WO2020208929A1 - Dispositif optique - Google Patents

Dispositif optique Download PDF

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Publication number
WO2020208929A1
WO2020208929A1 PCT/JP2020/005166 JP2020005166W WO2020208929A1 WO 2020208929 A1 WO2020208929 A1 WO 2020208929A1 JP 2020005166 W JP2020005166 W JP 2020005166W WO 2020208929 A1 WO2020208929 A1 WO 2020208929A1
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WIPO (PCT)
Prior art keywords
electro
material layer
optical material
optical
heating
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PCT/JP2020/005166
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English (en)
Japanese (ja)
Inventor
山岡　義和
平澤　拓
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パナソニックＩｐマネジメント株式会社
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Publication of WO2020208929A1 publication Critical patent/WO2020208929A1/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
    • 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
    • G02F1/29—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 position or the direction of light beams, i.e. deflection
    • 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
    • G02F1/29—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 position or the direction of light beams, i.e. deflection
    • G02F1/31—Digital deflection, i.e. optical switching
    • G02F1/313—Digital deflection, i.e. optical switching in an optical waveguide structure

Definitions

  • This disclosure relates to optical devices.
  • the present disclosure provides an optical device that can easily maintain a high electro-optical effect of an electro-optical material.
  • the optical device is an ammeter that measures a pair of electrodes to which a DC voltage is applied, an electro-optical material layer located between the pair of electrodes, and a current flowing through the electro-optical material layer.
  • the heating / cooling element is controlled based on the heating / cooling element that heats and cools the electro-optical material layer, the value of the DC voltage, and the value of the current measured by the ammeter. It includes a control circuit.
  • FIG. 1A is a side view of the optical device in the exemplary embodiment of the present disclosure schematically shown in the X direction.
  • FIG. 1B is a side view of the optical device in the exemplary embodiment of the present disclosure schematically shown from the Y direction.
  • FIG. 2A is a diagram showing the relationship between the bulk temperature and the resistance value of the KTN single crystal.
  • FIG. 2B is a diagram showing the relationship between the temperature and the resistance value of the KTN thin film.
  • FIG. 3A is a flowchart of the operation of the control circuit for determining the Curie temperature of the electro-optical material layer.
  • FIG. 3B is a flowchart of the operation of the control circuit for adjusting the electro-optical effect of the electro-optical material layer.
  • FIG. 1A is a side view of the optical device in the exemplary embodiment of the present disclosure schematically shown in the X direction.
  • FIG. 1B is a side view of the optical device in the exemplary embodiment of the present disclosure schematically shown from the
  • FIG. 3C is a flowchart of the operation of the control circuit for adjusting the electro-optical effect of the electro-optical material layer.
  • FIG. 4 is a diagram schematically showing an example in which an optical device further includes a heat insulating material.
  • FIG. 5 is a diagram schematically showing an example in which an optical device further includes an electromagnetic shield.
  • FIG. 6 is a diagram schematically showing an optical device in a modified example.
  • FIG. 7 is a flowchart showing a manufacturing process of the optical device.
  • FIG. 8 is a plan view schematically showing an example of a Mach-Zehnder type optical switching device.
  • FIG. 9A is a diagram schematically showing a first example of an optical phased array.
  • FIG. 9B is a diagram schematically showing a second example of an optical phased array.
  • FIG. 10 is a diagram schematically showing the relationship between the temperature of KTN and the dielectric constant.
  • Electro-optics materials that exhibit the Pockels effect include, for example, lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), potassium dihydrogen phosphate (KH 2 PO 4 ), and ammonium dihydrogen phosphate (NH 4 H). There are 2 PO 4 ).
  • the electro-optical material exhibiting the Kerr effect for example, barium titanate (BaTiO 3), strontium titanate (SrTiO 3), potassium titanate (KTaO 3), and there is a KTN.
  • the refractive index of the electro-optical material exhibiting the Kerr effect be n 0
  • the vacuum permittivity be ⁇ 0
  • the relative permittivity be ⁇ r
  • the Kerr coefficient be g
  • the magnitude of the applied electric field be E.
  • KTN has a large Kerr coefficient g and a large relative permittivity ⁇ r at room temperature.
  • Kerr coefficient g is of the order of about 0.1 m 4 C -2
  • FIG. 10 is a diagram schematically showing the relationship between the temperature T of KTN and the relative permittivity ⁇ r .
  • KTN is a ferroelectric substance.
  • the ferroelectric substance exhibits a phase transition from the ferroelectric phase to the normal dielectric phase at the Curie temperature T c .
  • the relative permittivity ⁇ r of the ferroelectric substance increases sharply in the ferroelectric phase as it approaches the Curie temperature T c, and gradually decreases in the normal dielectric phase.
  • the relative permittivity ⁇ r is maximized at the Curie temperature T c .
  • the temperature T of KTN is adjusted to be around the Curie temperature T c .
  • the electro-optical effect sharply decreases when the temperature T of KTN deviates from the Curie temperature Tc.
