Patent Application
20200341345
The present application is based upon and claims the benefit of the priority from Japanese patent application No. 2019-086296, filed on Apr. 26, 2019, which is hereby incorporated by reference in its entirety.
The present disclosure relates to a Mach-Zehnder modulator and an optical modulation device.
U.S. Pat. No. 9,069,223 discloses a Mach-Zehnder optical modulator.
The present disclosure provides a Mach-Zehnder modulator including a first arm waveguide; a second arm waveguide; a differential transmission path including a first metal body and a second metal body connected to the first arm waveguide and the second arm waveguide, respectively, and a third metal body for a reference potential; a conductive region for connecting the first arm waveguide and the second arm waveguide to each other; and a capacitor connected between the conductive region and the third metal body.
The present disclosure also provides an optical modulation device including the Mach-Zehnder modulator, an open collector differential drive circuit for driving the Mach-Zehnder modulator, and a terminator connected to the open collector drive circuit via the first metal body and the second metal body of the Mach-Zehnder modulator.
The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which:
U.S. Pat. No. 9,069,223 discloses a Mach-Zehnder optical modulator including strip lines having a plurality of ground surfaces, and a drive circuit connected to the strip lines with a characteristic impedance. The Mach-Zehnder optical modulator receives a differential signal through a transmission path. The differential signal is generated by the drive circuit and is applied to the transmission path of the Mach-Zehnder optical modulator through the characteristic impedance at an output end of the drive circuit.
It is desired to provide a Mach-Zehnder modulator and an optical modulation device capable of reducing a common mode.
Subsequently, some specific examples will be described.
A Mach-Zehnder modulator according to a specific example includes (a) a first arm waveguide, (b) a second arm waveguide, (c) a differential transmission path including a first metal body and a second metal body connected to the first arm waveguide and the second arm waveguide, respectively, and a third metal body for a reference potential, (d) a conductive region for connecting the first arm waveguide and the second arm waveguide to each other, and (e) a capacitor connected between the conductive region and the third metal body.
According to the Mach-Zehnder modulator, the first arm waveguide, the conductive region, and the second arm waveguide are connected between the first metal body and the second metal body of the transmission path, and a signal on the transmission path can drive the first arm waveguide and the second arm waveguide. The capacitor is connected between the conductive region and the third metal body and reduces a common mode in the transmission path.
In the Mach-Zehnder modulator according to the specific example, the capacitor includes a first metal-insulator-metal (MIM) element and a second MIM element. The differential transmission path passes between the first MIM element and the second MIM element.
According to the Mach-Zehnder modulator, the first MIM element and the second MIM element are provided on an outer side of the differential transmission path so that a ground surface formed by the differential transmission path is unlikely to be disturbed.
The Mach-Zehnder modulator according to the specific example further includes an additional metal body connected to the conductive region and applying a potential to the conductive region. The conductive region includes a III-V compound semiconductor.
According to the Mach-Zehnder modulator, the additional metal body supplies power to the conductive region independently from a reference potential line. The capacitor stabilizes a potential of power supplied from the metal body and reduces the common mode.
In the Mach-Zehnder modulator according to the specific example, the first metal body has a part extending along the first arm waveguide. The second metal body has a part extending along the second arm waveguide. The third metal body has a part extending between the part of the first metal body and the part of the second metal body.
According to the Mach-Zehnder modulator, the first arm waveguide and the second arm waveguide are driven using an SGS-type transmission path.
An optical modulation device according to a specific example includes (a) the Mach-Zehnder modulator, (b) an open collector-type differential drive circuit for driving the Mach-Zehnder modulator, and (c) a terminator connected to the differential drive circuit via the first metal body and the second metal body of the Mach-Zehnder modulator.
According to the optical modulation device, in the Mach-Zehnder modulator driven by the differential-type open collector drive circuit, the common mode can be reduced.
The Mach-Zehnder modulator may be driven by a back-termination driver and an open collector driver. Specifically, the Mach-Zehnder modulator is connected to an output end of the back-termination driver using a characteristic impedance. Alternatively, the Mach-Zehnder modulator is connected to an output end of the open collector driver without characteristic impedance.
