Patent Publication Number: US-2022236618-A1

Title: Heterogeneously integrated optical modulator and manufacturing method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. non-provisional patent application claims priority under 35 U.S.C. § 119 of Korean Patent Application No. 10-2021-0011402, filed on Jan. 27, 2021, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     The present disclosure herein relates to an optical modulator and a manufacturing method thereof, and more particularly, to a heterogeneously integrated optical modulator and a manufacturing method thereof. 
     The importance and growth speed of a data center, which has rapidly grown due to spread of multimedia and cloud services, are expected to increase sharply as hyper-realistic services such as AR/VR and artificial intelligence services are generalized. Also, the outbreak of global infectious diseases such as COVID-19 causes increase in a data capacity of a high-quality image signal for online education, a remote medical examination and treatment, a video conference, and a seminar. For example, almost all optical transmission modules in the data center may be required to transmit ultra-high speed optical signals of about 100 Gbaud or higher to deal with the above-described data capacity in the future. 
     SUMMARY 
     The present disclosure provides a heterogeneously integrated optical modulator capable of overcoming a limit of a modulation bandwidth of about 50 GHz and a manufacturing method thereof. 
     An embodiment of the inventive concept provides a heterogeneously integrated optical modulator including: a substrate having a trench; an input waveguide disposed on the substrate of one side of the trench; an output waveguide disposed on the substrate of the other side of the trench; a first Mach-Zehnder interferometer including first branch waveguides disposed between the input waveguide and the output waveguide and a heater disposed on one of the first branch waveguides; and second Mach-Zehnder interferometers connected to each of the first branch waveguides. Here, each of the second Mach-Zehnder interferometers includes: second branch waveguides disposed on the substrate of both sides of the trench; a modulation cell including a control block disposed in the trench and modulation waveguides disposed on the control block and disposed between the second branch waveguides; photonic wires connecting the modulation waveguides to the second branch waveguides; and a polymer clad covering the second branch waveguides and the modulation waveguides and covering the photonic wires. 
     In an embodiment, each of the first branch waveguides and the second branch waveguides may include a IV semiconductor material, and each of the modulation waveguides may include a III-V semiconductor material. 
     In an embodiment, each of the first branch waveguides and the second branch waveguides may include a silicon nitride, and each of the modulation waveguides may include indium phosphide. 
     In an embodiment, each of the second branch waveguides may be thicker and wider than each of the modulation waveguides. 
     In an embodiment, each of the photonic wires may include: a first mode converter connected to the second branch waveguides; a second mode converter connected to the modulation waveguides; and a core connecting the first mode converter to the second mode converter. 
     In an embodiment, the core may be thicker or thinner than each of the second branch waveguides and thicker than each of the modulation waveguide. 
     In an embodiment, the photonic wires may include a polymer having a refractive index of about 1.48 to about 1.55 greater than that of the polymer clad. 
     In an embodiment, the first branch waveguides may include: first input branch waveguides connected to the input waveguide; and first output branch waveguides connected to the output waveguide. 
     In an embodiment, the second branch waveguides may include: second input branch waveguides branched from each of the first input branch waveguides; and second output branch waveguides coupled to each of the first output branch waveguides. 
     In an embodiment, the control block may have a hexahedral shape. 
     In an embodiment of the inventive concept, a heterogeneously integrated optical modulator includes: a substrate having a trench; a dielectric clad layer disposed on the substrate of both sides of the trench; an input waveguide disposed on the dielectric clad layer of one side of the trench; first input branch waveguides branched from the input waveguide; second input branch waveguides branched from each of the first input branch waveguides; an output waveguide disposed on the dielectric clad layer of the other side of the trench; first output branch waveguides coupled to the output waveguide; second output branch waveguides coupled to each of the first output branch waveguides; a heater disposed on one of the first output branch waveguides; modulation cells disposed in the trench and including modulation waveguides connected between the second input branch waveguides and the second output branch waveguides; photonic wires connecting the modulation waveguides to the second input branch waveguides and the second output branch waveguides; and a polymer clad covering the second input branch waveguides and the modulation waveguides, covering the second output branch waveguides and the modulation waveguides, and covering the photonic wires. 
     In an embodiment, each of the modulation waveguides may further include the substrate disposed in the trench and a control block disposed between the modulation waveguides. 
