Monolithic Chip-Integrated Absorption Spectrometer from 3-5 microns

A monolithically integrated indium phosphide (InP) to silicon-on-sapphire (SoS) platform is being proposed for a monolithic portable or handheld spectrometer between 3-5microns. SoS provides the necessary refractive index contrast to fabricate slotted photonic crystal waveguide (PCW) structures for lab-on-chip sensing. Monolithic integration of quantum cascade laser (QCL) and quantum cascade detector (QCD) has been previously demonstrated by us at 9.5 micron wavelength on a solely InP platform in which PCWs cannot be fabricated without significant fabrication complexities. At 3.4 micron wavelength, we have also demonstrated 1ppm gas sensing by slow light and intensity enhancements of slotted PCWs in SoS. The Phase 1 proposal takes the crucial step of wafer bonding to integrate the best capabilities of the individual platforms and integrate into a full-fledged monolithic absorption spectrometer. The work plan is thus to demonstrate the technical objectives which are: 1) Design and fabricate slotted PCWs at 4.55 micron 2) Demonstrate feasibility for sub 10ppb detection sensitivity in our slotted PCW at 4.55 micron in SoS for carbon monoxide 3) Demonstrate monolithic integration of quantum cascade laser, quantum cascade detector and silicon-on-sapphire waveguide at 4.55 micron and 4) Design simultaneous QCL-QCD structures for operation around the selected wavelengths at 3.3 micron (CH4), 4.2 micron (CO2) and 4.55 micron (CO) for fabrication in Phase 2.