Fabrication Method of Bat-shaped Surface Nanoaxial Photonic Microcavity Device

Abstract

The present application discloses a method for fabricating a bat-shaped surface nano axial photonic microcavity device, which relates to the field of photonic device processing, and includes: placing the optical fiber with the coating layer stripped into a V-shaped optical fiber fixture horizontally aligned by a carbon dioxide laser fusion splicer for fixing, applying prestress to the optical fiber towards the outer sides of both ends to make it in a stretched state; determining the target positions of the left and right ear wings of the bat-shaped SNAP microcavity on the optical fiber, controlling the movement of the micro motor under the V-shaped optical fiber fixture, moving the target positions to the exposure position of the carbon dioxide laser fusion splicer, and focusing the light spot on the surface of the optical fiber at the target positions; determining the carbon dioxide laser exposure power and exposure time according to the axial length of the required bat-shaped SNAP microcavity and the ERV height of the ear wings, and performing exposure at the target positions corresponding to the left and right ear wings respectively. This solution can use a carbon dioxide laser fusion splicer to quickly and accurately fabricate bat-shaped SNAP microcavities with axial dimensions ranging from micrometers to millimeters, reducing time and cost investment.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of photon device processing, and particularly to a method for fabricating a bat-shaped surface nano-axial photon microcavity device. Background Art

[0002] The surface nanoscale axial photonics (SNAP) structure microcavity is an optical whispering gallery mode microcavity device based on fiber integration proposed in recent years. By introducing micro-nano scale small radius changes on the fiber surface, the whispering gallery mode can be localized in the fiber cross-section direction and slowly transmitted along the fiber axis. Compared with traditional whispering gallery microcavities, SNAP microcavities have the advantages of micro-nano size, ultra-high processing accuracy (sub-angstrom level), high quality factor (Q value), etc. In particular, diverse processing technologies enable the SNAP microcavity surface to have different effective radius variation (ERV) profiles along the fiber axis (hereinafter referred to as ERV profiles), prompting SNAP microcavities with different ERV profiles to exhibit great application value and potential in optical sensing, optical frequency filtering, optical delay devices, etc. Among them, the SNAP microcavity with a bat-shaped ERV profile has the characteristic that the fundamental mode field of the axial mode is uniformly distributed along the fiber axis. When particles in different states enter different positions along the fiber axis of the SNAP microcavity, it can cause changes in the fundamental mode field intensity. Therefore, the bat-shaped SNAP microcavity has important application value in microfluidic sensing and can be used for particle position tracking, real-time positioning monitoring, etc.

[0003] The technical key to realizing the preparation of a bat-shaped SNAP microcavity is to generate two ERV protrusions in the shape of bat ear wings on the fiber surface. The ERV height of the protrusions is generally only a few to dozens of nanometers, so that a bat-shaped SNAP microcavity device is formed between the two protrusions. In related technologies, the proposed methods for fabricating bat-shaped SNAP microcavities mainly include carbon dioxide laser annealing method and femtosecond laser direct writing method. The former carbon dioxide laser annealing method requires designing a complex carbon dioxide laser optical path, has higher requirements for instrument accuracy, and also requires manual positioning of the focus position of the carbon dioxide laser on the fiber. In order to generate a bat-shaped profile on the fiber surface, it is usually necessary to expose the carbon dioxide laser while manually controlling the stretching force of the fiber. The overall process is relatively complex and it is difficult to precisely control the axial dimensions of the SNAP microcavity. The latter femtosecond laser direct writing method requires precisely designing the path of the femtosecond laser written in the fiber and comprehensively coordinating many processing parameters such as femtosecond laser pulse energy and writing speed. Due to the limitation of the writing speed, this processing method takes a long time. Summary of the Invention

[0004] The present application provides a method for fabricating a bat-shaped surface nano axial photonic microcavity device, which solves the problems of time-consuming preparation and difficult flexible control of the axial dimension of the bat-shaped SNAP microcavity device in the related art. The method includes:

