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

Abstract

The invention provides an optical device containing a phase change material, a laser external cavity and a preparation method of the optical device. The optical device comprises a substrate, an input waveguide located on the substrate, a grating connected with the input waveguide in the light field propagation direction, and an output waveguide connected to the other end of the grating. The grating comprises a plurality of tunable units which are linearly arranged in the light field direction, and each tunable unit comprises a phase change area and a filling area. Wherein the phase change region is configured to change the effective refractive index along with the temperature change; the section shape of the phase change region in a plane perpendicular to the light field direction 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 is determined according to the central wavelength of a light beam coupled into the optical device. The embodiment of the invention has the advantages of simple structure and small occupied space, and is beneficial 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 many fields due to their small size, high integration, high mode confinement factor, and advantages in imaging, communication, etc. Among them, wavelength-selective optical devices can select light of a specific wavelength from the input wide spectrum for subsequent transmission, and can be used in devices such as filters and lasers.

[0003] At present, most optical devices that can achieve wavelength selection are fixed selections, that is, the wavelength of transmission or reflection has been determined during the design of the optical device, and after processing, only one or some fixed wavelengths can be selected and cannot be adjusted. A small number of optical devices are tunable wavelength-selective, which are generally tuned by microrings, MZI (Mach-Zehnder interferometer) and other devices combined with thermo-optical effects, but the tunable range that can be achieved is small, and the size of the optical device is large, which is not conducive to high integration.

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

[0005] In view of one or more defects 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 light field direction, and the tunable units include a phase change region and a filling region;

[0007] The phase change zone is configured so that the effective refractive index changes with temperature; the cross-sectional shape of the phase change zone 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 chalcogenide compound or a chalcogenide element.

[0008] According to one aspect of the present invention, 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, and lambda is the initial central 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 zone in a plane perpendicular to the light field direction, the length of the short side is not less than 30nm and not more than 220nm; 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 light field direction changes along the light field direction, the cross-sectional shape of the preset shape in a plane perpendicular to the light field direction is a rectangle, and the short sides of the rectangles at different positions along the propagation direction of the light field are approximately equal, 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 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.

[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 joining surfaces of the phase change zone and the filling zone in the plurality of tunable units are parallel to each other, the joining surfaces of the phase change zone and the filling zone have a preset inclination angle with the propagation direction of the light field, and the position of the output waveguide corresponds to the inclination direction of the joining surface of the phase change zone and the filling zone.

[0018] According to one aspect of the present invention, the grating further comprises at least one connecting unit, wherein the connecting unit is disposed between a plurality of the tunable units, and an optical path provided by a length of the connecting unit in a light field propagation direction is not equal to an optical path provided by a length of the tunable unit in the light field propagation direction; and an effective refractive index of the connecting unit is not equal to an 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, and the non-volatile phase change material switches between a crystalline state and an amorphous state with temperature changes, and the switching process is reversible.

[0020] According to one aspect of the present invention, the position deviation between the cross-section of the input waveguide and the output waveguide in the plane perpendicular to the light field propagation direction and the cross-section center of the phase change zone in the plane perpendicular to the light field propagation direction is not greater than 20%, and the cross-sectional dimensions of the input waveguide and the output waveguide in the plane perpendicular to the light field propagation direction and the cross-sectional dimensions of the phase change zone in the plane perpendicular to the light field propagation direction are not greater 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 comprises:

[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, the electrode layer covering the grating; and

[0026] A power source 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, 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 complete 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 also 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 mentioned 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] A laser external cavity as described above;

[0039] a gain region, the gain region being 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] Acquire the wavelength range of the 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 at the corresponding position of the tunable unit, and removing the photoresist in the exposed area;

[0053] Depositing phase change material at a corresponding position 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 with the prior art, the embodiment of the present invention provides an optical device including a phase change material, wherein the grating in the optical device includes a plurality of tunable units, and the effective refractive index of the phase change region in the tunable unit changes with temperature. By controlling the temperature of the tunable unit, the refractive index of the grating can be changed, thereby changing the transmittance of light signals of different wavelengths in the grating, and the tunable function can be realized when applied to a filter. In addition, the optical device in this embodiment has a simple structure and occupies a small space. At the same time, the tunability is realized by changing the effective refractive index, which is conducive to reducing the loss of light signals propagating in the grating.

