JP2017045012A - Optical modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon modulator of which an electrode has reduced electrode resistance.SOLUTION: An optical modulator of the present invention comprises: a substrate; a lower clad formed on the substrate; and a waveguide that is formed on the lower clad and includes a rib-shaped arm waveguide, one waveguide edge side from a center line in the width direction of the arm waveguide being a p-type semiconductor region, the other waveguide edge side from the center line in the width direction being an n-type semiconductor region, a pn junction being formed at the center line in the width direction, a high-concentration p-type semiconductor region being formed on part of the top surface opposite direction to the n-type semiconductor region in the p-type semiconductor region, and a high-concentration n-type semiconductor region being formed on part of the top surface opposite direction to the p-type semiconductor region in the n-type semiconductor region; two electrodes that are folded like bellows in the vertical direction to the substrate so that a fold line becomes the same direction as wave-guiding direction of light of the arm waveguide and that are each connected with the high-concentration p-type semiconductor region and the high-concentration n-type semiconductor region; and an upper clad formed on the waveguide.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical modulator, and more particularly to a silicon optical modulator formed on a silicon-on-insulator wafer.

  With the spread of optical communication in recent years, there is a demand for cost reduction of optical communication devices. As one of the solutions, there is a method of forming an optical circuit constituting an optical communication device on a large-diameter wafer such as a silicon wafer by using a micro optical circuit technique such as silicon photonics. As a result, the material cost per chip can be dramatically reduced, and the cost of the optical communication device can be reduced.

  As a typical optical modulator formed on a silicon substrate using such a technique, there is a carrier extraction type silicon optical modulator (for example, Patent Document 1). FIG. 1 is a view showing a conventional carrier extraction type silicon optical modulator. FIG. 1 (a) is a top view of the silicon optical modulator 100, and FIG. 1 (b) is an A- A sectional view at A 'is shown. The silicon optical modulator 100 includes a substrate 101, a lower clad 102 formed on the substrate 101, a waveguide 103 formed on the lower clad 102, and an upper portion formed on the lower clad 102 and the waveguide 103. And a clad 104. The waveguide 103 has an incident waveguide 103-1, an optical branching device 103-2 that demultiplexes light from the incident waveguide 103-1, and light from the optical branching device 103-2 propagates, and Mach-Zehnder interference. Arm waveguides 103-3 and 103-4 constituting the meter are provided. In addition, the waveguide 103 emits the light from the optical multiplexer 103-5 that combines the light from the arm waveguides 103-3 and 103-4 and the light from the optical multiplexer 103-5 from the silicon optical modulator 100. And an output waveguide 103-6.

  One waveguide edge side from the width direction center line of the arm waveguide 103-3 (103-4) is the p-type semiconductor region 111, and the other waveguide edge side from the width direction center line is the n-type semiconductor region 112. The center is a convex portion, and a pn junction 110 is formed on the center line in the width direction. Further, the p-type semiconductor region 111 has a part of the upper surface in the opposite direction to the n-type semiconductor region 112 as a high-concentration p-type semiconductor region 113, and the n-type semiconductor region 112 is in the opposite direction to the p-type semiconductor region 111. A part of the upper surface of the region is a high-concentration n-type semiconductor region 114. The high concentration p-type semiconductor region 113 is connected to the electrode 116 through the trench 115. The high concentration n-type semiconductor region 114 is connected to the electrode 118 through the groove 117.

  The silicon optical modulator 100 changes the voltage of the high frequency power applied from the signal generators 105-1 to 105-4 via the electrodes 116 and 117, thereby changing the pn of the arm waveguide 103-3 (103-4). The depletion layer region formed around the junction 110 is increased or decreased to change the phase of light propagating through the depletion layer region. The light whose phase has been changed is modulated by being interfered by the optical multiplexer 104.

