Expanded-Beam Through-Substrate Coupling Interface for Alignment Tolerant Packaging of Silicon Photonics

A compact three-laser source for optical sensing is presented. It is based on a low-noise implementation of the Pound-Drever-Hall method and comprises high-bandwidth optical phase-locked loops. The outputs from three semiconductor distributed feedback lasers, mounted on thermo-electric coolers (TEC), are coupled with micro-lenses into a silicon photonics (SiP) chip that performs beat note detection and several other functions. The chip comprises phase modulators, variable optical attenuators, multi-mode-interference couplers, variable ratio tap couplers, integrated photodiodes and optical fiber butt-couplers. Electrical connections between a metallized ceramic and the TECs, lasers and SiP chip are achieved by wirebonds. All these components stand within a 35 mm by 35 mm package which is interfaced with 90 electrical pins and two fiber pigtails. One pigtail carries the signals from a master and slave lasers, while another carries that from a second slave laser. The pins are soldered to a printed circuit board featuring a micro-processor that controls and monitors the system to ensure stable operation over fluctuating environmental conditions. This highly adaptable multi-laser source can address various sensing applications requiring the tracking of up to three narrow spectral features with a high bandwidth. It is used to sense a fiber-based ring resonator emulating a resonant fiber optics gyroscope. The master laser is locked to the resonator with a loop bandwidth greater than 1 MHz. The slave lasers are offset frequency locked to the master laser with loop bandwidths greater than 100 MHz. This high performance source is compact, automated, robust, and remains locked for days.

Light-emitting diodes (LEDs) based on III-V/II-VI materials have delivered a compelling performance in the mid-infrared (mid-IR) region, which enabled wide-ranging applications in sensing, including environmental monitoring, defense, and medical diagnostics. Continued efforts are underway to realize on-chip sensors via heterogeneous integration of mid-IR emitters on a silicon photonic chip, but the uptake of such an approach is limited by the high costs and interfacial strains, associated with the processes of heterogeneous integrations. Here, the black phosphorus (BP)-based van der Waals (vdW) heterostructures are exploited as room-temperature LEDs. The demonstrated devices emit linearly polarized light, and the spectra cover the technologically important mid-IR atmospheric window. Additionally, the BP LEDs exhibit fast modulation speed and exceptional operation stability. The measured peak extrinsic quantum efficiency is comparable to the III-V/II-VI mid-IR LEDs. By leveraging the integrability of vdW heterostructures, we further demonstrate a silicon photonic waveguide-integrated BP LED.

We present a flip-chip integration process in which the vertical alignment is guaranteed by a mechanical contact between pedestals defined in a recess etched into a silicon photonics chip and a laser or semiconductor optical amplifier. By selectively etching up to the active region of the III-V materials, we can make the accuracy of vertical alignment independent on the process control applied to layer thicknesses during silicon photonics or III-V chip fabrication, enabling alignment tolerances below ±10 nm in the vertical (Z-)direction.

We investigate the effect of tunable optical feedback on a commercial DFB laser edge coupled to a Silicon Photonics planar integrated circuit in which a tunable reflector has been implemented by means of a ring resonator based add-drop multiplexer. Controlled optical feedback allows for fine-tuning of the laser oscillation frequency. Under certain conditions it also allows suppression of bifurcation modes triggered by reflections occurring elsewhere on the chip. A semi-analytical model describing laser dynamics under combined optical feedback from the input facet of the edge coupler and from the tunable on-chip reflector fits the measurements. Compensation of detrimental effects from reflections induced elsewhere on a transceiver chip may allow moving isolators downstream in future communications systems, facilitating direct hybrid laser integration in Silicon Photonics chips, provided a suitable feedback signal for a control system can be identified. Moreover, the optical frequency tuning at lower feedback levels can be used to form a rapidly tunable optical oscillator as part of an optical phase locked loop, circumventing the problem of the thermal to free carrier effect crossover in the FM response of injection current controlled semiconductor laser diodes.

We present a strictly nonblocking 4 × 4 electrooptic silicon photonic switch fabric with on-chip gain. The switch integrates 12 Mach-Zehnder cells in a 3-stage topology equipped with fast electrooptic phase shifters, and thermooptic phase trimmers. To compensate for the losses of the fabric, a 4-channel GaInAsP/InP semiconductor optical amplifier array is flip-chip attached into an etched cavity in the silicon photonic chip with butt-coupled waveguide interfaces. The chip is wirebonded to a CMOS driver that provides push-pull drive to each elementary Mach-Zehnder cell. We demonstrate an optical switch assembly with net neutral insertion loss in the C-band together with nanosecond-scale reconfiguration time.

We demonstrate an integrated source of frequency-entangled photon pairs on a silicon photonics chip. The emitter has a coincidence-to-accidental ratio exceeding 103. We prove entanglement by showing two-photon frequency interference with a visibility of 94.6% ± 1.1%. This result opens the possibility of on-chip integration of frequency-bin sources with modulators and the other active and passive devices available in the silicon photonics platform.