[0063] The present invention also includes an embodiment of a laser external cavity, which uses the aforementioned optical device to select a laser beam of a specific wavelength for resonance and transmission or reflection 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 A schematic diagram showing the structure of an optical device in some embodiments of the present invention is shown;

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

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

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

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

[0072] Figure 6 A schematic diagram showing the structure 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 A block diagram of the structure of the laser external cavity in some embodiments of the present invention is shown;

[0075] Fig. 9 Shown is a schematic diagram of the structure of a laser in some embodiments of the present invention;

[0076] Fig.10 A schematic diagram showing a process of a method for preparing an optical device in some embodiments of the present invention;

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

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

[0079] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0080] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0081] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0082] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0083] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0084] The embodiments of the present invention are described below 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 a 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. Figure 1A-Figure 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 1 (from left to right in the figure) is arranged between the input waveguide 12 and the output waveguide 14. Light can be coupled in by the input waveguide 12, pass through the grating 13, and then be coupled out by the output waveguide 14. In different embodiments of the present invention, the input waveguide 12 and the output waveguide 14 can be aligned in the direction of light field propagation, or the output waveguide 14 can be arranged to deviate from the input waveguide 12, which will be described in detail in the subsequent embodiments.

[0087] The grating 13 includes a plurality of tunable units 131 arranged linearly along the direction of the light field, and the tunable unit 131 includes a phase change region 1311 and a filling region 1312. The phase change region 1311 is configured such that the effective refractive index changes with temperature, and the effective refractive index represents the ratio of the reflectivity and the refractive index of the light when it is incident on the phase change region 1311. For example, by changing the temperature of the phase change region 1311, or keeping 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, and accordingly, the wavelength of the light transmitted through the phase change region 1311 changes, so as to filter the light of different wavelengths. The phase change region 1311 may include a phase change material, and the phase change material is illustrated by way of example in the 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. 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 includes, for example, 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 light field direction ( Figure 1A and Figure 1BThe cross-sectional shape in the direction perpendicular to the light field (in the direction roughly horizontal) 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, 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 roughly a rectangle (an ideal shape, without considering the deviation caused by factors such as processing technology), wherein the long side represents the long side of the rectangle, which is parallel to the surface of the substrate 11, and the short side represents the short side of the rectangle, which is perpendicular to the surface of the substrate 11. The actual processed shape of the phase change region 1311 is described in the subsequent embodiments. In actual production, due to the limitation of the processing accuracy, the cross-sectional shape of the phase change region 1311 in the direction perpendicular to the light field may have convexities or concavities. In some embodiments, the long side can represent the average value, maximum value, minimum value, etc. of the length of the phase change region 1311 in the direction parallel to the surface of the substrate 11; the short side can represent the average value, maximum value, minimum value, etc. 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 Figure 1A The rectangular shape (ideal shape) shown in the figure can also be set to be inclined relative to the light field direction (non-vertical). For example, the phase change region 1311 is roughly a parallelogram (ideal shape), and its cross-section perpendicular to the light field direction is also roughly a rectangle, which is specifically described in subsequent embodiments.

[0091] In this embodiment, the ratio of the length of the long side to the short side of the cross-sectional shape of the phase change region 1311 in the direction perpendicular to the light field is not less than 3. Preferably, the size of the phase change region 1311 in the direction parallel to the surface of the substrate 11 is much larger than the size 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 according to the central wavelength of the light beam coupled into the optical device 10.

[0092] Specifically, in some embodiments, it can be determined according to 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, a designed operating wavelength range of the tunable filter, wherein the length ratio of the long side to the short side can be determined according to 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 light field direction increases accordingly, for example, the width of the phase change zone 1311 is increased.

[0094] Take the optical device 10 as a tunable filter, or use it in a tunable filter as an example. The existing tunable filter using phase change materials mainly covers a small area of ​​phase change material on the core layer of the waveguide, and uses the phase change material to disturb the light field in the core layer of the waveguide, and the adjustment range of the center wavelength (peak wavelength in the output light) is small. In this embodiment, the light passes through the phase change zone 1311, and the change in the effective refractive index of the phase change zone 1311 has a greater impact on the center wavelength. The phase change zone 1311 is used to strongly modulate the light field, so that a larger adjustable range of the center wavelength can be achieved.

