Point diffraction light source based on nanowire waveguide and light field regulation and control method thereof

Abstract

The invention relates to the technical field of wavefront detection, and discloses a nanowire waveguide-based point diffraction light source and a light field regulation and control method thereof.The point diffraction light source comprises a silicon substrate, a waveguide core layer, a full cladding and a gradient cladding, the waveguide core layer comprises a coupler, a coupling section straight waveguide, a bent waveguide and an emergent section straight waveguide, the gradient cladding comprises a silicon dioxide cladding and an air cladding, the coupler is connected with the coupling section straight waveguide, the coupling section straight waveguide is connected with the bent waveguide, the bent waveguide is connected with the emergent section straight waveguide, one side of the coupler and one side of the waveguide core layer are wrapped in the full cladding, and the other side of the coupler and one side of the waveguide core layer are wrapped in the air cladding. And the other side of the waveguide core layer is wrapped by the gradient cladding, so that the other side of the waveguide core layer is located in an air cladding. According to the technical scheme provided by one or more embodiments, the numerical aperture of the diffracted wavefront can be increased.

Description

Technical Field

[0001] The present application relates to the field of wavefront detection technology, and in particular to a point diffraction light source based on a nanowire waveguide and a light field control method thereof. Background Art

[0002] In the field of wavefront detection technology, when a point diffraction interferometer is used for optical detection, a diffraction wavefront that is approximately an ideal sphere and is generated by diffraction of a light field with an extremely small cross-section is usually used as a reference wavefront, and interferes with the wavefront to be measured to perform high-precision optical detection.

[0003] At present, the point diffraction light source using nanowire waveguides limits the light field to the wavelength or sub-wavelength level, which can produce a smaller light field cross section to form a stable diffraction wavefront, thereby improving the measurement accuracy of the point diffraction interferometer. However, in practical applications, the NA (Numerical Aperture) value of the diffraction wavefront is small, which limits the measurement range of the diffraction reference interferometer.

[0004] In view of this, how to increase the numerical aperture of the diffraction wavefront has become the current research focus in the field of wavefront detection. Summary of the invention

[0005] The present application provides a point diffraction light source based on a nanowire waveguide and a light field control method thereof, which can generate a diffraction wavefront with a large numerical aperture.

[0006] In a first aspect, the present application provides a point diffraction light source based on a nanowire waveguide structure, wherein the point diffraction light source comprises a silicon substrate, a waveguide core layer, a full cladding and a gradient cladding, wherein the waveguide core layer comprises a coupler, a coupling section straight waveguide, a curved waveguide and an output section straight waveguide, wherein the gradient cladding comprises a silica cladding and an air cladding, wherein the coupler is connected to the coupling section straight waveguide, the coupling section straight waveguide is connected to the curved waveguide, and the curved waveguide is connected to the output section straight waveguide, wherein one side of the coupler and the waveguide core layer is wrapped in the full cladding, and the other side of the waveguide core layer is wrapped in the gradient cladding, so that the other side of the waveguide core layer is in the air cladding.

[0007] In one embodiment, the waveguide core layer is composed of silicon nitride, and the full cladding and the silicon dioxide cladding are both composed of silicon dioxide.

[0008] In one embodiment, the gradient cladding further comprises a silica cladding, and the width of the silica cladding is gradiently distributed, wherein the width of the silica cladding is gradiently distributed according to a linear function; or the width of the silica cladding is gradiently distributed according to a Bezier curve.

[0009] In one embodiment, the coupler, the coupling section straight waveguide and the bent waveguide are wrapped in the full cladding.

[0010] In one embodiment, one end of the output section straight waveguide is wrapped in the full cladding, the middle part of the output section straight waveguide is wrapped in the silica cladding, and the other end of the output section straight waveguide is wrapped in the air cladding.

[0011] In one embodiment, the output straight waveguide outputs a diffraction wavefront, and the curved waveguide is used to rotate the propagation direction of the light field to reduce the influence of scattered light on the diffraction wavefront.

[0012] In one embodiment, the coupler is a Y-type coupler, wherein one side of the Y-type coupler includes two end faces, and the end faces are used to couple with optical fibers; the other side of the Y-type coupler is connected to a coupling section straight waveguide.

