Optical device containing phase change material, laser external cavity and preparation method of optical device

Abstract

The present invention provides an optical device containing phase change material, a laser external cavity, and a method for preparing the optical device, wherein the optical device includes a substrate, an input waveguide located on the substrate, a grating connected to the input waveguide along the direction of light field propagation, and an output waveguide connected to the other end of the grating. The grating includes a plurality of tunable units arranged linearly along the direction of the light field, and the tunable units include a phase change region and a filling region. The phase change region is configured so that the effective refractive index changes with temperature; the cross-sectional shape of the phase change region in a plane perpendicular to the direction of the light field has a long side and a short side, the long side is parallel to the surface of the substrate, and the short side is perpendicular to the surface of the substrate; the ratio of the length of the long side to the short side is not less than 3 and is determined based on the central wavelength of the light beam coupled into the optical device. The embodiments of the present invention have a simple structure, occupy a small space, and are conducive to reducing the loss of optical signals propagating in the grating.

Description

Technical Field

[0001] The present invention generally relates to the field of optical waveguide technology, and in particular to an optical device, a laser external cavity, and a method for preparing the optical device. Background Art

[0002] On-chip optical devices are widely used in a variety of fields, including imaging and communications, due to their small size, high integration density, and high mode confinement factor. Wavelength-selective optical devices, among others, can select specific wavelengths of light from a broad input spectrum for subsequent transmission, and are therefore suitable for applications in filters, lasers, and other devices.

[0003] Currently, most optical devices capable of wavelength selection are fixed-selective. This means the wavelengths they transmit or reflect are determined during design. After fabrication, they can only select one or more fixed wavelengths and cannot be adjusted. A small number of optical devices offer tunable wavelength selectivity, typically achieved through microrings, Mach-Zehnder interferometers (MZIs), and other devices combined with thermo-optical effects. However, the tunable range is limited, and the optical devices are bulky, making them difficult to integrate.

[0004] The contents of the background technology section are merely the technologies known to the inventors and do not necessarily represent the existing technologies in this field. Summary of the Invention

[0005] In order to address one or more deficiencies in the prior art, the present invention provides an optical device containing a phase change material, comprising: a substrate, an input waveguide located on the substrate, a grating connected to the input waveguide along a light field propagation direction, and an output waveguide connected to the other side of the grating;

[0006] The grating includes a plurality of tunable units arranged linearly along the direction of the light field, and the tunable units include a phase change region and a filling region;

[0007] The phase change region is configured such that the effective refractive index changes with temperature; the cross-sectional shape of the phase change region in a plane perpendicular to the direction of the light field has a long side and a short side, the long side is parallel to the surface of the substrate, and the short side is perpendicular to the surface of the substrate; the length ratio of the long side to the short side is not less than 3, and the length ratio of the long side to the short side is determined according to the central wavelength of the light beam coupled into the optical device, and the phase change material includes one or more of a chalcogen compound or a chalcogen element.

[0008] According to one aspect of the present invention, the length of the phase change region along the propagation direction of the light field satisfies m*l=lambda / (2*n), where m is an integer, l is the length of the tunable unit, and lambda is the initial center wavelength of the light beam coupled into the optical device.

[0009] According to one aspect of the present invention, m is less than 10; n is the effective refractive index of the tunable unit, which is substantially determined based on the area-weighted average of the effective refractive index of the phase change region and the effective refractive index of the filling region.

[0010] According to one aspect of the present invention, in the cross-sectional shape of the phase change region in a plane perpendicular to the light field direction, the length of the short side is not less than 30 nm and not more than 220 nm; the length ratio of the long side to the short side is greater than 5.

[0011] According to one aspect of the present invention, in the cross-sectional shape of the phase change region in a plane perpendicular to the light field direction, the sizes of the long side and the short side are configured to support coupling into the fundamental mode transmission of the working wavelength of the optical device.

[0012] According to one aspect of the present invention, the ideal shape of the phase change region is a rectangular parallelepiped, and the filling region fills other regions in the tunable unit except the phase change region.

[0013] According to one aspect of the present invention, the ideal shape of the phase change zone is a preset shape, the cross-sectional shape of the preset shape in a plane perpendicular to the direction of the light field changes along the direction of the light field, the cross-sectional shape of the preset shape in a plane perpendicular to the direction of the light field is a rectangle, and the short sides of the rectangles at different positions along the propagation direction of the light field are approximately equal in length, and the ratio of the length of the longest side to the short side of the rectangle is not less than 5.

[0014] According to one aspect of the present invention, the junction surfaces of the phase change region and the filling region in the plurality of tunable units are parallel to each other, and the junction surfaces of the phase change region and the filling region are perpendicular to the propagation direction of the light field.

[0015] The lengths of the plurality of tunable units in the light field propagation direction are equal; or

[0016] The lengths of the plurality of tunable units in the light field propagation direction increase or decrease continuously.

[0017] According to one aspect of the present invention, the junction surfaces of the phase change region and the filling region in the plurality of tunable units are parallel to each other, the junction surface of the phase change region and the filling region has a preset tilt angle with the propagation direction of the light field, and the position of the output waveguide corresponds to the tilt direction of the junction surface of the phase change region and the filling region.

[0018] According to one aspect of the present invention, the grating further includes at least one connecting unit, wherein the connecting unit is arranged between the plurality of tunable units, and the optical path provided by the length of the connecting unit in the direction of light field propagation is not equal to the optical path provided by the length of the tunable unit in the direction of light field propagation; and the effective refractive index of the connecting unit is not equal to the effective refractive index of the tunable unit.

[0019] According to one aspect of the present invention, the material of the phase change region is a non-volatile phase change material, which switches between a crystalline state and an amorphous state as the temperature changes, and the switching process is reversible.

[0020] According to one aspect of the present invention, the positional deviation between the cross-sections of the input waveguide and the output waveguide in a plane perpendicular to the light field propagation direction and the center of the cross-section of the phase change region in the plane perpendicular to the light field propagation direction is no more than 20%, and the cross-sectional dimensions of the input waveguide and the output waveguide in a plane perpendicular to the light field propagation direction and the cross-sectional dimensions of the phase change region in the plane perpendicular to the light field propagation direction are no more than 20%.

[0021] According to one aspect of the present invention, the material of the substrate includes one or more of silicon oxide on silicon, aluminum oxide, calcium fluoride, lithium niobate, and sapphire.

[0022] According to one aspect of the present invention, the optical device further includes:

[0023] A heater is located near the grating and is configured to change the temperature of the grating to change the central wavelength of a reflection peak or a transmission peak in the grating.

[0024] According to one aspect of the present invention, the heater comprises:

[0025] an electrode layer covering the grating; and

[0026] A power supply is electrically connected to the electrode layer and is configured to pass a preset current into the electrode layer to change the temperature of the grating by causing the electrode layer to generate Joule heat.

[0027] According to one aspect of the present invention, the heater further comprises:

[0028] An intermediate layer is located between the grating and the electrode layer.

[0029] According to one aspect of the present invention, the material of the intermediate layer comprises a transparent material within the wavelength range of the light beam coupled into the optical device; the material of the electrode layer comprises TiN x, one or more of W2N, I TO, FTO, W, Au, Cr, Ag and Cu.

[0030] According to one aspect of the present invention, the effective refractive index of the input waveguide and the output waveguide in the optical device is greater than the effective refractive index of the intermediate layer; the effective refractive index of the phase change zone is always greater than the effective refractive index of the intermediate layer within the entire variation range; and the effective refractive index of the filling zone is not less than the effective refractive index of the intermediate layer.

