CN118053920A - Photoelectric detector - Google Patents

Abstract

The invention provides a photoelectric detector which comprises a lower cladding layer, a signal light input waveguide, a multimode interference waveguide and a silicon slab waveguide, wherein the signal light input waveguide, the multimode interference waveguide and the silicon slab waveguide are arranged on the top surface of the lower cladding layer and are sequentially connected along the light propagation direction; the silicon slab waveguide comprises a first silicon slab waveguide part and 2 second silicon slab waveguide parts, wherein the 2 second silicon slab waveguide parts are arranged in parallel with the first silicon slab waveguide part and are respectively arranged at two sides of the first silicon slab waveguide part along the width direction of the silicon slab waveguide, and the thickness of the first silicon slab waveguide part is larger than that of the second silicon slab waveguide part; the top surface of the first silicon flat waveguide part is provided with an absorption area for absorbing mirror image light of the first silicon flat waveguide part to generate photocurrent; the top surface of the second silicon slab waveguide part is provided with a contact metal part to lead out photocurrent. The invention reduces the processing difficulty of the process and can reach the maximum coupling efficiency, thereby realizing the high responsivity of the photoelectric detector.

Description

Photoelectric detector

Technical Field

The invention relates to the technical field of optoelectronic devices, in particular to a photoelectric detector.

Background

The silicon-based photon technology is compatible with the CMOS process, has the advantages of mature process and high integration level, and can meet the requirements of integration and low cost of optoelectronic devices. In silicon-based photon technology, a silicon-based germanium photoelectric detector is a core device for realizing photoelectric conversion, and along with development of technology, higher and higher requirements are put forward on the performance and process compatibility of the detector, for example, the photoelectric detector is required to meet high responsivity and simultaneously put forward higher requirements on the process.

Current detectors typically employ a single mode waveguide coupling mode or a tapered waveguide-like lateral coupling mode. For example, literature (Optics Express,2009,17 (8): 6252-7) reports an evanescent coupling mode of a high-speed germanium-silicon photoelectric detector, light is input from bottom-layer silicon and enters upper-layer germanium through evanescent coupling, namely, a single-mode silicon waveguide is adopted to couple in a germanium region, the responsivity of the coupling mode is 0.85A/W, and the responsivity of the coupling mode is lower. The literature (vol.42, no.4/February 15 2017/Optics Letters) reports that an improved tapered waveguide-like lateral coupling mode is proposed, the size of the silicon waveguide needs to reach 100nm, the coupling mode has a complex process and high process requirements.

Accordingly, there is a need to provide a novel photodetector that solves the above-mentioned problems of the prior art.

Disclosure of Invention

The invention aims to provide a photoelectric detector, which reduces the processing difficulty of a process and can reach the maximum coupling efficiency, so that the high responsivity of the photoelectric detector is realized, and the responsivity of the photoelectric detector can reach 1.05A/W.

In order to achieve the above object, the photodetector of the present invention includes a lower cladding layer, a signal light input waveguide, a multimode interference waveguide, a silicon slab waveguide, an absorption region, and a contact metal portion; the signal light input waveguide is arranged on the top surface of the lower cladding layer and is used for converting a single-mode waveguide with smaller mode spots into a single-mode waveguide with larger mode spots; the multimode interference waveguide is arranged on the top surface of the lower cladding and connected with the signal light input waveguide, and is used for generating mirror image light of the incident light at the multimode interference waveguide output end through a self-imaging principle; the silicon slab waveguide is arranged on the top surface of the lower cladding layer and is connected with the multimode interference waveguide, the silicon slab waveguide is used for transmitting the mirror image light, the silicon slab waveguide comprises a first silicon slab waveguide part and 2 second silicon slab waveguide parts, the central line of the first silicon slab waveguide part along the length direction coincides with the central line of the multimode interference waveguide along the length direction, the 2 second silicon slab waveguide parts are arranged in parallel with the first silicon slab waveguide part and are respectively arranged on two sides of the first silicon slab waveguide part along the width direction of the silicon slab waveguide, and the thickness of the first silicon slab waveguide part is larger than that of the second silicon slab waveguide part; the absorption region is arranged on the top surface of the first silicon slab waveguide part and is used for absorbing the mirror image light of the first silicon slab waveguide part to generate photocurrent; the contact metal part is arranged on the top surface of the second silicon slab waveguide part and is used for leading out the photocurrent.

