Patent Description:
Grating waveguides have been widely applied in biosensors, augmented reality (AR), virtual reality (VR), telecommunication, and so on. In the field of biosensors, a grating coupling efficiency would affect the luminous efficiencies of fluorescence-labeled biomolecules, and several factors would impact the grating coupling efficiency. For example, an alignment between an external light and a grating structure, material properties of optical elements in the grating waveguide structure, and geometric structures of grating couplers.

Light propagating in a waveguide layer, which is used for uniform and localized excitation on the fluorescence-labeled biomolecules within the evanescence wave region on the waveguide core, could be generated by coupling the external light entering into the optical structure via a grating nanostructure. However, the coupling efficiency from a laser beam into the grating waveguide is relatively low, which would cause a low luminous efficiency of the fluorescent tags, due to the tight alignment request (including xyz-axis offsets and incident angle) and relatively small effective coupling width of the grating coupler compared to the diameter of a laser beam. Therefore, there is a need to solve the grating coupling efficiency of the grating waveguides to improve the luminous efficiency of fluorescence-labeled biomolecules in biosensor application. <CIT> describes an integrated optic read/write head for optical data storage including an electro-optic waveguide device having a substrate, an optically transparent lower buffer layer positioned atop the substrate, an optically transparent nonlinear optic (NLO) organic poled polymer waveguide positioned atop the lower buffer layer, and a GaAs laser diode optically coupled to the waveguide. <CIT> describes a lens array including a plurality of lenses that collect divided test light and form spots. Each lens includes a lens member, and a light shielding mask provided concentric to the lens member along a perimeter edge thereof, the light shielding mask shielding a part of the light and transmitting a part of the light. The light shielding mask is formed to satisfy a predetermined mathematical condition of light transmission
<CIT> describes optical delivery devices and integrated analytical systems comprising the optical delivery devices. The optical delivery devices include optical inputs, optical outputs, and integrated optical waveguides that are configured for coupling of optical energy to a target waveguide device through free space. <CIT> describes an apparatus, sensor chips and techniques for optical sensing of substances by using optical sensors on sensor chips. <CIT> describes a lens including a central optical portion, and a peripheral supporting portion surrounding the central optical portion. The peripheral supporting portion has a first surface and an opposite second surface. At least one of the first surface and second surface having a light absorbing polymer layer adhered thereon. <CIT> an optical lens including a lens member and two shade layers on opposite sides of the lens member. The lens member respectively has a lens portion on each side thereof. Each shade layer has an aperture above the corresponding lens portion of the lens member to serve the function of aperture.

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. It should be understood that the number of any elements/components is merely for illustration, and it does not intend to limit the present disclosure.

For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the embodiments.

The embodiment shown in <FIG> is not encompassed by the wording of the claims but is considered as useful for understanding the invention.

In the field of biosensors, the luminous efficiencies of fluorescence-labeled biomolecules would be affected by a grating coupling efficiency. When an external light including a single or multiple wavelengths enters into an optical structure through a binary (<NUM>-step) grating coupler (GC), only the light energy exposure on the effective coupling area (about <NUM>-<NUM> near the inner edge of the grating coupler) at precise incident angle (about +/-<NUM> degree) could be coupled into the waveguide. Thus, the grating coupling efficiency of the optical structure is usually low. The grating coupling efficiency can be caused by, for example, an alignment between the external light and the grating structure, the beam diameter of a laser light, the material properties of optical elements in the grating waveguide structure, geometric structures of grating couplers, and so on.

