Efficient wideband tunable radio frequency-optical conversion via triply resonant photonic molecules.

Electro-optic (EO) transduction of weak radio frequency (RF) and millimeter-wave signals, such as those received by an antenna, onto laser sidebands for processing in the optical domain requires efficient EO modulators. Microrings offer spatial density and efficiency advantages over Mach-Zehnder modulators (MZMs), but conventional single-ring modulators suffer a fundamental trade-off between resonantly enhanced conversion efficiency and the RF carrier frequency that it can accommodate. Dual-cavity "photonic molecule" modulators resolve this trade-off, allowing high efficiency independent of the RF carrier frequency by providing separate resonant supermodes to enhance the laser local oscillator (LO) and the narrowband RF-detuned sideband.

Cubic-wavelength mode volume photonic crystal nanobeam cavities in a monolithic CMOS platform.

We report on the design, fabrication, and experimental characterization of photonic crystal (PhC) nanobeam cavities with the smallest footprint, largest intrinsic quality factor, and smallest mode volume to be demonstrated to date in a monolithic CMOS platform. Two types of cavities were designed, with opposite spatial mode symmetries. The opposite mode symmetry, combined with evanescent coupling, allows the nanobeam cavities to be used in reflectionless topologies, desirable in complex photonic integrated circuits (PICs).

Vernier optical phased array lidar transceivers.

Optical phased arrays (OPAs) which beam-steer in two dimensions (2D) are currently limited to grating row spacings well above a half wavelength. This gives rise to grating lobes along one axis which limit the field of view (FOV), introduce return signal ambiguity, and reduce the optical efficiency in lidar applications. We demonstrate a Vernier transceiver scheme which uses paired transmit and receive phased arrays with different row periodicities, leading to mismatched grating lobe angular spacings and only a single aligned pair of transmit and receive lobes.

Polarization-insensitive 1D grating coupler based on a zero-birefringence subwavelength corelet waveguide.

Grating coupler devices provide efficient, foundry-compatible vertical fiber-to-chip coupling solutions in integrated photonic platforms. However, standard grating coupler designs are highly polarization sensitive, which hinders their adoption. We present a new, to the best of our knowledge, type of 1D polarization-insensitive grating coupler (PIGC) that is based on a zero-birefringence subwavelength "corelet" waveguide.

Optical isolation using microring modulators.

Optical isolators, while commonplace in bulk and fiber optical systems, remain a key missing component in integrated photonics. Isolation using magneto-optic materials has been difficult to integrate into complementary metal-oxide-semiconductor (CMOS) fabrication platforms, motivating the use of other paths to effective non-reciprocity such as temporal modulation. We demonstrate a non-reciprocal element comprising a pair of microring modulators and a microring phase shifter in an active silicon photonic process, which, in combination with standard bandpass filters, yields an isolator on-chip.