Traveling wave light modulation element and traveling wave light modulator

Abstract

The invention discloses a traveling wave light modulation element and a traveling wave light modulator, and the traveling wave light modulation element is used for receiving a first light signal, so that the first light signal is transmitted along the advancing direction. The traveling wave light modulation element comprises a first electrode, a second electrode, a first optical waveguide and a plurality of matching inductors. The first optical waveguide is used for transmitting a first optical signal between the first optical waveguides, and the two sides of the first optical waveguide are electrically connected to the first electrode and the second electrode respectively. The matching inductors are sequentially arranged in the advancing direction, the inductance values of the matching inductors are gradually increased in the advancing direction, and the inductance value of the first matching inductor arranged in the advancing direction is smaller than that of the last matching inductor arranged in the advancing direction. A first voltage is applied between the first electrode and the second electrode to modulate the phase of the first optical signal.

Description

Technical Field

[0001] The present invention relates to an optical modulation element and an optical modulator, and particularly to a traveling-wave optical modulation element and a traveling-wave optical modulator. Background Art

[0002] The working principle of an MZM modulator (Mach-Zehnder Modulator) is to change the electric field distribution and carrier concentration change inside the waveguide by applying electrical signals to two phase modulation arms, thereby changing the refractive indices of the two phase modulation arms, so that the light waves passing through the two arms generate a phase difference. If the two light waves are in the same phase at the output combiner, the light wave superposition will form a complete constructive interference; if the phase difference between the two light waves at the output combiner is 180 degrees, the light wave superposition will form a complete destructive interference. The output signal is 1 for complete constructive interference and 0 for complete destructive interference. In this way, the modulated optical signal can be obtained.

[0003] The MZM modulator can be divided into two types of modulators, namely, a lumped electrode and a traveling wave electrode, according to the design of its modulation electrode.

[0004] The bandwidth of the lumped electrode modulator is mainly limited by the parasitic capacitance of the electrode. The size of the electrode is usually much smaller than the wavelength of the electrical signal. Therefore, the refractive index of the optical waveguide is modulated by the electrical signal of the electrode. Although increasing the size of the electrode can improve the modulation efficiency, its parasitic capacitance will also increase, thereby limiting the available bandwidth. Therefore, the lumped electrode modulator requires a very high driving voltage to produce a large enough modulation effect in a small modulation range.

[0005] To improve the disadvantages of the lumped electrode modulator, the traveling wave electrode modulator lengthens the modulation electrode length and designs it as a transmission line. The electrical signal travels along the transmission line, and its transmission direction is the same as the transmission direction of the optical signal. Among them, the impedance of the driver and the terminal impedance both need to match the impedance of the transmission line electrode to avoid reflection. At this time, the optical signal will travel along the optical waveguide and be modulated by the electrical signal at the same time. The modulation efficiency is the highest when the traveling speeds of the electrical signal and the optical signal are the same.

[0006] Taking the optical waveguide formed by a P-N junction as an example, the modulation signal on the transmission electrode changes the voltage across the P-N junction through the P-type semiconductor layer and the N-type semiconductor layer to control the refractive index of the optical waveguide. Among them, the equivalent series resistance of the P-type semiconductor layer / N-type semiconductor layer will generate an R-C low-pass effect with the capacitance of the P-N junction, resulting in a reduction in the operating bandwidth. Therefore, to reduce this series resistance, the distance between the two electrodes of the ground electrode and the signal electrode is generally reduced. And to control the impedance of the transmission line electrode, the width of the signal electrode needs to be reduced. However, this narrow electrode will increase the loss of the signal when propagating on the electrode and reduce its modulation efficiency. Summary of the Invention

[0007] The present invention provides a traveling-wave optical modulation element and a traveling-wave optical modulator, which can increase the overall bandwidth of the system and have the advantage of impedance matching.

[0008] An embodiment of the present invention provides a traveling-wave optical modulation element. The traveling-wave optical modulation element is used to receive a first optical signal and transmit the first optical signal in the traveling direction. The traveling-wave optical modulation element includes a first electrode, a second electrode, a first optical waveguide, and a plurality of matching inductors. The first optical waveguide is used to transmit the first optical signal between the first optical waveguides, and is electrically connected to the first electrode and the second electrode on both sides respectively. The matching inductors are arranged in sequence along the traveling direction, and their inductance values increase along the traveling direction, and the inductance value of the first matching inductor arranged along the traveling direction is less than the inductance value of the last matching inductor arranged along the traveling direction. A first voltage is applied between the first electrode and the second electrode to modulate the phase of the first optical signal.

