WO2015180149A1

WO2015180149A1 - Electro-optic modulator

Info

Publication number: WO2015180149A1
Application number: PCT/CN2014/078965
Authority: WO
Inventors: 冀瑞强; 曾理
Original assignee: 华为技术有限公司
Priority date: 2014-05-30
Filing date: 2014-05-30
Publication date: 2015-12-03
Also published as: CN106461985B; CN106461985A

Abstract

An electro-optic modulator (100), used for modulating an electrical signal into an optical carrier. The electro-optic modulator (100) comprises an input waveguide (g1), a beam splitter (g2), two symmetrical modulation arms (e, f), a beam combiner (h2), and an output waveguide (h1). The modulation arms (e, f) each comprise a modulation area waveguide, a traveling wave electrode (190), and a grating structure (a, b). The modulation area waveguide is of a metal-oxide-semiconductor (MOS) structure. The grating structures (a, b) are disposed on two sides of the modulation area waveguide. An effective refractive index of the electrical signal on the traveling wave electrode (190) matches a group refractive index of the optical carrier on the modulation area waveguide provided with the grating structures on two sides; therefore, the bandwidth of the electro-optic modulator can be increased.

Description

Electro-optic modulator

Technical field

The present invention relates to the field of optoelectronic communications, and in particular to an electro-optic modulator. Background technique

In recent years, as silicon-based materials continue to make breakthroughs in the field of optics, people have re-recognized the development prospects of silicon materials in the field of optoelectronic integration. Silicon photonic devices are moving in the direction of small size, high speed and high stability. Silicon-based electro-optic modulators have evolved as a common device for silicon photonic devices. The silicon-based electro-optic modulator utilizes the carrier dispersion effect in the silicon material, i.e., changes the concentration of carriers in the silicon material to change the refractive index of the silicon material, thereby modulating the light passing through the silicon material. Changing the concentration of carriers in a silicon material depends on a certain electrical structure. The three structures commonly used in silicon-based electro-optic modulators are PIN structure (pin Junction), PN structure (PN Junction), and MOS structure (Metal Oxide Semiconductor). The modulation efficiency of the PIN structure and the electro-optic modulator of the PN structure is low, and the silicon-based electro-optic modulator of the MOS structure has high modulation efficiency and thus is widely cited, but its bandwidth is small, thereby affecting the silicon base via the MOS structure. The information transmission speed of the electro-optic modulator. Summary of the invention

A technical problem to be solved by embodiments of the present invention is to provide an electro-optic modulator capable of effectively increasing its bandwidth.

first,

An electro-optic modulator for modulating an electrical signal into an optical carrier, the electro-optic modulator comprising an input waveguide, a beam splitter, two symmetric modulation arms, a combiner, and an output waveguide;

The modulation arm includes a modulation region waveguide, a traveling wave electrode, and a grating structure;

The modulation region waveguide is a metal-oxide-semiconductor MOS structure;

The grating structure is disposed on both sides of the modulation region waveguide;

An effective refractive index of the electrical signal on the traveling wave electrode is matched with a group refractive index of the optical carrier in a modulation region waveguide on which both sides of the grating structure are disposed. In a first possible implementation manner, the structural parameter of the grating structure and the structural parameter of the MOS structure are configured such that an effective refractive index of the electrical signal on the traveling wave electrode, and the optical carrier The group refractive indices in the modulator waveguides configured with grating structures on both sides are matched.

In conjunction with the first possible implementation, in a second possible implementation, the electro-optic modulator further includes:

Wafer substrate

a first insulating layer disposed on the silicon substrate;

The input waveguide, the beam splitter, the modulation arm, the combiner, and the output waveguide are disposed on the first insulating layer.

In conjunction with the second possible implementation, in a third possible implementation, the electro-optic modulator further includes:

a first type of lightly doped region disposed on the first insulating layer and forming the grating structure in a first direction, the grating structure comprising a first grating structure and a second grating structure, the first grating structure And forming a void region between the second grating structure, the void region extending along the second direction, wherein the first grating structure and the second grating structure are symmetric about the void region;

a second insulating layer disposed on the first grating structure and the second grating structure, and forming two of the modulation arms in a third direction;

a second type of lightly doped region disposed on the second insulating layer, wherein the second type of lightly doped region and the first type of lightly doped region are loaded with an electrical signal, wherein the first type of lightly doped A portion in which the impurity region, the second insulating layer, and the second type of lightly doped region are sequentially overlapped forms the metal-oxide-semiconductor MOS structure.

With reference to a third possible implementation, in a fourth possible implementation, for a fixed wavelength optical carrier, and a first grating structure and a second grating structure whose structural parameters have been configured, the second insulation When the width to thickness ratio of the layer is configured to increase, the effective refractive index of the electrical signal on the traveling wave electrode increases, and the bandwidth of the electro-optic modulator increases.