The photoelectric detector has the beneficial effects that: by arranging the multimode interference waveguide between the signal light input waveguide and the silicon slab waveguide, light entering the silicon slab waveguide and the absorption region passes through the multimode interference waveguide, so that the multimode interference waveguide can utilize the self-imaging principle of light, the incident light can generate image light of an input end at the output end of the multimode interference waveguide, the image light output by the multimode interference waveguide is coupled into the absorption region, the light coupled into the absorption region can be effectively prevented from being scattered, the light field distribution coupled into the absorption region is optimized, the processing difficulty of a process is reduced, the maximum coupling efficiency is favorably achieved, the photoelectric detector is enabled to perform high performance, and the high responsivity of the photoelectric detector is realized; meanwhile, the silicon flat waveguide comprises a first silicon flat waveguide part and 2 second silicon flat waveguide parts, wherein the central line of the first silicon flat waveguide part along the length direction coincides with the central line of the multimode interference waveguide along the length direction, the 2 second silicon flat waveguide parts are arranged in parallel with the first silicon flat waveguide part and are respectively arranged at two sides of the first silicon flat waveguide part along the width direction of the silicon flat waveguide, the thickness of the first silicon flat waveguide part is larger than that of the second silicon flat waveguide part, so that the mirror light is reflected at the interface of the first silicon flat waveguide part and the second silicon flat waveguide part, namely, the mirror light at the interface is reflected back to the first silicon flat waveguide part, and only a small amount of the mirror light enters the second silicon flat waveguide part and is absorbed by the contact metal part, thereby reducing the loss of the mirror light and enabling the responsivity of the photoelectric detector to reach 1.05A/W.

Preferably, the difference between the thickness of the first silicon slab waveguide portion and the thickness of the second silicon slab waveguide portion is 50nm to 160nm. The beneficial effects are that: the mirror light is reflected at the interface of the first silicon flat waveguide part and the second silicon flat waveguide part, namely, the mirror light at the interface is reflected back to the first silicon flat waveguide part, and only a small amount of mirror light enters the second silicon flat waveguide part to be absorbed by the contact metal part, so that the loss of the mirror light is reduced, and the high responsivity of the photoelectric detector is realized.

Preferably, the multimode interference waveguide has a width of 4 μm to 8 μm and a length of 8 μm to 100 μm. The beneficial effects are that: so that the multimode interference waveguide can excite multiple modes and form a mirror image light field of an input light field at the output end of the multimode interference waveguide.

Preferably, the length of the signal light input waveguide is 20 μm to 50 μm. The beneficial effects are that: the length of the signal light input waveguide is not smaller than 20 mu m, so that the length of the signal light input waveguide is long enough to meet adiabatic transmission, and only a single-mode optical field is ensured to be transmitted in the signal light input waveguide; the length of the signal light input waveguide is not more than 50 μm, and too long a length of the signal light input waveguide increases the transmission loss of light in the waveguide and also increases the device size.

Preferably, the length of the absorbent region is greater than 10 μm. The beneficial effects are that: so as to ensure that the mirror image light can be absorbed by the absorption area to the maximum extent and converted into photocurrent.

Preferably, the top surface of the first silicon slab waveguide portion includes a covering portion where the absorption region is disposed and an exposed portion where the absorption region is not disposed, and the thickness of the covering portion is less than or equal to the thickness of the exposed portion. The beneficial effects are that: the absorption region and the first silicon slab waveguide part have flexible positional relationship, the process complexity is reduced, the method is suitable for various processing processes, and the universality is strong.

Preferably, the top surface of the first silicon slab waveguide portion is provided with a groove portion, and the absorption region is embedded in the groove portion. The beneficial effects are that: to facilitate absorption of the light field and to reduce reflection of the mirrored light into the absorption region.

Preferably, when the length of the first silicon slab waveguide portion is greater than or equal to the length of the absorption region, and the length of the first silicon slab waveguide portion is greater than the length of the absorption region, the following features are provided: the difference between the length of the first silicon slab waveguide portion and the length of the absorption region is not greater than the length of the multimode interference waveguide. The beneficial effects are that: the absorption region and the first silicon slab waveguide part have flexible positional relationship, the process complexity is reduced, the method is suitable for various processing processes, and the universality is strong.

Preferably, the contact metal part includes at least 2 contact metal units, at least 2 contact metal units are separately provided on 2 second silicon slab waveguide parts, and the contact metal units include at least one of a rectangular structure, a circular structure and an elliptical structure, which are arranged along the length direction of the second silicon slab waveguide part, or at least 2 rectangular structures, which are sequentially and equidistantly arranged along the length direction of the second silicon slab waveguide part.

Preferably, the thickness of the signal light input waveguide, the thickness of the multimode interference waveguide and the thickness of the first silicon slab waveguide portion are equal, or at least two of the thickness of the signal light input waveguide, the thickness of the multimode interference waveguide and the thickness of the first silicon slab waveguide portion are unequal. The beneficial effects are that: the thickness of the signal light input waveguide, the thickness of the multimode interference waveguide and the thickness of the silicon slab waveguide are equal, and the arrangement mode is beneficial to ensuring that mirror image light is absorbed by an absorption area to the maximum extent, so that the maximum coupling efficiency is achieved, and the high responsivity of the photoelectric detector is realized; the thickness of the signal light input waveguide, the thickness of the multimode interference waveguide and the thickness of the first silicon slab waveguide part are at least two unequal, and the arrangement mode has simple processing technology and is suitable for application scenes with low coupling efficiency requirements and low responsiveness requirements.

Preferably, the refractive index of the lower cladding layer is smaller than the refractive index of any one of the signal light input waveguide, the multimode interference waveguide and the silicon slab waveguide. The beneficial effects are that: the optical field distribution of the coupled-in absorption region can be optimized by controlling the refractive index of each structural component, so that the maximum coupling efficiency is achieved, and the high responsivity of the photoelectric detector is realized.

