Ultrasonic sensing and imaging based on whispering gallery mode (wgm) microelectromechanical resonators

Abstract

Disclosed are an acoustic sensor based on an optical whispering gallery mode (WGM) resonator, an imaging system using the acoustic sensor, and a method of detecting ultrasonic waves using the acoustic sensor.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 901,883, filed on September 18, 2019, the entire contents of which are incorporated herein by reference.

[0003] Statement regarding federally funded research or development

[0004] This invention was completed with government support, under licenses W911NF1710189 and W911NF1210026 granted by the Army Research Office. The government holds certain rights to this invention. Technical Field

[0005] This disclosure generally relates to systems and methods for performing ultrasonic imaging using acoustic transducers including whispering-gallery mode resonators. Background Technology

[0006] Ultrasound technology has garnered increasing attention across various fields, particularly in non-invasive measurement, remote sensing, and biomedical imaging. Ultrasound imaging is used in a variety of settings to non-invasively image a patient's internal structures by detecting ultrasound pulses reflected from tissue boundaries within the patient's body. Ultrasound detectors used in imaging applications typically feature low noise equivalent pressure (NEP) and operate at high frequencies and wide bandwidths. Currently available piezoelectric-based ultrasound detectors generally meet these requirements. However, for imaging applications requiring smaller detectors, the use of piezoelectric-based ultrasound detectors is limited by noise, as the reduction in size is accompanied by an increase in noise associated with ultrasound detection.

[0007] Furthermore, as the resolution of ultrasound increases due to the application of higher frequency sound waves, its penetration depth decreases due to increased acoustic attenuation. This trade-off between resolution and penetration depth presents a challenge in the context of conventional piezoelectric ultrasonic sensors.

[0008] Photonic devices (e.g., gratings, etalons, etc.) and optical pressure detection technologies have shown great promise in ultrasonic testing, attracting increasing attention due to their ability to be fabricated at the microscale without sacrificing ultrasonic detection performance or sensitivity. In photonic devices, refractive index modulation and / or shape deformation caused by acoustically induced strain are translated into changes in the detected light intensity or the device's spectral characteristics. In some existing devices, optical resonators have been used as highly sensitive ultrasonic detectors. In these resonators, the arrival of ultrasonic waves leads to modulation of the resonant frequency or transmitted light intensity. Typically, the performance of an optical resonator is limited by its quality factor Q (i.e., the higher the Q, the lower the optical loss and the smaller the detectable resonant displacement) and the acousto-optic and mechanical properties of the materials used to fabricate the resonator.

[0009] Other purposes and features will be apparent in part and indicated in part below. Summary of the Invention

[0010] In one aspect, an acoustic sensor is disclosed, comprising an optical whispering-gallery mode resonator; a coupling waveguide for optical coupling to the resonator; and a polymer encapsulating a portion of the coupling waveguide and the resonator. The coupling waveguide is spaced apart from the resonator by a gap. Each of the resonator and the coupling waveguide has a refractive index higher than the corresponding refractive index of the polymer.

[0011] In other aspects, an acoustic sensing system is disclosed, comprising an optical whispering-gallery mode resonator; a coupling waveguide for optical coupling to the resonator; a polymer encapsulating a portion of the coupling waveguide and the resonator; a light source coupled to a first end of the coupling waveguide and protruding from the low-refractive-index polymer; and a photodetector coupled to a second end of the coupling waveguide and protruding from the low-refractive-index polymer. The coupling waveguide has the first end and a second end opposite to the first end, and the coupling waveguide is spaced apart from the resonator by a gap. Each of the resonator and the coupling waveguide has a refractive index higher than the corresponding refractive index of the polymer.

[0012] Furthermore, a photoacoustic imaging device is disclosed, comprising an acoustic sensor. The acoustic sensor includes an optical whispering-gallery mode resonator; a coupling waveguide for optical coupling to the resonator; a polymer encapsulating a portion of the coupling waveguide and the resonator; a transducer light source coupled to a first end of the coupling waveguide and protruding from the low-refractive-index polymer; a transducer photodetector coupled to a second end of the coupling waveguide opposite to the first end and protruding from the low-refractive-index polymer; and a photoacoustic light source. The coupling waveguide has a first end and a second end opposite to the first end, and the coupling waveguide is spaced apart from the resonator by a gap. Each of the resonator and the coupling waveguide has a refractive index higher than the corresponding refractive index of the polymer.

[0013] In other additional aspects, a method for detecting ultrasound is disclosed, the method comprising providing an acoustic sensing system including an optical whispering-gallery mode resonator; a coupling waveguide for optical coupling to the resonator; a polymer encapsulating a portion of the coupling waveguide and the resonator; a light source; and a photodetector. The coupling waveguide has a first end and a second end opposite to the first end, and the coupling waveguide is spaced apart from the resonator by a gap. The light source is coupled to the first end of the coupling waveguide and protrudes from the low-refractive-index polymer; and the photodetector is coupled to the second end of the coupling waveguide and protrudes from the low-refractive-index polymer. The polymer forms a sample contact surface. Each of the resonator and the coupling waveguide has a refractive index higher than the corresponding refractive index of the polymer. The method further includes acoustically coupling the sample contact surface to the sample such that ultrasonic waves emitted from the sample are conducted through the polymer to the resonator and the portion of the coupling waveguide; introducing light generated by the light source into the first end of the coupling waveguide; converting light detected by the photodetector from the second end of the coupling waveguide into a detector signal encoding the amplitude of the detected light; and converting the detector signal into pressure using a predetermined calibration rule.

[0014] Other purposes and features will be apparent in part and indicated in part below. Attached Figure Description

[0015] Those skilled in the art will understand that the accompanying drawings described below are for illustrative purposes only. The drawings are not intended to limit the scope of this teaching in any way.

[0016] Figure 1A It is a graph that summarizes the refractive index of optical fiber modes of several different diameter optical fibers in air as a function of wavelength.

[0017] Figure 1B It shows Figure 1A The diagram shows the fiber mode distribution of the 1.6-μm optical fiber;

[0018] Figure 1C It is a graph that summarizes the fiber mode refractive index of several different diameter optical fibers in a polymer with a refractive index (n) of 1.33 as a function of wavelength;

[0019] Figure 1D It shows Figure 1C The diagram shows the fiber mode distribution of the 1.6-μm optical fiber;

[0020] Figure 2A This is an overview of optical fibers (n) encapsulated in a polymer with a refractive index (n) of 1.33. fiber ) and miniature toroidal resonators (m WGM,trA graph showing the effective refractive index of light transmission at 883 nm within the range;

[0021] Figure 2B It shows Figure 2A The diagram shows the fiber mode distribution of the optical fiber.

[0022] Figure 2C This is an overview of optical fibers (n) encapsulated in a polymer with a refractive index (n) of 1.33. fiber ) and miniature toroidal resonators (m WGM,tr A graph showing the effective refractive index of light transmission at 778 nm within the range;

[0023] Figure 2D It shows Figure 2C The diagram shows the fiber mode distribution of the optical fiber.

[0024] Figure 2E This is an overview of optical fibers (n) encapsulated in a polymer with a refractive index (n) of 1.33. fiber ) and miniature toroidal resonators (m WGM,tr A graph showing the effective refractive index of light transmission at 709 nm within the range;

[0025] Figure 2F It shows Figure 2E The diagram shows the fiber mode distribution of the optical fiber.

[0026] Figure 3 This is an image of a sound pressure sensor based on an optical resonator according to one aspect of this disclosure;

[0027] Figure 4A yes Figure 3 The diagram shows a cross-sectional view of an optical resonator-based acoustic sensor, in which the acoustic pressure sensor based on the optical resonator is embedded in a package made of a low-refractive-index polymer material.

[0028] Figure 4B yes Figure 4A A schematic side view of an embedded optical resonator-based acoustic sensor;

[0029] Figure 5 This is a diagram of an acoustic imaging system including an acoustic sensing probe based on an optical resonator, according to one aspect of this disclosure;

[0030] Figure 6 It is the spectrum of transmitted light intensity as a function of transmitted light wavelength, obtained by an acoustic sensing probe based on an optical resonator.

[0031] Figure 7 This is a diagram illustrating an example of a signal generated by an optical resonator-based acoustic sensing probe in response to an ultrasonic pulse;

[0032] Figure 8This is a schematic block diagram of a system according to one aspect of the present disclosure;

[0033] Figure 9 This is a schematic block diagram of a computing device according to one aspect of the present disclosure;

[0034] Figure 10 This is a schematic block diagram of a remote or user computing device according to one aspect of this disclosure;

[0035] Figure 11 This is a schematic block diagram of a server system according to one aspect of the present disclosure;

[0036] Figure 12 This is a schematic diagram illustrating a method for manufacturing a miniature toroidal resonator according to one aspect of this disclosure;

[0037] Figure 13A This is a schematic side view illustrating a method for assembling an acoustic sensor according to one aspect of this disclosure;

[0038] Figure 13B This is a schematic top view illustrating a method for assembling an acoustic sensor according to one aspect of this disclosure;

[0039] Figure 14 This is a screenshot of a display of a portable device for obtaining transmitted readings from an optical acoustic sensor, according to one aspect of this disclosure;

[0040] Figure 15 This is a schematic diagram illustrating the elements of an ultrasonic imaging system including an acoustic sensor based on an optical resonator, according to one aspect of this disclosure;

[0041] Figure 16A This is a graph outlining the gap detuning of the sensitivity load factor relative to the critical coupling of an optical resonator-based acoustic sensor in air;

[0042] Figure 16B This is a graph outlining the sensitivity loading factor relative to the gap detuning of the critical coupling of an acoustic sensor based on an optical resonator encapsulated in a polymer of n=1.33;

[0043] Figure 17A It shows a graph illustrating the penetration depth of an ultrasound sensor as a function of ultrasound frequency for various sensor enhancements, achieved by placing optical resonator-based acoustic sensors with varying degrees of sensor enhancement in tissue samples representing fat or breast tissue.

[0044] Figure 17BThis is a graph showing the penetration depth of an ultrasound sensor as a function of ultrasound frequency for various sensor enhancements, achieved by placing optical resonator-based acoustic sensors with varying degrees of sensor enhancement into a tissue sample representing blood.

[0045] Figure 18A It is a chart that outlines the various existing imaging modalities (OCT / optical coherence tomography, PAT / photoacoustic tomography, US / ultrasound, and MRI / magnetic resonance imaging) based on image resolution and penetration depth;

[0046] Figure 18B Is with Figure 18A The corresponding graphs show the effect of the improved sensitivity provided by the optical resonator-based acoustic sensor in various imaging modes according to one aspect of this disclosure.

