WO2023248490A1 - Modulateur optique - Google Patents

Modulateur optique Download PDF

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Publication number
WO2023248490A1
WO2023248490A1 PCT/JP2022/037012 JP2022037012W WO2023248490A1 WO 2023248490 A1 WO2023248490 A1 WO 2023248490A1 JP 2022037012 W JP2022037012 W JP 2022037012W WO 2023248490 A1 WO2023248490 A1 WO 2023248490A1
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optical modulator
waveguide
phase modulation
optical
semiconductor layer
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PCT/JP2022/037012
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English (en)
Japanese (ja)
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百合子 川村
雅之 高橋
祥吾 山中
健太郎 本田
陽介 雛倉
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日本電信電話株式会社
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Publication of WO2023248490A1 publication Critical patent/WO2023248490A1/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 
    • G02F1/015—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 semiconductor elements having potential barriers, e.g. having a PN or PIN junction
    • G02F1/025—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 semiconductor elements having potential barriers, e.g. having a PN or PIN junction in an optical waveguide structure

Definitions

  • the present invention relates to a Mach-Zehnder interferometer type optical modulator used in optical communications.
  • a Mach-Zehnder interferometer type optical modulator has small wavelength dependence, has no wavelength chirp component in principle, and can operate at high speed. For this reason, it is widely used in medium and long-distance optical communication systems using a coherent method, and IMDD (direct detection direct modulation) optical communication systems for short distances of several hundred meters.
  • IMDD direct detection direct modulation
  • a Mach-Zehnder interferometer type optical modulator splits the light incident on the input optical waveguide into two optical waveguides (arm optical waveguides) with an intensity of approximately 1:1, and propagates the split light over a fixed length. It has a structure in which the signals are combined again and then output. By changing the phase of the two lights using the phase modulation region provided in the optical waveguide that is split into two, the interference conditions of the lights when they are combined are changed, and the intensity and phase of the output light are modulated. be able to.
  • dielectrics such as LiNbO 3 and semiconductors such as InP, GaAs, and Si (silicon) are used.
  • semiconductors such as InP, GaAs, and Si (silicon)
  • Non-Patent Document 1 discloses a Si Mach-Zehnder optical modulator with a modulator length of about several millimeters.
  • FIG. 1 shows the structure of a conventional traveling wave electrode type Mach-Zehnder optical modulator.
  • FIG. 1 is a perspective view of the structure of an optical waveguide and electrodes of a single-electrode Mach-Zehnder optical modulator, viewed from above.
  • FIG. 2 shows a cross section taken along II-II' in FIG.
  • the Si optical modulator 100 includes an input optical coupler (or Y-shaped splitter) 101 connected to an input optical waveguide, and one-to-two parallel first waveguides 102 that guide split input light into two. It includes a second waveguide 103 and an output optical coupler 104 that combines output light from the two waveguides and outputs it to an output optical waveguide.
  • the optical waveguide of the Si optical modulator 100 is composed of a Si layer 2 sandwiched between upper and lower SiO 2 cladding layers 1 and 3.
  • the Si waveguide for confining light has a structure called a rib waveguide with different thicknesses. That is, as shown in FIG. 2, the rib waveguide is composed of thick Si layers 151a and 151b at the center and thin slab regions 152a to 152c on both sides thereof.
  • the central thick Si layers 151a and 151b of the Si layer 2 are used as the cores of the first waveguide 102 and the second waveguide 103, respectively, and the difference in refractive index with the surrounding SiO 2 cladding layers 1 and 3 is utilized. , constitutes an optical waveguide that confines light propagating in a direction perpendicular to the plane of the paper.
  • the optical waveguide core of the Si layer 2 each has a pn junction in which the p-type semiconductor layers 105a, 105b and the n-type semiconductor layer 106 are joined at the center of the core.
  • a metal bias electrode 107 is provided on the n-type semiconductor layer 106 sandwiched between the two optical waveguides, a first high-frequency electrode 108 is provided on the p-type semiconductor layer 105a, and a first high-frequency electrode 108 is provided on the p-type semiconductor layer 105b.
