Creating Chip-Scale Mid-Infrared Spectroscopy

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Mid-infrared spectroscopy is a technique that is used to identify molecular constituents based on the interactions of light with matter. Current system implementations require large, bulky, and discrete optical and electronic components, inherently limiting sensitivity, power efficiency, functionality, stability, reproducibility, compactness, and economies of scale. This award supports research to overcome these fundamental limits by realizing a complete mid-infrared spectroscopic sensor system fully integrated on an optoelectronic integrated circuit at the micrometer scale. The research brings together concepts from optical physics, material science, and electrical engineering allowing for both fundamental science and technological applications to be advanced in tandem. Opportunities are created for chemical and biological sensing with societally important applications including medical sensing, bio-agent defense, environmental process control, and atmospheric chemistry. In addition to specific applications, the convergence of photonics and electronics broadly impacts the optical networking, computing, and sensing industries. The cross-disciplinary nature of the research drives the focus of the integrated educational plan that responds to the challenge of preparing students to be successful in an increasingly interdisciplinary and global environment. Graduate students, undergraduate students, underrepresented groups, and minorities are engaged in a curriculum that fosters integrative research thinking and links societal issues to science and engineering. Silicon is the established material of choice for the microelectronics industry and is attractive for integrated electronic and optical systems on a chip. The lack of second order susceptibility in silicon is, however, a major obstacle to achieving chip-scale mid-infrared spectroscopy. The objective of this research is to overcome this barrier by hybridizing the silicon platform with lithium niobate, a ferroelectric material exhibiting second order susceptibility. New horizons become apparent when exploiting the capability of silicon to provide submicrometer spatial confinement of light and the ability of lithium niobate to mediate strong second order nonlinear optical effects. The research team will perform design, modeling, fabrication, and test to create chip-scale mid-infrared spectroscopy for the first time. The design and modeling approach is based on numerical solutions to nonlinear coupled amplitude equations based on Maxwell's equations. The chip will be physically realized using nanometer scale fabrication techniques. Species will be measured for the purpose of test, measurement, and validation. Results will be compared with the high-resolution transmission molecular absorption database. These concepts provide a new method of attack to achieve complete chip-scale functionalities in hybrid-monolithic silicon and lithium niobate photonic integrated circuits.