[0005] S1, placing the optical fiber with the coating layer removed into two horizontally aligned V-shaped optical fiber fixtures of a carbon dioxide laser fusion splicer for fixation, and applying prestress to the optical fiber towards the outer sides of both ends to make it in a stretched state;

[0006] S2, determining the target positions of the left ear wing and the right ear wing of the bat-shaped SNAP microcavity on the optical fiber, and controlling the movement of the micro motors below the V-shaped optical fiber fixtures to move the target positions to the exposure position of the carbon dioxide laser focused beam of the carbon dioxide laser fusion splicer, and focusing the light spot on the surface of the optical fiber at the target positions;

[0007] S3, determining the carbon dioxide laser exposure power and exposure time according to the required axial length of the bat-shaped SNAP microcavity and the effective radius variation ERV height of the ear wings, and performing exposure at the corresponding target positions of the left ear wing and the right ear wing respectively, so that the surface of the optical fiber at the target positions generates protrusions under the action of laser exposure and prestress, and the bat-shaped SNAP microcavity is formed in the axial region of the two protruding optical fibers.

[0008] Specifically, after fixing the optical fiber in the V-shaped optical fiber fixture, control the two micro motors to move 50 μm respectively towards the left and right outer sides, and the optical fiber is in a stretched state under the prestress generated by the movement.

[0009] Specifically, set the carbon dioxide laser exposure power to be between -40 bits and -100 bits less than the standard power, and the duration of a single exposure is less than 1 s.

[0010] Specifically, step S3 includes: determining the initial exposure power, exposure time and carbon dioxide laser processing parameters, and performing primary exposure at the target positions of the optical fiber;

[0011] Obtaining the ERV height generated on the surface of the optical fiber at the target positions after exposure, and adjusting the exposure power, exposure time and the number of iterative exposures according to the difference from the target ERV height;

[0012] Continue to perform iterative laser exposure on the target positions until bat-shaped ear wings with the target ERV height are obtained, and record the ear wing exposure parameters; wherein, the exposure power is negatively correlated with the optical fiber diameter and positively correlated with the ERV height.

[0013] Specifically, after obtaining one side of the bat - shaped ear wing, the method further includes: controlling the two micro - motors to move simultaneously in the direction of the bat - shaped ear wing to be fabricated on the opposite side by an axial length, and determining it as the target exposure position;

[0014] Obtaining the ear - wing exposure parameters, and performing exposure based on the ear - wing exposure parameters to generate a bat - shaped ear wing with a target ERV height.

[0015] Specifically, the optical fiber materials for exposure include silica materials, polymer materials, semiconductor materials, and crystal materials.

[0016] The beneficial effects brought by the above - mentioned technical solution at least include: When preparing the bat - shaped SNAP micro - cavity, directly using a common scientific instrument in the field of engineering basic science, a carbon dioxide laser welding machine, as the preparation device, the entire operation process does not require additional construction and manufacturing of other precision scientific instruments, and the operation is simple. During the preparation process, the V - shaped optical fiber fixture and micro - motors of the carbon dioxide laser welding machine are used to control the left - right directional movement of the optical fiber, so the axial length of the micro - cavity is completely controllable. The carbon dioxide laser focused beam of the carbon dioxide laser welding machine can achieve complete control of the exposure power and exposure time. The surface of the optical fiber undergoes minute deformation under the action of specific laser exposure and the prestress on the optical fiber, and the two formed protrusions constitute the two ear wings of the bat - shaped ERV contour, thereby generating a bat - shaped SNAP micro - cavity with corresponding dimensions. Based on this solution, bat - shaped SNAP micro - cavities with axial dimensions ranging from micrometers to millimeters can be prepared quickly and accurately. Its principle is simple, the time consumption is short, and existing integrated equipment is used, avoiding complex optical path adjustment devices, having the advantages of simple device, low manufacturing cost, and high success rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of preparing a bat - shaped SNAP micro - cavity using a carbon dioxide laser welding machine provided by an embodiment of the present application;

[0018] Figure 2 is a flowchart of a method for preparing a bat - shaped SNAP micro - cavity using a carbon dioxide laser welding machine provided by an embodiment of the present application;

