Spot-size converter structures and photonic devices

Abstract

A spot size converter structure and photonic device are provided, the spot size converter structure comprising a first end face configured to be coupled to an integrated optical waveguide and a second end face parallel to the first end face and configured to be coupled to an optical fiber. The spot size converter structure comprises a substrate; an isolation layer disposed on one side of the substrate, the isolation layer comprising a first etched portion, a second etched portion, and a first transmission portion extending in a longitudinal direction to a second end face, the first transmission portion being disposed between the first etched portion and the second etched portion and having a longitudinal direction perpendicular to the second end face; a waveguide layer disposed on one side of the isolation layer away from the substrate, the waveguide layer having a width that decreases in a gradient in a direction approaching the second end face, the width direction being perpendicular to the longitudinal direction and parallel to a bottom surface of the substrate; and a cladding layer disposed on one side of the waveguide layer away from the substrate and covering the waveguide layer, the cladding layer comprising a second transmission portion extending in a longitudinal direction to the second end face and protruding in the form of a ridge on a surface of the first transmission portion.

Description

[Technical Field]

[0001] The present disclosure relates to the field of photonics, and more particularly to spot size converter structures and photonic devices. [Background technology]

[0002] An optical waveguide is a dielectric device that guides the propagation of light waves, also known as a dielectric optical waveguide. There are two main types of optical waveguides: one type, the integrated optical waveguide, includes planar dielectric optical waveguides and slab dielectric optical waveguides, and generally functions as part of an optoelectronic integrated device, so they are called integrated optical waveguides; the other type, the cylindrical optical waveguide, is usually called an optical fiber.

[0003] The technology of coupling integrated optical waveguides to optical fibers has very wide and important applications in the fields of optical communications, microwave photonics, laser beam deflection, wavefront modulation, etc. Edge coupling is a common method used to couple integrated optical waveguides to optical fibers.

[0004] However, due to the large difference in spot size between an integrated optical waveguide and an optical fiber, how to improve the coupling efficiency between an integrated optical waveguide and an optical fiber has always been an important research topic. Summary of the Invention

[0005] According to one aspect of the present disclosure, there is provided a spot size converter structure comprising a first end face configured to be coupled to an integrated optical waveguide and a second end face parallel to the first end face and configured to be coupled to an optical fiber, the spot size converter structure comprising a substrate and an isolation layer disposed on one side of the substrate, the isolation layer comprising a first etched portion extending longitudinally to the second end face, a second etched portion, and a first transmitting portion, the first transmitting portion being separated from the first etched portion and the second etched portion. the first transmitting portion and the second end face, and the longitudinal direction of the first transmitting portion is perpendicular to the second end face; a waveguide layer disposed on one side of the isolation layer away from the substrate, the width of the waveguide layer decreasing at a gradient in a direction approaching the second end face, the width direction being perpendicular to the longitudinal direction and parallel to the bottom surface of the substrate; and a cover layer disposed on one side of the waveguide layer away from the substrate and covering the waveguide layer, the cover layer extending in the longitudinal direction to the second end face and comprising a second transmitting portion protruding in the form of a ridge on a surface of the first transmitting portion.

[0006] In some embodiments, the first etched portion and the second etched portion are each etched blind grooves having an etch depth less than the thickness of the isolation layer and extending to the second end face.

[0007] In some embodiments, the first etched portion and the second etched portion are each etched through grooves having an etch depth equal to the thickness of the isolation layer and extending to the second end face.

[0008] In some embodiments, the substrate comprises an etched recess, and the etched through channel communicates with the etched recess.

[0009] In some embodiments, the first etched portion and the second etched portion each include a plurality of longitudinally arranged etched through holes, the etched through hole closest to the second end face being an open hole and having an opening facing the second end face.

[0010] In some embodiments, the substrate comprises an etched recess, and the plurality of etched through holes communicate with the etched recess.

[0011] In some embodiments, the first transmission portion has a constant width and the second transmission portion has a constant width.

[0012] In some embodiments, the width of the first transmission portion gradually decreases in a direction toward the second end face, and the width of the second transmission portion gradually decreases in a direction toward the second end face.

[0013] In some embodiments, the second transmission portion is centrally located relative to two sides of the first transmission portion.

[0014] In some embodiments, the width of the covering layer decreases in a gradient toward the second end face.

[0015] In some embodiments, the waveguide layer comprises a planar layer and a ridge layer disposed on one side of the planar layer away from the substrate.

[0016] In some embodiments, the waveguide layer extends to the second end face.