Preferably, the signal light input waveguide includes an input end portion and an output end portion, the output end portion is connected with the multimode interference waveguide, and a width of the input end portion is smaller than a width of the output end portion. The beneficial effects are that: i.e. the signal light input waveguide is a tapered waveguide to ensure that only a single mode optical field is transmitted within the signal light input waveguide.

Preferably, the signal light input waveguide is a tapered waveguide, the width of the input end of the tapered waveguide is 0.4 μm to 0.6 μm, and the width of the output end of the tapered waveguide is 0.6 μm to 1.2 μm. The beneficial effects are that: the length of the signal light input waveguide is long enough to meet adiabatic transmission, and only a single-mode optical field is ensured to be transmitted in the signal light input waveguide.

Preferably, the signal light input waveguide is any one of a silicon waveguide, a silicon nitride waveguide, a silicon oxynitride waveguide, a lithium niobate waveguide, an indium phosphide waveguide, an alumina waveguide, and a polymer waveguide. The beneficial effects are that: can be selected according to actual demands, and has wide application range and strong applicability.

Preferably, the bus of the changing surface of the signal light input waveguide adopts at least one of a linear, an exponential, a parabolic, a Bezier curve, a sin curve, an Euler curve and a sub-wavelength structure. The beneficial effects are that: facilitating coupling and optimizing the size of the signal light input waveguide.

Preferably, the composition material of the absorption region is germanium or indium phosphide. The beneficial effects are that: the absorption efficiency is high, and the output of photocurrent is facilitated.

Preferably, the photodetector further includes an upper cladding layer, the upper cladding layer covers the top surface of the signal light input waveguide, the top surface of the multimode interference waveguide, the top surface of the absorption region, the top surface of the contact metal portion, and the top surface of the exposed portion of the silicon slab waveguide where the absorption region and the contact metal portion are not disposed, and the refractive index of the upper cladding layer is smaller than the refractive index of any one of the signal light input waveguide, the multimode interference waveguide, and the silicon slab waveguide. The beneficial effects are that: so that not only an optical field can be limited but also the signal light input waveguide, the multimode interference waveguide, the absorption region, the contact metal portion, and the silicon slab waveguide can be protected by the upper cladding layer.

Drawings

FIG. 1 is a top view of a photodetector according to a first embodiment of the invention;

FIG. 2 is a cross-sectional view of the photodetector shown in FIG. 1 taken along line AA 1;

FIG. 3 is a cross-sectional view of the photodetector shown in FIG. 1 taken along BB 1;

FIG. 4 is a top view of a photodetector according to a second embodiment of the invention;

FIG. 5 is a cross-sectional view of the photodetector shown in FIG. 4 taken along line AA 1;

FIG. 6 is a cross-sectional view of the photodetector shown in FIG. 4 taken along BB 1;

fig. 7 is a cross-sectional view of a photodetector according to a third embodiment of the present invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. Unless otherwise defined, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. As used herein, the word "comprising" and the like means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof without precluding other elements or items.

In the prior art, two modes are arranged at the position between an absorption region for absorbing light to generate photocurrent and a silicon slab waveguide for transmitting light, one is that the absorption region is arranged in the middle region of the silicon slab waveguide, namely, the absorption region is far away from the edge part of the silicon slab waveguide, and the mode has simple processing technology, but can lead to low coupling efficiency and lower responsivity; the other is that the length of the absorption region is equal to the length of the silicon slab waveguide, the coupling efficiency is high in the mode, the process is complex, and the processing difficulty of the process is increased.

In order to overcome the problems in the prior art, the embodiment of the invention provides the photoelectric detector, the processing difficulty of the process is reduced, and the maximum coupling efficiency can be achieved, so that the high responsivity of the photoelectric detector is realized, and the responsivity of the photoelectric detector can reach 1.05A/W.

FIG. 1 is a top view of a photodetector according to a first embodiment of the invention; FIG. 2 is a cross-sectional view of the photodetector shown in FIG. 1 taken along line AA 1; fig. 3 is a cross-sectional view of the photodetector shown in fig. 1 along BB 1.

