Crow-based sis type mach-zehnder optical modulator and optical module comprising same

Abstract

An optical modulator of the present invention comprises: a first insulating layer on a semiconductor substrate; a first semiconductor layer provided on the first insulating layer and including a waveguide region and a pad region, wherein the waveguide region includes a CROW structure including a plurality of resonators which protrude upward from the surface of the pad region and are arranged in one direction; a second insulating layer provided on the first semiconductor layer; and a second semiconductor layer provided on the second insulating layer, wherein the thickness of a region of the second insulating layer on the CROW structure is less than the thickness of other regions of the second insulating layer, and the resonator may include a plurality of resonators having a lattice resonance structure, wherein on a plane, the lattice resonance structure has a plurality of protruding regions protruding from both sides of a direction in which the resonators are arranged, and a recessed region having a recessed shape between adjacent protruding regions.

Description

CROW-based SIS type Mach-Zehnder optical modulator and optical module including the same

[0001] The present invention relates to a CROW-based SIS type Mach-Zehnder optical modulator and an optical module including the same, and more particularly, to a CROW-based SIS type Mach-Zehnder optical modulator and an optical module including the same, which combines a CROW (Coupled-Resonator Optical Waveguide) structure having a continuous grating resonator structure and an SIS structure, thereby minimizing loss due to doping and improving modulation efficiency while maintaining a small size and a stable bandwidth.

[0002] An optical modulator is generally a device that modulates the intensity, phase, polarization state, wavelength / frequency, direction of propagation, etc. of an optical signal that transmits information, for example, by using external electrical, magnetic, mechanical, acoustic, and optical means. Among these modulation devices, devices that modulate the intensity or phase of an optical signal by using electrical means have been widely used in the past from the viewpoints of operating speed (operating bandwidth) and controllability.

[0003] Representative examples of devices that modulate light intensity include a Mach-Zehnder modulator that converts the change in refractive index of a material of a component caused by an electric field application and the accompanying phase change of an optical signal into an intensity change using the interference effect of a Mach-Zehnder interferometer, and an absorption modulator that modulates the intensity of light propagated to a material constituting a component (transmits or absorbs light) by controlling the optical absorption coefficient of the material by applying an electric field to the component.

[0004] However, while the Mach-Zehnder modulator has the advantage of low temperature dependence and wavelength dependence, it has low modulation efficiency due to relatively large optical loss, and must have a relatively large area compared to other modulators.

[0005] Accordingly, the inventor of the present invention completed the present invention after a long period of research and trial and error to solve these problems and requirements.

[0006] The present invention was created to solve the problems of the prior art as described above, and one object of the present invention is to provide a CROW-based SIS type Mach-Zehnder optical modulator and an optical module including the same, which minimizes loss due to doping and improves modulation efficiency while maintaining a small size and stable bandwidth by combining a CROW (Coupled-Resonator Optical Waveguide) structure having a continuous grating resonator structure and an SIS structure.

[0007] Meanwhile, other unspecified purposes of the present invention will be additionally considered within the scope that can be easily inferred from the detailed description and effects thereof below.

[0008] An optical modulator according to one aspect of the present invention comprises: a first insulating layer on a semiconductor substrate; a first semiconductor layer provided on the first insulating layer, the first semiconductor layer including a CROW structure, the first semiconductor layer including a waveguide region and a pad region, the waveguide region protruding above a surface of the pad region and including a plurality of resonators arranged in one direction; a second insulating layer provided on the first semiconductor layer; and a second semiconductor layer provided on the second insulating layer, wherein a thickness of an upper region of the CROW structure of the second insulating layer is smaller than a thickness of another region of the second insulating layer, the resonator including a lattice resonance structure, and in a plane, the lattice resonance structure may include a plurality of resonators including a plurality of protruding regions protruding on both sides of a direction in which the resonators are arranged, and a recessed region having a recessed shape between adjacent protruding regions.

[0009] In one embodiment of the present invention, the waveguide region is divided into a rib region corresponding to a CROW structure and a slab region on both sides of the rib region, and the doping concentration of the first semiconductor layer and the second semiconductor layer in the rib region may be lower than the doping concentration of the first semiconductor layer and the second semiconductor layer in the slab region.

[0010] In one embodiment of the present invention, the first semiconductor layer and the second semiconductor layer in the rib region are 10 17 cm -3 10 inland 18 cm -3 With a doping concentration of , the first semiconductor layer and the second semiconductor layer in the slab region are 10 19 10 inland 20 cm -3 It can have a doping concentration of .

[0011] In one embodiment of the present invention, the thickness of the upper region of the CROW structure of the second insulating layer may be 5 nm to 10 nm.

[0012] In one embodiment of the present invention, on a plane, the lattice resonant structure may have 10 to 30 protruding regions on each side in the direction in which the resonators are arranged.

