All-optical tunable controllable optical comb generation system and method based on functionalized microvessel cavity

Abstract

The application discloses a kind of based on functional echo wall mode optical microbottle cavity Full light tuning controllable optical comb generation method. Including 1550nm narrow line width continuous wave laser, single-mode optical fiber, erbium-doped fiber amplifier, polarization controller, optical isolator, functional microbottle cavity-fiber taper coupling system, optical attenuator, optical spectrum analyzer and 1550nm power adjustable laser. The unique axial characteristics of echo wall mode microbottle cavity are used, the free spectral range of microcavity is reduced, the axial mode microcavity optical frequency comb with small free spectral range is generated, and based on full light tuning method, functional microbottle cavity is prepared, and the axial mode microcavity optical frequency comb generated is tuned by photo-thermal material titanium dioxide, and significant spectral range tuning is realized. The application solves the limitation that WGM microcavity optical frequency comb cannot be effectively tuned due to large free spectral range, and helps the practical application in the field of microcavity optical frequency comb optical communication, optical frequency synthesis and the like.

Description

Technical Field

[0001] The present invention relates to microcavity optical frequency comb technology, which can be used in optical communications, optical frequency synthesis, and other fields. Specifically, the present invention relates to an all-optically tunable and controllable optical comb generation system and method based on a functionalized whispering gallery mode optical microbottle cavity. Background Art

[0002] Whispering gallery mode (WGM) optical microcavities have seen rapid development in recent years. Due to their exceptionally small mode volume, ultra-high quality factor, fast dynamic response, and ultra-high sensitivity, they have found important applications in high-sensitivity sensing, microlasers, and nonlinear optics. WGM optical microcavities can generate optical frequency combs with unique advantages such as high repetition rate, wide spectrum, and high integration, offering promising research prospects in fields such as low-threshold microlasers, atomic clocks, and optical communications.

[0003] However, in practical applications such as wavelength division multiplexing coherent communications and optical frequency synthesis, the tunability of an optical frequency comb to adjust the comb lines at any position within the free spectral range (FSR) is a key feature. However, the comb tooth frequency distribution of a microcavity optical frequency comb is affected by the microcavity material and structure. Without external assistance, when the microcavity is deterministically prepared, the generated optical frequency comb cannot be effectively tuned.

[0004] All-optical tuning is an effective means of tuning the resonant frequency of a microcavity. By coating the microcavity surface with photothermal materials and applying an external control light source, the photothermal effect alters the microcavity size and refractive index, thereby changing the resonant mode and tuning the optical frequency comb. However, the FSR of a microcavity typically ranges from GHz to THz, which hinders the tunability of the optical frequency comb. Currently, the maximum tuning range of a microcavity optical frequency comb is less than 70% of the FSR, and comb tuning exceeding the FSR has not yet been achieved.

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention is proposed. Summary of the Invention

[0006] To address the shortcomings of traditional WGM microcavity frequency combs, this paper provides an all-optically tunable and controllable optical comb generation system and method based on a functionalized microbottle cavity. This system aims to reduce the FSR by leveraging the unique axial properties of the WGM microbottle cavity and achieve significant tuning of the microcavity frequency comb spectrum through all-optical tuning using the photothermal material titanium dioxide.

[0007] To achieve the above object, the technical solution provided by the present invention is:

[0008] A functionalized WGM micro-bottle cavity all-optically tunable and controllable optical comb generation system, comprising a 1550nm narrow-linewidth continuous-wave laser 1, a 1550nm single-mode optical fiber 2, an erbium-doped fiber amplifier 3, a polarization controller 4, an optical isolator 5, a functionalized micro-bottle cavity-fiber taper coupling system 6, an optical attenuator 7, an optical spectrum analyzer 8, and a 1550nm power-tunable laser 9;

[0009] The 1550nm narrow linewidth continuous wave laser 1 is used to output 1550nm tunable continuous laser light to excite the functionalized microbottle cavity-fiber taper coupling system 6 to generate a microcavity optical frequency comb;

[0010] The erbium-doped fiber amplifier 3 is connected to the 1550nm narrow-linewidth continuous-wave laser 1 via a single-mode optical fiber 21, and is used to increase the power of the laser output from the 1550nm narrow-linewidth continuous-wave laser 1, so that the laser power coupled into the WGM microcavity is greater than the threshold for excitation of the microcavity optical frequency comb.

[0011] The polarization controller 4 is connected to the erbium-doped fiber amplifier 3 via the optical fiber 22 and is used to adjust the polarization state of the laser input into the functionalized micro-bottle cavity-fiber taper coupling system 6;

[0012] The optical isolator 5 is connected to the polarization controller 4 through the optical fiber 23, and is used to isolate the reverse transmission light through the forward transmission light to prevent the reverse transmission light from damaging the instrument;

[0013] The functionalized microbottle cavity-fiber taper coupling system 6 includes: a functionalized fiber WGM microbottle cavity and a fiber taper 62 .