[0009] An embodiment of the present invention provides a traveling-wave optical modulator, which includes a beam splitter, a traveling-wave optical modulation element, and a combiner. The beam splitter is used to receive an optical signal and divide the optical signal into a first optical signal and a second optical signal. The traveling-wave optical modulation element is connected to the first beam splitter and is used to receive the first optical signal and the second optical signal, and cause the first optical signal and the second optical signal to be transmitted along the traveling direction. The traveling-wave optical modulation element includes a first electrode, a second electrode, a first optical waveguide, a third electrode, a fourth electrode, a second optical waveguide, and a plurality of matching inductors. The first optical waveguide is used to transmit the first optical signal between the first optical waveguides, and is electrically connected to the first electrode and the second electrode on both sides respectively. The second optical waveguide is used to transmit the second optical signal between the second optical waveguides, and is electrically connected to the third electrode and the fourth electrode on both sides respectively. The matching inductors are arranged in sequence along the traveling direction beside the first optical waveguide or the second optical waveguide, and are electrically connected between the first electrode and the first optical waveguide, between the second electrode and the first optical waveguide, between the third electrode and the second optical waveguide, or between the fourth electrode and the second optical waveguide respectively. The inductance values of the matching inductors increase along the traveling direction, and the inductance value of the first matching inductor arranged along the traveling direction is less than the inductance value of the last matching inductor arranged along the traveling direction. The combiner is connected to the first optical waveguide and the second optical waveguide and is used to receive the first optical signal and the second optical signal. A first voltage is applied between the first electrode and the second electrode to modulate the phase of the first optical signal, and a second voltage is applied between the third electrode and the fourth electrode to modulate the phase of the second optical signal. After the modulated first optical signal and the second optical signal are received by the combiner, a modulated optical signal is generated.

[0010] Based on the above, in the traveling-wave optical modulation element of an embodiment of the present invention and the traveling-wave optical modulator using the traveling-wave optical modulation element, the traveling-wave optical modulation element includes a first electrode, a second electrode, a first optical waveguide, and a plurality of matching inductors, and the matching inductors are designed to be arranged in sequence along the traveling direction, their inductance values increase along the traveling direction, and the inductance value of the first matching inductor arranged along the traveling direction is less than the inductance value of the last matching inductor arranged along the traveling direction. Therefore, the overall bandwidth of the system increases and it has the advantage of impedance matching, thereby reducing problems such as signal reflection. Description of the Drawings

[0011] Figure 1 is a schematic diagram of a traveling-wave optical modulator according to an embodiment of the present invention;

[0012] Figure 2A is Figure 1 a simplified schematic diagram of the element model of the traveling-wave optical modulation element in

[0013] Figure 2B is Figure 1 a cross-sectional schematic diagram of the traveling-wave optical modulation element in

[0014] Figure 3 It is a schematic cross-sectional view of the traveling-wave optical modulator according to an exemplary embodiment of the present invention at the first optical waveguide;

[0015] Figure 4 It is a schematic cross-sectional view of the traveling-wave optical modulator according to another exemplary embodiment of the present invention at the first optical waveguide;

[0016] Figure 5 It is a simplified schematic diagram of the equivalent circuit model of the traveling-wave optical modulator according to an embodiment of the present invention;

[0017] Figure 6 It is a graph of different frequency responses obtained by the traveling-wave optical modulator according to an embodiment of the present invention using matching inductors with different inductance values;

[0018] Figure 7 It is a graph of different return losses obtained by the traveling-wave optical modulator according to an embodiment of the present invention using matching inductors with different inductance values;

[0019] Figure 8 It is a schematic diagram of the traveling-wave optical modulator according to another embodiment of the present invention.

