Dritan Celo

High-performance silicon photonic tri-state switch based on balanced nested Mach-Zehnder interferometer

AbsatrctThis work proposes a novel silicon photonic tri-state (cross/bar/blocking) switch, featuring high-speed switching, broadband operation, and crosstalk-free performance. The switch is designed based on a 2 × 2 balanced nested Mach-Zehnder interferometer structure with carrier injection phase tuning. As compared to silicon photonic dual-state (cross/bar) switches based on Mach-Zehnder interferometers with carrier injection phase tuning, the proposed switch not only has better performance in cross/bar switching but also provides an extra blocking state. The unique blocking state has a great advantage in applications of N × N switch fabrics, where idle switching elements in the fabrics can be configured to the blocking state for crosstalk suppression. According to our numerical experiments on a fully loaded 8 × 8 dilated Banyan switch fabric, the worst output crosstalk of the 8 × 8 switch can be dramatically suppressed by more than 50 dB, by assigning the blocking state to idle switching elements in the fabric. The results of this work can extend the functionality of silicon photonic switches and significantly improve the performance of on-chip N × N photonic switching technologies.

Highly tunable microwave and millimeter wave filtering using photonic technology

Abstract. The design for a photonic microwave filter tunable in both bandwidth and operating frequency is proposed and experimentally demonstrated. The circuit is based on a single sideband modulator used in conjunction with two or more transmission fiber Bragg gratings (FBGs) cascaded in series. It is demonstrated that the optical filtering characteristics of the FBGs are instrumental in defining the shape of the microwave filter, and the numerical modeling was used to optimize these characteristics. A multiphase-shift transmission FBG design is used to increase the dynamic range of the filter, control the filter ripple, and maximize the slope of the filter skirts. Initial measurements confirmed the design theory and demonstrated a working microwave filter with a bandwidth tunable from approximately 2 to 3.5 GHz and an 18 GHz operating frequency tuning range. Further work is required to refine the FBG manufacturing process and reduce the impact of fabrication errors.

Silicon Photonic Switch Subsystem With 900 Monolithically Integrated Calibration Photodiodes and 64-Fiber Package

Monolithic germanium photodiodes on every cell calibrate a 32×32 silicon photonic switch of 448 Mach-Zehnders in 10 minutes. 64 fibers permanently attached through a waveguide concentrator in a wire-bonded BGA achieve 2.9dB C-band TE fiber-to-die.

Three-mode synthesis of slab Gaussian beam in ultra-low-loss in-plane nanophotonic silicon waveguide crossing

We demonstrate experimentally a fundamentally new low-loss silicon nanophotonic in-plane crossing. The crossing operation uses a three-mode synthesis of a 1-D Gaussian beam. The measured loss is 0.007 dB ± 0.004 dB, which is the lowest reported loss for silicon waveguide crossings.

Optical proximity correction in geometry sensitive silicon photonics waveguide crossings

Silicon waveguide crossings using multi-mode interferometers are highly sensitive to geometry at the internal corners. Optical proximity correction was developed using design-of-experiments without sophisticated foundry modeling. This simple technique improved loss by a factor of 2, to <30 mdB, while maintaining flatness over C-band.

2×2 multimode interference coupler with low loss using 248 nm photolithography

We demonstrate a 2×2 multimode interference coupler in 220 nm silicon photonics, with 3.8 μm by 152 μm footprint. Loss is ≤0.15±0.01 dB for 1530-1565 nm, across the 200 mm wafer using 248 nm lithography. This is the lowest loss reported for sub-micron silicon 2×2 MMI.

Electrostatic discharge sensitivity of silicon photonic photodetectors and thermo-optic tuning elements

ESD sensitivity of silicon photonics critically affects manufacturability. We report the ESD sensitivity of monolithic silicon photonic elements, using ESDA/JEDEC tests. TiN heaters were class 1C, requiring JEDEC Basic ESD Control. Ge-photodiodes were class 0B, requiring Detailed ESD Control, unless on-chip ESD solutions are implemented.

Thermo-optic silicon photonics with low power and extreme resilience to over-drive

Operating power of silicon photonic thermo-optic tuners and switches using undercut is inversely proportional to response time. Aggressively undercut devices have 23x power reduction and excellent ruggedness, with reversible behavior up to 60x operating power, and rapid failure when the core temperature reaches a remarkably high 1500°C. Hence device length can be greatly reduced.