     In an embodiment, each of the control block and the modulation waveguides may include a III-V semiconductor material. 
     In an embodiment, each of the input waveguide, the output waveguide, the first and second input branch waveguides, and the first and second output branch waveguides may include a silicon nitride, and each of the control block and the modulation waveguides may include indium phosphide. 
     In an embodiment, each of the photonic wires may include: a first mode converter connected to the second input branch waveguides and the second output branch waveguides; a second mode converter connected to the modulation waveguides; and a core connecting the first mode converter to the second mode converter, and each of the first and second mode converters may include a tapered spot-size converter. 
     In an embodiment of the inventive concept, a method for manufacturing a heterogeneously integrated optical modulator includes: forming a dielectric clad layer on a substrate; forming an input waveguide, an output waveguide, first branch waveguides, and second branch waveguides on the dielectric clad layer; forming a heater on one of the first branch waveguides; forming a trench by etching a portion of the second branch waveguides, the dielectric clad layer, and the substrate; mounting modulation cells including modulation waveguides connected to the second branch waveguides of both sides of the trench into the trench; forming photonic wires connecting the modulation waveguides to the second branch waveguides; and forming a polymer clad over the photonic wires disposed between the second branch waveguides and the modulation waveguides. 
     In an embodiment, the photonic wires may include a polymer formed by a 3D nano-printing method. 
     In an embodiment, the polymer clad may be formed by a dropping and local-coating method. 
     In an embodiment, the polymer clad may be formed in the trench. 
     In an embodiment, the modulation cells may be fixed onto a bottom of the trench by silver paste, solder paste, and solder. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings are included to provide a further understanding of the inventive concept, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the inventive concept and, together with the description, serve to explain principles of the inventive concept. In the drawings: 
         FIGS. 1 to 3  are a perspective view, a plan view, and a side view illustrating an example of a heterogeneously integrated optical modulator according to an embodiment of the inventive concept; 
         FIG. 4  is a perspective view illustrating a connected portion of a photonic wire and a modulation cell of a second Mach-Zehnder interferometer in a portion A of  FIG. 1 ; 
         FIG. 5  is a perspective view illustrating an example of the photonic wire of  FIG. 4 ; and 
         FIG. 6  is a flowchart showing a method for manufacturing a heterogeneously integrated optical modulator according to an embodiment of the inventive concept. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Further, the present disclosure is only defined by scopes of claims. Like reference numerals refer to like elements throughout. 
     In the specification, the technical terms are used only for explaining a specific exemplary embodiment while not limiting the present invention. In the specification, the terms of a singular form may include plural forms unless referred to the contrary. The meaning of ‘comprises’ and/or ‘comprising’ specifies a component, a step, an operation and/or an element does not exclude other components, steps, operations and/or elements. Also, it will be understood that each of an interferometer, a waveguide, a core, and a refractive index used in this specification has a meaning generally used in the optical field. Since preferred embodiments are provided below, the order of the reference numerals given in the description is not limited thereto. 
       FIGS. 1 to 3  are views illustrating an example of a heterogeneously integrated optical modulator  100  according to an embodiment of the inventive concept. 
     Referring to  FIGS. 1 to 3 , the heterogeneously integrated optical modulator  100  according to an embodiment of the inventive concept may be a SiN/InP heterogeneously integrated In-phase and Quadrature phase (IQ) optical modulator. For example, the heterogeneously integrated optical modulator  100  according to an embodiment of the inventive concept may include a substrate  10 , an input waveguide  20 , an output waveguide  30 , a first Mach-Zehnder interferometer  40 , and second Mach-Zehnder interferometers  50 . 
     The substrate  10  may provide a flat surface to the input waveguide  20 , the output waveguide  30 , the first Mach-Zehnder interferometer  40  and the second Mach-Zehnder interferometers  50 . For example, the substrate  10  may include a silicon substrate of a IV semiconductor. Alternatively, the substrate  10  may include Quartz or Alkali-based glass of a silicon oxide (SiO 2 ). However, the embodiment of the inventive concept is not limited thereto. For example, the substrate  10  may have a trench  12 . The trench  12  may be disposed on a center of the substrate  10 . The trench  12  may have a depth of about 10 μm to about 150 μm. The depth of trench  12  may correspond to a thickness of modulation cells  54 . A dielectric clad layer  14  may be disposed on the substrate  10  of both sides of the trench  12 . The dielectric clad layer  14  may include silicon nitride (SiN) having a low refractive index. Alternatively, the dielectric clad layer  14  may include a silicon oxide (SiO 2 ). However, the embodiment of the inventive concept is not limited thereto. 