[0047] Figure 19 This shows an optical microscopic image of a single miniature ring-core sensor according to one aspect of this disclosure;

[0048] Figure 20A This is a graph outlining the signals measured by a polymer-encapsulated miniature ring-core pressure sensor in response to 5-MHz ultrasonic pulses delivered at various pressures;

[0049] Figure 20B This is a graph summarizing the signals measured by a polymer-encapsulated miniature ring-core pressure sensor in response to 20-MHz ultrasonic pulses delivered at various pressures;

[0050] Figure 21 This is a graph outlining the change in signal amplitude obtained using a polymer-encapsulated miniature ring-core pressure sensor as a function of frequency detuning used to evaluate the SNR of the polymer-encapsulated miniature ring-core pressure sensor.

[0051] Figure 22 This is a graph showing the normalized signal amplitude obtained by detecting ultrasonic pulses delivered within a certain frequency range using a polymer-encapsulated miniature ring-core pressure sensor;

[0052] Figure 23A This is a schematic diagram illustrating the sign rule for the direction of incident sound waves on the surface of a miniature ring-core pressure sensor used for quantifying polymer encapsulation.

[0053] Figure 23B It detects pressure using a polymer-encapsulated miniature ring-shaped pressure sensor. Figure 23A A graph showing the normalized signal intensity obtained from ultrasonic pulses delivered within the incident sound angle range defined in the diagram;

[0054] Figure 24This is a schematic diagram illustrating the detection of acoustic signals using a miniature ring-shaped pressure sensor according to one aspect of this disclosure; and

[0055] Figure 25 Includes graphs showing wavelength detuning and transmission within the resonator during wavelength upscan.

[0056] Figure 26 This is a schematic diagram of a photoacoustic imaging system according to one aspect of this disclosure.

[0057] The arrangement currently under discussion is illustrated in the accompanying drawings; however, it should be understood that this embodiment is not limited to a precise arrangement and is merely an illustrative means. Although several embodiments have been disclosed, other embodiments of this disclosure will become apparent to those skilled in the art from the following detailed description, which illustrates and describes the illustrative aspects of this disclosure. As will be appreciated, modifications can be made to various aspects of the invention without departing from the spirit and scope of this disclosure. Therefore, the drawings and detailed description are to be considered illustrative rather than restrictive in nature. Detailed Implementation

[0058] In various aspects, a pressure sensor is disclosed, comprising an ultra-high quality optical whispering-gallery mode (WGM) resonator encapsulated in a low-refractive-index polymer. In other aspects, the polymer-encapsulated WGM resonator can be included in a pressure detection system. In various additional aspects, medical imaging systems, including but not limited to ultrasound imaging systems, can include optical whispering-gallery mode (WGM) resonators as acoustic sensors. Compared to conventional hydrophones based on piezoelectric materials, optical resonators can utilize the high sensitivity of circulating light to mechanical disturbances caused by incident sound waves, thereby achieving higher sensitivity to acoustic signals. Simultaneously, the sub-millimeter footprint achievable using WGM microresonators can (1) offer the potential for forming compact sensor arrays; and (2) extend the acoustic response bandwidth to higher frequencies.

[0059] In all aspects, the polymer-encapsulated WGM resonator exhibits a high optical quality factor (Q ~ 10⁷) and a rich array of mechanical modes responding to incoming acoustic signals, as described in more detail below. The polymer package maintains the fixedly coupled fiber taper and WGM resonator, ensuring robust optical actuation of the system free from mechanical disturbances. The polymer package further simplifies the optical packaging process during manufacturing and simplifies the integration of the polymer-encapsulated WGM resonator as a pressure sensor in the design of various devices, including but not limited to ultrasonic imaging systems.

[0060] I. Acoustic sensors based on optical resonators, sensor systems, and usage methods

[0061] The details and various embodiments of the invention can be better understood by referring to the accompanying drawings. (Reference) Figure 3 The illustration shows an optical resonator-based acoustic sensor system 100. In various aspects, system 100 may include a light source 101, which includes, but is not limited to, a tunable laser. System 100 also includes a WGM resonator 102 attached to a substrate 113, and a coupling waveguide 104 that introduces and removes laser energy into and out of the resonant modes of resonator 102. System 100 may also include an optical coupler 103 configured to introduce laser energy generated by light source 101 into coupling waveguide 104. Non-limiting examples of suitable light sources include semiconductor lasers (DFB or FP laser diodes), GaN or similar on-chip LED light sources, or on-chip WGM microlasers, the wavelength of which can be finely tuned by temperature control or by controlling the drive current. An optical receiver 106 (or photodetector) coupled to the opposite end of coupling waveguide 104 can be used to detect laser signal 108 at output port 110 of coupling waveguide 104.

[0062] In various aspects, both the light source 101 and the light receiver 106 are linked to a computing device 112 (not shown). In various aspects, the computing device is configured to control the operation of the light source 112 and process the output from the light receiver 106 to extract information relating to light transmission from the resonator 102. In another aspect, the computing device 112 of the system 100 also includes a processor and non-volatile computer-readable memory (not shown), as described in more detail below.

[0063] Figure 4A and Figure 4B They are respectively with Figure 3 The illustrated system is a cross-sectional and side view of a system 100 similar to the one shown, in which a portion 114 of a coupled waveguide 104 and a WGM resonator 102 are encapsulated in a low-refractive-index polymer 116. In one aspect, the low-refractive-index polymer 116 holds the portion 114 of the coupled waveguide 104 and the WGM resonator 102 in a fixed arrangement. In some aspects, the fixed arrangement may include a gap 118 separating the coupled waveguide 104 from the WGM resonator 102. In one aspect, the gap 118 is selected to result in critical coupling 102 of the laser energy introduced into the WGM resonator through the coupled waveguide 104. In another aspect, the gap 118 is slightly offset by a gap distance relative to the critical coupling so that the operation of the WGM resonator 102 is closer to the maximum load factor associated with enhanced sensor sensitivity, as described in more detail below.

[0064] In various aspects, the selected value of the gap is influenced by any one or more of a number of factors, including, but not limited to, the size and material of the optical WGM resonator, the size and material of the coupling waveguide, the size and material of the encapsulating polymer, the operating parameters of the pressure sensor based on the optical WGM oscillator, and any other relevant factors. A more detailed description of the relationship between at least some of the above factors is described below.

[0065] Refer again Figure 4A and Figure 4B The low-refractive-index polymer 116 is configured to efficiently transmit light between the coupling waveguide 104 and the WGM resonator 102, and to efficiently receive ultrasound waves from tissue being imaged using an ultrasound imaging system, as described in more detail below. In various aspects, the low-refractive-index polymer 116 is applied in an uncured state over the WGM resonator 102, the coupling waveguide 104, and the substrate 113, and then cured in situ using a curing method. Any known curing method can be used to cure the low-refractive-index polymer 116 without limitation, provided that the curing method is compatible with the selected polymer material. Non-limiting examples of suitable curing methods include UV curing, moisture curing, and cross-linking curing. In some aspects, the degree of curing can be varied to adjust the acoustic impedance and / or refractive index of the low-refractive-index polymer 116 to a level that enables the system 100 to operate effectively, as described in more detail below. As a non-limiting example, the curing method can produce a cured polymer characterized by having a refractive index suitable for efficient light transmission between the WGM resonator 102 and the coupling waveguide 104, and a mechanical refractive index matching the tissue to be imaged using ultrasound. Without being limited to any particular theory, the mechanical matching of low-refractive-index polymer 116 with tissue can facilitate the effective transmission of ultrasound pulses originating from the imaging tissue.

[0066] On the other hand, the low-refractive-index polymer 116 may be covered with an additional film layer 120. In various aspects, the film layer 120 may be selected to seal the underlying polymer 116, thereby providing a barrier to prevent oxygen from contacting the polymer 116, thus facilitating curing processes, such as the UV curing process described in more detail below. In some aspects, the film layer 120 may be removed from the low-refractive-index polymer 116 of the system 100 after the curing process is complete. In other aspects, the film layer 120 may be left above the exposed surface of the low-refractive-index polymer 116. In these other aspects, the material of the film layer 120 may be selected to acoustically match the tissue being imaged using an ultrasound imaging system (including the sensor system 100 described in more detail below).

[0067] In all respects, membrane 120 is any suitable material capable of preventing oxygen permeation into the underlying low-refractive-index polymer layer 116. Non-limiting examples of suitable membrane materials include coverslips, polymer layers, and any other suitable membrane materials. Without being limited to any particular theory, the refractive index of the membrane does not affect the performance of the encapsulated WGM resonator 102 and coupling waveguide 104 described herein. In some respects, membrane 120 can be produced using a material acoustically matched to the tissue to be imaged, as described above.

[0068] In various aspects, the membrane 120 can be pre-formed and applied over the low-refractive-index polymer 116, or the membrane 120 can be applied over the low-refractive-index polymer 116 in an uncured state and cured in situ. As a non-limiting example, applying a pre-formed membrane over the low-refractive-index polymer can facilitate curing within the low-refractive-index polymer as described above, followed by membrane removal. As another non-limiting example, an acoustically matched membrane material to the tissue being imaged can be applied and cured in situ to enhance the contact tightness between the membrane and the low-refractive-index polymer, thereby promoting effective transmission of acoustic signals from the tissue to the underlying sensor.

[0069] In all aspects, the thickness of the film layer is in the range of approximately 0.1 mm to approximately 5 mm. In other aspects, the thickness of the film layer is in the range of approximately 0.1 mm to approximately 0.3 mm, approximately 0.2 mm to approximately 0.4 mm, approximately 0.3 mm to approximately 0.5 mm, approximately 0.5 mm to approximately 0.7 mm, approximately 0.6 mm to approximately 0.8 mm, approximately 0.7 mm to approximately 0.9 mm, approximately 0.8 mm to approximately 1.0 mm, approximately 0.9 mm to approximately 1.1 mm, approximately 1.0 mm to approximately 2 mm, approximately 1.5 mm to approximately 2.5 mm, approximately 2 mm to approximately 3 mm, approximately 2.5 mm to approximately 3.5 mm, approximately 3 mm to approximately 4 mm, approximately 3.5 mm to approximately 4.5 mm, and approximately 4 mm to approximately 5 mm.