We demonstrate on-chip non-invasive monitoring of orthogonal modes transmitted in a silicon photonic waveguide. The proposed technique exploits a recently developed ContactLess Integrated Photonic Probe (CLIPP) realizing a fully transparent integrated light detector. The optical intensity of the modes propagating in the waveguide is tracked in time by the CLIPP, with no signal quality degradation induced by monitoring operations. We exploit this concept for the simultaneous monitoring of two intensity modulated 10 Gbit/s data channels transmitted at the same wavelength and multiplexed on the fundamental transverse electric and magnetic modes of the silicon waveguide. By labeling each signal with a weakly modulated pilot tone, the CLIPP can discriminate at the same time the two channels, the monitoring of one signal not affecting the readout of the other one. The scalability of the presented technique to several modes on arbitrary polarization states, along with the fabrication simplicity and CMOS compatibility of the CLIPP detector, makes this approach promising for the monitoring and control of integrated components for mode-division multiplexing systems.

We propose a new opto-mechanical ultrasound sensor (OMUS) enabled by an innovative silicon photonics waveguide. We present experimental results up to 30 MHz, a 10-sensor array proof-of-concept and our latest findings.

We propose a new opto-mechanical ultrasound sensor (OMUS) enabled by an innovative silicon photonics waveguide. We present experimental results up to 30 MHz, a 10-sensor array proof-of-concept and our latest findings.

Unitary optical processors (UOPs) are task-specific computing units that can ultimately enable ultrafast and energy-efficient unitary matrix-vector multiplications based on the interference between coherent optical beams. The UOP using multiport directional couplers (MDCs) holds great promise in large-scale integration because of its unique robustness against fabrication errors. Here, we demonstrate a 10-port robust UOP on a silicon photonic chip, which is so far the largest-scale UOP using multiport directional couplers. We further show the unique flexibility of this architecture by demonstrating operations for both the transverse electric (TE) and the transverse magnetic (TM) polarizations, which has never been realized in previous UOPs. This flexible and robust architecture is suitable for various scenarios in deep learning, optical communication, and quantum information processing.

We fabricated an autocorrelator on a silicon photonic chip, which had pulse-width-range switch function. Multiple autocorrelators having different lengths are integrated together, and the range switching is done by selecting one of them. This approach is very simple but shows a great advantage in scalability.

Particle detectors for future experiments at the HL-LHC will require new optical data transmitters that can provide high data rates and be resistant against high levels of radiation. Furthermore, new design paths for future optical readout systems for HL-LHC could be opened if there was a possibility to integrate the optical components with their driving electronics and possibly also the silicon particle sensors themselves. All these functionalities could potentially be combined in the silicon photonics technology which currently receives a lot of attention for conventional optical link systems. Silicon photonic test chips were designed in order to assess the suitability of this technology for deployment in high-energy physics experiments. The chips contain custom-designed Mach-Zehnder modulators, pre-designed ``building-block'' modulators, photodiodes and various other passive test structures. The simulation and design flow of the custom designed Mach-Zehnder modulators and some first measurement results of the chips are presented.

Chip‐on‐board silicon photonics O‐band wavelength‐division multiplexing transceivers have been developed that will eventually enable high‐throughput on‐board optical communication for multi‐socket on‐board communication. This direct, any‐to‐any configuration yields low‐latency, low‐power optical communication among multiple compute nodes on the board. Silicon photonic transceiver chips are flip‐chipped on a polymer waveguide containing an electro‐optical circuit board using adiabatic coupling and then completed with driver and amplifier electronic chips. A transceiver assembly based on wire‐bond technology verifies 50 Gb/s operation per channel, and the flip‐chip version demonstrates the chip on‐board assembly techniques for compact on‐board transceivers.

We present a 425-Gbps/λ dual-polarization (DP) IMDD pluggable transceiver in an OSFP form factor for intra- data center application scenario. Both DP transmitter (Tx) and receiver (Rx) are monolithically integrated in a silicon photonics (SiPh) chip. The Tx multiplexes two 212.5Gbps polarization tributaries onto a single wavelength optical carrier, forming a 425-Gbps/λ data stream into the transmission link. The Rx performs a robust polarization tracking based on a proposed fast converging eigenvector-decomposition-based polarization recovery algorithm. Aided by off-the-shelf digital signal processing (DSP) and transimpedance amplifier (TIA) chips, the transceiver demonstrates a real-time 2×212.5Gbps transmission over 1km single mode fiber (SMF). A stable pre-FEC bit-error ratio (BER) floor of 2×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> level is obtained in both dynamic polarization scrambling and fiber handling cases. The experiment proves the feasibility that the DP solution is capable of doubling system capacity for short-reach transmission with robust polarization tracking.

We present the design and characterization of a microelectronic chip consisting of 32 independent single-photon counting and multi-photon time-coincidence channels, based on Single Photon Avalanche Diodes (SPADs). The chip aims at easing the assembly together with Silicon Photonics substrates and chips, for a broad spectrum of quantum applications. The chip provides not only 32 independent pulse outputs for multi-channel single-photon counting, but it features other two operation modalities. For single-photon applications, the chip provides the single-hit digital address of the channel detecting the photon among the 32 ones. For multi-photon applications, the chip provides an event-driven pulse every time more than n photons (n selectable between 2 and 4) concurrently trigger different channels. Each detection channel consists of 4 independent SPADs with different diameter (5 μm, 10 μm, 20 μm, and 50 μm), to easily match the waveguides and collection efficiency.