  • the relative permittivity ⁇ r can be easily maintained in a high state by adjusting the temperature T of KTN to the vicinity of the Curie temperature T c .
  • the Curie temperature T c of KTN can be set to around room temperature by setting the composition ratio of Nb and Ta to an appropriate ratio.
  • Patent Document 1 and Patent Document 2 disclose a technique for adjusting the temperature T of KTN based on the measured electric capacity of an electro-optical material in order to obtain a high electro-optical effect.
  • An AC voltage is applied to the pair of electrodes for measuring the electric capacity.
  • An LCR meter or an electrochemical measurement system is used to measure the electric capacity. Therefore, the structure of the optical device becomes complicated.
  • the optical device includes a pair of electrodes to which a DC voltage is applied, an electro-optical material layer located between the pair of electrodes, and an ammeter that measures a current flowing through the electro-optical material layer.
  • the electro-optical material layer is heated or cooled by a heating / cooling element based on the value of the voltage applied to the pair of electrodes and the value of the current measured by the ammeter. This makes it easy to maintain a high electro-optical effect of the electro-optical material.
  • the optical device according to the second item is the optical device according to the first item, in which the control circuit changes the value of the DC voltage to change the refractive index of the electro-optical material layer.
  • a pair of electrodes is used not only to measure the resistance value of the electro-optical material layer but also to change the refractive index of the electro-optical material layer. This makes it possible to simplify the structure of the optical device.
  • the optical device according to the third item controls the phase of light guided through the electro-optical material layer by the change in the refractive index in the optical device according to the second item.
  • the optical device according to the fourth item is the optical device according to any one of the first to third items, and the DC voltage is a DC pulse voltage.
  • the averaged value of the DC pulse voltage can be adjusted as the value of the DC voltage.
  • the optical device according to the fifth item is the resistance of the electro-optical material layer from the DC voltage value and the current value in the optical device according to any one of the first to fourth items.
  • the value is calculated, and the heating / cooling element is controlled based on the change in the resistance value due to at least one of heating and cooling by the heating / cooling element.
  • the heating / cooling device can be controlled based on the DC voltage value and the current value.
  • the optical device according to the sixth item is the optical device according to any one of the first to fifth items, and the optical device further includes a thermometer.
  • the control circuit causes the heating / cooling element to heat the electro-optical material layer, and the temperature measured by the thermometer is the reference temperature.
  • the heating / cooling element causes the electro-optical material layer to cool.
  • the temperature of the electro-optical material layer at the start of operation can be known by a thermometer. Based on the temperature, the electro-optical material layer can be heated or cooled.
  • the optical device according to the seventh item is the optical device according to the sixth item, in which the electro-optical material layer is made of a ferroelectric substance.
  • the reference temperature is the Curie temperature of the ferroelectric substance.
  • a high electro-optical effect can be obtained by the electro-optical material layer composed of a ferroelectric substance.
  • the optical device according to the eighth item is the optical device according to the sixth or seventh item, wherein the control circuit applies a DC voltage to the pair of electrodes, and the electro-optical material layer is applied to the heating / cooling element.
  • the reference temperature is determined based on the change in the value of the current due to heating or cooling the electro-optical material layer and the value of the DC voltage.
  • the reference temperature is determined based on the temperature dependence of the electro-optical material layer.
  • the optical device according to the ninth item is the optical device according to any one of the first to eighth items, wherein the heating / cooling element includes a Peltier element.
  • the electro-optical material layer is heated or cooled by a heating / cooling element including a Peltier element.
  • the optical device according to the tenth item further includes a heat insulating material that covers at least a part of the electro-optical material layer in the optical device according to any one of the first to ninth items.
  • the heat insulating material can suppress the temperature change of the electro-optical material layer due to the temperature change of the outside air.
  • the optical device according to the eleventh item further includes an electromagnetic shield that covers at least a part of the electro-optical material layer in the optical device according to any one of the first to tenth items.
  • the electromagnetic shield can shield electromagnetic noise from the outside of the optical device and / or from the heating / cooling element.
  • the optical device according to the twelfth item is the optical device according to any one of the first to eleventh items, wherein the electro-optical material layer contains potassium niobate tantalate.
  • the optical device according to the thirteenth item is the optical device according to any one of the first to twelfth items, in which the thickness of the electro-optical material layer is 0.1 ⁇ m or more and 10 ⁇ m or less.
  • the cost of the electro-optical material layer can be reduced by the electro-optical material layer having a thickness of 0.1 ⁇ m or more and 10 ⁇ m or less.
  • the optical device according to the fourteenth item is a dielectric breakdown of the electro-optical material layer between the ammeter and one of the pair of electrodes in the optical device according to any one of the first to thirteenth items. Further equipped with a resistor for prevention.
  • the above-mentioned resistor can prevent dielectric breakdown of the electro-optical material layer even if a high voltage is applied to the pair of electrodes.
  • the optical device includes a plurality of electrode pairs to which a DC voltage is applied, an electro-optical material layer located between each of the plurality of electrode pairs, and each of the plurality of electrode pairs.