[0070] Figure 4B yes Figure 4A A side view of system 100 shown. (As shown) Figure 4B As shown, the end of the adjacent package portion 114 of the coupling waveguide 104 protrudes from the low-refractive-index polymer package 116 to enable the light source 101 to be coupled to the coupling waveguide 104 via the optical coupler 103, and to enable the coupling waveguide 104 to be coupled to the photodetector 106. The photodetector 106 is configured to detect laser signal transmission at the output port 110 of the coupling waveguide 104 and transmit a detector output signal 122 representing the detected laser signal output.

[0071] In various aspects, the computing device 112 is also configured to operate the optical resonator-based acoustic sensor system 100 in a scanning mode to select an operating wavelength, and to operate the system 100 locked at the operating wavelength to detect acoustic signals, as described in more detail below. In one aspect, the computing device 112 is also configured to control and tune a light source to scan the wavelength introduced into the coupling waveguide 104, and to execute a selection algorithm to analyze the transmission spectrum of the detector output signal to obtain a detected polarizability value and select a matching polarizability value from a plurality of polarizability values, as described in more detail below.

[0072] In various aspects, the optical resonator can be characterized by a diameter ranging from approximately 50 μm to approximately 200 μm. In other aspects, the resonator diameter ranges from approximately 50 μm to approximately 60 μm, from approximately 55 μm to approximately 65 μm, from approximately 60 μm to approximately 70 μm, from approximately 65 μm to approximately 75 μm, from approximately 70 μm to approximately 80 μm, from approximately 75 μm to approximately 85 μm, from approximately 80 μm to approximately 90 μm, from approximately 85 μm to approximately 95 μm, from approximately 90 μm to approximately 100 μm, and from approximately 95 μm to... Approximately 105 μm, from approximately 100 μm to approximately 120 μm, from approximately 110 μm to approximately 130 μm, from approximately 120 μm to approximately 140 μm, from approximately 130 μm to approximately 150 μm, from approximately 140 μm to approximately 160 μm, from approximately 150 μm to approximately 170 μm, from approximately 160 μm to approximately 180 μm, from approximately 170 μm to approximately 190 μm, and from approximately 180 μm to approximately 200 μm.

[0073] Without being limited to any particular theory, the diameter of an optical resonator can affect at least one of several factors related to the performance of an optical resonator-based pressure sensor, including but not limited to: the resonant wavelength and center frequency of the pressure sensor.

[0074] In all other respects, the coupling waveguide may include any suitable waveguide without any limitations. One aspect is that the coupling waveguide is a tapered optical fiber. In all other respects, the minimum diameter of the tapered optical fiber ranges from approximately 0.5 μm to approximately 5 μm. In all other respects, the minimum diameter of the tapered optical fiber ranges from approximately 0.5 μm to approximately 0.7 μm, from approximately 0.6 μm to approximately 0.8 μm, from approximately 0.7 μm to approximately 0.9 μm, from approximately 0.8 μm to approximately 1.0 μm, from approximately 0.9 μm to approximately 1.1 μm, from approximately 1 μm to approximately 2 μm, from approximately 1.5 μm to approximately 2.5 μm, from approximately 2 μm to approximately 3 μm, from approximately 2.5 μm to approximately 3.5 μm, from approximately 3 μm to approximately 4 μm, from approximately 3.5 μm to approximately 4.5 μm, and from approximately 4 μm to approximately 5 μm. Without being limited to any particular theory, a smaller tapered diameter is thought to optimize the coupling of shorter light wavelengths to the WGM resonator of the acoustic sensor disclosed herein.

[0075] In one aspect, the coupling waveguide comprises a tapered optical fiber having a minimum diameter of at least 1.5 μm, a tapered length of approximately 2 cm, and an optical fiber end diameter of approximately 125 μm. In various additional aspects, the coupling waveguide may be constructed from any suitable material known in the art, including but not limited to fused silica, low-loss optical polymers, and any other suitable material.

[0076] In all aspects, any suitable and unrestricted existing analytical method can be used to evaluate the performance of WGM-based acoustic sensors. In one aspect, the measurement of ultrasonic amplitude obtained from a ring-core resonator-based acoustic sensor can be used... Figure 21 The standard method shown is used to analyze and evaluate the SNR and noise equivalent pressure. On the other hand, the measurement of the response amplitude of a ring-core resonator-based acoustic sensor under a range of ultrasonic pressures can be analyzed using standard methods to determine the sensor's sensitivity at different ultrasonic frequencies. As a non-limiting example, the signal amplitudes of the ring-core resonator-based acoustic sensor in response to 5MHz and 20MHz ultrasonic waves at different wave pressures are respectively... Figure 20A and Figure 20B This is shown in the diagram. On the other hand, the measurement of the response amplitude of a toroidal resonator-based acoustic sensor to a range of ultrasonic frequencies can be analyzed using standard methods to determine the sensor's bandwidth, such as... Figure 22 As shown. The acoustic sensing performance of acoustic sensors including WGM resonators encapsulated in polymers as described herein is summarized in Table 1:

[0077] Table 1: Performance of acoustic sensors with encapsulated WGM resonators.

[0078]

[0079] As another non-limiting example, the acoustic sensing performance of the acoustic sensors characterized in Table 1 is compared with the corresponding performance of conventional piezoelectric transducers in Table 2 below:

[0080] Table 2: Performance comparison of acoustic sensors with encapsulated WGM resonators and conventional medical-grade ultrasound equipment.

[0081]

[0082] Refer again Figure 6 Transmission spectra obtained from high-Q WGM typically exhibit a Lorentz line shape. For example... Figure 24 As shown, incoming ultrasound can cause refractive index modulation and / or shape deformation (see...). Figure 24 (Left image in the image), this refractive index modulation and / or shape distortion is translated into a resonance shift in the transmission spectrum (see the left image in the image). Figure 24 (See the right-hand diagram). If the operating wavelength is fixed, the change in resonant frequency reflects the oscillation of transmitted light power over time (see the diagram on the right). Figure 24 (The output power signal in the right figure). In one aspect, in order to maximize the amplitude of the output oscillation caused by the incoming ultrasound, the operating wavelength is set to the wavelength corresponding to the point 2402 with the maximum slope on the transmission spectrum.

[0083] It should be noted that only the thermally stable side is favored. Without being limited to any particular theory, whether the thermally stable side is the short-wavelength side or the long-wavelength side depends on at least one factor, including but not limited to the material-related thermo-optic coefficient of the resonator. If the thermo-optic coefficient of the resonator is dominated by dielectric materials including but not limited to silicon dioxide, silicon, and silicon nitride (characterized by a positive thermo-optic coefficient), then the short-wavelength side ( Figure 6 Region 606 in the diagram is thermally stable. If the thermo-optical coefficient of the resonator is dominated by the polymer material (characterized by a negative thermo-optical coefficient), then the long-wavelength side ( Figure 6 Region 608 in the middle is thermally stable.

[0084] like Figure 25 As shown, the thermally stable region in the transmission spectrum of the high-Q microresonator is identified as having a triangular shape 2502 during wavelength scanning. As a non-limiting example, for a high-Q quartz microresonator made of a dielectric material with a positive thermo-optical coefficient (dn / dT>0), when the pump laser wavelength approaches the resonant wavelength during wavelength up-scanning, the cavity begins to heat up, causing a redshift in the resonant wavelength. This makes the up-scanning process a tracking process between the resonant wavelength and the scanning pump wavelength, i.e., the resonant wavelength and the scanning pump wavelength shift in the same direction. Specifically, the resonant wavelength and the pump wavelength increase linearly, while the wavelength detuning between them decreases linearly. During this tracking process, the pump wavelength (in...) Figure 25The above figure shows (dashed line) tracking the moving resonant wavelength (in Figure 25 (Seen as solid lines in the diagram above), and the detuning between them is within the resonant bandwidth. Therefore, the resonator operates in the resonant state, and pump laser energy is coupled into the resonator. This tracking process continues until the pump wavelength catches up with the resonant wavelength. Beyond this point, the resonant state is rapidly lost in the region of 2504, where the resonant wavelength has shifted, because the pump laser cannot further push the resonant wavelength.

[0085] It should be noted that the thermally stable region can be scanned upwards at wavelengths of resonator materials with the aforementioned positive thermo-optic coefficient (see...). Figure 25 The thermo-optic coefficient is identified during the wavelength downscan (not shown) of a resonator material with a negative thermo-optic coefficient. If the thermo-optic coefficient of the resonator is dominated by a dielectric material (such as silicon dioxide, silicon, or silicon nitride with a thermo-optic coefficient > 0), the wavelength upscan side (short wavelength side) is thermally stable. If the thermo-optic coefficient of the resonator is dominated by a polymer (thermo-optic coefficient < 0), the wavelength upscan side (long wavelength side) is thermally stable.

[0086] a. Arrangement of resonators and optical fibers

[0087] In various aspects, the size and arrangement of the optical fiber and optical resonator are determined according to one or more rules that combine various factors related to sensor performance. In one aspect, separation rules can be used to determine the gap separating the tapered optical fiber from the outer circumference of the optical resonator. In another aspect, the size and arrangement of the optical fiber and optical resonator may be influenced by several factors, as described below.

[0088] Without being limited to any particular theory, the dimensions of the fiber waveguide determine the effective refractive index of the waveguide mode, and the gap between the fiber taper and the resonator determines the coupling strength, which can also be quantified as the coupling-induced loss. An ideally excited WGM (also referred to as critical coupling in this paper) is characterized by a narrow and deep Lorentz tilt shape within the transmission spectrum of the coupled WGM and the fiber taper. This critical coupling is achieved when i) the effective refractive index of the fiber waveguide mode matches the effective refractive index of the WGM, and ii) the coupling-induced loss equals the inherent loss within the resonator.

[0089] b. Determination of the ideal fiber taper

[0090] In all respects, the ideal fiber taper for exciting optical modes in a whispering-gallery mode (WGM) micro-ring core resonator is determined using various standards, which will be described in more detail below.

[0091] In one respect, an ideal fiber taper should satisfy a phase-matching condition with the target WGM, expressed as:

[0092] n fiber=n WGM，tr Equation (1)

[0093] Where, n WGM，tr The transformed effective refractive index (n) of the WGM miniature ring-core resonator WGM );n fiber The value is determined by the diameter and refractive index of the fiber taper; and n WGM It is determined by the size and refractive index of the resonator and the refractive index of the surrounding medium. In various aspects, n fiber and n WGM Numerical calculations can be performed using any suitable method known in the art, including but not limited to the finite element method (FEM).

[0094] n fiber :

[0095] In one aspect, FEM mode analysis is applied to simulate the mode distribution and effective refractive index of optical fiber modes with different diameters and surrounding materials, such as air (…). Figure 1A and Figure 1B Neutralizing low refractive index (n=1.3) polymers ( Figure 1C and Figure 1D Several different cone diameters in ) Figures 1A-1D As shown in the image.