  • a second high frequency electrode 109 is provided. Modulated electrical signals and bias voltages are applied via these electrodes.
  • the phase modulation region formed in the first waveguide 102 is referred to as a first modulation region 110
  • the phase modulation region formed in the second waveguide 103 is referred to as a second modulation region 111. Since these modulation regions are pn junctions, they can be regarded as capacitive pn diodes. That is, as shown in the equivalent circuit of FIG. 3, the first modulation region 110 and the second modulation region 111 are connected in series as a pn diode, and then the first high-frequency electrode 108 and the second high-frequency electrode It is loaded between 109 and 109.
  • the n-type semiconductor layer and the p-type semiconductor layer may be formed in reverse. Furthermore, the vicinity of the central thick Si layers 151a and 151b may be a low concentration region, and the side of the slab regions 152a to 152c connected to the electrodes may be a high concentration region.
  • the Si optical modulator 100 unless the pn junction is in a reverse bias state, the modulation speed will deteriorate. Therefore, a voltage is applied to the metal bias electrode 107 such that the pn junction is in a reverse bias state, no matter what bias state each of the first modulation region 110 and the second modulation region 111 is in. .
  • a differential modulated electrical signal is input to the first modulation region 110 and the second modulation region 111 from a driver amplifier connected to the first high-frequency electrode 108 and the second high-frequency electrode 109, respectively. This modulates the light.
  • the Si optical modulator 100 has a first modulation region 110 and a second modulation region 111 connected in series, and a first high-frequency electrode 108 and a second high-frequency electrode It is loaded between the electrode 109. Therefore, the differential modulated electrical signals applied to the first high-frequency electrode 108 and the second high-frequency electrode 109 are voltage-divided. In other words, if the amplitude voltage value of each differential modulator signal is X, then only a voltage of X/2 is applied to each of the first modulation region 110 and the second modulation region 111, which reduces the modulation efficiency. will deteriorate. On the other hand, when the amplitude voltage value is increased in order to improve modulation efficiency, there is a problem in that power consumption increases.
  • An object of the present invention is to provide an optical modulator with high modulation efficiency without increasing power consumption.
  • one embodiment of the present invention includes an input optical coupler, and a pair of first and second optical fibers that guide the input light branched into two by the input optical coupler.
  • a Mach-Zehnder interferometer type optical modulator including a waveguide and an output optical coupler that combines output lights of the first and second waveguides, the optical waveguides of the first and second waveguides
  • the core is made of a semiconductor layer having a pn junction and is connected to the first high frequency electrode in an optical modulator including first and second high frequency electrodes for applying a modulated electric signal and a bias voltage to the semiconductor layer.
  • phase modulation region formed in the first waveguide having a first conductivity type semiconductor layer connected to the second high frequency electrode;
  • a second waveguide formed in the second waveguide having a second conductive type semiconductor layer connected to the first high frequency electrode and a first conductive type semiconductor layer connected to the second high frequency electrode.
  • FIG. 1 is a plan view showing the structure of a conventional traveling wave electrode type Mach-Zehnder optical modulator.
  • FIG. 2 is a cross-sectional view showing the structure of a conventional traveling wave electrode type Mach-Zehnder optical modulator.
  • FIG. 3 is a diagram showing an equivalent circuit in the modulation region of a conventional traveling wave electrode type Mach-Zehnder optical modulator.
  • FIG. 4 is a plan view showing the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to Embodiment 1 of the present invention;
  • FIG. 5 is a cross-sectional view showing the structure of the traveling wave electrode type Mach-Zehnder optical modulator of Example 1, FIG.