[0031] According to one aspect of the present invention, the preset current is a pulse current, and the power supply controls the temperature and time of the grating heating by changing the size, pulse width and number of pulses of the pulse voltage passed into the electrode layer to change the effective refractive index of the grating.

[0032] According to one aspect of the present invention, the present invention further relates to a laser external cavity, the laser external cavity comprising:

[0033] An input end, through which the laser beam is coupled into the laser external cavity;

[0034] an output end, through which the laser beam is coupled out of the laser external cavity;

[0035] The optical device as described above, wherein the optical device is arranged between the input end and the output end;

[0036] The optical device is configured to selectively resonate a laser beam of a specific wavelength and transmit or reflect it by adjusting the effective refractive index.

[0037] According to one aspect of the present invention, the present invention also relates to a laser, comprising:

[0038] The laser external cavity as described above;

[0039] a gain region configured to amplify energy of the laser beam when the laser beam passes through the gain region;

[0040] The optical device is configured to adjust the effective refractive index so that light of a specific wavelength in the laser beam passes through the gain region multiple times.

[0041] According to one aspect of the present invention, the present invention also relates to a method for preparing an optical device, which is used to prepare the optical device as described above, and the preparation method comprises:

[0042] Obtaining a wavelength range of a light beam coupled into the optical device;

[0043] determining a phase change material according to a wavelength range of a light beam coupled into the optical device;

[0044] Calculating structural parameters of a grating in the optical device according to a wavelength range of a light beam coupled into the optical device and material parameters of a phase change material;

[0045] Optical devices are prepared according to the structural parameters of the grating.

[0046] According to one aspect of the present invention, the step of preparing the optical device comprises:

[0047] providing a substrate;

[0048] Processing the surface of the substrate to form an input waveguide and an output waveguide;

[0049] According to the structural parameters of the grating, a plurality of tunable units are formed between the input waveguide and the output waveguide; wherein the structural parameters of the grating include the structural size of the tunable unit, the number of the tunable units, and the length relationship of the plurality of tunable units in the propagation direction of the light field.

[0050] According to one aspect of the present invention, the step of forming a plurality of tunable units comprises:

[0051] coating a photoresist on a substrate;

[0052] exposing the area corresponding to the position of the tunable unit and removing the photoresist in the exposed area;

[0053] Depositing phase change material at corresponding positions of the tunable unit to form a phase change region;

[0054] Remove all photoresist and excess materials;

[0055] A filling area is formed at a corresponding position of the tunable unit.

[0056] According to one aspect of the present invention, the preparation method further comprises: forming a heater on the grating; the step of forming a heater on the grating comprises:

[0057] forming an intermediate layer on the grating surface;

[0058] Coating a photoresist on a surface of the intermediate layer away from the grating;

[0059] Exposing an area at a preset position and removing the photoresist in the exposed area;

[0060] Depositing a conductive material at a preset position to form an electrode layer;

[0061] Remove all photoresist and excess material.

[0062] Compared to the prior art, embodiments of the present invention provide an optical device containing phase-change material. The grating in the optical device includes multiple tunable units. The effective refractive index of the phase-change regions in the tunable units changes with temperature. By controlling the temperature of the tunable units, the refractive index of the grating can be changed, thereby varying the transmittance of optical signals of different wavelengths through the grating. This device, when applied to a filter, can achieve tunable functionality. Furthermore, the optical device in this embodiment has a simple structure and occupies a small space. Furthermore, tunability achieved by varying the effective refractive index helps reduce losses in optical signals propagating through the grating.

[0063] The present invention also includes an embodiment of a laser external cavity, which uses the aforementioned optical device to selectively resonate a laser beam of a specific wavelength and transmit or reflect it by adjusting the effective refractive index.

[0064] The present invention also includes an embodiment of a laser, which uses the aforementioned laser external cavity to reflect the light beam, and can adjust the wavelength of the reflected light beam according to application requirements, thereby expanding the application range of the laser. The optical device can also adjust the output power of the laser or control the laser switch.

[0065] The present invention also includes an embodiment of a method for preparing an optical device, which is used to prepare the aforementioned optical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0067] Figure 1A and Figure 1B Shown are schematic structural diagrams of optical devices in some embodiments of the present invention;

[0068] Figure 2A and Figure 2B shows a schematic cross-sectional view of an optical device in some embodiments of the present invention;

[0069] Figure 3A and Figure 3B Schematic cross-sectional views showing actual processing of optical devices in some embodiments of the present invention;

[0070] Figures 4A-4F Shows a schematic structural diagram of an optical device in different embodiments of the present invention;

[0071] Figures 5A-5D Schematic diagrams showing tuning of optical devices in different embodiments of the present invention are shown;

[0072] Figure 6 A schematic structural diagram of an optical device including a heater in some embodiments of the present invention is shown;

[0073] Figure 7 A schematic cross-sectional view of an optical device including a heater in some embodiments of the present invention is shown;

[0074] Figure 8 Shown is a block diagram of the structure of the laser external cavity in some embodiments of the present invention;

[0075] Figure 9 shows a schematic structural diagram of a laser in some embodiments of the present invention;

[0076] Figure 10 A schematic flow chart showing a method for preparing an optical device in some embodiments of the present invention is shown;

[0077] Figure 11 A schematic diagram of the process of preparing an optical device in some embodiments of the present invention is shown;

[0078] Figure 12 A schematic flow chart showing a process for forming a heater in some embodiments of the present invention is shown. DETAILED DESCRIPTION

[0079] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated 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 invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0080] In the description of the present invention, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," "counterclockwise," and the like, indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely for the purpose of facilitating the description of the present invention and simplifying the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features referred to. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise expressly or specifically defined.

[0081] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, removable, or integral connections; mechanical, electrical, or intercommunication connections; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0082] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may also include the first and second features not being in direct contact but being in contact via another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or diagonally above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or diagonally below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0083] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0084] The following describes embodiments of the present invention in conjunction with the accompanying drawings. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0085] Figure 1A and Figure 1B The structure of an optical device 10 including a phase change material according to some embodiments of the present invention is shown. Figure 2A shows a cross section of the phase change region 1311 according to some embodiments of the present invention, Figure 2B The cross section of the filling area 1312 according to some embodiments of the present invention is shown below. Figures 1A-2B The optical device 10 will be described.

[0086] like Figure 1A and Figure 1BAs shown, the optical device 10 includes a substrate 11, an input waveguide 12, a grating 13 and an output waveguide 14, wherein the input waveguide 12 and the output waveguide 14 are both formed on the substrate 11, and the grating 13 is arranged along the direction of light field propagation ( Figure 1A and Figure 1B grating 13) is disposed between input waveguide 12 and output waveguide 14. Light can be coupled into input waveguide 12, pass through grating 13, and then be coupled out of output waveguide 14. In various embodiments of the present invention, input waveguide 12 and output waveguide 14 can be aligned in the direction of light field propagation, or the output waveguide 14 can be offset relative to the input waveguide 12, as will be described in detail in subsequent embodiments.

[0087] The grating 13 includes a plurality of tunable units 131 arranged linearly along the direction of the light field. The tunable units 131 include a phase change region 1311 and a filling region 1312. The phase change region 1311 is configured such that its effective refractive index changes with temperature. The effective refractive index represents the ratio of the reflectivity to the refractive index of light incident on the phase change region 1311. For example, by changing the temperature of the phase change region 1311, or by maintaining the phase change region 1311 at a certain temperature for a period of time, the effective refractive index of the phase change region 1311 changes. Accordingly, the wavelength of light transmitted through the phase change region 1311 changes, thereby filtering light of different wavelengths. The phase change region 1311 may include a phase change material, which will be described by way of example in subsequent embodiments.