[0096] n WGM :

[0097] On the other hand, FEM characteristic frequency analysis (2D rotationally symmetric model) was applied to simulate the mode distribution and characteristic frequencies of the WGM micro-toroidal resonator. In this regard, n WGM The following equation is used to derive:

[0098] n WGM =mc / ωR e Equation (2)

[0099] Where m is the azimuth modulus; c is the speed of light; ω is the simulated characteristic frequency; and Re is the radial position of the "modal centroid," given by the following equation:

[0100] R e =∫∫n(r) 2 E 2 rdS / ∫∫n(r) 2 E 2 Equation (3) for dS

[0101] Where E is the amplitude of the electric field and n(r) is the refractive index.

[0102] n WGM，tr :

[0103] On the other hand, n WGM，trUse the following expression to determine:

[0104]

[0105] Where, d sep It is the distance between the WGM "modal centroid" and the center of the optical fiber.

[0106] When the coupling gap is very small, i.e. the fiber taper almost touches the resonator:

[0107] d sep ~2a+a f +R p -R e Equation (5)

[0108] Where a and a f These are the small radius of the microring and the radius of the fiber taper, respectively, R. p It is the large radius of the miniature ring resonator.

[0109] Figure 2A , Figure 2C and Figure 2E This outlines the effective refractive index n generated using the above equations and methods, which has different fiber taper diameters at wavelengths of 883 nm, 778 nm, and 709 nm. WGM，tr and n fiber The chart. Figure 2B , Figure 2D and Figure 2F They are respectively Figure 2A , Figure 2C and Figure 2E The optical fiber mode distribution diagram of the optical fiber. Figure 2A , Figure 2C and Figure 2E The ideal cone diameters against the polymer background are shown to be 1.41 μm, 1.31 μm, and 1.25 μm at wavelengths of 883 nm, 778 nm, and 709 nm, respectively.

[0110] c. Low-refractive-index polymer layer

[0111] In various aspects, a portion of the coupled waveguide and the WGM resonator are encapsulated in a low-refractive-index polymer material. The polymer encapsulation performs various functions related to the fabrication, integration into various devices (such as ultrasonic imaging systems), and pressure detection using WGM-based optical pressure sensors, as described herein. In some respects, the polymer encapsulation performs a triple function: i) protecting the coupling region, 2) efficiently transmitting the input acoustic signal, and iii) serving as a damping layer for the oscillation structure. The multiple functions performed by the encapsulated polymer impose constraints on the choice of encapsulation polymer material and polymer layer dimensions.

[0112] In one aspect, the encapsulating polymer material is selected to achieve rapid curing with minimal changes in refractive index and density. In another aspect, the encapsulating polymer material is selected to be acoustically transparent to input signals, including but not limited to ultrasound pulses from tissue to be imaged using an ultrasound or photoacoustic imaging system. In yet another aspect, the acoustic signal transmitted to a WGM-based pressure sensor can be enhanced by designing the dimensions of the encapsulating polymer layer. In this additional aspect, the thickness of the encapsulation layer can be set to (1 / 4 + n / 2) times the acoustic center wavelength, and / or a convex upper boundary can be formed in the polymer encapsulation layer to enhance acoustic focusing on the WGM resonator. In yet another additional aspect, the encapsulating polymer material is selected to enhance effective damping of the resonator structure's mechanical oscillations in response to received pressure pulses, thereby eliminating response tailing to pulsed acoustic inputs.

[0113] In one exemplary aspect, the encapsulating polymer material can be selected and designed to enhance sensor sensitivity by shaping the aforementioned encapsulating polymer layer, while minimizing response tailing due to mechanical oscillations or multiple reflections by selecting a polymer with a suitable acoustic damping level.

[0114] In all respects, the encapsulating polymer material can be a low-refractive-index polymer, defined herein as a polymer with a refractive index less than the corresponding refractive indices of the WGM resonator and the coupled waveguide. Without being limited to any particular theory, the inclusion of the encapsulating polymer material results in enhanced coupling-induced mode broadening of the WGM resonator and the coupled waveguide relative to the equivalent system in air. As a non-limiting example, the fiber mode distribution of an optical fiber encapsulated in a low-refractive-index polymer (see [link to documentation]). Figure 1D The corresponding fiber mode distribution of optical fibers in air (see) Figure 1B The refractive index of the chosen encapsulation polymer is wider. Therefore, the refractive index of the selected polymer can improve the sensor's sensitivity to precise positioning of the coupled fiber at the optimal gap separation distance, as described in more detail below. Without being limited to any particular theory, the refractive index contrast (n) is described in more detail below. contrast =n resonator / n polymer The Lorentz line shape of the WGM resonator is affected. Figure 6 ) and load curve ( Figure 16B In particular, when n contrast As the curve approaches uniformity, the Lorentz curve and load curve widen, and the Q factor decreases.

[0115] In other respects, the acoustic impedance of the encapsulating polymer material can be matched to the corresponding acoustic impedance of a sample being ultrasound-imaged using an ultrasound imaging system incorporating a pressure sensor based on a WGM resonator. As a non-limiting example, PDMS is a polymer with a relatively low degree of acoustic mismatch (approximately 2-fold) with typical biological tissue. In various additional aspects, the acoustic damping of the encapsulating polymer material can be selected to suppress internal echoes of ultrasound waves within the encapsulated pressure sensor while maintaining effective transmission of ultrasound waves to the WGM resonator.

[0116] In all respects, any suitable optical polymer known in the art may be selected as the encapsulation polymer without any limitation. In all respects, the encapsulation polymer includes, but is not limited to, UV-curable polymers or water-curable polymers. Non-limiting examples of suitable encapsulation polymer materials include PDMS, PFOA, and non-PFOA types of fluoro(meth)acrylates.

[0117] d. Center frequency

[0118] In all respects, the center frequency of the acoustic response band of a WGM-based sensor is determined by the inherent mechanical modes of the resonator. As a non-limiting example, in a microsphere, the mechanical resonant frequency of the same order mechanical mode is inversely correlated with the diameter of the microsphere resonator, consistent with theoretical expectations based on the free-sphere model. As another non-limiting example, for chip-based microdisks or microtoroidal resonators, the mechanical resonant frequency is approximately inversely correlated with the length (i.e., undercut dimension) of the free-standing disk diaphragm.

[0119] e. Coupling gap

[0120] In various aspects, the coupling gap of the WGM resonator-based pressure sensor is selected to enhance any one or more of at least several sensor performance parameters, including but not limited to the critical coupling of the WGM resonator and the coupled waveguide, and the sensor sensitivity.

[0121] Not limited to any specific theory, the discovery of coupling-induced mode broadening κ c It is positively correlated with exp(-2γd), where γ is the field attenuation coefficient outside the resonator (from...). (estimated), and d is the width of the coupling gap. In an air background, n contrast =n resonator In polymer encapsulation, n contrast =n resonator / n polymer .

[0122] In some respects, the sensitivity of WGM-based pressure sensors is enhanced when the laser frequency is locked at the center of the Lorentz line side of the WGM resonator, as is the case for sensors without encapsulation (air). Figure 16AAnd for sensors with low refractive index polymer packages Figure 16B As shown. When thermally locked, the short-wavelength side is stable for materials with a positive thermo-optic coefficient (dielectric materials), while the long-wavelength side is stable for materials with a negative thermo-optic coefficient (polymers). Analytically, this can be expressed as:

[0123]

[0124]

[0125]

[0126] Where Δω is the angular frequency detuning between the pump laser and the real-time resonant, and T is the observable transmission.

[0127] In other respects, ideal operational detuning occurs at the maximum slope in the transmission spectrum, thereby maximizing the amplification of small signals indicated by the resonance shift. Furthermore, coupling-induced κ... c The depth and width are related to the Lorentz line shape of the transmission. By way of a non-limiting example, Figure 6 It is a transmission spectrum, marked with a depth of 602, a width of 604, and a maximum slope of 606.

[0128] In one respect, the standard coupling criterion is defined as "critical coupling", where k0 = k c Furthermore, the deepest line shape is achieved through a direct index of the full extension of transmitted power. This is due to the presence of κ. c =κ0exp(-2γΔd), where Δd is the gap width at which the critical coupling detunes, therefore, with T′(Δω ideal The theoretically positively correlated sensitivity can be written as a function of Δd:

[0129] The coupling-induced load coefficient is defined by normalizing the sensitivity at the critical coupling point:

[0130]

[0131] like Figure 16A and 16B As shown, the loading factor at 780 nm in air and polymer (n = 1.33) was plotted.

[0132] f. Micro-ring core manufacturing method

[0133] In all respects, miniature toroidal WGM resonators can be fabricated on silicon wafers or any other suitable substrate using any suitable method known in the art. As a non-limiting example, Figure 12This is an overview of one aspect of the fabrication method for micro-ring cores. (Reference) Figure 12 A silicon dioxide layer is oxidized on a single-crystal silicon substrate (step 1), and HDMS is deposited on top of the silicon dioxide layer by any suitable method, including but not limited to thermal evaporation and spin coating (step 2). In this regard, a UV mask is deposited on top of photoresist, followed by UV exposure (step 3) to remove the unmasked photoresist during development (step 4). The exposed portion of the silicon dioxide layer after photoresist removal is removed using any suitable method without any limitations. A portion of the silicon substrate is removed using any suitable method to form support pillars (step 6), and then a silicon dioxide lip is formed around the periphery of the silicon dioxide layer by any known method, including but not limited to CO2 laser reflow (step 7) to complete the microring core. Figure 19 The image provided is of a miniature ring core manufactured using the method described above.

[0134] In all aspects, optical resonators can be provided in any suitable form, including but not limited to microrings, microdisks, microrings, microspheres, and any other suitable forms. In other aspects, optical resonators can be made of any suitable material, including but not limited to silicon, silicon dioxide, lithium niobate, and any other suitable material without any limitations.

[0135] g. Sensor packaging method

[0136] In various aspects, acoustic sensors based on optical WGM resonators are characterized by a sub-millimeter footprint, enabling the formation of compact sensor arrays. In some respects, on-chip designs of optical WGM resonator-based acoustic sensors can be used to construct 1D or 2D sensor arrays with periods as small as 0.3 mm.

[0137] On one hand, the WGM resonator described herein can be fabricated on commercial silicon wafers using any suitable existing manufacturing method without any limitations. On the other hand, the cost of the sensor can be significantly reduced because suitable manufacturing methods are compatible with current semiconductor industry manufacturing systems and methods.