  • a plurality of current meters measuring the current flowing through the portion of the electro-optical material layer sandwiched by the corresponding one electrode pair of the above, and each sandwiched by the corresponding one electrode pair of the plurality of electrode pairs.
  • the corresponding one electrode pair of the plurality of electrode pairs is based on the value of the voltage applied to each of the plurality of electrode pairs and the value of the current measured by each of the plurality of ammeters.
  • the electro-optical material layer sandwiched between the electrodes is heated or cooled by the heating / cooling element. This makes it easy to maintain a high electro-optical effect of the electro-optical material.
  • 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.
  • FIGS. 1A and 1B are diagrams schematically showing an optical device 100 according to an exemplary embodiment of the present disclosure.
  • the coordinate system consisting of the X, Y, and Z axes 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”.
  • FIG. 1A schematically shows the structure of the optical device 100 as viewed from the + X direction.
  • FIG. 1B schematically shows the structure of the optical device 100 as viewed from the ⁇ Y direction.
  • FIG. 1B shows only some of the components shown in FIG. 1A.
  • the optical device 100 includes a substrate 10, a first electrode 20a and a second electrode 20b, an electro-optical material layer 30, an ammeter 40, a resistor 42, a heating / cooling element 50, a thermometer 60, and the like. It includes a control circuit 70.
  • the substrate 10, the first electrode 20a, the electro-optical material layer 30, and the second electrode 20b are laminated in this order.
  • the substrate 10 has a first surface 10s1 and a second surface 10s2 parallel to the XY plane.
  • the first electrode 20a is located on the first surface 10s1 of the substrate 10.
  • the electro-optical material layer 30 is located on the first electrode 20a.
  • the second electrode 20b is located on the electro-optical material layer 30.
  • the first electrode 20a and the second electrode 20b may be referred to as a "pair of electrodes 20".
  • the electro-optical material layer 30 is located between the pair of electrodes 20.
  • the ammeter 40 is connected to the second electrode 20b.
  • a resistor 42 is connected between the ammeter 40 and the second electrode 20b. The resistor 42 is provided to prevent an excessively high voltage from being applied to the electro-optical material layer 30.
  • the resistor 42 is provided to prevent dielectric breakdown of the electro-optical material layer 30.
  • the resistor 42 is provided as needed.
  • the heating / cooling element 50 is in contact with the second surface 10s2 of the substrate 10.
  • the substrate 10 and the heating / cooling element 50 each have a warp. Therefore, the substrate 10 and the heating / cooling element 50 may be fixed by using a heat conductive adhesive.
  • the thermometer 60 is located, for example, in the vicinity of the electro-optical material layer 30.
  • the substrate 10, the first electrode 20a and the second electrode 20b, the electro-optical material layer 30, and the heating / cooling element 50 have a structure extending in the X direction.
  • the substrate 10 supports a pair of electrodes 20 and an electro-optical material layer 30.
  • the substrate 10 can be formed, for example, from at least one selected from the group consisting of strontium titanate (SrTIO 3 : STO), magnesium oxide (MgO), tantalum pentoxide (Ta 2 O 5 ).
  • SrTIO 3 strontium titanate
  • MgO magnesium oxide
  • Ta 2 O 5 tantalum pentoxide
  • the substrate 10 may be omitted if it is unnecessary.
  • a DC voltage is applied to the pair of electrodes 20.
  • the first electrode 20a is grounded, and a DC voltage having a voltage value of VDC is applied to the second electrode 20b.
  • a DC voltage having a voltage value of VDC is applied to the second electrode 20b.
  • the electric field changes the refractive index of the electro-optical material layer 30.
  • the potential applied to the second electrode 20b may be positive or negative.
  • the DC voltage may be a DC pulse voltage. By changing the duty ratio of the DC pulse voltage, the value obtained by averaging the DC pulse voltage can be adjusted as the value of the DC voltage.
  • the pair of electrodes 20 is also used for measuring the resistance value R of the electro-optical material layer 30.
  • At least one of the pair of electrodes 20 may be a metal electrode or a transparent electrode.
  • the first electrode 20a can be, for example, a transparent electrode formed of strontium ruthenate (SrRuO 3 : SRO).
  • the second electrode 20b can be, for example, a transparent electrode formed of tin-doped indium oxide (ITO).
  • the electro-optical material layer 30 functions as an optical waveguide layer that propagates light 32 along the X direction by total reflection.
  • the phase of the light 32 propagating in the electro-optical material layer 30 can be changed by the amount of change ⁇ n in the refractive index of the electro-optical material layer 30 due to the application of an electric field.
  • 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 length of the electro-optic material layer 30 in the X direction is L
  • the electro-optical material layer is
  • the electro-optical material layer 30 may be formed from a bulk or a thin film, as will be described later.
  • the thickness of the thin film can be, for example, 0.1 um or more and 10 um or less.
  • the cost of thin films is lower than the cost of bulk.
  • the electro-optical material layer 30 contains a ferroelectric substance having a Curie temperature T c .
