CN112317285A - High-directivity optical fiber photoacoustic transducer and method - Google Patents
High-directivity optical fiber photoacoustic transducer and method Download PDFInfo
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- CN112317285A CN112317285A CN202011164058.1A CN202011164058A CN112317285A CN 112317285 A CN112317285 A CN 112317285A CN 202011164058 A CN202011164058 A CN 202011164058A CN 112317285 A CN112317285 A CN 112317285A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/255—Splicing of light guides, e.g. by fusion or bonding
Abstract
The invention discloses a high-directivity optical fiber photoacoustic transducer and a method, wherein the optical fiber photoacoustic transducer comprises a nanosecond pulse laser, a lens and a quartz optical fiber which are sequentially arranged: the tail end of the quartz optical fiber is provided with a concave cavity, gold nanoparticles are uniformly distributed in the concave cavity, and nanosecond pulse laser can be converted into ultrasonic pulses based on the photoacoustic conversion principle of resonance absorption of the gold nanoparticles. Compared with the traditional piezoelectric electroacoustic transducer, the invention has the advantages of simple structure, flexible use, contribution to miniaturization and integration, flexibility and electromagnetic interference resistance.
Description
Technical Field
The invention relates to the technical field of photoacoustic transduction, in particular to a high-directivity optical fiber photoacoustic transducer and a method.
Background
The ultrasonic wave refers to sound wave with frequency higher than 20000Hz, has the advantages of strong penetrability and easy generation of physical, chemical, biological and other effects, and is widely applied to the fields of medicine, machinery, national defense and the like. An ultrasonic transducer is a device that converts energy in one form into mechanical energy to excite an ultrasonic signal. The traditional ultrasonic transducer mainly comprises a piezoelectric transducer, a mechanical transducer, a magnetic-to-telescopic transducer, a capacitive transducer and the like, has larger size, complex working structure and inflexible operation, is not easy to be applied to a tiny environment, and has higher energy consumption in high-frequency working.
The photoacoustic effect refers to a phenomenon in which an object generates an acoustic signal in periodically varying illumination. When laser irradiates an object, the elastic object absorbs heat energy to generate periodic vibration, the heat energy is converted into mechanical energy, and an acoustic signal is excited. The ultrasonic waves generated based on the photoacoustic effect are generally over MHz, are high-frequency ultrasonic waves, and have the advantage of high directivity. At present, two types of ultrasonic transducers based on the photoacoustic effect are mainly used, one type of ultrasonic transducer is based on space optical excitation, the optical path is complex, the working state is unstable, the excitation point is fixed, and the ultrasonic transducer cannot be flexibly used; the utility model provides an it stimulates to lead to light based on optical fiber, has compact structure, higher stability, is favorable to the miniaturization of ultrasonic equipment, integrates, and has anti-electromagnetic interference, flexible characteristics, but at present the ultrasonic transducer based on optical fiber mostly coats optoacoustic coating on the optic fibre surface, and ultrasonic signal emission is dispersed, does not have good directionality, is unfavorable for using in little environment.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a high-directivity optical fiber photoacoustic transducer and a method, which can be widely applied to the technical fields of ultrasonic precision cleaning, nanofluid agglomeration prevention, ultrasonic gene introduction, ultrasonic microfluidics and the like.
The purpose of the invention is realized by the following technical scheme:
a high-directivity fiber optic acoustic transducer comprises a nanosecond pulse laser, a lens and a quartz fiber which are arranged in sequence: the tail end of the quartz optical fiber is provided with a concave cavity, gold nanoparticles are uniformly distributed in the concave cavity, and nanosecond pulse laser can be converted into ultrasonic pulses based on the photoacoustic conversion principle of resonance absorption of the gold nanoparticles.
Furthermore, the quartz optical fiber is a multimode optical fiber, and the diameter of the fiber core is 50-500 mu m.
Further, the nanosecond pulse laser can generate nanosecond pulse laser with the wavelength of 532nm, the pulse width of 10-200ns, the repetition frequency of 1-100kHz and the average power of 400-800mW, and the nanosecond pulse laser is focused by a lens and then coupled into the quartz optical fiber.
Furthermore, the size of the concave cavity is equivalent to the diameter of the fiber core of the optical fiber and is 50-500 mu m; the grain diameter of the gold nano-particle is 40-60nm, and the corresponding resonance absorption peak is 530-535 nm.