  • FIG. 6 is a cross-sectional view showing the structure of the traveling wave electrode type Mach-Zehnder optical modulator of Example 1
  • FIG. 7 is a diagram showing an equivalent circuit in the modulation region of the traveling wave electrode type Mach-Zehnder optical modulator of Example 1
  • FIG. 8 is a plan view showing the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to a second embodiment of the present invention
  • FIG. 9 is a cross-sectional view showing the structure of the traveling wave electrode type Mach-Zehnder optical modulator of Example 2
  • FIG. 10 is a diagram showing the relationship between the maximum modulation frequency bandwidth and wavelength of a modulated electrical signal;
  • FIG. 10 is a diagram showing the relationship between the maximum modulation frequency bandwidth and wavelength of a modulated electrical signal
  • FIG. 11 is a plan view showing the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to Embodiment 3 of the present invention
  • FIG. 12 is a diagram showing the loss when a rib waveguide made of a silicon waveguide is bent by 90 degrees
  • FIG. 13 is a diagram showing the structure of a rib waveguide according to Example 3
  • FIG. 14 is a plan view showing the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to Example 4 of the present invention
  • FIG. 15 is a plan view showing the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to Example 5 of the present invention
  • FIG. 16 is a cross-sectional view showing the structure of the traveling wave electrode type Mach-Zehnder optical modulator of Example 5
  • FIG. 17 is a diagram showing an equivalent circuit in the modulation region of the traveling wave electrode type Mach-Zehnder optical modulator of Example 5
  • FIG. 18 is a diagram showing an example of application of capacitance in the traveling wave electrode type Mach-Zehnder optical modulator of Example 5
  • FIG. 19 is a diagram showing another application example of the capacitance in the traveling wave electrode type Mach-Zehnder optical modulator of Example 5
  • FIG. 20 is a diagram showing simulation results for the traveling wave electrode type Mach-Zehnder optical modulator of Example 5.
  • FIG. 4 shows the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to Example 1 of the present invention.
  • FIG. 4 is a perspective view of the structure of the optical waveguide and electrodes of the single-electrode Mach-Zehnder optical modulator 200, viewed from above.
  • FIG. 5 shows a cross section taken along line V-V' in FIG.
  • FIG. 6 shows a cross section taken along VI-VI' in FIG.
  • the Si optical modulator 200 includes an input optical coupler (or Y-shaped splitter) 101 connected to an input optical waveguide, and two parallel first waveguides 102 that guide split input light into two. It includes a second waveguide 103 and an output optical coupler 104 that combines output light from the two waveguides and outputs it to an output optical waveguide.
  • the optical waveguide of the Si optical modulator 200 is composed of a Si layer 2 sandwiched between upper and lower SiO 2 cladding layers 1 and 3.
  • the Si waveguide for confining light has a structure called a rib waveguide with different thicknesses. That is, as shown in FIGS. 5 and 6, the rib waveguide is composed of thick Si layers 151a and 151b in the center and thin slab regions 152a to 152d on both sides thereof.
  • the central thick Si layers 151a and 151b of the Si layer 2 are used as the cores of the first waveguide 102 and the second waveguide 103, respectively, and the difference in refractive index with the surrounding SiO 2 cladding layers 1 and 3 is utilized.
  • the insulating layer 121 is a region in which the Si layer 2 is not doped with anything.
  • the optical waveguide core of the Si layer 2 has a pn junction in which p-type semiconductor layers 105a, 105b and n-type semiconductor layers 106a, 106b are joined at the center of the core.
  • a first high-frequency electrode 108 is provided on the p-type semiconductor layer 105a
  • a second high-frequency electrode 109 is provided on the p-type semiconductor layer 105b.
  • the n-type semiconductor layer 106a is connected to the second high-frequency electrode 109
  • the n-type semiconductor layer 106b is connected to the first high-frequency electrode 108. Modulated electrical signals and bias voltages are applied via these electrodes.
  • n-type semiconductor layers 106a, 106b and the high-frequency electrodes are connected by extending T-shaped electrodes from the first high-frequency electrode 108 and the second high-frequency electrode 109, as shown in FIG.
  • the connection is not limited to this, and may be connected in any shape.