In conjunction with the third possible implementation, in a fifth possible implementation, the electro-optic modulator further includes:

a first type of heavily doped region having three numbers, disposed on the first insulating layer along the second direction, a first type heavily doped region disposed in the void region and the first Grating structure And the second grating structure is connected, and the other two first type of heavily doped regions are respectively disposed at the other ends of the two grating structures and respectively opposite to the other ends of the two grating structures, the first type is heavily doped a doping concentration of the region is greater than a doping concentration of the first type of lightly doped region;

a second type of heavily doped region disposed on the second type of lightly doped region along the third direction, and a concentration of the second type of heavily doped region is greater than a concentration of the second type of lightly doped region Doping concentration

The first type of heavily doped region and the second type of heavily doped region are respectively loaded with electrical signals such that the first type of lightly doped regions and the second type of lightly doped regions are loaded with modulated electrical signals.

In conjunction with the fifth possible implementation, in a sixth possible implementation, the electro-optic modulator further includes:

a third insulating layer disposed on the first grating structure, the second grating structure, the first type heavily doped region, and the second type heavily doped region, wherein the third insulating layer corresponds to the first a first type of doped region and a second type of heavily doped region are respectively provided with a first via hole and a second via hole, and the first via hole and the second via hole are filled with a conductive substance, a via and the second via loading an electrical signal to respectively apply an electrical signal to the first type of heavily doped region and the second type of heavily doped region, the traveling wave electrode being disposed on the third insulating layer The traveling wave electrode is electrically connected to the first via and the second via filled with the conductive material, and the traveling wave electrode is used for transmitting an electrical signal.

In conjunction with the sixth possible implementation, in a seventh possible implementation, the electro-optic modulator further includes:

An ohmic contact layer disposed between the first via filled with the conductive material and the first type of heavily doped region, and the second via filled with the conductive material and the second Type between heavily doped regions.

With reference to the seventh possible implementation manner, in an eighth possible implementation manner, the second type of heavily doped region includes a first portion and a second portion, the first portion completely covering the second type of lightly doped a second region extending outward from one end of the first portion and not covering the second type of lightly doped region, the second via being disposed corresponding to the second portion.

In a third possible implementation manner, the first direction is perpendicular to the second direction, and the second direction is parallel to the third direction.

In a third possible implementation manner, the first type is an N type, and the second type is a P Type; or the first type is P type, and the second type is N type.

In a third possible implementation, the electro-optic modulator further includes:

a first type of heavily doped region having a number, the void region disposed on the first insulating layer along the third direction and connected to the first grating structure and the second grating structure, a doping concentration of the first type of heavily doped regions is greater than a doping concentration of the first type of lightly doped regions; and a second type of heavily doped regions having a number of two, disposed along the third direction and Located in the same layer as the second type of lightly doped region, the concentration of the second type of heavily doped region is greater than the doping concentration of the second type of lightly doped region;

In conjunction with the eleventh possible implementation, in the twelfth possible implementation, the electro-optic modulator further includes:

a third insulating layer disposed on the first grating structure, the second grating structure, the first type heavily doped region, the second type lightly doped region, and the second type heavily doped region The first insulating layer and the second type of heavily doped region are respectively provided with a first via and a second via, and the first via and the first via The second via hole is filled with a conductive material, and the first via hole and the second via hole are respectively loaded with electrical signals to the first type heavily doped region and the second type heavily doped region, respectively. The wave electrode is disposed on the third insulating layer, and the traveling wave electrode is electrically connected to the first via hole and the second via hole filled with the conductive material to transmit an electrical signal.

In conjunction with the twelfth possible implementation, in the thirteenth possible implementation, the electro-optic modulator further includes:

In a fourteenth possible implementation manner, an effective refractive index of the electrical signal on the traveling wave electrode is equal to a refractive index of the group in the modulation region waveguide in which the optical carrier is disposed on both sides of the grating structure So that the effective refractive index of the electrical signal on the traveling wave electrode is equal to the refractive index of the group in the adjustment region waveguide in which the grating structure is disposed on both sides.

Compared with the prior art, the electro-optic modulator provided by each of the above embodiments passes the electrical signal The effective refractive index on the traveling wave electrode is matched with the group refractive index of the optical carrier in the modulation region waveguide on which the grating structure is disposed on both sides, thereby improving the modulation bandwidth of the electro-optic modulator. On the other hand, the arrangement of the grating structure brings about a slow light effect, which improves the modulation efficiency of the optical carrier. Therefore, the present invention adjusts the effective refractive index of the electrical signal on the traveling wave electrode, the group index matching in the modulator waveguide in which the optical carrier is disposed on both sides of the grating structure, and the grating structure. The setting improves the modulation efficiency of the optical carrier while increasing the bandwidth of the electro-optic modulator. Further, the structure in which the first type lightly doped region, the second insulating layer, and the second type heavily doped region are sequentially overlapped is a MOS capacitor structure. And the MOS capacitor structure is disposed on the silicon substrate through the first insulating layer, and the structure is referred to as SOI. Such a structure can reduce the parasitic capacitance between the MOS capacitor structure and the silicon substrate and increase the response speed of the MOS capacitor structure. DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings to be used in the embodiments will be briefly described below. Obviously, the drawings in the following description are only some of the present invention. For the embodiments, those skilled in the art can obtain other drawings according to the drawings without any creative work.

