SBIR Phase I: A Photonic Crystal Based Spectrometer For Manufacturing Process Control

This Small Business Innovation Research Phase I project investigates the development of an inexpensive ultra-compact optical spectrometer. The photonic crystal spectrometer uses the leaky modes of photonic crystals patterned on a multimode waveguide to selectively extract wavelength specific light to a two-dimensional detector array. This pattern can be analyzed to reconstruct the spectrum. The photonic crystal spectrometer's geometry scales in a fundamentally different manner from a diffractive grating spectrometer. Three significant differences in the operation allow this device miniaturization. First, light interacts along two dimensions in the photonic crystal array, allowing waveguided light to be distributed through a waveguide plate, shortening the optical path. Second, wavelengths can be resolved along two dimensions, allowing the use of a two-dimensional photodetector to achieve spectral separation, shrinking the detector size. Lastly, resolution is a function of the photonic crystal array elements employed, not the separation between the diffractive element and detector. The goals of this project are to develop a miniature spectrometer prototype using a low-cost imaging module, and to achieve improvements in range and resolution through redesign of the photonic crystal array. The anticipated result of this project is a low-cost broadband spectrometer physically smaller than any commercially available comparable device. The broader impact/commercial potential of this project lies in the applications where size and/or cost are critical. Commercially available optical spectrometers cost at least $1000 with a minimum volume of 200 cm3 and as a result cannot penetrate markets where size and/or cost are critical. The anticipated cost of the new photonic crystal spectrometer is under $100, with a potential size below 1 cm3, allowing the use of these devices in applications such as on-line process monitoring, solid state lighting characterization and testing, emissions control, portable sensing, and health care. Pollution control applications, for example, will have the potential for significant broader impact through on-board optimization and monitoring of combustion systems, allowing a measurable improvement in environmental impact, while process monitoring, such as on-line spectral monitoring for nanocrystal synthesis, will enable greater oversight in nanomanufacturing, increasing the quality of nanomanufactured materials used for solid state lighting and reducing waste.