[0013] In one embodiment, the preparation of the point diffraction light source includes dry etching and wet etching, wherein: a silicon nitride layer is formed by thin film deposition, and a first mask is made by photolithography, and the silicon nitride layer is dry etched according to the first mask to obtain a waveguide core layer of a specified shape; silicon dioxide is deposited above the core layer, and a second mask is made by photolithography, and the silicon dioxide layer is dry etched according to the second mask, and a specified area is wet etched by a specified etching solution to obtain a full cladding and a gradient cladding of a specified shape.

[0014] The second aspect of the present application provides a light field control method for a point diffraction light source based on a gradient nanowire waveguide, wherein the point diffraction light source is used to generate a diffraction wavefront; the point diffraction light source includes a coupler, a coupling section straight waveguide, a curved waveguide and an exit section straight waveguide, and the light field control method for the point diffraction light source includes: acquiring an external light field, and coupling the light field into the coupling section straight waveguide through the coupler; the coupling section straight waveguide receives the light field, stabilizes the light field into a first mode field, and transmits the first mode field to the curved waveguide; the curved waveguide changes the propagation direction of the first mode field, and transmits the first mode field to the exit section straight waveguide; the exit section straight waveguide converts the first mode field into a second mode field, and propagates the second mode field to the far field to form a diffraction wavefront.

[0015] The technical solution provided by one or more embodiments of the present application uses a gradual cladding structure to reduce the loss and mode field area of ​​mode field conversion, thereby generating a diffraction wavefront with a large numerical aperture. Specifically, a nanowire waveguide is used for light transmission, and a gradual cladding structure is used at the exit waveguide, that is, a gradual transition from a silica cladding to an air cladding, which can increase the refractive index difference between the core layer and the cladding to increase the confinement ability of the light field, thereby reducing the mode field area of ​​the waveguide, and then generating a diffraction wavefront with a larger numerical aperture.

[0016] It can be seen that the technical solution provided by the present application adopts a gradient cladding structure including an air cladding and a silica cladding, which can increase the numerical aperture of the generated diffraction wavefront to improve the optical measurement range. At the same time, adding a gradient cladding structure can avoid sudden changes in the mode, thereby reducing light loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A schematic diagram of the structure of a point diffraction light source provided in one embodiment of the present application; Figure 2 A schematic diagram of the structure of a waveguide core layer provided in one embodiment of the present application; Figure 3 A schematic diagram of the steps of a method for controlling the light field of a point diffraction light source based on a gradient nanowire waveguide provided in one embodiment of the present application; Figure 4 A schematic structural diagram of a nanowire waveguide-based point diffraction light source with a full silicon dioxide cladding provided in one embodiment of the present application; FIG5( a) is a schematic diagram of a simulation of a far-field diffraction wavefront image provided by an embodiment of the present application; FIG5( b ) is a simulation diagram of the relationship between the NA value and the core layer size provided by an embodiment of the present application; FIG6( a) is a simulation schematic diagram of a far-field diffraction wavefront image provided by another embodiment of the present application; FIG6( b ) is a simulation diagram of the relationship between the NA value and the core layer size provided in another embodiment of the present application.

[0019] Description of reference numerals: 110-silicon substrate, 111-waveguide core layer, 112-full cladding, 113-gradient cladding, 210-coupler, 211-coupling section straight waveguide, 212-bent waveguide, 213-exit section straight waveguide, 310-waveguide core layer, 311-full cladding, 312-silicon substrate, 313-coupler, 314-coupling section straight waveguide, 315-bent waveguide, 316-exit section straight waveguide. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application.

[0021] In addition, the descriptions involving "first", "second", etc. in this application are for descriptive purposes only and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more. In addition, the use of "based on" or "according to" means openness and inclusiveness, because the process, steps, calculations or other actions "based on" or "according to" one or more of the conditions or values ​​can be based on additional conditions or beyond the described values ​​in practice.

[0022] With the continuous development of the optical industry, the settings of point diffraction interferometers are also being continuously optimized and improved. Generally speaking, point diffraction interferometers can generate diffraction wavefronts through the diffraction of the light field at the pinhole or the end of the optical fiber, and use the diffraction wavefront as the reference wavefront for interference detection to interfere with the wavefront to be measured to generate interference fringes, and the wavefront to be measured can be detected through the interference fringes.

