Method of manufacturing microbubble resonator and laser system

Abstract

The application provides a manufacturing method of a microbubble resonant cavity, comprising the following steps: S1, cleaning a silica capillary outer polymer cladding with a strong oxidizing solution; S2, etching the silica capillary with an acid solution to reduce the thickness of the capillary wall; S3, heating and stretching the silica capillary to reduce the diameter of the capillary; S4, pressurizing the silica capillary and irradiating the capillary with a carbon dioxide laser to soften and expand the capillary, thereby forming the microbubble resonant cavity. In addition, the application also provides a laser system. The laser system (with the microbubble resonant cavity) provided by the application has the advantages of low threshold and super-sensitivity in biological detection, and meanwhile, the gain medium is not damaged by high-energy pumping light, and the laser system has an important development prospect in the medical application direction.

Description

Technical Field

[0001] This invention relates to the fields of quantum optics and laser technology, and particularly to a method for manufacturing a high-quality factor microbubble resonator, and a laser system including the microbubble resonator. Background Technology

[0002] Lasers are optical oscillators that play an irreplaceable role in a wide range of applications, including information storage, holography, materials processing, computer science, geology, and clinical medicine. In recent decades, with the development of lasers, their types, performance, and applications have seen unprecedented improvements, which have also driven progress in the field of optics and in human society.

[0003] Based on the working medium, lasers can be classified into solid-state lasers, gas lasers, liquid lasers, and semiconductor lasers. According to the laser output method, lasers can be classified into continuous-wave lasers and pulsed lasers. Based on output power, lasers can be classified into low-power (below 1000W), medium-power (1000–3000W), and high-power (above 3000W). Based on output wavelength, lasers can be classified into infrared lasers, visible-light lasers, etc. (Green fluorescent protein lasers are green visible-light band lasers, and mCherry fluorescent protein lasers are red visible-light band lasers).

[0004] The most common types of lasers currently available are carbon dioxide lasers, semiconductor lasers, and fiber lasers. While these lasers are technologically mature, they also suffer from drawbacks such as large size, low quality factor, high energy consumption, slow heat dissipation, and the toxicity of some of their light-emitting materials. For example, due to their large size and the fact that the gain medium is solid, they exhibit high heat loss.

[0005] Fluorescent protein lasers are lasers whose gain medium is an organic light-emitting material. Organic light-emitting materials such as fluorescent proteins exhibit good biocompatibility and high optical gain. Microbubble resonators can amplify optical feedback structures in a whispering-gallery mode. Therefore, the quality factor of the microbubble resonator has a significant impact on the energy consumption and signal-to-noise ratio of fluorescent protein lasers. Based on this, how to fabricate microbubble resonators with high quality factors has become an urgent problem to be solved. Summary of the Invention

[0006] In view of the problems existing in the background art, one aspect of the present invention provides a method for manufacturing a microbubble resonant cavity, comprising:

[0007] S1: Clean the polymer coating on the outside of the silica capillary with a strong oxidizing solution;

[0008] S2: Etch the silica capillary with an acidic solution to reduce the wall thickness;

[0009] S3: Heat the silica capillary and stretch it to reduce the capillary diameter;

[0010] S4: Pressurize the silica capillary and irradiate it with a carbon dioxide laser to soften and expand the capillary, forming a microbubble resonant cavity.

[0011] In some embodiments of the present invention, the strong oxidizing solution is a piranha solution.

[0012] In some embodiments of the present invention, the acidic solution is hydrofluoric acid.

[0013] In some embodiments of the present invention, the silica capillary is etched with an acidic solution to reduce the wall thickness to 10–11 μm.

[0014] In some embodiments of the present invention, the silica capillary is heated to 1400°C to 1500°C and stretched to reduce the capillary diameter to 30μm to 50μm.

[0015] In some embodiments of the present invention, the silica capillary is heated to 1430°C and stretched to reduce the capillary diameter to 40 μm.

[0016] In some embodiments of the present invention, the silica capillary is pressurized to (1.68–2.16) × 10⁻⁶. 5 Pa.

[0017] In some embodiments of the present invention, the silica capillary is pressurized to 2 × 10⁻⁶. 5 Pa.

[0018] In some embodiments of the present invention, the formed microbubble resonant cavity has a diameter of 90–120 μm and a wall thickness of 1.5–2 μm.

[0019] In some embodiments of the present invention, the formed microbubble resonant cavity has a diameter of 110 μm and a wall thickness of 1.5 μm.

[0020] Another aspect of the present invention provides a laser system comprising:

[0021] A pump laser used to emit pump light of a specific wavelength;

[0022] The microbubble resonator manufactured by the method described above can generate laser light by exciting the gain medium filled in the microbubble resonator with the pump light of the specific wavelength.