[0017] In some embodiments, there is a gap between the narrow end of the waveguide layer proximate the second end face and the second end face.

[0018] According to one aspect of the present disclosure, there is provided a photonic device comprising a spot size converter structure according to any one of the preceding embodiments.

[0019] These and other aspects of the present disclosure will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0020] More details, features and advantages of the present disclosure are disclosed in the following description of exemplary embodiments with reference to the accompanying drawings. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic structural perspective view of a spot-size converter structure according to some exemplary embodiments of the present disclosure. [Figure 2] FIG. 2 is a schematic structural top view of a waveguide layer of a spot size converter structure according to some exemplary embodiments of the present disclosure. [Figure 3] FIG. 3 is a diagram illustrating a simulated comparison between the spot size formed on the second end face of a spot size converter structure according to some exemplary embodiments of the present disclosure and the spot size formed on the light output end face of a spot size converter structure of the related art. [Figure 4] FIG. 4 is a schematic structural perspective view of a spot size converter structure according to some exemplary embodiments of the present disclosure. [Figure 5] FIG. 5 is a schematic structural perspective view of a spot size converter structure according to some exemplary embodiments of the present disclosure. [Figure 6] FIG. 6 is a schematic structural perspective view of a spot size converter structure according to some exemplary embodiments of the present disclosure. [Figure 7] FIG. 7 is a schematic structural perspective view of a spot size converter structure according to some exemplary embodiments of the present disclosure. [Figure 8] FIG. 8 is a structural block diagram of a photonic device according to some exemplary embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0022] Some merely exemplary embodiments are briefly described below. As will be understood by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure. Accordingly, the accompanying drawings and description are to be regarded as illustrative in nature and not restrictive.

[0023] Although existing spot-size converters can functionally realize coupling between integrated optical waveguides and optical fibers, the coupling efficiency between integrated optical waveguides and optical fibers is not high due to the large difference in spot size between the integrated optical waveguide and the optical fiber, resulting in significant optical energy loss. For example, the spot size of an integrated optical waveguide is generally on the order of hundreds of nanometers, while the spot size of an optical fiber, such as a flat-end optical fiber, is on the order of tens of microns. The loss of optical energy can lead to severe heating of the coupling end face, thereby affecting the reliability and service life of the device. Coupling efficiency can be understood as the ratio of the optical power emitted by the integrated optical waveguide to the optical power accepted by the optical fiber, or the ratio of the optical power emitted by the optical fiber to the optical power accepted by the integrated optical waveguide.

[0024] Embodiments of the present disclosure provide spot-size conversion structures and photonic devices that improve coupling efficiency between integrated optical waveguides and optical fibers and reduce optical loss during spot-size conversion.

[0025] As shown in FIG. 1 , a spot size converter structure 100 provided in some embodiments of the present disclosure includes a first end face 100a configured to be coupled to an integrated optical waveguide (not shown) and a second end face 100b configured to be coupled to an optical fiber (not shown) and parallel to the first end face 100a. The spot size converter structure 100 includes a substrate 101, an isolation layer 102, a waveguide layer 103, and a cover layer 104, arranged in this order. The isolation layer 102 is disposed on one side of the substrate 101 and includes a first etched portion 22, a second etched portion 23, and a first transmitting portion 21, which extend longitudinally to the second end face 100b. The first transmitting portion 21 is disposed between the first etched portion 22 and the second etched portion 23, and its longitudinal direction is perpendicular to the second end face 100b. The waveguide layer 103 (as shown in FIG. 2) is disposed on one side of the isolation layer 102 away from the substrate 101 and has a width that gradually decreases in a direction approaching the second end face 100b. As shown in FIG. 1, the width direction is perpendicular to the longitudinal direction and parallel to the bottom surface of the substrate 101. The cover layer 104 is disposed on one side of the waveguide layer 103 away from the substrate 101, covers the waveguide layer 103, extends in the longitudinal direction to the second end face 100b, and comprises a second transmitting portion 41 protruding in the form of a ridge on the surface of the first transmitting portion 21.

[0026] In an embodiment of the present disclosure, a longitudinal direction perpendicular to the first end face 100a (or the second end face 100b) is defined as the main transmission direction of light in the waveguide layer 103, and a width direction perpendicular to the longitudinal direction is parallel to the bottom surface of the substrate 101. In addition to the first end face 100a and the second end face 100b, the spot size converter structure 100 further comprises a first side face 100c and a second side face 100d that intersect with the first end face 100a and the second end face 100b. In one embodiment, the first side face 100c and the second side face 100d are perpendicular to the first end face 100a and the second end face 100b.