     The input waveguide  20  may be disposed on the substrate  10  of one side of the trench  12 . The input waveguide  20  may be disposed on the dielectric clad layer  14 . The input waveguide  20  may be a rib waveguide or a ridge waveguide. For example, the input waveguide  20  may include silicon nitride (SiN) having a high refractive index. Alternatively, the input waveguide  20  may include crystalline silicon. However, the embodiment of the inventive concept is not limited thereto. The input waveguide  20  may receive light  110  from a light source and provide the light  110  to the first Mach-Zehnder interferometer  40 , the second Mach-Zehnder interferometers  50  and the output waveguide  30 . 
     The output waveguide  30  may be disposed on the substrate  10  of the other side of the trench  12 . The output waveguide  30  may be disposed on the dielectric clad layer  14 . The output waveguide  30  may be a rib waveguide or a ridge waveguide. The output waveguide  30  may include the same material as the input waveguide  20 . The output waveguide  30  may include silicon nitride (SiN). Alternatively, the output waveguide  30  may include crystalline silicon. However, the embodiment of the inventive concept is not limited thereto. The output waveguide  30  may receive the light  110  from the first Mach-Zehnder interferometer  40  and the second Mach-Zehnder interferometers  50  and provide the light to a light reception device. 
     The first Mach-Zehnder interferometer  40  may be disposed between the input waveguide  20  and the output waveguide  30 . The first Mach-Zehnder interferometer  40  may generate an optical signal having a modulated light intensity and phase by using the light  110 . For example, the first Mach-Zehnder interferometer  40  may include first branch waveguides  42  and a heater  44 . 
     The first branch waveguides  42  may be disposed on the dielectric clad layer  14  of the both sides of the trench  12 . The first branch waveguides  42  may be a rib waveguide or a ridge waveguide. The first branch waveguides  42  may be connected to the input waveguide  20  on the dielectric clad layer  14  of the one side of the trench  12  and connected to the output waveguide  30  on the dielectric clad layer  14  of the other side of the trench  12 . Each of the first branch waveguides  42  may include the same material as each of the input waveguide  20  and the output waveguide  30 . The first branch waveguides  42  may include a silicon nitride (SiN). The first branch waveguides  42  of the silicon nitride (SiN) may reduce a light propagation loss to be equal to or less than about 0.1 dB/cm. Alternatively, the first branch waveguides  42  may include amorphous silicon. However, the embodiment of the inventive concept is not limited thereto. The first branch waveguides  42  may transmit the light  110  between the input waveguide  20  and the output waveguide  30 . For example, the first branch waveguides  42  may include first input branch waveguides  41  and first output branch waveguides  43 . 
     The first input branch waveguides  41  may be connected to the input waveguide  20  on the dielectric clad layer  14  of the one side of the trench  12 . The first input branch waveguides  41  may be branched from the input waveguide  20 . The input waveguide  20  and the first input branch waveguides  41  may have a Y-branch splitter structure. The first input branch waveguides  41  may split and/or divide the light  110  from the input waveguide  20 . 
     The first output branch waveguides  43  may be connected to the output waveguide  30  on the dielectric clad layer  14  of the other side of the trench  12 . The first output branch waveguides  43  may be branched from the output waveguide  30 . The output waveguide  30  and the first output branch waveguides  43  may have the Y-branch splitter structure. The first branch waveguides  42  may provide the light  110  into the output waveguide  30 . 
     The heater  44  may be disposed on one of the first output branch waveguides  43 . The heater  44  may heat the first output branch waveguide  43  to change a phase of light traveling along the first output branch waveguide  43  by 90°. The heater  44  may function as a phase shifter of the light  110 . The heater  44  may heat the first output branch waveguide  43  to change a refractive index thereof. The heater  44  may delay the phase of the traveling light by using the refractive index change of the first output branch waveguide  43 . The light from the plurality of first output branch waveguide  43  may be provided to the output waveguide  30 . For example, the heater  44  may include a Nickel-Chromium alloy. Although not shown, an upper clad layer may be disposed between the heater  44  and the first output branch waveguide  43 . 