[0013] In one embodiment of the present invention, the distance at which the protruding region protrudes may be 5 nm to 300 nm.

[0014] In one embodiment of the present invention, the device may further include a first electrode connected to the pad region; and a second electrode connected to a region other than a region corresponding to the CROW structure of the second semiconductor layer.

[0015] An optical module according to one aspect of the present invention comprises: a semiconductor substrate; a light source provided on one side of the semiconductor substrate; and an optical modulator disposed on the other side of the semiconductor substrate facing the light source, wherein the optical modulator comprises: a first insulating layer on the semiconductor substrate; a first semiconductor layer provided on the first insulating layer, the first semiconductor layer including a waveguide region and a pad region, the waveguide region protruding above a surface of the pad region and including a CROW structure including a plurality of resonators arranged in one direction; a second insulating layer provided on the first semiconductor layer; and a second semiconductor layer provided on the second insulating layer, wherein a thickness of an upper region of the CROW structure of the second insulating layer is smaller than a thickness of another region of the second insulating layer, the resonator including a lattice resonance structure, and in a plane, the lattice resonance structure may include a plurality of resonators including a plurality of protruding regions protruding on both sides of a direction in which the resonators are arranged, and a recessed region having a recessed shape between the protruding regions.

[0016] In one embodiment of the present invention, the light source may be connected to one end of the CROW structure in the direction in which the resonators are arranged.

[0017] The CROW-based SIS type Mach-Zehnder optical modulator and the optical module including the same according to the present invention can minimize loss due to doping and improve modulation efficiency while maintaining a small size and stable bandwidth by combining a CROW (Coupled-Resonator Optical Waveguide) structure with a continuous grating resonator structure and an SIS structure.

[0018] FIG. 1 is a perspective view illustrating a Mach-Zehnder optical modulator according to one embodiment of the present invention.

[0019] Figure 2 is a drawing for explaining a cross-section along line II' of Figure 1.

[0020] FIG. 3 is a drawing for explaining the first insulating layer, n-type doping layer, and second insulating layer of the Mach-Zehnder optical modulator.

[0021] Fig. 4 is an enlarged view for explaining the EA area shown in Fig. 3, and is a drawing for explaining the lattice resonance structure of the resonator in the CROW structure.

[0022] Figure 5 is a diagram for explaining the transmission rate and phase shift of a CROW-based SIS type Mach-Zehnder optical modulator.

[0023] Fig. 6 is a diagram for explaining the results of calculating the refractive index for the passband within the transmission rate of a CROW-based SIS type Mach-Zehnder optical modulator.

[0024] Figure 7 is a drawing for explaining the transmission rate and group refractive index for the grating width, number of gratings, and number of resonators of the grating resonance structure of the CROW structure.

[0025] Figure 8 is a drawing for explaining the change in the width of the passband and the group refractive index according to the grating width and number of gratings of the grating resonance structure of the CROW structure.

[0026] FIG. 9 is a drawing for explaining the CROW-based SIS type Mach-Zehnder optical modulator illustrated in FIG. 2.

[0027] FIG. 10 is a drawing for explaining the TE (Transverse Electric) mode distribution of the CROW-based SIS type Mach-Zehnder optical modulator illustrated in FIG. 9.

[0028] FIG. 11 is a diagram for explaining the carrier distribution in the CROW-based SIS type Mach-Zehnder optical modulator illustrated in FIG. 9.

[0029] FIG. 12 is a diagram for explaining the loss, refractive index variation, resistance and capacitance, and bandwidth and TP (transmitter penalty) according to the thickness of the second insulating layer in the rib region of a CROW-based SIS type Mach-Zehnder optical modulator.

[0030] Figure 13 is a diagram for explaining the optical loss and refractive index change, resistance and capacitance, and bandwidth and TP according to the doping concentration of a CROW-based SIS type Mach-Zehnder optical modulator.

[0031] Fig. 14 is a diagram for explaining the passband and bandwidth according to the group refractive index of a CROW-based SIS type Mach-Zehnder optical modulator.

[0032] Figure 15 is a drawing for comparing and explaining the performance of a CROW-based SIS type Mach-Zehnder optical modulator with the performance of a general Mach-Zehnder optical modulator.

[0033] It is to be understood that the attached drawings are provided for reference only to help understand the technical concept of the present invention, and the scope of the present invention is not limited thereby.

[0034] The purpose, specific advantages, and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments, taken in conjunction with the accompanying drawings. In this specification, when reference numerals are assigned to components in each drawing, it should be noted that, where possible, identical components are assigned the same reference numerals even if they appear in different drawings. Furthermore, in describing the present invention, a detailed description of a related known technology will be omitted if it is determined that it may unnecessarily obscure the gist of the present invention.