[0088] The filling region 1312 may be disposed between the phase change region 1311 and the phase change region 1311 of another tunable unit 131 and space the adjacent tunable units 131 apart, for example. Figure 1A Alternatively, the filling area 1312 may also be configured as Figure 1B As shown in , adjacent tunable units 131 are partially spaced apart. Figure 2B As shown, the filling region 1312 comprises a material different from that of the phase change region 1311. The material of the filling region 1312 is preferably a material with a stable refractive index. Figure 1A and Figure 1B As shown in , the filling area 1312 can also be set to be empty, filled with air, or set to a vacuum.

[0089] The phase change region 1311 is perpendicular to the direction of the light field ( Figure 1A and Figure 1BThe cross-sectional shape of the phase change region 1311 in the direction perpendicular to the light field (in the substantially horizontal direction) has a long side and a short side, where the long side is parallel to the surface of the substrate 11 and the short side is perpendicular to the surface of the substrate 11. For example, the phase change region 1311 is attached to the surface of the substrate 11. For example, in some embodiments, the cross-sectional shape of the phase change region 1311 in the direction perpendicular to the light field is approximately rectangular (an ideal shape, not considering deviations due to factors such as processing limitations). The long side represents the long side of the rectangle, parallel to the surface of the substrate 11, and the short side represents the short side of the rectangle, perpendicular to the surface of the substrate 11. The actual processed shape of the phase change region 1311 will be described in subsequent embodiments. In actual production, due to limitations in processing accuracy, the cross-sectional shape of the phase change region 1311 in the direction perpendicular to the light field may have protrusions or depressions. In some embodiments, the long side may represent the average, maximum, or minimum value of the length of the phase change region 1311 in the direction parallel to the surface of the substrate 11; the short side may represent the average, maximum, or minimum value of the width of the phase change region 1311 in the direction perpendicular to the surface of the substrate 11.

[0090] In some embodiments, the phase change region 1311 may be configured as follows: Figure 1A The rectangular shape (ideal shape) shown in the figure can also be set to be inclined relative to the direction of the light field (non-vertical). For example, the phase change region 1311 is roughly a parallelogram (ideal shape), and its cross-section perpendicular to the direction of the light field is also roughly rectangular, which will be described in detail in subsequent embodiments.

[0091] In this embodiment, the ratio of the length of the long side to the short side of the cross-section of the phase change region 1311 in the direction perpendicular to the light field is not less than 3. Preferably, the dimension of the phase change region 1311 in the direction parallel to the surface of the substrate 11 is much larger than the dimension in the direction perpendicular to the surface of the substrate 11. The ratio of the length of the long side to the short side can be determined based on the central wavelength of the light beam coupled into the optical device 10.

[0092] Specifically, in some embodiments, the ratio of the length of the long side to the short side can be determined based on the application requirements of the optical device 10. For example, the optical device 10 can be used as a tunable filter, and the light beam coupled into the optical device 10 is a light beam (optical signal) that needs to be filtered, for example, a wide spectrum, that is, the designed operating wavelength range of the tunable filter, wherein the ratio of the length of the long side to the short side can be determined based on the center wavelength of the designed operating wavelength range of the tunable filter.

[0093] In this embodiment, the aspect ratio of the rectangular cross-section is determined according to the central wavelength of the light beam coupled into the optical device 10. For example, when the central wavelength of the light beam coupled into the optical device 10 is larger, the length ratio of the long side to the short side of the phase change zone 1311 in the cross-section perpendicular to the direction of the light field is correspondingly increased, for example, the width of the phase change zone 1311 is increased.

[0094] Taking the optical device 10 as a tunable filter, or its application in a tunable filter, as an example, existing tunable filters using phase change materials primarily cover a small area of ​​phase change material above the core layer of a waveguide, using the phase change material to perturb the light field in the waveguide core layer, resulting in a relatively small adjustment range for the center wavelength (the peak wavelength in the emitted light). In this embodiment, however, light passes through the phase change region 1311, and the change in the effective refractive index of the phase change region 1311 has a significant impact on the center wavelength. Using the phase change region 1311 to strongly modulate the light field can achieve a larger adjustable range for the center wavelength.

[0095] In some preferred embodiments, the ratio of the length of the long side to the short side of the phase change region 1311 in a cross section perpendicular to the light field direction is large, with the long side of the phase change region 1311 (e.g., the long side of a rectangular cross section) being one to two orders of magnitude larger than the short side (e.g., the short side of a rectangular cross section). For example, in a cross section of the phase change region 1311 in a plane perpendicular to the light field direction, the length of the short side is no less than 30 nm and less than 220 nm, such as 60 nm, 80 nm, 100 nm, 150 nm, 200 nm, etc., and the length of the long side is five times or more the length of the short side. Preferably, the length of the long side is ten times or more the length of the short side.

[0096] In this embodiment, increasing the ratio of the length of the long side to the short side of the phase change region 1311 in a cross section perpendicular to the light field direction facilitates reducing the volume of the optical device 10, providing an optical device 10 having a thickness (the dimension of the short side in a direction perpendicular to the substrate 11, for example, the short side of a rectangular cross section) much smaller than that of a conventional waveguide. This not only facilitates miniaturization, reduces processing difficulty, and improves stability, but also enhances the operating performance of the optical device 10. For example, reducing the length of the short side of the phase change region 1311 in a cross section perpendicular to the light field direction (i.e., the thickness of the phase change region 1311 on the substrate 11) can increase the temperature change rate of the phase change region 1311 when the effective refractive index of the phase change region 1311 needs to be changed, thereby reducing energy consumption and making the temperature change of the phase change region 1311 more uniform.

[0097] In this embodiment, the phase change material includes one or more of a chalcogen compound or a chalcogen element. Specifically, the phase change material may include a chalcogen compound, such as SbxSey, SbxSy, etc. Alternatively, in other embodiments, the phase change material includes a chalcogen element, and the chalcogen element is, for example, selenium. Alternatively, the phase change material includes a mixture of the aforementioned multiple phase change materials. According to a preferred embodiment of the present invention, the material of the phase change region 1311 is a non-volatile phase change material, wherein the non-volatile phase change material changes between a crystalline state and an amorphous state with temperature, and the conversion process is reversible. Different types of non-volatile materials have different refractive indices and different temperatures at which phase change occurs, which can be selected according to the actual application requirements of the optical device 10, for example, according to the wavelength range or center wavelength of the light beam coupled into the optical device 10.

[0098] According to a preferred embodiment of the present invention, the length of the phase change region 1311 along the light field propagation direction satisfies m*l=lambda / (2*n).

[0099] Wherein m represents an integer. Preferably, m represents the harmonic order causing resonance. In a preferred embodiment of the present invention, m is less than 10, for example, 1, 2 or 3, etc. Preferably, m is less than 5. l represents the length of the tunable unit 131, including the length of the phase change region 1311 and the filling region 1312 in the direction of light field propagation. l ambda represents the initial center wavelength of the light beam coupled into the optical device 10. In some embodiments, the initial center wavelength of the light beam coupled into the optical device 10 is a range value (for example, the optical device 10 acts as a tunable filter, and the light beam coupled into the optical device 10 is a wide spectrum), and l ambda is the median of the range value. n represents the effective refractive index of the tunable unit 131. The effective refractive index n of the tunable unit 131 can be determined based on the area-weighted average of the effective refractive index of the phase change region 1311 and the effective refractive index of the filling region 1312, wherein the area represents the area of ​​the phase change region 1311 (and the filling region 1312) in the cross-sectional shape perpendicular to the direction of light field propagation, for example Figure 1A As shown in , the filling region 1312 is arranged to extend through the phase change region 1311 along its longitudinal direction, spacing adjacent tunable units 131 from each other. The cross-sectional areas of the phase change region 1311 and the filling region 1312 perpendicular to the direction of light propagation are equal, and their weights are equal. In some embodiments, the filling region 1312 is air or a vacuum, wherein the cross-sectional area of ​​the filling region 1312 perpendicular to the direction of light propagation is set to be equal to the cross-sectional area of ​​the phase change region 1311 perpendicular to the direction of light propagation.