The knowledge of the present disclosure can be understood easily by taking the following detailed description into consideration with reference to the accompanying drawings illustrated as examples. Subsequently, with reference to the accompanying drawings, the optical modulation device and the Mach-Zehnder modulator according to the present embodiment will be described. If possible, the same reference signs are applied to the same parts.
The differential drive circuit 15 includes an open collector (or an open drain) differential circuit, and the open collector differential circuit drives the Mach-Zehnder modulator 13 in response to a drive signal received by inputs (22a and 22b). The Mach-Zehnder modulator 13 is connected to the terminator 17 via a transmission line. Specifically, the Mach-Zehnder modulator 13 receives a differential signal from the differential drive circuit 15 at one end thereof and is terminated by the terminator 17 at the other end.
The Mach-Zehnder modulator 13 includes an input waveguide WG1, a splitter DP, a first arm waveguide A1RM, a second arm waveguide A2RM, a multiplexer MP, and an output waveguide WG2. The splitter DP is coupled to the first arm waveguide A1RM and the second arm waveguide A2RM to receive a continuous light beam from the input waveguide WG1 and to provide the first arm waveguide A1RM and the second arm waveguide A2RM with a continuous light beam. The multiplexer MP is coupled to the first arm waveguide A1RM and the second arm waveguide A2RM to multiplex modulation light beams of the first arm waveguide A1RM and the second arm waveguide A2RM and is connected to the output waveguide WG2.
The Mach-Zehnder modulator 13 further includes a conductive region 19 (for example, a conductive semiconductor layer) and transmission paths 21. The conductive region 19 is connected to one end of the first arm waveguide A1RM and one end of the second arm waveguide A2RM and connects the first arm waveguide A1RM and the second arm waveguide A2RM to each other. The transmission paths 21 include a first line 21a and a second line 21b for transmitting a differential signal, and at least one third line 21c. In the present example, a single third line 21c is provided between the first line 21a and the second line 21b, forms the SGS-type transmission path, and is also insulated from the conductive region related to the Mach-Zehnder modulator 13. Specifically, the first line 21a and the second line 21b are respectively connected to the other end of the first arm waveguide A1RM and the other end of the second arm waveguide A2RM. The transmission paths 21 apply differential signals between the other end of the first arm waveguide A1RM and the other end of the second arm waveguide A2RM connected to each other by the conductive region 19. The third line 21c is disposed such that it coincides with the electrical ground surface.
The differential drive circuit 15 generates a modulation signal for modulating light of the Mach-Zehnder modulator 13 from a signal received by the inputs (22a and 22b). Specifically, the differential drive circuit 15 includes a pair of open collector circuits 25a and 25b, a current source 25c (current source circuit), and a transmission line 27. The open collector circuits 25a and 25b are connected to the current source 25c, and the current source 25c is connected to a power source line (for example, VEE). The transmission line 27 includes a pair of signal lines (for example, 27a and 27b) and a pair of grounding lines (for example, 27c and 27d). The first signal line 27a and the second signal line 27b are provided between the first reference potential line 27c and the second reference potential line 27d and form a GSSG-type transmission path. The open collector circuits 25a and 25b are connected to the Mach-Zehnder modulator 13 via the transmission line 27.
The terminator 17 includes a first termination resistor RL1 and a second termination resistor RL2 serving as termination elements. One end of the first termination resistor RL1 and one end of the second termination resistor RL2 are respectively connected to the first line 21a and the second line 21b. The other end of the first termination resistor RL1 and the other end of the second termination resistor RL2 are connected to a power source line (for example, VCC). In the present example, the third line 21c of the transmission paths 21 is not connected to the termination element of the terminator 17.
