Lateral transceiving integrated optical fiber ultrasonic endoscope and preparation method

Abstract

The invention discloses a lateral transceiving integrated optical fiber ultrasonic endoscope and a preparation method, and belongs to the field of ultrasonic endoscopic imaging. Comprising a double-clad optical fiber, an excitation film, a dielectric mirror and a sensing film. A part of the inner cladding of the optical fiber is etched into a concave spherical surface and coated with an excitation film, excitation light transmitted in the inner cladding is absorbed, and focused ultrasonic waves transmitted in the lateral direction are excited. A part of an inner cladding layer and a fiber core of the optical fiber are etched, and a Fabry-Perot (Fabry-Perot, F-P) cavity is prepared. When an ultrasonic signal laterally transmitted into the ultrasonic endoscope acts on the sensing film of the cavity, the effective refractive index and the F-P cavity length of the sensing film are changed, and the change is demodulated through signal light in the fiber core to complete ultrasonic detection. According to the lateral transmitting-receiving integrated optical fiber ultrasonic endoscope, the inner cladding is etched and coated with the excitation thin film to excite laterally focused ultrasonic waves, an F-P cavity is formed through lateral etching of the optical fiber to achieve lateral ultrasonic detection, and the lateral transmitting-receiving integrated optical fiber ultrasonic endoscope is formed.

Description

Technical Field

[0001] The present invention belongs to the field of ultrasonic endoscopic imaging, and more specifically, relates to a lateral transceiver integrated optical fiber ultrasonic endoscope and a preparation method thereof. Background Art

[0002] Ultrasonic waves are widely used in biomedical and other fields, especially in the field of endoscopic imaging in medical imaging, because of their good directionality, strong penetrating ability, and easy acquisition of concentrated sound energy. Fiber-optic ultrasonic endoscopes can use the characteristics of ultrasonic waves to provide internal information of the object to be tested, thereby adjusting surgical strategies based on this information to improve the safety and success rate of the operation. The imaging principle is that the ultrasonic transducer emits an ultrasonic signal that propagates to a certain part of the object to be tested. The ultrasonic signal is reflected by the object to be tested and then received by the ultrasonic transducer. The image or structural information of the object to be tested is obtained by demodulating the signal.

[0003] Compared with traditional piezoelectric ultrasonic devices, fiber-optic ultrasonic endoscopes have the characteristics of small size, high sensitivity, good flexibility, and resistance to electromagnetic interference. Fiber-optic ultrasonic endoscopes are composed of two types: fiber-optic ultrasonic transmitters and ultrasonic detectors. The first type of ultrasonic transmitter is composed of light-absorbing materials and thermal expansion materials. The main mechanism is thermal expansion after absorbing laser. The light-absorbing materials are currently mainly high-light-absorbing materials such as metal materials and carbon-based materials, such as gold, chromium, germanium, carbon black, carbon nanotubes, candle ash, etc. For thermal expansion materials, PDMS is widely used due to its high thermal expansion and transparency. The second type of ultrasonic detector obtains the ultrasonic signal to be measured by measuring the shape of the detector or the changes in its physical parameters caused by ultrasonic waves. At present, the main types of ultrasonic detectors are fiber grating type, Mach-Zehnder interferometer type, FP interferometer and microring resonator type.

[0004] Fiber-optic ultrasound endoscopes mainly image tissues laterally, but the ultrasound transmitter in current fiber-optic endoscopes usually works on the front end of the optical fiber, and additional devices are required to steer the ultrasound to achieve lateral imaging. Existing lateral ultrasound transmitters mainly transmit light in the fiber core, and couple the excitation light to the cladding through mechanical structure destruction or gratings. Therefore, the excitation light energy is weak, resulting in a small ultrasound signal, which limits its application. Summary of the invention

[0005] In view of the defects of the prior art or the need for improvement, the purpose of the present invention is to provide a lateral transceiver integrated fiber optic ultrasonic endoscope and a preparation method, aiming to solve the problems of existing fiber optic endoscopes, such as large size, small excitation ultrasonic signal, and complex system.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided a lateral transceiver integrated optical fiber ultrasonic endoscope, comprising: a double-clad optical fiber, an excitation film, a dielectric mirror, and a sensing film;

[0007] The double-clad optical fiber includes a core, an inner cladding and an outer cladding arranged from the inside to the outside; the transmission mode of the core at the signal light wavelength is single mode, and is used for the transmission of the signal light;