[0023] In the related art, the light source of the point diffraction interferometer can adopt a point diffraction light source based on nanowire waveguide. By coupling the light in the single-mode optical fiber into the point diffraction light source structure, the light is transmitted in the nanowire waveguide and diffracted at the end face of the waveguide emission section to produce a diffraction wavefront that approximates an ideal sphere. The point diffraction light source based on the nanowire waveguide can limit the light field to the wavelength or subwavelength level, produce a smaller light field cross section, and at the same time suppress and cut off the transmission of high-order modes to achieve stable single-mode light field transmission. The diffraction wavefront formed is relatively stable and has a high light intensity. Therefore, the introduction of a point diffraction light source of a nanowire waveguide can significantly improve the measurement accuracy of the point diffraction interferometer.

[0024] However, in practical applications, point diffraction interferometers need to have not only high measurement accuracy but also a large measurement range when performing optical inspections. When detecting targets over a large range, due to the small numerical aperture of the diffraction wavefront, it is usually necessary to perform inspections in separate areas in sequence, resulting in low detection efficiency, and the detection in separate areas will inevitably lead to some artificial errors. Therefore, there is an urgent need for a point diffraction light source that can generate a diffraction wavefront with a large numerical aperture, increase the measurement range and thus improve the detection efficiency, and generate a more intuitive interference pattern of the target to be measured, which is convenient for the inspection personnel to make judgments.

[0025] In view of this, one or more embodiments of the present application provide a point diffraction light source based on a gradient nanowire waveguide, which can solve the above-mentioned problem and generate a diffraction wavefront with a large numerical aperture to increase the measurement range.

[0026] See also Figure 1 and Figure 2 One embodiment of the present application provides a point diffraction light source based on a nanowire waveguide, the point diffraction light source includes a silicon substrate 110, a waveguide core layer 111, a full cladding 112 and a gradient cladding 113, the waveguide core layer 111 includes a coupler 210, a coupling section straight waveguide 211, a curved waveguide 212 and an output section straight waveguide 213, the coupling section straight waveguide 211 is connected to the curved waveguide 212, the curved waveguide 212 is connected to the output section straight waveguide 213, wherein one side of the coupler 210 and the waveguide core layer 111 is wrapped in the full cladding 112, and the other side of the waveguide core layer 111 is wrapped in the gradient cladding 113, so that the other side of the waveguide core layer 111 is in the air cladding.

[0027] Specifically, Figure 1 Schematic diagram of the structure of the point diffraction light source in this embodiment. Figure 1 As shown, the point diffraction light source includes a silicon substrate 110, a full cladding 112, a waveguide core layer 111 and a gradient cladding 113, wherein the gradient cladding includes a silica cladding and an air cladding, the full cladding 112 and the silica cladding are both composed of silica, the waveguide core layer 111 is composed of silicon nitride, one side of the waveguide core layer 111 is wrapped in the full cladding 112, and the other side of the waveguide core layer 111 is wrapped in the gradient cladding 113, so that the end face portion of the other side of the waveguide core layer 111 is exposed to the air, that is, it is in the air cladding.

[0028] also, Figure 2 FIG. 1 is a schematic diagram of the structure of the waveguide core layer in this embodiment. Figure 2As shown, the waveguide core layer includes a coupler 210, a coupling section straight waveguide 211, a curved waveguide 212 and an output section straight waveguide 213, and the respective parts are sequentially connected, wherein the coupler 210, the coupling section straight waveguide 211, the curved waveguide 212 and one end of the output section straight waveguide 213 are wrapped in the above-mentioned full cladding, the middle part of the output section straight waveguide 213 is wrapped in the above-mentioned silica cladding, and the other end of the output section straight waveguide 213 is wrapped in the above-mentioned air cladding.

[0029] The coupler 210 may be a Y-type coupler, the two end faces of which are coupled to the optical fiber, and the coupled light is converged into a nanowire waveguide to be transmitted to the waveguide core layer 111, thereby improving the coupling efficiency. Alternatively, a vertical coupler may be used to couple the light into the waveguide core layer 111 through a grating.

