Optical Absorber and Optical Absorption Chip of Integrated Media Optical Waveguide

Abstract

The present invention provides an integrated media light guide light absorber and a light absorbing chip, the light absorber includes a waveguide cladding layer, a media light guide core, and an absorbing material layer, the waveguide cladding layer surrounds the media light guide core and the absorbing material layer, the media light guide core includes a first end and a second end, the radial dimension of the media light guide core gradually decreases from the first end to the second end, the material of the absorbing material layer can be metal or silicon, and can be located on the upper layer of the media light guide core, or be located on the side of the media light guide core, or be located on the lower layer of the media light guide core, the light absorber can reduce back reflection, and make the light be absorbed as completely as possible.

Description

Technical Field

[0001] The present invention relates to the field of integrated optical components, and particularly to an optical absorber and an optical absorption chip of an integrated dielectric optical waveguide.

Background Art

[0002] Optical absorbers, also called optical cancellers or optical sinks, are important assemblies in integrated optical components.

[0003] They are used to remove unwanted light with low return loss (reflection). In silicon-based integrated photonics technology, a silicon (Si) waveguide, as a semiconductor waveguide, can be doped by an ion implantation process to form an optical absorber. In this way, light can be eliminated by the absorption of free carriers. In addition to silicon waveguides, several dielectric optical waveguides (such as waveguides of silica, polymer, silicon nitride, aluminum nitride, etc.) are also widely applied in integrated photonics technology. Since dielectric optical waveguides usually cannot be doped like silicon waveguides to form absorbers, currently, a simple method is to make the transition structure transmit light from the dielectric optical waveguide to silicon and use doped silicon as the absorber. However, in this way, an extra transition structure is introduced, and the component structure becomes complicated. Currently, another method is to use an absorption material, such as germanium (Ge). Germanium on silicon is widely applied in integrated optical components and can be used as a photodetector. However, the epitaxial growth of germanium affects the yield of integrated optical components and further affects the cost. In addition, some unwanted back reflections can be introduced on the surfaces of the dielectric optical waveguide and the germanium absorber. Therefore, in order to improve the above problems, a new type of optical absorber for integrated dielectric optical waveguides is urgently needed.

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide an optical absorber and an optical absorption chip for an integrated waveguide for reducing retroreflection and enabling light to be absorbed as completely as possible.

Means for Solving the Problems

[0005] According to a first aspect, the present invention provides an optical absorber for an integrated medium optical waveguide, the optical absorber including a waveguide cladding layer, a medium optical waveguide core, and an absorption material layer, the waveguide cladding layer surrounding the medium optical waveguide core and the absorption material layer, the medium optical waveguide core including a first end and a second end, the radial dimension of the medium optical waveguide core gradually decreasing from the first end toward the second end, the absorption material layer being located on an upper layer of the waveguide, or on a side of the waveguide, or on a lower layer of the waveguide, and the optical absorber being capable of reducing retroreflection and enabling light to be absorbed as completely as possible.

[0006] Optionally, the shape of the medium optical waveguide is a tapered shape or a wedge shape. The tapered shape or wedge shape of the medium optical waveguide gradually increases the optical mode dimension, so that as the optical mode profile becomes larger and larger, the end portion of the optical mode begins to contact the upper absorption material layer, and the absorption material layer introduces absorption to attenuate the optical power propagating along the waveguide. The adiabatic mode gradation is smooth enough to avoid sudden changes, so that retroreflection can be significantly reduced.

[0007] Optionally, the width of the medium optical waveguide core gradually changes from one side to the other side, and the material of the medium waveguide may be, but is not limited to, silica, polymer, silicon nitride, aluminum nitride, etc.

[0008] Optionally, the medium optical waveguide core is installed in a spatially spiral or folded ring shape, which helps to save space on the optical integrated circuit component and results in a higher degree of integration of the optical integrated circuit component.

[0009] Optionally, the material of the absorption material layer is a metal. Also, the light absorber does not need to use an ion implantation doping process, does not need to introduce other materials such as germanium, and makes its structure easy to manufacture.

[0010] Optionally, the material of the absorption material layer is silicon that can be used to absorb light of a certain wavelength (for example, the visible light band).

[0011] Optionally, a PN junction or a PIN junction may be formed on the silicon by an ion implantation doping process. By applying a reverse bias voltage in this way, free carriers generated by the absorption and conversion of light can be removed.

[0012] According to a second aspect, the present invention provides an optical absorption chip including a polarization rotator for rotating an input TE polarization by 90 degrees to convert it into TM polarization and outputting the TM polarization, and a light absorber for absorbing TM polarization as described in the first aspect. Since the absorption efficiency of the TM polarization of the light absorber is higher, this structure can absorb light waves more effectively.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figures 4 - 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0014] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings of the present invention. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein have the ordinary meanings understood by those skilled in the art. Similar terms such as "including" used in this specification mean that the elements or things appearing before the term include the elements or things listed after the term and their equivalents, but do not exclude other elements or things.

[0015] <Example 1> In response to the problems existing in the prior art, Example 1 of the present invention provides an optical absorber of an integrated optical waveguide including a waveguide cladding layer 10, a medium optical waveguide core 20, and an absorption material layer 30 as shown in FIG. 1.