[0023] In some embodiments of the present invention, the laser system includes:

[0024] A polarizer for adjusting the energy of the pump light generated by the pump laser;

[0025] A beam expander for adjusting the beam diameter of the pump light after passing through the polarizer; and

[0026] A convex lens is used to focus the pump light after passing through the beam expander onto the microbubble resonant cavity, so that the focused pump light can excite the gain medium to generate laser light.

[0027] The laser system (microbubble resonator with high quality factor) provided by this invention breaks away from traditional lasers that use non-biological gain medium materials such as crystals and semiconductors, and demonstrates its unique value:

[0028] (1) The laser system provided by the present invention can use fluorescent protein as a gain medium. Due to the fluidity of liquid and the small size of protein itself, the heat loss of laser is greatly reduced compared with traditional lasers. The size is only on the order of hundreds of micrometers. Its gain medium has low toxicity and high biocompatibility.

[0029] The quality factor of the laser system of this invention is 5.3 × 10⁻⁶. 7 (This can also be viewed as the quality factor of a microbubble resonant cavity being 5.3 × 10⁻⁶) 7 It possesses the highest quality factor to date in green fluorescent protein laser systems. Due to this high quality factor, the laser threshold can be as low as 500 nJ / mm². 2 Considering the ultra-small mode volume of the microbubble resonator, the pump energy required to excite the green fluorescent protein that interacts with the resonator's optical field is only 380 fJ, which is two orders of magnitude lower than the threshold of existing laser systems.

[0030] (2) The laser system of this invention belongs to an important branch of optofluidic lasers, which is a new research field that combines the advantages of microfluidics and optics. Therefore, it has the advantages of microfluidics: the gain medium in the cavity can be easily changed by pumping, and the concentration of the gain medium can be changed, which can form a laser device with small volume and low energy consumption. This not only promotes the development of microfluidics, but also solves the problems of high energy consumption and slow heat dissipation of traditional lasers by using the fluidity of liquids for circulation.

[0031] (3) The laser system provided by this invention leads laser technology from the non-biological field to the biological field, and also has its unique advantages in the biological field. Its superior characteristics such as narrow linewidth, high signal-to-noise ratio and threshold behavior give it unique advantages in bioimaging, biosensing, cell labeling, cell tracking and adjuvant treatment of tissue mutation diseases. Attached Figure Description

[0032] Figure 1 A flowchart illustrating a method for manufacturing a microbubble resonant cavity according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the excitation-collection system provided in an embodiment of the present invention;

[0034] Figure 3 To adopt Figure 1 Microscopic images of the microbubble resonant cavity fabricated by the method shown, and theoretical simulation results of the optical mode;

[0035] Figure 4 To adopt Figure 1 The microbubble resonator fabricated by the method shown has laser emission spectra at different pump energies and normalized laser intensity as a function of pump energy density (the gain medium is 10 μM green fluorescent protein). Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Although exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to facilitate a thorough understanding of the invention and to fully convey the inventive concept to those skilled in the art.

[0037] like Figure 1 As shown, one embodiment of the present invention provides a method for manufacturing a microbubble resonant cavity, comprising:

[0038] S1: Clean the polymer coating on the outside of the silica capillary with a strong oxidizing solution;

[0039] S2: Etch the silica capillary with an acidic solution to reduce the wall thickness;

[0040] S3: Heat the silica capillary and stretch it to reduce the capillary diameter;

[0041] S4: Pressurize the silica capillary and irradiate it with a carbon dioxide laser to soften and expand the capillary, forming a microbubble resonant cavity.

[0042] The dimensions of the silica capillary used in step S1 (i.e., the initial dimensions of the silica capillary to be processed) can be an outer diameter of 140 μm, an inner diameter of 100 μm, and a wall thickness of 20 μm, but are not limited to these dimensions.

[0043] In step S1, after cleaning the polymer coating outside the tube with a strong oxidizing solution, the cleanliness of the surface can be determined by observing it under a microscope, thus confirming whether the cleaning is complete.

[0044] Further, the strong oxidizing solution in step S1 is a piranha solution (concentrated sulfuric acid to hydrogen peroxide in a ratio of 7:3). Preferably, the piranha solution is heated to 150°C–160°C before cleaning the polymer coating on the silica capillary. More preferably, the piranha solution is heated to 155°C before cleaning the polymer coating on the silica capillary.

[0045] Furthermore, in step S2, the acidic solution is hydrofluoric acid.