[0027] The first end face 100a of the spot size converter structure 100 can function as the light input end face of the spot size converter structure 100, and the second end face 100b can function as the light output end face of the spot size converter structure 100. Light enters the spot size converter structure 100 from the wide end of the waveguide layer 103 at the first end face 100a and exits from the ends of the first and second transmission portions 21 and 41 at the second end face 100b. Alternatively, the first end face 100a of the spot size converter structure 100 can function as the light output end face of the spot size converter structure 100, and the second end face 100b can function as the light input end face of the spot size converter structure 100. Light enters the spot size converter structure 100 from the ends of the first and second transmission portions 21 and 41 at the second end face 100b, is guided into the waveguide layer 103, and exits from the wide end of the waveguide layer 103.

[0028] As shown in FIG. 2 , the waveguide layer 103 can be a ridge waveguide, including a planar layer 31 and a ridge layer 32 disposed on one side of the planar layer 31 away from the substrate 101. The ridge waveguide has characteristics such as a low fundamental mode cutoff frequency, a wide bandwidth, and low impedance. In some embodiments of the present disclosure, the refractive index n1 of the waveguide layer 103, the refractive index n2 of the cladding layer 104, and the refractive index n3 of the isolation layer 102 satisfy n1 > n2 and n1 > n3, respectively. The refractive indices of the isolation layer 102 and the cladding layer 104 are smaller than the refractive index of the waveguide layer 103. As a result, light is confined to propagate mainly within the ridge waveguide, thereby better achieving the above-mentioned advantages of the ridge waveguide.

[0029] In an embodiment of the present disclosure, the width of the waveguide layer 103 decreases in a gradient toward the second end face 100b, resulting in a relatively gradual spot size modulation for light transmitted within the waveguide layer 103, thereby minimizing light transmission losses and improving the coupling efficiency of the spot size converter structure 100. By "decreasing in a gradient toward the second end face 100b," it can be understood that the width of the waveguide layer 103 can be broadly divided into at least two sections depending on how it varies, and each section can use a constant width design or a gradually varying width design. Furthermore, the closer a section of the waveguide layer is to the second end face 100b, the narrower its average width is.

[0030] 2 , in some embodiments, the flat layer 31 of the waveguide layer 103 includes a first constant width portion 301, a first gradually increasing width portion 306, a second constant width portion 302, a second gradually increasing width portion 307, and a third constant width portion 303, which are arranged in this order in a direction away from the second end face 100b, and the ridge layer 32 includes a fourth constant width portion 304, a third gradually increasing width portion 308, and a fifth constant width portion 305, which are arranged in this order in a direction away from the second end face 100b. The width of each of the constant width portions is constant, and the width of each of the gradually increasing width portions gradually increases linearly or non-linearly in a direction away from the second end face 100b.

[0031] In this embodiment, the waveguide layer 103 extends generally to the second end face 100b. In some other embodiments of the present disclosure, there may also be a gap between the narrow end of the waveguide layer generally closer to the second end face and the second end face. In addition, there may also be a gap between the narrow end of the ridge layer and the narrow end of the waveguide layer.

[0032] 1, in an embodiment of the present disclosure, the width of the cladding layer 104 may also decrease in a general gradient toward the second end face 100b, so that more light is guided into the waveguide layer 103 and the second transmitting portion 41, thereby further improving the coupling efficiency of the spot size converter structure 100.

[0033] In the embodiment of the present disclosure, the first transmitting portion 21 is disposed between the first etched portion 22 and the second etched portion 23, which have the effect of preventing the optical mode field from diffusing in the width direction, so that the light can propagate more centrally through the first transmitting portion 21, the second transmitting portion 41, and the waveguide layer 103. The second transmitting portion 41 protrudes from the surface of the first transmitting portion 21 in the form of a ridge, i.e., the width of the second transmitting portion 41 is narrower than that of the first transmitting portion 21, so that it has a sinking modulation effect on the optical mode field. As a result, the spot size formed on the second end face 100b by the isolation layer 102 can essentially match the size of the spot size of the optical fiber, thereby reducing optical loss during spot size conversion and improving coupling efficiency.

[0034] 3, which is a diagram illustrating a simulated comparison between the spot size formed at the second end face 100b of the spot size converter structure 100 according to some embodiments of the present disclosure and the spot size formed at the optical output end face of a spot size converter structure of the related art. It can be seen that the spot size formed at the second end face 100b of the spot size converter structure 100 according to embodiments of the present disclosure has larger dimensions and, as a result, can be better coupled to an optical fiber.

