Gerald Leake

Monolithic erbium- and ytterbium-doped microring lasers on silicon chips

We demonstrate monolithic 160-µm-diameter rare-earth-doped microring lasers using silicon-compatible methods. Pump light injection and laser output coupling are achieved via an integrated silicon nitride waveguide. We measure internal quality factors of up to 3.8 × 105 at 980 nm and 5.7 × 105 at 1550 nm in undoped microrings. In erbium- and ytterbium-doped microrings we observe single-mode 1.5-µm and 1.0-µm laser emission with slope efficiencies of 0.3 and 8.4%, respectively. Their small footprints, tens of microwatts output powers and sub-milliwatt thresholds introduce such rare-earth-doped microlasers as scalable light sources for silicon-based microphotonic devices and systems.

Demonstration of an Optical Chip-to-Chip Link in a 3D Integrated Electronic-Photonic Platform

A full optical chip-to-chip link is demonstrated for the first time in a wafer-scale heterogeneous platform, where the photonics and CMOS chips are 3D integrated using wafer bonding and low-parasitic capacitance thru-oxide vias (TOVs). This development platform yields 1000s of functional photonic components as well as 16M transistors per chip module. The transmitter operates at 6Gb/s with an energy cost of 100fJ/bit and the receiver at 7Gb/s with a sensitivity of 26μA (-14.5dBm) and 340fJ/bit energy consumption. A full 5Gb/s chip-to-chip link, with the on-chip calibration and self-test, is demonstrated over a 100m single mode optical fiber with 560fJ/bit of electrical and 4.2pJ/bit of optical energy.

Four-port integrated polarizing beam splitter.

In this Letter, we report on the first integrated four-port polarizing beam splitter. The device operates on the principle of mode evolution and was implemented in a silicon-on-insulator silicon photonics platform and fabricated on a 300 mm CMOS line using 193 nm optical immersion lithography. The adiabatic transition forming of the structure enabled over a 150 nm bandwidth from λ~1350 to λ~1500  nm, achieving a cross-talk level below -10  dB over the entire band.

Two-dimensional apodized silicon photonic phased arrays

In this Letter, we demonstrate an 8×8 apodized silicon photonic phased array where the emission from each of 64 nanoantennas was tailored to exhibit Gaussian-shaped intensity distributions in the near field so that the sidelobes of the generated far-field optical beam were suppressed compared to that of a uniform phased array. With the aid of the 72 thermo-optic phase tuners directly integrated within the phased array, we dynamically shaped the generated optical beam in the far field in a variety of ways.

Generating and identifying optical orbital angular momentum with silicon photonic circuits.

We demonstrate a fully integrated silicon photonic circuit capable of generating light carrying optical orbital angular momentum. Experimentally, orbital angular momentum wavefronts are identified by interfering with another on-chip generated Gaussian beam.

C-band swept wavelength erbium-doped fiber laser with a high-Q tunable interior-ridge silicon microring cavity

We demonstrate an erbium-doped fiber laser with a tunable silicon microring cavity. We measured a narrow laser linewidth (16 kHz) and single-mode continuous-wave emission over the C-band (1530nm-to-1560nm) at a swept-wavelength rate of 22,600nm/s or 3106THz/s.

Athermal synchronization of laser source with WDM filter in a silicon photonics platform

In an optical interconnect circuit, microring resonators (MRRs) are commonly used in wavelength division multiplexing systems. To make the MRR and laser synchronized, the resonance wavelength of the MRR needs to be thermally controlled, and the power consumption becomes significant with a high-channel count. Here, we demonstrate an athermally synchronized rare-earth-doped laser and MRR. The laser comprises a Si3N4 based cavity covered with erbium-doped Al2O3 to provide gain. The low thermo-optic coefficient of Al2O3 and Si3N4 and the comparable thermal shift of the effective index in the laser and microring cross-sections enable lasing and resonance wavelength synchronization over a wide range of temperatures. The power difference between matched and unmatched channels remains greater than 15 dB from 20 to 50 °C due to a synchronized wavelength shift of 0.02 nm/°C. The athermal synchronization approach reported here is not limited to microring filters but can be applied to any Si3N4 filter with integrated lasers using rare earth ion doped Al2O3 as a gain medium to achieve system-level temperature control free operation.

Silicon wavelength-selective partial-drop broadcast filter bank.

We propose an approach to a wavelength-selective 1×N port optical broadcast network demonstrating the approach in a 1×8 port parallel optical drop filter bank utilizing adiabatic micro-ring tunable filters. The micro-ring filters exhibit first-order 92.7±3.7 GHz full width at half-maximum bandwidths with a 36.2 nm free spectral range, low-drop power variation (0.11 dB), and aggregate excess loss of only 1.1 dB in all drop ports. Error-free operation at a 10 Gbit/s data rate is achieved for all eight drop ports with less than a 0.5 dB power penalty among the ports. This wavelength-selective parallel-drop approach serves as a building block for on-chip all-to-all communication networks.

Ultra-Compact CMOS-Compatible Ytterbium Microlaser

We demonstrate a waveguide-coupled trench-based ytterbium microlaser, achieving a sub-milliwatt lasing threshold and a 1.9% slope efficiency within an ultra-compact 40-µm-radius cavity while maintaining full compatibility with a CMOS foundry process.

Large-Scale Integrated Silicon Photonic Circuits for Optical Phased Arrays

We present several optical phased arrays enabled by state-of-the-art large-scale silicon photonic integration which could find potential applications in optical switching, optical communications, light detection and ranging, and holography.