[0014] Furthermore, the functionalized WGM fiber micro-bottle cavity includes a main micro-bottle cavity 60 and a secondary micro-bottle cavity 61, wherein the secondary micro-bottle cavity 61 is doped with titanium dioxide, a photothermal material. The secondary micro-bottle cavity 61 is a spherical cavity, the purpose of which is to increase the doping area of ​​the photothermal material.

[0015] Furthermore, the preparation method of the functionalized WGM optical fiber microbottle cavity comprises the following steps:

[0016] The method for preparing the functionalized WGM optical fiber microbottle cavity comprises the following steps:

[0017] SⅠ. Take a section of single-mode G652D bare fiber, remove the coating with a wire stripper, wipe it clean with alcohol, and use a fiber cleaver to cut the fiber end flat; then fusion-splice the other end of the fiber to the fiber jumper.

[0018] SII, placing the cut optical fiber end in step S1 above in an optical fiber fusion splicer; starting the optical fiber fusion splicer and performing a discharge treatment on the optical fiber end using a high-voltage arc; the optical fiber end is heated and melted, and microspheres are formed under the action of surface tension;

[0019] SIII, another section of single-mode optical fiber G652D bare fiber is taken, and the section of optical fiber is stripped of coating, cleaned and cut according to the steps in step SI; then the end of the optical fiber and the microsphere in step SII are placed in the optical fiber fusion splicer at the same time, and the two are aligned and attached in the horizontal position; the optical fiber fusion splicer is started, and the microsphere and the end of the optical fiber are discharged by high-voltage arc; under the action of surface tension, a micro-bottle cavity structure is formed;

[0020] SIV, the end of the optical fiber jumper wire in step SIII is cut using wire strippers, and a length of about 100 μm of the optical fiber rod is reserved;

[0021] SV, the optical fiber vertical clamp is placed at the edge of the Z-axis lifting table 1, and the main micro-bottle cavity is placed on the vertical optical fiber clamp, wherein the end of the optical fiber rod in step SIV is downward, and the clamping position is above the optical fiber rod and the micro-bottle cavity; the micro-bottle cavity and the optical fiber rod are observed through the microscope, and the micro-bottle cavity is ensured to be in the middle of the imaging screen of the microscope;

[0022] SVI, the slide containing the mixture of titanium dioxide powder and ultraviolet glue is placed on another Z-axis lifting table 2, and the central position of the slide is placed directly below the slide in step SI;

[0023] SVII, the Z-axis lifting table 2 in step S2 is controlled to rise until the optical fiber rod is in sufficient contact with the mixture in step S6 is observed in the imaging screen of the microscope;

[0024] SVIII, the Z-axis lifting table 2 is controlled to descend until the optical fiber rod is separated from the mixture, and then the optical fiber rod with the mixture in the above step is irradiated under the ultraviolet lamp;

[0025] SIX, the optical fiber microcavity in step SIII is placed into the optical fiber fusion splicer again, wherein the middle part of the optical fiber rod is placed in the center of the electrode of the optical fiber fusion splicer; the optical fiber fusion splicer is started, and the optical fiber rod is fused into a microsphere under the action of surface tension, wherein the microsphere is doped with the photo-thermal material titanium dioxide.

[0026] The optical fiber taper 62 is connected with the optical isolator 5 through the optical fiber 24. After the laser passes into the optical fiber taper, an evanescent field is generated in the waist taper region of the optical fiber taper, and then the light is coupled in and out of the functionalized optical fiber WGM micro-bottle cavity through the evanescent field;

[0027] Further, the waist taper diameter of the optical fiber taper is 1.8-2.2 μm, and preferably 2 μm, and the diameters of the two ends are 125 μm;

[0028] Further, the optical fiber taper 62 needs to be coupled with the main microbottle cavity 60 in the functionalized optical fiber WGM microbottle cavity. The equatorial circumference of the main microbottle cavity 60 is in contact with the optical fiber taper 662, which is used to stabilize the microcavity-fiber taper system and make the light better enter the main microbottle cavity 60. When the light is transmitted into the main microbottle cavity 60 through the optical fiber taper 62, it will continuously undergo total reflection on the inner wall of the cavity, and the light satisfying the WGM microcavity resonance wavelength will be confined in the cavity.

