 100 in this embodiment can be applied to, for example, an optical phased array 300.
  • 6A and 6B are diagrams schematically showing an example of an optical phased array 300.
  • the optical phased array 300 includes a plurality of optical waveguides 300w arranged in the Y direction.
  • Each of the plurality of optical waveguides 300w includes the optical phase modulator 100 in this embodiment.
  • the plurality of lights output from the plurality of optical waveguides 300w interfere with each other.
  • the interference light output from the optical phased array 300 propagates in a specific direction.
  • the broken lines represent the wave planes of the plurality of lights output from the plurality of optical waveguides 300w, respectively.
  • the solid line represents the wave surface of the interference light output from the optical phased array 300.
  • the plurality of optical waveguides 300w are arranged at equal intervals, but may be arranged at different intervals.
  • the phases of the light output from the plurality of optical waveguides 300w are in phase. Therefore, the interference light output from the optical phased array 300 propagates in the same direction as the X direction in which the plurality of optical waveguides 300w extend.
  • the phase of the light output from the plurality of optical waveguides 300w is ⁇ along the Y direction. It increases little by little. Therefore, the interference light output from the optical phased array 300 propagates in a direction different from the X direction in which the plurality of optical waveguides 300w extend.
  • the propagation direction of the interference light output from the optical phased array 300 can be adjusted by changing the DC voltage applied to the pair of electrodes 20 in the optical phase modulator 100. That is, light beam scanning becomes possible. Further, the optical phased array 300 can also detect light incident from a specific direction. In the example shown in FIGS. 6A and 6B, the optical phased array 300 can detect incident light from the direction opposite to the arrow.
  • the optical phase modulator 100 capable of modulating the refractive index at high speed makes it possible to reduce the size of the optical phased array 300 and to increase the speed and widening of the optical scan of the optical phased array 300.
  • the optical phased array 300 can be used, for example, as an antenna in an optical scanning system such as a LiDAR (Light Detection and Ranking) system and / or an optical detection system.
  • an optical scanning system such as a LiDAR (Light Detection and Ranking) system and / or an optical detection system.
  • the LiDAR system electromagnetic waves having a short wavelength such as visible light, infrared rays, or ultraviolet rays are used as compared with a radar system using radio waves such as millimeter waves. Therefore, the distance distribution of the object can be scanned and detected with high resolution.
  • a LiDAR system can be mounted on a moving body such as an automobile, a UAV (Unmanned Aerial Vehicle, so-called drone), or an AGV (Automated Guided Vehicle), and can be used as one of collision avoidance technologies.
  • UAV Unmanned Aerial Vehicle, so-called drone
  • AGV Automatic Guided Vehicle
  • the optical phase modulator that modulates the phase of the light propagating in the optical waveguide has been described, but the present invention is not limited to this.
  • the present disclosure can be applied to any optical device that modulates the refractive index.
  • the optical device according to the embodiment of the present disclosure can be used, for example, as a Mach-Zehnder type optical switching device or a LiDAR system mounted on a vehicle such as an automobile, UAV, or AGV.
  • Substrate 10s Main surface 20: Electrode 20a: First electrode 20b: Second electrode 30: Electro-optical material layer 32: Light 35: Interface 40: Electrolyte layer 50: Control circuit 100: Optical phase modulator 200: Optical switching device 200a: Input waveguide 200b: Optical waveguide 200c: Output waveguide 300: Optical phased array 300w: Optical waveguide

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  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

Dispositif optique (100) pourvu d'une couche de matériau électro-optique (30) ; d'une couche d'électrolyte (40) en contact avec la couche de matériau électro-optique (30) et formée à partir d'un matériau représenté par LixZrzSi1 - zOy (où x > 0, y = x/2 + 2 et 0 ≤ z ≤ 1) ; ainsi que d'une première et d'une seconde électrode (20a, 20b) pour appliquer une tension à la couche de matériau électro-optique (30) et à la couche d'électrolyte (40).
PCT/JP2020/013065 2019-04-12 2020-03-24 Dispositif optique et son procédé de production WO2020209049A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
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CN115274298A (zh) * 2022-05-20 2022-11-01 沈阳工业大学 一种锆酸铅纳米复合电介质薄膜及其制备方法

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JPS5960814A (ja) * 1982-09-29 1984-04-06 株式会社日立製作所 酸化リチウム系非晶質イオン導電体
JPH10282044A (ja) * 1997-04-04 1998-10-23 Tokuyama Corp 固体電解質型ガスセンサ素子
US20080212914A1 (en) * 2004-09-13 2008-09-04 Marks Tobin J Transparent conducting components and related electro-optic modulator devices
JP2013238651A (ja) * 2012-05-11 2013-11-28 Mitsubishi Electric Corp 分極反転素子の製造方法、導波路型波長変換素子の製造方法および導波路型波長変換素子
JP2017044856A (ja) * 2015-08-26 2017-03-02 パナソニックＩｐマネジメント株式会社 光変調装置

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Publication number Priority date Publication date Assignee Title
JPS5960814A (ja) * 1982-09-29 1984-04-06 株式会社日立製作所 酸化リチウム系非晶質イオン導電体
JPH10282044A (ja) * 1997-04-04 1998-10-23 Tokuyama Corp 固体電解質型ガスセンサ素子
US20080212914A1 (en) * 2004-09-13 2008-09-04 Marks Tobin J Transparent conducting components and related electro-optic modulator devices
JP2013238651A (ja) * 2012-05-11 2013-11-28 Mitsubishi Electric Corp 分極反転素子の製造方法、導波路型波長変換素子の製造方法および導波路型波長変換素子
JP2017044856A (ja) * 2015-08-26 2017-03-02 パナソニックＩｐマネジメント株式会社 光変調装置

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115274298A (zh) * 2022-05-20 2022-11-01 沈阳工业大学 一种锆酸铅纳米复合电介质薄膜及其制备方法
CN115274298B (zh) * 2022-05-20 2023-10-03 沈阳工业大学 一种锆酸铅纳米复合电介质薄膜及其制备方法

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