The invention also provides a preparation method of the high-directivity optical fiber photoacoustic transducer, which comprises the following steps of:
cutting off two ends of the quartz optical fiber by using an optical fiber cutter to ensure that two end surfaces of the quartz optical fiber are smooth so as to form a regular and stable concave cavity structure under the action of high-power-density laser; adjusting the positions of the nanosecond pulse laser, the lens and the quartz optical fiber to enable the nanosecond pulse laser to be effectively coupled into one end of the quartz optical fiber, and immersing the other end of the quartz optical fiber into an aqueous solution containing gold nanoparticles, wherein the concentration of the solution is 0.03-0.06 mg/mL;
high-power-density laser transmitted in the quartz optical fiber interacts with gold nanoparticles in the aqueous solution to generate ablation on the end face of the optical fiber to form a regular and stable cavity structure, and the gold nanoparticles are attached to the surface of the cavity; the laser and the gold nanoparticles attached to the surface of the cavity are subjected to photoacoustic conversion through resonance coupling, ultrasonic waves with directionality are formed under the self-focusing action of the cavity, an aqueous solution is driven to generate jet flow, when the jet flow is stable, the cavity structure and the gold nanoparticles attached to the surface are stably distributed, and the preparation of the optical fiber photoacoustic transducer is completed.
Further, by changing the size and the structure of the concave cavity, the fiber optic acoustic transducer with different focuses and directivities can be obtained.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. compared with the traditional piezoelectric electroacoustic transducer, the invention has the advantages of simple structure, flexible use, contribution to miniaturization and integration, flexibility and electromagnetic interference resistance.
2. The preparation method is simple, can be completed only by the nano gold particle solution with a certain concentration and the common multimode silica fiber, has low cost, can directly intercept the tail end if the end surface structure is damaged, and can be immersed in the nano gold particle solution again to reduce the structure through ablation, thereby being easy to maintain.
3. The tail end of the quartz optical fiber of the transducer is provided with the concave cavity, the self-focusing performance is realized, the stronger sound pressure can be generated at the focus, the high directivity is realized, and the photoacoustic transducer signal which is coated with the photoacoustic coating on the surface of the traditional optical fiber is dispersed and is transmitted to all directions.
4. The ultrasonic transducer generates ultrasonic waves based on the photoacoustic effect, generally nanosecond pulse laser excites the ultrasonic waves to have the frequency above MHz, is high-frequency ultrasonic waves, and has higher directivity compared with the traditional low-frequency piezoelectric ultrasonic transducer.
5. The invention can generate obvious jet flow phenomenon in fluid due to high directivity and concentrated sound pressure, can perform micro control on the fluid in the liquid through the light-sound-flow conversion process, and has important application value in the fields of ultrasonic gene introduction, ultrasonic micro-fluidic control and the like.
6. The invention can process a set concave cavity at the tail end of the quartz optical fiber in a precise processing mode besides the direct laser ablation preparation, manually ablates and attaches nanoparticles, and designs and manufactures the optical fiber photoacoustic transducer with different sound pressure focuses and different photoacoustic characteristics by setting the aperture size, the corresponding diameter and the density distribution of the nano gold particles in the concave cavity.
Drawings
FIG. 1 is a schematic diagram of the structure of a fiber optic electroacoustic transducer of the present invention;
FIG. 2 is a flow chart of a method of making a fiber optic acoustic transducer of the present invention;
FIG. 3 is a schematic diagram of the fabrication of a fiber optic photoacoustic transducer of the present invention;
FIG. 4 is a schematic diagram of the optical path of the tail end of the optical fiber.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1 and fig. 3, the high-directivity fiber optic-acoustic transducer of the present embodiment includes a nanosecond pulse laser 1, a lens 2, and a quartz fiber 3, which are sequentially disposed, wherein a concave cavity 4 is disposed at a tail end of the quartz fiber 3, and gold nanoparticles 5 are uniformly distributed in the concave cavity 4, and based on a photoacoustic conversion principle of resonance absorption of the gold nanoparticles, the nanosecond pulse laser can be converted into an ultrasonic pulse.
Fig. 2 shows a process of manufacturing the high-directivity fiber optic acoustic transducer according to this embodiment, and the following explains a process of manufacturing the high-directivity fiber optic acoustic transducer based on the photoacoustic effect:
firstly, turning on a nanosecond pulse laser 1, determining the optimal position of a lens according to the light propagation direction, measuring the size of a light spot passing through the lens 2, and determining the position of a focus;
stripping a coating layer of the quartz optical fiber 3 by using an optical fiber wire stripper, and cutting off two ends of the optical fiber by using an optical fiber cutting knife to ensure that end faces of two ends of the optical fiber are smooth so as to form a regular concave cavity under the action of high-power-density laser ablation;
immersing the tail end of the quartz optical fiber into a nano gold particle solution 6 with the concentration of 0.05mg/ml and the particle size of 50nm, and fixing the first section of the quartz optical fiber at the focal position of the coupling lens;
setting a nanosecond pulse green laser, coupling the nanosecond pulse green laser into the quartz fiber through a coupling lens, generating obvious jet flow at the tail end of the quartz fiber in the nano-gold particle solution, and after the jet flow is stable, indicating that nano-gold particles are uniformly attached to the tail end of the ablated quartz fiber, thereby completing the manufacture of the fiber optic-acoustic transducer;
thus, for the high-directivity optical fiber photoacoustic transducer prepared according to the steps, the nanosecond pulse laser emits laser which is coupled into the quartz optical fiber through the lens, the laser is uniformly radiated on the nano gold particle concave surface array at the tail end of the quartz optical fiber due to the fact that the optical fiber has a certain numerical aperture, the nano particles are excited to vibrate to generate ultrasonic waves, and the ultrasonic waves are focused on the corresponding focus position of the concave surface due to the self-focusing property of the concave cavity structure, so that the transmission of the photoacoustic focusing ultrasonic waves is achieved.