[0100] According to a preferred embodiment of the present invention, the dimensions of the long and short sides of the cross-sectional shape of the phase change region 1311 in a plane perpendicular to the direction of the light field are determined based on the operating wavelength of the light beam coupled into the optical device 10, so that the operating wavelength of the light beam coupled into the optical device 10 maintains fundamental mode transmission within the phase change region 1311. Specifically, for example, when the optical device 10 is used in a laser, the dimensions of the long and short sides are determined based on the designed emission wavelength of the laser. Preferably, the dimensions of the long and short sides of the cross-sectional shape of the phase change region 1311 in a plane perpendicular to the direction of the light field are configured to support only fundamental mode transmission of the operating wavelength of the light beam coupled into the optical device 10 within the phase change region 1311, thereby preventing the occurrence of multiple peaks or valleys and meeting the use requirements of the optical device 10.

[0101] In a preferred embodiment of the present invention, the filling region 1312 fills other regions in a tunable unit 131 except the phase change region 1311, and in this embodiment, the effective refractive index of the phase change region 1311 is always greater than or always less than the effective refractive index of the material of the filling region 1312 within the complete variation range.

[0102] Figure 3A and Figure 3B A schematic cross-sectional view of a phase change region 1311 after actual processing according to some embodiments of the present invention is shown. Due to the small size of the phase change region 1311 and the limitations of existing processing techniques, the shape of the phase change region 1311 after actual processing is not a standard shape.

[0103] For example, the phase change region 1311 is formed by using a vacuum coating process, which is affected by the coating equipment and target material, resulting in the following Figure 3A As shown in , there may be a collection of ridges at the edges and ridges or depressions in the middle. Or as Figure 3B As shown in FIG, the thickness decreases at the edge and there is a convexity or concaveness in the middle part. Figure 3A and Figure 3B The cross-sectional shape of the phase change region 1311 shown in FIG also has a long side and a short side, wherein the long side is parallel to the surface of the substrate 11 and the short side is perpendicular to the surface of the substrate 11. In some embodiments, the edge position of the phase change region 1311 is not neat (non-straight edge), such as Figure 3A and Figure 3B As shown, the lengths of the short sides at different locations are not equal. Preferably, the length of the short side can be selected from the length of the short side passing through the center of the cross section of the phase change region 1311; or the length of the short side can be selected from the average value of the short sides at different locations of the cross section of the phase change region 1311; or the length of the short side conforms to a normal distribution, with the length at the 80% quantile being the length of the short side.

[0104] Deviations in the cross-sectional shape of the phase change region 1311 caused by the manufacturing process have a certain impact on the emitted light. Optimizing manufacturing precision can control this impact within an acceptable range, but it cannot be completely avoided with current technology. In the subsequent embodiments, the ideal cross-sectional shape of the phase change region 1311 is used as an example for illustration, ignoring the impact of manufacturing errors on the emitted light. The ideal shape represents the shape of the phase change region 1311 when designing the optical device 10.

[0105] Figures 4A-4F The structures of the optical device 10 according to different embodiments of the present invention are shown and will be described below respectively.

[0106] like Figure 4A and Figure 4B As shown, the ideal shape of the phase change region 1311 in the tunable unit 131 can be roughly set to the shape of a cuboid. Preferably, the junction surfaces of the phase change region 1311 and the filling region 1312 in multiple tunable units 131 can be set to be parallel to each other, and the junction surfaces of the phase change region 1311 and the filling region 1312 are perpendicular to the direction of light field propagation.

[0107] In each tunable unit 131, the length ratio of the phase change region 1311 and the filling region 1312 in the light field propagation direction may be equal, for example Figure 4A As shown in FIG, the multiple tunable units 131 can be designed to have approximately the same shape and size, or as shown in FIG. Figure 4B As shown, the length ratios of the phase change regions 1311 and the filling regions 1312 in the plurality of tunable units 131 may be set to be unequal.

[0108] In some preferred embodiments, Figure 4A As shown, the lengths of the multiple tunable units 131 in the propagation direction of the light field are equal, and the multiple tunable units 131 are arranged periodically along the propagation direction of the light field. The central wavelength of the reflection peak in this embodiment is, for example, Figure 5A As shown, when the effective refractive index n of the tunable unit 131 is different, the peak wavelength of the optical device 10 coupled out changes. Figure 5A The center wavelengths of three different reflection peaks are shown in FIG. , which does not limit the optical device 10 to being able to switch only between three different center wavelengths. In this embodiment, the effective refractive index n of the tunable unit 131 changes continuously, and the center wavelength of the corresponding reflection peak also changes continuously.

[0109] Or in other embodiments, such as Figure 4BAs shown, the lengths of the multiple tunable units 131 in the light field propagation direction are continuously increased, and the values ​​of the increase or decrease in the lengths of the multiple tunable units 131 in the light field propagation direction can be the same or different. In other embodiments, the lengths of the multiple tunable units 131 in the light field propagation direction can also be set to continuously decrease. In this embodiment, by adjusting the lengths of the multiple tunable units 131 in the light field propagation direction, it can be used to change the width of the reflection peak (or transmission peak), for example Figure 5B and Figure 5C The wide peak and narrow peak shown in the figure can be adapted to different application scenarios. For application scenarios with a larger peak range tolerance, a wide peak can be selected to increase the intensity of the optical signal. For application scenarios with higher accuracy requirements, a narrow peak can be selected to improve the accuracy of the peak.

[0110] In other embodiments of the present invention, the ideal shape of the phase change region 1311 may also be set to a preset shape other than a rectangular parallelepiped, for example Figure 4C and Figure 4D As shown in , the cross-sectional shape in the plane perpendicular to the light field direction changes along the light field direction, and specifically can be a continuous change, such as Figure 4C The junction surface of the phase change region 1311 and the filling region 1312 shown in FIG is a curved surface, and a sudden change may also occur along the direction of the light field, for example Figure 4D As shown in , the junction surface between the phase change region 1311 and the filling region 1312 is a broken line surface. In this embodiment, adjusting the shape of the phase change region 1311 can also change the peak value or peak width of the reflection peak (or transmission peak), which can be selected according to the specific application scenario.

[0111] The phase change region 1311 in this embodiment has a rectangular cross-sectional shape in any plane perpendicular to the light field direction, but the length and width of the rectangular cross-section may vary. Preferably, the short sides (the dimensions perpendicular to the substrate 11) of the rectangular cross-section can be set to be approximately equal, that is, in this embodiment, the thickness of the phase change region 1311 at different locations is approximately equal. The length of the rectangular cross-section has a maximum value, and the ratio of the longest long side to the short side is not less than 10. The maximum length of the rectangular cross-section is preferably approximately equal to the width of the input waveguide 12 and the output waveguide 14, for example, with a dimensional deviation of no more than 20%.

[0112] For a non-rectangular phase change region 1311, multiple tunable units 131 may be arranged periodically, that is, the length of each tunable unit 131 and the ratio of the phase change region 1311 to the filling region 1312 therein are approximately equal. In other embodiments, multiple tunable units 131 may also be arranged so that the length in the direction of light field propagation continuously increases or decreases.