Special Table 2002-540469

  One factor that limits the modulation efficiency of a silicon optical modulator is the resistance of the electrode. The silicon optical modulator 100 is operated by applying high frequency power to the two arm waveguides 103-3 and 103-4 constituting the Mach-Zehnder interferometer. High frequency power is supplied from the electrodes 116 and 118 to the high concentration p-type semiconductor region 113 and the high concentration n-type semiconductor region 114. Here, since the electrode material of the electrodes 116 and 118 has resistance, the high-frequency power attenuates due to the resistance of the electrodes 116 and 118 as it propagates in the traveling direction (direction in which the electrodes are formed). Therefore, when the arm waveguide 103-3 (103-4) is lengthened, the electrodes 116 and 118 are also lengthened, and the power attenuation is increased. Therefore, there is a problem in that the modulation efficiency of the silicon optical modulator 100 is reduced as a result of consuming electric power for supplying power to the silicon optical modulator 100 as an electric resistance.

  The present invention solves such problems, and an object of the present invention is to provide a silicon optical modulator in which the electrode resistance of the electrode is reduced.

  In order to achieve such an object, a first aspect of the present invention is an optical modulator comprising a substrate, a lower clad formed on the substrate, a rib-shaped rib formed on the lower clad. A waveguide having an arm waveguide, wherein one waveguide edge side from the width direction center line of the arm waveguide is a p-type semiconductor region, and the other waveguide edge side from the width direction center line is an n-type semiconductor region. The center line in the width direction is formed with a pn junction, and the p-type semiconductor region is formed with a high-concentration p-type semiconductor region on a part of the upper surface in the direction opposite to the n-type semiconductor region, and the n-type The semiconductor region includes a waveguide in which a high-concentration n-type semiconductor region is formed on a part of an upper surface in a direction opposite to the p-type semiconductor region, the lower cladding, and an upper cladding formed on the waveguide; Formed on the upper cladding, and Respectively, via a plurality of grooves formed in the head is characterized in that it comprises a two electrode connected to the high-concentration p-type semiconductor region and the high-concentration n-type semiconductor region.

  According to a second aspect of the present invention, there is provided the optical modulator according to the first aspect, wherein all the grooves of the two electrodes are formed in the high-concentration p-type semiconductor region or the high-concentration n-type semiconductor region. It is connected.

  According to a third aspect of the present invention, there is provided the optical modulator according to the first aspect, wherein only one of the grooves of the two electrodes is the high concentration p-type semiconductor region or the high concentration. It is connected to an n-type semiconductor region.

  According to a fourth aspect of the present invention, there is provided the optical modulator according to any one of the first to third aspects, wherein the two electrodes are further bent in a bellows shape in the horizontal direction of the substrate. It is characterized by that.

  According to a fifth aspect of the present invention, there is provided an optical modulator comprising a substrate, a lower clad formed on the substrate, a waveguide formed on the lower clad and having a rib-shaped arm waveguide. The one waveguide edge side from the width direction center line of the arm waveguide is a p-type semiconductor region, and the other waveguide edge side from the width direction center line is an n-type semiconductor region, and the width direction center line Is formed with a pn junction, the p-type semiconductor region is formed with a high-concentration p-type semiconductor region on a part of the upper surface in the direction opposite to the n-type semiconductor region, and the n-type semiconductor region is formed with the p-type semiconductor region. A waveguide in which a high-concentration n-type semiconductor region is formed on a part of an upper surface in a direction opposite to the semiconductor region, the lower cladding, an upper cladding formed on the waveguide, and an upper surface of the upper cladding; Metal plate and the high-concentration p-type semiconductor The metal plate which connects the band and the high concentration n-type semiconductor region, the cross section in a direction perpendicular to the waveguide direction of the light, characterized in that it comprises an electrode formed in a comb shape.

  According to a sixth aspect of the present invention, there is provided the optical modulator according to the fifth aspect, wherein the metal plate connecting the high concentration p-type semiconductor region and the high concentration n-type semiconductor region is all the high concentration. It is connected to the concentration p-type semiconductor region or the high concentration n-type semiconductor region.