[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 the cross section perpendicular to the light field direction is large, and the long side of the phase change region 1311 (e.g., the long side of the rectangular cross-sectional shape) is one to two orders of magnitude larger than the short side (e.g., the short side of the rectangular cross-sectional shape). For example, in the cross-sectional shape of the phase change region 1311 in the plane perpendicular to the light field direction, the length of the short side is not less than 30nm and less than 220nm, such as 60nm, 80nm, 100nm, 150nm, 200nm, 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, the ratio of the length of the long side to the short side of the phase change zone 1311 in the cross section perpendicular to the light field direction is increased, which is conducive to reducing the volume of the optical device 10, and providing an optical device 10 with a thickness (the size of the short side in the direction perpendicular to the substrate 11, such as the short side of the rectangular cross section) much smaller than that of a conventional waveguide, which is not only conducive to miniaturization, reducing the difficulty of processing, and improving stability, but also can improve the working performance of the optical device 10. For example, by reducing the length of the short side of the phase change zone 1311 in the cross section perpendicular to the light field direction (i.e., the thickness of the phase change zone 1311 on the substrate 11), when the effective refractive index of the phase change zone 1311 needs to be changed, the temperature change speed of the phase change zone 1311 can be increased, the energy consumption can be reduced, and the temperature change of the phase change zone 1311 can be made 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 zone 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 changes occur, 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 lengths of the phase change zone 1311 and the filling zone 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 is used 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, and 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 zone 1311 and the effective refractive index of the filling zone 1312, wherein the area represents the area of ​​the phase change zone 1311 (and the filling zone 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 penetrate the phase change region 1311 in the long side direction of the phase change region 1311, so that adjacent tunable units 131 are spaced apart from each other, and the cross-sectional areas of the phase change region 1311 and the filling region 1312 perpendicular to the light field propagation direction are equal, and the weights of the two are equal. In some embodiments, the filling region 1312 is air or vacuum, wherein the cross-sectional area of ​​the filling region 1312 perpendicular to the light field propagation direction is set to be equal to the cross-sectional area of ​​the phase change region 1311 perpendicular to the light field propagation direction.

[0100] According to a preferred embodiment of the present invention, in the cross-sectional shape of the phase change zone 1311 in the plane perpendicular to the direction of the light field, the sizes of the long side and the short side are determined according to the working wavelength of the light beam coupled into the optical device 10, so that the working wavelength of the light beam coupled into the optical device 10 maintains fundamental mode transmission in the phase change zone 1311. Specifically, for example, when the optical device 10 is used in a laser, the sizes of the long side and the short side are determined according to the designed emission wavelength of the laser. Preferably, in the cross-sectional shape of the phase change zone 1311 in the plane perpendicular to the direction of the light field, the sizes of the long side and the short side are configured to only support the fundamental mode transmission of the working wavelength of the light beam coupled into the optical device 10 in the phase change zone 1311, which can prevent the occurrence of multiple peaks or valleys, so as to meet the use requirements of the optical device 10.

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

[0102] Figure 3A and Figure 3B The cross-sectional schematic diagram of the phase change region 1311 actually processed according to some embodiments of the present invention is shown. Due to the small size of the phase change region 1311 and the limitation of the existing processing technology, the structural shape of the phase change region 1311 actually processed 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 the target material, resulting in Figure 3A As shown in , there may be a collection of bulges at the edges and bulges or depressions in the middle. Figure 3B As shown in , the thickness decreases at the edge and there is a convexity or concavity in the middle part. Figure 3A and Figure 3B The cross-sectional shape of the phase change region 1311 shown in FIG. 1 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 positions 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 shape 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 positions of the cross section of the phase change region 1311; or the length of the short side conforms to the normal distribution, and the length of the 80% quantile is used as the length of the short side.