[0046] Further, in step S2, the silicon dioxide capillary is etched with an acidic solution to reduce the wall thickness to 10 μm to 11 μm.

[0047] Further, in step S3, the silica capillary is heated to 1400°C to 1500°C and stretched to reduce the capillary diameter to 30μm to 50μm. Preferably, the silica capillary is heated to 1430°C and stretched to reduce the capillary diameter to 40μm.

[0048] Further, in step S4, the silica capillary is pressurized to (1.68~2.16)×10⁻⁶. 5 Pa. Preferably, the silica capillary is pressurized to 2 × 10 Pa. 5 Pa.

[0049] Further, in step S4, the irradiation time with carbon dioxide laser is 1 to 2 seconds, and the irradiation intensity is 4.5 to 6.5 watts. Preferably, the irradiation time is 1.5 seconds, and the irradiation intensity is 5.5 watts.

[0050] Further, in step S4, the diameter of the formed microbubble resonant cavity is 90–120 μm and the wall thickness is 1.5–2 μm. Preferably, the diameter of the formed microbubble resonant cavity is 110 μm and the wall thickness is 1.5 μm.

[0051] like Figure 2 As shown, one embodiment of the present invention provides a laser system including a pump laser 1 for emitting pump light of a specific wavelength and a microbubble resonant cavity 15 manufactured by any of the manufacturing methods described above. The pump light of the specific wavelength can excite the gain medium filled in the microbubble resonant cavity to generate laser light.

[0052] Taking green fluorescent protein as the gain medium (its excitation wavelength is 473nm) as an example, the wavelength of the pump light should be 473nm, and the wavelength of the generated green fluorescent protein laser is about 520nm.

[0053] Furthermore, the gain medium can be any of the following luminescent materials: fluorescent protein (green fluorescent protein, enhanced green fluorescent protein, mCherry red protein, DsRed red protein, etc.), dye (rhodamine, etc.), nv color center, and pentacene. The gain medium can be pressurized and injected into the microbubble resonant cavity using a syringe pump.

[0054] Furthermore, when laser 1 is a pulsed laser (OPO laser) and the gain medium is fluorescent protein, the pulsed laser can complete the excitation more effectively.

[0055] Furthermore, the laser system includes a polarizer 2 for adjusting the energy of the pump light generated by the pump laser 1, a beam expander 3 for adjusting the beam diameter of the pump light after passing through the polarizer 2, and a convex lens 4 for focusing the pump light after passing through the beam expander 3 onto the microbubble resonator 15, so that the focused pump light can excite the gain medium to generate laser light.

[0056] Continue to refer to Figure 2 An embodiment of the present invention provides an excitation-collection system for verifying the quality of the aforementioned laser system (microbubble resonator). The excitation-collection system includes the laser system as described above, a dichroic mirror 8 for filtering light of a specific wavelength, the dichroic mirror 8 capable of filtering pump light and transmitting laser light generated after being excited by a gain medium, a multimode fiber 13 for collecting the filtered laser light, and a spectrometer 14 for generating a spectrum based on the collected laser light.

[0057] Furthermore, the excitation-collection system includes an optical long-pass filter 11 for filtering light of a specific wavelength, the optical long-pass filter 11 for further filtering the pump light after it has been filtered by the dichroic mirror 8, and a convex lens 12 for focusing the light, the laser light focused by the convex lens 12 being collected by the multimode fiber 13.

[0058] Furthermore, the excitation-collection system includes a beam splitter 9 for equally dividing the laser light filtered by the dichroic mirror 8, wherein a portion (e.g., 50%) of the laser light is collected by the camera 10 for imaging, and a portion (e.g., 50%) of the laser light is collected by the multimode fiber 13.

[0059] Furthermore, to further reduce the size of the excitation-collection system, it may also include a plane mirror 5 to reflect the pump light passed through the convex lens 4 to another path. The excitation-collection system may also include an objective lens 6 (to collect and observe the laser light after the green fluorescent protein is excited) and an illuminator 7 (to emit blue visible light with adjustable intensity; the illuminator 7 and the camera 10 together monitor the position of the microbubble resonator in the excitation-collection system).

[0060] In use, taking the injection of green fluorescent protein (GFP) into a microbubble resonant cavity as an example (the excitation wavelength of GFP is 473 nm), laser 1 (OPO laser) emits pulsed light (pump light) with a wavelength of 473 nm. Polarizer 2 adjusts the energy of the pump light, and beam expander 3 reduces the beam diameter of the pump light. After being focused by convex lens 4 and reflected by plane mirror 5, the GFP in the microbubble resonant cavity 15 is excited to generate laser light (the spot of the focused and reflected pump light is sufficient to cover the entire microbubble resonant cavity 15). The laser light generated after the GFP is excited is collected and observed by objective lens 6. Objective lens 6 (illuminator 7 can emit blue visible light with adjustable intensity to supplement the illumination of objective lens 6) and camera 10 jointly monitor the position of microbubble resonant cavity 15 to ensure that the injected GFP can be fully excited by the pump light.