The Mach-Zehnder modulator 13 integrates capacitors 25 together with the input waveguide WG1, the splitter DP, the first arm waveguide A1RM, the second arm waveguide A2RM, the multiplexer MP, and the output waveguide WG2. The capacitors 25 are connected between the conductive region 19 and the third line 21c. According to the optical modulation device 11, the capacitors 25 are connected between the conductive region 19 and the third line 21c so that the common mode can be reduced in the Mach-Zehnder modulator 13 connected between the differential drive circuit 15 and the terminator 17.
The Mach-Zehnder modulator 13 further includes a bias line LBIAS. The bias line LBIAS is connected to the conductive region 19 and applies a potential to the conductive region 19. The conductive region 19 is connected to a bias voltage source VBIAS.
The Mach-Zehnder modulator 14 includes a first arm waveguide 61, a second arm waveguide 62, differential transmission paths 64, capacitors 65, and a semiconductor layer 66. The first arm waveguide 61 and the second arm waveguide 62 are provided on the semiconductor layer 66. The first arm waveguide A1RM and the second arm waveguide A2RM respectively include the first arm waveguide 61 and the second arm waveguide 62. The conductive region 19 includes the semiconductor layer 66. The semiconductor layer 66 has conductivity.
Each of the first arm waveguide 61 and the second arm waveguide 62 includes an EO modulation portion changing the phases of light beams propagated in the arm waveguides in response to an electrical signal applied from the metal bodies of the differential transmission paths 64.
The differential transmission paths 64 include a first metal body 35, a second metal body 37, and a third metal body 39. The first metal body 35, the second metal body 37, and the third metal body 39 realize the first line 21a, the second line 21b, and the third line 21c. The first metal body 35 and the second metal body 37 are respectively connected to the first arm waveguide 61 and the second arm waveguide 62. The third metal body 39 applies the ground surface of the reference potential to the differential transmission paths 64. The capacitors 65 are connected between the semiconductor layer 66 and the third metal body 39.
The Mach-Zehnder modulator 14 includes a support body 29, and the support body 29 has a main surface 29a including a semi-insulating semiconductor. The semiconductor layer 66 is provided on the main surface 29a.
According to the Mach-Zehnder modulator 14, the first metal body 35 and the second metal body 37 of the differential transmission paths 64 are respectively connected to the first arm waveguide 61 and the second arm waveguide 62 and can drive the first arm waveguide 61 and the second arm waveguide 62. The capacitors 65 are connected between the semiconductor layer 66 and the third metal body 39 and reduce the common mode in the differential transmission paths 64.
The Mach-Zehnder modulator 14 (13) further includes an additional metal body 34. The additional metal body 34 is connected to the semiconductor layer 66 (conductive region 19) and applies a potential to the semiconductor layer 66 (conductive region 19). The additional metal body 34 is connected to the bias voltage source VBIAS illustrated in
The capacitors 65 include MIM-type capacitance elements. In the present example, the capacitors 25 include four capacitance elements (26a, 26b, 26c, and 26d), for example. The capacitance elements (26a and 26b) of the capacitors 25 are respectively connected to upstream sides of the EO modulation portions of the first arm waveguide 61 and the second arm waveguide 62. The capacitance elements (26c and 26d) of the capacitors 25 are respectively connected to downstream sides of the EO modulation portions of the first arm waveguide 61 and the second arm waveguide 62.
According to the Mach-Zehnder modulator 14, the additional metal body 34 supplies power to the semiconductor layer 66 independently from the reference potential line. The capacitors 65 stabilize a potential of power supplied from the metal body and reduce the common mode.
The semiconductor layer 66 includes a III-V compound semiconductor. The first arm waveguide 61 and the second arm waveguide 62 include a III-V compound semiconductor.
With reference to
The Mach-Zehnder modulator 14 may further include an embedding region 90. In the embedding region 90, the semiconductor layer 66, the first arm waveguide 61, and the second arm waveguide 62 are embedded. Specifically, the embedding region 90 may include a resin body and an inorganic insulating film.
The differential transmission paths 64 are provided on the embedding region 90, whereas the capacitors 65 are provided within the embedding region 90. The embedding region 90 can change the levels (heights) of the differential transmission paths 64 to be different from the levels of the capacitors 65. Accordingly, disturbance of high-frequency signals propagated in the differential transmission paths 64 due to the added capacitors 65 can be reduced.