[0104] The cross-sectional shape deviation of the phase change region 1311 caused by the processing technology has a certain influence on the emitted light. Optimizing the processing accuracy can control the influence within an acceptable range, but it cannot be completely avoided with the existing technical level. In the subsequent embodiments, the ideal shape of the cross-sectional shape of the phase change region 1311 is used as an example for explanation, and the influence of the processing error on the emitted light is not considered. The ideal shape represents the shape of the phase change region 1311 when designing the optical device 10.

[0105] Figure 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 zone 1311 in the tunable unit 131 can be roughly set to a rectangular shape. Preferably, the joint surfaces of the phase change zone 1311 and the filling zone 1312 in multiple tunable units 131 can be set to be parallel to each other, and the joint surfaces of the phase change zone 1311 and the filling zone 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 plurality of tunable units 131 may be designed to have substantially equal shapes and sizes, or as 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 light field propagation direction are equal, and the multiple tunable units 131 are arranged periodically along the light field propagation direction. 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 coupled out of the optical device 10 changes. Figure 5A The figure shows the central wavelengths of three different reflection peaks, which does not limit the optical device 10 to be able to switch only between three different central wavelengths. In this embodiment, the effective refractive index n of the tunable unit 131 changes continuously, and the central 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 of 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 be continuously decreased. 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 some 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 of 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 specific application scenarios.

[0111] The cross-sectional shape of the phase change zone 1311 in this embodiment in any plane perpendicular to the light field direction is a rectangle, but the length and width of the rectangular cross section may vary. Preferably, the short sides (dimensions perpendicular to the substrate 11) in the rectangular cross section can be set to be approximately equal, that is, in this embodiment, the thickness of the phase change zone 1311 at different positions 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 value of the 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, the size deviation is not greater than 20%.

[0112] For the phase change zone 1311 of a non-rectangular shape, the multiple tunable units 131 can be arranged periodically, that is, the length of each tunable unit 131, and the ratio of the phase change zone 1311 and the filling zone 1312 therein are approximately equal. In other embodiments, the multiple tunable units 131 can 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 plurality of tunable units 131 may also be arranged so that the joint 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 (axis along the propagation direction of the light field) of the plurality of tunable units 131 may be equal or unequal.

[0114] In this embodiment, the junction surface of the phase change region 1311 and the filling region 1312 is tilted, so that the angle of the emitted light can be changed, for example Figure 4E As shown in the figure, the output waveguide 14 (the solid line in the middle is removed) is not aligned with the input waveguide 12 in the propagation direction of the light field, and the output light enters the output waveguide 14 through the inclination angle of the joint surface of the phase change region 1311 and the filling region 1312. This embodiment is conducive to improving the degree of freedom of setting the position of the output waveguide 14 on the substrate 11 in the optical device 1, is conducive to optimizing the structural size and layout of the optical device 1, and is conducive to the cooperation of the optical device 10 with other devices. For example, the output waveguide 14 can be selected as an optical fiber.

[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 arranged between the plurality of tunable units 131. One or more connecting units 132 may be arranged in the grating 13, and the connecting unit 132 may separate the plurality of tunable units 131 into different parts, wherein the parameters of the plurality of tunable units 131 in the parts separated by the connecting unit 132 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 propagation direction of the light field, 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 variation, the arrangement method, etc. of the multiple tunable units 131 in the first part may 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, and a sudden valley value is formed within the peak value range, for example Figure 5D As shown in , the position corresponding to the peak value represents the reflection peak, and 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 so that the optical device 1 meets the use requirements. 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 among the multiple tunable units 131 ( Figure 4F (The figure is only an example and does not represent the 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 the adjustable range.