The optical structure of the present disclosure combines a microlens structure for the conversion of a large and collimating laser beam to a condensed focusing light that is exposed on the effective coupling area. The present disclosure provides a variety of grating structures, such as n-step (n>=<NUM>), blazed, or slanted grating, having the features of greater coupling angle tolerance and high grating coupling efficiencies which allows for the possibilities of coupling a single or multiple wavelengths into one grating waveguide for the excitation of fluorescence-labeled biomolecules. Specifically, it may cause less variety of fluorophores that could be excited and emit fluorescence signals when only single wavelength couples into one grating waveguide. By contrast, it may cause more variety of fluorophores that could be excited and emit fluorescence signals when multiple wavelengths couple into one grating waveguide. However, the present disclosure does not limit to coupling single or multiple wavelengths. The present disclosure can also provide a large alignment tolerance in the optical structure including xyz-axis and the angle of incidence, thereby increasing the overall coupling efficiency of the optical structure for bio-detections.

<FIG> is a cross-sectional view of an optical structure <NUM> in accordance with some embodiments of the present disclosure. The optical structure <NUM> includes a substrate <NUM>, a core layer <NUM>, and a grating coupler <NUM>. The substrate <NUM> is covered by the core layer <NUM>. In some embodiments, the substrate <NUM> is transparent and includes sapphire or glass. When the substrate <NUM> is transparent, the substrate <NUM> has a refractive index in a range from <NUM> to <NUM>, such as <NUM> or <NUM>. The core layer <NUM> covers the substrate <NUM>. In some embodiments, a refractive index of the core layer <NUM> is relatively higher than the refractive index of the substrate <NUM>. In some embodiments, the core layer <NUM> includes Nb<NUM>O<NUM>, Ta<NUM>O<NUM>, TiO<NUM>, Si<NUM>N<NUM>, or other suitable materials. The grating coupler <NUM> is adjacent to the core layer <NUM> and is configured to receive a laser light <NUM>. For example, the grating coupler <NUM> is embedded in the core layer <NUM>. In some embodiments, a thickness of the core layer <NUM> is around <NUM>-<NUM>, and more specifically, <NUM>-<NUM>. In some embodiments, a material of the grating coupler <NUM> is the same as a material of the core layer <NUM>. In some embodiments, a material of the grating coupler <NUM> is different from a material of the core layer <NUM>.

Please refer to <FIG> illustrates an enlargement view of the grating coupler <NUM> in <FIG>. The grating coupler <NUM> has multiple convex parts and multiple recesses. The convex part of the grating coupler <NUM> has a height h from a top surface <NUM> of the convex part to a bottom surface <NUM> of the recess. The grating coupler <NUM> has a grating period p between two adjacent convex parts. The grating coupler <NUM> has a continuous surface including the top surface <NUM>, a sidewall <NUM>, a bottom surface <NUM>, and a sidewall <NUM>, and the continuous surface faces away from the substrate <NUM> of the optical structure <NUM>. In some embodiments, the grating coupler <NUM> includes a step grating structure, a blazed grating structure, or a slanted grating structure. It should be understood that the grating coupler <NUM> shown in <FIG> is merely a schematic diagram, and the detailed structure of the grating coupler <NUM> will be described in <FIG> below.

Please refer to <FIG> again. The optical structure <NUM> includes an upper cladding layer <NUM>, a microlens <NUM>, a laser light <NUM>, and a metal shielding <NUM>. The upper cladding layer <NUM> covers the core layer <NUM>. Specifically, the upper cladding layer <NUM> extends and covers a surface of the core layer <NUM> and a surface of the grating coupler <NUM>. In some embodiments, the upper cladding layer <NUM> includes silicon dioxide or polymer, and the refractive index of the core layer <NUM> is greater than a refractive index of the upper cladding layer <NUM>. In some embodiments, the refractive index of the upper cladding layer <NUM> is less than <NUM>, such as <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In some embodiments, a dielectric constant of the upper cladding layer <NUM> less than <NUM> at visible light wavelength, such as <NUM>, <NUM>, or <NUM>. The microlens <NUM> is above the upper cladding layer <NUM>, and the microlens <NUM> is configured to change incident angles of a single or multiple wavelengths of the laser light <NUM> entering the grating coupler <NUM>. In <FIG>, three arrows pointing to the microlens <NUM> indicate travel direction of the laser light <NUM>. Specifically, the travel direction of the laser light <NUM> is changed when the laser light <NUM> enters into the microlens <NUM>. In some embodiments, a diameter D of the microlens <NUM> is in a range from <NUM> to <NUM>, such as <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In some embodiments, a refractive index of the microlens <NUM> is the same as or similar to the refractive index of the upper cladding layer <NUM>. The laser light <NUM> is an external light. In some embodiments, a laser beam of the laser light <NUM> has a diameter in a range from <NUM> to <NUM>, such as <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. The metal shielding <NUM> covers the microlens <NUM>. The metal shielding <NUM> has an opening <NUM> configured to make a portion of the laser light <NUM> enter the microlens <NUM>. The opening <NUM> of the metal shielding <NUM> allows the laser light <NUM> entering an effective coupling region Reff of the grating coupler <NUM>. In other words, an effective beam EB would enter the microlens <NUM>. A diameter of the effective beam EB is less than the diameter of the laser beam of the laser light <NUM>.