[0020] Symbol Explanation

[0021] 10: Traveling-wave optical modulator

[0022] 100: Beam splitter

[0023] 200, 200A: Traveling-wave optical modulator element

[0024] 210: First electrode

[0025] 220: Second electrode

[0026] 230: First optical waveguide

[0027] 231, 261, 238, 268: Metal layer

[0028] 232, 262: First-type high-concentration semiconductor layer

[0029] 233, 263: First-type semiconductor layer

[0030] 234, 264: First-type junction layer

[0031] 235, 265: Second-type junction layer

[0032] 236, 266: Second-type semiconductor layer

[0033] 237, 267: Second-type high-concentration semiconductor layer

[0034] 240: Third electrode

[0035] 250: Fourth electrode

[0036] 260: Second optical waveguide

[0037] 270: Matching inductor

[0038] 271: First sub - matching inductor

[0039] 272: Second sub - matching inductor

[0040] 273: Third sub - matching inductor

[0041] 274: Fourth sub - matching inductor

[0042] 300: Optical combiner

[0043] A1, A2: Regions

[0044] C1, C2, C3, C4, C5, D1, D2, D3, D4, D5, D6, D7, D8: Curves

[0045] Ca, Cu: Capacitors

[0046] L, L’: Optical signals

[0047] L1: First optical signal

[0048] L2: Second optical signal

[0049] Lu: Inductor

[0050] Ra, Ru: Resistors

[0051] TD: Traveling direction

[0052] u1: First voltage

[0053] u2: Second voltage Detailed implementation manners

[0054] Figure 1 is a schematic diagram of a traveling - wave optical modulator according to an embodiment of the present invention. Please refer to Figure 1 , an embodiment of the present invention provides a traveling - wave optical modulator 10, which includes a beam splitter 100, a traveling - wave optical modulation element 200, and an optical combiner 300. The beam splitter 100 is used to receive an optical signal L and split the optical signal L into a first optical signal L1 and a second optical signal L2. The traveling - wave optical modulation element 200 is connected to the first beam splitter 100 and is used to receive the first optical signal L1 and the second optical signal L2, and make the first optical signal L1 and the second optical signal L2 propagate along the traveling direction TD.

[0055] Figure 2A is Figure 1 a simplified schematic diagram of the element model of the traveling - wave optical modulation element inFigure 2B Yes Figure 1 is a schematic cross-sectional view of a traveling-wave optical modulation element. Among them, Figure 2B For example, it corresponds to Figure 2A the section line A-A' in Figures 1 to 2B , in this embodiment, the traveling-wave optical modulation element 200 includes a first electrode 210, a second electrode 220, a first optical waveguide 230, and a plurality of matching inductors 270. The first optical waveguide 230 is used to transmit the first optical signal L1 between the first optical waveguides 230, and its (opposite) two sides are electrically connected to the first electrode 210 and the second electrode 220 respectively. The matching inductors 270 are arranged in sequence along the traveling direction TD, and their inductance values increase along the traveling direction TD, and the inductance value of the first matching inductor 270 arranged along the traveling direction TD is less than the inductance value of the last matching inductor 270 arranged along the traveling direction TD. Among them, the increase in the inductance value of the foregoing matching inductor 270 along the traveling direction TD can be defined as: the inductance value of each matching inductor 270 is greater than or equal to the inductance value of the previous matching inductor 270 of each matching inductor 270 in the traveling direction TD or less than or equal to the inductance value of the next matching inductor 270 of each matching inductor 270 in the traveling direction TD. A first voltage u1 is applied between the first electrode 210 and the second electrode 220 to modulate the phase of the first optical signal L1.

[0056] In this embodiment, the traveling-wave optical modulation element 200 is, for example, a P-N junction type optical modulation element. For example, the first optical waveguide 230 includes a first-type junction layer 234 and a second-type junction layer 235, and the traveling-wave optical modulation element 200 further includes a plurality of connection layers connected to the first optical waveguide 230: a metal layer 231, a first-type high-concentration semiconductor layer 232, a first-type semiconductor layer 233, a second-type semiconductor layer 236, a second-type high-concentration semiconductor layer 237, and a metal layer 238. The first type can be a P type or an N type, and the second type can be an N type or a P type. The first-type high-concentration semiconductor layer 232, the first-type semiconductor layer 233, the first-type junction layer 234, the second-type junction layer 235, the second-type semiconductor layer 236, and the second-type high-concentration semiconductor layer 237 are arranged in a coplanar manner along the direction perpendicular to the traveling direction TD. A P-N junction is formed between the first-type junction layer 234 and the second-type junction layer 235 to serve as an optical waveguide. The first-type high-concentration semiconductor layer 232 is electrically connected to the metal layer 231, and the metal layer 231 is electrically connected to the first electrode 210. The second-type high-concentration semiconductor layer 237 is electrically connected to the metal layer 238, and the metal layer 238 is electrically connected to the second electrode 220. Therefore, when a first voltage u1 is applied between the first electrode 210 and the second electrode 220, the refractive index of the optical waveguide formed by the P-N junction is changed to modulate the first optical signal L1.

[0057] In this embodiment, the traveling-wave optical modulation element 200 further includes a third electrode 240, a fourth electrode 250, and a second optical waveguide 260. The second optical waveguide 260 is configured to enable the second optical signal L2 to be transmitted between the second optical waveguides 260, and is electrically connected to the third electrode 240 and the fourth electrode 250 on (opposite) two sides respectively. Among them, a second voltage u2 is applied between the third electrode 240 and the fourth electrode 250 to modulate the phase of the second optical signal L2.