[0035] In addition, the spot size formed on the second end facet 100b has larger dimensions and can be better coupled to the optical fiber, so the dependency on the structural design and processing accuracy of the waveguide layer 103 is appropriately reduced, thereby reducing the difficulty of micro-nano processing (e.g., photolithography, coating, etching, ion implantation, microfluidic control, and masking) and reducing manufacturing costs.

[0036] As shown in FIG. 1 , in an embodiment of the present disclosure, the second transmitting portion 41 is centered relative to the two sides of the first transmitting portion 21. In this manner, the resulting spot size is symmetrical and more uniform in the left-right direction, as shown in FIG. 3 , making the structural design and fabrication easier. In other embodiments of the present disclosure, the second transmitting portion does not have to be centered relative to the two sides of the first transmitting portion. For example, the second transmitting portion may be closer to one of the sides of the first transmitting portion or may be flush with the side of the first transmitting portion on the same side.

[0037] In an embodiment of the present disclosure, the first etched portion 22 and the second etched portion 23 may be formed by etching at least a portion of the thickness of the isolation layer 102 .

[0038] As shown in FIG. 1, in some embodiments, the first etched portion 22 and the second etched portion 23 are each etched blind grooves 220 having an etching depth less than the thickness of the isolation layer 102 and extending to the second end surface 100b.

[0039] As shown in FIG. 4, in some other embodiments, the first etched portion 22 and the second etched portion 23 are each etched through grooves 221 having an etching depth equal to the thickness of the isolation layer 102 and extending to the second end surface 100b.

[0040] The etched blind grooves 220 or etched through grooves 221 in the above embodiments have the effect of preventing the diffusion of the optical mode field in the width direction, so that the light can be propagated more centrally in the first transmitting portion 21, the second transmitting portion 41, and the waveguide layer 103.

[0041] 5, in some other embodiments, the first etched portion 22 and the second etched portion 23 are each etched through grooves 221 having an etching depth equal to the thickness of the isolation layer 102 and extending to the second end surface 100b. The substrate 101 includes an etched recess 11, and the etched through grooves 221 are in communication with the etched recess 11.

[0042] Since light is mainly transmitted through the medium, designing the recess 11 etched in the substrate 101 has the effect of restricting the input and output of light from the second end face 100b, thereby reducing the diffusion of light into the substrate 101, thereby reducing the transmission loss of light, achieving better coupling to the optical fiber, and further improving the coupling efficiency between the integrated optical waveguide and the optical fiber.

[0043] 6, in some embodiments, the first etched portion 22 and the second etched portion 23 each include a plurality of longitudinally arranged etched through-holes 222. The etched through-hole 222 closest to the second end face 100b is an open hole, with an opening facing the second end face 100b.

[0044] The discretely arranged multiple etched through holes 222 also have the effect of preventing the optical mode field from diffusing in the width direction, so that the light can propagate more centrally in the first transmitting portion 21, the second transmitting portion 41, and the waveguide layer 103.

[0045] As shown in FIG. 7, in some other embodiments, based on the embodiment shown in FIG. 6, the substrate 101 is also further designed with an etched recess 11, and a plurality of etched through holes 222 communicate with the etched recess 11, so that the diffusion of light into the substrate 101 is reduced, thereby reducing the transmission loss of light and further improving the coupling efficiency between the integrated optical waveguide and the optical fiber.

[0046] As shown in FIGS. 1 and 4 to 7, in the embodiment of the present disclosure, the width of the first transmitting portion 21 is constant, and the width of the second transmitting portion 41 is also constant. That is, both the first transmitting portion 21 and the second transmitting portion 41 have a constant width design. However, the present disclosure is not limited thereto. For example, at the same cross-sectional position, as long as the width of the second transmitting portion is narrower than the width of the first transmitting portion, the width of the first transmitting portion can gradually decrease toward the second end face, and the width of the second transmitting portion can gradually decrease toward the second end face, which can also have a sedimentation modulation effect on the optical mode field.

[0047] 8, an embodiment of the present disclosure further provides a photonic device 1 comprising the spot size converter structure 100 according to any one of the aforementioned embodiments. The specific product type of the photonic device 1 is not limited, and may be, for example, an electro-optic modulator, a splitter, a star coupler, a variable optical attenuator (VOA), an optical switch, a frequency comb, an arrayed waveguide grating (AWG), etc.