  • the phase modulation region formed in the first waveguide 102 is referred to as a first modulation region 110
  • the phase modulation region formed in the second waveguide 103 is referred to as a second modulation region 111. Since these modulation regions are pn junctions, they can be regarded as capacitive pn diodes. That is, as shown in the equivalent circuit of FIG. 7, the first modulation region 110 is loaded between the first high-frequency electrode 108 and the second high-frequency electrode 109, and the second modulation region 111 is loaded between the It is loaded between the high frequency electrode 109 and the first high frequency electrode 108.
  • the Si optical modulator 200 as shown in the equivalent circuit of FIG. are loaded independently between them. Therefore, the differential modulated electrical signal applied to the first high-frequency electrode 108 and the second high-frequency electrode 109 is not voltage-divided, and the amplitude voltage value X of the differential modulated electrical signal is different from the first modulated region 110. It is applied to each of the second modulation regions 111. Therefore, compared to a conventional traveling wave electrode type Mach-Zehnder optical modulator, the optical modulator can be driven with twice the modulation efficiency.
  • the structure of the Si optical modulator 200 may be such that the n-type semiconductor layer and the p-type semiconductor layer are formed in reverse. Furthermore, the vicinity of the central thick Si layers 201a and 201b may be a low concentration region, and the side of the slab regions 202a to 202c connected to the electrodes may be a high concentration region. Furthermore, with regard to Example 1, the case of a Si modulator using a Si semiconductor has been described. It may be used as a semiconductor.
  • FIG. 8 shows the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to a second embodiment of the present invention.
  • FIG. 8 is a perspective view of the structure of the optical waveguide and electrodes of the single-electrode Mach-Zehnder optical modulator 300, viewed from above.
  • FIG. 9 shows a cross section taken along line IX-IX' in FIG. Descriptions of components common to the first embodiment will be omitted.
  • the difference from the conventional traveling wave electrode type Mach-Zehnder optical modulator is that the first modulation region 110 formed in the first waveguide 102 and the second modulation region 111 formed in the second waveguide 103 are different from the conventional traveling wave electrode type Mach-Zehnder optical modulator. , which are divided into a plurality of points along the light propagation direction and arranged alternately.
  • the first modulation region 110 and the second modulation region 111 are connected to the first high-frequency electrode 108 and the second high-frequency electrode 109 by extending T-shaped electrodes, as in the first embodiment. ing.
  • the core of the second waveguide 103 adjacent to the first modulation region 110 of the first waveguide 102 is a rib waveguide in which the Si layer 2 is not doped with anything. , acts as an insulating layer.
  • the Si optical modulator 300 Similar to the first embodiment, in the Si optical modulator 300, as shown in the equivalent circuit of FIG. It is independently loaded between the two high frequency electrodes 109. Therefore, the differential modulated electrical signals applied to the first high-frequency electrode 108 and the second high-frequency electrode 109 are not voltage-divided, and compared to the conventional traveling wave electrode type Mach-Zehnder optical modulator, the optical modulation efficiency is twice as high. A modulator can be driven.
  • a method of dividing the first modulation area 110 and the second modulation area 111 will be explained.
  • the length of each divided modulation region in the light propagation direction is set to be 1/20 or less of the wavelength included in the modulated electrical signal.
  • n of the cores of the first waveguide 102 and the second waveguide 103 is set to 3.5
  • a modulated electric signal propagating through the first high-frequency electrode 108 and the second high-frequency electrode 109 is shown. shows the relationship between maximum modulation frequency bandwidth and wavelength.
  • the modulated electrical signal includes a signal of maximum 60 GHz
  • 70 ⁇ m is obtained from the relationship: speed of light x refractive index/maximum modulation frequency bandwidth/20.
  • the first high frequency electrode 108 and the second high frequency electrode 109 are traveling wave electrodes.
  • the traveling wave electrode is an electrode that matches the velocity of the modulated electrical signal and the light propagating through the optical waveguide (phase velocity matching), and interacts with the light while propagating the electrical signal.