In some embodiments of the present invention, referring to fig. 1 to 3, the photodetector includes a lower cladding layer 10, a signal light input waveguide 20, a multimode interference waveguide 30, a silicon slab waveguide 40, an absorption region 50, and a contact metal portion 60; the signal light input waveguide 20 is disposed on the top surface of the lower cladding 10, and the signal light input waveguide 20 is configured to convert a single-mode waveguide with a smaller mode spot into a single-mode waveguide with a larger mode spot; the multimode interference waveguide 30 is disposed on the top surface of the lower cladding 10 and connected to the signal light input waveguide 20, and the multimode interference waveguide 30 is configured to generate a mirror image of an incident light at an input end of the multimode interference waveguide 30 through a self-mapping principle at an output end of the multimode interference waveguide 30; the silicon slab waveguide 40 is disposed on the top surface of the lower cladding layer 10 and is connected to the multimode interference waveguide 30, the silicon slab waveguide 40 is configured to transmit the mirror light, the silicon slab waveguide 40 includes a first silicon slab waveguide portion 41 and 2 second silicon slab waveguide portions 42, a center line of the first silicon slab waveguide portion 41 along the length direction coincides with a center line of the multimode interference waveguide 30 along the length direction, the 2 second silicon slab waveguide portions 42 are disposed parallel to the first silicon slab waveguide portion 41 and are disposed on two sides of the first silicon slab waveguide portion 41 along the width direction of the silicon slab waveguide 40, and the thickness of the first silicon slab waveguide portion 41 is greater than that of the second silicon slab waveguide portion 42; the absorption region 50 is disposed on the top surface of the first silicon slab waveguide portion 41, and the absorption region 50 is configured to absorb the mirror light of the first silicon slab waveguide portion 41 to generate a photocurrent; the contact metal portion 60 is disposed on the top surface of the second silicon slab waveguide portion 42, and the contact metal portion 60 is used for guiding out the photocurrent.

The signal light input waveguide 20, the multimode interference waveguide 30, and the silicon slab waveguide 40 are disposed on the top surface of the lower cladding layer 10 and are sequentially connected along the propagation direction of light, i.e., the direction indicated by X in fig. 1. The center line of the first silicon slab waveguide portion 41 along the length direction is the center line between the two ends of the first silicon slab waveguide portion 41 along the width direction, the center line of the multimode interference waveguide 30 along the length direction is the center line between the two ends of the multimode interference waveguide 30 along the width direction, that is, the center line of the first silicon slab waveguide portion 41 along the length direction and the center line of the multimode interference waveguide 30 along the length direction are all coincident with the line BB1 in fig. 1.

Specifically, by arranging the multimode interference waveguide 30 between the signal light input waveguide 20 and the silicon slab waveguide 40, the light entering the silicon slab waveguide 40 and the absorption region 50 passes through the multimode interference waveguide 30 first, so that the multimode interference waveguide 30 can generate mirror image light of an input end at an output end of the multimode interference waveguide 30 by using a self-imaging principle of light, and then the mirror image light output by the multimode interference waveguide 30 is coupled into the absorption region 50, so that light coupling into the absorption region 50 can be effectively prevented from scattering, light field distribution coupling into the absorption region 50 is optimized, and therefore, processing difficulty is reduced, maximum coupling efficiency is facilitated to be achieved, and high responsivity of the photoelectric detector is realized; meanwhile, the silicon slab waveguide 40 includes a first silicon slab waveguide portion 41 and 2 second silicon slab waveguide portions 42, the center line of the first silicon slab waveguide portion 41 along the length direction coincides with the center line of the multimode interference waveguide 30 along the length direction, the 2 second silicon slab waveguide portions 42 are disposed parallel to the first silicon slab waveguide portion 41 and are disposed on two sides of the first silicon slab waveguide portion 41 along the width direction of the silicon slab waveguide 40, and the thickness of the first silicon slab waveguide portion 41 is greater than the thickness of the second silicon slab waveguide portion 42, so that the mirror light is reflected at the interface between the first silicon slab waveguide portion 41 and the second silicon slab waveguide portion 42, that is, the mirror light at the interface is reflected back to the first silicon slab waveguide portion 41, and only a small amount of mirror light enters the second silicon slab waveguide portion 42 and is absorbed by the contact metal portion 60, thereby reducing the loss of the mirror light, and enabling the responsivity of the photoelectric detector of the invention to reach 1.05A/W.

In the embodiment of the present invention, the direction of the length is the direction indicated by X in the figure, the direction of the width is the direction indicated by Y in the figure, and the direction of the thickness is the direction indicated by Z in the figure.

In some embodiments of the present invention, the width of the first silicon slab waveguide portion and the width of the multimode interference waveguide are both greater than the width of the signal light input waveguide.

In some embodiments of the invention, the width of the first silicon slab waveguide portion is greater than the width of the multimode interference waveguide.

In other embodiments of the present invention, the width of the first silicon slab waveguide portion is less than the width of the multimode interference waveguide.

In still other embodiments of the present invention, the width of the first silicon slab waveguide portion is equal to the width of the multimode interference waveguide.

In some embodiments of the present invention, the refractive index of the lower cladding layer is smaller than the refractive index of any one of the signal light input waveguide, the multimode interference waveguide, and the silicon slab waveguide. The optical field distribution of the coupled-in absorption region can be optimized by controlling the refractive index of each structural component, so that the maximum coupling efficiency is achieved, and the high responsivity of the photoelectric detector is realized.

In some embodiments of the present invention, the refractive index of the signal light input waveguide is greater than that of the lower cladding, which is favorable for improving the coupling efficiency, thereby realizing high responsivity of the photodetector.

In some embodiments of the present invention, the signal light input waveguide is any one of a silicon waveguide, a silicon nitride waveguide, a silicon oxynitride waveguide, a lithium niobate waveguide, an indium phosphide waveguide, an alumina waveguide and a polymer waveguide, which can be selected according to actual requirements, and has a wide application range and strong applicability.