[0008] The transmission mode of the inner cladding at the excitation light wavelength is multimode, which is used for the transmission of the excitation light; the signal light and the excitation light are bounded by the outer cladding; the inner cladding of the double-clad optical fiber away from the optical fiber end face is a concave spherical surface, and the excitation film is located on the surface of the concave spherical surface; the excitation film is coated on the surface of the concave spherical surface by pulling;

[0009] The inner cladding of the double-clad optical fiber, which is close to the optical fiber end face and in the same direction as the concave spherical surface, is partially recessed inwardly to the fiber core to form an open microcavity;

[0010] The dielectric mirror and the sensing film are sequentially covered inside the microcavity to form an FP cavity;

[0011] When the fiber-optic ultrasonic endoscope is used for lateral ultrasonic excitation, the excitation light is transmitted along the inner cladding of the double-clad optical fiber, and when the excitation light is transmitted to the excitation film, it is absorbed and generates a focused ultrasonic signal that propagates laterally;

[0012] When the fiber optic ultrasonic endoscope is used for lateral ultrasonic detection, the signal light is transmitted along the core of the double-clad optical fiber and is reflected back to the double-clad optical fiber by the dielectric mirror as a detection signal; when the ultrasonic wave reflected by the object to be measured is transmitted laterally to the sensing film, the geometric displacement caused by the ultrasonic wave and the elasto-optical effect interact with each other, causing the FP cavity length and the effective refractive index of the sensing film to change, thereby changing the phase difference of the electric fields of the two reflections of adjacent signal lights, thereby modulating the ultrasonic wave reflected by the object to be measured to the phase of the signal light reflected by the dielectric mirror, thereby changing the optical power of the signal light, and realizing lateral ultrasonic detection by detecting its optical power.

[0013] Preferably, the contact area between the excitation film and the excitation light is greater than 0.01 mm 2 , thereby increasing the sound pressure of the ultrasonic signal.

[0014] Preferably, the focal length of the concave spherical surface is 0.5 mm to 10 mm, which is used to excite the laterally propagating ultrasonic waves and focus them on the object to be measured.

[0015] Preferably, a femtosecond laser is used to accurately etch the microcavity length into 5 um to 200 um, so as to reduce the aperture size for detecting ultrasound and improve the imaging resolution.

[0016] Preferably, the dielectric mirror is a dielectric film formed by alternately depositing two different inorganic materials with a refractive index of 1.2 to 2.5, and has a reflectivity of more than 97% for the wavelength of the signal light.

[0017] Preferably, the sensing film has an elastic coefficient greater than 10 -7 / RIU and a polymer material with a transmittance of more than 90% for the signal light wavelength, and a large elastic-optical coefficient is used to improve the sensitivity of ultrasonic detection.

[0018] Preferably, the signal light is a narrow linewidth laser, and the excitation light is a narrow pulsewidth pulse light or a modulated continuous light.

[0019] Preferably, the excitation film has a light absorption coefficient of more than 1.5 for the excitation light wavelength, and the specific surface area of ​​the light absorption material is 30m 2 g -1 The thermal expansion coefficient of the thermal expansion material is greater than 10 -4 / ℃, has fast thermal diffusion and high thermal elastic expansion coefficient, and the light absorbing material and the thermal expansion material have a ratio of 1:2 to 1:10 with high photoacoustic conversion efficiency.

[0020] According to another aspect of the present invention, a method for preparing a lateral transceiver integrated optical fiber ultrasonic endoscope is provided, comprising the following steps:

[0021] S1, use a fiber stripper to strip a section of the coating away from the fiber end face of the double-clad fiber, and use a dust-free cloth dipped in alcohol and deionized water to wipe the bare fiber part. Then use a femtosecond pulse laser to focus on the upper surface of the fiber, and programmatically control the three-dimensional movement of the platform until it scans the entire concave spherical surface of the preset focus. Then clean the resulting concave spherical surface structure with alcohol and deionized water.

[0022] S2, mixing the polymer obtained by mixing PDMS and the curing agent with carbon black according to a mass ratio, stirring the mixture evenly with a magnetic stirrer, and then placing the mixture in a vacuum drying oven to remove bubbles in the mixture.

[0023] S3, using a pulling machine to immerse the etched part of the optical fiber into a mixture of carbon black and PDMS, and slowly pull out the optical fiber, and then slowly move the optical fiber to a constant temperature drying oven for solidification to form an excitation film.

