A resistance wire bare cavity and preparation method thereof, tunable device and tunable equipment

Abstract

The present invention discloses a resistance wire bare cavity and a preparation method thereof, a tunable device and a tunable equipment. The resistance wire bare cavity comprises: a resistance wire and a whispering gallery microcavity, wherein the whispering gallery microcavity wraps the resistance wire in a circumferential direction; wherein the resistance wire is used to release heat to the whispering gallery microcavity when current is passed through; the whispering gallery microcavity can couple a first optical signal, and after being heated, can modulate the first optical signal based on changes in thermally induced volume and thermally induced refractive index, wherein the first optical signal is transmitted by an optical fiber, and the whispering gallery microcavity is coupled with the optical fiber. Thus, a frequency sweep function can be realized by applying a periodic voltage to the resistance wire, and a desired resonance mode can be captured or locked by adjusting the voltage applied to the resistance wire.

Description

Technical Field

[0001] The invention relates to the field of optical technology, and in particular to a resistance wire bare cavity and a preparation method thereof, a tunable component and a tunable device. Background Art

[0002] Whispering Gallery Mode (WGM) optical resonators have attracted great interest in optoelectronic devices, nonlinear optics, and sensing due to their high-quality Q factor and small cavity size. Since the formation of WGM in the cavity is not unique and the mode quality varies, a tunable laser is needed to accurately capture the resonant cavity mode. However, tunable lasers, especially those with a wide tunable range, are expensive, so researchers have gradually focused on tuning the WGM optical resonator itself to achieve so-called "passive" tuning.

[0003] In the past few decades, the tuning methods of WGM resonance have been comprehensively developed. There are two main types of mature methods: pressure / strain tuning and thermal tuning. In addition, unconventional methods include electro-optical tuning, electrothermal tuning, laser polishing and chemical etching techniques. However, these methods require strict tuning conditions or involve highly selective use of materials, making them less suitable as efficient and universal tuning methods. Among the two currently popular methods, pressure / strain tuning can mostly only achieve large-scale tuning in the GHz range when the microcavity undergoes significant deformation, which poses a potential risk to the long-term stability of the device. Although traditional thermal tuning is the most direct and applicable to whispering gallery microcavities of all morphologies and materials, the essential external heating elements not only pose challenges to device miniaturization, but also prolong the tuning response time to a certain extent due to the heat transfer process. Summary of the invention

[0004] The present invention provides a resistance wire bare cavity and a preparation method thereof, a tunable device and a tunable equipment, which can not only realize the frequency sweeping function, but also do not require preheating during the tuning process, have a short response time, and are easy to capture and lock the required resonance mode.

[0005] According to one aspect of the present invention, a resistance wire bare cavity is provided, comprising: a resistance wire and a whispering gallery microcavity, wherein the whispering gallery microcavity wraps the resistance wire along a circumferential direction;

[0006] The resistance wire is used to release heat to the whispering gallery microcavity when current is passed through it; the whispering gallery microcavity can couple a first optical signal, and after being heated, can modulate the first optical signal based on changes in thermally induced volume and thermally induced refractive index, wherein the first optical signal is transmitted by an optical fiber, and the whispering gallery microcavity is coupled to the optical fiber; the resistivity of the resistance wire is constant.

[0007] Optionally, the resistivity of the resistance wire is in the range of 1.59*10 -8 (Ω·m) to 9.5*10 -8 (Ω·m).

[0008] Optionally, the outer diameter of the resistance wire ranges from 10 to 150 um.

[0009] Optionally, the outer diameter of the whispering gallery microcavity is greater than 1 times the outer diameter of the resistance wire, and less than or equal to 2 times the outer diameter of the resistance wire.

[0010] Optionally, the light-transmitting material includes one of polystyrene, methyl methacrylate, polydimethylsiloxane, aluminum oxide or silicon dioxide.

[0011] According to a second aspect of the present invention, a method for preparing a resistance wire bare cavity is provided, which is used to prepare the resistance wire bare cavity described in any embodiment of the present invention, and the preparation method comprises the following steps:

[0012] Pre-treating the resistance wire so that the surface roughness of the resistance wire is less than 50 nm; and straightening and horizontally fixing the pre-treated resistance wire on a fixture;

[0013] Using a microfluidic pump to transfer the material for making the whispering gallery microcavity to the resistance wire in the form of droplets, and keeping the microscope focused and monitored during the transfer process, wherein the material of the whispering gallery microcavity has fluidity before solidification, and the viscosity is greater than 300 cps (centipoise) and less than 10000 cps;

[0014] The resistance wire is adjusted from a horizontally stretched state to a vertically stretched state, and the whispering gallery microcavity is formed by utilizing the gravity and surface tension of the material of the whispering gallery microcavity, wherein the microscope is kept in focus during the adjustment process;

[0015] The preparation is completed by lightly touching the surface of the whispering gallery microcavity with an optical fiber and observing whether the optical fiber will produce adhesion on the surface of the whispering gallery microcavity, and whether the whispering gallery microcavity is completely cured. The microscope is kept focused for monitoring during the curing process.

[0016] According to a third aspect of the present invention, a tunable device is provided, comprising the resistance wire bare cavity according to any embodiment of the present invention, and further comprising: an optical fiber;

[0017] The optical fiber, the resistance wire and the whispering gallery microcavity form a coupling structure.