  • the electro-optical material layer 30 is formed of, for example, KTN.
  • the ammeter 40 measures the current flowing through the electro-optical material layer 30 by applying a DC voltage to the pair of electrodes 20.
  • the resistance value R of the electro-optical material layer 30 is calculated from the ratio of the DC voltage value and the current value.
  • the electro-optical material layer 30 generally has a high resistance. Therefore, it is not necessary to use the four-terminal method for measuring the resistance of the electro-optical material layer 30. As shown in FIG. 1A, a two-terminal method using terminals connected to the first electrode 20a and the second electrode 20b, respectively, is sufficient.
  • the resistor 42 is not always necessary for the optical device 100.
  • the heating / cooling element 50 performs at least one of heating and cooling of the electro-optical material layer 30.
  • the heating / cooling element 50 is, for example, a Peltier element. When an electric current is passed through the Peltier element of the flat plate, heat is generated on one surface of the flat plate and heat is absorbed on the other surface. When the direction of current flow is reversed, endothermic reaction occurs on one surface and heat generation occurs on the other surface.
  • the heating / cooling element 50 heats or cools the electro-optical material layer 30 via the substrate 10 and the first electrode 20a. At this time, it is considered that the substrate 10, the first electrode 20a, and the electro-optical material layer 30 have substantially the same temperature.
  • the heating / cooling element 50 is in contact with the entire second surface 10s2 of the substrate 10.
  • the arrangement of the heating / cooling element 50 is not limited to the examples shown in FIGS. 1A and 1B.
  • the heating / cooling element 50 may be provided so as to heat or cool only the portion of the electro-optical material layer 30 whose refractive index changes due to the application of an electric field.
  • the heating / cooling element 50 may be in direct contact with a plane parallel to the XZ plane of the electro-optical material layer 30.
  • Thermometer 60 measures the ambient temperature T a of the electro-optical material layer 30. Before operation for starting heating or cooling of the electro-optical material layer 30 by heating the cooling element 50, the temperature T of the electro-optical material layer 30 is believed to ambient temperature T a to be approximately the same. Therefore, it is possible to know from the ambient temperature T a which is measured by the thermometer 60, the temperature T of the electro-optical material layer 30 before the operation of the heating and cooling elements 50.
  • the thermometer 60 may be an analog thermometer or a digital thermometer. The thermometer 60 is not always necessary for the optical device 100.
  • the control circuit 70 applies a DC voltage to the pair of electrodes 20.
  • the control circuit 70 measures the current with an ammeter 40.
  • the control circuit 70 inputs a signal for heating or cooling the electro-optical material layer 30 to the heating / cooling element 50 based on the value of the DC voltage and the value of the current measured by the ammeter 40.
  • the control circuit 70 measures the ambient temperature Ta with a thermometer 60.
  • the dashed line with the arrow shown in FIG. 1A represents the input and output of signals between the control circuit 70 and other components. Due to the operation of the control circuit 70, the temperature T of the electro-optical material layer 30 approaches the Curie temperature T c . Thereby, the electro-optical effect of the electro-optical material layer 30 can be enhanced.
  • the control circuit 70 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.
  • PLD programmable logic device
  • DSP digital signal processor
  • FPGA field programmable gate array
  • CPU central processing unit
  • GPU image processing arithmetic processor
  • FIGS. 2A and 2B are diagrams showing the relationship between the temperature T and the resistance value R of the bulk of the KTN single crystal and the KTN thin film, respectively.
  • a pair of electrodes were formed on each surface of the bulk of the KTN single crystal and the surface of the KTN thin film. The voltage and current applied to the pair of electrodes were measured.
  • Each of the pair of electrodes is a comb-shaped electrode with an interelectrode gap of 200 ⁇ m.
  • a parallel plate electrode may be used instead of the comb-shaped electrode.
  • the vertical dashed line represents the Curie temperature T c of the electro-optical material layer 30.
  • the resistance value R of the electro-optical material layer 30 is obtained from the ratio of the value of the DC voltage and the value of the current measured by the ammeter 40.
  • the bulk thickness of the KTN single crystal in the Z direction is 500 ⁇ m.
  • the thickness of the KTN thin film in the Z direction is 1 ⁇ m.
  • the Curie temperature of the bulk of the KTN single crystal is estimated to be T c ⁇ 30 ° C.
  • the rate of increase of the resistance value R increases as the temperature rises.
  • the Curie temperature of the KTN thin film is estimated to be T c ⁇ 28 ° C.
  • the rate of increase of the resistance value R decreases as the temperature rises.
  • the temperature characteristics of the thin film are considered to be similar to the temperature characteristics of the crystal.
  • the rate of increase in resistance value slowed down in the ferroelectric phase, and the resistance value increased or decreased slightly in the ferroelectric phase. It is considered that the temperature dependence of such resistance value in this thin film is due to the film quality of the thin film.
  • the resistance value R changes from an increase to a decrease with the Curie temperature T c as a boundary. This makes it possible to know the Curie temperature T c of the KTN thin film.
