High-performance silicon photonic single-sideband modulators for cold-atom interferometry.

The laser system is the most complex component of a light-pulse atom interferometer (LPAI), controlling frequencies and intensities of multiple laser beams to configure quantum gravity and inertial sensors. Its main functions include cold-atom generation, state preparation, state-selective detection, and generating a coherent two-photon process for the light-pulse sequence. To achieve substantial miniaturization and ruggedization, we integrate key laser system functions onto a photonic integrated circuit.

Non-resonant Bragg scattering four-wave mixing at near-visible wavelengths in low-confinement silicon nitride waveguides.

Quantum state coherent frequency conversion processes-such as Bragg-scattering four-wave mixing (BSFWM)-hold promise as a flexible technique for networking heterogeneous and distant quantum systems. In this Letter, we demonstrate BSFWM within an extended (1.2-m) low-confinement silicon nitride waveguide and show that this system has the potential for near-unity frequency conversion in visible and near-visible wavelength ranges.

110 GHz, 110 mW hybrid silicon-lithium niobate Mach-Zehnder modulator.

High bandwidth, low voltage electro-optic modulators with high optical power handling capability are important for improving the performance of analog optical communications and RF photonic links. Here we designed and fabricated a thin-film lithium niobate (LN) Mach-Zehnder modulator (MZM) which can handle high optical power of 110 mW, while having 3-dB bandwidth greater than 110 GHz at 1550 nm. The design does not require etching of thin-film LN, and uses hybrid optical modes formed by bonding LN to planarized silicon photonic waveguide circuits.

Narrowband microwave-photonic notch filters using Brillouin-based signal transduction in silicon.

The growing demand for bandwidth makes photonic systems a leading candidate for future telecommunication and radar technologies. Integrated photonic systems offer ultra-wideband performance within a small footprint, which can naturally interface with fiber-optic networks for signal transmission. However, it remains challenging to realize narrowband (∼MHz) filters needed for high-performance communications systems using integrated photonics.

Nonreciprocal Frequency Domain Beam Splitter.

The canonical beam splitter-a fundamental building block of quantum optical systems-is a reciprocal element. It operates on forward- and backward-propagating modes in the same way, regardless of direction. The concept of nonreciprocal quantum photonic operations, by contrast, could be used to transform quantum states in a momentum- and direction-selective fashion.

Characterization of suspended membrane waveguides towards a photonic atom trap integrated platform.

We demonstrate an optical waveguide device, capable of supporting the high, in-vacuum, optical power necessary for trapping a single atom or a cold atom ensemble with evanescent fields. Our photonic integrated platform, with suspended membrane waveguides, successfully manages optical powers of 6 mW (500 μm span) to nearly 30 mW (125 μm span) over an un-tethered waveguide span. This platform is compatible with laser cooling and magneto-optical traps (MOTs) in the vicinity of the suspended waveguide, called the membrane MOT and the needle MOT, a key ingredient for efficient trap loading.

Gamma radiation effects on passive silicon photonic waveguides using phase sensitive methods.

Passive silicon photonic waveguides are exposed to gamma radiation to understand how the performance of silicon photonic integrated circuits is affected in harsh environments such as space or high energy physics experiments. The propagation loss and group index of the mode guided by these waveguides is characterized by implementing a phase sensitive swept-wavelength interferometric method. We find that the propagation loss associated with each waveguide geometry explored in this study slightly increases at absorbed doses of up to 100 krad (Si).

III/V silicon hybrid laser based on a resonant Bragg structure.

We demonstrate a laser tunable in intensity with gigahertz tuning speed based on a III/V reflective semiconductor optical amplifier (RSOA) coupled to a silicon photonic chip. The silicon chip contains a Bragg-based Fabry-Perot resonator to form a passive bandpass filter within its stopband to enable single-mode operation of the laser. We observe a side mode suppression ratio of 43 dB, linewidth of 790 kHz, and an optical output power of 1.

A heterogeneously integrated silicon photonic/lithium niobate travelling wave electro-optic modulator.

Silicon photonics is a platform that enables densely integrated photonic components and systems and integration with electronic circuits. Depletion mode modulators designed on this platform suffer from a fundamental frequency response limit due to the mobility of carriers in silicon. Lithium niobate-based modulators have demonstrated high performance, but the material is difficult to process and cannot be easily integrated with other photonic components and electronics.

Improved broadband performance of an adjoint shape optimized waveguide crossing using a Levenberg-Marquardt update.

We derive an adjoint shape optimization algorithm with a compound figure of merit and demonstrate its use with both gradient descent and Levenberg-Marquart updates for the case of SiO-buried SOI coplanar waveguide crossings. We show that a smoothing parameter, basis function width, can be used to eliminate small feature sizes with a small cost to device performance. The Levenberg-Marquardt update produces devices with larger bandwidth.

Bonded thin film lithium niobate modulator on a silicon photonics platform exceeding 100 GHz 3-dB electrical modulation bandwidth.

We demonstrate an ultra-high-bandwidth Mach-Zehnder electro-optic modulator (EOM), based on foundry-fabricated silicon (Si) photonics, made using conventional lithography and wafer-scale fabrication, oxide-bonded at 200C to a lithium niobate (LN) thin film. Our design integrates silicon photonics light input/output and optical components, such as directional couplers and low-radius bends. No etching or patterning of the thin film LN is required.

Accurate photonic waveguide characterization using an arrayed waveguide structure.

Measurement uncertainties in the techniques used to characterize loss in photonic waveguides becomes a significant issue as waveguide loss is reduced through improved fabrication technology. Typical loss measurement techniques involve environmentally unknown parameters such as facet reflectivity or varying coupling efficiencies, which directly contribute to the uncertainty of the measurement. We present a loss measurement technique, which takes advantage of the differential loss between multiple paths in an arrayed waveguide structure, in which we are able to gather statistics on propagation loss from several waveguides in a single measurement.