1 is a top plan view of an electro-optic modulator of a first preferred embodiment of the present invention;

2 is a schematic cross-sectional view of the electro-optic modulator of the first preferred embodiment of the present invention taken along line A-A';

3 is a schematic cross-sectional view of the electro-optic modulator of the first preferred embodiment of the present invention taken along line BB′;

4 is a top plan view of an electro-optic modulator according to a second preferred embodiment of the present invention;

5 is a schematic cross-sectional view of the electro-optic modulator of the second preferred embodiment of the present invention taken along line C-C';

FIG. 6 is a cross-sectional structural view of the electro-optic modulator of the second preferred embodiment of the present invention taken along line DD′. detailed description The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without departing from the inventive scope are the scope of the present invention.

1 to FIG. 3, FIG. 1 is a top view of an electro-optic modulator according to a first preferred embodiment of the present invention; FIG. 2 is a schematic view of an electro-optic modulator according to a first preferred embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of the electro-optic modulator of the first preferred embodiment of the present invention taken along line BB′. In the present embodiment, the electro-optic modulator 100 is configured to modulate an electrical signal into an optical carrier. The electro-optic modulator 100 includes an input waveguide gl, a beam splitter g2, two modulation arms e, f, a combiner h2, and an output waveguide hl. The modulation arm includes a modulation region waveguide, a traveling wave electrode 190, and a grating structure. The modulation region waveguide is a metal-oxide-semiconductor MOS (Metal-Oxide-Semiconductor) structure, the grating is disposed on both sides of the modulation region waveguide, and the electrical signal is effective on the traveling wave electrode 190 The refractive index matches the refractive index of the group in the modulation region waveguide in which the optical carrier is disposed on both sides. At this time, the effective refractive index of the electrical signal on the traveling wave electrode 190 is matched with the group refractive index of the optical carrier in the modulation region waveguide on which the grating structure is disposed on both sides to make the electro-optic Modulator 100 has a large bandwidth. In one embodiment, the effective refractive index of the electrical signal on the traveling wave electrode 190 is equal to the group refractive index matching in the modulator waveguide in which the optical carrier is disposed on both sides of the grating structure. The effective refractive index of the electrical signal on the traveling wave electrode is equal to the refractive index of the group in the modulation region waveguide in which the grating structure is disposed on both sides of the optical carrier. Wherein the structural parameters of the grating structure and the structural parameters of the MOS structure are configured such that an effective refractive index of the electrical signal on the traveling wave electrode 190 and a grating structure are disposed on both sides of the optical carrier The group refractive indices in the modulator waveguide match. The structural parameters of the grating include the period of the grating structure and the duty cycle.

The electro-optic modulator 100 includes: a silicon substrate 110 and a first insulating layer 120. The material of the silicon substrate 110 is silicon, and the first insulating layer 120 is disposed on the silicon substrate 110. The input waveguide g, the beam splitter, the modulation arm, the combiner, and the output waveguide are disposed on the first insulating layer 120. The input waveguide g, the beam splitter, the modulation arm, the combiner and the output waveguide are disposed on the first insulating layer 120. This structure is called silicon on insulator (silicon on Insulation, SOI ). Such a structure can reduce the parasitic capacitance between the device disposed on the first insulating layer 120 and the silicon substrate 110, and can improve the placement in the first insulating layer The response speed of the device on 120.

The electro-optic modulator 100 further includes a first type of lightly doped region 130, a second insulating layer 140, and a second type of lightly doped region 150. The first type of lightly doped region 130 is disposed on the first insulating layer 120 and forms the grating structure in a first direction dl. The grating structure includes a first grating structure a and a second grating structure 13. A gap region c is formed between the first grating structure a and the second grating structure b, and the gap region c extends along the second direction d2, the first grating structure a and the second grating structure b is symmetric about the void region c. The second insulating layer 140 is disposed on the first grating structure a and the second grating structure b, and forms two of the modulation arms of the electro-optic modulator 100 in a third direction d3: The arm e and the second modulation arm f are modulated. A second type of lightly doped region 150 is disposed on the second insulating layer 140, and the second type of lightly doped region 150 and the first type of lightly doped region 130 are loaded with electrical signals. The electrical signal is used to modulate an optical signal passing through the first modulation arm e and the second adjustment arm f. The portions of the first type of lightly doped regions 130, the second insulating layer 120, and the second type of lightly doped regions 150 sequentially overlapping form the metal-oxide-semiconductor MOS structure. The first direction dl is a direction in which the tooth structures of the first grating structure a and the second grating structure b extend. As shown in FIG. 1 , the first direction and the first grating structure a and Any one of the second grating structures b is parallel. That is, the first direction is the direction along AA, or the direction of BB'. In Fig. 1, the second direction d2 is parallel to the direction of the longer side of the void region c. The third party to d3 is the direction in which the two modulation arms extend. Preferably, the first direction d1 is perpendicular to the second direction d2, and the second direction d2 is parallel to the third direction d3.