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

[0119] According to a preferred embodiment of the present invention, the effective refractive index of the input waveguide 12 and the output waveguide 14 is a fixed value, and further, the effective refractive index of the input waveguide 12 and the output waveguide 14 is equal, for example, the material and structure of the input waveguide 12 and the output waveguide 14 are substantially the same. In addition, in this embodiment, the effective refractive index of the input waveguide 12 and the output waveguide 14 is greater than the effective refractive index of the substrate 11, and the effective refractive index of the filling area 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 (for example, 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 is 150℃-550℃, and the heating time is 0.1min-5min. In the process of Sb2Se3 transforming from crystalline to amorphous, 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 energy absorption of light in the phase change region 1311 is less than 3 dB / mm within the wavelength range of the light beam coupled into the optical device 10, which is beneficial to reduce the loss of the light signal passing through the phase change region 1311, so as to retain a larger intensity of the light signal to be coupled out by the output waveguide 14. The energy absorption of light in 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 according to 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 the 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 the plane perpendicular to the propagation direction of the light field (for example, Figure 2A The position deviation of the rectangular cross-section shape center shown in the figure is not greater than 20%, for example, 10%, and the deviation of the cross-sectional dimensions of the input waveguide 12 and the output waveguide 14 in the plane perpendicular to the propagation direction of the light field and the cross-sectional dimensions of the phase change zone 1311 in the plane perpendicular to the propagation direction of the light field is not greater than 20%, for example, 10%. In practical applications, when the temperature of the phase change zone 1311 is changed to adjust the effective refractive index of the phase change zone 1311, the volume of the phase change zone 1311 will also change. In this embodiment, the cross-sectional shapes of the input waveguide 12 and the output waveguide 14 and the phase change zone 1311 in the plane perpendicular to the propagation direction of the light field are roughly aligned. In the process of adjusting the effective refractive index of the phase change zone 1311, the alignment can still be roughly maintained, so as to prevent the phase change zone 1311 from deviating from the input waveguide 12 and the output waveguide 14, which is beneficial to reducing the 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 comprises 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 may be attached to the grating 13 to improve the efficiency of changing the temperature of the grating 13. For example, the heater 15 may be arranged to cover the top of the grating 13, or the heater 15 may be arranged to cover the top and both sides of the grating 13. Figure 6 As shown in FIG. 5 , the heater 15 is disposed on the substrate 11, and the grating 13 is located between the substrate 11 and the heater 15. In other embodiments, the heater 15 and the grating 13 may be arranged to have a certain interval to prevent the heater 15 from absorbing the optical signal in the grating 13, resulting in a large loss of the optical signal. The dotted line in FIG. 5 represents the upper surface of the substrate 11 and the grating 13 blocked by the 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 includes, for example, a conductive material. In some embodiments, the material of the electrode layer 151 includes, 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, an electrical connection contact 1511 is provided on the electrode layer 151. The power supply 152 passes a preset current into the electrode layer 151, and the electrode layer 151 generates Joule heat for changing the temperature of the grating 13.

[0126] In some preferred embodiments of the present invention, the preset current passed by the power supply 152 to the electrode layer 151 is a pulse current. The power supply 152 can be configured to control the temperature and time of the grating 13 heating by changing the size, pulse width and number of pulses passed into the electrode layer 151, thereby improving the control accuracy of the temperature of the grating 13, so that the temperature of the grating 13 remains stable, and the effective refractive index of the grating 13 remains within a preset range, thereby improving the tuning accuracy and degree of accuracy. Specifically, for example, in the aforementioned embodiment, the material of the phase change region 1311 is Sb2Se3, and the temperature required for the transformation from amorphous state to crystalline state is 200℃-350℃, and the heating time is 0.1min-5min. The phase change region 1311 can be uniformly heated by applying multiple pulse currents with lower amplitudes. In the process of Sb2Se3 transforming from crystalline state to amorphous state, a temperature of 600℃ and above is required. A small amount of pulse current with higher amplitude and smaller width can be applied to quickly transform Sb2Se3 into amorphous state and restore 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 refers to 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 the optical signal loss between the grating 13 and the heater 15, and prevent the electrode layer 151 from being directly formed on the grating 13, and the electrode layer 151 from absorbing a large amount of optical signals. At the same time, the intermediate layer 153 can also ensure the heat conduction efficiency between the electrode layer 151 and the grating 13, so that the grating 13 can quickly adjust the 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 zone 1311 is always greater than the effective refractive index of the intermediate layer 153 within the complete variation range, and the effective refractive index of the filling zone 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 simultaneously, which is beneficial to simplify the preparation process of the optical device 10 .