     The second Mach-Zehnder interferometers  50  may be connected into the first Mach-Zehnder interferometer  40 . The second Mach-Zehnder interferometers  50  may be Mach-Zehnder interferometers nested in the first Mach-Zehnder interferometer  40 . Each of the second Mach-Zehnder interferometers  50  may be connected between one pair of the first input branch waveguide  41  and the first output branch waveguide  43 , which face each other. 
     For example, the second Mach-Zehnder interferometers  50  may include second branch waveguides  52 , the modulation cells  54 , photonic wires  60 , and a polymer clad  70 . 
     The second branch waveguides  52  may be disposed on the dielectric clad layer  14  of the both sides of the trench  12 . The second branch waveguides  52  may be a rib waveguide or a ridge waveguide. The second branch waveguides  52  may be connected to the first input branch waveguide  41  and the first output branch waveguide  43 . The second branch waveguides  52  may include the same material as the first branch waveguides  42 . The second branch waveguides  52  may include silicon nitride (SiN). Alternatively, the second branch waveguides  52  may include amorphous silicon. However, the embodiment of the inventive concept is not limited thereto. For example, the second branch waveguides  52  may include second input branch waveguides  51  and second output branch waveguides  53 . 
     The second input branch waveguides  51  may be connected to the first input branch waveguides  41  at the one side of the trench  12 . The second input branch waveguides  51  may be branched from the first input branch waveguide  41 . The first input branch waveguide  41  and the second input branch waveguides  51  may have the Y-branch splitter structure. The second input branch waveguides  51  may split and/or divide the light  110  from the first input branch waveguide  41 . 
     The second output branch waveguides  53  may be connected to the first output branch waveguides  43  at the other side of the trench  12 . The second output branch waveguides  53  may be coupled to the first output branch waveguide  43 . The first output branch waveguide  43  and the second output branch waveguides  53  may have the Y-branch splitter structure. The second output branch waveguides  53  may provide the light  110  into the first output branch waveguide  43 . When the modulation cells modulate the light  110 , the light  110  may be interfered in the first output branch waveguide  43 . 
     Referring to  FIGS. 1 to 3  again, the modulation cells  54  may be disposed in the trench  12 . The modulation cells  54  may be disposed between the second input branch waveguides  51  and the second output branch waveguides  53 . The modulation cells  54  may modulate the light  110 . For example, the light  110  may have a frequency of about 50 GHz or higher. For example, each of the modulation cells  54  may include a control block  55  and modulation waveguides  56 . 
     The control block  55  may be disposed in the trench  12 . The control block  55  may have a cuboid shape. The control block  55  may be fixed on a bottom of the trench  12 . For example, the control block  55  may be fixed and/or integrated on the bottom of the trench  12  by silver paste, solder paste, and solder. For example, a top surface of the control block  55  and a top surface of the dielectric clad layer  14  may provide a coplanar surface. The control block  55  may provide an electric field to the modulation waveguides  56  to control a phase and/or an amplitude of the light  110  in the modulation waveguides  56 . Although not shown, the control block  55  may include a plurality of electrodes disposed adjacent to the modulation waveguides  56 . However, the embodiment of the inventive concept is not limited thereto. For example, the control block  55  may include a III-V semiconductor of indium phosphide (InP) and/or gallium arsenide (GaAs). 
     The modulation waveguides  56  may be disposed on the control block  55 . The modulation waveguides  56  may be a rib waveguide or a ridge waveguide. The modulation waveguides  56  may be disposed between the second input branch waveguides  51  and the second output branch waveguides  53 . The modulation waveguides  56  may be arranged in the same direction as the second input branch waveguides  51  and the second output branch waveguides  53 . Each of the modulation waveguides  56  may have a thickness less than that of each of the second input branch waveguides  51  and the second output branch waveguides  53 . The modulation waveguides  56  may transmit the light  110  between the second input branch waveguides  51  and the second output branch waveguides  53 . The control block  55  may modulate the light  110  in the modulation waveguides  56  at a high speed. 