In some embodiments of the present invention, the signal light input waveguide is a silicon waveguide, the refractive index of the silicon waveguide in the 1310nm band is 3.5, the lower cladding layer is made of silicon dioxide, and the refractive index of the silicon dioxide in the 1310nm band is 1.45.

In other embodiments of the present invention, the signal light input waveguide is a silicon nitride waveguide, the refractive index of the silicon nitride waveguide in the 1310nm band is 2.0, the lower cladding layer is made of silicon dioxide, and the refractive index of the silicon dioxide in the 1310nm band is 1.45.

In some embodiments of the present invention, the length of the signal light input waveguide is 20 μm to 50 μm, that is, the length of the signal light input waveguide is not less than 20 μm, so that the length of the signal light input waveguide is long enough to satisfy adiabatic transmission, and only a single-mode optical field is ensured to be transmitted in the signal light input waveguide; the length of the signal light input waveguide is not more than 50 μm, and too long a length of the signal light input waveguide increases the transmission loss of light in the waveguide and also increases the device size.

In some embodiments of the invention, the signal light input waveguide has a length of any one of 20 μm, 25 μm, 30 μm, 37 μm, 40 μm, 52 μm, 45 μm, and 50 μm.

In some embodiments of the present invention, referring to fig. 1, the signal light input waveguide 20 includes an input end 21 and an output end 22, the output end 22 is connected to the multimode interference waveguide 30, and the width of the input end 21 is smaller than the width of the output end 22. I.e. the signal light input waveguide 20 is a tapered waveguide to ensure that only a single mode optical field is transmitted within the signal light input waveguide.

In some specific embodiments of the present invention, referring to fig. 1, the signal light input waveguide 20 is a tapered waveguide, and the width of the input end 21 is smaller than the width of the output end 22, that is, when the photodetector is horizontally placed, the projection of the signal light input waveguide 20 on the top surface of the lower cladding layer 10 is a trapezoid structure.

In some embodiments of the present invention, referring to fig. 1, the signal light input waveguide 20 is a tapered waveguide, the input end 21 of the tapered waveguide has a width of 0.4 μm to 0.6 μm, and the output end of the tapered waveguide has a width of 0.6 μm to 1.2 μm, so that the length of the signal light input waveguide is long enough to satisfy adiabatic transmission, and only a single-mode optical field is guaranteed to be transmitted in the signal light input waveguide.

In some embodiments of the present invention, the bus of the changing surface of the signal light input waveguide adopts at least one of a linear, exponential, parabolic, bezier curve, sin curve, euler curve and sub-wavelength structure, which is favorable for coupling and optimizing the size of the signal light input waveguide.

FIG. 4 is a top view of a photodetector according to a second embodiment of the invention; FIG. 5 is a cross-sectional view of the photodetector shown in FIG. 4 taken along line AA 1; fig. 6 is a cross-sectional view of the photodetector shown in fig. 4 along BB 1.

In some embodiments of the present invention, referring to fig. 3 and 6, the thickness of the signal light input waveguide 20, the thickness of the multimode interference waveguide 30 and the thickness of the first silicon slab waveguide portion 41 are equal, and as shown in fig. 3, the arrangement is beneficial to ensuring that the mirror light is absorbed by the absorption region to the maximum extent, and the maximum coupling efficiency is achieved, thereby realizing high responsivity of the photodetector. Or at least two of the thickness of the signal light input waveguide 20, the thickness of the multimode interference waveguide 30 and the thickness of the first silicon slab waveguide portion 41 are unequal, as shown in fig. 6, the arrangement mode has a simple processing technology, and is suitable for application scenarios with low coupling efficiency requirements and low responsivity requirements.

In some embodiments of the present invention, referring to fig. 3, the thickness of the signal light input waveguide 20, the thickness of the multimode interference waveguide 30, and the thickness of the first silicon slab waveguide portion 41 are all equal. Because the top surface areas of the lower cladding layer 10 are arranged flush, the central line of the signal light input waveguide 20 along the length direction of the photoelectric detector, the central line of the multimode interference waveguide 30 along the length direction of the photoelectric detector and the central line of the first silicon slab waveguide portion 41 along the length direction of the photoelectric detector are on the same straight line, and the arrangement is favorable for achieving the maximum coupling efficiency, so that the high responsivity of the photoelectric detector is realized.

In other embodiments of the present invention, referring to fig. 6, the thickness of the signal light input waveguide 20 is equal to the thickness of the multimode interference waveguide 30, and the thickness of the multimode interference waveguide 30 is not equal to the thickness of the first silicon slab waveguide portion 41. Because the top surface areas of the lower cladding layer 10 are flush, the central line of the signal light input waveguide 20 along the length direction of the photoelectric detector and the central line of the multimode interference waveguide 30 along the length direction of the photoelectric detector are on the same straight line, but the central line of the multimode interference waveguide 30 along the length direction of the photoelectric detector and the central line of the first silicon slab waveguide portion 41 along the length direction of the photoelectric detector are arranged in a staggered manner.