<FIG> is a cross-sectional view of an optical structure <NUM> in accordance with some embodiments of the present disclosure. The optical structure <NUM> in <FIG> further includes a bottom cladding layer <NUM> compared to the optical structure <NUM> in <FIG>. The bottom cladding layer <NUM> is between the substrate <NUM> and the core layer <NUM>. In some embodiments, the bottom cladding layer <NUM> includes silicon dioxide or polymer, and the refractive index of the core layer <NUM> is greater than a refractive index of the bottom cladding layer <NUM>. In some embodiments, the refractive index of the bottom cladding layer <NUM> is less than <NUM>, such as <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In some embodiments, the bottom cladding layer <NUM> has a dielectric constant less than <NUM> at visible light wavelength, such as <NUM>, <NUM>, or <NUM>. In some embodiments, a refractive index of the microlens <NUM> is the same as or similar to the refractive index of the bottom cladding layer <NUM>. In some embodiments, substrate <NUM> is opaque and includes a silicon wafer or a CMOS (complementary metal oxide semiconductor). In some embodiments, the substrate <NUM> is transparent, and the substrate <NUM> has a refractive index in a range from <NUM> to <NUM>, such as <NUM> or <NUM>, <NUM>, <NUM>, or <NUM>. When the substrate <NUM> is opaque or transparent with a refractive index larger than <NUM>, the bottom cladding layer <NUM> would be disposed between the substrate <NUM> and the core layer <NUM>.

Please refer to <FIG> again. Two dotted lines illustrating from the microlens <NUM> to the grating coupler <NUM> form a light area <NUM>. The light area <NUM> is an area allowing the laser light <NUM> to couple into the grating coupler <NUM>. A length of each of the dotted line has a lens focal length F, and the two dotted lines form an angle θ and a focal point P. In some embodiments, the angle θ is in a range from <NUM> degree to <NUM> degrees, such as <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> degrees. The focal point P of the optical structure <NUM> in <FIG> is in the grating coupler <NUM>. After the laser light <NUM> is coupled into the grating coupler <NUM> through the microlens <NUM> and the upper cladding layer <NUM>, the laser light <NUM> would transmit in the core layer <NUM>, thereby making fluorescence-labeled biomolecules above the core layer <NUM> luminous. The grating coupler <NUM> has the effective coupling region Reff less than around <NUM>. The effective coupling region Reff is a region where the laser light <NUM> can couple and transmit in the core layer <NUM>. In other words, if the light area <NUM> is focused and exposed on the effective coupling region Reff and the incident angles are in the effective coupling angle of the grating coupler <NUM>, the laser light <NUM> would couple and transmit in the core layer <NUM>. However, if the light area <NUM> is out of the effective coupling region Reff or out of the range of effective coupling angles of the grating coupler <NUM>, the laser light <NUM> would not couple and transmit in the core layer <NUM>.