With reference to
The second metal body 37 has a first part 37a, a second part 37b, and a third part 37c. In the second metal body 37, the first part 37a connects a pad electrode 47b to the second part 37b. The second part 37b extends to the third part 37c along the second arm waveguide 62. The third part 37c connects the second part 37b to a pad electrode 48c.
The second part 37b includes a plurality of segment electrodes 38 arranged on the second arm waveguide 62.
The third metal body 39 has a first part 39a, a second part 39b, and a third part 39c. In the third metal body 39, the first part 39a connects a pad electrode 49a (49b) to the second part 39b. The second part 39b extends to the third part 39c along at least one of the first arm waveguide 61 and the second arm waveguide 62. The third part 39c connects the second part 39b to a pad electrode 48a.
The second part 39b of the third metal body 39 may be provided between the second part 35b of the first metal body 35 and the second part 37b of the second metal body 37. According to the Mach-Zehnder modulator 14, the first arm waveguide 61 and the second arm waveguide 62 are driven using the SGS-type differential transmission paths 64.
The first arm waveguide 61 includes a first part 61a, a second part 61b, and a third part 61c which are arranged in order. The first metal body 35 is connected to the second part 61b of the first arm waveguide 61 and forms an EO modulation portion. The second arm waveguide 62 includes a first part 62a, a second part 62b, and a third part 62c which are arranged in order. The second metal body 37 is connected to the second part 62b of the second arm waveguide 62 and forms an EO modulation portion. The semiconductor layer 66 includes a first part 66a, a second part 66b, and a third part 66c which are arranged in order. The first part 66a of the semiconductor layer 66 is equipped with the first part 61a of the first arm waveguide 61 and the first part 62a of the second arm waveguide 62. The second part 66b of the semiconductor layer 66 is equipped with the second part 61b of the first arm waveguide 61 and the second part 62b of the second arm waveguide 62. The third part 66c of the semiconductor layer 66 is equipped with the third part 61c of the first arm waveguide 61 and the third part 62c of the second arm waveguide 62. The capacitors 65 are connected to at least one of the first part 66a and the third part 66c of the semiconductor layer 66.
According to the Mach-Zehnder modulator 14, the semiconductor layer 66 equipped with the first arm waveguide 61 and the second arm waveguide 62 electrically connects the first arm waveguide 61 and the second arm waveguide 62 to each other. High-frequency electricity flowing between the second part 61b of the first arm waveguide 61 and the second part 62b of the second arm waveguide 62 flows in the second part 66b of the semiconductor layer 66.
The capacitors 65 are connected to portions near a border between the first part 66a and the second part 66b of the semiconductor layer 66, and the common mode can be reduced without hindering high-frequency signals applied to the second part 61b of the first arm waveguide 61 and the second part 62b of the second arm waveguide 62. In addition, the capacitors 65 are connected to portions near a border between the second part 66b and the third part 66c of the semiconductor layer 66, and the common mode can be reduced without hindering high-frequency signals applied to the second part 61b of the first arm waveguide 61 and the second part 62b of the second arm waveguide 62.
The capacitors 65 include the first MIM element 26a and the second MIM element 26b. The first MIM element 26a and the second MIM element 26b may be connected to any one of the first part 39a and the third part 39c of the third metal body 39. In the present example, they are connected to the first part 39a of the third metal body 39.
The differential transmission paths 64 pass between the first MIM element 26a and the second MIM element 26b. According to the Mach-Zehnder modulator 14, the first MIM element 26a and the second MIM element 26b are provided on outer sides of the differential transmission paths 64 so that the ground surfaces of the differential transmission paths 64 are unlikely to be disturbed. The first MIM element 26a and the second MIM element 26b are embedded by the embedding region 90 and are positioned on a lower side based on the levels of the ground surfaces of the differential transmission paths 64.