In some embodiments of the invention, the refractive index of the multimode interference waveguide is greater than the refractive index of the lower cladding. The optical field distribution coupled into the absorption region can be optimized by controlling the refractive index of the multimode interference waveguide, so that the maximum coupling efficiency is achieved, and the high responsivity of the photoelectric detector is realized.

In some embodiments of the present invention, the multimode interference waveguide is a silicon waveguide, the refractive index of the silicon waveguide in the 1310nm band is 3.5, the lower cladding layer is made of silicon dioxide, and the refractive index of the silicon dioxide in the 1310nm band is 1.45.

In some embodiments of the present invention, the multimode interference waveguide has a width of 4 μm to 8 μm and a length of 8 μm to 100 μm, so that the multimode interference waveguide can excite multiple modes, and a mirror light field of an input light field is formed at an output end of the multimode interference waveguide.

In some embodiments of the invention, the multimode interference waveguide has a width of any one of 4 μm, 4.5 μm, 5 μm, 7 μm, 7.5 μm, and 8 μm.

In some embodiments of the invention, the multimode interference waveguide has a length of any one of 8 μm, 8.5 μm, 10 μm, 20 μm, 35 μm, 40 μm, 55 μm, 70 μm, 80 μm, and 100 μm.

In some embodiments of the present invention, the refractive index of the silicon slab waveguide is greater than the refractive index of the lower cladding layer. The optical field distribution of the coupled absorption region can be optimized by controlling the refractive index of the silicon slab waveguide, so that the maximum coupling efficiency is achieved, and the high responsivity of the photoelectric detector is realized.

In some embodiments of the present invention, the silicon slab waveguide is a silicon waveguide, the refractive index of the silicon waveguide in the 1310nm band is 3.5, the lower cladding layer is made of silicon dioxide, and the refractive index of the silicon dioxide in the 1310nm band is 1.45.

In some embodiments of the present invention, referring to fig. 2 and 5, the difference between the thickness of the first silicon slab waveguide portion 41 and the thickness of the second silicon slab waveguide portion 42 is 50nm to 160nm. The mirror light is reflected at the interface of the first silicon flat waveguide part and the second silicon flat waveguide part, namely, the mirror light at the interface is reflected back to the first silicon flat waveguide part, and only a small amount of mirror light enters the second silicon flat waveguide part to be absorbed by the contact metal part, so that the loss of the mirror light is reduced, and the high responsivity of the photoelectric detector is realized.

In some embodiments of the present invention, the difference between the thickness of the first silicon slab waveguide portion 41 and the thickness of the second silicon slab waveguide portion 42 is any one of 50nm, 60nm, 75nm, 100nm, 120nm, 135nm, 150nm, and 160 nm.

In some embodiments of the present invention, referring to fig. 1 to 6, the top surface of the first silicon slab waveguide portion 41 includes a covering portion 411 where the absorption region 50 is disposed and an exposed portion 412 where the absorption region 50 is not disposed, and the thickness of the covering portion 411 is less than or equal to the thickness of the exposed portion 412. The absorption region 50 and the first silicon slab waveguide portion 41 have flexible positional relationship, reduce process complexity, and are suitable for various processing technologies and have strong versatility.

In other embodiments of the present invention, referring to fig. 1 to 3, the top surface of the first silicon slab waveguide portion 41 includes a covered portion (not shown) where the absorption region 50 is disposed and an uncovered portion (not shown) where the absorption region 50 is not disposed, and the thickness of the covered portion (not shown) is equal to the thickness of the uncovered portion (not shown).

In some embodiments of the present invention, referring to fig. 4 to 6, the top surface of the first silicon slab waveguide portion 41 includes a covering portion 411 where the absorption region 50 is disposed and an exposed portion 412 where the absorption region 50 is not disposed, and the thickness of the covering portion 411 is smaller than the thickness of the exposed portion 412.

In some embodiments of the present invention, referring to fig. 4 to 6, the top surface of the first silicon slab waveguide portion 41 is provided with a groove portion (not labeled in the drawing), and the absorption region 50 is embedded in the groove portion (not labeled in the drawing) so as to promote the absorption of the optical field and reduce the reflection of the mirror image light entering the absorption region, so that the positional relationship between the absorption region 50 and the first silicon slab waveguide portion 41 is flexible, the process complexity is reduced, and the method is suitable for various processing technologies and has strong versatility.

In some embodiments of the present invention, referring to fig. 1 to 6, when the length of the first silicon slab waveguide portion 41 is greater than or equal to the length of the absorption region 50, and the length of the first silicon slab waveguide portion 41 is greater than the length of the absorption region 50, the following features are provided: the difference between the length of the first silicon slab waveguide portion 41 and the length of the absorption region 50 is not greater than the length of the multimode interference waveguide 30. The absorption region 50 and the first silicon slab waveguide portion 41 have flexible positional relationship, reduce process complexity, and are suitable for various processing technologies and have strong versatility.

In some embodiments of the present invention, referring to fig. 1 to 3, the length of the first silicon slab waveguide portion 41 is equal to the length of the absorption region 50.