[0029] Further, the resonance condition of the main microbottle cavity 60 is:

[0030]

[0031] where λ is the microcavity resonance wavelength, R is the microbottle cavity equatorial radius, n neff is the effective refractive index of the microbottle cavity, m is the effective refractive index of the microbottle cavity, q is the axial quantum number of the microbottle cavity, which is related to the axial length of the microbottle cavity, △E m is the energy level interval energy difference;

[0032] Further, due to the unique axial characteristics of the WGM microbottle cavity, there are two transmission modes of optical signals in the WGM microbottle cavity: along the equatorial circumference inner wall and along the axial spiral transmission. The existence of the axial spiral transmission greatly increases the mode distribution in the cavity and reduces the FSR of the microbottle cavity. Compared with the microsphere cavity with the same radius, the FSR of the microbottle cavity is one order of magnitude smaller, and this small axial FSR makes it easy to realize the tuning within one FSR range for WGM;

[0033] Further, the FSRs corresponding to the two transmission modes of light in the WGM microbottle cavity are respectively:

[0034]

[0035] where FSR m is the free spectral range of the microbottle cavity when the light is transmitted along the equatorial circumference inner wall, and FSR q is the free spectral range of the microbottle cavity when the light is transmitted along the axial spiral transmission. λ0 is the input light wavelength, and △k is the curvature of the microbottle cavity;

[0036] Further, when the optical power transmitted into the main microbottle cavity 60 is higher than the microcavity optical frequency comb excitation threshold and satisfies the condition, the microcavity optical frequency comb can be generated by scanning the wavelength of the narrow linewidth continuous wave laser from the blue detuning region of the resonant mode of the microcavity to the red detuning region;

[0037] Further, due to the rich mode distribution of the WGM microbottle cavity, the microcavity optical frequency comb can be generated by directly and continuously manually increasing the wavelength of the narrow linewidth continuous wave laser 1. And multiple scans can repeatedly generate the same microcavity optical frequency comb at the same wavelength;

[0038] Furthermore, due to the unique axial characteristics of the WGM micro-bottle cavity, the WGM micro-bottle cavity has an axial resonance mode with a smaller FSR. Therefore, compared with a microsphere cavity with the same radius, the WGM micro-bottle cavity can excite an axial mode microcavity optical frequency comb with a smaller FSR.

[0039] The optical attenuator 7 is connected to the optical fiber cone 62 via the optical fiber 25 and is used to attenuate the optical power transmitted from the functionalized optical fiber WGM micro-bottle cavity to the optical fiber cone 60, thereby protecting the optical spectrum analyzer 8;

[0040] The optical spectrum analyzer 8 is connected to the optical attenuator 7 via the optical fiber 26 and is used to receive the light transmitted from the functionalized optical fiber WGM microbottle cavity and measure the spectral information;

[0041] The 1550nm power adjustable laser 9 is connected to the functionalized fiber WGM microbottle cavity via an optical fiber 27 to generate a power adjustable laser to excite the titanium dioxide to generate heat, thereby changing the temperature of the microcavity and thus changing the resonant wavelength of the microcavity;

[0042] Furthermore, changes in temperature will affect the radius and refractive index of the microcavity. The effect of temperature on the radius and refractive index of the microcavity can be expressed as:

[0043]

[0044] Wherein, α is the thermo-optical coefficient of the microcavity material; β is the thermal expansion coefficient of the microcavity material;

[0045] Furthermore, changes in the radius and refractive index of the microcavity will cause changes in the resonant wavelength of the microcavity. The change in the resonant wavelength can be expressed as:

[0046]

[0047] Right now:

[0048] dλ=λ(α+β)dT (7)

[0049] Furthermore, gradually increasing the laser power of the 1550nm power-adjustable laser 9 will gradually increase the microcavity temperature. At this time, the resonant wavelength of the microcavity gradually redshifts.

[0050] Furthermore, after exciting the axial-mode microcavity optical frequency comb, the laser power of the 1550nm power-tunable laser 9 is increased to redshift the resonance wavelength of the microbottle cavity. At this time, the output laser wavelength of the 1550nm narrow-linewidth continuous-wave laser 1 is increased to align the pump wavelength with the redshifted resonance wavelength, thereby generating the same axial-mode microcavity optical frequency comb as that in the untuned state.

[0051] Further, since the FSR of the axial mode microcavity optical frequency comb is one order of magnitude smaller than that of the equatorial azimuthal mode microcavity optical frequency comb, the spectral tuning range can be more than the FSR by tuning the axial mode optical frequency comb.

[0052] The application also provides a method for generating a full-optical tunable controllable optical comb based on a functionalized microbottle cavity, comprising the following steps:

[0053] S1, system building;

[0054] The system for generating a full-optical tunable controllable optical comb based on a functionalized microbottle cavity is built, comprising a narrow linewidth laser 1, an erbium-doped fiber amplifier 3, a polarization controller 4, an optical isolator 5, a functionalized microbottle cavity-fiber taper coupling system 6, an optical attenuator 7, an optical spectrum analyzer 8 and a 1550nm power adjustable laser 9 sequentially linked by 1550nm single mode optical fibers.