[0113] like Figure 4EAs shown, in some embodiments of the present invention, the multiple tunable units 131 can also be arranged so that the junction surfaces of the phase change region 1311 and the filling region 1312 are parallel to each other and have a preset tilt angle (not 90°) relative to the propagation direction of the light field. In different embodiments, the lengths of the multiple tunable units 131 (along the axis of the light field propagation direction) can be equal or unequal.

[0114] In this embodiment, the junction surface of the phase change region 1311 and the filling region 1312 is tilted, which can change the angle of the emitted light, for example Figure 4E As shown in FIG, the output waveguide 14 (the solid line in the middle is removed) is misaligned with the input waveguide 12 in the direction of light field propagation. The tilt angle of the interface between the phase change region 1311 and the filling region 1312 allows the output light to enter the output waveguide 14. This embodiment improves the degree of freedom in positioning the output waveguide 14 on the substrate 11 in the optical device 1, optimizes the structural size and layout of the optical device 1, and facilitates the coordination of the optical device 10 with other devices. For example, an optical fiber can be used as the output waveguide 14.

[0115] According to a preferred embodiment of the present disclosure, Figure 4F As shown, the grating 13 further includes at least one connecting unit 132, which is provided between the plurality of tunable units 131. One or more connecting units 132 may be provided in the grating 13, and the connecting unit 132 may separate the plurality of tunable units 131 into different parts. In the parts separated by the connecting unit 132, the parameters of the plurality of tunable units 131 may be the same or different, wherein the parameters include, for example, the number of tunable units 131, the length of each tunable unit 131 in the direction of light field propagation, the arrangement of the plurality of tunable units 131, etc. For example Figure 4F In the figure, the multiple tunable units 131 located on the left side of the connecting unit 132 are defined as the first part, and the multiple tunable units 131 located on the right side of the connecting unit 132 are defined as the second part, wherein the number of tunable units 131, the length change, the arrangement method, etc. of the multiple tunable units 131 in the first part can be the same as or different from those in the second part.

[0116] In this embodiment, by providing the connection unit 132 in the grating 13, the reflection peak (or transmission peak) of the grating 13 can be changed, forming a sudden valley value within the peak range, for example Figure 5D As shown in , the position corresponding to the peak value represents the reflection peak, while the valley value represents the transmission peak. By changing the number and position of the connecting units 132, the position of the transmission peak can be adjusted to meet the needs of the optical device 1. The specific selection can be based on the actual application scenario, for example, the design can be based on the coupled optical signal and the optical signal to be filtered out.

[0117] In this embodiment, the optical path provided by the length of the connecting unit 132 in the light field propagation direction is not equal to the optical path provided by the tunable unit 131, and the effective refractive index of the connecting unit 132 is not equal to the effective refractive index of the tunable unit 131. In a preferred embodiment, the length of the connecting unit 132 in the light field propagation direction can be set to an integer multiple of 1 / 4 of the length of the tunable unit 131a connected to the input waveguide 12 in the light field propagation direction ( Figure 4F (This is only an example and does not represent a length ratio relationship). The effective refractive index of the connecting unit 132 can be set to a fixed value, and the effective refractive index of the tunable unit 131 is not equal to the effective refractive index of the connecting unit 132 within an adjustable range.

[0118] In other embodiments, the multiple tunable units 131 can also be configured to have discontinuous changes in length in the direction of light field propagation. For example, near the input waveguide 12 and the output waveguide 14, the tunable units 131 can be configured to have equal lengths in the direction of light field propagation and be arranged periodically. In the middle area of ​​the grating 13, the lengths of the multiple tunable units 131 in the direction of light field propagation can be configured to be different, forming a jump structure.

[0119] According to a preferred embodiment of the present invention, the effective refractive indexes of the input waveguide 12 and the output waveguide 14 are fixed. Furthermore, the effective refractive indexes of the input waveguide 12 and the output waveguide 14 are equal, for example, the materials and structures of the input waveguide 12 and the output waveguide 14 are substantially the same. In this embodiment, the effective refractive indexes of the input waveguide 12 and the output waveguide 14 are greater than the effective refractive index of the substrate 11, and the effective refractive index of the filling region 1312 is set to be no less than the effective refractive index of the substrate 11. In some embodiments, the material of the substrate 11 includes one or more of silicon oxide on silicon, aluminum oxide, calcium fluoride, lithium niobate (e.g., lithium niobate single crystal thin film LNO I), and sapphire.

[0120] For example, in some embodiments, the nonvolatile phase change material includes Sb x Se y For example, the temperature required for Sb2Se3 to transform from amorphous to crystalline state is 150℃-550℃, and the heating time is 0.1min-5min. In the process of Sb2Se3 transforming from crystalline to amorphous state, a temperature of 600℃ or above is required and maintained for a certain time to completely transform Sb2Se3 into amorphous state and restore the initial state.

[0121] In a preferred embodiment, the phase change region 1311 absorbs less than 3 dB / mm of light energy within the wavelength range of the light beam coupled into the optical device 10. This helps reduce the loss of the optical signal passing through the phase change region 1311, thereby retaining a higher intensity of the light signal coupled out of the output waveguide 14. The amount of light energy absorbed by the phase change region 1311 within the wavelength range of the light beam coupled into the optical device 10 is related to the material of the phase change region 1311. For example, the material of the phase change region 1311 can be selected based on the wavelength range of the light beam coupled into the optical device 10.

[0122] According to some embodiments of the present invention, the cross-section of the input waveguide 12 and the output waveguide 14 in a plane perpendicular to the propagation direction of the light field is parallel to the center of the cross-section of the phase change region 1311 in a plane perpendicular to the propagation direction of the light field (for example, Figure 2A The positional deviation of the center of the rectangular cross-section shown in FIG1 is no greater than 20%, for example, 10%, and the cross-sectional dimensions of the input waveguide 12 and the output waveguide 14 in a plane perpendicular to the direction of light propagation deviate from the cross-sectional dimensions of the phase change region 1311 in a plane perpendicular to the direction of light propagation by no greater than 20%, for example, 10%. In practical applications, when the temperature of the phase change region 1311 is changed to adjust the effective refractive index of the phase change region 1311, the volume of the phase change region 1311 will also change. In this embodiment, the cross-sectional shapes of the input waveguide 12 and the output waveguide 14 are substantially aligned with the phase change region 1311 in a plane perpendicular to the direction of light propagation. During the process of adjusting the effective refractive index of the phase change region 1311, the alignment is maintained, preventing the phase change region 1311 from deviating from the input waveguide 12 and the output waveguide 14, thereby reducing energy loss of the optical signal propagating in the optical device 10.

[0123] like Figure 6 As shown, according to a preferred embodiment of the present invention, the optical device 10 further includes a heater 15 . The heater 15 is close to the grating 13 and is configured to change the temperature of the grating 13 , thereby changing the central wavelength of the reflection peak in the grating 13 .

[0124] In some embodiments, the heater 15 can be attached to the grating 13 to improve the efficiency of changing the temperature of the grating 13. For example, the heater 15 can be arranged to cover the top of the grating 13, or the heater 15 can be arranged to cover the top and both sides of the grating 13, such as Figure 6 As shown in FIG5 , heater 15 is disposed on substrate 11, and grating 13 is located between substrate 11 and heater 15. In other embodiments, heater 15 and grating 13 may be spaced apart to prevent heater 15 from absorbing the optical signal in grating 13, which would result in significant optical signal loss. The dotted lines in FIG5 represent the upper surface of substrate 11 and grating 13 that are blocked by heater 15.