[0018] Optionally, the optical fiber is a tapered optical fiber, the resistance wire is intersected with the tapered region of the tapered optical fiber to form an intersection, and the whispering gallery microcavity is located on the resistance wire corresponding to the intersection.

[0019] Optionally, the optical fiber is a U-shaped optical fiber, the resistance wire is folded in half to form a folding point, the folding point is arranged close to a bending point of the U-shaped optical fiber, and the whispering gallery microcavity is located at the folding point.

[0020] Optionally, it also includes: packaging material, fixing material and packaging substrate;

[0021] The fixing material is used to fix the coupling structure on the packaging substrate, and the packaging material is used to package the coupling structure, wherein the effective refractive index of the packaging material is smaller than the effective refractive index of the whispering gallery microcavity.

[0022] According to a fourth aspect of the present invention, a tunable device is provided, comprising the tunable device according to any one of the embodiments of the present invention, and further comprising: an electrical signal output unit, a laser, a photodetector and an image display;

[0023] Wherein, the electrical signal output unit is electrically connected to the resistance wire in the tunable device, and is used to provide an electrical signal to the resistance wire;

[0024] The output end of the laser is connected to one end of the optical fiber in the tunable device, the other end of the optical fiber is located at the detection surface of the photodetector, and the image display is electrically connected to the photodetector, wherein the laser is used to output a first optical signal, the optical fiber is used to transmit the first optical signal, the photodetector is used to receive a second optical signal modulated by the whispering gallery microcavity in the tunable device, and the image display is used to display the second optical signal; the electrical signal output unit includes a voltage amplifier and a signal generator, or a signal generator, or a programmable constant current source.

[0025] According to the resistance wire bare cavity and the preparation method thereof, the tunable device and the tunable equipment proposed in the embodiment of the present invention, the resistance wire bare cavity includes: a resistance wire and a whispering gallery microcavity, the whispering gallery microcavity wraps the resistance wire in the circumferential direction; wherein the resistance wire is used to release heat to the whispering gallery microcavity when current is passed; the whispering gallery microcavity can couple into a first optical signal, and after being heated, can modulate the first optical signal based on the change of thermally induced volume and thermally induced refractive index, wherein the first optical signal is transmitted by an optical fiber, and the whispering gallery microcavity is coupled with the optical fiber. Thus, the frequency sweep function can be realized by applying a periodic voltage to the resistance wire, and by adjusting the voltage applied to the resistance wire, the desired resonance mode can be captured or locked, so that the light is bound in the whispering gallery microcavity for a long time after being coupled into the whispering gallery microcavity, thereby increasing the light energy density in the cavity, and the photon lifetime is increased from the picosecond level to the nanosecond level, thereby the photons can fully interact with electrons, molecules and lattices, so that very rich nonlinear effects can be observed. Furthermore, the resistance wire bare cavity can also be adapted to tunable lasers or single-frequency lasers, with higher adaptability.

[0026] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 is a schematic diagram of the structure of the resistance wire bare cavity proposed in an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of the geometric optical structure of a whispering gallery microcavity proposed in an embodiment of the present invention;

[0030] Figure 3 It is a flow chart of a method for preparing a resistance wire bare cavity proposed in an embodiment of the present invention;

[0031] Figure 4 It is a flow chart of a method for preparing a resistance wire bare cavity proposed in a specific embodiment of the present invention;

[0032] Figure 5 is a schematic structural diagram of a tunable device proposed in an embodiment of the present invention;

[0033] Figure 6 is a schematic structural diagram of a tunable device provided by an embodiment of the present invention;

[0034] Figure 7 is a schematic diagram of the structure of a tunable device proposed in an embodiment of the present invention;

[0035] Figure 8 is a schematic structural diagram of a tunable device provided in another embodiment of the present invention;

[0036] Fig. 9 is a structural schematic diagram of a tunable device proposed in yet another embodiment of the present invention;

[0037] Fig.10 It is a schematic diagram of the structure of a tunable device proposed in yet another embodiment of the present invention.

[0038] Figure numerals: 101, resistance wire; 102, whispering gallery microcavity; 103, optical fiber; 104, UV curing glue; 105, low refractive index glue; 106, substrate; 200, tunable device; 201, electrical signal output unit; 202, laser; 204, photodetector; 205, image display; 206, BNC signal line; 207, electrical wire. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] The existing more mature microcavity tuning methods, such as pressure / strain tuning, often require a large deformation of the microcavity to achieve large-scale tuning. Large deformation will cause the Q value of the microcavity to decrease and affect the long-term stability of the tunable microcavity. Currently, many large-scale tuning methods based on pressure / strain are basically unidirectional tuning, and cannot achieve the important frequency sweeping function by periodically applying force to the microcavity.

[0042] Thermal tuning is currently the most widely used and most stable tuning method. The combination of TEC (Thermo Electric Cooler) semiconductor cooling plate and microcavity is currently the most widely used and partially commercialized method, but it also has certain limitations. For example, an external TEC will introduce additional volume to the tunable microcavity device, which runs counter to the current mainstream idea of ​​miniaturizing the device. At the same time, a uniquely designed thermal structure is generally required as a buffer layer between the cooling plate and the microcavity, which undoubtedly increases the design packaging cost and prolongs the heat transfer time. The extended heat transfer time makes it impossible for this method to achieve real-time tuning while prolonging the PID algorithm setting time. Since TEC is temperature-set by the PID control algorithm, the algorithm setting requires a certain amount of time cost, and the startup requires preheating time. In addition, during the tuning process, due to the setting of the PID algorithm, the temperature will also produce corresponding oscillations, corresponding to the mode drift, which has a non-negligible impact on the rapid mode conversion and long-term locking during use.