[0024] S4, use a dust-free cloth dipped in alcohol and deionized water to wipe the part of the mixture near the end face of the optical fiber to remove the mixture, use a fiber stripper to remove a coating layer of the double-clad optical fiber to remove the mixture, and use a dust-free cloth dipped in alcohol and deionized water to wipe the bare fiber part. Then use a femtosecond pulse laser to etch a microcavity in the same direction as the concave spherical surface, and ensure that the etching depth of the microcavity exceeds the lower surface of the optical fiber core. Then use alcohol and deionized water to clean the resulting microcavity structure.

[0025] S5, using a vacuum evaporation coating method to alternately deposit multiple layers of silicon dioxide and titanium dioxide on the inner surface of the optical fiber microcavity as a dielectric mirror.

[0026] S6, dip-coat a small amount of high-elastic-optical-coefficient polymer material on the ultra-fine optical fiber obtained by oxyhydrogen flame taper under a microscope, fix it on a three-dimensional displacement platform, slowly move it to the microcavity structure to fill the polymer material in the microcavity, ensure that the height of the polymer material is higher than the upper surface of the fiber core, and then slowly move the optical fiber to a constant temperature drying oven to solidify and form a sensing film. The dielectric mirror and the sensing film together form the FP cavity, completing the preparation of the fiber-optic ultrasonic endoscope.

[0027] S7. Finally, the excitation light and narrow linewidth laser are input into the multi-mode input end and single-mode input end of the double-clad coupler respectively by using an optical circulator, and the light is further coupled to the fiber optic ultrasonic endoscope. A lateral transceiver integrated fiber optic ultrasonic endoscope is built in conjunction with a three-dimensional rotating translation stage and a signal processing and control system.

[0028] Compared with the prior art, the above technical solutions conceived by the present invention can achieve the following

[0029] Beneficial effects:

[0030] 1. The present invention provides a fiber-optic ultrasonic endoscope that realizes lateral transmission and reception in one body using a single optical fiber. A single double-clad optical fiber is used to realize ultrasonic transmission and ultrasonic detection functions, so as to reduce the size of the fiber-optic ultrasonic endoscope to about 245um, which can meet the needs of medical endoscopic imaging.

[0031] 2. The present invention utilizes the inner cladding of the optical fiber to transmit the excitation light and perform lateral excitation. Compared with the core of the optical fiber transmitting the excitation light and performing lateral excitation, the present invention has greater light energy, thereby increasing the sound pressure of the ultrasonic wave.

[0032] 3. The present invention utilizes femtosecond laser etching technology to accurately and programmatically etch the inner cladding into a concave spherical structure with a focal length of 0.5mm-10mm, which is commonly used in ultrasonic endoscopes. The sound beam at the focus is narrow, which can achieve an ultrasonic focusing effect, thereby improving the lateral resolution of imaging.

[0033] 4. The microcavity etched by femtosecond laser etching technology in the present invention is relatively short, which can reduce the aperture size and improve the imaging resolution. The microcavity structure is in contact with media such as blood and water, and can directly detect lateral ultrasonic signals, which is suitable for the application scenario of lateral active detection.

[0034] 5. The present invention forms an FP cavity by preparing a dielectric mirror and filling it with a polymer having a large elasto-optic coefficient, and realizes a high-sensitivity ultrasonic detection function by utilizing the dual effects of the elasto-optic effect and the change in the geometric cavity length.

[0035] 6. The fiber optic ultrasonic endoscope and preparation method provided by the present invention have the advantages of high sensitivity, good stability, simple preparation, low cost, and easy practical application, and can be widely used in the field of medical endoscopic imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a structural schematic diagram of the lateral transmitting and receiving integrated optical fiber ultrasonic endoscope provided by the present invention;

[0037] Figure 2 It is a schematic diagram of the manufacturing process of the lateral transmitting and receiving integrated optical fiber ultrasonic endoscope provided by the present invention;