[0035] In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0036] Additionally, terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0037]

[0038] In a preferred embodiment of the present invention, a CROW-based SIS type Mach-Zehnder optical modulator and an optical module including the same are proposed and described.

[0039] A preferred embodiment of the present invention comprises a SIS type Mach-Zehnder optical modulator and an optical module including the same having a CROW structure based on a grating resonance structure in an n-type semiconductor layer. Here, the grating resonance structure constituting the CROW structure may be formed of a reflective structure composed of a central phase shift region and a predetermined number of gratings on both sides. The reflective structure causes an interference effect that blocks light of a specific wavelength from passing through, and the phase shift region allows only light of a specific wavelength band to pass through. Therefore, the grating resonance structure constituting the CROW structure increases the group refractive index at a specific wavelength, thereby increasing the interaction between light and a medium through a slow-light effect, thereby improving modulation efficiency and reducing the size of the optical modulator element.

[0040]

[0041] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0042] FIG. 1 is a perspective view illustrating a Mach-Zehnder optical modulator according to an embodiment of the present invention. FIG. 2 is a drawing for explaining a cross-section taken along line II' of FIG. 1. FIG. 3 is a drawing for explaining a first insulating layer, an n-type doping layer, and a second insulating layer of the Mach-Zehnder optical modulator according to FIG. 4 is an enlarged view for explaining the EA region illustrated in FIG. 3, and is a drawing for explaining the lattice resonance structure of the resonator within the CROW structure.

[0043] Referring to FIGS. 1 to 4, a Mach-Zehnder optical modulator according to one embodiment of the present invention is provided on one side of a semiconductor substrate (100) and may form an optical module together with a light source provided on the other side of the semiconductor substrate (100). The Mach-Zehnder optical modulator as described above may include a first insulating layer (200), a first semiconductor layer (300), a second insulating layer (400), a second semiconductor layer (500), a first electrode (600), and a second electrode (700).

[0044] The semiconductor substrate (100) may be a silicon substrate. For example, the semiconductor substrate (100) may be a bulk silicon substrate.

[0045] The first insulating layer (200) may be provided on the semiconductor substrate (100). That is, the first insulating layer (200) may be provided between the semiconductor substrate (100) and the first semiconductor layer (300). The first insulating layer (200) may perform a lower cladding function with respect to the first semiconductor layer (300). The first insulating layer (200) may include silicon oxide (SiOx) or silicon nitride (SiNx). Preferably, the first insulating layer (200) may include silicon oxide (SiOx).

[0046] A first semiconductor layer (300) may be provided on a first insulating layer (200). The first semiconductor layer (300) may include one of an n-type semiconductor and a p-type semiconductor. For example, the first semiconductor layer (300) may include an n-type semiconductor. In particular, the first semiconductor layer (300) may include n-type silicon.

[0047] The n-type silicon of the first semiconductor layer (300) may be one of semiconductor materials such as amorphous silicon, polysilicon, grainsize enhanced polysilicon, grain-boundary passivated polysilicon, grain-boundary aligned polysilicon, and single crystal silicon.

[0048] At least a portion of the first semiconductor layer (300) may function as a waveguide for transmitting light. For example, the first semiconductor layer (300) may include a pad region (300P) and a waveguide region (300W).

[0049] The pad region (300P) may be a region connected to one of the first electrode (600) and the second electrode (700). For example, the pad region (300P) may be electrically connected by contacting the first electrode (600). In addition, the pad region (300P) may be provided on at least one side and both sides of the waveguide region (300W). The pad region (300P) may be provided on both sides of the waveguide region (300W).

[0050] Additionally, a portion of the pad area (300P), for example, an area in contact with the first electrode (600), may be thicker than other areas. That is, the area of ​​the pad area (300P) in contact with the first electrode (600) may have a shape that protrudes upward.

[0051] The waveguide region (300W) is provided in the central portion of the first semiconductor layer (300) and can provide a path for light to be guided.

[0052] A CROW structure (Coupled Resonator Optical Waveguide) as illustrated in FIGS. 3 and 4 may be provided in a portion of the waveguide region (300W). The CROW structure includes a plurality of resonators (310), and each resonator (310) may have a shape that protrudes upward from the surface of the pad region (300P). In addition, the resonator (310) has a lattice resonance structure, and provides an improved control function for dispersion characteristics compared to the waveguide of a general Mach-Zehnder optical modulator, and can be applied to delay, storage, and buffering of optical pulses.

