Nonlinear Photonics & Integrated Lasers
We generate a Kerr frequency comb in a SiN ring spanning over 150nm with 23mW pump power. Self-injection locking of a multi-mode chip-based gain allows access to high pump power while maintaining single mode operation.
We demonstrate a supercontinuum light source for OCT imaging in a compact 1 mm2 Si3N4 chip. We achieve 105 dB sensitivity and a 6-dB sensitivity roll-off at 1.81 mm with only 300 µW incident power.
We demonstrate transverse and longitudinal modal collapse of a highly multi-mode Fabry-Perot laser coupled to a silicon-nitride resonator, via self-injection locking. We show coupling to single transverse mode with more than 50% efficiency and sub-MHz linewidth.
Visible Photonics for Emerging Fields
Widely-tunable and narrow-linewidth integrated lasers across all visible wavelengths are necessary to enable on-chip technologies such as quantum photonics, optical trapping, and biophotonics. However, such lasers have not been realized due to the strong wavelength sensitivity and high loss of integrated optical devices at short wavelengths. Here we overcome these challenges and demonstrate a chip-scale visible lasers platform by using tightly-confined, micrometer-scale silicon nitride resonators and commercial Fabry-Perot laser diodes. We achieve tunable and narrow-linewidth lasing in the deep blue (450 nm), blue (488 nm), green (520 nm), red (660 nm) and near-IR (785 nm) with coarse tuning up to 12 nm, fine tuning up to 33.9 GHz, linewidth down to sub-kHz, side-mode suppression ratio > 35 dB, and fiber-coupled power up to 10 mW. These specifications of our chip-scale lasers are comparable to those of state-of-the-art commercial laser systems, making them stand out as powerful tools for the next generation of visible-light technologies.
We demonstrate the first phased array operating at blue wavelengths. We show wide-angle beam steering over a 50° field-of-view with a beam width of less than 0.17° using a high confinement silicon nitride waveguide platform.
2D Material Nanophotonics
We show a platform for electrically tuning the degree of coupling in micro-ring resonators from the under-coupled to the over-coupled regime, based on graphene-TMD composite waveguides.
Novel Concepts in Integrated Photonics
We show tuning of the cavity-bus coupling rate by more than 160% by imparting a nonlinear differential parametric gain between the clockwise and counterclockwise propagating modes.
We experimentally demonstrate waveguiding at the critical angle in a dielectric multi-layered structure. At this exceptional point, the waveguide becomes scale invariant and the field is confined to the low-index region, with a spatially-uniform transverse profile.
We demonstrate passive PT symmetry breaking between the spatial modes within a single SOI waveguide with metal deposited directly on top. By leveraging this effect, we show low propagation loss of < 1 dB for a 100 μm long, 10 μm wide waveguide partially covered with 100 nm thick metal.
We demonstrate robust mode conversion up to the 12th higher order mode in silicon waveguides by using an optimized adiabatic directional coupler and using subwavelength waveguides. The conversion efficiency is better than -1.5 dB over a 75 nm bandwidth and tolerating ±30 nm fabrication variations.
Manipulating Mid-IR and Far-IR Light
We demonstrate a single longitudinal mode, tunable mid-IR laser by self-injection locking a multiple longitudinal mode Interband Cascade Laser (ICL) to a high-Q Si microresonator at 3.4 μm.
We demonstrate a platform for heat-to-electricity conversion based on near-field radiative heat transfer. The platform is based on tens-of-μm long suspended micro-heaters at >400˚C, placed <100 nm away from a room temperature photodetector.