[0043] Therefore, the present invention proposes a resistance wire bare cavity and a preparation method thereof, a tunable device and a tunable equipment to solve the problems caused by thermal tuning in the related art.

[0044] Figure 1 Schematic diagram of the structure of the resistance wire bare cavity proposed in the embodiment of the present invention. Figure 1 As shown, the resistance wire bare cavity comprises: a resistance wire 101 and a whispering gallery microcavity 102, wherein the whispering gallery microcavity 102 wraps the resistance wire 101 along the circumferential direction;

[0045] The resistance wire 101 is used to release heat to the whispering gallery microcavity 102 when current is passed through it; the whispering gallery microcavity 102 can couple a first optical signal, and after being heated, can modulate the first optical signal based on changes in thermally induced volume and thermally induced refractive index, wherein the first optical signal is transmitted by an optical fiber, and the whispering gallery microcavity 102 is coupled to the optical fiber.

[0046] It should be noted that the whispering gallery microcavity 102 can be prepared in advance on the resistance wire 101, and the two ends of the resistance wire 101 can be connected to an external power supply to apply voltage so as to pass current into the resistance wire 101. After the current is passed through the resistance wire 101, heat is generated and released into the whispering gallery microcavity 102. After the whispering gallery microcavity 102 is heated, the volume will change and the refractive index will also change. Therefore, under the conditions of consistent material and size of the resistance wire, and on the basis of knowing in advance the changes in the thermally induced volume and thermally induced refractive index of the material of the whispering gallery microcavity 102, by controlling the size of the voltage at both ends of the resistance wire 101, the heat released to the whispering gallery microcavity 102 can be controlled, thereby, the change amplitude of the whispering gallery microcavity 102 after being heated can be controlled. In this way, the optical path of the optical signal coupled into the whispering gallery microcavity 102 can be controlled, that is, the corresponding modulation intensity can be controlled.

[0047] In the above embodiment, the material of the resistance wire 101 can be copper, iron, gold, silver, etc., and the present invention does not impose any specific limitation on this. Figure 2 As shown. The circle represents the equatorial cross-section of the whispering gallery microcavity with a radius of R, n is the refractive index of the resonant cavity material, and i is the angle of the total reflection propagation light beam in the whispering gallery microcavity. Since the resonant cavity is a strictly symmetrical circular structure, the angle of each reflection of light in the resonant cavity remains unchanged. When the light beam reflection angle i is greater than the critical value, it will continue to be totally reflected in the resonant cavity, and the energy is confined in the resonant cavity. When the optical path of light propagating around the circumference is equal to an integer multiple of the wavelength, a WGM is eventually formed. When the radius R of the resonant cavity is much larger than λ, the propagation path of light on the equatorial circumference of the resonant cavity is approximately a circle, and the formation condition of WGM is: 2πRn=lλ; l is the mode number, and λ is the wavelength of light. In this embodiment, the shape of the whispering gallery microcavity 102 can be spherical or bottle-shaped.

[0048] Thus, by placing the whispering gallery microcavity 102 on the resistance wire 101, the setting of the cooling plate and the thermal structure is avoided, and the tunable device is miniaturized. And by heating the resistance wire 101 by energizing it, the resistance wire is located inside the whispering gallery microcavity 102, and the heating time is short, which can achieve real-time tuning, making it possible to quickly switch the mode and lock the mode for a long time. Among them, the resistivity of the resistance wire 101 is constant.

[0049] It is understandable that the resistivity of the resistor 101 is basically not affected by temperature, magnetic field or pressure, so as to ensure that the resistance value of the resistor 101 is constant after the resistor 101 is powered on, and minimize the number of variables in the device, so that the influence of the power-on current on the optical signal modulation can be better analyzed later.

[0050] Optionally, the resistivity of the resistance wire 101 is in the range of 1.59*10 -8(Ω·m) to 9.5*10 -8 (Ω·m).

[0051] It is understandable that too small a resistivity will generate less heat under the same voltage, affecting the tuning capability of the tunable device. Too large a resistivity will generate more heat, which will lead to a larger tuning range, but will easily cause a large expansion of the volume of the whispering gallery microcavity 102, and will easily damage the portion corresponding to the optical fiber coupled to the whispering gallery microcavity 102.

[0052] Optionally, the outer diameter of the resistance wire 101 ranges from 10 to 150 um.

[0053] Among them, since the diameter of the optical fiber is generally in the scale space of several microns, in order to ensure the effective coupling between the whispering gallery microcavity 102 and the optical fiber, the size of the whispering gallery microcavity 102 should not be too large, and the diameter of the resistance wire 101 directly affects the size of the whispering gallery microcavity 102, so the diameter of the resistance wire 101 needs to be controlled within the range of 10-150um. The whispering gallery microcavity 102 formed within this range can not only avoid the higher technical operation threshold brought by the coupling with the optical fiber and the glue filling process due to the small cavity size, but also reduce the increase in heat transfer time caused by the overly large cavity while ensuring the Q value factor, and does not affect the tuning response rate.

[0054] Optionally, the outer diameter of the whispering gallery microcavity 102 is greater than 1 times the outer diameter of the resistance wire 101 , and less than or equal to 2 times the outer diameter of the resistance wire 101 .