[0125] like Figure 6 As shown, according to a preferred embodiment of the present invention, the heater 15 includes an electrode layer 151 and a power supply 152. In this embodiment, the electrode layer 151 covers the grating 13. The electrode layer 151 comprises, for example, a conductive material. In some embodiments, the material of the electrode layer 151 comprises, for example, one or more of TiN, W2N, ITO, FTO, W, Au, Cr, Ag, and Cu. The power supply 152 is electrically connected to the electrode layer 151. For example, electrical connection contacts 1511 are provided on the electrode layer 151. The power supply 152 flows a predetermined current into the electrode layer 151, causing the electrode layer 151 to generate Joule heat, which is used to change the temperature of the grating 13.

[0126] In some preferred embodiments of the present invention, the preset current supplied by power supply 152 to electrode layer 151 is a pulsed current. Power supply 152 can be configured to control the temperature and duration of heating of grating 13 by varying the magnitude, pulse width, and number of pulses supplied to electrode layer 151, thereby improving the precision of temperature control of grating 13, thereby maintaining the temperature of grating 13 stable and maintaining the effective refractive index of grating 13 within a preset range, thereby improving tuning precision and accuracy. Specifically, for example, in the aforementioned embodiment, the material of phase change region 1311 is Sb2Se3, and the required temperature for transitioning from an amorphous state to a crystalline state is 200°C-350°C, with a heating time of 0.1 min-5 min. Multiple pulsed currents with relatively low amplitudes can be applied to uniformly heat phase change region 1311. The transition from crystalline to amorphous state of Sb2Se3 requires a temperature of 600°C or above. A small number of pulsed currents with relatively high amplitudes and relatively small widths can be applied to rapidly convert Sb2Se3 to an amorphous state, restoring the initial state.

[0127] According to a preferred embodiment of the present invention, Figure 6 and Figure 7 As shown, the heater 15 further includes an intermediate layer 153, which is located between the grating 13 and the electrode layer 151. The material of the intermediate layer 153 can be a transparent material within the wavelength range of the light beam coupled into the optical device 10, wherein the transparent material means a material through which the light beam coupled into the optical device 10 can pass, and its extinction coefficient k is, for example, less than 10 -2 Preferably, the extinction coefficient k of the transparent material is less than 10 -5 For example, the absorption of light waves is less than 3 dB / mm, and the thermal conductivity of the material of the intermediate layer 153 is greater than 1 W / (m·K). Specifically, in some embodiments, the material of the intermediate layer 153 may include one or more of Al2O3, SiO2, and Si3N4.

[0128] In this embodiment, the intermediate layer 153 can reduce optical signal loss between the grating 13 and the heater 15, preventing the electrode layer 151 from being directly formed on the grating 13, which would otherwise absorb a large amount of the optical signal. Furthermore, the intermediate layer 153 can ensure efficient heat conduction between the electrode layer 151 and the grating 13, enabling the grating 13 to quickly adjust its effective refractive index.

[0129] According to a preferred embodiment of the present invention, the effective refractive indexes of the input waveguide 12 and the output waveguide 14 in the optical device 10 are both greater than the effective refractive index of the intermediate layer 153, and the effective refractive index of the phase change region 1311 is always greater than the effective refractive index of the intermediate layer 153 within the entire variation range, and the effective refractive index of the filling region 1312 is not less than the effective refractive index of the intermediate layer 153, so as to reduce the optical signal entering the intermediate layer 153 and reduce the loss.

[0130] In some embodiments, the filling region 1312 and the intermediate layer 153 can be configured to be formed of the same material. For example, when preparing the optical device 10 , after forming the phase change region 1311 , the filling region 1312 and the intermediate layer 153 are formed at the same time, which is beneficial to simplify the preparation process of the optical device 10 .

[0131] The optical device 10 of the present invention can be used as a tunable filter. For example, a signal source is located upstream of the input waveguide 11 in the optical device 10 and is capable of emitting a light beam (a broad spectrum requiring filtering). The signal source is not limited to an active light source; the signal source can also receive light signals from other light sources, or the light beam can be reflected or refracted and then coupled into the optical device 10 by the signal source.

[0132] The length ratio of the long side to the short side of the cross section of the phase change region 1311 in the optical device 10 in a plane perpendicular to the light field direction is determined according to the central wavelength of the light beam emitted by the signal source 20 .

[0133] In some embodiments, the wavelength of the light beam emitted by the signal source is a range value, and the optical device 10 can be used to filter (or select) a light beam of a desired wavelength within the wavelength range. According to specific needs, the effective refractive index of the phase change region 1311 in the optical device 10 is changed so that the light beam of the desired wavelength is coupled out of the optical device 10 or reflected within the optical device 10 to achieve a filtering effect.

[0134] The present invention also relates to a laser external cavity. Figure 8 As shown, the laser external cavity 1 includes the optical device 10, the input end 20 and the output end 30 as described in the above embodiments.

[0135] The laser beam can be coupled into the laser external cavity 1 through the input end 20, and can be coupled out of the laser external cavity 1 through the output end 30. The optical device 10 is located between the input end 20 and the output end 30. The laser beam coupled into the laser external cavity 1 has a wide wavelength range. After the laser beam is coupled into the optical device 10, by adjusting the effective refractive index of the phase change region 1311 in the optical device 10, some wavelengths of light within the wide wavelength range of the laser beam can be transmitted or reflected and coupled out of the output end 30. The optical device 10 can be used to control the wavelength of the emitted laser beam.

[0136] In some embodiments, the input end 20, optical device 10, and output end 30 in the laser external cavity 1 are not limited to being arranged in a linear arrangement. The optical device 10 being located between the input end 20 and the output end 30 means that the optical device 10 is located between the optical path of the input end 20 and the output end 30, rather than between the physical locations. For example, in some embodiments, the laser beam reflected by the optical device 10 can be coupled out through the output end 30.

[0137] The present invention also relates to a laser 2, Figure 9 The structure of the laser 2 in some embodiments of the present invention is shown below. Figure 9 The laser 2 will be described.

[0138] The laser 2 includes the laser external cavity 1 and the gain region 40 as shown in the aforementioned embodiment. The gain region 40 is configured to amplify the energy of the laser beam when it passes through the gain region 40. Specifically, the gain region 40 includes, for example, a gain medium. The gain medium may include, for example, erbium-doped aluminum oxide, and when the light beam passes through the gain medium, it is excited and the energy of the light beam is amplified. The laser external cavity 1 in this embodiment can resonate a laser beam of a specific wavelength. The light beam in the cavity will partially transmit back to the gain region, so that the laser beam can pass through the gain region 40 multiple times, amplifying the energy of the laser beam and meeting the use requirements of the laser 2. Part of it is directly emitted from the output end, achieving the function of tunable output wavelength.

[0139] For example Figure 9 As shown in the figure, a reflector is provided on one side of the gain region 40, and the laser external cavity 1 is provided on the other side of the gain region 40. After the laser beam is coupled into the laser external cavity 1, a partially compensated beam is coupled out from the right side, and the beam of another portion of the wavelength is reflected by the laser external cavity 1 and reflected multiple times between the reflector and the laser external cavity 1, passing through the gain region 40 multiple times, thereby amplifying the energy of the laser beam of a portion of the wavelength.

[0140] In some embodiments, the gain region 40 is located within the laser external cavity 1, for example, the gain region 40 is located between two optical devices 10, and the laser beam can be reflected multiple times between the two optical devices 10. In some embodiments, the gain region 40 can also be integrated into the optical device 10, for example, the gain region 40 is integrated into the grating 13.