Please refer to <FIG> is a cross-sectional view of an optical structure <NUM> in accordance with some embodiments of the present disclosure. The grating coupler <NUM> is adjacent to the core layer <NUM> and is configured to receive a laser light 160a having offset angles due to the misalignment of an optical system. An irradiation area of the laser light 160a is greater than the effective coupling region Reff of the grating coupler <NUM>. Compared to the optical structure <NUM> in <FIG>, an incident angle of the laser light 160a of the optical structure <NUM> in <FIG> offsets the offset angle Δθ, so that a new light area 164a is formed. The light area 164a forms a new lens focal length F', a new focal point P', and a new angle θ'. The focal point P' of the optical structure <NUM> in <FIG> is out of the grating coupler <NUM>. The light area 164a exposed on the surface of the grating coupler <NUM> in <FIG> is greater than the light area <NUM> exposed on the surface of the grating coupler <NUM> in <FIG>. The lens focal length F' in <FIG> is greater than the lens focal length F in <FIG>. The angle θ' in <FIG> is less than the angle θ in <FIG>. In some embodiments, the offset angle Δθ is ±<NUM> degrees, ±<NUM> degrees, ±<NUM> degrees, or ±<NUM> degrees. The microlens <NUM> is above the upper cladding layer <NUM>, in which when the laser light 160a enters the microlens <NUM>, the microlens <NUM> is configured to focus the laser light 160a in the effective coupling region Reff of the grating coupler <NUM>. Despite the fact that the laser light 160a is offset, the light area 164a covers the effective coupling region Reff of the grating coupler <NUM>, and the new angle θ' is smaller than the angle θ which means the new incident angles due to the offset Δθ of the laser beam 160a are smaller than the designed effective coupling angles of the grating coupler <NUM>. Therefore, the laser light 160a can still couple and transmit in the core layer <NUM>. The optical structure of the present disclosure can provide a large alignment tolerance in the optical structure, thereby increasing the overall coupling efficiency of the optical structure for bio-detections. It is noticed that the following optical structures are illustrated for clarity of discussion, but the offset of the laser light <NUM> should also include therein.

It should be understood that <FIG> may include the substrate <NUM> in <FIG>, and may further include the bottom cladding layer <NUM> in <FIG>. Similarly, <FIG> and <FIG> below may include the substrate <NUM> in <FIG>, and may further include the bottom cladding layer <NUM> in <FIG>.

<FIG>, <FIG> are cross-sectional views of optical structures 100a, 100b, 100c, and 100d in accordance with alternative embodiments of the present disclosure.

Please refer to <FIG>, <FIG> at the same time. The differences between the optical structures 100a, 100b and the optical structures <NUM> are sizes of the openings <NUM>. As shown in <FIG>, an opening 172a of the metal shielding 170a of the optical structures 100a is greater than the opening <NUM> of the metal shielding <NUM> of the optical structures <NUM>. A greater effective beam EBa of the optical structures 100a is greater than the greater effective beam EB of the optical structures <NUM>. A light area 164a of the optical structures 100a is greater than the light area <NUM> of the optical structures <NUM>, and an angle in the light area 164a is in a range from -θ to θ. The laser light <NUM> (see <FIG>) would couple and transmit in the core layer <NUM> because the light area 164a is focused and exposed on the effective coupling region Reff and the incident angles are in the effective coupling angles of the grating coupler <NUM>. Therefore, the grating coupling efficiency would be increased. As shown in <FIG>, an opening 172b of the metal shielding 170b of the optical structures 100b is on the left side of the microlens <NUM>. A light area 164b of the optical structures 100b forms an angle -θ. The laser light <NUM> would couple and transmit in the core layer <NUM> because the light area 164b is focused and exposed on the effective coupling region Reff and the incident angles are in the effective coupling angles of the grating coupler <NUM>. In some embodiments, the angle θ is in a range from <NUM> to <NUM> degrees depending on the effective coupling angles of the grating couplers.