[0138] As a non-restrictive example, such as Figure 13A and Figure 13BAs shown, a miniature toroidal resonator 1302 is fabricated on a substrate 1312, having an engineering mechanical spectrum and support walls on its sides. A tapered optical fiber 1304 of optimal diameter is fabricated and positioned within an encapsulating polymer 1306 to couple the tapered optical fiber 1304 to the miniature toroidal resonator 1302. In one aspect, an optical fiber guide 1308 is fabricated on the substrate 1312 to facilitate the positioning of the tapered optical fiber 1304 adjacent to the miniature toroidal resonator 1302. In this aspect, the substrate 1312 may be coupled to an adjustable platform, including but not limited to a miniature platform or miniature manipulator, configured to move the platform relative to the tapered optical fiber 1304 and the attached optical fiber guide 1308 and miniature toroidal resonator 1302.

[0139] In this respect, the micro-ring core 1302 and optical fiber 1304 are covered with a UV-curable low-refractive-index polymer, such as Figure 13A and Figure 13B As shown. Then, the polymer-covered microring 1302 and fiber optic guide 1308 are moved to tune to the optimal coupling gap in the polymer by adjusting the gap 1310 between the microring 1302 and the fiber optic 1304. In one aspect, this can be achieved by using... Figure 14 The computational device shown iteratively obtains transmission spectra for different gap distances to identify the optimal tuning gap. Once the micro-ring core 1302 and optical fiber 1304 are positioned at the desired gap as described above, the low-refractive-index polymer is directly exposed to UV light, and the real-time transmission spectrum is monitored, such as... Figure 14 As shown, the curing indication of the coupling region is detected until a curing indication is found. In one aspect, the curing indication of the coupling region includes a rapid shift in the optical resonance in the transmission spectrum. In another aspect, the entire sensor device can be covered with a plastic film to establish an inert environment for UV curing of the polymer layer. In this inert environment, the entire encapsulated polymer layer can be cured in this manner.

[0140] In one respect, Figure 14 The driving system for the optical resonator shown can be provided as a telephone-sized system. This telephone-sized system can be used to evaluate device performance, while simultaneously positioning optical fibers and micro-ring cores, and operating pressure sensors in the various devices described herein.

[0141] II. Imaging System

[0142] In all respects, the aforementioned optical resonator-based acoustic sensor simultaneously achieves high sensitivity and wide bandwidth to levels never before seen in previous acoustic sensor configurations. In some aspects, at least one optical resonator-based acoustic sensor can be used as an acoustic detector in clinical imaging systems, including but not limited to ultrasound acoustic imaging systems, photothermal imaging systems, and any other suitable clinical imaging systems that include the detection of acoustic signals.

[0143] a. Ultrasonic imaging system

[0144] In one aspect, an optical resonator-based acoustic sensor is incorporated into the ultrasonic imaging system 1500, such as... Figure 15 As shown. In this respect, an optical resonator-based acoustic sensor 1502 replaces the existing piezoelectric transducer to detect ultrasound in the probe array 1504, while the piezoelectric transducer is retained within the ultrasound probe 1506 to generate US pulses that are scattered, reflected, or otherwise altered by the imaged tissue. With enhanced sensitivity and broadening compared to conventional devices such as piezoelectric sensors, the optical resonator-based acoustic sensor 1502 can collect sufficient information for image reconstruction even from high-frequency, strongly attenuated ultrasound signals. Therefore, incorporating the optical resonator-based acoustic sensor 1502 can help overcome the trade-off between resolution (defined frequency) and penetration depth in current clinical ultrasound systems.

[0145] In various aspects, the ultrasound imaging system comprises ultrasound waves of any frequency above approximately 20 kHz without any limitations. As described above, the whispering-gallery mode microresonator can be configured to detect a wide range of acoustic frequencies. In some aspects, the ultrasound imaging system utilizes waves with frequencies ranging from approximately 20 kHz to approximately 200 MHz or higher. In other aspects, the ultrasound imaging system utilizes waves with frequencies ranging from approximately 20 kHz to approximately 200 MHz or higher (including, but not limited to, those from approximately 2 MHz to approximately 20 MHz used in existing ultrasound imaging systems), ultra-high frequency ultrasound ranging from approximately 100 MHz to approximately 300 MHz, and any other suitable ultrasound frequencies. By using high-frequency ultrasound for applications requiring deep penetration, the disclosed optical resonator-based ultrasound detector can significantly improve the resolution of ultrasound imaging.

[0146] Refer again Figure 15 Ultrasonic signals are transmitted through a conventional transducer 1506, while echo signals are collected by optical resonator-based ultrasound sensors 1502 in the probe array 1504. A portable optical control module 1508 is used to drive the optical sensors 1502 in the probe array 1504 to detect ultrasound signals generated by the tissue to be imaged in response to ultrasound pulses generated by the conventional transducer 1506. The optical control module 1508 is operatively coupled to each optical resonator-based ultrasound sensor 1502 in the probe array 1504. Furthermore, the optical control module 1508 is operatively coupled to an imaging control and analysis system 1520, which is configured to operate the conventional transducer 1506 to receive signals from the probe array 1504 and reconstruct ultrasound images based on the signals received from the probe array 1504.

[0147] Refer again Figure 15The optical control module 1508 includes a light source 1516 and a light receiver 1514 operably coupled to a probe array 1504 for an optical resonator-based ultrasound sensor 1502. The light source 1516 generates light introduced into at least one coupling waveguide (not shown) for coupling light into the optical resonator-based ultrasound sensor 1502. The light receiver 1514 includes at least one photodetector (not shown) configured to detect light modulated by the optical resonator-based ultrasound sensor 1502 received from at least one coupling waveguide. The optical control module 1508 also includes a signal processing module 1512 configured to convert the output of at least one photodetector of the light receiver 1514 into an electrical signal encoding the photodetector output. The electrical signal generated by the signal processing module 1512 is transmitted to a signal output 1510 of the probe array 1504 generated in response to a detected ultrasound signal from the tissue-to-imaging control and analysis system 1520.

[0148] In various aspects, the probe array 1504 includes at least one optical resonator-based ultrasonic sensor 1502. In some aspects, the probe array 1504 includes a plurality of optical resonator-based ultrasonic sensors 1502 arranged in an array pattern, including but not limited to 1D linear array patterns and 2D array patterns. 2D array patterns include any suitable 2D array pattern without any limitations. Non-limiting examples of suitable 2D array patterns include Cartesian grid patterns, circular patterns, such as a single circle of a sensor or multiple concentric circles of a sensor, and any combination thereof. In one aspect, the probe array 1504 is a 1D linear array including a plurality of sensors 1502, such as... Figure 15 As shown, as described above, all sensors in the probe array are encapsulated within a continuous layer of low-refractive-index polymer.

[0149] In various aspects, the spacing between adjacent sensors 1502 within the sensor array 1504 can be uniform, or the spacing between different adjacent sensors 1502 can be different. The spacing between sensors 1502 within the probe array 1504 can be based on any one or more of at least several factors, including, but not limited to, the required spatial resolution of the imaging system without any limitations, the dimensions of the WGM resonator and coupling waveguide, the architecture of the sensor array, the avoidance of crosstalk between adjacent sensors, and any other relevant factors. In some aspects, the minimum spacing between adjacent sensors 1502 within the probe array 1504 is at least 5 μm to avoid crosstalk between the sensors 1502.

[0150] In various additional aspects, the sensors in the sensor array have substantially equal dimensions. In other aspects, at least a portion of sensor 1502 may have different dimensions. Without being limited to any particular theory, a range of sensor dimensions can provide the sensor array with enhanced sensitivity to acoustic signals across a wide frequency range.

[0151] In various additional aspects, each sensor 1502 of the probe array 1504 may be coupled to separate, separate coupling waveguides, such that the number of sensors 1502 equals the number of coupling waveguides. In other additional aspects, at least a portion of the sensors may share coupling to a shared coupling waveguide. In some additional aspects, the probe array may include one or more shared coupling waveguides shared by one or more portions of the sensors and additional portions of the sensors respectively coupled to separate coupling waveguides.

[0152] Figure 5 This demonstrates the introduction of ultrasound pulses into tissues and their use with... Figure 15 This diagram illustrates a similar ultrasound imaging system 500 to the system 1500, which uses an optical resonator-based acoustic sensor system 100 to detect ultrasound signals generated by tissue. (Reference) Figure 5 At least one WGM microresonator 102 and coupling waveguide 104 of the acoustic sensor system 100 can be acoustically coupled to the tissue 504 to be imaged. A conventional ultrasonic transducer 506 introduces ultrasonic pulses 508 into the tissue 504 to induce an acoustic signal 502. In one aspect, the light coupled to the WGM microresonator 102 is generated using a laser 101 guided by a polarization controller (not shown). The acoustic signal 502 interacts with the WGM microresonator 102 as described above and is detected in the form of a change in the laser signal detected by a photodetector 106 coupled to the output port 108 of the coupling waveguide 104. The output signal 106 of the photodetector is transmitted to a computing device 112, which acts as a signal analyzer. In one aspect, the computing device 112 converts the output signal of the photodetector 106 into an acoustic signal in the form of the optical resonance amplitude of the microresonator, such as... Figure 7 As shown. On the other hand, the computing device 112 converts the output signal of the photodetector 106 into an acoustic signal in the form of a resonant wavelength identified from the spectral response of the microresonator 600, such as... Figure 6 As shown.

[0153] In some applications, ultrasound imaging systems are equipped with a single optical resonator-based acoustic sensor system. In this case, a focused ultrasound source emits ultrasound waves, while the single optical resonator-based acoustic sensor system collects the echoes and locates the depth of the reflector (A-scan image). A B-scan image is acquired by mechanically scanning the bounded source and sensor.

[0154] In other aspects, ultrasound imaging systems are equipped with acoustic sensor arrays based on optical resonators, such as... Figure 15 As shown. In this respect, the focusing and scanning of ultrasound waves are achieved through a transducer phase array. In some aspects, real-time B-scan images can be acquired by applying a suitable beamforming algorithm to the signal collection group of the optical sensor. In other aspects, tilted plane wave ultrasound waves can be transmitted through the transducer phase array and the transmission angle can be scanned. The reflected signals can be collected by an acoustic sensor array based on an optical resonator. Using a suitable beamforming algorithm, ultrafast B-scan image acquisition can be achieved.