[0038] In all the drawings, the same figure numbers are used to represent the same elements or structures, including: 1. double-clad optical fiber; 2. excitation light; 3. excitation film; 4. signal light; 5. dielectric mirror; 6. sensing film. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] Figure 1 FIG. 1 is a schematic diagram of the structure of the lateral transceiver integrated fiber optic ultrasonic endoscope of the present invention. Figure 1 As shown, the present invention proposes a lateral transceiver integrated fiber optic ultrasonic endoscope, comprising a double-clad optical fiber 1, an excitation film 3, a dielectric mirror 5, and a sensing film 6. The inner cladding in the double-clad optical fiber is used to transmit the excitation light 2, and the core is used to transmit the signal light 4. The inner cladding portion away from the end face of the optical fiber is etched into a concave spherical surface, and a mixture of carbon black and PDMS is coated on the concave spherical surface area by a pulling method as the excitation film 3. According to the photoacoustic effect, when the excitation light is transmitted to the concave spherical surface, a focused ultrasonic signal propagating laterally is generated. The inner cladding portion and the core portion close to the end face of the optical fiber are etched into a microcavity, and the etching depth exceeds the lower surface of the core. A dielectric film with wavelength selective transmittance is deposited on the inner surface of the microcavity as the dielectric mirror 5, and a polymer material is filled into the microcavity as the sensing film 6. The dielectric mirror 5 and the sensing film 6 constitute an FP cavity, which is subjected to the geometric displacement caused by the side-reflected ultrasonic signal and the interaction of the elasto-photoelectric effect, so that the FP cavity length and the effective refractive index of the sensing film 6 change, thereby changing the phase difference of the electric fields of two adjacent reflections of the signal light 4, thereby modulating the side-reflected ultrasonic signal to the phase of the signal light 4, resulting in a change in the intensity of the reflected light, and thereby changing the optical power of the signal light 4.

[0041] Specifically, the core diameter is less than 10 microns, the transmission mode is single mode, and the signal light 4 is transmitted in the core. The inner cladding diameter is greater than 10 microns, the transmission mode is multimode, and the excitation light 2 is transmitted in the inner cladding. Further, the outer cladding is used to bind the excitation light 2 and the signal light 4.

[0042] Specifically, the core diameter is 9 microns, the inner cladding diameter is 105 microns, the outer cladding diameter is 125 microns, the input signal light 4 is a narrow linewidth laser, and the excitation light 2 is a pulse light or a modulated continuous light.

[0043] Specifically, the substrate of the excitation film 3 is precisely etched into a concave spherical surface with a preset focus by a programmed femtosecond laser to excite a focused ultrasonic signal that propagates laterally.

[0044] Specifically, the light absorbing material has a specific surface area of ​​30 m 2 g -1 The carbon black with high light absorption at the excitation light wavelength is more than 10 -4 / ℃, the excitation film 3 has high photoacoustic conversion efficiency and good adsorption with the concave spherical surface.

[0045] Specifically, the length of the optical fiber microcavity is 5um to 200um, the dielectric mirror 5 is a dielectric film formed by alternately depositing silicon dioxide and titanium dioxide, has a reflectivity of more than 97% for the wavelength of the signal light 4, and has good adsorption properties with the optical fiber microcavity and the sensing film 6.

[0046] Specifically, the sensing film 6 has an elastic coefficient greater than 10 -7 / RIU and a polymer material with a transmittance of more than 90% for the signal light wavelength, which increases the responsiveness between ultrasound and the effective refractive index and improves the sensitivity of ultrasonic detection.

[0047] Further, the present invention also proposes a method for preparing the above-mentioned lateral transceiver integrated optical fiber ultrasonic endoscope, such as Figure 2 As shown, the specific steps include:

[0048] S1, use a fiber stripper to strip a coating layer of a section of the double-clad optical fiber 1 away from the optical fiber end face, and use a dust-free cloth dipped in alcohol and deionized water to wipe the bare fiber part. Then use a femtosecond pulse laser to focus on the upper surface of the optical fiber, and programmatically control the three-dimensional movement of the platform until it scans the entire concave spherical surface with a preset focus of 2mm. Then use alcohol and deionized water to clean the resulting concave spherical surface structure.

[0049] S2, the next step is to prepare the excitation film 3, mix the polymer and carbon black in a mass ratio of 10:1 of PDMS and curing agent, stir evenly with a magnetic stirrer, and then put it in a vacuum drying oven for 30 minutes to remove bubbles in the mixture.

[0050] S3, using a pulling machine to immerse the etched part of the optical fiber into a mixture of carbon black and PDMS, let it stand for 2 minutes and slowly pull out the optical fiber at a certain speed, and then slowly move the optical fiber to a constant temperature drying oven for curing.