[0053] The CROW structure is a device used in the fields of optical communications and optoelectronics, and as illustrated in FIGS. 3 and 4, a plurality of resonators (310) are coupled to each other to effectively modulate and transmit optical waves. Each resonator (310) of the CROW structure has a lattice resonance structure as illustrated in FIG. 4, and can resonate optical waves at a specific frequency. The resonators (310) of the CROW structure as described above are optically coupled to each other, and can generate an interference effect when optical waves are transmitted from one resonator (310) to another resonator (310).

[0054] The CROW structure described above is composed of an array of resonators (310) that resonate at a specific wavelength and can only pass light of a specific frequency or specific wavelength.

[0055] Additionally, the characteristics of the CROW structure can be controlled by adjusting the coupling strength between each resonator (310). Therefore, the CROW structure can be useful for transmitting and manipulating light waves.

[0056] The CROW structure can operate over a wide frequency range, making it suitable for a variety of applications.

[0057] As illustrated in Fig. 4, the resonator (310) may be provided with a lattice resonance structure. The lattice resonance structure may have a shape in which, for example, the first insulating layer (200) extends in one direction from the surface on a plane. The lattice resonance structure may include a plurality of protruding regions (311) protruding on both sides in the longitudinal direction, and a recessed region (315) having a recessed shape between adjacent protruding regions (311). A light source may be connected to one end of the CROW structure described above in the direction in which the resonator (310) is arranged.

[0058] Additionally, on a plane, the lattice resonance structure may have 10 to 30 protruding regions (311) on each side of the direction in which the resonators (310) are arranged. Here, the protruding regions (311) may be referred to as a lattice.

[0059] Additionally, the distance at which the protruding region (311) protrudes from the sunken region (315), i.e., the width of the grating, may have a range of 5 nm to 300 nm.

[0060]

[0061] The lattice resonance structure described above has an effective refractive index that changes between the protruding region (311) and the recessed region (315), and light waves of a specific wavelength can be phase-delayed according to the change in the effective refractive index. Between the protruding region (311) and the recessed region (315), the phase-delayed light waves can cause strong reflection.

[0062] Due to the phase shift region in the center, a specific passband that meets the phase matching conditions within the reflection band is formed, which can be utilized as an optical bandwidth.

[0063]

[0064] The second insulating layer (400) may be provided on the first semiconductor layer (300). That is, the second insulating layer (400) may be provided between the first semiconductor layer (300) and the second semiconductor layer. The second insulating layer (400) may perform an upper clad function with respect to the first semiconductor layer (300). The second insulating layer (400) may include silicon oxide (SiOx) or silicon nitride (SiNx). Preferably, the second insulating layer (400) may include silicon oxide (SiOx).

[0065] The thickness of the upper region of the CROW structure of the second insulating layer (400) may be smaller than the thickness of other regions. The thickness of the upper region of the CROW structure of the second insulating layer (400) may range from 5 nm to 10 nm.

[0066]

[0067] The second semiconductor layer (500) may be provided on the second insulating layer (400). The second semiconductor layer (500) may include the other of an n-type semiconductor and a p-type semiconductor. For example, the second semiconductor layer (500) may include a p-type semiconductor. In particular, the second semiconductor layer (500) may include p-type silicon.

[0068] Additionally, the p-type silicon of the second semiconductor layer (500) may be one of semiconductor materials such as amorphous silicon, polysilicon, grainsize enhanced polysilicon, grain-boundary passivated polysilicon, grain-boundary aligned polysilicon, and single crystal silicon.

[0069]

[0070] Meanwhile, since the CROW structure has a shape protruding upward, the waveguide region (300W) can be divided into a rib region (300R) corresponding to the CROW structure and substantially acting as an optical waveguide, and slab regions (300S) on both sides of the rib region (300R).

[0071] Here, the first semiconductor layer (300) and the second semiconductor layer (500) in the rib region (300R) are 10 17 cm -3 10 inland 18 cm -3 may have a doping concentration of about 10 . In addition, the first semiconductor layer (300) and the second semiconductor layer (500) of the slab region (300S) may have a doping concentration of about 10 . 19 10 inland 20 cm -3 It can have a doping concentration of .

[0072] As described above, when the doping concentration of the first semiconductor layer (300) and the second semiconductor layer (500) of the rib region (300R) is smaller than the doping concentration of the first semiconductor layer (300) and the second semiconductor layer (500) of the slab region (300S), the carrier concentration of the rib region (300R) of the first semiconductor layer (300) can increase.

[0073] The first electrode (600) can be electrically connected to one of the first semiconductor layer (300) and the second semiconductor layer, for example, the first semiconductor layer (300). Here, the first electrode (600) can be connected to both ends of the first semiconductor layer (300), i.e., the pad area (300P) of the first semiconductor layer (300).

[0074] The second electrode (700) may be electrically connected to the other of the first semiconductor layer (300) and the second semiconductor layer, for example, the second semiconductor layer (500). Here, the second electrode (700) may be connected to both ends of the second semiconductor layer (500).