In the present embodiment, a structure formed by sequentially stacking portions of the first type lightly doped region 130, the second insulating layer 140, and the second type heavily doped region 170 is referred to as a MOS capacitor structure. The MOS capacitor structure is disposed on the silicon substrate 110 through the first insulating layer 120. This structure is called Silicon on Insulation (SOI). Such a structure can reduce the parasitic capacitance between the MOS capacitor structure and the silicon substrate 110 and increase the response speed of the MOS capacitor structure, further increasing the corresponding speed of the electro-optic modulator 100.

For a fixed wavelength optical carrier, and the first grating structure a and the second grating structure b having a certain structural parameter, adjusting the electrical signal by adjusting a width to thickness ratio of the second insulating layer 140 The effective refractive index of the traveling wave electrode 190 further adjusts the bandwidth of the electro-optic modulator 100. Specifically, for a fixed wavelength optical carrier, and the structure of the first grating junction And the second grating structure b, when the width to thickness ratio of the second insulating layer 140 is increased, the effective refractive index of the electro-optic modulator 100 to the modulated electrical signal is increased, and further, The bandwidth of the electro-optic modulator 100 is increased; when the width to thickness ratio of the second insulating layer 140 is reduced, the effective refractive index of the modulated electrical signal is reduced by the electro-optic modulator 100, and further, The bandwidth of the electro-optic modulator 100 is reduced.

The electro-optic modulator 100 also includes a first type of heavily doped region 160 and a second type of heavily doped region 170. The number of the first type heavily doped regions 160 is three, and is disposed on the first insulating layer 120 along the second direction d2. A first type of heavily doped region 160 is disposed in the void region c and is connected to the first grating structure a and the second grating structure b. The other two first type of heavily doped regions 160 are respectively disposed at the other ends of the first grating structure a and the second grating structure b, and the other ends of the first grating structure a and the second grating structure b Connected, and in the present embodiment, is in the same plane as the first grating structure a and the second grating structure b. The first type of heavily doped region 160 is doped with impurities of the same nature as the first type of lightly doped region 130, and the doping concentration of the first type of heavily doped type region 160 is greater than the first type The doping concentration of the lightly doped region 130. A second type of heavily doped region 170 is disposed on the second type of lightly doped region 150 along the third direction d3, and the second type of heavily doped region 170 and the second type of lightly doped region 150 is doped with impurities of the same nature and is different from the first type of doping. The doping concentration of the second type heavily doped region 170 is greater than the doping concentration of the second type lightly doped region 150. The first type of heavily doped region 160 and the second type of heavily doped region 170 are respectively loaded with electrical signals to load the first type of lightly doped region 130 and the second type of lightly doped region 150 with electrical signals. In this embodiment, the first type doping is N-type doping, and correspondingly, the second type doping is P-type doping. In other embodiments, the first type of doping may be P-type doping, and correspondingly, the second type of doping is N-type doping.

The electro-optic modulator 100 also includes a third insulating layer 180. The third insulating layer 180 is disposed on the first grating structure a, the second grating structure b, the first type heavily doped region 160, and the second type heavily doped region 170. The first insulating layer 180 and the second type of heavily doped region 170 are respectively provided with a first via 181 and a second via 182. The first via 181 and the second via 182 are filled with a conductive material, and the first via 181 and the second via 182 are loaded with an electrical signal to be heavily doped to the first type, respectively. Region 160 and second type heavily doped region 170 are loaded with electrical signals. In this embodiment, the first insulation The layer 120, the second insulating layer 140, and the third insulating layer 180 may be silicon dioxide.

Preferably, the electro-optic modulator 100 further includes an ohmic contact layer 183 disposed between the first via 181 filling the conductive material and the first type heavily doped region 160 to The contact resistance between the first via 181 and the first type heavily doped region 160 is reduced. The ohmic contact layer 183 is also disposed between the second via 182 filling the conductive material and the second type heavily doped region 170 to reduce the second via 182 and the second type heavily doped region Contact resistance between 170.

The electro-optic modulator 100 further includes two traveling wave electrodes 190. The traveling wave electrodes 190 are disposed on the third insulating layer 180, and the traveling wave electrodes 190 and the first vias 181 and the filling conductive material The two vias 182 are electrically connected, and the traveling wave electrode 190 is used to transmit electrical signals. In the present embodiment, the traveling wave electrode 190 is a metal electrode.