  According to a seventh aspect of the present invention, there is provided the optical modulator according to the sixth aspect, wherein the electrode further includes a metal plate extending in a horizontal direction of the substrate, and is orthogonal to the light guiding direction. The cross section in the direction to be formed is formed in a two-stage comb-teeth shape.

  According to an eighth aspect of the present invention, there is provided an optical modulator comprising a substrate, a lower clad formed on the substrate, and a waveguide having a rib-shaped arm waveguide formed on the lower clad. The one waveguide edge side from the width direction center line of the arm waveguide is a p-type semiconductor region, and the other waveguide edge side from the width direction center line is an n-type semiconductor region, and the width direction center line Is formed with a pn junction, the p-type semiconductor region is formed with a high-concentration p-type semiconductor region on a part of the upper surface in the direction opposite to the n-type semiconductor region, and the n-type semiconductor region is formed with the p-type semiconductor region. A waveguide in which a high-concentration n-type semiconductor region is formed on a part of the upper surface in the direction opposite to the semiconductor region, the lower cladding, the upper cladding formed on the waveguide, and the horizontal direction of the upper cladding. The high-concentration p-type semiconductor region and A metal plate connected to the high-concentration n-type semiconductor region and a plurality of metal plates connected to a metal plate formed in a horizontal direction form a cross section in a direction perpendicular to the light guiding direction in a comb shape. It is characterized by providing the electrode made by this.

  According to the present invention, the resistance of the electrode to which high frequency power is applied can be lowered, so that power can be supplied to the silicon optical modulator over a long length, low voltage driving can be realized, and thus the silicon optical modulator can be realized. High efficiency can be achieved.

It is a figure which shows the conventional carrier extraction type | mold silicon optical modulator, (a) shows the top view of a silicon optical modulator, (b) has shown sectional drawing in AA 'of (a). BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the silicon optical modulator concerning the 1st Embodiment of this invention, (a) shows the top view of a silicon optical modulator, (b) shows sectional drawing in BB 'of (a). ing. It is a figure which shows sectional drawing of the direction orthogonal to the light waveguide direction of the silicon optical modulator concerning the modification of the 1st Embodiment of this invention. It is a figure which shows sectional drawing of the direction orthogonal to the light waveguide direction of the silicon optical modulator concerning the modification of the 1st Embodiment of this invention. It is a figure which shows sectional drawing of the direction orthogonal to the light waveguide direction of the silicon optical modulator concerning the 2nd Embodiment of this invention. It is a figure which shows sectional drawing of the direction orthogonal to the light waveguide direction of the silicon optical modulator concerning the modification of the 2nd Embodiment of this invention. It is a figure which shows sectional drawing of the direction orthogonal to the light waveguide direction of the silicon optical modulator concerning the modification of the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 2 is a diagram showing a silicon optical modulator according to the first embodiment of the present invention. FIG. 2A is a top view of the silicon optical modulator 200, and FIG. ) Is a cross-sectional view taken along line AA ′. The silicon optical modulator 200 includes a substrate 201, a lower clad 202 formed on the substrate 201, a waveguide 203 formed on the lower clad 202, and an upper clad 204 formed on the waveguide 203. The waveguide 203 propagates the incident waveguide 203-1, the optical branching device 203-2 that demultiplexes the light from the incident waveguide 203-1, and the light from the optical branching device 203-2, and Mach-Zehnder interference. Arm waveguides 203-3 and 203-4 constituting the meter are provided. In addition, the waveguide 203 emits light from the optical multiplexer 203-5 that combines the light from the arm waveguides 203-3 and 203-4 and the light from the optical multiplexer 203-5 from the silicon optical modulator 200. And an output waveguide 203-6.

  The arm waveguide 203-3 (203-4) is configured by a rib-shaped waveguide. Here, the one waveguide edge side from the width direction center line of the arm waveguide 203-3 (203-4) is the p-type semiconductor region 211, and the other waveguide edge side from the width direction center line is the n-type semiconductor region 212. It is. The center is a convex part, and the pn junction part 210 is formed in the center line in the width direction. In addition, the p-type semiconductor region 211 has a part of the upper surface in the opposite direction to the n-type semiconductor region 212 as a high-concentration p-type semiconductor region 213, and the n-type semiconductor region 212 is opposite to the p-type semiconductor region 211. A part of the upper surface of the region is a high-concentration n-type semiconductor region 214.