[0055] It should be noted that due to the limitations of the manufacturing process, the diameter of the whispering gallery microcavity 102 is determined by the diameter of the selected resistance wire 101. The diameter of the whispering gallery microcavity 102 is 1 to 2 times the diameter of the resistance wire 101. The final microcavity diameter ranges from 20um to 300um. A microcavity diameter that is too large is more easily affected by gravity and difficult to attach to the resistance wire 101, and will increase the heat transfer time and affect the tuning response speed.

[0056] Optionally, the material of the whispering gallery microcavity 102 is a light-transmitting material, and the effective refractive index of the whispering gallery microcavity 102 is greater than the effective refractive index of the optical fiber.

[0057] Among them, since the whispering gallery microcavity 102 needs to couple the optical signal in the optical fiber, the material used to make the whispering gallery microcavity 102 needs to be a light-transmitting material, and further can be a highly light-transmitting material (with a light transmittance greater than 99%). And after the light-transmitting material is solidified on the resistance wire 101 to form the whispering gallery microcavity 102, the effective refractive index of the whispering gallery microcavity 102 needs to be greater than the effective refractive index of the optical fiber, but not too large, which will cause a large light deflection angle in the optical fiber and cannot be coupled into the whispering gallery microcavity 102. The effective refractive index of the whispering gallery microcavity 102 cannot be less than the effective refractive index of the optical fiber, which is easy to be totally reflected, and the optical signal in the optical fiber is less likely to be coupled into the whispering gallery microcavity 102.

[0058] Optionally, the difference between the effective refractive index of the whispering gallery microcavity 102 and the effective refractive index of the optical fiber is greater than 0 and less than or equal to 0.1.

[0059] When the difference between the effective refractive index of the whispering gallery microcavity 102 and the effective refractive index of the optical fiber is within this range, coupling is easier. For example, taking an optical fiber with a standard diameter of 125 um as an example, the effective refractive index of the core of the optical fiber is 1.45, so a light-transmitting material with an effective refractive index of 1.50 can be selected to form the whispering gallery microcavity 102.

[0060] Optionally, the light-transmitting material includes one of polystyrene, methyl methacrylate, polydimethylsiloxane, aluminum oxide or silicon dioxide.

[0061] Among them, the above materials all have a certain fluidity before curing, can be better attached to the resistance wire 101, and are colorless and transparent after curing, meeting the requirements of the whispering gallery microcavity 102.

[0062] Furthermore, this embodiment can have a tuning range of hundreds of GHz, can achieve good frequency sweeping at low cost, a tuning response speed of ms level, does not require the introduction of an external heat source that increases the volume, has excellent long-term stability and is suitable for most working conditions.

[0063] Figure 3 It is a flow chart of the method for preparing the resistance wire bare cavity proposed in an embodiment of the present invention. Figure 4 1 is a flow chart of a method for preparing a bare resistance wire cavity according to a specific embodiment of the present invention. The method is used to prepare a bare resistance wire cavity according to any embodiment of the present invention, such as Figure 3 and Figure 4 As shown, the preparation method comprises the following steps:

[0064] S101, pre-treating the resistance wire so that the surface roughness of the resistance wire is less than 50 nm; and horizontally straightening and fixing the pre-treated resistance wire on a fixture.

[0065] The surface of the resistance wire is relatively rough and the damping is too large. Direct use will make it difficult for the droplets used to prepare the whispering gallery microcavity to form a standard microcavity around the resistance wire through their own cohesion / surface tension. The resistance wire will have different shapes and uneven surfaces, which will cause great loss to the performance of the whispering gallery microcavity. Therefore, the surface of the resistance wire needs to be treated to make its surface roughness less than 50nm. The treatment methods include but are not limited to sandpaper polishing, polishing with polishing liquid, and hot melt treatment. After pre-treatment of the resistance wire, it needs to be cleaned with an ultrasonic cleaning tank and ultrapure water. After taking it out, wipe it clean with dust-free paper or non-woven fabric, and use a high-definition microscope to ensure that there are no obvious impurities and dust on the surface of the resistance wire. Then use a clamp with a stepper motor to straighten the resistance wire horizontally to facilitate subsequent operations.

[0066] S102, using a microfluidic pump to transfer the material for making the whispering gallery microcavity to the resistance wire in the form of droplets, and keeping the microscope focused and monitoring during the transfer process, wherein the material of the whispering gallery microcavity is fluid before solidification, and the viscosity is greater than 300cps and less than 10000cps.

[0067] Among them, the material needs to have a certain fluidity before curing to allow it to better adhere to the resistance wire. The recommended viscosity is greater than 300cps and less than 10000cps. The material with a viscosity of less than 300cps is too low in viscosity, and the whispering gallery microcavity formed on the resistance wire is prone to displacement before curing, affecting the control of the position of the whispering gallery microcavity. For materials with a viscosity greater than 10000cps, it is difficult to independently form a microcavity with a standard shape on the resistance wire. In addition, it is necessary to ensure that the selected material is colorless and transparent after complete curing. Among them, the material can be a polymer material, such as polydimethylsiloxane (PDMS).