  • One end of the traveling wave electrode is connected to a driver amplifier, and the other end is terminated by a terminating resistor, and the traveling wave electrode therebetween is configured as a high frequency line having characteristic impedance.
  • the first modulation region 110 and the second modulation region 111 are divided into 1/20 or less of the maximum wavelength of the modulated electrical signal.
  • the length of the T-shaped electrode in the light propagation direction that applies a modulated electrical signal to the n-type semiconductor layer 106 becomes a length that is not affected by frequency dependence.
  • the T-shaped electrode that applies a modulated electrical signal to the p-type semiconductor layer 105 also has the same configuration. Therefore, in addition to the effects of the first embodiment, the Si optical modulator 300 can suppress the quality deterioration of the modulated electrical signal applied to the semiconductor layer and improve the high frequency characteristics.
  • the number of first modulation regions 110 and second modulation regions 111 should be approximately the same in the light propagation direction. This is to equalize the amount of phase modulation in each of the first waveguide 102 and second waveguide 103 divided by the input optical coupler 101 in the Mach-Zehnder optical modulator. This is because modulated output light without chirp (waveform distortion) can be output.
  • FIG. 11 shows the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to Example 3 of the present invention.
  • FIG. 11 is a perspective view of the structure of the optical waveguide and electrodes of the single-electrode Mach-Zehnder optical modulator 400, viewed from above. Descriptions of components common to Example 2 will be omitted.
  • the difference from the conventional traveling wave electrode type Mach-Zehnder optical modulator is that the first modulation region 110 formed in the first waveguide 102 and the second modulation region 111 formed in the second waveguide 103 are different from the conventional traveling wave electrode type Mach-Zehnder optical modulator. , are points divided into multiple parts. Furthermore, the first modulation region 110 and the second modulation region 111 are optically connected by curved rib waveguides 412 and 413, respectively.
  • the rib waveguides 412 and 413 have a structure including four 90 degree bends, and are formed of undoped insulating silicon waveguides.
  • the cross-sectional structures of the rib waveguides 312 and 313 are the same as those of the first waveguide 102 and the second waveguide 103, respectively.
  • the capacity loaded per unit length is halved. .
  • two capacitances Cpn across the pn junction of the first modulation region 110 and a capacitance Cpn across the pn junction of the second modulation region 111 are connected between the signal electrodes 108 and 109. are connected.
  • only one capacitor Cpn is connected between the signal electrodes 108 and 109.
  • the propagation speed of a high-frequency signal propagating through an optical modulator is inversely proportional to the square root of the interelectrode capacitance. becomes late.
  • the signal propagation speed can be adjusted by changing the width and spacing of the signal electrodes, it is difficult to adjust a larger capacitance than in the conventional configuration.
  • bent rib waveguides 412 and 413 are provided to serve as delay lines for optical signals, thereby effectively slowing down the propagation of the optical signals. That is, the optical signal is also delayed in accordance with the delay of the high frequency signal due to the increase in the interelectrode capacitance, so that the propagation speeds of the optical signal and the high frequency signal are made equal. Thereby, when modulating an optical signal with a high frequency signal, it is possible to prevent band deterioration due to speed mismatch between the two.
  • optical signal delay lines have been realized not by rib waveguides but by channel waveguides.
  • the channel waveguide has a rectangular cross section and can be bent at a smaller radius without loss.
  • a delay line using a channel waveguide is created in the optical modulation region formed by the rib waveguide via a rib-channel waveguide converter, and then a delay line is created using a channel waveguide via a rib-channel waveguide converter, and then a delay line is created using a channel waveguide via a rib-channel waveguide converter. It was coupled to a light modulation region formed by a waveguide.
  • This Ribou channel waveguide converter has an optical loss of about 0.2 dB per conversion, and when a large number of them are arranged in one optical modulator, the optical loss becomes a problem.