[0055] Sb, the 1550nm laser output by the narrow linewidth continuous wave laser 1 is amplified by the erbium-doped fiber amplifier 3; when the light enters the fiber taper 62 of the functionalized microbottle cavity-fiber taper coupling system 6, it is coupled in and out of the functionalized WGM microbottle resonant cavity at the waist taper position through the evanescent field; then, the light passes through the attenuator 7 and is connected to the optical spectrum analyzer 8; at this time, only the 1550nm pump light spectrum can be observed on the optical spectrum analyzer 8;

[0056] Sc, the wavelength of the narrow linewidth continuous wave laser 1 is continuously increased by 0.1nm as a step, until a stable microcavity optical frequency comb is observed on the optical spectrum analyzer 8, and the optical wavelength for generating the optical frequency comb is recorded for repeated tuning to generate the optical frequency comb; the tuning range of the laser wavelength of the narrow linewidth continuous wave laser 1 is 1550nm-1570nm; the scanning is repeated until the generation of a small free spectral range axial mode microcavity optical frequency comb is observed on the optical spectrum analyzer 8;

[0057] Sd, when the axial mode microcavity optical frequency comb is observed on the optical spectrum analyzer 8, the 1550nm power adjustable laser 9 is turned on, the power of the laser 9 is increased by 10mW as a step, and the wavelength of the narrow linewidth continuous wave laser 1 is increased by 0.001nm as a step at each power, until an optical frequency comb with the same free spectral range as the initial axial mode microcavity optical frequency comb is observed;

[0058] Se, the step Sd is continuously repeated until the tuning range of the optical frequency comb is more than the free spectral range.

[0059] Compared with the prior art, the application has the following beneficial effects:

[0060] 1. A WGM micro-bottle cavity was fabricated using a fiber fusion splicer, and microspheres doped with titanium dioxide were fabricated at one end of the micro-bottle cavity. The presence of the titanium dioxide-doped microspheres ensured a high doping content of the photothermal material to fully stimulate the photothermal effect, while also ensuring that the photothermal material content did not decrease over a long period of time. Therefore, the micro-cavity device maintained stable all-optical tuning performance over a long period of time.

[0061] 2. Leveraging the unique advantages of the WGM micro-bottle cavity, an axial-mode microcavity frequency comb with a smaller FSR is generated for spectral tuning of the microcavity optical comb. This allows for tuning resonant modes beyond the FSR range, thereby achieving a comb-tooth tuning range exceeding the mode spacing. This advantage makes the present invention applicable to fields such as optical communications and optical frequency synthesis.

[0062] 3. Based on the unique advantages of the WGM micro-bottle cavity, an axial-mode microcavity frequency comb with a smaller FSR is generated. All-optical tuning of the microcavity frequency comb requires lower laser power, reducing the laser energy consumption required for tuning.

[0063] Explanation of terms:

[0064] WGM micro-bottle cavity is the abbreviation of whispering gallery mode optical micro-bottle cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0066] Figure 2 Schematic diagram of the fiber-optic WGM microbottle cavity;

[0067] Figure 3 This is the optical frequency comb spectrum of the micro-bottle cavity. DETAILED DESCRIPTION

[0068] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings.

[0069] Figure 1 Schematic diagram of the overall structure of the present invention; Figure 1 As shown, a functionalized micro-bottle cavity all-optically tunable and controllable optical comb generation system of the present invention includes a 1550nm narrow-linewidth continuous-wave laser 1, a 1550nm single-mode optical fiber 2, an erbium-doped fiber amplifier 3, a polarization controller 4, an optical isolator 5, a functionalized micro-bottle cavity-fiber taper coupling system 6, an optical attenuator 7, an optical spectrum analyzer 8, and a 1550nm power-tunable laser 9;

[0070] The 1550nm narrow linewidth continuous wave laser 1 is used to output tunable continuous laser light in the 1550nm band to excite the WGM microcavity to generate a light comb;

[0071] The erbium-doped fiber amplifier 3 is connected with the 1550nm narrow linewidth continuous wave laser 1 through an optical fiber 21, for increasing the power of the light output by the 1550nm narrow linewidth continuous wave laser 1, so that the laser power coupled into the WGM microcavity is greater than the threshold value of the microcavity optical comb excitation;

[0072] The polarization controller 4 is connected with the erbium-doped fiber amplifier 3 through an optical fiber 22, for keeping the constant of the light polarization state in the system;

[0073] The optical isolator 5 is connected with the polarization controller 4 through an optical fiber 23, for allowing the light transmitted in the forward direction to pass through and isolating the light transmitted in the reverse direction, so as to avoid the damage of the equipment by the light transmitted in the reverse direction;

[0074] The functionalized microbottle cavity-fiber taper coupling system 6 comprises a functionalized WGM microbottle cavity and a fiber taper 62.

[0075] The functionalized WGM microbottle cavity comprises a main microbottle cavity 60 and a secondary microcavity 61, and the secondary microcavity 61 is doped with a photothermal material titanium dioxide.