[0019] Figure 3 is a schematic process flow diagram of fabricating a bat - shaped SNAP micro - cavity provided by an embodiment of the present application;

[0020] Figure 4 is a spectral distribution diagram of a bat - shaped SNAP micro - cavity with an axial length of 700 μm and an ERV height of 24.3 nm fabricated in this embodiment;

[0021] Figure 5It is the spectral distribution diagram of the bat-shaped SNAP microcavity with an axial length of 1250 μm and an ear wing ERV height of 32.4 nm fabricated in this embodiment. Detailed implementation manners

[0022] To make the objectives, technical solutions and advantages of this application clearer, the following will further describe the implementation manners of this application in detail with reference to the accompanying drawings.

[0023] As used herein, "a plurality of" means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0024] As Figure 1 is a schematic structural diagram of a bat-shaped SNAP microcavity prepared using a carbon dioxide laser welding machine. The carbon dioxide laser welding machine includes two horizontally aligned V-shaped optical fiber fixtures (left fixture 3 and right fixture 4) for placing the optical fiber 5 to be processed. The V-shaped optical fiber fixtures are installed on two micro motors that can move horizontally (left micro motor and right micro motor). The carbon dioxide laser focused beam 6 is symmetrically arranged in the longitudinal space of the optical fiber 5, and the carbon dioxide laser focused beam 6 can move in the longitudinal direction.

[0025] As Figure 2 shown, it is the flowchart of preparing a bat-shaped SNAP microcavity using a carbon dioxide laser welding machine provided by the embodiment of this application. The steps are as follows:

[0026] S1, Place the optical fiber with the coating removed into the two horizontally aligned V-shaped optical fiber fixtures of the carbon dioxide laser welding machine and fix it. Apply prestress to the optical fiber towards the outer sides of both ends to make it in a stretched state.

[0027] Placed between the left and right V-shaped fiber optic clamps is the fiber with the coating removed. Bat-shaped ear wings are formed on the fiber with the coating removed by the left clamp 3 and the right clamp 4. The placement process is manual. The axial length of the bat-shaped SNAP microcavity is usually on the order of micrometers to millimeters. To ensure the accuracy of the process, it is necessary to perform positioning correction on the placed fiber and generate a certain prestress. The positioning correction by the micro motor is to ensure the accuracy of the axial dimension and position, and the prestress is to stretch the fiber tightly to ensure the accuracy of the subsequent axial dimension and exposure. Since the fiber generates a small convex deformation by releasing the internal prestress and being heated by exposure, the prestress needs to be applied in advance by an external force, and the heat generated by exposure requires precise control of the spot size on the fiber surface. Although traditional fiber fusion splicers and carbon dioxide laser fusion splicers can both heat or expose the fiber, the carbon dioxide laser spot size is smaller, and the arc discharge area of ordinary fusion splicers is large. The small spot can more precisely control the height of the generated ERV.

[0028] In this solution, during the process of stretching and positioning correction of the fiber, two micro motors are respectively controlled to move 50 μm to the left and right outer sides, that is, the whole fiber is stretched outward by 100 μm. The fiber is in a stretched state under the action of the prestress generated during the movement of the micro motor.

[0029] S2. Determine the target positions of the left and right ear wings of the bat-shaped SNAP microcavity on the fiber, and control the movement of the micro motor under the V-shaped fiber optic clamp to move the target positions to the exposure position of the carbon dioxide laser focused beam of the carbon dioxide laser fusion splicer, and focus the spot on the surface of the fiber at the target positions.

[0030] The movement control and automatic alignment process of the micro motor are all automatically completed by setting the control parameters of the carbon dioxide laser fusion splicer. The distance between the carbon dioxide laser focused beam and the fiber surface is determined according to the fiber diameter and the specific design of the fusion splicer. This application does not limit this.

[0031] S3. Determine the carbon dioxide laser exposure power and exposure time according to the required axial length of the bat-shaped SNAP microcavity and the ERV height of the ear wings, and perform exposure at the corresponding target positions of the left and right ear wings respectively.

