Optical nonlinearities in high-confinement silicon carbide waveguides.

We demonstrate strong nonlinearities of n2=8.6±1.1×10(-15)  cm2 W(-1) in single-crystal silicon carbide (SiC) at a wavelength of 2360 nm.

Silicon-chip mid-infrared frequency comb generation.

Optical frequency combs are a revolutionary light source for high-precision spectroscopy because of their narrow linewidths and precise frequency spacing. Generation of such combs in the mid-infrared spectral region (2-20 μm) is important for molecular gas detection owing to the presence of a large number of absorption lines in this wavelength regime. Microresonator-based frequency comb sources can provide a compact and robust platform for comb generation that can operate with relatively low optical powers.

WDM-compatible mode-division multiplexing on a silicon chip.

Significant effort in optical-fibre research has been put in recent years into realizing mode-division multiplexing (MDM) in conjunction with wavelength-division multiplexing (WDM) to enable further scaling of the communication bandwidth per fibre. In contrast, almost all integrated photonics operate exclusively in the single-mode regime. MDM is rarely considered for integrated photonics because of the difficulty in coupling selectively to high-order modes, which usually results in high inter-modal crosstalk.

Overcoming Si₃N₄ film stress limitations for high quality factor ring resonators.

Silicon nitride (Si₃N₄) ring resonators are critical for a variety of photonic devices. However the intrinsically high film stress of silicon nitride has limited both the optical confinement and quality factor (Q) of ring resonators. We show that stress in Si₃N₄ films can be overcome by introducing mechanical trenches for isolating photonic devices from propagating cracks.

Linearized silicon modulator based on a ring assisted Mach Zehnder inteferometer.

We demonstrate a Linearized Ring Assisted Mach-Zehnder Interferometer (L-RAMZI) modulator in a miniature silicon device. We measure a record high degree of linearization for a silicon device, with a Spurious Free Dynamic Range (SFDR) of 106dB/Hz²/³ at 1GHz, and 99dB/Hz²/³ at 10GHz.

High Q SiC microresonators.

We demonstrate photonic devices based on standard 3C SiC epitaxially grown on silicon. We achieve high optical confinement by taking advantage of the high stiffness of SiC and undercutting the underlying silicon substrate. We demonstrate a 20 μm radius suspended microring resonator with Q=14,100 fabricated on commercially available SiC-on-silicon substrates.

High quality factor and high confinement silicon resonators using etchless process.

We demonstrate high quality factor and high confinement in a silicon ring resonator fabricated by a thermal oxidation process. We fabricated a 50 μm bending radius racetrack resonator, with a 5 μm coupling region. We achieved an intrinsic quality factor of 760,000 for the fundamental TM mode, which corresponds to a propagation loss of 0.

Near-field radiative cooling of nanostructures.

We measure near-field radiative cooling of a thermally isolated nanostructure up to a few degrees and show that in principle this process can efficiently cool down localized hotspots by tens of degrees at submicrometer gaps. This process of cooling is achieved without any physical contact, in contrast to heat transfer through conduction, thus enabling novel cooling capabilities. We show that the measured trend of radiative cooling agrees well theoretical predictions and is limited mainly by the geometry of the probe used here as well as the minimum separation that could be achieved in our setup.

CMOS compatible reconfigurable filter for high bandwidth non-blocking operation.

We design, fabricate and characterize a CMOS-compatible, Mach-Zehnder-coupled, second-order-microring-resonator filter with large Free Spectral Range and demonstrate non-blocking thermo-optical filter reconfiguration. The device consists of 10-μm radius silicon microring resonators, with an FSR equivalent to that of a structure consisting of 5-μm radii microrings. The structure is reconfigurable over an 8.

Wide-bandwidth continuously tunable optical delay line using silicon microring resonators.

We demonstrate a distortion free tunable optical delay as long as 135 ps with a 10 GHz bandwidth using thermally tuned silicon microring resonators in the novel balanced configuration. The device is simple, easy to control and compact measuring only 30 µm wide by 250 µm long.

High bandwidth on-chip silicon photonic interleaver.

We demonstrate a 120 GHz 3-dB bandwidth on-chip silicon photonic interleaver with a flat passband over a broad spectral range of 70 nm. The structure of the interleaver is based on an asymmetric Mach-Zehnder interferometer (MZI) with 3 ring resonators coupled to the arms of the MZI. The transmission spectra of this device depict a rapid roll-off on the band edges, where the 20-dB bandwidth is measured to be 142 GHz.

Ultrashort free-carrier lifetime in low-loss silicon nanowaveguides.

We demonstrate reduction of the free-carrier lifetime in a silicon nanowaveguide from 3 ns to 12.2 ps by applying a reverse bias across an integrated p-i-n diode. This observation represents the shortest free-carrier lifetime demonstrated to date in silicon waveguides.

Focusing light in a curved-space.

We use transformation optics to demonstrate 2D silicon nanolenses, with wavelength-independent focal point. The lenses are designed and fabricated with dimensions ranging from 5.0 microm x 5.

Deposited silicon high-speed integrated electro-optic modulator.

We demonstrate a micrometer-scale electro-optic modulator operating at 2.5 Gbps and 10 dB extinction ratio that is fabricated entirely from deposited silicon. The polycrystalline silicon material exhibits properties that simultaneously enable high quality factor optical resonators and sub-nanosecond electrical carrier injection.

Low loss etchless silicon photonic waveguides.

We demonstrate low loss silicon waveguides fabricated without any silicon etching. We define the waveguides by selective oxidation which produces ultra-smooth sidewalls with width variations of 0.3 nm.

Wide temperature range operation of micrometer-scale silicon electro-optic modulators.

We demonstrate high bit rate electro-optic modulation in a resonant micrometer-scale silicon modulator over an ambient temperature range of 15 K. We show that low bit error rates can be achieved by varying the bias current through the device to thermally counteract the ambient temperature changes. Robustness in the presence of thermal variations can enable a wide variety of applications for dense on chip electronic photonic integration.

High-speed electro-optic control of the optical quality factor of a silicon microcavity.

We demonstrate electro-optic ultrafast control of the optical quality factor of an on-chip silicon microcavity. The micrometer-sized cavity is formed by light confinement between two microring resonators acting as frequency selective mirrors. The ring resonators are integrated into p-i-n junctions enabling ultrafast injection and extraction of carriers.