  • the first modulation region 110 and the second modulation region 111 are arranged alternately, and the rib waveguides 412 and 413 are arranged in the region where the PN junction is not arranged. is forming. Therefore, since a sufficient length in the propagation direction of the optical signal can be secured between the modulation regions, a rib waveguide with a large bending radius for low loss can be used, and a delay line with a desired amount of delay can be formed. can be provided.
  • FIG. 12 shows the loss when a rib waveguide made of a silicon waveguide is bent by 90 degrees.
  • the length of the divided modulation regions (110, 111) is set to be 1/20 or less of the wavelength included in the modulated electrical signal.
  • the length of 1/20 of the wavelength is about 100 ⁇ m.
  • bending loss increases rapidly when the bending radius becomes smaller than about 10 ⁇ m.
  • the length of the rib waveguides 412 and 413 is 80 ⁇ m with respect to the light propagation direction of the Si optical modulator 400, it is possible to arrange them between the modulation regions (110 and 111) divided as described above. can. Furthermore, an appropriate delay amount for the delay line can be set by providing a straight line portion as shown in FIG. 13 and adjusting its length Lst.
  • FIG. 14 shows the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to Example 4 of the present invention.
  • FIG. 14 is a perspective view of the structure of the optical waveguide and electrodes of the single-electrode Mach-Zehnder optical modulator 500, viewed from above. Descriptions of components common to Example 2 will be omitted.
  • the difference from the conventional traveling wave electrode type Mach-Zehnder optical modulator is that the first modulation region 110 formed in the first waveguide 102 and the second modulation region 111 formed in the second waveguide 103 are different from the conventional traveling wave electrode type Mach-Zehnder optical modulator. , are points divided into multiple parts. Furthermore, the difference from the Si optical modulator 300 of Example 2 is that the divided modulation regions are not arranged alternately, but are arranged collectively on one side. As shown in FIG. 14, by providing bent portions in the first waveguide 102 and the second waveguide 103, the first modulation region 110 and the second modulation region 111 can be bent along the propagation direction of light. The layout is arranged in such a way that the
  • the configurations of the divided first high-frequency electrode 108 and second high-frequency electrode 109 are substantially the same as the Si optical modulator 300 of the second embodiment, and in addition to the effects of the first embodiment, there are also the advantages of the second embodiment. The same effects can be achieved. Furthermore, since the divided modulation regions do not have a periodic structure, there is a high degree of freedom in manufacturing design.
  • FIG. 15 shows the structure of a traveling wave electrode type Mach-Zehnder optical modulator according to Example 5 of the present invention.
  • FIG. 15 is a perspective view of the structure of the optical waveguide and electrodes of the single-electrode Mach-Zehnder optical modulator 600, viewed from above.
  • FIG. 16 shows a cross section taken along line XVI-XVI' in FIG. 15. Descriptions of components common to Example 2 will be omitted.
  • the p-type semiconductor layer 105 of the first modulation region 110 is connected to the first high-frequency electrode 108, and the n-type semiconductor layer 106 is electrically connected to the electrode 109 via the capacitor 113.
  • the p-type semiconductor layer 105 of the second modulation region 111 is connected to the second high-frequency electrode 109, and the n-type semiconductor layer 106 is electrically connected to the first high-frequency electrode 108 via the capacitor 113.
  • the electrode structure between the n-type semiconductor layer 106 and the capacitor 113 will be referred to as a node 116 for the following explanation.
  • the capacitor 113 has a structure in which the second high-frequency electrode 109 and the node 116 are opposed to each other by a predetermined distance in the light propagation direction with a predetermined interval.
  • a bias electrode 115 is connected to the node 116 via a resistor 114.
  • An external bias power supply is connected to the bias electrode 115, so that a bias voltage can be applied separately from the modulated electrical signal.
  • the bias electrode 115 is formed using a metal wiring layer below the second high frequency electrode 109.
  • the Si optical modulator 600 can further improve high frequency characteristics.
  • the PN junction may become forward biased depending on the amplitude of the modulated electrical signal. do.