[0068] In one embodiment, the material is a polymer, and the resistance wire is a copper wire. In this step, a microfluidic pump and a precision translation stage can be used to transfer the polymer droplets to the copper wire. During this process, the microscope is kept focused and monitored. The microfluidic pump can accurately control the output of the polymer droplets, thereby ensuring the consistency of the microcavity morphology. The output of the polymer droplets depends on the selected resistance wire diameter, and the output of the droplets is related to the diameter of the microcavity. The diameter of the microcavity is 1 to 2 times the diameter of the copper wire. The range of the diameter of the microcavity is greater than 20um and less than 300um. An excessively large microcavity diameter is more susceptible to the influence of gravity and is difficult to attach to the copper wire, and it will increase the heat transfer time and affect the tuning response speed.

[0069] S103, adjusting the resistance wire from a horizontally stretched state to a vertically stretched state, and forming a whispering gallery microcavity by utilizing the gravity and surface tension of the material of the whispering gallery microcavity, wherein the microscope is kept in focus for monitoring during the adjustment process.

[0070] After the polymer droplets are transferred to the resistance wire, the fixture needs to be removed from the translation stage and the position of the resistance wire needs to be adjusted (for example, the resistance wire is rotated, or the resistance wire is stood up, or twisted, etc.), so that the polymer can rely on its own gravity and surface tension to cohere and form a standard microcavity.

[0071] When the pretreated resistance wire is placed horizontally on the displacement stage, after the polymer droplets are dropped onto the resistance wire, the resistance wire can be placed vertically, thereby relying on the gravity and surface tension of the polymer itself to form a standard microcavity.

[0072] S104, lightly touching the surface of the whispering gallery microcavity with an optical fiber; observing whether the optical fiber will produce adhesion on the surface of the whispering gallery microcavity to determine whether the whispering gallery microcavity is completely cured; and after the whispering gallery microcavity is cured on the resistance wire, the preparation is completed, wherein the microscope is kept focused for monitoring during the curing process.

[0073] Furthermore, after the polymer droplets are formed into a bottle or sphere shape and solidified on the resistance wire, a whispering gallery microcavity is formed.

[0074] Among them, the curing means is mainly selected according to the type of polymer selected, such as PDMS (polydimethylsiloxane) curing requires 150 ° C, 10 minutes or 125 ° C, 20 minutes. It should be noted here that due to different manufacturers or batches, the curing means cannot strictly follow the manufacturer's nominal data. Since the microcavity is a high-precision optical device, surface adhesion caused by incomplete curing, or surface wrinkles caused by too long curing time, will seriously affect the performance of the microcavity. Therefore, during curing, it is recommended to monitor the surface in real time with a microscope, and adjust the curing means and duration of the selected material through experiments. For example, in this embodiment, by touching the optical fiber lightly, it is observed whether the optical fiber will produce adhesion on the surface of the microcavity to determine whether the microcavity is completely cured. If it is not completely cured, the curing time is extended by time gradient grouping, such as 10 minutes as a gradient, and 10 minutes for a test, to ensure the time used for the best curing degree of the microcavity, to avoid wrinkles on the surface of the microcavity caused by too long curing time, thereby affecting the performance of the microcavity.

[0075] Therefore, the bare cavity of the resistance wire is composed of a micron-scale micro-polymer droplet agglomerated on the resistance wire, relying on the surface tension and cohesion of the droplet to form a bottle cavity (a form of micro-cavity). Through this preparation method, the tunable micro-morphology, size, position and Q factor can be accurately controlled to ensure the consistency of the performance of the whispering gallery micro-cavity.

[0076] Figure 5 It is a structural diagram of a tunable device proposed in an embodiment of the present invention. Figure 6 FIG. 1 is a structural diagram of a tunable device according to an embodiment of the present invention. Figure 5 and Figure 6 As shown, the tunable device includes the resistance wire bare cavity of any embodiment of the present invention, and further includes: optical fiber 103;

[0077] The optical fiber 103, the resistance wire 101 and the whispering gallery microcavity 102 form a coupling structure.

[0078] Among them, the optical fiber 103 is used to transmit the first optical signal. The optical fiber 103 is coupled with the whispering gallery microcavity 102. After the resistance wire 101 releases heat to the whispering gallery microcavity 102, it can modulate the volume and refractive index of the whispering gallery microcavity 102, thereby modulating the first optical signal coupled into the whispering gallery microcavity 102.

[0079] Alternatively, if Figure 5 As shown, the optical fiber 103 is a tapered optical fiber, the resistance wire 101 and the tapered region of the tapered optical fiber are intersected to form an intersection, and the whispering gallery microcavity 102 is located on the resistance wire 101 corresponding to the intersection.

[0080] The crossing angle between the tapered optical fiber (optical fiber 103) and the resistance wire 101 can be 90 degrees. The tapered optical fiber is generally prepared by chemical etching, grinding or melting and drawing, and is used to couple with the whispering gallery microcavity 102; when transmitting laser energy, the tapered optical fiber can reduce the number of reflections of the laser beam in the optical fiber, and gradually increase the incident angle of the laser during the transmission process, thereby shortening the propagation path of the light beam and increasing the reflectivity, so that the transmission loss of the optical fiber is further reduced, which is much smaller than that of the cylindrical optical fiber of the same type.

[0081] According to mode coupling theory, the coupling of laser diode (LD) to optical fiber is essentially the mode field matching between the two. If a flat-end optical fiber is used for direct coupling, the coupling efficiency is very low, about 10%, due to the mode field mismatch. However, using a tapered optical fiber for coupling can greatly improve the coupling efficiency, up to 99.99%. The radius of the tapered area here is determined by the size of the self-assembled cavity.

