Micromachined Optical and Acoustic Waveguide Systems for Advance Sensing and Imaging Applications
Evolving from the IC fabrication processes, micromachining technologies allow mass production of 2D or 3D microstructures, which are otherwise difficult to achieve with traditional machining techniques. In this research, novel micromachining processes have been developed to enable new micro optical and acoustic waveguide systems for advanced optical sensing and acoustic imaging applications. The investigated applications include non-invasive cancer detection inside human body, in-field soil characterization, and time-delayed and multiplexed ultrasound and photoacoustic tomography.
Micromachining technology enables miniaturized optical waveguide system for efficient light transmission. The small size and light-guiding capabilities are particularly useful for optical sensing at places deep inside the human body or underground. Two micromachined optical waveguide systems were fabricated and tested. The first one was used to conduct oblique incidence diffuse reflectance spectroscopy (OIDRS) for the determination of tumor margins on human pancreas specimens. The second one was used to conduct visible-near-infrared diffuse reflectance spectroscopy (VNIR-DRS) for extracting the compositional information of soil samples.
Micromachining technology also makes it possible to utilize single-crystalline silicon as a structural material for acoustic wave propagation. It enables the development of high-performance integrated acoustic circuits and allows direct acoustic signal processing and control. The acoustic properties and propagation inside silicon waveguides were characterized, and the acoustic signal processing using micromachined acoustic waveguide system was investigated. Based on the results, two acoustic waveguide systems were designed and constructed. The first system utilized micromachined acoustic delay lines to passively delay acoustic signal thereby reducing the required transceivers and processing electronics; while the second system employed micromachined acoustic multiplexer to actively control the transmission of acoustic signals. Both techniques are expected to provide new solutions to reduce the complexity and cost of the acoustic receiver systems in ultrasound and photoacoustic imaging.