[0155] In various aspects, the optical resonator-based acoustic sensor array includes at least two WGM resonators arranged in a spatial array, including but not limited to linear arrays, 2D arrays (such as planar or ring arrays), and 3D arrays (such as cylindrical or hemispherical arrays). In some aspects, the at least two WGM resonators in the array are each coupled to separate coupling optical fibers, light sources, and photodetectors. In other aspects, the at least two WGM resonators in the array are coupled to the same coupling optical fiber, light source, and photodetector.

[0156] In other additional aspects, at least two WGM-based pressure sensor systems in the array are substantially identical in size, center frequency, operating wavelength, sensitivity, and any other relevant operating parameters. In further additional aspects, the at least two WGM-based pressure sensor systems may differ in one or more parameters, including but not limited to resonator diameter, resonator material, gap spacing, operating wavelength, encapsulation polymer material, coupling cone material, coupling cone diameter, and any other relevant parameters.

[0157] In another aspect, optical resonator-based acoustic sensor systems can be integrated into existing ultrasound imaging systems to improve the quality of harmonic ultrasound imaging. Harmonic ultrasound imaging offers high sensitivity and specificity due to the high-frequency nonlinear ultrasonic echoes from the imaging target. However, the weak and broadband characteristics of the nonlinear signals pose challenging requirements for the ultrasound detectors. Optical resonator-based acoustic sensors can be used to (1) effectively collect nonlinear ultrasonic echoes; and (2) allow for a sufficiently wide detection bandwidth to achieve pump ultrasound with higher frequencies and shorter pulse durations (for higher resolution).

[0158] b. Photoacoustic imaging system

[0159] In various aspects, an optical resonator-based acoustic sensor is incorporated into an ultrasound imaging system. Without being limited to any particular theory, at least one optical pulse is introduced into the tissue to be imaged, and the energy of the incident photons is absorbed by the structures within the tissue and re-emitted as a photoacoustic signal in the form of ultrasound waves. The emitted ultrasound waves are then detected by at least one ultrasound transducer, and the detected signal is used to reconstruct a photoacoustic image. In various aspects, the optical resonator-based acoustic sensor configured to detect the photoacoustic signal is compatible with any existing ultrasound imaging system without any limitations. Non-limiting examples of ultrasound systems compatible with optical resonator-based acoustic sensors include photoacoustic microscopy (PAM) systems and photocomputed tomography (PACT) systems.

[0160] refer to Figure 26 The photoacoustic system 2600 includes, in one aspect, a photoacoustic (PA) light source 2602, including but not limited to at least one pulsed laser, configured to generate a plurality of laser pulses 2604 introduced into tissue 2606 using at least one optical element of the PA optical module 2608. In one aspect, each laser pulse 2604 generated by the PA light source 2602 is configured to induce a plurality of PA signals 2610 from a structure 2612 within a portion of tissue 2606 to which the laser pulse 2604 is directed. As described above, the plurality of PA signals 2610 induced by a single laser pulse 2604 are detected by a transducer array 2614 and reconstructed into a PA image (not shown) using any suitable reconstruction method known in the art.

[0161] Refer again Figure 26 In one aspect, PA signals 2610 comprising multiple ultrasonic waves are collected by at least one optical resonator-based ultrasonic sensor 2616 in the transducer array 2614. Without any limitation, any suitable optical sensor described herein can be incorporated into the transducer array 2614 as a resonator-based ultrasonic sensor 2616. Figure 26 As shown, the photoacoustic system 2600 also includes at least one transducer light source 2618 and at least one transducer photodetector 2620 operably coupled to the transducer array 2614 and the optical resonator-based ultrasonic sensor 2616. Light generated by the light source 2618 is introduced into at least one coupling waveguide 2622 for coupling the light to at least one coupling waveguide 2622 in the optical resonator-based ultrasonic sensor 2616. The transducer photodetector 2620 includes at least one photodetector (not shown) configured to detect light received from at least one coupling waveguide 2622 and modulated by the WGM resonator 2624 of the optical resonator-based ultrasonic sensor 2616.

[0162] Controller 2626 is used to drive the photosensors 2616 in the transducer array 2614 to detect tissue 2606 in response to a PA signal 2610 generated by a laser pulse 2604 generated by the PA light source 2602. Controller 2626 is operably coupled to each of the optical resonator-based ultrasound sensors 2616 in the transducer array 2614 via the transducer light source 2618 and the transducer photodetector 2620. In some aspects, the controller may include a signal processing module (not shown) configured to convert the output of at least one transducer photodetector 2620 into an electrical signal encoding the detector output. Furthermore, controller 2626 is operably coupled to a PA imaging analysis module 2628 configured to reconstruct an ultrasound image based on signals received from the transducer array 2614. In some aspects, controller 2626 may be provided in the form of an optical control module, similar to those described above and... Figure 14 and Figure 25 The portable drive system shown is similar.

[0163] In various aspects, each of at least one pulsed laser in the PA light source 2602 can generate multiple laser pulses of pulsed wavelengths. The pulsed wavelengths can be selected based on any one or more of at least several factors, including but not limited to enhanced penetration of the pulsed wavelength into the specific tissue to be imaged; enhanced contrast of the structure of interest relative to surrounding structures; label-free visualization of circulating tumor cells; and enhanced contrast of exogenous structures of interest for SIP-PACT imaging perfused with contrast agents (e.g., NIR dyes). In one aspect, pulsed wavelengths ranging from approximately 650 nm to approximately 1350 nm can be selected to maximize light penetration through the entire mammalian body to be imaged, as this wavelength range includes pulsed wavelengths that attenuate less within mammalian tissues relative to wavelengths falling outside this "optical window." In a particular aspect, a pulsed wavelength of approximately 1064 nm can be selected for PA imaging in mammalian tissues using the PA imaging system 2600.

[0164] In various aspects, the PA light source 2602 can generate laser pulses of a single wavelength, two (dual) wavelengths, or three or more wavelengths as needed. In various aspects, multiple laser pulses can be generated at one or more wavelengths in the range of approximately 650 nm to approximately 1350 nm, thereby achieving maximum light penetration for whole-body imaging of animal subjects. Without being limited to any particular theory, this wavelength range is characterized by enhanced penetration through biological tissues; for example, it is previously known that this wavelength range corresponds to pulse wavelengths of light with minimal attenuation in mammalian tissues.

[0165] In various other aspects, the PA imaging system 2600 can use a single pulse wavelength selected to enhance penetration of a specific tissue to be imaged and / or to enhance the contrast of the structure of interest relative to surrounding structures. On the other hand, the PA imaging system 2600 can use two and / or more pulse wavelengths to achieve functional imaging, including but not limited to determining oxygen saturation in blood and other tissues. For example, a first pulse wavelength can be selected to achieve maximum contrast for oxyhemoglobin, and a second pulse wavelength can be selected to achieve maximum contrast for deoxyhemoglobin, or to achieve maximum contrast for all hemoglobins. Two / more pulse wavelengths can also be selected to enhance the contrast of different structures, such as blood cells, CTCs, leukocytes, contrast agents (such as NIR dyes), or to enhance the contrast of exogenous structures of interest (i.e., perfusion of contrast agents, such as NIR dyes). In various aspects, the PA imaging system 2600 may include a pulsed laser that generates laser pulses of a single pulse wavelength, including but not limited to: a 720 nm laser, such as the LS-2145-LT-150 Ti-Sa pulsed laser (SymphoticTii), with a repetition rate of 20 Hz and a pulse width of 12 ns; a 1064 nm laser, such as the DLS9050 pulsed laser (Continuum), with a repetition rate of 50 Hz and a pulse width in the range of approximately 5 ns to approximately 9 ns; and any other suitable pulsed laser.

[0166] In various aspects, the PA imaging system 2600's PA optical module 2608 includes one or more optical elements configured to introduce multiple laser pulses generated by the PA light source 2602 into the tissue 2606 to be imaged. In some aspects, the focal region of the ultrasonic transducer array 2614 coincides with at least a portion of the tissue to be imaged, irradiated by the laser pulses 2604, such that PA signals 2610 induced by the multiple laser pulses 2604 are detected by the transducer array 2614 and used to reconstruct one or more PA images.

[0167] In various aspects, one or more optical elements (not shown) of the PA optical module 2608 are operatively coupled to the PA light source 2602 to receive a plurality of laser pulses generated by at least one pulsed laser. Furthermore, the one or more optical elements are configured to perform various transformations of the plurality of laser pulses, including but not limited to: changing the direction of travel of each laser pulse; redistributing the distribution of light energy across the cross-section of each laser pulse to a substantially uniform spatial distribution of light energy; changing the cross-sectional size and / or shape of each laser pulse; modulating the light intensity or flux of each laser pulse; modulating the relative arrival time of two different laser pulses generated by two corresponding pulsed lasers; selectively transmitting or blocking the transmission of laser pulses from one or more pulsed lasers; and performing any other suitable transformations on the plurality of laser pulses.

[0168] Non-limiting examples of suitable optical elements for incorporating into the PA imaging system 2600's PA optical module 2608 include prisms, mirrors, diffusers, condensers, lenses, beam splitters, beam combiners, optical fibers, waveguides, and any other known optical elements suitable for modifying one or more properties of a laser pulse. Non-limiting examples of laser pulse properties that can be modified and / or modulated using one or more optical elements include: cross-sectional profile, cross-sectional dimensions, direction of travel, wave velocity, wavelength, polarization, intensity, phase, wavefront shape, superposition with other laser pulses, cross-sectional energy uniformity, pulse width, delay relative to other laser pulses in the pulse series, and any other relevant characteristics of the laser pulse.

[0169] In one aspect, the diffuser can be configured to homogenize the profile of the laser pulse, such that the energy intensity is uniformly distributed across the cross-section of the laser pulse. Non-limiting examples of suitable diffusers include various engineered diffusers, such as ring diffusers. In one aspect, the diffuser can be a commercially available engineered diffuser, including but not limited to EDC-10-A-1r (RPCPhotonics). Non-limiting examples of suitable condensers include various custom-made condensers, such as custom-made ring condensers. Non-limiting examples of suitable prisms include triangular prisms, rhomboid prisms, and any other suitable prisms. Non-limiting examples of suitable lenses include convex lenses, concave lenses, cylindrical lenses, semi-cylindrical lenses, compound lenses, and any other suitable lenses. In another aspect, the lens can be a commercially available lens, including but not limited to the AX-FS-1-140-0 conical lens (DelMar Photonics). Non-limiting examples of suitable reflectors include plane mirrors, convex mirrors, and concave mirrors.