[0058] In this embodiment, similar to the first optical waveguide 230, the second optical waveguide 260 includes a first-type contact layer 264 and a second-type contact layer 265, and the traveling-wave optical modulation element 200 further includes a plurality of connection layers connected to the second optical waveguide 260: a metal layer 261, a first-type high-concentration semiconductor layer 262, a first-type semiconductor layer 263, a second-type semiconductor layer 266, a second-type high-concentration semiconductor layer 267, and a metal layer 268. The first-type high-concentration semiconductor layer 262, the first-type semiconductor layer 263, the first-type contact layer 264, the second-type contact layer 265, the second-type semiconductor layer 266, and the second-type high-concentration semiconductor layer 267 are arranged in a direction perpendicular to the traveling direction TD and are coplanar. A P-N junction is formed between the first-type contact layer 264 and the second-type contact layer 265 to serve as an optical waveguide. The first-type high-concentration semiconductor layer 262 is electrically connected to the metal layer 261, and the metal layer 261 is electrically connected to the third electrode 240. The second-type high-concentration semiconductor layer 267 is electrically connected to the metal layer 268, and the metal layer 268 is electrically connected to the fourth electrode 250. Therefore, when a second voltage u2 is applied between the third electrode 240 and the fourth electrode 250, the refractive index of the optical waveguide formed by the P-N junction is changed to modulate the second optical signal L2.

[0059] In addition, in this embodiment, the matching inductor 270 is formed by using, for example, a semiconductor manufacturing process. The matching inductor 270 can be designed as a spiral inductor, a stacked inductor, or a solenoidal inductor, but the present invention is not limited thereto. Among them, when the matching inductor 270 is designed as a stacked inductor, the matching inductor 270 may include multiple metal layers and connect these metal layers through vias.

[0060] Figure 3 is a cross-sectional schematic view of the traveling-wave optical modulation element according to an exemplary embodiment of the present invention at the first optical waveguide. Figure 4 is a cross-sectional schematic view of the traveling-wave optical modulation element according to another exemplary embodiment of the present invention at the first optical waveguide. Please refer to Figure 3 and Figure 4, in one embodiment, the matching inductors 270 are arranged in sequence along the traveling direction TD beside the first optical waveguide 230, and are electrically connected between the first electrode 210 and the first optical waveguide 230 or between the second electrode 220 and the first optical waveguide 230 respectively. For example, all the matching inductors 270 are electrically connected between the first electrode 210 and the first optical waveguide 230, as shown in Figure 3 or all the matching inductors 270 are electrically connected between the second electrode 220 and the first optical waveguide 230, as shown in Figure 4 . In another embodiment, one of the matching inductors 270 may include a first sub-matching inductor 271 and a second sub-matching inductor 272. Among them, the first sub-matching inductor 271 is electrically connected between the first electrode 210 and the first optical waveguide 230, and the second sub-matching inductor 272 is electrically connected between the second electrode 220 and the first optical waveguide 230. However, the present invention is not limited thereto. In other embodiments, each matching inductor 270 may include a first sub-matching inductor 271 and a second sub-matching inductor 272. The first sub-matching inductor 271 is electrically connected between the first electrode 210 and the first optical waveguide 230, and the second sub-matching inductor 272 is electrically connected between the second electrode 220 and the first optical waveguide 230.

[0061] In yet another embodiment, the matching inductors 270 are arranged in sequence along the traveling direction TD beside the first optical waveguide 230 or the second optical waveguide 260, and are electrically connected between the first electrode 210 and the first optical waveguide 230, between the second electrode 220 and the first optical waveguide 230, between the third electrode 240 and the second optical waveguide 260, or between the fourth electrode 250 and the second optical waveguide 260 respectively, as shown in Figure 2A and Figure 2B . In other embodiments, one of the matching inductors 270 includes a first sub-matching inductor 271 and a second sub-matching inductor 272. Among them, the first sub-matching inductor 271 is electrically connected between the first electrode 210 and the first optical waveguide 230 or between the second electrode 220 and the first optical waveguide 230, and the second sub-matching inductor 272 is electrically connected between the third electrode 240 and the second optical waveguide 260 or between the fourth electrode 250 and the second optical waveguide 260. However, the present invention is not limited thereto. Each matching inductor 270 may include a first sub-matching inductor 271 and a second sub-matching inductor 272. The first sub-matching inductor 271 is electrically connected between the first electrode 210 and the first optical waveguide 230 or between the second electrode 220 and the first optical waveguide 230, and the second sub-matching inductor 272 is electrically connected between the third electrode 240 and the second optical waveguide 260 or between the fourth electrode 250 and the second optical waveguide 260.

[0062] In yet another embodiment, one of the matching inductors 270 includes a first sub-matching inductor 271, a second sub-matching inductor 272, and a third sub-matching inductor 273. Among them, the first sub-matching inductor 271 is electrically connected between the first electrode 210 and the first optical waveguide 230, the second sub-matching inductor 272 is electrically connected between the second electrode 220 and the first optical waveguide 230, and the third sub-matching inductor 273 is electrically connected between the third electrode 240 and the second optical waveguide 260 or between the fourth electrode 250 and the second optical waveguide 260. However, the present invention is not limited thereto. In other embodiments, each matching inductor 270 may include a first sub-matching inductor 271, a second sub-matching inductor 272, and a third sub-matching inductor 273. The first sub-matching inductor 271 is electrically connected between the first electrode 210 and the first optical waveguide 230, the second sub-matching inductor 272 is electrically connected between the second electrode 220 and the first optical waveguide 230, and the third sub-matching inductor 273 is electrically connected between the third electrode 240 and the second optical waveguide 260 or between the fourth electrode 250 and the second optical waveguide 260.