[0075]

[0076] Fig. 5 is a diagram for explaining the transmission rate and phase change of a CROW-based SIS type Mach-Zehnder optical modulator. Fig. 5 shows the results of measuring the transmission rate when the CROW structure of the Mach-Zehnder optical modulator has a grating resonance structure with a grating width of 250 nm and the number of gratings and resonators being 20 and 15, respectively. In addition, in Fig. 5, the horizontal axis may represent wavelength, the left vertical axis may represent transmission, and the right vertical axis may represent phase response.

[0077] Referring to Fig. 5, it can be seen that the grating resonance structure of the CROW structure exhibits a passband of 4 nm with a center wavelength around 1312.5 nm. In addition, it can be seen that the phase of the passband decreases consistently with wavelength.

[0078] Through the results described above, it can be seen that the CROW-based SIS-type Mach-Zehnder optical modulator according to an embodiment of the present invention operates as a linear phase modulator. In addition, it can be seen that the CROW-based SIS-type Mach-Zehnder optical modulator according to an embodiment of the present invention can perform optical filtering and perform optical modulation through linear phase modulation because it only passes light in a specific wavelength band near the center wavelength.

[0079] In addition, it can be seen that by using a CROW-based SIS type Mach-Zehnder optical modulator according to one embodiment of the present invention, compensation for delay dispersion is possible, an optical spectrum can be controlled, and an optical pulse can be compressed.

[0080]

[0081] Figure 6 is a diagram illustrating the results of calculating the refractive index for the passband within the transmission rate of a CROW-based SIS-type Mach-Zehnder optical modulator. In Figure 6, the horizontal axis represents the wavelength, and the vertical axis represents the group index of refraction.

[0082] Referring to FIG. 6 together with FIG. 5, it can be seen that the passband exhibits an average group refractive index of 14 between the peaks on both sides of the passband. Therefore, it can be seen that the CROW-based SIS type Mach-Zehnder optical modulator according to one embodiment of the present invention can minimize chromatic dispersion.

[0083] That is, the CROW-based SIS type Mach-Zehnder optical modulator according to one embodiment of the present invention can be used to expand the optical bandwidth.

[0084]

[0085] Fig. 7 is a diagram for explaining the transmission rate and group refractive index of the CROW-structured lattice resonance structure with respect to the lattice width, number of lattices, and number of resonators. In Fig. 7, (a) shows the transmission rate of the pass band with respect to the lattice width, Fig. 7 (b) shows the transmission rate of the pass band with respect to the number of lattices, Fig. 7 (c) shows the transmission rate of the pass band with respect to the number of resonators, Fig. 7 (d) shows the group refractive index of the pass band with respect to the lattice width, Fig. 7 (e) shows the group refractive index of the pass band with respect to the number of lattices, and Fig. 7 (f) shows the group refractive index of the pass band with respect to the number of resonators. Here, the lattice width increased from 5 nm to 300 nm in 25 nm units, the number of lattices increased from 10 to 30 in 5 units, and the number of resonators increased in the order of 5, 7, and 10.

[0086] Referring to Figure 7, as shown in (a) and (d), it can be seen that as the width of the grating increases, the width of the pass band decreases, but the group refractive index increases. In addition, as shown in (b) and (e), it can be seen that as the number of gratings increases, the width of the pass band decreases, but the group refractive index increases.

[0087] In contrast, as shown in (c) and (f), it can be seen that the change in the number of resonators has little or no effect on the width of the passband and the group refractive index.

[0088] That is, it can be seen that the CROW-based SIS type Mach-Zehnder optical modulator according to one embodiment of the present invention can adjust the width of the passband and the group refractive index by adjusting the width and number of gratings.

[0089]

[0090] Figure 8 is a diagram for explaining the change in the width of the passband and the group refractive index according to the lattice width and number of lattices of the CROW-structured lattice resonance structure. In Figure 8, (a) shows the dependence on the width of the passband, and (b) shows the dependence on the group refractive index. In addition, in Figure 8, the horizontal axis represents the width of the lattice, and the vertical axis represents the number of lattices.

[0091] Referring to Figure 8, as shown in (a), it can be seen that as the width of the passband increases, the color reddens. Also, as shown in (b), it can be seen that as the group refractive index increases, the color reddens.

[0092] That is, as the width of the grating and the number of gratings increase, the width of the passband decreases and the group refractive index increases.