[0051] S4, use a dust-free cloth dipped in alcohol and deionized water to wipe the part of the mixture near the end face of the optical fiber to remove the mixture, use a fiber stripper to remove a coating layer of the double-clad optical fiber to remove the mixture, and use a dust-free cloth dipped in alcohol and deionized water to wipe the bare fiber part. Then use a femtosecond pulse laser to etch a microcavity in the same direction as the concave spherical surface, and ensure that the etching depth of the microcavity exceeds the lower surface of the optical fiber core. Then use alcohol and deionized water to clean the resulting microcavity structure.

[0052] S5, using a vacuum evaporation coating method to alternately deposit multiple layers of silicon dioxide and titanium dioxide on the inner surface of the optical fiber microcavity to serve as a dielectric mirror 5.

[0053] To further explain, the dielectric mirror 5 is a dielectric film formed by alternating deposition of multiple layers of silicon dioxide and titanium dioxide, which is a periodically modulated refractive index structure that can produce high reflectivity for light of a specific wavelength. By designing the parameters of the dielectric film, it has a reflectivity of more than 97% for the wavelength of the signal light 4.

[0054] S6, according to the PDMS and curing agent 10:1 mixed polymer, using a magnetic stirrer to stir evenly and put into a vacuum drying oven to remove bubbles in the mixture. Under a microscope, dip a small amount of PDMS on the ultra-fine optical fiber obtained by oxyhydrogen flame taper, fix it on a three-dimensional displacement platform, slowly move it to the microcavity structure to fill the PDMS in the microcavity, ensure that the PDMS height is higher than the height of the upper surface of the fiber core, and then slowly move the optical fiber to a constant temperature drying oven to solidify and form a sensing film 6. The dielectric mirror 5 and the sensing film 6 together constitute the FP cavity.

[0055] S7. Finally, the excitation light and narrow linewidth laser are input into the multi-mode input end and single-mode input end of the double-clad coupler respectively by using an optical circulator, and the light is further coupled to the fiber optic ultrasonic endoscope. A lateral transceiver integrated fiber optic ultrasonic endoscope is built in conjunction with a three-dimensional rotating translation stage and a signal processing and control system.

[0056] When the excitation light 2 is input into the ultrasonic endoscope, it irradiates the concave spherical surface, causing the temperature of the excitation film 3 to rise and undergo thermoelastic expansion in the lateral direction, compressing the surrounding medium and generating focused ultrasound waves that are transmitted laterally.

[0057] The ultrasonic wave generated by the ultrasonic endoscope is reflected by the object to be measured and the ultrasonic wave carrying the imaging information of the object to be measured is directly detected laterally by the sensing film 6. The geometric displacement caused by the reflected ultrasonic signal and the interaction of the elastic-optical effect cause the FP cavity length and the effective refractive index of the sensing film 6 to change, thereby changing the phase difference of the electric field of two adjacent reflections, resulting in a change in the intensity of the reflected light. The ultrasonic signal is detected by using a tunable laser through a bevel edge demodulation method;

[0058] When the signal light 4 is input to the ultrasonic endoscope, multi-beam interference occurs due to the effect of the FP cavity formed by the dielectric mirror 5 and the sensor film 6, forming interference light that is transmitted in the reverse direction along the optical fiber core. The intensity of the interference light is:

[0059]

[0060] Among them I i is the intensity of the incident signal light 4, R is the reflectivity of the single-side surface of the dielectric mirror 5 at the wavelength of the signal light 4, δ=4πnh / λ is the optical path of the signal light 4 reflected once on the two side surfaces of the dielectric mirror 5, n is the refractive index of the material of the sensing film 6, and h is the physical length between the two side surfaces of the dielectric mirror 5.

[0061] The ultrasonic wave to be measured acts on the sensing film 6 to change the physical length h between the two sides of the dielectric mirror 5, and according to the photoelastic effect, the ultrasonic wave to be measured acts on the sensing film 6 to change the effective refractive index n of the sensing film 6. This in turn changes the optical path of the signal light 4, and realizes intensity modulation of the interference light through multi-beam interference.

[0062] The all-fiber ultrasonic endoscope proposed in the present invention can be used for ultrasonic excitation and detection in different medium environments, such as water, air and other liquid environments.