[0063] In yet another embodiment, as Figure 2A shown in Figure 2B , one of the matching inductors 270 includes a first sub-matching inductor 271, a second sub-matching inductor 272, a third sub-matching inductor 273, and a fourth sub-matching inductor 274. Among them, the first sub-matching inductor 271 is electrically connected between the first electrode 210 and the first optical waveguide 230, the second sub-matching inductor 272 is electrically connected between the second electrode 220 and the first optical waveguide 230, the third sub-matching inductor 273 is electrically connected between the third electrode 240 and the second optical waveguide 260, and the fourth sub-matching inductor 274 is electrically connected between the fourth electrode 250 and the second optical waveguide 260. However, the present invention is not limited thereto. In other embodiments, each matching inductor 270 may include a first sub-matching inductor 271, a second sub-matching inductor 272, a third sub-matching inductor 273, and a fourth sub-matching inductor 274. The first sub-matching inductor 271 is electrically connected between the first electrode 210 and the first optical waveguide 230, the second sub-matching inductor 272 is electrically connected between the second electrode 220 and the first optical waveguide 230, the third sub-matching inductor 273 is electrically connected between the third electrode 240 and the second optical waveguide 260, and the fourth sub-matching inductor 274 is electrically connected between the fourth electrode 250 and the second optical waveguide 260.

[0064] In addition, in one embodiment, the inductance value of the matching inductor 270 increases along the traveling direction TD. For example, the inductance value of the first inductor in the traveling direction TD is less than or equal to the next inductance value, but the inductance value of the first inductor in the traveling direction TD is less than the last inductance value. In other embodiments, the inductance value of the matching inductor 270 increases strictly along the traveling direction TD. For example, the inductance value of the matching inductor 270 increases strictly along the traveling direction TD in an arithmetic progression, a geometric progression, or an exponential law. Among them, the aforementioned inductance value of the matching inductor 270 increasing strictly along the traveling direction TD can be defined as: the inductance value of each matching inductor 270 is greater than the inductance value of the previous matching inductor 270 of each matching inductor 270 in the traveling direction TD or less than the inductance value of the next matching inductor 270 of each matching inductor 270 in the traveling direction TD.

[0065] Please refer to Figure 1 , in this embodiment, the optical combiner 300 is connected to the first optical waveguide 230 and the second optical waveguide 260 to receive the first optical signal L1 and the second optical signal L2. Moreover, after the modulated first optical signal L1 and the second optical signal L2 are received by the optical combiner 300, a modulated optical signal L' is generated.

[0066] Figure 5 is a simplified schematic diagram of an equivalent circuit model of a traveling-wave optical modulator according to an embodiment of the present invention. Figure 6 is a graph of different frequency responses obtained by using matching inductors with different inductance values in a traveling-wave optical modulator according to an embodiment of the present invention. Figure 7 is a graph of different return losses obtained by using matching inductors with different inductance values in a traveling-wave optical modulator according to an embodiment of the present invention.

[0067] In Figure 5 , the traveling-wave optical modulation element 200 in the traveling-wave optical modulator 10 is divided into 9 regions A1, A2,... along the traveling direction TD, and each region includes 5 units. For the units within the same region, the inductance values of their matching inductors 270 are the same. The inductance values from region A1 to region A9 (not shown) are La1, La2,... La9 respectively. Each unit includes an inductor Lu, a resistor Ru, a capacitor Cu, a resistor Ra, a matching inductor 270, and a capacitor Ra. Among them, the inductor Lu, the resistor Ru, and the capacitor Cu are the equivalent inductance, equivalent resistance, and equivalent capacitance from the first electrode 210, the second electrode 220, the third electrode 240, and the fourth electrode 250. The resistor Ra and the capacitor Ca are the parasitic resistance and parasitic capacitance from the first optical waveguide 230 and the second optical waveguide 260. Incidentally, due to cost considerations and better implementation in design (for example, it is not easy to perfectly achieve different inductance values for each matching inductor 270 in the manufacturing process), Figure 5The traveling-wave optical modulator element 200 is divided into multiple regions A1, A2, …. The inductance values of the matching inductors 270 in the same region can be the same, and the inductance value of the matching inductor 270 in each region is less than or equal to the inductance value of the matching inductor 270 in the next region along the traveling direction TD, thereby achieving the condition of gradually increasing inductance values. However, in other embodiments, the inductance values of the matching inductors 270 of the traveling-wave optical modulator element 200 may be different from each other, or the inductance values of the matching inductors 270 in the same region may also increase or strictly increase along the traveling direction TD.

