Intellectual Merit: Recent years have witnessed remarkable developments on Raman sources and amplifiers in silica optical microstructures and silicon waveguides. Based on either ultra-high quality factors (Q) found in silica microspheres for long photon-matter interaction times or tight wavelength-scale confinement in silicon waveguides, these efforts point to the feasibility of achieving on-chip optical signal gain and lasing at tunable wavelengths in silicon. The PI proposes to address these possibilities and further the advancements by investigating the significantly enhanced Raman phenomena in silicon-based photonic crystal nanostructures. Photonic crystals offer the unique ability to achieve high Q/Vm nanocavities (where Vm is the modal volume), and the arbitrary control of the dispersion characteristics to increase the photon-matter interaction times. The PI will study various low-loss photonic crystal cavities, consisting of one-dimensional and two-dimensional, single and coupled, as well as interaction with waveguides for high-density photonic integrated circuits, for enhancement of stimulated Raman scattering. The PI's theoretical developments will be complemented with experimental efforts and results in both device nanofabrication and physical measurements. This investigation presents a route to silicon-based optical amplification and wavelength-selectable lasing for electronic-photonic integrated circuits, and supports the study of cavity-enhanced nonlinear optics in subwavelength nanostructures.
Broader Impact: This program investigates the important goal of low-threshold wavelength-selectable silicon lasing through Raman scattering in photonic crystals. This program will support the training and education of students at the graduate, undergraduate and high-school levels. Specific outreach modules on nanotechnology and nanophotonics will be developed for K-12 school teachers and presented at schools with a high proportion of minority and underrepresented students around the New York metropolitan area. The PI will participate actively in existing outreach programs as well as provide an enriching laboratory environment for the training and education of graduate, undergraduate, and high-school students.
Intellectual Merit: in this program we demonstrated for the first time enhanced Raman scattering in photonic crystals, with the experimental observations supported by theory and numerical simulations, and device nanofabrication. Slow-light photonic crystal waveguides and nanostructured optical cavities were proposed and examined. Measurements include characterization of the group velocity and higher-order dispersion in the slow-light photonic crystal waveguides, along with forward- and backward-scattering linear and nonlinear losses. Nonlinear measurements then include forward and backward-scattering of the Stokes converted signal with different group velocities, with doubly slow light at both the pump and Stokes frequencies, with measurements of the enhanced conversion efficiency and Raman bandwidths, for on-chip silicon light amplification. Secondly, we demonstrated measurements of enhanced slow-light four-wave mixing in photonic crystals, determining the enhanced efficiency at the slow group velocity regions for increased light-matter interactions and parametric conversion bandwidth. Thirdly and furthermore, we observed for the first time ultrafast temporal soliton compression in chip-scale photonics. The presence of the temporal solitons – through the balance of Kerr self-phase modulation and group velocity dispersion – was experimentally confirmed through autocorrelation measurements, as well as compressing the mode-locked pulses from 2 ps to 580 ps (or shorter). A InGaP material was used in order to completely suppress the two-photon absorption and related free-carrier nonlinearities. The pulses were observed near the Fourier transform limit, along with characterization of the RF jitter and pulse quality (pedestal). Broader Impact: this effort represents a route towards chip-scale wavelength-selectable optical amplification and frequency conversion for electronic-photonic integrated circuits, and supports the study of ultrafast nonlinear optics in subwavelength nanostructures. The program supported the training and education of a PhD student each year, along with research opportunities for undergraduates, and outreach to high-school students. This study at the interface of nanoscale science and engineering with optics and optoelectronics brings scientific and engineering advances for the larger community.