Referring to FIG. 2, the second type of heavily doped region 170 has a lateral dimension greater than the first type of lightly doped region 150. The second type heavily doped region 170 includes a first portion 171 and a second portion

172. The first portion 171 completely covers the second type of lightly doped region 150. The second portion 172 extends outwardly from the first portion 171 and does not cover the second type of lightly doped region 150, and the second via 181 is disposed corresponding to the second portion 172. With this configuration, the loss of light passing through the second insulating layer 240 is effectively reduced.

Adjusting the electrical signals of the first type of lightly doped region 130 and the second type of lightly doped region 150 coupled to the one of the modulation arms can adjust the effective refractive index of the current modulation arm to light. When light passes through the modulation arm, since the effective refractive index of the current modulation arm changes, the phase of the light passing through the modulation arm changes accordingly, so that the phase change of the light passing through the two modulation arms can be adjusted. And to achieve the modulation of light.

When adjusting the electrical signals loaded in the first type of lightly doped region 130 and the second type of lightly doped region 150 connected to a modulation arm such that the concentration of carriers on the modulation arm is reduced, the current modulation arm pair The effective refractive index of the photoelectric is increased. When adjusting the electrical signal loaded in the first type region 130 and the second type lightly doped region 150 to which the modulation arm is connected such that the carrier concentration in the modulation arm is increased, the effective refractive index of the current modulation arm to light Decrease, the phase of the light output by the modulation arm is reduced. Then, the phase difference of the light outputted from the two modulation arms is changed to realize the modulation of the light.

Referring to FIG. 1, in the embodiment, the electro-optic modulator 100 is a typical Mach-Zehnder interferometer (MZI) electro-optic modulator. The electro-optic modulator 100 includes Two "Y"-shaped structures are named as the first "Υ"-shaped structure g and the second "Y"-shaped structure h for convenience of description. The first "Y"-shaped structure g and the second "Y"-shaped structure are h-axis symmetric, and the two branch portions of the first "Y"-shaped structure g pass through the two modulation arms e, f and the second "Y", respectively. "The two branches of the shaped structure h are connected to form a transmission path of light. Specifically, the first "Y" type structure g includes an input waveguide gl and a beam splitter g2. The input waveguide gl is configured to receive an input optical carrier, and the beam splitter g2 is connected to the input waveguide gl and two adjustment arms e, f for dividing the input optical carrier into two optical carriers, and The two optical carriers are output to two modulation arms e, f, respectively. At least one of the two modulation arms e, f is used to modulate the optical carrier. The second "Y" type structure h includes an output waveguide hi and a combiner h2. The combiner h2 connects the two modulation arms e, f and the output waveguide hl for synthesizing two optical carriers modulated by the two modulation arms e, f into one optical carrier. The combiner h2 is configured to output the synthesized optical carrier.

The adjustment of the bandwidth of the electro-optic modulator 100 of the first preferred embodiment of the present invention and the modulation process of the modulation arm of the electro-optic modulator 100 are described below.

For convenience of description, the following is an example in which light of the first "Y"-shaped structure g is evenly divided into two beams.

/ = 1.39c/[ π\{ n ₀ -n _e , _load )] 1

Wherein, ^ is the bandwidth of the electro-optic modulator 100, c is the speed of vacuum light, and 1 is the length of the modulation arm of the electro-optic modulator 100, n. The group refractive index in the modulation region waveguide in which the grating structure is disposed on both sides of the optical carrier is the effective refractive index of the electrical signal on the traveling wave 190 of the electro-optic modulator 100. It can be seen from Equation 1 that by adjusting the effective refractive index of the electrical signal on the traveling wave electrode 190, the group refractive index matching in the modulation region waveguide in which the optical carrier is disposed on both sides of the grating structure can be Modulation of the bandwidth of the modulator 100 is achieved. In other words, the bandwidth of the electro-optic modulator 100 is related to the difference between no and ie, the bandwidth/and (of the bandwidth of the electro-optic modulator 100)

The bandwidth/increase of the electro-optic modulator 100; when decreasing (η.-, 1∞ ₍₁ ), the bandwidth/reduction of the electro-optic modulator 100. In summary, on the one hand, The present invention enhances the group refractive index matching in the modulator waveguide in which the grating carrier is disposed on both sides of the grating carrier by adjusting the effective refractive index of the electrical signal on the traveling wave electrode 190 The bandwidth of the electro-optic modulator 100. On the other hand, the arrangement of the grating structure brings about a slow light effect, which improves the modulation efficiency of the optical carrier. Therefore, the present invention adjusts the electrical signal at the traveling wave. An effective refractive index on the electrode 190, configured with the optical carrier on both sides The group index matching in the modulator waveguide of the grating structure, as well as the arrangement of the grating structure, enhances the modulation efficiency of the optical carrier while increasing the bandwidth of the electro-optic modulator 100.