[0082] This embodiment adopts a tapered optical fiber coupling method, which has the advantages of high coupling efficiency, easy production, low cost, and few output modes.

[0083] In another embodiment, the optical fiber used to make the tapered optical fiber may also be preferably a polarization-maintaining optical fiber, so that the polarization of the optical path remains unchanged, which is conducive to better capture and stabilization of the device mode.

[0084] Alternatively, if Figure 6 As shown, the optical fiber 103 is a U-shaped optical fiber, the resistance wire 101 is folded in half to form a folding point, the folding point is arranged close to the bending point of the U-shaped optical fiber, and the whispering gallery microcavity 102 is located at the folding point.

[0085] The U-shaped optical fiber is made by bending the tapered optical fiber through a high-precision displacement stage on the basis of the tapered optical fiber. After the whispering gallery microcavity 102 is formed on the resistance wire 101, the resistance wire 101 can be folded in half.

[0086] Alternatively, if Figure 5 As shown, the tunable device also includes: packaging material, fixing material and packaging substrate;

[0087] The fixing material is used to fix the coupling structure on the packaging substrate, and the packaging material is used to package the coupling structure, wherein the effective refractive index of the packaging material is smaller than the effective refractive index of the whispering gallery microcavity.

[0088] It should be noted that the method of packaging it into a device is to fill the coupling area with low refractive index glue 105, and fix it on the substrate 106 by spot sealing with ultraviolet curing glue 104 outside the coupling area. Specific packaging methods include but are not limited to planar packaging (such as Figure 5 as shown) and probed packaging (as Figure 6 as shown).

[0089] The planar package is composed of a resistance wire 101, (tapered fiber) optical fiber 103, a whispering gallery microcavity 102, a substrate 106 (glass substrate), a low refractive index glue 105 and a UV curing glue 104. The probe package is composed of a resistance wire 101, (U-shaped fiber) optical fiber 103, a whispering gallery microcavity 102 and a low refractive index glue 105. Figure 5 The planar package is shown in the figure. Figure 6 The probe packaging is shown in the figure.

[0090] It is understandable that the substrate 106 is used to support the optical fiber 103-whispering gallery microcavity 102-resistance wire 101 coupling structure. The UV curing glue 104 is used to fix the coupling structure on the glass substrate. The low refractive index glue 105 plays the role of guiding light and protecting the coupling structure, and its effective refractive index is required to be lower than the refractive index of the core of the optical fiber 103, and the lower the better.

[0091] Figure 7 Schematic diagram of the structure of the tunable device proposed in the embodiment of the present invention. Figure 7 As shown, the tunable device includes a tunable device 200 according to any embodiment of the present invention, and further includes: an electrical signal output unit 201, a laser 202, a photodetector 204, and an image display 205;

[0092] The electrical signal output unit 201 is electrically connected to the resistance wire 101 in the tunable device 200 and is used to provide an electrical signal to the resistance wire 101;

[0093] The output end of the laser 202 is connected to one end of the optical fiber 103 in the tunable device 200, the other end of the optical fiber 103 is located at the detection surface of the photodetector 204, and the image display 205 is electrically connected to the photodetector 204, wherein the laser 202 is used to output a first optical signal, the optical fiber 103 is used to transmit the first optical signal, the photodetector 204 is used to receive a second optical signal modulated by the whispering gallery microcavity 102 in the tunable device 200, and the image display 205 is used to display the second optical signal.

[0094] The laser 202 may be a single-frequency laser for generating laser light. The laser wavelength generated by the single-frequency laser matches the wavelength of the optical fiber, which may be 1550 nm, 1064 nm, 980 nm, 785 nm, 532 nm, etc.

[0095] The photodetector 204 is used to realize the conversion between optical signals and electrical signals. The photodetector is composed of a photodiode. When designing and manufacturing the photodiode, the area of ​​the PN junction is as large as possible to receive the incident light. When the photodiode is working under reverse voltage, the reverse current is extremely weak when there is no light, which is called dark current; when there is light, the reverse current increases rapidly to tens of microamperes, which is called photocurrent. The greater the intensity of light, the greater the reverse current. The change of light causes the change of the current of the photodiode, which can convert the optical signal into an electrical signal.

[0096] The image display 205 may be an oscilloscope, which converts electrical signals into visual images, can monitor the current output waveform of the electrical signal output unit 201 and the signal output waveform of the photodetector 204, and convert the output electrical signals into images to detect changes in the WGM mode. The photodetector 204 and the image display 205 may be connected via a BNC (Bayonet NutConnector) signal line 206.

[0097] The electrical signal output unit 201 is used to output a periodic electrical signal to the tunable device 200 to achieve tuning.

[0098] It should be noted that the working principle of the above tuning device is as follows: laser light is emitted from the laser 202 and transmitted to the tunable device 200 via the optical fiber 103 .

[0099] In the whispering gallery microcavity 102, most of the light beams are coupled into the whispering gallery microcavity 102 in the form of evanescent waves. When the WGM formation conditions mentioned above are met, the whispering gallery mode can be excited. The accumulated light information is converted into an electrical signal through the photodetector 204 and then transmitted to the oscilloscope (image display 205) through the BNC signal line 206 to display the power line image.