[0030] The point diffraction light source adopts dry etching and wet etching to form a core layer structure and a gradient cladding structure of a specific shape on a silicon substrate. Specifically, a mask of a specific shape is made by spin coating photoresist, exposing, and developing the waveguide core layer and the silicon dioxide cladding, and the deposited thin film is subjected to plasma beam etching, cleaning, degumming, and other dry etching on the mask to obtain a core layer structure and a cladding structure with a fixed shape corresponding to the specific shape of the mask, wherein the area covered by the mask is not affected by the etching of the plasma beam, and the area not covered by the mask will be etched away to form a waveguide core layer, a full cladding, and a gradient cladding corresponding to the shape of the mask. After the above-mentioned dry etching step, the formed gradient cladding is further wet-etched, and the silicon dioxide below the end of the straight waveguide of the output section of the gradient cladding is removed by a selective etching liquid to form an air cladding of the straight waveguide of the output section. Preferably, when the core material is silicon nitride and the cladding material is silicon dioxide, hydrofluoric acid can be used as the above-mentioned etching liquid to etch the silicon dioxide. After the etching is completed, the surface needs to be cleaned to remove the photoresist and residual impurities on the surface, and finally the above-mentioned point diffraction light source based on the nanowire waveguide is obtained.

[0031] Exemplarily, the first mask of the silicon nitride core layer is first made on the wafer by electron beam lithography. A silicon dioxide lower layer is formed on the wafer by thin film deposition, and a silicon nitride layer is deposited on the silicon dioxide lower layer. A mask is formed by coating photoresist, exposing and developing, and the mask pattern is printed on the silicon nitride layer. After plasma dry etching, the silicon nitride not protected by the mask is removed to form the silicon nitride core layer of the waveguide core layer pattern.

[0032] Furthermore, silicon dioxide is continuously deposited on the silicon nitride core layer to form a silicon dioxide upper layer, and a second mask with a pattern of a gradient cladding structure is produced by photolithography. The mask is printed on the silicon dioxide upper layer, and the silicon dioxide not protected by the mask is removed after plasma dry etching to expose the output straight waveguide to the air, thereby forming a gradient cladding structure.

[0033] Furthermore, hydrofluoric acid etching solution is used to remove the unetched silicon dioxide below the output section straight waveguide by wet etching. Since the wet etching solution is selective, the different reaction rates of hydrofluoric acid to silicon dioxide and silicon nitride are utilized to achieve a certain degree of selective etching.

[0034] See also Figure 3 In one embodiment of the present application, a method for controlling the light field of a point diffraction light source based on a gradient nanowire waveguide is provided. The point diffraction light source is used to generate a diffraction wavefront. The point diffraction light source includes a coupler, a coupling section straight waveguide, a curved waveguide, and an output section straight waveguide. The method for controlling the light field of the point diffraction light source is performed according to the following steps: S1: Acquire an external light field, and couple the light field into the coupling-segment straight waveguide through a coupler.

[0035] S3: The coupled straight waveguide receives the light field, stabilizes the light field into a first mode field, and transmits the first mode field to the bent waveguide.

[0036] S5: The curved waveguide changes the propagation direction of the first mode field and transmits the first mode field to the output straight waveguide.

[0037] S7: The output straight waveguide converts the first mode field into a second mode field, and propagates the second mode field to a far field to form a diffraction wavefront.

[0038] It should be noted that the light field can be understood as the electric field and magnetic field distribution of the light wave in time and space, and the mode field can be understood as the fixed distribution of the electromagnetic wave field in the waveguide. Among them, the mode field is divided into transverse mode and longitudinal mode. In this embodiment, the waveguide only adopts a single-mode propagation mode of transverse mode propagation, that is, fundamental mode propagation.

[0039] In this embodiment, the light field is coupled into the waveguide core layer, and the light field is transmitted to the coupling straight waveguide connected to the coupler. Specifically, the optical fiber spot is aligned with the end face of the coupler for coupling, and after the light enters the coupler, its transmission form is converted from the light field to the mode field in the waveguide, and is transmitted to the coupling straight waveguide in the waveguide core layer in the form of the mode field.

[0040] In this embodiment, a light field is received and stabilized into a first mode field, and the first mode field is transmitted to a curved waveguide, wherein the first mode field represents the fundamental mode of the light field in the silica cladding. Since the component of the waveguide core layer is silicon nitride, and the component of the full cladding where the coupled straight waveguide is located is silicon dioxide, the refractive index difference between the waveguide core layer and the cladding is the refractive index difference between silicon dioxide and silicon nitride, and the mode field of light in the coupled straight waveguide is the first mode field. In addition, the coupled straight waveguide stabilizes the light field into the first mode field, which can avoid greater loss of the light field during transmission in the curved waveguide.

