使用微环谐振器和激光产生的超声聚焦的超声检测和成像

Ultrasound Detection and Imaging Using Microring Resonators and Laser Generated Focused Ultrasound

超声的光学检测是基于应变场与光场的相互作用的新兴技术,通过调节谐振腔的光学特性进行高灵敏检测。与传统的压电换能器相比,这种检测方案具有宽频带响应,以及灵敏度与尺寸无关的优点。检测器的高灵敏度对于较深的穿透深度至关重要,特别是对于高分辨率成像,因为检测物对高频超声波有强衰减。此外,小器件尺寸具有在超声检测中实现宽接受角的优势。介绍了基于聚合物光子微环谐振器的超声波高灵敏度和宽带检测,并展示其在高分辨率光声层析与光声显微技术中的应用。类似原理还可应用于太赫兹检测,微环可以"听到"吸收太赫兹能量的纳米材料产生的声波。还介绍了产生和聚焦超声波的薄膜光学发射器,用于强振幅聚焦超声成像与治疗。光声源由碳纳米管和弹性体聚合物制成。纳米复合材料作为优异的光吸收器和高效的热转化器,可以产生具有强振幅的输出压力,并具有显示出高频特性的对应频谱。这种方法可以为收集和图形化等细胞工程提供多功能的工具,更重要的是,非热破坏裂可以促进靶向细胞的药物输运与基因治疗。

Optical detection of ultrasound is an emerging technique based on the interaction of strain field and optical field,modulating the optical properties of the resonance cavity for sensitive detection. Such a detection scheme can have several unique advantages,such as broadband response and size-independent sensitivity,compared with conventional piezoelectric transducers. Detector s high sensitivity is essential for deep penetration depth,especially for high-resolution imaging because of the strong attenuation of high-frequency ultrasound. Besides,small element size has the advantage of realizing wide acceptance angle of ultrasound detection. This paper will describe highly sensitive and broad band detection of ultrasound by polymer photonic microring resonators,and demonstrate its application for high resolution photoacoustic tomography and photoacoustic microscopy. Similar principle can be applied to THz detection,where the microring can "listen to" the sound wave generated by the nano-material absorbing the THz energy. This paper will also present thin-film optical transmitters to generate and focus the ultrasound,targeting high-amplitude focused ultrasound for imaging and therapeutic applications. The optoacoustic sources are made of carbon-nanotubes(CNTs)and elastomeric polymers. As the nano-composite works as excellent optical absorbers and efficient heat converters,output pressure with strong amplitudes can be generated and has a corresponding frequency spectrum showing high-frequency characteristics. This approach could provide a versatile tool for cell engineering in terms of harvesting and patterning,and more importantly,non-thermal disruption to facilitate drug delivery and gene therapy for targeted cells.