In this embodiment, a specific group of components of the ultrasonic transducer and their structural dimensions are given:
the quartz fiber is 105/125Low NA Launch fiber, and is based on a full-quartz fiber structure, the standard core diameter is 105 mu m, the cladding diameter is 125 mu m, and a double-acrylate coating layer is easy to peel.
The nano gold particle solution is a nano gold particle solution with the diameter of 50nm and the concentration of 0.05mg/ml, and the corresponding nano particle absorption peak is positioned at the position of 535 nm.
Selecting a plano-convex lens with the diameter of 25.4m and the focal length of 100mm, wherein the size of a light spot at the focal point is less than hundred microns;
the nanosecond pulse laser has the wavelength of 532nm, the pulse width of 50ns, the repetition frequency of 10kHz and the average power of 400-800 mW.
The tail end of the quartz optical fiber can be manufactured into a specific concave cavity structure in an ablation mode, the processing precision can reach the micron level, and the nano gold particle particles can be uniformly distributed in a specific quartz tail end concave surface in a micro-nano processing mode.
Details not described in the present invention are well known to those skilled in the art.
The present invention is not limited to the above-described embodiments. The foregoing description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above specific embodiments are merely illustrative and not restrictive. Those skilled in the art can make many changes and modifications to the invention without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (6)
1. The high-directivity optical fiber photoacoustic transducer is characterized by comprising a nanosecond pulse laser, a lens and a quartz optical fiber which are sequentially arranged: the tail end of the quartz optical fiber is provided with a concave cavity, gold nanoparticles are uniformly distributed in the concave cavity, and nanosecond pulse laser can be converted into ultrasonic pulses based on the photoacoustic conversion principle of resonance absorption of the gold nanoparticles.
2. The high directivity fiber optic acoustic transducer according to claim 1, wherein the silica fiber is a multimode fiber having a core diameter of 50 to 500 μm.
3. The high-directivity fiber optic acoustic transducer according to claim 1, wherein the nanosecond pulse laser is capable of generating nanosecond pulse laser with a wavelength of 532nm, a pulse width of 10-200ns, a repetition frequency of 1-100kHz, and an average power of 400-800mW, and the nanosecond pulse laser is focused by a lens and then coupled into the quartz fiber.
4. The high directivity fiber optic acoustic transducer according to claim 1, wherein the size of the cavity is equivalent to the fiber core diameter, and is 50 to 500 μm; the grain diameter of the gold nano-particle is 40-60nm, and the corresponding resonance absorption peak is 530-535 nm.
5. A preparation method of a high-directivity optical fiber photoacoustic transducer is characterized by comprising the following steps of:
cutting off two ends of the quartz optical fiber by using an optical fiber cutter to ensure that two end surfaces of the quartz optical fiber are smooth so as to form a regular and stable concave cavity structure under the action of laser; adjusting the positions of the nanosecond pulse laser, the lens and the quartz optical fiber to enable the nanosecond pulse laser to be effectively coupled into one end of the quartz optical fiber, and immersing the other end of the quartz optical fiber into an aqueous solution containing gold nanoparticles, wherein the concentration of the solution is 0.03-0.06 mg/mL;
the laser transmitted in the quartz optical fiber interacts with the gold nanoparticles in the aqueous solution to generate ablation on the end face of the optical fiber to form a regular and stable concave cavity structure, and meanwhile, the gold nanoparticles are attached to the surface of the concave cavity; the laser and the gold nanoparticles attached to the surface of the cavity are subjected to photoacoustic conversion through resonance coupling, ultrasonic waves with directionality are formed under the self-focusing action of the cavity, an aqueous solution is driven to generate jet flow, when the jet flow is stable, the cavity structure and the gold nanoparticles attached to the surface are stably distributed, and the preparation of the optical fiber photoacoustic transducer is completed.
6. The method as claimed in claim 5, wherein the size and structure of the cavity are changed to obtain different focuses and directivities of the fiber optic electroacoustic transducer.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113820781A (en) * | 2021-11-24 | 2021-12-21 | 之江实验室 | Point sound source generating device based on optical fiber optoacoustic and manufacturing method thereof |
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