D. J. Thomson

High-contrast 40 Gb/s operation of a 500 μm long silicon carrier-depletion slow wave modulator

In this Letter, we demonstrate a highly efficient, compact, high-contrast and low-loss silicon slow wave modulator based on a traveling-wave Mach-Zehnder interferometer with two 500 μm long slow wave phase shifters. 40u2009u2009Gb/s operation with 6.6 dB extinction ratio at quadrature and with an on-chip insertion loss of only 6 dB is shown. These results confirm the benefits of slow light as a means to enhance the performance of silicon modulators based on the plasma dispersion effect.

Analytical Model for Calculating the Nonlinear Distortion in Silicon-Based Electro-Optic Mach–Zehnder Modulators

In this study, an analytical model for calculating the nonlinear harmonic/intermodulation distortion for RF signals in silicon-based electro-optic modulators is investigated by considering the nonlinearity on the effective index change curve with the operation point and the device structure simultaneously. Distortion expressions are obtained and theoretical results are presented showing that optimal modulator parameters can be found to linearize it. Moreover, the harmonic distortion of a 1 mm silicon-based asymmetric MZI is RF characterized and used to corroborate the theoretical results. Based on the present model, the nonlinear distortion in terms of bias voltage or operating wavelength is calculated and validated by comparing with the experimental data, showing a good agreement between measurements and theory. Analog photonic link quality parameter like carrier-to-distortion is one of the parameters that can be found with that model. Finally, the modulation depth is measured to assure that no over-modulation is produced.

Low drive voltage 10 Gb/s and high contrast 40 Gb/s silicon slow wave modulators

We demonstrate the use of slow light to reduce the drive voltage and shrink the footprint of carrier depletion-based silicon modulators. Hence, low drive voltage 10 Gb/s modulation and high contrast 40Gb/s modulation is achieved.

Silicon slow-light-based photonic mixer for microwave-frequency conversion applications

We describe and demonstrate experimentally a method for photonic mixing of microwave signals by using a silicon electro-optical Mach-Zehnder modulator enhanced via slow-light propagation. Slow light with a group index of ~11, achieved in a one-dimensional periodic structure, is exploited to improve the upconversion performance of an input frequency signal from 1 to 10.25 GHz. A minimum transmission point is used to successfully demonstrate the upconversion with very low conversion losses of ~7 dB and excellent quality of the received I/Q modulated QPSK signal with an optimum EVM of ~8%.

A 30 Gb/s CMOS driver integrated with silicon photonics MZM

A voltage mode modulator driver is proposed in the TSMC 65nm low power CMOS process. In the electrical testing, the driver itself can achieve a bit rate of 40Gb/s with the single-ended output swing of 1.65V. Unlike equivalent CML modulator drivers, when the proposed driver is integrated with the silicon photonic MZM, it does not require an additional biasing network. The integrated electro-optic transmitter can achieve 30Gb/s with an extinction ratio of 4.05dB, with the power consumption of main driver being 323mW.

An alignment tolerant high speed ring resonator based silicon optical modulator

Optical modulation up to 40Gbit/s from a silicon ring resonator based device is demonstrated. A self-aligned process is used to form the pn junction reducing performance variations. The power consumption of the device is 8fJ/bit.

Group IV photonic devices for the mid-infrared

Group IV mid-infrared photonics is attracting more research interest lately. The main reason is a host of potential applications ranging from sensing, to medicine, to free space communications and infrared countermeasures. The field is, however, in its infancy and there are several serious challenges to be overcome before we see progress similar to that in the near-infrared silicon photonics. The first is to find suitable material platforms for the mid-infrared. In this paper we present experimental results for passive mid-infrared photonic devices realised in silicon-on-insulator, silicon-on-sapphire, and silicon on porous silicon. We also present relationships for the free-carrier induced electro-refraction and electro-absorption in silicon and germanium in the mid-infrared wavelength range. Electro-absorption modulation is calculated from impurity-doping spectra taken from the literature, and a Kramers-Kronig analysis of these spectra is used to predict electro-refraction modulation. We examine the wavelength dependence of electro-refraction and electro-absorption, finding that the predictions suggest longer-wave modulator designs will in many cases be different than those used in the telecom range.

Recent Developments in Silicon Optical Modulators

One of the key enabling-components for silicon photonics is a high-performance modulator. An overview is given of the modulator research that has been pursued at the University of Surrey and the worldwide state-of the art.

Analysis and Implementation of an Ultra-Wide Tuning Range CMOS Ring-VCO With Inductor Peaking

A novel ring voltage controlled oscillator (VCO) topology is proposed which uses monolithic inductors as a peaking load. Four design examples have been fabricated and tested to verify the proposed circuit structure. The highest measured oscillation frequency is 25.07 GHz, with a tuning range of more than four octaves, and the active area is 0.0085 mm2. The design has the highest combined frequency and tuning range with the best figure of merit (≈ 195) comparable to previously published work.

High speed and low power silicon-based receiver front-end for optical interconnect

We demonstrate an optical receiver front-end using a CMOS TIA with a germanium-on-silicon PD. The amplifier only occupies 0.09 mm2 with 12 mW power consumption, and achieves a 27.5 GHz 3-dB bandwidth. The integrated silicon-based receiver shows well opened eye diagrams up to 20 Gb/s.