[0061] Figure 3 The figures show the microscopic images and theoretical simulation results of the optical modes of the microbubble resonant cavity. Figure 4 The emission spectra of the laser at different pump energies and the normalized laser intensity as a function of pump energy density are shown (the gain medium is 10 μM green fluorescent protein). When the injected green fluorescent protein is excited, such as... Figure 3 As shown, the optical mode of the microbubble resonator exhibits a significant evanescent field within the hollow cavity, suitable for the interaction between the resonator and the green fluorescent protein solution. The quality factor of the (green fluorescent protein) laser system is as high as 5.3 × 10⁻⁶. 7 (This can also be viewed as the microbubble resonant cavity having a quality factor as high as 5.3 × 10⁻⁶) 7 This is higher than the quality factor of existing (green fluorescent protein) laser systems. For example... Figure 4 As shown, the normalized laser intensity varies with pump energy density (threshold 500 nJ / mm). 2 (Close-up of the low pump energy region), the curve shows a twist, which is sufficient to indicate that the threshold is 500 nJ / mm. 2 The evanescent field that can directly interact with the gain medium in the microbubble resonator is only 8 / 100,000 of the total volume of the microbubble cavity, and the threshold pump energy on the entire microbubble resonator is only 4.75 nJ (the energy used to excite green fluorescent protein can be reduced to 380 fJ, which is two orders of magnitude lower than the lowest known excitation energy of the GFP laser). Furthermore, it has been confirmed that the (green fluorescent protein) laser system with this microbubble resonator can operate stably for a long period, maintaining its optical properties for at least 23 days. This green protein laser system can be used for highly sensitive detection of green fluorescent protein concentration.

[0062] Based on this, the microbubble resonator (or laser system) manufactured using this invention has the advantages of low threshold and ultra-sensitive biological detection, while ensuring that the gain medium is not destroyed by high-energy pump light, and it has important development prospects in medical applications.

[0063] In the description of this specification, the references to terms such as "certain embodiments," "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0064] In this invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; the term "multiple" refers to two or more unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for manufacturing a microbubble resonant cavity, characterized in that, include: S1: Clean the polymer coating on the outside of the silica capillary with a strong oxidizing solution; S2: Etch the silica capillary with an acidic solution to reduce the wall thickness of the silica capillary to 10-11 μm; S3: Heat the silica capillary to 1400℃~1500℃ and stretch it to reduce the capillary diameter to 30μm~50μm; S4: Pressurize the silica capillary to (1.68~2.16)×10 5 Pa, and irradiated with a carbon dioxide laser for 1 to 2 seconds at an intensity of 4.5 to 6.5 W to soften and expand the capillary, forming a microbubble resonant cavity, wherein the diameter of the formed microbubble resonant cavity is 90 to 120 μm and the wall thickness is 1.5 to 2 μm.

2. The method for manufacturing a microbubble resonant cavity according to claim 1, characterized in that: The strong oxidizing solution is a piranha solution.

3. The method for manufacturing a microbubble resonant cavity according to claim 1, characterized in that: The acidic solution is hydrofluoric acid.

4. The method for manufacturing a microbubble resonant cavity according to claim 1, characterized in that: The silica capillary was heated to 1430°C and stretched to reduce the capillary diameter to 40 μm.

5. The method for manufacturing a microbubble resonant cavity according to claim 1, characterized in that: Pressurize the silica capillary to 2×10 5 Pa.

6. The method for manufacturing a microbubble resonant cavity according to claim 1, characterized in that: The formed microbubble resonant cavity has a diameter of 110 μm and a wall thickness of 1.5 μm.

7. A laser system, characterized in that, include: A pump laser used to emit pump light of a specific wavelength; The microbubble resonant cavity manufactured according to any one of claims 1 to 6, wherein the pump light of a specific wavelength can excite the gain medium filled in the microbubble resonant cavity to generate laser light.

8. The laser system according to claim 7, characterized in that, include: A polarizer for adjusting the energy of the pump light generated by the pump laser; A beam expander used to adjust the beam diameter of the pump light after passing through the polarizer; as well as A convex lens is used to focus the pump light after passing through the beam expander onto the microbubble resonant cavity, so that the focused pump light can excite the gain medium to generate laser light.

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