The capacitors 65 include a third MIM element 26c and a fourth MIM element 26d. The third MIM element 26c and the fourth MIM element 26d may be connected to the other of the first part 39a and the third part 39c of the third metal body 39. In the present example, the third MIM element 26c and the fourth MIM element 26d are connected to the third part 39c of the third metal body 39.
The differential transmission paths 64 pass between the third MIM element 26c and the fourth MIM element 26d. According to the Mach-Zehnder modulator 14, the third MIM element 26c and the fourth MIM element 26d are also provided on the outer sides of the differential transmission paths 64 so that the ground surfaces formed by the differential transmission paths are unlikely to be disturbed. The third MIM element 26c and the fourth MIM element 26d are also embedded by the embedding region 90 and are positioned on the lower side based on the level (height) of the ground surface (an upper surface and/or a lower surface of the second part 39b of the third metal body 39).
With reference to
As illustrated in
With reference to
With reference to
In the present example, the first metal body 35 and the second metal body 37 respectively include the upper metal layers 41. The upper metal layers 41 apply differential signals from the pad electrodes 49a and 49b to the arm waveguides. The third metal body 39 includes the upper metal layer 41 and the intermediate metal layer 51.
Specifically, the second part 39b of the third metal body 39 includes the upper metal layer 41 and extends along the arm waveguide. The first part 39a of the third metal body 39 includes the wide intermediate metal layer 51 extending on the lower sides of the upper metal layers 41 of the first metal body 35 and the second metal body 37. The intermediate metal layer 51 can provide the upper metal layers 41 of the first metal body 35 and the second metal body 37 with wide ground surfaces. In addition, the first part 39a is connected to the lower metal layer 40 of the lower electrode in each of the capacitor MIMs (26a and 26b) via the intermediate metal layer 51. Since the ground surfaces have wide widths, even when the upper metal layers 41 are disposed to cross upper portions of the arm waveguides 61 and 62, potentials of the upper metal layers 41 can be prevented from being disturbed.
The lower metal layer 40 of the lower electrode in each of the capacitors 65 (26a and 26b) is connected to the intermediate metal layer 51 through a penetration hole 32a of the second inorganic insulating film 31b. The intermediate metal layer 51 extends on the lower sides of the upper metal layers 41 of the first metal body 35 and the second metal body 37 to cross the upper metal layers 41.
Specifically, the intermediate metal layer 51 of the upper electrode in each of the capacitors 65 (26a and 26b) is connected to the upper metal layer 41 through a through-hole TH90a of the second resin body 90b and leads to the additional metal body 34. The upper metal layer 41 of the additional metal body 34 is connected to the semiconductor layer 66 via the upper metal layer 41 inside the through-hole TH90a of the second resin body 90b and the intermediate metal layer 51 inside a through-hole TH90b of the first resin body 90a (when necessary, the lower metal layer 40 inside the through-hole TH90b of the first resin body 90a).
With reference to
In the present example, the first metal body 35 and the second metal body 37 respectively include the upper metal layers 41. The upper metal layers 41 are connected to the pad electrodes 48b and 48c to be connected in order to apply differential signals which have driven the arm waveguides to the terminator 17. The third part 39c of the third metal body 39 includes the upper metal layer 41 and extends between the upper metal layer 41 of the first metal body 35 and the upper metal layer 41 of the second metal body 37.
The lower metal layer 40 of the lower electrode in each of the capacitor MIMs (26c and 26d) is connected to the intermediate metal layer 51 through a penetration hole 32b of the second inorganic insulating film 31b. The intermediate metal layer 51 extends on the lower side of the upper metal layer 41 of the first metal body 35 or the second metal body 37 and is connected to the third part 39c of the third metal body 39 to cross the upper metal layer 41 through a through-hole TH90c of the second resin body 90b.
The intermediate metal layer 51 of the upper electrode in each of the capacitor MIMs (26c and 26d) is connected to the upper metal layer 41 through a through-hole TH90d of the second resin body 90b and leads to the additional metal body 34. The upper metal layer 41 of the additional metal body 34 is connected to the semiconductor layer 66 via the upper metal layer 41 inside a through-hole TH90e of the second resin body 90b and the intermediate metal layer 51 inside a through-hole TH90f of the first resin body 90a (when necessary, the lower metal layer 40 inside the through-hole TH90f of the first resin body 90a).