Please refer to <FIG> and <FIG>. The difference between the optical structure 100c and the optical structure <NUM> is the positions of the metal shielding <NUM>. As shown in <FIG>, the metal shielding 170c is below the microlens <NUM>. In other words, the metal shielding 170c is disposed between the microlens <NUM> and the grating coupler <NUM>. Specifically, the metal shielding 170c is between the microlens <NUM> and the upper cladding layer <NUM>. The metal shielding 170c has an opening 172c to make a portion of the laser light <NUM> enter the grating coupler <NUM>. The laser light <NUM> would couple and transmit in the core layer <NUM> because the light area 164c is focused and exposed on the effective coupling region Reff and the incident angles are in the effective coupling angles of the grating coupler <NUM>.

Please refer to <FIG> and <FIG>. The difference between the optical structure 100d and the optical structure <NUM> is the arrangement of the upper cladding layer <NUM> and an air gap <NUM>. The upper cladding layer <NUM> in the optical structures <NUM> is replaced by the air gap <NUM>, as shown in <FIG>. In some embodiments, a thickness of the air gap <NUM> is in a range from <NUM> to <NUM>, such as <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>.

<FIG>, <FIG>, <FIG>, and <FIG> are cross-sectional views of optical structures <NUM>, 800a, 800b, 800c in accordance with alternative embodiments of the present disclosure. It is noticed that the main differences between <FIG>, <FIG>, <FIG>, <FIG>, and <FIG> are the positions of the grating coupler <NUM>. As shown in <FIG>, the grating coupler <NUM> is embedded in the core layer <NUM>.

Please refer to <FIG>. In the optical structure <NUM>, the grating coupler <NUM> is on a surface <NUM> of the core layer <NUM> facing toward the microlens <NUM>, and the core layer <NUM> has a portion between the grating coupler <NUM> and the substrate <NUM>. Specifically, the grating coupler <NUM> is lower than the microlens <NUM> and higher than the core layer <NUM>, and the grating coupler <NUM> is embedded in the upper cladding layer <NUM>. In some embodiments, a material of the grating coupler <NUM> is the same as a material of the core layer <NUM>. In some embodiments, a material of the grating coupler <NUM> is different from a material of the core layer <NUM>. An enlargement view of the grating coupler <NUM> in <FIG> may refer to <FIG>.

Please refer to <FIG>. In the optical structure 800a, the grating coupler <NUM> is disposed on a surface <NUM> of the core layer <NUM> facing toward the substrate <NUM>, and the core layer <NUM> has a portion between the microlens <NUM> and the grating coupler <NUM>. Specifically, the grating coupler <NUM> is embedded in the substrate <NUM>. Please refer to <FIG> illustrates an enlargement view of the grating coupler <NUM> in <FIG>. The continuous surface (the top surface <NUM>, the sidewall <NUM>, the bottom surface <NUM>, and the sidewall <NUM>) of the grating coupler <NUM> faces toward the substrate <NUM>.

Please refer to <FIG>. The optical structure 800b further includes a metal reflector <NUM> comparing to the optical structure 800a. Please refer to <FIG> illustrates an enlargement view of the grating coupler <NUM> in <FIG>. The metal reflector <NUM> is disposed on a surface (the top surface <NUM>, the sidewall <NUM>, the bottom surface <NUM>, and the sidewall <NUM>) of the grating coupler <NUM> facing toward the substrate <NUM>.

Please refer to <FIG>. The optical structure 800c further includes a metal reflector <NUM> compared to the optical structure <NUM>. Specifically, the grating coupler <NUM> and the metal reflector <NUM> are embedded in the core layer <NUM>. Please refer to <FIG> illustrates an enlargement view of the grating coupler <NUM> in <FIG>. The grating coupler <NUM> has a surface (the top surface <NUM>, the sidewall <NUM>, the bottom surface <NUM>, and the sidewall <NUM>) facing toward the substrate <NUM> and a sidewall <NUM> adjoining the surface. The metal reflector <NUM> is disposed on the surface (the top surface <NUM>, the sidewall <NUM>, the bottom surface <NUM>, and the sidewall <NUM>) and the sidewall <NUM> of the grating coupler <NUM>.