[0041] In addition, the distance between the port of the straight waveguide in the output section and the light source can be adjusted by appropriately adjusting the length of the straight waveguide in the coupling section, thereby reducing the influence of scattered light from the light source on the diffracted wavefront.

[0042] In this embodiment, the first mode field is received and the propagation direction of the first mode field is changed, and the first mode field is transmitted to the exit section straight waveguide. Specifically, in order to avoid the point diffraction light source device from blocking the generated diffraction wavefront and the interference of the scattered light of the light source, the propagation direction of the light in the waveguide can be changed. Preferably, a curved waveguide is provided between the coupling section straight waveguide and the exit section straight waveguide so that the coupling section straight waveguide is perpendicular to the exit section straight waveguide to change the propagation direction of the light.

[0043] In addition, the first mode field will have a certain bending loss in the curved waveguide. Specifically, when the light wave propagates in the curved waveguide, a part of the first mode field will extend to the outside of the waveguide, causing the mode field to overflow and thus causing energy loss. Among them, the smaller the radius of curvature of the curved waveguide, the more serious the mode field overflow. Therefore, the radius of curvature of the curved waveguide can be appropriately increased to make the mode field distribution more easily adapt to the change of the waveguide shape to reduce the bending loss. Preferably, the radius of curvature is set to 5μm.

[0044] In this embodiment, the first mode field is converted into a second mode field, and the second mode field represents the fundamental mode of the light field in the air cladding. Since one side of the straight waveguide of the output section is located in the air cladding, the refractive index difference between its waveguide core layer and the cladding is the refractive index difference between silicon nitride and air. At this time, the mode field is converted into the second mode field, that is, converted into the fundamental mode in the air cladding. Since the refractive index difference between silicon nitride and silicon dioxide is 0.5, and the refractive index difference between silicon nitride and air is 0.96, the refractive index difference of the second mode field is greater than the refractive index difference of the first mode field, and the numerical aperture of the diffraction wavefront generated by it is larger.

[0045] It should be noted that the greater the refractive index difference between the cladding and the core, the stronger the waveguide's ability to constrain light waves, the smaller its mode field area, and the larger the beam divergence angle. At the same time, according to NA = nsinθ, within a certain angle range, the larger the beam divergence angle, the larger the numerical aperture. Among them, NA is the numerical aperture, n is the core refractive index, and θ is the beam divergence angle.

[0046] In this embodiment, the straight waveguide in the output section adopts a structure of a gradient cladding, which can reduce the loss of mode conversion in different claddings. Specifically, the width of the silica cladding in the gradient cladding is gradually distributed according to a variation function until the cladding of the straight waveguide in the output section is an air cladding. By adopting the above-mentioned gradient cladding, a gradual transition can be made from the first mode field to the second mode field, avoiding the phenomenon of mode mismatch caused by mode mutation, thereby reducing unnecessary mode loss.

[0047] Optionally, the silicon dioxide cladding is distributed according to a linear function along the propagation direction of light.

[0048] Optionally, the silicon dioxide cladding is distributed along the propagation direction of light according to a Bezier curve, which can shorten the length of the gradient cladding.

[0049] Optionally, the waveguide core layer adopts single-mode transmission, and its mode field distribution is TE mode (transverse electric mode).

[0050] For example, see Figure 4 and Figure 2 The present application provides one or more embodiments of using a nanowire waveguide as a point diffraction light source to control the light field to generate a diffraction wavefront, wherein a nanowire waveguide of silicon nitride material is selected as the waveguide core layer, and a silicon dioxide material is used as the cladding layer. Among them, the refractive index of the silicon nitride material is 1.96, the width is preferably 250nm, and the width is preferably 270nm. The refractive index of the silicon dioxide material is 1.46, the operating wavelength range is 633nm, and the operating polarization state is TE polarization. Specifically: In one embodiment, using Figure 4 The point diffraction light source based on nanowire waveguide with full silica cladding shown in the figure performs far-field diffraction. Among them, the waveguide core layer 310 is completely wrapped in the full cladding 311 above the silicon substrate 312. Specifically, the light field is output through the optical fiber, and the light field of the optical fiber is aligned with the coupler port, and the light is coupled into the waveguide core layer 310 through the coupler 313, and transmitted from the coupling section straight waveguide 314 for a distance to stabilize the light field in the waveguide as a TE0_SiO2 mode field, and then the propagation direction is rotated 90° through the curved waveguide 315 to enter the output section straight waveguide 316, and the light field distribution of the TE0_SiO2 mode field is output at the port of the output section straight waveguide, and propagated to the far field to form a diffraction wavefront.