[0131] The optical device 10 in the present invention can be used as a tunable filter. For example, the signal source is located upstream of the input waveguide 11 in the optical device 10 and can emit a light beam (a wide spectrum that needs to be filtered). The signal source is not limited to a light source that can actively emit light, and the signal source can also receive light signals emitted by other light sources, or the light beam is coupled into the optical device 10 by the signal source after reflection or refraction.

[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 an optical device 10, an input end 20 and an output end 30 as described in the above embodiments.

[0135] The laser beam can be coupled into the laser external cavity 1 from the input end 20, and the laser beam can be coupled out of the laser external cavity 1 from 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 large 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, part of the wavelength of the laser beam in the large wavelength range can be transmitted or reflected and coupled out from the output end 30. The wavelength of the emitted laser beam can be controlled by using the optical device 10.

[0136] In some embodiments, the input end 20, the optical device 10, and the output end 30 in the laser external cavity 1 are not limited to a linear arrangement. The optical device 10 is located between the input end 20 and the output end 30, which 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 positions. For example, in some embodiments, the laser beam reflected by the optical device 10 can be coupled out from the output end 30.

[0137] The present invention also relates to a laser 2, Fig. 9 The structure of the laser 2 according to some embodiments of the present invention is shown below. Fig. 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 above-mentioned embodiment. The gain region 40 is configured to amplify the energy of the laser beam when the laser beam 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, and the light beam in the cavity will be partially transmitted 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 Fig. 9 As shown in the figure, a reflector is arranged on one side of the gain region 40, and the laser external cavity 1 is arranged 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 part of the wavelength is reflected by the laser external cavity 1, and is reflected multiple times between the reflector and the laser external cavity 1, and passes through the gain region 40 multiple times, thereby amplifying the energy of the laser beam of a part of the wavelength.

[0140] In some embodiments, the gain region 40 is located in 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 in the optical device 10, for example, the gain region 40 is integrated in the grating 13.

[0141] The laser external cavity 1 in this embodiment can change the wavelength of the resonance in the cavity by adjusting the effective refractive index of the phase change zone 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 to the gain zone from the left side, so that the light beam with a specific wavelength in the light beam is amplified by the gain zone 40 and part is emitted from the right output end. In some embodiments, for example Fig. 9 As shown in FIG. 1 , the shadow-filled area on the right is the laser external cavity 1 , and 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. Fig.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. Fig.10 A method 100 for manufacturing an optical device is described.

[0143] like Fig.10 As shown, in step S101, the wavelength range of the light beam coupled into the optical device is obtained. For example, the optical device is applied to a tunable filter. The working 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 according to 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. According to the wavelength range of the light beam coupled into the optical device, the variation range of the central wavelength of the reflection peak (or transmission peak) is determined, and a phase change material that can be adjusted within the variation range of the central wavelength is selected. In some embodiments, the phase change material can be a single type of compound, such as the examples 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 according to 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 size of the tunable unit, the number of tunable units, and the length relationship of multiple tunable units in the propagation direction of the light field. The effective refractive index of the grating is not only related 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 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 processing method of the optical device is not limited in the present invention. In a preferred embodiment of the present invention, the optical device can be prepared by a photolithography deposition process, which is specifically described in subsequent embodiments.

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

[0148] In step S1041, a substrate is provided. The substrate is, for example, a sheet or plate with a stable structure and a flat surface. The substrate may also be processed into different structures, for example, a groove is provided at a position corresponding to the grating, the grating may be sunk into the groove, and the upper surface of the grating does not protrude from the surface of the substrate. In other embodiments, the substrate may also be processed to have a cavity, and the grating is partially or completely located above the cavity and 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 arranged to have substantially the same structure made of the same material, for example, the shape is substantially a rectangular parallelepiped.

[0150] In a subsequent step, 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, and the position of the groove corresponds to the position of the tunable unit, so as to form 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 a phase change material is formed at a position corresponding to the phase change region by sputtering or vacuum coating. For the filling area in the tunable unit, the position of the corresponding filling area can be obtained by shielding or removing part of the phase change material at the position of the deposited phase change material.