[0063] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A lateral transceiver integrated fiber optic ultrasonic endoscope, characterized in that: It comprises a double-clad optical fiber (1), an excitation film (3), a dielectric mirror (5), and a sensing film (6); The inner cladding of the double-clad optical fiber (1) that is away from the optical fiber end face is a concave spherical surface, and the excitation film (3) is located on the surface of the concave spherical surface; the inner cladding of the double-clad optical fiber (1) that is close to the optical fiber end face and in the same direction as the concave spherical surface is recessed inwardly to the fiber core to form an open microcavity, and the dielectric mirror (5) and the sensing film (6) are sequentially covered inside the microcavity to form an FP cavity; When the fiber optic ultrasonic endoscope is used for lateral ultrasonic excitation, the excitation light is transmitted along the inner cladding of the double-clad optical fiber (1), and when the excitation light is transmitted to the excitation film (3), it is absorbed, thereby generating a focused ultrasonic signal that propagates laterally; When the fiber optic ultrasonic endoscope is used for lateral ultrasonic detection, the signal light is transmitted along the core of the double-clad optical fiber (1) and is reflected by the dielectric mirror (5); when the ultrasonic wave reflected by the object to be detected is transmitted laterally to the sensing film (6), the FP cavity length and the effective refractive index of the sensing film (6) are changed, thereby changing the phase difference of the electric field of two adjacent reflections of the signal light, thereby modulating the ultrasonic wave reflected by the object to be detected to the phase of the signal light reflected by the dielectric mirror (5), thereby changing the optical power of the signal light, and realizing lateral ultrasonic detection by detecting its optical power.

2. The lateral transmitting and receiving integrated optical fiber ultrasonic endoscope according to claim 1, characterized in that: The contact area between the excitation film (3) and the excitation light is greater than 0.01 mm 2 .

3. The lateral transmitting and receiving integrated optical fiber ultrasonic endoscope according to claim 1, characterized in that: The focal length of the concave spherical surface is 0.5 mm to 10 mm.

4. The lateral transmitting and receiving integrated optical fiber ultrasonic endoscope according to claim 1, characterized in that: The excitation film (3) comprises a specific surface area of ​​30 m 2 g -1 The above light absorbing material and thermal expansion material, the excitation film (3) has a light absorption rate of more than 90% for the excitation light wavelength.

5. The lateral transmitting and receiving integrated optical fiber ultrasonic endoscope according to claim 1, characterized in that: The etching depth of the microcavity exceeds the lower surface of the core of the double-clad optical fiber (1).

6. The lateral transmitting and receiving integrated optical fiber ultrasonic endoscope according to claim 1, characterized in that: The dielectric mirror (5) is a dielectric film formed by alternately depositing two different inorganic materials with a refractive index of 1.2 to 2.5, and has a reflectivity of more than 97% for the wavelength of the signal light.

7. The lateral transmitting and receiving integrated optical fiber ultrasonic endoscope according to claim 1, characterized in that: The sensing film (6) is a polymer material having a transmittance of more than 90% for the wavelength of the signal light.

8. The lateral transmitting and receiving integrated optical fiber ultrasonic endoscope according to claim 1, characterized in that: The dielectric mirror (5) and the sensing film (6) on the inner surface of the microcavity together form an FP cavity, so that the signal light is repeatedly reflected on two reflection surfaces of the FP cavity and multi-beam interference occurs in the optical fiber core.

9. A method for preparing a lateral transmitting and receiving integrated optical fiber ultrasonic endoscope according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, stripping a coating layer of a section of the double-clad optical fiber (1) away from the optical fiber end face, focusing a femtosecond pulse laser on the upper surface of the stripped optical fiber, and scanning the entire concave spherical surface of the preset focus; S2, mixing the polymer obtained by mixing PDMS and a curing agent with carbon black according to a mass ratio, stirring the mixture evenly and removing bubbles from the mixture; S3, immersing the etched portion of the optical fiber into the mixture, and solidifying it to form an excitation film (3); S4, stripping a coating layer of a section of the double-clad optical fiber (1) close to the optical fiber end face, using a femtosecond pulse laser to etch a microcavity in the same direction as the concave spherical surface, and ensuring that the etching depth of the microcavity exceeds the lower surface of the optical fiber core; S5, depositing multiple layers of silicon dioxide and titanium dioxide alternately on the inner surface of the optical fiber microcavity as a dielectric mirror (5); S6, dip-coating the ultra-fine optical fiber obtained by oxyhydrogen flame taper with a polymer material having a large elastic-optical coefficient, moving it to the microcavity to fill the polymer material in the microcavity, ensuring that the height of the polymer material is higher than the upper surface of the fiber core, and solidifying it to form a sensing film (6) to constitute an ultrasonic detection area.

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