In other embodiments of the present invention, referring to fig. 4 to 6, the length of the first silicon slab waveguide portion 41 is greater than the length of the absorption region 50. Specifically, the absorption region 50 is disposed in the middle region of the first silicon slab waveguide portion 41, that is, the absorption region 50 is far away from the edge portion of the first silicon slab waveguide portion 41, so that the processing technology is simple, and since the multimode interference waveguide 30 is disposed between the signal light input waveguide 20 and the silicon slab waveguide 40, light entering the first silicon slab waveguide portion 41 and the absorption region 50 passes through the multimode interference waveguide 30 first, light coupling into the absorption region 50 can be effectively prevented from scattering, light field distribution coupling into the absorption region 50 is optimized, maximum coupling efficiency is facilitated, and high responsivity of the photodetector is achieved.

In some embodiments of the present invention, the composition material of the absorption region is germanium or indium phosphide. The absorption efficiency is high, and the output of photocurrent is facilitated. The constituent material of the absorption region can also be other materials which can be used for preparing the detector.

In some embodiments of the present invention, the length of the absorption region is greater than 10 μm, so as to ensure that the mirror light can be absorbed by the absorption region to the maximum extent and converted into photocurrent.

In some embodiments of the invention, the absorbent region has a length of 10 μm to 50 μm.

In some embodiments of the invention, the absorbent region has a length of any one of 10 μm, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm.

In some embodiments of the present invention, it is preferable that the contact metal portion includes at least 2 contact metal units, at least 2 contact metal units are separately disposed in the 2 second silicon slab waveguide portions, and the contact metal units include at least one of a rectangular structure, a circular structure, and an elliptical structure disposed along a length direction of the second silicon slab waveguide portion, or at least 2 rectangular structures, which are sequentially disposed at equal intervals along the length direction of the second silicon slab waveguide portion.

In some embodiments of the present invention, referring to fig. 1 and 4, the contact metal portion 60 includes 4 contact metal units (not shown), each of the second silicon slab waveguide portions 42 is provided with 2 contact metal units (not shown), and the contact metal units (not shown) are elongated structures disposed along the length direction of the second silicon slab waveguide portions 42.

Fig. 7 is a cross-sectional view of a photodetector according to a third embodiment of the present invention.

In other embodiments of the present invention, referring to fig. 7, the contact metal portion 60 includes 4 contact metal units (not shown), each of the second silicon slab waveguide portions 42 is provided with 2 contact metal units (not shown), and each of the contact metal units (not shown) includes a plurality of rectangular structures sequentially and equally spaced along the length direction of the second silicon slab waveguide portion 42.

In some embodiments of the invention, the contact metal is connected to other metals to conduct photocurrent out of the chip.

In some embodiments of the present invention, referring to fig. 1 to 6, the photodetector further includes an upper cladding layer 70, the upper cladding layer 70 covers the top surface of the signal light input waveguide 20, the top surface of the multimode interference waveguide 30, the top surface of the absorption region 50, the top surface of the contact metal portion 60, and the top surface of the exposed portion of the silicon slab waveguide 40 where the absorption region 50 and the contact metal portion 60 are not disposed, and the refractive index of the upper cladding layer 70 is smaller than the refractive index of any one of the signal light input waveguide 20, the multimode interference waveguide 30, and the silicon slab waveguide 40. So that not only the optical field can be limited but also the signal light input waveguide 20, the multimode interference waveguide 30, the absorption region 50, the contact metal portion 60, and the silicon slab waveguide 40 can be protected by the upper cladding layer 70.

In some embodiments of the invention, the upper cladding layer has a refractive index less than that of the signal light input waveguide. The signal light input waveguide is a silicon waveguide, the refractive index of the silicon waveguide at a 1310nm wave band is 3.5, the upper cladding is made of silicon dioxide, and the refractive index of the silicon dioxide at the 1310nm wave band is 1.45.

In some embodiments of the invention, the upper cladding has a refractive index that is less than the refractive index of the multimode interference waveguide. The multimode interference waveguide is a silicon waveguide, the refractive index of the silicon waveguide at a 1310nm wave band is 3.5, the upper cladding is made of silicon dioxide, and the refractive index of the silicon dioxide at the 1310nm wave band is 1.45.

In some embodiments of the present invention, the refractive index of the upper cladding layer is smaller than the refractive index of the silicon slab waveguide. The silicon slab waveguide is a silicon waveguide, the refractive index of the silicon waveguide at a 1310nm wave band is 3.5, the upper cladding is made of silicon dioxide, and the refractive index of the silicon dioxide at the 1310nm wave band is 1.45.

In some embodiments of the invention, the material of the upper cladding layer is the same as or different from the material of the lower cladding layer.

In some embodiments of the present invention, referring to fig. 1 to 6, the photodetector further includes a substrate 80, and the lower cladding layer 10 is disposed on the top surface of the substrate 80.

In some embodiments of the invention, the substrate is made of silicon dioxide.

While embodiments of the present invention have been described in detail hereinabove, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. It is to be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the following claims. Moreover, the invention described herein is capable of other embodiments and of being practiced or of being carried out in various ways.