According to the Mach-Zehnder modulator 14, the first metal body 35, the second metal body 37, and the third metal body 39 can extend at levels different from those of the first MIM element (for example, 26a) and the second MIM element (for example, 26b).
As illustrated in
Example of Structure of Mach-Zehnder Modulator 14
Example of First Arm Waveguide 61 and Second Arm Waveguide 62
Example of Applied Voltage
Each of the first arm waveguide 61 and the second arm waveguide 62 according to the example forms a PIN diode including the first conductive semiconductor layer 67, the core layer 68, and the second conductive semiconductor layer 69. Anodes of the PIN diodes of the first arm waveguide 61 and the second arm waveguide 62 are respectively connected to the first metal body 35 and the second metal body 37. Cathodes of the PIN diodes of the first arm waveguide 61 and the second arm waveguide 62 are connected to the semiconductor layer 66. Power is supplied to the semiconductor layer 66 from the bias voltage source VBIAS through a resistance of the semiconductor layer 66 itself.
The first MIM element 26a and the second MIM element 26b are connected to the outer sides of the EO modulation portions (61b and 62b) of the first arm waveguide 61 and the second arm waveguide 62, that is, in the vicinity of one ends of the EO modulation portions (61b and 62b). The third MIM element 26c and the fourth MIM element 26d are connected to the outer sides of the EO modulation portions (61b and 62b) of the first arm waveguide 61 and the second arm waveguide 62, that is, in the vicinity of the other ends of the EO modulation portions (61b and 62b).
According to an examination of the example and other examinations, the capacitors 65 may have a capacitance within a range of 1 to 100 picofarads.
The parallel upper metal layers 41 and the wide intermediate metal layer 51 can form similar transmission paths in microstrip lines in the first metal body 35 and the second metal body 37. Specifically, in the first part 39a of the third metal body 39, the levels of the upper metal layers 41 from the pad electrodes 49a and 49b are converted into the level of the intermediate metal layer 51 through penetration holes V1A and V2A.
The microstrip line including the upper metal layer 41 of each of the first metal body 35 and the second metal body 37 and the intermediate metal layer 51 of the first part 39a of the third metal body 39 is positioned between the first MIM element 26a and the second MIM element 26b and is unlikely to receive disturbance from the first MIM element 26a and the second MIM element 26b. In the output section, for example, the level of the third part 39c of the third metal body 39 is converted into the level of the intermediate metal layer 51, and the upper metal layer 41 of each of the first metal body 35 and the second metal body 37 extends on the intermediate metal layer 51 of the third part 39c of the third metal body 39 so that a microstrip line can be formed in a similar manner. This microstrip line may be positioned between the third MIM element 26c and the fourth MIM element 26d.
With reference to
As previously described above, the Mach-Zehnder modulator 14 provides each of the first metal body 35 (the first part 35a, the second part 35b, and the third part 35c) and the second metal body 37 (the first part 37a, the second part 37b, and the third part 37c) with the upper metal layer 41. The second part 35b of the first metal body 35 and the second part 37b of the second metal body 37 respectively extend along the first arm waveguide 61 and the second arm waveguide 62. Differential signals on the upper metal layers 41 of the first metal body 35 and the second metal body 37 respectively drive the first arm waveguide 61 and the second arm waveguide 62.
In the second part 39b of the third metal body 39, the intermediate metal layer 51 is connected to the single upper metal layer 41 through a penetration hole T1H. In the first part 35a of the first metal body 35 and the first part 37a of the second metal body 37, the upper metal layers 41 from the pad electrodes 47a and 47b pass above the intermediate metal layer 51 of the first part 39a of the third metal body 39 and reach the second part 35b of the first metal body 35 and the second part 37b of the second metal body 37.