  The high concentration p-type semiconductor region 213 is connected to the electrode 216 through the grooves 215-1 to 215-3. The high concentration n-type semiconductor region 214 is connected to the electrode 218 through the grooves 217-1 to 217-3. The electrodes 216 and 218 are supplied with high frequency modulation power from the signal generators 205-3 and 205-4.

  The electrode 216 (218) has a bellows cross-sectional structure. That is, a single metal plate is bent in a bellows shape in the horizontal direction of the substrate 201 so that the fold is in the same direction as the light guiding direction of the arm waveguide. At this time, a structure in which all the folded ends (on the substrate 201 side) of the bellows are connected to the high-concentration p-type semiconductor region 213 (high-concentration n-type semiconductor region 214), in other words, a plurality of grooves 215-1 to 215. 3 (217-1 to 217-3). The electrode 216 (218) increases the electrode surface area by making the cross-sectional structure bellows. Since high frequency power propagates on the electrode surface, the resistance of the electrode can be reduced by increasing the electrode surface area. The grooves 215-1 to 215-3 (217-1 to 217-3) may be filled with a clad.

(Modification)
3 and 4 are cross-sectional views in a direction perpendicular to the light guiding direction of the silicon optical modulator according to the modification of the first embodiment of the present invention.

  The silicon optical modulator 300 of FIG. 3 is the same as the silicon optical modulator 200 of FIG. 2 in that the electrode 316 (318) has a bellows cross section. However, the silicon optical modulator 300 of FIG. 3 has a configuration in which only one of the folded ends of the bellows on the substrate 301 side is connected to the high-concentration p-type semiconductor region 313 (high-concentration n-type semiconductor region 314). It has become.

  In the silicon optical modulator 400 of FIG. 4, the cross section of the electrode 416 (418) is formed in a bellows shape in a two-dimensional direction. That is, the optical modulator is not only folded in the vertical direction but also folded in the horizontal direction.

  The electrodes of any of the silicon light modulators shown in FIGS. 2 to 4 can be realized by lithography techniques and damascene techniques used in ordinary semiconductor manufacturing processes.

[Second Embodiment]
FIG. 5 is a cross-sectional view of the silicon optical modulator according to the second embodiment of the present invention in a direction orthogonal to the light guiding direction. 5 includes a substrate 501, a lower clad 502 formed on the substrate 501, an arm waveguide 503 formed on the lower clad 502, and an upper clad formed on the arm waveguide 503. 504.

  The arm waveguide 503 is configured by a rib-shaped waveguide. Here, the one waveguide edge side from the width direction center line of the arm waveguide 503 is the p-type semiconductor region 511, and the other waveguide edge side from the width direction center line is the n-type semiconductor region 512. The center is a convex part, and the pn junction part 510 is formed in the center line in the width direction. In addition, the p-type semiconductor region 511 has a part of the upper surface in the direction opposite to the n-type semiconductor region 512 as a high-concentration p-type semiconductor region 513, and the n-type semiconductor region 512 is opposite to the p-type semiconductor region 511. A part of the upper surface of the region is a high-concentration n-type semiconductor region 514.

  The high concentration p-type semiconductor region 513 is connected to the electrode 516. The high concentration n-type semiconductor region 514 is connected to the electrode 518. The electrode 516 (518) has a comb-like cross-sectional structure. That is, one metal plate 516-1 (518-1) is formed on the upper surface of the upper clad 504 and the light guiding direction of the arm waveguide 503, and a plurality of metal plates 516-2 to 516 to N (518-). 2-518 -N) is formed in the upper cladding 504 in the light guiding direction of the arm waveguide 503 and in the direction perpendicular to the substrate. At this time, one metal plate 516-1 (518-1) is connected to one edge of a plurality of metal plates 516-2 to 516-N (518-2 to 518-N), The other edges of the plurality of metal plates 516-2 to 516 to N (518-2 to 518-N) are connected to the high-concentration p-type semiconductor region 513 (high-concentration n-type semiconductor region 514). Yes. The electrode 516 (518) increases the electrode surface area by making the cross-sectional structure comb-like. Since high frequency power propagates on the electrode surface, the resistance of the electrode can be reduced by increasing the electrode surface area.