Typically, the group of optical carriers has a refractive index n. Related to the following factors. For an optical carrier of a fixed wavelength, the group refractive index n of the optical carrier. Corresponding to the structures of the first grating a and the second grating b, for example, the period of the first grating a and the second grating b, the duty ratio, and the like. For a first grating a and a second grating b having a certain structure, the group refractive index n ₀ of the optical carrier is related to the wavelength of the optical carrier passing through the electro-optic modulator 100. That is, when the optical carriers of different wavelengths pass through the first grating a and the second grating b, the group refractive index n ₀ of the optical carriers in the electro-optic modulator 100 is different.

In the case where the first grating a and the second grating b are fixed in structure, and the wavelengths of the optical carriers passing through the first grating a and the second grating b are constant, the optical carrier Group refractive index n. Is a fixed value. In the present embodiment, the group refractive index n of the optical carrier. Greater than the above, and the group refractive index n of the optical carrier. Greater than a predetermined refractive index. The predetermined refractive index is a group refractive index of a normal optical carrier. For example, the group refractive index n of the optical carrier. Is 4. See Equation 2 and Equation 3 for the formula described.

C = ε ₀ . e _r .W/t 3 where L and C are the inductance and capacitance per unit length of the traveling wave electrode 190 under no load, respectively. In the present embodiment, the load refers to a MOS structure. Cj is the capacitance value of the unit length modulation arm, and its unit is F/m, which is an adjustable value. The W and t are the width and thickness of the second insulating layer 140, respectively. The value of the dielectric constant of the vacuum is a fixed value. The relative dielectric constant of the second insulating layer is a fixed value when the material of the second insulating layer is constant.

It can be seen from Equations 2 and 3 that the structural parameters in the MOS structure are as follows: The thickness W of the second insulating layer 140 is related to the width t. The increase is increased when the ratio of the width W to the thickness t of the second insulating layer 140 is increased; when the ratio of the width W to the thickness t of the second insulating layer 140 is decreased, the decrease is made.

It can be seen from the above analysis of Equations 1 to 3 that the MOS structure cooperates with the first grating structure a and the second grating structure b to adjust the bandwidth / of the electro-optic modulator 100.

According to the formula 1, 2, 3, you can get: /= 1.39c/ rl{n ₀ - c [L(e ₀ . e _r .W/t + Cj) ^1/2 ] } 4 is obtained by Equation 4, when the group refractive index n ₀ of the optical carrier is When the value is fixed, that is, the first grating a and the second grating b are fixed in the electro-optic modulator 100, and for the optical carrier of a certain wavelength, when the second insulating layer 140 is increased Bandwidth/increase of the electro-optic modulator 100 when the ratio of the width W to the thickness t; the bandwidth/minus of the electro-optic modulator 100 when the ratio of the width W to the thickness of the second insulating layer 100 is reduced small. Thus, it can be seen that when the optical carrier has a group refractive index n. When the value is a fixed value, that is, the first grating a and the second grating b are fixed in the electro-optic modulator 100, and for the optical carrier of a certain wavelength, the electro-optic modulator 100 can be added. The ratio of the width to the thickness of the second insulating layer 140 in the middle enhances the bandwidth of the electro-optic modulator 100.

The process of adjusting the light by the modulation arm of the electro-optic modulator 100 is described below. In an embodiment, when the second type of lightly doped region 150 connected to a modulation arm of the electro-optic modulator 100 is loaded with a positive electrical signal, the first type of lightly doped region connected to the modulation arm When grounding 130. The concentration of the carriers in the second insulating layer 140 is increased. Specifically, the second insulating layer 140 collects electrons adjacent to the interface of the first type of lightly doped region 120, and the second insulating layer 140 is adjacent to the The interface of the second type of lightly doped region 150 aggregates holes. As the concentration of the carriers in the second insulating layer 140 increases, the effective refractive index of the light passing through the modulation arm decreases, and the phase of the light output by the modulation arm decreases. The modulation of light is achieved by adjusting the wide phase of the two modulation arms.

Please refer to FIG. 4 to FIG. 6 . FIG. 4 is a top view of an electro-optic modulator according to a second preferred embodiment of the present invention; FIG. 5 is a second embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of the electro-optic modulator of the second preferred embodiment of the present invention taken along line DD′. In the present embodiment, the electro-optic modulator 300 includes a silicon substrate 310, a first insulating layer 320, a first type of lightly doped region 330, a second insulating layer 340, and a second type of lightly doped region 350. The material of the silicon substrate 310 is silicon. The first insulating layer 320 is disposed on the silicon substrate 310. The first type of lightly doped region 330 is disposed on the first insulating layer 320 and forms a first grating structure a and a second grating structure b along the first direction d1. A gap region c' is formed between the first grating structure a' and the second grating structure b', and the gap region c' extends along the second direction d2, the first grating structure a, and The second grating structure b is symmetrical about the void region c. The second insulating layer 340 is disposed on the first grating structure a, and the second The grating structure b, up, and in the third direction d3, form two modulation arms of the electro-optic modulator 300: a first modulation arm e, and a second modulation arm f. A second type of lightly doped region 350 is disposed on the second insulating layer 340, and the second type of lightly doped region 350 and the first type of lightly doped region 330 are loaded with electrical signals. The bandwidth of the electro-optic modulator 300 is adjusted by adjusting the width to thickness ratio on the second insulating layer. Preferably, the first direction d1, the second direction d2, and the second direction d2 are parallel to the third direction d3.