[0141] In this embodiment, the laser external cavity 1 can change the wavelength of the cavity resonance by adjusting the effective refractive index of the phase change region 1311 in the optical device 10 therein, so that part of the light beam in the cavity is emitted from the right output end and part is output from the left to the gain region, so that the light beam of a specific wavelength in the light beam is amplified by the gain region 40 and part is emitted from the right output end. In some embodiments, for example Figure 9 As shown in FIG, the shadow-filled area on the right is the laser external cavity 1. Preferably, the shadow-filled area in the middle filled with vertical lines is a jump structure.

[0142] The present invention also relates to a method for preparing an optical device. Figure 10 The process of the method 100 for preparing an optical device according to some embodiments of the present invention is shown, which is used to prepare the optical device 10 as described in the above embodiments. Figure 10 A method 100 for manufacturing an optical device will be described.

[0143] like Figure 10 As shown, in step S101, the wavelength range of the light beam coupled into the optical device is obtained. For example, if the optical device is used in a tunable filter, the operating wavelength of the tunable filter can be designed according to the use requirements of the tunable filter, such as determining the range of the transmission peak center wavelength of the tunable filter.

[0144] In step S102, a phase change material is determined based on the wavelength range of the light beam coupled into the optical device. Different phase change materials have different effective refractive indices and adjustable ranges of effective refractive indices. Based on the wavelength range of the light beam coupled into the optical device, the range of variation of the central wavelength of the reflection peak (or transmission peak) is determined, and a phase change material that is adjustable within this range of the central wavelength is selected. In some embodiments, the phase change material can be a single compound, such as in the aforementioned embodiments, or a mixture of multiple compounds.

[0145] In step S103, the structural parameters of the grating in the optical device are calculated based on the wavelength range of the light beam coupled into the optical device and the material parameters of the phase change material. The material parameters of the phase change material include the effective refractive index of the phase change material, and the structural parameters of the grating include the structural dimensions of the tunable unit, the number of tunable units, and the length relationship of the multiple tunable units in the direction of light field propagation. The effective refractive index of the grating is related not only to the effective refractive index of the phase change material, but also to the structural parameters of the grating. For example, in the aforementioned embodiment, the effective refractive index of the tunable unit is obtained by taking a weighted average of the effective refractive index of the phase change region and the effective refractive index of the filling region.

[0146] In step S104, an optical device is prepared according to the structural parameters of the grating. In different embodiments, the optical device can be prepared in different ways, for example, it can be prepared by etching, sputtering deposition, evaporation and other processes. The present invention does not limit the processing method of the optical device. In a preferred embodiment of the present invention, the optical device can be prepared by a photolithography deposition process, which will be specifically described in subsequent embodiments.

[0147] Figure 11 The process of preparing an optical device S104 according to a preferred embodiment of the present invention is shown below. Figure 11 Step S104 is described below.

[0148] In step S1041, a substrate is provided. The substrate can be, for example, a sheet or plate with a stable structure and a flat surface. The substrate can also be processed into various structures. For example, a groove can be formed at the position corresponding to the grating, and the grating can be sunken into the groove, so that the upper surface of the grating does not protrude from the surface of the substrate. In other embodiments, the substrate can also be processed to have a cavity, with the grating partially or entirely located above the cavity, suspended relative to the substrate, to reduce the loss caused by the optical signal entering the substrate.

[0149] In step S1042, an input waveguide and an output waveguide are formed on the surface of the substrate. The input waveguide and the output waveguide can be formed on the surface of the substrate by etching or pasting. In some embodiments, the input waveguide and the output waveguide can be configured to have substantially the same structure made of the same material, for example, a substantially rectangular parallelepiped shape.

[0150] In subsequent steps, a tunable unit is formed between the input waveguide and the output waveguide according to the structural parameters of the grating. According to a preferred embodiment of the present invention, the process of forming the tunable unit includes the following steps.

[0151] In step S1043, photoresist is coated on the substrate. Specifically, the photoresist can be coated on the entire surface of the substrate, or can be coated at positions corresponding to the grating, as long as the position of the grating is covered.

[0152] In step S1044, the area corresponding to the position of the tunable unit is exposed, and the photoresist in the exposed area is removed to form a groove on the substrate. The position of the groove corresponds to the position of the tunable unit, so as to facilitate the formation of the tunable unit on the substrate in subsequent steps.

[0153] In step S1045, a phase change material is deposited at a corresponding position of the tunable unit to form a phase change region. For example, a target made of the phase change material is formed at the position corresponding to the phase change region by sputtering or vacuum coating. For the filling region in the tunable unit, the position corresponding to the filling region can be formed by shielding or removing a portion of the phase change material at the position where the phase change material was deposited.

[0154] In step S1046, all photoresist and excess material are removed. The excess material represents the phase change material deposited on the photoresist in step S1045. In step S1047, a fill region is formed at the corresponding position of the tunable element, for example, by deposition. In various embodiments, steps S1046 and S1047 are performed in any order.

[0155] According to a preferred embodiment of the present invention, the method 100 for manufacturing an optical device further includes step S105 of forming a heater on the grating, for example, by pasting, welding or forming an electrode layer in the heater on the grating by other means.

[0156] Figure 12 The process of forming a heater in step S105 according to a preferred embodiment of the present invention is shown below. Figure 12 Step S105 will be described.

[0157] In step S1051, an intermediate layer is formed on the grating surface. The intermediate layer can be formed by deposition or attached to the surface of the grating or the grating and substrate. The material of the intermediate layer can be selected according to the above embodiments. Preferably, the intermediate layer is arranged to be bonded to the grating surface.

[0158] In step S1052, photoresist is coated on the surface of the intermediate layer away from the grating. Preferably, in this step, photoresist is coated on the entire surface of the intermediate layer away from the grating.

[0159] In step S1053, the area at the preset position is exposed, and the photoresist in the exposed area is removed. The preset position is the position of the electrode layer, which can be arranged to correspond to the position of the grating. Furthermore, the electrode layer can also include electrical connection contacts to facilitate connection between the electrode layer and a power source.

[0160] In step S1054, a conductive material is deposited at a predetermined location to form an electrode layer. The process for depositing the conductive material in this step can be substantially the same as the process for depositing the phase change material in the aforementioned embodiment, with the electrode layer formed on the surface of the intermediate layer using vacuum coating. In some embodiments, electrical connection contacts can be formed on the intermediate layer by simultaneous deposition. In other embodiments, the electrical connection contacts can also be welded to the conductive material deposited on the intermediate layer.

[0161] In step S1055 , all the photoresist and excess material are removed, wherein the excess material refers to the conductive material deposited on the photoresist in step S1054 .

[0162] Furthermore, a power source may be provided, and the electrode layer may be connected to the power source via electrical connection contacts. The power source may be configured to supply a preset current, preferably a pulse current, to the electrode layer.

[0163] Finally, it should be noted that the above descriptions are merely embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An optical device comprising a phase change material, characterized in that: include: A substrate, an input waveguide located on the substrate, a grating connected to the input waveguide along a light field propagation direction, and an output waveguide connected to the other side of the grating; The grating includes a plurality of tunable units arranged linearly along the direction of the light field, and the tunable units include a phase change region and a filling region; The phase change region is configured such that its effective refractive index changes with temperature; a cross-sectional shape of the phase change region in a plane perpendicular to the direction of the light field comprises a long side and a short side, the long side is parallel to the surface of the substrate, and the short side is perpendicular to the surface of the substrate; a ratio of the lengths of the long side to the short side is not less than 3, and the ratio of the lengths of the long side to the short side is determined based on the central wavelength of a light beam coupled into the optical device; and the phase change material comprises one or more of a chalcogen compound or a chalcogen element; The output waveguide and the input waveguide are both formed on the substrate; and the phase change region is attached to the surface of the substrate.

