Photonic neural probe enabled microendoscopes for light-sheet light-field computational fluorescence brain imaging.

Significance: Light-sheet fluorescence microscopy is widely used for high-speed, high-contrast, volumetric imaging. Application of this technique to brain imaging in non-transparent organisms has been limited by the geometric constraints of conventional light-sheet microscopes, which require orthogonal fluorescence excitation and collection objectives. We have recently demonstrated implantable photonic neural probes that emit addressable light sheets at depth in brain tissue, miniaturizing the excitation optics.

Implantable photonic neural probes with 3D-printed microfluidics and applications to uncaging.

Advances in chip-scale photonic-electronic integration are enabling a new generation of foundry-manufacturable implantable silicon neural probes incorporating nanophotonic waveguides and microelectrodes for optogenetic stimulation and electrophysiological recording in neuroscience research. Further extending neural probe functionalities with integrated microfluidics is a direct approach to achieve neurochemical injection and sampling capabilities. In this work, we use two-photon polymerization 3D printing to integrate microfluidic channels onto photonic neural probes, which include silicon nitride nanophotonic waveguides and grating emitters.

Three-electrode germanium-on-silicon avalanche photodiode array.

In this Letter, we report a bridge-connected three-electrode germanium-on-silicon (Ge-on-Si) avalanche photodiode (APD) array compatible with the complementary metal-oxide semiconductor (CMOS) process. In addition to the two electrodes on the Si substrate, a third electrode is designed for Ge. A single three-electrode APD was tested and analyzed.

Microcantilever-integrated photonic circuits for broadband laser beam scanning.

Laser beam scanning is central to many applications, including displays, microscopy, three-dimensional mapping, and quantum information. Reducing the scanners to microchip form factors has spurred the development of very-large-scale photonic integrated circuits of optical phased arrays and focal plane switched arrays. An outstanding challenge remains to simultaneously achieve a compact footprint, broad wavelength operation, and low power consumption.

On-chip generation of Bessel-Gaussian beam via concentrically distributed grating arrays for long-range sensing.

Bessel beam featured with self-healing is essential to the optical sensing applications in the obstacle scattering environment. Integrated on-chip generation of the Bessel beam outperforms the conventional structure by small size, robustness, and alignment-free scheme. However, the maximum propagation distance (Z) provided by the existing approaches cannot support long-range sensing, and thus, it restricts its potential applications.

Fully Integrated Line Array Angular Displacement Sensing Chip.

The angular displacement sensor is a digital angular displacement measurement device that integrates optics, mechanics, and electronics. It has important applications in communication, servo control, aerospace, and other fields. Although conventional angular displacement sensors can achieve extremely high measurement accuracy and resolution, they cannot be integrated because complex signal processing circuitry is required at the photoelectric receiver, which limits their suitability for robotics and automotive applications.

Thermo-Optic Phase Shifter with Interleaved Suspended Design for Power Efficiency and Speed Adjustment.

Conventional thermo-optic devices-which can be broadly categorized to that with and without a thermal isolation trench-typically come with a tradeoff between thermal tuning efficiency and tuning speed. Here, we propose a method that allows us to directly define the tradeoff using a specially designed thermo-optic phase shifter with an interleaved isolation trench. With the design, the tuning efficiency and speed can be precisely tailored simply by controlling the duty ratio (suspended length over total heater length) of the suspended design.

Power-efficient silicon nitride thermo-optic phase shifters for visible light.

We demonstrate power-efficient, thermo-optic, silicon nitride waveguide phase shifters for blue, green, and yellow wavelengths. The phase shifters operated with low power consumption due to a suspended structure and multi-pass waveguide design. The devices were fabricated on 200-mm silicon wafers using deep ultraviolet lithography as part of an active visible-light integrated photonics platform.

Two-dimensional multi-layered SiN-on-SOI optical phased array with wide-scanning and long-distance ranging.