<FIG>, <FIG> are cross-sectional views of optical structures <NUM>, 1200a, 1200b, 1200c in accordance with alternative embodiments of the present disclosure. It is noticed that the main differences between <FIG>, <FIG>, <FIG>, <FIG> and <FIG>, <FIG> are the arrangements of the upper cladding layer <NUM> and the air gap <NUM>. Specifically, the upper cladding layers <NUM> in <FIG>, <FIG>, <FIG>, and <FIG> are replaced by the air gaps <NUM> in <FIG>, <FIG>. Reference numerals are repeated herein to show the same or similar features, and the description above applies equally to the embodiments described below, and the details thereof are not repeatedly described.

Please refer to <FIG> is a cross-sectional view of an optical structure <NUM> in accordance with alternative embodiments of the present disclosure. Specifically, the optical structure <NUM> in <FIG> is similar to the optical structure 100b in <FIG>, but the optical structure <NUM> further includes the substrate <NUM> below the core layer <NUM> and the grating coupler <NUM>.

<FIG> is a top view of the metal shielding 170b of the optical structure <NUM> in <FIG>. <FIG> is a top view of the substrate <NUM>, the core layer <NUM>, and the grating coupler <NUM> of the optical structure <NUM> in <FIG>. <FIG> is a cross-sectional view of the substrate <NUM>, the core layer <NUM>, and the grating coupler <NUM> taken along line A-A' in <FIG>. As shown in <FIG>, the metal shielding 170b includes a straight shape. As shown in <FIG>, a cross-sectional shape of the microlens <NUM> is half-cylindrical. As shown in <FIG>, the core layer <NUM> includes a planar waveguide.

<FIG> is a top view of the metal shielding 170b of the optical structure <NUM> in <FIG>. <FIG> is a top view of the substrate <NUM>, the core layer <NUM>, and the grating coupler <NUM> of the optical structure <NUM> in <FIG>. <FIG> is a cross-sectional view of the substrate <NUM>, the core layer <NUM>, and the grating coupler <NUM> taken along line B-B' in <FIG>. As shown in <FIG>, the grating coupler <NUM> includes a curved shape. As shown in <FIG>, the core layer <NUM> includes a plurality of channel waveguides.

<FIG> are top views of the substrate <NUM>, the core layer <NUM>, and the grating coupler <NUM> of the optical structure <NUM> in <FIG>. <FIG>, <FIG>, <FIG> are cross-sectional views of <FIG> taken along line C-C'. Similarly, <FIG>, <FIG> also are cross-sectional views of <FIG> taken along line D-D'.

Each of the grating couplers <NUM> in <FIG> has multiple recesses. Each of the grating couplers <NUM> in <FIG> has multiple convex parts. In some embodiments, a material of the grating coupler <NUM> is different from a material of the core layer <NUM>. In <FIG>, <FIG>, the laser light <NUM> would couple into the grating coupler <NUM> and then transmit in the core layer <NUM>. In some embodiments, the grating coupler <NUM> has a tapered thickness, as shown in <FIG> or <FIG>.

Please refer to <FIG> are cross-sectional views of various grating structures of the grating coupler <NUM> (see <FIG>) in accordance with some embodiments of the present disclosure. The grating coupler <NUM> includes at least one of a step grating structure 130a, a blazed grating structure 130b, and slanted grating structures 130c-130f. Please refer to the enlargement view of grating coupler <NUM> in <FIG> again. The grating coupler <NUM> has the grating period p and the height h. The grating structures 130a-130f in <FIG> can be selectively used in the grating coupler <NUM> of <FIG>. In addition, the grating structures 130a-130f in <FIG> can be mirror symmetry structures depending on the transmit directions (such as to the right side or the left side) of the laser light <NUM> or the laser light 160a. For example, a first vertical sidewall <NUM> of the step grating structure 130a may face toward to the right side, an oblique sidewall <NUM> of the blazed grating structure 130b may face toward to the right side, or a first oblique sidewall <NUM> of the slanted grating structures 130c-130f may face toward to the right side.