[0051] Please refer to Figures 5(a) and 5(b), which represent the simulation patterns after the full silica cladding is used in this embodiment. Figure 5(a) is the far-field diffraction wavefront image in this embodiment, where the dotted circle marked position is the position where the far-field total electric field intensity is 1 / e intensity, which is the boundary of the effective wavefront, and the NA value of the above 1 / e intensity position is calculated, and Figure 5(b) is the relationship between the NA value and the core size. Among them, when the core size is preferably 0.33, the maximum NA value is 0.483.

[0052] In another embodiment, using Figure 2 The point diffraction light source based on the graded nanowire waveguide with graded cladding is shown to perform far-field diffraction. The optical field is output through the optical fiber, and the optical field of the optical fiber is aligned with the coupler port in the full cladding 112, and the full cladding 112 is closely attached to the top of the silicon substrate 110. The light is coupled into the waveguide core layer 111 through the coupler 210, and is transmitted from the coupling section straight waveguide 211 for a distance so that the light field in the waveguide is stabilized as the TE0_SiO2 mode field. Subsequently, the TE0_SiO2 mode field rotates the propagation direction by 90° through the curved waveguide 212 and enters the output section straight waveguide 213, while maintaining the TE0_SiO2 mode field to continue to propagate to the gradient cladding 113 of the output section straight waveguide. The cladding gradually transitions from the silica cladding to the air cladding. With the gradual change of the cladding and the propagation of light, the mode field of the waveguide gradually transitions from the TE0_SiO2 mode field to the TE0_air mode field, and is finally output at the port of the output section straight waveguide with the light field distribution of the TE0_air mode field, and propagates to the far field to form a diffraction wavefront.

[0053] Please refer to Figure 6 (a) and Figure 6 (b), which represent the simulation patterns after the gradient cladding is used in this embodiment. Figure 6 (a) is a far-field diffraction wavefront image, where the dotted circle marked position is the position where the far-field total electric field intensity is 1 / e intensity, and the NA value of the above 1 / e intensity position is calculated, and Figure 6 (b) is the relationship between the NA value and the core layer size. Among them, when the core layer size is preferably 0.3um, the maximum NA value is 0.549. The maximum NA value in this embodiment is higher than the maximum NA value in the above-mentioned silica cladding embodiment. It can be seen that the diffraction wavefront numerical aperture generated by this embodiment is larger.

[0054] The technical solution provided by one or more embodiments of the present application uses a gradual cladding structure to reduce the mode field area, thereby generating a diffraction wavefront with a large numerical aperture. Specifically, a nanowire waveguide is used for light transmission, and a gradual cladding structure is used at the exit waveguide, that is, a gradual transition from a silica cladding to an air cladding, which can increase the refractive index difference between the core layer and the cladding to increase the confinement ability of the light field, thereby reducing the mode field area of ​​the waveguide, and then generating a diffraction wavefront with a larger numerical aperture.

[0055] It can be seen that the technical solution provided by the present application adopts a gradient cladding structure including an air cladding and a silica cladding, which can increase the numerical aperture of the generated diffraction wavefront to improve the optical measurement range. At the same time, adding a gradient cladding structure can avoid sudden changes in the mode, thereby reducing light loss.

[0056] In addition, an embodiment of the present application provides an example scenario of using a point diffraction light source based on a gradient nanowire waveguide for objective lens detection.

[0057] In this embodiment, the reference wave generated by the point diffraction light source can be used for objective lens detection. The diffraction wavefront of the approximate spherical surface emitted by the point diffraction light source is used as a reference wave to interfere with the detection wave passing through the objective lens to be tested, and the interference fringes are recorded on the CCD as an image, and the quality of the objective lens to be tested can be judged by the interference fringes. For the objective lens to be tested with a large aperture, the diffraction wavefront with a large numerical aperture can cover the entire objective lens to be tested, and the overall situation of the objective lens to be tested can be detected by only one measurement, while the diffraction wavefront with a small numerical aperture needs to be detected multiple times in different regions to achieve the overall detection of the objective lens to be tested.