Silicon based optoelectronic integrated optical phased array is attractive owing to large-dense integration, large scanning range and CMOS compatibility. In this paper, we design and fabricate a SiN-on-SOI two-dimensional optical phased array chip. We demonstrate a two-dimensional scanning range of 96°×14.

Investigation and demonstration of a high-power handling and large-range steering optical phased array chip.

The optical power handling of an OPA scanning beam determines its targeted detection distance. So far, a limited number of investigations have been conducted on the restriction of the beam power. To the best of our knowledge, we for the first time in this paper explore the ability of the silicon photonics based OPA circuit for the high power application.

Unidirectional large-scale waveguide grating with uniform radiation for optical phased array.

Two novel waveguide gratings for optical phased array transmitters are investigated. By offsetting the grating structures along the waveguide on the upper and lower surfaces of the silicon nitride (SiN) waveguide, the dual-level chain and dual-level fishbone structures can achieve 95% of unidirectional radiation with a single SiN layer by design. With apodized perturbation along the gratings, both structures can achieve uniform radiation without compromising the unidirectional radiation performance.

Surface illuminated interdigitated Ge-on-Si photodetector with high responsivity.

To address the problem of traditional surface illuminated detectors being of low responsivity, this work proposes a large-size interdigitated "finger-type" germanium-on-silicon (Ge-on-Si) photodetector (PD) based on the surface illumination approach. For 1550 nm light with a surface incident power of -20 dBm at room temperature, the best responsivity of the PD achieved is ∼0.64 A/W at 0.

Gbps physical random bit generation based on the mesoscopic chaos of a silicon photonics crystal microcavity.

We present an experimental and theoretical physical random bit (PRB) generator using the mesoscopic chaos from a photonic-crystal optomechanical microcavity with a size of ∼10µm and very low operating intracavity energy of ∼60 Femto-Joule that was fabricated with CMOS compatible processes. Moreover, two kinds of PRB generation were proposed with rates over gigabits per second (Gbps). The randomness of the large PRB strings was further verified using the NIST Special Publication 800-22.

Visible-light silicon nitride waveguide devices and implantable neurophotonic probes on thinned 200 mm silicon wafers.

We present passive, visible light silicon nitride waveguides fabricated on ≈ 100 µm thick 200 mm silicon wafers using deep ultraviolet lithography. The best-case propagation losses of single-mode waveguides were ≤ 2.8 dB/cm and ≤ 1.

Thermal annealing study of the mid-infrared aluminum nitride on insulator (AlNOI) photonics platform.

Aluminum nitride on insulator (AlNOI) photonics platform has great potential for mid-infrared applications thanks to the large transparency window, piezoelectric property, and second-order nonlinearity of AlN. However, the deployment of AlNOI platform might be hindered by the high propagation loss. We perform thermal annealing study and demonstrate significant loss improvement in the mid-infrared AlNOI photonics platform.

Broadband couplers for hybrid silicon-chalcogenide glass photonic integrated circuits.

We report on the design, fabrication and testing of three types of coupling structures for hybrid chalcogenide glass GeSbS-Silicon (GeSbS-Si) photonic integrated circuit platforms. The first type is a fully etched GeSbS grating coupler defined directly in the GeSbS film. Coupling losses of 5.

Aluminum nitride on insulator (AlNOI) platform for mid-infrared photonics.

We report an aluminum nitride on insulator platform for mid-infrared (MIR) photonics applications beyond 3 μm. Propagation loss and bending loss are studied, while functional devices such as directional couplers, multimode interferometers, and add/drop filters are demonstrated with high performance. The complementary metal-oxide-semiconductor-compatible aluminum nitride offers advantages ranging from a large transparency window, high thermal and chemical resistance, to piezoelectric tunability and three-dimensional integration capability.

Efficient and broadband subwavelength grating coupler for 3.7 μm mid-infrared silicon photonics integration.