[0076] The preparation method of the functionalized WGM microbottle cavity comprises the following steps:

[0077] SⅠ, a section of single-mode optical fiber G652D bare fiber is taken, the coating layer is removed using wire strippers, cleaned with alcohol, and the end of the optical fiber is cut flat using an optical fiber cutting knife; the other end of the optical fiber is fusion spliced with an optical fiber jumper;

[0078] SⅡ, the cut optical fiber end in step S1 is placed in an optical fiber fusion splicer; the optical fiber end is discharged by high-voltage arc; the optical fiber end is heated and melted, and a microsphere is formed under the action of surface tension;

[0079] SⅢ, another section of single-mode optical fiber G652D bare fiber is taken, and the coating layer, cleaning and cutting of the optical fiber are performed according to the steps in step SⅠ; then the end of the optical fiber and the microsphere in step SⅡ are placed in the optical fiber fusion splicer at the same time, and the two are aligned and attached in the horizontal position; the microsphere and the optical fiber end are discharged by high-voltage arc using the optical fiber fusion splicer; a microbottle cavity structure is formed under the action of surface tension;

[0080] SⅣ, the end of the optical fiber jumper not fusion spliced in step SⅢ is cut using wire strippers, and a length of about 100μm of the optical fiber rod is reserved;

[0081] S V, place the optical fiber vertical clamp at the edge of the Z-axis lifting platform 1, and place the main micro-bottle cavity on the vertical optical fiber clamp, wherein the optical fiber rod end in the step S IV is downward, and the clamping position is above the optical fiber rod and the micro-bottle cavity; observe the micro-bottle cavity and the optical fiber rod through the microscope, and ensure that the micro-bottle cavity is in the middle of the imaging screen of the microscope;

[0082] S VI, place the slide containing the mixture of titanium dioxide powder and ultraviolet glue on the other Z-axis lifting platform 2, so that the central position of the slide is directly below the step S I;

[0083] S VII, control the Z-axis lifting platform 2 in the step S2 to rise until the optical fiber rod is in sufficient contact with the mixture in the step S6 is observed in the imaging screen of the microscope;

[0084] S VIII, control the Z-axis lifting platform 2 to descend until the optical fiber rod is separated from the mixture is observed in the imaging screen of the microscope, and then the optical fiber rod with the mixture in the above step is irradiated under the ultraviolet lamp;

[0085] S IX, place the optical fiber micro-cavity in the step S VIII into the optical fiber fusion machine again, wherein the middle part of the optical fiber rod is placed at the center of the electrode of the optical fiber fusion machine; start the optical fiber fusion machine, and the optical fiber rod is melted into a microsphere under the action of surface tension, wherein the microsphere is doped with the photo-thermal material titanium dioxide.

[0086] The optical fiber taper 62 is connected with the optical isolator 5 through the optical fiber 24. After the laser passes into the optical fiber taper, an evanescent field is generated in the waist taper region of the optical fiber taper, and then the light is coupled in and out of the functionalized optical fiber WGM micro-bottle cavity through the evanescent field;

[0087] The waist taper diameter of the optical fiber taper is 1.8-2.2 μm, preferably 2 μm, and the diameter of both ends is 125 μm;

[0088] The optical fiber taper 62 needs to be coupled with the main micro-bottle cavity 60 in the functionalized optical fiber WGM micro-bottle cavity. The equatorial circumference of the main micro-bottle cavity 60 is in contact with the optical fiber taper 62, which is used to stabilize the micro-cavity-optical fiber taper system and make the light enter the main micro-bottle cavity 60 better. When the light is transmitted into the main micro-bottle cavity 60 through the optical fiber taper 62, continuous total reflection will occur on the inner wall of the cavity, and the light meeting the WGM micro-cavity resonance wavelength will be confined in the cavity.

[0089] The resonance condition of the main micro-bottle cavity 60 is:

[0090]

[0091] Wherein, λ is the micro-cavity resonance wavelength, R is the equatorial radius of the micro-bottle cavity, n neff is the effective refractive index of the micro-bottle cavity, m is the effective refractive index of the micro-bottle cavity, q is the axial quantum number of the micro-bottle cavity, which is related to the axial length of the micro-bottle cavity, and ΔEm is the energy difference between the energy levels;

[0092] Due to the unique axial characteristics of the WGM micro-bottle cavity, there are two transmission modes of light in the WGM micro-bottle cavity: along the equatorial circumferential inner wall and along the axial spiral. The existence of the axial spiral transmission greatly increases the mode distribution in the cavity and reduces the FSR of the micro-bottle cavity. Compared with the micro-sphere cavity with the same radius, the FSR of the micro-bottle cavity is one order of magnitude smaller. This small axial FSR makes it easy to realize the tuning within one FSR range for WGM;

[0093] The FSRs corresponding to the two transmission modes of light in the WGM micro-bottle cavity are respectively:

[0094]

[0095] wherein, FSR m is the free spectral range of the micro-bottle cavity when the light is transmitted along the equatorial circumferential inner wall, and FSR q is the free spectral range of the micro-bottle cavity when the light is transmitted along the axial spiral. λ0 is the input light wavelength, and Δk is the curvature of the micro-bottle cavity;

[0096] When the optical power of the light transmitted into the main micro-bottle cavity 60 is higher than the micro-cavity optical frequency comb excitation threshold and satisfies the condition, the micro-cavity optical frequency comb can be generated by scanning the wavelength of the narrow linewidth continuous wave laser from the blue detuning region of the resonant mode of the micro-cavity to the red detuning region;

[0097] Due to the rich mode distribution of the WGM micro-bottle cavity, the micro-cavity optical frequency comb can be generated by directly and continuously manually increasing the wavelength of the narrow linewidth continuous wave laser 1. And multiple scans can repeatedly generate the same micro-cavity optical frequency comb at the same wavelength;

[0098] Due to the unique axial characteristics of the WGM micro-bottle cavity, the WGM micro-bottle cavity has an axial resonant mode with a smaller FSR. Therefore, compared with the micro-sphere cavity with the same radius, the WGM micro-bottle cavity can excite a micro-cavity optical frequency comb with a smaller FSR axial mode;

[0099] The optical attenuator 7 is connected with the optical fiber taper 62 through the optical fiber 25, and is used for attenuating the optical power transmitted from the micro-cavity to the optical fiber taper 62, so as to protect the optical spectrum analyzer 8;

[0100] The optical spectrum analyzer 8 is connected with the optical attenuator 7 through the optical fiber 26, and is used for receiving the light transmitted from the functionalized optical fiber WGM micro-bottle cavity and measuring the spectral information;

[0101] The 1550nm power adjustable laser 9 is connected with the functionalized optical fiber WGM micro-bottle cavity through the optical fiber 27, and is used for generating a power adjustable laser to excite titanium dioxide to generate heat, change the temperature of the micro-cavity, and further change the resonant wavelength of the micro-cavity.

[0102] Generally, the microcavity optical frequency comb can be generated by scanning the wavelength of the narrow linewidth continuous wave laser from the blue detuning region to the red detuning region of the microcavity resonant mode. Since the WGM microbottle cavity has a rich mode distribution, the microcavity optical frequency comb can be generated by directly and continuously increasing the wavelength of the narrow linewidth continuous wave laser 1, and the same microcavity optical frequency comb can be repeatedly generated at the same wavelength through multiple scans. Compared with the microsphere cavity with the same radius, the WGM microbottle cavity can excite the axial mode microcavity optical frequency comb with a smaller FSR.

[0103] The present application provides a method for generating a full-optical tunable controllable optical comb based on a functionalized microbottle cavity, and the microcavity optical frequency comb generation and tuning steps are as follows:

[0104] Sa, system building;

[0105] The system for generating a full-optical tunable controllable optical comb based on a functionalized microbottle cavity is built as claimed in claims 1-3, including a narrow linewidth laser 1, an erbium-doped fiber amplifier 3, a polarization controller 4, an optical isolator 5, a functionalized microbottle cavity-fiber taper coupling system 6, an optical attenuator 7, an optical spectrum analyzer 8 and a 1550nm power adjustable laser 9 connected in sequence by a 1550nm single mode optical fiber to form an optical path link;

[0106] Sb, turn on the narrow linewidth continuous wave laser 1 to output 1550nm laser, which is amplified by the erbium-doped fiber amplifier 3; when the light enters the fiber taper 62 of the functionalized microbottle cavity-fiber taper coupling system 6, it is coupled in and out of the functionalized WGM microbottle resonant cavity at the waist taper position through the evanescent field; then, the light passes through the attenuator 7 and is connected to the optical spectrum analyzer 8; at this time, only the 1550nm pump light spectrum can be observed on the optical spectrum analyzer 8;

[0107] Sc, continuously increase the wavelength of the narrow linewidth continuous wave laser 1 with a step of 0.1nm, until a stable microcavity optical frequency comb is observed on the optical spectrum analyzer 8, and the optical wavelength of the optical frequency comb generation is recorded for repeated tuning to generate the optical frequency comb; the tuning range of the laser wavelength of the narrow linewidth continuous wave laser 1 is 1550nm-1570nm; repeat the scanning until the generation of the axial mode microcavity optical frequency comb with a small free spectral range is observed on the optical spectrum analyzer 8;

[0108] Sd, when the axial mode microcavity optical frequency comb is observed on the optical spectrum analyzer 8, turn on the 1550nm power adjustable laser 9, increase the power of the laser 9 with a step of 10mW, and at each power, increase the wavelength of the narrow linewidth continuous wave laser 1 with a step of 0.001nm, until the optical frequency comb with the same free spectral range as the initial axial mode microcavity optical frequency comb is observed;

[0109] Se. Repeat step Sd until the tuning range of the optical frequency comb exceeds the free spectrum range.