  • the resistance value R of KTN has a significantly different temperature dependence near the Curie temperature T c .
  • Patent Document 1 and Patent Document 2 it has been known that the electric capacity of KTN has a significantly different temperature dependence near the Curie temperature T c . This is because the electric capacity depends on the relative permittivity ⁇ r shown in FIG.
  • the resistance value R of KTN had the above temperature dependence.
  • the present inventor has found that the electro-optical effect of KTN can be easily maintained high based on the relationship between the temperature T and the resistance value R of the electro-optical material layer 30.
  • control circuit 70 The details of the operation of the control circuit 70 will be described below.
  • the Curie temperature T c of the electro-optical material layer 30 is estimated before the operation of maintaining the electro-optical effect of the electro-optical material layer 30 high.
  • FIG. 3A is a flowchart of the operation of the control circuit 70 that determines the Curie temperature T c of the electro-optical material layer 30.
  • step S101 the control circuit 70 applies a DC voltage to the pair of electrodes 20.
  • step S102 the control circuit 70 measures the current flowing through the electro-optical material layer 30 with the ammeter 40.
  • step S103 the control circuit 70 causes the heating / cooling element 50 to heat or cool the electro-optical material layer 30. By heating or cooling the electro-optical material layer 30, the current flowing through the electro-optical material layer 30 changes.
  • the change in the resistance value R of the electro-optical material layer 30 is monitored from the change in the current value measured by the ammeter 40 and the value of the DC voltage. From the change in the resistance value R, the temperature dependence of the resistance value R can be known.
  • step S104 the control circuit 70 based on the change in the resistance value R of the electro-optical material layer 30, estimates the Curie temperature T C.
  • the Curie temperature T c can be estimated based on the relationship between the temperature T of the electro-optical material layer 30 and the resistance value R, as described with reference to FIGS. 2A and 2B. From the temperature dependence of the resistance value R, the phase transition point of the crystal phase in the electro-optical material layer 30 can be estimated, and the temperature corresponding to the phase transition point can be estimated to be the Curie temperature T c .
  • the control circuit 70 may record the determined Curie temperature T c of the electro-optical material layer 30 on a storage medium (not shown) such as a memory. As a result, it is not necessary to obtain the Curie temperature T c of the electro-optical material layer 30 immediately before each operation.
  • the control circuit 70 may record the relationship between the temperature T and the resistance value R of the electro-optical material layer 30 shown in FIGS. 2A and 2B in a storage medium. As a result, the Curie temperature T c of the electro-optical material layer 30 can be estimated from the temperature dependence of the resistance value R of the electro-optical material layer 30.
  • the storage medium may be built in the control circuit 70 or may be provided externally.
  • FIG. 3B is a flowchart showing an example of the operation of the control circuit 70 that maintains a high electro-optical effect of the electro-optical material layer 30.
  • step S201 the control circuit 70, at the start of operation, the ambient temperature T a of the electro-optical material layer 30 is measured by the thermometer 60.
  • the thermometer 60 is arranged in the vicinity of the electro-optical material layer 30, the ambient temperature Ta of the electro-optical material layer 30 corresponds to the temperature T of the electro-optical material layer 30.
  • step S202 the control circuit 70, the ambient temperature T a of the electro-optical material layer 30 determines whether lower or not than the Curie temperature T c. If the determination in step S202 is Yes ( Ta ⁇ T c ), the control circuit 70 executes the next step S203.
  • step S203 the control circuit 70 causes the heating / cooling element 50 to heat the electro-optical material layer 30.
  • step S204 If the determination in step S204 is Yes, the control circuit 70 executes the next step S206.
  • step S206 the control circuit 70 causes the heating / cooling element 50 to cool the electro-optical material layer 30, or stops the operation of the heating / cooling element 50. If the cooling rate of the electro-optical material layer 30 is not taken into consideration, the operation of the heating / cooling element 50 may be stopped to allow the electro-optical material layer 30 to cool naturally. After that, the control circuit 70 executes step S204 again.
  • the control circuit 70 executes the next step S207.
  • step S208 the control circuit 70 causes the heating / cooling element 50 to cool the electro-optical material layer 30.
  • step S209 If the determination in step S209 is Yes (T e ⁇ T c) , the control circuit 70 executes the next step S211.
  • step S211 of the control circuit 70 the heating / cooling element 50 heats the electro-optical material layer 30 or stops the operation of the heating / cooling element 50. If the heating rate of the electro-optical material layer 30 is not taken into consideration, the operation of the heating / cooling element 50 may be stopped to naturally warm the electro-optical material layer 30. After that, the control circuit 70 executes step S209 again.
  • the control circuit 70 repeatedly executes step S204 or step S209, for example, every second during operation.
  • the control circuit 70 may stop operating after any step from step S201 to step S211.
  • Step S204 calculates, in step S205, step S209, and step S210, the control circuit 70, the estimated temperature T e of the electro-optical material layer 30 is determined from the resistance value R, by a predetermined arithmetic expression based on the resistance value R You may.