[0093]

[0094] Fig. 9 is a diagram for explaining the CROW-based SIS type Mach-Zehnder optical modulator illustrated in Fig. 2. Fig. 10 is a diagram for explaining the TE (Transverse Electric) mode distribution of the CROW-based SIS type Mach-Zehnder optical modulator illustrated in Fig. 9. Fig. 11 is a diagram for explaining the carrier distribution within the CROW-based SIS type Mach-Zehnder optical modulator illustrated in Fig. 9. In Fig. 11, the horizontal axis represents the upper vertical distance based on the center of the CROE structure, the vertical axis represents the carrier concentration, and the gray area within the graph represents the second insulating layer.

[0095] Referring to FIGS. 9 to 11, in a CROW-based SIS type Mach-Zehnder optical modulator, a first semiconductor layer (300), a second insulating layer (400), and a second semiconductor layer (500) may be provided in a rib region (300R), which is the center of an optical waveguide in a waveguide region (300W). Here, the first semiconductor layer (300) and the second semiconductor layer (500) in the rib region (300R) may be provided at a thickness of about 10 18 cm -3 It can have a doping concentration of .

[0096] In a CROW-based SIS type Mach-Zehnder optical modulator, a first semiconductor layer (300) and a second semiconductor layer (500) may be provided in a slab region (300S) on both sides of the optical waveguide. Here, the first semiconductor layer (300) and the second semiconductor layer (500) of the slab region (300S) have a thickness of about 10 19 10 inland 20 cm -3 It can have a doping concentration of .

[0097] As shown in FIG. 10, it can be seen that the CROW-based SIS type Mach-Zehnder optical modulator described above can restrict light to a rib region (300R) by utilizing the difference in refractive index between the first semiconductor layer (300) and the second insulating layer (400).

[0098] In addition, as illustrated in FIG. 11, it can be seen that the carrier concentration increases as voltage is applied near the second insulating layer (400). That is, it can be seen that as the carrier concentration increases, the optical modulation efficiency and operating speed of the CROW-based SIS type Mach-Zehnder optical modulator according to one embodiment of the present invention are improved.

[0099] In addition, as the carrier concentration increases, it can be seen that the CROW-based SIS-type Mach-Zehnder optical modulator according to an embodiment of the present invention has reduced optical spectral distortion, reduced internal optical absorption, and reduced optical noise of the optical signal. That is, it can be seen that the CROW-based SIS-type Mach-Zehnder optical modulator according to an embodiment of the present invention has improved performance.

[0100]

[0101] Fig. 12 is a diagram for explaining the loss, refractive index variation, resistance and capacitance, bandwidth and TP (transmitter penalty) according to the thickness of the second insulating layer in the rib region of a CROW-based SIS type Mach-Zehnder optical modulator. In Fig. 12, (a) is a graph comparing the loss and refractive index variation of the optical modulator according to the thickness of the second insulating layer, in which the horizontal axis represents the thickness of the second insulating layer, the left vertical axis represents the loss of the optical modulator, and the right vertical axis represents the refractive index variation of the optical modulator. In Fig. 12, (b) is a graph comparing the resistance and capacitance of the optical modulator according to the thickness of the second insulating layer, in which the horizontal axis represents the thickness of the second insulating layer, the left vertical axis represents the resistance, and the vertical axis represents the capacitance. In Fig. 12, (c) is a graph comparing the TP of the optical modulator according to the bandwidth, in which the upper horizontal axis represents the thickness of the second insulating layer, the lower horizontal axis represents the bandwidth, and the vertical axis represents the modulation efficiency.

[0102] Referring to FIG. 12, as shown in (a), as the thickness of the second insulating layer (400) of the rib region (300R) increases, it can be seen that the change in the refractive index of the CROW structure decreases, but the change in the optical loss in the CROW structure is small.

[0103] As shown in (b), it can be seen that as the thickness of the second insulating layer (400) of the rib region (300R) increases, the resistance and capacitance of the CROW structure decrease.

[0104] As shown in (c), it can be seen that as the thickness of the second insulating layer (400) of the rib region (300R) increases, the bandwidth increases, but TP also increases. Here, TP refers to the modulation efficiency of the optical modulator, and the smaller the TP value, the better the modulation efficiency of the optical modulator. In addition, the larger the bandwidth, the faster the transmission speed of the optical modulator.

[0105] That is, as shown in (c), as the thickness of the second insulating layer (400) of the rib region (300R) increases, the bandwidth increases, thereby increasing the transmission speed of the optical modulator, but TP also increases, thereby lowering the modulation efficiency. Therefore, it is necessary to set an appropriate thickness of the second insulating layer (400).