[0016] Here, the waveguide cladding layer 10 includes the medium optical waveguide core 20 and the absorption material layer 30. The medium optical waveguide core 20 includes a first end and a second end. The radial dimension of the medium optical waveguide core 20 gradually decreases from the first end towards the second end. The absorption material layer 30 is located on the upper layer of the medium optical waveguide core. Note that FIG. 2 is a plan view, a side view, and a cross-sectional view of the optical absorber in FIG. 1. The plan view is shown in (a) in FIG. 2, the side view is shown in (b) in FIG. 2, and the cross-sectional view is shown in (c) in FIG. 2.

[0017] Exemplarily, the value range of the radial dimension of the first end is [500 nm, 2000 nm], and the value range of the radial dimension of the second end is [100 nm, 200 nm].

[0018] Note that, although FIG. 1 shows the wedge-shaped medium optical waveguide core 20 as an example, the medium optical waveguide core 20 may be in a tapered shape as shown in FIG. 3.

[0019] In another possible embodiment, as shown in FIG. 4, the absorption material layer 30 may be located on one side of the medium optical waveguide core 20, or, as shown in FIG. 5, the absorption material layer 30 may be located under the medium optical waveguide core 20, and furthermore, or, as shown in FIG. 6, the absorption material layer 30 may be located on both sides of the medium optical waveguide core 20.

[0020] Optionally, the medium optical waveguide core 20 may be installed in a spatially spiral or folded ring shape. The plan view of the light absorber in a spiral shape is shown in (a) in FIG. 7, and the plan view of the light absorber in a folded ring shape is shown in (b) in FIG. 7. This helps to save space on the optical integrated circuit components, and the degree of integration of the optical integrated circuit components is higher.

[0021] Optionally, since the absorption material layer 30 and the medium optical waveguide core 20 in the present invention can be provided by a standard integrated photonics foundry, their structures are compatible with the standard process flow. The material of the absorption material layer 30 may be a metal, for example, aluminum, copper, or tungsten, but is not limited thereto. The light absorber does not need to be embedded, and it is not necessary to introduce other materials such as germanium, so as to make its structure easy to manufacture. The material of the medium waveguide may be silica, polymer, silicon nitride, aluminum nitride, etc., but is not limited thereto.

[0022] Optionally, the absorption material layer 30 may be a silicon layer. The silicon layer can absorb light of a certain wavelength (for example, the visible light band) and can be used to convert the light into free carriers. As shown in FIG. 2, a silicon layer is provided under the medium optical waveguide core 20. The silicon layer can absorb the visible light propagated by the medium optical waveguide core 20, and the silicon layer may be the top silicon on an SOI base.

[0023] Optionally, a PN junction or a PIN junction may be formed on the silicon layer by an ion implantation doping process, whereby light absorbs free carriers converted by silicon by applying a reverse bias voltage and sweeps them out.

[0024] <Example 2> Example 2 is a solution based on Example 1, and the present invention is improved in that it further provides an optical absorption chip including a polarization rotator and the optical absorber described in Example 1. The polarization rotator is used to rotate the input transverse electric (TE) mode polarization by 90 degrees to convert it into a transverse magnetic (TM) mode polarization and output the TM polarization, and the optical absorber is used to absorb the TM polarization. Since the absorption efficiency of the TM polarization of the optical absorber is higher, this structure can absorb light waves more effectively.

[0025] In FIG. 8, (a) and (b) respectively show the simulation mode intensity cross-sections of the narrow silicon nitride waveguide cross-section of TE and TM polarizations, and in FIG. 8, (c) and (d) respectively show the simulation mode intensity contours after introducing an absorption material layer above the waveguide. The absorption material layer interferes with the optical mode distribution. Based on the test data, the loss of the TM mode polarization is, for example, 10 times higher than that of the TE mode polarization, so it can be seen that the absorption efficiency of the optical absorber for the TM mode polarization is much higher.

[0026] As shown in FIG. 9, based on the above optical absorption chip, the polarization of the light wave is first converted from the TE mode polarization to the TM mode polarization, and then the optical absorber can absorb the TM mode polarization more effectively.

[0027] It should be noted that the above optical absorber and optical absorption chip can be applied to scenes such as optical sensing, optical computing, optical communication, optical memory, and lidar, and the present invention is not limited thereto.

[0028] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes fall within the scope and spirit of the present invention described in the claims. In addition, the present invention described in this specification may have other embodiments and may be implemented or realized in a plurality of ways.

Description of Reference Numerals

[0029] 10 Waveguide cladding layer 20 Medium optical waveguide core 30 Absorbing material layer

Claims

1. A waveguide cladding layer surrounding a media optical waveguide core and an absorption material layer, The media optical waveguide core includes a first end and a second end, and the radial dimension gradually decreases from the first end toward the second end, and is installed in a spatially spiral shape or in a folded shape, An absorption material layer located above the media optical waveguide core, or located on the side of the media optical waveguide core, or located below the media optical waveguide core, The absorption material layer is metal or silicon, the silicon has an ion-doped PN junction or PIN junction, and the PN junction or PIN junction is used to remove free carriers generated by light absorption and conversion by applying a reverse bias voltage. The absorption material layer is provided on one or both sides of the media optical waveguide core. An optical absorber for an integrated media optical waveguide, characterized in that.

2. The shape of the media optical waveguide core is a tapered shape or a wedge shape. The optical absorber according to claim 1, characterized in that.

3. An optical absorption chip including a polarization rotator and the optical absorber according to any one of claims 1 or 2, The polarization rotator is used to rotate the input transverse electric field TE mode polarization by 90 degrees to convert it into transverse magnetic field TM mode polarization and output TM polarization. The optical absorber is used to absorb the TM polarization. An optical absorption chip, characterized in that.

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