(Modification)
6 and 7 are cross-sectional views in a direction perpendicular to the light guiding direction of the silicon optical modulator according to the modification of the second embodiment of the present invention.

  The silicon optical modulator 600 of FIG. 6 is the same as the silicon optical modulator 500 of FIG. 5 in that the electrode 616 (618) has a comb-like cross section. However, in the silicon optical modulator 600 of FIG. 6, a single metal plate 616-1 (618-1) is formed in the upper cladding 604 in the horizontal direction of the substrate and in the light guiding direction of the arm waveguide 603. On one metal plate 616-1 (618-1), a plurality of metal plates 616-2 to 616 to N (618-2 to 618-N) are arranged in the light guiding direction of the arm waveguide 603 and the substrate. It is formed in the vertical direction.

  One metal plate 616-1 (618-1) is L-shaped in cross section and has an edge connected to the high-concentration p-type semiconductor region 613 (high-concentration n-type semiconductor region 614). The upper surface of the metal plate 616-1 (618-1) is connected to one edge of the plurality of metal plates 616-2 to 616 to N (618-2 to 618-N). The other edges of the plurality of metal plates 616-2 to 616 -N (618-2 to 618 -N) are exposed on the upper clad 604.

  In the silicon optical modulator 700 of FIG. 7, the cross section of the electrode 716 (718) is formed in a two-stage comb-teeth shape. That is, the electrode 716 (718) includes two horizontal metal plates 716-1 and 716-2 (718-1 and 718-2) and a plurality of vertical metal plates 716-3 to 716-N (718). -3 to 718-N). The two metal plates 716-1 and 716-2 (718-1 and 718-2) are connected to the metal plates 716-3 to 716-N (718-3 to 718-N), respectively, and the metal plate 716-3. One edge of ˜716-N (718-3 to 718-N) is connected to the high-concentration p-type semiconductor region 713 (high-concentration n-type semiconductor region 714).

  The electrodes of any of the silicon optical modulators shown in FIGS. 5 to 7 can be realized by lithography techniques and damascene techniques used in ordinary semiconductor manufacturing processes.

100, 200, 300, 400, 500, 600, 700 Silicon optical modulator 101, 201, 301, 401, 501, 601, 701 Substrate 102, 202, 302, 402, 502, 602, 702 Lower cladding 103, 203, 303, 403, 503, 603, 703 Waveguide 103-1, 203-1 Incident waveguide 103-2, 203-2 Optical demultiplexer 103-3, 103-4, 203-3, 203-4 Arm waveguide 103-5, 203-5 Optical multiplexer 103-6, 203-6 Outgoing waveguides 104, 204, 304, 404, 504, 604, 704 Upper clad 105-1 to 105-4, 205-1 to 205-4 Signal generators 110, 210, 310, 410, 510, 610, 710 pn junctions 111, 211, 311, 411, 51 , 611, 711 p-type semiconductor regions 112, 212, 312, 412, 512, 612, 712 n-type semiconductor regions 113, 213, 313, 413, 513, 613, 713 high-concentration p-type semiconductor regions 114, 214, 314, 414, 514, 614, 714 High-concentration n-type semiconductor regions 115, 117, 215-1 to 215-3, 217-1 to 217-3, 315-1 to 315-3, 317-1 to 317-3, 415 -1, 415-2, 417-1, 417-2 Grooves 116, 118, 216, 218, 316, 318, 416, 418, 516, 518, 616, 618, 716, 718 Electrodes 516-1 to 516-N 518-1 to 518-N, 6161-1 to 616-N, 618-1 to 618-N, 716-1 to 716-N, 718-1 to 718- Metal sheet

