Yangjin Ma

Low power 50 Gb/s silicon traveling wave Mach-Zehnder modulator near 1300 nm

A silicon traveling-wave Mach-Zehnder modulator near 1300 nm is demonstrated to operate at 50 Gb/s with a differential 2 Vpp signal at 0 V reverse bias, achieving a 800 fJ/bit power consumption.

Ultralow loss single layer submicron silicon waveguide crossing for SOI optical interconnect

We demonstrate compact, broadband, ultralow loss silicon waveguide crossings operating at 1550 nm and 1310 nm. Cross-wafer measurement of 30 dies shows transmission insertion loss of - 0.028 ± 0.009 dB for the 1550 nm device and - 0.017 ± 0.005 dB for the 1310 nm device. Both crossings show crosstalk lower than - 37 dB. The devices were fabricated in a CMOS-compatible process using 248 nm optical lithography with a single etch step.

High-Speed Silicon Modulator With Slow-Wave Electrodes and Fully Independent Differential Drive

We demonstrate a fully independent differential-drive capable of traveling-wave modulator in silicon using slow-wave transmission line electrode. The reported 3.5-mm device achieves a bandwidth of 27 GHz at -1 V bias with 7.8-V small signal Vπ and 50-Ω impedance. Raising the impedance to this extent requires effectively expanding the RF mode size and radically changes the RF phase velocity, but we show that this can be done with minimal crosstalk effects between the two arms and overall velocity mismatch, and thus, with a high EO bandwidth achieved. 40-Gb/s operation is demonstrated with 1.6-Vpp differential-drive, and performance comparisons to Lithium Niobate modulators are made.

A Compact Low-Power 320-Gb/s WDM Transmitter Based on Silicon Microrings

We demonstrate a compact and low-power wavelength-division multiplexing transmitter near a 1550-nm wavelength using silicon microrings. The transmitter is implemented on a silicon-on-insulator photonics platform with a compact footprint of 0.5 mm2. The transmitter incorporates 8 wavelength channels with 200-GHz spacing. Each channel achieved error-free operation at 40 Gb/s, resulting in an aggregated data transmission capability of 320 Gb/s. To our knowledge, this is the highest aggregated data rate demonstrated in silicon wavelength-division multiplexing transmitters. Owing to the small device capacitance and the efficient pn-junction modulator design, the transmitter achieves low energy-per-bit values of 36 fJ/bit under 2.4 Vpp drive and 144 fJ/bit under 4.8 Vpp drive. Comparisons are made to a commercial lithium niobate modulator in terms of bit-error-rate versus optical signal-to-noise ratio.

Ultracompact silicon-on-insulator polarization rotator for polarization-diversified circuits.

We present an ultracompact (15.3 μm long) and high-efficiency silicon-on-insulator polarization rotator designed for polarization-diversified circuits. The rotator is comprised of a bilevel-tapered TM0-to-TE1 mode converter and a novel bent-tapered TE1-to-TE0 mode converter. The rotator has a simulated polarization conversion loss lower than 0.2 dB and a polarization-extinction ratio larger than 25 dB over a wavelength range of 80 nm around 1550 nm. The rotator has a SiO2 top-cladding and can be fabricated in a CMOS-compatible process.

A CMOS-compatible silicon photonic platform for high-speed integrated opto-electronics

We have developed a CMOS-compatible Silicon-on-Insulator photonic platform featuring active components such as pi- n and photoconductive (MIM) Ge-on-Si detectors, p-i-n ring and Mach-Zehnder modulators, and traveling-wave modulators based on a p-n junction driven by an RF transmission line. We have characterized the yield and uniformity of the performance through automated cross-wafer testing, demonstrating that our process is reliable and scalable. The entire platform is capable of more than 40 GB/s data rate. Fabricated at the IME/A-STAR foundry in Singapore, it is available to the worldwide community through OpSIS, a successful multi-project wafer service based at the University of Delaware. After exposing the design, fabrication and performance of the most advanced platform components, we present our newest results obtained after the first public run. These include low loss passives (Y-junctions: 0.28 dB; waveguide crossings: 0.18 dB and cross-talk -41±2 dB; non-uniform grating couplers: 3.2±0.2 dB). All these components were tested across full 8” wafers and exhibited remarkable uniformity. The active devices were improved from the previous design kit to exhibit 3dB bandwidths ranging from 30 GHz (modulators) to 58 GHz (detectors). We also present new packaging services available to OpSIS users: vertical fiber coupling and edge coupling.

Silicon microring modulator for 40 Gb/s NRZ-OOK metro networks in O-band

A microring-based silicon modulator operating at 40 Gb/s near 1310 nm is demonstrated for the first time to our knowledge. NRZ-OOK signals at 40 Gb/s with 6.2 dB extinction ratio are observed by applying a 4.8 Vpp driving voltage and biasing the modulator at 7 dB insertion loss point. The energy efficiency is 115 fJ/bit. The transmission performance of 40 Gb/s NRZ-OOK through 40 km of standard single mode fiber without dispersion compensation is also investigated. We show that the link suffers negligible dispersion penalty. This makes the modulator a potential candidate for metro network applications.

Silicon Mod-MUX-Ring transmitter with 4 channels at 40 Gb/s

We propose for the first time the Mod-MUX-Ring architecture for microring based WDM transmitter. A prototype Mod-MUX-Ring transmitter with 4 channels and 400 GHz channel spacing is demonstrated and fully characterized at 40 Gb/s channel rate. Under 2.7 V driving voltage, error-free (BER < 10(-12)) operation is achieved on all channels, with 3 dB extinction ratio. Performance comparisons to Lithium Niobate modulators are made.

A compact and low-loss silicon waveguide crossing for O-band optical interconnect

Silicon photonics has attracted extensive attention in recent years as a promising solution for next generation high-speed, low energy consumption, and low cost data transmission systems. Although a few experiments indicated board-level and long haul communication capability, major and near-future application of silicon photonics is commonly seen as Ethernet at 100Gb/s and beyond, such as interconnects in data centers, where O-Band (near 1310 nm wavelength) has been standardized for its low fiber dispersion. However, almost all silicon photonics devices demonstrated up to date operate at C-Band (1530 nm to 1560 nm), the fiber loss and erbium amplification window, probably due to the wider availability of lasers and testing apparatus at this wavelength. Typical C-Band devices cannot operate at O-Band, thus the whole device library needs to be redesigned and recalibrated for O-Band applications. In this paper, we present an ultra compact, low loss, and low crosstalk waveguide crossing operating at O-Band. It is designed using the finite difference time domain method coupled with a particle swarm optimization. Device footprint is only 6 μm × 6 μm. The measured insertion loss is 0.19±0.02 dB across an 8-inch wafer. Cross talk is lower than -35 dB. We also report a second waveguide crossing with a 9 μm × 9 μm footprint with 0.017±0.005 dB insertion loss. Finally we summarize the performance of our overall O-Band device library, including low-loss waveguides, high-speed modulators, and photodetectors.

30GHz silicon platform for photonics system

We present a silicon photonic platform offering low loss passive components, integrated highspeed silicon traveling wave MZ modulators (30GHz), ring modulators (45GHz) and inductance peaking Germanium photodetectors (58GHz). The bandwidth of the photonic devices is sufficient to support 50Gb/s bit rate. Our platform is available to the community as part of the OpSIS project.