[0154] In step S1046, all photoresists and excess materials are removed, where the excess materials represent the phase change material deposited on the photoresist in step S1045. In step S1047, a filling region is formed at a corresponding position of the tunable unit, for example, by deposition. In different embodiments, steps S1046 and S1047 are not limited in order and can be performed in any order.

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

[0156] Fig.12 The process of forming a heater in step S105 according to a preferred embodiment of the present invention is shown below. Fig.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 can be pasted on the surface of the grating or the grating and the substrate. The material of the intermediate layer can be selected according to the above-mentioned embodiments. Preferably, the intermediate layer is arranged to fit 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 complete 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, and the electrode layer can be set to correspond to the position of the grating. Further, the electrode layer can also include electrical connection contacts to facilitate the connection between the electrode layer and the power supply.

[0160] In step S1054, a conductive material is deposited at a preset position to form an electrode layer. In this step, the process of depositing the conductive material can be substantially the same as the process of depositing the phase change material in the aforementioned embodiment, and the electrode layer is formed on the surface of the intermediate layer by vacuum coating. In some embodiments, the electrical connection contacts can be formed on the intermediate layer by simultaneous deposition. In other embodiments, the electrical connection contacts can also be welded on 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, and the power source may be configured to deliver a preset current, preferably a pulse current, to the electrode layer.

[0163] Finally, it should be noted that the above description is only an embodiment of the present invention and is 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 can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An optical device comprising a phase change material, characterized in that: include: A substrate, an input waveguide 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 light field direction, and the tunable units include a phase change region and a filling region; The phase change zone is configured so that the effective refractive index changes with temperature; the cross-sectional shape of the phase change zone 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 chalcogenide compound or a chalcogenide element.

2. The optical device according to claim 1, characterized in that: The length of the phase change zone along the propagation direction of the light field meets m*l=lambda / (2*n), where m is an integer, l is the length of the tunable unit, and lambda is the initial central wavelength of the light beam coupled into the optical device.

3. The optical device according to claim 2, characterized in that: Wherein, m is less than 10; and n is the effective refractive index of the tunable unit, which is substantially determined according to the area-weighted average of the effective refractive index of the phase change region and the effective refractive index of the filling region.

4. The optical device according to claim 1, characterized in that: 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 light field direction, the sizes of the long side and the short side are configured to support the fundamental mode transmission of the working wavelength coupled into the optical device.

6. The optical device according to claim 1, characterized in that: 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, characterized in that: 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 light field direction changes along the light field direction, the cross-sectional shape of the preset shape in a plane perpendicular to the light field direction 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 in the rectangle is not less than 5.

8. The optical device according to claim 6, characterized in that: 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, characterized in that: The joint surfaces of the phase change zone and the filling zone in the multiple tunable units are parallel to each other, the joint surfaces of the phase change zone and the filling zone have a preset inclination angle with the propagation direction of the light field, and the position of the output waveguide corresponds to the inclination direction of the joint surface of the phase change zone and the filling zone.

10. The optical device according to claim 8, characterized in that: The grating further comprises at least one connecting unit, wherein the connecting unit is arranged between the plurality of tunable units, the optical path provided by the length of the connecting unit in the light field propagation direction is not equal to the optical path provided by the length of the tunable unit in the light field propagation direction; 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 position deviation between the cross-section of the input waveguide and the output waveguide in the plane perpendicular to the light field propagation direction and the cross-section center of the phase change zone in the plane perpendicular to the light field propagation direction is not greater than 20%, and the cross-sectional dimensions of the input waveguide and the output waveguide in the plane perpendicular to the light field propagation direction and the cross-sectional dimensions of the phase change zone in the plane perpendicular to the light field propagation direction are not greater 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, characterized in that: The heater comprises: an electrode layer, the electrode layer covering the grating; and A power source 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, characterized in that: 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 Ti N x , one or more of W2N, ITO, FTO, W, Au, Cr, Ag and Cu.

18. The optical device according to claim 17, characterized in that: 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 complete 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 as claimed in claim 20; a gain region, the gain region being 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: Used to prepare an optical device according to any one of claims 1 to 19, the preparation method comprising: Acquire the wavelength range of the 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 at the corresponding position of the tunable unit, and removing the photoresist in the exposed area; Depositing phase change material at a corresponding position 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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