Claims (8)

A substrate,
A lower cladding formed on the substrate;
A waveguide having a rib-shaped arm waveguide formed on the lower clad, wherein one waveguide edge side from the width direction center line of the arm waveguide is a p-type semiconductor region, and from the width direction center line The other waveguide edge is an n-type semiconductor region, the width direction center line is formed with a pn junction, and the p-type semiconductor region has a high concentration p on a part of the upper surface in the direction opposite to the n-type semiconductor region. A waveguide in which a high-concentration n-type semiconductor region is formed on a part of an upper surface in a direction opposite to the p-type semiconductor region;
An upper clad formed on the lower clad and the waveguide;
Two electrodes formed on the upper cladding and connected to the high-concentration p-type semiconductor region and the high-concentration n-type semiconductor region, respectively, through a plurality of grooves formed in the upper cladding. An optical modulator characterized by.   2. The optical modulator according to claim 1, wherein all the grooves of the two electrodes are connected to the high-concentration p-type semiconductor region or the high-concentration n-type semiconductor region.   2. The optical modulator according to claim 1, wherein only one of the grooves of the two electrodes is connected to the high-concentration p-type semiconductor region or the high-concentration n-type semiconductor region.   4. The optical modulator according to claim 1, wherein the two electrodes are further bent in a bellows shape in the horizontal direction of the substrate. 5. A substrate,
A lower cladding formed on the substrate;
A waveguide having a rib-shaped arm waveguide formed on the lower clad, wherein one waveguide edge side from the width direction center line of the arm waveguide is a p-type semiconductor region, and from the width direction center line The other waveguide edge is an n-type semiconductor region, the center line in the width direction is formed with a pn junction, and the p-type semiconductor region is highly concentrated on a part of the upper surface in the direction opposite to the n-type semiconductor region. a waveguide in which a p-type semiconductor region is formed, and the n-type semiconductor region includes a high-concentration n-type semiconductor region formed on a part of an upper surface in a direction opposite to the p-type semiconductor region;
An upper clad formed on the lower clad and the waveguide;
The metal plate formed on the upper surface of the upper clad and the metal plate connecting the high-concentration p-type semiconductor region and the high-concentration n-type semiconductor region have a cross section in a direction perpendicular to the light waveguide direction. An optical modulator comprising: an electrode formed in a tooth shape.   The metal plate connecting the high-concentration p-type semiconductor region and the high-concentration n-type semiconductor region is all connected to the high-concentration p-type semiconductor region or the high-concentration n-type semiconductor region. Item 6. The optical modulator according to Item 5.   7. The electrode according to claim 6, further comprising a metal plate extending in a horizontal direction of the substrate, wherein a cross section in a direction orthogonal to the light guiding direction is formed in a two-step comb shape. An optical modulator according to 1. A substrate,
A lower cladding formed on the substrate;
A waveguide having a rib-shaped arm waveguide formed on the lower clad, wherein one waveguide edge side from the width direction center line of the arm waveguide is a p-type semiconductor region, and from the width direction center line The other waveguide edge is an n-type semiconductor region, the center line in the width direction is formed with a pn junction, and the p-type semiconductor region is highly concentrated on a part of the upper surface in the direction opposite to the n-type semiconductor region. a waveguide in which a p-type semiconductor region is formed, and the n-type semiconductor region includes a high-concentration n-type semiconductor region formed on a part of an upper surface in a direction opposite to the p-type semiconductor region;
An upper clad formed on the lower clad and the waveguide;
A metal plate formed in the upper clad horizontal direction and connected to the high-concentration p-type semiconductor region and the high-concentration n-type semiconductor region; and a plurality of metal plates connected to the metal plate formed in the horizontal direction, An optical modulator comprising: an electrode having a cross-section in a direction perpendicular to a light guide direction formed in a comb shape.

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