     For example, the light  110  may have a frequency of about 50 GHz or higher. Thus, the heterogeneously integrated optical modulator  100  according to an embodiment of the inventive concept may have a modulation bandwidth of about 50 GHz or higher by using the modulation cell  54  of a III-V semiconductor, which is mounted in the trench  12  of the silicon substrate  10 . For example, the modulation waveguide  56  may include a III-V semiconductor of indium phosphide (InP). 
       FIG. 4  is a view illustrating a connected state of a photonic wire and the modulation cell of the second Mach-Zehnder interferometer  50  in a portion A of  FIG. 1 . 
     Referring to  FIGS. 1 to 4 , the photonic wires  60  of the second Mach-Zehnder interferometers  50  may connect the modulation waveguides  56  to the second input branch waveguides  51  and the second output branch waveguides  53 . When each of the modulation waveguides  56  has a thickness less than that of each of the second input branch waveguides  51  and the second output branch waveguides  53 , each of the photonic wires  60  may have a thickness thicker than that of each of the modulation waveguides  56  and thicker or thinner than that of each of the second input branch waveguides  51  and the second output branch waveguides  53 . The photonic wires  60  may transmit the light  110  between the second input branch waveguides  51  and the modulation waveguides  56  in a state of minimizing an optical coupling loss of the light  110 . Also, the photonic wires  60  may transmit the light  110  between the second output branch waveguides  53  and the modulation waveguides  56  in the state of minimizing the optical coupling loss of the light  110  (here, an optical mode converter allows an optical mode to be adiabatically changing, i.e., the optical coupling loss to be minimized, by slowly changing a size of the optical mode). For example, the photonic wires  60  may include a polymer having a refractive index of about 1.48 to about 1.55. 
     The polymer clads  70  may be disposed on the photonic wires  60 . The polymer clads  70  may be disposed in the trench  12 . The polymer clads  70  may be disposed on a portion of the control block  55  adjacent to the trench  12 , the dielectric clad layer  14 , the second input branch waveguides  51 , and the second output branch waveguides  53 . The polymer clads  70  may have a refractive index less than that of the photonic wires  60 . The light  110  may be transmitted through the photonic wires  60  in the polymer clads  70 . 
       FIG. 5  is a view illustrating an example of the photonic wire  60  of  FIG. 4 . 
     Referring to  FIG. 5 , the photonic wire  60  may include a first mode converter  62 , a second mode converter  64 , and a core  66 . 
     The first mode converter  62  may be connected to the second input branch waveguide  51 . Although not shown, the first mode converter  62  may be connected to the second output branch waveguide  53 . The first mode converter  62  may include a tapered spot-size converter. The first mode converter  62  may have a cross-section corresponding to a mode field diameter (MFD) of each of the second input branch waveguide  51  and the second output branch waveguide  53 . For example, the first mode converter  62  may have a cross-section greater than that of the second input branch waveguide  51 . When the second input branch waveguide  51  has a rectangular cross-section, the first mode converter  62  may have an elliptical cross-section having a major axis greater than a diagonal line of the second input branch waveguide  51 . Alternatively, the first mode converter  62  may have a rectangular cross-section having a line greater than that of the second input branch waveguide  51 . Although not shown, the first mode converter  62  may have a cross-section greater than that of the second output branch waveguide  53 . 
     The second mode converter  64  may be connected to the modulation waveguide  56 . The second mode converter  64  may be less in size than the first mode converter  62 . The second mode converter  64  may have the same shape as the first mode converter  62 . The second mode converter  64  may include a tapered spot-size converter. When the modulation waveguide  56  has a rectangular cross-section, the second mode converter  64  may have an elliptical cross-section having a major axis greater than a diagonal line of the modulation waveguide  56 . The second mode converter  64  may have a rectangular cross-section having a line greater than that of the modulation waveguide  56 . The first mode converter  62 , the second mode converter  64 , and the core  66  may reduce an optical coupling loss of the light  110  between the second input branch waveguides  51  and the second output branch waveguides  53  to be equal to or less than about 1 dB. 
     The core  66  may be connected between the first mode converter  62  and the second mode converter  64 . The core  66  may have a circular or rectangular cross-section. The core  66  may have a constant diameter. For example, the core  66  may be thinner than each of the second input branch waveguide  51  and the second output branch waveguide  53  and thicker than the modulation waveguide  56 . The core  66  may transmit the light  110  between the first mode converter  62  and the second mode converter  64 . 