[0110] In summary, the present invention proposes a method for generating an all-optically tunable, controllable optical comb based on a functionalized microbottle cavity. This method utilizes the unique axial transmission mode of the WGM microbottle cavity to significantly reduce the FSR of the microcavity, generating an axial-mode microcavity optical frequency comb with a small FSR. The generated axial-mode microcavity optical frequency comb is then tuned using an all-optical tuning method, enabling spectral tuning beyond the FSR range. The present invention proposes a method for preparing a functionalized microbottle cavity, comprising a main microbottle cavity and a sub-cavity. By doping the sub-cavity with a photothermal material, the quality factor of the main microbottle cavity is not reduced. While maintaining a high doping content of the photothermal material, efficient excitation of the photothermal effect is achieved, ensuring that the microcavity device exhibits stable all-optical tuning performance over a prolonged period. This method overcomes the limitation of the WGM microcavity optical frequency comb, which cannot achieve wavelength tuning beyond the FSR, and facilitates the practical application of microcavity optical frequency combs in fields such as optical communications and optical frequency synthesis.

Claims

1. An all-optical tunable and controllable light comb generation system based on a functionalized microbottle cavity, characterized in that: The invention comprises a 1550 nm narrow linewidth continuous wave laser (1), an erbium-doped fiber amplifier (3), a polarization controller (4), an optical isolator (5), a functionalized WGM microbottle cavity-fiber taper coupling system (6), an optical attenuator (7), an optical spectrum analyzer (8), and a 1550 nm power tunable laser (9) externally connected to the functionalized microbottle cavity-fiber taper coupling system (6); wherein, The 1550 nm narrow linewidth continuous wave laser (1) is used to output tunable continuous laser light in the 1550 nm band to excite the WGM microbottle cavity to generate a light comb; The erbium-doped fiber amplifier (3) is connected to the 1550 nm narrow linewidth continuous wave laser (1) via an optical fiber (21) and is used to increase the power of the output light of the 1550 nm narrow linewidth continuous wave laser (1) so that the laser power coupled into the functionalized WGM microbottle cavity is greater than the threshold value of the functionalized WGM microbottle cavity light comb excitation; The polarization controller (4) is connected to the erbium-doped fiber amplifier (3) via an optical fiber (22) and is used to adjust the polarization state of the laser input into the functionalized WGM microbottle cavity-fiber taper coupling system (6) to maintain the constant polarization state of the light in the system; The optical isolator (5) is connected to the polarization controller (4) via an optical fiber (23) and is used to allow forward-transmitted light to pass through while isolating reverse-transmitted light to prevent the reverse-transmitted light from damaging the device. The functionalized WGM microbottle cavity comprises a main microbottle cavity (60) and a sub-microbottle cavity (61), wherein the sub-microbottle cavity (61) is doped with titanium dioxide, a photothermal material; the equatorial plane of the main microbottle cavity (60) of the functionalized optical fiber WGM microbottle cavity contacts the lumbar part of the optical fiber cone (62), which is used to stabilize the system and better couple the evanescent field light into the cavity; when light is transmitted through the optical fiber cone into the functionalized main microbottle cavity (60), it will continue to be totally reflected on the inner wall of the cavity, and the light meeting the resonant wavelength of the WGM microbottle will be confined in the cavity; The optical fiber cone (62) is connected to the optical isolator (5) through the optical fiber (24). After the laser passes into the optical fiber cone (62), an evanescent field is generated in the waist cone region thereof, and then the light is coupled into and out of the functionalized WGM micro-bottle through the evanescent field; The optical attenuator (7) is connected to the optical fiber cone (62) via the optical fiber (25) and is used to attenuate the optical power transmitted from the microcavity to the optical fiber cone (62) to protect the optical spectrum analyzer (8); The optical spectrum analyzer (8) is connected to the optical attenuator (7) via an optical fiber (26) and is used to receive light transmitted from the functionalized optical fiber WGM microbottle cavity and measure spectral information; The 1550nm power adjustable laser (9) is connected to the functionalized fiber WGM microbottle cavity via an optical fiber (27) to generate power adjustable laser to excite titanium dioxide (13) to generate heat and change the temperature of the microbottle.

2. The all-optical tunable controllable light comb generation system based on a functionalized micro-bottle cavity according to claim 1, characterized in that: The fiber taper has a waist diameter of 1.8~2.2μm and a diameter of 125μm at both ends. It is prepared by the melt-drawing method.