Correspondingly, the structure formed by the first type lightly doped region 330, the second insulating layer 340, and the second type heavily doped region 370 may be referred to as a MOS capacitor structure. The MOS capacitor structure is disposed on the silicon substrate 310 through the first insulating layer 320. This structure is referred to as SOI. Such a structure can reduce the parasitic capacitance between the MOS capacitor structure and the silicon substrate 310 and increase the response speed of the MOS capacitor structure.

The electro-optic modulator 300 also includes a first type of heavily doped region 360 and a second type of heavily doped region 370. The number of the first type of heavily doped regions 360 is one, and along the third direction d3, is disposed in the void region c of the first insulating layer 320, and the first grating structure a, and The two grating structures b' are connected, and the doping concentration of the first type heavily doped region 360 is greater than the doping concentration of the first type lightly doped region 330. The number of the second type of heavily doped regions 370 is two, disposed along the third direction d3, and located in the same layer as the second type of lightly doped regions 350. The doping concentration of the second type heavily doped region 360 is greater than the doping concentration of the first type of lightly doped region 330. The first type of heavily doped region 330 and the second type of heavily doped region 360 respectively load electrical signals to load the first type of lightly doped region 330 and the second type of lightly doped region 370 signal.

The electro-optic modulator 300 also includes a third insulating layer 380. The third insulating layer 380 is disposed on the first grating structure a', the second grating structure b', the first type heavily doped region 360, the second type lightly doped region 350, and The second type of heavily doped region 370 is described. The first insulating layer 380 is respectively provided with a first via 381 and a second via 382 corresponding to the first type heavily doped region 360 and the second type heavily doped region 370. The first via 381 and the second via 382 are filled with a conductive material, and the first via 381 and the second via 382 are respectively respectively directed to the first type heavily doped region 360 and The second type heavily doped region 370 is loaded with an electrical signal, and the electrical signals loaded in the first type heavily doped region 360 and the second type heavily doped region 370 are respectively loaded in the The first type of lightly doped region 330 and the second type of lightly doped region 350 are described.

The electro-optic modulator 300 also includes an ohmic contact layer 383. The ohmic contact layer 383 is disposed between the first via 381 filling the conductive material and the first type heavily doped region 360 to reduce the first via 381 filling the conductive material and the Contact resistance between the first type of heavily doped regions 360. The ohmic layer 383 is also disposed between the second via 382 filling the conductive material and the second type heavily doped region 370 to reduce the second via 382 filled with the conductive material and the Contact resistance between the second type of heavily doped regions 370.

The electro-optic modulator 300 further includes a traveling wave electrode 390 disposed on the third insulating layer 380, the traveling wave electrode 390 and the first via 381 filled with the conductive material and filling The second vias 382 of the conductive material are electrically connected. The traveling wave electrode 390 is configured to transmit an electrical signal, and the electrical signal is respectively transmitted to the first type of re-doping through the first via 381 filling the conductive material and the second via 382 filling the conductive material. Miscellaneous region 360 and second type heavily doped region

370.

The electro-optical modulator 300 provided in the second embodiment of the present invention has the same modulation principle as the electro-optic modulator 100 provided in the first embodiment of the present invention, and details are not described herein again.

Compared with the prior art, the electro-optic modulator of the present invention passes the effective refractive index of the electrical signal on the traveling wave electrode, and the group in the modulation region waveguide of the grating structure configured on both sides of the optical carrier The refractive indices are matched to increase the modulation bandwidth of the electro-optic modulator. On the other hand, the arrangement of the grating structure brings about a slow light effect, which improves the modulation efficiency of the optical carrier. Therefore, the present invention adjusts the group refractive index in the modulator waveguide in which the grating structure is disposed on both sides by adjusting the effective refractive index of the electric signal on the traveling wave electrode, and the grating structure. The setting improves the modulation efficiency of the optical carrier while increasing the bandwidth of the electro-optic modulator. Further, the first type of lightly doped regions 130, 330, the second insulating layer 140, 340, and the second type of heavily doped regions 170, 370 are sequentially overlapped to form a MOS capacitor structure. The MOS capacitor structure is disposed on the silicon substrates 110, 310 through the first insulating layers 120, 320. This structure is referred to as SOI. Such a structure can reduce the parasitic capacitance between the MOS capacitor structure and the silicon substrate 110, 310 and increase the response speed of the MOS capacitor structure.

It should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention, and are not intended to be limiting thereof; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art It should be understood that the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived within the technical scope of the present invention are within the scope of the present invention. . Therefore, the scope of the invention should be determined by the scope of the claims.

