Tuesday, February 5, 2013
SPIE Photonics West 2013, Synthesis and Photonics of Nanoscale Materials X (San Francisco, CA)
Abstract Development of integrated photonic devices is becoming increasingly important in technological applications. Hydrogenated amorphous silicon (a-Si:H) provides a promising platform. Variations in hydrogen content produce large changes in refractive index and band gap, on the order of 0.1-1. Previous research has demonstrated waveguide fabrication using photolithography and ion implantation techniques, which requires many steps and is limited to 2D patterns. We have developed a laser micromachining technique to locally reduce the hydrogen content of a-Si:H in the laser focus to directly write waveguides and optical devices. Using pulsed lasers operating in the near infrared with photon energies below the band gap will enable direct writing of 3D photonic structures and will greatly simplify the fabrication process to two steps; film deposition and laser exposure. Developing a-Si:H laser micromachining has significant advantages over glass micromachining. Greater compatibility with the silicon material platform can provide applications in silicon photonics and direct integration with existing device platforms. Refractive index changes can be significantly higher than those produced by glass micromachining, where typical changes are fractions of a percent. We have demonstrated reductions in hydrogen content within a-Si:H films using a 1050 nm femtosecond pulsed laser. Raman spectroscopy was used to study the silicon structure and hydrogen content of unaltered and laser treated material. We are now studying the index changes and are optimizing the process for 2D waveguide writing before expanding the study to 3D fabrication. Project Summary Hydrogenated amorphous silicon (a-Si:H) is a promising platform for the development of integrated photonic devices. Variations in hydrogen content produce changes in refractive index on the order of 0.1-1. We have developed a laser micromachining process to directly write photonic devices in a-Si:H by locally reducing the hydrogen content in the laser focus. Laser micromachining of a-Si:H has significant advantages over glass micromachining with higher changes in refractive index and compatibility with the silicon material platform. We have demonstrated changes in hydrogen content of a-Si:H films using a 1050 nm femtosecond pulsed laser and are optimizing direct waveguide writing.