[0100] Then, the electrical signal output unit 201 is used to input a periodic triangular wave voltage to the resistor 101 in the tunable device 200 to generate a corresponding current. The resistor 101 also generates a periodic thermal field change that affects the whispering gallery microcavity 102. Due to the change in the optical path caused by the photothermal refractive index and the expansion and contraction of the whispering gallery microcavity 102, the frequency sweep is realized, and the oscilloscope (image display 205) displays the change of the periodic mode. Adjust the voltage value, select the interval of the mode with a deep coupling depth, turn off the frequency sweep function, and use the programmed PID algorithm to let the electrical signal output unit 201 output a voltage interval value to achieve mode selection and stability.

[0101] The meaning of locking into the mode is that after light is coupled into the whispering gallery microcavity 102, it will be trapped in the cavity for a long time, so that the light energy density in the cavity is increased, and the photon lifetime is increased from the picosecond level to the nanosecond level; photons can fully interact with electrons, molecules and lattices, so very rich nonlinear effects can be observed. At the same time, its sensitive perception of the outside world can also make its device used as a highly sensitive sensor.

[0102] In one embodiment, in the tunable device, an electrical signal amplifier, a filter, etc. may be added between the photodetector 204 and the oscilloscope (image display 205) to amplify or filter the electrical signal, so that the image displayed by the oscilloscope is clearer and more stable.

[0103] In one embodiment, a polarization controller may be further added between the laser 202 and the tunable device 200; this example is applicable when the optical fiber is a polarization-maintaining optical fiber.

[0104] In one embodiment, before the light passes through the tunable device 200 for output, an optical amplifier device such as a semiconductor optical amplifier (SOA) or an erbium doped fiber application amplifier (EDFA) may be added to make it easier for the photodetector 204 to capture the optical signal.

[0105] In one embodiment, the packaging of the tunable device 200 is not limited to planarization and probe-based packaging. In the same way, packaging methods using the resistance wire 101 as a cavity carrier and a heat source should also be considered within the scope of protection.

[0106] The electrical signal output unit 201 includes a voltage amplifier and a signal generator, or a signal generator, or a programmable constant current source.

[0107] That is, the electrical signal output unit 201 may be a signal generator, a programmable constant current source, or a signal generator and a voltage amplifier.

[0108] Figure 8 is a schematic structural diagram of a tunable device provided by an embodiment of the present invention; Fig. 9 is a schematic structural diagram of a tunable device provided in another embodiment of the present invention; Fig.10 FIG. 1 is a schematic diagram of a tunable device according to another embodiment of the present invention. Figure 8 As shown in the figure, the voltage amplifier is a device for increasing the signal voltage. In this device structure, it can also act as a voltage output device for the tunable device. Specifically, the signal generator outputs a periodic modulation signal to the voltage amplifier, and the voltage amplifier outputs a periodic voltage to realize the tuning and frequency sweeping function. Fig. 9 As shown in the figure, the signal generator is a device that can output various frequencies, waveforms and electrical signals. At the same time, it can be used as a low-power power supply to directly output current or periodically modulate current to tunable devices, and as a lower-level replacement device for programmable constant current sources. Fig.10 As shown, the programmable constant current source is used to stably and accurately output current to the resistor wire. The purpose of programming is to make the constant current source output a periodic triangular wave current through programming means to realize the frequency sweeping function of the device. At the same time, by programming and inputting the PID (Proportional, Integral, Differential) control algorithm, the WGM mode can be stably placed in the output frequency of the single-frequency laser for a long time. The electrical signal output unit 201 is connected to the tunable device 200 through the wire 207. The wire 207 carries the output voltage of the electrical signal output unit 201, and the wire with a clamping port can be selected.

[0109] In one embodiment, the device that provides current to the tunable device 200 is not limited to a signal generator, a programmable constant current source, or a voltage amplifier. In theory, any device that can output a stable voltage based on a modulation signal should be included in the usable device.

[0110] Furthermore, in this embodiment, by processing the resistance wire, combining the droplet manipulation capability of the microfluidic pump, and monitoring the curing process, the consistency of the performance of the tunable device can be highly ensured, while ensuring a high success rate. Using a resistance wire with a micron-scale diameter as both a carrier and a heater optimizes the heat transfer process, while eliminating the problem of increased device volume caused by an external heating device, making the device easier to integrate into various systems. Thanks to the optimized heat transfer process and the advantage of a large specific surface area of ​​the cavity, the tuning response speed is stabilized at the ms level. Using polymer as the material for the whispering gallery microcavity, its excellent thermo-optical coefficient and low Young's modulus properties enable the device to achieve ultra-wide tuning of hundreds of GHz at extremely low currents. The tuning device is suitable for laboratories under various conditions. It realizes frequency sweeping and capturing of specific modes through a programmable constant current source, and can allow the use of low-cost single-frequency lasers instead of expensive tunable lasers. It has low requirements for current support devices and high selectivity. In addition to the three current support devices shown in the three tuning devices given in the present invention, theoretically, any device that can accept a periodic modulation signal to stabilize the output voltage can be included in the protection scope.