Four input pad electrodes (47a, 47b, 49a, and 49b) are arranged along a lateral side of the element in the order of the upper metal layer 41 of the grounding line, the upper metal layer 41 of the signal line, the upper metal layer 41 of the signal line, and the upper metal layer 41 of the grounding line. This arrangement will be referred to as “GSSG arrangement”. In the first arm waveguide 61 and the second arm waveguide 62, they are arranged in the order of the upper metal layer 41 of the signal line, the upper metal layer 41 of the grounding line, and the upper metal layer 41 of the signal line. This arrangement will be referred to as “SGS arrangement”.
With reference to
The wide intermediate metal layer 51 is connected to the second part 39b of the third metal body 39 and the second part 43b of the fourth metal body 43 at the other end. Specifically, the wide intermediate metal layer 51 is connected to the upper metal layer 41 of the third metal body 39 and the upper metal layer 41 of the fourth metal body 43, and the upper metal layers 41 are positioned on the outer sides of the first metal body 35 and the second metal body 37.
In the first part 39a of the third metal body 39, the levels of the upper metal layers 41 from the pad electrodes 49a and 49b are converted into the level of the intermediate metal layer 51 through the penetration holes V1A and V2A. The intermediate metal layer 51 is connected to the upper metal layer 41 of the second part 39b of the third metal body 39 through the penetration hole T1H and is connected to the upper metal layer 41 of the second part 43b of the fourth metal body 43 through a penetration hole T2H. In the first part 35a of the first metal body 35 and the first part 37a of the second metal body 37, the upper metal layers 41 from the pad electrodes 47a and 47b pass above the single intermediate metal layer 51 and reach the second part 35b of the first metal body 35 and the second part 37b of the second metal body 37. The single intermediate metal layer 51 is shared between the first part 39a of the third metal body 39 and a first part 43a of the fourth metal body 43 and extends at a level different from those of the upper metal layers 41, thereby facilitating power supply to the capacitors 65.
Four input pad electrodes (47a, 47b, 49a, and 49b) are arranged along a lateral side of the element in the order of the upper metal layer 41 of the grounding line, the upper metal layer 41 of the signal line, the upper metal layer 41 of the signal line, and the upper metal layer 41 of the grounding line (GSSG arrangement). This arrangement becomes the arrangement of a pair of upper metal layers 41 of the signal lines extending along the first arm waveguide 61 and the second arm waveguide 62 through an intersection of the upper metal layers 41 and the intermediate metal layer 51 and a pair of upper metal layers 41 of the grounding lines positioned on the outer sides of this pair (GSSG arrangement).
With reference to
The wide intermediate metal layer 51 of the microstrip line is connected to the second part 39b of the third metal body 39, the second part 43b of the fourth metal body 43, and the second part 45b of the fifth metal body 45 at the other end thereof. Specifically, the wide intermediate metal layer 51 is connected to the upper metal layer 41 of the third metal body 39, the upper metal layer 41 of the fourth metal body 43, and the upper metal layer 41 of the fifth metal body 45. The upper metal layers 41 are positioned on the outer sides of the first metal body 35 and the second metal body 37.
The intermediate metal layer 51 is connected to the upper metal layer 41 of the second part 39b of the third metal body 39 through the penetration hole T1H, and the intermediate metal layer 51 is connected to the upper metal layer 41 of the second part 43b of the fourth metal body 43 through the penetration hole T2H. In the first part 35a of the first metal body 35 and the first part 37a of the second metal body 37, the upper metal layers 41 from the pad electrodes 47a and 47b pass above the intermediate metal layer 51 and reach the second part 35b of the first metal body 35 and the second part 37b of the second metal body 37. The intermediate metal layer 51 is shared between the first part 39a of the third metal body 39 and the first part 43a of the fourth metal body 43 and extends at a level different from those of the upper metal layers 41, thereby facilitating power supply to the capacitors 65.