  • the Si optical modulator 500 has a configuration similar to a so-called bias T, consisting of a capacitor 113 and a resistor 114, so that a bias voltage can be applied separately from the modulated electrical signal. can. With this configuration, the PN junction can always be set to forward bias, so high-speed operation is possible.
  • phase modulation efficiency with respect to the applied voltage of the Si modulator changes depending on the bias voltage of the PN junction.
  • the modulation efficiency can be further improved by operating at the bias voltage that provides the best modulation efficiency.
  • the voltage X applied to the first high frequency electrode 108 and the second high frequency electrode 109 is proportional to the reciprocal sum of the capacitance (1/Cbias+1/Cpn), and the voltage applied to Cpn involved in phase modulation is the reciprocal of the capacitance 1/Cbias. is proportional to.
  • the modulation efficiency is Cpn/(Cbias+Cpn), so in order to obtain twice the modulation efficiency as compared to the conventional traveling wave electrode type Mach-Zehnder optical modulator, Cbias should be set to the same capacitance value or more with respect to Cpn. There is a need to. For example, when Cpn per unit length is about 100 fF/mm, Cbias is set to 5 pF/mm, and the value of the resistor 114 is set to approximately 1 k ⁇ or more.
  • FIG. 18 shows an application example of the capacitor 113.
  • the length of the capacitor 113 in the light propagation direction is limited by the structure of the divided modulation regions.
  • a desired capacitance value may not be obtained simply by making the second high-frequency electrode 109 and the node 116 face each other. Therefore, it may be possible to implement it by providing an MIM (Metal-Insulator-Metal) structure using a lower wiring layer.
  • MIM Metal-Insulator-Metal
  • FIG. 19 shows another application example of the capacitor 113.
  • a pn junction connecting a p-type semiconductor layer and an n-type semiconductor layer is manufactured separately from the modulation region.
  • a desired capacitance value can also be obtained by using this pn junction as the capacitor 113.
  • FIG. 20 shows simulation results when a modulated electrical signal is applied to the Si optical modulator 500 of Example 5.
  • the above-mentioned Cpn is set to 100 fF/mm
  • Cbias is set to 5 pF/mm
  • the resistance value of the resistor 114 is set to 10 k ⁇ .
  • a differential modulated electrical signal of 30 Gbaud and an amplitude of 2 V was input to the first high frequency electrode 108 and the second high frequency electrode 109 shown in FIG.
  • FIG. 20(a) shows an eye pattern of a modulated electrical signal input from the driver amplifier to each high-frequency electrode.
  • FIG. 20(b) shows an eye pattern at the termination resistor after propagating through the high-frequency electrode.
  • FIG. 20(c) is an eye pattern of the voltage signal applied to the PN junction of the first modulation region 110.
  • FIG. 20(c) a voltage signal of approximately -2V to -4V is applied, and it is found that the device operates with reverse bias. Furthermore, since a voltage signal of about -2V to -4V is applied to the phase modulation section 111, the Mach-Zehnder optical modulator operates with an amplitude of about 4V in response to a differential input signal with an amplitude of 2V. . Furthermore, FIGS. 20(b) and 20(c) show good eye openings, and it can be seen that quality deterioration of the modulated electrical signal is suppressed. Therefore, compared to the conventional traveling wave electrode type Mach-Zehnder optical modulator, it is possible to drive the optical modulator with twice the modulation efficiency, realizing an optical modulator with high modulation efficiency without increasing power consumption. It can be seen that
  • the differential modulated electric signal applied to the first high-frequency electrode 108 and the second high-frequency electrode 109 is not voltage-divided, and is different from the conventional traveling wave electrode type Mach-Zehnder optical modulator.
  • the modulation region of the Si optical modulator of this embodiment only the polarity of the n-type semiconductor layer and the p-type semiconductor layer has been described, but the region near the thick Si layer at the center, which becomes the optical waveguide core, is a low concentration region, and the electrode
  • the side of the slab region to be connected may be a high concentration region.