  • the control circuit 70, the estimated temperature T e may be determined by referring to the data table shown and the resistance value R of the relationship between the estimated temperature T e.
  • the data table is recorded on a storage medium (not shown).
  • step S204, step S205, step S209, and in step S210 it is not necessary to calculate or reference to the estimated temperature T e.
  • the control circuit 70 heats the electro-optical material layer 30 when the resistance value R of the electro-optical material layer 30 is lower than the threshold value.
  • the control circuit 70 cools the electro-optical material layer 30 when the resistance value R of the electro-optical material layer 30 is higher than the threshold value.
  • control circuit 70 heats the electro-optical material layer 30 when the rate of change of the resistance value R of the electro-optical material layer 30 is higher than the threshold value.
  • the control circuit 70 cools the electro-optical material layer 30 when the rate of change of the resistance value R of the electro-optical material layer 30 is lower than the threshold value.
  • the control circuit 70 can adjust the temperature T of the electro-optical material layer 30 to the vicinity of the Curie temperature T c .
  • the electro-optical effect of the electro-optical material layer 30 can be maintained high.
  • the temperature above the Curie temperature T c as the reference temperature T s, may adjust the temperature T of the electro-optical material layer 30.
  • the electricity of the electro-optical material layer 30 is generated in the normal dielectric phase in which the relative permittivity ⁇ r gradually changes as shown in FIG.
  • the optical effect does not drop sharply.
  • ⁇ T can be set to, for example, 5 ° C. or lower.
  • FIG. 3C is a flowchart showing the operation of the control circuit 70 when the heating / cooling control is directly performed by the resistance value R without obtaining the estimated temperature of the electro-optical material layer. In this case, it is not always necessary to use a thermometer.
  • step S301 the control circuit 70 applies a DC voltage to the pair of electrodes 20 and measures the current flowing through the electro-optical material layer 30 with an ammeter 40.
  • step S302 the control circuit 70 causes the heating / cooling element 50 to heat or cool the electro-optical material layer 30.
  • step S303 the control circuit 70 monitors the rate of change of the resistance value of the electro-optical material layer 30 with respect to the temperature change based on the change of the current value due to heating or cooling.
  • step S304 the control circuit 70 determines whether or not the rate of change of the resistance value is larger than a predetermined threshold value. If the determination in step S304 is Yes, the control circuit 70 executes step S305.
  • step S305 the control circuit 70 causes the heating / cooling element 50 to heat the electro-optical material layer 30. If the determination in step S304 is No, the control circuit 70 executes step S306. In step S306, the control circuit 70 causes the heating / cooling element 50 to cool the electro-optical material layer 30. After step S305 and step S306, the control circuit 70 executes step S303 again.
  • the value of the Curie temperature T c of the electro-optical material layer 30 and the temperature of the electro-optical material layer 30 are adjusted to be near the Curie temperature T c even if the current temperature is unknown. Can be done. As a result, the electro-optical effect can be maintained high.
  • the ambient temperature Ta may be measured by a thermometer, and whether the temperature should be heated or cooled in step S302 may be determined depending on whether the temperature is higher or lower than the reference temperature stored in the memory. Good.
  • the pair of electrodes 20 can be used not only for applying an electric field to change the refractive index, but also for measuring the resistance value R of the electro-optical material layer 30.
  • the structure of the optical device 100 can be simplified.
  • the electro-optical material layer 30 has a variation in crystallinity and / or a variation in the composition ratio in the electro-optical material layer 30. It is not necessary to consider the difference in Curie temperature T c at each position.
  • a DC voltage is applied instead of an AC voltage to measure the resistance value R. This facilitates the measurement of the resistance value R, which is the ratio of the DC voltage to the DC current.
  • the optical device 100 may further include the following components.
  • FIG. 4 is a diagram schematically showing an example in which the optical device 100 further includes the heat insulating material 80. In FIG. 4, some components are not shown.
  • the heat insulating material 80 covers at least a part of the electro-optical material layer 30.
  • the portion of the electro-optical material layer 30 shown in FIG. 1A that comes into contact with the outside air is covered with the heat insulating material 80. Thereby, the temperature change of the electro-optical material layer 30 due to the temperature change of the outside air can be suppressed.
  • the heat insulating material 80 does not need to be in direct contact with the above portion of the electro-optical material layer 30. Further, as shown in FIG.
  • the portion of the substrate 10, the first electrode 20a, and the second electrode 20b shown in FIG. 1A that comes into contact with the outside air may be covered with a heat insulating material.
  • a heat insulating material 80 does not need to be in direct contact with the substrate 10, the first electrode 20a, and the above portion of the second electrode 20b.
  • the insulation 80 can be formed from, for example, an epoxy resin.
  • FIG. 5 is a diagram schematically showing an example in which the optical device 100 further includes an electromagnetic shield 90.
  • the electromagnetic shield 90 covers at least a part of the electro-optical material layer 30.
  • the substrate 10, the first electrode 20a, the electro-optical material layer 30, and the second electrode 20b are covered with the electromagnetic shield 90.