[0048] The spot size converter structure 100 is incorporated into the photonic device 1. Because the spot size converter structure 100 has a high coupling efficiency, the optical loss of the photonic device 1 is smaller and the performance is improved.

[0049] In this description, the relationship of orientation or position or dimensions indicated by terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are the relationship of orientation or position or dimensions shown based on the accompanying drawings, and it should be understood that these terms are used merely for ease of description and do not indicate or imply that the referred-to devices or elements must have a particular orientation and be configured and operated in a particular orientation, and therefore should not be construed as limiting the scope of protection of the present disclosure.

[0050] Additionally, the terms "first," "second," and "third" are merely descriptive and should not be construed as indicating or implying relative importance, nor do they imply the number of technical features depicted. Thus, features defined as "first," "second," and "third" may explicitly or implicitly comprise one or more features. In the description of this disclosure, the term "plurality" means two or more, unless otherwise explicitly and specifically defined.

[0051] In this disclosure, unless otherwise expressly stated or defined, terms such as "attach," "connect," "connected," and "secure" should be interpreted broadly, for example, they may be fixed, detachable, or integral connections, may be mechanical or electrical connections or communications, may be direct connections or indirect connections through intermediate media, or may be internal communications or interactions between two elements. For those skilled in the art, the specific meanings of the above terms in this disclosure may be understood according to the specific environment.

[0052] In this disclosure, unless expressly stated or limited otherwise, a reference to a first feature being "above" or "below" a second feature may include a case where the first feature is in direct contact with the second feature, or a case where the first feature and the second feature are not in direct contact but are in contact via another feature. Furthermore, a reference to a first feature being "above," "above," or "on" a second feature may include a case where the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher level than the second feature. A reference to a first feature being "below," "below," or "below" a second feature may include a case where the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower level than the second feature.

[0053] This description provides many different embodiments or examples that can be used to implement the present disclosure. It should be understood that these different embodiments or examples are purely illustrative and are not intended to limit the scope of protection of the present disclosure in any way. Based on the disclosure of the description of the present disclosure, those skilled in the art may think of various modifications or alternatives. All of these modifications or alternatives shall fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the scope of protection of the claims.

Claims

1. 1. A spot size converter structure comprising a first end face configured to be coupled to an integrated optical waveguide and a second end face parallel to the first end face and configured to be coupled to an optical fiber, A substrate; an isolation layer disposed on one side of the substrate, the isolation layer comprising a first etched portion extending longitudinally to the second end face, a second etched portion, and a first transmission portion, the first transmission portion being disposed between the first etched portion and the second etched portion, the longitudinal direction of the isolation layer being perpendicular to the second end face; a waveguide layer disposed on one side of the isolation layer away from the substrate, the width of the waveguide layer decreasing in a gradient direction toward the second end face, the width direction being perpendicular to the longitudinal direction and parallel to a bottom surface of the substrate; a cladding layer disposed on one side of the waveguide layer remote from the substrate and covering the waveguide layer, the cladding layer extending in the longitudinal direction to the second end face and including a second transmitting portion protruding in the form of a ridge on a surface of the first transmitting portion; Equipped with the first etched portion and the second etched portion are each an etched blind groove; Spot size converter structure.

2. 2. The spot size converter structure of claim 1, wherein the first etched portion and the second etched portion are each etched blind grooves having an etching depth less than a thickness of the isolation layer and extending to the second end face.

3. 2. The spot size converter structure of claim 1, wherein the first transmitting portion has a constant width and the second transmitting portion has a constant width.

4. 2. The spot size converter structure of claim 1, wherein the width of the first transmission portion gradually decreases in a direction toward the second end face, and the width of the second transmission portion gradually decreases in a direction toward the second end face.

5. 2. The spot size converter structure of claim 1, wherein the second transmitting portion is centrally located relative to two sides of the first transmitting portion.

6. 2. The spot size converter structure of claim 1, wherein the width of the covering layer decreases in a gradient toward the second end face.

7. 2. The spot size converter structure of claim 1, wherein the waveguide layer comprises a planar layer and a ridge layer disposed on one side of the planar layer remote from the substrate.

8. A spot size converter structure according to claim 1 , wherein the waveguide layer extends to the second end face.

9. 8. The spot size converter structure of claim 1, wherein there is a gap between a narrow end of the waveguide layer near the second end face and the second end face.

10. A photonic device comprising a spot size converter structure according to any one of claims 1 to 7.

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