[0032] When the carbon dioxide laser focused beam performs exposure, optionally, first fine-tune the distance between the upper and lower laser heads and the fiber surface position, and then perform exposure. The exposure power is usually determined according to the fiber material, size, and ear wing height. However, to provide a more flexible operation method and improve fault tolerance, a relatively small standard power is selected for multiple iterations. The exposure time is usually set within 1 s to avoid damaging the fiber due to too long time. The exposure process specifically further includes the following steps:

[0033] Step 1: Determine the initial exposure power, exposure time, and carbon dioxide laser processing parameters, and perform the first exposure at the target position on the optical fiber.

[0034] When the carbon dioxide laser focused beam is used for exposure, optionally, first fine-tune the distance between the upper and lower laser heads to the surface of the optical fiber, and then perform the exposure. The exposure power is usually determined according to the optical fiber material, size, and ear wing height. However, in order to provide a more flexible operation method and improve fault tolerance, a relatively small standard power is selected for multiple iterations. The exposure time is usually set within 1 s, and the carbon dioxide laser exposure power is between -40 bits and -100 bits less than the standard power to avoid damaging the optical fiber due to too long time and facilitate subsequent adjustment of relevant parameters. It should be noted that the optical fiber materials exposed in this solution include, but are not limited to, silica materials, polymer materials, semiconductor materials, and crystal materials, etc. The specific materials are not limited in this solution.

[0035] Step 2: Obtain the ERV height generated on the surface of the optical fiber at the target position after exposure, and adjust the exposure power, exposure time, and the number of iterative exposures according to the height difference from the target ERV height.

[0036] In this solution, the ERV height of the bat-shaped ear wing is the height of the optical fiber surface protruding relative to the unexposed area. During the first exposure, the optical fiber releases the prestress generated inside the optical fiber during the tensioning by the micro-motor and the exposure heating process, thereby introducing minute deformations, and then forming a bat-shaped ear wing-like protrusion on the surface of the optical fiber.

[0037] Specific reference Figure 3 , which is a schematic process flow diagram for fabricating a bat-shaped SNAP microcavity. After single or multiple exposures, ear wings with a certain ERV height are finally formed at the target position. After determining the initial ERV height, the actual height difference can be calculated based on the target ERV height, and then the exposure parameters and the number of iterative exposures can be adjusted according to the height difference. Usually, when the exposure time remains unchanged, the exposure power is negatively correlated with the optical fiber diameter and positively correlated with the ERV height. That is, the larger the optical fiber diameter, the smaller the set exposure power, and the smaller the ERV height generated during single exposure.

[0038] Step 3: Continue to perform iterative laser exposure on the target position until bat-shaped ear wings with the target ERV height are obtained, and record the ear wing exposure parameters.

[0039] The left and right ear wings of the bat-shaped SNAP microcavity are symmetric structures. After forming the bat-shaped ear wing on one side, record and store the relevant parameters of this exposure as the exposure parameters for generating the ear wing on the other side.

[0040] Step 4: Control the two micro-motors to move simultaneously towards the direction of the bat ear wing to be fabricated on the opposite side by an axial length, and determine it as the target exposure position.

[0041] As Figure 3 shown, assume that the left ear wing is generated by exposure first, and then control the two micro-motors to move simultaneously towards the right side (the direction of the ear wing to be generated on the opposite side) by an axial length. This axial length is the axial distance between the highest points of the two ear wings, that is, the axial dimension of this SNAP microcavity. During the movement, the two micro-motors need to move simultaneously, and the distance between the two V-shaped optical fiber fixtures remains unchanged during the movement. The purpose is to keep the same prestress of the optical fiber before and after, and ensure that the ERV heights of the ear wings generated on both sides are consistent.

[0042] Step 5: Obtain the ear wing exposure parameters, and perform exposure based on the ear wing exposure parameters to generate a bat-shaped ear wing with the target ERV height.

[0043] This step refers to the Figure 3 process. After the micro-motors move an axial length from point A and are positioned at point B, which is the exposure position of the right ear wing, read the relevant exposure parameters of the left ear wing and then perform exposure to generate the right ear wing.

