This Small Business Innovation Research (SBIR) Phase I project proposes to implement a low-cost compact, wide-band, and high-resolution on-chip spectrometer and other components for Raman spectroscopy applications. The proposed architecture consists of silicon-nitride (SiN) spectrometer bonded with a silicon detector array to detect the output power of different spectral channels. A bandwidth of 25 nm with a resolution of 0.6 nm will be demonstrated for the proposed spectrometer. A notch-filter for pump rejection (> 25 dB) will also be demonstrated. Appropriate software for data acquisition from the detector array and for compensating any fabrication-induced non-uniformity in the spectral channels will also be developed as part of this work. The spectroscopy chip and the software will then be used to measure spectrum of a wideband source and the results compared with that of a commercial spectrometer.
The broader impact/commercial potential of this project includes low-cost Raman spectroscopy solution for biomedical applications. Raman spectroscopy has shown great promise for many biomedical applications such as blood analysis, and cancer detection. However, the existing Raman spectroscopy solutions are expensive, bulky and well beyond the comprehension of a common medical professional. The proposed solution will be low-cost, accurate and easy to use to allow health care professionals to use this technology to detect cancers and do blood analysis with the same accuracy, faster time, less patient anxiety, and less sample volume than the currently existing tests, which are currently performed in centralized laboratories, require specially trained staff, and are expensive. The silicon-nitride platform (being transparent in visible and NIR wavelength range) will allow easy extension of the on-chip spectroscopy solution for other commercial applications of interest such as fluorescence, and absorption spectroscopy.
Raman spectroscopy has shown a lot of promise for many biomedical applications including routine blood tests, minimally invasive and early detection of various forms of cancers. However Raman spectroscopy solutions are expensive, bulky, complex and require specially trained staff to carry out these tests. Sinoora proposes to develop an on-chip Raman spectroscopy solution to greatly reduce the size, cost, power requirement, and complexity of a Raman system for biomedical applications. The goal of this Phase I effort was to demonsrate the feasability of an on-chip demonstration of a Raman spectroscopy solution that can be used for bio-medical and other spectroscopy applications. While the on-chip architecture with multi-component integration as proposed by Sinoora allows greatly reducing the size, cost, power requirements, and complexity of spectroscopy solutions, the biggest challenge of such an on-chip spectrometer is the demonstration of large bandwidth (> 150 nm) single mode operation. In Phase I, Sinoora concentrated on demonstrating proof of being able to deliver the bandwidth and multi-component integration requirements of a Raman spectroscopy solution. Towards this end, Sinoora developed a new material platform along with complete fabrication process that allowed world record highest quality factor and largest bandwidth microresonators. Sinoora also came up with a two-stage spectrometer design, and proved with extensive simulations that this design will allow to deliver more than 150 nm single mode operation. The building blocks for this two-stage architecture were theoretically and experimentally investigated to show that experimental demonstration of a high resolution spectrometer with more than 150 nm bandwidth is possible by the end of Phase II of this project. In addition to spectrometer development, and towards the multi-component integration goal, Sinoora also developed 1) an on-chip pump rejection filter to be co-integrated with spectromters, 2) an elaborate process to allow extremely accurate, efficient and mechanically robust coupling of light from input fibers to on-chip waveguides, 3) polarization splitting couplers to enhance signal to noise ratio, and 4) designs for on-chip laser locking. In addition, Sinoora performed a detailed market analysis to obain required spectroscopy specifications (bandwidth, resolution, and channel uniformity etc.) for different targeted markets to ensure that our designs meet these specifications. We conducted inteviews with potential end users of our technology to ensure that a solution as proposed by Sinoora is needed and will be well received. These technical acheivements along with market studies has set a stage for Sinoora to further develop the proposed solution and have a prototype ready by the end of Phase II of this project.