<FIG> illustrates the step grating structure 130a of the grating coupler <NUM>. In some embodiments, the step grating structure 130a has n steps, in which n is in a range from <NUM> to <NUM>. For example, n is <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. Specifically, <FIG> illustrates a <NUM>-step grating structure. The step grating structure 130a includes the first vertical sidewall <NUM>, a second vertical sidewall <NUM>, and a horizontal surface <NUM>. The horizontal surface <NUM> adjoins the first vertical sidewall <NUM> and the second vertical sidewall <NUM>. In some embodiments, a top width Wt of the step grating structure 130a is <NUM>, a bottom width Wb of the step grating structure 130a is <NUM>, the height h of the step grating structure 130a is <NUM>, the first vertical sidewall <NUM> of the step grating structure 130a has a <NUM> height, the second vertical sidewall <NUM> of the step grating structure 130a has a <NUM> height, and the horizontal surface <NUM> of the step grating structure 130a has a <NUM> width.

<FIG> illustrates the blazed grating structure 130b of the grating coupler <NUM>. The blazed grating structure 130b includes the oblique sidewall <NUM>. The oblique sidewall <NUM> extends from a top of the blazed grating structure 130b to a bottom of the blazed grating structure 130b, and a width of the blazed grating structure 130b gradually increases from the top of the blazed grating structure to the bottom of the blazed grating structure 130b. In some embodiments, the bottom width Wb of the blazed grating structure 130b is <NUM> and the height h of the blazed grating structure 130b is <NUM>.

<FIG> illustrates the slanted grating structures 130c-130f of the grating coupler <NUM>. Each of the slanted grating structures 130c-130f includes the first oblique sidewall <NUM>, a second oblique sidewall <NUM>, and a top surface <NUM>. The top surface <NUM> adjoins the first oblique sidewall <NUM> and the second oblique sidewall <NUM>. Each of the first oblique sidewalls <NUM> of the slanted grating structures 130c-130f has a first slope and each of the second oblique sidewalls <NUM> of the slanted grating structures 130c-130f has a second slope. In some embodiments, the first slope is the same as the second slope. In some embodiments, the first slope is less than the second slope.

In some embodiments, the bottom width Wb is <NUM>, the top width Wt is <NUM>, and the height h is <NUM>, as shown in <FIG>. In some embodiments, the bottom width Wb is <NUM>, the top width Wt is <NUM>, and the height h is <NUM>, as shown in <FIG>. In some embodiments, the bottom width Wb is <NUM>, the top width Wt is <NUM>, and the height h is <NUM>, as shown in <FIG>. In some embodiments, the bottom width Wb is <NUM>, the top width Wt is <NUM>, and the height h is <NUM>, as shown in <FIG>.

<FIG>, <FIG>, <FIG>, <FIG> are incident angle-intensity charts for a green light GL having <NUM> wavelength under different grating structures in accordance with some embodiments of the present disclosure. Specifically, the step grating structure 130a, the blazed grating structure 130b, and the slanted grating structure 130c-130f are used in the simulation. More specifically, the grating period p is <NUM> and the height h is <NUM> (please refer to <FIG>). The simulation results show the relationships between intensities of different grating couplers <NUM> and the incident angles of the green light GL under different refractive index of the grating coupler <NUM> and different refractive index of the upper cladding layer <NUM>. It should be understood that the "intensity" herein represents a coupling efficiency of the grating coupler <NUM>, and the "incident angle" herein represents the angle relative to the normal direction of the surface of the grating coupler <NUM>. In addition, the "full width at half maximum (FWHM)" herein can be understood as an effective coupling angle of the grating coupler. Rigorous Coupled Wave Analysis (RCWA) method is used.