[0044] The following details this solution through an embodiment.

[0045] Embodiment 1: Fabricate a bat-shaped SNAP microcavity with an axial length of 700 μm on a single-mode optical fiber with a diameter of 125 μm.

[0046] 1) Set the "fusion mode" in the carbon dioxide laser fusion splicer to the "optical fiber processing" mode, and turn on the "motor automatic alignment" function. Then place the optical fiber 5 with the coating removed in the two horizontal V-groove optical fiber fixtures of the fusion splicer, so that both ends of the optical fiber 5 are fixed on the two one-dimensional translation stages 1 and 2 respectively. Enter the "motor drive" in the "edit fusion mode" function for setting, and move the left and right motors 50 μm respectively, so that the optical fiber 5 is stretched towards both axial sides and kept in a taut state, generating a prestress applied axially to the optical fiber 5.

[0047] 2) Set the light passing power to "standard power - 50 bits" and the light passing time to 0.5 s through the "edit fusion mode" of the fusion splicer, so that the focused beam 6 of the carbon dioxide laser is exposed at position A of the optical fiber 5 to fabricate the left "ear wing" of the bat-shaped SNAP microcavity.

[0048] 3) Enter the "motor drive" in the "edit fusion mode" function of the fusion splicer for setting, and move the left and right motors 700 μm to the right respectively, which is the axial length of the bat-shaped SNAP microcavity to be fabricated.

[0049] 4) Repeat the operation in step 2) to expose the carbon dioxide laser focused beam 6 at position B of the optical fiber 5, and fabricate the right "ear wing" of the bat-shaped SNAP microcavity.

[0050] Figure 4 Spectral distribution diagram of the bat-shaped SNAP microcavity with an axial length of 700 μm and an ERV height of the ear wing of 24.3 nm fabricated in this embodiment. From Figure 4 it can be seen that the ERV profile of the fabricated SNAP microcavity is bat-shaped. The two "ear wings" on both sides of the bat are formed by stretching the optical fiber twice with a carbon dioxide laser, causing tiny protrusions to appear on the surface of the optical fiber. The axial distance between A and B is 700 μm, which is consistent with the parameter of the bat-shaped SNAP microcavity with a required axial length of 700 μm.

[0051] As can be seen from the above embodiments, it can be achieved by controlling the two side micro-motors to move in the same direction by 700 μm. This operation is simple and convenient. In addition, Figure 4 shows the wavelength distribution along the optical fiber axis when two adjacent axial eigenmodes are simultaneously excited, so there are two adjacent bat-shaped profiles.

[0052] Embodiment 2: Fabricate a bat-shaped SNAP microcavity with an axial length of 1250 μm on a 125-μm single-mode optical fiber.

[0053] On the basis of Embodiment 1, change the relevant parameters in step 2) to "the light passing power of the carbon dioxide laser is'standard power - 40 bits', and the exposure time is 0.7 s", and in step 3), "move the left and right motors 1250 μm to the right respectively" to fabricate a bat-shaped SNAP microcavity with an axial length of 1250 μm and an ERV height of the ear wing of 32.4 nm. The corresponding spectral distribution diagram is as Figure 5 shown. Compared with Figure 4 it can be found that for step 2), after increasing the exposure power and exposure time, the ERV height of the ear wing of the bat-shaped SNAP microcavity can be significantly increased. In addition, for step 3), changing the moving distances of the left and right micro-motors can match the required axial length of the bat-shaped SNAP microcavity.

[0054] In summary, when preparing the bat-shaped SNAP microcavity, a carbon dioxide laser welding machine, a scientific instrument commonly used in the field of engineering basic science, is directly used as the preparation device. No additional precision scientific instruments need to be built or manufactured during the whole operation process, and the operation is simple. During the preparation process, the V-shaped fiber fixture and the micro motor of the carbon dioxide laser welding machine are used to control the left-right directional movement of the optical fiber, so the axial length of the microcavity is completely controllable. The carbon dioxide laser focused beam of the carbon dioxide laser welding machine can achieve complete control of the exposure power and exposure time. Under the action of specific laser exposure and prestress on the fiber surface, the fiber undergoes a small deformation, and the two formed protrusions constitute the two ear wings of the bat-shaped ERV profile, thereby generating a bat-shaped SNAP microcavity with corresponding dimensions.