[0058] Therefore, the use of a point diffraction light source based on a gradient nanowire waveguide can increase the measurement range, improve detection efficiency, and produce a more intuitive interference pattern of the target to be measured, making it easier for detection personnel to make judgments.

[0059] The above description is only an example scenario provided in the specification and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0060] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0061] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0062] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

[0063] Although the embodiments of the present application have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A point diffraction light source based on nanowire waveguide, characterized in that: The point diffraction light source comprises a silicon substrate, a waveguide core layer, a full cladding and a gradient cladding, the waveguide core layer comprises a coupler, a coupling section straight waveguide, a curved waveguide and an output section straight waveguide, the gradient cladding comprises a silicon dioxide cladding and an air cladding, the coupler is connected to the coupling section straight waveguide, the coupling section straight waveguide is connected to the curved waveguide, and the curved waveguide is connected to the output section straight waveguide, wherein: The coupler and one side of the waveguide core layer are wrapped in the full cladding, and the other side of the waveguide core layer is wrapped in the gradient cladding, so that the other side of the waveguide core layer is in the air cladding.

2. The point diffraction light source according to claim 1, characterized in that: The width of the silicon dioxide cladding is gradually distributed, wherein: The width of the silicon dioxide cladding is gradually distributed according to a linear function; or The width of the silicon dioxide cladding is gradually distributed according to a Bezier curve.

3. The point diffraction light source according to claim 1, characterized in that: The waveguide core layer is composed of silicon nitride, and the full cladding and the silicon dioxide cladding are both composed of silicon dioxide.

4. The point diffraction light source according to claim 1, characterized in that: The coupler, the coupling-segment straight waveguide and the bent waveguide are wrapped in the full cladding.

5. The point diffraction light source according to claim 1, characterized in that: One end of the output section straight waveguide is wrapped in the full cladding, the middle part of the output section straight waveguide is wrapped in the silicon dioxide cladding, and the other end of the output section straight waveguide is wrapped in the air cladding.

6. The point diffraction light source according to claim 1, characterized in that: The point diffraction light source is used to generate a diffraction wavefront, and the curved waveguide is used to rotate the propagation direction of the light field to reduce the influence of scattered light on the diffraction wavefront.

7. The point diffraction light source according to claim 1, characterized in that: The coupler is a Y-type coupler, wherein: one side of the Y-type coupler includes two end faces, and the end faces are used to couple with the optical fiber; The other side of the Y-type coupler is connected to the coupling section straight waveguide.

8. The point diffraction light source according to claim 1, characterized in that: The preparation of the point diffraction light source includes dry etching and wet etching, wherein: Forming a silicon nitride layer by thin film deposition, making a first mask by photolithography, and dry-etching the silicon nitride layer according to the first mask to obtain a waveguide core layer of a specified shape; Silicon dioxide is deposited on the waveguide core layer, and a second mask is made by photolithography. The silicon dioxide layer is dry-etched according to the second mask, and a designated area is wet-etched by a designated etching solution to obtain a full cladding and a gradient cladding of a designated shape.

9. A method for controlling the light field of a point diffraction light source based on a nanowire waveguide, characterized in that: The point diffraction light source comprises a coupler, a coupling section straight waveguide, a curved waveguide and an exit section straight waveguide, and the light field control method of the point diffraction light source comprises: acquiring an external light field, and coupling the light field into the coupling section straight waveguide through the coupler; The coupling section straight waveguide receives the light field, stabilizes the light field into a first mode field, and transmits the first mode field to the curved waveguide; The curved waveguide changes the propagation direction of the first mode field and transmits the first mode field to the output straight waveguide; The exit straight waveguide converts the first mode field into a second mode field and propagates the second mode field to a far field to form a diffraction wavefront.

10. The method according to claim 9, characterized in that The optical field is transmitted in single mode in the waveguide core layer, the first mode field and the second mode field are TE fundamental modes under different claddings, and the mode field area of ​​the first mode field is larger than that of the second mode field.

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