Claims

Rights request

What is claimed is: 1. An electro-optic modulator for modulating an electrical signal into an optical carrier, wherein:

The electro-optic modulator comprises an input waveguide, a beam splitter, two symmetric modulation arms, a combiner, and an output waveguide;

The modulation region waveguide is a metal-oxide-semiconductor MOS structure;

The effective refractive index of the electrical signal on the traveling wave electrode is matched to the refractive index of the group in the modulation region waveguide in which the optical carrier is disposed on both sides.

2. An electro-optic modulator according to claim 1, wherein the structural parameters of the grating structure and the structural parameters of the MOS structure are configured such that an effective refraction of the electrical signal on the traveling wave electrode The rate is matched to the group refractive index of the modulator carrier in which the optical carrier is disposed on both sides of the grating structure.

3. The electro-optic modulator of claim 2, wherein the electro-optic modulator further comprises:

Silicon substrate

a first insulating layer disposed on the silicon substrate;

4. The electro-optic modulator according to claim 3, wherein the electro-optic modulator further comprises: a first type of lightly doped region disposed on the first insulating layer and forming the first direction a grating structure, the grating structure includes a first grating structure and a second grating structure, a gap region is formed between the first grating structure and the second grating structure, and the gap region extends along a second direction, The first grating structure and the second grating structure are symmetrical about the void region; a second insulating layer disposed on the first grating structure and the second grating structure, and forming two of the modulation arms in a third direction;

The electro-optic modulator according to claim 4, wherein, for a fixed wavelength optical carrier, and the first grating structure and the second grating structure whose structural parameters have been configured, the second insulating layer When the width to thickness ratio is configured to increase, the effective refractive index of the electrical signal on the traveling wave electrode increases, and the bandwidth of the electro-optic modulator increases.

6. The electro-optic modulator of claim 4, wherein the electro-optic modulator further comprises:

a first type of heavily doped region having three numbers, disposed on the first insulating layer along the second direction, a first type heavily doped region disposed in the void region and the first The grating structure and the second grating structure are connected, and the other two first type of heavily doped regions are respectively disposed at the other ends of the two grating structures and respectively connected to the other ends of the two grating structures, the first type The doping concentration of the heavily doped region is greater than the doping concentration of the first type of lightly doped region;

The first type of heavily doped region and the second type of heavily doped region are respectively loaded with electrical signals to cause the first type of lightly doped regions and the second type of lightly doped regions to be loaded with electrical signals.

7. The electro-optic modulator of claim 6, wherein the electro-optic modulator further comprises:

a third insulating layer disposed on the first grating structure, the second grating structure, the first type heavily doped region, and the second type heavily doped region, wherein the third insulating layer corresponds to the first a type of blend The first via and the second via are respectively disposed in the impurity region and the second via, and the first via and the second via are filled with a conductive material through the first via And the second via loading electrical signal to respectively apply an electrical signal to the first type of heavily doped region and the second type of heavily doped region, the traveling wave electrode being disposed on the third insulating layer, The traveling wave electrode is electrically connected to the first via and the second via filled with the conductive material, and the traveling wave electrode is used for transmitting an electrical signal.

8. The electro-optic modulator of claim 7, wherein the electro-optic modulator further comprises:

9. The electro-optic modulator of claim 8, wherein the second type of heavily doped region comprises a first portion and a second portion, the first portion completely covering the second type of lightly doped region The second portion extends outward from one end of the first portion and does not cover the second type of lightly doped region, and the second via is disposed corresponding to the second portion.

10. The electro-optic modulator according to claim 4, wherein the first direction is perpendicular to the second direction, and the second direction is parallel to the third direction.

The electro-optic modulator according to claim 4, wherein the first type is an N type, and the second type is a P type; or the first type is a P type, and the second type is a N type.

12. The electro-optic modulator of claim 4, wherein the electro-optic modulator further comprises:

a first type of heavily doped region having a number, the void region disposed on the first insulating layer along the third direction and connected to the first grating structure and the second grating structure, The doping concentration of the first type of heavily doped region is greater than the doping concentration of the first type of lightly doped region; a second type of heavily doped region having two numbers, disposed along the third direction and located in the same layer as the second type of lightly doped region, the concentration of the second type heavily doped region being greater than Doping concentration of the second type of lightly doped region;

The electro-optic modulator according to claim 12, wherein the electro-optic modulator further comprises:

14. The electro-optic modulator of claim 13, further comprising: an ohmic contact layer disposed on the first via filled with the conductive material and the first type of heavily doped Between the impurity regions, and between the second via filled with the conductive material and the second heavily doped region.

The electro-optic modulator according to claim 1, wherein an effective refractive index of the electrical signal on the traveling wave electrode is equal to a modulation region waveguide in which the optical carrier is disposed on both sides of the grating structure The group of refractive indices is equal such that the effective refractive index of the electrical signal on the traveling wave electrode is equal to the refractive index of the group in the adjustment region waveguide in which the grating structure is disposed on both sides.