[0170] In various aspects, one or more optical elements may also be configured to enable selection of the irradiation method based on the area or tissue to be imaged and / or the type of imaging to be performed using the PA imaging system 2600. In one aspect, one or more optical elements may be configured to implement a top irradiation method (see...). Figure 26 ( ) or side illumination method. A series of specific optical elements incorporated into the PA imaging system 2600 can be at least partially affected by the illumination method used by the PA imaging system 2600.

[0171] III. Computing Systems and Devices

[0172] Figure 8 A simplified block diagram of a computing device 800 for implementing the methods described herein is shown. Figure 8 As shown, computing device 800 can be configured to use the disclosed optical resonator-based pressure sensor system to perform at least a portion of the tasks associated with the disclosed method. Computer system 800 may include computing device 802. In one aspect, computing device 802 is part of server system 804, which also includes database server 806. Computing device 802 communicates with database 808 via database server 806. Computing device 802 is communicatively coupled to system 810 and user computing device 830 via network 850. Network 850 can be any network that allows local or wide area communication between devices. For example, network 850 may allow communicative coupling to the Internet via at least one of a number of interfaces, including but not limited to at least one of the following networks: such as the Internet, Local Area Network (LAN), Wide Area Network (WAN), Integrated Services Digital Network (ISDN), dial-up connection, Digital Subscriber Line (DSL), cellular telephone connection, and cable modem. User computing device 830 can be any device capable of accessing the Internet, including but not limited to desktop computers, laptop computers, personal digital assistants (PDAs), cellular phones, smartphones, tablet computers, phablets, wearable electronics, smartwatches, or other network-based connected devices or mobile devices.

[0173] In other respects, computing device 802 is configured to perform multiple tasks associated with the operation of an optical resonator-based acoustic sensor and / or an imaging system incorporating an optical resonator-based acoustic sensor (including, but not limited to, the aforementioned ultrasound (US) and photoacoustic (PA) imaging systems). Figure 9 A component configuration 900 of computing device 902 is shown, which includes a database 910 and other related computing components. In some aspects, computing device 902 is similar to computing device 802 (e.g., Figure 8(As shown). User 904 can access components of computing device 902. In some respects, database 910 is similar to database 808 (e.g., Figure 8 (As shown).

[0174] In one aspect, database 910 includes imaging data 918 and algorithm data 912. Non-limiting examples of suitable imaging data 918 may include medical imaging data, including but not limited to ultrasound imaging data or photoacoustic imaging data. Non-limiting examples of suitable algorithm data 912 include any parameter values ​​defining the operation of an acoustic sensor, ultrasound imaging system, and photoacoustic imaging system based on an optical WGM resonator. Non-limiting examples of suitable algorithm data 912 include any parameter values ​​defining algorithms associated with the disclosed methods as described herein and / or any image reconstruction algorithms used to reconstruct ultrasound or photoacoustic images as described above.

[0175] The computing device 902 also includes multiple components for performing specific tasks. In an example embodiment, the computing device 902 includes a data storage device 930, an imaging component 940, an acoustic sensor component 950, and a communication component 960. The data storage device 930 is configured to store data received or generated by the computing device 902, such as any data stored in the database 910 or any output of a process implemented by any component of the computing device 902.

[0176] Communication component 960 is configured to allow computing device 902 and other devices (e.g., Figure 8 The user computing device 830 and system 810 shown communicate with each other via a network 850 (such as...). Figure 8 (As shown) a network, or multiple network connections using predefined network protocols such as TCP / IP (Transmission Control Protocol / Internet Protocol) to achieve communication.

[0177] Figure 10 The configuration of a remote or user computing device 1002 is shown, such as user computing device 830 (e.g., Figure 8 (As shown). Computing device 1002 may include processor 1005 for executing instructions. In some aspects, executable instructions may be stored in memory area 1010. Processor 1005 may include one or more processing units (e.g., in a multi-core configuration). Memory area 1010 may be any device that allows information such as executable instructions and / or other data to be stored and retrieved. Memory area 1010 may include one or more computer-readable media.

[0178] The computing device 1002 may also include at least one media output component 1015 for presenting information to the user 1001. The media output component 1015 can be any component capable of conveying information to the user 1001. In some aspects, the media output component 1015 may include an output adapter, such as a video adapter and / or an audio adapter. The output adapter is operatively coupled to the processor 1005 and operatively coupled to an output device, such as a display device (e.g., a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, a cathode ray tube (CRT), or an "electronic ink" display) or an audio output device (e.g., a speaker or headphones). In some aspects, the media output component 1015 may be configured to present an interactive user interface (e.g., a web browser or client application) to the user 1001.

[0179] In some aspects, computing device 1002 may include input device 1020 for receiving input from user 1001. Input device 1020 may include, for example, a keyboard, pointing device, mouse, stylus, touch-sensitive panel (e.g., touchpad or touchscreen), camera, gyroscope, accelerometer, position detector, and / or audio input device. A single component such as a touchscreen may be used as both an output device and an input device 1020 for media output component 1015.

[0180] The computing device 1002 may also include a communication interface 1025, which can be communicatively coupled to a remote device. The communication interface 1025 may, for example, include a wired or wireless network adapter or a wireless data transceiver for use with mobile phone networks (e.g., Global System for Mobile Communications (GSM), 3G, 4G, or Bluetooth) or other mobile data networks (e.g., Global System for Microwave Access Interoperability (WIMAX)).

[0181] Storing in storage area 1010 are, for example, computer-readable instructions for providing a user interface to user 1001 via media output component 1015, and optionally receiving and processing input from input device 1020. The user interface may include a web browser and client applications, as well as other possible applications. The web browser enables user 1001 to display and interact with media and other information typically embedded in web pages or websites from a web server. Client applications allow user 1001 to interact with server applications, such as those associated with vendors or businesses.

[0182] Figure 11 An example configuration of server system 1102 is shown. Server system 1102 may include, but is not limited to, database server 806 and computing device 802 (both in... Figure 8(As shown in the diagram). In some respects, server system 1102 is similar to server system 804 (e.g., Figure 8 (As shown). Server system 1102 may include processor 1105 for executing instructions. For example, instructions may be stored in memory 1110. Processor 1105 may include one or more processing units (e.g., in a multi-core configuration).

[0183] The processor 1105 is operatively coupled to the communication interface 1115, enabling the server system 1102 to communicate with devices such as user computing devices 830 (e.g., Figure 8 (as shown) or another remote device such as server system 1102. For example, communication interface 1115 can communicate via network 850 (such as... Figure 8 (As shown) Receives a request from user computing device 830.

[0184] The processor 1105 is also operatively coupled to the storage device 1110. The storage device 1110 can be any computer hardware suitable for storing and / or retrieving data. In some aspects, the storage device 1110 can be integrated into the server system 1102. For example, the server system 1102 may include one or more hard disk drives as storage device 1110. In other aspects, the storage device 1110 may be external to the server system 1102 and accessible by multiple server systems 1102. For example, the storage device 1110 may include multiple storage units, such as hard disks or solid-state drives in a Redundant Array of Inexpensive Disks (RAID) configuration. The storage device 1110 may include a Storage Area Network (SAN) and / or Network Attached Storage (NAS) system.

[0185] In some respects, processor 1105 is operatively coupled to storage device 1110 via storage interface 1120. Storage interface 1120 can be any component capable of providing processor 1105 with access to storage device 1110. Storage interface 1120 may, for example, include an Advanced Technology Attachment (ATA) adapter, a Serial ATA (SATA) adapter, a Small Computer System Interface (SCSI) adapter, a RAID controller, a SAN adapter, a network adapter, and / or any component that provides processor 1105 with access to storage device 1110.

[0186] Storage area 1010 (e.g.) Figure 10As shown) and 1110 may include, but are not limited to, random access memory (RAM) such as dynamic RAM (DRAM) or static RAM (SRAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and non-volatile RAM (NVRAM). The memory types described above are merely examples and therefore do not limit the types of memory that can be used to store computer programs.

[0187] The computer systems and computer-implemented methods discussed herein may include more, fewer, or alternative actions and / or functions, including those discussed elsewhere herein. Computer systems may include or be implemented via computer-executable instructions stored on or via non-transitory computer-readable media. Methods may be implemented via one or more local or remote processors, transceivers, servers, and / or sensors (such as those mounted on a vehicle or mobile device, or associated with intelligent infrastructure or remote servers), and / or via computer-executable instructions stored on non-transitory computer-readable media or mediums.

[0188] As will be understood from the foregoing description, the above aspects of this disclosure can be implemented using computer programming or engineering techniques, including computer software, firmware, hardware, or any combination or subset thereof. According to some aspects discussed in this disclosure, any such generated program having computer-readable code means can be embodied or provided in one or more computer-readable media to create a computer program product, i.e., an article of manufacture. Computer-readable media can be, for example, but not limited to, fixed (hard disk) drives, floppy disks, optical disks, magnetic tapes, semiconductor memory such as read-only memory (ROM), and / or any transmitting / receiving medium such as the Internet or other communication networks or links. Articles of manufacture containing computer code can be made and / or used by executing code directly from the medium, by copying code from one medium to another, or by transmitting code over a network.

[0189] These computer programs (also referred to as programs, software, software applications, "apps," or code) include machine instructions for a programmable processor and may be implemented in high-level procedural and / or object-oriented programming languages, and / or in assembly / machine language. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, apparatus, and / or device (e.g., disk, optical disk, memory, programmable logic device (PLD)) used to provide machine instructions and / or data to a programmable processor, including machine-readable media that receive machine instructions as machine-readable signals. However, "machine-readable medium" and "computer-readable medium" do not include transient signals. The term "machine-readable signal" refers to any signal used to provide machine instructions and / or data to a programmable processor.

[0190] As used herein, a processor can include any programmable system, including those using microcontrollers, reduced instruction set circuitry (RISC), application-specific integrated circuits (ASICs), logic circuits, and any other circuitry or processor capable of performing the functions described herein. The examples above are merely illustrative and are therefore not intended to limit the definition and / or meaning of the term "processor" in any way.

[0191] As used herein, the terms “software” and “firmware” are used interchangeably and include any computer program stored in memory for execution by a processor, including RAM, ROM, EPROM, EEPROM, and non-volatile RAM (NVRAM). The memory types described above are merely examples and therefore do not limit the types of memory that can be used to store computer programs.

[0192] In one aspect, a computer program is provided, and the program is embodied on a computer-readable medium. In another aspect, the system executes on a single computer system and does not require connection to a server computer. In the third aspect, the system... Running in an environment (Windows is a registered trademark of Microsoft Corporation, located in Redmond, Washington). On the other hand, the system runs in mainframe environments and... It runs in a server environment (UNIX is a registered trademark of X / Open Company Limited, located in Reading, Berkshire, UK). The application is highly flexible and designed to run in a variety of different environments without affecting any of its core functionality.