     A method for manufacturing the above-described heterogeneously integrated optical modulator  100  according to an embodiment of the inventive concept will be described as follows. 
       FIG. 6  is a flowchart showing the method for manufacturing the heterogeneously integrated optical modulator  100 . 
     Referring to  FIGS. 1 to 3 and 6 , the dielectric clad layer  14  is formed on the substrate  10  in a process S 10 . The substrate  10  may include a silicon substrate. Alternatively, the substrate  10  may include silicon oxide (SiO 2 ). However, the embodiment of the inventive concept is not limited thereto. The dielectric clad layer  14  may include silicon nitride (SiN) having a low refractive index, which is formed through a chemical vapor deposition process. 
     Thereafter, the input waveguide  20 , the output waveguide  30 , the first branch waveguides  42 , the and second branch waveguides  52  are formed in a process S 20 . Each of the input waveguide  20 , the output waveguide  30 , the first branch waveguides  42 , and the second branch waveguides  52  may include a silicon nitride (SiN). Each of the input waveguide  20 , the output waveguide  30 , the first branch waveguides  42 , and the second branch waveguides  52  may be a rib waveguide or a ridge waveguide. Each of the input waveguide  20 , the output waveguide  30 , the first branch waveguides  42 , and the second branch waveguides  52  may include a silicon nitride (SiN) having a high refractive index, which is formed by a photolithography process and an etching process. The first branch waveguides  42  may be branched from the input waveguide  20  and coupled to the output waveguide  30 . For example, each of the first branch waveguides  42  may include the first input branch waveguide  41  and the first output branch waveguide  43 . The first branch waveguide  42  may be connected to the input waveguide  20 , and the first output branch waveguide  43  may be connected to the output waveguide  30 . The second branch waveguides  52  may be connected between the first input branch waveguide  41  and the first output branch waveguide  43 . 
     Thereafter, the heater  44  is formed on one of the first output branch waveguides  43  in a process S 30 . The heater  44  may include a Nickel-Chromium alloy formed through an e-beam or sputtering deposition process, a photolithography process, and an etching process. 
     Thereafter, the trench  12  is formed by etching a portion of the second branch waveguides  52 , the dielectric clad layer  14 , and the substrate  10  in a process S 40 . The process of etching the second branch waveguides  52 , the dielectric clad layer  14 , and the substrate  10  may include inductive coupled plasma (ICP) or deep reactive ion etching (DRIE). The trench  12  may divide the second branch waveguides  52  in a longitudinal direction thereof to form the second input branch waveguides  51  and the second output branch waveguides  53 . The trench  12  may expose a bottom of the substrate  10 . 
     Thereafter, the modulation cells  54  are mounted into the trench  12  in a process S 50 . The modulation cells  54  may be fixed on the bottom of the substrate  10  in the trench  12  by using silver paste, solder paste, and solder. Each of the modulation cells  54  may include the control block  55  and the modulation waveguides  56 . For example, each of the control block  55  and the modulation waveguide  56  may include a III-V semiconductor of indium phosphide (InP). The control block  55  may modulate light  110  at a frequency of about 50 GHz or higher by applying an electric field to the modulation waveguides  56 . The modulation waveguides  56  may be arranged between the second input branch waveguides  51  and the second output branch waveguides  53 . 
     Also, the photonic wires  60  are formed in a process S 60 . The photonic wires  60  may connect the modulation waveguides  56  to the second input branch waveguides  51  and the second output branch waveguides  53 . The photonic wires  60  may include a polymer formed by a 3D nano-printing method. The photonic wires  60  may have a refractive index of about 1.48 to about 1.55. 
     Finally, the polymer clads  70  are formed over the photonic wires  60 . The polymer clads  70  may be formed by a dropping and local-coating method. The polymer clads  70  may be formed in the trench  12 . The polymer clads  70  may have a refractive index less than that of the photonic wires  60 . 
     As described above, the heterogeneously integrated optical modulator according to the embodiment of the inventive concept may obtain the modulation bandwidth of about 50 GHz or higher by using the modulation cell of the III-V semiconductor, which is mounted into the trench of the IV semiconductor substrate. 
     Although the embodiments of the present invention have been described, it is understood that the present invention should not be limited to these embodiments but various changes and modifications can be made by one ordinary skilled in the art within the spirit and scope of the present invention as hereinafter claimed.