[0106]

[0107] Fig. 13 is a diagram for explaining the optical loss and refractive index variation, resistance and capacitance, and bandwidth and TP according to the doping concentration of a CROW-based SIS type Mach-Zehnder optical modulator. Here, the doping concentration refers to the doping concentration of the first semiconductor layer and the second semiconductor layer illustrated in Fig. 9. In Fig. 13, (a) is a graph comparing the loss and refractive index variation of the optical modulator according to the doping concentration, in which the horizontal axis refers to the doping concentration, the left vertical axis refers to the loss of the optical modulator, and the right vertical axis refers to the refractive index variation of the optical modulator. In Fig. 13, (b) is a graph comparing the resistance and capacitance of the optical modulator according to the doping concentration, in which the horizontal axis refers to the doping concentration, the left vertical axis refers to the resistance, and the vertical axis refers to the capacitance. In Fig. 13, (c) is a graph comparing the TP of an optical modulator according to bandwidth, where the upper horizontal axis represents the doping concentration, the lower horizontal axis represents the bandwidth, and the vertical axis represents the modulation efficiency.

[0108] Referring to Fig. 13, as shown in (a), it can be seen that as the doping concentration increases, the optical loss in the CROW structure increases, but the change in the refractive index of the CROW structure is small.

[0109] As shown in (b), as the doping concentration increases, the resistance of the CROW structure decreases, but the change in capacitance is small.

[0110] As shown in (c), the bandwidth increases as the doping concentration increases, but the change in TP is small. However, when the doping concentration is 10 13 cm -3 When it exceeds , it can be seen that TP increases rapidly, and the modulation efficiency of the optical modulator is reduced.

[0111]

[0112] Fig. 14 is a diagram for explaining the passband and bandwidth according to the group refractive index of a CROW-based SIS type Mach-Zehnder optical modulator. In Fig. 14, (a) is a graph explaining the passband according to the group refractive index of the optical modulator, where the horizontal axis represents the group refractive index and the vertical axis represents the passband. In Fig. 14, (b) is a graph explaining the bandwidth according to the group refractive index of the optical modulator, where the horizontal axis represents the group refractive index and the vertical axis represents the bandwidth.

[0113] Referring to Figure 14, as shown in (a), it can be seen that the passband decreases as the group refractive index increases. It can be seen that as the passband decreases, the operating wavelength range of the optical modulator decreases.

[0114] In (b), the total bandwidth (Total BW) may include the bandwidth for resistance and capacitance (RC BW) and the optical bandwidth (Optical BW). Therefore, as shown in (b), the change in the bandwidth for resistance and capacitance according to the change in the group refractive index is very small, but it can be seen that the optical bandwidth decreases as the group refractive index increases. In other words, it can be seen that the change in the total bandwidth according to the increase in the group refractive index is due to the change in the optical bandwidth according to the increase in the group refractive index.

[0115]

[0116] Fig. 15 is a diagram for comparing and explaining the performance of a CROW-based SIS type Mach-Zehnder optical modulator with the performance of a general Mach-Zehnder optical modulator. In Fig. 15, the horizontal axis represents bandwidth, and the vertical axis represents TP. In addition, in Fig. 15, the performance of a general optical modulator is represented by '□' and '○', and the performance of a CROW-based SIS type Mach-Zehnder optical modulator according to an embodiment of the present invention is represented by '■', and n g stands for group refractive index.

[0117] Referring to Figure 15, it can be seen that as the group refractive index of the optical modulator increases, the TP decreases at the same bandwidth. In other words, it can be seen that as the group refractive index of the optical modulator increases, the modulation efficiency of the optical modulator improves at the same bandwidth. In addition, it can be seen that as the group refractive index of the optical modulator increases, the bandwidth decreases at the same TP.

[0118] Meanwhile, in Fig. 15, the gray dotted line represents the performance trend line of a typical Mach-Zehnder optical modulator, and the red dotted line represents the performance trend line of a CROW-based SIS-type Mach-Zehnder optical modulator according to an embodiment of the present invention. That is, it can be seen that the TP of the CROW-based SIS-type Mach-Zehnder optical modulator according to an embodiment of the present invention is smaller than the TP of the typical Mach-Zehnder optical modulator at the same bandwidth. That is, it can be seen that the modulation efficiency of the CROW-based SIS-type Mach-Zehnder optical modulator according to an embodiment of the present invention is superior to the modulation efficiency of the typical Mach-Zehnder optical modulator.

[0119] It can be seen that the bandwidth of the CROW-based SIS type Mach-Zehnder optical modulator according to an embodiment of the present invention is larger than that of a typical Mach-Zehnder optical modulator at the same TP. That is, it can be seen that the CROW-based SIS type Mach-Zehnder optical modulator according to an embodiment of the present invention has superior performance, such as a superior data transmission speed, reduced distortion of optical pulses and optical spectrum, and reduced optical noise, compared to a typical Mach-Zehnder optical modulator.

[0120]

[0121] The present invention is not limited to the embodiments described above, and may include new embodiments that combine at least two of the above embodiments or combine at least one of the above embodiments with a known technology.