  • electromagnetic noise from the outside of the optical device 100 and / or from the heating / cooling element 50 can be shielded.
  • the electromagnetic shield 90 does not need to be in direct contact with the electro-optical material layer 30.
  • the electromagnetic shield 90 is formed from at least one selected from the group consisting of silver, copper, gold, aluminum, nickel, and iron.
  • the heat insulating material 80 shown in FIG. 4 may be provided inside the electromagnetic shield 90 shown in FIG.
  • a DC voltage may be applied to the electro-optical material layer 30 by a plurality of electrode pairs.
  • FIG. 6 is a diagram schematically showing the optical device 110 in the modified example. In FIG. 6, some components are not shown.
  • the third electrode 20ba, the fourth electrode 20bb, and the fifth electrode 20bc are located in place of the second electrode 20b shown in FIG. 1A.
  • the third electrode 20ba, the fourth electrode 20bb, and the fifth electrode 20bc have a DC voltage having a first voltage value V DCa , a second voltage value V DCb , and a third voltage value V DCc , respectively. Is applied.
  • Each of the third electrode 20ba, the fourth electrode 20bb, and the fifth electrode 20bc and a part of the first electrode 20a facing each other can be considered as a pair of electrodes.
  • a first ammeter 40a, a second ammeter 40b, and a third ammeter 40c are provided.
  • the heating / cooling element 50 shown in FIG. 1A instead of the heating / cooling element 50 shown in FIG. 1A, the first heating / cooling element 50a, the second heating / cooling element 50b, and the third heating / cooling element 50c are located.
  • the refractive index of the three portions of the electro-optical material layer 30 can be changed separately by the third electrode 20ba, the fourth electrode 20bb, and the fifth electrode 20bc. Thereby, the phase of the light propagating in each of the above three portions of the electro-optical material layer 30 can be adjusted separately.
  • the first voltage value V DCa , the second voltage value V DCb , and the third voltage value V DCc are all equal, the amount of change in the refractive index of the above three parts of the electro-optical material layer 30 is equal.
  • the amount of change in the refractive index of the above three parts of the electro-optical material layer 30 At least some of them are different.
  • the first voltage value V DCa , the second voltage value V DCb , and the third voltage value V DCc are all different, the amount of change in the refractive index of the above three parts of the electro-optical material layer 30 is all different.
  • the first ammeter 40a, the second ammeter 40b, and the third ammeter 40c, and the first heating / cooling element 50a, the second heating / cooling element 50b, and the third The temperature of the above three parts of the electro-optical material layer 30 can be adjusted separately by the heating / cooling element 50c of the above.
  • the Curie temperature T c at the three parts may be different. Even in this case, a high electro-optical effect can be obtained by adjusting the temperatures of the above three portions to the vicinity of the respective Curie temperatures T c .
  • the above three parts of the electro-optical material layer 30 may be separated.
  • the optical device 110 in this modification includes a plurality of electrode pairs, an electro-optical material layer 30, a plurality of heating / cooling elements, and a control circuit 70.
  • a DC voltage is applied to each of the plurality of electrode pairs.
  • the electro-optical material layer 30 is located between each of the plurality of electrode pairs.
  • Each of the plurality of heating and cooling elements performs at least one of heating and cooling of a portion of the electro-optical material layer 30 sandwiched by one corresponding electrode pair among the plurality of electrode pairs.
  • the control circuit 70 inputs a signal for heating or cooling the portion of the electro-optical material layer 30 to each of the plurality of heating / cooling elements based on the resistance value of the portion of the electro-optical material layer 30.
  • the resistance value of the portion of the electro-optical material layer 30 is determined by the ratio of the value of the DC voltage applied to each of the plurality of electrode pairs to the value of the current measured by each of the plurality of ammeters.
  • the operation of the control circuit 70 for heating or cooling the portion of the electro-optical material layer 30 is as shown in FIGS. 3A and 3B.
  • FIG. 7 is a flowchart showing the manufacturing process of the optical device 100.
  • the method for manufacturing the optical device 100 includes the following steps S401 to S405.
  • step S401 the STO substrate is prepared.
  • the STO substrate corresponds to the substrate 10 shown in FIG. 1A.
  • an SRO thin film and a KTN thin film are formed by epitaxial growth on the first surface of the STO substrate.
  • the SRO thin film corresponds to the first electrode 20a shown in FIG. 1A.
  • the KTN thin film corresponds to the electro-optical material layer 30 shown in FIG. 1A.
  • a PLD (Pulsed Laser Deposition) apparatus is used for film formation.
  • the STO substrate and the target formed from the SRO are arranged to face each other.
  • the facing distance is 25 mm.
  • the STO substrate is heated to 650 ° C.
  • the target formed from the SRO is irradiated with an excimer laser.
  • an SRO thin film is formed by epitaxial growth on the first surface 10s1 of the STO substrate.
  • the STO substrate on which the SRO thin film is formed on the first surface 10s1 is heated to 800 ° C., and the target formed from KTN is irradiated with an excimer laser.