[0055] The micro motor maintains the same prestress during the movement to ensure the same height of the left and right ear wings. The moving distance of the micro motor is the axial dimension of the bat-shaped SNAP microcavity. This process can automatically complete steps such as positioning, calibration, laser focusing, and exposure by setting the parameters of the welding machine, realizing automated operation.

[0056] Based on this solution, bat-shaped SNAP microcavities with axial dimensions ranging from micrometers to millimeters can be prepared quickly and accurately. Its principle is simple, the time consumption is short, and existing integrated devices are used, avoiding complex optical path adjustment devices. It has the advantages of simple device, low manufacturing cost, and high success rate.

[0057] The above describes the preferred embodiments of the present invention; it should be understood that the present invention is not limited to the above specific embodiments. The devices and structures not described in detail should be understood to be implemented in a common manner in the art; any person skilled in the art can make many possible changes and modifications without departing from the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes, which does not affect the essence of the present invention; therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of the protection of the technical solution of the present invention.

Claims

1. A manufacturing method of a bat-shaped surface nano-axial photon microcavity device, characterized in that, The method includes: S1. Place the optical fiber with the coating layer removed into two horizontally aligned V-shaped optical fiber fixtures of a carbon dioxide laser fusion splicer for fixation, and apply prestress to the optical fiber towards the outer sides of both ends to make it in a stretched state; S2. Determine the target positions of the left earwing and the right earwing of the bat-shaped SNAP microcavity on the optical fiber, and control the movement of the micro motor below the V-shaped optical fiber fixture to move the target positions to the exposure position of the carbon dioxide laser focused beam of the carbon dioxide laser fusion splicer, and focus the light spot on the surface of the optical fiber at the target positions; S3. Determine the carbon dioxide laser exposure power and exposure time according to the axial length of the bat-shaped SNAP microcavity required and the ERV height change of the effective radius of the earwings, and perform exposure at the corresponding target positions of the left earwing and the right earwing respectively, so that the surface of the optical fiber at the target positions generates protrusions under the action of laser exposure and prestress received, and form the bat-shaped SNAP microcavity in the axial regions of the two protruded optical fibers; Step S3 includes: Determine the initial exposure power, exposure time and carbon dioxide laser processing parameters, and perform primary exposure at the target positions of the optical fiber; Obtain the ERV height generated on the surface of the optical fiber at the target positions after exposure, and adjust the exposure power, exposure time and iterative exposure times according to the difference from the target ERV height; Continue to perform iterative laser exposure on the target positions until bat-shaped earwings with the target ERV height are obtained, and record the earwing exposure parameters; wherein, the exposure power is negatively correlated with the optical fiber diameter and positively correlated with the ERV height; After obtaining one side of the bat-shaped earwings, the method further includes: Control the two micro motors to move towards the direction of the bat-shaped earwings to be fabricated on the opposite side by an axial length at the same time, and determine it as the target exposure position; wherein, the axial length is the axial distance between the highest points of the two earwings; Obtain the earwing exposure parameters, and perform exposure based on the earwing exposure parameters to generate bat-shaped earwings with the target ERV height.

2. The method according to claim 1, wherein After fixing the optical fiber in the V-shaped optical fiber fixture, control the two micro motors to move 50 μm respectively towards the left and right outer sides, and the optical fiber is in a stretched state under the prestress generated by the movement.

3. The method according to claim 2, wherein Set the carbon dioxide laser exposure power to be between -40 bits and -100 bits less than the standard power, and the duration of one exposure is less than 1 s.

4. The method according to any one of claims 1-3, characterized in that, The optical fiber materials used for exposure include silica materials, polymer materials, semiconductor materials and crystal materials.

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