Four input pad electrodes (47a, 47b, 49a, and 49b) are arranged along a lateral side of the element in the order of the upper metal layer 41 of the grounding line, the upper metal layer 41 of the signal line, the upper metal layer 41 of the signal line, and the upper metal layer 41 of the grounding line (GSSG arrangement). This arrangement becomes the arrangement of a pair of upper metal layers 41 of the signal lines extending along the first arm waveguide 61 and the second arm waveguide 62 through an intersection of the upper metal layers 41 and the intermediate metal layer 51, a pair of upper metal layers 41 of the grounding lines positioned on the outer sides of the pair of upper metal layers 41 of the signal lines, and an upper metal layer 41 of the grounding line positioned between a pair of upper metal layers 41 of the signal lines (GSGSG arrangement).
As will be understood from the foregoing description, in the input section and the output section, utilizing of the intermediate metal layer 51 allows any arrangement of “SGS arrangement”, “GSSG arrangement”, and “GSGSG arrangement” to be connected to any arrangement of “SGS arrangement”, “GSSG arrangement”, and “GSGSG arrangement”.
With reference to
A substrate product SP illustrated in
The substrate product SP is manufactured as follows.
Semiconductor layers for the first conductive semiconductor layer 67, the core layer 68, and the second conductive semiconductor layer 69 are grown on the substrate WF of semi-insulating InP, and a semiconductor laminate is formed on the substrate WF. The semiconductor layers may be formed by an organic metal vapor phase growth method or a molecular beam epitaxy method, for example.
A semiconductor laminate is processed through photolithography and etching, and semiconductor mesas (MS61 and MS62) for the first arm waveguide 61 and the second arm waveguide 62 are formed.
Moreover, the semiconductor laminate is subjected to processing for element isolation through photolithography and etching. The semiconductor layer 66 is formed through this processing.
After these steps of processing, the first inorganic insulating film 95a is formed on the entire surface of the substrate WF. The first inorganic insulating film 95a includes silicon-based inorganic substances such as SiO2, SiON, and SiN. The upper part of the first inorganic insulating film 95a is coated with a resin and desired processing is performed, thereby forming the lower embedding region BR1. The lower embedding region BR1 includes a resin body, and the resin body includes BCB or polyimide, for example. The lower embedding region BR1 has openings AP1 and AP2 for exposing the upper surfaces of the first arm waveguide 61 and the second arm waveguide 62.
After the substrate product SP is prepared, as illustrated in
After the recessed portions 90e and the penetration holes 90f are formed in the substrate product SP, as illustrated in
After the metal films for the lower metal layers 40 are deposited, as illustrated in
An insulating film for the second inorganic insulating film 95b is subjected to processing using photolithography and etching, and penetration holes 94a and 94b positioned on the lower metal layers 40 are formed. The penetration holes 94a are positioned on the lower metal layers 40 for the lower electrodes and reach the lower metal layers 40. The penetration holes 94b are positioned on the semiconductor layer 66 inside the penetration holes 90f and reach the semiconductor layer 66.
In addition, at the same time as this processing or through separate processing using photolithography and etching, penetration holes 94c reaching the upper surfaces of the first arm waveguide 61 and the second arm waveguide 62 are formed in the first inorganic insulating film 95a and the second inorganic insulating film 95b.
After the penetration holes 94a, 94b, and 94c are formed, as illustrated in
After the intermediate metal layer 51 is formed, as illustrated in
After the coated inorganic insulating film 95c and the upper embedding region BR2 are formed, as illustrated in
After the coated inorganic insulating film 95c and the upper embedding region BR2 are processed, as illustrated in
After the third inorganic insulating film 95d is formed, as illustrated in
Through these steps, the Mach-Zehnder modulator 14 illustrated in
The principle of the present disclosure has been illustrated and described with a preferable embodiment. However, those skilled in the art will recognize that the present disclosure can be changed in disposition and details without departing from the foregoing principle. The present disclosure is not limited by any specific constitution disclosed the present embodiment. Therefore, the rights are claimed on all the modifications and the changes from the claims and the scope of the spirit thereof.
As described above, according to the present embodiment, it is possible to provide a Mach-Zehnder modulator capable of reducing a common mode, and an optical modulation device including the Mach-Zehnder modulator.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-086296 | Apr 2019 | JP | national |