3. The all-optical tunable controllable light comb generation system based on a functionalized micro-bottle cavity according to claim 1, characterized in that: Titanium dioxide particles of the photothermal material are melt-doped into the secondary microcavity (61) of the functionalized WGM optical fiber microbottle cavity by a fiber fusion splicer; the preparation method of the functionalized WGM optical fiber microbottle cavity comprises the following steps: SⅠ. Take a section of single-mode G652D bare fiber, remove the coating with a wire stripper, wipe it clean with alcohol, and use a fiber cleaver to cut the fiber end flat; then fusion-splice the other end of the fiber to the fiber jumper. SII, placing the cut optical fiber end in the above step SⅠ in a fiber optic fusion splicer; The fiber fusion splicer is started, and a high-voltage arc is used to discharge the fiber end. The fiber end is heated and melted, and microspheres are formed under the action of surface tension. Step SIII: Take another section of single-mode G652D bare fiber, strip the coating, clean, and cleave it according to the steps in step SⅠ above. Then, place the fiber end and the microsphere described in step SⅡ simultaneously in the fiber fusion splicer, ensuring that they are aligned and attached horizontally. Start the fiber fusion splicer and use high-voltage arc to discharge the microspheres and the ends of the optical fibers. Under the action of surface tension, a micro-bottle cavity structure is formed. SIV. Use wire strippers to cut off the unsplice-free end of the fiber microbottle cavity in step SIII, leaving a fiber rod of about 100 μm in length. Step SⅤ: Place the vertical fiber fixture at the edge of the Z-axis lifting platform 1 and place the main micro-vial cavity on the vertical fiber fixture, with the fiber rod end described in step SⅣ facing downward and the clamping position above the fiber rod and the micro-vial cavity; observe the micro-vial cavity and fiber rod through a microscope to ensure that the micro-vial cavity is centered on the microscope imaging screen; SVI, placing the glass slide containing the mixture of titanium dioxide powder and UV adhesive on another Z-axis lifting platform 2, so that the center of the glass slide is directly below the position described in step SⅠ above; SVII, controlling the Z-axis lifting platform 2 described in step S2 to rise until the optical fiber rod is observed to be in full contact with the mixture described in step S6 on the microscope imaging screen; SⅧ, controlling the Z-axis lifting platform 2 to descend until the optical fiber rod and the mixture are separated as observed on the microscope imaging screen, and then fully irradiating the optical fiber rod with the mixture in the above step under ultraviolet light; SIX. Place the optical fiber microcavity prepared in step SⅧ again into the optical fiber fusion splicer, wherein the middle portion of the optical fiber rod is placed in the center of the electrode of the optical fiber fusion splicer; start the optical fiber fusion splicer, and the optical fiber rod is melted into microspheres under the action of surface tension, wherein the microspheres are doped with titanium dioxide, a photothermal material.

4. A method for generating an all-optically tunable controllable light comb based on a functionalized microbottle cavity, characterized in that: The following steps are involved: Sa, system construction; Construct an all-optical tunable and controllable optical comb generation system based on a functionalized microbottle cavity as described in any one of claims 1 to 3, comprising a narrow-linewidth continuous-wave laser (1) connected in an optical path via a 1550 nm single-mode optical fiber, an erbium-doped fiber amplifier (3), a polarization controller (4), an optical isolator (5), a functionalized microbottle cavity-fiber taper coupling system (6), an optical attenuator (7), an optical spectrum analyzer (8), and a 1550 nm power-tunable laser (9); Sb, turns on the narrow linewidth continuous wave laser (1) to output 1550 nm laser, which is amplified by the erbium-doped fiber amplifier (3); when the light enters the fiber cone (62) of the functionalized microbottle cavity-fiber cone coupling system (6), it is coupled into and out of the functionalized WGM microbottle resonant cavity at the waist cone position through the evanescent field; then, the light passes through the attenuator (7) and is connected to the spectrum analyzer (8); at this time, only the 1550 nm pump light spectrum can be observed on the spectrum analyzer (8); Sc, continuously increasing the wavelength of the narrow linewidth continuous wave laser (1) in steps of 0.1 nm wavelength until a stable microcavity optical frequency comb is observed on the spectrum analyzer (8), and recording the wavelength of light generated by the optical frequency comb for repeated tuning to generate the optical frequency comb; the laser wavelength tuning range of the narrow linewidth continuous wave laser (1) is 1550 nm-1570 nm; repeatedly scanning until the generation of a small free spectral range axial mode microcavity optical frequency comb is observed on the spectrum analyzer (8); Sd, when the presence of the axial mode microcavity optical frequency comb is observed on the spectrum analyzer (8), the 1550 nm power-adjustable laser (9) is turned on, and the power of the laser (9) is increased in steps of 10 mW. At each power, the wavelength of the narrow linewidth continuous wave laser (1) is increased in steps of 0.001 nm until an optical frequency comb with the same FSR as the free spectrum range of the initial axial mode microcavity optical frequency comb is observed; Se. Repeat step Sd until the tuning range of the optical frequency comb exceeds the free spectrum range.

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