Claims (17)

1. A photodetector, comprising:

A lower cladding layer;

The signal light input waveguide is arranged on the top surface of the lower cladding and is used for converting a single-mode waveguide with smaller mode spots into a single-mode waveguide with larger mode spots;

the multimode interference waveguide is arranged on the top surface of the lower cladding layer and is connected with the signal light input waveguide, and the multimode interference waveguide is used for generating mirror image light of the incident light at the multimode interference waveguide output end through a self-imaging principle;

The silicon slab waveguide is arranged on the top surface of the lower cladding layer and is connected with the multimode interference waveguide, the silicon slab waveguide is used for transmitting the mirror image light, the silicon slab waveguide comprises a first silicon slab waveguide part and 2 second silicon slab waveguide parts, the central line of the first silicon slab waveguide part along the length direction coincides with the central line of the multimode interference waveguide along the length direction, the 2 second silicon slab waveguide parts are arranged in parallel with the first silicon slab waveguide part and are respectively arranged on two sides of the first silicon slab waveguide part along the width direction of the silicon slab waveguide, and the thickness of the first silicon slab waveguide part is larger than that of the second silicon slab waveguide part;

the absorption region is arranged on the top surface of the first silicon slab waveguide part and is used for absorbing the mirror image light of the first silicon slab waveguide part to generate photocurrent;

and the contact metal part is arranged on the top surface of the second silicon slab waveguide part and is used for leading out the photocurrent.

2. The photodetector of claim 1, wherein a difference between a thickness of the first silicon slab waveguide portion and a thickness of the second silicon slab waveguide portion is 50nm to 160nm.

3. The photodetector of claim 1 wherein the multimode interference waveguide has a width of 4 μm to 8 μm and a length of 8 μm to 100 μm.

4. The photodetector of claim 1 wherein the signal light input waveguide has a length of 20 μm to 50 μm.

5. The photodetector of claim 1 wherein the absorption region is greater than 10 μm in length.

6. The photodetector of claim 1, wherein the top surface of the first silicon slab waveguide portion includes a covered portion where the absorption region is disposed and an uncovered portion where the absorption region is not disposed, the covered portion having a thickness less than or equal to a thickness of the uncovered portion.

7. The photodetector of claim 1 or 6, wherein a top surface of said first silicon slab waveguide portion is provided with a groove portion, said absorption region being embedded in said groove portion.

8. The photodetector of claim 1, wherein the length of the first silicon slab waveguide portion is equal to or greater than the length of the absorption region, and wherein the length of the first silicon slab waveguide portion is greater than the length of the absorption region, has the following characteristics:

The difference between the length of the first silicon slab waveguide portion and the length of the absorption region is not greater than the length of the multimode interference waveguide.

9. The photodetector of claim 1, wherein the contact metal portion comprises at least 2 contact metal units, at least 2 of the contact metal units are disposed on the 2 second silicon slab waveguide portions, and the contact metal units comprise at least one of a rectangular structure, a circular structure, and an elliptical structure disposed along a length direction of the second silicon slab waveguide portion, or at least 2 of the rectangular structure, the circular structure, and the elliptical structure disposed at equal intervals in sequence along the length direction of the second silicon slab waveguide portion.

10. The photodetector of claim 1, wherein the thickness of the signal light input waveguide, the thickness of the multimode interference waveguide, and the thickness of the first silicon slab waveguide portion are equal, or at least two of the thickness of the signal light input waveguide, the thickness of the multimode interference waveguide, and the thickness of the first silicon slab waveguide portion are unequal.

11. The photodetector of claim 1 wherein the lower cladding layer has a refractive index less than the refractive index of any one of the signal light input waveguide, the multimode interference waveguide, and the silicon slab waveguide.

12. The photodetector of claim 1 wherein said signal light input waveguide comprises an input end and an output end, said output end being connected to said multimode interference waveguide and said input end having a width that is less than a width of said output end.

13. The photodetector of claim 1 or 12, wherein the signal light input waveguide is a tapered waveguide having an input end with a width of 0.4 μm to 0.6 μm and an output end with a width of 0.6 μm to 1.2 μm.

14. The photodetector of claim 1 wherein the signal light input waveguide is any one of a silicon waveguide, a silicon nitride waveguide, a silicon oxynitride waveguide, a lithium niobate waveguide, an indium phosphide waveguide, an alumina waveguide, and a polymer waveguide.

15. The photodetector of claim 1 wherein the generatrix of the varying surface of the signal light input waveguide is at least one of linear, exponential, parabolic, bezier, sin, euler, and sub-wavelength structures.

16. The photodetector of claim 1 wherein said absorption region is comprised of germanium or indium phosphide.

17. The photodetector of claim 1, further comprising an upper cladding layer covering a top surface of the signal light input waveguide, a top surface of the multimode interference waveguide, a top surface of the absorption region, a top surface of the contact metal portion, and a top surface of the exposed portion of the silicon slab waveguide where the absorption region and the contact metal portion are not provided, and having a refractive index smaller than that of any one of the signal light input waveguide, the multimode interference waveguide, and the silicon slab waveguide.