2. The optical device according to claim 1, wherein: The length of the phase change zone along the propagation direction of the light field satisfies m*l=lambda / (2*n), where m is an integer, l is the length of the tunable unit, lambda is the initial center wavelength of the light beam coupled into the optical device, and n is the effective refractive index of the tunable unit, which is basically determined based on the area-weighted average of the effective refractive index of the phase change zone and the effective refractive index of the filling zone.

3. The optical device according to claim 2, wherein: wherein m is less than 10.

4. The optical device according to claim 1, wherein In the cross-sectional shape of the phase change region in a plane perpendicular to the light field direction, the length of the short side is not less than 30 nm and not more than 220 nm; and the ratio of the length of the long side to the short side is greater than 5.

5. The optical device according to claim 4, characterized in that Wherein, in the cross-sectional shape of the phase change region in a plane perpendicular to the direction of the light field, the sizes of the long side and the short side are configured to support coupling into the fundamental mode transmission of the working wavelength of the optical device.

6. The optical device according to claim 1, wherein: The ideal shape of the phase change region is a rectangular parallelepiped, and the filling region fills other regions in the tunable unit except the phase change region.

7. The optical device according to claim 1, wherein: The ideal shape of the phase change zone is a preset shape, the cross-sectional shape of the preset shape in a plane perpendicular to the direction of the light field changes along the direction of the light field, the cross-sectional shape of the preset shape in a plane perpendicular to the direction of the light field is a rectangle, and the short sides of the rectangles at different positions along the propagation direction of the light field are approximately equal in length, and the ratio of the length of the longest side to the short side of the rectangle is not less than 5.

8. The optical device according to claim 6, wherein: The junction surfaces of the phase change regions and the filling regions in the plurality of tunable units are parallel to each other, and the junction surfaces of the phase change regions and the filling regions are perpendicular to the propagation direction of the light field. The lengths of the plurality of tunable units in the light field propagation direction are equal; or The lengths of the plurality of tunable units in the light field propagation direction increase or decrease continuously.

9. The optical device according to claim 1, wherein: The junction surfaces of the phase change region and the filling region in the plurality of tunable units are parallel to each other, the junction surfaces of the phase change region and the filling region have a preset tilt angle with the propagation direction of the light field, and the position of the output waveguide corresponds to the tilt direction of the junction surface of the phase change region and the filling region.

10. The optical device according to claim 8, wherein: The grating further includes at least one connecting unit, which is arranged between the multiple tunable units. The optical path provided by the length of the connecting unit in the direction of light field propagation is not equal to the optical path provided by the length of the tunable unit in the direction of light field propagation; and the effective refractive index of the connecting unit is not equal to the effective refractive index of the tunable unit.

11. The optical device according to any one of claims 1 to 10, characterized in that: The material of the phase change region is a non-volatile phase change material, which switches between a crystalline state and an amorphous state as the temperature changes, and the switching process is reversible.

12. The optical device according to any one of claims 1 to 10, characterized in that: The positional deviation between the cross-sections of the input waveguide and the output waveguide in a plane perpendicular to the light field propagation direction and the center of the cross-section of the phase change region in the plane perpendicular to the light field propagation direction is no more than 20%, and the cross-sectional dimensions of the input waveguide and the output waveguide in a plane perpendicular to the light field propagation direction and the cross-sectional dimensions of the phase change region in the plane perpendicular to the light field propagation direction are no more than 20%.

13. The optical device according to any one of claims 1 to 10, characterized in that: The material of the substrate includes one or more of silicon oxide on silicon, aluminum oxide, calcium fluoride, lithium niobate, and sapphire.

14. The optical device according to any one of claims 1 to 10, characterized in that: Also includes: A heater is located near the grating and is configured to change the temperature of the grating to change the central wavelength of a reflection peak or a transmission peak in the grating.

15. The optical device according to claim 14, wherein: The heater comprises: an electrode layer covering the grating; and A power supply is electrically connected to the electrode layer and is configured to pass a preset current into the electrode layer to change the temperature of the grating by causing the electrode layer to generate Joule heat.

16. The optical device according to claim 15, characterized in that The heater further comprises: An intermediate layer is located between the grating and the electrode layer.

17. The optical device according to claim 16, wherein: The material of the intermediate layer includes a transparent material within the wavelength range of the light beam coupled into the optical device; the material of the electrode layer includes TiN x , one or more of W2N, ITO, FTO, W, Au, Cr, Ag and Cu.

18. The optical device according to claim 17, wherein: The effective refractive index of the input waveguide and the output waveguide in the optical device is greater than the effective refractive index of the intermediate layer; the effective refractive index of the phase change zone is always greater than the effective refractive index of the intermediate layer within the entire variation range; and the effective refractive index of the filling zone is not less than the effective refractive index of the intermediate layer.

19. The optical device according to any one of claims 15 to 18, characterized in that: The preset current is a pulse current, and the power supply controls the temperature and time of the grating heating by changing the size, pulse width and number of pulses of the pulse voltage passed into the electrode layer to change the effective refractive index of the grating.

20. A laser external cavity, characterized in that: include: An input end, through which the laser beam is coupled into the laser external cavity; an output end, through which the laser beam is coupled out of the laser external cavity; The optical device according to any one of claims 1 to 19, wherein the optical device is arranged between the input end and the output end; The optical device is configured to selectively resonate a laser beam of a specific wavelength and transmit or reflect it by adjusting the effective refractive index.

21. A laser, characterized in that: include: The laser external cavity according to claim 20; a gain region configured to amplify energy of the laser beam when the laser beam passes through the gain region; The optical device is configured to adjust the effective refractive index so that light of a specific wavelength in the light beam passes through the gain region multiple times.

22. A method for preparing an optical device, characterized in that: For preparing an optical device according to any one of claims 1 to 19, the preparation method comprising: Obtaining a wavelength range of a light beam coupled into the optical device; determining a phase change material according to a wavelength range of a light beam coupled into the optical device; Calculating structural parameters of a grating in the optical device according to a wavelength range of a light beam coupled into the optical device and material parameters of a phase change material; Optical devices are prepared according to the structural parameters of the grating.

23. The preparation method according to claim 22, characterized in that The steps of preparing the optical device include: providing a substrate; Processing the surface of the substrate to form an input waveguide and an output waveguide; According to the structural parameters of the grating, a plurality of tunable units are formed between the input waveguide and the output waveguide; wherein the structural parameters of the grating include the structural size of the tunable unit, the number of the tunable units, and the length relationship of the plurality of tunable units in the propagation direction of the light field.

24. The preparation method according to claim 22, characterized in that The step of forming a plurality of tunable units comprises: coating a photoresist on a substrate; exposing the area corresponding to the position of the tunable unit and removing the photoresist in the exposed area; Depositing phase change material at corresponding positions of the tunable unit to form a phase change region; Remove all photoresist and excess materials; A filling area is formed at a corresponding position of the tunable unit.

25. The preparation method according to claim 24, characterized in that Also includes: forming a heater on the grating; The step of forming a heater on the grating comprises: forming an intermediate layer on the grating surface; Coating a photoresist on a surface of the intermediate layer away from the grating; Exposing an area at a preset position and removing the photoresist in the exposed area; Depositing a conductive material at a preset position to form an electrode layer; Remove all photoresist and excess material.

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