[0068] Table 1

[0069] Inductance value (nH) 3dB bandwidth (GHz) Bandwidth increase ratio (%) 0 27.6 0.00 0.2 28.9 4.71 0.4 29.6 7.25 0.6 29.9 8.33 0.8 29.6 7.25 1 29.2 5.80 1.2 28.5 3.26 0～1.3 31.9 15.58

[0070] Table 2

[0071]

[0072]

[0073] In Figure 6 , the horizontal axis is the frequency (GHz), and the vertical axis is the frequency response (dB). The equivalent circuit model of the traveling-wave optical modulator 10 adopts the following simulation parameters: Lu = 0.062 nH, Ru = 2.5 ohm, Cu = 12.800 fF, Ra = 160 ohm, Ca = 13.000 fF. The inductance values of the matching inductors 270 are set to be all 0 nH (the inductance value in curve C1 or Table 1 is 0, that is, the case where the matching inductor 270 is not provided), 0.2 nH (the inductance value in Table 1 is 0.2), 0.4 nH (the inductance value in curve C2 or Table 1 is 0.4), 0.6 nH (the inductance value in Table 1 is 0.6), 0.8 nH (the inductance value in curve C3 or Table 1 is 0.8), 1 nH (the inductance value in Table 1 is 1), or 1.2 nH (the inductance value in curve C4 or Table 1 is 1.2). In curve C5 or the inductance value in Table 1 is 0 to 1.3, the inductance values of the matching inductors 270 are set as shown in Table 2: The inductance value increases with 9 regions, from region A1, region A2, region A3 ( Figure 5 not shown), …, region A9 ( Figure 5 not shown). However, the present invention does not limit the number of regions into which the traveling-wave optical modulator element 200 can be divided.

[0074] Please first refer to Figure 5 , Figure 6 and Table 1. When the matching inductor 270 is not provided, the 3 dB bandwidth of the system is the smallest. On the contrary, when the matching inductor 270 is provided, the 3 dB bandwidth of the system increases. Among them, when the system is designed such that the inductance value of the matching inductor 270 increases along the traveling direction TD, that is, curve C5, the system has the best 3 dB bandwidth.

[0075] InFigure 7 Among them, the horizontal axis is the frequency (GHz), and the vertical axis is the input return loss in dB. Curve D1 is when the inductance value of the matching inductor 270 is set to 0 nH for all. Curves D2 to D7 are when the inductance values of the matching inductor 270 are set to fixed values of 0.2 nH, 0.4 nH, 0.6 nH, 0.8 nH, 1.0 nH, and 1.2 nH respectively. The inductance value setting of the matching inductor 270 in curve D8 is shown in Table 2 and will not be elaborated here.

[0076] Please refer to Figure 7 , when the system does not have a matching inductor, that is, curve D1, the return loss of the system is less than -15 dB, indicating impedance matching, thus avoiding signal reflection. However, when the system has a matching inductor 270 and the inductance value is set to a fixed value, that is, curves D2 to D7, the return loss of the system becomes larger. That is to say, although the system bandwidth increases (such as Figure 6 curves C2 to C4 or the inductance values in Table 1 are from 0.2 to 1.2), the impedance mismatch instead causes signal reflection, thus degrading the signal quality. When the system is designed such that the inductance value of the matching inductor 270 increases along the traveling direction TD, that is, curve D8, the return loss of the system is less than -15 dB in the entire frequency band. Therefore, the system has the advantages of increasing the 3 dB bandwidth and impedance matching, thus avoiding signal reflection.

[0077] Based on the above, in the traveling-wave optical modulation element 200 of an embodiment of the present invention and the traveling-wave optical modulator 10 employing the traveling-wave optical modulation element 200, the traveling-wave optical modulation element 200 is used to receive the first optical signal L1 and make the first optical signal L1 propagate along the traveling direction TD. The traveling-wave optical modulation element 200 includes a first electrode 210, a second electrode 220, a first optical waveguide 230, and a plurality of matching inductors 270. Among them, the matching inductors 270 are arranged in sequence along the traveling direction TD, their inductance values increase along the traveling direction TD, and the inductance value of the first matching inductor 270 arranged along the traveling direction TD is less than the inductance value of the last matching inductor 270 arranged along the traveling direction TD. Therefore, the overall bandwidth of the system increases and has the advantage of impedance matching, thus reducing problems such as signal reflection.