[0122] Although the present invention has been described in detail through specific examples, this is intended to specifically explain the present invention, and the present invention is not limited thereto, and it will be apparent that modifications and improvements can be made by those skilled in the art within the technical spirit of the present invention.

[0123] All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

[0124] [Explanation of symbols]

[0125] 100: Semiconductor substrate

[0126] 200: First insulation layer

[0127] 300: First semiconductor layer

[0128] 400: Second insulation layer

[0129] 500: Second semiconductor layer

[0130] 600: First electrode

[0131] 700: Second electrode

Claims

1. First insulating layer on the semiconductor substrate; A first semiconductor layer provided on the first insulating layer, including a waveguide region and a pad region, wherein the waveguide region protrudes upward from a surface of the pad region and includes a CROW structure including a plurality of resonators arranged in one direction; A second insulating layer provided on the first semiconductor layer; and Including a second semiconductor layer provided on the second insulating layer, The thickness of the upper region of the CROW structure of the second insulating layer is smaller than the thickness of the other regions of the second insulating layer, The above resonator comprises a lattice resonant structure, An optical modulator comprising a plurality of resonators, wherein the lattice resonance structure comprises a plurality of protruding protrusion regions on both sides of the direction in which the resonators are arranged, and a recessed region having a recessed shape between adjacent protruding regions.

2. In paragraph 1, The above waveguide region is divided into a rib region corresponding to the CROW structure and a slab region on both sides of the rib region. An optical modulator in which the doping concentration of the first semiconductor layer and the second semiconductor layer in the rib region is lower than the doping concentration of the first semiconductor layer and the second semiconductor layer in the slab region.

3. In paragraph 2, In the above rib area, the first semiconductor layer and the second semiconductor layer are 10 17 cm -3 10 inland 18 cm -3 With a doping concentration of In the above slab area, the first semiconductor layer and the second semiconductor layer are 10 19 10 inland 20 cm -3 An optical modulator having a doping concentration of .

4. In paragraph 2, An optical modulator in which the thickness of the upper region of the CROW structure of the second insulating layer is 5 nm to 10 nm.

5. In paragraph 4, On a plane, the grating resonant structure is an optical modulator having 10 to 30 protruding regions on each side of the direction in which the resonators are arranged.

6. In paragraph 5, An optical modulator in which the protruding area protrudes at a distance of 5 nm to 300 nm.

7. In paragraph 6, a first electrode connected to the above pad area; and An optical modulator further comprising a second electrode connected to an area other than an area corresponding to the CROW structure of the second semiconductor layer.

8. Semiconductor substrate; A light source provided on one side of the semiconductor substrate; and Including an optical modulator arranged on the other side of the semiconductor substrate facing the light source, The above optical modulator A first insulating layer on a semiconductor substrate; A first semiconductor layer provided on the first insulating layer, including a waveguide region and a pad region, wherein the waveguide region protrudes upward from a surface of the pad region and includes a CROW structure including a plurality of resonators arranged in one direction; A second insulating layer provided on the first semiconductor layer; and Including a second semiconductor layer provided on the second insulating layer, The thickness of the upper region of the CROW structure of the second insulating layer is smaller than the thickness of the other regions of the second insulating layer, The above resonator comprises a lattice resonant structure, An optical module comprising a plurality of resonators, each of which has a plurality of protruding protrusion regions on both sides of the direction in which the resonators are arranged, and a recessed region having a recessed shape between the protruding regions, on a plane.

9. In paragraph 8, The above light source is an optical module connected to one end of the CROW structure in the direction in which the resonators are arranged.

10. In paragraph 9, The above waveguide region is divided into a rib region corresponding to the CROW structure and a slab region on both sides of the rib region. An optical module in which the doping concentration of the first semiconductor layer and the second semiconductor layer in the rib region is lower than the doping concentration of the first semiconductor layer and the second semiconductor layer in the slab region.

11. In paragraph 10, In the above rib area, the first semiconductor layer and the second semiconductor layer are 10 17 cm -3 10 inland 18 cm -3 With a doping concentration of In the above slab area, the first semiconductor layer and the second semiconductor layer are 10 19 10 inland 20 cm -3 An optical module having a doping concentration of .

12. In paragraph 10, An optical module wherein the thickness of the upper region of the CROW structure of the second insulating layer is 5 nm to 10 nm.

13. In paragraph 12, An optical module in which the lattice resonant structure has 10 to 30 protruding regions on each side of the direction in which the resonators are arranged on a plane.

14. In paragraph 13, An optical module in which the protruding area protrudes at a distance of 5 nm to 300 nm.

15. In paragraph 14, a first electrode connected to the above pad area; and An optical module further comprising a second electrode connected to an area other than an area corresponding to the CROW structure of the second semiconductor layer.

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