[0193] In some aspects, the system includes multiple components distributed among multiple computing devices. One or more components may be in the form of computer-executable instructions embodied in a computer-readable medium. The system and processes are not limited to the specific aspects described herein. Furthermore, each component and each process of the system may be implemented independently of or separately from the other components and processes described herein. Each component and process may also be packaged and used in conjunction with other accessories and processes. Various aspects of the present invention can enhance the functionality and capabilities of computers and / or computer systems.

[0194] The definitions and methods described herein are provided to better define this disclosure and to guide those skilled in the art in practicing it. Unless otherwise stated, the terms will be understood in accordance with their conventional usage by those skilled in the art.

[0195] In some embodiments, the numbers used to describe and claim certain embodiments of this disclosure representing the amount and properties of components (such as molecular weight, reaction conditions, etc.) should be understood to be modified by the term "about" in certain circumstances. In some embodiments, the term "more than about" is used to indicate that a value includes the standard deviation of the average of the devices or methods used to determine that value. In some embodiments, the numerical parameters presented in the written description and the appended claims are approximations that may vary depending on the desired properties sought to be obtained in a particular embodiment. In some embodiments, numerical parameters should be interpreted according to the number of significant figures reported and by applying common rounding techniques. Although the numerical ranges and parameters that illustrate a broad range of some embodiments of this disclosure are approximations, the numerical values ​​illustrated in specific embodiments are reported as accurately as possible. The numerical values ​​presented in some embodiments of this disclosure may contain some errors, which are necessarily due to the standard deviations found in their respective test measurements. References to numerical ranges herein are intended only as a shorthand method for individually referring to each individual value within that range. Unless otherwise stated herein, each individual value is included in the specification as if individually referenced herein. References to discrete values ​​are understood to include a range between each value.

[0196] In some embodiments, the terms “a,” “an,” and “the,” as well as similar references, used in the context of describing a particular embodiment (particularly in the context of certain claims below) may be interpreted as encompassing one or more, unless explicitly stated otherwise. In some embodiments, as used herein including the claims, the term “or” is used to mean “and / or,” unless explicitly stated to indicate only an alternative, or that the alternatives are mutually exclusive.

[0197] The terms “comprise,” “have,” and “include” are open-ended connecting verbs. Any form or tense of one or more of these verbs, such as “comprises,” “comprising,” “has,” “having,” “includes,” and “including,” is also open-ended. For example, any method that “comprises,” “has,” and “includes” one or more steps is not limited to having only those steps but may also cover other steps not listed. Similarly, any composition or device that “comprises,” “has,” and “includes” one or more features is not limited to having only those features but may also cover other features not listed.

[0198] All methods described herein may be performed in any suitable order unless otherwise stated herein or clearly contradicted by the context. The use of any and all examples or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended only to better illustrate this disclosure and does not impose any limitation on this disclosure unless otherwise required. No language in the specification should be construed as indicating any unclaimed element essential to the practice of this disclosure.

[0199] The grouping of alternative elements or embodiments disclosed herein should not be construed as limiting. Each member of a group may be mentioned and claimed individually or in any combination with other members of that group or other elements found herein. For convenience or patentability reasons, one or more members of a group may be included in or removed from the group. When any such inclusion or removal occurs, this specification is hereby deemed to include the modified group, thereby satisfying the written description of all Markush groups used in the appended claims.

[0200] The entire contents of any publications, patents, patent applications and other references cited in this application are incorporated herein by reference for all purposes as if the entire contents of each individual publication, patent, patent application or other reference were specifically and individually incorporated by reference for all purposes.

[0201] Having described this disclosure in detail, it will be apparent that modifications, variations, and equivalent embodiments are possible without departing from the scope of this disclosure as defined by the appended claims. Furthermore, it should be understood that all examples in this disclosure are provided as non-limiting examples.

Claims

1. An acoustic sensor, comprising: Optical whispering-gallery mode resonator; A coupling waveguide for optical coupling to the resonator, the coupling waveguide being separated from the resonator by a gap; as well as A polymer that encapsulates a portion of the coupled waveguide and the resonator and fills the gap, the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator, wherein the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator includes the polymer having a convex upper boundary. Each of the resonator and the coupling waveguide has a refractive index higher than that of the polymer. The gap is selected such that the acoustic sensor operates under critical coupling conditions or at the maximum load factor when the polymer fills the gap.

2. The acoustic sensor according to claim 1, wherein, The resonator has a diameter ranging from 50 μm to 200 μm.

3. The acoustic sensor according to claim 1, wherein, The gap ranges from 0.6 μm to 0.8 μm.

4. The acoustic sensor according to claim 1, wherein, The gap causes the maximum load factor during the operation of the acoustic sensor.

5. The acoustic sensor according to claim 1, wherein, The coupling waveguide is a tapered optical fiber with a minimum tapered diameter of less than 1.5 μm.

6. The acoustic sensor according to claim 1, wherein, The acoustic sensor encodes pressure fluctuations as fluctuations in the transmitted amplitude through the resonator.

7. The acoustic sensor according to claim 1, wherein, The polymer is a UV-curable polymer with a refractive index of 1.

33.

8. An acoustic sensing system, comprising: Optical whispering-gallery mode resonator; A coupling waveguide for optical coupling to the resonator, the coupling waveguide having a first end and a second end opposite to the first end, the coupling waveguide being separated from the resonator by a gap; as well as A polymer that encapsulates a portion of the coupled waveguide and the resonator and fills the gap, the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator, wherein the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator includes the polymer having a convex upper boundary. A light source, which is coupled to the first end of the coupled waveguide and protrudes from the polymer; as well as A photodetector, which is coupled to the second end of the coupled waveguide and protrudes from the polymer; Each of the resonator and the coupling waveguide has a refractive index higher than that of the polymer. The gap is selected such that the acoustic sensing system operates under critical coupling conditions or at the maximum load factor when the polymer fills the gap.

9. The acoustic sensing system according to claim 8, further comprising: A driving system having a computing device with a processor, the driving system being operatively coupled to the light source and the photodetector, wherein the driving system is configured to: A transmission spectrum is obtained by operating the light source within a wavelength range and receiving multiple detector signals from the photodetector, the detector signals encoding the transmission of light from the light source through a coupling optical fiber coupled to the resonator; Based on the transmission spectrum, a working wavelength for detecting pressure fluctuations is selected; and These spacing intervals are selected based on at least one transmission spectrum; and Pressure fluctuations are detected by operating the light source at the operating wavelength and receiving a second plurality of signals from the photodetector.

10. The acoustic sensing system according to claim 9, wherein, The acoustic sensor encodes pressure fluctuations as fluctuations in the transmission amplitude through the optical whispering galvanic mode resonator.

11. An ultrasound imaging device, comprising: An acoustic sensor, comprising: Optical whispering-gallery mode resonator; A coupling waveguide for optical coupling to the resonator, the coupling waveguide having a first end and a second end opposite to the first end, the coupling waveguide being separated from the resonator by a gap; A polymer that encapsulates a portion of the coupled waveguide and the resonator and fills the gap, the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator, wherein the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator includes the polymer having a convex upper boundary. A light source, which is coupled to the first end of the coupled waveguide and protrudes from the polymer; and A photodetector, which is coupled to the second end of the coupled waveguide and protrudes from the polymer; Each of the resonator and the coupling waveguide has a refractive index higher than that of the polymer. The gap is selected such that the acoustic sensor operates under critical coupling conditions or at the maximum load factor when the polymer fills the gap.

12. The ultrasonic imaging device according to claim 11, wherein, The acoustic sensor encodes pressure fluctuations as fluctuations in the transmitted amplitude through the resonator.

13. The ultrasonic imaging device according to claim 11, wherein, The acoustic sensor is configured to detect ultrasonic pulses generated in the region of interest in response to excitatory ultrasonic pulses guided by an ultrasonic transducer to the region of interest.

14. A photoacoustic imaging device, comprising: An acoustic sensor, comprising: Optical whispering-gallery mode resonator; A coupling waveguide for optical coupling to the resonator, the coupling waveguide having a first end and a second end opposite to the first end, the coupling waveguide being separated from the resonator by a gap; A polymer that encapsulates a portion of the coupled waveguide and the resonator and fills the gap, the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator, wherein the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator includes the polymer having a convex upper boundary. A transducer light source, which is coupled to the first end of the coupled waveguide and protrudes from the polymer; A transducer photodetector, coupled to a second end of the coupled waveguide opposite to the first end and protruding from the polymer; and Optical and acoustic light sources; Each of the resonator and the coupled waveguide has a refractive index higher than that of the polymer, and the gap is selected such that the acoustic sensor operates under critical coupling conditions or at the maximum load factor when the polymer fills the gap.

15. The photoacoustic imaging device according to claim 14, wherein, The acoustic sensor encodes pressure fluctuations as fluctuations in the transmitted amplitude through the resonator.

16. The photoacoustic imaging device according to claim 14, wherein, The acoustic sensor is configured to detect photoacoustic signals generated in the region of interest in response to irradiation by laser pulses generated by the photoacoustic light source.

17. A method for detecting ultrasound, the method comprising: Provide an acoustic sensing system, which includes: Optical whispering-gallery mode resonator; A coupling waveguide optically coupled to the resonator, the coupling waveguide having a first end and a second end opposite to the first end, the coupling waveguide being separated from the resonator by a gap; A polymer that encapsulates a portion of the coupled waveguide and the resonator and fills the gap, the polymer further forming a sample contact surface, the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator, wherein the polymer having dimensions designed to enhance acoustic focusing on the optical whispering-gallery mode resonator includes the polymer having a convex upper boundary. A light source, which is coupled to the first end of the coupled waveguide and protrudes from the polymer; and A photodetector for coupling to the second end of the coupled waveguide and protruding from the polymer; Each of the resonator and the coupled waveguide has a refractive index higher than that of the polymer, and the gap is selected such that the acoustic sensing system operates under critical coupling conditions or at the maximum load factor when the polymer fills the gap. The sample contact surface is acoustically coupled to the sample so that ultrasonic waves emitted from the sample are conducted through the polymer to the resonator and the portion of the coupling waveguide; The light generated by the light source is introduced into the first end of the coupled waveguide; The light detected by the photodetector from the second end of the coupled waveguide is converted into a detector signal that encodes the amplitude of the detected light; and The detector signal is converted into pressure using a predetermined calibration rule.

Images