[0078] Figure 8 is a schematic diagram of a traveling-wave optical modulation element according to another embodiment of the present invention. Please refer to Figure 8 , the traveling-wave optical modulation element 200A and Figure 2Bis substantially the same as the traveling-wave optical modulation element 200, and the main difference is that: in this embodiment, the second electrode 220 and the third electrode 240 form a common electrode. At the same time, the metal layer 238 connected to the first optical waveguide 230 and the metal layer 268 connected to the second optical waveguide 260 can be designed as a common metal layer, and the second-type high-concentration semiconductor layer 237 connected to the first optical waveguide 230 and the second-type high-concentration semiconductor layer 267 connected to the second optical waveguide 260 can also be designed as a common second-type high-concentration semiconductor layer.

[0079] Based on the above, in an embodiment of the present invention, since the second electrode 220 and the third electrode 240 form a common electrode, a traveling-wave modulator using the traveling-wave optical modulation element 200A can form a push-pull type optical modulator, so the space utilization rate of the system is relatively high. The remaining advantages of the traveling-wave optical modulation element 200A are the same as those of Figure 2B the traveling-wave optical modulation element 200 and will not be elaborated here.

[0080] In summary, in the traveling-wave optical modulation element and the traveling-wave modulator using the traveling-wave optical modulation element according to an embodiment of the present invention, the traveling-wave optical modulation element includes a first electrode, a second electrode, a first optical waveguide, and a plurality of matching inductors. Among them, the matching inductors are designed to be arranged in sequence along the traveling direction, the inductance value increases along the traveling direction, and the inductance value of the first matching inductor arranged along the traveling direction is less than the inductance value of the last matching inductor arranged along the traveling direction. Therefore, the overall bandwidth of the system increases and has the advantage of impedance matching, thereby reducing problems such as signal reflection.

Claims

1. A traveling-wave optical modulation element for receiving a first optical signal and causing the first optical signal to propagate in a traveling direction, the traveling-wave optical modulation element comprising: A first electrode; A second electrode; A first optical waveguide for causing the first optical signal to propagate between the first optical waveguides, and electrically connected to the first electrode and the second electrode on both sides respectively; And A plurality of matching inductors arranged in sequence along the traveling direction, the inductance values of which increase along the traveling direction, and the inductance value of the first matching inductor arranged along the traveling direction is less than the inductance value of the last matching inductor arranged along the traveling direction, Wherein a first voltage is applied between the first electrode and the second electrode to modulate the phase of the first optical signal.

2. The traveling-wave optical modulation element according to claim 1, wherein the matching inductors are arranged in sequence along the traveling direction beside the first optical waveguide, and are respectively electrically connected between the first electrode and the first optical waveguide or between the second electrode and the first optical waveguide.

3. The traveling-wave optical modulation element according to claim 2, wherein one of the matching inductors includes a first sub-matching inductor and a second sub-matching inductor, wherein: The first sub-matching inductor is electrically connected between the first electrode and the first optical waveguide, and the second sub-matching inductor is electrically connected between the second electrode and the first optical waveguide.

4. The traveling-wave optical modulation element according to claim 1, wherein the inductance values of the matching inductors increase strictly along the traveling direction.

5. The traveling-wave optical modulation element according to claim 1, wherein the traveling-wave optical modulation element has a plurality of regions, and the inductance values of the matching inductors in the same region are the same.

6. The traveling-wave optical modulation element according to claim 1, further comprising: A third electrode; A fourth electrode; And A second optical waveguide, wherein the traveling-wave optical modulation element is used to receive a second optical signal and cause the second optical signal to propagate in the traveling direction, and the second optical waveguide is used to cause the second optical signal to propagate between the second optical waveguides, and is electrically connected to the third electrode and the fourth electrode on both sides respectively, Wherein a second voltage is applied between the third electrode and the fourth electrode to modulate the phase of the second optical signal.

7. The traveling-wave optical modulation element according to claim 6, wherein the matching inductors are arranged in sequence along the traveling direction beside the first optical waveguide or the second optical waveguide, and are respectively electrically connected between the first electrode and the first optical waveguide, between the second electrode and the first optical waveguide, between the third electrode and the second optical waveguide, or between the fourth electrode and the second optical waveguide.

8. The traveling-wave optical modulation element according to claim 7, wherein one of the matching inductors includes a first sub-matching inductor and a second sub-matching inductor, wherein: The first sub-matching inductor is electrically connected between the first electrode and the first optical waveguide or between the second electrode and the first optical waveguide, and the second sub-matching inductor is electrically connected between the third electrode and the second optical waveguide or between the fourth electrode and the second optical waveguide.

9. The traveling-wave optical modulation element according to claim 7, wherein one of the matching inductors includes a first sub-matching inductor, a second sub-matching inductor, and a third sub-matching inductor, wherein: The first sub-matching inductor is electrically connected between the first electrode and the first optical waveguide, the second sub-matching inductor is electrically connected between the second electrode and the first optical waveguide, and the third sub-matching inductor is electrically connected between the third electrode and the second optical waveguide or between the fourth electrode and the second optical waveguide.