Please refer to <FIG>. In the simulation results of <FIG>, the refractive index of the grating coupler <NUM> is <NUM> and the refractive index of the upper cladding layer <NUM> is <NUM>. In other words, the upper cladding layer <NUM> is the air gap <NUM> (see <FIG>). In <FIG>, the step grating structure 130a, the blazed grating structure 130b, and the slanted grating structure 130c have high intensities when the incident angle is less than around <NUM> degrees. In <FIG>, the slanted grating structure 130c, the slanted grating structure 130d, the slanted grating structure 130e, and the slanted grating structure 130f have high intensities when the incident angle is less than around <NUM> degrees.

Please refer to <FIG>. In the simulation results of <FIG>, the refractive index of the grating coupler <NUM> is <NUM> and the refractive index of the upper cladding layer <NUM> is <NUM>. In other words, the upper cladding layer <NUM> is the air gap <NUM> (see <FIG>). In <FIG>, the step grating structure 130a and the blazed grating structure 130b have higher intensities than the slanted grating structure 130c. However, the slanted grating structure 130c still has high intensity when the incident angle is less than around <NUM> degrees. In <FIG>, the slanted grating structure 130c, the slanted grating structure 130d, the slanted grating structure 130e, and the slanted grating structure 130f have high intensities when the incident angle is less than around <NUM> degrees. The slanted grating structure 130f has a greater effective coupling angle tolerance than the slanted grating structure 130c.

Please refer to <FIG>. In the simulation results of <FIG>, the refractive index of the grating coupler <NUM> is <NUM> and the refractive index of the upper cladding layer <NUM> is <NUM>. In <FIG>, the slanted grating structure 130c has a higher intensity than those of the step grating structure 130a and the blazed grating structure 130b. In <FIG>, the slanted grating structure 130c, the slanted grating structure 130d, the slanted grating structure 130e, and the slanted grating structure 130f have similar intensities as the incident angle increases.

Please refer to <FIG>. In the simulation results of <FIG>, the refractive index of the grating coupler <NUM> is <NUM> and the refractive index of the upper cladding layer <NUM> is <NUM>. In <FIG>, the slanted grating structure 130c has a higher intensity than those of the step grating structure 130a and the blazed grating structure 130b when the incident angle is less than around <NUM> degrees. In <FIG>, the slanted grating structure 130c, the slanted grating structure 130d, the slanted grating structure 130e, and the slanted grating structure 130f have high intensities when the incident angle is less than around <NUM> degrees.

Despite the fact that <FIG> shows the simulation results of the green light GL having <NUM> wavelength, other lights having different wavelengths (for example, <NUM> and <NUM>) can be also simulated. In the simulation results, the step grating structure 130a, the blazed grating structure 130b, the slanted grating structure 130c-130f show good coupling efficiency and have large effective coupling angle tolerance to some extent.

Claim 1:
An optical structure, comprising:
a grating coupler (<NUM>) configured to receive a laser light (<NUM>);
a core layer (<NUM>) adjacent to the grating coupler (<NUM>); and
a microlens (<NUM>) above the grating coupler (<NUM>), characterized in that a metal shielding (<NUM>) covers the microlens (<NUM>) and has an opening to allow the laser light (<NUM>) entering an effective coupling region (Reff) of the grating coupler (<NUM>),
wherein the opening of the metal shielding (<NUM>) is configured to make a portion of the laser light (<NUM>) enter the microlens (<NUM>), and the opening has an angle (θ) in a range from -<NUM> degrees to <NUM> degrees,
wherein the effective coupling region (Reff) is a region where the laser light (<NUM>) can couple and transmit in the core layer (<NUM>), and a light area (<NUM>) covers the effective coupling region (Reff), wherein the light area (<NUM>) is an area allowing the laser light (<NUM>) to couple into the grating coupler (<NUM>).