  • a pin junction may be used in which an undoped i-type (intrinsic) semiconductor is sandwiched between pn junction structures.
  • the material of the modulation region can also be made of other materials such as InP. This is because even in an InP modulator, reverse bias operation can be performed using a pn junction or a pin junction.
  • the present invention can be generally used in optical communication systems. In particular, it can be applied to an optical modulator in an optical transmitter of an optical communication system.

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

Abstract

La présente invention concerne un modulateur optique ayant une efficacité de modulation élevée sans augmenter la consommation d'énergie. L'invention concerne un modulateur optique qui est un modulateur optique de type interféromètre de Mach-Zehnder (200) dans lequel des cœurs de guide d'ondes optiques de premier et second guides d'ondes (102, 103) comprennent des couches semi-conductrices ayant une jonction p-n, et comprend des première et seconde électrodes haute fréquence (108, 109) pour appliquer un signal électrique modulé et une tension de polarisation aux couches semi-conductrices, le modulateur optique comprenant : une première région de modulation de phase (110) qui est formée dans le premier guide d'ondes et a une couche semi-conductrice de premier type de conductivité (105a) connectée à la première électrode haute fréquence (108) et une couche semi-conductrice de second type de conductivité (106a) connectée à la seconde électrode haute fréquence (109) ; et une seconde région de modulation de phase (111) qui est formée dans le second guide d'ondes (103) et a une couche semi-conductrice de second type de conductivité (106b) connectée à la première électrode haute fréquence et une couche semi-conductrice de premier type de conductivité (105b) connectée à la seconde électrode haute fréquence.
PCT/JP2022/037012 2022-06-21 2022-10-03 Modulateur optique WO2023248490A1 (fr)

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US20050123242A1 (en) * 2002-01-19 2005-06-09 Bookham Technology, Plc Optical modulators operated in parallel push-pull mode
US20150043866A1 (en) * 2013-08-09 2015-02-12 Sifotonics Technologies Co., Ltd. Electro-Optic Silicon Modulator With Capacitive Loading In Both Slots Of Coplanar Waveguides
US20170285437A1 (en) * 2016-03-29 2017-10-05 Acacia Communications, Inc. Silicon modulators and related apparatus and methods
JP2018025610A (ja) * 2016-08-08 2018-02-15 住友電気工業株式会社 光変調装置
JP2018097093A (ja) * 2016-12-09 2018-06-21 日本電信電話株式会社 光変調器
US20190324345A1 (en) * 2018-04-24 2019-10-24 Elenion Technologies, Llc Optical waveguide modulator
JP2020027204A (ja) * 2018-08-14 2020-02-20 国立研究開発法人産業技術総合研究所 光変調器
US20210080796A1 (en) * 2019-09-17 2021-03-18 Lumentum Operations Llc Electrical-optical modulator

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050123242A1 (en) * 2002-01-19 2005-06-09 Bookham Technology, Plc Optical modulators operated in parallel push-pull mode
US20150043866A1 (en) * 2013-08-09 2015-02-12 Sifotonics Technologies Co., Ltd. Electro-Optic Silicon Modulator With Capacitive Loading In Both Slots Of Coplanar Waveguides
US20170285437A1 (en) * 2016-03-29 2017-10-05 Acacia Communications, Inc. Silicon modulators and related apparatus and methods
JP2018025610A (ja) * 2016-08-08 2018-02-15 住友電気工業株式会社 光変調装置
JP2018097093A (ja) * 2016-12-09 2018-06-21 日本電信電話株式会社 光変調器
US20190324345A1 (en) * 2018-04-24 2019-10-24 Elenion Technologies, Llc Optical waveguide modulator
JP2020027204A (ja) * 2018-08-14 2020-02-20 国立研究開発法人産業技術総合研究所 光変調器
US20210080796A1 (en) * 2019-09-17 2021-03-18 Lumentum Operations Llc Electrical-optical modulator

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