10. The traveling-wave optical modulation element according to claim 7, wherein one of the matching inductors includes a first sub-matching inductor, a second sub-matching inductor, a third sub-matching inductor, and a fourth sub-matching inductor, wherein: The first sub-matching inductor is electrically connected between the first electrode and the first optical waveguide, the second sub-matching inductor is electrically connected between the second electrode and the first optical waveguide, the third sub-matching inductor is electrically connected between the third electrode and the second optical waveguide, and the fourth sub-matching inductor is electrically connected between the fourth electrode and the second optical waveguide.

11. The traveling-wave optical modulation element according to claim 6, wherein the second electrode and the third electrode form a common electrode.

12. A traveling-wave optical modulator, comprising: A beam splitter for receiving an optical signal and splitting the optical signal into a first optical signal and a second optical signal; A traveling-wave optical modulation element connected to the first beam splitter for receiving the first optical signal and the second optical signal and causing the first optical signal and the second optical signal to be transmitted along a traveling direction, comprising: A first electrode; A second electrode; A first optical waveguide for causing the first optical signal to be transmitted between the first optical waveguides and being electrically connected to the first electrode and the second electrode on both sides; A third electrode; A fourth electrode; A second optical waveguide for causing the second optical signal to be transmitted between the second optical waveguides and being electrically connected to the third electrode and the fourth electrode on both sides; and A plurality of matching inductors arranged in sequence along the traveling direction beside the first optical waveguide or the second optical waveguide and electrically connected between the first electrode and the first optical waveguide, between the second electrode and the first optical waveguide, between the third electrode and the second optical waveguide, or between the fourth electrode and the second optical waveguide, the inductance values of the matching inductors increasing along the traveling direction, and the inductance value of the first matching inductor arranged along the traveling direction being less than the inductance value of the last matching inductor arranged along the traveling direction; and A combiner connected to the first optical waveguide and the second optical waveguide for receiving the first optical signal and the second optical signal, wherein a first voltage is applied between the first electrode and the second electrode to modulate the phase of the first optical signal, and a second voltage is applied between the third electrode and the fourth electrode to modulate the phase of the second optical signal, wherein the modulated first optical signal and the second optical signal are received by the combiner to generate the modulated optical signal.

13. The traveling-wave optical modulator according to claim 12, wherein the matching inductors are arranged in sequence along the traveling direction beside the first optical waveguide and are electrically connected between the first electrode and the first optical waveguide or between the second electrode and the first optical waveguide.

14. The traveling-wave optical modulator according to claim 13, wherein one of the matching inductors includes a first sub-matching inductor and a second sub-matching inductor, wherein: The first sub-matching inductor is electrically connected between the first electrode and the first optical waveguide, and the second sub-matching inductor is electrically connected between the second electrode and the first optical waveguide.

15. The traveling-wave optical modulator according to claim 12, wherein the inductance values of the matching inductors strictly increase along the traveling direction.

16. The traveling-wave optical modulator according to claim 12, wherein the traveling-wave optical modulation element has a plurality of regions, and the inductance values of the matching inductors in the same region are the same.

17. The traveling-wave optical modulator according to claim 12, wherein one of the matching inductors includes a first sub-matching inductor and a second sub-matching inductor, wherein: The first sub-matching inductor is electrically connected between the first electrode and the first optical waveguide or between the second electrode and the first optical waveguide, and the second sub-matching inductor is electrically connected between the third electrode and the second optical waveguide or between the fourth electrode and the second optical waveguide.

18. The traveling-wave optical modulator according to claim 12, wherein one of the matching inductors includes a first sub-matching inductor, a second sub-matching inductor, and a third sub-matching inductor, wherein: The first sub-matching inductor is electrically connected between the first electrode and the first optical waveguide, the second sub-matching inductor is electrically connected between the second electrode and the first optical waveguide, and the third sub-matching inductor is electrically connected between the third electrode and the second optical waveguide or between the fourth electrode and the second optical waveguide.

19. The traveling-wave optical modulator according to claim 12, wherein one of the matching inductors includes a first sub-matching inductor, a second sub-matching inductor, a third sub-matching inductor, and a fourth sub-matching inductor, wherein: The first sub-matching inductor is electrically connected between the first electrode and the first optical waveguide, the second sub-matching inductor is electrically connected between the second electrode and the first optical waveguide, the third sub-matching inductor is electrically connected between the third electrode and the second optical waveguide, and the fourth sub-matching inductor is electrically connected between the fourth electrode and the second optical waveguide.

20. The traveling-wave optical modulator according to claim 12, wherein the second electrode and the third electrode form a common electrode.

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