[0111] According to the resistance wire bare cavity and the preparation method thereof, the tunable device and the tunable equipment proposed in the embodiment of the present invention, the resistance wire bare cavity includes: a resistance wire and a whispering gallery microcavity, the whispering gallery microcavity wraps the resistance wire in the circumferential direction; wherein the resistance wire is used to release heat to the whispering gallery microcavity when current is passed; the whispering gallery microcavity can couple into a first optical signal, and after being heated, can modulate the first optical signal based on the change of thermally induced volume and thermally induced refractive index, wherein the first optical signal is transmitted by an optical fiber, and the whispering gallery microcavity is coupled with the optical fiber. Thus, the frequency sweep function can be realized by applying a periodic voltage to the resistance wire, and by adjusting the voltage applied to the resistance wire, the desired resonance mode can be captured or locked, so that the light is bound in the whispering gallery microcavity for a long time after being coupled into the whispering gallery microcavity, thereby increasing the light energy density in the cavity, and the photon lifetime is increased from the picosecond level to the nanosecond level, thereby the photons can fully interact with electrons, molecules and lattices, so that very rich nonlinear effects can be observed. Furthermore, the resistance wire bare cavity can also be adapted to tunable lasers or single-frequency lasers, with higher adaptability.

[0112] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0113] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A resistance wire bare cavity, It is characterized in that include: A resistance wire and a whispering gallery microcavity, wherein the whispering gallery microcavity wraps the resistance wire along a circumferential direction; The resistance wire is used to release heat to the whispering gallery microcavity when current is passed through it; the whispering gallery microcavity can couple a first optical signal, and after being heated, can modulate the first optical signal based on changes in thermally induced volume and thermally induced refractive index, wherein the first optical signal is transmitted by an optical fiber, the whispering gallery microcavity is coupled to the optical fiber, and the resistivity of the resistance wire is constant; the material of the whispering gallery microcavity is a light-transmitting material.

2. The resistance wire bare cavity according to claim 1, It is characterized in that The resistivity of the resistance wire is in the range of 1.59*10 -8 (Ω·m) to 9.5*10 -8 (Ω·m).

3. The resistance wire bare cavity according to claim 1, It is characterized in that The outer diameter of the resistance wire ranges from 10 to 150 um.

4. The resistance wire bare cavity according to claim 3, It is characterized in that The outer diameter of the whispering gallery microcavity is greater than 1 times the outer diameter of the resistance wire, and less than or equal to 2 times the outer diameter of the resistance wire.

5. The resistance wire bare cavity according to claim 1, It is characterized in that The light-transmitting material includes one of polystyrene, methyl methacrylate, polydimethylsiloxane, aluminum oxide or silicon dioxide.

6. A method for preparing a bare resistance wire cavity, It is characterized in that Used to prepare the resistance wire bare cavity according to any one of claims 1 to 5, the preparation method comprises the following steps: Pre-treating the resistance wire so that the surface roughness of the resistance wire is less than 50 nm; and horizontally straightening and fixing the pre-treated resistance wire on a fixture; Using a microfluidic pump to transfer the material for making the whispering gallery microcavity to the resistance wire in the form of droplets, and keeping the microscope focused and monitoring during the transfer process, wherein the material of the whispering gallery microcavity has fluidity before solidification, and the viscosity is greater than 300 cps and less than 10000 cps; The resistance wire is adjusted from a horizontally stretched state to a vertically stretched state, and the whispering gallery microcavity is formed by utilizing the gravity and surface tension of the material of the whispering gallery microcavity, wherein the microscope is kept in focus during the adjustment process; The preparation is completed by lightly touching the surface of the whispering gallery microcavity with an optical fiber and observing whether the optical fiber will adhere to the surface of the whispering gallery microcavity to determine whether the whispering gallery microcavity is completely cured; and the preparation is completed after the whispering gallery microcavity is cured on the resistance wire, wherein the microscope is kept focused for monitoring during the curing process.

7. A tunable device, It is characterized in that The device comprises the resistance wire bare cavity as claimed in any one of claims 1 to 5, and further comprises: an optical fiber; The optical fiber, the resistance wire and the whispering gallery microcavity form a coupling structure.

8. The tunable device according to claim 7, It is characterized in that The optical fiber is a tapered optical fiber, the resistance wire and the tapered region of the tapered optical fiber are intersected to form an intersection, and the whispering gallery microcavity is located on the resistance wire corresponding to the intersection.

9. The tunable device according to claim 7, It is characterized in that The optical fiber is a U-shaped optical fiber, the resistance wire is folded in half to form a folding point, the folding point is arranged close to the bending point of the U-shaped optical fiber, and the whispering gallery microcavity is located at the folding point.

10. The tunable device according to claim 7, It is characterized in that Also includes: Packaging materials, fixing materials and packaging substrates; The fixing material is used to fix the coupling structure on the packaging substrate, and the packaging material is used to package the coupling structure, wherein the effective refractive index of the packaging material is smaller than the effective refractive index of the whispering gallery microcavity.

11. A tunable device, It is characterized in that The tunable device according to any one of claims 7 to 10 further comprises: an electrical signal output unit, a laser, a photodetector and an image display; Wherein, the electrical signal output unit is electrically connected to the resistance wire in the tunable device, and is used to provide an electrical signal to the resistance wire; The output end of the laser is connected to one end of the optical fiber in the tunable device, the other end of the optical fiber is located at the detection surface of the photodetector, and the image display is electrically connected to the photodetector, wherein the laser is used to output a first optical signal, the optical fiber is used to transmit the first optical signal, the photodetector is used to receive a second optical signal modulated by the whispering gallery microcavity in the tunable device, and the image display is used to display the second optical signal; Wherein, the electrical signal output unit includes a voltage amplifier and a signal generator, or a signal generator, or a programmable constant current source.

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