A grating coupler is an essential building block for compact and flexible photonics integration. In order to meet the increasing demand of mid-infrared (MIR) integrated photonics for sensitive chemical/gas sensing, we report a silicon-on-insulator (SOI) based MIR subwavelength grating coupler (SWGC) operating in the 3.7 μm wavelength range.

Wavelength-Flattened Directional Coupler Based Mid-Infrared Chemical Sensor Using Bragg Wavelength in Subwavelength Grating Structure.

In this paper, we report a compact wavelength-flattened directional coupler (WFDC) based chemical sensor featuring an incorporated subwavelength grating (SWG) structure for the mid-infrared (MIR). By incorporating a SWG structure into directional coupler (DC), the dispersion in DC can be engineered to allow broadband operation which is advantageous to extract spectroscopic information for MIR sensing analysis. Meanwhile, the Bragg reflection introduced by the SWG structure produces a sharp trough at the Bragg wavelength.

Silicon Photonics Transmitter with SOA and Semiconductor Mode-Locked Laser.

We experimentally investigate an optical link relying on silicon photonics transmitter and receiver components as well as a single section semiconductor mode-locked laser as a light source and a semiconductor optical amplifier for signal amplification. A transmitter based on a silicon photonics resonant ring modulator, an external single section mode-locked laser and an external semiconductor optical amplifier operated together with a standard receiver reliably supports 14 Gbps on-off keying signaling with a signal quality factor better than 7 for 8 consecutive comb lines, as well as 25 Gbps signaling with a signal quality factor better than 7 for one isolated comb line, both without forward error correction. Resonant ring modulators and Germanium waveguide photodetectors are further hybridly integrated with chip scale driver and receiver electronics, and their co-operability tested.

Real-time dynamics and cross-correlation gating spectroscopy of free-carrier Drude slow-light solitons.

Optical solitons-stable waves balancing delicately between nonlinearities and dispersive effects-have advanced the field of ultrafast optics and dynamics, with contributions spanning from supercontinuum generation to soliton fission, optical event horizons, Hawking radiation and optical rogue waves, among others. Here, we investigate picojoule soliton dynamics in silicon slow-light, photonic-bandgap waveguides under the influence of Drude-modeled, free-carrier-induced nonlinear effects. Using real-time and single-shot amplified dispersive Fourier transform spectroscopy simultaneously with high-fidelity cross-correlation frequency resolved optical gating at femtojoule sensitivity and femtosecond resolution, we examine the soliton stability limits, the soliton dynamics including free-carrier quartic slow-light scaling and acceleration, and the Drude electron-hole plasma-induced perturbations in the Cherenkov radiation and modulation instability.

Mesoscopic chaos mediated by Drude electron-hole plasma in silicon optomechanical oscillators.

Chaos has revolutionized the field of nonlinear science and stimulated foundational studies from neural networks, extreme event statistics, to physics of electron transport. Recent studies in cavity optomechanics provide a new platform to uncover quintessential architectures of chaos generation and the underlying physics. Here, we report the generation of dynamical chaos in silicon-based monolithic optomechanical oscillators, enabled by the strong and coupled nonlinearities of two-photon absorption induced Drude electron-hole plasma.

Experimental realization of an O-band compact polarization splitter and rotator.

We experimentally realize a compact wideband polarization splitter and rotator (PSR) with CMOS compatibility. The fabricated PSR is then tested by utilizing a fabrication-tolerant TE-pass on-chip polarizer we propose to practically solve the issue of accurately aligning the polarizations in fiber and modes on chip. Both of these polarization handling devices take the advantage of bend structure that confines TE mode better than TM mode.

Compact highly-efficient polarization splitter and rotator based on 90° bends.

We propose a compact highly-efficient CMOS-compatible polarization splitter and rotator (PSR) with a wide bandwidth covering the whole O-band. It benefits from the different confinement capability of TE and TM modes in bend structure. This bend structure helps shorten the PSR and maintain high efficiency, achieving the bending, polarization splitting, rotating of light beam at the same time.