  • a KTN thin film is formed on the SRO thin film by epitaxial growth.
  • the STO substrate on which the SRO thin film and the KTN thin film are formed above the first surface 10s1 is taken out of the vacuum chamber.
  • an ITO thin film is formed on the KTN thin film by using a high frequency sputtering apparatus.
  • the ITO thin film corresponds to the second electrode 20b shown in FIG. 1A.
  • the STO substrate and the target formed of ITO are arranged so as to face each other.
  • the facing distance is 70 mm.
  • the STO substrate includes an SRO thin film and a KTN thin film to which a metal mask for sputtering is attached.
  • the ITO thin film is not formed at the place where the metal mask is attached. As a result, an ITO thin film is formed. A metal mask is not always necessary.
  • the pressure inside the vacuum chamber becomes 1 Pa.
  • an ITO thin film having a film thickness of 100 nm is formed on the KTN thin film.
  • step S404 the heating / cooling element 50 is attached to the second surface 10s2 of the STO substrate.
  • step S405 the ammeter 40 shown in FIG. 1A is attached to the ITO thin film.
  • the control circuit 70 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.
  • the phase of the light 32 propagating in the electro-optical material layer 30 changes.
  • the temperature T of the electro-optical material layer 30 as described above, the electro-optical effect of the electro-optical material layer 30 can be maintained high.
  • the phase of the light 32 can be significantly changed.
  • the optical device 100 in this embodiment can be applied to, for example, a Mach-Zehnder type optical switching device.
  • FIG. 8 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 device 100 in this embodiment.
  • VDC 0V
  • ⁇ 0.
  • 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.
  • the intensity I out of the light output from the output waveguide 200c of the optical switching device 200 is continuously increased from I in to 0. Can be adjusted.
  • the optical device 100 in this embodiment can be applied to, for example, an optical phased array 300.
  • 9A and 9B 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 device 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 increases by ⁇ in the Y direction by adjusting the value of the DC voltage applied to the pair of electrodes 20 in the optical device 100. To do. 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 device 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. 9A and 9B, the optical phased array 300 can detect incident light from the direction opposite to the arrow.
  • 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 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.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

L'invention concerne un dispositif optique qui est pourvu : d'une paire d'électrodes auxquelles une tension continue est appliquée ; d'une couche de matériau électro-optique située entre la paire d'électrodes ; d'un ampèremètre qui mesure le courant circulant dans la couche de matériau électro-optique ; un élément de chauffage/refroidissement qui chauffe et/ou refroidit la couche de matériau électro-optique ; et un circuit de commande qui provoque le chauffage ou le refroidissement de la couche de matériau électro-optique sur la base d'une valeur de la tension continue et d'une valeur du courant mesuré par l'ampèremètre.
PCT/JP2020/005166 2019-04-09 2020-02-10 Dispositif optique WO2020208929A1 (fr)

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60118822A (ja) * 1983-11-30 1985-06-26 Hoya Corp 音響光学変調装置
JP2005532695A (ja) * 2002-07-11 2005-10-27 キネティック リミテッド 光検出器回路
JP2006003683A (ja) * 2004-06-18 2006-01-05 Hitachi Cable Ltd ファイバ型光スイッチ及びホーリー光ファイバ
JP2015018175A (ja) * 2013-07-12 2015-01-29 日本電信電話株式会社 光偏向器およびその制御方法
JP2015052701A (ja) * 2013-09-06 2015-03-19 株式会社Ｓｃｒｅｅｎホールディングス 光変調器および露光ヘッド
JP2015125439A (ja) * 2013-12-27 2015-07-06 日本電信電話株式会社 誘電体デバイス
JP2016014793A (ja) * 2014-07-02 2016-01-28 日本電信電話株式会社 光偏向器
US20180246390A1 (en) * 2015-11-17 2018-08-30 Korea Advanced Institute Of Science And Technology Nanophotonic radiators with tunable grating structures for photonic phased array antenna

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60118822A (ja) * 1983-11-30 1985-06-26 Hoya Corp 音響光学変調装置
JP2005532695A (ja) * 2002-07-11 2005-10-27 キネティック リミテッド 光検出器回路
JP2006003683A (ja) * 2004-06-18 2006-01-05 Hitachi Cable Ltd ファイバ型光スイッチ及びホーリー光ファイバ
JP2015018175A (ja) * 2013-07-12 2015-01-29 日本電信電話株式会社 光偏向器およびその制御方法
JP2015052701A (ja) * 2013-09-06 2015-03-19 株式会社Ｓｃｒｅｅｎホールディングス 光変調器および露光ヘッド
JP2015125439A (ja) * 2013-12-27 2015-07-06 日本電信電話株式会社 誘電体デバイス
JP2016014793A (ja) * 2014-07-02 2016-01-28 日本電信電話株式会社 光偏向器
US20180246390A1 (en) * 2015-11-17 2018-08-30 Korea Advanced Institute Of Science And Technology Nanophotonic radiators with tunable grating structures for photonic phased array antenna

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